Comparison of on-line RF circuitry calibration methods for adaptive antenna array beam forming transmitter in forward link

This paper experimentally compares on-line RF circuitry calibration methods (i.e., real-time compensation methods for the phase/amplitude fluctuations of parallel RF receiver and transmitter circuitries during communication), which are inevitably used for adaptive antenna array beam-forming (AAA-BF) transmitter in the forward link. Experimental results elucidate that the residual phase and amplitude fluctuations after the RF receiver circuitry calibration employing an exclusive calibration signal are within only 0.4 degrees and 0.1 dB, respectively, while still achieving a loss in the required average received E_b/N₀ due to the insertion of the calibration signal in the reverse link within 0.1 dB. We also clarify that the required average transmit E_b/N₀ before adaptive antenna weigh multiplication at the average block error rate (BLER) of 10^-2 by using RF receiver circuitry calibration employing the exclusive calibration signal in the forward link is reduced by approximately 1.2 dB compared to that using the method employing the actual received signal when the received packet frame length is 10 msec and the average total received signal power in the reverse link is -95 dBm. Furthermore, the loss is slight in the required average transmit E_b/N₀ at the average BLER of 10^-2 using an AAA-BF transmitter based on minimum mean square error (MMSE) receiver antenna weight generation associated with RF receiver/transmitter circuitry calibration in three-user environments (transmission power of two-interfering users was higher by 15dB compared to that of the desired user) from that in a single user channel. These results indicate that the AAA-BF transmitter in the forward link sufficiently suppresses strong multipath interference (MPI) from interfering users with high transmission power.