1. Location of Mobile Device
Group 3

2. Basic Terminology and Concept
1. Standalone
eg. dead reckoning
2. Satellite-based
eg. GPS
3. Terrestrial-radio-based
eg. Long Range Navigation

3. 1. Cell-ID-Based Position Method
Procedure:
1. Base Transceiver Station (BTS) broadcast cell-ID
2. Mobile Station (MS) request cell-ID from BTS
2. use timing advance to improve accuracy

4. 1. Cell-ID-Based Position Method
Features:
1. can be applied to all user
2. default location method
3. cheap but low accuracy

5. 2. OTDOA Position Method OTDOA (Observed Time Difference Of Arrival)
Observed time difference of Arrival is based on the mobile measurements of the relative arrival times of pilot signals from different base stations (Node Bs) in UMTS networks
Signals from at least three Node Bs must be received by the mobile for location determination
Timing synchronization of the different Node Bs is essential. This is obtained by a location measurement unit (LMU) at the BS

6. OTDOA Position Method Real Time Difference (RTD):
the synchronization difference between the two base stations
Geometric Time Difference (GTD):
the propagation time difference between the two base stations
Observed Time Difference (OTD):
Time difference measured by the mobile between the
receptions of bursts transmitted from the reference
BTS and each neighboring BTS

7. Mechanism

8. Mechanism IPDL
In UMTS(Universal Mobile Telecommunications System) NodeB transmissions are synchronously ceased for a short period of time – Idle Period.
Terminal can measure neighbor NodeBs during Idle Periods Maximizes the hearability of distant pilots. During the ‘common’ idle period each node B transmits a signal ONLY useful for location estimation, randomly, pseudo-randomly or periodically.
OTDOA of these common pilots is measured in the MS for different Node Bs. Positioning is done as in the standard OTDOA algorithm.

9. Pros & Cons Pros： Cons： Widely Applied Indoor Cases
Acceptable Location Accuracy m
Quick Response Time s
Low cost Software, LMU
Cons：
Error in Application (eq. power control, Altitude)
Added complexity to the network operation
Reduced communication efficiency

10. 3. Assisted GPS Position Method
Create a GPS reference network whose receivers have clear views of the sky and operate continuously
GPS reference network is also connected with the cellular infrastructure
The assist data derived from the GPS reference network aids fast startup and increase sensor sensitivity
It also allows for rapid search speed and a much narrower signal search bandwidth

11. 4. Comparison Cell-ID-based
worst positional accuracy, close to the radius of the cell
OTDOA
accuracy < 100m
A-GPS
best positional accuracy, < 20m
has better coverage in obstructed environments

12. Comparison