On the Feasibility of Codebook-Based Beamforming in Millimeter Wave Systems With Multiple Antenna Arrays

In this paper, we study multiple-input multiple-output (MIMO) systems with a large number of antennas at a base station serving a number of users in a cell. The antennas at the base station are assembled into multiple antenna arrays (MAA), which are well separated to keep independence between the arrays, but in each array, antennas are densely installed. The MAA can be viewed as a flexible configuration of multiple antennas to reduce the space for installing the antennas and benefit from beamforming. In order to determine how dense the MAA can be designed, we define antenna area efficiency, that is the ratio of the achievable rate and the 2-D space required for installing the antennas. Then, we analyze the achievable rate of the massive MIMO system with K uplink users and NM antenna elements at the base station placed in N square arrays and each array having √M × √M antennas densely deployed. Specifically, the analytical uplink sum rate is first derived. Then, the sum rate in the low-SNR and highSNR regimes is studied. A case study is provided to show how dense MAA can be designed in a massive MIMO system. Our analytical and simulations results show that, for ten users in low SNR, a single dense antenna array with 11 ×11 antennas in a square requires only 1/200 of the area of conventional 100 independent antennas to achieve the same rate. For ten users in high SNR, we find that two 8 × 8 square arrays can achieve the highest antenna area efficiency in comparison with one 16 × 16 antenna array, four 5 × 5 antenna arrays, and 100 independent antennas.

Angle of arrival localization systems generally rely on multiple antenna arrays, estimating the position of a mobile node by measuring the line-of-sight directions. However, indoor multipath effects tend to deteriorate system performance. In this paper, an alternative system for in-room positioning is proposed and tested, consisting of a mobile transmitter and a single antenna array for angle of arrival estimation of direct and reflected signals. With the help of a floor plan of the room and a ray tracing algorithm, antenna array outputs can be calculated for every possible position of the mobile node. These simulation outputs are compared to the measurement results to determine the position of the transmitter. The system is evaluated in an extreme multipath environment, being a 2.25 m × 3 m room with metallic walls. Measurements are performed with a 2.45 GHz and a 5.2 GHz 8-element antenna array, followed by an MVDR beamforming algorithm with a variable number of spatial smoothing operations. Two distinct localization algorithms are tested, as well as the influence of various parameters on localization accuracy, resulting in an optimal setup with an average localization error under 1 m.

In this contribution we propose and investigate a transmitter preprocessing scheme designed for downlink transmission in multicarrier direct-sequence code-division multiple-access (MC DS-CDMA) systems using multiple base-station antenna arrays, where each antenna array employs multiple array elements. The transmitter preprocessing scheme is derived based on the singular value decomposition (SVD). Our transmitter preprocessing design is capable of supporting a high number of MC DS-CDMA users, while maintaining a high diversity gain at a low detection complexity at the remote mobile stations (MSs). The characteristics of MC DS-CDMA using the proposed transmitter preprocessing scheme are discussed and the achievable bit-error-rate (BER) performance is investigated, when assuming that each subcarrier experiences flat Rayleigh fading. Our simulation results demonstrate that for a SVD-assisted MC DS-CDMA system using M distinct transmit antenna arrays and time (T)-domain spreading sequences of length Ne chips, the number of users supported can be as high as MNe, since Ne and M number of users may be distinguished in the T-domain and spatial- or S-domain, respectively. Furthermore, the SVD-assisted MC DS-CDMA system is capable of supporting MNe number of users at a near single-user BER performance.

In millimeter Wave (mmWave) cellular communication systems, transmission range is inherently limited to only a short distance. In order to overcome this drawback, the mmWave-based cellular communications systems are limited to “pencilbeam” configuration to achieve larger cell radius. Small beam-width (typically 10°), coverage requirements, and physical constraint of small number of beams from an antenna array lead to requiring multiple antenna arrays at a mmWave cellular base-station. For such systems, we advocate the need for a structured approach to beam assignment for various users. We provide a problem formulation where beam assignment is done to achieve system-wide stability, design a learning algorithm to achieve the beam assignment under dynamically varying users' activity, and way of performing call admission control. Given the introductory nature of this problem, we intentionally refrain from delving into detailed scheduling aspects from point of view of fairness - with a remark that such a fairness-providing scheme will run as an inner loop to our proposed system.

We introduce a novel merger of direct sequence code division multiple access (DS-CDMA) and smart antenna arrays. With regard to the DS-CDMA scheme, we employ carrier interferometry DS-CDMA (CI/DS-CDMA), a novel implementation of DS-CDMA where chips are decomposable into N narrowband frequency components. With regard to the antenna array, we deploy the oscillating-beam smart array. Here, applying proper time-varying phases to the array elements, we create small movement (oscillation) in the antenna array's pattern, while steering the antenna pattern main lobe to the position of the intended user. The oscillating antenna pattern creates a time-varying channel with a controllable coherence time. This, in turn, provides transmit diversity in the form of a time diversity gain at the mobile receiver side. At the receiver, three stages of combining are available: combining time components of the received signal within symbol duration Ts (each experiencing a different fade) to enhance performance via time diversity; combining frequency components which make up the CI/DS-CDMA chip to enhance the performance via frequency diversity; and combining across chips to eliminate the interfering users on the system. Merging CI/DS-CDMA with the oscillating-beam smart antenna at the base station, we achieve very high capacity via the merger of SDMA (available through directionality of the antenna array) and code division multiple access (inherent in CI/DS-CDMA), and very high performance via the construction of receivers that exploit both transmit diversity and frequency diversity. We present the performance gains of the proposed merger.

A simple and low-cost multiple beam phased array is designed using a microstrip Rotman lens and multi-line phase shifter controlled by a piezoelectric transducer (PET) at Ka-band. A microstrip Rotman lens with five beam ports and nine array ports is used as a feed for a multiple beam antenna array to generate five beams centered at the angles of 0/spl deg/, /spl plusmn/15/spl deg/, and /spl plusmn/30/spl deg/. The lens fed nine-element patch array shows the antenna gain of 10 dBi and sidelobe suppression of 10 dB. Each beam is steered over /spl plusmn/8/spl deg/ using two PET-controlled phase shifters, and the five beams cover /spl plusmn/38/spl deg/ from the broadside.

This paper introduces a novel technique and mathematical formulation of two dimensional elastic footprint variations and adaptive sector configuration variations by using a hybrid adaptive amplitude control antenna array system. The antenna array system can control the elevation beam-widths from 6.84° to 13° and the azimuth beam-widths from 33° to 93° for obtaining the adaptive capacity and coverage. The work illustrates the application of the antenna array system in the energy efficient W-CDMA network. The antenna array half-power beam width variation is achieved by using the antenna array amplitude control and co-located multiple antenna array switching. The Node-Bs can adaptively switch to three, four, five, six and non uniform sector configurations with the antenna array beam width control and adaptive neighbor relations. Sector configurations will vary according to the pre-defined specific traffic loading percentages out of Node-B’s total channel capacity to reduce the energy consumption of the entire network. The paper introduces an adaptive footprint overlaps shifting technique, where the sector with less traffic load will expand its footprint towards the sector with higher traffic load and the sector with higher traffic load will shrink its footprint by maintaining a fixed footprint overlaps to improve the coverage and the capacity of the network. The footprints overlap shifting is applicable only for the active sector antennas facing each other. The results confirm that the proposed antenna array system outperforms the automatic tilt optimization and can control coverage, capacity and improve the energy efficiency of the W-CDMA network.

In this paper, two auxiliary beam pair schemes, i.e., auxiliary-half (AH) and auxiliary-full (AF) are proposed to improve the initial access (IA) mechanism in millimeter wave (mmWave) systems. In AH, a uniform linear array (ULA) is split equally to form two beams simultaneously to detect a user in the scan region. On the other hand, AF utilizes the full antenna array to form a beam to search the same sector but at different time slots. We compare our schemes with the already existing schemes in literature, i.e., exhaustive and iterative algorithms. It is shown that both, AH and AF exhibit a high dependence on the separation between the beam pair. For a reasonable value of beam separation, AH achieves a balance between exhaustive and iterative schemes, i.e., it achieves a lower probability of miss detection (PMD) than iterative search and also a lower discovery delay (DD) than exhaustive method. Moreover, AF outperforms all other schemes in terms of PMD and also achieves lower DD than exhaustive search algorithm.

For a single channel Shannon's classical capacity formula predicts a capacity increase of 1 bit/cycle for every 3 dB increase in signal to noise ratio (SNR). Consequently in multiple antenna arrays, the increase in capacity can be in the order of almost n more bits/cycle for each 3 dB increase in SNR. This tremendous gain in capacity exhibited by MIMO channels over single antenna systems illustrates the enormous potential in wireless communications systems. This paper provides an analysis of multi-element antenna systems in a wireless channel. A geometric model incorporating local scatterers around the fixed user is presented. This space-time model considers non-isotropic scattering using the von Mises pdf at the user. This space-time cross correlation function includes some key elements, such as antenna element spacing, degree of scattering, angle of arrival at user and array configuration in MIMO channels. The capacity of the MIMO fading channel with varying; number of antenna elements, the degree of isotropic scattering at receiver and the spacing between the antenna elements are investigated and presented for the chosen model

Breast cancer is the second leading cause of cancer death after lung cancer among the women. In this paper we reviewed some breast cancer detection techniques like Mammography, Magnetic Resonance Imaging (MRI), ultra Sound and Ultra Wide Band (UWB) and its performances. Current UWB systems having some limitations including they are not able to detect the tumor at early stages, a multiple antenna array in terms of complex system and in all systems no pictorial 3D representation of tumor size. To overcome this limitation, a thorough investigation is done here, to find out the limitations of existing and proposed systems followed by the open issues which need to be resolved.KeywordsUltra Wide bandBreast CancerTumor Detection

In this paper, two receive beamforming techniques (Method 1 and Method 2) are proposed for a mobile station (MS) with multiple antenna arrays in an OFDM-based millimeter-wave (mm-wave) cellular communication system. Since the MS in mm-wave cellular communication requires fast processing due to its frequent movement and rotation, a receive beamforming technique with reduced computation complexity and processing time is proposed in Method 2. Of particular interest, estimation techniques for 2-dimensional (2D) direction-of-arrivals (DoAs) corresponding to each cell ID are proposed for uniform circular arrays (UCAs) and uniform rectangular arrays (URAs). Also, a cell selection technique for MSs with multiple antenna arrays is described that use the candidate cell IDs and parameters estimated for all antenna arrays to provide combining gain in addition to array gain in multipath channels. The proposed beamforming techniques are evaluated by computer simulation using a simple model of amm-wave cellular communication system with 3-dimensional spatial channel model (3D SCM).

An adaptive space time transmit diversity scheme with simple feedback is proposed for the next generation wireless communication systems. By combining orthogonal space time block codes with adaptive sub-group antenna encoding, this new diversity scheme can effectively exploit the diversity potential provided by multiple antenna arrays without introducing interference among the signals transmitted at different antennas. In order to reduce the amount of feedback information as well as the computational complexity, a new quadrant phase constraining method is introduced to formulate the feedback information. With simple operations at both the transmitter and the receiver, the new adaptive diversity scheme outperforms not only open loop space time block encoding techniques, but also some close loop transmit diversity techniques with the same amount of feedback.

Pattern Search optimization with applications on synthesis of linear antenna arrays

Non-orthogonal multiple access (NOMA) and mmWave are considered to be promising techniques for 5G and beyond cellular network communication systems. While the mmWave band provides a very wide under-utilized bandwidth, NOMA enhances the spectral efficiency compared to orthogonal multiple access (OMA). The combination of these two techniques could be considered as the key solution to the high required data rates in next-generation communication systems. The implementation of NOMA is studied and verified under an ideal condition with perfect knowledge of the channel state information (CSI) at the base station (BS). However, under the practical conditions, the fluctuation of the wireless channel makes perfect CSI unachievable at the BS. Hence, we proposed to use the angle of departure (AoD) as feedback information from UEs to the BS. We assume that, mobile users (UEs) perfectly estimate the channel by detecting the pilot signals. Then, UEs quantize the AoD and feed back to the BS. Finally, the BS uses the AoD to perform user clustering, power allocation and beamforming. To reduce the feedback overhead further, we proposed a user clustering algorithm which uses one-bit feedback to determine the change of the AoD. Numerical results demonstrate that the proposed NOMA system outperforms the conventional orthogonal multiple-access (OMA) system with the same amount of feedback information.

This paper outlines how the direction finder technology was exploited in the design of a device; capable of locating the where about of a UHF transmitter. The value of amplitude and frequency of the signal were employed in the determination of the signal source direction. The study emphasized on the utilization of low cost components. The assembled prototype offers 22.5˚ bearing coverage. The determination of the direction was achieved by differentiating the received frequency signal involving multiple antenna arrays. Direction of transmitter was determined by making the receiver antenna arrays emulating condition of motion with the use of antenna switcher. Received signals were converted into tones where larger signal amplitude translates to louder tone. Antenna arrays were arranged in specific manner where the tone volumes were compared and the direction within 360˚ position was determined. The result suggests that the system can provide the detection coverages up to 22.5 degree which is better than the existing solutions in terms of equipment selection, cost, and coverage.