Achieving the Near-Capacity of Two-Way Relay Channels With Modulation-Coded Physical-Layer Network Coding

We propose and design a practical modulation-coded (MC) physical-layer network coding (PNC) scheme to approach the capacity limits of Gaussian and fading two-way relay channels (TWRCs). In the proposed scheme, an irregular repeat-accumulate (IRA) MC over GF(q) with the same random coset is employed...

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Bibliographic Details
Published in:IEEE transactions on wireless communications Vol. 14; no. 9; pp. 5225 - 5239
Main Authors: Yang, Lei, Yang, Tao, Yuan, Jinhong, An, Jianping
Format: Journal Article
Language:English
Published: New York IEEE 01.09.2015
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
compute-and-forward (CF)
Fading
irregular repeat-accumulate (IRA) code
Modulation
Network coding
physical-layer network coding (PNC)
Relays
Reliability
Signal to noise ratio
two-way relay channel (TWRC)
Wireless communication
Two-way relay channel (TWRC)
compute-and-forward (CF)
physical-layer network coding (PNC)
irregular repeat-accumulate (IRA) code
ISSN:1536-1276, 1558-2248
Online Access:Get full text
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Summary:We propose and design a practical modulation-coded (MC) physical-layer network coding (PNC) scheme to approach the capacity limits of Gaussian and fading two-way relay channels (TWRCs). In the proposed scheme, an irregular repeat-accumulate (IRA) MC over GF(q) with the same random coset is employed at two users, which directly maps the message sequences into coded PAM or QAM symbol sequences. The relay chooses appropriate network coding coefficients and computes the associated finite-field linear combinations of the two users' message sequences using an iterative belief propagation algorithm. For a symmetric Gaussian TWRC, we show that, by introducing the same random coset vector at the two users and a time-varying accumulator in the IRA code, the MC-PNC scheme exhibits symmetry and permutation-invariant properties for the soft information distribution of the network-coded message sequence (NCMS). We explore these properties in analyzing the convergence behavior of the scheme and optimizing the MC to approach the capacity limit of a TWRC. For a block fading TWRC, we present a new MC linear PNC scheme and an algorithm used at the relay for computing the NCMS. We demonstrate that our developed schemes achieve near-capacity performance in both Gaussian and Rayleigh fading TWRCs. For example, our designed codes over GF(7) and GF(3) with a code rate of 3/4 are within 1 and 1.2 dB of the TWRC capacity, respectively. Our method can be regarded as a practical embodiment of the notion of compute-and-forward with a good nested lattice code, and it can be applied to a wide range of network configurations.
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ISSN:1536-1276
1558-2248
DOI:10.1109/TWC.2015.2434874