Zawar Shah

Particle Filters and Position Tracking in Wi-Fi Networks

In this work we quantify the usefulness of particle filters applied to the problem of mobile device tracking in Wi-Fi networks, under the assumption of log-normal fading. Our principal aim was to determine if a real-time deployment of a particle filter was possible while still providing factor two gains in the prediction performance relative to a stand-alone optimal Wi-Fi positioning algorithm. We conclude that the required gains are achieved in our adopted filter algorithm when the particle number is set to the relatively small number of 300, meaning that a real-time deployment is possible. In addition, we quantify the performance gain of the particle filter when intermittent GPS information is available to the mobile device. We propose the fusion of the GPS information be implemented as a renormalization of the particle cloud. Finally, we probe the limits of the filter performance under biased-error distributions. Our simulations show that tracking of people, vehicles and robotic devices in an outdoor Wi-Fi network, where non-linear and non-Gaussian conditions exist, can be significantly enhanced by the pragmatic real-time particle filter algorithm presented here

An Architecture for Location Tracking Using SIP

Location tracking in wireless networks has many applications, including enhanced network performance. In this report we investigate a new SIP-based architecture for wireless networks that allows for the fusion of different positioning technologies (GPS and Particle Filters). The architecture is specifically designed for outdoor users possessing intermittent GPS availability, a characteristic commonly found in real outdoor wireless networks. The architecture also includes the novel use of a user profile database in the particle filter algorithm, which we show can lead to factor two gains in position accuracy. Implementation of our architecture is described, and simulations of its performance in the multi-user setting are provided. We show how the architectures effect on network operations is minimal. The architecture we propose here, builds on our already deployed particle filter tracking algorithms in wireless networks.

VoIP and Tracking Capacity over WiFi Networks

Wireless VoIP is becoming an increasingly important application in recent years. This fact, coupled with the increasing interest in location based services, strongly suggest that tracking of wireless VoIP clients will become a widely deployed feature in emerging wireless applications. In this paper, we evaluate the capacity of WiFi networks carrying VoIP and tracking sessions for our novel architectures developed specifically to support such applications. We first present an upper bound on a maximum number of users who can be supported by the proposed architecture for tracking only applications via simulations and experiments. We then vary the transmission frequency of tracking data and observe that it has a significant impact on the tracking capacity. Finally, we utilize one of our other locations tracking architecture that is designed for wireless VoIP to investigate how the transmission frequency affects the capacity of combined VoIP and tracking sessions. We develop an insight that at high packetization intervals (e.g. 60 ms) of VoIP traffic, there is a 30% decrease in combined VoIP and tracking capacity in comparison to VoIP only capacity. We further evaluate the capacity of proposed architecture using UDP (User Datagram Protocol) and DCCP (Datagram Congestion Control Protocol) in the presence of TCP (Transmission Control Protocol) traffic. Our studies suggest that compared to UDP, DCCP not only improves the combined VoIP and tracking capacity but also enables TCP to get a reasonable bandwidth share.

Throughput comparison of IEEE 802.11ac and IEEE 802.11n in an indoor environment with interference

IEEE 802.11ac is an emerging standard that operates in 5GHz frequency band and provides high data rate as compared to IEEE 802.11n. In this paper we carry out experiments in a real indoor environment and quantify the gain in average throughput provided by IEEE 802.11ac compared to IEEE 802.11n in the presence of interference caused by other IEEE 802.11n sources. The experiments are performed for both Line of Sight (LoS) and Non-Line of Sight (NLoS) conditions. We note that IEEE 802.11n (2.4GHz) provides the worst average throughput due to the highly congested 2.4GHz frequency band in our experimental environment. We find that IEEE 802.11n (5GHz) with 40MHz channel width provides a gain of 36% in average throughput compared to 20MHz channel width at a distance of 20m from the wireless router in LoS conditions. Our experimental results reveal that IEEE 802.11ac achieves 42% better average throughput when compared to the IEEE 802.11n (5GHz) at a distance of 5m in LoS conditions. Similarly, IEEE 802.11ac provides 55% improvement over IEEE 802.11n (5GHz) at a distance of 15m in NLoS conditions. We conclude that IEEE 802.11ac can effectively handle interference caused by other IEEE 802.11n (5GHz) sources and provides higher throughput than IEEE 802.11n for both LoS and NLoS conditions.

State aware enhancement in DCCP for multimedia handovers

The multi-radio-access enabled mobile devices have enabled the integration of fourth generation networks with the legacy technologies. However, this integration has numerous issues for the multimedia applications, such as to smoothly continue over new connection without any service disruption during vertical handover. In this paper, we propose a State-Aware Feedback extension to Datagram Congestion Control Protocol (i.e. S-DCCP) that meets the Quality of Service (QoS) requirements of multimedia applications. We consider the mobile subscribers as roaming among heterogeneous access technologies from highly unstable to more stable access environment and model their mobility patterns as uniform, pareto and exponentially distributed. We first evaluate the performance of both types of S-DCCP i.e. S-TFRC and S-TCPLike and observe end-to-end delay and packet loss during the handover process. We develop an insight that S-TFRC maintains better QoS constraints meant for multimedia traffic for various link stability environments than S-TCPLike. We then consider transmission delay, throughput and transmission rate as performance metrics and compare the performance of S-TFRC with the standard TFRC during vertical handover. Our results show that for various mobility patterns S-TFRC is capable of providing better QoS to multimedia applications than the standard TFRC as it significantly reduces the transmission delay and provides better throughput to the multimedia applications.

Improving QoS of IPTV and VoIP over IEEE 802.11n

Tremendous growth rates of Internet Protocol Television (IPTV) and Voice over Internet Protocol (VoIP) have demanded the shift of paradigm from wired to wireless applications. Increased packet loss with continuously varying wireless conditions make the transmission a challenging task in wireless environment. Our study investigates and proposes improvement in the transmission of combined IPTV and VoIP over the IEEE 802.11n WLAN. Our major contributions include the analytical and experimental investigations of (1) transport layer protocol UDP/TFRC for IPTV and VoIP, (2) optimal physical layer parameters for IPTV and VoIP, (3) proposition of wireless enhancement of TFMCC (W-TFMCC) to enhance the capacity and Quality of Service (QoS) of wireless IPTV and VoIP. Analytical and experimental evaluations show a 25% increase in capacity using TFRC with 167% more bandwidth share to TCP. Our study shows that use of W-TFMCC with optimal parameters can enhance IPTV and VoIP capacity by 44%.

Reliability Issues in a SIP based Location Tracking Architecture

In this work reliability issues regarding a new SIP-based architecture for location tracking are investigated. This new architecture works across different positioning technologies (particle filters and GPS) and provides optimal position tracking in real time for an outdoor mobile user. A new adaptive SIP retransmission timer is proposed that is designed specifically for real time location tracking in an outdoor environment. This new retransmission timer is aligned with the motion model of the mobile user. We extend the architecture to allow other location based network information, such as that residing in quality of service (QoS) aware servers, to be seamlessly incorporated. The architecture we propose here, builds on our already deployed GPS-assisted particle filter tracking algorithms and our position-based QoS presence system.

Effect of transmission opportunity and frame aggregation on VoIP capacity over IEEE 802.11n WLANs

Wireless Fidelity (WiFi) networks have gained unprecedented growth in recent years and have played an important role in the popularity of wireless VoIP. IEEE 802.11n is the most widely used WiFi standard today. Transmission Opportunity (TXOP) and Frame Aggregation (FA) are two important Medium Access Control (MAC) Layer enhancements provided by IEEE 802.11n standard. In this work our focus is on the determination of optimal values of TXOP and FA that maximize VoIP capacity. We first determine the optimal value of FA that maximizes VoIP capacity. Our simulation results show that optimal value of FA that maximizes VoIP capacity is 14. At 10 ms packetization interval this value of FA provides a gain of 26% in VoIP capacity as compared to the VoIP capacity with no FA. Secondly, we find that the optimal value of TXOP that maximizes VoIP capacity is 13. At 10ms packetization interval this value of TXOP gives a gain of 32% in VoIP capacity as compared to VoIP capacity with default value of TXOP. We then determine the VoIP capacity when optimal values of TXOP and FA are simultaneously used. Our study reveals that simultaneous use of optimal values of both FA and TXOP further increase VoIP capacity. A gain of 44% in VoIP capacity is achieved when optimal values of TXOP and FA are used simultaneously as compared to the VoIP capacity with default values of both FA and TXOP. We further determine VoIP capacity over User Datagram Protocol (UDP) and TCP Friendly Rate Control (TFRC) protocol in the presence of Transmission Control Protocol (TCP) traffic. We note that in the presence of TCP traffic, TFRC with optimal values of TXOP and FA provides an average gain of 37% as compared to TFRC with default values of FA and TXOP.

IPTV Capacity Analysis Using DCCP over IEEE 802.11n

Internet Protocol Television (IPTV) has gained an enormous growth rate by revolutionizing personal entertainment. High data rates with increased coverage radius of IEEE 802.11n Wireless Local Area Networks (WLANs) motivate the concept of wireless IPTV. Streaming of Television contents over highly pervasive wireless environment with satisfactory Quality of Service (QoS) is a challenging task. Focusing on wireless IPTV, our work deals with the capacity evaluation of IPTV users over IEEE 802.11n. We first present an upper capacity limit for supporting maximum number of users over IEEE 802.11n. We then propose that 4-times packet size is the optimal frame aggregation size for IPTV which maximizes users capacity and QoS. Finally, we suggest the use of Datagram Congestion Control Protocol (DCCP) at transport layer for IPTV. We show that DCCP capacity for IPTV increases upto 35% by reducing packet losses at Access Point (AP), compared to User Datagram Protocol (UDP). We further evaluate fairness of IPTV traffic in the presence of Transmission Control Protocol (TCP) traffic in the network. Our study concludes that IPTV using DCCP over IEEE 802.11n not only provides increased users capacity but also co-exists fairly with TCP traffic.

Capacity analysis of combined IPTV and VoIP over IEEE 802.11n

Internet Protocol Television (IPTV) and Voice over Internet Protocol (VoIP) have gained unprecedented growth rates in the past few years. Data rate and high coverage area of IEEE 802.11n motivate the concept of combined IPTV and VoIP over IEEE 802.11n. Transmission of combined IPTV and VoIP over a wireless network is a challenging task. In this paper, we deal with the capacity evaluation of combined IPTV and VoIP over IEEE 802.11n. We evaluate the use of Datagram Congestion Control Protocol (DCCP) at transport layer of IPTV and VoIP. Our study shows that DCCP can enhance capacity of IPTV by 25%. Our study confirms that performance of DCCP deteriorates severely in presence of any other UDP flow because of congestion-less mechanism of UDP. Our fairness analysis with TCP traffic shows that IPTV and VoIP using DCCP provides fair share in bandwidth to TCP with 19% increase in combined capacity. We study the effect of IEEE 802.11n parameters and obtain optimal values. We show the optimal values and trends of Access Point (AP) parameters including Queue size, Transmission Opportunity, Aggregation and Block ACK etc. Our study shows that nearly 9 more VoIP users are supported with a queue size of 70 packets and transmission opportunity of 9. Our study concludes that selection of DCCP and optimized parameters over IEEE 802.11n can enhance the capacity of IPTV and VoIP by atleast 25% and 19% respectively as compared to the use of UDP.