This document summarizes an experiment analyzing the adaptivity of modulation mode and error correction coding rate in 802.11g wireless networks based on channel conditions. The experiment measured signal strength and throughput at different locations in an indoor environment. Simulation results modeling different modulation modes and coding rates under varying noise levels were also presented and compared to experimental measurements. The analysis found that more robust modulation/coding combinations were selected in noisier channel conditions to maintain reliability and throughput. Adding an additional access point was recommended to further improve quality of service for users.
The Mobile WiMAX simulation model is
implemented by using MATLAB code. The simulation model
consists of different phases which will help us to model the
transmitter and receiver section. In the next phase, the data is
being modulated by using the modulation methods QPSK and
QAM followed by OFDM transmitter. These phases can be
used to show the performance of these modulation methods
under varying condition. The Multipath Rician fading model is
implemented to introduce the fading in the transmitter data.
Receiver section is used to receive data from channel will be fed
into the OFDM demodulation. In the next phase, Fast Fourier
Transform is used to disassemble OFDM frame. After that
convolution encoding is applied to data and interleaving is
carried on by using MATLAB function. BPSK method is used
to change the data in the form of bit information to be symbols.
We had used
This paper analyzes the impact of network scalability on various physical attributes of Zigbee networks. Simulations were conducted using Qualnet to evaluate the performance of the Zigbee physical layer based on energy consumption and throughput. Energy consumption was analyzed for different modulation schemes (ASK, BPSK, OQPSK), network sizes (2-50 nodes), and clear channel assessment modes. The results showed that OQPSK and ASK had lower energy consumption than BPSK. Throughput was highest for OQPSK. While carrier sense had slightly higher throughput than other CCA modes, the energy consumption differences between CCA modes were minor.
This paper presents the design and performance comparison of a two stage
operational amplifier topology using CMOS and BiCMOS technology. This conventional op
amp circuit was designed by using RF model of BSIM3V3 in 0.6 μm CMOS technology and
0.35 μm BiCMOS technology. Both the op amp circuits were designed and simulated,
analyzed and performance parameters are compared. The performance parameters such as
gain, phase margin, CMRR, PSRR, power consumption etc achieved are compared. Finally,
we conclude the suitability of CMOS technology over BiCMOS technology for low power
RF design.
In wireless distributed sensor networks, one open problem is how to guarantee the reliable relay
selection based on the quality of services diversity. To address this problem, we focus on the reliable
adaptive relay selection approach and adaptive QoS supported algorithm, based on which we present a
Markov chain model, in consideration of different packet states and error control algorithm assignment.
The mathematical analyses and MATLAB simulation results show that the proposed relay selection
approach could perform better in terms of saturation throughput, reliability, and energy efficiency,
compared with the traditional approaches. More importantly, the quality of real-time multimedia streaming
is improved significantly, in terms of decodable frame ratio and delay.
Efficient power allocation method for non orthogonal multiple access 5G systemsIJECEIAES
This document proposes a new power allocation method for non-orthogonal multiple access (NOMA) systems like interleave division multiple access (IDMA). The method uses forward error correction (FEC) code rates to determine the optimal number of users per power level group. Simulation results show that each FEC code can support a limited number (kmax) of equal power users before bit error rate (BER) degrades. The proposed method divides users into groups sized up to but not exceeding kmax. It aims to minimize total transmit power while maintaining a target BER, by finding the minimum required power ratio between groups. Results show the method outperforms conventional techniques with complex computations.
1) The document analyzes how carrier aggregation (CA) in LTE-Advanced affects the total power transmitted by eNodeBs to meet users' quality of service (QoS) requirements.
2) It derives a general expression showing that the eNodeB's total transmit power is inversely proportional to the channel bandwidth and directly proportional to the cell radius and number of users.
3) Numerical analysis of single-cell and multi-cell scenarios show that using two-carrier CA can reduce the eNodeB's required transmit power by around 65% compared to a single carrier, improving energy efficiency.
Link Adaptation for Microwave Link using both MATLAB and Path-Loss Toolijeei-iaes
The inherent multipath transmission on wireless channels usually leads to signal fading which eventually degrades the system performance. In mitigating this problem, link adaptation has been identified as a promising scheme that helps in maximizing the system spectral efficiency (SE) in dispersive wireless channels. In this paper, link adaptation based on adaptive modulation and coding was used to study the performance of M-ary quadrature amplitude modulation radio system subjected to multipath fading. MATLAB® scripts and Simulink model were developed to compare the effect of wireless channel on different constellation sizes. Also, transmission link on Federal University of Technology Akure campus’ path terrain was designed with the aid of path-loss® tool application software in order to further analysis the effect of using different modulation formats on the system performance. The results show that, employment of link adaptation scheme offers better performance regarding the system availability and SE
Energy efficient and reliable communication in IEEE 802.15.6 IR UWB WBANaravind m t
This paper presents an exhaustive study on the use of one-relay and two-relay cooperative communication schemes and 2-hop communication scheme for improving the energy efficiency and reliability of ultra-wideband based wireless body area networks (UWB WBANs). Various investigations have been performed to study the impact of the parameters like packet size, hop distance, transmit power and channel error rate on the energy efficiency and reliability. An optimal packet size is obtained for the maximization of energy efficiency for both on-body communication and in-body communication. The analytical and simulation results show enhanced reliability with cooperative communication than direct communication and 2-hop communication, for all values of source to destination distances. The results also depict a threshold behaviour for energy efficiency which separates the hoplength for direct transmission from the hoplength where cooperation and 2-hop communication will be useful. The simulation results reveal that if the channel conditions are poor, when the source to destination distance is larger than the threshold value, 2-hop communication gives higher energy efficiency compared with direct and cooperative communications.
The Mobile WiMAX simulation model is
implemented by using MATLAB code. The simulation model
consists of different phases which will help us to model the
transmitter and receiver section. In the next phase, the data is
being modulated by using the modulation methods QPSK and
QAM followed by OFDM transmitter. These phases can be
used to show the performance of these modulation methods
under varying condition. The Multipath Rician fading model is
implemented to introduce the fading in the transmitter data.
Receiver section is used to receive data from channel will be fed
into the OFDM demodulation. In the next phase, Fast Fourier
Transform is used to disassemble OFDM frame. After that
convolution encoding is applied to data and interleaving is
carried on by using MATLAB function. BPSK method is used
to change the data in the form of bit information to be symbols.
We had used
This paper analyzes the impact of network scalability on various physical attributes of Zigbee networks. Simulations were conducted using Qualnet to evaluate the performance of the Zigbee physical layer based on energy consumption and throughput. Energy consumption was analyzed for different modulation schemes (ASK, BPSK, OQPSK), network sizes (2-50 nodes), and clear channel assessment modes. The results showed that OQPSK and ASK had lower energy consumption than BPSK. Throughput was highest for OQPSK. While carrier sense had slightly higher throughput than other CCA modes, the energy consumption differences between CCA modes were minor.
This paper presents the design and performance comparison of a two stage
operational amplifier topology using CMOS and BiCMOS technology. This conventional op
amp circuit was designed by using RF model of BSIM3V3 in 0.6 μm CMOS technology and
0.35 μm BiCMOS technology. Both the op amp circuits were designed and simulated,
analyzed and performance parameters are compared. The performance parameters such as
gain, phase margin, CMRR, PSRR, power consumption etc achieved are compared. Finally,
we conclude the suitability of CMOS technology over BiCMOS technology for low power
RF design.
In wireless distributed sensor networks, one open problem is how to guarantee the reliable relay
selection based on the quality of services diversity. To address this problem, we focus on the reliable
adaptive relay selection approach and adaptive QoS supported algorithm, based on which we present a
Markov chain model, in consideration of different packet states and error control algorithm assignment.
The mathematical analyses and MATLAB simulation results show that the proposed relay selection
approach could perform better in terms of saturation throughput, reliability, and energy efficiency,
compared with the traditional approaches. More importantly, the quality of real-time multimedia streaming
is improved significantly, in terms of decodable frame ratio and delay.
Efficient power allocation method for non orthogonal multiple access 5G systemsIJECEIAES
This document proposes a new power allocation method for non-orthogonal multiple access (NOMA) systems like interleave division multiple access (IDMA). The method uses forward error correction (FEC) code rates to determine the optimal number of users per power level group. Simulation results show that each FEC code can support a limited number (kmax) of equal power users before bit error rate (BER) degrades. The proposed method divides users into groups sized up to but not exceeding kmax. It aims to minimize total transmit power while maintaining a target BER, by finding the minimum required power ratio between groups. Results show the method outperforms conventional techniques with complex computations.
1) The document analyzes how carrier aggregation (CA) in LTE-Advanced affects the total power transmitted by eNodeBs to meet users' quality of service (QoS) requirements.
2) It derives a general expression showing that the eNodeB's total transmit power is inversely proportional to the channel bandwidth and directly proportional to the cell radius and number of users.
3) Numerical analysis of single-cell and multi-cell scenarios show that using two-carrier CA can reduce the eNodeB's required transmit power by around 65% compared to a single carrier, improving energy efficiency.
Link Adaptation for Microwave Link using both MATLAB and Path-Loss Toolijeei-iaes
The inherent multipath transmission on wireless channels usually leads to signal fading which eventually degrades the system performance. In mitigating this problem, link adaptation has been identified as a promising scheme that helps in maximizing the system spectral efficiency (SE) in dispersive wireless channels. In this paper, link adaptation based on adaptive modulation and coding was used to study the performance of M-ary quadrature amplitude modulation radio system subjected to multipath fading. MATLAB® scripts and Simulink model were developed to compare the effect of wireless channel on different constellation sizes. Also, transmission link on Federal University of Technology Akure campus’ path terrain was designed with the aid of path-loss® tool application software in order to further analysis the effect of using different modulation formats on the system performance. The results show that, employment of link adaptation scheme offers better performance regarding the system availability and SE
Energy efficient and reliable communication in IEEE 802.15.6 IR UWB WBANaravind m t
This paper presents an exhaustive study on the use of one-relay and two-relay cooperative communication schemes and 2-hop communication scheme for improving the energy efficiency and reliability of ultra-wideband based wireless body area networks (UWB WBANs). Various investigations have been performed to study the impact of the parameters like packet size, hop distance, transmit power and channel error rate on the energy efficiency and reliability. An optimal packet size is obtained for the maximization of energy efficiency for both on-body communication and in-body communication. The analytical and simulation results show enhanced reliability with cooperative communication than direct communication and 2-hop communication, for all values of source to destination distances. The results also depict a threshold behaviour for energy efficiency which separates the hoplength for direct transmission from the hoplength where cooperation and 2-hop communication will be useful. The simulation results reveal that if the channel conditions are poor, when the source to destination distance is larger than the threshold value, 2-hop communication gives higher energy efficiency compared with direct and cooperative communications.
Modulation aware connection admission control and uplink scheduling algorithm...ijwmn
Mobile WiMAX standard defines air interface for mobile broadband wireless access (BWA) systems and aimed to provide high data rate with seamless mobility while maintaining the quality of service (QoS). However, QoS of real-time applications depends on the link quality, which necessitate the channel-aware connection admission control (CAC) and scheduling schemes. In this paper Modulation aware CAC scheme and base station (BS) uplink scheduling algorithm are proposed to improve the system capacity and QoS performance respectively. The proposed CAC scheme aims to increase the admission of higher priority real time services by degrading the bandwidth of admitted lower priority connections on the basis of their channel status without deteriorating their QoS performance much. The performances of proposed algorithms are evaluated through simulation by considering the metrics like throughput, delay and number of connections admitted.
Performance Analysis of A Ds-Cdma System by using Rayleigh and Nakagami-M Fad...IRJET Journal
1) The document analyzes the performance of a DS-CDMA system using Rayleigh and Nakagami-M fading channels.
2) It studies expressions for signal-to-noise plus interference ratio with and without receive diversity under Nakagami-m fading.
3) The analysis is extended to a Rake receiver with maximal ratio combining technique and multiple receive antennas to determine the improvement in bit error rate and receiver sensitivity due to diversity.
Enhancement of qos in multihop wireless networks by delivering cbr using lb a...eSAT Publishing House
This document summarizes a research paper that proposes using the Leaky Bucket Algorithm to enhance quality of service (QoS) in multi-hop wireless networks delivering constant bit rate (CBR) traffic. The Leaky Bucket Algorithm aims to reduce transmission delay by delivering packets at a constant rate even when packets arrive in bursts. It combines joint congestion control and a scheduling algorithm to not only achieve provable throughput guarantees, but also place explicit upper bounds on the end-to-end delay of each flow. Simulation results show the proposed approach reduces transmission time and improves throughput compared to existing scheduling algorithms that do not consider delay performance.
Enhancement of qos in multihop wireless networks by delivering cbr using lb a...eSAT Journals
Abstract One of the most complicated issues is to measuring the delay performance of end to end nodes in Multi-hop Wireless Networks. The two nodes are communicating via hopping over the multiple wireless links. The fact that is each node has to concentrate not only its own generated traffic, but also relayed one. Observing unfairness particularly for transmissions among nodes that are more than one hop Most of the existing works deals with the joint congestion control and scheduling algorithm, which does not focusing the delay performance. In turn, considering the throughput metric alone although for congestion control flows, throughput is the repeated difficult performance metric Packet delay is also important because practical congestion control protocols need to establish the timeouts for the retransmissions based on the packet delay, such parameters could significantly impact the speed of recovery when loss of packets occurred. The related issues on the delay-performance First, for long flows, the end to end delay may grow in terms of square with based on the number of hops. Second, it is difficult to control the end-to-end delay of each flows. TDMA schedules the transmissions in a fair way, in terms of throughput per connection, considering the communication requirements of the active flows of the network. It does not work properly in the multi-hop scenario, because it is generated only for single hop networks, We propose The Leaky Bucket Algorithm, in addition to joint congestion control and scheduling algorithm in multi-hop wireless networks. The proposed algorithm not only achieves the provable throughput and also considering the upper bounds of the delay of each flow. It reduces the transmission time by delivering packets at a constant bit rate even it receives the packet at a busty way. Keywords- Multi-hop wireless networks, congestion control, Performance, Delay, Flow, Throughput.
Quadrant Based DIR in CWin Adaptation Mechanism for Multihop Wireless NetworkIJCI JOURNAL
In Multihop Wireless Networks, traffic forwarding capability of each node varies according to its level of contention. Each node can yield its channel access opportunity to its neighbouring nodes, so that all the nodes can evenly share the channel and have similar forwarding capability. In this manner the wireless channel is utilized effectively, which is achieved using Contention Window Adaptation Mechanism (CWAM). This mechanism achieves a higher end-to-end throughout but consumes the network power to a higher level. So, a newly proposed algorithm Quadrant- Based Directional Routing Protocol (Q-DIR) is implemented as a cross-layer with CWAM, to reduce the total network power consumption through limited flooding and also reduce the routing overheads, which eventually increases overall network throughput. This algorithm limits the broadcast region to a quadrant where the source node and the destination nodes are located. Implementation of the algorithm is done in Linux based NS-2 simulator
Implementing a Session Aware Policy Based Mechanism for QoS Control in LTEIJERA Editor
Quality of Service (QoS) provisioning has become significant with the widely growth of multimedia applications and high increase in the number of users in both wireless and wired networks. In this paper, we implemented a session-aware policy based mechanism for QoS provisioning and control in LTE (Long Term Evolution) networks. Policies are a set of rules identifying the QoS parameters for users. Implementation included DiffServ (Differentiated Services) configuration and setting policies inside the PCRF (Policy Charging Rules Function) which is the brain entity in LTE, then mapping from QCI (QoS Class ID) to DiffServ. Moreover, the dialogue between PCEF (Policy Charging Enforcement Function) and PCRF was implemented. Simulations on four different traffic application types: VoIP (voice over IP), video, web, and ftp (file transfer protocol) were performed under the network simulator (ns2). Results showed that applying PCEF over the different traffic applications has a great effect in controlling these applications and specifically UDP (User Datagram Protocol) based applications such as video.
AN EFFICIENT SPECTRUM SHARING METHOD BASED ON GENETIC ALGORITHM IN HETEROGENE...IJCNCJournal
With advances in wireless communication technologies, users can have rich contents not only via wired
networks but also via wireless networks such as Cellular, WiFi, and WiMAX. On the other hand, however, lack of spectrum resources becomes an important problem for future wireless networks. To overcome this problem, dynamic spectrum access technology receives much attention. In this paper, we propose a novel spectrum sharing method based on genetic algorithm in which a WiFi system temporarily uses a spectrum band of WiMAX system in WiFi/WiMAX integrated networks as a typical
heterogeneous wireless network. Finally, we confirm the effectiveness of the proposed method by simulation experiments
Performance Model of Key Points At the IPTV NetworksCSCJournals
In this paper we propose a new analytical model for modeling of the key points at the IPTV networks. This model uses Gamma distribution with Intergroup Characteristics for modeling self similar nature of processes in key points of IPTV network. Enclosed Gamma Distribution results are compared with results from real measurements. Calculated discrepancies confirm that enclosed analytical model is optimal estimation model for process modeling of the key points at the IPTV network. The used methodology for real-time analyses of the key points at the IPTV Network is very important for achieving IPTV service best performance.
Investigation and Evaluation of IEEE 802.11n Wlans Link Features Performance ...pijans
For an efficient design of wireless local-area networks (WLANs), the simulation tools are important to accurately estimate the IEEE 802.11n/ac link features for WLANs. However, this true simulation of network behavior is critical in designing high-performance WLANs. Through testing, analysis, and modeling of the proposed scheme repetitively, the design of the WLAN can be enhanced with a small budget before making its practical implementation. Many network simulation tools have been established to give solutions for this request and ns-3 is the most widely used tools among them by the research industry as an open-source network simulator. In this paper, we examine the various link features of the 802.11n WLANs under several conditions. We investigate the effects of 802.11n WLAN modulation and coding schemes (MCSs), 20MHz single channel or 40 MHz bonded channel, guard intervals (GI), frame aggregation, data encoding, number of antennas and their data rate, and link distance features of 802.11n WLAN in ns-3 when only a unique host connects with the access point (AP) and generates data traffic. Besides, the performance for an enterprise scenario proposed by the IEEE 802.11ax study group is evaluated when several hosts are simultaneously creating traffic with their associated APs. The results demonstrate that ns-3 support most of the link features of the 802.11n protocol with significant accuracy.
B ENCHMARKING OF C ELL T HROUGHPUT U SING P ROPORTIONAL F AIR S CHEDULE...ijwmn
The proportional fair (PF) scheduling algorithm com
promises between cell throughput and fairness. Many
research findings have been published by various re
searchers about PF algorithm based on mathematical
model and simulations. In this paper we have taken
the practical route to analyse the algorithm based
on
three types of subscription. In this benchmarking s
tudy, the user subscriptions are differentiated as
Gold,
Silver and Bronze schemes and they are provisioned
with certain throughputs. Apart from subscriptions
plans, the channel condition also plays a major rol
e in determining the throughput. So in order to ens
ure
fairness among different subscriptions even in the
bad channel conditions and to deliver the provision
ed
throughputs certain priorities are attached with th
e subscriptions. As per the subscription plans Gold
subscribers are assigned with 50% of the speed offe
red by the network as maximum based on CAT3 speed
(100 Mbps in DL and 50 Mbps in UL), Silver is assig
ned with 25% of the max speed and Bronze is
assigned with 12% of the max speed. The priorities
assigned to subscribers determines the fairness in
the
unfavourable channel conditions - Bronze (high), Si
lver and Gold (medium). In this paper, an
benchmarking tests have been performed with all of
three types of subscribers for nearly two hours in
the
live single cell network without any heterogeneous
cells influencing it. Furthermore, the results are
compared with the simulation results.
Performance analysis on modulation techniques of w cdma in multipath fading c...Ashish Ranjan
This document is a thesis that analyzes the performance of different modulation techniques in a W-CDMA system operating in multipath fading channels. It first introduces background on modulation schemes like QPSK and QAM. It then discusses theoretical models for the W-CDMA transmitter, receiver, and channel. The thesis focuses on simulating the W-CDMA system using MATLAB to evaluate the bit error rate and signal-to-noise ratio for different modulation techniques under AWGN and Rayleigh fading conditions. The goal is to determine the most suitable modulation for various channel qualities.
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Performance evaluation of the IEEE 802.11n random topology WLAN with QoS appl...IJECEIAES
The IEEE 802.11n supports high data rate transmissions due its physical layer Multiple Input Multiple Output (MIMO) advanced antenna system and MAC layer enhancement features (frame aggregation and block acknowledgement). As a result this standard is very suitable for multimedia services through its Enhanced Distributed Channel Access (EDCA). This paper focuses on evaluating the Quality of Service (QoS) application on the performance of the IEEE 802.11n random topology WLAN. Three different number of nodes (3, 9 and 18) random topology with one access point are modeled and simulated by using the Riverbed OPNET 17.5 Modular to investigate the Wireless Local Area Network (WLAN) performance for different spatial streams. The result clarified the impact of QoS application and showed that its effect is best at the 18 node number topology. For a 4x4 MIMO, when QoS is applied and with respect to the no QoS application case, simulation results show a maximum improvement of 86.4%, 33.9%, 52.2% and 68.9% for throughput, delay, data drop and retransmission attempts, respectively.
This document describes the design and implementation of 4-bit QPSK and 256-bit QAM modulation techniques using MATLAB. It compares the two techniques based on SNR, BER, and efficiency. The key steps of implementing each technique in MATLAB are outlined, including generating random bits, modulation, adding noise, and measuring BER. Simulation results show scatter plots and eye diagrams of the modulated signals. A table compares the results, showing that 256-bit QAM provides better performance than 4-bit QPSK. The document concludes that QAM modulation is more effective for digital transmission systems.
This document analyzes the performance of adaptive subcarrier allocation in coherent optical OFDM systems. It proposes two allocation schemes: proportional allocation and equal allocation. Proportional allocation aims to maximize data rate while ensuring fairness among users by assigning subcarriers to the user with the highest SNR for that subcarrier, as long as it does not exceed their proportional share. Equal allocation simply divides subcarriers equally among all users. The document models an optical OFDM system transmitting over 1000km of single-mode fiber and investigates how adaptive subcarrier allocation can improve performance compared to static allocation schemes.
Performance analysis of image transmission with various channel conditions/mo...TELKOMNIKA JOURNAL
This paper investigates the impact of different modulation techniques for
digital communication systems that employ quadrature phase shift keying
(QPSK) and quadrature amplitude modulation (16-QAM and 64-QAM) to
transmit images over AWGN and Rayleigh fading channels for the cellular
mobile networks. In the further steps, wiener and median filters has been
adopted to the simulation are used at the receiver side to remove the impulsive
noise present in the received image. This work is performed to evaluate
the transmission of two dimensional (2D) gray-scale and color-scale (RGB)
images with different values from signal to noise ratios (SNR), such as;
(5, 10 and 15) dB over different channels. The correct conclusions are made
by comparing many of the observed Matlab simulation results. This was
carried out through the results that measure the quality of received image,
which is analyzes in terms of SNRimage peak signal to noise ratio (PSNR) and
mean square error (MSE).
Wireless sensor networks (WSN) have been widely used in various applications.
In these networks nodes collect data from the attached sensors and send their data to a base
station. However, nodes in WSN have limited power supply in form of battery so the nodes
are expected to minimize energy consumption in order to maximize the lifetime of WSN. A
number of techniques have been proposed in the literature to reduce the energy
consumption significantly. In this paper, we propose a new clustering based technique
which is a modification of the popular LEACH algorithm. In this technique, first cluster
heads are elected using the improved LEACH algorithm as usual, and then a cluster of
nodes is formed based on the distance between node and cluster head. Finally, data from
node is transferred to cluster head. Cluster heads forward data, after applying aggregation,
to the cluster head that is closer to it than sink in forward direction or directly to the sink.
This reduction in distance travelled improves the performance over LEACH algorithm
significantly.
This document discusses improving network lifetime in ad hoc networks through energy efficient routing. It proposes a routing mechanism that considers both the minimum hop count and residual energy of nodes to select paths for data transmission. The key points are:
1) Existing routing mechanisms only consider hop count and do not account for node energy levels, which can reduce network lifetime.
2) The proposed mechanism selects paths based on both minimum hop count and maximum residual energy of nodes. This avoids overusing certain nodes and depleting their energy.
3) It describes the routing procedure, energy efficient data transmission, and modules for calculating packet numbers, inserting values in routing lists, selecting paths, and handling residual routing when nodes have low energy.
Quality of service adaptive modulation and coding scheme for IEEE 802.11acIJECEIAES
Nowadays, the rising demand for digital communication technologies has contributed to the increase in the volume of traffic. This continuous trend of internet traffic has led to the deterioration of the quality of service (QoS) with reduced throughput and increased latency. This also is due to the proliferation of new broadband applications which require low latency and high throughput such as virtual reality and real-time gaming. Therefore, considering the aforementioned challenge in QoS of wireless networks, a link adaptation method is suggested in this study, in order to enhance the performance of the QoS in IEEE 802.11ac amendment wireless local-area network (WLAN). The proposed technique adaptively changes the transmission data rate by increasing or decreasing the modulation and coding scheme (MCS) level according to the traffic conditions. With the use of an OMNeT++ computer-aided design (CAD)-based simulation model, the effectiveness of the suggested approach is examined. Simulated findings were compared with the link adaptation approach of the default condition. The results of the simulation demonstrate that the proposed technique significantly increases throughput (36.48%) and decreases latency in comparison to the default situation. These findings demonstrate the technique's potential to improve WLAN QoS efficiency, notably in regard to throughput and latency.
This document appears to be a student paper submission for a networking course. It discusses using a microwave backhaul link to connect two company branch offices located on different Greek islands. The paper will analyze how the bit error rate of the microwave link at different signal-to-noise ratios can impact the TCP throughput between the two branches. It will include simulations of the microwave link and the network implementation to examine this relationship and draw conclusions. The paper is divided into sections covering the theoretical background of the communication channel, analysis of error correction coding and modulation, and the planned simulations.
Data Transmission Analysis using MW-5000 at 5.8 GHz Frequency IJECEIAES
This document summarizes an experiment on data transmission analysis using a MW-5000 module at 5.8 GHz frequency. The experiment found that the duration for data transmission depends on the length of the message and the baud rate setting. Testing various message lengths at a fixed baud rate of 4800 resulted in similar transmission durations. However, transmitting the same message at different baud rates showed that higher baud rates reduced the transmission duration. Specifically, a message sent at 4800 baud took 1.14 seconds while at 9600 baud it took 0.60 seconds. The document concludes that transmission duration is influenced by message length and baud rate.
ESTIMATION AND COMPENSATION OF INTER CARRIER INTERFERENCE IN WIMAX PHYSICAL L...ijngnjournal
WiMAX is Wireless Interoperability for Microwave Access has emerged as a promising solution for transmission of higher data rates for fixed and mobile applications. IEEE 802.16d and e are the standards proposed by WiMAX group for fixed and mobile. As the wireless channel have so many limitation Such as Multipath, Doppler spread, Delay spread and Line Of Sight (LOS)/Non Line Of Sight (NLOS) components. To attain higher data rates the Multi Carrier System with Multiple Input and Multiple Output (MIMO) is incorporated in the WiMAX. The Orthogonal Frequency Division Multiplexing (OFDM) is a multi carrier technique used with the WiMAX systems. In OFDM the available spectrum is split into numerous narrow band channels of dissimilar frequencies to achieve high data rate in a multi path fading environment. And all these sub carriers are considered to be orthogonal to each other. As the number of sub carriers is increased there is no guarantee of sustained orthogonality, i.e. at some point the carriers are not
independent to each other, and hence where the orthogonality can be loosed which leads to interference and also owing to the synchronization between transmitter and receiver local oscillator, it causes interference known as Inter Carrier Interference (ICI). The systems uses MIMO-OFDM will suffer with the effects of ICI and Carrier Frequency Offset (CFO) “ε”. However these affect the power leakage in the midst of sub carriers, consequently degrading the system performance. In this paper a new approach is proposed in order to reduce the ICI caused in WiMAX and improve the system performance. In this scheme at the transmitter side the modulated data and a few predefined pilot symbols are mapped onto the non
neighboring sub carriers with weighting coefficients of +1 and -1. With the aid of pilot symbols the frequency offset is exactly estimated by using Maximum Likelihood Estimation (MLE) and hence can be minimized. At demodulation stage the received signals are linearly combined along with their weighted
coefficients and pilot symbols, called as Pilot Aided Self Cancellation Method (PASCS). And also to realize the various wireless environments the simulations are carried out on Stanford University Interim (SUI) channels. The simulation results shows that by incorporating this method into WiMAX systems it performs better when the Line Of Sight (LOS) component is present in the transmission and also it improves the Bit Error Rate (BER) and Carrier to Interference Ratio (CIR). The CIR can be improved 20 dB. In this paper the effectiveness of PASCS scheme is compared with the Self Cancellation Method (SCM). It provides accurate estimation of frequency offset and when residual CFO is less significant the ICI can be diminished successfully.
Modulation aware connection admission control and uplink scheduling algorithm...ijwmn
Mobile WiMAX standard defines air interface for mobile broadband wireless access (BWA) systems and aimed to provide high data rate with seamless mobility while maintaining the quality of service (QoS). However, QoS of real-time applications depends on the link quality, which necessitate the channel-aware connection admission control (CAC) and scheduling schemes. In this paper Modulation aware CAC scheme and base station (BS) uplink scheduling algorithm are proposed to improve the system capacity and QoS performance respectively. The proposed CAC scheme aims to increase the admission of higher priority real time services by degrading the bandwidth of admitted lower priority connections on the basis of their channel status without deteriorating their QoS performance much. The performances of proposed algorithms are evaluated through simulation by considering the metrics like throughput, delay and number of connections admitted.
Performance Analysis of A Ds-Cdma System by using Rayleigh and Nakagami-M Fad...IRJET Journal
1) The document analyzes the performance of a DS-CDMA system using Rayleigh and Nakagami-M fading channels.
2) It studies expressions for signal-to-noise plus interference ratio with and without receive diversity under Nakagami-m fading.
3) The analysis is extended to a Rake receiver with maximal ratio combining technique and multiple receive antennas to determine the improvement in bit error rate and receiver sensitivity due to diversity.
Enhancement of qos in multihop wireless networks by delivering cbr using lb a...eSAT Publishing House
This document summarizes a research paper that proposes using the Leaky Bucket Algorithm to enhance quality of service (QoS) in multi-hop wireless networks delivering constant bit rate (CBR) traffic. The Leaky Bucket Algorithm aims to reduce transmission delay by delivering packets at a constant rate even when packets arrive in bursts. It combines joint congestion control and a scheduling algorithm to not only achieve provable throughput guarantees, but also place explicit upper bounds on the end-to-end delay of each flow. Simulation results show the proposed approach reduces transmission time and improves throughput compared to existing scheduling algorithms that do not consider delay performance.
Enhancement of qos in multihop wireless networks by delivering cbr using lb a...eSAT Journals
Abstract One of the most complicated issues is to measuring the delay performance of end to end nodes in Multi-hop Wireless Networks. The two nodes are communicating via hopping over the multiple wireless links. The fact that is each node has to concentrate not only its own generated traffic, but also relayed one. Observing unfairness particularly for transmissions among nodes that are more than one hop Most of the existing works deals with the joint congestion control and scheduling algorithm, which does not focusing the delay performance. In turn, considering the throughput metric alone although for congestion control flows, throughput is the repeated difficult performance metric Packet delay is also important because practical congestion control protocols need to establish the timeouts for the retransmissions based on the packet delay, such parameters could significantly impact the speed of recovery when loss of packets occurred. The related issues on the delay-performance First, for long flows, the end to end delay may grow in terms of square with based on the number of hops. Second, it is difficult to control the end-to-end delay of each flows. TDMA schedules the transmissions in a fair way, in terms of throughput per connection, considering the communication requirements of the active flows of the network. It does not work properly in the multi-hop scenario, because it is generated only for single hop networks, We propose The Leaky Bucket Algorithm, in addition to joint congestion control and scheduling algorithm in multi-hop wireless networks. The proposed algorithm not only achieves the provable throughput and also considering the upper bounds of the delay of each flow. It reduces the transmission time by delivering packets at a constant bit rate even it receives the packet at a busty way. Keywords- Multi-hop wireless networks, congestion control, Performance, Delay, Flow, Throughput.
Quadrant Based DIR in CWin Adaptation Mechanism for Multihop Wireless NetworkIJCI JOURNAL
In Multihop Wireless Networks, traffic forwarding capability of each node varies according to its level of contention. Each node can yield its channel access opportunity to its neighbouring nodes, so that all the nodes can evenly share the channel and have similar forwarding capability. In this manner the wireless channel is utilized effectively, which is achieved using Contention Window Adaptation Mechanism (CWAM). This mechanism achieves a higher end-to-end throughout but consumes the network power to a higher level. So, a newly proposed algorithm Quadrant- Based Directional Routing Protocol (Q-DIR) is implemented as a cross-layer with CWAM, to reduce the total network power consumption through limited flooding and also reduce the routing overheads, which eventually increases overall network throughput. This algorithm limits the broadcast region to a quadrant where the source node and the destination nodes are located. Implementation of the algorithm is done in Linux based NS-2 simulator
Implementing a Session Aware Policy Based Mechanism for QoS Control in LTEIJERA Editor
Quality of Service (QoS) provisioning has become significant with the widely growth of multimedia applications and high increase in the number of users in both wireless and wired networks. In this paper, we implemented a session-aware policy based mechanism for QoS provisioning and control in LTE (Long Term Evolution) networks. Policies are a set of rules identifying the QoS parameters for users. Implementation included DiffServ (Differentiated Services) configuration and setting policies inside the PCRF (Policy Charging Rules Function) which is the brain entity in LTE, then mapping from QCI (QoS Class ID) to DiffServ. Moreover, the dialogue between PCEF (Policy Charging Enforcement Function) and PCRF was implemented. Simulations on four different traffic application types: VoIP (voice over IP), video, web, and ftp (file transfer protocol) were performed under the network simulator (ns2). Results showed that applying PCEF over the different traffic applications has a great effect in controlling these applications and specifically UDP (User Datagram Protocol) based applications such as video.
AN EFFICIENT SPECTRUM SHARING METHOD BASED ON GENETIC ALGORITHM IN HETEROGENE...IJCNCJournal
With advances in wireless communication technologies, users can have rich contents not only via wired
networks but also via wireless networks such as Cellular, WiFi, and WiMAX. On the other hand, however, lack of spectrum resources becomes an important problem for future wireless networks. To overcome this problem, dynamic spectrum access technology receives much attention. In this paper, we propose a novel spectrum sharing method based on genetic algorithm in which a WiFi system temporarily uses a spectrum band of WiMAX system in WiFi/WiMAX integrated networks as a typical
heterogeneous wireless network. Finally, we confirm the effectiveness of the proposed method by simulation experiments
Performance Model of Key Points At the IPTV NetworksCSCJournals
In this paper we propose a new analytical model for modeling of the key points at the IPTV networks. This model uses Gamma distribution with Intergroup Characteristics for modeling self similar nature of processes in key points of IPTV network. Enclosed Gamma Distribution results are compared with results from real measurements. Calculated discrepancies confirm that enclosed analytical model is optimal estimation model for process modeling of the key points at the IPTV network. The used methodology for real-time analyses of the key points at the IPTV Network is very important for achieving IPTV service best performance.
Investigation and Evaluation of IEEE 802.11n Wlans Link Features Performance ...pijans
For an efficient design of wireless local-area networks (WLANs), the simulation tools are important to accurately estimate the IEEE 802.11n/ac link features for WLANs. However, this true simulation of network behavior is critical in designing high-performance WLANs. Through testing, analysis, and modeling of the proposed scheme repetitively, the design of the WLAN can be enhanced with a small budget before making its practical implementation. Many network simulation tools have been established to give solutions for this request and ns-3 is the most widely used tools among them by the research industry as an open-source network simulator. In this paper, we examine the various link features of the 802.11n WLANs under several conditions. We investigate the effects of 802.11n WLAN modulation and coding schemes (MCSs), 20MHz single channel or 40 MHz bonded channel, guard intervals (GI), frame aggregation, data encoding, number of antennas and their data rate, and link distance features of 802.11n WLAN in ns-3 when only a unique host connects with the access point (AP) and generates data traffic. Besides, the performance for an enterprise scenario proposed by the IEEE 802.11ax study group is evaluated when several hosts are simultaneously creating traffic with their associated APs. The results demonstrate that ns-3 support most of the link features of the 802.11n protocol with significant accuracy.
B ENCHMARKING OF C ELL T HROUGHPUT U SING P ROPORTIONAL F AIR S CHEDULE...ijwmn
The proportional fair (PF) scheduling algorithm com
promises between cell throughput and fairness. Many
research findings have been published by various re
searchers about PF algorithm based on mathematical
model and simulations. In this paper we have taken
the practical route to analyse the algorithm based
on
three types of subscription. In this benchmarking s
tudy, the user subscriptions are differentiated as
Gold,
Silver and Bronze schemes and they are provisioned
with certain throughputs. Apart from subscriptions
plans, the channel condition also plays a major rol
e in determining the throughput. So in order to ens
ure
fairness among different subscriptions even in the
bad channel conditions and to deliver the provision
ed
throughputs certain priorities are attached with th
e subscriptions. As per the subscription plans Gold
subscribers are assigned with 50% of the speed offe
red by the network as maximum based on CAT3 speed
(100 Mbps in DL and 50 Mbps in UL), Silver is assig
ned with 25% of the max speed and Bronze is
assigned with 12% of the max speed. The priorities
assigned to subscribers determines the fairness in
the
unfavourable channel conditions - Bronze (high), Si
lver and Gold (medium). In this paper, an
benchmarking tests have been performed with all of
three types of subscribers for nearly two hours in
the
live single cell network without any heterogeneous
cells influencing it. Furthermore, the results are
compared with the simulation results.
Performance analysis on modulation techniques of w cdma in multipath fading c...Ashish Ranjan
This document is a thesis that analyzes the performance of different modulation techniques in a W-CDMA system operating in multipath fading channels. It first introduces background on modulation schemes like QPSK and QAM. It then discusses theoretical models for the W-CDMA transmitter, receiver, and channel. The thesis focuses on simulating the W-CDMA system using MATLAB to evaluate the bit error rate and signal-to-noise ratio for different modulation techniques under AWGN and Rayleigh fading conditions. The goal is to determine the most suitable modulation for various channel qualities.
To Get any Project for CSE, IT ECE, EEE Contact Me @ 09849539085, 09966235788 or mail us - ieeefinalsemprojects@gmail.co¬m-Visit Our Website: www.finalyearprojects.org
Performance evaluation of the IEEE 802.11n random topology WLAN with QoS appl...IJECEIAES
The IEEE 802.11n supports high data rate transmissions due its physical layer Multiple Input Multiple Output (MIMO) advanced antenna system and MAC layer enhancement features (frame aggregation and block acknowledgement). As a result this standard is very suitable for multimedia services through its Enhanced Distributed Channel Access (EDCA). This paper focuses on evaluating the Quality of Service (QoS) application on the performance of the IEEE 802.11n random topology WLAN. Three different number of nodes (3, 9 and 18) random topology with one access point are modeled and simulated by using the Riverbed OPNET 17.5 Modular to investigate the Wireless Local Area Network (WLAN) performance for different spatial streams. The result clarified the impact of QoS application and showed that its effect is best at the 18 node number topology. For a 4x4 MIMO, when QoS is applied and with respect to the no QoS application case, simulation results show a maximum improvement of 86.4%, 33.9%, 52.2% and 68.9% for throughput, delay, data drop and retransmission attempts, respectively.
This document describes the design and implementation of 4-bit QPSK and 256-bit QAM modulation techniques using MATLAB. It compares the two techniques based on SNR, BER, and efficiency. The key steps of implementing each technique in MATLAB are outlined, including generating random bits, modulation, adding noise, and measuring BER. Simulation results show scatter plots and eye diagrams of the modulated signals. A table compares the results, showing that 256-bit QAM provides better performance than 4-bit QPSK. The document concludes that QAM modulation is more effective for digital transmission systems.
This document analyzes the performance of adaptive subcarrier allocation in coherent optical OFDM systems. It proposes two allocation schemes: proportional allocation and equal allocation. Proportional allocation aims to maximize data rate while ensuring fairness among users by assigning subcarriers to the user with the highest SNR for that subcarrier, as long as it does not exceed their proportional share. Equal allocation simply divides subcarriers equally among all users. The document models an optical OFDM system transmitting over 1000km of single-mode fiber and investigates how adaptive subcarrier allocation can improve performance compared to static allocation schemes.
Performance analysis of image transmission with various channel conditions/mo...TELKOMNIKA JOURNAL
This paper investigates the impact of different modulation techniques for
digital communication systems that employ quadrature phase shift keying
(QPSK) and quadrature amplitude modulation (16-QAM and 64-QAM) to
transmit images over AWGN and Rayleigh fading channels for the cellular
mobile networks. In the further steps, wiener and median filters has been
adopted to the simulation are used at the receiver side to remove the impulsive
noise present in the received image. This work is performed to evaluate
the transmission of two dimensional (2D) gray-scale and color-scale (RGB)
images with different values from signal to noise ratios (SNR), such as;
(5, 10 and 15) dB over different channels. The correct conclusions are made
by comparing many of the observed Matlab simulation results. This was
carried out through the results that measure the quality of received image,
which is analyzes in terms of SNRimage peak signal to noise ratio (PSNR) and
mean square error (MSE).
Wireless sensor networks (WSN) have been widely used in various applications.
In these networks nodes collect data from the attached sensors and send their data to a base
station. However, nodes in WSN have limited power supply in form of battery so the nodes
are expected to minimize energy consumption in order to maximize the lifetime of WSN. A
number of techniques have been proposed in the literature to reduce the energy
consumption significantly. In this paper, we propose a new clustering based technique
which is a modification of the popular LEACH algorithm. In this technique, first cluster
heads are elected using the improved LEACH algorithm as usual, and then a cluster of
nodes is formed based on the distance between node and cluster head. Finally, data from
node is transferred to cluster head. Cluster heads forward data, after applying aggregation,
to the cluster head that is closer to it than sink in forward direction or directly to the sink.
This reduction in distance travelled improves the performance over LEACH algorithm
significantly.
This document discusses improving network lifetime in ad hoc networks through energy efficient routing. It proposes a routing mechanism that considers both the minimum hop count and residual energy of nodes to select paths for data transmission. The key points are:
1) Existing routing mechanisms only consider hop count and do not account for node energy levels, which can reduce network lifetime.
2) The proposed mechanism selects paths based on both minimum hop count and maximum residual energy of nodes. This avoids overusing certain nodes and depleting their energy.
3) It describes the routing procedure, energy efficient data transmission, and modules for calculating packet numbers, inserting values in routing lists, selecting paths, and handling residual routing when nodes have low energy.
Quality of service adaptive modulation and coding scheme for IEEE 802.11acIJECEIAES
Nowadays, the rising demand for digital communication technologies has contributed to the increase in the volume of traffic. This continuous trend of internet traffic has led to the deterioration of the quality of service (QoS) with reduced throughput and increased latency. This also is due to the proliferation of new broadband applications which require low latency and high throughput such as virtual reality and real-time gaming. Therefore, considering the aforementioned challenge in QoS of wireless networks, a link adaptation method is suggested in this study, in order to enhance the performance of the QoS in IEEE 802.11ac amendment wireless local-area network (WLAN). The proposed technique adaptively changes the transmission data rate by increasing or decreasing the modulation and coding scheme (MCS) level according to the traffic conditions. With the use of an OMNeT++ computer-aided design (CAD)-based simulation model, the effectiveness of the suggested approach is examined. Simulated findings were compared with the link adaptation approach of the default condition. The results of the simulation demonstrate that the proposed technique significantly increases throughput (36.48%) and decreases latency in comparison to the default situation. These findings demonstrate the technique's potential to improve WLAN QoS efficiency, notably in regard to throughput and latency.
This document appears to be a student paper submission for a networking course. It discusses using a microwave backhaul link to connect two company branch offices located on different Greek islands. The paper will analyze how the bit error rate of the microwave link at different signal-to-noise ratios can impact the TCP throughput between the two branches. It will include simulations of the microwave link and the network implementation to examine this relationship and draw conclusions. The paper is divided into sections covering the theoretical background of the communication channel, analysis of error correction coding and modulation, and the planned simulations.
Data Transmission Analysis using MW-5000 at 5.8 GHz Frequency IJECEIAES
This document summarizes an experiment on data transmission analysis using a MW-5000 module at 5.8 GHz frequency. The experiment found that the duration for data transmission depends on the length of the message and the baud rate setting. Testing various message lengths at a fixed baud rate of 4800 resulted in similar transmission durations. However, transmitting the same message at different baud rates showed that higher baud rates reduced the transmission duration. Specifically, a message sent at 4800 baud took 1.14 seconds while at 9600 baud it took 0.60 seconds. The document concludes that transmission duration is influenced by message length and baud rate.
ESTIMATION AND COMPENSATION OF INTER CARRIER INTERFERENCE IN WIMAX PHYSICAL L...ijngnjournal
WiMAX is Wireless Interoperability for Microwave Access has emerged as a promising solution for transmission of higher data rates for fixed and mobile applications. IEEE 802.16d and e are the standards proposed by WiMAX group for fixed and mobile. As the wireless channel have so many limitation Such as Multipath, Doppler spread, Delay spread and Line Of Sight (LOS)/Non Line Of Sight (NLOS) components. To attain higher data rates the Multi Carrier System with Multiple Input and Multiple Output (MIMO) is incorporated in the WiMAX. The Orthogonal Frequency Division Multiplexing (OFDM) is a multi carrier technique used with the WiMAX systems. In OFDM the available spectrum is split into numerous narrow band channels of dissimilar frequencies to achieve high data rate in a multi path fading environment. And all these sub carriers are considered to be orthogonal to each other. As the number of sub carriers is increased there is no guarantee of sustained orthogonality, i.e. at some point the carriers are not
independent to each other, and hence where the orthogonality can be loosed which leads to interference and also owing to the synchronization between transmitter and receiver local oscillator, it causes interference known as Inter Carrier Interference (ICI). The systems uses MIMO-OFDM will suffer with the effects of ICI and Carrier Frequency Offset (CFO) “ε”. However these affect the power leakage in the midst of sub carriers, consequently degrading the system performance. In this paper a new approach is proposed in order to reduce the ICI caused in WiMAX and improve the system performance. In this scheme at the transmitter side the modulated data and a few predefined pilot symbols are mapped onto the non
neighboring sub carriers with weighting coefficients of +1 and -1. With the aid of pilot symbols the frequency offset is exactly estimated by using Maximum Likelihood Estimation (MLE) and hence can be minimized. At demodulation stage the received signals are linearly combined along with their weighted
coefficients and pilot symbols, called as Pilot Aided Self Cancellation Method (PASCS). And also to realize the various wireless environments the simulations are carried out on Stanford University Interim (SUI) channels. The simulation results shows that by incorporating this method into WiMAX systems it performs better when the Line Of Sight (LOS) component is present in the transmission and also it improves the Bit Error Rate (BER) and Carrier to Interference Ratio (CIR). The CIR can be improved 20 dB. In this paper the effectiveness of PASCS scheme is compared with the Self Cancellation Method (SCM). It provides accurate estimation of frequency offset and when residual CFO is less significant the ICI can be diminished successfully.
This report discusses the planning Associate in
nursing the implementation of an OFDM system
in several information module schemes like MQPSK,
M-QAM. First, a short introduction is
provided by explaining the background and the
specification of the project. Then the report deals
with the system model, every block of the OFDM
system is represented (IFFT, FFT, Cyclic prefix,
modulation / reception, Channel estimation, bit
error rate). System design is analyzed. The
transmission techniques, further because the
system parameters for transmission and reception
are explained well. Finally, the results are
provided.
COMPARISON OF BIT ERROR RATE PERFORMANCE OF VARIOUS DIGITAL MODULATION SCHEME...ijasa
This document compares the bit error rate (BER) performance of different digital modulation schemes (BPSK, QPSK, 16-QAM) over AWGN and Rayleigh fading channels using Simulink simulations. It finds that BPSK outperforms QPSK and 16-QAM in both channels. The BER is evaluated for these modulation schemes using two equalization techniques: constant modulus algorithm (CMA) and maximum likelihood sequence estimation (MLSE). According to the results, BPSK has better BER performance than QPSK and 16-QAM when using either equalizer, especially at lower SNR values. CMA equalization works better than MLSE equalization for all modulation schemes based on the BER values obtained.
Powerful business model for fixed wireless data using outdoor antennas - PaperAndre Fourie
Paper presented at the 2nd Africa Radio Comms Conference in Johannesburg - Nov 2015
By Andre Fourie
The revenue that can be generated by an LTE base station is influenced by the quality of the signal received by the customer premise equipment (CPE). Most CPE come with omni-directional indoor antennas, but have provision for the connection to external antennas.
Substituting the indoor antennas for directional outdoor antennas has a marked effect on the data transfer speeds of the network. There are two reasons for this. Firstly, outdoor antennas are physically larger than their indoor counterparts and thus have a higher gain. The increase in antenna gain translates directly to an increase in received signal strength. The second advantage is that the outdoor antenna sits in an environment that has much better propagating properties than the indoor antenna. Tests have shown that data speeds 3-5 times faster are possible using external antennas compared to indoor antennas.
It is shown, using a primitive financial model that fairly large financial gains can be made by equipping CPE devices with external antennas.
Comparative study of_digital_modulation (1)Bindia Kumari
This document compares different digital modulation techniques that can be used in orthogonal frequency division multiplexing (OFDM) and WiMAX networks. It simulates BPSK, QPSK, 16-QAM and 64-QAM modulation in MATLAB and measures their performance in terms of bit error rate and throughput. The results show that higher order modulations like 64-QAM provide much higher throughput but also higher bit error rates compared to lower order modulations at a given signal-to-noise ratio. The best configuration balances low bit error rates and high throughput.
This document discusses cost-effective deployment of relay stations in WiMAX networks. It first outlines the costs associated with base stations and relay stations, including capital expenditures and operational expenditures. It then discusses challenges in planning relay station placement to both improve quality of service and reduce costs. Specifically, it examines dividing the network into zones based on signal strength and using different modulation and coding schemes in each zone. The goal is to determine optimal relay station locations and configurations to enhance network performance while minimizing overall deployment costs.
The document discusses channel estimation techniques for wireless communication systems. It describes that channel estimation is important for mobile wireless networks as the channel changes over time due to movement. It summarizes that channel estimation algorithms allow the receiver to approximate the time-varying channel impulse response. The document then compares two popular channel estimation algorithms - LMS and RLS. LMS uses estimates of the gradient vector to iteratively minimize the mean square error, while RLS recursively finds filter coefficients to minimize a weighted linear least squares cost function.
Iaetsd gmsk modulation implementation for gsm in dspIaetsd Iaetsd
This document describes the implementation of a GMSK modulator on a TMS320C6713 digital signal processor. GMSK modulation is used in GSM cellular systems due to its bandwidth efficiency. The author designed a simple algorithm to accurately generate GMSK signals in DSP. Key components included a numerically controlled oscillator and Gaussian low-pass filter implemented as a finite impulse response filter. Simulation results were obtained using Elanix software to verify the GMSK modulator design.
Improving quality of service using ofdm technique for 4 th generation networkeSAT Journals
This document summarizes a research paper that compares the performance of 32QAM and 64QAM digital modulation techniques when used with OFDM for 4G networks. It finds that 32QAM has better performance with lower bit and packet loss over 64QAM. Specifically, when transmitting 1920 bits over an AWGN channel, 32QAM had 65 bit losses and 0 packet losses, while 64QAM had 80 bit losses and 0.04167 packet losses. Therefore, the document concludes 32QAM can be more efficiently used than 64QAM for digital transmission in 4G networks when combined with OFDM modulation.
Improving quality of service using ofdm technique for 4 th generation networkeSAT Publishing House
This document summarizes a research paper that compares the performance of 32QAM and 64QAM digital modulation techniques when used with OFDM for 4G networks. It finds that 32QAM has better performance with lower bit and packet loss over 64QAM. Specifically, when transmitting 1920 bits over an AWGN channel, 32QAM had 65 bit losses and 0 packet losses, while 64QAM had 80 bit losses and 0.04167 packet losses. Therefore, the document concludes 32QAM can be more efficiently used than 64QAM for digital transmission in 4G networks when combined with OFDM modulation.
SERVICES AS PARAMETER TO PROVIDE BEST QOS : AN ANALYSIS OVER WIMAXijngnjournal
In this paper it is proposed to provide the QoS to the user by using the degradation of service under hostile environment being itself be a parameter to improve the QoS. Here the relation between the service and environment of its best performance drawn on the basis of simulation and analysis .The service then taken as a parameter to decide present environment of the user and to take measurable steps to improve the QoS either doing handover to nearby station or increasing power or to provide some marginal bandwidth etc.All analysis done over a WiMax network i.e. being designed and simulated using the Qualnet wireless simulator.
Performance analysis of 802.11ac with frame aggregation using NS3 IJECEIAES
802.11ac is an interesting standard of IEEE bringing multiple advantages than its predecessor 802.11n. 802.11ac is faster and more scalable version of 802.11n offering the capabilities of wireless Gigabit Ethernet. 802.11ac will enable access points (AP) to support more STAs with a better experience for clients and more channel bonding increasing from a maximum of 40 MHz with 802.11n up to 80 or 160 MHz with 802.11ac standard. In this paper, we analyze and evaluate the 802.11ac performance using NS3 simulator (v3.26) relying on several features like channel bonding, modulation and coding schemes, guard interval and frame aggregation. Then, we presentthe effect of the variation of d istance between STAs and AP on the network performance in term of throughput. Finally, we capture the most relevant simulations outcomes and we indicate some research challenges for the future work.
An enhanced available bandwidth estimation technique for an end to end networ...redpel dot com
The document describes an enhanced technique for estimating available bandwidth (ABW) of an end-to-end network path. It proposes a unique probing scheme using a probing train structure with a high-density region to detect the turning point more accurately. It also includes a rate adjustment algorithm and a modified excursion detection algorithm to estimate ABW more accurately and less intrusively. Experimental results using an Android device over a 4G/LTE network and a testbed show the technique outperforms other state-of-the-art methods in terms of accuracy, intrusiveness, and convergence time.
This document summarizes research on performance analysis of adaptive multi-user OFDM systems. It describes using adaptive modulation to maximize throughput by selecting modulation schemes on a per-subcarrier basis to maintain bit error rate while maximizing spectral efficiency. Adaptive user allocation is also analyzed to improve signal power by optimizing user-subcarrier combinations based on frequency selective fading differences between users. Simulation results show adaptive modulation providing 12-16dB SNR improvement over fixed modulation. Adaptive user allocation provides an additional 3-5dB average signal power gain. The document concludes these adaptive techniques allow OFDM systems to approach channel capacity limits given constraints of the radio channel, transmitter power and quality of service requirements.
1. The document discusses performance enhancement of WiMAX mobile handover using OFDM with M-QAM modulation and best relay selection.
2. It analyzes the bit error rate performance of M-QAM OFDM systems for different modulation schemes, numbers of relays, and subchannels.
3. The results show that M-QAM OFDM with best relay selection provides higher performance and lower error communication compared to other techniques.
A Review of Relay selection based Cooperative Wireless Network for Capacity E...IRJET Journal
This document discusses relay selection in cooperative wireless networks to enhance network capacity. It reviews cooperative communication techniques like amplify-and-forward and decode-and-forward that achieve spatial diversity without requiring multiple antennas on a device. The selection of relay nodes has a significant impact on the total network capacity. It aims to study cooperative relay node assignment that allows multiple source-destination pairs to compete for the same pool of relay nodes, with each pair able to be assigned multiple relays.
Performance analysis of IEEE 802.11ac based WLAN in wireless communication sy...IJECEIAES
IEEE 802.11ac based wireless local area network (WLAN) is emerging WiFi standard at 5 GHz, it is new gigabit-per-second standard providing premium services. IEEE 802.11ac accomplishes its crude speed increment by pushing on three distinct measurements firstly is more channel holding, expanded from a maximum of 80 MHz up to 160 MHz modes. Secondly, the denser modulation, now using 256-QAM, it has the ability to increase the data rates up to 7 Gbps using an 8×8 multiple input multiple output (MIMO). Finally, it provides high resolution for both narrow and medium bandwidth channels. This work presents a study to improve the performance of IEEE 802.11ac based WLAN system.
Similar to WiFi-802.11g -Adaptivity of modulation mode and encoding rate for an improved Quality of Service.DOC (20)
Performance analysis of IEEE 802.11ac based WLAN in wireless communication sy...
WiFi-802.11g -Adaptivity of modulation mode and encoding rate for an improved Quality of Service.DOC
1. K1465164
Abstract—Nowadays the majority of people are users of the
Wi-Fi and their demands of a better Quality of Service are
increasing day by day. Most of users use the 802.11g standard
in their indoor environment and they enjoy their connection on
the Internet. In order to satisfy the user's demands, this
connection should always be reliable and stable. That is why
802.11g has mechanisms to achieve this goal. In this thesis we
will analyze the mechanisms of digital modulation adaptivity
and Forward Error Correction adaptivity in an indoor
environment depending on the coverage conditions of the
channel. Based on coverage measurements and channel
conditions in different scenarios (including a real indoor
experiment) we will record the RSSI's (Received Sign al
Strength Indicator) and the Throughput's thresholds where we
can locate the change of the modulation mode and the change of
FEC in 802.11g networks. Afterwards, by setting a desirable
level of service (Quality of Service, QoS) and knowing the fore
mentioned thresholds we will recommend a new topology by
using one more access point. For the indoor experiment we used
the open source programs inSSIder and Netstress and for the
simulation we used Matlab.
Index Terms—802.11g ; Throughput ; RSSI ; BER; QoS;
BPSK;QPSK;QAM;OFDM;FEC
I.INTRODUCTION
In the last decades the need for a better quality of service in
Wlan systems increases constantly. Many devices such as
mobile phones, tablets and other devices are able to be
connected wireless to the internet. In order to establish that
kind of connection we create the 802.11 Wi-Fi protocol. One
of the variations of 802.11 protocol is the 802.11g (f0=2.4
GHz).At the present, the Wi-Fi and the usage of 802.11g
protocol is widespread. The Wi-Fi is applicable for business,
education and home environments, that is why it is so
popular.
Although the 802.11 is a protocol that provides easy
connectivity to the user, that type of connectivity is not always
reliable and stable. The Wi-Fi uses the air as a medium to
communicate with the devices via electromagnetic signals.
The electromagnetic signal has to overcome the conditions of
the channel, which influence the channel propagation. The
channel conditions are variable. The radio channel has severe
delay spread due to multipath propagation. The delay spread
causes "Inter Symbol Interference"(ISI), which influences the
throughput (data rate) [1],[2].Also extra neighboring
sources
that transmit in the same or adjoining channel cause inter-
symbol interference. Another factor that influences the
propagation is the SNR (Signal to Noise Ratio) problem that
occurs due to the distance between transmitter and receiver
and also due to the non-line of sight connection. Therefore,
channel estimation is very important for finding suitable
modulation and coding schemes.
The different modulation schemes such as BPSK (Binary
Phase Shift Keying), QPSK (Quadrature Phase Shift Keying)
and QAM (Quadrature Amplitude Modulation) with different
encoding rates such as 1/2, 2/3, 3/4 are the solutions for these
problems. By using these mechanisms we achieve better
values of Bit Error Rate (BER) and so our transmitted
information arrives with safety to the node(end user).Another
mechanism that we use is the OFDM(Orthogonal Frequency
Division Multiplexing). OFDM is based in inverse Fourier
transform and is a mechanism that reduces the phenomenon
of interference from multipath and neighboring channels. As
we know in the field of communications, there is always a
tradeoff. In that case, the profit is a more stable channel and
the loss is that the throughput (data rate) decreases rapidly
.The user also realizes that the throughput is sharply
decreased. However, the user demands higher speed and so
higher throughput .Users always demand higher quality of
service and therefore we should find a way to provide that. As
we understand these parameters are interrelated. Our goal is
to find where we should change a modulation and encoding
scheme in order to have better Quality of Service (QoS).
In this paper we will analyze the mechanisms of modulation
schemes and encoding rate and more specifically the
adaptivity of those two mechanisms in a wireless channel in
different scenarios. Also , we will cite a real word scenario
experiment where we will study our measurements that have
been selected from an indoor environment (indoor
experiment).Nevertheless , we proceed to a simulation of an
802.11g channel by using Matlab and we compare our
simulation results to our experimental results. In addition, we
use the IEEE 802.11a 1999 specifications to compare them
with our experimental results .Finally, we use another AP in
our experiment so we can achieve a better quality of service
for the user, which is our goal.
II.A THEORITICAL APPROACH
A.Modulation schemes
As we fore mentioned the wireless channel, that we use, is an
analog medium. Over this channel we have to send analog
waveforms. In order to achieve that, the digital modulator at
the transmitter has to convert the digital data, which is
produced from the source, to analog waveforms. The receiver
is responsible for recovering the bits from the received
Wi-Fi 802.11g: Adaptivity of modulation mode and
encoding rate for an improved Quality of Service
(January 2015)
Xevgenis M. Author, Postgraduate Student, Kingston University of London
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waveform by using the digital demodulator. The type of
modulation that we use determines if the analog waveform
represents one bit or a group of bits. By choosing a
modulation scheme in a wireless system, we determine the
bandwidth and the energy that we want to use in order to
transmit as much information as possible over the channel
and assuring a certain transmission quality (BER).There are
two basic criteria that we should consider before choosing a
modulation mode:
-The spectrum efficiency of the modulation mode should be
as high as possible. We can accomplish that by using a
"higher order" modulation mode, so we can transmit many
data bits with each symbol.
- The interference from adjacent channel and from multipath
propagation must be small. In addition, the analog signal
must be filtered before the transmission.
-The sensitivity with respect to noise should be very small. By
using a low order modulation the waveforms of the alphabet
are largest.
- Robustness with respect to delay and Doppler dispersion
should be as large as possible. The signal that we transmit
should be filtered as little as possible because filtering creates
more delay and dispersion.
- Waveforms should be easy to generate with hardware that is
easy to produce and it is highly energy efficient. That means
that the hardware should be able to generate the necessary
waveforms.
Many of the above criteria are contradictory. So considering
the above criteria we should choose a modulation scheme
according to the requirements of our system and application
[3].
B.Modulations schemes and Constellation diagrams
The binary modulation BPSK is the simplest because we can
represent +1-bit value with one specific waveform and -1-
bit value with a different waveform. In this modulation
scheme the carrier phase is shifted by ±π/2. In BPSK the
number of bits is equal to the number of symbols.
Figure 1. Constellation diagram BPSK
A Quadrature-Phase Shift Keying (QPSK)-modulated signal
is a Pulse Amplitude Modulation. The signal carries 1bit per
symbol interval on both the in-phase and quadrature-phase
component. The QPSK is twice more efficient than BPSK.
The reason is that, both the in-phase and the quadrature-
phase components are exploited for the transmission of
information. However, the signal shows strong envelope
fluctuations.
Figure 2. Constellation diagram QPSK
Higher Order QAM transmits multiple bits in both the in-
phase and the quadrature-phase component .It does so by
sending a signal with positive or negative polarity, as well as
multiple amplitude levels, on each component [3].
Figure 3. Constellation diagram 16QAM
Figure 4. Constellation diagram 64QAM
C.Encoding Rate
The convolutional codes that we use, can give us a specific
subset of coding rates, like Rc = 1/2, 1/3, 1/4. The easiest
way, which we use for the adaption of encoding rate, is by
structuring a code that has a rate lower than the desired.
Certain bits of the coded sequence are excused from the
transmission. Considering that, the code includes
considerable redundancy that is similar to the loss of code-
bits due to fading in the physical layer. Therefore it is not a
problem. In this situation it is required that the "punctured"
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bits are appropriately distributed throughout the code-word,
so that not all information about a certain bit is loosed.
A basic problem that we face with the encoding is the
reduction in spectral efficiency. Considering that we have to
transmit more bits, we need more bandwidth as we add check
bits. We can control the dimensions of this problem by using
higher order modulation schemes. The higher order
modulation schemes allow the transmission of more bits with
the usage of the same bandwidth. Finally, we assume that
modulation and encoding are designed as a "joint process".
Their combination gives us the result that we search for [3].
Table 1. 802.11a-1999 [4]
The above table displays the change of modulation mode and
coding rate according to the change of the actual throughput
(Data rate in Mbits/s) that ends up to the user. This table is
very important and helpful for our study because we will
compare our experimental and simulation results with the
content of that table, in order to realize when and how the
modulation scheme and the encoding rate change.
III. AN OVERVIEW OF THE SIMULATED SYSTEM
A.Introduction to our Simulink model
In this section we will proceed to the simulation of the
wireless channel. The simulation will help us to understand
the propagation of the signal from the source until the
destination where we receive the information. We will run a
few tests with deferent modulation schemes and encoding
rates in different scenarios. These scenarios differ in the field
of noise. Considering that the ultimate goal of 802.11g is to
maintain a reliable and stable connection, the factor that
concerns us is the BER (Bit-Error Rate).The flow chart below
displays an overview of the simulated system.
Figure 5. Simplified simulation diagram
As we fore mentioned we will run a few simulation tests in
order to realize how the electromagnetic signal changes. The
modulation schemes that we use are: BPSK with encoding
rate 1/2 , BPSK with encoding rate 3/4 ,QPSK with encoding
rate 1/2 ,QPSK with encoding rate 3/4, 16 QAM with
encoding rate 1/2 ,16 QAM with encoding rate 3/4 ,64 QAM
with encoding rate 2/3 and 64 QAM with encoding rate 3/4.It
is very important to understand the behavior of the signal
with the above modulation schemes and encoding rate with
different values of SNR. The value of SNR represents the
field of noise. Before we begin our simulation we should
make clear that as the SNR value decreases the noise
increases. It is important to mention that our simulation
model is built according to the specifications of IEEE 802.11
g.
Based on our experimental results, we will use the values of
SNR that we measured to our simulation model and we will
run the simulation to find the value of BER. Based on the
values of BER we will order the modulation schemes and the
encoding rates according to their robustness. As we evaluate
the performance of an indoor 802.11g channel we took
samples of SNR when we have non-line of site
communication and when we have an interfere signal. We
used the channel 13 in our access point and here are the
results of SNR in different degrees and meters.
Table 2. Calculated SNR
degrees 1
m
2m 3m 4m 5m 6m 7m 8m
157 - - - - 7.46 11.55 7.34 11.98
180 - - - - 22.32 15.24 13.52 2.95
202 - - - - 17.37 18.31 - -
315 - 14.97 11.96 - - - - -
In order to calculate the Signal to Noise ratio we use the
following type :
SNR(dB)=Preceived(dBm) - Pinterference(dBm) (1)
B.ResultsTable 3. BER in deferent SNR
values
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C.Discussion
The table above displays the BER value for each modulation
and encoding schemes in different values of SNR. According
to the results from our simulation, we can realize that the
BPSK modulation with encoding rate 1/2 is the most robust
scheme. The way that we have sorted the modulations
schemes and the encoding rates reflects the order from the
most robust combination to the least robust combination.
Based on the Table 1 we realize that the throughput is
influenced from the combination of modulation and encoding
rate. So the connection between the node and the access point
is based in channel estimation. According to the SNR value
and in addition, the BER, the connection is influenced and
therefore the combination of modulation and encoding rate
changes ,in order to have a reliable and stable connection. At
this point we can realize the adaptivity of modulation and
encoding rate according to the channel estimation.
As we fore mentioned according to the channel estimation the
access point and the node agree to the combination of
modulation and encoding rate that they use. It is very
important for us to realize where the change happens.
Therefore we set a BER threshold, which is set to 10-5
[5]. We
compare the BER values to our BER threshold and we can
locate where the change of modulation and encoding rate
takes place. If BER ≥ BERthreshold the modulation and the
encoding rate changes. However, when BER<BERthreshold the
modulation and the encoding rate does not change. Also,
when the BER value reaches the 0.5 we assume that we do
not have connection.
IV. INDOOR EXPERIMENT
A.Introduction to our indoor experiment
In this section we proceed to a real world experiment. The
ultimate goal of our experiment is to study the performance of
an indoor channel, which uses 802.11g protocol. We will
examine how and where the modulation mode and encoding
rate change according to the conditions of the channel, in order to
have a stable and reliable connection. To achieve our
experiment we use a HUAWEI Echolife HG520c access point
that we configure to transmit in 802.11g mode. We choose
the channel 13 because in that channel we do not have many
interfere signals. Assuming that the signals are transmitted
orthogonally the only interference that we have is by access
points that transmit in the same channel. We use the insider
[6] program to measure the signals that our NIC receives.
Furthermore, we use the Netstress [7] program to measure the
throughput that our NIC receives. The inSSIder and the
Netstress are open source programs. Our NIC is a Realtek
RTL8188CE Wireless LAN 802.11n COMBO PCI-E NIC.
Furthermore, we divide our indoor environment into sections
according to meters and degrees from our access point in
order to make a radio coverage of our environment. In that
way we cover all the possible points that the node can be. In
addition we calculate the signal that our NIC receives and in
that way we calculate the interferences from other access
point that transmit to the same channel. As our measurements
are in dBms we calculate the Signal to Noise ratio in Table 2
BER 2.95
dB
7.34
dB
7.468
dB
11.5
dB
11.961
dB
11.979
dB
13.524
dB
14.968
dB
15.243
dB
17.37
dB
18.3
dB
22.3
dB
BPSK
1/2
0 0 0 0 0 0 0 0 0 0 0 0
BPSK
3/4
0.0007 0 0 0 0 0 0 0 0 0 0 0
QPSK
1/2
0.13 0 0 0 0 0 0 0 0 0 0 0
QPSK
3/4
0.44 0.02 0.016 0 0 0 0 0 0 0 0 0
16QAM
1/2
0.4 0.02 0.016 0 0 0 0 0 0 0 0 0
16QAM
3/4
0.49 0.34 0.33 0.009 0.0045 0.0043 0.0002 0 0 0 0 0
64QAM
2/3
0.5 0.48 0.48 0.32 0.27 0.27 0.116 0.027 0.019 0.0005 0 0
64QAM
3/4
0.5 0.5 0.5 0.4 0.38 0.38 0.254 0.113 0.09 0.008 0.002 0
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by the type (1).For the previous procedure we use the
inSSIder. However, we calculate our throughput in Mbps by
using the Netstress. To accomplish these measurements we
connect our desktop computer with our access point via
Ethernet and then we transmit and receive TCP frames from
our laptop to our desktop. We use only TCP with MTU size
1500 bytes. Finishing with our experiment we gather our
measurements and we create diagrams in order to evaluate
our channel's performance.
B.Experimental results
In this part we gather our measurements and we create
diagrams. Below we display two diagrams, each diagram
refers to the type of propagation that we have. The first
diagram refers to line of sight propagation (LOS) and the
second refers to non-line of sight propagation (NLOS).
Diagram 1. Line of sight propagation
The diagram above shows us the throughput that our NIC
detects, according to the meters and degrees that we stand.
The lines that are colored symbolize the degrees that we are
located. In this diagram we have line of sight propagation.
The diagram below displays in the same way, the throughput
that we detect in non-line of sight propagation.
Diagram 2. Non-line of sight propagation
C.Discussion
As we fore mentioned the throughput that we receive depends
on the conditions of the channel. However, we can realize
that our measurements from our experiment differ from those
that we gather from our simulation. The fact that we have this
difference is because we measure a real channel performance
in an indoor environment. That is why we can accept the fact
that when we have line of sight propagation and we are
located 90 degrees and 1 meter away from our access point
we have 22Mbps throughput.
Nevertheless, it is clear that we have a better channel
performance when we have line of sight propagation than
when we have non-line of sight propagation. Based on our
measurements and on our Table 1 we can locate what type of
modulation and encoding rate we use each time. Combining
our measurements and the Table1we can also locate where
the modulation mode and the encoding rate changes. Now we
can realize the adaptivity of modulation and encoding
schemes in order to have a stable and reliable connection.
The node realizes that the throughput decreases as it moves
away from the access point and that fact influences his data
rate. Also, in some situations the connection drops and we
have no service. In order to have a stable and reliable
connection and furthermore a better Quality of service we
place another same access point with the same configuration
at the point that we have low throughput. We decide to place
our second access point 202 degrees and 5 meters away from
the first access point. Then we divide our area into sections
and we set our center at the point of the second access point.
Then we repeat our experiment and we create diagrams with
our extracted measurements.
Diagram 3. Access Point 2 (LOS)
Considering that we place the second access point in a
different place of our indoor environment it is reasonable to
have different measurements. Now we cover a larger section
when we have line of site propagation as we can see from the
diagram above.
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Diagram 4. Access Point 2 (NLOS)
Nevertheless, the measurements that we have when we have
non-line of sight propagation are taken when we are 1 meter
away from our second access point. The 45 degrees of the
second access point match to the 202 degrees of the first
access point that we use. So the 202 degrees and 4 meters
point of the first access point matches to the 45 degrees and 1
meter point of the second access point. That is a detail that
we will exploit by using the Handover mechanism in order to
achieve a better channel performance and a better Quality of
service.
V. CONCLUSIONS
Finishing with our current study we end up with conclusions.
Firstly, it is clear that the combination of modulation schemes
and the encoding rates is determined by the channel
characteristics. Also we achieved to realize how and when we
have changes in the modulation mode and in the encoding
rate according to the specification and according to our
measurements. We also made clear how the adaptivity of the
modulation mode and encoding rate influences the node and
how we can achieve better Quality of Service .Furthermore,
we saw the difference between simulation and experiment
and we were able to make a channel estimation.
REFERENCES
[1] K. Deok Soo, etal, "Performance analysis of OFDM system
based on IEEE 802.11a", Int. Tech. Conf. on Circuits, Systems,
Computers and Communications, July, 2002.
[2] H. Kyung Son and H. Soo Lee, "Performance analysis of
802.1 la WLAN in real indoor environments", IEEE Ant. &
Prop. Society Int. Symposium, Jun, 2003.
[3] Wireless Communications, Second Edition Andreas F. Molisch , Fellow,
IEEE
University of Southern California, USA
[4] Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY)
specifications
High-speed Physical Layer in the 5 GHz Band, IEEE Std 802.11a-1999
[5] A QoS-based Rate Adaptation Strategy for IEEE a/b/g
PHY Schemes using IEEE 802.11e in Ad-hoc Networks
[6] InSSIder. http://inssider.en.softonic.com/
[7] Netstress. http://nutsaboutnets.com/netstress/
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Diagram 4. Access Point 2 (NLOS)
Nevertheless, the measurements that we have when we have
non-line of sight propagation are taken when we are 1 meter
away from our second access point. The 45 degrees of the
second access point match to the 202 degrees of the first
access point that we use. So the 202 degrees and 4 meters
point of the first access point matches to the 45 degrees and 1
meter point of the second access point. That is a detail that
we will exploit by using the Handover mechanism in order to
achieve a better channel performance and a better Quality of
service.
V. CONCLUSIONS
Finishing with our current study we end up with conclusions.
Firstly, it is clear that the combination of modulation schemes
and the encoding rates is determined by the channel
characteristics. Also we achieved to realize how and when we
have changes in the modulation mode and in the encoding
rate according to the specification and according to our
measurements. We also made clear how the adaptivity of the
modulation mode and encoding rate influences the node and
how we can achieve better Quality of Service .Furthermore,
we saw the difference between simulation and experiment
and we were able to make a channel estimation.
REFERENCES
[1] K. Deok Soo, etal, "Performance analysis of OFDM system
based on IEEE 802.11a", Int. Tech. Conf. on Circuits, Systems,
Computers and Communications, July, 2002.
[2] H. Kyung Son and H. Soo Lee, "Performance analysis of
802.1 la WLAN in real indoor environments", IEEE Ant. &
Prop. Society Int. Symposium, Jun, 2003.
[3] Wireless Communications, Second Edition Andreas F. Molisch , Fellow,
IEEE
University of Southern California, USA
[4] Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY)
specifications
High-speed Physical Layer in the 5 GHz Band, IEEE Std 802.11a-1999
[5] A QoS-based Rate Adaptation Strategy for IEEE a/b/g
PHY Schemes using IEEE 802.11e in Ad-hoc Networks
[6] InSSIder. http://inssider.en.softonic.com/
[7] Netstress. http://nutsaboutnets.com/netstress/
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