Adaptive coded modulation for fading channels

Abstract

Abstract-We apply coset codes to adaptive modulation in fading channels. Adaptive modulation is a powerful technique to improve the energy efficiency and increase the data rate over a fading channel. Coset codes are a natural choice to use with adaptive modulation since the channel coding and modulation designs are separable. Therefore, trellis and lattice codes designed for additive white Gaussian noise (AWGN) channels can be superimposed on adaptive modulation for fading channels, with the same approximate coding gains. We first describe the methodology for combining coset codes with a general class of adaptive modulation techniques. We then apply this methodology to a spectrally efficient adaptive M-ary quadrature amplitude modulation (MQAM) to obtain trellis-coded adaptive MQAM. We present analytical and simulation results for this design which show an effective coding gain of 3 dB relative to uncoded adaptive MQAM for a simple four-state trellis code, and an effective 3.6-dB coding gain for an eight-state trellis code. More complex trellis codes are shown to achieve higher gains. We also compare the performance of trellis-coded adaptive MQAM to that of coded modulation with built-in time diversity and fixed-rate modulation. The adaptive method exhibits a power savings of up to 20 dB.

Iterative (Turbo) Joint Rate and Data Detection in Coded CDMA Networks

“…In Figs. 2 and 3 the probability of erroneous rate detection (PERD) and of bit error probability conditioned on correct rate In particular a DS/CDMA system with data frames of length P = 100 on a frequency-flat Rayleigh fading channel has been considered. The largest processing gain is N R1 = 16, and S = 2 data rates with a rate ratio vector given by m = [1,2] has been used. The number of users is K = 6, while a convolutional code of rate 1/2 has been used.…”

“…Variable-rate CDMA systems wherein each user transmits at one out of a set of available data-rates are nowadays of widespread interest, since they are able to support transmission of heterogeneous kinds of data , such as streaming video, voice, bulk data, etc., with different data-rates. These systems are part of current 3G wireless networks, and, also, they can support adaptive rate strategies that allow to achieve a larger system throughput [1,2] than a fixed data-rate CDMA systems. Obviously, in a variable-rate CDMA system the receiver generally needs knowledge of the actual data-rate of each user in order to perform data detection, and this information is usually conveyed on a separate multiplexed channel.…”

Network-Coded Bi-Directional Relaying Over an Asymmetric Channel

“…i.e.,   does not change until the whole transmission of a block over each link. Even whilst we consider the uncoded system in the current analyses and numerical examples, our results can be extended to the coded systems using the adaptive-coded schemes in [11] .…”

Multiple regression analysis of IEEE 802.16j relay network throughput

“…Previous studies [8]- [11] have proposed heuristic algorithms for time slot assignment since the problem is NP-hard [12]. Furthermore, when adaptive modulation and coding (AMC) [13] is applied to data transmission, the transmission rate depends strongly on the link quality because AMC selects the most suitable modulation method depending on the SINR of the link in the assigned time slot. The communication quality of links is also influenced by various factors such as background noise level, path loss exponent, density of relay nodes, and transmission signal strength.…”