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Location Based Ranking, effects on routing

November 17th, 2010 Leave a comment Go to comments

Using the simple formula for calculating the ranking of users, as follows:

Popularity of user i = \sum_j \tau_{ij} ( p_j )
where \tau_{ij} is the time (or number of times) user i has visited the tower jp_j is the popularity of tower j.

Create a list of towers, with an associated number of times the tower is reported in the dataset, call this the set p,

SELECT count(celltower_oid) as count, celltower_oid FROM cellspan GROUP by celltower_oid ORDER BY count DESC

then for each user, get a list of the cell towers, with an associated number of reading for that user, and call this set  \tau

SELECT count(celltower_oid) as count, celltower_oid FROM cellspan WHERE person_oid = {USER_ID} GROUP by celltower_oid ORDER BY count DESC

then, for each member of  \tau, multiply the number of time the tower is seen in  \tau  by the number of time the tower is seen in total from  p.

This yields a number for each user, which can be used when initialising nodes in ContactSim (aka LocationSim). I added new properties into the the configuration files, which reflected the ranking of each node, and created new classes in LocationSim, which reflected a new protocol called LBR. When a node is instantiated, is looks up its ranking metric with an oracle class (which reads the data from the configuration file). During the operation of the simulator, when a node get’s an onConnect() event call, it checks it messages to see:

  1. if it has any message for the node it is connected to, it passes them on
  2. if the node it is connected to has a higher ranking, then it passes all messages on

The initial results show a good delivery ratio compared to PBR

Delivery COST of messages for LBR and PBR using 7 day periodicity, where messaging starts at the first timestep (PBR 7 day Period Start, LBR Start), or after 1 week.

Delivery Ratio of messages for LBR and PBR using 7 day periodicity, where messaging starts at the first timestep (PBR 7 day Period Start, LBR Start), or after 1 week.

This suggest that simply knowing the rank of the users, based on location, significantly improves routing. However, I need to check the algorithm is working before I can say the results are accurate:

  • Does the node remove it from it’s buffer when it passes the message on? Yes it does
  • Is the node correctly recording deliveries?

Currently working on: Graph of all connected users. Taking a long time……

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