Antenna Selection in LTE: From Motivation to Specification
Transmit Antenna Selection (TAS) technology has been adopted for the uplink by the next generation Long Term Evolution (LTE) wireless standard in order to harness the spatial diversity offered by multiple antennas at the mobile transmitter, while keeping the hardware complexity and cost of a mobile low. In TAS, the number of Radio Frequency (RF) chains for processing/up-conversion is smaller than the number of available antenna elements, so that at any time the signals can only be transmitted from a (dynamically optimized) subset of antenna elements. As a result, the training procedure for AS needs to be carefully engineered. In LTE, this is accomplished by reusing the wideband Sounding Reference Signal (SRS) for the purpose of AS training.