A Study to Ensure Communication Reliability of Bus Location System Using LoRa Communication

Abstract

We have developed a bus location system, “Busdoko,” that utilizes LoRa. Recently, LoRa has been increasingly used in local cities. As a result, it has become difficult to maintain real-time performance. Conventional TDMA does not allow transmission overlap between slots, and requires guard gaps. The transmission time of LoRa covering the city is long. There is a report that it takes about 13 seconds. In this case, the slot interval should be set to about 30 seconds including the guard gap. The distance between bus stops of community buses is short, and there are several places where the running time is about 30 seconds. We can't make the bus location systems in conventional TDMA, because it is necessary to display the position of the bus at least once between bus stops. We propose a communication scheme using multi-channel multiple access communication. In the scheme, the slot interval is designed to allow overlap within a permissible range. We evaluated the proposed scheme on a bus route. We confirmed that the system works correctly even if we allow a few percent transmission overlap between slots. The experimental results showed that the proposed scheme made effective use of the channels and improved reliability.