This document provides an overview, learning objectives, and content for an Air Interface-Modulation (AI-MOD) module. The module covers basic modulation concepts like amplitude modulation and frequency modulation. It then focuses on frequency modulation techniques used for mobile radio communications, including different types of shift keying and constant envelope modulation. The document lists industry contributors who provided support and materials for the module and individual contributors who helped develop the curriculum content.
Regulatory approaches in the femto environmentArief Gunawan
The document discusses various regulatory approaches for femtocells. It covers standards and implementation, regulatory issues around human protection and interconnection charging. It also addresses ownership and provider models, use of shared or exclusive frequency bands, and other considerations like roaming and fraud. Regulators may take a class licensing approach and exempt femtocells from reporting requirements due to their low power, similar to WiFi access points. Charging approaches could depend on who provides the femtocell access point functionality.
VOLTE (Voice over LTE) is a mobile technology that allows users to make voice calls over an LTE data network. It provides higher voice capacity and quality compared to 3G networks. The first commercial VOLTE services launched in 2014 in Singapore and other parts of Asia and the world. VOLTE services are now widely available and mark an important step towards fully integrated 4G/LTE networks.
This document provides an overview of LTE and LTE-Advanced mobile communication standards. It discusses the history and development of LTE beginning in 2004. The benefits of LTE include higher bandwidth, data rates, and efficiency. The network architecture of LTE includes evolved Node Bs, serving gateways, packet data network gateways, and mobility management entities. Key technologies that enable LTE are OFDMA, MIMO, and SC-FDMA. LTE-Advanced was standardized in 2011 and first implemented commercially in 2012, providing further enhanced capabilities over LTE.
LTE Advanced is an enhancement of the LTE mobile communication standard that aims to improve spectrum efficiency, flexibility, and throughput. Key features of LTE Advanced include support for wider bandwidths up to 100MHz, advanced MIMO technologies with up to 8 antenna ports, improved cell edge performance using Coordinated Multi-Point transmission, and integration of relay nodes to enhance coverage. LTE Advanced is designed to meet the ITU requirements for 4G networks by providing peak data rates of at least 1 Gbps for high mobility communication.
Ec8394 - Analog and Digital Communication unit IManojKumar791621
The document describes the syllabus for the course EC8394 Analog and Digital Communication. The course is divided into 5 units that cover topics such as analog communication techniques including amplitude, frequency, and phase modulation, pulse and data communication, digital communication techniques like ASK, FSK, PSK, and source and error control coding. The course objectives are to understand analog and digital communication techniques, learn data and pulse communication, get familiar with source and error coding, and gain knowledge of multi-user radio communication.
This document discusses AM radio transmission and reception. It describes how AM radio works by taking an input signal like audio and modulating a carrier wave to transmit it through the air. It explains that modulation involves modifying a high frequency carrier signal with a low frequency audio signal. It also discusses how early radio receivers worked by tuning different radio frequency channels, but that modern radios use the superheterodyne principle to convert signals to a fixed intermediate frequency for better selectivity.
Introduction for telecommunication technology basic terms and concepts.
Referring the wikipedia, Slideshare and lecture note of Fudan university.
I got a reference documents from Google.
Regulatory approaches in the femto environmentArief Gunawan
The document discusses various regulatory approaches for femtocells. It covers standards and implementation, regulatory issues around human protection and interconnection charging. It also addresses ownership and provider models, use of shared or exclusive frequency bands, and other considerations like roaming and fraud. Regulators may take a class licensing approach and exempt femtocells from reporting requirements due to their low power, similar to WiFi access points. Charging approaches could depend on who provides the femtocell access point functionality.
VOLTE (Voice over LTE) is a mobile technology that allows users to make voice calls over an LTE data network. It provides higher voice capacity and quality compared to 3G networks. The first commercial VOLTE services launched in 2014 in Singapore and other parts of Asia and the world. VOLTE services are now widely available and mark an important step towards fully integrated 4G/LTE networks.
This document provides an overview of LTE and LTE-Advanced mobile communication standards. It discusses the history and development of LTE beginning in 2004. The benefits of LTE include higher bandwidth, data rates, and efficiency. The network architecture of LTE includes evolved Node Bs, serving gateways, packet data network gateways, and mobility management entities. Key technologies that enable LTE are OFDMA, MIMO, and SC-FDMA. LTE-Advanced was standardized in 2011 and first implemented commercially in 2012, providing further enhanced capabilities over LTE.
LTE Advanced is an enhancement of the LTE mobile communication standard that aims to improve spectrum efficiency, flexibility, and throughput. Key features of LTE Advanced include support for wider bandwidths up to 100MHz, advanced MIMO technologies with up to 8 antenna ports, improved cell edge performance using Coordinated Multi-Point transmission, and integration of relay nodes to enhance coverage. LTE Advanced is designed to meet the ITU requirements for 4G networks by providing peak data rates of at least 1 Gbps for high mobility communication.
Ec8394 - Analog and Digital Communication unit IManojKumar791621
The document describes the syllabus for the course EC8394 Analog and Digital Communication. The course is divided into 5 units that cover topics such as analog communication techniques including amplitude, frequency, and phase modulation, pulse and data communication, digital communication techniques like ASK, FSK, PSK, and source and error control coding. The course objectives are to understand analog and digital communication techniques, learn data and pulse communication, get familiar with source and error coding, and gain knowledge of multi-user radio communication.
This document discusses AM radio transmission and reception. It describes how AM radio works by taking an input signal like audio and modulating a carrier wave to transmit it through the air. It explains that modulation involves modifying a high frequency carrier signal with a low frequency audio signal. It also discusses how early radio receivers worked by tuning different radio frequency channels, but that modern radios use the superheterodyne principle to convert signals to a fixed intermediate frequency for better selectivity.
Introduction for telecommunication technology basic terms and concepts.
Referring the wikipedia, Slideshare and lecture note of Fudan university.
I got a reference documents from Google.
This document discusses considerations for establishing long distance WiFi links using directional antennas. It covers improving the power budget through increasing antenna gain via careful alignment techniques. When the receiving end is not visible, it recommends using a GPS, compass, and software to calculate the direction without direct line of sight. It also discusses modifying the media access method to eliminate acknowledgments and increase throughput over long distances.
Hnc2014 wan interconnection huawei new-generation ip long haul microwave solu...eieiswe
Huawei's new-generation IP long haul microwave solution provides more flexibility, efficiency and longer transmission distances compared to previous solutions. It covers transmission over sea, land and sky via microwave channels. The document discusses challenges in developing long haul microwave technologies and how Huawei's solution addresses issues like difficult terrains, harsh environments and high capacity needs. It provides case studies of the solution's deployment for customers in scenarios such as remote mountains, islands, deserts and reconstructing networks.
This document outlines the key steps and considerations for planning and budgeting a wireless network implementation project. It discusses performing a viability study of the location, developing an implementation plan including network topology and radio simulations, selecting appropriate equipment, obtaining necessary licenses and permits, budgeting for hardware, human resources, and other expenses, importing any needed equipment, and ensuring quality assurance during the implementation phase. The overall message is that a realistic and well-planned budget that accounts for all costs is essential to a successful wireless network project.
Basic of 3 g technologies (digi lab_project).pptx [repaired]Shahrin Ahammad
The document provides an overview of 3G standards and the radio access network architecture. It discusses the reasons for switching from 2G to 3G technologies, including higher data rates and improved security. It then describes the components of the UMTS network architecture, including user equipment, Node B base stations, radio network controllers, mobile switching centers, and connections to external networks. The document also compares 2G and 3G network structures.
LTE Advanced carrier aggregation, it is possible to utilise more than one carrier and in this way increase the overall transmission bandwidth. These channels or carriers may be in contiguous elements of the spectrum, or they may be in different bands.
LTE & Wi-Fi: Options for Uniting Them for a Better User ExperienceAricent
Most national governments consider the radio spectrum a valuable national resource and heavily regulate its commercial use. Governments typically auction off licenses for the right to transmit over a portion of the spectrum, which can be very expensive. The traditional business model for cellular
carriers is based on access to this licensed business has coalesced worldwide around a single 4th generation (4G) radio technology standard called Long Term Evolution, commonly referred to as LTE.
LTE is an emerging mobile network technology that offers faster data speeds and increased network capacity compared to 3G. It is being widely adopted internationally, with over 80 commercial LTE networks expected by the end of 2012. Early country adopters include Sweden, Norway, and South Korea. Mobile operators are investing heavily in LTE networks to handle rapidly growing mobile data traffic and meet consumer demand for bandwidth-intensive applications. LTE is available in different spectrum bands depending on the country and is projected to accelerate the growth of mobile broadband subscribers and data usage worldwide.
Industry-supported field trials are already demonstrating the viability of many of the
technical concepts in LTE-Advanced. The approach is to increase data rates for all
users, bring more out of small cells, dynamically adapt to network load and use of
more carriers for more speeds. Also there will be unprecedented ecosystem of handset-manufacturer, software-developers and chip-designers that will support this intelligent
network.
In this presentation we will briefly discuss principle technologies that are being adopted
in LTE-Advanced. We will understand the basics of the technologies that are under
developmental stages and look if we can contribute to their future enhancements.
This document provides an overview of TD-LTE technology. It discusses why TD-LTE is relevant for operators, Nokia Siemens Networks' involvement and references in TD-LTE, the TD-LTE development progress, and key aspects of the TD-LTE technology such as frame structure, uplink/downlink configurations, and coexistence with other standards.
This document discusses Long Term Evolution (LTE) and LTE Advanced technologies. It provides information on key features of LTE Advanced such as improved peak data rates up to 1 Gbps, increased spectrum efficiency up to 30 bps/Hz, and enhanced capabilities to support advanced applications and services. The document also discusses technologies enabling LTE Advanced like OFDMA and MIMO as well as differences between wireless generations and advantages/disadvantages of LTE networks.
LTE-Advanced is an evolution of LTE that enables faster speeds and improved performance. It utilizes carrier aggregation to combine multiple component carriers to increase bandwidth up to 100MHz. It enhances MIMO technology to support up to 8 antenna pairs for downloads and 4 pairs for uploads. It also introduces relay nodes to extend network coverage and capacity to cell edges. These new technologies allow LTE-Advanced to achieve peak download speeds of 1Gbps and upload speeds of 500Mbps, providing a true 4G experience.
This seminar will provide the basics of this fascinating technology. After attending this seminar you will understand OFDM-principles,
including SC-FDMA as the transmission scheme of choice for the LTE uplink. Multiple antenna technology (MIMO) is a fundamental
part of LTE and its impact on the design of device and network architecture will be explained. Further LTE-related physical layer
aspects such as channel structure and cell search will be presented with an overview of the LTE protocol structure.
The second part of the seminar provides an overview of the evolution in LTE towards 3GPP specification Release 9 and 10. This
includes features and methods for location based services like GNSS support or time delay measurements and the concept of
multimedia broadcast. Finally, we’ll introduce the main features of LTE-Advanced (3GPP Release-10) including carrier aggregation for
a larger bandwidth and backbone network aspects like self-organizing networks and relaying concepts.
The basic components of a communication system are information source, input transducer, transmitter, communication channel, receiver, output transducer, and destination.........
The document discusses different types of microwave equipment, including trunk microwave equipment, all outdoor microwave equipment, and split-mount microwave equipment. Split-mount microwave equipment has the RF unit located outdoors in an outdoor unit connected via an IF cable to an indoor unit containing the IF, signal processing, and multiplexing/demultiplexing units. This equipment type is widely used due to its easy installation and maintenance capabilities. The document also describes microwave antenna types and adjustment, as well as specifications for outdoor and indoor units.
IRJET- Reducing Papr and Channel Equalisation in OFDMIRJET Journal
This document discusses reducing peak-to-average power ratio (PAPR) and channel equalization in orthogonal frequency division multiplexing (OFDM). It begins with an introduction to OFDM and the problem of high PAPR. It then reviews existing PAPR reduction techniques and their limitations. The proposed system uses a moving average filter and stationary wavelet transform to reduce PAPR, along with machine learning. It transmits the OFDM signal over a channel. At the receiver, cyclic prefix removal, fast Fourier transform, channel estimation, and channel equalization are performed before demodulation and decoding. The document evaluates PAPR reduction using complementary cumulative distribution function analysis.
Wireless LANs (WLANs) allow computers to connect to a local network using radio transmissions rather than wires. They use technologies like Wi-Fi that transmit data over the 2.4 GHz or 5 GHz radio bands. WLANs provide mobility within a limited range and can be used to avoid installing network cables. However, they have less range than wired networks and can experience interference from other devices.
This document provides an overview of digital microwave communication principles and concepts. It begins with an introduction explaining that the course is intended to educate engineers on the basics of digital microwave communications. It then outlines the learning objectives, which include explaining the concepts, components, networking modes, propagation principles, anti-fading technologies, and design of microwave transmission links. The document also includes sections on the history and development of microwave communication, definitions of key terms, modulation techniques, frame structures, equipment types, and antenna technology.
Microwave communication by abhishek mahajanabhimaha09
This document discusses microwave communication and digital microwave communication systems. It defines microwave frequencies as ranging from 300 MHz to 300 GHz, but focuses on 3 GHz to 30 GHz for communication. Digital microwave communication modulates a digital baseband signal onto an intermediate frequency or directly onto a microwave carrier using techniques like PSK, QAM, ASK, and FSK. It describes the development of analog and digital microwave systems over time with increasing transmission capacities. It also discusses different types of digital microwave stations and relay stations.
Lecture 1 introduction to communication systemsavocado1111
This document provides an introduction to communication systems. It defines communication as the exchange of information from a source to a destination. An electronic communication system is defined as the whole mechanism of sending, receiving, and processing information electronically from source to destination. The main objectives of a communication system are to produce an accurate replica of the transmitted information and to transfer information between two or more points with minimum error. The basic elements of a communication system are an information source, transmitter, channel, receiver, and destination. Modulation is the process of modifying a carrier wave systematically by a modulating signal to make it suitable for transmission through a channel. There are two main types of modulation: analog modulation and digital modulation.
This document provides an overview of baseband radio transmission and digital signal processing techniques. It describes the key functions performed in baseband processing including analog to digital conversion, digital speech coding, channel coding and error correction, modulation and demodulation, multiplexing and multiple access, and digital signal processing. Standardization bodies and industry contributors that support wireless technologies are also acknowledged.
iaetsd Software defined am transmitter using vhdlIaetsd Iaetsd
This document discusses the design and implementation of an amplitude modulation (AM) software defined radio transmitter using an FPGA. It begins with an abstract describing the goals of the project. It then provides an overview of the system design, including discussion of the individual components like the microphone, analog to digital converter, digital to analog converter, carrier frequency generator, and antenna. It describes how these components will be implemented on the FPGA, including using behavioral modeling with VHDL. It also discusses designing filters and modulation/demodulation circuits. The overall summary is that this document outlines the goals and high-level system design for creating an AM transmitter using an FPGA that can transmit an audio signal by digitally modulating a carrier frequency.
This document discusses considerations for establishing long distance WiFi links using directional antennas. It covers improving the power budget through increasing antenna gain via careful alignment techniques. When the receiving end is not visible, it recommends using a GPS, compass, and software to calculate the direction without direct line of sight. It also discusses modifying the media access method to eliminate acknowledgments and increase throughput over long distances.
Hnc2014 wan interconnection huawei new-generation ip long haul microwave solu...eieiswe
Huawei's new-generation IP long haul microwave solution provides more flexibility, efficiency and longer transmission distances compared to previous solutions. It covers transmission over sea, land and sky via microwave channels. The document discusses challenges in developing long haul microwave technologies and how Huawei's solution addresses issues like difficult terrains, harsh environments and high capacity needs. It provides case studies of the solution's deployment for customers in scenarios such as remote mountains, islands, deserts and reconstructing networks.
This document outlines the key steps and considerations for planning and budgeting a wireless network implementation project. It discusses performing a viability study of the location, developing an implementation plan including network topology and radio simulations, selecting appropriate equipment, obtaining necessary licenses and permits, budgeting for hardware, human resources, and other expenses, importing any needed equipment, and ensuring quality assurance during the implementation phase. The overall message is that a realistic and well-planned budget that accounts for all costs is essential to a successful wireless network project.
Basic of 3 g technologies (digi lab_project).pptx [repaired]Shahrin Ahammad
The document provides an overview of 3G standards and the radio access network architecture. It discusses the reasons for switching from 2G to 3G technologies, including higher data rates and improved security. It then describes the components of the UMTS network architecture, including user equipment, Node B base stations, radio network controllers, mobile switching centers, and connections to external networks. The document also compares 2G and 3G network structures.
LTE Advanced carrier aggregation, it is possible to utilise more than one carrier and in this way increase the overall transmission bandwidth. These channels or carriers may be in contiguous elements of the spectrum, or they may be in different bands.
LTE & Wi-Fi: Options for Uniting Them for a Better User ExperienceAricent
Most national governments consider the radio spectrum a valuable national resource and heavily regulate its commercial use. Governments typically auction off licenses for the right to transmit over a portion of the spectrum, which can be very expensive. The traditional business model for cellular
carriers is based on access to this licensed business has coalesced worldwide around a single 4th generation (4G) radio technology standard called Long Term Evolution, commonly referred to as LTE.
LTE is an emerging mobile network technology that offers faster data speeds and increased network capacity compared to 3G. It is being widely adopted internationally, with over 80 commercial LTE networks expected by the end of 2012. Early country adopters include Sweden, Norway, and South Korea. Mobile operators are investing heavily in LTE networks to handle rapidly growing mobile data traffic and meet consumer demand for bandwidth-intensive applications. LTE is available in different spectrum bands depending on the country and is projected to accelerate the growth of mobile broadband subscribers and data usage worldwide.
Industry-supported field trials are already demonstrating the viability of many of the
technical concepts in LTE-Advanced. The approach is to increase data rates for all
users, bring more out of small cells, dynamically adapt to network load and use of
more carriers for more speeds. Also there will be unprecedented ecosystem of handset-manufacturer, software-developers and chip-designers that will support this intelligent
network.
In this presentation we will briefly discuss principle technologies that are being adopted
in LTE-Advanced. We will understand the basics of the technologies that are under
developmental stages and look if we can contribute to their future enhancements.
This document provides an overview of TD-LTE technology. It discusses why TD-LTE is relevant for operators, Nokia Siemens Networks' involvement and references in TD-LTE, the TD-LTE development progress, and key aspects of the TD-LTE technology such as frame structure, uplink/downlink configurations, and coexistence with other standards.
This document discusses Long Term Evolution (LTE) and LTE Advanced technologies. It provides information on key features of LTE Advanced such as improved peak data rates up to 1 Gbps, increased spectrum efficiency up to 30 bps/Hz, and enhanced capabilities to support advanced applications and services. The document also discusses technologies enabling LTE Advanced like OFDMA and MIMO as well as differences between wireless generations and advantages/disadvantages of LTE networks.
LTE-Advanced is an evolution of LTE that enables faster speeds and improved performance. It utilizes carrier aggregation to combine multiple component carriers to increase bandwidth up to 100MHz. It enhances MIMO technology to support up to 8 antenna pairs for downloads and 4 pairs for uploads. It also introduces relay nodes to extend network coverage and capacity to cell edges. These new technologies allow LTE-Advanced to achieve peak download speeds of 1Gbps and upload speeds of 500Mbps, providing a true 4G experience.
This seminar will provide the basics of this fascinating technology. After attending this seminar you will understand OFDM-principles,
including SC-FDMA as the transmission scheme of choice for the LTE uplink. Multiple antenna technology (MIMO) is a fundamental
part of LTE and its impact on the design of device and network architecture will be explained. Further LTE-related physical layer
aspects such as channel structure and cell search will be presented with an overview of the LTE protocol structure.
The second part of the seminar provides an overview of the evolution in LTE towards 3GPP specification Release 9 and 10. This
includes features and methods for location based services like GNSS support or time delay measurements and the concept of
multimedia broadcast. Finally, we’ll introduce the main features of LTE-Advanced (3GPP Release-10) including carrier aggregation for
a larger bandwidth and backbone network aspects like self-organizing networks and relaying concepts.
The basic components of a communication system are information source, input transducer, transmitter, communication channel, receiver, output transducer, and destination.........
The document discusses different types of microwave equipment, including trunk microwave equipment, all outdoor microwave equipment, and split-mount microwave equipment. Split-mount microwave equipment has the RF unit located outdoors in an outdoor unit connected via an IF cable to an indoor unit containing the IF, signal processing, and multiplexing/demultiplexing units. This equipment type is widely used due to its easy installation and maintenance capabilities. The document also describes microwave antenna types and adjustment, as well as specifications for outdoor and indoor units.
IRJET- Reducing Papr and Channel Equalisation in OFDMIRJET Journal
This document discusses reducing peak-to-average power ratio (PAPR) and channel equalization in orthogonal frequency division multiplexing (OFDM). It begins with an introduction to OFDM and the problem of high PAPR. It then reviews existing PAPR reduction techniques and their limitations. The proposed system uses a moving average filter and stationary wavelet transform to reduce PAPR, along with machine learning. It transmits the OFDM signal over a channel. At the receiver, cyclic prefix removal, fast Fourier transform, channel estimation, and channel equalization are performed before demodulation and decoding. The document evaluates PAPR reduction using complementary cumulative distribution function analysis.
Wireless LANs (WLANs) allow computers to connect to a local network using radio transmissions rather than wires. They use technologies like Wi-Fi that transmit data over the 2.4 GHz or 5 GHz radio bands. WLANs provide mobility within a limited range and can be used to avoid installing network cables. However, they have less range than wired networks and can experience interference from other devices.
This document provides an overview of digital microwave communication principles and concepts. It begins with an introduction explaining that the course is intended to educate engineers on the basics of digital microwave communications. It then outlines the learning objectives, which include explaining the concepts, components, networking modes, propagation principles, anti-fading technologies, and design of microwave transmission links. The document also includes sections on the history and development of microwave communication, definitions of key terms, modulation techniques, frame structures, equipment types, and antenna technology.
Microwave communication by abhishek mahajanabhimaha09
This document discusses microwave communication and digital microwave communication systems. It defines microwave frequencies as ranging from 300 MHz to 300 GHz, but focuses on 3 GHz to 30 GHz for communication. Digital microwave communication modulates a digital baseband signal onto an intermediate frequency or directly onto a microwave carrier using techniques like PSK, QAM, ASK, and FSK. It describes the development of analog and digital microwave systems over time with increasing transmission capacities. It also discusses different types of digital microwave stations and relay stations.
Lecture 1 introduction to communication systemsavocado1111
This document provides an introduction to communication systems. It defines communication as the exchange of information from a source to a destination. An electronic communication system is defined as the whole mechanism of sending, receiving, and processing information electronically from source to destination. The main objectives of a communication system are to produce an accurate replica of the transmitted information and to transfer information between two or more points with minimum error. The basic elements of a communication system are an information source, transmitter, channel, receiver, and destination. Modulation is the process of modifying a carrier wave systematically by a modulating signal to make it suitable for transmission through a channel. There are two main types of modulation: analog modulation and digital modulation.
This document provides an overview of baseband radio transmission and digital signal processing techniques. It describes the key functions performed in baseband processing including analog to digital conversion, digital speech coding, channel coding and error correction, modulation and demodulation, multiplexing and multiple access, and digital signal processing. Standardization bodies and industry contributors that support wireless technologies are also acknowledged.
iaetsd Software defined am transmitter using vhdlIaetsd Iaetsd
This document discusses the design and implementation of an amplitude modulation (AM) software defined radio transmitter using an FPGA. It begins with an abstract describing the goals of the project. It then provides an overview of the system design, including discussion of the individual components like the microphone, analog to digital converter, digital to analog converter, carrier frequency generator, and antenna. It describes how these components will be implemented on the FPGA, including using behavioral modeling with VHDL. It also discusses designing filters and modulation/demodulation circuits. The overall summary is that this document outlines the goals and high-level system design for creating an AM transmitter using an FPGA that can transmit an audio signal by digitally modulating a carrier frequency.
The document discusses the conceptual design and experimental setup of a Visible Light Communication system called VIDAS for transmitting traffic information to vehicles. VIDAS uses LED traffic lights to transmit data to onboard vehicle receivers via visible light modulation. Key components discussed include the multiple LED emitter source, PIN photodiode detector, front-end amplifier, direct sequence spread spectrum modulation, and considerations for noise and signal variation over distance. Experimental results showed VIDAS enabled reception of traffic information from 100m away and adaptation to changing signal strength as vehicles approached intersections.
This document provides information about radio frequency (RF) planning and optimization roles and responsibilities in a wireless network. It discusses the key performance indicators (KPIs) that RF planners and optimizers are responsible for maintaining to ensure adequate coverage, capacity, and network performance. The document also outlines training courses that cover topics like network planning procedures, site surveys, frequency planning, optimization features, and monitoring KPIs.
EFFECTS OF FILTERS ON THE PERFORMANCE OF DVB-T RECEIVERijwmn
Digital Video Broadcasting-Terrestrial (DVB-T) is an international standard for digital television
services. Orthogonal Frequency Division Multiplexing (OFDM) is the core of this technology. OFDM
based system like DVB-T can handle multipath fading and hence it can minimize Inter Symbol
Interference (ISI). DVB-T has some limitations too namely large dynamic range of the signals and
sensitivity to frequency error. In order to overcome these limitations DVB-T receivers should be optimally
designed. In this paper we address the issues related to optimal DVB-T receiver design. There of several
signal processing units in a DVB-T receiver. A low-pass filter is one of them. In this paper, we consider
some classic filters namely Butterworth, Chebyshev, and elliptic in the DVB-T receiver. The effects of
different filters on the performances of DVB-T receiver have been investigated and compared in this
paper under AWGN channel condition
A simulation study of wi max based communication system using deliberately cl...eSAT Journals
This document summarizes a study on reducing peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems using deliberate clipping. It begins with an introduction to WiMAX technology and OFDM. It then discusses the PAPR problem in OFDM systems and different techniques to reduce PAPR, including signal scrambling and signal distortion methods. It focuses on deliberate clipping as a simple method to limit PAPR by distorting the signal before amplification. The document presents a simulation of an OFDM system using deliberate clipping at the Nyquist sampling rate to investigate its effect on bit error rate performance compared to an unclipped system.
A simulation study of wi max based communication system using deliberately cl...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
This document provides an overview of orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) systems. It discusses the basic principles of OFDM, including signal representation and pulse shaping. It also compares single-carrier and multi-carrier modulation schemes. The document then describes the long-term evolution (LTE) architecture, including components like the eNodeB base station and the evolved packet core. It explains voice over LTE (VoLTE) technology and time-division duplexing used in TD-LTE systems.
Billions of people are watching valuable TV content and advertising on a daily basis.
Different distribution networks transport this content from the content owner to the
consumer. The consumer has the choice to receive a full set of TV channels from many
service providers, be it telco, cable, terrestrial or DTH operators.
This document provides an overview and specifications for Motorola's fixed point-to-point wireless bridge solutions, including the PTP 100, 200, 300, 400, 500, and 600 series. It describes the key technologies used, performance capabilities, frequency bands, product options, warranties, and accessories. The document is intended to help Motorola account teams and sales channels communicate the features and benefits of these wireless bridge solutions to customers.
Implementation of Algorithms For Multi-Channel Digital Monitoring ReceiverIOSR Journals
Abstract: Monitoring Receivers form an important constituent of the Electronic support. In Monitoring
Receiver we can monitor, demodulate or scan the multiple channels.
In this project, the Implementation of algorithm for multi channel digital monitoring receiver. The
implementation will carry out the channelization by the way of Digital down Converters (DDCs) and Digital
Base band Demodulation. The Intermediate Frequency (IF) at 10.7 MHz will be digitalized using Analog to
Digital Converter (ADC) with sampling frequency 52.5 MHz and further converted to Base band using DDCs.
Virtually all the digital receivers perform channel access using a DDC. The Base band data will be streamed to
the appropriate demodulators. Matlab Simulink will be used to simulate the logic modules before the
implementation. This system will be prototyped on an FPGA based COTS (Commercial-off-the-shelf)
development board. Xilinx System Generator will be used for the implementation of the algorithms.
Keywords: DDC, ADC, Digital Base band demodulation, IF, Monitoring Receiver.
This document discusses adaptive modulation and coding (AMC) techniques in wireless communications. It provides an introduction to AMC and describes how it allows matching modulation, coding, and other signal parameters to radio link conditions. The document then outlines the development roadmap for broadband wireless access (BWA) and WiMAX, including added support for mobility, advanced antennas, and modulation/coding schemes. It discusses the advantages of AMC in improving transmission rates and bit error rates by exploiting channel state information. Finally, it notes challenges around AMC being sensitive to measurement errors and delay in selecting the appropriate modulation.
Modulation techniques allow information to be transmitted over long distances by modulating a carrier signal. Analog techniques include AM, FM and PM and are used to transmit audio and video. Digital techniques like ASK, FSK and PSK convert information to digital before modulating the carrier. Both have advantages like efficient bandwidth use but analog is susceptible to noise and digital requires more complex equipment. Understanding the pros and cons of each technique is important for communication system design.
The tutorial is designed for all those readers who are planning or pursuing the CDMA course to make their career in this field. However, it is also meant for the common readers who simply want to understand − what is CDMA Technology?
multi standard multi-band receivers for wireless applicationsHossam Hassan
This document discusses multi-standard receivers for wireless applications. It outlines the motivation for multi-standard receivers to support modern wireless technologies. It then covers an overview of wireless communications and evolution, highlighting features of multi-carrier, multi-band, multi-standard and multi-mode systems. Challenges of multi-standard receivers are presented along with solutions like software defined radio. Key technology challenges of software defined radio include implementation and reconfigurability.
A DAS is a network of antennas connected by cable that provides wireless coverage inside buildings. DAS are needed for public safety to improve coverage and reliability for first responders. The benefits of a public safety DAS include 95% building coverage, high quality of service, and improved reliability. Proper DAS design is important to ensure adequate coverage levels are met based on standards from NFPA and IFC. Components like filtered repeaters, backup power, and antennas supporting all public safety frequencies are important. New FCC rules require registration of bi-directional amplifiers used on public safety networks.
This document summarizes Alvarion's BreezeACCESS VL, a flexible point-to-multipoint wireless broadband solution. It offers outdoor connectivity for various applications using frequencies between 4.9-5.875 GHz and 900 MHz. The solution provides a carrier-class outdoor link with security, capacity, and quality of service for data, voice, and video. It supports a wide range of subscriber units to meet different performance and cost needs.
The document provides an overview of optical transport networks (OTNs) as defined by ITU-T G.709. It describes the OTN layers including optical channel (OCh), optical multiplex section (OMS), optical transmission section (OTS), and optical channel transport unit (OTU). The OTU layer introduces forward error correction and a digital wrapper with overhead to manage digital functions. Client signals are adapted at the optical channel payload unit (OPU) layer and then mapped into the optical channel data unit (ODU) for transport over the OTN.
The document provides information about the Communication Engineering course offered at Karpagam Institute of Technology. It includes details about the 5 units that make up the course, their objectives and outcomes.
Unit I covers analog modulation techniques including amplitude modulation, angle modulation techniques like frequency and phase modulation, and their modulators and demodulators. It also discusses the advantages and disadvantages of different analog modulation methods.
The course aims to introduce students to various analog and digital modulation techniques, principles of information theory and coding, and digital communication techniques. Upon completion, students should be able to apply communication techniques, understand data and pulse communication, analyze source and error coding, and more.
This white paper discusses future technologies for fixed-mobile convergence including LTE and SAE. It defines fixed-mobile convergence as providing consistent services via any fixed or mobile access point. The paper describes the motivation for convergence including mobility and consistent services. It outlines the LTE/SAE introduction and technologies including the evolved packet core and all-IP architecture. Key aspects of LTE such as physical layer channels and protocols are also summarized. The purpose is to support an integrated network through the IP Multimedia Subsystem for high-speed mobile experiences comparable to fixed broadband.
This document provides an overview of 3GPP LTE technology. It discusses the evolution of 3GPP standards and the advancement needed for high data rates, including the use of OFDM(A) and SC-FDMA. It provides a brief introduction to LTE including its radio interface architecture, downlink and uplink transmissions, and cell search procedure. Relevant 3GPP specifications for LTE are also listed.
The document discusses the evolution of mobile network architectures from GSM to LTE and SAE. It introduces LTE and SAE, describing them as the radio access network and core network respectively for 3GPP's Evolved Packet System. It provides an overview of the SAE architecture, which includes the Evolved Packet Core and eUTRAN. The core network provides access to external networks and performs functions like QoS, security and mobility management, while the radio access network handles radio interface functions.
This document proposes a concatenated coding scheme with iterative decoding for a bit-shift channel. Specifically, it considers the serial concatenation of an outer error-correcting code and an inner modulation code, possibly preceded by an accumulator. It searches for optimal encoder mappings from an iterative decoding perspective for the inner code, which has been designed to correct single bit-shift errors and have large average power. This is important for inductively coupled channels, as the receiver gets its power from the received signal and the information should maximize the power transferred.
The document proposes LTE Release 10 and beyond (LTE-Advanced) as a candidate radio interface technology for IMT-Advanced. It provides an overview of 3GPP standardization activities, including LTE Release 8 and the work underway in 3GPP to develop LTE-Advanced to meet IMT-Advanced requirements. Key aspects of LTE-Advanced include utilizing carrier aggregation to support wider bandwidth up to 100MHz and advanced MIMO techniques with up to 8-layer transmission to achieve peak data rates of 1Gbps.
The document summarizes radio frequency aspects of 3GPP Release 10 LTE-Advanced technology. Key points discussed include operating bands and transmission bandwidth configurations up to 100MHz supported by carrier aggregation. Feasibility studies covered aspects like UE and base station transmitter/receiver architectures, power levels and emissions for supporting wider channel bandwidths through multiple component carriers. Radio resource management requirements were also addressed to ensure good mobility performance across networks utilizing LTE-Advanced.
This document discusses enhancements to the physical layer of LTE-Advanced (3GPP Release 10). It describes the downlink and uplink physical layer designs, including orthogonal multiple access schemes, reference signals, control signaling, and data transmission methods. It also covers support for time division duplexing, half-duplex frequency division duplexing, and UE categories defined in 3GPP Release 8. The goal of LTE-Advanced is to further improve the LTE standard to meet the requirements of IMT-Advanced.
LTE was developed to meet increasing demands for mobile data by offering significantly higher data rates, lower latency, and improved system capacity compared to HSPA. It transitions to a simplified all-IP architecture. Key LTE technologies include flexible bandwidths up to 20 MHz, OFDMA, MIMO, and channel-dependent scheduling. LTE is expected to provide peak data rates of over 300 Mbps downlink and 75 Mbps uplink for high-end devices.
Mobile broadband growth has led to increased traffic, subscriptions, and revenue for many mobile operators globally. This growth is challenging existing mobile networks and driving operators to evolve their networks to LTE, which can provide significantly higher capacity to support ongoing growth in demand. The mobile industry is largely converging on LTE as the next generation mobile standard, with over 100 operators committed or exploring deployment. LTE promises benefits like lower costs per bit and higher speeds to better meet consumer and business needs in a mobile world.
The document provides an overview of 3GPP Long Term Evolution (LTE) and System Architecture Evolution (SAE). It discusses the motivation for LTE to evolve UMTS towards a packet-only system with higher data rates. The workplan for LTE included feasibility studies from 2004-2006 and standardization work beginning in 2007. Key requirements for LTE included improved peak data rates, latency, spectral efficiency, and reduced infrastructure costs. The LTE air interface uses OFDMA in the downlink and SC-FDMA in the uplink with adaptive modulation up to 64-QAM. Multiple antenna techniques including beamforming, spatial multiplexing, and diversity are supported.
The document proposes LTE Release 10 and beyond (LTE-Advanced) as a candidate radio interface technology for IMT-Advanced. It provides an overview of 3GPP standardization activities, including LTE Release 8 which focused on improving spectral efficiency and reducing latency. LTE-Advanced is being studied to further evolve LTE to meet ITU-R requirements for IMT-Advanced and future needs, with a feasibility study currently ongoing in 3GPP.
This document discusses estimating the performance of concatenated coding schemes. It introduces the Information Processing Characteristic (IPC) which can be used to lower bound the performance of any concatenated coding scheme. The IPC is obtained through asymptotic analysis using EXIT charts or the Approximate Message Passing Convergence Analyzer (AMCA). This provides a lower bound on the IPC that can be achieved with infinite interleaving and iterations. Estimates for realistic schemes with a limited number of iterations are also possible. The IPC can then be used to estimate the resulting bit error ratio.
This document summarizes the key technologies that enable LTE-Advanced, which is an enhancement of LTE to meet the requirements for IMT-Advanced. LTE-Advanced introduces carrier aggregation to support transmission bandwidths up to 100MHz by aggregating multiple LTE carriers. It also enhances multiple antenna technologies to support up to 8 antennas in the downlink and 4 antennas in the uplink. Other technologies introduced include coordinated multipoint transmission and reception, enhanced uplink transmission schemes, and the use of intelligent relay nodes.
This document provides an overview of the book "Understanding UMTS Radio Network Modelling, Planning and Automated Optimisation". It discusses radio network modelling and planning for UMTS/3G cellular networks. The book contains chapters on propagation modelling, theoretical models, planning fundamentals, network design aspects, compatibility of UMTS systems, and specialised network design topics. It aims to help readers understand the theory and practice of UMTS radio network modelling, planning and optimization.
This document provides a summary of key performance indicators (KPIs) for measuring performance in UMTS terrestrial radio access networks (UTRAN). It begins with the basics of performance measurement, including what KPIs are, how performance data is captured and filtered in UTRAN, and definitions from 3GPP. It then describes selected KPIs to measure aspects like block error rate, radio link quality, throughput, handover success rates, call setup rates, and more. The document aims to provide a practical guide for understanding and using KPIs to evaluate UTRAN network performance.
The document is a preface and table of contents for a book about UMTS networks and radio access technology. It introduces the growth of mobile communications and the requirements for 3G systems, including new services and radio access aspects. It also briefly discusses enhancing technologies for 3G like smart antennas, multi-user detection, software defined radio, and integration challenges. The preface and contents set up the topics to be covered in the book at a high level.
This document provides an introduction and overview of the book "HSDPA/HSUPA for UMTS: High Speed Radio Access for Mobile Communications". The book is edited by Harri Holma and Antti Toskala of Nokia Networks, Finland. It covers the standardization of HSDPA and HSUPA in 3GPP, the key technologies and principles of HSDPA and HSUPA including new physical channels and protocols, radio resource management, performance metrics such as bit rates and capacity, and applications over HSPA such as voice-over-IP.
This document is the third edition of the book "WCDMA for UMTS" which provides an overview of the WCDMA radio access technology for third generation mobile communications. It was edited by Harri Holma and Antti Toskala of Nokia and covers topics such as the standardization process, network architecture, protocols, and services supported by UMTS networks using WCDMA. The book serves as a technical reference for 3G cellular communication standards and their implementation.
WiMAX is a wireless technology that provides broadband connections over long distances. It allows high-speed wireless data, voice and video connectivity. The technology uses various standards and frequency bands to provide broadband access up to 30 miles. Products supporting WiMAX standards are expanding and include chips, modules, customer premise equipment and base stations. Many companies are developing WiMAX network infrastructure and devices to deliver wireless internet access using this technology.
12. FM Signaling A Constant-Amplitude Carrier A Modulating Signal Center Frequency Above Center Frequency Below Center Frequency Center Frequency Center Frequency Frequency Modulation
Partial support for this curriculum material was provided by the National Science Foundation's Course, Curriculum, and Laboratory Improvement Program under grant DUE-9972380 and Advanced Technological Education Program under grant DUE‑9950039. GWEC EDUCATION PARTNERS: This material is subject to the legal License Agreement signed by your institution. Please refer to this License Agreement for restrictions of use.
During this module, the following topics will be discussed: Modulation basics Frequency modulation for mobile cellular Shift keying Types and uses Constant envelope modulation
After completing this module and all of its activities, you will be able to: Explain basic modulation concepts. Describe frequency modulation for mobile radio. Explain different types of shift keying and when each one is used. Describe constant envelope modulation.
Modulation is a process by which an input signal is encoded in a particular format suitable for transmission. Common transmission mediums include optical fiber, coaxial cable (coax), wave guide, or over-the-air. The baseband is the band of frequencies that must be sent to a particular destination. In audio systems these frequencies are typically in the 20-200 kHz range. For this baseband to be transmitted unmodulated the antenna would have to handle a wavelength ratio higher than 200:1, which is highly impractical. Thus, these baseband signals are transmitted at a much higher frequency bandpass signal level. Commercial frequency modulated (FM) broadcast bands have one hundred 200 kHz bandwith channels centered at about 100 MHz, which gives a 20% wavelength ratio. Advanced mobile phone service (AMPS) uses 832-30 kHz channels in a 25 MHz band centered at about 860 MHz, which is less than a 3% wavelength ratio. A smaller antenna is practical at the shorter wavelength. Antennas must be at least one-fourth wavelength of the propagation frequency to be efficient. Radio reception degrades when the transmitted signals bounce off of objects and arrive at the receiving antenna at different times or out of phase. “Ghosts” on television receivers are an example of the problem. Modulation schemes can be used to counter the effects of multipath fading and time-delay spread in mobile radio communication. (For more information on this topic, refer to the GWEC module RT- RF Propagation .)
AM means amplitude modulation or changing of the amplitude of a signal in response to a second modifying signal. The signal whose amplitude is modulated is the carrier signal ; the modifying signal is the information signal . The information signal is also known as the baseband (BB) signal or the modulating signal . AM modulation is used in wireless telecommunications and in broadcast AM radio. In amplitude modulation, the receiver can be very simple in design; the early crystal radio set is an example of this. The information signal modulates (modifies) the carrier signal by being multiplied with it. The resulting composite signal is the amplitude-modulated carrier that is transmitted , i. e., the AM signal. The envelope of the AM signal is constantly changing because the amplitude is constantly being adjusted proportionally to the input signal. AM is a variable envelope type of transmission. When an AM receiver decodes an AM signal, it strips the carrier frequency from the composite signal, leaving the information signal to be heard. When you tune into an AM radio, you are matching the carrier signal’s frequency. AM radio is still very susceptible to noise (lightning, ignition, etc.) and is not used due to this detrimental factor in spite of its inherent simplicity of hardware.
FM means frequency modulation , or changing the frequency of a carrier signal based on the amplitude of an information (baseband) signal. Frequency modulation is a special case of angle modulation ( phase modulation is another special case) in which the angle of the carrier is varied proportionately to the amplitude of the baseband signal. In angle modulation, the amplitude of the carrier signal is kept constant; hence, angle modulation methods are constant envelope transmissions. The diagram above illustrates amplitude, phase, and frequency modulation by a sine wave. The remainder of this module will focus on FM for mobile radio.
In FM signaling , the frequency of the carrier signal is varied in accordance with the information signal being transmitted. The amplitude of the modulated wave does not change, no matter how strong the modulating signal is. When the modulating signal is zero, the carrier signal (modulated wave) is at the center frequency (resting frequency). When the FM frequency is not modulated, it is at the value F. When it is modulated, it deviates from F-f to F+f , where f is the change representing the modulation information. In the FM detection process the noise or interference amplitude increases linearly with frequency variation from the carrier. Therefore, noise power at the detector output will vary proportionately with the square of the frequency. An advantage of this is that input noise components close to the carrier frequency are suppressed. This makes narrowband FM relatively “noise free” and it produces a much higher quality signal. An FM receiver captures the strongest FM signal in the receiver bandwidth. FM uses more bandwidth than an equivalent AM signal and is relatively insensitive to received signal strength. The increased bandwidth required by FM is exploited to make FM relatively insensitive to noise. One disadvantage of FM is that it suppresses weaker signals. For this reason, air traffic systems do not use FM signals. If they did, air traffic controllers would hear urgent message superimposed on the message being listened to.
Sampled speech can be transmitted over a radio channel by amplitude modulation (AM), frequency modulation (FM), or phase modulation (PM) signals. When a signal is converted to energy pulses or waves, it is known as shift keying . In this section, we will look at four types of shift keying: Frequency shift keying Amplitude shift keying Phase shift keying Multilevel shift keying
Frequency shift keying is represented in the diagram above.
After analog to digital signal conversion is completed, the signal is modulated such that the zeros and ones are converted into on-off discrete energy pulses. This is known as on-off keying or amplitude shift keying (ASK). This method of on and off pulsing is not used much for today’s radio transmission since multipath fading distorts the amplitude of the carrier. However, fiber optic and infrared transmission use on-off pulsing of the light signal for transmitting digital information. (For more information on multipath fading, refer to the GWEC module RT-RF Antennas and RT-RF Propagation .)
Another way to modulate digital signals is to have two distinct frequencies that are offset from the carrier frequency. These two frequencies represent the zeros and ones from the original digital signal. This is called frequency shift keying (FSK). If you have two distinct frequencies, there are two states, 0 (on) and 1 (off). If you have four distinct frequencies, there are four states: 00, 01, 10, and 11. With eight frequencies there are eight states: 000, 001, 010, 100, 011, 101, 110, and 111. When a signal element changes states it is called a baud . With two states, there is one bit to one baud. With four states, there are two bits to one baud, and with eight states there are three bits to one baud. FSK is used in low transmission rates such as paging and for the control channel in some cellular systems.
Another way to modulate digital signals is phase shift keying (PSK) whereby the carrier frequency is modulated by a phase angle. The simplest example is binary PSK. Each 180-degree shift in phase represents a change from 0 to 1. Phase relationships can also be drawn without using sine waves by using a phase plan diagram. In a phase plan diagram, each vector represents a sine wave. In the example shown above, waves are 180 degrees out of phase with each other. Most digital radio signals use some form of PSK.
Modulation can be explained in terms of degrees of freedom. Amplitude, frequency, and phase are the variables. Simple systems generally hold two of the three variables constant, varying only one of them. This makes decoding quite easy, but subject to error. More complex systems vary combinations of the variables, creating more reliable systems. Complex systems may also have more than the two-state binary levels to support higher data rates. Efficiency of the spectrum is defined by the number of bits that can be transmitted in a period of time (usually one second) with a defined bandwidth or channel. Since the width of the channel is in kilohertz (kHz) or megahertz (MHz), spectrum efficiency is the number of bits per second per hertz. In other words, it is how many bits per hertz that can be “stuffed” into the radio channel. With ASK, FSK, or two-state PSK, each change of state represents one bit. Under ideal conditions, one bit per second per hertz of channel can be transmitted. With a 30 kHz channel, like cellular, 30,000 bits per second (30 kb/s) can be transmitted. Using ASK, FSK, or two-state PSK is inefficient. If there were four states (four amplitudes, four frequencies, or four phases), the number of bits per second per hertz would double from one to two, and the occupied bandwidth would be cut in half. The modulation scheme would be more complex, but double the efficiency. On the other hand, eight levels allow for three bits. Now the efficiency of three bits per second per hertz could be achieved. By modulating at sixteen levels (four bits), the efficiency is four bits per second per hertz.
Because multipath fading distorts the amplitude of the carrier in a mobile radio, the signal is sent by modulating the phase or frequency of the carrier, which has no impact on the amplitude. These modulations are called constant envelope modulations since no signal is modulated on the amplitude. Distortion of carrier amplitude by other factors such as fading or nonlinear amplification will not affect the signal, making it possible to use a nonlinear amplifier. Constant envelope modulation can be a linear or a nonlinear modulation in digital mobile systems. Linear modulation is where the carrier signal is linearly proportional to the input signal. It can vary based on a constant factor. Nonlinear modulation allows the carrier signal to be a more complex mathematical proportion of the input signal. Constant envelope modulation is used in digital mobile systems and for the nonlinear modulation in analog mobile systems. A number of different modulation schemes are used by today’s digital cellular and PCS systems.
The diagram above and on the following page illustrate quadrature phase shift keying. Used by both cellular and PCS systems, quadrature phase shift keying (QPSK) increases the modulation efficiency from binary PSK. In binary PSK, one symbol phase (0 or 180 degrees) at the modulation stage represents one bit. In QPSK, one symbol (one of four phases) at the modulation stage represents two bits. The four phases used are 0, +90, -90, and 180 degrees. Half of the bit stream goes to the I (in-phase) multiplier, which has phase’s 0 and 180 degrees, and the other half goes to the Q (quadrature or out-of-phase) multiplier, which has the phase’s +90 and –90 degrees. QPSK can be thought of as two binary PSK modulators. While this is a relatively robust signal, it has a significant component of amplitude variation. The envelope of amplitude of the composite signal varies with modulation. Occasionally, the 180-degree phase shift can cause the envelope to go to zero instantly. Therefore, transmitter amplifiers should be linear. This type of modulation is typically used to transmit from the base station to the mobile (forward link). Since this form of modulation is the linear combination of two constant envelope modulation schemes, the result has a constant envelope as well.
The circles in the diagram above represent the target areas in which the receiver looks for zeros and ones. It is not a single point due to the presence of noise, interference, or phase errors in the equipment, but is an area or search window defined by phase relationships. This adds reliability when wave forms are warped and reflected.
The diagram above and on the following page illustrate offset QPSK. Like QPSK, the unfiltered offset quadrature phase shift keying (OQPSK) signal has a constant envelope. However, the two streams do not change status at the same time, thus eliminating the 180-degree phase change. The envelope will not go to zero as it does with QPSK, meaning that nonlinear amplification can be used. Less linear but more efficient amplifiers can be used, which makes this modulation technique ideal for battery-powered transmitters. OQPSK is typically used for mobile to base station station (reverse link) modulation. Because the number of OQPSK bits per second is the same as in QPSK, OQPSK requires the same bandwidth. The slight delay avoids the 180-degree zero crossing shift. This allows cell phone manufacturers to use cheaper, l ess linear and more efficient amplifiers. This modulation technique is ideal for battery-powered transmitters.
The circles in the diagram above represent the target areas where the receiver looks for zeros and ones. It is not a single point, but is an area or search window defined by phase relationships. This adds reliability when wave forms are warped and reflected.
Also used for cellular and PCS systems is /4-DQPSK (differential quadrature phase shift keying ). /4-DQPSK is a type of QPSK . This modulation architecture uses symbols represented as the relative changes in phase rather than the absolute phase. Two carriers in quadrature with each other generate the waveform. The information source drives two amplifiers: s I and s Q. When their outputs are 0 & 0 the -3 /4 phase code is transmitted .
The angle k is the phase shift based on the input symbols s I and s Q, which form a pair. Gray code is used in mapping the two-bit symbol. All possible combinations are shown in the table above. The reason for choosing /4-DQPSK is based on having the choice of a power-efficient modulation or a spectral-efficient modulation. For a power-efficient modulation, the dynamic power range of the nonlinear amplifier is applied to increase power efficiency. For example, a 4 watt RF amplifier can operate only at a 1 watt maximum power (when operating in the linear range) due to a 6 db output back off. A nonlinear amplifier does not have this back off, so it has a gain of 6 db. In a power-efficient modulation, spectral regrowth is a problem that reduces spectral efficiency. For a modulation with spectral efficiency, a linear amplifier is used to reduce the spectral regrowth.
QPSK has an instantaneous 180 o phase shift, which leads to significant spectral regrowth. /4-DQPSK has an instantaneous phase transition of 135 o , and a OQPSK system has only 90 o instantaneous phase transitions, making it the lowest spectral regrowth and the highest spectral efficiency of all three. Demodulation of OQPSK is much more difficult than with /4-DQPSK. /4-DQPSK with a linear amplifier is used to achieve the spectral efficiency for the cellular and PCS systems because it can be easily demodulated and it has an easier hardware implementation.
Gaussian filtered minimal shift keying (GMSK ) is used in PCS systems and European GSM cellular systems. It is a variant of binary FSK. GMSK is a type of constant envelope FSK whereby the frequency modulation is a carefully handled phase modulation. The constant amplitude of the GMSK signal makes it suitable for use with high-efficiency amplifiers. The carrier signal has two frequency versions: high frequency and low frequency. The signals also carry a “sense”, which can be either positive or negative. When the carrier frequency is unchanged, the sense is positive. When the sense is negative, the frequency is upside down. The resulting waveform has a relatively smooth phase transition from one frequency to the next which reduces the spectral regrowth. In the QPSK family of modulations, phase transitions are discontinuous. Therefore, the power spectrum density of OQPSK has a wider spectral re-growth than that of GMSK.
Modulation enables analog audio voice information to be efficiently transferred over the air interface. Modulation is also used in data transmission in modems. Each modulation method has strengths and weaknesses, as discussed in the module. An understanding of modulation methods will help wireless professionals support current radio systems and adapt to third generation (3G) technology. (For more information on third generation technology, refer the GWEC module AI-3GES .)