A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> This paper proposes S-MAC, a medium-access control (MAC) protocol designed for wireless sensor networks. Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with individual nodes remaining largely inactive for long periods of time, but then becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in almost every way: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important. S-MAC uses three novel techniques to reduce energy consumption and support self-configuration. To reduce energy consumption in listening to an idle channel, nodes periodically sleep. Neighboring nodes form virtual clusters to auto-synchronize on sleep schedules. Inspired by PAMAS, S-MAC also sets the radio to sleep during transmissions of other nodes. Unlike PAMAS, it only uses in-channel signaling. Finally, S-MAC applies message passing to reduce contention latency for sensor-network applications that require store-and-forward processing as data move through the network. We evaluate our implementation of S-MAC over a sample sensor node, the Mote, developed at University of California, Berkeley. The experiment results show that, on a source node, an 802.11-like MAC consumes 2-6 times more energy than S-MAC for traffic load with messages sent every 1-10 s. <s> BIB001 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> In this paper we describe T-MAC, a contention-based Medium Access Control protocol for wireless sensor networks. Applications for these networks have some characteristics (low message rate, insensitivity to latency) that can be exploited to reduce energy consumption by introducing an activesleep duty cycle. To handle load variations in time and location T-MAC introduces an adaptive duty cycle in a novel way: by dynamically ending the active part of it. This reduces the amount of energy wasted on idle listening, in which nodes wait for potentially incoming messages, while still maintaining a reasonable throughput.We discuss the design of T-MAC, and provide a head-to-head comparison with classic CSMA (no duty cycle) and S-MAC (fixed duty cycle) through extensive simulations. Under homogeneous load, T-MAC and S-MAC achieve similar reductions in energy consumption (up to 98%) compared to CSMA. In a sample scenario with variable load, however, T-MAC outperforms S-MAC by a factor of 5. Preliminary energy-consumption measurements provide insight into the internal workings of the T-MAC protocol. <s> BIB002 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> Contrary to present conjectures, our medium access control (MAC) based performance studies revealed that battery capacity may not be used as the sole means for achieving energy-based fairness and system longevity for wireless mobile multi-hop ad hoc and sensor networks. Moreover, energy conservation may be attained only if valuable MAC (and PHY) input is passed to the network layer. Hence, we propose two schemes, the objective of which is to enhance the operation of existing power-based multi-path routing protocols via cross-layer designs and optimal load assignments. Our proposed schemes, namely, energy-constrained path selection (ECPS) and energy-efficient load assignment (E2LA), employ probabilistic dynamic programming techniques and utilize cross-layer interactions between the network and MAC layers. To the best of the authors' knowledge, this is the first time that MAC-originated information is used as the basis for achieving energy-efficient routing. <s> BIB003 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> Efficient use of energy while providing an adequate level of connection to individual sessions is of paramount importance in multi-hop wireless networks. Energy efficiency and connection quality depend on mechanisms that span several communication layers due to the existing co-channel interference among competing flows that must reuse the limited radio spectrum. Although independent consideration of these layers simplifies the system design, it is often insufficient for wireless networks when the overall system performance is examined carefully. The multi-hop wireless extensions and the need for routing users' sessions from source to the destination only intensify this point of view. In this work, we present a framework for cross-layer design towards energy-efficient communication. Our approach is characterized by a synergy between the physical and the medium access control (MAC) layers with a view towards inclusion of higher layers as well. More specifically, we address the joint problem of power control and scheduling with the objective of minimizing the total transmit power subject to the end-to-end quality of service (QoS) guarantees for sessions in terms of their bandwidth and bit error rate guarantees. Bearing to the NP-hardness of this combinatorial optimization problem, we propose our heuristic solutions that follow greedy approaches. <s> BIB004 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> Summary form only given. In many sensor network applications the major traffic pattern consists of data collected from several source nodes to a sink through a unidirectional tree. We propose DMAC, an energy efficient and low latency MAC that is designed and optimized for such data gathering trees in wireless sensor networks. We first show that previously proposed MAC protocols for sensor networks that utilize activation/sleep duty cycles suffer from a data forwarding interruption problem, whereby not all nodes on a multihop path to the sink are notified of data delivery in progress, resulting in significant sleep delay. DMAC is designed to solve the interruption problem and allow continuous packet forwarding by giving the sleep schedule of a node an offset that depends upon its depth on the tree. DMAC also adjusts the duty cycles adaptively according to the traffic load in the network. We further propose a data prediction mechanism and the use of more-to-send (MTS) packets in order to alleviate problems pertaining to channel contention and collisions. Our simulation results show that by exploiting the application-specific structure of data gathering trees in sensor networks, DMAC provides significant energy savings and latency reduction while ensuring high data reliability. <s> BIB005 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> With increasing interest in energy constrained multi-hop wireless networks (Bambos, N. et al., 1991), a fundamental problem is one of determining energy efficient communication strategies over these multi-hop networks. The simplest problem is one where a given source node wants to communicate with a given destination, with a given rate over a multi-hop wireless network, using minimum power. Here the power refers to the total amount of power consumed over the entire network in order to achieve this rate between the source and the destination. There are three decisions that have to be made (jointly) in order to minimize the power requirement. (1) The path(s) that the data has to take between the source and the destination. (Routing). (2) The power with each link transmission is done. (Power Control). (3) Depending on the interference or the MAC characteristics, the time slots in which specific link transmissions have to take place. (Scheduling). (4) To the best of our knowledge, ours is the first attempt to derive a performance guaranteed polynomial time approximation algorithm for jointly solving these three problems. We formulate the overall problem as an optimization problem with non-linear objective function and non-linear constraints. We then derive a polynomial time 3-approximation algorithm to solve this problem. We also present a simple version of the algorithm, with the same performance bound, which involves solving only shortest path problems and which is quite efficient in practice. Our approach readily extends to the case where there are multiple source-destination pairs that have to communicate simultaneously over the multi-hop network. <s> BIB006 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> We consider sensor networks where energy is a limited resource so that energy consumption must be minimized while satisfying given throughput requirements. Moreover, energy consumption must take into account both the transmission energy and the circuit processing energy for short-range communications. We emphasize that the energy efficiency must be supported across all layers of the protocol stack through a cross-layer design. In this context, we analyze energy-efficient joint routing, scheduling, and link adaptation strategies that maximize the network lifetime. We propose variable-length TDMA schemes where the slot length is optimally assigned according to the routing requirement while minimizing the energy consumption across the network. We show that the optimization problems can be transformed into or approximated by convex problems that can be efficiently solved using known techniques. The results show that multihop routing schemes are more energy-efficient when only transmission energy is considered, but single-hop transmissions may be more efficient when the circuit processing energy is considered. <s> BIB007 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> For a wireless sensor network, the primary design criterion is to save the energy consumption as much as possible while achieving the given task. Most of recent research works have only focused on the individual layer issues and ignore the importance of interworking between different layers in a sensor network. In this paper, we use a cross-layer approach to propose an energy-efficient sensor network - CoLaNet, which takes (a) the characteristics and requirements of the applications, (b) routing in the network layer, and (c) the data scheduling in MAC layer into consideration. Specifically, we use the characteristics of the applications to construct the routing tree and then formulate the routing and MAC issues into a vertex-coloring problem. By solving that problem, CoLaNet is able to determine the proper data transmission schedule for each sensor node. We evaluate CoLaNet through extensive simulations and the results show that such cross-layer approach is energy-efficient and able to achieve significant performance improvement as well. <s> BIB008 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> Wireless sensor networks represent a key technology enabler for enhanced health care and assisted living systems. Recent standardization eorts to ensure compatibility among sensor network systems sold by dierent vendors have produced the IEEE 802.15.4 standard, which specifies the MAC and physical layer behavior. This standard has certain draw-backs: it supports only single-hop communication; it does not mitigate the hidden terminal problem; and it does not coordinate node sleeping patterns. The IEEE 802.15.4 standard design philosophy assumes that higher layer mechanisms will take care of any added functionality. Building on IEEE 802.15.4, this paper proposes TImezone COordinated Sleep Scheduling (TICOSS), a mechanism inspired by MERLIN [2] that provides multi-hop support over 802.15.4 through the division of the network into timezones. TICOSS is cross-layer in nature, as it closely coordinates MAC and routing layer behavior. The main contributions of TICOSS are threefold: (1) it allows nodes to alternate periods of activity and periods of inactivity to save energy; (2) it mitigates packet collisions due to hidden terminals belonging to nearby star networks; (3) it provides shortest path routing for packets from a node to the closest gateway. Simulation experiments confirm that augmenting IEEE 802.15.4 networks with TICOSS doubles the operational lifetime for high trac scenarios. TICOSS has also been implemented on the Phillips AquisGrain modules for testing and eventual deployment in assisted living systems. <s> BIB009 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> Cross-layer design has been proposed as a promising paradigm to tackle various problems of wireless communication systems. Recent research has led to a variety of protocols that rely on intensive interaction between different layers of the classical layered OSI protocol architecture. These protocols involve different layers and introduce new ideas how layers shall communicate and interact. In existing cross-layer approaches, the violation of the OSI architecture typically consists in passing information between different adjacent or non-adjacent layers of one single station's protocol stack to solve an optimization problem and exploiting the dependencies between the layers. This paper proposes to go a step further and to consider cross-layer information exchange across different layers of multiple stations involved in multi-hop communication systems. It outlines possible application scenarios of this approach, and trades off between advantages and disadvantages of the proposed \emph {multi-hop cross-layer design}. It examines an application scheme in a scenario of a wireless sensor network environment operating with a recent energy-efficient power saving protocol. <s> BIB010 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> This paper proposes a distributed energy-efficient routing algorithm for mobile Ad Hoc networks (MANETs). We adopt the cross-layer design paradigm. The distance from the source node to the destination node is estimated based on the received signal strength indication(RSSI) of the packets and is used to adaptively adjust the backoff time of the MAC layer. A distance threshold and a packet count threshold are used to schedule the transmissions of packets in the Network layer. The algorithm is distributed and works without needing any global network information or control packet. Experimental results show that the routing algorithm is energy-efficient and drastically alleviates the Broadcast Storm Problem. <s> BIB011 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> This article presents SCSP (for “Sleep Collect and Send Protocol”) for wireless sensor networks, a network-MAC cross layer design that resolves the inherent conflict between energy efficiency and throughput. The protocol uses in its MAC layer a new paradigm that we call “sleep, collect and send”. The idea of SCSP is that a router sleeps for a given amount of time, wakes up and collects data from its children and other routers and then send them into a burst during a period of time that we call transmission period. In its network layer, the protocol uses a hierarchical tree structure as network architecture and a tree routing protocol. SCSP does not require synchronization between routers and dynamically calculates the sleep and collect periods according to the amount of incoming traffic. The protocol is implemented and simulated in OPNET simulator. <s> BIB012 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network and MAC Layer Schemes <s> Recent advancements in processor, memory and radio technologies have enabled cheap and small sensors which are capable of sensing, communication and computation. Most of the Wireless Sensor Networks have limitation of battery power and in most of the applications it is not possible to replace the battery of a node. Considering this scarce energy and processing resources of WSN, we try to establish a joint optimization and design of networking layers i.e., cross layer design which could be a promising alternative to the inefficient traditional layered protocol design. In this paper we propose energy efficient cross layer design of the MAC and Routing protocol namely Energy Efficient cross-layer design protocol by using token passing mechanism for WSN. This proposed protocol proves to be better than some of the existing protocols and it is shown with the help of simulations. <s> BIB013
The network layer is responsible for selecting the optimal routing path for data packets. Different routing decisions alter the set of links to be scheduled and thereby influence the performance of the MAC layer, e.g., if the routing protocol chooses flow paths that are closer to each other, the subsequently higher interference and potential contention in the network make it harder for the MAC to resolve the transmission conflicts. When QoS requirements are ignored and link costs that accurately quantify the energy consumption can be assigned, the network layer becomes the sole determinant of energy consumption BIB004 . These link costs, however, depend on the transmit power which is a function of decisions made at the MAC and physical layers. In many areas of adaptive MAC protocol design: S-MAC BIB001 , T-MAC BIB002 , and DMAC BIB005 , the research is focused on the adaptation of the MAC layer and ignores the inter-working between different layers thereby attempting to avoid collisions among neighbor nodes without considering any routing information from the network layer or traffic patterns from the application. The best routing path can be identified by extracting key information from the lower layers, such as traffic volume, link quality, and collision data, to enhance performance at the network layer  BIB011 BIB013 BIB006 . It could be argued that integrating routing with MAC as part of a cross-layer jointly optimized solution makes sense as the two functions are very closely coupled and a case can be made for integrating the layers either as one complete module or two closely coupled modules in the same layer. If routing is not taken into account by the MAC layer, optimal performance can only be achieved locally  . Cui et al. BIB007 proposed that energy efficiency must be supported across all layers of the protocol stack through cross-layer design. The proposed scheme incorporated a variable length TDMA protocol where the slot length is optimally assigned depending on the network layer routing requirement while minimizing the energy consumption across the network. CoLaNet BIB008 considered characteristics of the application to make better routing path choices at the network layer and demonstrated energy savings over S-MAC. Safwati et al. BIB003 proposed schemes to utilize cross-layer interactions between the MAC and network layers where the MAC sublayer provides the network layer with information pertaining to successfully receiving a CTS or an ACK frame or failure to receive one. This allows the network layer to choose the route that minimizes the probability of error to achieve the most energy effective route. Most cross-layer designs look at the integration of adjacent or non-adjacent layers to adapt the protocol stack to deliver efficiencies over the traditional stack architecture. Schemes that extend the optimizing techniques to layers of intermediate nodes can provide additional energy saving benefits BIB010 . The network layer of a source node could be made aware of the channel conditions in the lower layers of the nodes in the neighborhood as part of a multi-hop scenario. Nodes could detect congestion and interference at the MAC layer and immediately react to it at the network layer. Routing decisions could be better addressed as more knowledge about the MAC and physical layers of adjacent nodes is available. Ruzzelli et al. BIB009 proposed Timezone Coordinated Sleep Scheduling (TICOSS) protocol as a cross-layer energy efficient multi-hop protocol based on 802.15.4. The network was divided up into time zones where each one takes turn in the transmission where nodes in the farthest time zone start the transmission. In the next slot the farthest but one sends its data and so on until the sink is reached. The protocol mitigates the hidden node problem, provides configurable shortest path routing to the PAN coordinator and almost doubles node lifetime for high traffic scenarios compared to standard WSN protocols. Any protocol operating at the network layer needs to resolve the inherent conflict between energy efficiency and throughput. Sleep Collect and Send Protocol (SCSP) BIB012 dynamically calculates the node sleep and data receive (collect) periods depending on the amount of incoming traffic. The network layer uses a modified version of ZigBee routing that is more tolerant to node failures. The MAC layer provides the list of neighbor nodes to the network layer, which in turn provides multiple forwarding choices to it. Therefore, the MAC protocol has the option to change to the next hop router during transmission if the message is not successfully transmitted after n number tries. SCSP saves energy consumption by switching between active and sleep periods by dynamically adapting them depending on the amount of received traffic. The protocol uses a simple but efficient routing protocol that does not need route maintenance or discovery and works jointly with the MAC layer to enhance its fault tolerance properties. Simulations show that SCSP extends the network lifetime and connectivity in comparison with 802.15.4. As the channel quality can vary due to the changing characteristics inherent in the physical layer of a wireless network, resource at the MAC layer is therefore, variable  . These variations can result in fluctuations of link capacity and transmission since transmission rate is related to many factors, not just link quality. Joint optimization for rate control coupled with resource allocation and routing in the context of multichannel operation is a complex challenge for network/MAC designers.