# Data Access Based on a Guide Map of the Underwater Wireless Sensor Network
## 6 Experiments and Analysis
### Experiment Results and Comparative Analysis  
In the process of the experiment, we assume there are no retransmissions in data storage, metadata diffusion, query data and specific application data transmission. The delay of processing data in the sensor node is less than the delay of the data transmitted, therefore, it is neglected. In the process of data query, there are two kinds of different query methods, which include global query and partial query in the network. In the partial query, one area is randomly selected in the network. In the case of existing application data meeting the requirement, the experiment results of the three methods are shown in Figure 6. In particular, in DAGM the storage time not only includes the time that the sensor node sends the data to the storage node to be stored, but also includes the time where the storage node sends the metadata to the center ring and the diffusion is completed. From the experimental results, we can draw the following conclusions:  
* When it comes to storage time performance, in DAGM the senor node generates data and sends it to the storage node. After the storage node stores the data, it also generates the corresponding metadata, and then the metadata is sent to the center ring node and is diffused and synchronized. However, the GHT only saves the data and does not generate metadata; there is no process of diffusing and synchronizing the metadata. Therefore, the time of DAGM in the data storage is more relative than that of GHT (shown in Figure 6a, State 1 is 33 s to 20 s; State 2 and State 3 are both 13 s to 7 s). At the same time, in the global and partial queries, the experimental data storage times have the same results. 2. In terms of the data query time, this is the interval from the user sending a query sentence to the user receiving specific application data or a query result. In DAGM, the corresponding storage node is purposely located through the data map, so whether it is the global query or a partial query, the storage node will be checked out first. Then, the storage node will send the specific application data through data transmission routing to the user. Thus, the experimental data query times show the same results for a global query and a partial query. However, in GHT, the query sentence is sent to all storage nodes through GHT routing in the network. The specific application data that is required returns along the same routing. Hence, data query delay of DAGM is much better than that of GHT (in global queries, shown in left side of Figure 6b, State 1 is 66 s to 108 s; State 2 is 54 s to 92 s; and State 3 is 57 s to 98 s. In partial query, shown in left side of Figure 6c, State 1 is 66 s to 91 s; State 2 is 54 s to 78 s; and State 3 is 57 s to 80 s). 3. When it comes to energy consumption, the DAGM sends the query sentence to the nearest center ring node. The center ring node finds the metadata set and then sends specific data requests and data transmission routing to the data storage node with purpose. After that, the storage node will transmit the specific application data to the user through data transmission routing. Data query of GHT directly floods the sentences to all storage nodes in network. The energy consumption is increased exponentially compared with that of DAGM (in global query, shown in right side of Figure 6b, State 1 is 49,649 J to 578 J; State 2 is 259,875 J to 1487 J; State 3 is 264,934 J to 797 J. In the partial query, shown in right side of Figure 6c, State 1 is 3763 J to 578 J; State 2 is 14,700 J to 1487 J; and State 3 is 9575 J to 797 J). 4. In three different states, the minimal energy consumption of the network is the lowest in state 1 (in DAGM, shown in right side of Figure 6b,c, global query and partial query are 578 J; in GHT, global query is 49,649 J and partial query is 3763 J). This is because the distance between senor nodes is small and there are more connectivity paths between nodes, but the time of data access in State 1 is generally a little more than in states 2 and 3.