High-speed cellular data systems demand fast downlink scheduling algorithms and multiple-input multiple-output (MIMO) techniques. The associated multiuser diversity and antenna diversity play a central role in achieving high system throughput and fair resource allocation among multiple users. For such systems we evaluate the cross-layer interactions between channel-dependent scheduling schemes and MIMO techniques, such as space-time block coding (STBC) or Bell Laboratories Layered Space-Time (BLAST), and propose a new scheduling algorithm named the alpha-rule. The evaluation shows that the STBC/MIMO provides a reliable channel but at a certain cost of spectral efficiency. Comparatively BLAST/MIMO provides larger capacity and enables higher scheduling throughput. Thus BLAST/MIMO may be a more suitable technique for high-rate packet data transmission at the physical layer. At the medium access control (MAC)-layer, the alpha-rule is shown to be more flexible or efficient to exploit the diversity gains than the exiting max-C/I or proportionally fair (PF) scheduling schemes. It enables online tradeoff between aggregate throughput, per-user throughput, and per-user resource allocation.
['Aimin Sang', 'Xiaodong Wang', 'Mohammad Madihian', 'Richard D. Gitlin']
Downlink scheduling schemes in cellular packet data systems of multiple-input multiple-output antennas