Adaptive Algorithm For Multi-Traffic QoS Guarantee Under B3G System

With the rapid growth of wireless broadband multimedia traffic, more requirements for wireless communication system have been put forward, such as high speed data transmission, high spectrum efficiency and QoS(Quality of Service). Therefore a new technique in 3GPP (3rd Generation Partner Project), HSDPA(High Speed Downlink Packet Access), which embraces LA(Link Adaptation) and MIMO(Multiple Input Multiple Output) comes out. It can support a transmission rate up to 10Mpbs. In order to support more mobile stations, broadband wireless communication system which adopts MIMO,OFDM(Orthogonal Frequency Division Multiplexing) and LA has become a popular subject. Today, LA research in MIMO-OFDM system concentrates on physical layer. It is too sensitive on the physical channel estimate error and feedback delay, and hasn't taken upper layer traffic QoS into consideration. Thus application of LA technique is restricted by these disadvantages, especially when reliable physical channel information are required. At present, a simple cross-layer research which combined the maximum retransmission times in ARQ(Automatic Repeat Request) and LA is proposed, but available information in ARQ is far from this. In this case, adaptive strategy research which combines more channel information of different layer or sub-layer communication protocols is of great importance. In this dissertation, cross-layer design is proposed, and its main research methods and achievements are list below: (1) Under the wireless fading channel environment, the dissertation gives a queue management method based on time and average queue length ,and a cross-layer intelligent MIR(Maximum Information Rate)adjustment strategy, which can maximize throughput, minimize the packets lost rate, and obtain a small queue delay and jitter. (2)A partial-window-multireject ARQ protocol is proposed which aims at overcoming the disadvantages of selective repeat ARQ and MR-ARQ(Multiple Rejects ARQ). Theoretical analysis and performance simulations have been explained in this dissertation. (3) Based on high performance ARQ, it gives two kinds of mechanism which can guarantee QoS of different traffic. One is multi-queue in one partial-window-multireject ARQ. The other is more than one ARQ in every user platform. Simulation which based on multi-queue in one ARQ and multi-ARQ has been done, and the results have been compared. (4) With all the researches done upon, we then put forward a cross-layer adaptive algorithm which combines ARQ and link adaptive technique in physical layer, in order to improve the spectrum efficiency and throughput. Performance analysis of cross-layer have been done. Due to the lack of combined simulation condition, it's difficult to go deep into the advantage of the cross-layer adaptive algorithm. Fortunately, partial algorithm designs have been practiced in another project, AirStream 5800 stationary wireless access products.