Abstract
We present a codeword adaptation algorithm for collaborative multibase wireless systems. The system is modeled with multiple inputs and multiple outputs (MIMO) in which information is transmitted using multicode CDMA, and codewords are adapted based on greedy maximization of the signal-to-interference-plus-noise ratio. The procedure monotonically increases the sum capacity and, when repeated iteratively for all codewords in the system, converges to a fixed point. Fixed-point properties and a connection with sum capacity maximization, along with a discussion of simulations that corroborate the basic analytic results, are included in the paper.
Highlights
Code division multiple access (CDMA) schemes have been proposed for use in future generation wireless systems due to the fact that they enable efficient utilization of communication resources like available spectrum and transmitted power, and have received increased attention from the wireless research community lately
We note that codeword optimization algorithms available in the literature have been defined in the context of single-cell CDMA systems in which all users communicate with a single base station which knows codewords for all users in the system and uses them to decode the transmitted information symbols
We assume that a multicode CDMA approach is used for transmitting information by users in the collaborative multi-base system, in which users transmit frames of data by assigning each symbol in a given user’s frame a distinct codeword for transmission, and we present a greedy algorithm for codeword adaptation based on selfish optimization of individual signal-to-interference-plus-noise ratio (SINR)
Summary
Code division multiple access (CDMA) schemes have been proposed for use in future generation wireless systems due to the fact that they enable efficient utilization of communication resources like available spectrum and transmitted power, and have received increased attention from the wireless research community lately. The problem of optimizing CDMA codewords has been addressed by several researchers which have established algorithms that yield optimal codeword ensembles for CDMA systems [1, 2, 3, 4, 5, 6]. Optimal codeword ensembles for CDMA systems have been obtained by application of interference avoidance methods [7, 8, 9, 10, 11, 12] which provide distributed algorithms for codeword optimization in CDMA systems by which users independently adjust codewords in response to changing patterns of interference. We note that codeword optimization algorithms available in the literature have been defined in the context of single-cell CDMA systems in which all users communicate with a single base station which knows codewords for all users in the system and uses them to decode the transmitted information symbols. When no cooperation among users/bases is assumed, the problem of decoding one user at its associated base station under interference generated by all the other users in the system is an instance of the interference channel [13, Chapter 14], and is still a mostly open research problem
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