Statistical distributions that arise in constrained beamforming with incomplete channel information

Abstract

Abstract-We examine the statistical distribution of received power when a subscriber terminal with multiple transmit antennas beamforms on the uplink of a wireless orthogonal frequencydivision multiplexing system to a basestation with multiple receive antennas. We assume that a time-division duplex terminal has incomplete uplink channel knowledge obtained by measuring the downlink channel during basestation transmissions. The basestation transmissions employ cyclic delay diversity, of which the terminal is unaware. The distribution of uplink power received at the basestation, with and without downlink cyclic delay diversity and with various types of power constraints at the terminal, allow us to make some surprising conclusions about how the power constraints and cyclic delay influence the performance of beamforming. We show that beamforming gains need to be examined critically beyond simple average performance metrics to conclude that they are superior to simpler channel-unaware methods. We also conclude that cyclic delay on the downlink is very beneficial to beamforming on the uplink, even with restrictive types of power constraints.

Opportunistic bi-directional scheduling under quality of experience demands

“…Joint UL-DL also extends to other areas. The problem of UL-DL unfairness in transmission control protocol (TCP) flows is discussed in [9], and the interactions between UL and DL while using cyclic delay diversity (CDD) are studied in [10].…”

Power Allocation in Multi-Antenna Wireless Systems Subject to Simultaneous Power Constraints

“…In [10], an optimization problem for a multiuser downlink channel with multiple transmit antennas at the base station subject to per-antenna power constraints is considered, which is transformed into a dual uplink problem. In [11], per-antenna power constraints are considered in MIMO wireless systems in the context of beamforming with incomplete CSI. Also, [12] studies optimal power allocation subject to p -norm constrained eigenvalues, which can be viewed as a suboptimal power allocation policy under shortterm and per-antenna power constraints.…”