M. S. I. M. Zin

Simulation of virtual MIMO base stations for mobile location in IMT-Advanced networks

The conventional Location and Positioning (L&P) methods rely on availability of base station (BS) locations as well as mitigation of propagation effects. It is known that the location estimation accuracy suffers from poor geometric dilution of precision (GDOP) caused by BS location as the conventional location algorithms which result in large GDOP values correspond to poor geometrical topology. In addition, NLOS effects cause a large error in time of arrival (TOA) reading; thus affecting mobile station (MS) estimation accuracy. In this paper a novel concept of virtual BS (VirBS) utilizing multiple input multiple output (MIMO) technology has been introduced and applied for improving L&P accuracy. The performance of the proposed algorithm has been evaluated via computer simulations. The simulation results demonstrate that the proposed algorithm allows up to 30 percent improvement in L&P accuracy without additional expenditure on network architecture.

Utilising MIMO for positioning in mobile WiMAX systems

Worldwide interoperability for microwave access (WiMAX) brings additional features that can be utilized for enhancing positioning accuracy. This paper deals with WiMAX positioning scheme based on the first arrival path (FAP) of the time of arrival (TOA) technique by utilising one of WiMAX offered features i.e multiple input multiple output (MIMO) system. Simulation results show that the performance of system in term of the positioning accuracy adheres to the Federal Communications Commission (FCC) requirements.

A novel technique of controlling signal propagation within array elements using switchable miniaturized electromagnetic band gap

In this paper, a novel miniaturized capacitive loaded electromagnetic band gap (EBG) has been developed with the patch size of approximately)./36. The dimension is controllable using the lumped capacitive elements values. The surface impedance characteristic of the EBG structure is switchable as pin vias have been inserted and removed within the EBG center and the ground plane. Switching the EBG surface impedance characteristic within the array elements has demonstrated the novel application of miniaturized EBG to control the signal propagation within the array elements. Radiation pattern for the middle antenna is enhanced toward the antenna which connected with low surface impedance EBG structure resulting approximately 12dB improvement in gain. The propagation characteristics and gain of the array have been analyzed using CST Microwave Studio (CST MWS). The new application of the EBG can be very useful to realize the controlling and channeling the signal within the array elements.

Enhance the Performance of EDCA Protocol by Adapting Contention Window

The real-time application is the main challenge that faces the wireless network. It must achieve the quality of service (QOS) requirements to success. IEEE802.11 standards use Enhanced Distributed Channel Access (EDCA) protocol and Distributed Coordinate Function (DCF) protocol in its Media Access Control (MAC) layer. EDCA protocol is used to overcome the drawback of supporting QOS in DCF protocol. The mechanism of EDCA protocol is based on dividing the data to four queues; voice, video, best effort and background. The queues have different priorities to access the medium. The voice queue has the highest priority and its data will serve firstly. Using the default parameter values for EDCA protocol will lead to increasing the collisions in the wireless network and decreasing the capacity. In this paper, the limitation of supporting QOS in EDCA protocol was presented by using OPNET simulation and mathematical model. The new mathematical model was designed by using Markov chain mechanism to evaluate the performance of the EDCA protocol under saturation and non-saturation conditions, aimed to separate between uplink and downlink throughput with different data types. Moreover, the new algorithm was proposed to enhance the capacity of the EDCA protocol and increase the number of the active voice users. Through our algorithm, the throughput was increased by 27.72% and the EDCA can support 14 voice users rather than 11 in the default EDCA protocol. The evaluation of our new algorithm was verified by using OPNET simulation and mathematical model.

Markov Chain Model and Performance Enhancement for EDCA Protocol

—The real-time application is the main challenge that faces the wireless network. It must achieve the quality of service (QOS) requirements to success. IEEE802.11 standards use Enhanced Distributed Channel Access (EDCA) protocol and Distributed Coordinate Function (DCF) protocol in its Media Access Control (MAC) layer. EDCA protocol is used to overcome the drawback of supporting QOS in DCF protocol. The mechanism of EDCA protocol is based on dividing the data to four queues; voice, video, best effort and background. The queues have different priorities to access the medium. The voice queue has the highest priority and its data will serve firstly. Using the default parameter values for EDCA protocol will lead to increasing the collisions in the wireless network and decreasing the capacity. In this paper, the limitation of supporting QOS in EDCA protocol was presented by using OPNET simulation and mathematical model. The new mathematical model was designed by using Markov chain mechanism to evaluate the performance of the EDCA protocol under saturation and non-saturation conditions, aimed to separate between uplink and downlink throughput with different data types. Moreover, the new algorithm was proposed to enhance the capacity of the EDCA protocol and increase the number of the active voice users. Through our algorithm, the throughput was increased by 38.3% and the EDCA can support 14 voice users rather than 11 in the default EDCA protocol. The evaluation of our new algorithm was verified by using OPNET simulation and mathematical model.

Analysis of Enhanced Distributed Channel Access protocol under non-saturation

Nowadays, there is an increase in the use of real time applications in public locations through wireless networks. Enhanced Distributed Channel Access protocol was issued to support quality of service for the real time applications. It came to overcome the lack in Distributed Coordination Function protocol in order to support quality of service. In this paper, Markov chain model is designed to analyze Enhanced Distributed Channel Access protocol under saturation and non-saturation. Our Markov chain model is able to calculate the throughput for uplink and downlink separately. Through the analysis, the access point is considered as the bottleneck of the wireless network, and affects supporting more real time applications users negatively. In addition, the analysis presents the effect of changing the value of contention window minimum on the throughput of the network.