Performance Analysis of Combined $$m$$ MCSK– $$m$$ MFSK Modulation in AWGN and Rayleigh Fading Channel

Abstract

As there are many use cases considered for robotics communications, the data rate variation may be very large. Some sensor applications may require very low data rate, telemetry data may require low-to-medium data rates and e.g. video application will require high data rates. On the other hand, robots may have to operate in very difficult radio propagation environments such as nuclear power plants or industrial facilities. To combat difficult propagation characteristics, an often used and well known mechanism is to use spread spectrum signal structures. Thus in this paper a novel modulation method is considered which offers the inherent signal structure and processing opportunities of spread spectrum signal and at the same time offers an easy mechanism to adapt the data rate from low to high depending on the requirement at hand thus addressing two important communication requirements for robotics. The introduction of $$m$$ MFSK generated the idea of applying the given approach to other modulation methods. To further enlarge the modulation alphabet sizes (with the price of larger spectrum usage) it was realized that combining the $$m$$ MFSK and $$m$$ MCSK would be an interesting choice. The $$m$$ MCSK--- $$m$$ MFSK modulation is hence considered. A method to analyze this two-component modulation is developed and the performance analyses give results for $$m$$ MCSK--- $$m$$ MFSK modulation in AWGN and flat Rayleigh fading channels for both coherent and non-coherent receivers. The performance was also assessed with orthogonal and non-orthogonal code constructs for coherent receiver.