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Issue No. 05 - May (2014 vol. 13)
ISSN: 1536-1233
pp: 979-991
Hong Xu , Dept. of Electr. & Comput. Eng., Univ. of Toronto, Toronto, ON, Canada
Baochun Li , Dept. of Electr. & Comput. Eng., Univ. of Toronto, Toronto, ON, Canada
This work seeks to address two questions in cooperative OFDMA networks: First, how network coding based cooperative diversity can be exploited effectively when overhearing is not readily available. Second, how to realize various forms of gains available, including multi-user diversity, cooperative diversity, and network coding. The main contribution of this paper is an unifying network utility maximization framework that jointly considers relay assignment, relay strategy selection, channel assignment and power allocation. We formulate the optimization problem both with and without XOR-CD, a simple XOR-assisted cooperative diversity scheme. We show that the optimization of physical layer resource allocation with XOR-CD is equivalent to a weighted 3-set packing problem, which is NP-complete, and can be efficiently solved with provably the best approximation factor. Without XOR-CD, the problem reduces to a weighted bipartite matching problem which can be optimally solved.
resource allocation, approximation theory, cellular radio, computational complexity, cooperative communication, diversity reception, frequency division multiple access, network coding, OFDM modulation, optimisation, relay networks (telecommunication)

Hong Xu and Baochun Li, "An Optimization Framework for XOR-Assisted Cooperative Relaying in Cellular Networks," in IEEE Transactions on Mobile Computing, vol. 13, no. 5, pp. 979-991, 2014.
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