The capacity of downlink multi-input multi-output (MIMO) systems is significantly limited by inter-cell co-channel interference (CCI). Improving the performance of cell edge users who suffers strong inter-cell CCI is still a crucial issue. In this paper, coordinated beamforming (CBF) algorithm for multicell multiuser MIMO system is proposed to cope with the presence of intel-cell CCI. In multicell environment with MIMO channel, limited base station (BS) cooperation is considered to design optimal transmit and receive beamformers which make interference-free at the receiver. Simulation results show that the proposed algorithms can improve the capacity of cell edge user effectively as well as the overall system capacity for multiuser multicell MIMO system.

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Channel prediction tools using ray-tracing scheme the WLAN service area. Besides, the channel can be used to get information of communication channel instead measurement system has limited resolution in itself and of channel measurement. Three dimensional (3D) ray-tracing the observational errors which are made during technique is known for the better accuracy compared to two dimensional (2D) ray-tracing. But it requires a lot of calculations, measurement procedure may not be ignorable [1]. thus 2D simulation has been generally performed. This paper shows how precious 3D ray-tracing predicts the received power Channel prediction tools using ray-tracing technique indoors compared to 2D one. For this work, wave propagation can be used as an alternative solution. They give the phenomena are analyzed using Finite Difference Time Domain channel information predicted from the blueprint of the (FDTD) method and the channel measurement data also will be offered as a standard of comparison.target environment using geometrical OptiCS simulaton without wasting time and labor. 2D Ray-tracing schemes Index terms -ray-tracing, 3D, channel measurement, are already well-known as good channel prediction simulation, FDTD, indoor, channel modeling. techniques in [2], [3]. Recently three dimension (3D) ray-tracing techniques have been studied as in [4], [5]. I.INTRODUCTIONGenerally, it is known that the prediction performance using 3D ray-tracing scheme is better than 2D one. A Wireless Local Area Network (WLAN) system does However, the reasonable comparison of prediction not always operate with its best performance. The data performance between 2D and 3D was not studied rate on the system can decrease below what was sufficiently. In this paper, we will give the channel expected or the communication link can be totally prediction performance using 3D ray tracing compared broken in many actual situations. There are many with 2D. And the channel measurement data are also adverse conditions which may deteriorate the given as a standard of channel prediction performance. performance of WLAN systems. Particularly in physical layer, the following situations can be counted. First, we This paper is organized as follows. Section II gives a can consider the situation that the transmitted power brief introduction about wave propagation modeling in from an Access Point (AP) do not spread over all the 2D. In Section III, wave propagation phenomena in 3D target area enough to detect the transmitted signal. are analyzed using FDTD method. Section IV shows Secondly, it can be due to the strong frequency how 3D ray-tracing scheme can be derived from 2D one. selectiveness in a multi-path channel. Badly distorted by In Section V, the performance of 3D ray-tracing is such a strong selectiveness in frequency domain, the compared to 2D ray-tracing and channel measurement transmitted signal cannot be recovered at the receiver data. Finally, Section VI presents the conclusions of this even being used equalizers or channel code-decode study. techniques. And...