A Detailed Characterization of 60 GHz Wi-Fi (IEEE 802.11ad)

The emergence of wireless local area network (WLAN) standards and the global system of mobile communication (GSM) in the early 1990s incited tremendous growth in the demand for wireless connectivity. Iterative technological enhancements to cellular and WLAN improved wireless capacity and created a breadth of new mobile applications. The continued increase in display resolutions and image quality combined with streaming displacing satellite/cable has created unprecedented demands on wireless infrastructure. Data-caps on cellular networks deter over consumption and increasingly shift the growing burden to Wi-Fi networks. The traditional 2.4/5 GHz Wi-Fi bands have become overloaded and the increasing number of wireless devices in the home, public, and workplace create difficult challenges to deliver quality service to large numbers of client stations. In dense urban areas, the wireless medium is subjected to increased interference due to overlapping networks and other devices communicating in the same frequency bands. Improvements to conventional Wi-Fi are approaching their theoretical limits and higher order enhancements require idealized conditions which are seldom attainable in practice. In an effort to supplant to scaling capacity requirements a very high frequency WLAN amendment has been proposed (IEEE 802.11ad). IEEE 802.11ad, also referred to as Wireless Gigabit (WiGig), operates in the globally unlicensed 60 GHz band and offers channel bandwidths nearly 100x as wide as 802.11n. The higher bandwidth facilitates multi-Gbps throughput even with the use of lower complexity modulation coding schemes (MCS). IEEE 802.11ad relies heavily on rate adaptation and high beamforming gain to mitigate interference and fading as signals in the 60 GHz band suffer from higher atmospheric ab- sorption and free space path loss (FSPL). Due to the unique nature of 60 GHz wireless there have been numerous research efforts. Many studies have been directed at simulation and modeling of the 60 GHz channel. However modeling the channel is difficult as real- world environments are highly dynamic with varying link quality and conditions which cannot be accurately predicted by conventional techniques. Some research is focused on medium access control (MAC) enhancements to improve overall capacity by coordinating concurrent links or reducing communication overhead for example. Lastly, there has been a limited amount of real world testing of 802.11ad due to lack of availability of commercial platforms and measurement instrumentation. Some researchers tested early generation devices in certain use cases such as in vehicles for media streaming, in data centers to augment the wired network, or in basic indoor and outdoor environments. This research contains two main components. In the first study, analytical models are applied to estimate line of sight (LOS) 802.11ad performance for realistic antenna param- eters. The second part contains a comprehensive evaluation of performance and reliability of early generation 802.11ad hardware. This characterization emphasizes environmen- tal performance (e.g. conference room, cubical farm, open office), multiple-client testing (multiclient), multiple network interference (spatial re-use), and stability in the presence of station mobility, physical obstructions, and antenna misalignment. In order to evaluate 802.11ad, early generation platforms from technology vendors were used in extensive test suites. The hardware tested included docks for wireless personal area networking (WPAN) applications, client laptop stations, and reference design access points (APs). Finally, a customized proof-of-concept (PoC) platform was engineered which allowed finer control over front end antenna configuration parameters such as: topology, placement and orienta- tion. The PoC also served as a suitable means to identify practical limitations and system design engineering challenges associated with supporting directional multi-Gbps (DMG) communication in the 60 GHz band

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Enhancing wireless local area networks by leveraging diverse frequency resources

In this thesis, signal propagation variations that are experience over the frequency resources of IEEE 802.11 Wireless Local Area Networks (WLANs) are studied. It is found that exploitation of these variations can improve several aspects of wireless communication systems. To this aim, frequency varying behavior is addressed at two different levels. First, the intra-channel scale is considered, i.e. variations over the continuous frequency block that a device uses for a cohesive transmission. Variations at this level are well known but current wireless systems restrict to basic equalization techniques to balance the received signal. In contrast, this work shows that more fine grained adaptation to these differences can accomplish throughput and connection range gains. Second, multi-frequency band enabled devices that access widely differing frequency resources in the millimeter wave range as well as in the microwave range are analyzed. These devices that are expected to follow the IEEE 802.11ad specification experience intense propagation variations over their frequency resources. Thus, a part of this thesis revises, the theoretical specification of the IEEE 802.11ad standard and complements it by a measurement study of first generation millimeter wave devices. This study reveals deficiencies of first generation millimeter wave systems, whose improvement will pose new challenges to the protocol design of future generation systems. These challenges are than addressed by novel methods that leverage from frequency varying propagation characteristics. The first method, improves the beam training process of millimeter wave networks, that need highly directional, though electronically steered, transmissions to overcome increased free space attenuation. By leveraging from omni-directional signal propagation at the microwave bands, efficient direction interference is utilized to provide information to millimeter wave interfaces and replace brute force direction testing. Second, deafness effects at the millimeter wave band, which impact IEEE 802.11 channel access methods are addressed. As directional communication on these bands complicates sensing the medium to be busy or idle, inefficiencies and unfairness are implied. By using coordination message exchange on the legacyWi-Fi frequencies with omnidirectional communication properties, these effects are countered. The millimeter wave bands can thus unfold their full potential, being exclusively used for high speed data frame transmission.Programa Oficial de Doctorado en Ingeniería TelemáticaPresidente: Ralf Steinmetz.- Secretario: Albert Banchs Roca.- Vocal: Kyle Jamieso

Ray-tracing-based mm-wave beamforming assessment

The use of large-size antenna arrays to implement pencil-beam forming techniques is becoming a key asset to cope with the very high throughput density requirements and high path-loss of future millimeter-wave (mm-wave) gigabit-wireless applications. Suboptimal beamforming (BF) strategies based on search over discrete set of beams (steering vectors) are proposed and implemented in present standards and applications. The potential of fully adaptive advanced BF strategies that will become possible in the future, thanks to the availability of accurate localization and powerful distributed computing, is evaluated in this paper through system simulation. After validation and calibration against mm-wave directional indoor channel measurements, a 3-D ray tracing model is used as a propagation-prediction engine to evaluate performance in a number of simple, reference cases. Ray tracing itself, however, is proposed and evaluated as a real-time prediction tool to assist future BF techniques