Location of Mobile Device Group 3

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

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

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

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

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

Mechanism

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.

Pros & Cons Pros： Cons： Widely Applied Indoor Cases Acceptable Location Accuracy 140-280m Quick Response Time 0.5-2s Low cost Software, LMU Cons： Error in Application (eq. power control, Altitude) Added complexity to the network operation Reduced communication efficiency

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

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

Comparison