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!

In one embodiment, the method includes receiving (S410) a pilot signal from a terminal (30) at a target antenna of the plurality of antennas (20) of the network element ( 10), determining (S420) an uplink channel estimate for the target antenna based on the received pilot signal, and obtaining (S430) a calibration coefficient associated with the target antenna. The calibration coefficient is based on a channel estimate between the target antenna and a different one of the plurality of antennas. The method further includes beamforming (S440) a transmission to the terminal using at least the target antenna based on the determined uplink channel estimate and the obtained calibration coefficient.

Method for beamforming transmissions from a network element having a plurality of antennas, and the network element

The papers in this special issue focus on large-scale multiple antenna wireless systems and services.

/pdf/guest-editorial-large-scale-multiple-antenna-wireless-1ucz3gxsfv.pdf

Guest Editorial: Large-Scale Multiple Antenna Wireless Systems

A method is provided, in which a base station allocates pilot signals to mobile terminals in a cell, obtains CSI from uplink pilot signals transmitted by mobile terminals, uses the CSI to precode messages, and transmits the messages in conformance with a TDD protocol. The CSI is obtained by comparing the pilot signal received from each mobile terminal to a known pilot signal associated with that mobile terminal. The known pilot signals are associated with respective mobile terminals according to a pilot signal reuse pattern in which adjacent cells are allocated mutually orthogonal reuse groups of mutually orthogonal pilot signals, and mobile terminals within a given cell are limited to transmitting only pilot signals allocated to that cell.

Method and apparatus of wireless communication using directional antennas

Cell-free massive multiple-input multiple-output (MIMO) was recently proposed as an alternative to partitioning coverage area into cells. The main idea is to have many access points (APs) distributed over the coverage area to serve a smaller number of users. Users are served by all APs simultaneously by sharing time and frequency resources. In this paper, we study the deployment of multi-antenna APs in cell-free massive MIMO systems. In particular, we study the advantages and disadvantages of using multi-antenna APs with respect to the achievable rates, the backhauling traffic, and the infrastructure cost to give results on how disperse antennas should be among APs.

Cell-free massive MIMO systems utilizing multi-antenna access points

A method is disclosed for generating unitary space-time signals for wireless communication using an array of M transmitting antennas. Each unitary space-time signal comprises T symbols. The method can be used to generate arbitrarily large signal constellations. The resulting unitary space-time signals have statistical properties that are favorable for reliable use in communication, and they can lead to very high data transmission rates. The disclosed method involves the mapping of binary strings of data to matrix products of the kind obtained by left-multiplying an initial T×M matrix by an ordered multiplicative sequence of exponentiated T×T unitary matrices, referred to as generator matrices. The result of each such multiplication is a unitary space-time signal matrix that may be transmitted. Each generator matrix corresponds to a single bit or a collection of bits of a binary string that is to be mapped. The value of the exponent of each generator matrix is determined by the pertinent bit or collection of bits.

Thomas L. Marzetta

Papers

Method for beamforming transmissions from a network element having a plurality of antennas, and the network element

Guest Editorial: Large-Scale Multiple Antenna Wireless Systems

Method and apparatus of wireless communication using directional antennas

Cell-free massive MIMO systems utilizing multi-antenna access points

Method of wireless communication using structured unitary space-time signal constellations