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!

Frequency-division multiplexing and demultiplexing systems and methods for use with M transmit and N receive antennas, M equaling at least two. In one embodiment, a frequency-division multiplexing system includes: (1) a differential modulator that generates M×M unitary space-frequency signals from incoming message bits and (2) a time-frequency transformer, coupled to the differential modulator, that transforms the M×M space-frequency signals into space-time transmit signals for the M transmit antennas.

Frequency-division multiplexing system and method for communication having enhanced reliability in fading environments

Methods for suppressing inter-cell interference during data transmission using a preceding matrix are provided. Inter-cell interference is suppressed by precoding data (or information) signals for transmission from base station to mobile or vice versa. Methods according to example embodiments also increase intra-cell data transmission rates. The precoding matrix is generated based on estimated channel coefficients for propagation channels between a base station and mobiles inside and outside the base station's coverage area.

Methods for reducing inter-cell interference by precoding signals for transmission in wireless MIMO system

Systems and methods for assigning pilot sequences include randomly assigning pilot sequences to a population of access terminals. A first pilot sequence assigned to a worst performing access terminal of the population of access terminals is updated to a different pilot sequence that improves performance of the worst performing access terminal. A second pilot sequence assigned to a best performing access terminal of the population of access terminals is updated to another pilot sequence that reduces performance of the best performing access terminal.

Pilot assignment in cell free massive MIMO wireless systems

Various embodiments generally relate to a method for synchronizing a receiver, said method including receiving a stream that includes a cyclic extension, estimating a size of the cyclic extension, extracting an amount of the stream according to the estimated size, and comparing the extracted amount to the stream to determine thereby a portion of the stream likely to include a symbol start point.

Method and apparatus for synchronizing a receiver

Imagine an array with a massive (possibly uncountably infinite) number of antennas in a compact space. We refer to a system of this sort as Holographic MIMO. Given the impressive properties of Massive MIMO, one might expect a holographic array to realize extreme spatial resolution, incredible energy efficiency, and unprecedented spectral efficiency. At present, however, its fundamental limits have not been conclusively established. A major challenge for the analysis and understanding of such a paradigm shift is the lack of mathematically tractable and numerically reproducible channel models that retain some semblance to the physical reality. Detailed physical models are, in general, too complex for tractable analysis. This paper aims to take a closer look at this interdisciplinary challenge. Particularly, we consider the small-scale fading in the far-field, and we model it as a zero-mean, spatially-stationary, and correlated Gaussian scalar random field. Physically-meaningful correlation is obtained by requiring that the random field be consistent with the scalar Helmholtz equation. This formulation leads directly to a rather simple and exact description of the three-dimensional small-scale fading as a Fourier plane-wave spectral representation. Suitably discretized, this leads to a discrete representation for the field as a Fourier plane-wave series expansion, from which a computationally efficient way to generate samples of the small-scale fading over spatially-constrained compact spaces is developed. The connections with the conventional tools of linear systems theory and Fourier transform are thoroughly discussed.

Thomas L. Marzetta

Papers

Frequency-division multiplexing system and method for communication having enhanced reliability in fading environments

Methods for reducing inter-cell interference by precoding signals for transmission in wireless MIMO system

Pilot assignment in cell free massive MIMO wireless systems

Method and apparatus for synchronizing a receiver

Spatial Characterization of Holographic MIMO Channels.