| IEEE 802.15.4 is a standard which specifies the physical layer (PHY) and medium access control (MAC) sublayer specifications for low-rate wireless personal area network(LR-WPAN). It could be applied in many fields, such as wireless sensor network, home automation and medical appliances, etc. In order to explore its potential applications and show the powerfulness of Software-Defined Radio, IEEE802.15.4 protocol has been implemented in the GNU radio and the USRP platform. At the same time, packets could be evaluated by Wireshark.Different with the existing method, which has many limitations and problems, the method in the paper has optimized the implementation of IEEE802.15.4 in the GNU Radio and the USRP platform and further studied the wireless link quality, thus optimizing the link quality indicator (LQI) algorithm. It goes as following.Firstly, in the method, the dispreading operation which was formerly performed in GNU Radio was moved to FPGA of the USRP, to reduce the burden of processing signal of CPU, thus taking full advantage of the FPGA, improving the performance of the protocol, and reducing the limit to the transmission rate and distance.Secondly, a great improvement is made on the chip matching algorithm. In the process of matching, the threshold only works for the source device address field which solves the prime problem of the high PER and guarantees the reliability of the packets.Thirdly, the paper reports a sound evaluation on the implementation process by Wireshark and a thoroughly analysis on the IEEE802.15.4 protocol.Finally, because of the importance of LQI in the IEEE802.15.4 network, the method optimizes the LQI algorithm, which makes the measurement of LQI more accurate. Moreover, an appropriate sample numbers so as to calculate the sample average and baseline LQI value of good link quality had been deduced, which will contribute a lot to the relating LQI researches. |
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