Abstract
We introduce a distributed protocol to achieve multiuser diversity in a multicell multiple-input multiple-output (MIMO) uplink network, referred to as a MIMO interfering multiple-access channel (IMAC). Assuming both no information exchange among base stations (BS) and local channel state information at the transmitters for the MIMO IMAC, we propose a joint beamforming and user scheduling protocol, and then show that the proposed protocol can achieve the optimal multiuser diversity gain, i.e., KMlog(SNRlog N), as long as the number of mobile stations (MSs) in a cell, N, scales faster than SNR K M − L 1 − ϵ for a small constant ϵ > 0, where M, L, K, and SNR denote the number of receive antennas at each BS, the number of transmit antennas at each MS, the number of cells, and the signal-to-noise ratio, respectively. Our result indicates that multiuser diversity can be achieved in the presence of intra-cell and inter-cell interference even in a distributed fashion. As a result, vital information on how to design distributed algorithms in interference-limited cellular environments is provided.
Highlights
We first propose a joint beamforming and user scheduling method (A part of this paper was presented at the IEEE PIMRC in 2014 [14].) as an achievable scheme in a time-division duplexing (TDD) K-cell multiple-input multiple-output (MIMO) interfering multiple-access channels (IMACs) model consisting of N mobile stations (MSs) with L antennas and one base station (BS) with
It is shown that the proposed method yields higher sum-rates for all signal-to-noise ratio (SNR) regimes than those of the baseline schemes, whereas the MIMO IMAC opportunistic IA (OIA) scheme [13] is even inferior to the max-SNR scheme in a low SNR regime since it cannot obtain the power gain
We introduced a joint design of beamforming and scheduling in the MIMO
Summary
Multiuser diversity has been studied by showing an asymptotic system throughput in terms of a large number of users via opportunistic scheduling in slow fading environments. In multi-cell downlink networks, known as interfering broadcast channels (IBCs), a multi-cell random beamforming technique was proposed in [6], where it was shown that the optimal multiuser diversity gain, i.e., M log log N, can be achieved even in the presence of inter-cell interference. The authors of [11] proved that the optimal multiuser diversity gain can be achieved by introducing a distributed user scheduling even in the presence of inter-cell interference when both MSs and BSs have a single antenna, which was later extended to the case deploying multiple antennas at each BS, i.e., the single-input multiple-output (SIMO) IMAC model [12]. In [13], the optimal multi-user diversity gain was not analyzed whereas the user scaling law was analyzed for a given degree-of-freedom in the MIMO IMAC model
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