Underwater Sensor Networks (UWSNs) are significantly different from land-based sensor networks. In UWSNs, the new features: low bandwidth, high latency, high network dynamics, high error probability, and 3-dimensional space, bring big challenges to network protocol design. In this technical report, we tackle one fundamental problem in UWSNs: scalable and energy efficient routing. We propose a novel routing protocol, called vector-based forwarding (VBF) to address these new challenges. VBF is scalable and energy efficient. In VBF, no state information is required on the sensor nodes and only a small fraction of the nodes are involved in routing. Moreover, we develop a localized and distributed self-adaptation algorithm to enhance the performance of VBF. The self-adaptation algorithm allows the nodes to weigh the benefit to forward packets and reduce energy consumption by discarding the low benefit packets. We evaluate the performance of VBF through extensive simulations. Our experiment results show that for networks with small or medium node mobility (2 m/s-10 m/s), VBF can effectively accomplish the goals of energy efficiency, high success of data delivery and low end-to-end delay.

This paper presents a highly efficient and accurate link-quality measurement framework, called EAR (Efficient and Accurate link-quality monitoR), for multi-hop wireless mesh networks, that has several salient features. First, it exploits three complementary measurement schemes: passive, cooperative, and active monitoring. EAR maximizes the measurement accuracy by (i) dynamically and adaptively adopting one of these schemes and (ii) opportunistically exploiting the unicast application traffic present in the network, while minimizing the measurement overhead. Second, EAR effectively identifies the existence of wireless link asymmetry by measuring the quality of each link in both directions of the link, thus improving the utilization of network capacity by up to 114%. Finally, its reliance on both the network layer and the IEEE 802.11-based device driver solutions makes EAR easily deployable in existing multi-hop wireless mesh networks without system recompilation or MAC firmware modification. EAR has been evaluated extensively via both ns-2-based simulation and experimentation on our Linux-based implementation. Both simulation and experimentation results have shown EAR to provide highly accurate link-quality measurements with minimum overhead.

In the context of IEEE 802.11b network testbeds, we examine the differences between unicast and broadcast link properties, and we show the inherent difficulties in precisely estimating unicast link properties via those of broadcast beacons even if we make the length and transmission rate of beacons be the same as those of data packets. To circumvent the difficulties in link estimation, we propose to estimate unicast link properties directly via data traffic itself without using periodic beacons. To this end, we design a data-driven routing protocol Learn on the Fly (LOF). LOF estimates link quality based on data traffic, and it chooses routes by way of a locally measurable metric ELD, the expected MAC latency per unit-distance to the destination. Using a realistic sensor network traffic trace and an 802.11b testbed of 195 Stargates, we experimentally compare the performance of LOF with that of existing protocols, represented by the geography-unaware ETX and the geography-based PRD. We find that LOF reduces end-to-end MAC latency by a factor of 3 and enhances energy efficiency by a factor up to 2.37, which demonstrate the feasibility as well as potential benefits of datadriven link estimation and routing.

In the context of IEEE 802.11b network testbeds, we examine the differences between unicast and broadcast link properties, and we show the inherent difficulties in precisely estimating unicast link properties via those of broadcast beacons even if we make the length and transmission rate of beacons be the same as those of data packets. To circumvent the difficulties in link estimation, we propose to estimate unicast link properties directly via data traffic itself without using periodic beacons. To this end, we design a data-driven routing protocol Learn on the Fly (LOF). LOF chooses routes based on ETX/ETT-type metrics, but the metrics are estimated via MAC feedback for unicast data transmission instead of broadcast beacons. Using a realistic sensor network traffic trace and an 802.11b testbed of ∼195 Stargates, we experimentally compare the performance of LOF with that of beacon-based protocols, represented by the geography-unaware ETX and the geography-based PRD. We find that LOF reduces end-to-end MAC latency by a factor of 3, enhances energy efficiency by a factor up to 2.37, and improves network throughput by a factor up to 7.78, which demonstrate the feasibility and the potential benefits of data-driven link estimation and routing.

Network-layer innovation has proven surprisingly difficult, in part because internetworking protocols ignore competing economic interests and because a few protocols dominate, enabling layer violations that entrench technologies. Many shortcomings of today’s internetwork layer result from its inflexibility with respect to the policies of the stakeholders: users and service providers. The consequences of these failings are well-known: various hacks, layering violations, and overloadings are introduced to enforce policies and attempt to get the upper hand in various “tussles”. The result is a network that is increasingly brittle, hostile to innovation, vulnerable to attack, and insensitive to concerns about accountability and privacy. Our project aims to design, implement, and evaluate through daily use a minimalist internetwork layer and auxiliary functionality that anticipates tussles and allows them to be played out in policy space, as opposed to in the packet-forwarding path. We call our approach postmodern internetwork architecture, because it is a reaction against many established network layer design concepts. The overall goal of the project is to make a larger portion of the network design space accessible without sacrificing the economy of scale offered by the unified Internet. We will use the postmodern architecture to explore basic architectural questions. These include: • What mechanisms should be supported by the network such that any foreseeable policy requirement can be

When the range of single-hop wireless communication is limited by distance or harsh radio propagation conditions, relays can be used to extend the communication range through multihop relaying. This paper targets the need in certain scenarios for rapid deployment of these relays when little or nothing is known in advance about a given environment and its propagation characteristics. Applications include first responders entering a large building during an emergency, search and rescue robots maneuvering a disaster sight, and coal miners working underground. The common element motivating this work is the need to maintain communications in an environment where single-hop communication is typically inadequate. This paper investigates the feasibility of the automated deployment of a multihop network. A deployment procedure is proposed that employs real-time link measurements and takes into account the physical layer characteristics of a mobile multipath fading environment and the radio in use. A prototype system is implemented based on 900 MHz TinyOS motes supporting low-speed data applications including text messaging, sensor data and Radio Frequency Identification (RFID)-assisted localization. Results of deployments in a hi-rise office building are presented.

Abstract—Greedy Distance Vector (GDV) is the first geographic routing protocol designed to optimize end-to-end path costs using any additive routing metric, such as: hop count, latency, ETX, ETT, etc. GDV requires no node location information. Instead, GDV uses estimated routing costs to destinations which are locally computed from node positions in a virtual space. GDV makes use of VPoD, a new virtual positioning protocol for wireless networks. Prior virtual positioning systems (e.g., Vivaldi and GNP) were designed for Internet hosts and require that each host measures latencies (routing costs) to distant hosts or landmarks. VPoD does not have this requirement and uses only routing costs between directly connected nodes. Experimental results show that the routing performance of GDV is better than prior geographic routing protocols when hop count is used as metric and much better when ETX is used as metric. As a geographic protocol, the storage cost of GDV per node remains low as network size increases. GDV provides guaranteed delivery for nodes placed in 2D, 3D, and higher dimensions. We also show that GDV and VPoD are highly resilient to dynamic topology changes. I.

In a Multi-hop Wireless Networks (MHWN), packets are routed between source and destination using a chain of intermediate nodes; chains are a fundamental communication structure in MHWNs whose behavior must be understood to enable building effective protocols. The behavior of chains is determined by a number of complex and interdependent processes that arise as the sources of different chain hops compete to transmit their packets on the shared medium. In this paper, we show that MAC level interactions play the primary role in determining the behavior of chains. We evaluate the types of chains that occur based on the MAC interactions between different links using realistic propagation and packet forwarding models. We discover that the presence of destructive interactions, due to different forms of hidden terminals, does not impact the throughput of an isolated chain significantly. However, due to the increased number of retransmissions required, the amount of bandwidth consumed is significantly higher in chains exhibiting destructive interactions, substantially influencing the overall network performance. These results are validated by testbed experiments. We finally study how different types of chains interfere with each other and discover that well behaved chains in terms of self-interference are more resilient to interference from other chains.

Abstract — Wireless sensor networks are characterized by multihop wireless lossy links and resource constrained nodes. Energy efficiency is a major concern in such networks. In this paper, we study Geographic Routing with Environmental Energy Supply (GREES) and propose two protocols, GREES-L and GREES-M, which combine geographic routing and energy-aware routing techniques and take into account the realistic lossy wireless channel condition and the renewal capability of environmental energy supply when making routing decisions. Simulation results show that GREESs are more energy efficient than the corresponding residual energy based protocols and geographic routing protocols without energy awareness. GREESs can maintain higher mean residual energy on nodes, and achieve better load balancing in terms of having smaller standard deviation of residual energy on nodes. Both GREES-L and GREES-M exhibit graceful degradation on end-to-end delay, but do not compromise the end-to-end throughput performance. I.

In the context of IEEE 802.11b network testbeds, we examine the differences between unicast and broadcast link properties, and we show the inherent difficulties in precisely estimating unicast link properties via those of broadcast beacons even if we make the length and transmission rate of beacons be the same as those of data packets. To circumvent the difficulties in link estimation, we propose to estimate unicast link properties directly via data traffic itself without using beacons. To this end, we design a beacon-free routing protocol Learn on the Fly (LOF). LOF estimates link quality based solely on data traffic, and it chooses routes by way of a locally measurable metric ELD, the expected MAC latency per unit-distance to the destination. Using a realistic sensor network traffic trace and an 802.11b testbed of 195 Stargates, we experimentally compare the performance of LOF with that of existing protocols, represented by the geographyunaware ETX and the geography-based PRD. We find that LOF reduces end-to-end MAC latency by a factor of 3, enhances energy efficiency by a factor up to 2.37, and improves route stability by 2 orders of magnitude. The results demonstrate the feasibility as well as potential benefits of data-driven beacon-free link estimation and routing. —experiment-based design and analysis, bursty convergecast, beacon-free geographic routing, data-driven link quality estimation, MAC latency, IEEE 802.11b, real time, energy, reliability 1