Wireless Network Information Flow: A Deterministic Approach

摘要

In a wireless network with a single source and a single destination and anarbitrary number of relay nodes, what is the maximum rate of information flowachievable? We make progress on this long standing problem through a two-stepapproach. First we propose a deterministic channel model which captures the keywireless properties of signal strength, broadcast and superposition. We obtainan exact characterization of the capacity of a network with nodes connected bysuch deterministic channels. This result is a natural generalization of thecelebrated max-flow min-cut theorem for wired networks. Second, we use theinsights obtained from the deterministic analysis to design a newquantize-map-and-forward scheme for Gaussian networks. In this scheme, eachrelay quantizes the received signal at the noise level and maps it to a randomGaussian codeword for forwarding, and the final destination decodes thesource's message based on the received signal. We show that, in contrast toexisting schemes, this scheme can achieve the cut-set upper bound to within agap which is independent of the channel parameters. In the case of the relaychannel with a single relay as well as the two-relay Gaussian diamond network,the gap is 1 bit/s/Hz. Moreover, the scheme is universal in the sense that therelays need no knowledge of the values of the channel parameters to(approximately) achieve the rate supportable by the network. We also presentextensions of the results to multicast networks, half-duplex networks andergodic networks.