Exploiting Multiple Antennas for Synchronization

Orthogonal frequency-division multiplex (OFDM) offers a low-complexity solution to equalization in multipath channels but does so by increasing the symbol period. This places a limit on the mobility of such systems since time variations in the channel during the symbol period introduce intercarrier interference (ICI), hence, degrading performance. Solutions to reduce ICI in the literature require a high degree of processing. Increasing terminal mobility also places greater requirements on synchronization processing to track the rapidly changing channel. This paper uses multiple antennas at the receiver so that the channel response can be decomposed into a number of more slowly varying channels. Independent synchronization processing and correction can be applied to each of the derived channels before combining the signals prior to the fast Fourier transform (FFT) process. By individually processing the channels, the effective channel is compressed in the time and frequency domains, improving system performance. Perfect tracking of the multipath clusters is initially assumed to show the potential benefits, followed by operation with an idealized tracking algorithm. Operation with more realistic processing algorithms using fixed sectored elements improving the bit error rate (BER) is investigated. Finally, the benefits are then demonstrated with real measured channels from an urban environment.