M.1 General

3GPP45.005GSM/EDGE Radio transmission and receptionTS

M.1.1 Abbreviations

A-GPS Assisted – Global Positioning System

C/A Coarse/Acquisition

ECEF Earth Centred, Earth Fixed

GPS Global Positioning System

HDOP Horizontal Dilution Of Precision

LOS Line Of Sight

TOW Time Of Week

TTFF Time To First Fix

WLS Weighted Least Squares

M.1.2 Measurement parameters

M.1.2.1 MS based A-GPS measurement parameters

In case of MS-based A-GPS, the measurement parameters are contained in the RRLP LOCATION INFORMATION IE. The measurement parameter in case of MS-based A-GPS is the horizontal position estimate reported by the MS and expressed in latitude/longitude.

M.1.2.2 MS assisted A-GPS measurement parameters

In case of MS-assisted A-GPS, the measurement parameters are contained in the RRLP GPS MEASUREMENT INFORMATION IE. The measurement parameters in case of MS-assisted A-GPS are the MS GPS Code Phase measurements. The MS GPS Code Phase measurements are converted into a horizontal position estimate using the procedure detailed in clause M.7.

M.1.3 Response time

Max Response Time is defined as the time starting from the moment that the MS has received the final RRLP MEASURE POSITION REQUEST sent before the MS sends the MEASURE POSITION RESPONSE containing the Location Information or the GPS Measurement Information, and ending when the MS starts sending the MEASURE POSITION RESPONSE containing the Location Information or the GPS Measurement Information on the Air interface. The response times specified for all test cases are Time-to-First-Fix (TTFF), i.e. the MS shall not re‑use any information on GPS time, location or other aiding data that was previously acquired or calculated and stored internally in the MS. A dedicated test message ‘RESET MS POSITIONING STORED INFORMATION’ has been defined in TS 44.014 for the purpose of deleting this information and is detailed in subclause M.3.1.10.

M.1.4 Time assistance

Time assistance is the provision of GPS time to the MS from the network via RRLP messages. Currently two different GPS time assistance methods can be provided by the network.

a) Coarse time assistance is always provided by the network and provides current GPS time to the MS. The time provided is within 2 seconds of GPS system time. This allows the GPS time to be known within one GPS navigation data sub-frame. It is signalled to the MS by means of the GPS Week and GPS TOW fields in the Reference Time assistance data IE.

b) Fine time assistance is optionally provided by the network and adds the provision to the MS of the relationship between the GPS system time and the current GSM time. The accuracy of this relationship is 10 s of the actual relationship. This addresses the case when the network can provide an improved GPS time accuracy. It is signalled to the MS by means of the FNm, TN and BN fields in the Reference Time assistance data IE.

The time of applicability of time assistance is the beginning of the Frame of the message containing the GPS Reference time.

M.1.4.1 Use of fine time assistance

The use of fine time assistance to improve the GPS performance of the MS is optional for the MS, even when fine time assistance is signalled by the network. Thus, there are a set minimum performance requirements defined for all MSs and additional minimum performance requirements that are valid for fine time assistance capable MSs only. These requirements are specified in subclause M.2.1.2.

M.1.4.2 2D position error

The 2D position error is defined by the horizontal difference in meters between the ellipsoid point reported or calculated from the MS MEASURE POSITION RESPONSE and the actual position of the MS in the test case considered.