A Comprehensive Study of CPM Trellis Initialization Methods

Short burst CPM transmission is of practical relevance in e.g. sensor or tactical networks. When an optimal symbol wise detection shall be carried out, the BCJR algorithm is deployed whose recursion must be initialized in one way or other to avoid performance impacts. While carrying out a fair and comprehensive comparison of several CPM schemes and trellis initialization methods, this paper also introduces the novel, yet simple method of terminating the trellis in a correlation zero state. Theoretical metrics as the channel symbol information as well as practical relevant error rates and computational complexities are examined. The novel method will show to be the best compromise between error rate and complexity and thus is regarded as the appropriate choice for most use cases.