Past projects


 


 

Unwanted Link Layer Traffic in Large IEEE 802.11 Wireless Networks

The monitoring of wireless networks continues to reveal key implementation deficiencies in congested environments that need to be corrected in order to improve protocol operation and end-to-end network performance. In wireless networks, where the medium is shared, unwanted traffic can pose significant overhead and lead to suboptimal network performance. Much of the previous analyses of unwanted traffic in wireless networks have focused on malicious traffic. However, another major contributor of unwanted traffic is incorrect link layer behavior. We are in the process of analyzing data we collected from the 67th Internet Engineering Task Force (IETF) meeting held in November 2006. Preliminary analysis has revealed that a significant portion of link layer traffic stems from mechanisms that initiate, maintain and change client-AP associations. Further, under conditions of high medium utilization and packet loss rate, handoffs are initiated incorrectly and can be counter-productive to the client's performance.

Students

Ramya Raghavendra
 

Faculty

Elizabeth BeldingKevin Almeroth
 

Collaborators

Konstantina Papagiannaki(Intel Research-Pittsburgh)

 


 

Understanding and Modeling WLAN Workload

This project entails ongoing research in understanding and being able to reproduce realistic workloads in wireless local area networks (WLANs). The research is foundational in the sense that it does not directly improve network performance, but rather informs how to conduct better research in wireless networks. In all experimental research in such networks, some workload is ultimately needed to test the effectiveness of new techniques. Unfortunately, performance predictions from experiments with synthetic workload may not accurately reflect performance once technologies are deployed and experience real usage conditions. Some of our research has shown that an unrealistic traffic model can distort important metrics (e.g. end-to-end delay, received throughput, jitter, network or link layer overhead) by as much as a factor of ten, on average. Everyone "knows" that constant bit-rate (CBR) traffic between randomly chosen nodes does not really resemble real-world usage patterns. However, the impact of this lack of realism has not previously been quantified. It turns out to have a more dramatic impact than expected.

Our current research follows two parallel prongs of attack: 1) evaluating existing and proposed workload and traffic models by differential performance analysis, realistic models should reproduce accurate performance results when compared with original trace behavior; 2) using advanced data-mining and statistical methodologies to better understand and reproduce realistic full-network collections of flow behaviors based on real WLAN traces.

Students

Stefan Karpinski
 

Faculty

Elizabeth BeldingKevin Almeroth
 

Collaborators

Sreenivasa Rao Jammalamadaka

 


 

UCSB MeshNet

The UCSB MeshNet is an experimental multi-radio 802.11 a/b/g wireless mesh network deployed on 4 floors of the Harold Frank Hall of UCSB. The network consists of 15 nodes used to deploy and evaluate wireless network systems, conduct research in scalable routing protocols, efficient network management, multimedia streaming, and QoS for multi-hop wireless networks.

Students

David JohnsonVeljko PejovicRamya RaghavendraAshish Sharma
 

Past Students

Amit JardoshIrfan SheriffPrashanth AcharyaKrishna RamachandranHenrik Lundgren
 

Faculty

Elizabeth BeldingKevin Almeroth
 

Project Homepage

http://moment.cs.ucsb.edu/meshnet

 

 


 

ParaNets

ParaNets introduce a new enhanced architecture of challenged networks that is based on the assumption that other networks with different characteristics exist in parallel. In previous research, the main trend in providing routing functions or transport services has been mainly through finding various techniques over the challenged network itself. Our project, exploits the availability of parallel networks to better serve challenged networks. We present a generalized architecture that formulates our vision and opens new areas of research in the direction of ParaNets. The main goal behind our evaluation in this project is to study the impact of the availability of parallel networks on the services and basic functionalities that can be provided to challenged networks.

People

Mike P. WittieKhaled A. Harras
 

Faculty

Kevin AlmerothElizabeth Belding
 

 


 

Energy Efficient White-Space Networking for Rural Areas

White space frequencies are highly attractive for long-distance communication due to greater signal propagation. The lack of standards and licensing issues with increased flexibility provided by the cognitive radio allow for sophisticated customized solutions for white spaces. Rural-area networks are seen as the main beneficiaries and white spaces communication is expected to outperform current wireless solutions in this domain. However, rural networks often have to rely on a constrained energy budget and highly benefit from energy-efficient operation.

We are developing two protocols that enable energy efficient communication in two different use cases. WhiteRate is a protocol that adapts the channel width and the the modulation and coding scheme to maximize energy savings in a network that is used primarily for real-time (voice and video) traffic. The protocol lowers the transmission time, thus the energy consumption, while exploiting the robustness of encoded voice and video to bit errors.PowerRate is a protocol that dynamically adjusts transmission parameters (transmission amplitude, modulation and coding and channel width) according to the channel state and the theoretically optimal settings. PowerRate either transmits with the optimal PHY settings or defers tfrom the transmission if the channel state is considered too poor. WhiteRate and PowerRate are complementary in the sense that the former provides maximal energy savings when the application is highly tolerant to transmission errors, such as encoded voice and video, while the later is targeted towards application that are tolerant to higher delays, such as non-interactive large file downloads. We are currently in the process of implementing both protocol in GNUradio.

People

Veljko Pejovic,

Faculty

Elizabeth Belding

Project Homepage

Energy efficient rural-area communication: WhiteRate and PowerRate

 


 

A White-Space Outdoor Laboratory

White space networks provide the ideal solution for long distance links in rural areas. These offer the ideal complement to 802.11 networks that are being used in current rural networks for longer range non-line-of-sight links. The purpose of this project will be to build a cognitive radio outdoor test bed to understand what can be achieved with outdoor long-range white spaces links. This system will be completely remotely programmable and permit reconfiguration at all layers of the protocol stack and hence allows for a highly dynamic network architecture. After the initial indoor tests, the links will be deployed in rural Zambia and South Africa.

People

David JohnsonVeljko Pejovic

Faculty

Elizabeth Belding

 
 


 

Airlab

AirLab is a publicly accessible distributed measurement system, designed to facilitate experimental research in the field of wireless networking. It consists of a number of measurement nodes, distributed in various locations across the world that are controlled by a central server located at UCSB. Each AirLab node is equipped with the same hardware and software stack and collects a consistent set of metrics. Data collected in this manner across a variety of heterogeneous network types, such as university, corporate, and residential, will allow cross-comparison of observed network phenomena within each of these settings.

People

Mariya ZhelevaMike Wittie, Jesper Pedersen

Faculty

Elizabeth BeldingKevin Almeroth

Project Homepage

airlab.cs.ucsb.edu


 

CellLab

The growing use of smart-phones have outlined rapid development of cellular networks. The focus, though, is more on provisioning infrastructure to meet the increasing traffic demand, while not too much is being done to audit what is currently available, pinpoint shortcomings and propose potential approaches to improving systems' performance and user experience. 

To enable these, we need a way to collect data that would help exploring and characterizing various aspects of mobile communications including usability trends, coverage availability and networks and applications performance. The collected data must provide information for variety of locations and should enable capturing the dynamics of changing Wi-Fi and cellular networks. 

To address these issues, we develop CellLab - a cellular phone monitoring system, that users can download onto their device to collect trace data on WiFi and cellular network connections. Our system will regularly capture a baseline metric set to facilitate analysis of general network performance while being minimally disruptive (or completely undisruptive) to the user. With the data sets, which will be offloaded to and stored on a central server, we will study network and application performance to pinpoint critical opportunities for cellular software, hardware, and network improvement.

People

Mariya ZhelevaManasa Chandrashekar

Faculty

Elizabeth BeldingKevin Almeroth

 


Past Projects

 

FreeMAC: Reconfigurable MAC development framework

FreeMAC is a reconfigurable radio platform that provides a framework for the development of single and multi channel MAC protocols using commodity 802.11 cards.The framework has been used to implement a TDMA based MAC protocol on Atheros chipset based WiFi cards. The FreeMAC framework provides fine control over several radio communication parameters and facilitates the design of cross layer networking protocols.

Students

Ashish Sharma

Faculty

Elizabeth Belding
 

Project Homepage

http://moment.cs.ucsb.edu/freemac
 


 

Green Mesh: Technology for Rural Mesh Networks

Wireless Mesh Networks have emerged as a promising technology to provide ubiquitous broadband Internet access in urban areas. Several city wide mesh networks have already been deployed and many more are in the process of being deployed. Wireless mesh networks are inexpensive to build, easy to deploy, and can operate reliably in harsh environments, and for these reasons mesh networks are also gaining focus as the technology of choice for local communication and Internet access in rural areas, especially in developing countries. One of the major challenges in sustaining these low-cost rural wireless mesh networks is to make these networks energy efficient. This requires analysis of existing network and MAC layer protocols from an energy efficiency point of view. We aim to build a complete framework that leverages better cross layer interaction between different layers of the protocol stack to achieve energy efficiency.

People

Ashish Sharma,

Faculty

Elizabeth BeldingKevin Almeroth

 


 

Millimeter Wave WPAN: Cross-Layer Modeling and Multihop Architecture

The 60 GHz band has been allocated worldwide for short range wireless communications because high atmospheric path loss due to oxygen absorption renders it unsuitable for long distance communications. This abundant unlicensed spectrum in the 60 GHz band offers the potential for multiGigabit indoor wireless personal area networking (WPAN). With recent advances in the speed of silicon (CMOS and SiGe) processes, low-cost transceiver realizations in this millimeter (mm) wave band are within reach. However, mm wave communication links are more fragile than those at lower frequencies (e.g., 2.4 or 5 GHz) because of larger propagation losses and reduced diffraction around obstacles. On the other hand, directional antennas that provide directivity gains and reduction in delay spread are far easier to implement at mm-scale wavelengths. We are working on cross-layer modeling methodology and a multihop medium access control (MAC) architecture for efficient utilization of the 60 GHz spectrum, taking into account the preceding physical characteristics. Our in-room WPAN architecture constrains every link to be directional for improved power efficiency (due to directivity gains) and simplicity of implementation (due to reduced delay spread). We have developed an elementary diffraction-based model to determine network link connectivity, and have defined a multihop MAC protocol that accounts for directional transmission/reception, procedures for topology discovery and recovery from link blockages.

People

Sumit Singh, Federico Ziliotto
 

Faculty

Upamanyu MadhowElizabeth BeldingMark Rodwell
 

Project Homepage

Millimeter Wave Communication Systems Research @ UCSB

 


 

A Resource Biasing Framework for Shaping Throughput Profiles in Multihop Wireless Networks

Throughput performance of multihop wireless networks is governed by how the network transport capacity is partitioned among different competing network flows. Max-min fair allocation leads to poor throughput performance for all flows because connections traversing a large number of hops consume a disproportionate share of resources. While proportional fair allocation provides a significant improvement, in this research, we show that there is a much richer space of resource allocation strategies for introducing a controlled bias against resource-intensive long connections in order to significantly improve the performance of shorter connections. Our simple analytical model offers insight into the impact of a particular resource allocation strategy on network performance while also capturing the effect of finite network size and spatial traffic patterns. Our simulation results demonstrate that ''mixed'' bias strategies that blend fair allocations with a strong bias against long connections can provide significantly better performance to shorter connections than max-min fair or proportional fair resource allocations, with minimal impact on the performance of long connections.

People

Sumit Singh,

Faculty

Upamanyu MadhowElizabeth Belding

 


 

SCUBA: Focus and Context for Mesh Network Health Diagnostics

SCUBA is an interactive focus and context visualization framework for metro-mesh health diagnosis. SCUBA places performance metrics into multiple tiers or contexts, and displays only the topmost context by default to reduce screen clutter and to provide a broad contextual overview of network performance. A network operator can interactively focus on problem regions and zoom to progressively reveal more detailed contexts only in the focal region.

Students

Amit JardoshPannuakdet Suwannatat

Faculty

Tobias HollererElizabeth BeldingKevin Almeroth
 

Project Homepage

http://moment.cs.ucsb.edu/conan/scuba
 


 

IQU: Practical Queue-based User Association Management for WLANs

We propose IQU, a practical queue-based user association management system for heavily loaded WLANs. IQU grants users fair opportunities to access the WLAN while maintaining high overall throughput, even when the WLAN is heavily loaded. The basic premise of IQU is to control user associations with the WLAN through request queues and work period allocations. We implement a prototype of IQU and evaluate it on a wireless testbed. Our evaluation demonstrates that IQU significantly improves network throughput under heavy load; the tradeoff is that users have to wait for network access. We explore the impact of IQU parameters on system performance, and validate the robustness of IQU under heavy load conditions. Through IQU, WLANs can be utilized efficiently and network collapse prevented

Students

Amit JardoshKrishna RamachandranKimaya Mittal
 

Faculty

Elizabeth BeldingKevin Almeroth
 

Project Homepage

http://moment.cs.ucsb.edu/conan
 


 

Congestion Measurement and Rate Adaptation in 802.11 Wireless Networks

Congestion in a wireless network can have adverse effects on the performance of the network such as reduced throughput. In particular, rate adaption algorithms do not react well to congestion. In this work, we develop tools to measure congestion levels of wireless networks in real-time. The congestion metric, as measured by these tools, is then used to develop a new congestion-aware rate adaptation algorithm.

Students

Prashanth Aravinda KumarAshish Sharma
 

Faculty

Elizabeth BeldingKevin Almeroth
 

Collaborators

Konstantina Papagiannaki(Intel Research-Pittsburgh)

 


 

Resource Estimation on Wireless Backhaul Networks

The increased usage of IEEE 802.11 wireless backhaul networks and the growing popularity of real time applications, such as VoIP, presents a challenging resource management problem due to the limited capacity of wireless networks. At high traffic volumes, measurements have shown that packet collisions and interference in 802.11 networks can lead to degraded performance to the extent that users experience unacceptably low throughput, which can ultimately lead to complete network breakdown. A resource management framework that limits network flows can prevent network breakdown and improve the performance of throughput and delay-sensitive multimedia applications. To address this problem, we present a measurement-driven framework that leverages wireless characteristics for intelligent admission control in a static wireless network. Experiments on a 25 node wireless testbed show that the proposed scheme can enhance network performance such that the QoS requirements of real time applications, such as VoIP, can be met.

Students

Irfan SheriffPrashanth Acharya
 

Faculty

Elizabeth Belding

 


 

Multi-radio Wireless Mesh Architecture

Wireless mesh routers equipped with multiple radios can alleviate capacity problems in 802.11 wireless networks. However, a practical, complete system architecture that can realize the benefits of multiple radios does not exist. The focus of this work is to offer such an architecture. Our architecture provides solutions to challenges in three key areas. The first is the construction of a wireless router that alleviates the interference that can occur between commodity radios within a single piece of hardware. The second is the design of a topology controller responsible for collecting information about internal and surrounding interference; executing a channel selection algorithm; and disseminating channel assignments to mesh routers. And the third is the design and implementation of several communication protocols, protocols that are necessary to make our architecture operational. The system that we then implement is deployed, tested, and finally, evaluated on a 20-node multi-radio 802.11a/b wireless testbed. Our evaluation focused on multiple aspects of our architecture, such as its ability to adapt to varying external interference levels; the performance gains offered in the presence of different traffic patterns; and the impact of changes in wireless link characteristics on system operation.

Students

Krishna RamachandranIrfan Sheriff
 

Faculty

Elizabeth BeldingKevin Almeroth

 


 

MARCONI

The objective of the Control-Based Mobile Ad-Hoc Networking (CBMANET) program is to research, design, develop and evaluate a revolutionary Mobile Ad-hoc NETwork (MANET) prototype that improves effective performance from network stakeholder (user and operator) perspectives by an order of magnitude or more relative to the state of the art. In particular, proposals are sought to develop software implementing a revolutionary CBMANET network stack and services. This software will be subject to independent test and evaluation by a government team, using a rigorous comparison against a baseline MANET representative of the state of the art. In Phase 1, performers must deliver high-fidelity models of that software for evaluation using government-specified scenarios and applications. In Phase 2, performers must deliver an integrated software/hardware solution for field demonstrations and evaluation. Specifically, the integrated solution will consist of the performer software, a compu ting platform of the performer's choice, a specified GFE physical layer (PHY), and a suitably equipped GFE field vehicle. (from http://www.darpa.mil/sto/solicitations/CBMANET/)

People

Mike P. Wittie
 

Faculty

Kevin AlmerothElizabeth Belding
 

 


 

Sticky CSMA/CA

We consider the problem of efficiently supporting a mix of real-time and delay-insensitive traffic over wireless mesh networks, assuming a narrowband physical layer with CSMA/CA capabilities. Classical CSMA/CA, as in IEEE 802.11, does not provide the delay guarantees required for real-time traffic. We introduce Sticky CSMA/CA, a MAC scheme that provides TDM-like performance without requiring explicit synchronization. We exploit the natural or artificially imposed periodicity of real-time flows to obtain implicit synchronization for efficient channel use and QoS guarantees. Nodes monitor the medium using the standard CSMA/CA and record the recent history of medium activity. A new real-time flow uses this information to grab the medium at the first available opportunity, and then sticks to a periodic schedule, providing delay and bandwidth guarantees. Delay-insensitive traffic fills the gaps left by the real-time flows. Large gains over standard CSMA/CA are demonstrated for a voice/data network.

People

Sumit SinghPrashanth Acharya
 

Faculty

Elizabeth BeldingUpamanyu Madhow

 


 

Obstacle Mobility Models

In this project, we propose to create realistic movement models through the incorporation of obstacles. These obstacles are utilized to both restrict node movement as well as wireless transmissions. In addition to the inclusion of obstacles, we construct movement paths using the Voronoi diagram of obstacle vertices. Nodes can then be randomly distributed across the paths, and can use shortest path route computations to destinations at randomly chosen obstacles. Simulation results show that the use of obstacles and pathways has a significant impact on the performance of ad hoc network protocols.

People

Amit Jardosh
 

Faculty

Elizabeth BeldingKevin AlmerothSubhash Suri
 

Project Homepage

http://moment.cs.ucsb.edu/mobility

 


 

Enhanced QoS for MANET using the MAC Layer

Current solutions for quality of service fail to address the unique characteristics of wireless communication and the highly dynamic topology in MANET. We believe the MAC layer is key to achieving QoS in MANET. By using MAC layer information (especially carrier sensing) and using a preagreed transmission protocol we propose multiple enhancements to increase the QoS for real-time traffic.

People

Ian ChakeresKimaya Sanzgiri
 

Faculty

Elizabeth Belding
 


 

Model-based Resource Prediction for Multi-hop Wireless Networks

This work presents a model-based resource prediction mechanism to support real-time communication in multi-hop wireless networks. Specifically, we develop an analytical model for differentiated MAC scheduling protocols, thereby enabling admission control of the flows and providing an efficient network management utility.

People

Yuan Sun
 

Faculty

Elizabeth Belding
 


 

Realistic Multimedia Evaluation

Looking at quantitative measurements alone is inadequate to judge multimedia quality. This is because quality varies significantly over time, quality degradation is not linear, and quality depends on the encoding scheme. Realistic multimedia evaluation is a necessity to see and hear actual audio and video, and qualitatively compare different protocols impact.

People

Yuan SunIan Chakeres
 

Faculty

Elizabeth Belding
 


 

Leveraging Mobility to Improve QoS in Wireless Network

Users in wireless networks are typically mobile and their connectivity is dependent on their location and the locations of other users. By changing their location, users can alter their connectivity characteristics and potentially obtain better service from the network. We explore how this idea can be applied to both infrastructured and ad hoc wireless networks.

People

Kimaya Sanzgiri
 

Faculty

Elizabeth BeldingSubhash Suri
 


 

Monitoring Tools for Mobile Networks

DAMON is a distributed system for monitoring mobile networks. DAMON uses agents within the network to monitor network behavior and send collected measurements to data repositories. DAMON's generic architecture supports the monitoring of a wide range of protocol, device, or network parameters. Other key features of DAMON include seamless support for multiple repositories, auto-discovery of sinks by the agents, and resiliency of agents to repository failures.

People

Krishna Ramachandran
 

Faculty

Elizabeth BeldingKevin Almeroth