ETSI TS 145 010 V13.5.0 (2019-05)

TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
GSM/EDGE Radio subsystem synchronization
(3GPP TS 45.010 version 13.5.0 Release 13)

R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
3GPP TS 45.010 version 13.5.0 Release 13 1 ETSI TS 145 010 V13.5.0 (2019-05)

Reference
RTS/TSGR-0645010vd50
Keywords
GSM
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3GPP TS 45.010 version 13.5.0 Release 13 2 ETSI TS 145 010 V13.5.0 (2019-05)
Intellectual Property Rights
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Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
http://webapp.etsi.org/key/queryform.asp.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
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Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 5
1 Scope . 6
1.1 References . 6
1.2 Definitions and abbreviations . 6
2 General description of synchronization system . 8
3 Timebase counters . 9
3.1 Timing state of the signals . 9
3.2 Relationship between counters . 9
4 Timing of transmitted signals . 9
5 BTS Requirements for Synchronization . 10
5.0 General . 10
5.1 Frequency source . 11
5.2 Timebase counters . 11
5.3 Internal BTS carrier timing . 11
5.4 Initial Timing advance estimation . 11
5.5 Maximum timing advance value . 11
5.6 Delay tracking . 12
5.6.1 For circuit switched channels. 12
5.6.2 For packet switched channels . 12
5.6.3 Delay assessment error . 12
5.6.4 Pico-BTS and Local Area multicarrier BTS delay tracking . 12
5.7 Timeslot length . 12
5.7.0 Implementation options . 12
5.7.1 Regular implementation with timeslot lengths of non-integral symbol periods . 13
5.7.2 Implementation option for reduced symbol period bursts when integral symbol period option is used
for normal symbol period bursts . 14
5.8 Range of Timing advance . 15
6 MS Requirements for Synchronization . 15
6.0 General . 15
6.1 MS carrier frequency . 16
6.2 Internal timebase . 16
6.3 Assessment of BTS timing . 16
6.4 Timing of transmission . 16
6.5 Application of Timing Advance . 16
6.5.1 For circuit switched channels. 16
6.5.2 For packet switched channels . 17
6.6 Access to a new BTS . 17
6.7 Temporary loss of signal . 18
6.8 Timing of channel change . 18
6.9 Application of new Timing Advance value . 19
6.10 Definition of "ready to transmit within x ms" . 19
6.11 Definition of additional reaction times for GPRS mobile stations . 19
6.11.1 Uplink and downlink assignment reaction times . 19
6.11.2 Change in channel coding scheme commanded by net work . 20
6.11.3 Contention resolution reaction time . 20
6.11.4 Reaction time in response to other commanding messages . 21
6.11.5 PAN related reaction times . 21
6.11.6 DTR related reaction times . 21
6.12 Observed Frequency Offset (OFO) reported by the CTS-MS . 22
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6.13 Timing of inter-RAT channel change from GSM to UTRAN . 22
6.13a Timing of inter-RAT channel change from GSM to E-UTRAN . 23
6.14 Timing of combined intracell channel change and packet assignment . 23
7 CTS-FP Requirements for Synchronization . 24
7.1 Frequency source default requirements . 24
7.2 Frequency source for a CTS-FP assisted by a CTS-MS . 24
7.3 Internal CTS-FP carrier timing . 24
7.4 Timeslot length . 24
7.5 Assessment of CTS-MS delay . 24
Annex A (normative): Additional requirements for pseudo-synchronization, synchronized
handovers and pseudo-synchronized handovers . 25
A.1 General descriptions and definitions . 25
A.1.1 Conventions . 25
A.1.2 Definitions . 25
A.1.3 Details of operations . 25
A.2 BTS requirements . 26
A.2.1 The pseudo-synchronization scheme . 26
A.2.1.1 BTS a time difference estimate . 26
A.2.1.2 The reception epoch criterion . 26
A.2.1.3 Pseudo-synchronized handover . 26
A.2.2 The synchronization scheme . 26
A.3 MS requirements . 27
A.3.1 Provision of time difference information . 27
A.3.2 After each successful circuit-switched handover . 27
A.3.3 Synchronized or a pseudo synchronized handover . 27
Annex B (informative): CTSBCH timeslot shifting properties for CTS-MS synchronization . 28
B.1 Determination of TN by the CTS-MS when CTSBCH shifting is not active . 28
B.2 Determination of TN by the CTS-MS when CTSBCH shifting is active . 28
Annex C (informative): BTS frequency source stability and E-OTD LMU reporting periods
for LCS . 29
C.1 BTS frequency source stability and E-OTD LMU reporting periods . 29
C.2 Frequency source stability . 29
C.3 Relationship to E-OTD reporting periods . 29
Annex D (informative): Change history . 31
History . 35

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Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
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1 Scope
The present document defines the requirements for synchronization on the radio sub-system of the digital cellular
telecommunications systems GSM. However, it does not define the synchronization algorithms to be used in the Base
Transceiver Station (BTS), CTS Fixed Part (CTS-FP) and Mobile Station (MS). These are up to the manufacturer to
specify.
1.1 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: “Vocabulary for 3GPP Specifications”.
[2] 3GPP TS 25.123: “Requirements for support of radio resource management (TDD)”.
[3] 3GPP TS 25.133: “Requirements for support of radio resource management (FDD)”.
[4] 3GPP TR 43.030: “Radio network planning aspects”.
[5] 3GPP TS 43.052: “Lower layers of the Cordless Telephony System (CTS) Radio Interface; Stage
2”.
[6] 3GPP TS 43.059: “Functional stage 2 description of Location Services (LCS) in GERAN”.
[7] 3GPP TS 43.064: “Overall description of the GPRS radio interface; Stage 2”.
[8] 3GPP TS 44.018: “Mobile radio interface layer 3 specification, Radio Resource Control Protocol”.
[9] 3GPP TS 44.060: “General Packet Radio Service (GPRS); Mobile Station (MS) - Base Station
System (BSS) interface; Radio Link Control/ Medium Access Control (RLC/MAC) protocol”.
[10] 3GPP TS 45.002: “Multiplexing and multiple access on the radio path”.
[11] 3GPP TS 45.005: “Radio transmission and reception”.
[12] 3GPP TS 45.008: “Radio subsystem link control”.
[13] 3GPP TS 45.050: “Background for RF Requirements”.
[14] 3GPP TS 45.056: “CTS-FP Radio Sub-system”.
[15] 3GPP TS 45.004: “Modulation”.
[16] 3GPP TS 36.133: “Evolved Universal Terrestrial Radio Access (E-UTRA); Requirements for
support of radio resource management”.
[17] 3GPP TS 36.211: “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and
Modulation”.
1.2 Definitions and abbreviations
In addition to those below, abbreviations used in the present document are listed in 3GPP TR 21.905.
BTS: Base Transceiver Station.
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BTTI: Basic TTI.
Coverage Class: see definition in 3GPP TS 43.064.
CTS-FP: CTS Fixed Part.
CTS-MS: MS operating in CTS mode.
Current Serving BTS: BTS on one of whose channels (TCH, DCCH, CCCH or PDCH) the MS is currently operating.
Current Serving CTS-FP: CTS-FP on one of whose channels (TCH or CTS control channels) the CTS-MS is
currently operating.
EC: Extended Coverage, see definition in 3GPP TS 43.064.
EC operation: see definition in 3GPP TS 43.064.
EC-GSM-IoT: Extended Coverage GSM for Internet of Things.
FANR (Fast Ack/Nack Reporting): Fast Ack/Nack Reporting enables the use of a PAN field within an RLC/MAC
block for EGPRS data transfer or for EGPRS2 data transfer. FANR enables the mobile station to transmit in the uplink
direction a PAN field corresponding to a downlink TBF. Similarly FANR enables the network to transmit in the
downlink direction a PAN field corresponding to an uplink TBF.
MS timing offset: delay of the received signal relative to the expected signal from an MS at zero distance under static
channel conditions with zero timing advance. This is accurate to ± 1 symbol, and reported once per SACCH or after a
RACH as. required (i.e. at the same rate as timing advance). For example, for an MS with a round trip propagation
delay of P symbols, but with a timing advance of T symbols, the reported timing offset will be P-T quantized to the
nearest symbol. For GPRS the MS timing offset is not reported.
Normal Symbol Period: duration of a symbol for bursts using a modulating symbol rate of 1625/6 ksymb/s (see 3GPP
TS 45.004); it is equal to 48/13 µs. This symbol duration is used for transmission of GMSK, 8PSK, 16QAM and
32QAM modulated bursts on downlink and GMSK, 8PSK and 16QAM modulated bursts on uplink (see 3GPP TS
45.004).
Observed Frequency Offset (OFO): difference of frequency of signals received by a CTS-MS from a CTS-FP and a
BTS. The Observed Frequency Offset is measured and reported by the CTS-MS on CTS-FP requirement. The Observed
Frequency Offset is expressed in ppm with an accuracy of 1/64 ppm (i.e. about 0,016 ppm).
PAN: Piggy-backed Ack/Nack.
Quarter symbol number: timing of quarter symbol periods (12/13 µs or 10/13 µs depending on the actual symbol
period used) within a timeslot. A symbol can represent 1 to 5 bits depending upon modulation.
Reduced Latency: refers to the use of FANR either in BTTI configuration or in RTTI configuration for EGPRS and
EGPRS2.
Reduced Symbol Period: duration of a symbol for bursts using a modulating symbol rate of 325 ksymb/s (see 3GPP
TS 45.004); it is equal to 40/13 µs. This symbol duration is used for transmission of QPSK, 16QAM and 32QAM
modulated bursts on uplink and downlink (see 3GPP TS 45.004).
RTTI: Reduced TTI.
Symbol Period: symbol period is the duration of a symbol and shall refer to normal symbol period unless explicitly
clarified to be the reduced symbol period.
TDMA frame number: count of TDMA frames relative to an arbitrary start point.
Timebase counters: set of counters which determine the timing state of signals transmitted by a BTS or MS.
Time group (TG): used for compact, time groups shall be numbered from 0 to 3 and a particular time group shall be
referred to by its time group number (TG) (see 3GPP TS 45.002).
Timeslot number (TN): timing of timeslots within a TDMA frame.
Timing Advance: signal sent by the BTS to the MS which the MS uses to advance its timings of transmissions to the
BTS so as to compensate for propagation delay.
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Timing Advance Index: Timing Advance Index TAI used for GPRS, which determines the position of the subchannel
on PTCCH (see 3GPP TS 45.002) used by the MS to send an access burst, from which the network can derive the
timing advance.
TTI: Transmission Time Interval.
2 General description of synchronization system
This clause gives a general description of the synchronization system. Detailed requirements are given in clauses 3 to 7.
The BTS sends signals on the BCCH carrier or, for COMPACT on the CPBCCH carrier, to enable the MS to
synchronize itself to the BTS and if necessary correct its frequency standard to be in line with that of the BTS. The
signals sent by the BTS for these purposes are:
a) Frequency correction bursts;
b) Synchronization bursts.
The timings of timeslots, TDMA frames, TCH frames, control channel frames, and (for COMPACT) the rotation of
time groups are all related to a common set of counters which run continuously whether the MS and BTS are
transmitting or not. Thus, once the MS has determined the correct setting of these counters, all its processes are
synchronized to the current serving BTS.
The MS times its transmissions to the BTS in line with those received from the BTS. The BTS sends to each MS a
"timing advance" parameter (TA) according to the perceived round trip propagation delay BTS-MS-BTS. The MS
advances its timing by this amount, with the result that signals from different MS's arriving at the BTS and compensated
for propagation delay. This process is called "adaptive frame alignment".
Additionally, synchronization functions may be implemented in both the MS and the BTS to support the so-called
pseudo synchronization scheme for circuit-switched handovers. The support of this scheme is optional except that MS
shall measure and report the Observed Timing Difference (OTD), which is a mandatory requirement. The detailed
specifications of the pseudo-synchronization scheme for circuit-switched handovers are included in annex A.
While in dual transfer mode an MS performs all the tasks of dedicated mode. In addition, upper layers can require the
release of all the packet resources, which triggers the transition to dedicated mode, or the release of the RR resources,
which triggers the transition either to idle mode and packet idle mode or, depending upon network and MS capabilities,
to packet transfer mode.
When handed over to a new cell, the MS leaves the dual transfer mode, enters the dedicated mode where it switches to
the new cell, may read the system information messages sent on the SACCH and may then enter dual transfer mode in
the new cell (see 3GPP TS 44.060).
In CTS, the CTS-FP sends signals on the CTSBCH to enable the MS to synchronize itself to the CTS-FP and if
necessary correct its frequency standard to be in line with that of the CTS-FP.
The signals sent by the CTS-FP for these purposes are:
a) Frequency correction bursts;
b) Synchronization bursts.
The timings of timeslots, TDMA frames, CTSBCH, CTSARCH, CTSAGCH and CTSPCH frames are all related to a
first common set of counters which run continuously whether the CTS-MS and CTS-FP are transmitting or not. Thus,
once the CTS-MS has determined the correct setting of these first counters, the CTS-MS is able to attach to the current
serving CTS-FP. In addition, during CTS-MS attachment, the CTS-FP sends to the CTS-MS the remaining counters for
SACCH and TCH frames. Then, all processes of the CTS-MS are synchronized to the current serving CTS-FP.
The CTS-MS times its transmissions to the CTS-FP in line with those received from the CTS-FP. The timing advance
parameter is set to zero for CTS.
Additionally, the CTS-FP may be assisted by a CTS-MS to adjust its frequency source. When required by the CTS-FP,
the CTS-MS estimates if possible and reports the Observed Frequency Offset of the CTS-FP with a specified BTS. The
CTS-FP may then adjust its frequency source according to this value.
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3 Timebase counters
3.1 Timing state of the signals
The timing state of the signals transmitted by a BTS (for normal symbol period), a MS (for normal symbol period), a
CTS-FP, or an Compact BTS and MS is defined by the following counters:
- Quarter symbol number QN (0 - 624)
- Symbol number BN (0 - 156);
- Timeslot number TN (0 - 7);
- TDMA frame number FN (0 to (26 x 51 x 2048) - 1 = 2715647); or
- for a non attached CTS-MS, TDMA frame number modulo 52 T4 (0 - 51); or
- for Compact, TDMA frame number FN (0 to (52 x 51 x 1024) -1 = 2715647).
In CTS, the CTS-MS shall manage different sets of counters for CTS operation and GSM operation.
Alternatively, in case of transmission using reduced symbol period, for a BTS or an MS the following counters have the
following ranges:
- Quarter symbol number QN (0-749)
- Symbol number BN (0-187)
3.2 Relationship between counters
The relationship between these counters is as follows:
- QN increments every 12/13 µs for normal symbol period and every 10/13µs for Reduced Symbol Period;
- BN = Integer part of QN/4;
- TN increments whenever QN changes from count 624 to 0 for normal symbol periodand whenever QN changes
from count 749 to 0 for reduced symbol period;
- FN increments whenever TN changes from count 7 to 0; or
- for a CTS-MS, T4 increments whenever TN changes from count 7 to 0.
4 Timing of transmitted signals
The timing of signals transmitted by the MS, BTS and CTS-FP is defined in 3GPP TS 45.002.
i) The MS can use the timing of receipt of the synchronization burst to set up its timebase counters as follows:
QN is set by the timing of the training sequence;
TN = 0 when the synch burst is received;
FN = 51 ((T3-T2) mod (26)) + T3 + 51 x 26 x T1 when the synch burst is received, (where T3 = (10 x T3') + 1,
T1, T2 and T3' being contained in information fields in synchronization burst).
ii) For Compact, the MS can use the timing of receipt of the synchronization burst to set up its timebase counters as
follows:
QN is set by the timing of the training sequence;
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FN = (R1 x 51 + R2) x 52 + 51 when the synch burst is received (where R1 and R2 are contained in
information fields in synchronization burst);
TN is determined from TG as described in 3GPP TS 45.002, where TG is contained in information fields in
synchronization burst.
iii) For CTS, the timebase counters are set as follows:
QN is set by the timing of the training sequence;
TN is set according to the CTSBCH-SB position (see Annex C);
T4 = 51 when the CTSBCH-SB is received (prior to attachment);
FN = (51 ((T3-T2) mod (26)) + T3 + 51 x 26 x T1) mod (2715648) when the CTS-MS receives the last
CTSAGCH burst of the non-hopping access procedure, where T2 = T4 mod (26), and T1 and T3 being
contained in this CTS immediate assignment message.
iv) For EC-GSM-IoT, the MS can use the timing of receipt of the synchronization burst on EC-SCH to set up its
timebase counters as follows:
QN is set by the timing of the training sequence;
TN = 1 when the synch burst is received
FN = RFN + 51 x 26 x 512 x QUARTER_HYPERFRAME_INDICATOR
QH
where,
RFN = FN within a quarter hyperframe = (51 x 52 x T1') + (4 x 51 x T2' + 51 x T2'') + T3 when the synch
QH
burst is received,
T1', T2' are contained in information fields in the synchronization burst, and,
T2'' is signalled through the cyclic shift pattern used on the EC-SCH, see 3GPP TS 45.003.
T3 is determined e.g. by the device through the identification of the mapping of the FCCH, or EC-SCH,
onto the specific TDMA frames within the 51-multiframe.
QUARTER_HYPERFRAME_INDICATOR is obtained in the immediate assignment, see 3GPP TS
44.018.
NOTE: Depending on the coverage condition, the MS may optionally use the timing of receipt of the
synchronization burst (SCH) to set up its timebase counters as described in i).
Thereafter, the timebase counters are incremented as in subclause 3.2.
(When adjacent BTS's are being monitored for handover purposes, or for cell reselection purposes in group receive
mode, the MS may choose to store the values of QN, TN and FN for all the BTS's whose synchronization bursts have
been detected relative to QN, TN and FN for its current serving BTS).
5 BTS Requirements for Synchronization
5.0 General
The conditions under which the requirements of subclauses 5.4 and 5.6 must be met shall be 3 dB below the reference
sensitivity level or input level for reference performance, whichever applicable, in 3GPP TS 45.005 and 3 dB less
carrier to interference ratio than the reference interference ratios in 3GPP TS 45.005.
For EC-GSM-IoT, the conditions shall be met at the input level for reference performance of EC-RACH, and at the
reference carrier to interference ratios of the EC-RACH, for the highest coverage class, as defined in 3GPP TS 45.005
for the supported TS option(s) of EC-RACH.
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5.1 Frequency source
The BTS shall use a single frequency source of absolute accuracy better than 0.05 ppm for both RF frequency
generation and clocking the timebase. The same source shall be used for all carriers of the BTS.
For the pico-BTS and Local Area multicarrier BTS classes the absolute accuracy requirement is relaxed to 0.1ppm.
NOTE: BTS frequency source stability is one factor relating to E-OTD LCS performance and the reader is
referred to Annex C for the relationship between BTS frequency source stability and E-OTD LCS
performance characteristics.
5.2 Timebase counters
It is optional whether the timebase counters of different BTS's are synchronized together.
For COMPACT inter base station time synchronization is required such that timeslot number (TN) = i (i = 0 to 7) and
frame number (FN) with FN mod 208 =0 shall occur at the same time in all cells. The timebase counters of different
BTSs shall be synchronized together such that the timing difference between different BTSs shall be less than 1 symbol
period, 48/13 μs (which can be 1 or 3 bits depending upon modulation) measured at the BTS antenna.
If a cell defines a COMPACT cell in its neighbour list, time synchronization is required such that timeslot number
(TN) = i (i = 0 to 7) and frame number (FN) with FN mod 208 =0 shall occur at the same time in both cells.
When extended DRX (eDRX) is supported in a routing area (RA) time synchronization is required such that any given
timeslot number (TN) and frame number (FN) shall occur at the same time in all cells within the RA subject to an
allowed tolerance. The timebase counters of different BTSs shall be synchronized together such that the timing
difference between different BTSs (allowed tolerance) shall be less than 4 seconds measured at the BTS antenna.
5.3 Internal BTS carrier timing
The channels of different carriers transmitted by a BTS shall be synchronized together, i.e. controlled by the same set of
counters. The timing difference between the different carriers shall be less than ¼ normal symbol periods, measured at
the BTS antenna.
For pico-BTS and Local Area multicarrier BTS, the timing difference between different carriers shall be less than
2 symbol periods, measured at the BTS antenna.
5.4 Initial Timing advance estimation
When the BTS detects an access burst transmission on RACH, PRACH, or one or a sequence of access burst(s) on EC-
RACH, it shall measure the delay of this signal relative to the expected signal from an MS at zero distance under static
channel conditions. This delay, called the timing advance, shall be rounded to the nearest normal symbol period and
included in a response from the BTS when applicable.
For the pico-BTS and Local Area multicarrier BTS, there is no requirement to measure this timing advance. However,
either this measured value or a programmable value of timing advance shall be included in the response from the BTS
when a timing advance value needs to be sent.
5.5 Maximum timing advance value
The maximum timing advance value TA shall be 63. If the BTS measures a value larger than this, it shall set the
max
timing advance to 63. In the case of GSM 400 the extended timing advance information element is supported and the
maximum timing advance value TA shall be 219. If the BTS measures a value larger than this, it shall set the timing
max
advance to 219. (3GPP TR 43.030 defines how the PLMN deals with MS's where the delay exceeds timing advance
value 63).
NOTE: The timing advance is always calculated in terms of number of symbols with normal symbol period
irrespective of the actual symbol period used on the uplink.
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5.6 Delay tracking
5.6.1 For circuit switched channels
For an MS in dedicated mode, the BTS shall thereafter continuously monitor the delay of the normal bursts sent by from
the MS. If the delay changes by more than one symbol period, the timing advance shall be advanced or retarded 1 and
the new value signalled to the MS.
Restricting the change in timing advance to 1 symbol period at a time gives the simplest implementation of the BTS.
However the BTS may use a larger change than this but great care must then be used in the BTS design.
5.6.2 For packet switched channels
The BTS shall perform the continuous timing advance procedure for all MS working in packet transfer mode or in
broadcast/multicast receive mode for which an PTCCH subchannel is assigned, except for an MS in dual transfer mode.
Therefore the BTS shall monitor the delay of the access bursts sent by the MS on PTCCH and respond with timing
advance values for all MS performing the procedure on that PDCH. These timing advance values shall be sent via a
downlink signalling message on PTCCH. PTCCH shall not be assigned in case of an EC-GSM-IoT capable MS in EC
operation.
The BTS shall update the timing advance values in the next downlink signalling message following the access burst.
The BTS may also monitor the delay of the normal bursts and access bursts sent by the MS on PDTCH and PACCH.
Whenever an updating of TA is needed, the BTS may send the new TA value in a power control/timing advance
message (see 3GPP TS 44.060).
For an MS in dual transfer mode the BTS shall follow the procedure described in subclause 5.6.1.
5.6.3 Delay assessment error
For circuit and packed switched channels, the delay shall be assessed in such a way that the assessment error (due to
noise and interference) is less than ½ normal symbol periods for stationary MS. For MS moving at a speed up to 500
km/h the additional error shall be less than ¼ normal symbol period. For EC-GSM-IoT MS assigned CC2, CC3 or CC4
(see 3GPP TS 45.002) on the UL, the assessment error shall be less than ¾ normal symbol period for MS moving at a
speed up to 50 km/h.
The control loop for the timing advance shall be implemented in such a way that it will cope with MSs moving at a
speed up to 500 km/h, except for EC-GSM-IoT MS when it enters EC operation, where 50 km/h applies.
5.6.4 Pico-BTS and Local Area multicarrier BTS delay tracking
The pico-BTS and the Local Area multicarrier BTS have no requirement to track timing advance for any class of
channels. However, it shall include either the measured timing advance as specified above or a programmable timing
advance value in the response from the BTS when a timing advance value needs to be sent.
5.7 Timeslot length
5.7.0 Implementation options
Optionally, the BTS may use a timeslot length of 157 normal symbol periods on timeslots with TN = 0 and 4, and
156 normal symbol periods on timeslots with TN = 1, 2, 3, 5, 6, 7, rather than 156,25 normal symbol periods on all
timeslots. This implementation option is illustrated in figure 5.7.4. When reduced symbol period is implemented, this
option is further elaborated in subclause 5.7.2.
A BTS shall follow the implementation option of timeslot length with integer symbol periods for normal symbol
periods, see subclause 5.7.2, on all transceivers in case EC-channels (EC-SCH, EC-BCCH, EC-CCCH, EC-PDTCH, or
EC-PACCH) are mapped onto one or more transceiver resources.
Figure 5.7.1: void
ETSI
3GPP TS 45.010 version 13.5.0 Release 13 13 ETSI TS 145 010 V13.5.0 (2019-05)

5.7.1 Regular implementation with timeslot lengths of non-integral symbol
periods
If the timeslot length for normal symbol period burst is 156.25 normal symbol periods for all bursts, then, a timeslot of
length 187.5 reduced symbol periods shall be used for all bursts using reduced symbol period. This case is shown in
Figure 5.7.2 and Table 5.7.1. In this case if there is a pair of different symbol period bursts on adjacent timeslots, then
the guard period between the two bursts shall be 8.5 normal symbol periods which equals 10.2 reduced symbol periods.
Total
normal symbol period Bursts in a TDMA frame (in a TDMA frame)
156.25x48/13 156.25x48/13 156.25x48/13 156.25x48/13 156.25x48/13 156.25x48/13 156.25x48/13 156.25x48/13
1250x48/13
us us us us us us us us
us
156.25 156.25 156.25 156.25 156.25 156.25 156.25 156.25
symbols
TN 4 TN 5 TN 6 TN 7
TN 0 TN 1 TN 2 TN 3
reduced symbol period Bursts in a TDMA frame
187.5x40/13 187.5x40/13 187.5x40/13 187.5x40/13 187.5x40/13 187.5x40/13 187.5x40/13 187.5x40/13
1500x40/13
us us us us us us us us
us
187.5 187.5 187.5 187.5 187.5 187.5 187.5 187.5
symbols
TN 7
TN 3 TN 4 TN 5 TN 6
TN 0 TN 1 TN 2
Figure 5.7.2: Implementation using non integral number of symbol periods in both Normal Symbol
Period burst and Reduced Symbol Period bursts.

Irrespective of the symbol duration used, the centre of the training sequence shall occur at the same point in time. This
is illustrated in Figure 5.7.3 below. This means that the active part of a reduced symbol period burst shall start 12/13 μs
(which is a quarter of a normal symbol period) later in time and ends 12/13 μs earlier.

Figure 5.7.3: Timing alignment between normal symbol period and reduced symbol period bursts

The duration of various components of the timeslot are illustrated in Table 5.7.1.
ETSI
3GPP TS 45.010 version 13.5.0 Release 13 14 ETSI TS 145 010 V13.5.0 (2019-05)
Table 5.7.1: Duration of various components of the time slot

reduced symbol period Bursts normal symbol period Bursts
Symbols Duration ( μs) Symbols Duration ( μs)
160 144
Tail (left) 4 3
13 13
2760 2784
69 58
Encrypted symbols (left)
13 13
1240 1248
Training sequence 31 26
13 13
2760 2784
Encrypted symbols (right) 69 58
13 13
160 144
Tail (right) 4 3
13 13
420 396
Guard period 10.5 8.25
13 13
7500 7500
187.5 156.25
Total
13 13
5.7.2 Im
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