David Cypher

Performance analysis of low rate wireless technologies for medical applications

In this article, we discuss what wireless technologies can be used for medical applications and how well they perform in a healthcare/hospital environment. We consider the emerging low-rate Wireless Personal Area Network technology as specified in the Institute of Electrical and Electronics Engineers 802.15.4 standard and evaluate its suitability to the medical environment. We focus on scalability issues and the need to support tens of communicating devices in a patients hospital room. We evaluate the effect of packet segmentation and backoff parameter tuning to improve the overall network performance that is measured in terms of packet loss, goodput, and access delay. We also evaluate the performance of 802.15.4 devices under interference conditions caused by other 802.15.4 devices and by wireless local area networks using IEEE 802.11b.

Prevailing over wires in healthcare environments: benefits and challenges

The objectives of this article are to survey the benefits and challenges posed by the deployment and operation of wireless communications in support of healthcare networks. While the main advantage of wireless communications remains to provide ubiquitous connectivity, thus allowing greater physical mobility and interoperability, a number of engineering issues need to be addressed before this vision is realized. Our intent in this article is to explore some of these issues, including deployment, interference, and mobility, and provide insights for potential solutions.

Timely Effective Handover Mechanism in Heterogeneous Wireless Networks

Next-generation wireless networks should be able to coordinate and integrate different communication systems. It has been a challenging problem to support a seamless handover in these diverse wireless network environments. Link level triggers can provide information about events which can help handover decision and layer 3 entities better streamline their handover related activities. In most conventional layer 2 triggering approaches, a pre-defined threshold for a specific perspective such as the received signal strength is used. This may cause too late or too early handover executions. In this paper we propose a new predictive handover framework that uses the neighbor network information to generate timely the link triggers so that the required handover procedures can appropriately finish before the current link goes down. First we estimate a required handover time for the given neighbor network conditions, then using a predictive link triggering mechanism the handover start time is dynamically determined to minimize handover costs. The handover costs are analyzed in terms of the total required handover time and the service disruption time. The numerical analysis and simulation results show that the proposed method significantly enhances the handover performance in heterogeneous wireless networks.

A Methodology to Evaluate Wireless Technologies for the Smart Grid

This paper presents a methodology for assessing the suitability of various wireless technologies for meeting the communication requirements of Smart Grid applications. It describes an approach for translating application requirements to link traffic characteristics, determining the transmission range or coverage area of a wireless technology, and modeling the link layer to obtain performance measures such as message reliability, delay, and throughput. To illustrate the use of this approach, we analyze the performance of three representative application use cases over an IEEE 802.11 link.

Performance evaluation of low rate WPANs for medical applications

In this article we consider the emerging low-rate wireless personal area network (WPAN) technology as specified in the IEEE 802.15.4 standard and evaluate its suitability for medical applications. The main objective for this effort is to develop a universal and interoperable interface for medical equipment . We focus on scalability issues and the need to support several communicating devices near a patients bedside. Given the nature and the diversity of the clinical environment, it is most likely that different medical applications will use different wireless technologies. We choose to quantify the performance of IEEE 802.15.4 devices in the presence of IEEE 802.11b devices since it may be the technology of choice for most Web access, E-mail, video, and printing applications.

LMS Predictive Link Triggering for Seamless Handovers in Heterogeneous Wireless Networks

Effective and timely link layer trigger mechanisms can significantly influence the handover performance. In this paper, a predictive link trigger mechanism for seamless horizontal and vertical handovers in heterogeneous wireless networks is proposed. Firstly, the time required to perform a handover is estimated based on the neighboring network conditions. Secondly, the time to trigger a Link_Going_Down to initiate a handover is determined using a Least Mean Square (LMS) linear prediction in which the prediction interval (kh) is dynamically determined based on the estimated handover time. Simulation results of the proposed predictive link triggering mechanism show that it provides a timely proactive handover. The packet loss rate observed in a Gaussian fading channel remains low during a handover.

Predictive handover mechanism based on required time estimation in heterogeneous wireless networks

In most conventional layer 2 triggering approaches, a pre-defined threshold for a specific perspective such as the received signal strength is used so that it may cause too late or too early handover executions. In this paper we propose a new predictive handover framework that uses the neighbor network information to generate timely the link triggers so that the required handover procedures can appropriately finish before the current link goes down. First we estimate a required handover time for the given neighbor network conditions, then using a predictive link triggering mechanism the handover start time is dynamically determined to minimize handover costs. The handover costs are analyzed in terms of the total required handover time and the service disruption time. The numerical analysis and simulation results show that the proposed method significantly enhances the handover performance.

Performance analysis of fast handover for proxy Mobile IPv6

In Proxy Mobile IPv6 (PMIPv6), any involvement by the Mobile Node (MN) is not required, so that any tunneling overhead can be removed from over-the-air. However, during the PMIPv6 handover process, there still exists a period when the MN is unable to send or receive packets because of PMIPv6 protocol operations, suffering from handover latency and data loss. Thus, to reduce the handover latency and data loss in PMIPv6, Fast Handover for PMIPv6 (PFMIPv6) is being standardized in the IETF. Nevertheless, PFMIPv6 has a few weaknesses: (1) handover initiation can be false, resulting in the PFMIPv6 handover process done so far becoming unnecessary. (2) Extra signaling is introduced in setting up an IP-in-IP tunnel between the serving and the new Mobile Access Gateways (MAGs). Therefore, in this paper, we present our study on the protocol overhead and performance aspects of PFMIPv6 in comparison with PMIPv6. We quantify the signaling overhead and the enhanced handover latency and data loss by conducting a thorough analysis of the performance aspects. The analysis is very meaningful to obtain important insights on how PFMIPv6 improves the handover performance over PMIPv6, especially in a highway vehicular traffic scenario where Base Stations (BSs)/Access Points (APs) can be placed in one dimensional space and MNs movements are quasi one-dimensional, so that the degree of certainty for an anticipated handover is increased. Further, our analytical study is verified by simulation results.

Fast Handover Latency Analysis in Proxy Mobile IPv6

In Proxy Mobile IPv6 (PMIPv6), any involvement by the Mobile Node (MN) is not required so that any tunneling overhead could be removed from over-the-air. However, during the PMIPv6 handover process, there still exists a service interruption period during which the MN is unable to send or receive data packets because of PMIPv6 protocol operations. To reduce the handover latency, Fast Handover for PMIPv6 (PFMIPv6) is being standardized in the IETF MIPSHOP working group. In PFMIPv6, however, handover initiation can be false, resulting in the PFMIPv6 handover process done so far becoming unnecessary. Therefore, in this paper, we provide a thorough analysis of the handover latency in PFMIPv6, considering the false handover initiation case. The analysis is very meaningful to obtain important insights on how PFMIPv6 improves the handover latency. Further, our analytical study is verified by simulation results.

Fast handover with low latency for proxy MIPv6 in vehicular networks

To reduce the handover latency in Proxy Mobile IPv6 (PMIP v6), fast handover for PMIPv6 (PFMIPv6) is also being standardized in the IETF. However, in the PFMIPv6 networks, a tunnel is established between the previous Mobile Access Gateway (MAG) and the new MAG only after the previous MAG receives an HAck (Handover Acknowledgement) message from the new MAG. This problem is aggravated by high mobility of MNs, which characterizes vehicular networks based on PMIPv6. To reduce the time for establishing the tunnel between MAGs in the vehicular networks, each MAG along the road, pre-configures the tunnel with its neighboring MAGs and then the tunnel will be activated when a new MN arrives. From the numerical and simulation results, it is shown that the proposed fast handover scheme can achieve lower handover latency than PFMIPv6.