1 Scope

05.103GPPRadio subsystem synchronizationTS

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 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms".

[2] 3GPP TS 03.60: "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Service Description Stage 2".

[3] 3GPP TS 03.64: "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); GPRS Radio Interface Stage 2".

[4] 3GPP TS 04.08: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3 specification".

[5] 3GPP TS 04.60: "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Mobile Station (MS) – Base Station System (BSS interface; Radio Link Control (RLC) and Medium Access Control (MAC) Layer Specification".

[6] 3GPP TS 05.02: "Digital cellular telecommunications system (Phase 2+); Multiplexing and multiple access on the radio path".

[7] 3GPP TS 05.05: "Digital cellular telecommunications system (Phase 2+); Radio transmission and reception".

[8] 3GPP TS 05.08: "Digital cellular telecommunications system (Phase 2+); Radio subsystem link control".

[9] 3GPP TS 03.30: "Digital cellular telecommunications system (Phase 2+); Radio network planning aspects".

[10] 3GPP TS 03.52: "Digital cellular telecommunications system (Phase 2+); GSM Cordless Telephony System (CTS), Phase 1; Lower layers of the CTS Radio Interface; Stage 2".

[11] 3GPP TS 05.56: "Digital cellular telecommunications system (Phase 2+); GSM Cordless Telephony System (CTS), Phase 1; CTS-FP Radio subsystem".

1.2 Definitions and abbreviations

In addition to those below, abbreviations used in the present document are listed in 3GPP TR 01.04.

For the purposes of the present document, the following terms and definitions apply:

BTS: Base Transceiver Station.

CTS-FP: CTS Fixed Part.

CTS-MS: MS operating in CTS mode.

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.

Quarter symbol number: timing of quarter symbol periods (12/13 µs) within a timeslot. Symbol period can be 1 or 3 bit periods depending upon modulation.

Timeslot number: timing of timeslots within a TDMA frame.

TDMA frame number: count of TDMA frames relative to an arbitrary start point.

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.

Timebase counters: set of counters which determine the timing state of signals transmitted by a BTS or MS.

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.

Timing Advance Index: Timing Advance Index TAI used for GPRS, which determines the position of the subchannel on PTCCH (see 3GPP TS 05.02) used by the MS to send an access burst, from which the network can derive the timing advance.

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).

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 05.02).