Performance Evolution of Scalable Multicasting Over Mobile Ad-Hoc Networks
K. Ramakrishnaiah, P. Prathibha, Dodde Hari Krishna · 2012
There is an increasing demand and a big challenge to design more scalable and reliable multicast protocol over a dynamic AdHoc network (MANET). In this paper, we propose an efficient and scalable geographic multicast protocol, EGMP, for MANET. The scalability of EGMP is achieved through a two-tier virtualzone-based structure, which takes advantage of the geometric information to greatly simplify the zone management and packet forwarding. A zone-based bi-directional multicast tree is built at the upper tier for more efficient multicast membership management and data delivery, while the intra-zone management is performed at the lower tier to realize the local membership management. The position information is used in the protocol to guide the zone structure building, multicast tree construction, maintenance, and multicast packet forwarding. Compared to conventional topology based multicast protocols, the use of location information in EGMP significantly reduces the tree construction and maintenance overhead, and enables quicker tree structure adaptation to the network topology change. We also develop a scheme to handle the empty zone problem, which is challenging for the zonebased protocols. Additionally, EGMP makes use of geographic forwarding for reliable packet transmissions, and efficiently tracks the positions of multicast group members without resorting to an external location server. We make a quantitative analysis on the control overhead of the proposed EGMP protocol and our results indicate that the per-node cost of EGMP keeps relatively constant with respect to the network size and the group size. We also performed extensive simulations to evaluate the performance of EGMP. Compared to the classical protocol ODMRP, both geometric multicast protocols SPBM and EGMP could achieve much higher delivery ratio in all circumstances, with respect to the variation of mobility, node density, group size and network range. However, compared to EGMP, SPBM incurs several times of control overhead, redundant packet transmissions and multicast group joining delay. Although SPBM is designed to be scalable to the group size, it has very low packet delivery ratio when the group size is small without a stable membership in each level of quad-tree square, and cannot perform well under a large network size due to the use of multi-level network-wide flooding of control messages. ODMRP takes advantage of broadcasting to achieve more efficient packet forwarding, but the transmissions are much more unreliable due to its difficulty of maintaining forwarding mesh under mobility, which leads to a lower packet delivery ratio. The multicast group joining delay of ODMRP is also much higher than that of EGMP. Our results indicate that geometric information can be used to more efficiently construct and maintain multicast structure, and to achieve more scalable and reliable multicast transmissions in the presence of constant topology change of MANET. Our simulation results demonstrate that EGMP has high packet delivery ratio, and low control overhead and multicast group joining delay under all cases studied, and s scalable to both the group size and the network size. Compared to the geographic multicast protocol SPBM, it has significantly lower control overhead, data transmission overhead, and multicast group joining delay.