Peter Slanina

Smart antennas for UTRA TDD

Due to the increasing number of users in mobile communications and the demand for mobile multimedia services with high data rates, third generation mobile radio systems are currently one of the key communication technologies in research, development, and international standardization bodies. Smart antennas can be used to increase the capacity of wireless communication systems even further. TDD systems are particularly attractive for the employment of smart antennas, since the channel information (e. g., in terms of spatial covariance matrices) estimated on the uplink can be used directly for downlink beamforming. In this paper, we discuss efficient uplink and downlink processing techniques with smart antennas for UTRA TDD, the TDD mode of third generation mobile radio systems that is based on TD—CDMA. On the uplink, joint space—time processing is used to eliminate co—channel interference created by other users that transmit on the same frequency and in the same time slot. These joint detection techniques are efficiently implemented in the frequency domain. On the downlink, the data is only transmitted in the direction of the desired mobile user while interference in the direction of co—channel users is avoided. Moreover, short—term spatial channel estimates can be improved by projecting them into the dominant subspace of the long—term spatial covariance matrix. System level simulations have been performed to evaluate the gain in spectral efficiency (available bit rate per bandwidth per cell) if simple downlink beamforming techniques are used at the base stations. There is a two— to three—fold spectral efficiency gain if antenna arrays of M = 8 elements are deployed in a sectorized macro—cellular environment.

A Cost-Function-Based Dynamic Channel Allocation and Its Limits

Design of efficient dynamic channel allocation (DCA) algorithms has an important impact on performance optimization of wireless mobile networks. The previously proposed DCA algorithms are shown to have good performance but only for certain services and under certain load conditions. Within this paper, we propose a new cost-function-based DCA algorithm, which is fully adaptive to service and load conditions and includes some well-known DCA algorithms such as random, minimum interference, and autonomous reuse partitioning DCA as special cases. By using dynamic system-level simulations, we show that the algorithm provides the same or substantially better performance than these DCA algorithms, with low signalization and computation overhead. We also show the general limits of DCA algorithms in the presence of other interference reduction techniques such as power control and smart antennas.

Scheduling algorithm for UTRA TDD mode

A method of assigning resources to different non-real time (NRT) bearers within a cell of UMTS Terrestrial Radio Access/Time Division Duplex (UTRA/TDD) system is discussed. A very important measure of the quality of such a scheduling algorithm is the ratio of satisfied users at a certain system load. Different criteria for a satisfied user requires different scheduling methods. We propose an adaptive algorithm that can deal with different satisfied user criteria by simply adjusting a single parameter. Simulations have been performed for downlink traffic for various data rates. The available results include ratio of satisfied users, data throughput and block delay. Considering these results we can conclude that the proposed algorithm works quite well due to the possibility of optimizing different output parameters (ratio of satisfied users, data throughput, block delay) by adjusting a single scheduling parameter.

Inter-cell Interference Management by Dynamic Channel Allocation, Scheduling and Smart Antennas

An impact of dynamic channel allocation, opportunistic scheduling and smart antennas on inter-cell interference, and consequently on system performance is studied in this paper. It is shown that from the receiver point of view the most effective inter-cell interference reduction method is the opportunistic scheduling, followed by smart antennas, and dynamic channel allocation. Furthermore, interesting trade-offs that can be made by combining these techniques are observed as well.

A Self-Adaptive, Utility-based Scheduling for Wireless Cellular Networks

Design of efficient scheduling algorithms has an important impact on performance of wireless mobile networks. The previously proposed scheduling algorithms like Best CQI and Proportional Fair have good performance, but only for certain load and services types. Within this work, we propose a novel Utility based Scheduling algorithm, which is fully adaptive to service and load conditions and includes some well known scheduling algorithms as special cases. We show by using dynamic system level simulations that the algorithm provides same or substantially better performance than these scheduling algorithms, with low signalization and computation overhead.