Downlink Beamforming for Mobile Communication Systems Based on Different Antenna Arrays
0
Citation
0
Reference
20
Related Paper
Abstract:
Downlink beamforming for modile communication systems based on antenna arrays have been discussed. Computer simulations for circular array and linear array have also been carried out. The results of simulations show that circular array or linear array can be used in different downlink beamforming model, which means that circular array is suitable for switch-beam downlink beamforming, while linear array for selective downlink beamforming. If Chebyshev linear array in selective downlink beamforming model is adopt, the beamforming will be optimized. In addition, the complexity of system will be reduced greatly, which makes beamforming easier to be realized.Keywords:
WSDMA
Circular buffer
Cite
Next-generation wireless communication systems will rely on multiple-antenna deployments enabling the beamforming functionality. In contrast to data transmission that benefits from user-specific beamforming (i. e., focusing the radiation at a particular user terminal), broadcasting of control information over a public channel requires cell-specific beamforming (i.e., cell-wide coverage). This paper presents a simple beamforming technique for cell-specific signaling for a four-port linear antenna array, based on exploiting two orthogonal polarizations and a maximum-ratio combining receiver. For instance, it is shown that by carefully tuning the excitation weights it is possible to design radiation patterns with any half-power beamwidth in the range from that of a narrow DFT beam to that of a single antenna element, while preserving the constant-modulus property of the excitation weights, thereby assuring excellent power utilization. The paper, furthermore, shows a direct connection between the underlying beamforming technique and the well-known concept of Alamouti space-time coding.
Beamwidth
WSDMA
Array gain
Cite
Citations (4)
This paper studies the multi-user downlink transmit beamforming algorithms for the broadband single-carrier distributed antenna network (SC-DAN). The distributed antennas will be used as antenna arrays by using transmit beamforming. In this work, the beamforming weight is designed in order to avoid the interference cancellation from the mobile terminals. Two methods are adopted. One is to use the maximum ratio transmission (MRT) beamforming weight to maximize the desired signal's power at each mobile terminal. The other one is to use the null steering beamforming weight to minimize the interference power at each mobile terminal. The beamforming algorithms using the two methods are described and their performances are compared by computer simulations.
WSDMA
Transmitter power output
Cite
Citations (2)
The ever-increasing traffic crunch for the wireless communication has drawn attention to the large spectrum available in the millimeter-wave bands as a potential means to achieve several fold mobile data traffic increase. While the channel characteristics at the millimeter-wave bands are known to be unfavorable for the mobile wireless communication purpose, the high gain available from massive array antenna facilitated by the short wavelength makes it possible to overcome the large path-loss. In this paper, we propose a hybrid beamforming architecture that combines an analog beamforming with array antennas and a digital precoding with multiple RF chains. Furthermore, we propose a multi-beam transmission diversity scheme for single stream transmission for single user MIMO operation. It is shown through various simulation results that the proposed hybrid beamforming scheme leads to considerable performance improvements even with limited feedback.
Diversity gain
Spectral Efficiency
Diversity scheme
Array gain
Cite
Citations (127)
The potential of using of millimeter wave (mmWave) frequency for future wireless cellular communication systems has motivated the study of large-scale antenna arrays for achieving highly directional beamforming. However, the conventional fully digital beamforming methods which require one radio frequency (RF) chain per antenna element is not viable for large-scale antenna arrays due to the high cost and high power consumption of RF chain components in high frequencies. To address the challenge of this hardware limitation, this paper considers a hybrid beamforming architecture in which the overall beamformer consists of a low-dimensional digital beamformer followed by an RF beamformer implemented using analog phase shifters. Our aim is to show that such an architecture can approach the performance of a fully digital scheme with much fewer number of RF chains. Specifically, this paper establishes that if the number of RF chains is twice the total number of data streams, the hybrid beamforming structure can realize any fully digital beamformer exactly, regardless of the number of antenna elements. For cases with fewer number of RF chains, this paper further considers the hybrid beamforming design problem for both the transmission scenario of a point-to-point multipleinput multiple-output (MIMO) system and a downlink multiuser multiple-input single-output (MU-MISO) system. For each scenario, we propose a heuristic hybrid beamforming design that achieves a performance close to the performance of the fully digital beamforming baseline. Finally, the proposed algorithms are modified for the more practical setting in which only finite resolution phase shifters are available. Numerical simulations show that the proposed schemes are effective even when phase shifters with very low resolution are used.
WSDMA
Cite
Citations (1,244)
Beamforming is a well-known signal processing technique to increase the received signal strength to a chosen direction. Recently, the three dimensional (3D) beamforming technique has gained a growing interest due to its potential to enable various strategies like user specific elevation beam-forming and vertical sectorization. Compared with conventional horizontal beamforming, 3D beamforming exploits the channel's degrees of freedom in the elevation direction with the active antenna system (AAS). Currently, 3GPP is on the study phase of this advanced MIMO technique and is working on the 3D channel model specification. In this paper, we propose a new 3D beamforming algorithm which combines conventional horizontal beamforming and elevation beamforming. Simulations are used to evaluate our proposed beamforming algorithm in urban macro environment with different inter-site distance (ISD).
WSDMA
SIGNAL (programming language)
Cite
Citations (14)
The use of the millimeter (mm) wave spectrum for next generation (5G) mobile communication has gained significant attention recently. The small carrier wavelengths at mmwave frequencies enable synthesis of compact antenna arrays, providing beamforming gains that compensate the increased propagation losses. In this work, we investigate the feasibility of employing multiple antenna arrays (at the transmitter and/or receiver) to obtain diversity/multiplexing gains, where each of the arrays is capable of beamforming independently. Considering a codebook based beamforming system (the set of possible beamforming directions is fixed a priori, e.g., to facilitate limited feedback), we observe that the complexity of jointly optimizing the beamforming directions across the multiple arrays is highly prohibitive, even for very reasonable system parameters. To overcome this bottleneck, we develop two complementary approaches, premised on the sparse multipath structure of the mmwave channel. Specifically, we reduce the complexity of the joint beamforming optimization problem by restricting attention to a small set of candidate directions, based on: (a) computation of a novel spatial effective power metric, and (b) estimation of the channel's angles of arrival. Our methods enable a drastic reduction of the optimization search space (a factor of 100 reduction), while delivering close to optimal performance, thereby indicating the potential feasibility of achieving diversity and multiplexing gains in mmwave systems.
Extremely high frequency
Cite
Citations (33)
Millimeter wave (mmW) communication has been viewed as a way of offloading users from lower frequencies, where currently deployed cellular networks operate. The short wavelength of mmW frequencies allows for electrically large arrays to be deployed in small mobile devices. Electrically large arrays (in terms of wavelength) are needed in order to compensate for the high signal attenuation in mmW frequencies by means of transmit-receive beamforming. Two beamforming architectures are typically considered in practice, namely a fully digital solution in which every antenna has a dedicated radio frequency (RF) chain, and a so-called hybrid solution that consists of an analog beamforming stage prior to digital beamforming. Hybrid beamforming trades-off the versatility of a fully digital architecture for lower power-consumption and cost. In this paper we focus on fully analog beamforming architectures for circular arrays comprised of patch antennas. In particular, we propose two architectures for analog beamforming with circular arrays, and provide a detailed study regarding the number of simultaneously active beams (i.e, number of RF chains), the amount of antennas per beam, as well as the number of required phase-shifters. The proposed analog beamforming scheme is compared to a fully digital beamforming approach on a realistic 5G system level platform simulating an urban environment. Results show that the performance of the proposed analog beamforming architecture is comparable to that of a fully digital beamforming scheme in terms of user throughput.
WSDMA
Cite
Citations (1)
Large-scale multiple-input multiple-output (MIMO) systems enable high spectral efficiency by employing large antenna arrays at both the transmitter and the receiver of a wireless communication link. In traditional MIMO systems, full digital beamforming is done at the baseband; one distinct radio-frequency (RF) chain is required for each antenna, which for large-scale MIMO systems can be prohibitive from either cost or power consumption point of view. This paper considers a two-stage hybrid beamforming structure to reduce the number of RF chains for large-scale MIMO systems. The overall beamforming matrix consists of analog RF beamforming implemented using phase shifters and baseband digital beamforming of much smaller dimension. This paper considers precoder and receiver design for maximizing the spectral efficiency when the hybrid structure is used at both the transmitter and the receiver. On the theoretical front, bounds on the minimum number of transmit and receive RF chains that are required to realize the theoretical capacity of the large-scale MIMO system are presented. It is shown that the hybrid structure can achieve the same performance as the fully-digital beamforming scheme if the number of RF chains at each end is greater than or equal to twice the number of data streams. On the practical design front, this paper proposes a heuristic hybrid beamforming design strategy for the critical case where the number of RF chains is equal to the number of data streams, and shows that the performance of the proposed hybrid beamforming design can achieve spectral efficiency close to that of the fully-digital solution.
Spectral Efficiency
WSDMA
Cite
Citations (135)
To satisfy increased data quantity demanded by users, millimeter-wave (mmWave) communication using large bandwidth and numerous antennas has considerable promise as a new technology for wireless communication. Also, it is possible to increase more data rate by using a dual polarized array antenna (DPAA). On the other hand, beamforming techniques have to be used in mmWave communication to overcome high path-loss. Conventional beamformers, however, have problems of high costs, high power consumption, and difficulties of implementation to be used in mmWave communication. Thus, a hybrid analog radio frequency and digital baseband beamformer is used to solve these problems. Since, it is very hard to achieve perfect channel state information, it is necessary to use limited feedback information based on beam training. In this letter, a hybrid beamforming system based on DPAA considering practical antenna radiation pattern is developed in a multi-user channel environment. Furthermore, two hybrid beamforming algorithms using only limited feedback channel information are proposed and analyzed.
Channel state information
Cite
Citations (10)
Large-scale array aided beamforming improves the spectral efficiency (SE) as a benefit of high angular resolution. When dual-beam downlink beamforming is applied to the train moving towards cell edge, the inter-beam ambiguity (IBA) increases as the directional difference between beams becomes smaller. An adaptive antenna activation based beamforming scheme was proposed to mitigate IBA. In the district near the base station (BS), all antenna elements (AEs) were activated to generate two beams. As the distance from the train to the BS increased, only the minimum number of AEs satisfying the resolution criterion would be activated. At the cell edge, one beam was switched off due to intolerable IBA. The proposed scheme can achieve SE gain to the non-adaptive scheme and show more robustness against the direction-of-arrival (DOA) estimation error.
Robustness
Adaptive beamformer
Spectral Efficiency
Direction of arrival
Cite
Citations (10)