Thavisak Manodham

A Novel Wireless Positioning System for Seamless Internet Connectivity based on the WLAN Infrastructure

Nowadays, several positioning systems are available for outdoor localization, such as the global positioning system (GPS), assisted GPS (A-GPS), and other systems working on cellular networks, for example, time difference of arrival (TDOA), angle of arrival (AOA) and enhanced observed time difference of arrival (E-OTD). However, with the increasing use of mobile computing devices and an expansion of wireless local area networks (WLANs), there is a growing interest in indoor wireless positioning systems based on the WLAN infrastructure. Wireless positioning systems (WPS) based on this infrastructure can be used for indoor localization to determine the position of mobile users. In this paper, we present a novel wireless positioning system, based on the IEEE 802.11b standard, using a novel access point (AP) with two transceivers to improve the performance of WPS in terms of accuracy of the location estimation and to avoid service connectivity interruption. In our proposed system, the novel AP uses the second transceiver to find information from neighboring mobile stations (STAs) in the transmission range and then sends information in advance to associated APs, which estimate the location of the STA based on an internal database. We also use a TDOA technique to estimate the location of the STA when there is not enough information in the database (in this case, the STA moves into a new area where the system has not run the calibration phase). Using TDOA, the database can be generated and updated automatically. The initial results from our simulations show that the proposed system provides higher accuracy of location estimation than other related work and does not interrupt the Internet connection for end users in contrast with other proposed schemes.

A seamless handoff scheme with new AP module for wireless LANs support VoIP

Recently, wireless LANs based on the IEEE 802.11 standard have become popular and widely used, and voice over IP (VoIP) is one of the most promising to be used in mobile devices over wireless networks. Up to date, new technologies have improved providing high data rate to support various kind of real-time applications. However, besides the need for higher data rates, seamless handoff is another important issue to be addressed in order to continue supporting realtime services across wireless LANs. In this paper, we proposed a seamless handoff scheme that uses access point (AP) module with 2 transceivers in order to improve network efficiency in terms of supporting seamless handoff and balancing the traffic load in wireless network. In our proposed scheme, APs use the second transceiver to search for information of neighbor STAs in the transmission range, and later send the result back to associate AP, which in turn compare and analyze whether the STA should perform a handoff or not. The initial results from our simulations show the proposed handoff scheme is more effective than the conventional scheme in terms of low latency and traffic load is fairly balanced.

A novel handover scheme for reducing latency in WLANs

Recently, wireless LANs have become widely used. New technologies have improved providing high data rate and support for real-time services such as Voice over IP (VoIP). However, besides the need for higher data rates, handover latency time is another important issue to be addressed in order to avoid the bottleneck problem and support real-time services. In this scheme, we improve network efficiency in terms of reducing the latency time in the handover process. We neglect both Detection phase and Search phase by proposing a Pre-Active Scan phase, which works during normal connectivity. This phase will scan for information of neighbor Access Points (AP) by using an active scan mode, which in turn is used to decide whether to perform a handover or not. The initial results from our simulations show that the proposed handover scheme is more effective than the conventional scheme in terms of latency and reveals a rather small effect on network traffic load. requirements of real-time applications such as Voice over IP. The detection phase is the longest phase in all cases, while the execution phase could be neglected. So, we consider that a new handover scheme is necessary to improve the latency time in WLAN. This can be achieved by reducing the delay of handover process as much as possible in order to support real-time services and avoid packet losses. In this paper, we propose a new phase called pre-active scan phase to replace both detection phase and search phase in the conventional handover scheme. The pre-active scan phase scan neighbor APs and compare the results with the current AP, then STA will make a decision when and which AP the STA will handover in order to reduce latency time in WLANs.

Weighted Hop Priority Control Scheme for Multihop Wireless Ad Hoc Networks

Packet scheduling problem experienced in wireless ad hoc networks is presented. Flow of packets coming from different node locations and concurring at intermediate nodes could overflow resources rapidly, stressing packet forwarding and increasing packet dropping. An intelligent packet priority control technique named weighted hop priority control scheme is used, that assures a data arrival end-to-end and reduced packet dropping ratio. Technique is based on periodically calculating two hop threshold values by weighting hop information carried by incoming and outgoing packet flows (hops already traversed and still remaining) respectively with their correspondent data rates, and using these thresholds to prioritize packet forwarding. Proposed scheme is compared with conventional queuing control based on first-in first-out queue dispatcher. Data arrival ratio and downloading response time are evaluated as our main estimator parameters. An ad hoc network scenario is simulated and results show that our proposed priority control scheme is a promising technique to efficiently handle packet flow forwarding in wireless ad hoc communications

A Novel Handover Scheme for Improving the Performance of WLANs based on IEEE802.11

Recently, new technologies improve WLANs to provide high quality of service (QoS) and support real time applications. In this paper, we improve network efficiency in terms of reducing the latency time in handover process and support traffic load sharing among neighbor access points (APs). We neglect both detection phase and search phase in the conventional handover scheme by proposing a pre-active scan phase, which works during normal connectivity. This phase will scan for the information of neighbor APs, which in turn is used to decide whether to perform a handover or not. The results from our simulation show the proposed handover scheme is more effective than the conventional one in terms of providing low latency time and support traffic load sharing among neighbor APs

The Concept of Referential Loss Recovery for Real-Time Applications and its Improvements of QoS Provision

Real-time multimedia streaming is expected to grow rapidly in the near future. Packet losses during transmission are a serious problem for these multimedia applications since they result in degradation of the quality of service (QoS). Forward error correction (FEC) is a promising technique to recover the lost packets and improve the QoS of streaming media. However, FEC may degrade the QoS of all streaming due to the increased congestion caused by FEC overhead when streaming sessions increase. In this paper, a novel FEC method that avoids the adverse effect of FEC overhead during media streaming is proposed. Also, we define the maximum percentage of network load where FEC can improve the packet loss ratio to clarify the effective ranges where each FEC and automatic repeat request (ARQ) scheme works well. The numerical analyses show that our proposed method highly improves the packet loss ratio compared to conventional method

A Novel AP for Improving the Performance of Wireless LANs Supporting VoIP

Recently, wireless LANs based on the IEEE 802.11 standard have become popular and widely used, and Voice-over-IP (VoIP) is one of the most promising technologies to be used in mobile devices over wireless networks. Up-to-date, new technologies have improved, providing a high data rate to support various kinds of realtime applications. However, besides the need for higher data rates, seamless handoff is another important issue to be addressed in order to continue supporting real-time services across wireless LANs. In this paper we introduce a novel Access Point (AP) with two transceivers to improve network efficiency in terms of supporting seamless handoff and balancing the traffic load in a wireless network. In our proposed scheme, the novel AP will use the second transceiver to scan and find neighboring STAs in the transmission range and later send the result to its associate AP, which in turn compares and analyzes whether or not the STA should perform a handoff. The initial results from our simulations show the novel AP module is more effective than the conventional one in terms of providing a handoff process with low latency and support traffic load sharing with neighbor APs.

A Seamless Handoff Scheme with Access Point Load Balance for Real-Time Services Support in 802.11 Wireless LANs

IEEE 802.11 wirelesses LANs (WLANs) have been rapidly deployed in enterprises, public areas, and households. Voice-over-IP (VoIP) and similar applications are now commonly used in mobile devices over wireless networks. Recent works have improved the quality of service (QoS) offering higher data rates to support various kinds of real-time applications. However, besides the need for higher data rates, seamless handoff and load balancing among APs are key issues that must be addressed in order to continue supporting real-time services across wireless LANs and providing fair services to all users. In this paper, we introduce a novel access point (AP) with two transceivers that improves network efficiency by supporting seamless handoff and traffic load balancing in a wireless network. In our proposed scheme, the novel AP uses the second transceiver to scan and find neighboring STAs in the transmission range and then sends the results to neighboring APs, which compare and analyze whether or not the STA should perform a handoff. The initial results from our simulations show that the novel AP module is more effective than the conventional scheme and a related work in terms of providing a handoff process with low latency and sharing traffic load with neighbor APs.

A Novel Path Protection Scheme with FEC Path in Connection Oriented Networks

The QoS provided by todays best effort Internet is not good enough for real-time premium traffic. It is believed that QoS guarantees could be better provided by the connection oriented networks. Multi protocol label switching (MPLS) is one such technology and these connection oriented networks are inherently more prone to network failures. Conventional path protections perform re-routing to cope with them. However, rerouting always causes packet losses and results in service outage. These losses are bursty in nature and highly degrade QoS of the real-time premium traffic. The novel path protection proposed in this paper recovers the bursty packet losses due to re-routing using forward error correction (FEC) path. It provides the network architecture with no service outage for such traffic. The numerical results show that the proposed method can achieve a very high availability for the real-time premium traffic in future IP/MPLS networks