89,062 research outputs found
Space-Time Trellis and Space-Time Block Coding Versus Adaptive Modulation and Coding Aided OFDM for Wideband Channels
No full textAbstract—The achievable performance of channel coded spacetime trellis (STT) codes and space-time block (STB) codes transmitted over wideband channels is studied in the context of schemes having an effective throughput of 2 bits/symbol (BPS) and 3 BPS. At high implementational complexities, the best performance was typically provided by Alamouti’s unity-rate G2 code in both the 2-BPS and 3-BPS scenarios. However, if a low complexity implementation is sought, the 3-BPS 8PSK space-time trellis code outperfoms the G2 code. The G2 space-time block code is also combined with symbol-by-symbol adaptive orthogonal frequency division multiplex (AOFDM) modems and turbo convolutional channel codecs for enhancing the system’s performance. It was concluded that upon exploiting the diversity effect of the G2 space-time block code, the channel-induced fading effects are mitigated, and therefore, the benefits of adaptive modulation erode. In other words, once the time- and frequency-domain fades of the wideband channel have been counteracted by the diversity-aided G2 code, the benefits of adaptive modulation erode, and hence, it is sufficient to employ fixed-mode modems. Therefore, the low-complexity approach of mitigating the effects of fading can be viewed as employing a single-transmitter, single-receiver-based AOFDM modem. By contrast, it is sufficient to employ fixed-mode OFDM modems when the added complexity of a two-transmitter G2 scheme is affordable
Kad Hari Raya
No full textKad ucapan hari raya yang diutuskan kepada Profesor Diraja Ungku Abdul Aziz daripada F. S. Liew dan K. S. Li
Space-Time Codes and Concatenated Channel Codes for Wireless Communications
No full textFollowing a brief historical perspective on channel coding, an introduction to space–time block codes is given. The various space–time codes considered are then concatenated with a range of channel codecs, such as convolutional and block-based turbo codes as well as conventional and turbo trellis codes. The associated estimated complexity issues and memory requirements are also considered. These discussions are followed by a performance study of various space–time and channel-coded transceivers. Our aim is first to identify a space–time code/channel code combination constituting a good engineering tradeoff in terms of its effective throughput, bit-error-rate performance, and estimated complexity. Specifically, the issue of bit-to-symbol mapping is addressed in the context of convolutional codes (CCs) and convolutional coding as well as Bose–Chaudhuri–Hocquenghem coding-based turbo codes in conjunction with an attractive unity-rate space–time code and multilevel modulation is detailed. It is concluded that over the nondispersive or narrow-band fading channels, the best performance versus complexity tradeoff is constituted by Alamouti’s twin-antenna block space–time code concatenated with turbo convolutional codes. Further comparisons with space–time trellis codes result in similar conclusions. Keywords—Channel coding, concatenated coding, FEC, history of channel coding, space–time coding, STBC, STTC
Turbo-Coded Adaptive Modulation Versus Space-Time Trellis Codes for Transmission over Dispersive Channels
No full textDecision feedback equalizer (DFE)-aided turbocoded wideband adaptive quadrature amplitude modulation (AQAM) is proposed, which is capable of combating the temporal channel quality variation of fading channels. A procedure is suggested for determining the AQAM switching thresholds and the specific turbo-coding rates capable of maintaining the target bit-error rate while aiming for achieving a highly effective bits per symbol throughput. As a design alternative, we also employ multiple-input/multiple-output DFE-aided space–time trellis codes, which benefit from transmit diversity and hence reduce the temporal channel quality fluctuations. The performance of both systems is characterized and compared when communicating over the COST 207 typical urban wideband fading channel. It was found that the turbo-coded AQAM scheme outperforms the two-transmitter space–time trellis coded system employing two receivers; although, its performance is inferior to the space–time trellis coded arrangement employing three receivers. Index Terms—Coded adaptive modulation, dispersive channels, space–time trellis codes
Systematic redundant residue number system codes: analytical upper bound and iterative decoding performance over AWGN and Rayleigh channels
No full textThe novel family of redundant residue number system (RRNS) codes is studied. RRNS codes constitute maximum–minimum distance block codes, exhibiting identical distance properties to Reed–Solomon codes. Binary to RRNS symbol-mapping methods are proposed, in order to implement both systematic and nonsystematic RRNS codes. Furthermore, the upper-bound performance of systematic RRNS codes is investigated, when maximum-likelihood (ML) soft decoding is invoked. The classic Chase algorithm achieving near-ML soft decoding is introduced for the first time for RRNS codes, in order to decrease the complexity of the ML soft decoding. Furthermore, the modified Chase algorithm is employed to accept soft inputs, as well as to provide soft outputs, assisting in the turbo decoding of RRNS codes by using the soft-input/soft-output Chase algorithm. Index Terms—Redundant residue number system (RRNS), residue number system (RNS), turbo detection
Burst-by-Burst Adaptive Turbo-Coded Radial Basis Function-Assisted Decision Feedback Equalization
No full textThe performance of the proposed radial basis function (RBF) assisted turbo-coded adaptive modulation scheme is characterized in a wideband channel scenario. We commence by introducing the novel concept of the Jacobian RBF equalizer, which is a reduced-complexity version of the conventional RBF equalizer. Specifically, the Jacobian logarithmic RBF equalizer generates its output in the logarithmic domain and hence it can be used to provide soft outputs for the turbo-channel decoder. We propose using the average magnitude of the log-likelihood ratio (LLR) of the bits in the received transmission burst before channel decoding as the channel quality measure for controlling the mode-switching regime of our adaptive scheme
Adaptive Coding and Transmission Paradigms for Wireless Channels
No full textFollowing a brief historical perspective on channel coding the concept of near-instantaneously adaptive wireless transceivers is introduced as a counter-measure of mitigating the channel-quality fluctuations experienced in wireless communications. It is argued that channel coded adaptive modulation schemes can be viewed as a lower complexity alternative of mitigating the channel quality fluctuations of wideband wireless channels in comparison to multiple-transmitter and multiple-receiver based space-time codes. However, provided that the complexity of the latter schemes employing multiple transmitters and receivers is affordable, the performance advantages of adaptive modulation and adaptive channel coding schemes erode, since the channel quality fluctuations of the wireless channel are effectively mitigated
Reduced-Complexity I/Q Turbo Detector for Convolutional-Coding Assisted Space-Time Trellis Coding
No full textThis paper presents a reduced-complexity turbo detector for convolutional-coding aided space-time trellis coded (STTC) schemes. The proposed technique is based on the separate in-phase/quadrature-phase (I/Q) detection principle developed for single-transmitter and single-receiver systems. Essentially, the reduced-complexity I/Q turbo detector (R-TD) decomposes the received signal into its constituent I and Q components and detects these components separately, hence reducing the number of possible signal combinations to be ‘tested’ by the detector. It is observed that the R-TD is capable of approaching the performance of the full-complexity turbo detector, while achieving a complexity reduction factor of 4.2 for a R = 1/2 convolutional-coded 4-PSK 4-state STTC system communicating over two-path equal-weight Rayleigh fading channels. The performance of the convolutional-coded STTC schemes is also compared to that of the STTC benchmarker refraining from using channel coding, while maintaining a particular throughput. It was found that the convolutional-coded STTC system achieved a gain of 1.2 dB at BER=10E?5, although at the expense of a significant increase in complexity
Adaptive redundant residue number system coded multicarrier modulation
No full textThe novel class of nonbinary maximum minimum distance redundant residue number system (RRNS) codes is invoked in the context of adaptively RRNS coded, symbol-by-symbol adaptive multicarrier modulation, in order to combat the effects of frequency-selective fading inflicted by dispersive wide-band channels. The system’s performance can be adjusted in order to maintain a given target bit error rate (BER) and bit per symbol (BPS) performance. The proposed adaptive RRNS scheme outperforms the convolutional constituent code based turbo coded benchmarker system for channel signal-to-noise ratios (SNR) in excess of about 15 dB at a target BER of 10-4. Index Terms—Adaptive channel coding, adaptive modulation, adaptive OFDM, coded multicarrier modulation, OFDM, redundant residue number system
Turbo Coding, Turbo Equalisation and Space-Time Coding
No full textAgainst the backdrop of the emerging 3G wireless personal communications standards and broadband access network standard proposals, this volume covers a range of coding and transmission aspects for transmission over fading wireless channels. It presents the most important classic channel coding issues and also the exciting advances of the last decade, such as turbo coding, turbo equalisation and space-time coding. It endeavours to be the first book with explicit emphasis on channel coding for transmission over wireless channels. Divided into 4 parts: Part 1 - explains the necessary background for novices. It aims to be both an easy reading text book and a deep research monograph. Part 2 - provides detailed coverage of turbo conventional and turbo block coding considering the known decoding algorithms and their performance over Gaussian as well as narrowband and wideband fading channels. Part 3 - comprehensively discusses both space-time block and space-time trellis coding for the first time in literature. Part 4 - provides an overview of turbo equalisations, also referred to as turbo demodulation. The book systematically converts the lessons of Shannon's information theory into design principles applicable to practical wireless systems. It provides overall design performance studies, giving cognizance to the contradictory design requirements of bit error rate, implementational complexity, coding and interleaving delay, effective throughput, coding rate and other related systems design aspects in a comprehensive manner
- …
