Babak Daneshrad - US grants

WHYNET: Scalable Testbed for Next Generation Mobile Wireless Networking Technologies
The next generation of wireless communication technology is likely to rely on cross-layer interactions
that extend from the application layer down to the physical devices. This project proposes to design and
develop WHYNET, a Wireless HYbrid NETwork testbed to facilitate detailed study of such interactions and
their impact on application level performance in heterogeneous wireless systems. The eventual technical
impact of this testbed will be to redefine how specific innovations in wireless communication technologies are
evaluated in terms of their potential to improve application-level performance as well as how alternative
approaches are compared with each other. Its broader impact will be to redefine how students are trained in
wireless technologies by providing a multi-disciplinary 'hands on' environment to complement purely
theoretical classroom training.

WHYNET is envisaged as a hybrid testbed that combines the realism of physical testing with the
scalability and flexibility of simulations. The hybrid testbed will be a networked federation of geographically
distributed, heterogeneous wireless physical testbeds with multiple protocol stacks (CDMA 2000 cellular and IP), next generation physical technologies including UWB (Ultra Wide Band), MIMO (Multiple Inputs,
Multiple Outputs) and SDR (Software Defined Radios), and a parallel & distributed multi-tool simulation
framework. Beyond providing a more accurate & flexible evaluation framework, the hybrid testbed will
facilitate a smooth transition from an abstract simulation model to an operational implementation within a
single framework. For instance, protocol prototypes can communicate with simulated lower layers for
repeatable results, or receive and process variable rate real multimedia application inputs for perceptual
evaluation. Once the physical hardware devices are ready for testing, a portion of the target network system
can be configured with real devices while the rest of the network can still reside in the simulated hardware
domain. The effort will also generate a repository of wireless networking scenarios, measurements, models
and implementations. A representative set of studies will be used to demonstrate the unique contributions of
WHYNET for cross-layer optimization studies in particular, and mobile wireless networking in general. These include sensor networks, energy-aware networking, protocols & middleware for multi-access networking, and adaptive transport and security protocols. The testbed itself will be accessible by the research community via a web-based mechanism that will allow remote uploading of models, implementations, and configurations.

The proposed research is likely to have a broader impact on two fronts: the training of future generation
of wireless engineers and wireless technology standards. Wireless engineers will need significant technical
depth to contribute to a rapidly developing technology and significant technical breadth to understand how this
technology fits into a market driven economy. The latter category requires engineers who are trained in
insystemslt aspects with an in-depth understanding of trade-offs and interactions across layers of a wireless
communication system. The current course structure is not designed to produce well-trained engineers of the
second type. The project team feels strongly that broad systems training can only be accomplished in i.hands-
onlo experimental courses or projects where the students see the tradeoffs involved in real system design. The proposed testbed can enable these types of courses across the curriculum. Even though today wireless is a
vertical technology, 4-5 years from now, the most interesting and challenging problems will be those related to wireless systems, so we believe that an inter-disciplinary yet closely-knit engineering program such as ours is well suited for the training of wireless engineer of tomorrow. By providing a scalable platform, methodology, and tools to support objective and accurate evaluation of protocol and technology alternatives, we expect that the testbed will also play an important role in shaping standards activity in IETF and related bodies.

A multi-disciplinary, multi-institution team has been formed to achieve the ambitious objectives of the
WHYNET project. The team members have substantial expertise in design and management of physical and
simulation testbeds (Bagrodia, Gerla, Rao, Takai), development of novel radio technology (Daneshrad, Fitz,
Mitra), wireless systems (Mitra, Rao, Srivastava), protocol design (Gerla, Krishnamurthy, Mohapatra, Royer, Shen, Srivastava, Tripathi) and performance evaluation (Bagrodia, Gerla, Molle, Rao, Tripathi). Many of thePIs have successfully worked together on previous collaborative projects. We have also received strong support from a number of companies that play a critical role in this space including Microsoft, Hughes
Research Laboratories (now part of Boeing), ST Electronics, HP, Ericsson, Intel, and Xtreme Spectrum.

This effort brings together experimental PHY researchers from UCLA, networking research from UCI, and engineering expertise from Umachines to develop a highly flexible radio platform for the networking community. The availability of such a platform will spawn innovative and groundbreaking networking research for years to come.
The main thrusts of this proposal are two fold: (1) Specification, design, and development of a versatile radio platform with a fully defined API and a user friendly GUI. Two classes of radio nodes will be developed. The first is an inexpensive platform built entirely on DSP processors. This platform can handle bandwidths of a few MHz and can accommodate one or two antennas. The second node leverages FPGA technology and will provide real time operation in 25 MHz of bandwidth and can support up to 4 antenna elements. (2) Networking research carried out by UCI culminating in the implementation of the resulting algorithms on the developed nodes. The work will investigate MAC enhancements for both SISO and MIMO enabled nodes such that the physical layer parameters are controlled through the MAC layer for higher overall performance (cross-layer design). In addition to providing research results of great interest to the community, this work will push the nodes to their limits of flexibility and drives the definition and implementation of the MAC/PHY interface.

0401310
Hua

This project investigates a novel concept of wireless communications, which is based on cooperative nature of multiple wireless mobile nodes within the framework of mobile ad hoc networks. But unlike the previously explored approaches that are mostly medium access control (MAC) protocols, this project aims at improving the capacity of the most fundamental physical link via multiple distributed wireless relays. These relays that are clustered and located anywhere between a source and a destination do not perform the conventional store-and-forward operations, but rather they are programmed to perform space-time modulation on their received baseband signals that are corrupted by both fading and noise. These relays do not need to exchange symbols with each other, and no feedback of channel state information is necessary. Hence, the burden on the MAC layer is reduced, and the ability to adapt to fast time-varying environment is improved. Such an array of relays performs like an array of wireless antennas, and reduces the negative effect of small scale fading on the signals received at the destination. With the space diversity achieved by the relays, the effective channel between the source and the destination becomes virtually free of small scale fading, which resembles wireline communications. The relays to be developed in this project are a function rather than a rigid device, and this function can be embedded in all mobile nodes, and more importantly can be embedded under the MAC based cooperative schemes. This project goes beyond the traditional mode of research, and the PIs of complementary strength have laid out a vertically integrated research plan to rapidly further develop the concept of distributed wireless relays, which is already proven to be promising based on a preliminary study.

Broader Impact:

Wireless communication technology will continue to evolve to meet the needs of future generations of mankind. One of the desired features of wireless communications is a fully mobile wireless network where neither base-station nor pre-existing infrastructure is required. Such a communication network is desired by people working and moving in remote areas and by the general public in the events of catastrophe. Distributed wireless relays may also be a useful solution to enhance the capacity of the cellular mobile systems, and the quality of future wireless communications may become seamless from that of wireline communications. A preliminary study by the PI shows that with distributed wireless relays, the total power consumption can be reduced by more than 10 dB from the baseline of the traditional single relay system. When fully proven and implemented, this power saving may imply that all batteries used in mobile nodes in a dense mobile network could last more than ten times longer. This project is not only likely to lead to technological breakthrough, but also will help the training of graduate students and undergraduate students (especially minority students) from two campuses of the University of California, who may become the first entrepreneurs to benefit the society by using distributed wireless relays in wireless communications.

This project is supporting the NSF Wireless Networking PI meeting in December 2005. The meeting will be rich in new, exciting results in several areas of the wireless networks field. Important contributions are expected from the projects related to spectrum sharing, agile radio usage, and efficiency. In the past few years the wireless industry has become acutely aware of the spectrum limitations that have bounded communication system to a specific frequency band with a pre-selected modulation scheme. Progress in emerging technologies like Software Definable Radios (SDRs) and Cognitive Radios (CRs) will be reported by the PIs. Other significant breakthroughs will be likely announced in mesh and ad hoc architectures, cooperative wireless networking, and other areas.

This research characterizes the benefits of feedback in communication and develops techniques to achieve those benefits. Today's communication systems seek to move information as rapidly as possible from transmitter to receiver. This research involves using feedback (messages sent from the receiver back to the transmitter) to allow communication systems to approach the highest possible communication rate (the channel capacity) using less transmission time (latency) and lower-complexity decoding. A key aspect of this research is the development of new error control codes and new techniques to use those codes to facilitate transmissions that approach capacity with much lower latency than systems that do not use feedback. Broader impacts include training high school students through the UCLA Engineering (HSSEAS) High School Summer Research program and training undergraduates through the UCLA Engineering undergraduate research program.

Traditional techniques approach capacity without feedback by using long block lengths and complex decoding. However, information theory indicates that feedback permits capacity to be approached with shorter block lengths and simpler decoding. This research employs a rate-compatible sphere-packing analysis to provide a quantitative analysis of the latency reduction possible with feedback. This analysis provides decoding error trajectories that guide the development of rate-compatible code families needed to approach capacity with feedback. Practical benefits of these rate-compatible code families with feedback will be characterized in the context of a typical wireless communication system operating in additive white Gaussian noise. These techniques are extended to fading channels and higher-order modulations. The overall goal of this research project is the development and promulgation of a fundamental understanding of how code families should be designed to work with feedback to achieve capacity with very short block lengths.

THIS IS AN EXCELLENT PROPOSAL WHICH WILL MAKE SIGNIFICANT CONTRIBUTIONS TO WIRELESS COMMUNICATION RECEIVERS AND WILL ALLOW ENHANCED ACCESS TO THE RADIO SPECTRUM. THIS IS BECOMING VERY CRITICAL SINCE SPECTRUM ACCESS IS BECOMING A MAJOR SOCIETAL ISSUE. THIS RESEARCH, IF SUCCESSFUL, WILL ALLEVIATE SOME OF THESE PROBLEMS AND WILL RESULT IN MAJOR SOCIETAL BENEFITS. IT ALSO CONTAINS A COMPREHENSIVE PLAN FOR OUTREACH ACTIVITIES AND INTEGRATION OF RESEARCH AND EDUCATION.


BROADER IMPACTS
The broader impacts of the project are at least two fold. First, the research activity brings a breakthrough in the design of reconfigurable integrated filters that is crucial to the re-search on software-defined and cognitive radios and the growth of communication systems in particular and the electronics industry in general. In particular, enabling cognitive radios can po-tentially support the increasing demand for more private and public connectivity in the near fu-ture. Second, the results and discoveries of the research activities will be useful in developing academic material and training future circuits and systems designers in the importance of multi-disciplinary thinking for solving current and future communication systems problems.


INTELLECTUAL MERIT
The objective of the proposed research is to develop sharp, programmable integrated fil-ters that will enable a wide range of applications including software defined and cognitive radios. Such filters will reduce the bandwidth and the dynamic range of the received communication signals rendering them amenable to digitization and subsequent receiver processing. The proposed approach is to employ simple but periodically time-varying circuit components to significantly enhance effective filtering at sampling instances prior to digitization. The intellectual merit of the research is that the use of periodically time-varying components is a much more efficient and fundamentally different approach to circuit design. Today, most filters are of the time-invariant variety and particularly in the wireless receiver, they need high quality acoustic filter components that are bulky, expensive, difficult to integrate and most importantly, not programmable. The proposed approach will obviate the need for such inflexible components. Specific goals of the proposed research are validation using a prototype integrated circuit and the development of necessary theoretical methods to analyze time-varying circuits. It is expected that the latter will also enable wider acceptance of periodically time varying circuits beyond filter design applications.