TECH DIGITAL RESOURCE LIBRARY

Georgia Institute of Technology


Latest Content From Georgia Institute of Technology

Whitepaper: MIMO-OFDM Channel Estimation Based on Subspace Tracking

by Georgia Institute of TechnologyJan 01, 2008

MIMO-OFDM is an attractive technique for high data rate transmission and channel estimation for MIMO-OFDM systems is essential for coherent detection. This research paper proposes a subspace-based channel estimation algorithm for MIMO-OFDM systems. By tracking the slow varying subspace spanned by the frequency responses of different multipaths, the optimum basis for LS channel estimation is obtained. The proposed algorithm considerably reduces the leakage of low-rank channel estimation, which is dominant at high SNR’s and the corresponding performance improvement is shown by simulation.


Whitepaper: Adaptive Subcarrier and Power Allocation in OFDM Based on Maximizing Utility

by Georgia Institute of TechnologyJan 01, 2008

This paper explores adaptive resource allocation on the downlink of multi user OFDM networks to achieve both multi user diversity and fairness. Utility functions are applied to quantify the level of users satisfaction derived from the radio resources they occupy. Cross layer optimization problem is formulated as one that maximizes the sum of the utilities over all active users subject to the feasible rate region, which is determined by adaptive resource allocation schemes deployed and the current channel conditions. The conditions for optimal sub carrier assignment and power allocation based on utility is presented and investigates the optimality properties.


Whitepaper: Bandwidth and Power Efficiency Considerations for Optimal Training in OFDM

by Georgia Institute of TechnologyJan 01, 2008

Orthogonal Frequency Division Multiplexing (OFDM) has been adopted by many high speed transmission standards. Pilot tone assisted modulation (PTAM) is a well known technique to estimate the channel state information (CSI) in OFDM but is not bandwidth efficient. To achieve high bandwidth efficiency, it is proposed to carry out superimposed training with techniques described in this research paper to improve the quality of the CSI estimate. To improve the power efficiency, a blind Selected Mapping (SLM) PAR reduction method in conjunction with superimposed training is employed.


Whitepaper: Implementation of an Anti-Collision Differential-Offset Spread Spectrum RFID System

by Georgia Institute of TechnologyJan 01, 2008

This research paper offers a novel anti-collision solution by using the spread spectrum algorithm to solve the anti-collision problem and eliminates the need for a twoway communication link. The solution requires minimal hardware to accommodate multiple tags and is consequently low cost, low power and fast. Radio Frequency Identification (RFID) describes a system by which any product can be labeled with any information that can be accessed at any time without having direct contact with the item.


Whitepaper: Delay-Constrained Rate Adaptation for Robust Video Transmission Over Home Networks

by Georgia Institute of TechnologyJan 01, 2008

This white paper addresses the problem of transmission of high-quality video over home networks, in particular IEEE 802.11 wireless LANs, for display on SD and HD TVs. The paper proposes a delay-constrained rate adaptation algorithm to select an optimal bit rate, subsequently enforced by a video transcoder. It examines the effectiveness of the novel delay-constrained rate adaptation algorithm, utilizing a simulation environment based on NS-2.


Whitepaper: Per-User Authentication and Key Management in Consumer Wireless Networking

by Georgia Institute of TechnologyJan 01, 2008

Wireless networking use has exploded over the last few years, but security problems keep the technology from becoming as pervasive as it could be. Almost all current wireless networking employs an implementation of the 802.11 standard; unfortunately, the security aspects of this standard are severely flawed. 802.11 utilize an encryption scheme called WEP to provide confidentiality and integrity to wireless communications. The goal of this research paper is to create a functional RADIUS server that will run on a consumer-grade wireless access point/router, including the administration interface.


Whitepaper: Bandwidth Estimation and Robust Video Streaming Over 802.11e Wireless LANs

by Georgia Institute of TechnologyJan 01, 2008

The approach discussed here is to adjust the video bit-rate dynamically in order to improve the experienced audiovisual quality. The effectiveness of rate adaptation depends on the accurate and timely estimation of the available bandwidth. Streaming high quality Audio/Video (AV) from home media sources to TV sets over a Wireless Local Area Network (WLAN) is a challenging problem because of the fluctuating bandwidth caused by interference.


Whitepaper: Exploiting the Predictability of TCP Steady-State to Speed Up Network Simulation

by Georgia Institute of TechnologyJan 01, 2008

An important portion of resources are dedicated to the processing of packet events, in discrete-event network simulations. For large-scale network simulations, the processing of packet events is the most time consuming aspect of the simulation. This paper highlights a technique that saves on the processing of packet events for TCP flows using the well established results showing that the average behavior of a TCP flow is predictable given a steady-state path condition.


Whitepaper: Ubiquitous Broadband Access Networks With Peer-To-Peer Application Support

by Georgia Institute of TechnologyJan 01, 2008

Technologies such cable, DSL (Digital Subscriber Line), powerline, free-space optics, and broadcast satellite which is attractive for both urban and rural areas exist. These technologies represent a significant bottleneck between highspeed residential network and largely overbuilt core backbone network. This in turn makes it difficult to support end-to-end Quality of Service (Qos) for wide variety of applications, including emerging Peer-To-Peer (PTP) applications and non-elastic applications such as voice and video, which cannot tolerate variable or excessive delay or data loss. This research paper from Georgia Institute of Technology presents architecture to help realize widespread broadband access connectivity with PTP application support.


Whitepaper: Searching For Patterns Of Competitive And Relational Contracting Over Time

by Georgia Institute of TechnologyJan 01, 2008

This paper published by the Georgia Institute of Technology explores and compares two sets of contractual relationships over a twelve-year period: the patterns of contracting between a state transportation agency and its prime contractors providing engineering design services, and between the prime- and sub-contractors. While the patterns of agency-prime contracting are indicative or relational contracting, the patterns of prime-sub contracting imply relatively more competitive processes. Implications for policy and theory of outsourcing are discussed.