Equalization Of Demodulation Technique In 802.11ad Systems

The proposition of IEEE 802.11 ad provide a new field for indoor high speed wireless communication, offering Gbps bit rates in totally 7GHz broadband around 60GHz spectrum bands while raditional wideband communication with 2.4GHz and 5GHz has the drawback of limited spectrum band and low speed bit rates. As wireless communication is influenced by Inter-symbol Interference (ISI)obviously especially for high speed transmission, this article mainly surveys equalization technique in IEEE 802.11 ad systems with the consideration of characteristics in 60GHz indoor channel, providing theoretical reference for application.Channel equalization can overcome severe fading caused by multipath effect, which is important integrant of demodulation in communication systems. This article designed frequency domain equalizer for Single-Carrier and OFDM according to their frame format in 802.11ad. We use two linear method (Zero-Forcing, ZF and Minimum Mean Square Error, MMSE) to discuss the performance of equalizer of SC-FDE and OFDM.This article also put light on a kind of Hard Decision-Iterative Block Decision Feedback Equalizer (HD-IBDFE) and came up with several methods to optimize relevant parameters which make good use of Guard Interval to increase the accuracy of tap coefficients which give about 0.5dB 11.5dB performance gains compared with original HD-IBDFE. Also we discuss the reason that HD-IBDFE cannot be applied in the situations of non-equipower modulation. In addition, a simplified IBDFE algorithm is proposed in this paper, which reduces the computational cost of the equalization algorithm while maintaining the performance gain almost unchanged. Based on this, two improved algorithms are proposed to improve the defect that the original algorithm can not be applied to 16QAM.Combining the characteristics of 802.11ad single-carrier frame format, this paper designs a frequency domain adaptive equalization system combining channel estimation and adaptive tracking. By using the training sequence in the preamble, the channel impulse response is obtained by the correlation method, and then the equalization coefficient is calculated, which greatly reduces the convergence time of the adaptive algorithm. In this paper, LMS adaptive tracking is performed using the guard interval (GI) between each block of data. When a suitable iteration step is selected and after several times of iterations, the adaptive tracking algorithm with non-ideal channel estimation can achieve the performance of the linear equalization algorithm with the ideal channel estimation.Based on some existing research results, we proposed an intra-frame time-variant channel modeling program. Since the dynamic nature of the 802.11 ad standard channel modeling approach is presented between each frame, it is assumed that the intra-frame channel is statically invariant. However, according to 802.11ad protocol, a physical frame transmission time can reach several milliseconds or more, channel modeling should also be considered intra-frame time-variant. Therefore,in this paper, we propose an intra-frame time-varying channel modeling scheme based on the influence of human occlusion on the channel, and make a reasonable supplement to the standard channel modeling scheme.