Study On Technology Of Power Control In Broadband Wireless Communication System

Wireless Metropolitan Area Network (IEEE802.16) standard is a wireless communications technology that has a high-bandwidth, low-input, and covers a wide range, with an important application prospect in the market of broadband wireless access. Power control is a technique in radio resource management. In the wireless MAN communication system, power control technology can be used to reduce co-channel interference and energy-saving devices, thereby it increases the system capacity, plays a very important role in the wireless communication system. How to apply the power control technology for wireless metropolitan area network and to enable maximally with a certain complexity is an important research topic in wireless metropolitan area network.Response to the above, the thesis has the following tasks:1 Based on understanding the power control techniques and criteria of wireless communication systems, analysis of each power control algorithm for the characteristics and the impact on system performance were completed, the factors that affect the power control performance was pointed out.2 The uplink open-loop, closed-loop power control algorithm in power control mechanisms of WiMAX systems were summarized and studied. Considering the advantages and disadvantages of the two algorithms, in order to improve accuracy and reduce the time delay, a practical power control algorithm which combines the power control algorithm of open-loop and closed-loop was drawn up. The algorithm firstly did a rough adjustment for transmitting power with power control algorithm of open-loop, and then compensated through a more accurate power control algorithm of closed-loop. Simulation analysis showed that the algorithm significantly reduced the transmission power with a certain BER and delay conditions, and the performance was better.3 For each subchannel of OFDM system with different degree of fading, combing with adaptive modulation and coding technology and power allocation technologies, the traditional power control algorithm was improved. Based on SNR for each subchannel, the algorithm adaptively adjusted modulation coding schemes and initial power allocation, by adjusting the modulation coding and initialing power allocation rather than adjusting transmitting power to reduce inter-channel interference.4 Based on the system data rate and the average error rate under the conditions of adaptive modulation coding mode, the SNR threshold of modulation coding and the target SNR which system performance required were respectively used to compare with the receiver SNR to determine the modulation coding and power control commands. The simulation showed that the algorithm reduced the transmission power of system, thereby reduced energy loss and interference to other links or cellular. Finally, analysis and simulation of the power control algorithm based on adaptive power allocation were achieved, with the condition of a minimum transmission power. It reduced the system BER and maximized spectrum utilization.The results showed that if the power control algorithm and adaptive technology were combined, the performance of system can be greatly improved, the transmission power can be reduced. And it was applicable to multi-path frequency selective fading channel to meet the BWA system, in order to improve spectrum utilization and system performance requirements.