Pilot Channel Assisted MMSE Combining in Forward Link for Broadband OFCDM Packet Wireless Access

Noriyuki MAEDA  Hiroyuki ATARASHI  Sadayuki ABETA  Mamoru SAWAHASHI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E85-A   No.7   pp.1635-1646
Publication Date: 2002/07/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Multi-dimensional Mobile Information Networks)
broadband packet wireless access,  forward link,  OFCDM,  pilot channel assisted MMSE combining,  

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This paper proposes a pilot channel assisted minimum mean square error (MMSE) combining scheme in orthogonal frequency and code division multiplexing (OFCDM) based on actual signal-to-interference power ratio (SIR) estimation, and investigates the throughput performance in a broadband channel with a near 100-MHz bandwidth. In the proposed MMSE combining scheme, the combining weight of each sub-carrier component is accurately estimated from the channel gain, noise power, and transmission power ratio of all the code-multiplexed channels to the desired one, by exploiting the time-multiplexed common pilot channel in addition to the coded data channel. Simulation results elucidate that the required average received signal energy per bit-to-noise spectrum density ratio (Eb/N0) for the average packet error rate (PER) = 10-2 is improved by 0.6 and 1.2 dB by using the proposed MMSE combining instead of the conventional equal gain combining (EGC) in a 24-path Rayleigh fading channel (exponential decay path model, maximum delay time is approximately 1 µsec) in an isolated cell environment, when the number of multiplexed codes = 8 and 32, respectively, with the spreading factor of 32. Furthermore, when the average received Eb/N0 = 10 dB, the achievable throughput, i.e., the number of simultaneously multiplexed codes for the average PER = 10-2 in the proposed MMSE combining, is increased by approximately 1.3 fold that of the conventional EGC.