| Summary: | 碩士 === 國立清華大學 === 通訊工程研究所 === 95 === In this thesis, we analyze the efficiency and delay of distributed source coding (DSC) in sensor networks under the random access setting. Consider a network of N sensors that observes correlated information from the environment and sends the local data to a central processor through direct transmission links. Due to the low message rate in sensor networks, we adopt the slotted ALOHA random access protocol where the time is divided into synchronized time slots and each sensor is allowed to access the time slots with independent probabilities. To eliminate the redundancy in the transmission data, the sensors encode the local messages based on the Slepian-Wolf DSC method. Specifically, the network is divided into K clusters and we assume that the sensors are encoded sequentially in a cluster such that the decoding of a particular message is reliant on the successful decoding of all the messages encoded earlier in the sequence.
In this case, the loss of one message may result in the failure of other messages and the delay in the successful decoding of a particular message also varies from sensor to sensor. In this article, we analyze the performance of DSC in random access networks in terms of the rate of successful decoding, the average delay and the average energy consumption of each message. Specifically, we propose and compare different transmission probability assignments for DSC in the ALOHA network and emphasize the importance of the MAC design. Finally, we propose an adaptive MAC protocol such that improve the performance of our system.
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