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"University of California, Berkeley"


Latest Content From "University of California, Berkeley"

Whitepaper: Co-Operative Downloading in Vehicular Ad-Hoc Wireless Networks

by "University of California, Berkeley"Jan 01, 2008

This paper, proposes SPAWN, a cooperative strategy for content delivery and sharing in future vehicular networks. It studies the issues involved in using such a strategy from the standpoint of Vehicular Ad-Hoc networks. In particular, it shows that not only content server but also wireless access network load reduction is critical. It proposes a ""Communication efficient"" swarming protocol which uses a gossip mechanism that leverages the inherent broadcast nature of the wireless medium, and a piece-selection strategy that takes proximity into account in decisions to exchange pieces.


Whitepaper: Wireless Multi-Access for Personal Area Networks: The Always Best Connected PAN Service

by "University of California, Berkeley"Jan 01, 2008

Wireless networking for the vast public is currently undergoing a dramatic change in terms of services and applications offered to the end user. Higher data rates and multimedia based Internet services and applications will be available to a growing set of wireless end user devices. This is the case for both the Wireless Wide Area Networking (WWAN) technologies as well as for the Wireless Local Area Networking (WLAN) technologies. This paper presents a network architecture that composes one single (IP) network access service for the end customer based on multiple access network services, the Always Best Connected (ABC) service.


Whitepaper: Improving TCP Congestion Control Over Internets With Heterogeneous Transmission Media

by "University of California, Berkeley"Jan 01, 2008

This paper proposes TCP Santa Cruz, which is a new implementation of TCP implementable as a TCP option by utilizing the extra 40 bytes available in the options field of the TCP header. TCP Santa Cruz detects not only the initial stages of congestion, but also identifies the direction of congestion, it determines if congestion is developing in the forward path and then isolates the forward throughput from events such as congestion on the reverse path. The direction of congestion is determined by estimating the relative delay that one packet experiences with respect to another, this relative delay is the foundation of the congestion control algorithm.


Whitepaper: CDMA Channel Parameters Maximizing TCP Throughput

by "University of California, Berkeley"Jan 01, 2008

This paper considers a single TCP session traversing a wireless channel, with a constant Signal to Noise Ratio (SINR) at the receiver. The difficulty of determining the optimal transmission energy per bit is considered, to maximize TCP throughput. Particularly, in the case where direct sequence spread spectrum modulation is used over a fixed bandwidth channel, it was found that the optimal processing gain m that maximizes TCP throughput. Block codes applied to each packet for forward error correction can also be used, and in that case the joint optimization of the coding rate to maximize TCP throughput is considered.


Whitepaper: TCP-Based Video Streaming Using Receiver-Driven Bandwidth Sharing

by "University of California, Berkeley"Jan 01, 2008

This research paper focuses on the common case of streaming video to receivers whose last mile connections to the Internet are bandwidth-limited and act as network bottlenecks. Users generally run multiple concurrent networking applications that compete for the scarce bandwidth resource. Standard TCP shares bottleneck link capacity according to connection Round-Trip Time (RTT), and therefore may not provide streaming applications with the necessary bit-rate. In this research paper the BWSS is utilized to perform video streaming over TCP and establish the benefits of the proposed approach over standard TCP through Internet experiments involving a prototype for the Linux operating system.


Whitepaper: Experimental Evaluation of Application Performance With 802.11 PHY Rate Adaptation Mechanisms in Diverse Environments

by "University of California, Berkeley"Jan 01, 2008

Wireless LAN (WLAN) technology based on IEEE 802.11 standard is being commonly used in offices and hotspots for indoor wireless Internet access. The success of 802.11 technology has led to newer usage scenarios, including community mesh networks and multimedia distribution/data networking in the home. The application performance with different rate adaptation mechanisms is dependent on the specific tradeoffs these mechanisms make at the link layer in an application-oblivious manner between improving throughput and limiting frame loss. This research paper focuses on PHYsical layer (PHY) data rate adaptation mechanisms that are usually implemented in the MAC layer.


Whitepaper: The Timing Of Broadband Provision: The Role Of Competition And Demographics

by "University of California, Berkeley"Jan 01, 2008

This research paper examines the supply of DSL (Digital Subscriber Line) broadband by the incumbent Local Exchange Company (LEC) in five Midwestern states in the earlier years of deployment in the U.S. Income, other demographics, and cost factors are important determinants of entry and availability. Active competition in broadband from competitive LECs reduces the possibility the incumbent deploys DSL, but potential competition from competitive LECs increases the likelihood of incumbent deployment.


Whitepaper: Path Selection for Multi-Path Streaming in Wireless Ad Hoc Networks

by "University of California, Berkeley"Jan 01, 2008

There are many challenges for supporting video communication over wireless ad hoc networks. This paper proposes a novel multi-path selection framework for streaming over wireless ad hoc networks. The approach is to approximately estimate the concurrent packet drop probability of two paths by taking into account the interference between different links, and to select the best path pair based on that estimation. The paper proves the optimal path selection problem to be NP-hard, and propose a heuristic solution, whose performance is shown to be close to that of the optimal solution, while significantly outperforming other heuristic protocols.


Whitepaper: Constant Envelope OFDM With Channel Coding

by "University of California, Berkeley"Jan 01, 2008

The major disadvantage of Orthogonal Frequency Division Multiplexing is the large peak to average power ratio. This research paper briefs a new constant envelope OFDM waveform. This is an application of convolutional coding to Constant Envelope Orthogonal Frequency Division Multiplexing. It studies the noise at the output of the phase demodulator is shown to be approximately Gaussian at high SNR and relatively low modulation indices. This allows the use of the conventional metric in the Viterbi decoding algorithm. A bound on the performance of convolutionally coded CE-OFDM is derived and is plotted along side the performance curves obtained through simulation.


Whitepaper: A Phase Noise Compensation Scheme for OFDM Wireless Systems

by "University of California, Berkeley"Jan 01, 2008

This research paper discusses the phase noise which causes significant degradation in the performance of Orthogonal Frequency Division Multiplexing (OFDM) based wireless communication systems. In the proposed compensation scheme, the communication between the transmitter and receiver blocks consists of two stages. In the first stage, block-type pilot symbols are transmitted and the channel coefficients are jointly estimated with the phase noise in the time domain. In the second stage, comb-type OFDM symbols are transmitted such that the receiver can jointly estimate the data symbols and the phase noise.