ECOPS: Energy-Efficient Collaborative Opportunistic Positioning for Heterogeneous Mobile Devices

Algorithm 3

ECOPS: CollaborativePR().

1: while non-GPS device ∣∣ (GPS-equipped device & 𝑝_𝑟<𝑝_min) do

2: sleep until the device needs to update location information

3: numofPBs = 0;

4: check the list of available PBs;

5: make connection to each PB and request GPS location

  information sequentially;

6: calculate the distance to each PB using the obtained

  RSSI value;

7: set numofPBs to the number of the detected PBs

8: if   numofPBs == 1∣∣ one of PBs is within the near field

  threshold (𝛽 meters) then

9:  use the received GPS location information immediately

  without trilateration;

10: continue;

11: end if

12: if   numofPBs == 2 then

13:  calculate two possible locations (PR) and get the

   middle location between the two possible locations;

14:  end if

15:  if   numofPBs >= 3 then

16:  select three PBs randomly and calculate the its cur-

   rent location (PR) with the GPS coordinates and

   distance information of the selected PBs;

17:  end if

18:  if GPS-equipped device then

19:   check the residual power (𝑝_𝑟);

20:  end if

21: end while

22: execute CollaborativePB();