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.
Highlights
1.1 Background Recently, two-way relay model, termed as bidirectional relay model [1,2,3,4,5,6], where two sources exchange information via some assisting relays, has attracted more and more attention, because such model has popular applications in modern communication systems, including relay-assisted cellular networks, satellite communications, and peer-to-peer settings in wireless ad hoc networks [1, 6, 7]
We focus on the resource allocation for digital network coding (DNC)-based two-way relay networks over Orthogonal frequency division multiplexing (OFDM) channels
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 very high probability
Summary
1.1 Background Recently, two-way relay model, termed as bidirectional relay model [1,2,3,4,5,6], where two sources exchange information via some assisting relays, has attracted more and more attention, because such model has popular applications in modern communication systems, including relay-assisted cellular networks, satellite communications, and peer-to-peer settings in wireless ad hoc networks [1, 6, 7]. Unlike previous works (see, e.g., [25]), our goal is to minimize the total transmission completion time for two-way relay flows to guarantee their fairness by jointly optimizing system resource allocation, including subcarriers, powers, and flows’ transmission rates. 1. A two-phase joint resource allocation and network coding transmission protocol is presented to minimize the total transmission completion time for two-way relay flows. Theorem 1 claims such an important fact in the view of network planning: to obtain the minimal transmission completion time in the source phase, the two sources should proportionally allocate their transmission rates, satisfying that This gives us an insight to design the suboptimal resource allocation schemes for source phase. We derive a suboptimal subcarrier allocation scheme for the transmission in the source phase, described in Algorithm 1
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