Effective RF codebook design and channel estimation for millimeter wave communication systems

Abstract

Millimeter wave (mmWave) technologies can enable current mobile communication systems to achieve higher data rates. However, wireless channels at mmWave frequencies experience higher isotropic path loss. Therefore, employing a suitable beamforming algorithm is an indispensable element of any mmWave system. Traditional multiple-input multipleoutput (MIMO) systems employ digital beamforming where each antenna element is equipped with one RF chain. In case of mmWave systems, however, the power consumption, signalling and hardware cost impose the designers to deploy analog or hybrid beamforming strategies. This paper addresses two key problems in beamforming for millimeter wave communication systems. First, an effective codebook is designed, using a genetic algorithm that achieves a near-optimal array gain in all directions. This RF codebook is shown to perform better compared to the state-of-the-art RF codebooks with fewer RF chains and lower resolution phase shifters. Secondly, a low complexity channel estimation scheme is proposed that requires less signalling overhead and is effective with low-resolution phase shifters. Finally, the performance of the proposed RF codebook and channel estimation scheme is thoroughly investigated in terms of spectral efficiency.

Hybrid Beamforming for Large Antenna Arrays With Phase Shifter Selection

“…In order to design hybrid beamformers, however, it is required to solve a complex nonconvex optimization problem due to the constant modulus constraint imposed by the phase shifters [3]. In addition, the phase shifters in practical systems have discrete resolution which converts the optimization to a computationally expensive combinatorial problem [8], [9].…”

“…In the hybrid beamforming approach, it has been shown that the baseband precoder and the RF beamformer can be designed either jointly [8]- [10] or in two stages [11]- [15]. For a point-to-point system, a joint design approach based on matching pursuit was proposed when the channel is sparse [8], [9]. In this method, firstly the singular vectors of the channel should be calculated, and then the hybrid beamformer is derived by solving an optimization problem to minimize the Euclidean distance between the matrices containing the singular vectors and the weights of the hybrid beamformer.…”

Low-Complexity and Robust Quantized Hybrid Beamforming and Channel Estimation

“…It is observed that our method provides almost the same performance as [12] which has higher complexity as multiple computations of SVD and inversions of matrices with larger dimension than K × K are required. In addition to observing a good match between the simulations and closed-forms in (5), (9) and (11), Fig. 2 shows that the proposed phase shifter selection based structures effectively reduce the number of the active phase shifters while providing a comparable performance to that of the subconnected structures with N active phase shifters.…”

“…Under perfect CSI and uncorrelated Rayleigh fading assumption, Fig. 2 presents the spectral efficiency achieved by simulations and the closed-forms in (5), (9) and (11) for N = 256, K = 4, β = 75% and S = 4. It is noted that β = 75% and S = 4 are equivalent to having only KL = N/4 = 64 active phase shifters.…”

A genetic algorithm-based beamforming approach for delay-constrained networks

“…For instance, [27] elaborates on the performance of scheduling in the return-link of a multi-beam satellite system. Moreover, [28] uses a genetic algorithm to achieve a nearoptimal array gain in all directions during codebook-based beamforming.…”