Nonlinear and Linear Broadcasting With QoS Requirements: Tractable Approaches for Bounded Channel Uncertainties

• Published in: IEEE transactions on signal processing Vol. 57; no. 5; pp. 1936 - 1947
• Main Authors: Shenouda, M.B., Davidson, T.N.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antennas; Applied sciences; Base stations; Broadcast channel; Broadcasting; channel uncertainty; Channels; Coding, codes; Design engineering; Detection, estimation, filtering, equalization, prediction; Downlink; Exact sciences and technology; Information, signal and communications theory; linear transceivers; Mathematical models; Mean square error methods; minimax design; Miscellaneous; Nonlinearity; Quality of service; quality of service constraints; Receiving antennas; robust transceiver design; Robustness; Signal and communications theory; Signal processing; Signal, noise; Studies; Telecommunications and information theory; Tomlinson-Harashima transceivers; Transceivers; Transmitting antennas; Uncertainty; Parameter estimation; Base station; Wireless telecommunication; Downlink; channel uncertainty; linear transceivers; Cell network; Transceiver; Mean square error; minimax design; Coding; Channel estimation; Broadcast channels; Broadcasting; Receiving antenna; Antenna array; quality of service constraints; Mobile radiocommunication; Broadcast channel; robust transceiver design; Tomlinson-Harashima transceivers; Transmitting antenna; Minimax method; User requirement; Signal processing; Numerical simulation; Signal to interference plus noise ratio; Service quality
• ISSN: 1053-587X; 1941-0476
• DOI: 10.1109/TSP.2009.2012904

We consider the downlink of a cellular system in which the base station employs multiple transmit antennas, each receiver has a single antenna, and the users specify certain quality of service (QoS) requirements. We study the design of robust broadcasting schemes that minimize the transmission power necessary to guarantee that the QoS requirements are satisfied for all channels within bounded uncertainty regions around the transmitter's estimate of each user's channel. Each user's QoS requirement is formulated as a constraint on the mean square error (MSE) in its received signal, and we show that these MSE constraints imply constraints on the received signal-to-interference-plus-noise ratio. Using the MSE constraints, we present a unified approach to the design of linear and nonlinear transceivers with QoS requirements that must be satisfied in the presence of bounded channel uncertainty. The proposed designs overcome the limitations of existing approaches that provide conservative designs or are only applicable to the case of linear precoding. Furthermore, we provide computationally efficient design formulations for a rather general model of bounded channel uncertainty that subsumes many natural choices for the uncertainty region. We also consider the problem of the robust counterpart to precoding schemes that maximize the fidelity of the weakest user's signal subject to a power constraint. For this problem, we provide quasi-convex formulations, for both linear and nonlinear transceivers, that can be efficiently solved using a one-dimensional bisection search. Our numerical results demonstrate that in the presence of bounded uncertainty in the transmitter's knowledge of users' channels, the proposed designs provide guarantees for a larger range of QoS requirements than the existing approaches that are based on bounded channel uncertainty models and require less transmission power to provide these guarantees.