Research On The Beam Technique Of 60GHz Communication Systems

Indoor wireless communications at 60 GHz have recently gained a lot of attentions from industry and academy in the research of the next generation communications over short distances because of their potential to deliver multi-gigabit rates. The main advantages of this technology are the huge license-free bandwidth which has been allocated worldwide at these frequencies, the low levels of interference on the same band, and easiness to highly integrate at a low cost.However, due to the severe propagation and penetration losses at these frequencies, 60 GHz communications are expected to experience a poor channel quality. In order to improve the link budget, it is essential to employ antenna beamforming techniques.This paper studies the topic of beamforming through three aspects:codebook design, beamforming algorithms based on direction of arriving estimation and beam tracing. The specific work and contributions are as follows:Firstly, a new codebook. According to the research on the beamforming mechanism and codebook in IEEE 802.15.3c and IEEE 802.11ad, we propose a new scheme of codebook design to against the shortcoming of that in IEEE 802.15.3c. This new codebook confines all beams to the particular direction which was selected by the former search.So we can gain a more precise beam pointing to the expected direction without adding antenna elements or beam numbers.Secondly, beamforming algorithms based on direction of arriving estimation. In this paper, we apply DOA (direction of arriving) estimation to beamfoming and carry out simulation to verify the performance of the algorithm. More specifically, we firstly estimate the arrival signals’ angles and amplitudes and select the desired signal, and then form the beam immediately according to the angle. Compared to beam-switch, this method can lead to a more precise main lobe direction. Also, the previous weights can be used in adaptive beamforming as the initial value to reduce iterations. And when the estimation error is large, adaptive algorithm can be used to optimize the beam.Thirdly, beam tracing. This paper firstly check the performance of gradient algorithm in 60GHz system. Considering the characteristic of 60GHz channel that the angles change slowly, we utilize the relation between the current and next results and put the current result as the original value of the next iteration which achieves decrease iterations. Also,this paper introduce a new method to calculate the step size of gradient algorithm, which reduces the amount of calculation further.