IEEE 802.16 鏈結調整演算法之研究

Abstract

During the last pass years, the broadband wireless access technologies, such as IEEE 802.11a/g/n have developed to become mature and provide high speed Internet services. At the same time, the mobile personal devices, such as personal digital assistant (PDA), laptops, and mobile phones have developed to cheaply, powerful functions, compactness, mobility, and less battery consumption. People can easily use mobile personal devices to access Internet services via broadband wireless access technologies. So, many of commercial and residential consumers have rapid grow on multimedia applications demand, such as Video conference, Video on Demand (VoD), Voice over IP (VoIP), online game, and peer to peer applications running on mobile personal devices. But IEEE 802.11 is not suitable for mobility and the radio coverage area is not too far. Therefore, another broadband wireless access technology that IEEE 802.16 is proposed. Due to it has mobility and long distance transmission characteristic. IEEE 802.16 is good for outside use. In any wireless network, the quality of the received signal may change over a short period of time due to noise, interference, multipath, and mobility effect. These characteristics of wireless can lead to occurring bit errors at the receiver. A good link adaptation scheme can take care of these conditions. In this paper, we proposed an efficient link adaptation algorithm, and compare it with several other algorithms in large and small scale fading environment. The idea of our algorithm is choice small transmission time with good protocol data unit (PDU) success rate to transmit a frame successfully. And the proposed link adaptation algorithm is also implemented burst error detector to prevent the burst errors condition after the rate is selected. The burst errors detector can fast reflect the wireless channel is changed violent. The proposed link adaptation algorithm uses ACKs, PDU success rate, transmission time, PDU size, and consecutive frame loss times as the parameters. We evaluate the performance of the proposed algorithm via Qualnet 4.0 emulator. According to the simulation results, we can clearly see that our proposed algorithm has better performance than other algorithms.