## 5 Performance Evaluations
### Evaluation Metrics  
The proposed mobility handling method for our geographical routing protocol is evaluated in terms of routing accuracy _i.e._, how well the proposed mechanism delivers messages to the region of interest defined in a query and in terms of communication overhead. The performance of two methods (_i.e._, global updates and local updates) for handling mobility in geocasting has been evaluated by varying the number of nodes, number of mobile nodes and speed of the mobile nodes with the following scenarios:  
* _Scenario 1_--The aim of this scenario is to see the scalability of the updating methods. For this purpose, we vary the number of nodes from 60 to 360, where 10% of the nodes are moving with a speed of around 10 \(m/s\). We keep the mobility rate and speed fixed while increasing the network size to evaluate the performance of updating mechanism in terms of routing accuracy and energy efficiency for networks of different sizes. * _Scenario 2_--This scenario is evaluated to see how well the updating methods can handle the dynamics of the network. If more nodes are moving in the network, more parts of the routing structure are affected by the mobility. We vary the number of mobile nodes from 10 to 50 in a network having 200 nodes. The speed of the mobile nodes is around 10 \(m/s\) reflecting moderately moving entities. * _Scenario 3_--Higher speed of nodes results in more frequent changes in the routing structure. To understand how accurate the updating methods (for keeping the routing structure up-to-date during the network lifetime) are, in this scenario we vary the speed of mobile nodes from 1 to 17 \(m/s\) in a network having 200 nodes with 20 mobile nodes. The speed of mobile nodes is varied from slowly moving entities such as firefighters (with a speed of 1-2 \(m/s\)) to highly mobile entities such as UAVs (with a speed of 15-17 \(m/s\)) in a firefighting scenario. In these multi-sink WSN scenarios, we have measured two metrics to evaluate the mobility handling mechanism for routing of queries towards a specific region:  
* _Execution ratio (ER)_--The ratio of nodes that are within the region of interest and execute the query with the total number of nodes within the region of interest. This metric measures how well the routing is able to deliver the query to the region of interest. It is defined to evaluate routing accuracy of queries in mobile WSN. * _Communication Overhead (CO)_--The total number of packets that are sent to construct and maintain the structure. It includes hello packets sent from sinks, beacon packets sent from mobile nodes and convex hull definition update messages. If more messages need to be transmitted to keep the geocast structure up-to-date, the energy expenditure in the WSN is likely to increase. We measure this effect with overall network load. Two other metrics are used to evaluate performance of geocasting in terms of routing accuracy and compare it with other known geocasting protocols:  
* _False execution ratio (FER)_--The ratio of nodes that are outside the region of interest and execute the query with the total number of nodes outside the region of interest. Energy is wasted when queries are executed outside the region of interest. The false execution ratio measures this effect. * _False injection ratio (FIR)_--The ratio of data sinks that inject the query while none of the nodes in its partition executes the query with the total number of data sinks. Irrelevant query lead to higher energy expenditure in the WSN partition when injected. We measure this effect with the false injection ratio. We define two final metrics to evaluate networking performance of geocasting and compare it with other known geocasting protocols:  
* _Average query delivery delay (AQDD)_--The total time elapsed between the query generation by a sink and its reception by a sensor node inside the target region, averaged over all sink-target node pairs. * _Network load (NL)_--The total number of query packets that are sent from sinks and sensors until reaching to target region.