We investigate the use of multiple transmitting and/or receiving antennas for single user communications over the additive Gaussian channel with and without fading. We derive formulas for the capacities and error exponents of such channels, and describe computational procedures to evaluate such formulas. We show that the potential gains of such multi-antenna systems over single-antenna systems is rather large under independenceassumptions for the fades and noises at different receiving antennas.

/pdf/capacity-of-multi-antenna-gaussian-channels-3axdfdd5ns.pdf

Capacity of Multi‐antenna Gaussian Channels

Cognitive radio is viewed as a novel approach for improving the utilization of a precious natural resource: the radio electromagnetic spectrum. The cognitive radio, built on a software-defined radio, is defined as an intelligent wireless communication system that is aware of its environment and uses the methodology of understanding-by-building to learn from the environment and adapt to statistical variations in the input stimuli, with two primary objectives in mind: /spl middot/ highly reliable communication whenever and wherever needed; /spl middot/ efficient utilization of the radio spectrum. Following the discussion of interference temperature as a new metric for the quantification and management of interference, the paper addresses three fundamental cognitive tasks. 1) Radio-scene analysis. 2) Channel-state estimation and predictive modeling. 3) Transmit-power control and dynamic spectrum management. This work also discusses the emergent behavior of cognitive radio.

/pdf/cognitive-radio-brain-empowered-wireless-communications-9m6gu0vz1z.pdf

Cognitive radio: brain-empowered wireless communications

Wireless Communications

What will 5G be? What it will not be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.

What Will 5G Be

The global bandwidth shortage facing wireless carriers has motivated the exploration of the underutilized millimeter wave (mm-wave) frequency spectrum for future broadband cellular communication networks. There is, however, little knowledge about cellular mm-wave propagation in densely populated indoor and outdoor environments. Obtaining this information is vital for the design and operation of future fifth generation cellular networks that use the mm-wave spectrum. In this paper, we present the motivation for new mm-wave cellular systems, methodology, and hardware for measurements and offer a variety of measurement results that show 28 and 38 GHz frequencies can be used when employing steerable directional antennas at base stations and mobile devices.

Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!

The singular value decomposition (SVD), a standard tool for theoretical and computational matrix analysis, represents a matrix as an ordered product of a unitary matrix, a nonnegative, real diagonal matrix, and a second unitary matrix. Our contribution is to extend the SVD representation to a matrix-valued impulse response. The representation involves a countably infinite number of vector-valued eigenfunctions and scalar singular values, and it provides the most concise and elegant description of the action of a matrix-valued filter (for example, a space-time communication channel) when driven by a finite-duration input signal.

Singular value decomposition of a matrix-valued impulse response

By calculating the effective max-min SINR (signal- to-interference-plus-noise ratio) and the corresponding power controls explicitly, and selectively dropping a small number of mobiles based on a simple and effective algorithm, we demonstrate that for both downlink and uplink, employing maximum-ratio or zero-forcing linear pre-coding and de-coding, Massive MIMO with max- min power control performs comparably in LoS (Line-of-Sight) and iid (independent and identically distributed) Rayleigh fading propagation environments.

Massive MIMO in Line-of-Sight Propagation

PROBLEM TO BE SOLVED: To achieve diversity merits without receiving demerits so much by transmitting respective data symbol sets to the respective users of a user group by the form plural mutually different signal sequences which are the linear connection of spreading code sequences belonging to a corresponding code group. SOLUTION: An antenna 1 (25.1) transmits signals (1/21/2) (b1c1+b2c2) and the antenna 2 (25.2) transmits the signals (1/21/2) (b2c1-b1c2). In such a manner, while only two pieces of spreading codes are used, the two codes are used for a data symbol to the user (20.1) and also the two codes are used for the data symbol to the user (20.2) as well. Thus, at the time of using plural transmitter antennas, a system for sufficiently achieving the diversity merits without receiving the demerits in the number of the codes required to be allocated per user so much, is realized.

Cdma communication method

A method is provided to reduce inter-cell interference in mobile wireless systems, and particularly in TDD wireless systems. In an embodiment, a base station receives a pilot signal from at least one of the mobile terminals that it serves at a plurality of base station antennas, which include both main antennas and auxiliary antennas. In response, each of the base station antennas provides an output that is processed to obtain a set of precoding weights for a transmission from the main antennas. The processing includes nulling at least one interfering signal using the outputs from at least the auxiliary antennas.

Multiple Antenna Method And Apparatus For Reducing Inter-Cell Interference In Multi-User Wireless Systems

For frequency division duplex channels, a simple pilot loop-back procedure has been proposed that allows the estimation of the uplink (UL) and downlink (DL) channel subspaces between an antenna array and a fully analog repeater. For this scheme, we derive the maximum likelihood (ML) estimators for the UL and DL subspaces, formulate the corresponding Cramer–Rao bounds, and show the asymptotic efficiency of both (singular value decomposition (SVD) based) estimators by means of Monte Carlo simulations. In addition, we illustrate how to compute the underlying (rank-1) SVD with quadratic time complexity by employing the power iteration method. To enable power control for the data transmission, knowledge of the channel gains is needed. Assuming that the UL and DL channels have on average the same gain, we formulate the ML estimator for the uplink channel vector norm, and illustrate its robustness against strong noise perturbations by means of simulations.

Thomas L. Marzetta

Papers

Singular value decomposition of a matrix-valued impulse response

Massive MIMO in Line-of-Sight Propagation

Cdma communication method

Multiple Antenna Method And Apparatus For Reducing Inter-Cell Interference In Multi-User Wireless Systems

Channel Training for Analog FDD Repeaters: Optimal Estimators and Cramér–Rao Bounds