基于扩频ALOHA的RFID防碰撞算法

在射频识别系统中，读写器作用范围内的多标签识别存在数据碰撞的问题。为此，在分析ALOHA算法的基础上，应用码分多址技术，提出一种基于Gold码扩频的ALOHA防碰撞算法，并进行算法的推导和仿真。该算法的吞吐量会随着标签数据帧发送延时的增大而减小，随着扩频码数量的增加而增大。当扩频码数量和负载相等时，系统吞吐量最小；当扩频码数量大于负载时，吞吐效率会随扩频码数量的增加而增大，系统吞吐效率高于时隙ALOHA。应用Simulink构建基于码分多址的多标签与阅读器通信系统，分别研究信噪比、上行速率和帧长对通信误码率的影响，实验结果表明，该算法可提高阅读器与标签之间的通信质量，在现实情况下误码率趋近于0。

Anti-collision Algorithm for RFID Based on Spread Spectrum ALOHA

In the Radio Frequency Identification（RFID） system, in order to solve data collision problems between multiply tags existing within the scope of the reader during identification process, based on the analysis of ALOHA algorithm and the application of Code Division Multiple Access（CDMA） technology, an anti-collision ALOHA algorithm Based on Spread Spectrum（ABSS） is proposed. The throughput of this algorithm decreases along with the increase of frame＇s transmission delay and increases as the number of spread codes increase. When the number of spreading codes is equal to the load, the minimum throughput of this system is gotten. When the number of spreading codes is larger than the load, the throughput will increase with the number of spreading codes, so the throughput of system will be higher than that of slot ALOHA. CDMA-based communication system model of multi-tag and reader is established on Simulink to respectively study influence of the signal-to-noise ratio, the uplink rate and flame size on the communication error rate. Experimental data show that communication quality between the reader and tags is reliable, and in reality, the error rate is close to zero.