Differential amplitude/phase space-time modulation

• Main Author: Zi, Juan
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/15339

In this thesis, a differential amplitude/phase space-time modulation (DAPSTM) is proposed for multiple transmit antenna wireless systems over flat Rayleigh fading channels. Two conventional noncoherent detection schemes, namely, simply heuristic (SH) differential detection (DD) and maximum likelihood (ML) DD are presented. Furthermore, two improved noncoherent detection schemes, multiple-symbol detection (MSD) and decisionfeedback DD (DF-DD) with lower decoding complexity are derived. By taking the dependencies among the received symbols into account, MSD and DF-DD can reduce the error floor of ML-DD. The pairwise error probability (PEP) based on SH-DD, and an approximation of the bit error rate (BER) based on the union bound, are derived. Analytical considerations agree well with the simulation results. Compared with the known differential unitary space-time modulation (DUSTM), DAPSTM can be said to generalize the diagonal structure from phase signals to a combination of phase signals and amplitude signals. This generalization potentially allows the spectral efficiency to be increased by carrying information, not only in phases, but also in amplitudes. DAPSTM is not as power efficient as space-time codes with differential amplitude/phase shift keying (STC-DAPSK), which is based on Alamouti's orthogonal space-time code (OSTC), when two transmit antennas are employed. However, DAPSTM allows easy implementation at the transmitter, due to the group property of its constellation under matrix multiplication. DAPSTM can be employed for an arbitrary number of transmit antennas while keeping full diversity and full rate. It is also suitable for exploiting time diversity when only one transmit antenna is used in the system. In contrast, STC-DAPSK can only achieve full diversity and full rate for two transmit antennas and can not exploit time diversity, due to its nondiagonal structure.