Research Of Single Carrier Frequency Domain Equalization Technology

Single carrier frequency domain equalization(SC-FDE) is a multicarrier transmission technology which is capable of resisting the inter-symbol interference(ISI) introduced by the frequency selective fading channel. Compared with traditional single carrier time domain equalization systems, SC-FDE systems can acquire a similar computational complexity and performance than that of OFDM. Because of its lower peak-to-average power ratio(PAPR), little sensitivity to carrier frequency offsets(CFO) in demodulation, SC-FDE system doesn’t need linear power amplification and the stringent requirements of highly accurate frequency synchronization as in OFDM. Therefore, it has been adopted by various wideband systems, for example, IEEE 802.16 air interface, MBWA IEEE802.20, and the uplink multiple access scheme of 3GPP LTE.Nevertheless, SC-FDE suffers several drawbacks, for example, low spectrally efficiency, without frequency diversity gain. Besides, traditional SC-FDE system cannot take advantage of the multipath diversity provided by the multipath fading channel, resulting in degradation on system capacity. To counteract these issues, many literatures focus on the STBC and SFBC applying in the SC-FDE system, which can obtain space, time, and frequency diversity gain. Because that transmit symbols of SC-FDE system are processed in time domain, SFBC cannot be directly applied. The SFBC based SC-FDE transmit diversity scheme transform time-domain symbols to frequency-domain by DFT firstly. After space frequency block coding, the frequency-domain symbol was transformed to time-domain data by IDFT. The complexity of the proposed scheme is very high, because of these DFT and IDFT operations. Discrete Hartley transform, as a similar Fourier transform, with low computational complexity, can be used in this scheme.The dissertation firstly focuses on the background and development trend of SC-FDE, analyzes the fading channel model of wireless communication, and build the mathematic model of SC-FDE, compared with that of OFDM. In SC-FDE systems, the designs of transmi t diversity scheme that uses DFT-based STBC and SFBC were presented for both theory and simulation. In order to reduce the computational complexity which caused by DFT operations, this paper proposed DHT-based SFBC SC-FDE system. But only one-dimensional signal can be processed by DHT, and DHT-based SC-FDE system cannot directly diagonalize the multipath channel matrix. In light of these problems, this paper makes a detailed analysis and research, and puts forward corresponding solutions.This scheme transforms the real and imaginary parts of the 2-dimensional complex signaling from time domain to frequency domain by using two DHTs. With the complementary property of DHT matrix, the DHT-based SC-FDE architecture can perfectly diagonalize the channel matrix, which similar to the DFT-SCFDE system. Finally, analysis and simulations are provided to show that this proposed scheme can achieve similar performance but halve the computational complexity of the receiver compared with the conventional DFT-based SC-FDE systems. Besides, since the definitions of DHT and IDHT are identical, we can use the same hardware or program to implement the modulator and demodulator of the proposed method.