Abstract:
Wireless sensor networks (WSNs) define the low level layers which include physical (PHY) layer, medium access control (MAC) layer and network (NWK) layer. This thesis will concentrate on DSP design on PHY layer, which contain DSSS transmitter and DSSS receiver. Spread spectrum communication system has strong ability to resist jam and multipath interference. Therefore, it has been universally used in military, commercial or even civilian communication. Two types of spreading sequences will be investigated: one is standard binary sequence that is 32-chip standard PN sequence for 2.4 GHz unlicensed frequency band based on IEEE 802.15.4 Standard, another one is chaotic sequence that is based on cubic map. In addition, O-QPSK modulation scheme will be adopted in our PHY design. Furthermore, in real-world environment, channel is existed between DSSS transmitter and DSSS receiver. As a consequence, AWGN and Rayleigh fading channel will be discussed. In this thesis, we will investigate three types of DSSS communication system: Only AWGN channel is presented in the channel based on standard binary spreading sequence communication system, Rayleigh fading and AWGN are presented in the channel based on standard binary spreading sequence communication system, as well as Rayleigh fading and AWGN are presented in the channel based on chaotic spreading sequence communication system. This thesis will establish each system model, and then the theoretical expression will be derived in discrete time domain. After that, corresponding Matlab simulator will be design so that the bit error rate (BER) curves will be drawn in order to comparison the theoretical and simulated performance of each system. Finally, two ADSP-BF533 EZ-kit Lite Evaluation boards were employed, and the corresponding DSSS systems will be implemented on digital signal processing (DSP) hardware platform for the sake of examining the real -world performance of each system on the DSP technology.