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Full-Text Articles in Computer Engineering

New Hybrid Automatic Repeat Request (Harq) Combining With Space Time Block Coding (Stbc) In Invariant And Variant Fading Channel, Guillem Ernest Malagarriga Vilella Dec 2005

New Hybrid Automatic Repeat Request (Harq) Combining With Space Time Block Coding (Stbc) In Invariant And Variant Fading Channel, Guillem Ernest Malagarriga Vilella

Theses

Hybrid Automatic Repeat reQuest (HARQ) combining for space time block coding Multiple Input Multiple Output (MIMO) system consisting of N transmit antennas and M receive antennas (NxM) in a time invariant channel and in a time varying channel is proposed and its performance is analyzed. Based on the measured channel matrix, the receiver chooses the best retransmission order and communicated it to the transmitter.

The scheme, where this algorithm is performed, is a combination of a precombining HARQ scheme and the Multiple Alamouti Space-Time Block Coding (MASTBC), which is suitable for more than 2 transmit antennas. The combination of this ...


An Analytical Model Of Mac Protocol Dependant Power Consumption In Multi-Hop Ad Hoc Wireless Sensor Networks, Komlan Egoh Aug 2005

An Analytical Model Of Mac Protocol Dependant Power Consumption In Multi-Hop Ad Hoc Wireless Sensor Networks, Komlan Egoh

Theses

Power efficiency is the most constraining requirement for viable operation of battery-powered networked sensors. Conventionally, dynamic power management (DPM) is used to put sensor nodes into different states such as active, idle, and sleep, each consuming a certain level of power. Within the active state, communication operational states, such as receive and transmit consume different levels of nodal power. This thesis shows how DPM states and protocol operational states can be combined into a single stochastic model to finely evaluate the power consumption performance of a medium access control (MAC) protocol. The model is formulated as a semi-Markov decision process ...


Evaluation Of Coding Scheme For Mimo Radar, Suresh Kumar Harikrishnan Aug 2005

Evaluation Of Coding Scheme For Mimo Radar, Suresh Kumar Harikrishnan

Theses

Multiple Input Multiple Output (MIMO) antenna systems have shown a great potential for wireless communication. These systems support high capacity, increased diversity and interference suppression. Recently it has been proposed MIMO constellations for Radar. MIMO Radar is not only a new research field, but also a very promising approach in terms of overcoming Radar Cross Section (RCS) fluctuations with diversity. This thesis explores the potential of coding schemes for MIMO Radar.

The ambiguity functions measures related to MIMO Radar are used to evaluate how much diversity gain can be coherently achieved with certain coding schemes. The results of this analysis ...


Cluster-Based Wireless Mobile Ad-Hoc Network Security, Mandur Bajra Bajracharya May 2005

Cluster-Based Wireless Mobile Ad-Hoc Network Security, Mandur Bajra Bajracharya

Theses

A wireless ad-hoc network is a cooperative communication network deployed with a specific purpose. It is characterized by dynamically changing topology with no fixed infrastructure which exhibits a perfectly vulnerable state for a number of different kinds of attacks.

This thesis proposes a novel technique of achieving security in wireless mobile ad hoc networks by integrating a simple clustering and a voting mechanism together. The purpose of forming a cluster is to facilitate security in the network and the voting is performed to support the decision making process in the cluster. A procedure of forming small homogenous clusters throughout the ...