Capacity Limits of Full-Duplex Cellular Network
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This paper explores the capacity limits of a wireless cellular network with full-duplex (FD) base station (BS) and half-duplex user terminals, in which three independent messages are communicated, i.e., uplink message m_1 from the uplink user to the BS, downlink message m_2 from the BS to the downlink user, and D2D message m_3 from the uplink user to the downlink user. Information theoretically, this wireless system can be interpreted as a generalization of the FD relay broadcast channel with side message transmitted from relay to destination. Our study starts with a simpler case that has only the uplink and the downlink transmissions of (m_1,m_2). For the discrete memoryless channel model, we propose a novel strategy that uses the BS as a FD relay to facilitate interference cancellation. The paper further provides a new converse which is strictly tighter than the cut-set bound. Taken together and specialized to the Gaussian case, our inner and outer bounds yield a characterization of the capacity to within a constant gap for the scalar and the vector Gaussian channel models. Furthermore, the paper studies a general setup with (m_1,m_2,m_3). For the discrete memoryless channel model, we incorporate Marton's broadcast coding to obtain an achievable rate region, which is larger than the existing ones. Regarding the converse, we derive a nontrivial outer bound by means of genie. For the scalar Gaussian channel model, it is shown that by using one of the two rate-splitting schemes depending on the channel condition, we can already achieve the capacity to within a constant gap. For the vector Gaussian channel model, we further show how dirty paper coding can be applied to coordinate the transmissions of (m_1,m_2,m_3) in three different ways. Finally, simulations demonstrate the advantages of using the BS as a relay in the FD cellular network.
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