4 Layer 1 specification
3GPP48.054Base Station Controller - Base Transceiver Station (BSC - BTS) interfaceLayer 1 structure of physical circuitsRelease 17TS
All the ITU-T recommendations referred to are Blue Book.
Layer 1 shall utilize digital transmission at a rate of 2 048 kbit/s with a frame structure of 32 x 64 kbit/s time slots, as specified in ITU-T Recommendation G.705 clause 3 or at a rate of 64 kbit/s.
The physical/electrical characteristics are defined in ITU-T Recommendation G.703.
Synchronization at the BTS/TRX for the transmitted bit stream toward the BSC shall be derived from the received bit stream from the BSC.
For transmission rate at 64 kbit/sec it shall be an interface as defined in ITU-T Recommendation G.703.
For transmission rate at 2 048 kbit/s the functional characteristics are defined in ITU-T Recommendation G.732 clauses 2 and 3, and fault conditions should be treated in accordance with ITU-T Recommendation G.732 clause 4.
The idle pattern must be transmitted on every timeslot that is not assigned to a channel, and to every timeslot of a channel that is not allocated to a call. The idle pattern shall be 01010100 for a 64 kbit/s channel and the 2-bit pattern 01 for 16 kbit/s channels. For 8 kbit/s channels, the idle pattern shall be consecutive ones or zeros according to the corresponding idle pattern bit of a 16 kbit/s channel.
If transcoders are located in BTS speech encoding shall be the A-law as defined in ITU-T Recommendation G.711.
If speech transcoders are located in the BSC the speech, data and signalling channels will utilize transmission rates of 8 kbit/s, 16 kbit/s or 64 kbit/s according to 3GPP TS 48.060 and 3GPP TS 48.061. They shall be rate adapted or multiplexed according to ITU-T Recommendation I.460 with fixed format, to fit into the physical interface.
Data encoding is covered in 3GPP TS 48.020.
In the case of a 2 048 kbit/sec circuit, multidrop solutions should be possible. Dynamic sharing of terrestrial 64 kbit/sec channels between BTS:s on a per-call basis must not be used.
Annex A (informative):
Change History
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TSG # |
TSG Doc. |
CR |
Rev |
Subject/Comment |
New |
|
January 2016 |
– |
– |
– |
Rel-13 version created based on v12.0.0 |
13.0.0 |
|
Change history |
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Date |
Meeting |
TDoc |
CR |
Rev |
Cat |
Subject/Comment |
New version |
|
2017-03 |
RP-75 |
– |
– |
– |
– |
Version for Release 14 (frozen at TSG-75) |
14.0.0 |
|
2018-06 |
RP-80 |
– |
– |
– |
– |
Update to Rel-15 version (MCC) |
15.0.0 |
|
2020-07 |
RP-88e |
– |
– |
– |
– |
Upgrade to Rel-16 version without technical change |
16.0.0 |
|
2022-03 |
RP-95e |
– |
– |
– |
– |
Upgrade to Rel-17 version without technical change |
17.0.0 |