Multiband MIMO antenna arrays

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 in mmwave systems, 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 reduced complexity algorithms for optimizing the choice of beamforming directions, premised on the sparse multipath structure of the mmwave channel. Specifically, we reduce the cardinality of the joint beamforming search space, by restricting attention to a small set of dominant candidate directions. To obtain the set of dominant directions, we develop two complementary approaches: 1) based on computation of a novel spatial power metric; a detailed analysis of this metric shows that, in the limit of large antenna arrays, the selected candidate directions approach the channel's dominant angles of arrival and departure, and 2) precise estimation of the channel's (long-term) dominant angles of arrival, exploiting the correlations of the signals received across the different receiver subarrays. 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.

Foschini's diagonally layered space-time transmission system known as D-BLAST is an architecture designed for a Rayleigh fading environment using multiple element antenna arrays at both the transmit and receive sites to achieve very high spectral efficiencies. In this paper, we propose a simple coding technique for D-BLAST that uses a single trellis code with finite-traceback Viterbi decoding. We examine the performance of universal trellis codes that are designed to have a distance structure that is matched to the periodic signal-to-noise ratio (SNR) variation of the channel created by D-BLAST, under the assumption that the channel is static during one burst but may change from burst to burst. We show that a universal 64-state trellis code on a 2/spl times/2 D-BLAST system with long enough block lengths displays universal behavior working on almost every 2/spl times/2 channel with at least the mutual information required by a standard 64-state AWGN trellis code. The only 2/spl times/2 channel where more mutual information is required is a certain rotation of the zero eigenvalue channel. We also present 4/spl times/4 and 8/spl times/8 examples.

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.

As a typical application scenario of the fifth generation (5G) mobile communication system, the high-speed mobile scenario is attracting attention, and the tunnel is a typical application scenario of high-speed rail communication. The traditional high-speed rail communication in the tunnel is covered by leaky coaxial cables, but its system spectrum efficiency is limited by deployment, and it is difficult to significantly improve. Using distributed micro-site coverage and using cooperative transmission is an effective way to increase system capacity. In order to study the distributed MIMO wireless communication system in the high-speed rail tunnel, it is necessary to establish a distributed MIMO channel model that can accurately describe the high-speed rail tunnel scene. In response to this question, this paper establishes a geometry-based single-bounced distributed multiple-input multiple-output (GBSB-DMIMO) channel model, which supports massively distributed MIMO with multiple array antennas in the vehicle and multiple RRU deployed in the tunnel. Under this model, this paper carries out simulation evaluation for massive distributed MIMO and massive vehicle-mounted cooperative relay. The simulation results show that the model well reflects the fading characteristics in the tunnel, and demonstrates the advantages of large-scale distributed MIMO and the capacity of the on-board cooperative relay system.

The capacity of multiple-antenna systems operating in Rayleigh flat fading is considered under the assumptions that channel state information (CSI) is available at both transmitter and receiver, and that the transmitter is subjected to an average power constraint. First, the capacity of such systems is derived for the special case of multiple transmit antennas and a single receive antenna. The optimal power-allocation scheme for such a system is shown to be a water-filling algorithm, and the corresponding capacity is seen to be the same as that of a system having multiple receive antennas (with a single transmitter antenna) whose outputs are combined via maximal ratio combining. A suboptimal adaptive transmission technique that transmits only over the antenna having the best channel is also proposed for this special case. It is shown that the capacity of such a system under the proposed suboptimal adaptive transmission scheme is the same as the capacity of a system having multiple receiver antennas (with a single transmitter antenna) combined via selection combining. Next, the capacity of a general system of multiple transmitter and receiver antennas is derived together with an equation that determines the cutoff value for such a system. The optimal power allocation scheme for such a multiple-antenna system is given by a matrix water-filling algorithm. In order to eliminate the need for cumbersome numerical techniques in solving the cutoff equation, approximate expressions for the cutoff transmission value are also provided. It is shown that, compared to the case in which there is only receiver CSI, large capacity gains are available with optimal power and rate adaptation schemes. The increased capacity is shown to come at the price of channel outage, and bounds are derived for this outage probability.

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.

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.

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.

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.

This paper proposes an effective cooperative communication scheme to obtain high reliability in a long-term evolution-advanced (LTE-A) uplink system. The proposed scheme constitutes the virtual multiple input multiple output antenna array by the cooperative communication scheme and suggests the transmission signal configuration applying spatial phase coding (SPC) with the modified hierarchical modulation. In the proposed transmission signal configuration, high diversity gain is provided by the SPC scheme and the data rate is improved by modified hierarchical modulation. The modified hierarchical modulation transforms the constellation of the conventional hierarchical-modulated signal in order to minimize the influence by noise in the proposed scheme. In the LTE-A uplink system, the proposed scheme is effective to a user equipment (UE) based on single carrier-frequency division multiple access because UE using only single antenna can obtain high reliability without additional antennas.

The sum-rate of the uplink multiuser massive multiple-input multiple-output (MIMO) system is investigated. For the considered massive MIMO systems, the base station (BS) is equipped with a large number of antennas, which are assembled into several sub-arrays. Meanwhile, in each of the sub-arrays, antennas are densely installed. With the analysis of the sum-rate, we find that, for given total number of antennas, the sum-rate achieved by the considered systems improves, when the number of sub-arrays increases. However, the improvement of the achievable sum-rate is marginal, when the number of sub-arrays keeps on increasing. Furthermore, when the system is lightly loaded, even when all of antennas are assembled into a single compact antenna array, the achievable sum-rate is very close to that when all antennas are independent.

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.