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Abis Interface » History » Version 5

laforge, 12/09/2017 10:13 AM

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The Abis interface consists of the protocols spoken between the BSC (Base Station Controller) and BTS (Base Transceiver Station).
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It is specified in the following GSM standards:
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* 3GPP TS 08.51 : BSC-BTS Interface General Aspects
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* 3GPP TS 08.52 : BSC-BTS Interface principles
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* 3GPP TS 08.54 : BSC-BTS Layer 1: Structure of Physical Circuits
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* 3GPP TS 08.56 : BSC-BTS Layer 2: Specification
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* 3GPP TS 08.58 : BSC-BTS Layer 3: Specification
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** This contains the specification of the RSL (Radio Signalling Link) on SAPI 0
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* 3GPP TS 12.21 : Network Management procedures and messages on the A-bis interface
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** This basically describes the OML (Organization and Maintenance Layer) on SAPI 62
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* 3GPP TS 04.08 : Mobile radio interface layer 3 specification
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** Description of the on-air (BTS-MS) layer 3, as carried in "DATA INDICATION" and other Abis messageS
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h2. RSL (Radio Signalling Link)
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The RSL contains two types of messages
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* transparent messages (forwarded by BTS without interpretation or changes). T-bit in message discriminator == 1
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* non-transparent messages (messages sent between BSC and BTS)
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furthermore, the messages are grouped into four main groups (see below).
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All messages are transmitted using LAPD I frames, except for MEASUREMENT RESULT (UI). T-bit in message discriminator == 0
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h3. Radio Link Layer Management
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All messsages are prefixed by 6-byte header:
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* 1 byte message discriminator
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* 1 byte message type
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* 2 byte channel number
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* 2 byte link identifier
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The actual message types are:
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* EST_IND: Link establishment indication (BTS->BSC)
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* EST_REQ: Link establishment request (BSC->BTS)
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* EST_CONF: Link establishment Confirmation (BTS->BSC)
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* REL_IND: Link release indication (BTS->BSC)
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* REL_REQ: Link release request (BSC->BTS)
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* REL_CONF: Link release confirmation (BTS->BSC)
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* 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)
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* UNIT_DATA_REQ: Transmission of transparent L3 message in unacknowledged mode (BSC->BTS)
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* UNIT_DATA_IND: Reception of transparent L3 message in unacknowledged mode (BTS->BSC)
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* ERROR_IND: Link error indication (BTS->BSC)
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h3. Dedicated Channel Management
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All messsages are prefixed by 4-byte header:
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* 1 byte message discriminator
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* 1 byte message type
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* 2 byte channel number
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The actual message types are:
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* CHAN_ACTIV: Channel activation (BSC->BTS)
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* CHAN_ACTIV_ACK: Channel activation acknowledgement (BTS->BSC)
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* CHAN_ACTIV_NACK: Channel activation not acknowledged (BTS->BSC)
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* MODE_MODIFY: Channel mode modify (BSC->BTS)
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* MODE_MODIFY_ACK: Channel mode modify acknowledgement (BTS->BSC)
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* MODE_MODIFY_NACK: Channel mode modify not acknowledged (BTS->BSC)
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* HANDO_DET: Handover detection (BTS->BSC)
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* ENCR_CMD: Start of Encryption (BSC->BTS)
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* MEAS_RES: Measurement result (BTS->BSC)
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* PREPROC_CONFIGURE: Configure pre-processed measurement report (BSC->BTS)
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* PREPROC_MEAS_RES: Preprocessed measurement report (BTS->BSC)
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* DEACT_SACCH: Deactivate SACCH (BSC->BTS)
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* RF_CHAN_REL: Radio channel release (BSC->BTS)
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* RF_CHAN_REL_ACK: Radio channel release ack (BTS->BSC)
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* MS_POWER_CONTROL: MS power control (BSC->BTS)
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* BS_POWER_CONTROL: Transmission power control (BSC->BTS)
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* CONN_FAIL_IND: Connection failure indication (BTS->BSC)
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* PHYS_CONTEXT_REQ: Physical context request (BSC->BTS)
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* PHYS_CONTEXT_CONF: Physical context confirmation (BTS->BSC)
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* SACCH_INFO_MODIFY: SACCH nformation modify (BSC->BTS)
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* TALKER_DET: Talker detection (BTS->BSC)
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* LISTENER_DET: Listener detection (BTS->BSC)
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* REMOTE_CODEC_CONF: Remote codec configuration (BTS->BSC)
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* RTD_REP: Round Trip Delay Report (BTS->BSC)
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* PRE_HANDO_NOTIF: Pre-handover warning (BSC->BTS)
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* CODEC_MOD_REQ: Multirate codec configuration change request (BSC->BTS)
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* CODEC_MOD_ACK: Multirate codec configuration change acknowledge (BTS->BSC)
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* CODEC_MOD_PERF: Multirate codec change performed (BTS->BSC)
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* TFO_REPORT: TFO Report / AMR (BTS->BSC)
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* TFO_MODIFICATION_REQ: TFO Modification Request (BSC->BTS)
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h3. Common Channel Management
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All messsages are prefixed by 4-byte header:
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* 1 byte message discriminator
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* 1 byte message type
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* 2 byte channel number
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The actual message types are:
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* CHAN_RQS: Channel request by MS (BTS->BSC)
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* PAG_CMD: Paging command (BSC->BTS)
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* DELETE_IND: Delete indication (BTS->BSC)
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* CCCH_LOAD_IND: CCCH load indication (BTS->BSC)
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* BCCH_INFO: Broadcast information modify (BSC->BTS)
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* SMS_BROADCAST_REQ: Short Message Cell Broadcast (BSC->BTS)
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* SMS_BROADCAST_CMD: Short Message Cell Broadcast (BSC->BTS)
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* IMM_ASS_CMD: Immediate Assign command (BSC->BTS)
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* NOTIF_CMD: Notification (BSC->BTS)
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h3. TRX Management
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All messsages are prefixed by 2-byte header:
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* 1 byte message discriminator
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* 1 byte message type
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The actual message types are:
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* RF_RES_IND: Radio resource indication (BTS->BSC)
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* SACCH_FILL: SACCH filling information modify (BSC->BTS)
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* OVERLOAD: Flow control (BTS->BSC)
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* ERROR_REPORT: Error reporting (BTS->BSC)
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