Cross Layer Scheduling in WiMAX QOS for Disaster Management

How a base station assigns free resource slots to BE service class is depending on the available channel bandwidth after all the other classes have been served. Generally, it is known that the performance of BE is always the worst and provides the lowest level of quality compared to all other classes. However, if somewhat unexpected natural disaster strikes or an environmental catastrophe occurs, when the major communication infrastructure has been destroyed, it is possible that the only available Quality of Service (QoS) service is BE. Under this condition, users or, particularly, a rescue team will not have any other options but to use the only available service class for any types of applications including voice communications or even video communications. Based on that scenario, we have performed simulations using OPNET modeler simulation tool to evaluate the rtPS and BE performance with particular focus on video conferencing/streaming and also data transfer applications. Simulation results show that in certain situations, a user with BE QoS could provide better throughput compared to a user with rtPS. In addition, we also propose a cross layer scheduling mechanism by assigning the video conferencing/streaming application to BE service class and file transfer application to the rtPS service class.  The results obtained indicate that for certain combinations of users and QoS, BE service class demonstrates a higher throughput than rtPS. This scenario can be practically applied by a rescue team in any disaster management operations apart from normal teleconference service

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

Design And Development Of Modified-Proportional Fair Scheduler For LTE/LTE-Advanced

Long Term Evolution (LTE) is well known as a cellular network that can support very high data rates in diverse traffic conditions. One way of achieving it is through packet scheduling which is the key scheme of Radio Resource Management (RRM) for LTE traffic processing that is functioning to allocate resources for both frequency and time dimensions. The main contribution of this paper is the design of a new scheduling scheme and its performance is compared with the Proportional Fair (PF) and Round Robin (RR) downlink schedulers for LTE by utilizing LTE Downlink System Level Simulator. The proposed new scheduling algorithm, namely the Modified-PF scheduler divides a single subframe into multiple time slots and allocates the resource block (RB) to the targeted User Equipment (UE) in all time slots for each subframe based on the instantaneous Channel Quality Indicator (CQI) feedback received from UEs. Simulation results show that the Modified-PF scheduler provides the best performance in terms of throughput and spectral efficiency with comparale fairness as compared to RR and PF schedulers. Although PF scheduler has the best fairness index, the Modified-PF scheduler provides a better compromise between the throughput/spectral efficiency and fairness. This shows that the newly proposed scheme improves the LTE output performances while at the same time maintains minimal required fairness among the UEs

Physical Performance and Cross Layer Design for Wireless Mesh Networks

Wireless mesh networks (WMNs) are an alternative technology for last-mile broadband Internet access that can support broadband services. However, for a WMN to be all it can be, considerable research efforts are still needed. In WMNs, the Orthogonal Frequency Division Multiplexing (OFDM) system is chose to provide the better performance at the physical layer design. OFDM is very tolerant to ISI and it's spectrally efficient. OFDM also very susceptible to phase and frequency offsets. This paper presents the physical layer design of an OFDM system for wireless mesh networkin

An Efficient Medium Access Control (MAC) Forwarding Technique for Multihop Network

The function of Medium Access Control (MAC) protocol in network communication is to efficiently facilitate the use of available channels when more nodes (i.e. laptop, PC, smart phones and etc) involving in transmission activity in the network. The protocol uses the well-known Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism to allow all nodes in the network to communicate between each other without collision. This mechanism has been standardized in IEEE 802.11 and it is proven to provide the better performance of throughput for single hop communication. The node which is uses CSMA/CA mechanism will perform a handshake (the exchange of RTS and CTS signalling packets) prior initiates any packet transmission. The handshake is very crucial in order to avoid the collision caused by simultaneously transmission to the single receiver. However, this mechanism undergoes bad throughput performance when directly implemented for multihop communication. The reason behind this poor performance is due to the inefficient forwarding in CSMA/CA mechanism which is caused larger signalling overheads. The exchange of RTS and CTS signalling that required at each hop throughout the multihop network eventually will cause the larger overheads and throughput degradation. Therefore, an efficient forwarding operation is proposed in this work to reduce the signalling overheads and ultimately allows a smooth forwarding of packet in the multihop network without any collision. In this work, the multihop network performances are evaluated analytically in terms of throughput and overhead. Through the simulation, it is proven that the proposed forwarding technique provides significant improvement in throughput and overhead

Location Estimation Utilising WiMAX Preamble Detection Under ITU-R Channel Models

In this paper, a novel mobile WiMAX location and positioning scheme utilizing WiMAX preamble has been proposed. The purpose of the scheme is to enhance the accuracy of location estimation in WiMAX services. Preamble detection for 10MHz and 20MHz FFT bandwidth under ITU-R channel models (Vehicular (A) and Pedestrian (B)) has been evaluated and analysed. Simulation results show that the 20MHz FFT outperformed the 10MHz bandwidth under various channel models. Best result for preamble detection in mobile WiMAX is best achieved when the mobile station is in low velocity with higher FFT bandwidth