Adaptive Error Control Schemes For Supporting Quality Of Service In Wireless Atm Networks

This thesis deals with the error control problems, which is one of the major issues for supporting quality of service (QoS) in wireless ATM (W A TM). Generally in wireless communication, error is induced by impairment prone wireless links. As a method of quality of service based error control, the design and performance evaluation of a retransmission based error control scheme is proposed to overcome wireless channel impairments for multimedia traffic support over wireless A TM networks. The purpose of the proposed error control scheme is to provide error-free services to the higher layers by either correcting the errors in a packet or recovering corrupted packets by retransmission in a wireless link. From the perspective of error control, multimedia traffic can be divided into two types: loss-sensitive traffic and delay-sensitive traffic. To support all these traffic over W ATM networks, we propose two approaches for error control. One approach is to utilize the reliable AAL protocol, which are referd to as AALXl and AALX2, as the end-to-end error control, based on our knowledge-based selectivereject automatic repeat request (KSRARQ) scheme, and adaptive header protection with KSRARQ scheme for loss-sensitive and delay-sensitive traffic, respectively

UWB imaging for breast cancer detection using neural network.

This paper presents a simple feed-forward back-propagation Neural Network (NN) model to detect and locate early breast cancer/tumor efficiently through the investigation of Electromagnetic (EM) waves. A spherical tumor of radius 0.25 cm was created and placed at arbitrary locations in a breast model using an EM simulator. Directional antennas were used to transmit and receive Ultra-Wide Band (UWB) signals in 4 to 8 GHz frequency range. Small training and validation sets were constructed to train and test the NN. The received signals were fed into the trained NN model to find the presence and location of tumor. Very optimistic results (about 100% and 94.4% presence and location detection rate of tumor respectively) have been observed for early received signal components with the NN model. Hence, the proposed model is very potential for early tumor detection to save human lives in the future

Homogeneous and heterogeneous breast phantoms for UWB imaging

This paper presents the fabrication of homogeneous and heterogeneous breast phantoms for experimental breast cancer detection use. The phantoms were developed for UWB imaging technique. The fabrication materials were affordable and the process was minimal. Experiments showed that the use of these phantoms was successful

A numerical approach for efficiency analysis of heat distribution through fin

In this paper an analysis is carried out to study the efficiency of heat distribution through fins using finite element method (FEM) and differential quadrature method (DQM). Numerical solutions are obtained using both methods for temperature distribution over the fin surface. Analysis of surface solutions in terms of temperature and error distributions has been presented here. Solutions are also obtained using equally spaced (conventional) and non-equally spaced (optimum) mesh (nodal points) distribution techniques. Two-dimensional heat conduction problem has been solved in both equal and non-equal nodal points distribution cases (called here conventional FEM and DQM, optimum FEM and DQM respectively as CFEM and CDQM, OFEM and ODQM). The obtained results are compared and investigated with exact results. The best results are found in OFEM solutions. It is also found that, ODQM solutions reach very close to OFEM solutions with negligible error, whereas CFEM and CDQM solutions diverge with increasing number of nodal (mesh) points

Performance enhancement of UWB power control using ranging and narrowband interference mitigation technique

Power control is a critical parameter for the design and evaluation of UWB-based WPAN networks due to its distributed control nature and non-fixed topology. The main issues in UWB PC are the channel gain fluctuations induced by indoor channel fluctuation and interference arising from narrowband systems. In this paper we introduce a joint PHY/MAC technique for DS-UWB power control design by exploiting the high time resolution of the UWB signal for channel gain improvement and mitigate the narrowband interference to reduce transmitted power. The results indicate that the proposed approach achieves better BER and throughput over previous works

Wireless Spread Spectrum Communication Channel Modelling and Simulation Technical Area: Wireless Communication

This paper deals with Wireless Spread Spectrum Communication Link design and planning using Direct Sequence Spread Spectrum (DSSS) technique. The theoretical and mathematical models are developed for simulation and performance evaluation. The purpose of simulating the system is to check validity and avoid unnecessary changes during the actual hardware implementation of the system. Another purpose of simulating the system before implementing it is to find the best possible way or method to fabricate it like the modulation technique, bandwidth, security etc. This type of communication link gives the ability to prevent other external sources from jamming and interfering with the transmission of information due to the use of Direct Sequence technique. This paper describes the design, development and simulation of an indoor digital wireless communication channel. The communication channel consists of a transmit-receive unit operating in the 900-915 MHz frequency range. For a reliable and secure wireless communication link, the Direct Sequence Spread Spectrum (DSSS) technique is used. The most challenging part is the receiver where the pseudo-random noise sequences must be synchronized to successfully recover the original transmitted message. Other key areas of investigation include selection of the pseudo-random noise code (P code), Amplitude Shift Keying (ASK), Differential Binary Phase Shift Keying (DBPSK) modulation/demodulation, Differential Phase Shift Keying (DPSK) modulation, coherent versus non-coherent detection, etc

An improved power consumption circuit of a 5.7 GHz variable-gain low noise amplifier (VGLNA) for RF applications

A low voltage topology that uses a capacitively coupled resonating element has been introduced using 0.18 mum CMOS technology. The topology utilizes the decoupling scheme to dc isolate circuit elements that are connected in series and share a common dc current. A 5.7 GHz variable-gain low noise amplifier (VGLNA) is presented with simulation results exhibiting a noise figure of 1.02 dB, power gain of 19.41 dB with gain tuning range of 6 dB and IIP3 of -1.11 dBm. The power consumption reported is 12.88 mW at supply of Vdd = 0.7 V for power optimization circuit. Simulation results show that the proposed VGLNA has better noise performance and improved power consumption compared to the conventional cascode VGLNA

Protection mechanism and deployment cost analysis for Ethernet PON FTTH access network

In this paper, a new protection method for access network is proposed where redundant equipments are not required and protection is provided to end user through sharing of available timeslots during the failure time