A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network Layer <s> Wireless distributed microsensor systems will enable the reliable monitoring of a variety of environments for both civil and military applications. In this paper, we look at communication protocols, which can have significant impact on the overall energy dissipation of these networks. Based on our findings that the conventional protocols of direct transmission, minimum-transmission-energy, multi-hop routing, and static clustering may not be optimal for sensor networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based protocol that utilizes randomized rotation of local cluster based station (cluster-heads) to evenly distribute the energy load among the sensors in the network. LEACH uses localized coordination to enable scalability and robustness for dynamic networks, and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. Simulations show the LEACH can achieve as much as a factor of 8 reduction in energy dissipation compared with conventional outing protocols. In addition, LEACH is able to distribute energy dissipation evenly throughout the sensors, doubling the useful system lifetime for the networks we simulated. <s> BIB001 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network Layer <s> The paper presents UWB channel measurements from 3 to 6 GHz for a body area network (BAN) in an anechoic chamber and an office room. Both, transmit and receive antenna were placed directly on the body. Channel parameters as delay spread and path loss are extracted from the measurements and the influence of the body is highlighted. We show that in some situations there are significant echoes from the body (e.g. from the arms) and we observed deterministic echoes from the floor that could help to simplify a RAKE receiver structure. Finally, we consider the overall energy consumption of the BAN and give decision regions for singlehop and multihop links in relation to signal processing energy. <s> BIB002 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network Layer <s> Implanted biological sensors are a special class of wireless sensor networks that are used in-vivo for various medical applications. One of the major challenges of continuous in-vivo sensing is the heat generated by the implanted sensors due to communication radiation and circuitry power consumption. This paper addresses the issues of routing in implanted sensor networks. We propose a thermal-aware routing protocol that routes the data away from high temperature areas (hot spots). With this protocol each node estimates temperature change of its neighbors and routes packets around the hot spot area by a withdraw strategy. The proposed protocol can achieve a better balance of temperature rise and only experience a modest increased delay compared with shortest hop, but thermal-awareness also indicates the capability of load balance, which leads to less packet loss in high load situations. <s> BIB003 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network Layer <s> One of the major applications of sensor networks in near future will be in the area of biomedical research. Implanted biosensor nodes are already being used for various medical applications. These in-vivo sensor networks collect different biometric data and communicate the data to the base station wirelessly. These sensor networks produce heat, as the nodes have to communicate among themselves wirelessly. The rise in temperature of the nodes due to communication should not be very high. A high temperature of the in-vivo nodes for a prolonged period might damage the surrounding tissues. In this paper, we propose a new routing algorithm that reduces the amount of heat produced in the network. In the simple form, the algorithm routes packets to the coolest neighbor without inducing routing loops. In the adaptive form, the algorithm uses mechanisms to adapt to topologies with low degree of connectivity and to switch to shortest path routing if a time threshold is exceeded. The proposed algorithm performs much better in terms of reducing the amount of heat produced, delay and power consumption compared to the shortest hop routing algorithm and a previously proposed Thermal Aware Routing Algorithm (TARA). <s> BIB004 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network Layer <s> In this paper, we propose Least Total-Route- Temperature (LTRT), a thermal aware routing algorithm, to reduce temperature caused by biomedical sensors implanted in human bodies. In the proposed scheme, nodes' temperatures are converted into graph weights and minimum temperature routes are obtained. Simulations are conducted to show the advantages of the proposed scheme when comparing with three other related schemes. <s> BIB005 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network Layer <s> Wireless body area networks (WBANs) offer many promising new applications in the area of remote health monitoring. An important element in the development of a WBAN is the characterization of the physical layer of the network, including an estimation of the delay spread and the path loss between two nodes on the body. This paper discusses the propagation channel between two half-wavelength dipoles at 2.45 GHz, placed near a human body and presents an application for cross-layer design in order to optimize the energy consumption of different topologies. Propagation measurements are performed on real humans in a multipath environment, considering different parts of the body separately. In addition, path loss has been numerically investigated with an anatomically correct model of the human body in free space using a 3-D electromagnetic solver. Path loss parameters and time-domain channel characteristics are extracted from the measurement and simulation data. A semi-empirical path loss model is presented for an antenna height above the body of 5 mm and antenna separations from 5 cm up to 40 cm. A time-domain analysis is performed and models are presented for the mean excess delay and the delay spread. As a cross-layer application, the proposed path loss models are used to evaluate the energy efficiency of single-hop and multihop network topologies. <s> BIB006 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network Layer <s> Modern diagnosis system has been evolved to equip human being with advanced health-service. In vivo sensors have come up to contribute in this field with its support in miniature, complex operation as implanted in a human body. Implanted sensor solutions like artificial retina, pacemaker and implanted cardioverter defibrillators, insulin pump, glucose monitor — are remarkable inventions in medical science. But, these implanted sensor nodes exhibit temperature at packet transmission or processing time that can be dangerous for surrounding human tissues. With the advancement of wireless communication and sensor network technology, thermal aware routing algorithms have been proposed for this type of sensor network. But, these algorithms suffer from disadvantages like hotspot creation, computational complexity overhead or redundant hop traversal etc. We also have to consider energy constraints like limited battery life of this miniature form of sensor nodes. We have tried to solve these problems with lightweight event-based communication (publish-subscribe system) in this type of sensor network. We have proposed a lightweight temperature scheduling routing algorithm for this implanted sensor network. Proposed routing protocol is considered to schedule temperature in implanted sensor nodes deployed in the joint operation of cancer hyperthermia, radio-therapy and chemo-therapy. <s> BIB007 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Network Layer <s> In wireless sensor network (WSN), the routing protocol is one of the most important aspects. LEACH (Low Energy Adaptive clustering Hierarchy) is the first routing protocol based on cluster structure. Though there are a lot of improvements on LEACH protocol at present, cluster heads still play the most important role in these routing protocols. Cluster heads are responsible for gathering information, transmitting packets and aggregating data. A mass of work processed by cluster head will make it consume too much energy. Then the lifetime of WSN will be shortened. Thus, in this paper we propose an improvement on LEACH protocol in order to monitor large-scale environment longer and stably. Gateways will construct a multi-hops path to transmit packet, Cluster heads are just responsible for gathering and aggregating data from cluster members. Thus, the task of transmitting packet is separated from cluster head. As the experiment results shown, the improved protocol can balance energy consumption and extend the lifetime of the network. <s> BIB008
In a traditional WSN context the network layer has to cater for numerous disparate nodes potentially spread over a wide geographical area. Network layer protocols make use of routing algorithms that use multi-hop to route packets to the destination node. In comparison to WSNs, WBAN nodes are mobile, likely to be clustered in specific areas and do not have the same extensive multi-hop requirement as WSNs. In comparison to WSNs, the bandwidth available to WBANs is limited, likely to be shared with other local ISM band devices and is subject to physical layer attributes such as interference, fading, and attenuation due to the specific characteristics of the human body. Existing WSN research at the network layer doesn't fully consider the range of heterogeneous nodes within a WBAN and are generally concerned with energy efficient routing via static nodes rather than the extensive body movements in a WBAN. The required routing algorithm complexity within WBANs is low in comparison to large-scale WSNs where nodes are potentially distributed across large-scale areas. However, the unique factors relating to communicating in and around the human body mean that network layer issues need to form an important part of WBAN protocol design. The standard WBAN architecture of a number of heterogeneous nodes linked to a BCU or sink device often assumes single hop routing where all node communications are transmitted directly to the BCU. Zawowski et al. BIB002 looked at the potential of multi-hop in a UWB based WBAN with an energy comparison for a transmission from a node located on the back of a patient to a node on the chest. Results showed that a multi-hop strategy is recommended if the energy for pulse generation and reception is higher than a ten thousandth part of the energy for bit encoding and decoding. The criteria to use multi-hop depends on the ratio of the energy consumption needed for decoding/coding and receiving/generating a UWB pulse. In experiments to evaluate path loss models for human body parts (torso, back, arm, leg) Reusens et al. BIB006 and later Joseph et al.  attempted to identify whether single or multi-hop transmissions are preferable in a WBAN. Observations in both showed that for nodes furthest away from the sink, there is scope for additional energy saving as these nodes consume the most energy and will die first. However, in the multi-hop scenario, the nodes closest to the sink consumed more energy as these nodes need to forward the data received from nodes further away. Results showed that a smart combination of single and multi-hop routing could yield the optimum energy efficiency. Implanted nodes as part of a WBAN can create a thermal effect due to the properties of RF signal communications in and around the human body. Specific Absorption Rate (SAR) is a measure of the rate at which radiation energy is absorbed by tissue per unit weight. Exposure to high levels of SAR could result in tissue damage. Tang et al. BIB003 proposed a Thermal Aware Routing Algorithm (TARA) that handled packet transmission in the presence of temperature hot spots by effectively routing round areas that exceeded temperature thresholds. Results showed it to be a safer routing solution whilst balancing transmission delay and less network congestion. Adaptive Least Temperature Routing (ALTR) BIB004 improves upon the performance of TARA by routing packets to the least highest temperature node. Least Total Route Temperature (LTRT) protocol BIB005 converts node temperatures into graph weights to generate minimum temperature routes. Since LTRT aims to send packets with the shortest hop counts, it prevents the entire network temperature from rising quickly. Results showed that packets required less hop counts in comparison with LTR and ALTR. Kamal et al. BIB007 proposed a lightweight rendezvous algorithm (LR) that divides nodes into small clusters and showed that LR generated lower levels of temperature than LTRT and ALTR. The clustering of nodes, where energy consumption from communications with the sink is equally divided between each of the nodes in the cluster, has been shown to deliver performance improvements in WSNs and could have potential for WBANs. One of the first protocols to demonstrate the advantages of clustering was the Low Energy Adaptive Clustering Hierarchy (LEACH) protocol BIB001 . LEACH introduces data fusion into the routing protocol to reduce the amount of information that is transmitted to the sink to deliver significant improvements when compared to conventional routing protocols. Qin et al. BIB008 highlighted that LEACH and many of its successors assumed that all nodes in the network can communicate with the sink directly at all times and that this can be inconsistent with the practical application. Qin et al. proposed a Balanced Energy Consumption and Cluster based Routing Protocol (BECCRP) that improved upon LEACH where it sets gateways to relay the data from the cluster heads to share the energy consumption equally at each node, thereby extending the overall network lifetime. The protocol however, did not consider the nodes location and distance from other nodes. The summary of the performance of network protocols for WBAN is shown in Table 4 . 