A Novel Push-To-Talk Service over Beidou-3 Satellite Navigation System

BDS-3(Beidou Navigation Satellite System) started to provide global services since Dec 2018. The two-way SMS(short message service) of the BDS is an advantage over other satellite navigation systems. However, BDS SMS only supports text, causes inconvenience in many situations. We had developed a 300bps vocoder in 2017, which led to a 2-second voice message over BDS-1. Based on it, we used a SELP (sinusoidal excitation linear prediction) algorithm to develop a 600bps vocoder over BDS-3. Compared with the former one, voice quality has been improved from MOS 2.3 to MOS 3.5, coding delay has been increased from more than 200ms to 100ms. The voice length has been increased to 25 seconds. Our effort can offer subscribers a Push-To-Talk service over BDS. In May 2018 the novel technology has been recommended as a candidate to "International Maritime Rescue Satellite Terminal Standard". Our efforts have very important theoretical research significance and practical reference value for BDS.