Muhammad Syahrir Johal

A smooth forwarding operation in wireless mesh network

The IEEE 802.11 Distributed Coordination Function (DCF) Medium Access Control (MAC) protocol is designed to efficiently facilitate the limited communication bandwidth of wireless channel. This protocol uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism. This mechanism continues suffer from throughput degradation when directly applied in multihop Wireless Mesh Network (WMN). The major reason for this poor performance is due to larger signaling overheads (RTS and CTS signaling packet) introduced in order to forward a single data packet in multihop WMN. This inefficient forwarding operation caused the throughput degradation signifficantly. Therefore, an efficient forwarding operation is proposed in this paper to reduce the amount of signaling overheads which are needed to forward a single packet in multihop WMN. The proposed protocol uses the capability of overhearing in order to forward the data packet from one hop to another hop. This process will continue until the data packet reaches the respective destination. As a result, the enhanced protocol reduces the latency caused by signaling thus improve its throughput in multihop WMN. The multihop network performances are evaluated analytically in terms of throughput and delay. Through the simulation, it is proven that the proposed protocol provides significant improvement in throughput and delay. The results show that the proposed protocol outperforms the existing IEEE DCF MAC protocol when it is evaluated in multihop WMN.

Concurrent MAC with Short Signaling for multi-hop Wireless Mesh Networks

The IEEE 802.11 Distributed Coordination Function (DCF) Medium Access Control (MAC) protocol continues to suffer from throughput degradation when directly applied in multi-hop Wireless Mesh Network (WMN). The Request-to-Send/Clear-to-Send (RTS/CTS) signaling partially solved hidden node problems however the exposed node problems remain unaddressed. The IEEE 802.11 MAC does not allow the exposed nodes to initiates its transmission for the entire duration of ongoing transmission over multi-hop network leads to throughput degradation. Moreover, the amount of needed signaling packets takes place at every hop reduces the overall multi-hop throughput significantly. This project proposes a set of enhancement to the existing IEEE 802.11 DCF MAC by enabling concurrent transmission by the exposed nodes and reduces the amount of signaling packets (CMAC-SS) required at every hop until the data packet reaches its destination. Analytical models are developed and simulated over quasi-static Rayleigh fading channel. The multi-hop network performances are evaluated in terms of throughput and delay. The CMAC-SS protocol outperforms the existing IEEE DCF MAC with more than 14% increase in overall throughput of multi-hop WMN.

Current developments in LTE-ADVANCED: Radio resource management review

This paper provides a review of current technology components currently used by OFDMA-based Long Term Evolution-Advanced (LTE-Advanced). LTE-Advanced significantly enhanced the previous versions of LTE Release 8/9 to support higher data rates and wider coverage resulting in best experience for users. Some of the technologies discussed in this paper are enhanced Multiple Input Multiple Output (MIMO), advanced repeaters or known as relaying systems, coordinated multipoint transmission/reception and carrier aggregation to expand the capability of the bandwidth spectrum. Among the issues addressed in this paper are related to balancing of transmit power control for both base stations and relay stations and also frequency spectrum allocation in order to avoid any interference within a mobile cell. This also includes how to manage different types of interferences such as intercell interference, intersymbol and intercarrier interferences in the LTE-Advanced system.

Design and fabrication of radio frequency amplifier with 3 dB π-network attenuator isolation

This paper presents the design and fabrication of radio frequency amplifier (RFA), which operates at 5.8 GHz unlicensed frequency for WiMAX application. The RFA designed used T-matching network consisting of lump reactive elements, 3 dB attenuator and microstrip line at the input and output impedance. The RFA developed in this project contribute a gain of 15.6 dB with overall noise figure of 2.4 dB. The overall measured bandwidth is 1.240 GHz with S parameters S11, S12 and S22 measured are -12.4 dB, -25.5 dB and -12.3 dB respectively. The isolation result shows that there is a significant contribution using 3 dB π-network. The RFA used FET transistor EPA018A from Excelics Semiconductor Inc.

Performance evaluation of multiple differential detection for third generation mobile communication system

Third generation mobile communication system is widely used nowadays. One of its parameter standard, which is QPSK modulation has been adopted by International Telecommunication Union (ITU) to be used in IMT-2000. However, due to amplitude variations introduced in QPSK, a rather robust and reliable data modulation technique, namely the pi/4-shift Differential QPSK is proposed. For detection purposes, two types of detectors are evaluated for their performance in AWGN and Rayleigh fading channels. A differential detection technique called multiple differential detection technique which uses maximum-likelihood sequence estimation (MLSE) of the transmitted phases is compared with conventional differential detection which uses symbol-by-symbol detection. By using some of the IMT-2000 standard parameters, the simulation results show that multiple differential detection scheme performs much better than conventional differential detection scheme.