Wireless data services, other than those for electronic mail or paging, have thus far been more promising than successful. We believe that future mobile information systems must be built upon heterogeneous wireless overlay networks', extending traditional wired and internetworked processing "islands" to hosts on the move over coverage areas ranging from in-room, in-building, campus, metropolitan, and wide-areas. Unfortunately, network planners continue to think in terms of homogeneous wireless communications systems and technologies. In this paper, we describe a new wireless data networking architecture that integrates diverse wireless technologies into a seamless internetwork. In addition, we describe the applications support services needed to make it possible for applications to continue to operate as mobile hosts roam across such networks. The architecture described herein is being implemented in a testbed at the University of California, Berkeley under joint government/industry sponsorship.

Cognitive radio promises a low cost, highly flexible alternative to the classic single frequency band, single protocol wireless device. By sensing and adapting to its environment, such a device is able to fill voids in the wireless spectrum and dramatically increase spectral efficiency. In this paper, the cognitive radio channel is defined as an n-transmitter, m-receiver interference channel in which sender i obtains the messages senders 1 through i − 1 plan to transmit. The two sender, two receiver case is considered. In this scenario, one user, a cognitive radio, obtains (genie assisted, or causally) knowledge of the data to be transmitted by the other user. The cognitive radio may then simultaneously transmit over the same channel, as opposed to waiting for an idle channel as in a traditional cognitive radio channel protocol. Dirty-paper coding and ideas from achievable region constructions for the interference channel are used, and an achievable region for the cognitive radio channel is computed. It is shown that in the Gaussian case, the described achievable region approaches the upper bounds provided by the 2×2 Gaussian MIMO broadcast channel, and an interference-free channel. Results are extended to the case in which the message is causally obtained.

With the emergence of broadband wireless networks and increasing demand of multimedia information on the Internet, wireless multimedia services are foreseen to become widely deployed in the next decade. Real-time video transmission typically has requirements on quality of service (QoS). However, wireless channels are unreliable and the channel bandwidth varies with time, which may cause severe degradation to video quality. In addition, for video multicast, the heterogeneity of receivers makes it difficult to achieve efficiency and flexibility. To address these issues, three techniques, namely, scalable video coding, network-aware adaptation of end systems, adaptive QoS support from networks, have been developed. This paper unifies the three techniques and presents an adaptive framework, which specifically addresses video transport over wireless networks. The adaptive framework consists of three basic components: (1) scalable video representations, (2) network-aware end systems, and (3) adaptive services. Under this framework, as wireless channel conditions change, mobile terminals and network elements can scale the video streams and transport the scaled video streams to receivers with a smooth change of perceptual quality. The key advantages of the adaptive framework are: (1) perceptual quality is changed gracefully during periods of QoS fluctuations and handoffs, and (2) the resources are shared in a fair manner.

Abstract—Motivated by the emergence of programmable radios, we seek to understand a new class of communication system where pairs of transmitters and receivers can adapt their modulation/demodulation method in the presence of interference to achieve better performance. Using signal to interference ratio as a metric and a general signal space approach, we present a class of iterative distributed algorithms for synchronous systems which results in an ensemble of optimal waveforms for multiple users connected to a common receiver (or colocated independent receivers). That is, the waveform ensemble meets the Welch Bound with equality and, therefore, achieves minimum average interference over the ensemble of signature waveforms. We derive fixed points for a number of scenarios, provide examples, look briefly at ensemble stability under user addition and deletion as well as provide a simplistic comparison to synchronous code-division multiple-access. We close with suggestions for future work. Index Terms—Adaptive modulation, code-division multiple-access systems, codeword optimization, interference avoidance, multiuser

Next-generation wireless (NextG) involves the concept that the next generation of wireless communications will be a major move toward ubiquitous wireless communications systems and seamless high-quality wireless services. This article presents the concepts and technologies involved, including possible innovations in architectures, spectrum allocation, and utilization, in radio communications, networks, and services and applications. These include dynamic and adaptive systems and technologies that provide a new paradigm for spectrum assignment and management, smart resource management, dynamic and fast adaptive multilayer approaches, smart radio, and adaptive networking. Technologies involving adaptive and highly efficient modulation, coding, multiple access, media access, network organization, and networking that can provide ultraconnectivity at high data rates with effective QoS for Next Gare are also described.

The integration of multimedia services over wireless channels calls for provision of variable quality of service (QoS) requirements. While radio resource management algorithms (such as power control and call admission control) can provide certain levels of variability in QoS, an alternate approach is to use reconfigurable radio architectures to provide diverse QoS guarantees. In this paper, we outline a novel reconfigurable architecture for linear multiuser detection, there by providing a wide range of bit-error-rate requirements amongst the constituent receivers of the reconfigurable architecture. Specifically, we focus on achieving this dynamic reconfiguration via a software radio implementation of linear multiuser receivers. Using a unified framework for achieving this reconfiguration, we partition functionality into two core technologies (field programmable gate arrays (FPGA) and digital signal processor (DSP) devices) based on processing speed requirements. We present experimental...

Abstract — An achievable region, outer bounds and a capacity result are established for two-sender two-receiver interference channels with one cognitive transmitter. Specifically, we assume that one transmitter knows either the full or, more realistically, the partial message of the other transmitter due to its cognitive capabilities. The achievable region is obtained by a rate-splitting strategy, which generalizes prior strategies under both weak and strong interference conditions. The outer bounds are based on an extension of the Nair-El Gamal outer bound for the broadcast channel capacity. When only the partial message is known to the cognitive user, the capacity region in strong interference is established. In this regime, the interference is such that both receivers can decode both messages with no rate penalty. I. INTRODUCTION AND RELATED WORK Two-sender, two-receiver channel models allow for various

The paper introduces a higher-order synchronous data-flow language in which communication channels may themselves transport programs. This provides a mean to dynamically reconfigure data-flow processes. The language comes as a natural and strict extension of both Lustre and Lucid Synchrone. This extension is conservative, in the sense that a first-order restriction of the language can receive the same semantics. We illustrate the expressivity of the language with some examples, before giving the formal semantics of the underlying calculus. The language is equipped with a polymorphic type system allowing types to be automatically inferred and a clock calculus rejecting programs for which synchronous execution cannot be statically guaranteed. To our knowledge, this is the first higher-order synchronous data-flow language where stream functions are first class citizens. Categories and Subject Descriptors C.3 [Special-purpose and application-based systems]: Real-time and embedded systems; D.3.2 [Language classifications]: Data-flow languages; F.3.2 [Semantics of programming languages]: Operational semantics.

Motivated by the emergence of programmable radios, we seek to understand a new class of communication system where pairs of transmitters and receivers can adapt their modulation/demodulation method in the presence of interference to achieve better performance. Using signal to interference ratio as a metric and a general signal space approach, we present a class of iterative distributed algorithms for synchronous systems which results in an ensemble of optimal waveforms for multiple users connected to a common receiver (or co-located independent receivers). That is, the waveform ensemble meets the Welch Bound with equality and therefore achieves minimum average interference over the ensemble of signature waveforms. We describe fixed points for a number of scenarios. 1 Introduction Wireless system designers have always had to contend with interference from both natural sources and other users of the medium. Thus, the classical wireless communications design cycle has consisted of measu...

This dissertation presents the design, implementation and evaluation of a novel software radio architecture based on wideband digitization, a general purpose processor and application level software. The goal of a software radio is to create a communications system in which any aspect of the signal processing can be dynamically modified to adapt to changing environmental conditions, traffic constraints, user requirements and infrastructure limitations. The coupling of wideband digitization with application level software running on a general purpose processor allows for the modification of a greater range of functionality than any existing solution