Sabharwal, AshutoshMitra, Urbashi2007-10-312007-10-312005-06-012005-06-11A. Sabharwal and U. Mitra, "Rate-constrained Relaying: A Model for Cooperation with Limited Relay Resources," <i>IEEE Transactions on Information Theory,</i> 2005.https://hdl.handle.net/1911/20314Journal PaperIn this paper, the impact of limited resources on achievable rates in relay channels is investigated. Resource limitation is modeled as a rate constraint, Rbar, which constrains the rate at which a relay can reliably <i>decode</i> or <i>source-code</i> data. With this constraint in hand, the achievable rates for several protocols are derived and compared: decode-and-forward, estimate-and-forward, a Markovian amplify-and-forward and a hybrid scheme that combines decode-and-forward and amplify-and-forward. The key result is that the relative performance of these protocols in the unconstrained case is not maintained in rate constrained scenarios. The case of severe resource limitation (Rbar --> 0) is also considered. Previously established rates for unconstrained decode-and-forward and estimate-and-forward are re-examined in the context of optimal parameters and asymptotic performance. For most relay locations (topologies), either decode-and-forward and estimate-and-forward offers superior performance. However, for severe rate constraints, amplify-and-forward generally offers the best performance.engRelay channelcomplexityachievable ratesdecode and forwardestimate and forwardamplify and forwardJournal articleRelay channelcomplexityachievable ratesdecode and forwardestimate and forwardamplify and forward