Swades De

Integrated cellular and ad hoc relaying systems: iCAR

Integrated cellular and ad hoc relaying systems (iCAR) is a new wireless system architecture based on the integration of cellular and modern ad hoc relaying technologies. It addresses the congestion problem due to unbalanced traffic in a cellular system and provides interoperability for heterogeneous networks. The iCAR system can efficiently balance traffic loads between cells by using ad hoc relaying stations (ARS) to relay traffic from one cell to another dynamically. This not only increases the systems capacity cost effectively, but also reduces the transmission power for mobile hosts and extends system coverage. We compare the performance of the iCAR system with conventional cellular systems in terms of the call blocking/dropping probability, throughput, and signaling overhead via analysis and simulation. Our results show that with a limited number of ARSs and some increase in the signaling overhead (as well as hardware complexity), the call blocking/dropping probability in a congested cell and the overall system can be reduced.

GPS free coordinate assignment and routing in wireless sensor networks

In this paper we consider the problem of constructing a coordinate system in a sensor network where location information is not available. To this purpose we introduce the virtual coordinate assignment protocol (VCap) which defines a virtual coordinate system based on hop distances. As compared to other approaches, VCap is simple and have very little requirements in terms of communication and memory overheads. We compare by simulations the performances of greedy routing using our virtual coordinate system with the one using the physical coordinates. Results show that the virtual coordinate system can be used to efficiently support geographic routing.

Meshed multipath routing with selective forwarding: an efficient strategy in wireless sensor networks

Due to limited functionalities and potentially large number of sensors, existing routing strategies proposed for mobile ad hoc networks are not directly applicable to wireless sensor networks. In this paper, we present a meshed multipath routing (M-MPR) protocol with selective forwarding (SF) of packets and end-to-end forward error correction (FEC) coding. We also describe a meshed multipath searching scheme suitable for sensor networks, which has a reduced signaling overhead and nodal database. Our performance evaluations show that (1) M-MPR achieves a much improved throughput over conventional disjoint multipath routing with comparable power consumption and receiver complexity; (2) to successfully route a message using FEC coding, selective forwarding (SF) consumes much less network resources, such as channel bandwidth and battery power, than packet replication (or limited flooding).

An integrated cross-layer study of wireless CDMA sensor networks

In this paper, we characterize analytically the multiaccess interference in wireless code-division multiple-access sensor networks with uniformly random distributed nodes and study the tradeoff between interference and connectivity. To provide a guideline for improving system behavior, three competitive deterministic topologies are evaluated along with the random topology in terms of link-level and network-level (routing) performance. The impact of signature code length and receiver design on the network performance for different topologies is also studied.

Bounds on hop distance in greedy routing approach in wireless ad hoc networks

Wireless ad hoc networks are generally characterised by random node locations and multi-hop routes. A quantitative knowledge of the relation between hop count and Euclidean distance could provide a better understanding of important network parameters such as end-to-end delay, power consumption along the route, and node localisation. In this paper, we present an analytic approach to capture the statistics on hop count for a given source-to-destination Euclidean distance in a greedy routing approach. We also show that, for a given hop count, the bounds on Euclidean distance can be computed from the distribution characteristics of per-hop progress.

Smart RF energy harvesting communications: challenges and opportunities

RF energy harvesting (RFH) is emerging as a potential method for the proactive energy replenishment of next generation wireless networks. Unlike other harvesting techniques that depend on the environment, RFH can be predictable or on demand, and as such it is better suited for supporting quality-of-service-based applications. However, RFH efficiency is scarce due to low RF-to-DC conversion efficiency and receiver sensitivity. In this article, we identify the novel communication techniques that enable and enhance the usefulness of RFH. Backed by some experimental observations on RFH and the current state of the art, we discuss the challenges in the actual feasibility of RFH communications, new research directions, and the obstacles to their practical implementation.

Integrated cellular and ad hoc relay (iCAR) systems: pushing the performance limits of conventional wireless networks

Performance of iCAR system - a new load balancing scheme in wireless networks - is analyzed. Traffic capacity enhancement of the iCAR system with respect to the conventional cellular system, without any load balancing, is evaluated. It is shown that, with a moderate amount of relay coverage, perfect load balancing can be achieved, thus enabling the system to support maximum possible traffic intensity for a given grade of service.

Meshed multipath routing: an efficient strategy in sensor networks

Due to limited functionalities and potentially large number of sensors, conventional routing strategies proposed for distributed control applications (such as mobile ad hoc networks) are not directly applicable in wireless sensor networks. In this paper, we propose a novel mesh multipath routing (M-MPR) with selective forwarding of packets. Our evaluation shows that M-MPR achieves much improved throughput performance over conventional disjoint multipath routing, with comparable power consumption and receiver complexity. We also show that for comparable throughput, M-MPR achieves better load distribution and requires lesser route maintenance overhead with respect to packet forwarding along a preferred route.

On hop count and euclidean distance in greedy forwarding in wireless ad hoc networks

In this letter, a probabilistic analysis is presented that captures the bounds on hop count from a given Euclidean distance between two nodes and vice versa in a greedy forwarding in wireless ad hoc networks. Accuracy of the analysis is verified via network simulations. The results could be useful in ad hoc and sensor network design and performance evaluation.

Trigger-based distributed QoS routing in mobile ad hoc networks

Performance of existing routing protocols in mobile ad hoc networks for real-time applications is limited by high control traffic and database maintenance overhead. We observe that by proper coupling of nodal mobility and location information, real-time applications can be served with limited control traffic and database requirements. In this paper, we investigate a trigger-based (on-demand) distributed routing protocol, called TDR, for supporting real-time applications in mobile ad hoc networks. For increased resource efficiency, the nodal database size is reduced by maintaining only the local neighborhood information. Only one route per session is maintained and the reroute routine is invoked before any active link fails. In addition, by making efficient use of the location information, the control overhead for rerouting is further reduced. Our evaluation shows that the TDR protocol provides better QoS and requires lower control overhead compared to the other existing real-time QoS aware ad hoc routing protocols.