https://www.cs.montana.edu/courses/csci566/Ref/CR-Survey.pdf

NeXt generation/dynamic spectrum access/cognitive radio wireless networks: a survey

Coding strategies that exploit node cooperation are developed for relay networks. Two basic schemes are studied: the relays decode-and-forward the source message to the destination, or they compress-and-forward their channel outputs to the destination. The decode-and-forward scheme is a variant of multihopping, but in addition to having the relays successively decode the message, the transmitters cooperate and each receiver uses several or all of its past channel output blocks to decode. For the compress-and-forward scheme, the relays take advantage of the statistical dependence between their channel outputs and the destination's channel output. The strategies are applied to wireless channels, and it is shown that decode-and-forward achieves the ergodic capacity with phase fading if phase information is available only locally, and if the relays are near the source node. The ergodic capacity coincides with the rate of a distributed antenna array with full cooperation even though the transmitting antennas are not colocated. The capacity results generalize broadly, including to multiantenna transmission with Rayleigh fading, single-bounce fading, certain quasi-static fading problems, cases where partial channel knowledge is available at the transmitters, and cases where local user cooperation is permitted. The results further extend to multisource and multidestination networks such as multiaccess and broadcast relay channels.

Cooperative strategies and capacity theorems for relay networks

Millimeter-wave (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multielement antenna arrays. This paper surveys measurements and capacity studies to assess this technology with a focus on small cell deployments in urban environments. The conclusions are extremely encouraging; measurements in New York City at 28 and 73 GHz demonstrate that, even in an urban canyon environment, significant non-line-of-sight (NLOS) outdoor, street-level coverage is possible up to approximately 200 m from a potential low-power microcell or picocell base station. In addition, based on statistical channel models from these measurements, it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities. Cellular systems, however, will need to be significantly redesigned to fully achieve these gains. Specifically, the requirement of highly directional and adaptive transmissions, directional isolation between links, and significant possibilities of outage have strong implications on multiple access, channel structure, synchronization, and receiver design. To address these challenges, the paper discusses how various technologies including adaptive beamforming, multihop relaying, heterogeneous network architectures, and carrier aggregation can be leveraged in the mmW context.

Millimeter-Wave Cellular Wireless Networks: Potentials and Challenges

Information Theory and Reliable Communication

In recent years, there has been an upsurge of interest in multihop-augmented infrastructure-based networks in both the industry and academia, such as the seed concept in 3GPP, mesh networks in IEEE 802.16, and converge extension of HiperLAN/2 through relays or user-cooperative diversity mesh networks. This article, a synopsis of numerous contributions to the working group 4 of the wireless world research forum and other research work, presents an overview of important topics and applications in the context of relaying. It covers different approaches to exploiting the benefits of multihop communications via relays, such as solutions for radio range extension in mobile and wireless broadband cellular networks (trading range for capacity), and solutions to combat shadowing at high radio frequencies. Furthermore, relaying is presented as a means to reduce infrastructure deployment costs. It is also shown that through the exploitation of spatial diversity, multihop relaying can enhance capacity in cellular networks. We wish to emphasize that while this article focuses on fixed relays, many of the concepts presented can also be applied to systems with moving relays.

/pdf/relay-based-deployment-concepts-for-wireless-and-mobile-4js7u1daca.pdf

Relay-based deployment concepts for wireless and mobile broadband radio

IEEE 802.11 Wireless Local Area Networks

The IEEE 802.11e medium access control protocol is an emerging standard for wireless local area networks providing quality of service. An overview of this standard based on the current draft is presented on this article. We analyze the enhancements in 802.11 standard. The new hybrid coordination function of the IEEE 802.11e with its contention-based and contention-free (controlled) medium access control schemes is evaluated. The capability to provide QoS support is discussed by means of simulations.

Analysis of IEEE 802.11e for QoS support in wireless LANs

The introduction of IEEE's 80211 standards has enabled a mass market, with a huge impact in the home, office, and public areas Today, laptops, PCs, printers, cellular phones, VoIP phones, MP3 players, Blu-Ray players, and many more devices incorporate wireless LAN technology With low-cost chipsets and support for high data rates, 80211 has become a universal solution for an ever increasing application space As a direct consequence of its high market penetration, several amendments to the basic 80211 standard have been developed or are under development They fix technology issues or add functionality expected to be required by future applications In this article we overview the emerging 80211 standard and address the technical context of its extensions The article highlights its finalized amendments and those under development

The IEEE 802.11 universe

The wireless local area network standard IEEE 802.11 is the preferred solution for lowcost data services. Key to its success are the 2.4 and 5 GHz unlicensed bands. The transmit power limitations imposed due to regulatory requirements limit the range (coverage) that can be achieved by WLANs in these bands. However, the demand for "larger" wireless infrastructure is emerging, ranging from office/university campuses to city-wide deployments. To overcome the limitations of singlehop communication, data packets need to traverse over multiple wireless hops, and wireless mesh networks are called for. Since 2004 Task Group S has been developing an amendment to the 802.11 standard to exactly address the aforementioned need for multihop communication. Besides introducing wireless frame forwarding and routing capabilities at the MAC layer, the 802.11s amendment brings new interworking and security. In this article, we provide insights into the latest developments in 802.11s and explain how the overall mesh concept fits into the 802 set of networking standards.

Bernhard Walke

Papers

Relay-based deployment concepts for wireless and mobile broadband radio

IEEE 802.11 Wireless Local Area Networks

Analysis of IEEE 802.11e for QoS support in wireless LANs

The IEEE 802.11 universe

IEEE 802.11s: The WLAN Mesh Standard