Study Of Equalization Technology In Single Carrier Communication Systems

Multipath channel in wireless communication systems will cause inter symbol interference, which will affect the communication quality, an important solution to this problem is the equalizer. In this paper, we study in the design of equalizer in single-carrier communication system, including time-domain minimum mean square error equalization algorithm, the frequency domain block iterative decision feedback equaliza-tion algorithm and time-frequency hybrid decision feedback equalization algorithm. Then we design the corresponding hardware systems for indoor visible light communication and tropospheric scatter communi-cation.Indoor visible light communication technology use the light of Light Emitting Diode(LED) as a carrier of information to transmit information, it is called "Lifi", which is likely to provide new solutions for indoor and short-distance communication, and tropospheric scatter communications can realize non-line of sight(NLOS) communication because the electromagnetic waves will be scattered by the troposphere, which is commonly used in military communications. For indoor visible light communication scenario, this paper established a multipath tap delay channel model and get the channel coefficients by measurements, and show the channel time domain impulse response and the amplitude-frequency response curve. For scatter communications systems scenario, this paper established a Rayleigh fading channel model whose delay power spectrum is exponentially decaying by channel characteristic analysis and literature review.Equalizer is an important part of single carrier communication systems, this paper start from the theory of equalization algorithm, introduce the Time Domain Minimum Mean Square Error Equalizer(TD-MMSEE), the Time Domain Decision Feedback Equalizer(TD-DFE), the Frequency Domain Iterative Block Decision Feedback Equalizer(FD-IBDFE) and the Hybrid Decision Feedback Equalizer(H-DFE), and shows the BER curve of these algorithm in visible light communication scenario and tropospheric scatter communications scenario. Taking computational complexity and channel characteristics into consideration, this paper chose the frequency domain Minimum Mean Square Error Equalizer algorithm for visible light communication system, and choose the time-frequency domain hybrid decision feedback equalization algorithm for scatter communications system.According to the iterative idea of the iterative receiver, we proposed two iterative interference cancella-tion decision feedback equalization algorithm based on hard and soft interference cancellation in this paper. Simulation results show that the hard interference cancellation iterative decision feedback equalization algo-rithm can get 0.2-0.3 dB gain at 3/4 code rate conditions, and get around 0.7dB gain at 1/2 code rate con-ditions, while soft interference cancellation iterative decision feedback equalization algorithm get 0.6-0.7 dB gain at 3/4 code rate conditions and get 1.2～1.3 dB gain at 1/2 code rate conditions, which prove the validity of the algorithm.Last chapter describes the hardware design and implementation for indoor visible light communication system and tropospheric scatter communication system. We use the Xilinx’s ML605 development board as hardware design platform. Starting from the framework, this chapter introduce the design principle and the major role of each module of the system, the scattering communication system use Quadrature Phase Shift Keying(QPSK) modulation, the system clock rate is 115.2MHz, the actual communication speed is 38.4Mbps, visible light communication system use On-Off Keying(OOK) modulation and the system clock rate is 200MHz, actual communication rate is 100Mbps, these two systems can transmit high-definition video services, which verified the correctness of the hardware system design.