BPSK is the basis of current GNSS (Global Navigation Satellite System) signals. BDS (Beidou navigation satellite system) RDSS (Radio Determination Satellite Service) system also adopts BPSK to realize communication and ranging simultaneously. To realize higher system capacity, RDSS signals overlap in time and frequency domain. The signal performance is heavily determined by the MAI (Multiple Access Interference) between overlapping signals. In this paper, SSMSK (spread spectrum MSK) is proposed. The signal performance is investigated under four conditions considering the main lobe bandwidth and the receiver bandwidth. The maximum number of overlapping signals for SSMSK is 11.7% higher than BPSK when the receiver bandwidth is for the side subcarrier. And the value is 10.6% when the receiver bandwidth is. SSMSK can be received utilizing BPSK local signal. When the receiving bandwidth is , the correlation peak of SSMSK_BPSK is identical to BPSK. The tracking accuracy of SSMSK is higher than BPSK when the correlation interval is between 0.2-1 chips. The accuracy of SSMSK_BPSK is higher than BPSK when the correlation interval is 0.5 chips. The disadvantage of SSMSK is larger quantization word length. SSMSK is a better modulation for RDSS based on the comprehensive performance.

中文翻译：

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用于BDS RDSS信号调制的扩频MSK的建议

BPSK是当前GNSS（全球导航卫星系统）信号的基础。BDS（北斗导航卫星系统）RDSS（无线电确定卫星服务）系统也采用BPSK来同时实现通信和测距。为了实现更高的系统容量，RDSS信号在时域和频域重叠。信号性能在很大程度上取决于重叠信号之间的MAI（多路访问干扰）。在本文中，提出了SSMSK（扩频MSK）。考虑到主瓣带宽和接收器带宽，在四种条件下研究了信号性能。当接收器带宽用于侧副载波时，SSMSK的最大重叠信号数比BPSK高11.7％。接收器带宽为10.6％时。可以使用BPSK本地信号来接收SSMSK。当接收带宽为 ，SSMSK_BPSK的相关峰与BPSK相同。当相关间隔在0.2-1个码片之间时，SSMSK的跟踪精度高于BPSK。当相关间隔为0.5码片时，SSMSK_BPSK的精度高于BPSK。SSMSK的缺点是量化字长较大。基于综合性能，SSMSK是对RDSS的更好调制。