Coding Strategies for Noise-Free Relay Cascades with Half-Duplex Constraint

Two types of noise-free relay cascades are investigated. Networks where a source communicates with a distant receiver via a cascade of half-duplex constrained relays, and networks where not only the source but also a single relay node intends to transmit information to the same destination. We introduce two relay channel models, capturing the half-duplex constraint, and within the framework of these models capacity is determined for the first network type. It turns out that capacity is significantly higher than the rates which are achievable with a straightforward time-sharing approach. A capacity achieving coding strategy is presented based on allocating the transmit and receive time slots of a node in dependence of the node's previously received data. For the networks of the second type, an upper bound to the rate region is derived from the cut-set bound. Further, achievability of the cut-set bound in the single relay case is shown given that the source rate exceeds a certain minimum value.Comment: Proceedings of the 2008 IEEE International Symposium on Information Theory, Toronto, ON, Canada, July 6 - 11, 200

Capacity for Half-Duplex Line Networks with Two Sources

The focus is on noise-free half-duplex line networks with two sources where the first node and either the second node or the second-last node in the cascade act as sources. In both cases, we establish the capacity region of rates at which both sources can transmit independent information to a common sink. The achievability scheme presented for the first case is constructive while the achievability scheme for the second case is based on a random coding argument.Comment: Proceedings of the IEEE International Symposium on Information Theory, Austin, TX, USA, June 12 - 18, 201

Design of diversity-achieving LDPC codes for H-ARQ with cross-packet channel coding

In wireless scenarios an effective protocol to increase the reliability for time-varying channels is the hybrid automatic repeat request (H-ARQ). The H-ARQ scheme with cross-packet channel coding (CPC) is a recently published extension of H-ARQ with several advantages. No full-diversity low-density parity-check (LDPC) code design for the whole range of coding rates yielding full-diversity has been published. In this paper the authors provide a new outage behavior analysis and a new structured LDPC code ensemble achieving full-diversity for H-ARQ with CPC by exploiting the rootcheck principle. Simulation results show that the new code design outperforms the previous approaches, providing full-diversity and good coding gain, also at high coding rates

Iterative Network and Channel Decoding for the Two-Way Relay Channel

Abstract — We introduce an extension of the relay channel that we call two-way relay channel. The two-way relay channel consists of two users which want to communicate to each other with the help of one relay. We consider the time-division twoway relay channel without power control, where the broadcast channels are orthogonalized in time and where the two users and the relay use the same transmission power. We describe a joint network-channel coding method for this channel model, where channel codes are used at both users and a network code is used at the relay. The channel code of one user and the network code form a distributed turbo code which we call turbo network code and which can be iteratively decoded at the other user. Moreover, we conjecture closed expressions for lower bounds for the channel capacities of the time-division relay and twoway relay channel without power control and deliver simulation results of the proposed turbo network code. I