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8/12/2019 Abis TS's

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The Abis protocol is the protocol spoken between the BSC (Base Station Controller) and BTS(Base Transceiver Station).

It is specified in the following GSM standards:

3GPP TS 08.51 : BSC-BTS Interface General Aspects

3GPP TS 08.52 : BSC-BTS Interface principles 3GPP TS 08.54 : BSC-BTS Layer 1: Structure of Physical Circuits 3GPP TS 08.56 : BSC-BTS Layer 2: Specification

3GPP TS 08.58 : BSC-BTS Layer 3: Specification

o This contains the specification of the RSL (Radio Signalling Link) on SAPI 0 3GPP TS 21.21 : Network Management procedures and messages on the A-bis

interface

o This basically describes the OML (Organization and Maintenance Layer) on

SAPI 62

3GPP TS 04.08 : Mobile radio interface layer 3 specification

o Description of the on-air (BTS-MS) layer 3, as carried in "DATA INDICATION"and other Abis messageS

RSL (Radio Signalling Link)

The RSL contains two types of messages

transparent messages (forwarded by BTS without interpretation or changes). T-bit inmessage discriminator == 1

non-transparent messages (messages sent between BSC and BTS)

furthermore, the messages are grouped into four main groups (see below). All messagesare transmitted using LAPD I frames, except for MEASUREMENT RESULT (UI). T-bit inmessage discriminator == 0

Radio Link Layer Management

All messsages are prefixed by 6-byte header:

1 byte message discriminator

1 byte message type

2 byte channel number 2 byte link identifier

The actual message types are:

EST_IND: Link establishment indication (BTS->BSC) EST_REQ: Link establishment request (BSC->BTS)

EST_CONF: Link establishment Confirmation (BTS->BSC)

REL_IND: Link release indication (BTS->BSC) REL_REQ: Link release request (BSC->BTS)

REL_CONF: Link release confirmation (BTS->BSC)

DATA_REQ: Transmission of transparent L3 message in acknowledged mode (BSC-

>BTS)

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DATA_IND: Reception of transparent L3 message in acknowledged mode (BTS-

>BSC)

UNIT_DATA_REQ: Transmission of transparent L3 message in unacknowledged mode(BSC->BTS)

UNIT_DATA_IND: Reception of transparent L3 message in unacknowledged mode(BTS->BSC)

ERROR_IND: Link error indication (BTS->BSC)

Dedicated Channel Management


1 byte message discriminator 1 byte message type 2 byte channel number


CHAN_ACTIV: Channel activation (BSC->BTS) CHAN_ACTIV_ACK: Channel activation acknowledgement (BTS->BSC)

CHAN_ACTIV_NACK: Channel activation not acknowledged (BTS->BSC)

MODE_MODIFY: Channel mode modify (BSC->BTS) MODE_MODIFY_ACK: Channel mode modify acknowledgement (BTS->BSC)

MODE_MODIFY_NACK: Channel mode modify not acknowledged (BTS->BSC)

HANDO_DET: Handover detection (BTS->BSC) ENCR_CMD: Start of Encryption (BSC->BTS)

MEAS_RES: Measurement result (BTS->BSC)

PREPROC_CONFIGURE: Configure pre-processed measurement report (BSC->BTS)

PREPROC_MEAS_RES: Preprocessed measurement report (BTS->BSC)

DEACT_SACCH: Deactivate SACCH (BSC->BTS)

RF_CHAN_REL: Radio channel release (BSC->BTS)

RF_CHAN_REL_ACK: Radio channel release ack (BTS->BSC) MS_POWER_CONTROL: MS power control (BSC->BTS)

BS_POWER_CONTROL: Transmission power control (BSC->BTS)

CONN_FAIL_IND: Connection failure indication (BTS->BSC) PHYS_CONTEXT_REQ: Physical context request (BSC->BTS)

PHYS_CONTEXT_CONF: Physical context confirmation (BTS->BSC)

SACCH_INFO_MODIFY: SACCH nformation modify (BSC->BTS)

TALKER_DET: Talker detection (BTS->BSC) LISTENER_DET: Listener detection (BTS->BSC)

REMOTE_CODEC_CONF: Remote codec configuration (BTS->BSC)

RTD_REP: Round Trip Delay Report (BTS->BSC) PRE_HANDO_NOTIF: Pre-handover warning (BSC->BTS)

CODEC_MOD_REQ: Multirate codec configuration change request (BSC->BTS) CODEC_MOD_ACK: Multirate codec configuration change acknowledge (BTS->BSC) CODEC_MOD_PERF: Multirate codec change performed (BTS->BSC)

TFO_REPORT: TFO Report / AMR (BTS->BSC) TFO_MODIFICATION_REQ: TFO Modification Request (BSC->BTS)

Common Channel Management


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1 byte message discriminator

1 byte message type 2 byte channel number


CHAN_RQS: Channel request by MS (BTS->BSC) PAG_CMD: Paging command (BSC->BTS) DELETE_IND: Delete indication (BTS->BSC)

CCCH_LOAD_IND: CCCH load indication (BTS->BSC)

BCCH_INFO: Broadcast information modify (BSC->BTS) SMS_BROADCAST_REQ: Short Message Cell Broadcast (BSC->BTS)

SMS_BROADCAST_CMD: Short Message Cell Broadcast (BSC->BTS)

IMM_ASS_CMD: Immediate Assign command (BSC->BTS) NOTIF_CMD: Notification (BSC->BTS)

TRX Management


1 byte message discriminator 1 byte message type


RF_RES_IND: Radio resource indication (BTS->BSC)

SACCH_FILL: SACCH filling information modify (BSC->BTS)

OVERLOAD: Flow control (BTS->BSC) ERROR_REPORT: Error reporting (BTS->BSC)

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