Per-antenna-rate-control (PARC) in frequency selective fading with SIC-GRAKE receiver

In this paper we consider a generalization of the per-antenna-rate-control (PARC) MIMO scheme for the HSDPA option of WCDMA. The scheme, called PARC-N, allows the number of transmitted data substreams N to be less than the number of transmit antennas M and selects the best N antennas for transmission. We investigate PARC-N specifically in frequency selective fading environments. First, we develop a novel receiver structure that combines successive interference cancellation (SIC) with generalized-RAKE technology that achieves a good balance between performance and complexity. We then draw several interesting conclusions: (1) data throughput can be maximized by using N ≤ M, where N may be adaptively selected based on operating conditions; (2) data throughput is maximized by allocating all non-data signal power (pilots, voice, overhead, etc.) to as few transmit antennas as possible; and (3) the use of pilot subtraction at the receiver is much more beneficial in MIMO systems than in single-antenna or receive diversity systems.