| Efficient use of bandwidth, power and faster transmission rates are a main concern in this research. For conventional bandwidth efficient digital modulation formats such as Pulse Amplitude Modulation (PAM), Phase Shift Keying (PSK), and Quadrature Amplitude Modulation (QAM), the error rate, the required transmission bandwidth and the signal transmission power can be traded one to another. In this research, we are searching for new modulation formats to increase the signal constellations while preserving the distance properties and maintaining the bandwidth expansion to a minimum. To increase the transmission rate, we add properly designed functions, called "extra phase variation functions" (EPVF), to the phase of conventional modulation formats, such as, M-PSK, QAM, and CPM. Adding constraints to these EPVF's that it is used in the decoding process generate an "embedded orthogonal structure". It is shown that, these new formats allow to increase the transmission rate and maintain the probability of bit error without the need of extra power and bandwidth. These signal constellations can work with different channel coding techniques, such as repetition codes, linear block codes, convolutional codes and trellis coded modulation to enhance the performance.; In this research, we also study the effect of channel errors on the distortion of the overall digital communication system. We design a channel modulator that is optimally mapped to the output of the source coder in order to minimize the overall system distortion. We show that the joint designed system based on our modified formats can achieve less distortion for SNR per bit larger than 3 dB. |
