Research On SC-FDMA Based On Continuous Phase Modulation

Single-carrier frequency division multiple access (SC-FDMA) is a multiple access technology relative to the orthogonal frequency division multiple access (OFDMA). It combines orthogonal frequency division multiplexing (OFDM) and single carrier frequency domain equalization (SC-FDE) and utilizes single carrier modulation at the transmitter and frequency domain equalization at the receiver, which has effective capacity against frequency selective fading channels. However, compared with OFDMA, SC-FDMA signal has lower peak-to-average power ratio (PAPR) and higher power efficiency, which reduces requirements of the power amplifier and benefits to reduce terminal cost. Therefore, SC-FDMA is selected as the uplink multiple access technology in 3rd Generation Partnership Project Long Term Evolution (3GPP LTE). As a good phase modulation technology, continuous phase modulation (CPM) has very wide applications in many communication systems, which has some properties such as constant envelope, high power efficiency, high spectral efficiency and favorable anti-interference capability.In this thesis,a novel CPM-SC-FDMA scheme combining the advantages of CPM and SC-FDMA is investigated, which is power efficient. Besides, by appropriate selection of the CPM parameters, it can achieve better bit error rate(BER) performance than the SC-FDMA in which the conventional modulations are used .The main work of this thesis can be summarized as follow:Firstly, the basic principles and system realization of OFDM and SC-FDE are discussed. And frequency domain equalization principle and common equalization algorithms are also introduced, and a performance simulation has been made. Furthermore, comparisons between OFDM and SC-FDE in channel capacity, PAPR and BER performance are made, and analysises are done.Secondly, the system structure and the subcarrier mapping of SC-FDMA are discussed. The theoretical derivation of the time domain expression of SC-FDMA signal is presented and the characteristic of the signal is analyzed. Then, after the introducation of the frame structure, the definition of the resource block and the design of the reference signal in LTE uplink, a simulation platform for uplink is built and the system performance is simulated.Finally, the principles of the modulation and the maximum likelihood demodulation of CPM are presented, and the simulation of BER performance is carried out. On the basis of the research on signal property, through the observation that the discrete-time samples from the CPM waveform have constant envelope, the CPM-SC-FDMA is proposed and the implementation process is explained. Afterward, through a simulation, the scheme is compared with the conventional SC-FDMA in BER performance.