Design of a Practical and Compact mm-Wave MIMO System with Optimized Capacity and Phased Arrays

In this paper we evaluate the feasibility of short range outdoor mm-wave MIMO links in the 70 GHz portion of the E-band (71–76 GHz). We use phased arrays in order to strongly reduce the impact of the multipath components, thus making the channel mainly line-of-sight (LOS). We design the array using a simple patch as a single element and simulate the performances for a 200 m link and a MIMO system with equal element spacing at the transmitter and the receiver. Each node of the MIMO system consists of a uniform rectangular array (URA) where the single element is a patch antenna, in order to achieve higher gains and narrow beams. Such configuration is much more compact compared to the antennas currently employed for the same bandwidth. We optimize the interelement distances at the transmitter and the receiver and evaluate the capacity achievable with different array sizes. The results show that, for the proposed link budget, capacity up to 29 bit/s/Hz is achievable at a range of 200 m, with practical dimensions. We also show that the beamforming capabilities make the design much more flexible than the single reflector antenna systems. In the last part of the paper, we verify that our antenna can also operate in rainy conditions and longer ranges

Robust Location-Aided Beam Alignment in Millimeter Wave Massive MIMO

Location-aided beam alignment has been proposed recently as a potential approach for fast link establishment in millimeter wave (mmWave) massive MIMO (mMIMO) communications. However, due to mobility and other imperfections in the estimation process, the spatial information obtained at the base station (BS) and the user (UE) is likely to be noisy, degrading beam alignment performance. In this paper, we introduce a robust beam alignment framework in order to exhibit resilience with respect to this problem. We first recast beam alignment as a decentralized coordination problem where BS and UE seek coordination on the basis of correlated yet individual position information. We formulate the optimum beam alignment solution as the solution of a Bayesian team decision problem. We then propose a suite of algorithms to approach optimality with reduced complexity. The effectiveness of the robust beam alignment procedure, compared with classical designs, is then verified on simulation settings with varying location information accuracies.Comment: 24 pages, 7 figures. The short version of this paper has been accepted to IEEE Globecom 201

Common Codebook Millimeter Wave Beam Design: Designing Beams for Both Sounding and Communication with Uniform Planar Arrays

Fifth generation (5G) wireless networks are expected to utilize wide bandwidths available at millimeter wave (mmWave) frequencies for enhancing system throughput. However, the unfavorable channel conditions of mmWave links, e.g., higher path loss and attenuation due to atmospheric gases or water vapor, hinder reliable communications. To compensate for these severe losses, it is essential to have a multitude of antennas to generate sharp and strong beams for directional transmission. In this paper, we consider mmWave systems using uniform planar array (UPA) antennas, which effectively place more antennas on a two-dimensional grid. A hybrid beamforming setup is also considered to generate beams by combining a multitude of antennas using only a few radio frequency chains. We focus on designing a set of transmit beamformers generating beams adapted to the directional characteristics of mmWave links assuming a UPA and hybrid beamforming. We first define ideal beam patterns for UPA structures. Each beamformer is constructed to minimize the mean squared error from the corresponding ideal beam pattern. Simulation results verify that the proposed codebooks enhance beamforming reliability and data rate in mmWave systems.Comment: 14 pages, 10 figure

Antenna Array Design for LOS-MIMO and Gigabit Ethernet Switch-Based Gbps Radio System

The high spectrum efficiency of multiple-input multiple-output (MIMO) transmission traditionally depends on the high multiplexing gain in rich scattering environments, which will not always hold in the line-of-sight (LOS) environments, especially at higher microwave frequency band. In this paper, a novel antenna array design rule is proposed to guarantee full multiplexing gain for LOS-MIMO systems with one- or two-dimensional antenna arrays in LOS scenarios, and the strict perpendicular constraint is released in the two-dimensional case. The minimum antenna array area and the performance sensitivity to the area error are also obtained to guide the practical system design. Then, a demo MIMO-OFDM system with the designed square antenna array at 15 GHz carrier is implemented on a novel Gigabit Ethernet (GE) switch-based software defined radio (SDR) platform, which combines the hardware accelerating units (HAUs) with the general-purpose processors (GPPs). The field evaluation results show that the system throughput and spectrum efficiency are greater than 1 Gbps and 15 bps/Hz, respectively. To the best of our knowledge, it is the first time to demonstrate the Gbps LOS-MIMO-OFDM system at such microwave bands in the world, which can be a successful design example for the next generation wireless backhaul or fixed wireless access

Analytical Model for Outdoor Millimeter Wave Channels using Geometry-Based Stochastic Approach

The severe bandwidth shortage in conventional microwave bands has spurred the exploration of the millimeter wave (MMW) spectrum for the next revolution in wireless communications. However, there is still lack of proper channel modeling for the MMW wireless propagation, especially in the case of outdoor environments. In this paper, we develop a geometry-based stochastic channel model to statistically characterize the effect of all the first-order reflection paths between the transmitter and receiver. These first-order reflections are generated by the single-bounce of signals reflected from the walls of randomly distributed buildings. Based on this geometric model, a closed-form expression for the power delay profile (PDP) contributed by all the first-order reflection paths is obtained and then used to evaluate their impact on the MMW outdoor propagation characteristics. Numerical results are provided to validate the accuracy of the proposed model under various channel parameter settings. The findings in this paper provide a promising step towards more complex and practical MMW propagation channel modeling.Comment: Accepted to appear in IEEE Transactions on Vehicular Technolog

Adaptive Multi-state Millimeter Wave Cell Selection Scheme for 5G communication

Millimeter wave bands have been introduced as one of the most promising solutions to alleviate the spectrum secrecy in the upcoming future cellular technology (5G) due the enormous amount of raw bandwidth available in these bands. However, the inherent propagation characteristics of mmWave frequencies could impose new challenges i.e. higher path loss, atmospheric absorption, and rain attenuation which in turn increase the outage probability and hence, degrading the overall system performance. Therefore, in this paper, a novel flexible scheme is proposed namely Adaptive Multi-State MmWave Cell Selection (AMSMC-S) through adopting three classes of mmWave base stations, able to operate at various mmWave carrier frequencies (73, 38 and 28 GHz). Two mmWave cellular Grid-Based cell deployment scenarios have been implemented with two inter-site-distances 200 m and 300 m, corresponding to target area of (2.1 km2) and (2.2 km2). The maximum SINR value at the user equipment (UE) is taken in to consideration to enrich the mobile user experience. Numerical results show an improvement of overall system performance, where the outage probability reduced significantly to zero while maintaining an acceptable performance of the 5G systems with approximately more than 50% of the mobile stations with more than 1Gbps data rate.