Markov-Decision-Based Hybrid ARQ for Flexible Communications in Wireless Links

• Main Author: 黃健智
• Other Authors: 廖維國
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/34460610789644274942

碩士 === 國立交通大學 === 電信工程系所 === 93 === We consider using an adaptive hybrid of FEC and ARQ via Reed–Solomon (RS) code for real-time flexible communication over fading wireless channel. Because quite often there is not enough bandwidth to correctly transmit the packet in time, so it is worthwhile to decide to send or early drop the packet according to the importance of the packet and its timing constraints. To handle such a problem, we extend Liao and Yeh’s approach which deals with the same problem but with only ARQ in use. However, our problem in hand is made more difficult by the fact that the bandwidth demands for packets are different because the size of packet is lengthened if the RS code is used. As their approach, we also formulate the problem as a Markov-Decision problem and we also use the policy-iteration method to find out a good policy. The main difference from theirs is that the action in our policy is in the form of not only dropping packets but also the code rate for packet to be sent. Besides, the worse case in our design is more complicated than that in theirs by involving the consideration of different packet size. In our simulation, as a comparison we introduce another method which adapts the RS code only according to the channel state, and we show that our policy from MDP is better.