A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> Scarcity of Resources: <s> Wireless sensor networks promise fine-grain monitoring in a wide variety of environments. Many of these environments (e.g., indoor environments or habitats) can be harsh for wireless communication. From a networking perspective, the most basic aspect of wireless communication is the packet delivery performance: the spatio-temporal characteristics of packet loss, and its environmental dependence. These factors will deeply impact the performance of data acquisition from these networks.In this paper, we report on a systematic medium-scale (up to sixty nodes) measurement of packet delivery in three different environments: an indoor office building, a habitat with moderate foliage, and an open parking lot. Our findings have interesting implications for the design and evaluation of routing and medium-access protocols for sensor networks. <s> BIB001 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> Scarcity of Resources: <s> We present Trickle, an algorithm for propagating and maintaining code updates in wireless sensor networks. Borrowing techniques from the epidemic/gossip, scalable multicast, and wireless broadcast literature, Trickle uses a "polite gossip" policy, where motes periodically broadcast a code summary to local neighbors but stay quiet if they have recently heard a summary identical to theirs. When a mote hears an older summary than its own, it broadcasts an update. Instead of flooding a network with packets, the algorithm controls the send rate so each mote hears a small trickle of packets, just enough to stay up to date. We show that with this simple mechanism, Trickle can scale to thousand-fold changes in network density, propagate new code in the order of seconds, and impose a maintenance cost on the order of a few sends an hour. <s> BIB002 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> Scarcity of Resources: <s> In wireless sensor networks (WSNs), sensor nodes are usually battery-powered. Hence, energy efficiency is a critical factor in WSNs. Orthogonal modulations suitable for energy-limited WSNs have been investigated under the assumption that batteries are linear and ideal. However, these analyses are not valid when more realistic nonlinear battery models are considered. Based on a general model integrating WSN transmission modules with realistic battery models, we derive two battery power-conserving schemes for M-ary pulse position modulation (PPM) and frequency shift keying (FSK). We analyze and compare their battery power efficiencies in various wireless channels. Our results reveal that FSK is more power-efficient than PPM in sparse WSNs, while PPM may outperform FSK in dense WSNs. We also show that in sparse WSNs, the power advantage of FSK over PPM is no more than 3 dB; whereas in dense WSNs, the power advantage of PPM over FSK can be significant. <s> BIB003 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> Scarcity of Resources: <s> The dynamic nature of wireless communication and the stringent energy constraints are major challenges for the design of low-power wireless sensor network applications. The link quality of a wireless link is known for its great variability, dependent on the distance between nodes, the antennapsilas radiation characteristic, multipath, diffraction, scattering and many more. Especially for indoor and urban deployments, there are numerous factors impacting the wireless channel. In an extensive experimental study contained in the first part of this paper, we show the magnitude of this problem for current Wireless Sensor Networks (WSNs) and that based on the overall connectivity graph of a typical multihop WSN, a large portion of the links actually exhibit very poor characteristics. We present a pattern based estimation technique that allows assessing the quality of a link at startup and as a result to construct an optimal neighbor table right at the beginning using a minimum of resources only. Our estimation technique is superior compared to other approaches where protocols continue to decide on the fly which links to use expending valuable energy both for unnecessary retransmissions and recursive link estimation. <s> BIB004 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> Scarcity of Resources: <s> This document presents home control and automation application ::: specific requirements for Routing Over Low power and Lossy networks ::: (ROLL). In the near future many homes will contain high numbers of ::: wireless devices for a wide set of purposes. Examples include ::: actuators (relay, light dimmer, heating valve), sensors (wall switch, ::: water leak, blood pressure) and advanced controllers (RF-based AV ::: remote control, Central server for light and heat control). Because ::: such devices only cover a limited radio range, routing is often ::: required. The aim of this document is to specify the routing ::: requirements for networks comprising such constrained devices in a ::: home control and automation environment. <s> BIB005 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> Scarcity of Resources: <s> Advancement in wireless technology born a new generation of WSN which is appropriate for networking on the human body or in the human body. For data transfer among sensor nodes a point to point topology or multi-hop topology is used in these networks. In wireless body area network, only few sensors are used which are implanted in body or positioned on the body. These tiny sensors placed on patient’s body measure vital signs like blood <s> BIB006
The resource-constrained nature of LLNs imposes a new set of restrictions on developing efficient routing protocols and primitives. Generally speaking, the smallbattery capacity of a sensor node is the most restrictive factor and must be carefully considered BIB003 .Thus, a routing protocol should opt to send just enough updates to ensure the freshness of the constructed routes while maintaining low-power profile. 'Justenough' updates can vary from transmitting one update every second to a bulk transmission every few minutes, depending on the current conditions of the network and the type of application so to ensure that the application energy budget is met BIB002 . Links Unreliability: LLNs are characterized by lossy and unreliable links, and an update is not guaranteed to reach its destination from its first transmission BIB004 BIB001 . In some cases, the link loss rate in a network cannot be predicted beforehand and, even worse, the same link may exhibit different loss rates over time due to factors such as collisions at the receiver, the hidden terminal problem and interference with the radio transmitters of neighboring nodes BIB004 . However, there are still cases where an a priori loss rate can be roughly predicted depending, for example, on the statistics of previous deployments. Hence, a routing protocol should have the capacity to operate efficiently under such unreliable conditions. Mobility and Network Dynamics: The sensor nodes in LLNs are conceived to be stationary in the vast majority of scenarios, however, there are still cases in which there are a considerable number of mobile nodes BIB005 [55]   . For instance, in health monitoring applications, the usual mode of deployment is mobile because sensor nodes are attached to the human body to monitor health conditions remotely while the subjects go about their business BIB006 . Therefore, general routing strategies must take account of possible node mobility.