# A Survey on Mobility Support in Wireless Body Area Networks
## 3 Mobility Model and Communication Protocol
### Individual Mobility
#### 3.1.2 Protocols for General Mobility
The mobility in IM-SIMPLE operates the same as M-ATTEMPT by finding a new forwarder node according to the position of the node. Another protocol to take link stability and remaining energy was proposed in [26]. Unlike the typical routing algorithm to focus on the path toward the sink node, the routing algorithm between multiple body coordinator and static coordinator was studied. That is, the proposed scheme handles inter-BAN and beyond-BAN communications. According to human mobility, topology changes frequently. To determine the next hop in unstable topology, energy and link stability are employed. In particular, link stability is computed by current node position, direction of movement and speed. In order to compute link stability between node \(i\) and \(j\), node \(i\) periodically sends a message and gets the coordinate information of node \(j\). Unlike store and forwarding scheme for mobility in WBAN, [PERSON] et al. proposed Mobility-Based Temperature-Aware Routing protocol (MTR) [27] that is based on store and carry, which is main principle of Delay Tolerant Networks (DTNS). Store and carry is used to re-route a packet when a packet is likely to be transmitted to a hot spot. This is to prevent the hot spot as well as packet loss by carrying this packet on mobile node instead of dropping. In MTR, the next hop is set to one of either low temperature or high probability to meet the sink node. Until now, we have presented the overview of communication protocols to achieve high delivery ratio by selecting the most suitable next hop with new link cost function. Table 1 shows the comparison of the existing protocols and a summary of them. In addition to them, there is still remaining research work to address the other issues such as unbalanced energy consumption. First, [PERSON] et al. proposed Critical data transmission in Emergency with Mobility Support in WBANs (CEMob) [28] to prevent duplicated data transmission by taking priority of packets. In CEMob, two types of communications, single-hop and multi-hop communications, are adaptively selected according to a person's movement. To be detailed, sensed value at each node is divided into either critical or normal data. In the case of critical data, all nodes send data packets to the sink in single-hop communications to reduce delay at the intermediate node. On the other hand, current value is compared with the previous value prior to transmission in normal data. If two values are identical, they are discarded to prevent resource consumption by duplicated transmission. Otherwise, a data packet is delivered to an advanced node that is defined to have the largest remaining battery. Upon receiving, this advanced node relays the data packet to the sink node. In this work, the \begin{table}
\begin{tabular}{c c c c c} \hline
**Protocol** & **Basic Principle** & **New Metric or Architecture** & **Underlying Technology** & **Target Performance Parameter** \\ \hline OBSFR & Store and forward & Distance to the sink & Flooding & Delay \\ PRPLC & Store and forward & Link Likelyhood Factor & Delay \\ DVPRPLC & Store and forward & Link Cost Factor & Delay \\ ETPA & Store and forward & Cost of transmission to neighbor & Energy and temperature \\ Opportunity Routing & Store and forward & Relay node & RTS/ACK & Energy \\ RTM-RP & Store and forward & Relay node & CSMA, TDMA & Energy and temperature \\ M-ATTEMT & Store and forward & Heterogeneous & TDMA & Energy and delivery ratio \\ MTR & Store and carry & Meeting probability with sink node & Temperature \\ \hline \end{tabular}
\end{table} 
Table 1: Comparison of routing protocols. Figure 4: Node movement by Mobility-supporting Adaptive Threshold-based Thermal-aware Energy-efficient Multi-hop ProTocol. Figure 3: Hot spot by Mobility-supporting Adaptive Threshold-based Thermal-aware Energy-efficient Multi-hop ProTocol. advanced node is the normal node but has a larger amount of battery than others. This surplus energy is used to reduce power and resource consumption with the help of data aggregation.