Binary Continuous Phase Modulations Robust to a Modulation Index Mismatch

TL;DR

This paper introduces new binary continuous phase modulation schemes with enhanced robustness to modulation index mismatch, achieved through specific precoding, improving performance in low-cost, low-power communication systems.

Contribution

Design of novel binary CPM schemes with precoding that significantly improve robustness against modulation index mismatch without altering CPM's recursive structure.

Findings

Enhanced robustness to modulation index mismatch.

Maintained spectral efficiency and detection simplicity.

Suitable for concatenation with channel encoders.

Abstract

We consider binary continuous phase modulation (CPM) signals used in some recent low-cost and low-power consumption telecommunications standard. When these signals are generated through a low-cost transmitter, the real modulation index can end up being quite different from the nominal value employed at the receiver and a significant performance degradation is observed, unless proper techniques for the estimation and compensation are employed. For this reason, we design new binary schemes with a much higher robustness. They are based on the concatenation of a suitable precoder with binary input and a ternary CPM format. The result is a family of CPM formats whose phase state is constrained to follow a specific evolution. Two of these precoders are considered. We will discuss many aspects related to these schemes, such as the power spectral density, the spectral efficiency, simplified detection, the minimum distance, and the uncoded performance. The adopted precoders do not change the recursive nature of CPM schemes. So these schemes are still suited for serial concatenation, through a pseudo-random interleaver, with an outer channel encoder.