Continuous Phase Modulation and Space-Time Coding: A Candidate for Wireless Robotics

The physical layer(s) of wireless robotics take advantage of current standards, like Bluetooth, Wifi, etc., each of them addressing a specific segment of wireless robotics. Wireless robotics has a wide range of needs, comprising low power, robustness and high data rate when video is used as well as the opportunity to use a large number of transceivers. To cover these needs and take benefit from these opportunities, we propose a new physical layer, based on continuous phase modulation (CPM) and space-time coding. CPM, already used in some standards like GSM and Bluetooth, enables the development of low power devices, but presents a low spectral efficiency. Space-time coding on the other hand yields high spectral efficiency as well as enhanced robustness against the wireless channel. Moreover, space-time coding can take benefit of the large number of transceivers using cooperative communications. In this paper, after analysing the opportunities given by wireless robotics as well as its specific needs, we propose a new physical layer based on L2-orthogonality for non-linear space-time codes. L2-orthogonality of our codes is ensured by a bank of phase correction functions, maintaining phase continuity, but at the same time enabling low complexity decoding. We show that the code achieves full diversity and has full rate, for any number of transmit/receive antennas and any CPM parameter.