Optimized Network Coding Efficiency under QoS Constraints in Two-Way Relay Networks with Timeouts

The paper considers a two-way relay network with network coding capabilities and an additional mechanism based on timeouts, used to ensure stability and bound the mean delay experienced by packets through the relay. Modeling of this system leads to simple closed form expressions that illustrate clearly the impact of the timeout parameters on the performance and efficiency metrics associated with the network coding operation. These results are subsequently employed for optimally tuning the timeout parameters, towards achieving the greatest network coding efficiency (and the corresponding throughput and energy efficiency improvement) that is possible for the given traffic profile, subject to a delay-related QoS requirement. Again, simple closed form results are obtained that support intuition and provide additional insight on the involved tradeoffs.