| With the rapid development of science technology, the field of scientific research steadily increased. In the bad and untouchable environment, the advantages of WSN are seemed outstanding especially. The gathered data of the traditional WSN are simple such as humidity, temperature, pressure etc. The technology is extended to the application of voice monitoring in this paper.Because of the characteristics of WSN(Wireless Sensor Network) such as wireless, multi-hops etc, choosing a reasonable route in the network layer is very critical in order to acquire better performance. Voice over WSN not only have the basic characteristics of the traditional WSN, but also have other characteristics such as large data volume, limited resources, sensitive delay and jitter, high requirement for packet loss rate, so, the routing protocol in voice over WSN is more complex. Many researchers at home and abroad have studied the problems related to voice over WSN, most of which are deal with the aspects of architecture, MAC(Media Access Control) layer protocol etc, but the QoS(Quality of Service) routing protocol is studied rarely, and most research results cannot meet the requirement for delay and bandwidth of transmitting speech without considering the new-add flow will cut down the quality of the flow existed. Furthermore, the topic of decreasing the influence that the new-added speech stream made to existed speech stream is desired for discussing.At the basis of the application filed and functions of WSN, the advantages and disadvantages of the existing QoS routing protocols and the admission control arithmetic are compared. The analysis results show that the existing QoS routing protocols are not suitable for the voice transmission, and the admission control policy of concentrating on the AP (Access Point) can not satisfy the characteristics of the nodes in WSN, such as random distribution, multi-hop transmission. In the paper, the evaluation standard for the quality of speech is discussed, the frame service delay and the available throughput of each streams under the EDCA mechanism of 802.11e protocol are analyzed, the method for computing max hop of the route is investigated, a QoS routing algorithm based on admission control is proposed finally. In the algorithm, the requirement that the hops of the route about to build must less than or equal to the max hop of route is seems to be the standard of selecting route, and the available throughput of each stream in network must satisfy the required bandwidth as same as the new-add speech stream will not reduce the quality of the transmitting streams is seemed to be the rule of admission control, Finally, the route is established, and the reliability of voice transmitting is also improved the at the same time.To check out the performance of the routing protocol proposed, a simulation experiment is carried out on the NS-2 simulation platform, the change result of single-hop average delay under the conditions of G.711 and G.729 coding algorithm, the conditions of different transmission probability and different number of speech streams are analyzed, furthermore, the influence that the number of speech stream effect to the available throughput and delay etc of each stream is analyzed. Finally, the routing protocol using admission control proposed in this paper is compared to the typical routing protocol-DAIQoS(Data Aggregation included QoS) protocol in WSN. The result shows that the algorithm proposed in the paper obtains better real time performance, the QoS of speech is guaranteed and the number of the speech stream in network is increased at the same time. |
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