Distributed Space-Time Transmission with CPM

In this paper, a class of distributed space-time (ST) codes for continuous-phase modulation (CPM) is introduced. The distributed ST codes are designed to operate in wireless networks containing a large set of nodes N , of which only a small a priori unknown subset S sub N will be active at any time. Under the proposed scheme, a relay node transmits a signal which is the product of a diagonal block-based ST (DBST) code (optimized specifically for ST-CPM transmission) and a signature vector of length Nc uniquely assigned to each node in the network. Two efficient methods are presented for the design and optimization of signature vector sets. If a properly designed signature vector set is employed it is shown that a diversity d = min{N_s ,N_c} can be obtained, where N_s is the number of active users. Further, the decoding complexity of the proposed scheme is shown to be independent of the number of active relay nodes. Through the combination of DBST-CPM codes and signature vector sets the proposed distributed DBST-CPM codes allow for power-efficient cooperative transmission, and low complexity coherent and noncoherent receiver implementations.