Auxiliary Beam Pair Research Articles

Two-Dimensional Channel Parameter Estimation for Millimeter-Wave Systems Using Butler Matrices

In this paper, a novel two-dimensional parameter estimation method is proposed for frequency-selective millimeter-wave (mmWave) channels by probing a limited number of Kronecker products of discrete Fourier transform (DFT) beams, which are efficiently implemented in the analog domain by a novel combination of Butler matrices. The proposed strategy firstly estimates the channel parameters by using a modified parameter estimation via interpolation based on a DFT grid (PREIDG) algorithm. In a second step, high-resolution channel parameter estimation is achieved even in the low signal-to-noise-ratio (SNR) using the space-alternating generalized expectation-maximization (SAGE) algorithm. The proposed modified PREIDG algorithm outperforms state-of-the-art methods, e.g., the auxiliary beam pair (ABP) method while the SAGE algorithm achieves the derived Cramér-Rao lower bound (CRLB). Numerical results demonstrate that excellent estimation performance can be achieved for angle of departure (AoD) azimuth and elevation with addition to delay and complex path gain of each path even in the low SNR regime.

Channel parameter estimation for millimeter-wave cellular systems with hybrid beamforming

To achieve high data rates defined in 5G, the use of millimeter-waves and massive-MIMO are indispensable. To benefit from these technologies, an accurate estimation of the channel parameters is crucial. We propose a novel two-stage algorithm for channel parameters estimation. In the first stage, coarse estimation is accomplished by applying parameter estimation via interpolation based on a DFT grid (PREIDG) with a fixed look-up table (LUT), while the second stage refines the estimates by means of the space-alternating generalized expectation maximization (SAGE) algorithm. The two-stage algorithm uses discrete Fourier transform beamforming vectors which are efficiently implemented by a Butler matrix in the analog domain. We found that this methodology improves the estimates compared to the auxiliary beam pair (ABP) method. The two-stage algorithm shows efficient performance in the low signal to noise ratio regime for the channel parameters i.e. angles of departure, complex path gains and delays of the multipaths. Finally, we derived the Cramér-Rao lower bound (CRLB) to assess the performance of our two-stage estimation algorithm.

Auxiliary beam pair enabled initial access for mmWave D2D networks

In this paper, we propose two auxiliary beam pair (ABP) schemes, i.e., auxiliary-half (AH) and auxiliary-full (AF) to improve the initial access (IA) mechanism in a millimeter wave (mmWave) device-to-device (D2D) network. In AH, a uniform linear array (ULA) is split equally to form two simultaneous beams at both transmitter (TX) and receiver (RX) for device detection. The detection process takes place through the generation of antenna scan sequences. On the other hand, AF utilizes the full antenna array to form one beam at a time at RX and TX and searches the same sector twice in a time division manner. We also employ beamforming (BF) technique in the already existing schemes in literature, i.e., oblivious directional neighbor discovery (ODND) and Polya’s Necklaces. We compare all the schemes and it is shown that both AH and AF exhibit a high dependence on the separation between the beam pair. We also prove the dependence of discovery delay (DD) on the signal-to-noise ratio (SNR) which is contrary to the worst-case DD upper-bound given by ODND. For a reasonable value of beam separation, high SNR threshold and high TX–RX separation, AH achieves a lower DD than all other schemes. Moreover, AF outperforms all other schemes in terms of probability of miss detection (PMD) and for a considerable beam separation, low SNR threshold and low RX–TX separation, it also achieves a lower DD than ODND, Polya’s Necklaces and AH.

Millimeter Wave Channel Estimation and Beam forming Techniques

Millimeter-wave(mm-wave) frequencies offer higher bandwidth communication channels. Most of the wireless communication equipment operates with 6GHZ carrier frequencies, where the millimeter-wave communication systems are operated in the frequency range of 30GHZ to 300GHZ. Channel estimation will become a difficult task when the number of antennas is more than the number of radiofrequency chains. Millimeter-wave communication has received large attention from research fraternity and industry. In this paper, we listed the evolution and advancements in antenna beam forming, at the same time we outline some of the channel estimation techniques such as Auxiliary Beam pair (ABP), Adaptive algorithm based Codebook design(AABCD), Estimation of Signal Parameters by Rotational Invariance Technique (ESPRIT).

High-Resolution Angle Tracking for Mobile Wideband Millimeter-Wave Systems With Antenna Array Calibration

Millimeter-wave (mmWave) systems use directional beams to support high-rate data communications. Small misalignment between the transmit and receive beams (e.g., due to the mobility) can result in significant drop of the received signal quality especially in line-of-sight communication channels. In this paper, we propose and evaluate high-resolution angle tracking strategies for wideband mmWave systems with mobility. We custom design pairs of auxiliary beams as the tracking beams, and use them to capture the angle variations, towards which the steering directions of the data beams are adjusted. Different from conventional beam tracking designs, the proposed framework neither depends on the angle variation model nor requires an on-grid assumption. For practical implementation of the proposed methods, we examine the impact of the array calibration errors on the auxiliary beam pair design. Numerical results reveal that by employing the proposed methods, good angle tracking performance can be achieved under various antenna array configurations, channel models, and mobility conditions.

Auxiliary Beam Pair Enabled AoD and AoA Estimation in Closed-Loop Large-Scale Millimeter-Wave MIMO Systems

Channel estimation is of critical importance in millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems. Due to the use of large antenna arrays, low-complexity mmWave specific channel estimation algorithms are required. In this paper, an auxiliary beam pair design is proposed to provide high-resolution estimates of the channel’s angle-of-departure (AoD) and angle-of-arrival (AoA) for mmWave MIMO systems. By performing an amplitude comparison with respect to each auxiliary beam pair, a set of ratio measures that characterize the channel’s AoD and AoA are obtained by the receiver. Either the best ratio measure or the estimated AoD is quantized and fed back to the transmitter via a feedback channel. The proposed technique can be incorporated into control channel design to minimize initial access delay. Though the design principles are derived assuming a high-power regime, evaluation under more realistic assumption shows that by employing the proposed method, good angle estimation performance is achieved under various signal-to-noise ratio levels and channel conditions.