Network MIMO With Linear Zero-Forcing Beamforming: Large System Analysis, Impact of Channel Estimation, and Reduced-Complexity Scheduling

• Published in: IEEE transactions on information theory Vol. 58; no. 5; pp. 2911 - 2934
• Main Authors: Hoon Huh, Tulino, A. M., Caire, G.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-05-2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antennas; Applied sciences; Array signal processing; Base stations; Beamforming; Channel estimation; Channels; Clusters; Codes; Communication channels; Cooperation; Detection, estimation, filtering, equalization, prediction; Downlink; downlink scheduling; Exact sciences and technology; Feedback control systems; Information theory; Information, signal and communications theory; large random matrices; linear zero-forcing beamforming; Mathematical analysis; MIMO; Monte Carlo methods; network MIMO; Radiocommunications; Scheduling; Signal and communications theory; Signal, noise; Stations; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Terminals; Throughput; Transmission and modulation (techniques and equipments); Wireless networks; Performance evaluation; State feedback; Parameter estimation; Random matrix; Base station; Transmitter; Equity; Feedback regulation; Data transmission; Downlink; Transmission zero; Beam forming; Learning; linear zero-forcing beamforming; Channel estimation; System analysis; Uplink; Antenna; Large scale system; MIMO system; Scheduling; large random matrices; downlink scheduling; Signal processing; Transmission loss; network MIMO
• ISSN: 0018-9448; 1557-9654
• DOI: 10.1109/TIT.2011.2178230

We consider the downlink of a multicell system with multiantenna base stations and single-antenna user terminals, arbitrary base station cooperation clusters, distance-dependent propagation pathloss, and general "fairness" requirements. Base stations in the same cooperation cluster employ joint transmission with linear zero-forcing beamforming, subject to sum or per-base station power constraints. Intercluster interference is treated as noise at the user terminals. Analytic expressions for the system spectral efficiency are found in the large-system limit where both the numbers of users and antennas per base station tend to infinity with a given ratio. In particular, for the per-base station power constraint, we find new results in random matrix theory, yielding the squared Frobenius norm of submatrices of the Moore-Penrose pseudo-inverse for the structured non-i.i.d. channel matrix resulting from the cooperation cluster, user distribution, and path-loss coefficients. The analysis is extended to the case of nonideal Channel State Information at the Transmitters obtained through explicit downlink channel training and uplink feedback. Specifically, our results illuminate the trade-off between the benefit of a larger number of cooperating antennas and the cost of estimating higher-dimensional channel vectors. Furthermore, our analysis leads to a new simplified downlink scheduling scheme that preselects the users according to probabilities obtained from the large-system results, depending on the desired fairness criterion. The proposed scheme performs close to the optimal (finite-dimensional) opportunistic user selection while requiring significantly less channel state feedback, since only a small fraction of preselected users must feed back their channel state information.