Research On Multi-Carrier And Multiple-Access Technologies Of High-Efficiecy Modulation

The rapid development of the emerging communication business such as wireless multimedia services and the limited radio spectrum resources become a contradiction in the field of modern wireless communications. It is the core index and generic technology of a new generation communication system to gain higher spectrum efficiency in a certain limited frequency band. Recently, high efficiency modulation technologies are paid more attention by many researchers, a series of efficient modulation technologies such as Extended Binary Phase Shift Keying (EBPSK) and M-ary Position Phase Shift Keying (MPPSK) are proposed. So far, the studies on efficient modulations are concerned mainly with single-carrier communication. How to realize multi-carrier and multiple-access transmission of efficient modulations must be taken into account next. Then this paper discusses the following aspects concentrating on multi-carrier and multiple-access technologies of efficient modulations:1. In order to realize multi-carrier transmission of efficient modulation, on the basis of superposition principle of linear filter, the cause of interference among multi-carrier signals of efficient modulation is analyzed by observing the output waveform of impacting filter. Then a realization method is proposed based on time-division. The judgment areas of EBPSK multi-carrier signals are separated by relatively delaying neighboring signals to avoid the judgment areas collision. And a realization method for multi-carrier MPPSK is also proposed. The interference among MPPSK signals is eliminated by reducing the modulation order of every MPPSK signal to a certain level and modulating MPPSK signals to different part of a same symbol cycle.2. In order to realize multiple-access communication of direct sequence spread spectrum extended binary phase shift keying (DS-SS/EBPSK) modulation, a realization method is researched based on code-division. First, based on the analysis of DS-SS/EBPSK modulation signal, the effective spread spectrum sequence which can be used for dispreading and code division multiple-access is obtained by formulizing the DS-SS/EBPSK modulation process. Then, the correlation receiver for DS-SS/EBPSK modulated signal detection is designed, and multiple-access transmission is realized by making use of the small-scale cross-correlation of different spread spectrum sequences. Also, a realization method based on impacting filter is researched according to the correlation between the spread spectrum sequences and the envelope obtained after DS-SS/EBPSK signal passes through the impacting filter.3. In order to realize multiple-access communication of MPPSK modulation, a realization method is researched based on time-hopping. The MPPSK time-hopping modulator diagram and demodulator diagram are designed, respectively. The sending signal is modulated on a continuous sine wave, of which the phase jumps in corresponding time slots according to the symbols ready to send and the time-hopping sequence exclusively assigned to one user. The envelope in corresponding time slots is obtained for demodulation according to the transmission delay and the time-hopping sequence after receipt signal passes through the impacting filter.4. As for the multi-user interference of M-ary high efficiency modulation represented by MPPSK modulation, the phase shifting of MPPSK modulation is substituted by waveform transition and suitable transition waveforms are designed to restrain MPPSK multi-user interference. The conditions that any transition waveform must meet are deduced. Then, a multiple-access method for M-ary high efficiency modulation based on transition waveform is proposed.5. The existence of carrier wave may make negative impact onMPPSK multi-user communication, so the pulse MPPSK modulation derived from MPPSK modulation is introduced. The advantages of pulse MPPSK modulation are analyzed and the power spectra density of it is derived. Furthermore, an improved pulse MPPSK modulation is introduced and the bipolar binary shift keying pulse modulation is researched.