Transmission Control in Two-way Relay Channels with Network Coding (XORing)---A Discounted Markov Decision Process Formulation with Structured Policies Monotonic in Queue and Channel states

Ni Ding (ANU)

APPLIED SIGNAL PROCESSING SERIES

DATE: 2013-06-20
TIME: 11:00:00 - 12:00:00
LOCATION: RSISE Seminar Room, ground floor, building 115, cnr. North and Daley Roads, ANU
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ABSTRACT:
We consider the downlink transmission control problem over two-way relay channels (TWRC), where network coding (XORing) is allowed but the symbol arrivals are random. We assume that there are two queues maintained in the relay to buffer message inflows from two users respectively, and the outflows of the queues are controlled by a scheduler. It has the right to decide whether or not to transmit a coded (XORed) or non-coded symbols periodically in order to minimize symbol delay, transmission power and downlink bit error rate (BER) simultaneously and in the long run. With the two downlink fading channels modelled by finite-state Markov Chains (FSMC), we formulate the problem by a discounted infinite-horizon Markov decision process (MDP). We show that the optimal transmission policy is monotonic in buffer occupancies and channel states by showing that the submodularity, L-natural convexity and multimodularity between the states and actions are propagating through dynamic programming.