Cell-Phone Location without Ephemeris

Cell-Phone Location without Ephemeris

A new method enables the mobile phone to compute its own position using
acquisition assistance data with increased resolution in some of the
fields. It benefits network operators as they can deliver the best
performance with minimum bandwidth requirements, making this especially
relevant in emergency-call situations.

See:
http://www.gpsworld.com/wireless/single-shot-position-11047?utm_source=GPS&utm_medium=email&utm_campaign=Navigate_02_14_2011&utm_content=single-shot-position-11047

In assisted GPS (A-GPS) and A-GNSS, some information in the form of
assistance data is sent to the mobile terminal equipped with a GNSS
receiver. This data helps the receiver acquire satellite signals faster
and at lower power levels as well as compute its own position.
Assistance data is essential in many GNSS use cases but it is especially
relevant in emergency calls from mobile terminals (e911, e112) where a
fast response and the best sensitivity are required. Mobile subscribers
are often in environments where direct satellite visibility is impaired
because the user is inside a building or there are other obstructions.
Emergency situations also require a very fast response (time-to
-first-fix or TTFF), typically within 30 seconds, so the performance
requirements imposed on the GNSS receiver are very stringent.

GNSS assistance data is standardized by 3GPP and 3GPP2 in two different
types, broadly known as mobile-station (MS) based and MS-assisted.
MS-assisted positions are computed by a server. MS-based methods enjoy
certain performance benefits in position accuracy and response time when
compared with MS-assisted methods. However, the amount of assistance
data required for MS-based operation is substantially larger than the
assistance data required by MS-assisted methods.

For this reason, some network operators choose the MS-assisted methods
for their emergency-call services. Larger bandwidth requirements are of
deep concern if many callers demand the services at the same time,
because network capacity could be challenged when it is most needed.

This article describes a method that enables the mobile terminal to
compute its own position, thus enjoying the benefits outlined above but
with the same assistance data as in MS-assisted methods, only with
increased resolution in some of the fields. We call this method
single-shot MS-based. Network operators benefit because they can deliver
the best performance with the minimum bandwidth requirements, especially
relevant in emergency call situations.

Some 3GPP specifications will need to be modified slightly to increase
the resolution of the relevant assistance data fields, namely, 3GPP TS
44.031, 3GPP TS 25.331, and 3GPP TS 36.355

See:
http://www.gpsworld.com/wireless/single-shot-position-11047?utm_source=GPS&utm_medium=email&utm_campaign=Navigate_02_14_2011&utm_content=single-shot-position-11047