Integration of GPS with Other Sensors and Network Assistance - Understanding GPS: Principles and Applications - page 549

standards organizations, location technology developers, handset manufacturers,
and carriers have been busy incorporating location technologies into their stan-
dards, whether it is GSM, TDMA, CDMA, CDMA2000, WCDMA/UMTS, or even
AMPS. The process to create a new over-the-air protocol to support a new technol-
ogy can take years (e.g., the process to develop the CDMA protocol IS-801 began in
late 1998 and completed with the first revision of the document in early 2000).
Work to upgrade the document to IS-801a status to include new features and capa-
bilities continued through 2003. The process of creating a new standard is contribu-
tion driven: interested parties contribute written descriptions of candidate features
to regular meetings. The contribution is discussed, merits of each idea are judged,
and the idea is voted upon for inclusion or exclusion. Needless to say, it's a long pro-
cess to obtain agreement among all parties and to publish the final specification;
ideas that are initially accepted can be removed when better ideas are created before
final publication is achieved.
Many requirements are generally covered by a standard. First, the methods and
procedures must be technically sound and have no holes. Second, messaging effi-
ciency is important—transporting the maximum of useful information in the least
number of bits is highly valued by the cellular carriers to minimize the incremental
feature burden on the cellular infrastructure and support the most number of users
without consuming all of the available bandwidth. Sometimes, a carrier's vote car-
ries more weight, as ultimately they are the final customer of the specification and
have to live with its ramifications as it impacts their cellular customer base.
Standards organizations involved are the Third Generation Partnership Project
(3GPP), 3GPP2, the European Telecommunications Standards Institute (ETSI),
Telecommunications Industry Association (TIA), and the T1P1 Committee. Listed
in Table 9.10 are technologies being standardized by these organizations.
As discussed earlier, there are two main types of A-GPS technology,
MS-assisted and MS-based. The GSM over-the-air protocol information elements
to support each will be discussed next.

MS-Assist Exchange
Referring to Figure 9.35, recall that the MS-assist method moves the position com-
putation element to the network-based position computation server, called a PDE in
a CDMA network or an serving mobile location center (SMLC) in a GSM network.
Information flows from the network to the handset to enable the handset-based
GPS receiver to acquire, detect, and measure pseudoranges to multiple satellites.

Table 9.10 Standardized Location Technologies

Handset
Technology (MA)

Location
Technology

Reference

Organization Standards Documents

AMPS TIA TR45.1 TIA/EIA/IS-817 A-GPS [77]

CDMA (IS-95) TIA TR45.5 IS-801/IS-801A A-GPS/AFLT [78]

CDMA-2000 3GPP2 IS-801/IS801A A-GPS/AFLT [78]

TDMA TIA TR45.3 TIA/EIA-136-740-C A-GPS [79]

GSM ETSI & T1P1.5 04.31 A-GPS/EOTD [76]

3GPP GERAN/
3GPP RAN2

WCDMA/UMTS 25.331 A-GPS [80]