Coding techniques for limited diversity fading channels

Santosh V Nagaraj, Purdue University


In this research, we propose novel techniques for digital communication over limited diversity channels. Limited diversity channels are characterized by a few independent fading realizations in every code block (typically 2–5). These channels are significantly different from commonly studied AWGN and ideal fading channel models. We outline code design and optimization criteria for such channels. We name the resulting design technique Concatenated Trellis Coded Modulation (CTCM). The indoor wireless LAN system is an important application for CTCM. We design CTCM codes based on physical channel models for indoor scenarios for the different modes supported by IEEE 802.11 based LAN standards. We also show information theoretic results based on cutoff rate analysis to support our arguments. Further, transfer function based analysis techniques are shown. User cooperation is a recently proposed technique that achieves the benefits of having multiple antennas at either transceiver, without actually having them. We have proposed a coded modulation (CM) protocol for uplink cooperation between users. The ideal scenario would be two nearby users cooperating to achieve reliable transmission with a distant base station. We outline the CM cooperation protocol which is actually a distributed TCM code designed from CTCM principles. The CM protocol can be represented in the CTCM framework, allowing analysis and optimization of codes. Codes so designed also attempt to maximize the reliability of the inter-user link. This is achieved by means of an appropriately labeled signal constellation. Simulations and analysis supporting the claims are presented.




Bell, Purdue University.

Subject Area

Electrical engineering

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