# An Efficient Routing Protocol with Overload Control for Group Mobility in Delay-Tolerant Networking
###### Abstract
In an RVGM, the mobility of each group is modeled by group velocity, and group members have velocities close to the group velocity, but the velocities have a slight deviation from group velocity. In [14], the authors proposed an ellipse group mobility (EGM) model for tactical MANET, where nodes in a group located in an elliptic region and compared the performance of the EGM model with that of the RPGM. The results showed that the EGM model is better for intergroup communication and worse for intragroup communication. Work on routing protocols by considering group mobility models have been carried out, too [15; 16; 17; 18; 19; 20; 21]. In [15], a DTN network for the military battlefield is considered, where nodes move in a group according to the reference point established by the leader node. Then, the authors compared the delay of the group mobility model with that of an entity mobility model using an Epidemic routing protocol. It was shown that the group mobility model has lower delay. In [16], the authors considered a group mobility model and compared the performance of three MANET routing protocols, such as destination sequence distance vector (DSDV), ad hoc on-demand distance vector (AODV), and dynamic source routing (DSR) by considering an RPGM model and by varying pause time and mobility speed in a single group environment and the connection ratio between intra- and intergroup communications in a multiple group environment. In [17], the authors proposed a novel group mobility model in tactical MANET, where wedge formation was used as the basic movement technique. The authors analyzed the effect of the dynamics of network connectivity of the proposed mobility model on the performance by assuming an AODVrouting protocol. In [18], a group Epidemic routing (G-ER) was proposed. In the G-ER, an AODV protocol was used for intragroup routing and an Epidemic protocol was used for intergroup routing. Additionally, the authors proposed a buffer sharing mechanism inside each group. In [19], the authors analyzed the performance of an RPGM for MANET from the aspects of average throughput, energy consumption, and average end-to-end delay. They considered a network with a static node and a network with an RPGM model and applied AODV protocol and an ad hoc on-demand multipath distance vector (AOMDV) protocol to these networks. Analysis results showed that the AOMDV with an RPGM model was more appropriate when higher throughput or lower energy consumption was required. On the other hand, an AODV with an RPGM model was more appropriate when less delay was required. In [20], the authors studied the feasibility of applying DTN architecture into an aircraft cluster network in order to cope with the intermittent communication links problem between aircraft--from the aspects of routing protocol, transport layer protocol, and safety issues. In [21], the authors considered a future tactical-battlefield network, where ground nodes formed several small groups and an unmanned aerial vehicle (UAV) was used to enlarge coverage and increase connectivity among small groups. Then, they formulated a group connectivity optimization problem and data slot allocation optimization problem. A UAV positioning mechanism was proposed to maximize group connectivity and a dynamic slot allocation mechanism was proposed to maximize group connectivity utility. In most of the work mentioned above, however, a MANET protocol was mainly assumed as the basic routing protocol for group mobility. In [18], although a DTN protocol was assumed for intergroup routing, a MANET protocol was assumed for intragroup routing. In this paper, we consider a DTN protocol for both intra- and intergroup routing, since connectivity between group members in the same group may be broken due to the mobility and the destruction of nodes in a battlefield environment, and thus, a MANET routing protocol cannot work well, even for intragroup routing.