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Wireless video is the main driver for rapid growth in cellular data traffic. Traditional methods for network capacity increase are very costly and do not exploit the unique features of video, especially asynchronous content reuse. In this paper we give an overview of our work that proposed and detailed a new transmission paradigm exploiting content reuse and the widespread availability of low-cost storage. Our network structure uses caching in helper stations (femtocaching) and/or devices, combined with highly spectrally efficient short-range communications to deliver video files. For femtocaching, we develop optimum storage schemes and dynamic streaming policies that optimize video quality. For caching on devices, combined with device-to-device (D2D) communications, we show that communications within clusters of mobile stations should be used; the cluster size can be adjusted to optimize the tradeoff between frequency reuse and the probability that a device finds a desired file cached by another device in the same cluster. In many situations the network throughput increases linearly with the number of users, and the tradeoff between throughput and outage is better than in traditional base-station centric systems. Simulation results with realistic numbers of users and channel conditions show that network throughput can be increased by two orders of magnitude compared to conventional schemes.

Wireless networks are on the verge of a third phase of growth. The first phase was dominated by voice traffic, and the second phase, which we are currently in, is dominated by data traffic. In the third phase we predict that the traffic will be dominated by video and will require new ways to optimize the network to prevent saturation. This increase in video traffic is one of the key drivers of the evolution to new mobile broadband standards like WiMAX IEEE 802.16m and 3G LTE and LTE-Advanced, motivating the need to enhance the video service capabilities of future cellular and mobile broadband systems. Therefore, it is important to understand both the potential and limitations of these networks for delivering video content in the future, which will include not only traditional video broadcasts, but also video streaming and uploading in the uplink direction. In that vein this article provides an overview of technology options for enabling multicast and unicast video services over WiMAX and LTE networks, quantifies and compares the video capacities of these networks in realistic environments, and discusses new techniques that could be exploited in the future to further enhance the video capacity and quality of user experience.

Ultra wide band (UWB) technology offers a promising high capacity solution for short-range wireless ad hoc networks, as in home networks or in wearable ad hoc networks. In this paper, we propose a novel multi-band MAC protocol for use in small ad hoc networks that deploy an underlying UWB based physical layer. In our approach, we divide the available UWB bandwidth into multiple simultaneously usable bands. In the absence of a sophisticated equalizer, the size of a slot for transmitting a UWB pulse is typically dictated by the delay spread of the channel. Therefore, using a wider frequency band to shorten the transmission time for each pulse does not increase the data rate in proportion to the available bandwidth. A multi-band approach that uses a plurality of bands that adhere to FCC specifications, with slightly elongated pulse durations, provides a solution that can effectively utilize the UWB spectrum. Our approach is based on the idea of conflict resolution using binary ‘something’/‘nothing’ feedback, which has not been widely studied in wireless and specifically in UWB networks. Our protocol unites binary conflict resolution and multi-band utilization to effectively utilize the available bandwidth. To ensure that our proposed approach is tightly knit with the underlying physical layer, we discuss physical–layer dependencies and the conformance to FCC-imposed emission limits. We evaluate our approach via extensive simulations. Our simulation results demonstrate the significant advantages of our approach over single-band solutions: the throughput increases significantly, and the number of collisions decreases considerably. Copyright © 2006 John Wiley & Sons, Ltd.

The paper provides a tutorial overview of ultrawideband (UWB) radio technology for high-speed wireless connectivity. Subsequent to establishing a historical and technological context, it describes the new impetus for UWB systems development and standardization resulting from the FCC's recent decision to permit unlicensed operation in the 3.1-10.6 GHz band subject to modified Part 15 rules and indicates the potential new applications that may result. Thereafter, the paper provides a system architect's perspectives on the various issues and challenges involved in the design of link layer subsystems. Specifically, we outline current developments in UWB system design concepts that are oriented to high-speed applications and describe some of the design tradeoffs involved.

Ultra Wide Band (UWB) technology offers a promis- ing high capacity solution for wireless networks with short-range links. However, MAC and higher-layer ad hoc network protocols that exploit the UWB technology are yet to mature. In this paper, we propose a MAC protocol for use in multi-hop wireless networks that deploy an underlying UWB based physical layer. We adopt a multi-band approach wherein we divide the available UWB band- width into multiple simultaneously usable bands. The motivation comes from the following observation: in the absence of a sophis- ticated equalizer, the size of a slot for transmitting a UWB pulse is typically dictated by the delay spread of the channel. There- fore, using a wider frequency band to shorten the transmission time for each pulse may not increase the data rate in proportion to the available bandwidth. Thus, we consider a multi-band ap- proach to better utilize the available spectrum, where each trans- mitter sends longer pulses in one of many narrower frequency bands. Unlike previous single hopped schemes that rely on time- hopping, our approach allows data transmissions to be contigu- ous, and thus, highly efficient. The approach also ensures that data communications are practically interference free and are only subject to thermal noise effects. To ensure that our proposed ap- proach is tightly knit with the underlying physical layer, we discuss physical-layer dependencies and the conformance of our approach to FCC-imposed emission limits. We evaluate our approach via ex- tensive simulations. Our simulation results demonstrate the signif- icant advantages of our approach over single-band solutions: the throughput increases significantly, and the number of collisions decreases considerably.

The FCC ruling in 2002 allowing for the unlicensed deployment of ultra-wideband (UWB) devices for communications purposes in the 3.1-10.6 GHz band has sparked great interest in the industry. In particular, the IEEE 802.15.3a task group is currently developing a standard for high-rate, short-range wireless communication systems that is expected to use UWB technology. One of the main challenges for UWB system design is minimizing the possible interference to other narrowband systems, while, at the same time, dealing with the large interference that may be coming from these narrowband systems into the UWB receiver. Traditional UWB systems have used very short time impulses that occupy several giga-hertz of bandwidth. This approach makes it difficult to efficiently avoid other system that may be sharing the same band. This paper will describe a channel model that has been adopted by the industry to evaluate the merits of different UWB physical layer approaches and introduce an alternate approach to a high-rate UWB system that is based upon the concatenation of multiple narrower band UWB waveforms.