TITLE
Coarse Location Technique – Analog Mode
SOURCE:
SiRF Technology, Inc.
148 East Brokaw Road
San Jose, CA 95112
Tel #: (408) 467-0410
Fax #: (408) 467-0420
CONTACTS:
Gengsheng Zhang
Tel #: (408) 392-8387
E-mail: gzhang@sirf.com
John Gabor
Tel #: (850) 893-8698
E-mail: jgabor@sirf.com
Mangesh Chansarkar
Tel #: (408) 392-8661
E-mail: mangesh@sirf.com
ABSTRACT:
Description of the coarse location technique by
broadcasting GPS almanac to the analog-mode mobile
stations.
RECOMMENDATION:
Review contribution and incorporate into text for
Analog mode.
Copyright Statement:
The contributor grants a free, irrevocable license to TIA to incorporate text contained in this contribution and any modification thereof
in the creation of a TIA standards publication; to copyright in TIA’s name any TIA standards publication, even though it may include
portions of this contribution; and at TIA sole’s discretion to permit others to reproduce in whole or part the resulting TIA standards
publication. Permission is granted to TIA participants to copy any portion of this document for the legitimate purpose of the TIA.
Copying for monetary gain or other non-TIA related purposes is prohibited.
The Contributor may hold one or more patents or copyrights that cover information contained in this contribution. A license will be
made available to applicants under reasonable terms and conditions that are demonstrably free of any unfair discrimination. Nothing
contained herein shall be constructed as conferring by implication, estoppel, or otherwise any license or right under any patent,
whether or not the use of information herein necessarily employs an invention of any existing or later issued patent, or copyright.
Notice:
This contribution has been prepared by SiRF Technology Inc. as a basis for discussion to assist the Technical Subcommittee TR45.1.
The document should not be construed as a binding proposal on SiRF Technology Inc.. Specifically, SiRF Technology reserves the
right to modify, amend or withdraw the contents of this contribution
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INTRODUCTION
This contribution proposes the coarse location technique by broadcasting current GPS
sub-almanacs to the analog-mode mobile stations. The base station broadcasts current
GPS sub-almanacs to the analog-mode mobile stations. The mobile station computes its
coarse position using received sub-almanacs and sends its coarse position location to the
PDE. Upon receiving the mobile station’s coarse position, the PDE corrects the coarse
position and computes accurate mobile station’s position.
DEFINITIONS
Almanac. GPS almanac is a set of orbit and clock correction parameters for all satellites.
It is a subset of the ephemeris data with reduced accuracy and allows calculation of
approximate GPS satellite positions and clock corrections.
Sub-Almanac. A sub-almanac is a portion of a GPS almanac and contains only the orbit
and clock parameters for one satellite.
THEORY OF OPERATION
The PDE determines if the mobile station supports the coarse location method and
whether or not to use the coarse location method.
1. The base station continuously broadcasts current GPS sub-almanacs. Mobile stations
collect sub-almanacs and store them in memory.
2. It is the PDE responsibility to determine whether or not to use the coarse location
method because the PDE has the knowledge of the mobile station GPS capability
(conveyed by the GPS_MODE field) before beginning a position determination
procedure. If the GPS_MODE field has the value ‘011’, which indicates the mobile
station is IS-817 capable, coarse location capable, and assisted GPS capable, and the
PDE chooses to utilize the coarse location method, the PDE shall send the following
message to the mobile station.

Calculated Coarse Position Report - Request
3. Upon receiving Calculated Coarse Position Report - Request message, the mobile
station computes acquisition assistance information based on the information in the
Calculated Coarse Position Report - Request message and stored GPS sub-almanacs,
and starts satellite acquisition.
4. After acquiring satellite signals and making pseudorange measurements, the mobile
station computes its coarse position from pseudorange measurements, stored current
sub-almanacs, reference latitude and longitude from the Calculated Coarse Position
Report - Request message. The mobile station then sends its calculated coarse
position to the PDE.
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5. Upon receiving the mobile station coarse position, the PDE then corrects the coarse
position and computes accurate mobile station’s position.
FLOW DIAGRAM FOR COARSE LOCATION METHOD
Receive PCI from MS
GPS_MODE = 011
Coarse Location + Assisted GPS
Send Calculated Coarse Position Report – Request
Receive Calculated Coarse Position
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GPS SUB-ALMANAC BROADCAST
The proposed broadcast is to use the Global Overhead Action message, which can be
broadcast every 0.8 seconds on the paging channel with up to 16 bits of information. This
kind of slow data rate is useful to transmit GPS sub-almanacs to mobile stations and
gives every mobile station an efficient method to collect GPS almanac. The sub-almanacs
will be used for GPS signal acquisition and mobile station coarse position computation.
Each Global Overhead Action message consists of one word. The Global Overhead
Action message types are listed in Table 3.7.1-4 in TIA/EIA-553-A. The format for the
global action overhead message is as follows.
T1T2
=11
2
21
22
23
24
25
26
27
DCC
2
ACT
4
RSVD
16
END
1
OHD=
100
3
P
12
Sixteen bits of data can be broadcast to all listening analog-mode mobile stations in the
RSVD field. The ACT field indicates the global action message types. There are 16
global action message types and currently 0000, 1100, 1101 are reserved. It is proposed
that 1100 will be used to broadcast GPS sub-almanac messages. The format for the GPS
sub-almanac message is as follows.
T1T2
=11
2
DCC
2
ACT=
1100
4
SubAlmanac
16
28
3
END
1
OHD=
100
3
P
12
1
2
The data in the sub-almanac messages include the following record:
Field
SYNC
PRN
WEEK_NUM
ECCENTRICITY
TOA
DELTA_INCLINATION
OMEGADOT
A_SQRT
OMEGA0
OMEGA
M0
AF0
AF1
EOM
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31
SYNC
Length (bits)
13
6
8
16
8
16
16
24
24
24
24
11
11
7
Scale Factor (LSB)
2-21
212
2-19
2-38
2-11
2-23
2-23
2-23
2-20
2-38
Units
seconds
semi-circles
semi-circles/sec
meters1/2
semi-circles
semi-circles
semi-circles
seconds
sec/sec
The synchronization bits.
The base station shall set this field to the value of
‘1111100110101’ to indicate the beginning of the subalmanac message.
PRN
The satellite PRN number.
This parameter specifies the satellite PRN number for
which the sub-almanac is valid. It is represented as an
unsigned value in the range from 1 to 32, where the binary
value of the field conveys the satellite PRN number minus
one.
WEEK_NUM
The sub-almanac reference week number.
This parameter specifies the reference week number of the
sub-almanac. The range of this field is from 0 to 255.
ECCENTRICITY
Eccentricity.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
TOA
The reference time of the sub-almanac.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
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DELTA_INCLINATION
Correction to inclination.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
OMEGADOT
Argument of perigee.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
A_SQRT
Square root of the semi-major axis.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
OMEGA0
Longitude of ascending node.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
OMEGA
Argument of perigee.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
M0
Mean anomaly at reference time.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
AF0
Apparent satellite clock correction af0.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
AF1
Apparent satellite clock correction af1.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
EOM
The end of message.
The base station shall set this field to the value of
‘1110010’ to indicate the end of the sub-almanac message.
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The Global Overhead Action Message can be transmitted at a rate of up to one message
every 0.8 second with up to 16 bits of information. At this rate, and given a typical
scenario where there are 24 satellites, the GPS almanac can be transmitted in 249.6
seconds.
PROPOSED MODIFICATIONS
This section describes the required modifications to TIA/EIA-817 (published on July 10,
2000) to implement the coarse location technique by broadcasting current GPS almanac.
All the page numbers, line numbers and table numbers mentioned below are referred to
TIA/EIA-817.
-----------------------------------------------------------------------------------------------------------page 1, add text between line 22 and 23
-----------------------------------------------------------------------------------------------------------Almanac. GPS almanac is a set of orbit and clock correction parameters for all satellites.
It is a subset of the ephemeris data with reduced accuracy and allows calculation of
approximate GPS satellite positions and clock corrections.
-----------------------------------------------------------------------------------------------------------page 3, add text between line 30 and 31
-----------------------------------------------------------------------------------------------------------Sub-Almanac. A sub-almanac is a portion of a GPS almanac and contains only the orbit
and clock parameters for one satellite.
-----------------------------------------------------------------------------------------------------------page 38, edit text between line 20 and 21
-----------------------------------------------------------------------------------------------------------GPS_MODE Indicates mobile’s current GPS capability:
000 - reserved for backward compatibility (indicates mobile station is
not GPS capable).
001 - indicates mobile station is IS-817 capable and autonomous GPS
capable.
010 - indicates mobile station is IS-817 capable and assisted GPS
capable.
011 - indicates mobile station is IS-817 capable, coarse location capable
and assisted GPS capable.
The other values are reserved.
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-----------------------------------------------------------------------------------------------------------edit text between line 20 on page 39 and line 1 on page 1
-----------------------------------------------------------------------------------------------------------GEO_DATA Geolocation data exchanged between a PDE and a mobile station.
GPS_MODE Indicates mobile’s current GPS capability:
000 - reserved for backward compatibility (indicates mobile station is
not GPS capable).
001 - indicates mobile station is IS-817 capable and autonomous GPS
capable.
010 - indicates mobile station is IS-817 capable and assisted GPS
capable.
011 - indicates mobile station is IS-817 capable, coarse location capable
and assisted GPS capable.
The other values are reserved.
-----------------------------------------------------------------------------------------------------------page 4, edit text between line 22 and 27
-----------------------------------------------------------------------------------------------------------To clarify the structure of this standard, six logical “blocks” of information1 are outlined
in Table 1.4-1. The first three “blocks” represent information conveyed from the PDE to
the mobile station. Their purpose is to provide assistance for the mobile-station GPS
receiver. The next two “blocks” represent information conveyed from the mobile station
to the PDE. Their purpose is to convey to the network the result of the GPS measurement
performed by the mobile-station GPS receiver. The last “block” is used for the coarse
location technique.
-----------------------------------------------------------------------------------------------------------page 5, edit Table 1.4-1 at line 1
-----------------------------------------------------------------------------------------------------------Direction
PDE
to
Mobile
Information Blocks
I. Acquisition
Assistance
Description
Information about the GPS system/signals that
aids the GPS receiver in acquiring (detecting)
signals from the GPS satellites.
7
Station
Mobile
Station
to
PDE
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II. Location
Assistance
III. Navigation Bits
Assistance
IV. GPS Measurement
Report
V. Calculated Position
Report
PDE
to
Mobile
Station
VI. Calculated Coarse
Position Report –
Request
Mobile
Station
to
PDE
VI. Calculated Coarse
Position Report
Information about the GPS system/signals that
enables the mobile to compute its own location
based on the GPS measurements.
Information about the 50-bps bit streams
modulated onto the GPS satellite signals.
Observed parameters of the GPS signals (e.g.,
code phase). These parameters are needed to
compute mobile station.
The geographical position data for the mobile
station (latitude, longitude, etc.) A mobile
station that is capable of computing its position
uses this block to report the results.
Information about the GPS system/mobile
station approximate location that aids the GPS
receiver in acquiring signals from the GPS
satellites and enables the mobile to compute its
own coarse location based on the GPS
measurements.
A mobile station that is capable of computing
its coarse position uses this block to report the
results.
-----------------------------------------------------------------------------------------------------------page 5, edit text between line 8 and 19
-----------------------------------------------------------------------------------------------------------To perform an assisted GPS geolocation, the PDE sends an information block of type 1 to
the mobile station. In response, the mobile may ask for additional assistance blocks of
type 2 and/or 3, as needed. Then, the mobile station performs a measurement of the GPS
satellite signals and reports the result to the PDE with a block of type 4 or 5. To perform
an unassisted GPS geolocation, the PDE simply sends a request for a block of type 5. To
perform coarse location, the PDE broadcasts current GPS sub-almanacs and sends a
request for a block of type 6. Then, the mobile station performs a measurement of the
GPS satellite signals and reports the calculated coarse position to the PDE with a block of
type 6.
For transmission over the air, each PDE-to-mobile information block is subdivided into
one or more messages. More specifically, PDE-to-mobile blocks 1, 2 and 3 are
subdivided into GPS Assistance messages, each of which is individually acknowledged
through a GPS Assistance – Response message. The details of how this subdivision is
performed are summarized in the sections that follow. Mobile-to-PDE blocks 4 and 5 are
embedded in a GPS Report message to be sent in response to GPS Report – Request
message issued by the PDE. PDE-to-Mobile block 6 is the Calculated Coarse Position
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Report – Request message issued by the PDE and Mobile-to-PDE block 6 is the
Calculated Coarse Position Report to be sent by the mobile station.
-----------------------------------------------------------------------------------------------------------page 6, edit text between line 6 and 10
-----------------------------------------------------------------------------------------------------------There are four capabilities that can be reported: Autonomous GPS capable, Assisted GPS
capable, not GPS capable, Coarse location and assisted GPS capable. Autonomous GPS
capable refers to a mobile station that is capable of determining its position without
assistance from the PDE. An Assisted GPS capable indication refers to a mobile station
that requires assistance data from the PDE in order to complete the position
determination procedure. Coarse location and assisted GPS capable refers to a mobile
station that is capable of determining its coarse position with GPS sub-almanac broadcast
from the PDE or that requires assistance data from the PDE in order to complete the
position determination procedure. It is the PDE responsibility to determine to use either
the coarse location method or the assisted GPS mode.
-----------------------------------------------------------------------------------------------------------page 8, edit Table 2.1-1 at line 1
-----------------------------------------------------------------------------------------------------------Table 2.1-1. Message Pairs Exchanged Between PDE and Mobile Station
Forward and Reverse Message Pairs
Over-the Air
MSG_ Info.
Format
TYPE block
9
GPS Acquisition Assistance Part 1
FVC order
GPS Acquisition Assistance Part 1 – Response
RVC ord. conf.
GPS Acquisition Assistance Part 2
FVC order
GPS Acquisition Assistance Part 2 – Response
RVC ord. conf.
GPS Location Assistance Part 1
FVC order
GPS Location Assistance Part 1 – Response
RVC ord. conf.
GPS Location Assistance Part 2
FVC order
GPS Location Assistance Part 2 – Response
RVC ord. conf.
GPS Location Assistance Part 3
FVC order
GPS Location Assistance Part 3 – Response
RVC ord. conf.
GPS Navigation Bits Assistance Part 1
FVC order
GPS Navigation Bits Assistance Part 1 – Response RVC ord. conf.
GPS Navigation Bits Assistance Part 2
FVC order
GPS Navigation Bits Assistance Part 2 – Response RVC ord. conf.
GPS Navigation Bits Assistance Part 3
FVC order
GPS Navigation Bits Assistance Part 3 – Response RVC ord. conf.
GPS Navigation Bits Assistance Part 4
FVC order
GPS Navigation Bits Assistance Part 4 – Response RVC ord. conf.
GPS Navigation Bits Assistance Part 5
FVC order
GPS Navigation Bits Assistance Part 5 – Response RVC ord. conf.
GPS Navigation Bits Assistance Part 6
FVC order
GPS Navigation Bits Assistance Part 6 – Response RVC ord. conf.
GPS Measurement Report - Request
FVC order
GPS Measurement Report
RVC ord. conf.
Calculated Position Report - Request
FVC order
Calculated Position Report
RVC ord. conf.
Calculated Coarse Position Report – Request
FVC order
Calculated Coarse Position Report
RVC ord. conf.
Other MSG_TYPE values are reserved
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‘00000’
I
‘00001’
I
‘00010’
II
‘00011’
II
‘00100’
II
‘00101’
III
‘00110’
III
‘00111’
III
‘01000’
III
‘01001’
III
‘01010’
III
‘01011’
IV
‘01100’
V
‘01101’
VI
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-----------------------------------------------------------------------------------------------------------
Calculated Coarse Position Report - Request
-
The mobile station shall send the Calculated Coarse Position Report
message with fields set as specified in 2.3.1.6.
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------------------------------------------------------------------------------------------------------------
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If the GPS_MODE field has the value ‘010’, or if the GPS_MODE field has the value
‘011’ and the assisted GPS mode is selected, the PDE shall produce and save the content
of the information fields for the following two messages as specified in 2.3.2.1.
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-----------------------------------------------------------------------------------------------------------
Coarse Location and Assisted GPS case
If the GPS_MODE field has the value ‘011’ the PDE shall choose to use either the
assisted GPS mode or the coarse location method. If the assisted GPS mode is
selected, the PDE shall follow the procedure for assisted GPS case.
If the coarse location method is selected, the PDE shall send to the mobile station a
Calculated Coarse Position Report – Request message and wait for a Calculated
Coarse Position Report message. If the ERROR_IND field of the Calculated Coarse
Position Report message has the value ‘0’,the PDE shall correct the coarse position
and compute accurate position. If the ERROR_IND field of the Calculated Coarse
Position Report message has the value ‘1’ and the ERROR_CODE field has the value
‘00000000’ or ‘00000100’, the position determination procedure is complete; it has
failed to achieve location fix. If the ERROR_IND field has the value ‘1’ and the
ERROR_CODE field has the value ‘00000001’, ‘00000010’ or ‘00000011’, the PDE
shall perform this procedure again after a delay specified by the value of
ERROR_CODE (see Table 2.3.1.4-1).
-----------------------------------------------------------------------------------------------------------page 23, edit Table 2.3.1.4-1 at line 2
-----------------------------------------------------------------------------------------------------------Table 2.3.1.4-1. Error Code
Error Code
The mobile station failed to perform a GPS measurement report, a
calculated position report or a calculated coarse position report
The GPS measurement report, calculated position report or
calculated coarse position report is not valid and not ready to
transmit, PDE shall request the GPS result again after a time delay
whose duration should be 1 second
The GPS measurement report, calculated position report or
calculated coarse position report is not valid and not ready to
transmit, PDE shall request the GPS result again after a time delay
whose duration should be 6 second
11
ERROR_CODE
(binary)
‘00000000’
‘00000001’
‘00000010’
‘00000011’
The GPS measurement report, calculated position report or
calculated coarse position report is not valid and not ready to
transmit, PDE shall request the GPS result again after a time delay
whose duration should be 10 seconds
Capability normally supported by the mobile station but
temporarily not available or not enabled
Other values a re reserved
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-----------------------------------------------------------------------------------------------------------2.3.1.6
Calculated Coarse Position Report
A Calculated Coarse Position Report message (MSG_TYPE=’01101’) shall include the
following fields:
Field
ERROR_IND
ERROR_CODE
SV_MAP
TIME_REF_SRC
TIME_REF
DELTA_LAT
DELTA_LON
DELTA_ALT
12
13
14
15
Length (bits)
1
8 or 0
0 or 8
0 or 1
0 or 17
0 or 17
0 or 17
0 or 12
The mobile station shall include one occurrence of the following field for each bit in the
SV_MAP field that is set to ‘1’.
INV_WEIGHT_FA
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23
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27
28
29
‘00000100’
ERROR_IND
6
The indicator for error in returning calculated coarse
position report.
If the mobile station cannot return the calculated coarse
position report, the mobile station shall set this field to ‘1’;
otherwise the mobile station shall set this field to ‘0’.
ERROR_CODE
Error code.
If ERROR_IND field is set to ‘1’, the mobile station shall
set this field to a value shown in Table 2.3.1.4-1; otherwise
the mobile station shall omit this field.
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If the ERROR_IND field is set to ‘1’, all remaining fields in this message shall be
omitted.
SV_MAP
Indicator of inclusion of inverse of weighting factor. The
order of the satellites in this field is the same as the order of
satellites in the Calculated Coarse Position Report –
Request message. Specifically, when the bits in SV_MAP
are ordered from MSB to LSB, each successive bit is
associated with a successive occurrence of the
SV_PRN_NUM field (from first to last occurrence) in the
Calculated Coarse Position Report – Request message.
If the inverse of weighting factor for a satellite is included
in this message, the mobile station shall set the
corresponding bit to ‘1’; otherwise, the mobile station shall
set the corresponding bit to ‘0’. For example,
SV_MAP=’11010010’ means that the inverse of weighting
factor for the first, second, fourth and seventh satellites are
included.
The mobile station shall set no more than 7 bits to ‘1’ in
this field.
TIME_REF_SRC
Timing Source.
This field indicates the source of timing used to specify the
“Time of Reference” parameter (see below). The mobile
station shall set this field according to Table 2.3.1.5-1.
TIME_REF
The time of Reference for the calculated coarse position.
If the TIME_REF_SRC field has value ‘1’, the mobile
station shall set this field to the GPS time at which the
Calculated Coarse Position information is applicable, in
units of 1 ms, in the range from 0 to 80,639 ms (Note: in
this case the action time is expressed as the GPS time of
week modulo 80,640 ms).
DELTA_LAT
Reference latitude correction.
The mobile station shall set this field to the two’s
complement value of the difference between the reference
latitude, which is given by the REF_LAT field in the
Calculated Coarse Position Report - Request message, and
the calculated coarse latitude in units of 0.5/216 degrees, in
the range from –0.5 to +0.5x(1-2-16) degrees, referenced to
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the WGS-84 reference ellipsoid. The sign of this quantity
shall be positive if the value of the reference latitude is
larger than the calculated coarse latitude; otherwise it shall
be negative.
DELTA_LON
Reference longitude correction.
The mobile station shall set this field to the two’s
complement value of the difference between the reference
longitude, which is given by the REF_LONG field in the
Calculated Coarse Position Report - Request message, and
the calculated coarse longitude in units of 0.5/216 degrees,
in the range from –0.5 to +0.5x(1-2-16) degrees, referenced
to the WGS-84 reference ellipsoid. The sign of this quantity
shall be positive if the value of the reference longitude is
larger than the calculated coarse longitude; otherwise it
shall be negative.
DELTA_ALT
Reference altitude corrections.
The mobile station shall set this field to the two’s
complement value of the calculated coarse altitude in units
of 5 meters, in the range from –10,240 to 10,235 meters,
referenced to the WGS-84 reference ellipsoid.
INV_WEIGHT_FA
Inverse of weighting factor.
The mobile station shall set this field to the inverse of the
weighting factor used for the satellite measurement as part
of the weighted least square algorithm implemented by the
mobile station to compute its coarse position, in the range
from 0.5 to 112 meters. A “floating-point” representation is
used where the 3 most significant bits constitute the
exponent and the least 3 significantly bits constitute the
mantissa as specified in the following Table.
Table XXX. Inverse of Weighting Factor Representation
Exponent, Mantissa, Index value, Floating-Point value, fi Inverse Weighting
X
Y
i = Y+8X
Factor value,  (m)
‘000’
‘000’
0
0.5
 < 0.5
‘000’
‘001’
1
0.5625
0.5  <0.5625
X
X
Y
2 i 61
0.5(1+Y/8) 2
fi-1   < fi
‘111’
‘110’
62
112
104  <112
‘111’
‘111’
63
Not Applicable
112 
38
39
14
1
2
3
4
5
6
7
8
9
-----------------------------------------------------------------------------------------------------------page 36, add text between line 6 and 7
-----------------------------------------------------------------------------------------------------------2.3.2.6.
Calculated Coarse Position Report - Request
A Calculated Coarse Position Report – Request message (MSG_TYPE=’01101’) shall
include the following fields:
Field
Length (bits)
TIMING_SRC
TOARR_PRED
REF_LAT
REF_LONG
CURR_ALM_WEEK
CURR_ALM_TOA
10
11
12
1
20
15
16
8
8
The PDE shall include eight occurrences of the following field.
SV_PRN_NUM
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
TIMING_SRC
5
Timing Source.
This field indicates the source of timing used to specify the
TOARR_PRED parameter in this message (see below). The
PDE shall set this field according to Table 2.3.2.1-1.
TOARR_PRED
Time-of-Arrival Prediction.
The PDE shall set this field to the PDE’s predicted time of
arrival, at the mobile station, of the Calculated Coarse
Position Report – Request message that contains this field.
If TIMING_SRC=’1’ this field shall be expressed as the
GPS time-of-week, in units of 1 second, in the range from 0
to 604799.
REF_LAT
Reference latitude.
The PDE shall set this field to the two’s complement value
of the latitude, in units of 180/215 degrees, in the range
from –90 degrees to +90x(1-2-15) degrees, referenced to the
WGS-84 reference ellipsoid, counting positive angles north
of the equator and negative angles south of the equator. The
reference latitude shall be the closest approximation of the
mobile station’s location for which the PDE has access for.
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
REF_LONG
Reference longitude.
The PDE shall set this field to the two’s complement value
of the longitude, in units of 360/216 degrees, in the range
from –180 degrees to +180x(1-2-16) degrees, referenced to
the WGS-84 reference ellipsoid, counting positive angles
east of the Greenwich meridian and negative angles west of
the Greenwich meridian. The reference longitude will be
the closest approximation on user location the PDE has
access for.
CURR_ALM_WEEK
The GPS week number of current almanac.
The PDE shall set this field to specify the 8 least significant
bits of the GPS week number of current almanac. The
range of this field is from 0 to 255. The mobile station shall
only use current almanac for coarse position computation.
CURR_ALM_TOA
The reference time of current almanac.
The PDE shall set this field to specify the reference time of
current almanac, in units of 4096, in the range from 0 to
602,112 s. The PDE shall only use current almanac for
coarse position computation.
SV_PRN_NUM
Satellite PRN number.
The PDE shall set this field to the value of satellite PRN
number, in the range from 0 to 31. The binary value of this
field conveys the satellite PRN number minus one.
-----------------------------------------------------------------------------------------------------------page 36, add text between line 6 and 7
-----------------------------------------------------------------------------------------------------------2.4
GPS Sub-Almanac Broadcast Procedure
The GPS sub-almanac broadcast procedure is based on the theory of operation section of
this document. The exact broadcast procedure will be provided when the concept is
agreed upon.
The PDE uses the Global Overhead Action message to continuously broadcast GPS subalmanac messages for all satellites.
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
The mobile station may read the broadcast GPS sub-almanac message at any point that it
determines appropriate.
-----------------------------------------------------------------------------------------------------------page 36, edit text between line 7 and 8
-----------------------------------------------------------------------------------------------------------2.5
Supplements to TIA/EIA-553-A to Support Analog Position Determination
Service
-----------------------------------------------------------------------------------------------------------page 41, add text between line 12 and 13
-----------------------------------------------------------------------------------------------------------3.7.1.2.2
Each global action overhead message consists of one word. The global action message
types are listed in Table 3.7.1-4. Any number of global action messages can be appended
to a system parameter overhead message.
[…]
Sub-Almanac Message
T1T2
=11
2
27
28
29
30
31
32
33
Global action overhead message
DCC
2
ACT=
1100
4
SubAlmanac
16
END
1
OHD=
100
3
P
12
The interpretation of the data fields is as follows:
[…]
Sub-Almanac Sub-Almanac parameter field. It includes the following record:
Field
SYNC
PRN
WEEK_NUM
ECCENTRICITY
TOA
DELTA_INCLINATION
OMEGADOT
A_SQRT
OMEGA0
Length (bits)
13
6
8
16
8
16
16
24
24
17
Scale Factor (LSB)
2-21
212
2-19
2-38
2-11
2-23
Units
seconds
semi-circles
semi-circles/sec
meters1/2
semi-circles
OMEGA
M0
AF0
AF1
EOM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
SYNC
2-23
2-23
2-20
2-38
24
24
11
11
7
semi-circles
semi-circles
seconds
sec/sec
The synchronization bits.
The base station shall set this field to the value of
‘1111100110101’ to indicate the beginning of the subalmanac message.
PRN
The satellite PRN number.
This parameter specifies the satellite PRN number for
which the sub-almanac is valid. It is represented as an
unsigned value in the range from 1 to 32, where the binary
value of the field conveys the satellite PRN number minus
one.
WEEK_NUM
The sub-almanac reference week number.
This parameter specifies the reference week number of the
sub-almanac. The range of this field is from 0 to 255.
ECCENTRICITY
Eccentricity.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
TOA
The reference time of the sub-almanac.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
DELTA_INCLINATION
Correction to inclination.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
OMEGADOT
Argument of perigee.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
A_SQRT
Square root of the semi-major axis.
18
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
OMEGA0
Longitude of ascending node.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
OMEGA
Argument of perigee.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
M0
Mean anomaly at reference time.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
AF0
Apparent satellite clock correction af0.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
AF1
Apparent satellite clock correction af1.
The base station shall set this field to the value contained in
the associated parameter of the specified GPS sub-almanac.
EOM
The end of message.
The base station shall set this field to the value of
‘1110010’ to indicate the end of the sub-almanac message.
Table 3.7.1-4 Global action message types
Action Code
0000
0001
0010
0011
0100
0101
0110
0111
1000
Type
Reserved
Rescan paging channels
Registration increment
Location Area
Reserved
Reserved
New access channel set
Random Challenge A
Overload control
19
1001
1010
1011
1100
1101
1110
1111
Access type parameters
Access attempt parameters
Random Challenge
Sub-Almanac Message
Reserved
Local control 1
Local control 2
1
20