Chunlei An

Virtual lifeline: Multimodal sensor data fusion for robust navigation in unknown environments

We present a novel, multimodal indoor navigation technique that combines pedestrian dead reckoning (PDR) with relative position information from wireless sensor nodes. It is motivated by emergency response scenarios where no fixed or pre-deployed global positioning infrastructure is available and where typical motion patterns defeat standard PDR systems. We use RF and ultrasound beacons to periodically re-align the PDR system and reduce the impact of incremental error accumulation. Unlike previous work on multimodal positioning, we allow the beacons to be dynamically deployed (dropped by the user) at previously unknown locations. A key contribution of this paper is to show that despite the fact that the beacon locations are not known (in terms of absolute coordinates), they significantly improve the performance of the system. This effect is especially relevant when a user re-traces (parts of) the path he or she had previously travelled or lingers and moves around in an irregular pattern at single locations for extended periods of time. Both situations are common and relevant for emergency response scenarios. We describe the system architecture, the fusion algorithms and provide an in depth evaluation in a large scale, realistic experiment.

Performance evaluation of radio disjoint multipath routing

Multipath routes in wireless multihop ad hoc networks have proven to increase performance compared to single path routing when providing backup paths in case of path failures and also distributing flows (i.e. data traffic) among several paths. The drawback of using multipath simultaneously in wireless multihop ad hoc networks is that the other nodes in the network located in the other active paths may interfere with their own communications, degrading the effective throughput. This work proposes an analytical model to find multiple non-interfering routes or routes with minimum interference between a source and a destination in a given network topology. These types of routing paths are called Radio Disjoint Multipath (RDM) routes. Compared to the previous work, this work pioneers the use of models to determine interference free routes in a wireless multihop ad hoc network considering two criteria: the mutual interference of each path and the background traffic load of the path. Further, simulation results are taken by implementing RDM routes in 802.11 based multihop ad hoc networks. Both analytical and simulation results are obtained and analysed for different network scenarios that use RDM routes by distributing packets of a single flow among multiple RDM paths. Analytical results show that the sustainable throughput can be doubled when using RDM paths for unidirectional flows. Simulation results also show that throughput can be improved with RDM routes by a factor of 1.5 and 1.8 in some cases, when using uni-and bidirectional UDP flows, respectively. Copyright

Virtual Sensor Network Lifeline for Communications in Fire Fighting Rescue Scenarios

Wireless Sensor Networks (WSNs) have been used mainly to collect environmental data and send it to a base station. Routing protocols are needed to efficiently direct the information to the base station. Most of the available routing protocols are designed for conventional WSN applications, where small volume data transmission is required and low power consumption is the fundamental. Support to mobility is generally out of interest, since in most scenarios sensor nodes are static after being deployed. However, in fire fighting rescue scenarios, WSN routing protocols are expected to be able to adapt to change of network topology (caused by nodes failure and fire fighters’ movement) rapidly. Moreover, routing protocols should be capable to transmit relatively large volume data (e.g. short voice message) without losing efficiency and reliability. In this paper we propose a broadcasting based communication protocol, which is dedicated to the fire fighting rescue scenarios under the framework of a European project wearIT@work. This protocol is applied to building up a virtual lifeline for fire fighters. The protocol is evaluated through experimental tests and simulations using variant scenarios. Performance metrics such as packet transmission time, jitter and packet loss rate are considered. Results show that our broadcasting based communication protocol is able to fulfill the requirements and is more suitable to fire fighting rescue scenarios.

Dimensioning of the IP-Based UTRAN with Multiple Node Bs for Elastic Traffic Using DiffServ QoS

This paper presents dimensioning of an IP-based UMTS Terrestrial Radio Access Network (UTRAN) with multiple Node Bs connected to one RNC, where the applied QoS architecture is based on Differentiated Service (DiffServ) with an integrated Weighted Fair Queue (WFQ) and Strict Priority (SP) scheduling. To provide an appropriate network dimensioning for guaranteeing a desired end-to-end QoS, a general analytical approach is proposed in this paper to dimension the individual links of the Iub interface (between the Node B and the RNC) and furthermore to derive overbooking for the backbone link for elastic traffic. The analytical approach is validated by simulations. Furthermore, based on the proposed analytical approach, important dimensioning rules are summarized. Keywords-UMTS; IP-based UTRAN; Iub; elastic traffic; DiffServ; dimensioning; overbooking

Switching of Routing Algorithms in Wireless Networks for Fire Fighting

Fire fighters often work in dangerous and dynamic environments, which results in frequent change of network topologies and routing requirements. While the existing routing protocols are not able to cope with such a changeable environment, this paper proposes a self adaptive hybrid routing algorithm. This routing algorithm can switch between the proactive routing algorithm and reactive routing algorithm for each node pair automatically. An analytical model is created to describe the routing switch decision making algorithm. This model is based on a set of the cost functions. A numerical example shows the necessity of switching routing algorithms to reduce the overall control message overhead.

Automatic Handover Decision in Content Centric Networking

The current Internet architecture was designed more than 30 years ago for a very different set of services than those used today. Several new architectures have been proposed for a Future Internet to better meet todays and future requirements. Content Centric Networking (CCN) is one of those new architectures gaining worldwide attention by researchers and the focus of this article. CCN is based on naming content instead of hosts allowing routers to cache popular content. It has been shown that CCN can also support point-to-point real-time conversations, for example voice or video calls. However, it has not been defined how node mobility can be achieved in such a real-time scenario with strong time constraints. In this paper a close study to the handover algorithms has been carried out. A handover decision maker, which is based on neuro-fuzzy system (NFS) is proposed and evaluated. The results show that the proposed decision maker meets the design targets.

Adaptive Routing in Wireless Sensor Networks for Fire Fighting

Fire fighters often work in dangerous and dynamic environments, which results in frequent change of network topologies and routing requirements. While the existing routing protocols are not able to cope with such a changeable environment, this paper proposes a self adaptive hybrid routing algorithm. This routing algorithm can switch between the proactive routing algorithm and reactive routing algorithm for each node pair automatically. An analytical model is created to describe the routing switch decision making algorithm. This model is based on a set of the cost functions. A numerical example shows the necessity of switching routing algorithms to reduce the overall control message overhead.

Efficient Sensor Data Gathering and Resilient Communication for Rescue Scenarios

Wireless Sensor Networks (WSNs) have been used mainly to collect environmental data and send it to a base station. Routing protocols are needed to efficiently direct the information flows to the base station. Since sensor nodes have strict energy constraints, data gathering and communication schemes for WSNs need to be designed for an efficient utilization of the available resources. An emergency management scenario is investigated, where a sensor network is deployed as virtual lifeline when entering a building. In addition to navigation support, the virtual lifeline is also used for two purposes. Firstly, to exchange short voice messages between fire fighter and command post. For the communication between command post and fire fighter a fast and reliable routing protocol (EMRO) has been developed based on a broadcasting scheme. Secondly, for data gathering a network coding based algorithm has been designed. The feasibility of simultaneously using this virtual lifeline for data gathering and communications is investigated in this paper by means of simulation and real experiments. The resilience to packet loss and node failure, as well as the transmission delay are investigated by means of short voice messages for the communication part and temperature readings for data gathering.