# Hybrid Zoning Algorithm to Optimize Overhead in Smart Mobile Communication
## 3 Problem Formulation  
The nature of mobile ad hoc networks and the routing protocols require the use of flooding mechanisms to function properly and to build a network. The flooding process ensures several functions such as neighborhood discovery, topology dissemination and maintenance, warning system, etc. The OLSR protocol elects dominant nodes based on topology-based heuristic to act as forwarders of broadcast messages. However, the forwarders can be grouped into one area and their density increases accordingly, creating large broadcast zones. The larger the broadcast zone is, the bigger the collision would be. The collision increases the loss of packets and decreases the reliability of the network.  
The broadcast messages are propagated from one node to another until covering the entire network. The MPR concept of OLSR reduces the number of transmissions of TC messages. However,it suffers from redundancies. We consider a transmission as redundant when a node receives the same message more than once since it is neighbor of multiple MPR. These useless messages consume resources such as bandwidth and cause packets loss. With the increase of the density and the number of nodes, the broadcasting becomes extremely resource-intensive.  
In this paper, we act on both nodes and messages to reduce the cost of topology dissemination in OLSR protocol. We combine the Z-MPR and GFR in the same protocol called Z-GFR, as shown in Figure 1. Both algorithms propose a context-based heuristic based on the location information of nodes. The Z-GFR exploits the position of nodes provided by the location service, such as GPS in open areas or Received Signal Strength Indicator in indoors [26; 27; 28]. We assume that each node knows its position while the coordinates of the other nodes are regularly advertised throughout the network during the topology building process.  
To reduce the cost of broadcasting, firstly, the Z-GFR acts on the election of the dominant nodes. It uses the technique of Z-MPR to divide the local area into several zones and elects a MPR in each zone. This technique reduces the risk of collision by geographically subdividing the nodes that send broadcast packets and collide in radio channel. Secondly, the Z-GFR acts on the transmission of messages. It uses GFR algorithm to separate the whole network into zones and avoids redundant transmission of TC messages between these zones. The zones are calculated while the TC messages are propagated, thus deleting the time delay usually associated with zoning formation. We already implemented and discussed the Z-MPR and GFR in previous works [15; 16]. However, this is the first time the two techniques are combined in one algorithm. The Z-GFR decreases the network maintenance cost and frees the channel to help nodes focus on data transmission to achieve maximum delivery of packets with unnecessary delay. Our solution optimizes the selection of MPR, reduces the collision and the loss of packets, and achieves good dissemination of TC messages while eliminating useless transmissions. Both reductions, local and global, represent a huge gain which is reflected on data communication between nodes.