Josef J. Blanz

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 mobile radio channel can be exploited by smart antennas to increase the spectral efficiency. In this paper, a novel smart antenna concept applying receiver antenna diversity at the uplink receiver is investigated for a time-slotted code-division multiple-access (CDMA) mobile radio air interface termed time-division CDMA (TD-CDMA), which has been selected by the European Telecommunications 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 scheme is presented, which is based on DOA estimation using the Unitary ESPRIT algorithm and maximum likelihood estimation of the channel impulse responses associated with the estimated DOAs, which can also be used as an input for advanced mobile positioning schemes in UMTS. The performance of the combined DOA and joint channel estimation is compared with the conventional channel estimation through simulations in rural and urban propagation environments. Moreover, a novel joint data detection scheme is considered, which explicitly takes into account the signal DOAs and the associated channel impulse responses. The link level performance of a TD-CDMA mobile radio system using these novel schemes is evaluated by Monte Carlo simulations of data transmission, and average bit error rates (BERs) are determined for rural and urban propagation environments. The simulation results indicate that, depending on the propagation environment, the exploitation of the knowledge of the directional inhomogeneity of the mobile radio channel can lead to considerable system performance enhancements.

On the Impact of Coarse Synchronization on the Performance of Broadcast/Multicast Single Frequency Network Operation in WCDMA

We evaluate the system-level performance and potential capacity gain of MBSFN (Multicast/Broadcast Single Frequency Network) operation in wideband CDMA (WCDMA) and compare it to conventional multimedia broadcast/multicast service (MBMS) provision with macro-diversity combining. MBSFN operation has recently been specified in the 3rd Generation Partnership Project (3GPP) as an enhancement to MBMS. It aims to mitigate the cell-edge problem of multicast/broadcast applications, which are typically dimensioned for a predefined coverage. In WCDMA as considered here, MBSFN operation refers to the use of a single common scrambling code and the same set of spreading codes to simultaneously broadcast bit identical MBMS data in a number of cells that form an MBMS cluster. Since intercell interference is drastically reduced by this concept, it has the potential of considerably increasing the spectral efficiency of MBMS. Nevertheless, coarse synchronization of the transmitting base stations is expected to degrade the performance of MBSFN. We study the system-level performance of MBSFN for WCDMA with imperfect synchronization of the base stations considering different equalization strategies.

WLC36-3: Selective Virtual Antenna Permutation for Layered OFDM-MIMO Transmission

In this paper we introduce selective virtual antenna permutation (S-VAP) for layered OFDM-MIMO transmission in downlink cellular environments. In the S-VAP scheme, the base station spatially permutes multiple independently encoded layers and then transmits the permuted layers over selected virtual antennas. The mobile station employs a successive interference cancellation (SIC) based receiver to maximize the spectral efficiency. The layer permutation enables a significant reduction of channel quality feedback information necessary to adjust the data rate of each layer. Transmission over selected virtual antennas instead of physical antennas enables efficient power amplifier utilization and thus brings out a quantized spatial water-filling gain.