PATH

A Token-Ring Medium-Access-Control Protocol with Quality of Service Guarantees for Wireless Ad-hoc Networks

Attias, Roberto
Lee, Duke
Puri, Anju
Tripakis, Starvros
Raja Sengupta
Varaiya, Pravin
2001

This report describes the design and implementation of a wireless token bus protocol for local area networks. This is the second wireless token passing protocol that has been jointly designed by the PATH program and the faculty and students of the EECS department at UC Berkeley.The first wireless token bus protocol, designed by Duke Lee and Professor Pravin Varaiya, was successfully implemented to provide the wireless network required by an automated vehicle platoon. The token passing mode of wireless medium access control was chosen to provide the delivery time guarantees required by the...

Geographical Routing Using Partial Information for Wireless Ad Hoc Networks

Jain, Rahul
Puri, Anuj
Raja Sengupta
2001

In this paper, we present an algorithm for routing in wireless ad hoc networks using information about geographical location of the nodes. We assume each node knows its geographical position and the position of the node to which it wants to send a packet. Initially, the nodes only know their neighbors but over time they discover other nodes in the network. The routing table at a node S is a list ((pi, Si)) where pi is a geographical position and Si is a neighbor of node 5’. When node S receives a packet for a node D at position pos(D), it finds the pi in its routing table which is closest...

Ad-Hoc Medium Access Control Protocol Design and Analysis for Vehicle Safety Communications

Raja Sengupta
Xu, Qing
Mak, Tony
Ko, Jeff
2004

This paper studies the design of ad-hoc Medium Access Control (MAC) protocols for a vehicle or the roadside to send safety messages to other vehicles. Such a protocol is needed by Advanced Vehicle Safety Systems (AVSS) and the national Dedicated Short Range Communications (DSRC) architecture. The problem is formulated to meet the communication requirements of vehicle safety applications and the DSRC multi-channel operation model. We propose several ah-hoc protocols, all based on the principles of repetition coding. Analytical bounds of the protocols' performance are derived. Simulations...

Cooperative Collision Warning: Enabling Crash Avoidance with Wireless Technology

Misener, James A.
Raja Sengupta
Krishnan, Hariharan
2005

In this paper we present an overview of the Cooperative Collision Warning (CCW) project conducted by the University of California Partners for Advanced Transit and Highways (PATH) program and General Motors Research and Development which examined and demonstrated wireless-enabled vehicle-to-vehicle cooperative safety systems for collision warning. We developed and demonstrated three Cooperative Collision Warning safety applications: a forward collision warning assistant, an intersection assistant, along with a blind-spot and lane change “situational awareness” assistant. The combination...

A Multi-channel VANET Providing Concurrent Safety and Commercial Services

Mak, Tony K.
Laberteaux, Kenneth P.
Raja Sengupta
2005

One of the key goals of a vehicular ad-hoc network (VANET) is providing sufficient quality of service (QoS) for real-time safety applications while concurrently supporting commercial services. This paper proposes a multi-channel wireless communication architecture and protocol for the scenario where commercial services are provided by roadside infrastructure. This solution extends the IEEE 802.11 wireless LAN protocol to schedule periodic safety messages in a "safety channel". It explicitly supports concurrent non-time-critical communications in separate, non-safety "service channels"....

Medium Access Control Protocol Design for Vehicle-Vehicle Safety Messages

Xu, Qing
Mak, Tony
Ko, Jeff
Raja Sengupta
2005

We propose a Medium Access Control (MAC) protocol design for a vehicle to send safety messages to other vehicles. We develop a QoS model for safety messages consistent with the active safety systems literature. Each message has a range and useful lifetime. The QoS target is to have each message be received with high probability within its specified lifetime by each vehicle within its specified range. The protocol design is based on rapidly re-broadcasting each message multiple times within its lifetime in combination with the 802.11 DCF. This makes the design compatible with the emerging...

Real-time Estimation of a Markov Process Over a Noisy Digital Communication Channel

Xu, Qing
Raja Sengupta
2005

We study the real-time estimation of a Markov process over a memoryless noisy digital communication channel. The goal of system design is to minimize the mean squared estimation error. We first show the optimal encoder and decoder can be memoryless in terms of the source symbols. We then prove the optimal encoder separates the real space with hyperplanes. In the case of the binary symmetric channel and scalar source, the optimal encoder can be a threshold. A recursive algorithm is given to jointly find a locally optimal encoder and decoder for the binary symmetric channel. For a memoryless...

Cooperative Collision Warning Systems: Concept Definition and Experimental Implementation

Raja Sengupta
Rezaei, Shahram
Shladover, Steven E.
Cody, Delphine
Dickey, Susan
Krishnan, Hariharan
2006

The concept of cooperative collision warning (CCW) systems is introduced and explained, followed by presentation of experimental results showing the performance of a first prototype CCW system. The CCW concept provides warnings or situation awareness displays to drivers based on information about the motions of neighboring vehicles obtained by wireless communications from those vehicles, without use of any ranging sensors. This has the advantages of a potentially inexpensive complement of onboard vehicle equipment (compared to ranging sensors that could provide 360 degree coverage), as...

Multi-Channel Medium Access Control for Dedicated Short Range Communications

Mak, Tony K.
Laberteaux, Kenneth P.
Raja Sengupta
Ergen, Mustafa
2006

This paper describes a medium access control (MAC) protocol to enable multi-channel operation for dedicated short range communication (DSRC). In particular, we focus on the challenge of supporting potentially high-bandwidth commercial or info-tainment communications between vehicle and roadside in hotspots over several service channels, while concurrently enabling time-critical vehicle-vehicle communication for safety in a separate channel. In our architecture, within hotspots, communication is aided by one of the access points in the hotspot. This access point is designated the...

Analysis of Channel Access Schemes for Model-based Estimation over Multi-access Networks

Huang, Ching-Ling
Raja Sengupta
2009

This report investigates the performance of model-based estima-tion over multi-access networks and emphasizes on the estimationMSE (mean squared error) while using different channel access schemes:probabilistic (random access), deterministic (round-robin scheduling),and combined (grouped channel access). We propose a mathematicalframework for estimation over a simple multi-access MAC protocol,the slotted ALOHA network. Estimation MSE, its asymptotic be-havior and stability condition are derived for different channel accessmethods. Our quantitative discussion can provide guidelines to...