The Research And Implementation On MSK DSSS Based Key Technology Of Baseband Transmission In Wireless Sensor Networks

Wireless Sensor Network(WSN) is a synthetical intelligent information processing platform which integrate sensor technique, modern network and wireless communication technique. It has broad application prospect while it is one of the most active hotspot in information field and also one of the most significant technique which can change our future life.The energy-limited feature of WSN is taken into account in this article, combining with the application environment and design requirement of the subject, the communication system is then discussed and designed, as a focal point, key technologies for baseband transmission is researched and analyzed aiming at designing algorithm scheme meeting system needs and completing corresponding implementation and debugging verification work in project, the concrete content is as follows:Firstly, combining with the application character and design guarantee figures of the WSN subject, base upon MSK and DSSS, the physical layer communication system MSK DSSS and the frame format of data transmited in physical layer is designed. As a key point, two baseband transmission algorithm MDBPM-A(MSK DSSS Baseband Processing Method A) and MDBPM-B(MSK DSSS Baseband Processing Method B) is researched and given, the link-level simulation result and relevant analysis shows that: MDBPM-A is simple and not sensitive to frequency offset while its BER(bit error ratio) performance is worse. MDBPM-B is relatively complex and comparatively sensitive to frequency offset, but its BER performance is excellent. The link budget analysis indicates that MDBPM-B can meet the application requirement of the system, which validates the feasibility for MDBPM-B to be used in project in theory.Secondly, the overall implemental scheme of the system is designed base upon FPGA, giving attention to both saving chip resource and reducing time delay of processing, the hardware implementing method of each module in MDBPM-B baseband processing algorithm is introduced particularly, timing simulation result shows that the design of each module of the algorithm is resonable and the implementation is correct, the baseband processing of signal can be completed by using finite resource in chip. At the same time, according to system demand, an AGC scheme is designed and implemented base on FPGA.Finally, each implemented module of MDBPM-B algorithm is debugged in experimental hardware platform to verify its function, then debugging taches such as digital self-loop circuit of baseband, anolog self-loop circuit of baseband, anolog self-loop circuit of RF (Radio Freqency), interface between physical layer and upper layer and AGC are accomplished in sequence, the communication function is implemented between sensor nodes in wireless circumstance ultimately. The debugging results show that the implemented MDBPM-B algorithm can complete real-time and correct data transmission function, which demonstrates the validity and feasibility of baseband transmission algorithm and FPGA implementation scheme design in engineering practice.