Blind CMA beamforming for narrowband signals with multipath arrivals

Abstract

SUMMARYThe constant modulus algorithm (CMA) is a popular and e ective method for blind adaptive beamforming in various wireless communication systems. Traditionally, signals of arrival are considered to be independent. However, multipath propagation in wireless systems often results in several correlated signal arrivals. Because of multipath arrivals, CMA beamformers cannot be expected to place nulls in the direction of all interferers as assumed in some existing beamforming. In this paper, we present a simple convergence analysis of CMA under multipath correlated arrival signals. We propose two adaptation techniques based on CMA to capture di erent source signals. One approach is to use an orthogonal projection constraint on the beamformer parameters. The other approach relies on the independence of source signals and exploits a Gram-Schmidt orthogonalization at the beamformer outputs. Both methods are tested through computer simulations. ? 1998 John Wiley & Sons, Ltd.

Joint Power Control and Blind Beamforming over Wireless Networks: A Cross Layer Approach

“…can be easily estimated at the receivers. The power allocation is balanced at the equilibrium when the power update in (11) has converged. The level of CCI depends on both channel gain and transmit power.…”

“…As a majority of communication systems often struggle with the limited bandwidth constraint, it is desirable for the receiver with multiple antennas to steer to the desired direction and to estimate the transmit signals without consuming much channel bandwidth. By eliminating the training sequence overhead, used for estimation, and maximizing the channel capacity for information transmission, blind estimation and beamforming [9,10,11,12,13,14,15,16] offer a bandwidth efficient solution to signal separation and estimation. Its importance also lies in the practical need for some communication receivers to equalize unknown channels without the assistance and the expense of training sequences.…”