Space-time Coded Systems with Continuous Phase Modulation
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Space-time coded systems developed in the last ten years have been designed primarily using linear modulation. Non-linear continuous phase modulation has desirable constant envelope properties and considerable potential in space-time coded systems. The work in this thesis is focussed on developing and analysing an integrated space-time coded continuous phase modulated (STC-CPM) system. The coding of the space-time encoder and the modulation is incorporated into a single trellis encoder. This allows state combining, which leads to complexity reduction due to the reduced number of states. Design criteria for STC-CPM are summarized and the Euclidean distance is shown to be important for code design. The integrated STC-CPM system design enables systematic spacetime code searches that find optimal space-time codes, to be easily implemented. Optimal rate-1/2 and rate-2/3 space-time codes are found by maximizing the system's minimum squared Euclidean distance. These codes can provide high throughput and good coding gains over un-optimized full rank codes, such as delay diversity, in a quasi-static flat fading environment. Performance bounds are developed using a union bound argument and the pairwise error probability. Approximations of the bounds are evaluated. These truncated upper bounds predict the slopes of the simulated performance curves at low error rates.