Performance improvement of UMTS uplink beamsteering with limited feedback at higher terminal velocity by designing adapted algorithms

So called open loop transmit diversity algorithms for the uplink of UMTS are a topic of recent studies within the 3rd Generation Partnership Project (3GPP). These algorithms use the power control commands of the fast power control mechanism as feedback information to iteratively determine the antenna weights, thus making them compatible with existing networks and procedures. The algorithms presented in literature so far are all designed for a fixed velocity of the mobile terminal. In this paper, evolutionary optimization techniques are employed to design beamsteering algorithms that are adapted to different mobile terminal velocities. These different algorithms are represented by lookup tables that can easily be stored in the terminal. A system is proposed that utilizes information about the current terminal velocity extracted from the downlink signal to always select the most suitable algorithm from a small set of such algorithms. With such a system, the transmit power at the terminal is reduced by 3.3 dB at low mobile velocities of 3 km/h and by 1.9 dB at medium velocities of 30 km/h. This transmit power gain of the proposed system with dynamic adaption of the beamsteering algorithm to the current mobile speed is 0.9 dB higher than with systems with a fixed beamsteering algorithm for all speeds.