Research And Simulation Of Millimeter Wave Wireless Communication System Access Technology

With the continuous improvement of people's demand for wireless local area network,the relevant standards of wireless local area network are also constantly being studied.From the IEEE802.11 a,802.11 b and 802.11 g standards which originally defined in the low frequency band(2.4/5GHz),to 802.11 n and 802.11 ac standards which are widely used in people's life,the data transmission rate is breaking through again and again and the system performance of WLAN system is gradually improving.However,due to the increasingly tense spectrum in the low frequency band,the existing spectrum resources no longer meet the growing needs.So wireless local area network began to be used in high frequency band,which named millimeter wave band at60 GHz,for data transmission.The current widely promising standard are IEEE 802.11 ad and its enhanced standards.The research background based on the millimeter-wave communication system and the standard of 802.11 ad.This paper studies the channel estimation technology and training sequence for the enhanced 802.11 ad communication system.Firstly,this paper gives a brief overview of the characteristics,advantages and applications of millimeter-wave data transmission band.Then,it focuses on the millimeter-wave wireless local area network communication protocol IEEE 802.11 ad standard which will be the most widely applied standard among three standards,and describes its three physical layer structures.In the wireless communication systems,the accuracy of channel estimation has a decisive impact on the detection performance of the receiver.Therefore,based on the standard of IEEE802.11 ad,the characteristics of the sequence used in channel estimation are analyzed.Some channel estimation methods are mainly studied by using golay sequence,such as the method based on the sequence correlation characteristics,based on Least Square(LS)algorithm and based on Minimum Mean Square Error(MMSE)algorithm.The simulation results show that the estimation method based on the correlation of training sequence has the same estimation performance as the least squares estimation algorithm.And the estimation performance of the least mean square error estimation algorithm is better than the former two,simply because it considers the influence of noise in the system.According to the characteristics of millimeter-wave wireless communication system,beamforming has become one of the key technologies to achieve high throughput transmission rate.The success of beam training will directly affect the quality of signal transmission.Therefore,this paper also introduces the sequence which are currently used in the beam training in the standard IEEE 802.11 ad,and verifies that its estimation performance in time domain is much lower than that in frequency domain through simulation.In order to guarantee the estimation performance and reduce the computational complexity,the correlation of different sequences is studied,and a serial of training sequences based on Loosely Synchronized code which is suitable for different scenarios,such as multi-antenna,large delay,are designed for beamforming training.The simulation results show that the design of the sequence not only avoids the influence of ISI in time domain estimation,but also avoids the mutual interference between antennas under the condition of multiple antennas.Compared with the traditional channel estimation method,it avoids the huge matrix inversion operation,greatly simplifies the computational complexity and increases the flexibility and operability of the system.The correlation analysis in this paper has certain reference value for low computational complexity channel estimation technology in millimeter-wave wireless communication system.