Transmission completion time minimization in digital network coding assisted two-way relay OFDM networks

Abstract

This paper investigates the two-way relay transmission over orthogonal frequency division multiplexing (OFDM) channels using digital network coding. For a given amount of data to be transmitted, we formulate an optimization problem to minimize the total transmission completion time by jointly allocating the power and assigning the subcarriers under individual power constraints. Due to the difficulty to derive the explicit solution to this optimization problem, we decompose it into two subproblems. Then, we design suboptimal algorithms with low complexity for the two subproblems, where subcarriers are assigned firstly and then the power is optimally allocated over the assigned subcarriers. The end-to-end delay is adopted to evaluate the system in a systematic view. Simulation results show that our proposed scheme achieves less than 1.06 times the minimal total transmission completion time achieved by exhaustive search for two-way relay OFDM systems and outperforms non-network coding schemes with a probability over 90%. Moreover, the corresponding distribution regions with performance gain are also discussed by simulations, which may give some insights in the application of network coding in OFDM systems.

Energy-efficient resource management for OFDM modulated bidirectional relaying with quality-of-service constraint

“…Currently, various physical-layer relaying and transmission techniques have been extended to orthogonal frequency division multiplexing (OFDM) modulated systems. The authors of [13] considered an OFDM modulated BDRS using digital network coding and proposed a joint resource allocation algorithm minimizing the total transmission completion time under individual power constraints. Considering a DF relay-assisted system, the authors of [14] developed a simultaneous wireless information and power transfer scheme.…”

“…Actually, the real probability of Pr p m T (k) > T m thr (k) can be kept below Q out if its upper bound is set to be less than Q out . Based on the above discussion, (14) leads to the closed-form expression of the threshold T m thr (k) as given in (13). Then, using the inequality 1 x+1 y ≥ 4 xy for x > 0 and y > 0 in [5] As depicted in Proposition 1, if p m T (k) > T m thr (k) holds, the system would be in outage.…”

“…Suppose that there are M relay nodes willing to forward messages for A and B. As such, the optimization problem at stage 2 can be written as (13…”

Network coding schemes with efficient LDPC coded MIMO–NOMA in two‐way relay networks

“…By applying network coding, the relay will receive the information from different sources so that the amount of transmitted information can be minimised and system throughput can be maximised [10,11]. Also, it is important to have effective and reliable communication in emergency conditions.…”