Study Based on MMSE Channel Estimation for IEEE 802.15.3c PHY Realization Method

IEEE 802.15. 3c standard is the first IEEE wireless standard for data rates over 1 Gb/s in 60 GHz band. The dissertation create a simulation system, which adopt the HSI PHY of IEEE 802.15. 3c and OFDM modulation method, realize the full process from the transmitter to the receiver. By using three types of channel, the dissertation analyses the performance of the standard under different channel conditions. The performance include the error rate in high speed wireless transmission and the feasibility of realizing Gigabit transmission. At last, by using the MMSE channel estimation algorithm, the system performance is improved, and the accuracy of data transmission is improved. Introduction IEEE 802.15. 3c standard is located in the frequency band of 60GHz, which belongs to millimeter wave communication[1-2]. It is a short distance high speed wireless connection technology. The 60GHz millimeter wave communication system mainly includes MAC and PHY. The high rate transmission is guaranteed by the PHY, which mainly defines the signal transceiver (front of RF and end of baseband processing), antenna control and modulation methods, etc[3]. 802.15. 3c working group put forward three different physical layer mode: (SC PHY ) single carrier physical layer, (HSI PHY) high speed interface physical layer, (AV PHY) video physical layer. In this paper, HSI PHY based on OFDM is used, data transmission rate is 1.54-5.78Gb/s, block size is 512.As a result, low density parity check (LDPC), 16-QAM modulation is the only choice[4]. Data communication in wireless environment is often limited by the influence of noise and inter symbol interference (ISI). Especially high speed data transmission, the system error rate will be increased significantly. The channel estimation can improve the accuracy of the received data and improve the performance of the communication system. In this paper, the minimum mean square error (MMSE) channel estimation is used to compare the bit error rate (BER) results under different communication environments, and the performance of the IEEE 802.15. 3c standard in the corresponding communication environment is obtained. MMSE Channel Estimation Algorithm Channel estimation is the key technique of channel equalization. In this paper, the simulation system environment is fast fading channel, using MMSE method based on comb pilot estimation for channel estimation, and assisted by LS algorithm for comparison. The MMSE minimizes the mean square error by using the two order statistics of the channel state. Simply, by seeking a suitable channel impulse response (CIR), which makes the difference between the received data calculated by the CIR and the actual data the smallest. [5] 2 H 1 1 mmse HH HH 1 ( ( ) ) n s H R R XX H − − = +s (1) Whenever the signal X changes, the matrix RHH to be changed, and the inverse calculation is 6th International Conference on Machinery, Materials, Environment, Biotechnology and Computer (MMEBC 2016) © 2016. The authors Published by Atlantis Press 1745 complex. In order to simplify the MMSE algorithm ,replacing the (XX) with E{(XX)}. The performance degradation caused by this approximation can be ignored. Description Of IEEE802.15. 3c Physical Layer Model Baseband Model Of OFDM System. The simulation model of 802.15. 3c IEEE physical layer is proposed in this paper based on OFDM (orthogonal frequency division multiplexing). The baseband model of OFDM system is shown in Figure 1. Fig.1. The baseband model of OFDM system OFDM Modulation. Each OFDM symbol sent by transmitter contains 576 subcarriers, which contains 336 data subcarriers, 16 pilot subcarriers, 16 protection sub carrier spacing, 141 null subcarriers, 3 DC subcarrier and 64 cyclic prefix. 336 data sub carrier is generated by Matlab. Transform bit stream into complex by 16QAM modulation, 16QAM constellation mapping is shown in Figure 2. Fig.2. 16QAM constellation I and Q stand for "In-phase" and "Quadrature" components, the symbol generated with 16QAM is [5]: 0 0 ( ) ( ) cos(2 ) ( )sin(2 ) X t I t f t Q t f t = + π π (2) Where: X(t) is the signal mapped in the constellation, f0 is the carrier frequency. Add the pilot to improve the accuracy of data, add zero added between OFDM symbols to protect the OFDM from interference between symbols. The positions of 16 pilot subcarriers are: [-166, -144, -122, -100, -78, -56, -34, -12, 12, 34, 56, 78, 100, 122, 144, 166]. The positions of 141 guard subcarriers and 16 guard subcarriers are [-256: -178 178:255]. The positions of 3 DC subcarriers are [-1, 0, 1]. Channel. Indoor wireless channel model is simulated by a FIR (impulse response finite) filter and Gauss white noise. The function is