Smart antennas for combined DOA and joint channel estimation in time-slotted CDMA mobile radio systems with joint detection

In cellular mobile radio systems, the directional inhomogeneity of the mobi le radio channel can be exploited by smart antennas to increase the spectra l efficiency. In this paper, a novel smart antenna concept applying receive r antenna diversity at the uplink receiver is investigated for a time-slott ed code-division multiple-access (CDMA) mobile radio air interface termed t ime-division CDMA (TD-CDMA), which has been selected by the European Teleco mmunications Standards Institute (ETSI) in January 1998 to form part of the Universal Mobile Telecommunications System (UMTS) air interface standard. First, a combined direction-of-arrival (DOA) and joint channel estimation s cheme is presented, which is based on DOA estimation using the Unitary ESPR IT algorithm and maximum likelihood estimation of the channel impulse respo nses associated with the estimated DOA's, which can also be used as an inpu t for advanced mobile positioning schemes in UMTS, The performance of the c ombined DOA and joint channel estimation is compared with the conventional channel estimation through simulations in rural and urban propagation envir onments. Moreover, a novel joint data detection scheme is considered, which explicitly takes into account the signal DOA's and the associated channel impulse responses. The link level performance of a TD-CDMA mobile radio sys tem using these novel schemes is evaluated by Monte Carlo simulations of da ta transmission, and average bit error rates (BER's) are determined for rur al and urban propagation environments. The simulation results indicate that , depending on the propagation environment, the exploitation of the knowled ge of the directional inhomogeneity of the mobile radio channel can lead to considerable system performance enhancements.