The Military is embracing the communication revolution, turning to a new generation of sophisticated systems
to enable faster, richer, less costly, more flexible, reliable, compact, mobile, jam resistant, low probability of
detection, re configurable and spectrally efficient communication. Many of these features can be added to a
great extent in the existing systems, by utilising MIMO technology appropriately and judiciously. MIMO finds
applications in wireless communication, NLOS communication, satellite communication, HF communication,
Optical Fibre Communication. MIMO makes these technologies more suitable by introducing features
mandatory for military communication such as Ant jamming capability, Low Probability of Intercept, low
visibility of satellite earth Antennas by reducing their aperture area. MIMO can also provide redundancy by
employing no extra resources, thereby increasing reliability. MIMO is highly effective to communicate with
Unmanned Aerial Vehicles (1).
Third Generation Wireless Modeling in Urban EnvironmentEECJOURNAL
The global mobile communication is fast growing in industry. This paper recommends appropriate settings to evaluate the performance of wireless mobile system deploying third generation networks in an urban environment. To meet this aim, a case Study of Sulaimanyia city is considered for this study by establishing suitable radio channel models. The work presents a statistical channel model, where fixed and nomadic analysis services are considered in the simulated radio coverage scenario. The cartographic dataset had been collected, and Matlab Software was used for showing the analysis and simulation results. Statistical channel models are derived that combine standard parameters such as separation distance, operating frequency and terminal height with more advanced and innovative parameters such as distance dependent shadowing and LOS probability.
Comparison of Various Waveform Contenders of 5G Wireless Communication Based ...ijtsrd
This paper presents an extensive and fair comparison among the most promising waveform contenders for the 5G air interface which includes- Filtered OFDM, Filter-bank multi carrier (FBMC), universal filtered multi-carrier (UFMC) has been compared with OFDM in terms of spectral efficiency and bit error rate using mat lab. The disadvantages of OFDM have been addressed and it has shown that (fofdm), (UFMC), (FBMC) could be a more effective solution. FBMC is a method for improving out of band (OOB) characteristics by filtering each subcarrier, it is also expected to improve the Inter-Carrier Interference (ICI) characteristics while UFMC is a method for improving OOB characteristics by filtering each block. Raksha Vishnoi | Saurabh Gaur | Ashish Verma"Comparison of Various Waveform Contenders of 5G Wireless Communication Based on OFDM" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd15637.pdf http://www.ijtsrd.com/engineering/electronics-and-communication-engineering/15637/comparison-of-various-waveform-contenders-of-5g-wireless-communication-based-on-ofdm/raksha-vishnoi
Multicarrier modulation can be implemented by using Orthogonal Frequency Division Multiplexing (OFDM) to achieve utmost bandwidth exploitation and soaring alleviation attributes profile besides multipath fading. To support delay sensitive and band bandwidth demanding multimedia applications and internet services, MIMO in addition with other techniques can be used to achieve high capacity and reliability. To obtain high spatial rate by transmitting data on several antennas by using MIMO with OFDM results in reducing error recovery features and the equalization complexities arise by sending data on varying frequency levels. Three parameters frequency OFDM, Spatial (MIMO) and time (STC) can be used to achieve diversity in MIMO-OFDM. This technique is dynamic and well-known for services of wireless broadband access. MIMO if used with OFDM is highly beneficial for each scheme and provides high throughput. There are several space time block codes to exploit MIMO OFDM; one of the techniques is called Alamouti Codes. The paper investigates adaptive Alamouti Codes and their application in IEEE 802.11n.
In recent past the influence of Radar has played a significant part in various fields. Radar sensing is one of
the prime application by which velocity and distance of a moving target can be found out. A joint RadCom
system to serve both radar sensing and wireless communication is proposed which ensures better
performance in terms of spectral efficiency, extended detection range and cost effectiveness. Such systems
demand for a common waveform which is designed in this work that perfectly matches to the system
requirements. OFDM multi carrier technique is chosen to generate a common waveform. Applicability of
multiple antenna technique for direction of arrival estimation is also considered. MIMO-OFDM technique
has gained much interest in the field of communication which improves the signal to noise ratio and lowers
the bit error rate. On the other hand the usage of MIMO reflects in the form of interference between
signals. In order to overcome this effect beamforming technique is used. In addition to theoretical
explanations we have also simulated and discussed the results for the proposed RadCom system using
MATLAB simulation tool.
This document proposes a received signal strength (RSS) based vertical handoff scheme for k-tier heterogeneous wireless networks. It estimates RSS for different network tiers using empirical and statistical propagation models suited for the Indian urban and suburban environments. Based on the estimated RSS across different tiers, a vertical handoff algorithm is proposed that allows user equipment to switch between networks to maintain seamless connectivity based on RSS thresholds. The performance of the proposed RSS estimation and vertical handoff scheme is validated through simulations conducted using statistical data collected from field measurements.
The document discusses the IEEE 802.22 standard for cognitive radio wireless regional area networks (WRANs). It describes how cognitive radio technology can help address the spectrum crunch by efficiently utilizing vacant TV bands and other licensed spectrum. The standard defines the MAC and PHY layer specifications for a cognitive radio system, including spectrum sensing, mobility, sharing, and a superframe structure to manage communication in available TV channels while avoiding interference with primary users. The goal is to provide wireless connectivity over distances of up to 30 km using the cognitive radio capabilities defined in the 802.22 standard.
Performance Analysis of Ultra Wideband Communication SystemEditor IJMTER
Ultra-Wideband (UWB) is a radio transmission scheme that uses extremely low power
pulses of radio energy spread across a wide spectrum of frequencies. UWB has several advantages
over conventional continuous wave radio communications including potential support for high data
rates, robustness to multipath interference and fading. The paper covers Ultra Wide-Band
technology. General description, Challenges, various modulation schemes such as OOK, PAM,
PPM, and BPSK under specified Ultra Wide Band regimes: low Power spectral density, large
spreading ratio and a highly dispersive channel. The capacity and BER performance of a single user
ultra wideband communication is investigated for various modulation schemes and coded, uncoded
methods also simulated. Fading channel like Ricean and Rayleigh are compared. Channelized digital
receiver concept is discussed.
Performance Analysis of Dedicated-In-Band Control for Cognitive Radio NetworksIJSRED
This document analyzes different strategies for dedicating in-band control channels for cognitive radio networks (CRNs). It models a scenario of an outdoor stadium with 16 access points and users in fixed seat locations. It evaluates the performance of entwined and underlay strategies for selecting a dedicated control channel in terms of success rate and throughput of control messages. The entwined strategy avoids using a channel as the control channel if a primary user becomes active on it, while the underlay strategy continues using the channel at reduced transmission power. Simulation results show that the underlay strategy achieves higher success rates and throughput of control messages compared to the entwined strategy.
Third Generation Wireless Modeling in Urban EnvironmentEECJOURNAL
The global mobile communication is fast growing in industry. This paper recommends appropriate settings to evaluate the performance of wireless mobile system deploying third generation networks in an urban environment. To meet this aim, a case Study of Sulaimanyia city is considered for this study by establishing suitable radio channel models. The work presents a statistical channel model, where fixed and nomadic analysis services are considered in the simulated radio coverage scenario. The cartographic dataset had been collected, and Matlab Software was used for showing the analysis and simulation results. Statistical channel models are derived that combine standard parameters such as separation distance, operating frequency and terminal height with more advanced and innovative parameters such as distance dependent shadowing and LOS probability.
Comparison of Various Waveform Contenders of 5G Wireless Communication Based ...ijtsrd
This paper presents an extensive and fair comparison among the most promising waveform contenders for the 5G air interface which includes- Filtered OFDM, Filter-bank multi carrier (FBMC), universal filtered multi-carrier (UFMC) has been compared with OFDM in terms of spectral efficiency and bit error rate using mat lab. The disadvantages of OFDM have been addressed and it has shown that (fofdm), (UFMC), (FBMC) could be a more effective solution. FBMC is a method for improving out of band (OOB) characteristics by filtering each subcarrier, it is also expected to improve the Inter-Carrier Interference (ICI) characteristics while UFMC is a method for improving OOB characteristics by filtering each block. Raksha Vishnoi | Saurabh Gaur | Ashish Verma"Comparison of Various Waveform Contenders of 5G Wireless Communication Based on OFDM" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd15637.pdf http://www.ijtsrd.com/engineering/electronics-and-communication-engineering/15637/comparison-of-various-waveform-contenders-of-5g-wireless-communication-based-on-ofdm/raksha-vishnoi
Multicarrier modulation can be implemented by using Orthogonal Frequency Division Multiplexing (OFDM) to achieve utmost bandwidth exploitation and soaring alleviation attributes profile besides multipath fading. To support delay sensitive and band bandwidth demanding multimedia applications and internet services, MIMO in addition with other techniques can be used to achieve high capacity and reliability. To obtain high spatial rate by transmitting data on several antennas by using MIMO with OFDM results in reducing error recovery features and the equalization complexities arise by sending data on varying frequency levels. Three parameters frequency OFDM, Spatial (MIMO) and time (STC) can be used to achieve diversity in MIMO-OFDM. This technique is dynamic and well-known for services of wireless broadband access. MIMO if used with OFDM is highly beneficial for each scheme and provides high throughput. There are several space time block codes to exploit MIMO OFDM; one of the techniques is called Alamouti Codes. The paper investigates adaptive Alamouti Codes and their application in IEEE 802.11n.
In recent past the influence of Radar has played a significant part in various fields. Radar sensing is one of
the prime application by which velocity and distance of a moving target can be found out. A joint RadCom
system to serve both radar sensing and wireless communication is proposed which ensures better
performance in terms of spectral efficiency, extended detection range and cost effectiveness. Such systems
demand for a common waveform which is designed in this work that perfectly matches to the system
requirements. OFDM multi carrier technique is chosen to generate a common waveform. Applicability of
multiple antenna technique for direction of arrival estimation is also considered. MIMO-OFDM technique
has gained much interest in the field of communication which improves the signal to noise ratio and lowers
the bit error rate. On the other hand the usage of MIMO reflects in the form of interference between
signals. In order to overcome this effect beamforming technique is used. In addition to theoretical
explanations we have also simulated and discussed the results for the proposed RadCom system using
MATLAB simulation tool.
This document proposes a received signal strength (RSS) based vertical handoff scheme for k-tier heterogeneous wireless networks. It estimates RSS for different network tiers using empirical and statistical propagation models suited for the Indian urban and suburban environments. Based on the estimated RSS across different tiers, a vertical handoff algorithm is proposed that allows user equipment to switch between networks to maintain seamless connectivity based on RSS thresholds. The performance of the proposed RSS estimation and vertical handoff scheme is validated through simulations conducted using statistical data collected from field measurements.
The document discusses the IEEE 802.22 standard for cognitive radio wireless regional area networks (WRANs). It describes how cognitive radio technology can help address the spectrum crunch by efficiently utilizing vacant TV bands and other licensed spectrum. The standard defines the MAC and PHY layer specifications for a cognitive radio system, including spectrum sensing, mobility, sharing, and a superframe structure to manage communication in available TV channels while avoiding interference with primary users. The goal is to provide wireless connectivity over distances of up to 30 km using the cognitive radio capabilities defined in the 802.22 standard.
Performance Analysis of Ultra Wideband Communication SystemEditor IJMTER
Ultra-Wideband (UWB) is a radio transmission scheme that uses extremely low power
pulses of radio energy spread across a wide spectrum of frequencies. UWB has several advantages
over conventional continuous wave radio communications including potential support for high data
rates, robustness to multipath interference and fading. The paper covers Ultra Wide-Band
technology. General description, Challenges, various modulation schemes such as OOK, PAM,
PPM, and BPSK under specified Ultra Wide Band regimes: low Power spectral density, large
spreading ratio and a highly dispersive channel. The capacity and BER performance of a single user
ultra wideband communication is investigated for various modulation schemes and coded, uncoded
methods also simulated. Fading channel like Ricean and Rayleigh are compared. Channelized digital
receiver concept is discussed.
Performance Analysis of Dedicated-In-Band Control for Cognitive Radio NetworksIJSRED
This document analyzes different strategies for dedicating in-band control channels for cognitive radio networks (CRNs). It models a scenario of an outdoor stadium with 16 access points and users in fixed seat locations. It evaluates the performance of entwined and underlay strategies for selecting a dedicated control channel in terms of success rate and throughput of control messages. The entwined strategy avoids using a channel as the control channel if a primary user becomes active on it, while the underlay strategy continues using the channel at reduced transmission power. Simulation results show that the underlay strategy achieves higher success rates and throughput of control messages compared to the entwined strategy.
This document summarizes a research paper on using time-domain signal cross-correlation for spectrum sensing in cognitive radio systems applied to vehicular ad-hoc networks (VANETs). It aims to address spectrum scarcity issues in VANETs by allowing vehicles to opportunistically access TV white space spectrum when licensed spectrum is unavailable. The time-domain symbol cross-correlation technique is analyzed for spectrum sensing performance over Rayleigh fading channels. Analytical expressions for average miss detection probability are derived and simulation results show the probability of miss detection decreases with increasing SNR and number of secondary users. The time-domain symbol cross-correlation method provides good spectrum sensing performance at low SNRs for cognitive radio in VANETs.
This thesis examines channel estimation techniques for 3GPP LTE downlink. It introduces LTE physical layer specifications including frame structure and reference signals. It describes propagation models and channel models specified for LTE. It then focuses on pilot-assisted channel estimation methods for single-input single-output systems, including least squares and minimum mean square error estimation. Performance is evaluated using bit error rate and symbol error rate. Space-frequency block coding for multiple antenna systems is also discussed along with corresponding channel estimation and decoding.
IRJET- Measurement of Second Harmonic Voltage with Wavelength Modulation Spec...IRJET Journal
This document discusses measurement of second harmonic voltage using wavelength modulation spectroscopy with MATLAB Simulink. It provides an overview of free-space optical communication systems and wavelength division multiplexing technology. It describes the basic components of an FSO system including the transmitter, receiver, and communication channel. Challenges of FSO systems include atmospheric effects like absorption, scattering and refraction. Applications of FSO include links between satellites, terrestrial networks, and deep space probes where it provides advantages over radio frequency technology.
This document presents a term project on 3D beamforming for 5G networks. It outlines the motivation for 3D beamforming to meet 5G goals and reduce interference. The objectives are to analyze narrow beam formation with different array geometries and track user movement. Results show narrow beams formed with linear, planar and cylindrical arrays using windowing. Future work includes incorporating 3D channel models and Coordinated Multi-Point features with 3D beamforming.
The document summarizes Deutsche Telekom's requirements and candidate technologies for 3GPP Release 12 and beyond. It discusses the need for significant capacity increases to meet growing mobile broadband demand through technologies like small cells, antenna arrays, and MIMO enhancements. It also addresses spectrum needs, improved inter-RAT functionality between LTE and UMTS, support for new services like proximity and M2M, and further HSPA enhancements. The presentation was given at a 3GPP workshop to discuss LTE evolution in Release 12 and future releases.
IRJET- BER Reduction of Distributed Spatial Modulation in Cooperative Relay N...IRJET Journal
This document summarizes a research paper on reducing bit error rate (BER) of distributed spatial modulation in cooperative relay networks for cellular systems. The key points are:
1) Distributed spatial modulation (DSM) is proposed to overcome limitations of spatial modulation for mobile terminals by using multiple cooperative relays to form a virtual antenna array.
2) In DSM, source information is broadcast to relays and one relay is selected to forward the information to the destination, reducing transmit power.
3) A DSM-OFDM protocol is proposed where only one relay transmits per OFDM subcarrier while others transmit zero power.
4) Simulation results show the proposed DSM-OFDM scheme achieves
Index modulation is one of the promising techniques for future communications systems due to many improvement over the classical orthogonal frequency division multiplexing systems such as single RF chain, increased throughput for the same modulation order, achieved tradeoff between the efficiencies of the power and the spectral, and elimination of inter-channel interference. Many forms of index modulation researches exist where symbols are conveyed in antennas, subcarriers, time slots, and the space-time matrix. Spatial modulation is one member of index modulation family where symbols are conveyed in activating transmit/receive antennas. In this paper, a modification to a standard multiple input single output scheme by integrating spatial modulation using simplified mathematical procedure is achieved. In the transmitter side, data and activation symbols are distributed simultaneously using mathematical module and floor functions. At the receiver, a simplified maximum likelihood detector is used to obtain transmitted pair of symbols. To verify this, MATLAB simulink is used to simulate a downlink system where spatial modulation is applied to a base station. Results for different transmit antenna number and modulation order are obtained in the form of bit error rate versus signal to noise ratio.
The innovative and effective use of information and communication technologies (ICT) is becoming increasingly important to improve the economy of the world [1]. Wireless communication networks are perhaps the most critical element in the global ICT strategy, underpinning many other industries. It is one of the fastest growing and most dynamic sectors in the world.
The European Mobile Observatory (EMO) reported that the mobile communication sector had total revenue of €174 billion in 2010, there- by bypassing the aerospace and pharmaceutical sectors [2]. The development of wireless technologies has greatly improved people’s ability to communicate and live in both business operations and social functions.
The phenomenal success of wireless mobile communications is mirrored by a rapid pace of technology innovation. From the second generation (2G) mobile communication system debuted in 1991 to the 3G system first launched in 2001, the wireless mobile network has transformed from a pure telephony system to a network that can transport rich multimedia contents. The 4G wireless systems were designed to fulfill the requirements of International Mobile Telecommunications-Advanced (IMT-A) using IP for all services [3]. In 4G systems, an advanced radio interface is used with orthogonal frequency-division multiplexing (OFDM), multiple-input multiple-output (MIMO), and link adaptation technologies. 4G wireless networks can support data rates of up to 1 Gb/s for low mobility, such as nomadic/local wireless access, and up to 100 Mb/s for high mobility, such as mobile access. Long-Term Evolution (LTE) and its extension, LTE-Advanced systems, as practical 4G systems, have recently been deployed or soon will be deployed around the globe.
However, there is still a dramatic increase in the number of users who subscribe to mobile broadband systems every year. More and more people crave faster Internet access on the move, trendier mobiles, and, in general, instant com- munication with others or access to information. More powerful smart phones and laptops are becoming more popular nowadays, demanding advanced multimedia capabilities. This has resulted in an explosion of wireless mobile devices and services. The EMO pointed out that there has been a 92 percent growth in mobile broadband per year since 2006 [2]. It has been predicted by the Wireless World Research Forum (WWRF) that 7 trillion wireless devices will serve 7 billion people by 2017; that is, the number of network-connected wireless devices will reach 1000 times the world’s population [4]. As more and more devices go wireless, many research challenges need to be addressed.
C-band spectrum offers a balance between coverage and bandwidth that benefits 5G applications. It provides wider bandwidth than low bands but more coverage than high bands. Ensuring spectrum is cleared of existing users, precise antenna alignment due to beamforming, and meeting stringent timing requirements for TDD are key challenges for C-band 5G deployment. Solutions like interference analyzers, antenna alignment tools, and synchronization testing equipment can help operators overcome these challenges.
Massive MIMO (also known as “Large-Scale Antenna Systems”, “Very Large MIMO”, “Hyper MIMO”, “Full-Dimension MIMO” and “ARGOS”) makes a clean break with current practice through the use of a large excess of service-antennas over active terminals and time division duplex operation. Extra antennas help by focusing energy into ever-smaller regions of space to bring huge improvements in throughput and radiated energy efficiency. Other benefits of massive MIMO include the extensive use of inexpensive low-power components, reduced latency, simplification of the media access control (MAC) layer, and robustness to intentional jamming. The anticipated throughput depend on the propagation environment providing asymptotically orthogonal channels to the terminals, but so far experiments have not disclosed any limitations in this regard. While massive MIMO renders many traditional research problems irrelevant, it uncovers entirely new problems that urgently need attention: the challenge of making many low-cost low-precision components that work effectively together, acquisition and synchronization for newly-joined terminals, the exploitation of extra degrees of freedom provided by the excess of service-antennas, reducing internal power consumption to achieve total energy efficiency reductions, and finding new deployment scenarios.
This document discusses techniques for determining the pinpoint location of mobile devices in Global System for Mobile Communication (GSM) networks. It begins with an introduction to the history and development of GSM standards. It then describes several outdoor propagation models that are commonly used to predict signal strength at different locations, including the Longley-Rice model, Durkin's model, and Okumura's model. These models take into account factors like terrain profile, buildings, foliage and antenna heights to estimate path loss between the base station and mobile.
VTC-location based channel estimation for massive full-dimensional MIMO systemsQian Han
This document proposes a two-dimensional location-based channel estimation method for massive full-dimensional MIMO systems. It uses an intra-cell pilot reuse scheme where users with the same pilots can be distinguished by their unique azimuth and elevation angles of arrival. The method applies a 2D FFT to the pilot-aided channel estimates followed by a 2D window function in the angle domain to isolate the different users. Simulation results show the proposed method outperforms conventional pilot-aided estimation and that 3D MIMO can improve sum capacity and serve more users compared to traditional MIMO systems.
WRAP is a medium access control (MAC) protocol for wavelength-routed passive optical networks (WR-PONs) that does not require a separate control channel, carrier sensing, or centralized scheduling. Each node has a single tunable transmitter and fixed receiver. Access is regulated through wavelength allocations made by destination nodes in response to requests. Simulations test three allocation algorithms and show the Preferential/Random algorithm provides better performance than alternatives. WRAP performance is also compared to two other applicable protocols, showing WRAP enables high utilization over a wide range of traffic conditions while guaranteeing minimum bandwidth between nodes.
A New Transmission Scheme for MIMO – OFDMijsrd.com
This contribution introduces a new transmission scheme for multiple-input multiple-output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems. The new scheme is efficient and suitable especially for symmetric channels such as the link between two base stations or between two antennas on radio beam transmission. This survey Paper presents the performance analysis of V-BLAST based multiple inputs multiple output orthogonal frequency division multiplexing (MIMO-OFDM) system with respect to bit error rate per signal to noise ratio (BER/SNR) for various detection techniques. A 2X2 MIMO-OFDM system is used for the performance evaluation. The simulation results shows that the performance of V-BLAST based detection techniques is much better than the conventional methods. Alamouti Space Time Block Code (STBC) scheme is used with orthogonal designs over multiple antennas which showed simulated results are identical to expected theoretical results. With this technique both Bit Error Rate (BER) and maximum diversity gain are achieved by increasing number of antennas on either side. This scheme is efficient in all the applications where system capacity is limited by multipath fading.
An Efficient Performance of Mimo - Ofdm Based Cognitieve Radio System for Arr...IOSR Journals
Abstract: The wireless channel is central within this context, thus estimating the channel is the key to make CR operational, taking in consideration that the transmission-reception technology is available. In this thesis, we design a MIMO system using OFDM modulation technology to transmit and receive two signals over the mobile wireless channel. First formulate the pilot design as a new optimization problem. We use MIMO concept to enhance system capacity and robustness of the wireless transmission. In Multi-Input Multi-Output (MIMO) based cognitive radio (CR) systems, with the increasing demand for data rate and reliability in Wireless communicationsand devices, several issues become very important like bandwidth efficiency, quality of service and radio coverage. In this new scheme, adaptive arrays are group-selected in the spatial domain. Simulation shows that the proposed system can get significant performance improvements over the conventional array based OFDM systems over frequency-selective multipath fading channels with cognitive radio (CR) system. Keywords: Cognitive radios, MIMO, OFDM, and Joint transmit and receive group selected arrays.
Improvement of crankshaft MAC protocol for wireless sensor networks: a simula...IJECEIAES
Due to the dramatic growth in the use of Wireless Sensor Network (WSN) applications ranging from environment and habitat monitoring to tracking and surveillance, network research in WSN protocols has been very active in the last decade. With battery-powered sensors operating in unattended environments, energy conservation becomes the key technique for improving WSN lifetimes. WSN Medium Access Control (MAC) protocols address energy awareness and reduced duty cycles. The focus of this study is to investigate, through simulation, the effect of variations in various factors that influence the performance results of WSNs. Using MiXiM framework with OMNeT++ simulator, this simulation study proposes modifications in Crankshaft MAC protocol in order to improve its performance. The impact of duration and number of slots, degree of connectivity among the nodes, mobility speed and mobility update interval and also, the impact of sending data packets without preambles are investigated. Based on the simulation results, an improved version of the Crankshaft protocol for WSN is suggested and a comparative study of the performances of the original and improved protocol is presented. The results clearly indicate the superiority of the improved protocol over its original version.
Rapid developments in modern wireless communication permit the trade of spectrum scarcity. Higher data rate and wider bandwidth emerge the development in growing demand of wireless communication system. The innovative solution for the spectrum scarcity is cognitive radio (CR). Cognitive radio is the significant technology used to utilize the spectrum effectively. The important aspect of CR is sensing the spectrum band and detects the presence or absence of the primary user in the licensed band. Moreover, another serious issue in next generation (5G) wireless communication is to decide the less complex 5G waveform candidate for achieving higher data rate, low latency and better spectral efficiency. Universal filtered multi-carrier (UFMC) is one of the noticeable waveform candidates for 5G and its applications. In this article, we investigate the spectrum sensing methods in multi-carrier transmission for cognitive radio network applications. Especially, we integrate the sensing algorithm into UFMC transceiver to analyze the spectral efficiency, higher data rates and system complexity. Through the simulation results, we prove that the UFMC based cognitive radio applications outperform the existing Orthogonal Frequency Division Multiplexing (OFDM) based CR applications.
In this presentation the effect of channel estimation errors on the energy efficiency of a down-link massive multiple-input multiple-output system is investigated and analyzed. The required down-link transmit power of the zero forcing (ZF) and maximum ratio transmission (MRT) precoding schemes are derived and analyzed under imperfect channel state information condition.
Performance Evaluation of PAPR Reduction with SER and BER by Modified Clippin...ijcsse
This paper work focuses on performance analysis of PAPR reduction of orthogonal frequency division multiplexing (OFDM) using amplitude clipping & filtering based design. Now a days one of the most proficient multi-carrier transmission techniques widely used today is orthogonal frequency division multiplexing (OFDM) which has been implemented by the next generation wireless communication technology: Long Term Evolution (LTE). Extra robustness to multipath fading and impulse noise is provided OFDM. It eliminates inter symbol interference (ISI) & inter carrier interference (ICI) with certain procedure. Therefore peak to average power ratio (PAPR) is the basic problem with OFDM. However in this paper we proposed a reduction procedure of the PAPR by using clipping and filtering. Here we use a composed high pass , low pass & Chevyshev band pass filter II after amplitude clipping to reduce the PAPR. The performance of the system in terms of bit error rate (BER) and symbol error rate (SER) is also investigated as a new filter based clipping method is proposed. Our proposed clipping method with and composed high pass the Chevyshev bandpass filter II in PAPR performance of the system with a little compromise of BER & SER showing the significant improvement in Quadrature Amplitude Modulation (QAM).
This document analyzes the capacity of MIMO wireless channels when accounting for impairments from physical transceiver hardware limitations. It is shown that when including the effects of transceiver impairments like non-linearities, phase noise, and quantization noise, the capacity of MIMO channels reaches a finite limit as SNR increases, rather than increasing without bound. This results in a zero multiplexing gain, unlike the ideal case without impairments. However, the relative capacity increase from MIMO over single-antenna channels remains at least as large when including impairments. Various figures are presented showing the capacity and multiplexing gain for different channel models and transceiver configurations. The document concludes by stating the analysis provides insights into understanding
This document summarizes a research paper on using time-domain signal cross-correlation for spectrum sensing in cognitive radio systems applied to vehicular ad-hoc networks (VANETs). It aims to address spectrum scarcity issues in VANETs by allowing vehicles to opportunistically access TV white space spectrum when licensed spectrum is unavailable. The time-domain symbol cross-correlation technique is analyzed for spectrum sensing performance over Rayleigh fading channels. Analytical expressions for average miss detection probability are derived and simulation results show the probability of miss detection decreases with increasing SNR and number of secondary users. The time-domain symbol cross-correlation method provides good spectrum sensing performance at low SNRs for cognitive radio in VANETs.
This thesis examines channel estimation techniques for 3GPP LTE downlink. It introduces LTE physical layer specifications including frame structure and reference signals. It describes propagation models and channel models specified for LTE. It then focuses on pilot-assisted channel estimation methods for single-input single-output systems, including least squares and minimum mean square error estimation. Performance is evaluated using bit error rate and symbol error rate. Space-frequency block coding for multiple antenna systems is also discussed along with corresponding channel estimation and decoding.
IRJET- Measurement of Second Harmonic Voltage with Wavelength Modulation Spec...IRJET Journal
This document discusses measurement of second harmonic voltage using wavelength modulation spectroscopy with MATLAB Simulink. It provides an overview of free-space optical communication systems and wavelength division multiplexing technology. It describes the basic components of an FSO system including the transmitter, receiver, and communication channel. Challenges of FSO systems include atmospheric effects like absorption, scattering and refraction. Applications of FSO include links between satellites, terrestrial networks, and deep space probes where it provides advantages over radio frequency technology.
This document presents a term project on 3D beamforming for 5G networks. It outlines the motivation for 3D beamforming to meet 5G goals and reduce interference. The objectives are to analyze narrow beam formation with different array geometries and track user movement. Results show narrow beams formed with linear, planar and cylindrical arrays using windowing. Future work includes incorporating 3D channel models and Coordinated Multi-Point features with 3D beamforming.
The document summarizes Deutsche Telekom's requirements and candidate technologies for 3GPP Release 12 and beyond. It discusses the need for significant capacity increases to meet growing mobile broadband demand through technologies like small cells, antenna arrays, and MIMO enhancements. It also addresses spectrum needs, improved inter-RAT functionality between LTE and UMTS, support for new services like proximity and M2M, and further HSPA enhancements. The presentation was given at a 3GPP workshop to discuss LTE evolution in Release 12 and future releases.
IRJET- BER Reduction of Distributed Spatial Modulation in Cooperative Relay N...IRJET Journal
This document summarizes a research paper on reducing bit error rate (BER) of distributed spatial modulation in cooperative relay networks for cellular systems. The key points are:
1) Distributed spatial modulation (DSM) is proposed to overcome limitations of spatial modulation for mobile terminals by using multiple cooperative relays to form a virtual antenna array.
2) In DSM, source information is broadcast to relays and one relay is selected to forward the information to the destination, reducing transmit power.
3) A DSM-OFDM protocol is proposed where only one relay transmits per OFDM subcarrier while others transmit zero power.
4) Simulation results show the proposed DSM-OFDM scheme achieves
Index modulation is one of the promising techniques for future communications systems due to many improvement over the classical orthogonal frequency division multiplexing systems such as single RF chain, increased throughput for the same modulation order, achieved tradeoff between the efficiencies of the power and the spectral, and elimination of inter-channel interference. Many forms of index modulation researches exist where symbols are conveyed in antennas, subcarriers, time slots, and the space-time matrix. Spatial modulation is one member of index modulation family where symbols are conveyed in activating transmit/receive antennas. In this paper, a modification to a standard multiple input single output scheme by integrating spatial modulation using simplified mathematical procedure is achieved. In the transmitter side, data and activation symbols are distributed simultaneously using mathematical module and floor functions. At the receiver, a simplified maximum likelihood detector is used to obtain transmitted pair of symbols. To verify this, MATLAB simulink is used to simulate a downlink system where spatial modulation is applied to a base station. Results for different transmit antenna number and modulation order are obtained in the form of bit error rate versus signal to noise ratio.
The innovative and effective use of information and communication technologies (ICT) is becoming increasingly important to improve the economy of the world [1]. Wireless communication networks are perhaps the most critical element in the global ICT strategy, underpinning many other industries. It is one of the fastest growing and most dynamic sectors in the world.
The European Mobile Observatory (EMO) reported that the mobile communication sector had total revenue of €174 billion in 2010, there- by bypassing the aerospace and pharmaceutical sectors [2]. The development of wireless technologies has greatly improved people’s ability to communicate and live in both business operations and social functions.
The phenomenal success of wireless mobile communications is mirrored by a rapid pace of technology innovation. From the second generation (2G) mobile communication system debuted in 1991 to the 3G system first launched in 2001, the wireless mobile network has transformed from a pure telephony system to a network that can transport rich multimedia contents. The 4G wireless systems were designed to fulfill the requirements of International Mobile Telecommunications-Advanced (IMT-A) using IP for all services [3]. In 4G systems, an advanced radio interface is used with orthogonal frequency-division multiplexing (OFDM), multiple-input multiple-output (MIMO), and link adaptation technologies. 4G wireless networks can support data rates of up to 1 Gb/s for low mobility, such as nomadic/local wireless access, and up to 100 Mb/s for high mobility, such as mobile access. Long-Term Evolution (LTE) and its extension, LTE-Advanced systems, as practical 4G systems, have recently been deployed or soon will be deployed around the globe.
However, there is still a dramatic increase in the number of users who subscribe to mobile broadband systems every year. More and more people crave faster Internet access on the move, trendier mobiles, and, in general, instant com- munication with others or access to information. More powerful smart phones and laptops are becoming more popular nowadays, demanding advanced multimedia capabilities. This has resulted in an explosion of wireless mobile devices and services. The EMO pointed out that there has been a 92 percent growth in mobile broadband per year since 2006 [2]. It has been predicted by the Wireless World Research Forum (WWRF) that 7 trillion wireless devices will serve 7 billion people by 2017; that is, the number of network-connected wireless devices will reach 1000 times the world’s population [4]. As more and more devices go wireless, many research challenges need to be addressed.
C-band spectrum offers a balance between coverage and bandwidth that benefits 5G applications. It provides wider bandwidth than low bands but more coverage than high bands. Ensuring spectrum is cleared of existing users, precise antenna alignment due to beamforming, and meeting stringent timing requirements for TDD are key challenges for C-band 5G deployment. Solutions like interference analyzers, antenna alignment tools, and synchronization testing equipment can help operators overcome these challenges.
Massive MIMO (also known as “Large-Scale Antenna Systems”, “Very Large MIMO”, “Hyper MIMO”, “Full-Dimension MIMO” and “ARGOS”) makes a clean break with current practice through the use of a large excess of service-antennas over active terminals and time division duplex operation. Extra antennas help by focusing energy into ever-smaller regions of space to bring huge improvements in throughput and radiated energy efficiency. Other benefits of massive MIMO include the extensive use of inexpensive low-power components, reduced latency, simplification of the media access control (MAC) layer, and robustness to intentional jamming. The anticipated throughput depend on the propagation environment providing asymptotically orthogonal channels to the terminals, but so far experiments have not disclosed any limitations in this regard. While massive MIMO renders many traditional research problems irrelevant, it uncovers entirely new problems that urgently need attention: the challenge of making many low-cost low-precision components that work effectively together, acquisition and synchronization for newly-joined terminals, the exploitation of extra degrees of freedom provided by the excess of service-antennas, reducing internal power consumption to achieve total energy efficiency reductions, and finding new deployment scenarios.
This document discusses techniques for determining the pinpoint location of mobile devices in Global System for Mobile Communication (GSM) networks. It begins with an introduction to the history and development of GSM standards. It then describes several outdoor propagation models that are commonly used to predict signal strength at different locations, including the Longley-Rice model, Durkin's model, and Okumura's model. These models take into account factors like terrain profile, buildings, foliage and antenna heights to estimate path loss between the base station and mobile.
VTC-location based channel estimation for massive full-dimensional MIMO systemsQian Han
This document proposes a two-dimensional location-based channel estimation method for massive full-dimensional MIMO systems. It uses an intra-cell pilot reuse scheme where users with the same pilots can be distinguished by their unique azimuth and elevation angles of arrival. The method applies a 2D FFT to the pilot-aided channel estimates followed by a 2D window function in the angle domain to isolate the different users. Simulation results show the proposed method outperforms conventional pilot-aided estimation and that 3D MIMO can improve sum capacity and serve more users compared to traditional MIMO systems.
WRAP is a medium access control (MAC) protocol for wavelength-routed passive optical networks (WR-PONs) that does not require a separate control channel, carrier sensing, or centralized scheduling. Each node has a single tunable transmitter and fixed receiver. Access is regulated through wavelength allocations made by destination nodes in response to requests. Simulations test three allocation algorithms and show the Preferential/Random algorithm provides better performance than alternatives. WRAP performance is also compared to two other applicable protocols, showing WRAP enables high utilization over a wide range of traffic conditions while guaranteeing minimum bandwidth between nodes.
A New Transmission Scheme for MIMO – OFDMijsrd.com
This contribution introduces a new transmission scheme for multiple-input multiple-output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems. The new scheme is efficient and suitable especially for symmetric channels such as the link between two base stations or between two antennas on radio beam transmission. This survey Paper presents the performance analysis of V-BLAST based multiple inputs multiple output orthogonal frequency division multiplexing (MIMO-OFDM) system with respect to bit error rate per signal to noise ratio (BER/SNR) for various detection techniques. A 2X2 MIMO-OFDM system is used for the performance evaluation. The simulation results shows that the performance of V-BLAST based detection techniques is much better than the conventional methods. Alamouti Space Time Block Code (STBC) scheme is used with orthogonal designs over multiple antennas which showed simulated results are identical to expected theoretical results. With this technique both Bit Error Rate (BER) and maximum diversity gain are achieved by increasing number of antennas on either side. This scheme is efficient in all the applications where system capacity is limited by multipath fading.
An Efficient Performance of Mimo - Ofdm Based Cognitieve Radio System for Arr...IOSR Journals
Abstract: The wireless channel is central within this context, thus estimating the channel is the key to make CR operational, taking in consideration that the transmission-reception technology is available. In this thesis, we design a MIMO system using OFDM modulation technology to transmit and receive two signals over the mobile wireless channel. First formulate the pilot design as a new optimization problem. We use MIMO concept to enhance system capacity and robustness of the wireless transmission. In Multi-Input Multi-Output (MIMO) based cognitive radio (CR) systems, with the increasing demand for data rate and reliability in Wireless communicationsand devices, several issues become very important like bandwidth efficiency, quality of service and radio coverage. In this new scheme, adaptive arrays are group-selected in the spatial domain. Simulation shows that the proposed system can get significant performance improvements over the conventional array based OFDM systems over frequency-selective multipath fading channels with cognitive radio (CR) system. Keywords: Cognitive radios, MIMO, OFDM, and Joint transmit and receive group selected arrays.
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Due to the dramatic growth in the use of Wireless Sensor Network (WSN) applications ranging from environment and habitat monitoring to tracking and surveillance, network research in WSN protocols has been very active in the last decade. With battery-powered sensors operating in unattended environments, energy conservation becomes the key technique for improving WSN lifetimes. WSN Medium Access Control (MAC) protocols address energy awareness and reduced duty cycles. The focus of this study is to investigate, through simulation, the effect of variations in various factors that influence the performance results of WSNs. Using MiXiM framework with OMNeT++ simulator, this simulation study proposes modifications in Crankshaft MAC protocol in order to improve its performance. The impact of duration and number of slots, degree of connectivity among the nodes, mobility speed and mobility update interval and also, the impact of sending data packets without preambles are investigated. Based on the simulation results, an improved version of the Crankshaft protocol for WSN is suggested and a comparative study of the performances of the original and improved protocol is presented. The results clearly indicate the superiority of the improved protocol over its original version.
Rapid developments in modern wireless communication permit the trade of spectrum scarcity. Higher data rate and wider bandwidth emerge the development in growing demand of wireless communication system. The innovative solution for the spectrum scarcity is cognitive radio (CR). Cognitive radio is the significant technology used to utilize the spectrum effectively. The important aspect of CR is sensing the spectrum band and detects the presence or absence of the primary user in the licensed band. Moreover, another serious issue in next generation (5G) wireless communication is to decide the less complex 5G waveform candidate for achieving higher data rate, low latency and better spectral efficiency. Universal filtered multi-carrier (UFMC) is one of the noticeable waveform candidates for 5G and its applications. In this article, we investigate the spectrum sensing methods in multi-carrier transmission for cognitive radio network applications. Especially, we integrate the sensing algorithm into UFMC transceiver to analyze the spectral efficiency, higher data rates and system complexity. Through the simulation results, we prove that the UFMC based cognitive radio applications outperform the existing Orthogonal Frequency Division Multiplexing (OFDM) based CR applications.
In this presentation the effect of channel estimation errors on the energy efficiency of a down-link massive multiple-input multiple-output system is investigated and analyzed. The required down-link transmit power of the zero forcing (ZF) and maximum ratio transmission (MRT) precoding schemes are derived and analyzed under imperfect channel state information condition.
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This paper work focuses on performance analysis of PAPR reduction of orthogonal frequency division multiplexing (OFDM) using amplitude clipping & filtering based design. Now a days one of the most proficient multi-carrier transmission techniques widely used today is orthogonal frequency division multiplexing (OFDM) which has been implemented by the next generation wireless communication technology: Long Term Evolution (LTE). Extra robustness to multipath fading and impulse noise is provided OFDM. It eliminates inter symbol interference (ISI) & inter carrier interference (ICI) with certain procedure. Therefore peak to average power ratio (PAPR) is the basic problem with OFDM. However in this paper we proposed a reduction procedure of the PAPR by using clipping and filtering. Here we use a composed high pass , low pass & Chevyshev band pass filter II after amplitude clipping to reduce the PAPR. The performance of the system in terms of bit error rate (BER) and symbol error rate (SER) is also investigated as a new filter based clipping method is proposed. Our proposed clipping method with and composed high pass the Chevyshev bandpass filter II in PAPR performance of the system with a little compromise of BER & SER showing the significant improvement in Quadrature Amplitude Modulation (QAM).
This document analyzes the capacity of MIMO wireless channels when accounting for impairments from physical transceiver hardware limitations. It is shown that when including the effects of transceiver impairments like non-linearities, phase noise, and quantization noise, the capacity of MIMO channels reaches a finite limit as SNR increases, rather than increasing without bound. This results in a zero multiplexing gain, unlike the ideal case without impairments. However, the relative capacity increase from MIMO over single-antenna channels remains at least as large when including impairments. Various figures are presented showing the capacity and multiplexing gain for different channel models and transceiver configurations. The document concludes by stating the analysis provides insights into understanding
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(DBPSK), Differential Pulse-position Modulation (DPPM) and On-off Keying (OOK), with coherent
and non-coherent detection. The increasing demand for wireless communication introduces efficient
spectrum utilization challenge. To address this challenge, cognitive radio (CR) is emerged as the key
technology; which enables opportunistic access to the spectrum. CR is a form of wireless
communication in which a transceiver can intelligently detect which communication channels are in
use and which are not, and instantly move into vacant channels while avoiding occupied ones..
Radio over fiber system based on a hybrid link for next generation of optical...IJECEIAES
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In this article, we show that Pilot contamination problem can be seen as a source separation problem using time, frequency, and space domains. Our method capitalizes on a nonunitary joint diagonalization of spatial quadratic time-frequency (STFD) signal representation to identify the desired and interfering users. We first compute the noise subspace from the STFD matrices selected appropriately. Secondly, we use the noise subspace obtained to estimate the Elevation (El) and the Azimuth (Az) angles for which the MUSIC cost function is maximized. Numerical simulations are provided to illustrate the effectiveness and the behavior of the proposed approach.
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IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
MIMO channels: optimizing throughput and reducing outage by increasing multip...TELKOMNIKA JOURNAL
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Next generation in wireless communication systems being deployed in the world, 5G/6G
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Performance Analsis of Clipping Technique for Papr Reduction of MB-OFDM UWB S...ijcisjournal
Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) is used as efficacious procedure for
ultra-wideband (UWB) wireless communication applications, which divides the spectrum into various subbands,
whose bandwidth is approximately 500MHz. Major arduousness in multiband-OFDM is ,it have
very large peak to average power ratio value which causes the signal to enter into dynamic region that
consequence in the loss of orthogonal properties and results in the interference of the carrier signals which
crops the amplifier saturation and finally limits the capacity of the system. Many PAPR amortize
algorithms have reported in the survey and pre-coding is PAPR reduction which is inserted after
modulation in the OFDM system. The Existing work presents the reduction of that value by different
clipping techniques namely Classical-Clipping (CC), Heavy side-Clipping (HC), Deep-Clipping (DC) and
Smooth-Clipping (SC) and their comparison analysis is done. Every clipping method is best at its own
level .The proficiency of these strategies are evaluated in locutions of average power disparity, complete
system decadence and PAPR reduction. Finally results show the MB OFDM yields better performance to
reduce PAPR in effective way.
System Consideration, Design and Implementation of Point To Point Microwave L...ijtsrd
Microwave technology is extremely used for point to point communications because it is more easily focused into narrower beams than radio waves, allowing frequency use, it is available higher data transmission rates and antenna sizes are smaller than at lower frequencies. The main aim of this system is to provide internet access for rural area using ePMP Force 180 5GHz subscriber module. The two sites are 1.45 km away from each other. GPS is used to determine the latitude and longitude of two sites location. Google Earth Pro software is used to check for line of sight in choosing potential terminal site locations. In this system, system consideration, design and analysis of line of sight microwave link and hardware implementations are to be carried out. In the analysis, path profile, Fresnel zone, link budget and other parameters are implemented using the link planner software Lay Nandar Soe | Kyaw Thet Zaw | Wai Phyo Aung "System Consideration, Design and Implementation of Point-To-Point Microwave Link for Internet Access" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26769.pdf Paper URL: https://www.ijtsrd.com/engineering/electronics-and-communication-engineering/26769/system-consideration-design-and-implementation-of-point-to-point-microwave-link-for-internet-access/lay-nandar-soe
Performance Investigation of OFDM-FSO System under Diverse Weather Conditions...IJECEIAES
Free space optical (FSO) communication systems which are deployed for last mile access, being considered as a suitable alternative technology for optical fiber networks. It is one of the emerging technologies for broadband wireless connectivity which has also been receiving growing attention due to high data rate transmission capability with low installation cost and license free spectrum. However, the widespread use of FSO technology has been hampered by the randomly time varying characteristics of propagation path mainly due to atmospheric turbulence, sensitivity to diverse weather conditions and the nonlinear responsivity of laser diode. This paper presents the performance investigation of an OFDM-FSO system over atmospheric turbulence channels under diverse weather conditions of Bangladesh. The channel is modeled with gamma-gamma distribution using 16-QAM modulation format and 4×4 multiple transceiver FSO system. All possible challenges are imposed on the system performance such as atmospheric attenuation, turbulence, pointing error, geometric loss etc. The refractive index structure parameter and atmospheric attenuation coefficient for different weather conditions are calculated by using the data, collected from Bangladesh Meteorological Department. The acquired results can be fruitful for scheming, forecasting and assessing the OFDM-FSO system’s ability to transmit wireless services over turbulent FSO links under actual conditions of Bangladesh.
An important role performed by Zero Padding (ZP) in multi-band OFDM (MB-OFDM) System.
This role show for low-complexity in résistance against multipath interference by reducing
inter-carrier interference (ICI) and eliminating the inter-symbol interference (ISI) Also, zeropadded
suffix can be used to eliminate ripples in the power spectral density in order to conform
to FCC requirements.
At the receiver of MB-OFDM system needs to use of a technique called as overlap-and-add
(OLA). Which maintain the circular convolution property and take the multipath energy of the
channel.
In this paper, we proposed a method of performing overlap-and-add length for zero padded
suffixes. Then, we studied the effect of this method, dynamic optimization of overlap-and-add
(OLA) equalization, on the performance of MBOFDM system on Bit Error Rate (BER) with
AWGN channel and Saleh-Valenzuela (S-V) Multipath channel Model.
In the dynamic optimization OLA, the Length of ZP depends on length of channel impulse
response (CIR). These measures, based on SNR, insert the ZP according to the measurement.
Dynamic optimization of length of ZP improves the Performance of MBOFDM system. In fact
we developed a technique to select the length of ZP as function of SNR and CIR
estimate(repetition). In our simulation this technique improve to 3 dB at BER=10-2 with a
multipath channels CM4.
DYNAMIC OPTIMIZATION OF OVERLAPAND- ADD LENGTH OVER MBOFDM SYSTEM BASED ON SN...cscpconf
An important role performed by Zero Padding (ZP) in multi-band OFDM (MB-OFDM) System.
This role show for low-complexity in résistance against multipath interference by reducing
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suffix can be used to eliminate ripples in the power spectral density in order to conform
to FCC requirements.
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(OLA). Which maintain the circular convolution property and take the multipath energy of the
channel.
In this paper, we proposed a method of performing overlap-and-add length for zero padded
suffixes. Then, we studied the effect of this method, dynamic optimization of overlap-and-add
(OLA) equalization, on the performance of MBOFDM system on Bit Error Rate (BER) with
AWGN channel and Saleh-Valenzuela (S-V) Multipath channel Model.
In the dynamic optimization OLA, the Length of ZP depends on length of channel impulse
response (CIR). These measures, based on SNR, insert the ZP according to the measurement.
Dynamic optimization of length of ZP improves the Performance of MBOFDM system. In fact
we developed a technique to select the length of ZP as function of SNR and CIR
estimate(repetition). In our simulation this technique improve to 3 dB at BER=10-2 with a
multipath channels CM4.
This document discusses techniques to enhance channel capacity in OFDM systems. It begins with an introduction to OFDM and discusses its advantages such as reduced inter-symbol interference and high spectral efficiency. Then it discusses two main techniques for enhancing channel capacity: singular value decomposition (SVD) and water filling algorithms. SVD decomposes the channel matrix to decouple the spatial channels, allowing transmission power to be distributed optimally. Water filling algorithms such as iterative water filling further optimize power allocation to increase capacity. The document provides an overview of how these techniques can enhance the capacity of OFDM wireless communication systems.
Promoting fractional frequency reuse performance for combating pilot contami...IJECEIAES
Massive multiple-input multiple-output (MIMO) improves spectrum efficiency by increasing the capacity of the wireless structure. Therefore, massive MIMO is promising for fifth generation (5G) wireless communications. In massive MIMO, channel estimation is a crucial part that should achieve reliable performance. Pilots are sent from the end-users to be used for estimating the channel. However, the problem of interference in pilot contamination affects the performance for cell-edge users. Specifically, pilot contamination appears when the same pilot sequence is utilized at the same time by more than one terminal. This lead to an inaccurate estimation of the channel. Consequently, the decoded data will not be reliable. For mitigating these pilot contamination effects, an enhanced fractional frequency reuse (eFFR) scheme is proposed that uses an algorithm in the allocation of pilot sequences to end users’ devices based on the locations of the users from the target base station (BS). The simulation results exhibit that the proposed scenario outweighs the traditional FFR within both signal to interference, and noise ratio (SINR), and capacity. Consequently, the suggested scenario enhances the performance of more than 80% of the cell terminals and the other 20% of the terminals have a slightly lower performance compared to the FFR.
Optical space division multiplexing uses multiple cores or modes in optical fibers to increase transmission capacity. A history of the technology was provided, noting the progression from single mode fibers to coherent detection and polarization multiplexing. Limits with single mode fibers were discussed, along with ways that multi-core and multi-mode fibers can overcome capacity constraints through spatial multiplexing across fiber cores and modes. Recent demonstrations showed record capacities of 57.6 Tb/s over multi-mode fiber and 24 Tb/s over hollow-core fiber. Integration challenges with spatial division multiplexing were also outlined.
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MIMO Systems for Military Communication/Applications.
1. Suresh Kumar Jindal . Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 6, Issue 3, (Part - 4) March 2016, pp.22-33
www.ijera.com 22|P a g e
MIMO Systems for Military Communication/Applications.
Suresh Kumar Jindal
Research Scholar.
ABSTRACT
The Military is embracing the communication revolution, turning to a new generation of sophisticated systems
to enable faster, richer, less costly, more flexible, reliable, compact, mobile, jam resistant, low probability of
detection, re configurable and spectrally efficient communication. Many of these features can be added to a
great extent in the existing systems, by utilising MIMO technology appropriately and judiciously. MIMO finds
applications in wireless communication, NLOS communication, satellite communication, HF communication,
Optical Fibre Communication. MIMO makes these technologies more suitable by introducing features
mandatory for military communication such as Ant jamming capability, Low Probability of Intercept, low
visibility of satellite earth Antennas by reducing their aperture area. MIMO can also provide redundancy by
employing no extra resources, thereby increasing reliability. MIMO is highly effective to communicate with
Unmanned Aerial Vehicles (1).
Keywords:MIMO, Military, Satellite, HF, OFC, MBC , Channel Capacity, LPI , UAV, Aperture, Radar,
Resolution , Survivability
I. Introduction
In the following paragraphs it is explained how the
following features are introduced by using MIMO
techniques.
i. Low Probability of Detection
ii. Anti-jamming capability
iii. Reduced visibility of equipment
iv. Communication on Unmanned vehicles moving
with a speed of the order of 500-800 km/hr.
v. Redundancy of infrastructure to increase
reliability
Fortunately all these attribute/requirements
are met by MIMO system. Accordingly MIMO
systems find their way in Military communication
also. It has been demonstrated that ability to operate at
speeds greater than 300 km/hr and a 17 dB reduction
is the required Tx power for Covert, LPD
communication, in addition to an interference/jammer
mitigation technique based on MIMO Eigen beam-
nulling has been demonstrated. It can be appreciated
that for a UAV vehicle to communicate with ground
has to face a hostile environment which includes
Doppler shift due to moving plate form. The Doppler
shift UAV moving at 300 km/h, operating at 4 GHz
can be calculated as follows.
0Doppler shift =Df f
C
(1)
9
8
300 1000 4 10
4MHz
3 10
The Doppler frequency drift is of the order of
4 MHz which has to be compensated to recover the
information bearing data
To overcome such a high Doppler shift we
adopt the following two approaches: We limit the size
of a packet in between channel updates. The use of an
advanced frequency-time pilot symbol insertion
strategy to improve immunity of high Doppler
communication.
1.2 Performance Vs Speed
The simulation results suggest for a 100 byte
payload and a target PER (Packet error rate) of 10% a
QPSK system suffers only a fraction of dB over two
orders of magnitude variation in speed (from 5mph to
500 mph). Whereas 16 QAM is viable at speeds of up
to 100 mph, and 64 QAM requires 42dB SNR at a
speed of 100 mph. the RF impairments and practical
synchronization algorithm introduces an approximate
loss of 4dB, 5dB, and 12 dB at 10% PER and 100
mph, for QPSK, 16 QAM, 64 QAM, respectively. It is
also clear that high constellation such as 64 QAM is
desired at high speed, the receiver needs to be
modified to combat the time varying fading which
will cause the effective channel to be different
between the start and end of the packet. The results at
a target PER of 1% are significantly different, only
QPSK can perform reasonable performance at speed
up to 100 mph.
1.3 MIMO for LDP and AJ
The use of multi antenna techniques in covert
or jam resistant communication is quite
complementary to traditional spread spectrum
techniques employing either direct sequence or
RESEARCH ARTICLE OPEN ACCESS
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frequency hopping. If covertness is needed (LDP),
then MIMO techniques can help minimize the
radiated energy via two or more distinct mechanisms.
The first one is a direct consequence the benefits of
spatial multiplexing, while the second is Eigen- beam
forming and is superset of traditional beam forming
techniques. In the case of AJ, multi antenna
techniques can be used as Eigen-beam mulling
subsystems or in the Eigen-spreading mode. The
Eigen-spreading mode has the unique advantage of
proving spatial averaging of jammer energy,
analogous to frequency averaging in FHSS system.
1.4 MIMO for LPD
MIMO spatial multiplexing systems can
provide LPD gain by simply trading off spatial
(MIMO) gains for transmit power. Our first approach
to gaining insight into the LPD properties of MIMO
systems was to estimate the SNR required to achieve
a capacity of 1 bit per second per Hertz. The study
generated five hundred Rayleigh flat fading matrix
channels and for each one the capacity equation given
below can be evaluated for the required SNR The
SNR when computed by setting the capacity (the left
hand side of the equation) to 1 and solving for .
2log det * / /nC E I H H bits s Hz
n
(2)
In the above equation C is the capacity, Inis
the nxnidentity matrix, H is the Rayleigh channel
matrix, n is the number of transmit antennas, and is
the average signal to noise ratio at each receive
branch. The table below shows that at 5% outage, a
gain of 22.1 dB is to be had if the number of receiver
and transmit antennas is increased from 1 to 8.
Another interpretation of the result is that if we want
to guarantee that 1bps/Hz can be supported in 95% of
all Rayliegh matrix channels encountered, then a lxl
system needs an average SNR of 12.8dB at the
receiver, whereas an 8x8 system requires an average
received SNR of minus 9.3 dB..
Table 1.Required SNR to achieve a 95% capacity
of 1 bps/Hz in Rayliegh channels.
MIMO Configuration Required SNR to achieve 1
bps/Hz of Capacity at 95%
lxl 12.8 dB
2x2 1.2 dB
4x4 -4.9 dB
8x8 -9.3 dB
1.5 Enhancing Connectivity of Unmanned
Vehicles through MIMO Communication (2)
The use of autonomous/unmanned vehicles
for various civilian and military applications has
become increasingly prevalent the absence of human
pilots on board those unmanned systems, however,
make it a challenging task to accomplish various
intended missions. For example, these unmanned
systems are often remotely piloted and thus having a
reliable and robust communication link between the
aerial systems and the ground control unit is
imperative. Even for systems that are semi-
autonomous, having a high throughput
communication link is often essential to
accomplishing any intended mission. Many remotely
piloted aircrafts (RPAs) are used for surveillance
applications and the need to stream surveillance data,
including real time video data requires a highly
reliable and high-throughput communication link
from the RPAs to ground units (3).
Many legacy communication links (e.g.,
Link 16 with a data rate not more than (16kb/s)
operate at a data rate that becomes highly inadequate
for applications where video streaming from aerial
systems to ground is needed. Merely scaling up the
power/band width is both limited by resource and
policy constraints as we1l as the fundamental
theoretical limits dictated by the Shannon theory. A
promising technology is the use of multiple antenna
communication systems (4)-(5). The soca1led
multiple-input multiple-output (MIMO)
communication scales up data rate linearly as the
number of antennas increase and thus provides great
potential for improving the throughput of air to
ground communication. This helps envisioned
applications that may otherwise be infeasible.
MIMO communications, however, are
traditionally designed for the so-called scattering
environment (6) where independent channel
variations between different transmit/receive antenna
pairs are exploited. For airborne platforms, however,
there has been a debate about the feasibility of MIMO
communications because of the lack of scattering.
However, for certain communication ranges, the large
aperture that an aircraft affords makes MIMO an
appealing choice of communication that can attain
significantly higher throughput given a fixed
power/bandwidth budget compared with single
antenna systems even in the absence of any stutterers
(7).Here we describes an ongoing research and
development effort that uses MIMO communications
to enable robust and high capacity connectivity
between RPAs and ground terminals. While the large
aperture may compensate for the lack of the
scattering, two unique challenges still exist for
airborne MIMO communications. The large aperture
is only attained when antennas are placed strategically
apart on a RPA. In the absence of scattering, i.e.,
when communications are limited by line-of-sight
channels, the fact that some antenna elements on a
RPA may be completely out of sight from its
communicating party may render the channel matrix
ill-conditioned. This is further complicated by the
high mobility and manoeuvrability of the RPA which
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make it infeasible to have complete channel state
information (CSI) at the transmitter. To address these
challenges, it is proposed a variable rate MIMO
communication scheme that combines the DBLAST
architecture with per antenna spreading to harvest the
maximum possible throughput gain allowed by the
channel.
1.6 MIMO System with Displaced Ground
Antennas for Board Band Military SATCOM
A powerful and reliable communications
infrastructure plays a fundamental role in today's
military foreign, operations for the provisioning of
real-time information to all stake-holders (see figure
1.for illustration) Modern reconnaissance systems
like unmanned aerial vehicle (UAVs), which are
fundamental for low-risk(8) .
Figure 1.Military SATCOM scenarios.
Operations with respect to human lives
produce an enormous amount of data. The immediate
and permanent transmission of those broadband video
and sensor data is essential to provide each combatant
with a complete picture of the current situation. The
entire raw data volume is usually gathered at a
centralized location in usually the forward operation
base where the sensor and video data is pre-evaluated,
filtered and aggregated. The transmission to the home
land is then performed via satellite. Geostationary
satellite communication (SATCOM) systems for
fixed-satellite services (FSS) are the backbone of
military wide area transmission networks, enabling
long-distance communication to almost any place or
trouble spot in the world. Moreover, in the absence of
any terrestrial communications infrastructure on site,
geostationary (GEO) satellites provide highly
available and wide range network coverage.
Unfortunately, like the frequency spectrum, accessible
orbit positions are a physically limited resource,
which has led to exploding prices for SATCOM
channels especially in regions that are in the global
limelight. Additionally, the variety of military
information and communication systems in today's
multinational operations produces an enormous and
further growing amount of data to be transmitted.
Therefore, bandwidth efficient transmission has
become a key performance indicator for customers
and providers of satellite capacity and is, therefore, in
the focus(28).
Due to the 'higher bandwidth efficiency
compared to commonly used single-input single-
output (SISO) systems, multiple-input multiple-output
(MIMO) systems are appropriate to serve future data
rate and bandwidth requirements in military
SATCOM. The application of the multi-antenna
technology leads to two basic system configurations
(10): Firstly, the single-satellite scenario foresees
multiple antennas on board one satellite. Secondly,
the multiple-satellite scenario assumes one antenna
element per satellite, i.e. two or multiple satellites act
together as a single MIMO relay. Here we investigate
the less complex single-satellite scenario with two
antennas. The system involves also two ground
antennas at the transmitter (Tx) and receiver (Rx)
terminals, respectively, Hence, a 2x2 MIMO system is
considered.
Moreover, we assume that the system
provides maximum' channel capacity. To obtain a
MIMO satellite channel with maximum multiplexing
gain, distinct positions of the MIMO antenna elements
are required. In this respect the inter-antenna distances
at the satellite and the ground terminals are key
parameters. In fact, in order to take full advantage of
the MIMO capacity gain, large antenna separations
either at the satellite or the ground terminals are
necessary (10). As we investigate a single-satellite
scenario, the inter antenna distance on board the
satellite is naturally limited to a few meters by the
satellite dimension. Thus, the inter antenna distances
of the ground terminals have to be in the order of
several tens of kilometres for maximum channel
capacity.
Fortunately, the requirement of large antenna
separations is well in line with military system
architectures because the dislocation of strategically
important objects is anyway fundamental. In order to
prevent a loss of the complete infrastructure in case of
an attack, generally a high degree of redundancy at
geographically separated sites is considered. But also
civilian SATCOM applications utilize separated
ground terminals. Satellite ranging measurements for
example demand large separations of the
measurement antennas for high accuracy. Therefore,
the proposed MIMO SATCOM systems for FSS just
takes advantage of the existing standard
infrastructure, adding the feature of increased
bandwidth efficiency.
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1.7 Reducing VAST Aperture for Satellite MIMO
For military communication while using
satellite communication it is V. likely that the VSAT
Antenna can be detected from the flying enemy
Aircraft or by spying satellite itself. Once the VAST
antenna is spotted it is likely to be destroyed. To
reduce the chances the detection of the VAST
antennas one of the potent approach is to reduce its
diameter. So to reduce the probability of its detection
and communication be achieved as required. To
achieve this, MIMO technology is found to be use full
to reduce the diameter / aperture of satellite Antenna
(11).
Figure 2.shows a conventional duplex
communication system using single satellite
transponder with independent forward and return
links. Typically, the hub- transmits informationto the
remotes using a wideband carrier via time division
multiple access (TDMA). The return link (from the
remote very small aperture terminals - VSATs- to the
hub)is typically single channel per carrier (SCPC,
otherwise termed frequency division multiplexing).
The SCPC and TDMA bands may not overlap
(conventional system) or overlap (interference
cancellation system, IC (13). A hub's antenna aperture
(and gain) is usually much greater than the VSAT‟s.
We demonstrate that VSAT antenna aperture can
further be reduced by using satellite diversity(SD),
space time codes (STC) or polarization diversity (PD)
.
Figure 2. Single antenna SCPC/TDMA system
with IC (Interference cancellation)
A VSAT‟s antenna gain, calculated as
4Ae/has half-power beam-width (in radians) of
/ eA , where Aeand , are effective antenna
apertureand wavelength respectively (4). Parabolic
reflector antennas with actual diameter of 36 have a
half-power beam-width slightly less than the typical
satellite spacing of 3°. When an earth-station's
antenna diameter is reduced by a factor of k, its gain is
reduced by nearly k2
. For a one satellite system, the
antenna points to a satellite, whereas for a dual
satellite system, the antenna points, as in Figure 3, to
the mid-point between two satellites.
Figure 3.Pointing for q two-satellite receiver.
Let each path's power be scaled by a
(pointing) loss factor corresponding to half the
satellite spacing, denoted by m0.5s(k). For unchanged
satellite transmit power for the land 2-satellite cases,
the total received signal power will be identical when
0.52 ( )sk m k (iterative solution is necessary as the
RHS is a function of k, but, practically, k is just >2-
0.5
). Adjacent satellite interference (AS1- worst for co-
polarized adjacent transponders) is a pointing factor
of msand m1.5s(k) for the 1- and 2-satellite cases
respectively. Main-lobe roll-off for antennas of
interest are even ,convex usually nearly cosn
(pp. 36 of (20)), being angular offset, or [1-2
/2]n
for
small , and n is divided by the first null beam-
width; k is the solution of:
2
2(1 0.125 )kn
k s
(3) The ASI ratio, , of
the single satellite system to the 2-satellite system
(with aperture reduced by k2
) is:
2
2
1 0.5
(1 0.125 )kn
s
s
(4)
is greater than 1 when:
2
2
log(1 0.5 )
log(1 0.125 )kn
s
k
s
(5)
For s=3°, >1 when k>0.4441. A dual-satellite VSAT
with the same uplink gain as a single-satellite VSAT
has 1>k>2-0·5
with reduced ASI that depends only on k
(and not modulation). In contrast, spread-spectrum
methods (DSS) reduce ASI power spectral density
(PSD) according to the bandwidth expansion factor.
Alternatively, a reduced-aperture VSAT's
(e.g. maritime or man-pack VSAT) transmit power
can be increased by a factor, r(<),less a small
performance loss (shown in following and subsequent
sections), yet maintaining lower ASI. Any gain-ASI
combination in between may be chosen, possibly
allowing bandwidth-efficient (high-order) modulation
to be used in the VSAT uplink (14).
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Benefits of reducing aperture (using SD and STC or
PD) are:
• Lower susceptibility to pointing errors and smaller
antenna aperture reduce demands on:
• SATCOM-on-the-move sensor resolution
and servo motor power (in adverse winds)
• Man-pack weight and terminal alignment
time
• Smaller ASI allows increased terminal transmit
power, allowing higher order modulations to be used
• Reduced antenna cost (for a phased-array by as
much as a 4 factor for a 2-satellite system case)
Leasing two transponders, each at the same
downlink power as just one, is offset by economy of
larger scale production of smaller VSATs, or where
small size has high intrinsic value (i.e.,
transportability and weight as in, man-packs).
The following section describes a scheme to
reduce VSAT antenna aperture for a point-to-point
system (the forward and return channels have the
same differential delay and Doppler) using 2
satellites. In this case, the differential delay and
Doppler are estimated via the return channel‟s
diversity combiner (DC, which weights and sums the
inputs of the IC‟s subtraction) (7). A rate 1 2xl STC
encoding is applied after one channel is delayed and
frequency shifted at the hub transmitter (differential
delay and Doppler being estimated by the hub‟s
receiver) so that the received signals are time- and
frequency- aligned at the VSAT. Thus, challenging
frequency offset and delay acquisition in STC
receivers, is circumvented. The STC output is
transmitted to the satellites via two large aperture hub
antennas (Figure 4) and received by a smaller VSAT
antenna pointed as in Figure 5.
Figure 4. Point-to-point satellite link using 2x1
STC
Reducing remote antenna aperture for a
point-to-multipoint system using 2 satellites, each
transmitter configured for one (but not both)
polarization at a time, is described in the subsequent
section. Polarization diversity (PD) allows two
channels' to be received from a single reduced
aperture antenna. When the two diversity channels are
repeated for transmission via two satellites. (Figure
4.), differential delay and Doppler are estimated via
IC at the remote station, is applied at the DC receiver.
When weather causes poor polarization isolation, the
receiver uses two more ICs. This DC method, which
acquires frequency and delay, does not require symbol
timing recovery; i.e., a post-DC off-the-shelf
demodulator may be used. The subsequent section's
method also extends to multiple (>2) satellites
(alternate satellites with same downlink polarizations)
to obtain increased system gain and reduced ASI,
VSAT power and aperture (but multiplying
transponder lease costs).
Figure 5. SD for point-to-multipoint topologies
II. Mimo In Hf Data Links
High frequency (HF) radians (3-30 MHz
range) provide tactical communications with the
ability to communicate over long distances and
around large obstacles without supporting
infrastructure of any type (satellite links, wired links,
Towers etc.). The limitation with HF Band
commutation is that the spectrum is V. limited and
link quality in poor and varies a lot, form day to night,
form summer season to winter season to rainy season
and so on (15).
The HF Communication has the following
main limitations which if overcome by using some
innovative technology, it will be extremely useful for
military application.
a) HF Communication quality varies as the ionosphere
characteristics vary diurnally, seasonally, and yearly.
The communication during sunrise and sunset is
always subjected to great fluctuations in levels, due to
changes in ionosphere.
b) A reliable HF Communication depends on the correct
choice of frequencies and proper choice of Antenna.
A minimum of three frequencies and proper antennas
are required for satisfactory communication. A
minimum of three frequencies are required for round
the clock operation. We can depend on the
ionospheric information provided by the committee of
council of Scientific and Industrial Research, as
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published by National physical Laboratory New Delhi
the working frequencies for the link can be computed.
c) The reliability of an HF Communication depends
on the working frequency and the takeoff angle of
beam.
d) The optimum working frequency in normally
85% of the maximum usable frequency.
Further HF data rates are currently too low to
support reliable video or other date-intensive
communication because of low Bandwidth allocations
and challenging propagation conditions. Recent
efforts have resulted in new waveform designed for
wider bandwidths and higher data raters, the highest
rates are only achievable in the most favorable
conditions. These conditions will not be consistently
observed due to the variability of the HF channel.
Further, extending HF rates through bandwidth
expansion is increasing difficult given the scarcity of
acquirable HF spectrum and the challenges of
changing international spectrum policy.
One approach to significantly increase data rates
without expanding the spectral footprint is to utilize
antennas, RF chains, and smart signal processing to
communicate multiple streams of data in parallel. This
techniques, known as Multiple-input Multiple-output
(MIMO), has been successfully deployed in
commercial wireless networks to provide
multiplicative gains in data rates, robustness to
interference, increased data link reliability, and
reduced transmit power.
It has been demonstrated that the MIMO is
feasible in a small-array configuration for near-
vertical incidence sky wave (NVIS) links. NVIS
communication also removes the limitation of HF
communication not in a position to effectively
communication for the short range of 50 Kms to 250
Kms and normally, the planning of fixed- to fixed
services is not done for such distances. Whereas
NVIS removes this limitation of HF communication
and gets additional technology rich fetuses form
MIMO usage.
It has been demonstrated that 2.27 times
large data rates, 9 times less transmit power, and
greater than 3 times fewer rink failure in 2x2 MIMO
HF NVIS channels with cross polarization antennas
by exploring both diversity and spatial multiplexing.
It also provided critical channel metrics, including
spatial correlation matrices, to enable base-band
designs to benchmark performance and design MIMO
HF protocols.
2.1MIMO Wave Form Design For Military
Applications for HF
We assume MIL-STD-188-110-C-
Appendix-D as the base line HF base line digital HF
waveform operations on a single carrier with variable
constellation configuration (including BPSK, QPSK,
8-PSK, 16-QAM, 32-QAM 64-QAM, 256 QAM, and
a 32-length 8-PSK Walch sequence) The constellation
symbols are transmitted at a variable rate between 2.4
kbp19.2 Kbps.( always an integer multiple of 2.4
Kbps) and filleted with a root raised Cosine fitter with
a 35% excess bandwidth factor. This leads to
spectrum occupation between 3-24 KHZ. Forward
error correction is accomplished through binary
convolution coding with two generators (with either 7
or 9 constraint length) producing a base rate ½ code.
Puncturing enables rates of 2/3, ¾, 5/6, 8/9, 9/10, &
9/16. Cascaded repetition coding enables rates of 1/3,
¼, 1/6, 1/8, 1/12, 1/16, 2/5 & 2/7. The modulation &
coding together provide data rates from 75 bps (in
3KHz spectrum with 32- symbol 80 PSK Walch
sequence) to 120 Kbps (in 24 HZ spectrum with 256-
QAM & rate 5/6 coding).
The properties of the proposed MIMO
wideband HF wave form, which shows a balance
between backward compatibility with legacy base line
waveform implementation and new features that
exploit MIMO to improve performance at all SNR.
The most noticeable new feature is the ability to
provide spatial multiplexing through the inclusion of
two simultaneous data symbol streams. A convention
of commercial standards is followed here, when
spatial multiplexing is enabled, each stream selects
the same constellation and the same coding
rate(16),(17).
The proposed wave form also support
diversity mode of transmission. Diversity made will
be available through delay diversity made and space-
time-block coding (format similar to Alamouti.)
Delay diversity delays the output of the second
transmit antenna by a fixed duration. At the receiver
this essentially looks like multipath, converting spatial
channel paths into temporal channel paths, which can
already be captured in legacy systems. For non-legacy
operation, space- time block coding is preferred.
Space time block coding intelligently address
redundancy across transmit antennas in a way such
that the receiver can capture full channel diversity
without knowledge of the cannel at the transmitter.
Digital beam forming and closed-loop precoding
diversity algorithm has been avoided since the
variability of the HF NVIS, channel suggests that
current work functionally operates on too large of a
time scale to make precoding (beam forming) reliable.
This may be revisited with justification of channel
stability.
It has been seen that MIMO offers HF Links
increased spectral efficiency, reduced transmit power,
interference/ jamming robustness and extended
reliability. Which are vital requirements for any
militancy communication links (13).
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2.2 HF Communication applying polarization
diversity Multiple- Input Multiple- Output
(MIMO) Can also be used as Military HF
Communication.
Beyond line of sight (BLOS)
Communications are predominately accomplished by
satellite owing to V. high data rate offered by satellite
system, due to the fact that spectrum available for
satellite is of the order of few hundreds of MHz In
spite of the fact that satellite communication is V.
Capable, but it is also expensive and can be
vulnerable to degradation and disruption. In order to
maintain connectivity in challenging or denied
environments, investigating the usefulness of HF
Communication by increasing its capacity, robustness,
and reliability is worth.
HF communication has generally been
constrained by limited to narrow bandwidths.
Traditional HF challenges also include channel fading
and the need for large Antennas. There has been a
number of efforts focused on increasing HF link
capacity that include large BW, high constellation
QAM signals (12-24 KHz), OFDM signaling with up
to 256-QAM and advanced error coding, multicarrier
1x2 MIMO with time, frequency and polarization
diversity and OFDM signaling & 2x2 HF MIMO with
polarization diversity.
This has achieved spectral efficiency ranging
from 1 to 4 b/s/Hz under favorable conditions and
high bower. A new waveform has been developed for
2-antenna MIMO through the use of spatial
multiplexing. Link Simulations on a 48-KHz Channel
that use channel measurements form an NVIS
Collection campaign show a doubling of data rate
and improvement in bit prorate (BER) by up to 15 dB
in comparison to single antenna. It has been
demonstrated a wideband HF one way communication
using a short hop (< 75 km) sky wave link. The new
techniques and technology to wideband HF (WBHF)
communication (up to 96 KHz). The development of
WBHF waveforms that are not contained to the MIL-
STD-188/110-C Appendix D family of wideband
waveform standards. The polarization diversity
MIMO technique coupled with advanced waveform
coding for interference rejections. We leverage
improved understanding and adaptation of HF channel
phenomenology to emphasize low power operations
with increased Bandwidths, Capacity, and reliability.
2.3 HF Communication Transmitter Proposed
diagram
High level block Diagram & Transmission of
higher data rate, polarization diversity HF
Communication Transmission waveform.
The goal of our HF Communication design is to
communicate reliably with acceptable bit error rate of
the order of 10 in one million bits, or so, with spectral
efficacy as high as of 1 to 4 bits/ S/ Hz. To achieve
this polarization diversity can be exploited, so that
data stream is split in to two parallel data streams of
half the bit rate of original stream and each stream
transmitted on two independent antennas after
required FEC and other baseband processing. These
modes of transmission an called X-and O-propagation
modes of the ionospheres uncorrelated waveforms
that carry independent information.
This approach approximately provides a
throughput of 2 times, using the same band width, of
curse at the cost of hard complexity and processing
power of the processor used. The also improves
robustness to multipath and channel fading.
In order that MIMO spatial multiplexing can
be used it is necessary to add coding to the different
channels so that the receiver can detect the correct
data.
In fig 6, we drew a high level Block diagram
of high data rate, polarization diversity HF
Communication Transmissions/ waveform. Here the
two independent data streams after processing at
Baseband level, modulation are transmitted parallely
on two separate polarized channels. At baseband level
the data stream is FEC coded using Reed- Solomon
and Convolutional forward error correction (EEC) to
improve the immunity against noise, thereby
improving BER performance in presence of both
burst like and multipath fading that typically occurs at
HF Communication media.
The coded data streams are then mapped to
baseband signal constellation for low data rate
(OFDM), medium data rate (BPSK), or high data rate
(QAM) communications. The resulting data packets
are assembled in to frames and orthogonal preamble
waveforms are added to the beginning of each frame
to distinguish the two polarization channel. The two
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baseband signal frames are then up converted in to a
dual channel and simultaneously transmitted using
orthogonal circler polarization, the left circular for
channel one and right circular for channel two.
2.4 Fig below 6shows the block diagram of the
signal processing employed in the receiver.
The baseband processing begins by reliably
detecting the preamble or synch waveforms for each
channel. This is accomplished using two dimensional
complex ambiguity function (CAF) processing to
estimate the delay, Doppler, and phase to the channels
as a function of time. This process is carried out for
every received data frame so that the current channel
conditions can be estimated and tracked over time.
The synch detections provide for accurate data packet
alignment and phase compensation form which an N-
point FFT follows to demodulate the received signal
constellation. Note that the OFDM single tones are
cleanly apparent in this example, the tone positions
and/ or phases define the data symbols that were
transmitted. A technique has also been developed for
detecting and nulling strong narrowband
interferences. This nulling process is followed by
spectrum spreading which produces a clean signal
constellation for subsequent processing. The next step
involves FEC decoding which attempts to correct for
any bit error that may have occurred during received
single demodulation and bit recovery process. In the
end the bit de-interlever, re-arranges the bits in the
original form and data is ready to be used.
2.5 HF MIMO:-
Ionosphere multipath propagation and
polarization diversity are explained to achieve an
increased data Transfer speed and a decrease of
necessary signal-to-noise ratio though HF Multiple
input Multiple out but (MIMO) technology. The
benefits of MIMO are discussed in (18) with
simulation of MIMO on HF propagation paths and
measurements at 12.5 MHz using narrow spaced
Antennas. MIMO measurements over an 1800 km
path between the Canary island and Spain (110) show
that the MIMO gain that the can be achieved. High
correlation factors ware measured however, even with
large Antenna spacing, HF MIMO experiments in the
United kingdom using near vertical incidence Sky
wave propagation (NVIS) on 5.2 MHz are described
in (19). Several antennas Configurations are
compared by measurement and the mean correlation
coefficient between 0.5-0.73 are established. Cross
dipoles are found to show less correlation than
vertical Antennas. The importance of the ordinary and
extraordinary wave mode for HF MIMO is explained
but no experiments are performed with circularly
polarized Antennas. (20) contains a feasibility study
of an HF MIMO system and investigates also the role
of the ordinary and the extraordinary wave, assuming
matched polarization. However, the study contains is
based on simulations & is not validated result.
III. Mimo Communicatin Over Multi Mode
Optical Fiber For Defence
Applicatiaons.
Multimode fiber (MMF) links are widely
implemented in current high speed local area
networks. They can provide the necessary bandwidth
for single mode fiber (SMF) solution, mainly due to
the ease of optical alignment and packaging. In
practical terms, the larger core size amplifies
connections and also allows the use of lower- cost
electronics as light-emitting diodes (LEDs) which
operate at the 850 nm and 1300 nm wavelength. MMF
can support DWDM or CWDM which makes links
less vulnerable to vibration and temperature
fluctuations as the source causing wavelength shifts.
New generations of lases- matched MMF has been
developed for high date rates over longer reaches
OM4, for example will support the following (21)
- 400 meters at 2Gbps
- 200 meters at 8Gbps
- 130 meters at 16Gbps.
The data rate capability of MMF is
augmented by using MIMO techniques. The required
transmitter/receiver diversity for MIMO operation is
realized by each transmitter launching light in to
MMF which is slightly different modal power
distribution, and furthermore, each receiver gats
power form all the transmitters via a different
distribution of modes too, as described schematically,
in figure below(112):
Fig 7. Multimode fibre with MIMO input/output
and intermodal coupling
The key feature of optical MIMO is that it
makes use of the modal dispersion MMF, rather than
avoids it. In Stuart‟s approach, RF sub carrier (app.1
GHz) with PSK data formant was used for
transmission modulation, followed by optical intensity
detection and RF Coherent modulation. The use of RF
subcarrier in intensity modulation and detection
requires a V. long MMF, and places a minimum of
subcarrier frequency in order to ensure enough model
diversity, which is requirement for MIMO operation.
In contrast, if coherent optical transmission is used the
required length is reduced by the ratio of the RF
subcarrier frequency to the optical carrier frequency.
This eliminates the requirement, marking MMF
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channels more amenable for MIMO operation.
Accordingly COMIMO has great potential in
unblocking the inherent capacity of MMF and the
coherent implementation is essential to ensure the
necessary diversity for physically large fiber length. It
also provides security benefit to the physical layer of
link (22).
To sum up the bandwidth limitation of MMF
as compared to SMF can be overcome by using
MIMO techniques; The MMF finds special
applications in military as follows:
1. Ease of optical alignment, when new connectors
are to be made in the field, it is less sensitive to
misalignment.
2. Low cost LEDs can be used as a light source
which operates at wavelengths of 850 and 1300
nm; as the diameter /aperture of MMF is much
more compared to SMF.
3. Since MMF can support DWDM (Dense Wave
Division Multiplexing). DWDM which makes
links vulnerable to vibrations and temperature
fluctuations which is a specific requirement of
military applications of fiber.
4. MMF provides security benefits to the physical
layer of link.
IV. Military Use Of Meteor Bust
Communications Using MIMO
Techniques.
Meteor bust communication faded interest
with the increasing use of satellite communication,
which started in let 1960s. In the late 1970s it became
clear that the satellite were not universally useful an
original thought, notably at high altitude or where
signal security was an issue. For these reasons,
The U.S. Air Force installed the Alaska air command
MBC System in 1970s.
MBC communication capacity is small and
with a bad Real-time performance. We want to
analyse the results by using MIMO techniques. As we
know MIMO uses multipath effects as a favourable
factor, to resist the influence of meteor Bust
communication channel decline and improve the
communication quality and improve the system
performance. The Space-time coding technology is
used to realize multi-antenna technology performance.
As a strategic communication system, MBC system
can work steadily over long distance under sever
conditions such as nuclear explosion, earthquake etc.
In military applications it is developed for the
minimum essential emergency communication
network. In addition is it can be useful in a number of
civilian applications essentially remote sensing where
it can provide inexpensive communication techniques
for hydrometeological date collection, polar
exploration. Natural disaster warning etc. (23).
Diagram meter Brest Communication
Fig 8. 2*2 MIMO Meteor Burst Communication
Diagram (Source: Experimental Equipment for
Communication Utilizing Meteor Bursts, by
Robert J. Carpenter &Gerard R.
Ochs.NationalBureo of Standards, Washington 25
D C)
5. MIMO Radar systems for military communication
It is a system of multi Antennas. Each
waveforms antenna can receive these signals. Due to
the different waveforms, the echo signals can be re-
assigned to the single transmitter. From an antenna
field of N transmitter and a field of K receivers
mathematically results in a virtual field of K.N.
elements within enlarged in a virtual aperture. MIMO
radar system can be used to improve the spatial
resolution, and they provide a substantially improved
immunity to interference. By improving the S/N ratio,
the probability of detection of the targets is also
increased.
The MIMO radar systems can be closeted in to two
categories
1. MIMO radar with collocated antennas (so called
„Monostatic‟ MIMO). The target is a point target as in
traditional radar systems.
MIMO radar with widely separated antennas (so
called „distributed‟ or „Bi-static‟ MIMO).
Fig.9. Generation of the virtual array for an
ARTINO-configuration (the array axes of the Tx
and Rx arrays may be parallel displaced leading to
the same virtual array)
(Source: System Architecture & algorithms for Radar
Imaging By: Joachim H.G. Eder. FGAN-FHR,
NeuenehrerStr 20, D-53343, Wachberg, Germany.)
‘Monostatic’ MIMO: - In the collocated radar case
the transmitting antennas are close enough such that
the radar cross section {Rcs} observed by the
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transmitting antenna elements are identical. This
system in similar to a thinned array of phased array
antenna in which each radiator has its own transceiver
module and its own A/D converter. However in a
phased array antenna, each radiator only transmits
(passively time-shifted) a copy to a transmission
signal, which has been generated in a central
waveform generator. In a MIMO reader system each
radiator has its own arbitrary waveform generator and
subsequently each radiator uses an individual
waveform. This individual waveform is also the basis
for an assignment of the echo signal to their source. It
can be seen that MIMO and phased array, the passed
array antenna is often described SIMO (Single input
Multioutput).
Bi- Static MIMO: - In this arrangement of the
antennas, the radar processing is much more complex.
In contrast to “MONO Static” MIMO, each radar
antenna looks at the target from a different angle.
Therefore the target provides a different radar cross
section of each radar Antenna. This requires much
more complex target models for radar data processing.
Like MIMO Communications, MIMO Radar offers a
new paradigm for signal processing research. MIMO
radar processes significant potentials for fading
mitigation, resolution enhancement, and interference
& jamming suppression.
Fully exploiting these potentials can result in
significant improved target detection, parameter
estimation, target tracking and recognition
performance. The MIMO Radar Technology has
rapidly drawn considerable attention from many
researchers. Several advantages of MIMO Radar have
been discovered by different researchers such as
increased diversity of the target in formation,
excellent interference rejection capability improved
parameter identifiability, and enhanced flexibility for
transmit beam pattern design. The degree of freedom
introduced by MIMO Radar improves the
performance of the radar systems in many different
aspects. However it also generates some issues. It
increases the number of dimensions of the received
signal. Consequently, this increased the complexity of
the receiver.
V. Applications Of MIMO –DSSS Based
System
Spread Spectrum originated as a mean of
secure communication in the military providing of
single in the frequency domain to give a low peak
power. To observers spread single looks similar to
white noise, and hence has a low probability of
intercept. Recently IEEE 802.11 task Gp. was
organised with the goal to increasing the application
throughput to as least 100 Mbps by making
modification in PHY and MAC layer. This major
variety in the PHY layer is the use of MIMO with
orthogonal frequency division multiplexing (OFDM)
system to support several parallel streams which is
likewise known as multicarrier based techniques. It
can mitigate ISI by addition of cyclic prefix as one of
the option in OFDM. It can also Improve capacity in
the wireless system with spectral efficiency in the
wireless system with spectacle efficiency (bps/Hz)
and assess specimen complicity in wireless broad
band systems.
Fig. 10. System model of MIMO-OFDM-DSSS
System
We can use MIMO technique for sustaining
high data rate transmission. Digital communication
using MIMO Processing comes forth as a break
thought for revolutionary wireless systems. It solves
two of the hardest problems facing the wireless
technology today. Speed andrange. MIMO systems
Promise to increase date rates. Reliability and
performance with acceptable BER without increasing
the transmit power and without consuming the extra
radio spectrum.But MIMO cannot achieve zero ISI
and hence easily be overlaid on a OFDM based
system. The MIMO signalling treats each sub-carrier
in OFDM as an independent narrowband channel. It
can be viewed as an N parallel systems operating with
flat fading channel Co-efficient. But MIMO suffers
from Co-channel interference problems. It is the
interference between uses in different cells using
same frequency (Known as frequency Reuse),
results in CCI. Solation to that is to apply DSSS
technique based on spread spectrum technology. The
main advantage of Appling DSSS is that it reduce
power signal that may mitigate CCI problem in
MIMO-OFDM based system.
VI. Conclusion
It has been seen that the basic advantages of
MIMO systems are blessed with the advantages of
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spatial multiplexing gain which increases the channel
capacity by delivering more number of bits compared
to SISO systems. Similarly it provides diversity gain
which can provide rugged, reliable and increases the
availability. MIMO also provides array gain which
increases SNR of a system which can be translated
into deducesBER,thereby improving the signal
quality. MIMO by way of beam forming provides
reduces inter system interference. All these
advantages are required by military
communication/systems. MIMO is specifically useful
for military wireless communication, satellite
communication, HF communication, OFC (Optical
Fibre Communication), Radar systems provide
improved resolution when MIMO is used. It is useful
in many other military communication features of
LPI,LPD,UAVs,to provide low visibility of satellite
antennas by reducing their aperture etc.
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