Opportunistic Forwarding Scheme Research Articles

Semi-Markov model for delivery delay prediction in multi-copy opportunistic networks with heterogeneous pairwise encounter rates

This work proposes an analytical model based on absorbing semi-Markov process for predicting the expected pairwise delivery delay for single and multi-copy opportunistic forwarding schemes. The framework can be applied to any inter-meeting times distribution. For the exponential case, it only requires the number of nodes and the pairwise encounter rates, which can be completely heterogeneous. Results show that the model predictions are quite accurate, with error values being less than 1% in some cases.

SACR: A Stability-Aware Cluster-Based Routing Protocol for Cognitive Radio Sensor Networks

Incorporating cognitive radio in traditional wireless sensor networks creates a new Internet of Things paradigm, which is termed as cognitive radio sensor networks (CRSNs). This paper proposes a novel stability-aware cluster-based routing (SACR) protocol for CRSNs. The major innovation of SACR lies in the seamless integration of opportunistic forwarding and a stable clustered architecture. In the aspect of cluster formation, we propose to take into consideration of spectrum dynamics and energy consumption in the clustering process. The resulting clustered architecture is stable and thus avoids large communication overhead due to high clustering frequency. For data routing, SACR adopts an opportunistic forwarding scheme which selects a unique cluster head by accounting for its cluster size, number of available channels, and hop distance to the gateway. Last but not least, SACR is a distributed routing protocol that does not require a dedicated common control channel. Simulation results show that SACR outperforms existing routing protocols for CRSNs in terms of packet delivery ratio, delay, energy consumption and signaling overhead.

POF: Probability-Driven Opportunistic Forwarding for Bike-Sharing System

The opportunistic networks and the bike-sharing systems have been attracting much research attention in these years. In this paper, the cycling trips and the buffers of bike stations are utilized to relay the large volume of data. The Markov chain is exploited to formulate and estimate the delivery ratio with the mathematical lattice model. Then, the probability-driven opportunistic forwarding (POF) scheme, which calculates the delivery potentials from the possible delivery paths, is proposed. The relay evaluations, which consider the proper sequence of cycling trips, are made to support the data forwarding decisions. Moreover, the strategies, i.e., the discard notification and the backward elimination, are exploited to drop the redundant replications of data as many as possible. The extensive simulation results show that the proposed scheme outperforms several benchmark algorithms, e.g., prophet, spray & wait, and JDER, in terms of the delivery ratio, the delivery latency, and the expected hop count.

A Light-Weight Opportunistic Forwarding Protocol with Optimized Preamble Length for Low-Duty-Cycle Wireless Sensor Networks

In wireless sensor networks, sensed information is expected to be reliably and timely delivered to a sink in an ad-hoc way. However, it is challenging to achieve this goal because of the highly dynamic topology induced from asynchronous duty cycles and temporally and spatially varying link quality among nodes. Currently some opportunistic forwarding protocols have been proposed to address the challenge. However, they involve complicated mechanisms to determine the best forwarder at each hop, which incurs heavy overheads for the resource-constrained nodes. In this paper, we propose a light-weight opportunistic forwarding (LWOF) scheme. Different from other recently proposed opportunistic forwarding schemes, LWOF employs neither historical network information nor a contention process to select a forwarder prior to data transmissions. It confines forwarding candidates to an optimized area, and takes advantage of the preamble in low-power-listening (LPL) MAC protocols and dual-channel communication to forward a packet to a unique downstream node towards the sink with a high probability, without making a forwarding decision prior to data transmission. Under LWOF, we optimize LPL MAC protocol to have a shortened preamble (LWMAC), based on a theoretical analysis on the relationship among preamble length, delivery probability at each hop, node density and sleep duration. Simulation results show that LWOF, along with LWMAC, can achieve relatively good performance in terms of delivery reliability and latency, as a receiver-based opportunistic forwarding protocol, while reducing energy consumption per packet by at least twice.

LAOF: location‐aware opportunistic forwarding scheme in mobile Ad hoc networks

AbstractDue to the high mobility of the nodes, the mobile ad hoc networks are expected to provide many opportunities for message forwarding in delay tolerant networks. Considering the typical mobility models, for example, the random waypoint (RWP) model and Manhattan model, we explore the probabilistic characteristics of the node contact provided by the mobile nodes. Following a progressive approach, we propose a location‐aware opportunistic forwarding scheme, which exploits the location information of the messages and the node mobility to conduct message forwarding. In order to provide a stable delivery ratio and avoid the extra network overhead, the message is forwarded to its destination regions or neighbor regions, which offer a better chance to reach the destination node. We construct a simulation environment, integrated with the RWP mobility trace and the Shanghai city taxis traces. Through extensive simulations, our scheme is demonstrated to outperform the best known opportunistic forwarding algorithms in terms of both delivery ratio/latency and transmission overhead. Copyright © 2014 John Wiley & Sons, Ltd.

Resilience and opportunistic forwarding: Beyond average value analysis

Opportunistic networks are systems with highly distributed operation, relying on the altruistic cooperation of highly heterogeneous, and not always software and hardware-compatible, user nodes. Moreover, the absence of central coordination and control makes them vulnerable to malicious attacks. In this paper, we study the resilience of popular forwarding protocols to a representative set of challenges to their normal operation. These include jamming locally disturbing message transfer between nodes, hardware/software failures and incompatibility among nodes rendering contact opportunities useless, and free-riding phenomena. We first formulate and promote the metric envelope concept as a tool for assessing the resilience of opportunistic forwarding schemes. Metric envelopes depart from the standard practice of average value analysis and explicitly account for the differentiated challenge impact due to node heterogeneity (device capabilities, mobility) and attackers’ intelligence. We then propose heuristics to generate worst- and best-case challenge realization scenarios and approximate the lower and upper bounds of the metric envelopes. Finally, we demonstrate the methodology in assessing the resilience of three popular forwarding protocols in the presence of the three challenges, and under a comprehensive range of mobility patterns. The metric envelope approach provides better insights into the level of protection path diversity and message replication provide against different challenges, and enables more informed choices in opportunistic forwarding when network resilience becomes important.

A Novel Opportunistic Greedy Forwarding Scheme in Wireless Sensor Networks

Greedy forwarding is a key mechanism of geographic routing using distance as a metric. As greedy forwarding only uses 1-hop neighbor node information, it minimizes routing overhead and is highly scalable. In existing greedy forwarding schemes, a node selects a next forwarding node based only on the distance. However, the signal strength in a realistic environment reduces exponentially depending on the distance, so that by considering only the distance, it may cause a large number of data packet retransmissions. To solve this problem, many greedy forwarding schemes have been proposed. However, they do not consider the unreliable and asymmetric characteristics of wireless links and thus cause the waste of limited battery resources due to the data packet retransmissions. In this paper, we propose a reliable and energy-efficient opportunistic greedy forwarding scheme for unreliable and asymmetric links (GF-UAL). In order to further improve the energy efficiency, GF-UAL opportunistically uses the path that is expected to have the minimum energy consumption among the 1-hop and 2-hop forwarding paths within the radio range. Comprehensive simulation results show that the packet delivery rate and energy efficiency increase up to about 17% and 18%, respectively, compared with the ones in PRR?Distance greedy forwarding.

An Opportunistic Forwarding Scheme Exploiting both Long Progress and Adaptive Rate in Wireless Networks

In Mobile Ad hoc Networks (MANET) geographic routing is characterized by local forwarding decision. Links with a long progress are preferred under the greedy forwarding rule. However in a real system long links tend to have a high packet loss rate due to multipath fading. A sub-optimal solution may separately exploit path diversity or rate adaptation. In this paper we study channel efficiency of multi-hop forwarding and try to jointly optimize rate adaptation and forwarder selection in geographic routing by the tradeoff between progress and instantaneous rate. We define a new metric-Bit Transfer Speed (BTS)-as the ratio of the progress made towards the destination to the equivalent time taken to transfer a payload bit. This metric takes overhead, rate and progress into account. Then we propose a packet forwarding scheme that Opportunistically exploits both long Progress and Adaptive Rate (OPAR) by a cross-layer design of routing and MAC. In OPAR each node selects for a packet the forwarder with the highest BTS. The forwarder changes as local topology (progress), packet size (overhead ratio) or channel state (data rate) varies. Simulation results show that compared with the normalized advance (NADV) [7] scheme and contention-based forwarding (CBF) [17] scheme, OPAR has lower packet loss and can effectively reduce channel occupation time by over 30% in the scenario with moderate mobility speeds.