MBOC: The New Optimized Spreading Modulation Recommended for GALILEO L1 OS and GPS L1C

Abstract

This paper describes the Multiplexed Binary Offset Carrier (MBOC) spreading modulation that has been recommended by the GPS-GALILEO Working Group on Interoperability and Compatibility. The MBOC(6,1,1/11) power spectral density is a mixture of BOC(1,1) spectrum and BOC(6,1) spectrum, that would be used by GALILEO for its Open Service (OS) signal at L1 frequency, and also by GPS for its modernized L1 Civil (L1C) signal. A number of different time waveforms can produce the MBOC(6,1,1/11) spectrum, allowing flexibility in implementation, although interoperable waveforms remains an objective for GALILEO and GPS. The time-multiplexed BOC (TMBOC) implementation interlaces BOC(6,1) and BOC(1,1) spreading symbols in a regular pattern, whereas composite BOC (CBOC) uses multilevel spreading symbols formed from the weighted sum of BOC(1,1) and BOC(6,1) spreading symbols, interplexed to form a constant modulus composite signal. This paper provides information on the history, motivation, and construction of MBOC signals. It then shows various performance characteristics, and summarizes their status in GALILEO and GPS signal design.