Opportunistic Forwarding Protocol Research Articles

Pushing the Limits of Transmission Concurrency for Low Power Wireless Networks

Concurrent transmission (CT) has been widely adopted to optimize the throughput of various data transmissions in wireless networks, such as bulk data dissemination and high-rate data collection. In CT, besides the possible data frame collision at receivers, we observe that acknowledgment frame (ACK) collision at senders can also significantly diminish concurrency opportunities. In this article, to avoid the potential ACK collision in CT, we propose ALIGNER which develops a new transmission pattern to coordinate concurrent senders in a distributed manner. The key idea is to align the silent periods of concurrent transmitters. To achieve this goal, we align the end of data frames concurrently transmitted by several senders. Therefore, the potentially arriving ACKs can avoid a collision with ongoing data transmissions because the concurrent senders are in a listening state to wait for receivers’ ACKs for a short and fixed period. ALIGNER can be applied for both deterministic and opportunistic forwarding protocols. It optionally uses a random back-off and slotted ACK mechanism to avoid a potential collision among simultaneously arrived ACKs in opportunistic forwarding. In addition, ALIGNER adopts a tailor-made metrics to analyze the throughput benefit of concurrent transmission for both deterministic and opportunistic data collection protocols. We have implemented ALIGNER in TinyOS and conducted extensive experiments on a real testbed. Experimental results show that ALIGNER can significantly increase the concurrency opportunities in both deterministic (up to 105%) and opportunistic (up to 89.7%) forwarding compared with the state-of-the-art CT methods.

An Efficient Delay Tolerant Networks Routing Protocol for Information-Centric Networking

Delay tolerant networks (DTN) is a good candidate for delivering information-centric networking (ICN) messages in fragmented networks due to disaster. In order to efficiently deliver ICN messages in DTN, the characteristics of multiple requester nodes for the same content and multiple provider nodes for the same request should be used efficiently. In this paper, we propose an efficient DTN routing protocol for ICN. In the proposed protocol, requester information for request packet, which is called an Interest in ICN, is shared by exchanging status table with requested Data ID, requester ID, and satisfaction flag, where satisfaction flag is defined to show the delivery status of Data, so that unnecessary forwarding of Data is avoided. Data is forwarded to a more probable node by comparing average delivery predictability to a set of requesters. Performance of the proposed protocol was evaluated using simulation from the aspect of Data delivery probability and Data overhead, for varying buffer sizes, number of relay nodes, and time-to-live (TTL) of Data. The results show that the proposed protocol has better Data delivery probability, compared to content distribution and retrieval framework in disaster networks for public protection (CIDOR) and opportunistic forwarding (OF) protocols, although there is a tradeoff from the aspect of Data overhead for varying buffer sizes and number of relay nodes.

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.

Duplicate Detectable Opportunistic Forwarding in Duty-Cycled Wireless Sensor Networks

Opportunistic routing, offering relatively efficient and adaptive forwarding in low-duty-cycled sensor networks, generally allows multiple nodes to forward the same packet simultaneously, especially in networks with intensive traffic. Uncoordinated transmissions often incur a number of duplicate packets, which are further forwarded in the network, occupy the limited network resource, and hinder the packet delivery performance. Existing solutions to this issue, e.g., overhearing or coordination based approaches, either cannot scale up with the system size, or suffer high control overhead. We present Duplicate-Detectable Opportunistic Forwarding (DOF), a duplicate-free opportunistic forwarding protocol for low-duty-cycled wireless sensor networks. DOF enables senders to obtain the information of all potential forwarders via a slotted acknowledgment scheme, so the data packets can be sent to the deterministic next-hop forwarder. Based on light-weight coordination, DOF explores the opportunities as many as possible and removes duplicate packets from the forwarding process. We implement DOF and evaluate its performance on an indoor testbed with 20 TelosB nodes. The experimental results show that DOF reduces the average duplicate ratio by 90%, compared to state-of-the-art opportunistic protocols, and achieves 61.5% enhancement in network yield and 51.4% saving in energy consumption.

Connectivity-based Cross-Layer Opportunistic Forwarding for MWSNs

ABSTRACTMobile wireless sensor networks (MWSNs) consist of many sensor nodes that are randomly distributed in the environment to gather information. In MWSNs, the transmission path is affected due to node mobility and node failures. Routing protocols in MWSNs must adjust to topology changes and should determine the path with minimum overheads. Some of the existing works on the opportunistic routing minimize the energy consumption, but have large overheads and duplicate packet transmissions. In this paper, we have designed and implemented a connectivity-based cross-layer opportunistic forwarding protocol for mobile wireless sensor networks. We estimate the expected energy consumption cost for forwarding the data using prioritized forwarder list and node's connectivity metric. Connectivity metric signifies the ability of node to partition the network on its failure. To reduce retransmissions, we implement forwarding agreement mechanism among the nodes in the forwarder list, if the desired relay node has moved or failed. Our analysis shows that our protocol consumes less energy compared to conventional routing protocols. Simulation results for our protocol are compared with Energy Efficient Opportunistic Routing (EEOR), Destination Sequenced Distance Vector and ad hoc on-demand multipath distance vector protocol for energy efficiency, overheads, and packet loss. Our protocol exhibits 22% improvement in energy consumption compared to energy efficient opportunistic routing (EEOR) and also significant improvements for other performance parameters.

Security and trust management in opportunistic networks: a survey

AbstractAs a new networking paradigm, opportunistic networking communications have great vision in animal migration tracking, mobile social networking, network communications in remote areas and intelligent transportation, and so on. Opportunistic networks are one of the evolutionary mobile ad hoc networks, whose communication links often suffer from frequent disruption and long communication delays. Therefore, many opportunistic forwarding protocols present major security issues, and the design of opportunistic networks faces serious challenges such as how to effectively protect data confidentiality and integrity and how to ensure routing security, privacy, cooperation, and trust management. In this paper, we first systematically describe the security threats and requirements in opportunistic networks; then propose a general security architecture of opportunistic networks; and then make an in‐depth analysis on authentication and access control, secure routing, privacy protection, trust management, and incentive cooperation mechanisms; and at the same time, we present a comparison of various security and trust solutions for opportunistic networks. Finally, we conclude and give future research directions. Copyright © 2014 John Wiley & Sons, Ltd.

Opportunistic RPL for reliable AMI mesh networks

Driven by the need to improve energy efficiency and reduce environmental impact, we observe a thrust towards enabling a Smart Grid. It is envisaged that to achieve these goals, the Smart Grid will be equipped with communications infrastructure and mechanisms that will enable near real-time control of the grid components. One of the key elements of the Smart Grid is the advanced metering infrastructure (AMI) which is expected to facilitate the transport of meter readings from a smart electricity meter at the customer premises to the utility provider, and control data in the other direction. These communications can be potentially realized by deploying a self-organizing mesh network composed of smart metering nodes connected to concentrator nodes which in turn are connected to the utility provider data management systems. This paper explores a cooperative communications approach to improve reliability of such mesh networks. The proposed opportunistic forwarding protocol called ‘ORPL’ has been realized as an enhancement on top of the routing protocol for low power and lossy networks, a connectivity enabling mechanism in AMI mesh networks. In ORPL, smart meter nodes select multiple candidate relays to facilitate reliable transport of smart metering data to the concentrator node. Moreover, it is designed to work in a distributed manner thereby ensuring scalability. We also present a further extension to ORPL, i.e., ORPLx with adaptive medium access control retransmit limit, which reduces unnecessary retransmissions. Our protocols have been evaluated and verified with comprehensive experimental results, demonstrating their effectiveness and favorable characteristics.

Offloading mobile data from cellular networks through peer-to-peer WiFi communication: A subscribe-and-send architecture

Currently cellular networks do not have sufficient capacity to accommodate the exponential growth of mobile data requirements. Data can be delivered between mobile terminals through peer-to-peer WiFi communications (e.g. WiFi direct), but contacts between mobile terminals are frequently disrupted because of the user mobility. In this paper, we propose a Sub-scribe-and-Send architecture and an opportunistic forwarding protocol for it called HPRO. Under Subscribe-and-Send, a user subscribes contents on the Content Service Provider (CSP) but does not download the subscribed contents. Some users who have these contents deliver them to the subscribers through WiFi opportunistic peer-to-peer communications. Numerical simulations provide a robust evaluation of the forwarding performance and the traffic offloading performance of Subscribe-and-Send and HPRO.

On Multicopy Opportunistic Forwarding Protocols in Nondeterministic Delay Tolerant Networks

Delay Tolerant Networks (DTNs) are characterized by nondeterministic mobility and connectivity. Message routing in DTNs usually employs a multicopy forwarding scheme. To avoid the cost associated with flooding, much effort has been focused on opportunistic forwarding, which aims to reduce the cost of forwarding while retaining high routing performance by forwarding messages only to nodes that have high delivery probabilities. This paper presents two multicopy forwarding protocols, called optimal opportunistic forwarding (OOF) and OOF-, which maximize the expected delivery rate and minimize the expected delay, respectively, while requiring that the number of forwardings per message does not exceed a certain threshold. Our contributions in this paper are summarized as follows: We apply the optimal stopping rule in the multicopy opportunistic forwarding protocol. Specifically, we propose two optimal opportunistic forwarding metrics to maximize delivery probability and minimize delay, respectively, with a fixed number of copies and within a given time-to-live. We implement and evaluate OOF and OOF- as well as several other representative forwarding protocols, i.e., Epidemic, Spray-and-wait, MaxProp* and Delegation. We perform trace-driven simulations using both real and synthetic traces. Simulation results show that, in the traces where nodes have regular intermeeting times, the delivery rates of OOF and OOF- can be 30 percent greater than the compared routing protocols.

An opportunistic forwarding protocol with relay acknowledgment for vehicular ad hoc networks

AbstractRobust and efficient data delivery in vehicular ad hoc networks (VANETs) with high mobility is a challenging issue due to unstable wireless links and dynamic topology changes. In this vehicular environment, the exchanges of topology information and discoveries of routing paths on an end‐to‐end basis are not desired, because the network topology changes rapidly and the information is out‐of‐date in short. In this paper, we propose a contention based forwarding mechanism, which locally exploits geographic location information in order to achieve robustness of data delivery for vehicular communications. A node that is closer to the destination node has a higher priority in competing for the wireless channel, and forwards packets as a relay node earlier than other adjacent nodes. When a packet is forwarded by a relay node, its preceding node informs adjacent nodes that it has been already relayed to prevent the duplications of packet delivery. Through ns‐2 simulations, we show that the proposed scheme can significantly improve the network performance in terms of the packet delivery ratio and the end‐to‐end delay in various synthetic and trace‐based realistic VANET scenarios with a wide range of vehicle speed and density. Copyright © 2010 John Wiley & Sons, Ltd.