Fangwei Tong

Experiment and Simulation Results of Adaptive Antenna Array System at Base and Mobile Stations in Mobile Environment

In a time division duplex (TDD) based adaptive antenna array (AAA) and space division multiple access (SDMA) systems, array weights determined from the up-link signals can be applied to the down-link signal transmission because of the channel reciprocity. However, under time-varying fading conditions, for example that created by a rapidly moving mobile station (MS), the channel change between the array weight determination time in the up-link and the down-link signal transmission degrades the accuracy of the array weight. Thus, the spectral efficiency of the system degrades in the down-link. In this paper, we introduce a prototype of an MS with a 2-element antenna array and present the down-link mobility performance results of computer simulations and field experiments in a field trial system of i-Burst, which is a TDD based wireless broadband system employing the AAA/SDMA techniques at the base station. Both results show that adaptive antenna processing at an MS is effective in improving the down-link mobility performance of TDD-AAA/SDMA systems.

Quasi field test results of adaptive array processing suitable for CDMA2000 1xEV-DO terminal

The performance of a terminal adaptive array for the CDMA2000 lxEV-DO system was evaluated. To reproduce the actual fading environment to which a mobile terminal is exposed, a field test was conducted utilizing a 4-element circular array experimental system in the commercial 800 MHz band cdmaOne environment. The fading features were extracted from the recorded cdmaOne forward link signals and applied to the simulation for the CDMA2000 1xEV-130 terminal adaptive array. An MMSE algorithm was used for the adaptation of the weight vector and the median of CIR (carrier to interference power ratio) was improved by more than 10 dB when the quasi field data was used in the simulation. Furthermore, this paper proposes a simple and effective method to save the calculation cost when obtaining the weight vector and thus, reducing the power consumption. Simulation results show that at the expense of 0.3 dB degradation of CIR compared with the full calculation, 76.6% of the calculation cost is saved by the proposed method.

Experimental Performance Results of Adaptive Antenna Array System at Base and Mobile Stations in Mobile Environment

In a TDD based AAA/SDMA system, the array weights determined from up-link signals are applied to the downlink transmission because of the channel reciprocity. However, under fast fading conditions, for example due to fast moving MS, the array weights are no longer optimum for the downlink signal transmission and hence the spectral efficiency of the system degrades. In this paper, we present the downlink performance of MS with two antenna elements moving at speeds of ~5, 20 and 40 kmph in the field trial system of i-Burst, which is a wireless broadband system employing AAA and SDMA techniques. The field experiment results show that adaptive antenna processing at MS is effective in improving the mobility performance of TDD-AAA/SDMA system

Experimental Results on Mobility Improvement Effects of Adaptive Antenna Arrays Applied to Mobile Stations in SDMA System

Space division multiple access (SDMA) technology attained increasing interest due to its ability to increase system capacity, and thereby to improve frequency usage efficiency. Especially in the Time Division Duplex (TDD) system, the SDMA system is simple due to the reciprocity of TDD channel. However in a fast fading environment, performance of the downlink transmission degrades significantly, since the adaptive control can not track fast changing channels due to the time difference between receive and transmit time slot. iBurst is a TDD broad band wireless communication system, which uses SDMA technology with its 12-element antenna array on the base station side to increase frequency usage efficiency. In this paper, a 2- element Adaptive Antenna Array was introduced into an iBurst mobile station and the field experiments were carried out. The field experiment results show that the performance degradation in fast fading channels is recovered and the mobility is enhanced.

A null-steering adaptive antenna array for mobile stations

A local virtual signal tuned (VST) null-steering adaptive antenna array applied to mobile stations is proposed in this paper. The VST adaptive array detects the spatial signature of the incident signals and generates local uncorrelated virtual signals based on the spatial signature to control the array weights in order to form the required array radiation pattern. The VST array can control its directivity pattern very flexibly and shows good performance for a practical CDMA mobile communication system with a continuous pilot signal. In this paper, the interference suppression performance of the VST array is evaluated for a burst pilot signal mobile communication system. The results show that the VST has better interference suppression performance under severe operation and poor reception conditions compared to an MMSE sense adaptive algorithm.