This paper provides a comprehensive study of interleave-division multiple-access (IDMA) systems. The IDMA receiver principles for different modulation and channel conditions are outlined. A semi-analytical technique is developed based on the density evolution technique to estimate the bit-error-rate (BER) of the system. It provides a fast and relatively accurate method to predict the performance of the IDMA scheme. With simple convolutional/repetition codes, overall throughputs of 3 bits/chip with one receive antenna and 6 bits/chip with two receive antennas are observed for IDMA systems involving as many as about 100 users.

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Interleave division multiple-access

This work provides a comprehensive study of IDMA systems. We first outline the basic IDMA principles in single-path and multi-path environments. We then describe a simple semi-analytical technique to assess the performance of IDMA systems, based on which we develop a power allocation scheme for performance optimization. We also discuss the use of low-rate codes to further enhance the power efficiency of IDMA systems. Simulation results demonstrate the advantages of the IDMA scheme in terms of both bandwidth and power efficiencies. For example, with simple convolutional/repetition codes an overall throughput of 8 bits/chip is achieved in single antenna systems. With turbo-Hadamard codes, performance at 1.4 dB away from the theoretical limit is demonstrated in a Gaussian MAC.

On interleave-division multiple-access

Adaptive Wireless Transceivers provides the reader with a broad overview of near-instantaneously adaptive transceivers in the context of TDMA, CDMA and OFDM systems The adaptive transceivers examined employ powerful turbo codecs, turbo equalisers and space-time codecs, equipping the reader with a future-proof technological road map It demonstrates that adaptive transceivers are capable of mitigating the channel quality fluctuations of the wireless channel as a lower-complexity alternative to space-time coding By contrast, if the higher complexity of multiple transmitters and multiple receiver-assisted systems is deemed acceptable, the advantages of adaptability erode • Provides an in-depth introduction to channel equalisers and Kalman filtering and discusses the associated complexity versus performance trade-offs • Introduces wideband near-instantaneously adaptive transceivers and studies their performance both with and without turbo channel coding • Describes how to optimise adaptive modulation mode switching and highlights a range of practical considerations • Introduces neural network based channel equalisers and discusses Radial Basis Function (RBF) assisted equalisers embedded into adaptive modems supported by turbo channel coding and turbo channel equalisation • Employs the above adaptive principles also in the context of CDMA and OFDM transceivers and discusses the pros and cons of space-time coding versus adaptive modulation Researchers, advanced students and practising development engineers working in wireless communications will all find this valuable text an informative read

Adaptive Wireless Transceivers: Turbo-Coded, Turbo-Equalized and Space-Time Coded TDMA, CDMA and OFDM Systems

This article outlines a multiple access scheme in which interleaving is the only means of user separation. As a special form of CDMA, the new scheme inherits many advantages of CDMA, such as dynamic channel sharing, mitigation of cross-cell interference, asynchronous transmission, ease of cell planning, and robustness against fading. Furthermore, it allows a low-cost interference cancellation technique applicable to systems with large numbers of users in multipath channels. Performance close to theoretical limits has been observed based on an unequal power control strategy.

Interleave-division multiple access and chip-by-chip iterative multi-user detection

As system requirements in terms of the BER performance and capacity increase, so will the need for more advanced detection techniques. The application of advanced receiver structures is optional for phase 2 of the UMTS FDD mode, while it is mandatory for the time-division duplex mode. Layer 1 of both modes is based on wideband direct sequence code-division multiple access technology, where a physical channel is characterized by the code, frequency, and, in the uplink, the relative phase (I/Q). Furthermore, in the TDD mode the physical channel is also characterized by the time slot (TDMA component).

Data detection techniques for DS/CDMA mobile systems: a review

A multiuser detection algorithm, applicable to asynchronous users having the same signaling waveform and power levels, is presented. Users are assumed to employ forward error correction coding but with different pseudorandom interleaving. The algorithm is derived from iterative techniques for cross-entropy minimization, similar to turbo decoding. Simulations show that the detector is limited by the theoretical channel capacity at low signal-to-noise ratio (SNR) and asymptotically achieves single user performance at high SNR.

P. Guinand

Papers

An iterative algorithm for asynchronous coded multiuser detection