ETSI TS 101 376-5-7 V3.1.1 (2009-07)

GEO-Mobile Radio Interface Specifications (Release 3); Third Generation Satellite Packet Radio Service; Part 5: Radio interface physical layer specifications; Sub-part 7: Radio Subsystem Synchronization; GMR-1 3G 45.010

RTS/SES-00309-5-7

General Information

• Status: Published
• Publication Date: 06-Jul-2009
• Technical Committee: SES MSS - SES WG on Mobile Satellite Systems
• Current Stage: 12 - Completion
• Due Date: 22-Jun-2009
• Completion Date: 07-Jul-2009

Standards Content (Sample)

Technical Specification
GEO-Mobile Radio Interface Specifications (Release 3);
Third Generation Satellite Packet Radio Service;
Part 5: Radio interface physical layer specifications;
Sub part 7: Radio Subsystem Synchronization;
GMR-1 3G 45.010
GMR-1 3G 45.010 2 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

Reference
RTS/SES-00309-5-7
Keywords
3G, GMPRS, GMR, GPRS, GSM, GSO,
interface, MES, mobile, MSS, radio, satellite,
S-PCN, synchronization, terminal, user
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ETSI
GMR-1 3G 45.010 3 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

Contents
Intellectual Property Rights . 5
Foreword . 5
Introduction . 6
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 9
3 Definitions and abbreviations . 9
3.1 Definitions . 9
3.2 Abbreviations . 10
4 General description of synchronization system . 10
4.1 System timing structure . 10
4.2 Timebase counter . 10
4.3 General requirement . 10
4.3.1 Timing and frequency reference point . 10
4.3.2 MES requirement . 10
4.3.3 Network requirement . 10
4.3.4 Measurement conditions . 11
5 Timing synchronization, TtG/GtT call . 11
5.1 General description. 11
5.2 Timing of forward link common channels . 11
5.2.1 FCCH/BCCH timing. 11
5.2.2 CCCH timing . 11
5.3 Idle mode timing synchronization . 11
5.3.1 Initial timing acquisition . 11
5.3.2 Paging mode . 12
5.3.3 Alerting mode . 12
5.4 Synchronization at initial access . 12
5.4.1 Synchronization process . 12
5.4.2 RACH timing pre-correction . 12
5.4.3 Description of parameters . 13
5.4.4 Timing accuracy . 13
5.5 Dedicated mode synchronization . 13
5.5.1 In-call timing relationship . 13
5.5.2 In-call synchronization scenario . 13
5.5.3 Transmission timing drift rate . 13
5.5.4 RX/TX guard time violation . 13
5.6 Packet transfer mode synchronization . 13
5.6.1 Packet transfer mode timing relationship. 13
5.6.2 Time synchronization for Packet switched channels . 14
5.6.3 Transmission timing drift rate . 16
5.6.4 Packet transfer mode timing relationship for handover to dedicated packet channel - Iu mode . 16
5.6.5 Packet transfer mode timing for handover to shared packet channel - Iu mode . 17
6 Frequency synchronization, TtG/GtT call . 17
6.1 General description. 17
6.2 Frequency of common channels . 17
6.3 Idle mode frequency synchronization. 18
6.3.1 Initial frequency acquisition . 18
6.3.2 Paging mode . 18
6.3.3 Alerting mode . 18
6.4 Synchronization at initial access . 18
6.4.1 Frequency compensation strategy . 18
ETSI
GMR-1 3G 45.010 4 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

6.4.2 Parameter description . 18
6.5 Dedicated mode synchronization . 18
6.6 Frequency synchronization for the packet switched channels . 18
7 Frame and message synchronization, TtG/GtT call . 19
7.1 Frame synchronization . 19
7.1.1 Frame number definition . 19
7.1.2 Frame synchronization scenario . 19
7.2 Message synchronization . 20
7.2.1 Power control message synchronization . 20
7.2.1.1 DCH power control message synchronization in forward direction . 20
7.2.1.2 DCH power control message synchronization in return direction . 20
7.2.2 SACCH message synchronization, TCH6/TCH9 call . 20
8 Synchronization for TtT call . 20
9 Aeronautical terminal synchronization scheme . 21
9.1 MES special features . 21
9.1.1 Speed . 21
9.1.2 Worst-case delay and Doppler features . 21
9.1.3 Frequency offset . 21
9.2 Frequency synchronization . 21
9.2.1 Frequency synchronization general description . 21
9.2.2 Idle mode frequency synchronization . 21
9.2.3 Synchronization at initial access . 21
9.2.4 Dedicated mode synchronization . 21
9.3 Timing synchronization . 21
Annex A (informative): Worst-case delay and Doppler features . 22
A.1 L-band . 22
A.2 S-band. 22
Annex B (informative): Range of timing correction factor . 24
Annex C (informative): Differential Doppler frequency . 25
Annex D (informative): SACCH message synchronization, TtG/GtT call . 26
Annex E (normative): Timer T3202 for packet mode of operation . 27
Annex F (normative): PTCCH/U and PTCCH/D scheduling . 28
Annex G (informative): Bibliography . 29
History . 30

ETSI
GMR-1 3G 45.010 5 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Satellite Earth Stations and
Systems (SES).
The contents of the present document are subject to continuing work within TC-SES and may change following formal
TC-SES approval. Should TC-SES modify the contents of the present document it will then be republished by ETSI
with an identifying change of release date and an increase in version number as follows:
Version 3.m.n
where:
• the third digit (n) is incremented when editorial only changes have been incorporated in the specification;
• the second digit (m) is incremented for all other types of changes, i.e. technical enhancements, corrections,
updates, etc.
The present document is part 5, sub-part 7 of a multi-part deliverable covering the GEO-Mobile Radio Interface
Specifications (Release 3); Third Generation Satellite Packet Radio Service, as identified below:
Part 1: "General specifications";
Part 2: "Service specifications";
Part 3: "Network specifications";
Part 4: "Radio interface protocol specifications";
Part 5: "Radio interface physical layer specifications":
Sub-part 1: "Physical Layer on the Radio Path: General Description";
Sub-part 2: "Multiplexing and Multiple Access; Stage 2 Service Description";
Sub-part 3: "Channel Coding";
Sub-part 4: "Modulation";
Sub-part 5: "Radio Transmission and Reception";
Sub-part 6: "Radio Subsystem Link Control";
Sub-part 7: "Radio Subsystem Synchronization";
Part 6: "Speech coding specifications";
Part 7: "Terminal adaptor specifications".
ETSI
GMR-1 3G 45.010 6 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

Introduction
GMR stands for GEO (Geostationary Earth Orbit) Mobile Radio interface, which is used for Mobile Satellite
Services (MSS) utilizing geostationary satellite(s). GMR is derived from the terrestrial digital cellular standard GSM
and supports access to GSM core networks.
The present document is part of the GMR Release 3 specifications. Release 3 specifications are identified in the title
and can also be identified by the version number:
• Release 1 specifications have a GMR 1 prefix in the title and a version number starting with "1" (V1.x.x).
• Release 2 specifications have a GMPRS 1 prefix in the title and a version number starting with "2" (V2.x.x).
• Release 3 specifications have a GMR-1 3G prefix in the title and a version number starting with "3" (V3.x.x).
The GMR release 1 specifications introduce the GEO-Mobile Radio interface specifications for circuit mode Mobile
Satellite Services (MSS) utilizing geostationary satellite(s). GMR release 1 is derived from the terrestrial digital cellular
standard GSM (phase 2) and it supports access to GSM core networks.
The GMR release 2 specifications add packet mode services to GMR release 1. The GMR release 2 specifications
introduce the GEO-Mobile Packet Radio Service (GMPRS). GMPRS is derived from the terrestrial digital cellular
standard GPRS (included in GSM Phase 2+) and it supports access to GSM/GPRS core networks.
The GMR release 3 specifications evolve packet mode services of GMR release 2 to 3rd generation UMTS compatible
services. The GMR release 3 specifications introduce the GEO-Mobile Radio Third Generation (GMR-1 3G) service.
Where applicable, GMR-1 3G is derived from the terrestrial digital cellular standard 3GPP and it supports access to
3GPP core networks.
Due to the differences between terrestrial and satellite channels, some modifications to the GSM or 3GPP standard are
necessary. Some GSM and 3GPP specifications are directly applicable, whereas others are applicable with
modifications. Similarly, some GSM and 3GPP specifications do not apply, while some GMR specifications have no
corresponding GSM or 3GPP specification.
Since GMR is derived from GSM and 3GPP, the organization of the GMR specifications closely follows that of GSM
or 3GPP as appropriate. The GMR numbers have been designed to correspond to the GSM and 3GPP numbering
system. All GMR specifications are allocated a unique GMR number. This GMR number has a different prefix for
Release 2 and Release 3 specifications as follows:
• Release 1: GMR n xx.zyy.
• Release 2: GMPRS n xx.zyy.
• Release 3: GMR-1 3G xx.zyy
where:
xx.0yy (z = 0) is used for GMR specifications that have a corresponding GSM or 3GPP specification. In this
case, the numbers xx and yy correspond to the GSM or 3GPP numbering scheme.
xx.2yy (z = 2) is used for GMR specifications that do not correspond to a GSM or 3GPP specification. In this
case, only the number xx corresponds to the GSM or 3GPP numbering scheme and the number yy is allocated
by GMR.
n denotes the first (n = 1) or second (n = 2) family of GMR specifications.
ETSI
GMR-1 3G 45.010 7 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

A GMR system is defined by the combination of a family of GMR specifications and GSM and 3GPP specifications as
follows:
• If a GMR specification exists it takes precedence over the corresponding GSM or 3GPP specification (if any).
This precedence rule applies to any references in the corresponding GSM or 3GPP specifications.
NOTE: Any references to GSM or 3GPP specifications within the GMR specifications are not subject to this
precedence rule. For example, a GMR specification may contain specific references to the corresponding
GSM or 3GPP specification.
• If a GMR specification does not exist, the corresponding GSM or 3GPP specification may or may not apply.
The applicability of the GSM and 3GPP specifications is defined in GMR 1 3G 41.201 [8].
ETSI
GMR-1 3G 45.010 8 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

1 Scope
The present document presents the requirements for synchronizing timing and frequency between the MES and the
Gateway Station (GS) in the GMR-1 3G Mobile Satellite System for circuit switch and packet switch modes of
operation.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• Non-specific reference may be made only to a complete document or a part thereof and only in the following
cases:
- if it is accepted that it will be possible to use all future changes of the referenced document for the
purposes of the referring document;
- for informative references.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are indispensable for the application of the present document. For dated
references, only the edition cited applies. For non-specific references, the latest edition of the referenced document
(including any amendments) applies.
[1] GMPRS-1 01.004 (ETSI TS 101 376-1-1): "GEO-Mobile Radio Interface Specifications
(Release 2) General Packet Radio Service; Part 1: General specifications;
Sub-part 1: Abbreviations and acronyms".
NOTE: This is a reference to a GMR-1 Release 2 specification. See the introduction for more details.
[2] GMR-1 3G 44.008 (ETSI TS 101 376-4-8): "GEO-Mobile Radio Interface Specifications
(Release 3); Third Generation Satellite Packet Radio Service; Part 4: Radio interface protocol
specifications; Sub-part 8: Mobile Radio Interface Layer 3 Specifications".
[3] GMR-1 3G 45.002 (ETSI TS 101 376-5-2): "GEO-Mobile Radio Interface Specifications
(Release 3); Third Generation Satellite Packet Radio Service; Part 5: Radio interface physical layer
specifications; Sub-part 2: Multiplexing and Multiple Access; Stage 2 Service Description".
[4] GMR-1 3G 45.005 (ETSI TS 101 376-5-5): "GEO-Mobile Radio Interface Specifications
(Release 3); Third Generation Satellite Packet Radio Service; Part 5: Radio interface physical layer
specifications; Sub-part 5: Radio Transmission and Reception".
[5] GMR-1 3G 45.008 (ETSI TS 101 376-5-6): "GEO-Mobile Radio Interface Specifications
(Release 3); Third Generation Satellite Packet Radio Service; Part 5: Radio interface physical layer
specifications; Sub-part 6: Radio Subsystem Link Control".
[6] GMR-1 05.010 (ETSI TS 101 376-5-7) (V1.3.1): "GEO-Mobile Radio Interface Specifications
(Release 1); Part 5: Radio interface physical layer specifications; Sub-part 7: Radio Subsystem
Synchronization".
NOTE: This is a reference to a GMR-1 Release 1 specification. See the introduction for more details.
ETSI
GMR-1 3G 45.010 9 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

[7] GMR-1 3G 44.060 (ETSI TS 101 376-4-12): "GEO-Mobile Radio Interface Specifications
(Release 3); Third Generation Satellite Packet Radio Service; Part 4: Radio interface protocol
specifications; Sub-part 12: Mobile Earth Station (MES) - Base Station System (BSS) interface;
Radio Link Control/Medium Access Control (RLC/MAC) protocol".
[8] GMR-1 3G 41.201 (ETSI TS 101 376-1-2): "GEO-Mobile Radio Interface Specifications
(Release 3); Third Generation Satellite Packet Radio Service; Part 1: General specifications;
Sub-part 2: Introduction to the GMR-1 family".
[9] GMR-1 3G 44.118 (ETSI TS 101 376-4-13): "GEO-Mobile Radio Interface Specifications
(Release 3); Third Generation Satellite Packet Radio Service; Part 4: Radio interface protocol
specifications; Sub-part 13: Radio Resource Control (RRC) protocol; Iu Mode".
2.2 Informative references
The following referenced documents are not essential to the use of the present document but they assist the user with
regard to a particular subject area. For non-specific references, the latest version of the referenced document (including
any amendments) applies.
Not applicable.
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in GMR-1 3G 41.201 [8] and the following
apply:
Frequency Correction (FC): in-call frequency correction sent over FACCH channel
frequency offset: frequency correction sent over AGCH channel
guard time violation: a message to indicate the violation of Rx/Tx burst guard time
MAC_FORWARD_TS_OFFSET: offset in number of timeslots of MAC-slot 0 or D-MAC-slot 0 relative to the start
of the downlink frame
MAC_RETURN_TS_OFFSET: offset in number of timeslots of MAC-slot 0 or D-MAC-slot 0 relative to the start of
the uplink frame
Precorrection Indication (PI): timing delay pre-compensated by the MES in the RACH transmission
RACH_TS_OFFSET: RACH window offset relative to the start of BCCH window within the same frame, measured in
number of timeslots
RACH_SYMBOL_OFFSET: RACH timing offset in symbols
NOTE: The offset between RACH window and the start of the reference frame seen from the MES. Measured in
number of symbols.
SA_BCCH_STN: BCCH window offset relative to the start of the frame, in number of timeslots
SA_FREQ_OFFSET: twice of the downlink beam centre Doppler due to satellite motion only
SA_SIRFN_DELAY: within each multiframe, the first FCCH channel frame number relative to the start of the
multiframe
SB_FRAME_TS_OFFSET: offset between downlink frame N and uplink frame N + 7 at the spot-beam centre,
measured in number of timeslots
ETSI
GMR-1 3G 45.010 10 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

SB_SYMBOL_OFFSET: additional offset between downlink frame N and uplink frame N + 7 at the spot beam centre,
measured in number of symbols
Timing Correction (TC): in-call timing correction sent over FACCH channel
timing offset: timing correction sent over AGCH channel
USF Delay Value: if an MES receives a USF in its receive downlink frame N, it applies the USF (i.e. transmits
corresponding to the received USF grant) on the uplink frame numbered (N + USF Delay Value)
NOTE: USF Delay Value is decoded from USF_DELAY and USF_DELAY Adjustment parameters in BCCH
System Information, and it can take values of 6, 7, 8, 9 or 10.
3.2 Abbreviations
For the purposes of the present document, the abbreviations defined in GMPRS-1 01.004 [1] apply.
4 General description of synchronization system
Same as clause 4 in GMR-1 05.010 [6], with addition of following at the end of the first paragraph.
The description above also applies to S-band.
4.1 System timing structure
Same as clause 4.1 in GMR-1 05.010 [6].
4.2 Timebase counter
Same as clause 4.2 in GMR-1 05.010 [6].
4.3 General requirement
4.3.1 Timing and frequency reference point
Same as clause 4.3.1 in GMR-1 05.010 [6].
4.3.2 MES requirement
Same as clause 4.3.2 in GMR-1 05.010 [6], with the addition of the following:
• MES receiver's time and frequency search ranges (apertures) shall be large enough to accommodate the
variations (specified in clause 4.3.3) in the network transmit time and frequency in addition to the
satellite-MES relative motion induced time and frequency shifts (see annex A for an informative description),
MES oscillator drifts, etc. The MES receiver, operating with such values of time and frequency apertures, shall
achieve the performance requirements (i.e. BER, FER, time and frequency estimation accuracies, etc.)
specified in GMR-1 3G 45.005 [4].
4.3.3 Network requirement
Same as clause 4.3.3 in GMR-1 05.010 [6], with the addition of the following:
• The network shall ensure that the maximum variation between the transmit time of a CCCH burst and the
transmit time of a PDCH burst does not exceed 12 μs. Similarly, the maximum burst-to-burst variation in the
PDCH transmit time shall not exceed 4 μs. Burst-to-burst variations in the network transmit frequency shall
not exceed 10 Hz.
ETSI
GMR-1 3G 45.010 11 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

4.3.4 Measurement conditions
Same as clause 4.3.4 in GMR-1 05.010 [6].
5 Timing synchronization, TtG/GtT call
Same as clause 5 in GMR-1 05.010 [6], except for the addition of the next paragraph, which follows the second
paragraph.
For the case in which the MES operates in the packet mode, shared or dedicated, receive timing shall be corrected by
monitoring BCCH, PCH, PDCH, or DCH and transmission timing shall be corrected with factors provided by the
Gateway Station (GS). The GS provides correction factors via AGCH, PACCH, or DACCH based on the MES mode
and situation, which is explained here.
5.1 General description
Same as clause 5.1 in GMR-1 05.010 [6], except for the addition of the next paragraph, which follows the fifth
paragraph.
If packet transfer mode is initiated via the RACH then the procedure is identical to that described for circuit switched
service in clause 5.3.1. Packet switched time and frequency synchronization for the PDCH and the PRACH is described
in clause 5.6.
5.2 Timing of forward link common channels
Same as clause 5.2 in GMR-1 05.010 [6], except for the addition of the following text.
When the FCCH3 is used, the timing of forward link common channels is defined in GMR-1 3G 45.002 [3]. An outline
is given below for convenience.
The BCCH/CCCH bursts occupy twelve consecutive timeslots. In each spot beam, a set of common channels are
defined: FCCH3, BCCH, PCH, GBCH3 and AGCH. These channels follow a fixed repetition pattern with repetition
duration equal to one multiframe. The position of the BCCH and FCCH3 between neighbouring beams shall be offset in
frames as well as in timeslots to facilitate MES fast timing/frequency acquisition and satellite power spread in time.
5.2.1 FCCH/BCCH timing
Same as clause 5.2.1 in GMR-1 05.010 [6], except for the addition of the following text.
For FCCH3/BCCH timing, refer to GMR-1 3G 45.002 [3].
5.2.2 CCCH timing
Same as clause 5.2.2 in GMR-1 05.010 [6], except for the addition of the following text.
When the FCCH3 is used, CCCH timing, is described in GMR-1 3G 45.002 [3].
5.3 Idle mode timing synchronization
5.3.1 Initial timing acquisition
Same as clause 5.3.1 in GMR-1 05.010 [6] except for the addition of the following text.
The specification applies identically when the FCCH3 is used except that reference should be made to
GMR-1 3G 45.008 [5].
ETSI
GMR-1 3G 45.010 12 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

5.3.2 Paging mode
Same as clause 5.3.2 in GMR-1 05.010 [6] except for the addition of the following text.
The specification applies identically when the FCCH3 is used except that reference should be made to
GMR-1 3G 45.005 [4] and GMR-1 3G 45.008 [5].
5.3.3 Alerting mode
Same as clause 5.3.3 in GMR-1 05.010 [6] except for the addition of the following text.
The specification applies identically when the FCCH3 is used except that reference should be made to
GMR-1 3G 45.002 [3] and GMR-1 3G 45.005 [4].
5.4 Synchronization at initial access
5.4.1 Synchronization process
Same as clause 5.4.1 in GMR-1 05.010 [6], with the following addition.
The synchronization process also applies to RACH3.
5.4.2 RACH timing pre-correction
Same as clause 5.4.2 in GMR-1 05.010 [6], with the following additions.
When transmitting RACH/RACH3 the MES shall not apply any pre-correction unless explicitly indicated by the
network. The MES shall always offset the transmission RACH/RACH3 with respect to the received control channel
reference frame, assuming that the MES located at the beam centre.
The network may send on the AGCH the Immediate Assignment Reject (IAR) message with a reject cause that
indicates that the class-2 information bits of the RACH burst are incorrect (e.g., if the RACH burst from the MES does
not entirely fit within the RACH window at the network). The IAR message shall contain Timing Correction and
Frequency Correction fields (see clauses 5.6.2 and 6.6, and GMR-1 3G 44.008 [2]).
The MES shall retransmit RACH when it receives the IAR message with the reject cause indicating incorrect
class-2 bits.
The MES shall apply entire value of the received Frequency Correction to the re-transmitted RACH/RACH3.
All MES Terminal Types except Terminal type C shall apply entire value of the received Timing Correction to the
re-transmitted RACH.
An MES of Terminal Type C shall retransmit RACH, in response to an IAR with reject cause indicating incorrect
Class-2 bits, with a new value of Precorrection Indication that is derived from the received Timing Correction, as
described below:
• The MES of Terminal Type C shall select one of the seven (non-reserved) values of Precorrection Indication
shown in the Compensation column of table 5.2 of GMR-1 05.010 [6] such that the selected value, in symbols,
is the one closest to one-half of the received Timing Correction converted to units of a symbol (the received
Timing Correction is in units of T /40, whereas the Precorrection Indication is in units of T
SB SB
(i.e. 1/23400 seconds)). Equivalently, the selected value of Precorrection Indication, in symbols, shall be the
th
one which is the closest to (1/80) of the received Timing Correction in units of T /40. The selected value
SB
shall be used as the new value of Precorrection Indication in calculation of RACH_SYMBOL_OFFSET (refer
to clause 5.4.3 of GMR-1 05.010 [6]). Furthermore, the MES shall send, in the retransmitted RACH, the
applied value of Precorrection Indication by converting it to one of the seven (non-reserved) values of the
three-bit code shown in table 5.2 of GMR-1 05.010 [6].
ETSI
GMR-1 3G 45.010 13 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

5.4.3 Description of parameters
Same as clause 5.4.3 in GMR-1 05.010 [6], with the following additions for MES of Terminal Type C.
For a retransmitted RACH resulting from receipt of Immediate Assignment Reject message from the network indicating
invalid Class-2 RACH information, the MES of Type C shall apply transmit timing offset based on computation of
RACH_SYMBOL_OFFSET derived as described in clause 5.4.2. For all other RACH transmissions, an MES of
Terminal Type C shall apply transmit timing offset based on computation of RACH_SYMBOL_OFFSET as described
in clause 5.4.3 of GMR-1 05.010 [6]. This offset is relative to the start of timeslot 0 of the received TDMA frame in the
forward direction.
5.4.4 Timing accuracy
Same as clause 5.4.4 in GMR-1 05.010 [6].
5.5 Dedicated mode synchronization
Same as clause 5.5 in GMR-1 05.010 [6], with the following addition.
Timing synchronization for packet dedicated mode refers to clause 5.6.
5.5.1 In-call timing relationship
Same as clause 5.5.1 in GMR-1 05.010 [6].
5.5.2 In-call synchronization scenario
Same as clause 5.5.2 in GMR-1 05.010 [6].
5.5.3 Transmission timing drift rate
Same as clause 5.5.3 in GMR-1 05.010 [6].
5.5.4 RX/TX guard time violation
Same as clause 5.5.4 in GMR-1 05.010 [6] except for the following changes.
For a terminal type C MES in the packet data mode, the available RX/TX guard time shall be monitored at least once
every 15 s. If the guard time is found to be smaller than a predefined threshold of 2 200 μs, the MES shall abort the
TBF and send RACH for requesting new packet resource.
For a terminal type E or above MES, the available RX/TX guard time shall be monitored at least once every 15 s. If the
guard time is found to be smaller than a predefined threshold of 1 000 μs, the MES shall abort the TBF and send
RACH3 for requesting new packet resource.
5.6 Packet transfer mode synchronization
In packet transfer mode, either the PDCH/PDCH3 channels, or the PRACH/PRACH3 channels are used. The
synchronization scheme addressed below applies to these channels.
5.6.1 Packet transfer mode timing relationship
The uplink and downlink frame timing relationship described in clause 5.5.1 shall apply to packet transfer mode. The
time between the start of receive frame N and the start of transmit frame N + 7 at the MES is given by, ΔT .
OF
ETSI
GMR-1 3G 45.010 14 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

To interpret the Uplink State Flag (USF) in the downlink PUI (see GMR-1 3G 44.060 [7]), the MES shall apply the
following rule. If the MES receives a USF in its receive downlink frame N, it shall apply the USF to the uplink frame
numbered (N + USF DELAY Value), where the USF Delay Value is decoded from the USF_DELAY and
USF_DELAY_Adjustment parameters that are contained in System Information (see GMR-1 3G 44.008 [2]). The USF
Delay Value, after adjustment if any, decodes to values of 6, 7, 8, 9 or 10.
Thus the MES response time is defined as the time measured from the end of the time slot in which the MES received a
PNB(m,3) PNB2(m,3), PNB2(m,12), or PNB3(m,n) containing the USF assigned to the MES, and the start of the time
slot in which the MES is granted uplink access by the USF (see GMR-1 3G 44.060 [7]).
For terminals assigned carrier type PDTCH(4,3), PDTCH(5,3), PDTCH2(5,3), PDTCH3(5,3) or PDTCH3(10,3) the
response time is given by:
T = ΔT - TS × MAC_FORWARD_TS_OFFSET + TS × MAC_RETURN_TS_OFFSET - 5 ms +
RESP-1 OF
(USF Delay Value - 7) × 40 ms.
For terminals receiving PDTCH2(5,12) or PDTCH(5,12), the response time is given by:
T = ΔT - TS × MAC_FORWARD_TS_OFFSET + TS × MAC_RETURN_TS_OFFSET - 20 ms +
RESP-1 OF
(USF Delay Value - 7) × 40 ms.
An MES receiving a PDTCH2(5,12) shall decode additional USF values in the Extended PUI. Refer to
GMR-1 3G 44.060 [7]) for T calculation for the USF values assigned through the Extended PUI.
RESP-1
An MES receiving a PDTCH3(m,n) shall decode additional USF values in the ULMAP. Refer to GMR-1 3G 44.060 [7]
for T calculation for the USF values assigned through ULMAP.
RESP-1
For terminals assigned carrier type PDTCH(2,6) and PDTCH(1,6) or receiving PDTCH3(1,6) or PDTCH3(2,6) the
response time is given by:
T = ΔT - TS × MAC_FORWARD_TS_OFFSET + TS × MAC_RETURN_TS_OFFSET - 10 ms +
OF
RESP-2
(USF Delay Value - 7) × 40 ms
The range of values for MAC_FORWARD_TS_OFFSET and MAC_RETURN_TS_OFFSET is given in
GMR-1 3G 44.008 [2].
The MES shall be able to transmit a PNB in the assigned time slot and frame provided the response time, T , is
RESP-2
greater than or equal to 40 ms.
The value of T may be such that the terminal type C MES can only partially receive PNB(2,6) when it transmits
RESP-2
PNB(1,6) on the uplink. Consider a value T such that the terminal type C MES can receive burst-header of
RESP-2
downlink PNB(2,6), but not the PRI. For such values of T , the MES of terminal type C shall receive, decode and
RESP-2
interpret the burst header of PNB(2,6) (see also GMR-1 3G 45.002 [3] and GMR-1 3G 44.060 [7]).
The GS shall determine USF_DELAY and USF_DELAY Adjustment (if applicable) values for a spot beam such than
for every MES within the boundary of the spot beam, the above requirement shall be satisfied.
During the packet transfer mode, the value of 2[]T −T may be updated via PTCCH/D or PACCH messages to
U 0
compensate for any timing drift caused by MES oscillator and MES-satellite relative motion as described in
clause 5.6.2.
5.6.2 Time synchronization for Packet switched channels
The MES receiver timing shall be derived from its internal timebase, but frequently corrected by timing detection of the
received PDCH and PDCH3 bursts during packet transfer mode. The task of receiver timing correction has to be
performed often enough to handle the worst case timing drift rate specified in clause 4.3.2. The target timing accuracy is
to achieve demodulation performances specified by GMR-1 3G 45.005 [4].
ETSI
GMR-1 3G 45.010 15 ETSI TS 101 376-5-7 V3.1.1 (2009-07)

In the uplink, a closed-loop synchronization scheme is used. The synchronization process is detailed below:
The GS shall perform the scheduled timing advance mechanism for all MES working in packet transfer mode on a
PDCH for which a PTCCH/U is assigned. The GS shall not assign a PTCCH/U on a PDCH3 packet channel. Therefore
the GS shall monitor the delay of the PNB bursts sent by the MES on PTCCH/U, if assigned to the MES and respond
with timing advance values for all MES performing the procedure on that PDCH. These timing advance values shall be
sent via a downlink signalling message on PTCCH/D (see GMR-1 3G 1 44.060 [7]), if assigned to the MES. These are
scheduled timing corrections.
The PTCCH/U and PTCCH/D shall be transmitted using the most conservative modulation and coding rate supported
by the MES for the shortest duration PDCH burst. The MCS values to be used for different terminal types are defined in
table 5.4. For MCS definitions, refer to GMR-1 3G 44.060 [7].
Table 5.4: MCS values and burst types for PTCCH/U and PTCCH/D
Downlink Terminal type MCS for PTCCH/D burst MCS for PTCCH/U burst
Channel type PTCCH/D PTCCH/U
PDTCH (binary) (binary)
(see note) (see note)
(2,6) C 000 PDCH(2,6) 000 PDCH (1,6)
(4,3) A 0000 PDCH(4,3) 0000 PDCH(4,3)
(5,3) A 0000 PDCH(5,3) 0000 PDCH(5,3)
(5,3) D 0011 PDCH(5,3) 0011 PDCH(5,3)
NOTE: MCS coding (3 bits or 4 bits) is dependent on channel type, see GMR-1 3G 44.060 [7].

The GS shall update the timing advance values for a MES in the next downlink signalling message addressed to that
MES following the reception of a packet access burst from the MES. These are initial timing corrections.
The GS may also monitor the delay of the packet normal bursts sent by the MES on PDTCH and PACCH. Whenever an
updating of Timing Advance (TA) is needed, the GS may send the new TA value in a link synchronization message
(see GMR-1 3G 44.060 [7]). This is unsolicited timing correction.
If the
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