Abstract
Transmit diversity is necessary in harsh environments to reduce the required transmit power for achieving a given error performance at a certain transmission rate. In networks, cooperative communication is a well-known technique to yield transmit diversity and network coding can increase the spectral efficiency. These two techniques can be combined to achieve a double diversity order for a maximum coding rate on the Multiple-Access Relay Channel (MARC), where two sources share a common relay in their transmission to the destination. However, codes have to be carefully designed to obtain the intrinsic diversity offered by the MARC. This paper presents the principles to design a family of full-diversity LDPC codes with maximum rate. Simulation of the word error rate performance of the new proposed family of LDPC codes for the MARC confirms the full diversity.
Highlights
Multipath propagation is an important salient effect of wireless channels, causing possible destructive adding of signals at the receiver
We focus on capacity achieving codes, more precisely, lowdensity parity-check (LDPC) codes [9], because their word error rate (WER) performance is quasi-independent of the block length [10] when the block length is becoming very large
Hausl and Dupraz obtained interesting results on joint network-channel coding for the Multiple Access Relay Channel (MARC) with turbo codes [14] and LDPC codes [15], [16], but these authors do not elaborate on a structure to guarantee full-diversity at maximum rate, which is the most important criterion for a good performance on fading channels
Summary
Multipath propagation (small-scale fading) is an important salient effect of wireless channels, causing possible destructive adding of signals at the receiver. When one common relay R for two users is used (a Multiple Access Relay Channel - MARC), it can be proven that the maximum achievable coding rate yielding full-diversity is Rc = 2/3 [12]. Hausl and Dupraz obtained interesting results on joint network-channel coding for the MARC with turbo codes [14] and LDPC codes [15], [16], but these authors do not elaborate on a structure to guarantee full-diversity at maximum rate, which is the most important criterion for a good performance on fading channels. A joint network-channel code construction is derived that guarantees full-diversity, irrespective of the parameters of the LDPC code (the degree distributions). To the best of authors’knowledge, this is the first time that a joint full-diversity network-channel LDPC code construction for maximum rate is proposed. In order to simplify the analysis, we consider orthogonal half-duplex devices that transmit in separate timeslots
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