The Design And Performance Analysis Of Communication Protocol For Wireless POS Based On TD-CDMA System

Along with the development of national economy, the mechanics of banking industry starts to make great strides towards the direction of financial computerization. At the same time, the wireless network and the wired network will also realize the seamless fusion, which will provide optional access for the users anytime and anywhere. The system of wireless POS, which is characteristic of rapid assembly and strong mobility, receives people's favor day by day and becomes a better option for businesses. Because of the high error rate and the delay of transmission in wireless communications, there will be an enormous challenge for the application of the mature technology in the wireless environment.The traditional POS transaction system use the traditional transfer protocol, which has resulted in a lot of questions such as working for a long time,low reliability and low bandwidth utilization. This paper, based on the characteristics of the trading system, under the conditions of reliability, designs a new special communication protocol- WPTP (Wireless POS Transfer Protocol), to increase the bandwidth utilization, and make the effective use of the limited and valuable wireless resource.In this paper, firstly introduces the status of the wireless POS system and give the purpose of the study. Secondly, from the aspect of system performance, give an overall design of the wireless POS systems, explain the multiple access, duplex mode, channel distribution methods and the choice of code of the wireless POS system. Thirdly, design the division of slots,message formats,transmission flows and error control method of the wireless POS system. And then, in order to reduce the probability of packet re-transmission, design the mixed method-RS(31,25) and CRC-16 for error-correcting. Finally, introduce network simulation tool-NS2, and give the steps of how to simulate WPTP protocol by a layered approach. Simulation results show that, because of the error-correcting functions in WPTP, the re-transmission of packets have been significantly reduced in the wireless channel, at the same time, effective data which has been sent by WPTP is three times as many as sent by TCP. Therefore WPTP improved the utilization of bandwidth, and saved the valuable wireless resources. At the same time, simulation results testify that the WPTP protocol has achieved the target BER of the system.