Enabling rural broadband via TV "white space"

The use of multiple frequency bands within a wireless network allows the advantages of each band to be exploited. In this paper we discuss how HopScotch, a rural wireless broadband access test bed running in the Scottish Highlands and Islands, uses both 5 GHz and ultra high frequency "white space" bands to offer large data rates and expansive coverage whilst reducing the number of base stations or required transmission power. This reduction in energy consumption allows HopScotch to provide a low-cost and green solution for rural broadband delivery

LTE-Advanced radio access enhancements: A survey

Long Term Evolution Advanced (LTE-Advanced) is the next step in LTE evolution and allows operators to improve network performance and service capabilities through smooth deployment of new techniques and technologies. LTE-Advanced uses some new features on top of the existing LTE standards to provide better user experience and higher throughputs. Some of the most significant features introduced in LTE-Advanced are carrier aggregation, enhancements in heterogeneous networks, coordinated multipoint transmission and reception, enhanced multiple input multiple output usage and deployment of relay nodes in the radio network. Mentioned features are mainly aimed to enhance the radio access part of the cellular networks. This survey article presents an overview of the key radio access features and functionalities of the LTE-Advanced radio access network, supported by the simulation results. We also provide a detailed review of the literature together with a very rich list of the references for each of the features. An LTE-Advanced roadmap and the latest updates and trends in LTE markets are also presented

A Study of the Impact of Various Geometric Factors on the Capacity of Short Range Indoor MIMO Communications Channels

MIMO antenna array systems have been proposed as a means of increasing the spectral efficiency of wireless systems. However, their performance is likely to be sub-optimal if typical uniform antenna array structures are arbitrarily positioned; as they depend on spatial multiplexing. This is particularly true for indoor environments in which transmission ranges are short resulting in a strong correlation of the main propagation paths, especially the line-of-sight components. This makes it difficult to achieve successful spatial multiplexing which depends on a decorrelated set of signal components. Thus, the physical propagation channel and geometry of the antenna arrays, especially the inter-element spacing, can determine how effectively spatial multiplexing can be realised. This thesis investigates MIMO communications channels involving a single transmitter and receiver operating in a simple indoor environment using a ray-tracing simulation model. The results and analysis provide system designers with an understanding of the limits of MIMO system performance in the context of both the geometric properties of the arrays and the propagation conditions. These results serve to explain the often contradictory results that appear in the wider literature on MIMO systems. Guidelines for the deployment of standard array structures in an indoor environment are provided. An original solution to optimising MIMO system performance by adjusting the geometry of uniform linear arrays is described. This is done using an iterative search method based on the Metropolis algorithm in which individual array elements are repositioned. It is demonstrated through computer simulation that capacity levels, similar to those predicted by the theory for ideal Rayleigh channels, are possible to achieve with realistic modifications to uniform linear arrays

Design of 28 GHz 4x4 RF Beamforming Array for 5G Radio Front-Ends

Current state of wireless infrastructure sees mass migration to higher frequencies as much of the already used spectrum is insufficient in supporting the influx of numerous users and various data intensive mobile applications. Data rates are projected to increase by an order of magnitude and harnessing the necessary bandwidth below 6 GHz is not feasible. A move to higher frequencies sees not only increased fractional bandwidth, but also significantly enhanced antenna apertures as a result of beamforming capabilities. Due to device level complications with frequencies nearing the unit gain frequency of transistor technology, high output power is seldom found, and in conjunction with severe path loss, communication links cannot be established without the usage of antenna arrays. Phased array systems offer significant upside to the traditional array implementation as it permits reconfigurable directive communication. However, Ka-Band phased arrays still struggle to arrive at a reasonable tradeoff between design complexity, cost and performance. With a divide between both organic and printed circuit board (PCB) based approaches to the development of an antenna-in-package (AiP), this thesis sides with the latter. An antenna-on-PCB variant of the AiP is developed, which implements both commercially available RF laminates and RFIC front end modules to produce a 28 GHz 4x4 RF beamforming phased array that is found to exhibit extremely low loss (-0.66 dB), adequate scan volume (+/- 45 degrees, in E and H planes) and large bandwidth (3 GHz) for a single layer, non-isolated patch antenna design. Unit cell, infinite array analysis is emphasized and lattice resizing is leveraged to obtain desired scan performance, while significantly reducing design complexity via the absence of intricate isolation enhancement techniques. In an effort to aid in application based design, the AiP is extended to application of linearization where it is found that the inclusion of dummy elements along the perimeter of the package not only serve as element pattern enhancement, but also provide reliable means of output signal capture. Negating the traditional transmitter observation receiver (TOR) architecture, the AiP design as a TOR for millimeter-wave communication proves optimistic in the quest for maximum system efficiency

MIMO Systems

In recent years, it was realized that the MIMO communication systems seems to be inevitable in accelerated evolution of high data rates applications due to their potential to dramatically increase the spectral efficiency and simultaneously sending individual information to the corresponding users in wireless systems. This book, intends to provide highlights of the current research topics in the field of MIMO system, to offer a snapshot of the recent advances and major issues faced today by the researchers in the MIMO related areas. The book is written by specialists working in universities and research centers all over the world to cover the fundamental principles and main advanced topics on high data rates wireless communications systems over MIMO channels. Moreover, the book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity

AirSync: Enabling Distributed Multiuser MIMO with Full Spatial Multiplexing

The enormous success of advanced wireless devices is pushing the demand for higher wireless data rates. Denser spectrum reuse through the deployment of more access points per square mile has the potential to successfully meet the increasing demand for more bandwidth. In theory, the best approach to density increase is via distributed multiuser MIMO, where several access points are connected to a central server and operate as a large distributed multi-antenna access point, ensuring that all transmitted signal power serves the purpose of data transmission, rather than creating "interference." In practice, while enterprise networks offer a natural setup in which distributed MIMO might be possible, there are serious implementation difficulties, the primary one being the need to eliminate phase and timing offsets between the jointly coordinated access points. In this paper we propose AirSync, a novel scheme which provides not only time but also phase synchronization, thus enabling distributed MIMO with full spatial multiplexing gains. AirSync locks the phase of all access points using a common reference broadcasted over the air in conjunction with a Kalman filter which closely tracks the phase drift. We have implemented AirSync as a digital circuit in the FPGA of the WARP radio platform. Our experimental testbed, comprised of two access points and two clients, shows that AirSync is able to achieve phase synchronization within a few degrees, and allows the system to nearly achieve the theoretical optimal multiplexing gain. We also discuss MAC and higher layer aspects of a practical deployment. To the best of our knowledge, AirSync offers the first ever realization of the full multiuser MIMO gain, namely the ability to increase the number of wireless clients linearly with the number of jointly coordinated access points, without reducing the per client rate.Comment: Submitted to Transactions on Networkin