Packet Control Unit

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The Packet Control Unit ( PCU ) is used to implement the GPRS core architecture in the GSM radio network.

The PCU communicates on the one hand via the Abis interface of the base station with the end device, on the other hand via the Gb interface with a GPRS Support Node (GSN).

The PCU is responsible for the following MAC and LLC functions:

  • Division of PDUs from the GSN into RLC data packets for transmission to the end device
  • Composition of RLC data packets from the terminal in PDUs for transmission to the GSN
  • Management of the uplink and downlink PDCH
  • Control of the PDCH uplink and downlink ARQ functionality
  • PDCH access control and management
  • RLC management functions such as power control, traffic control and management of the control channel

Integration into GSM radio technology is achieved by converting the data packets coming from the Serving GPRS Support Node (SGSN) into PCU frames that have the same format as the frames of the Transcoder and Rate Adaptation Unit (TRAU) - i.e. 20 ms long Data frame. The Transcoder and Rate Adaptation Unit is for the compression of GSM voice services from 64 kbit / s to 13 kbit / s for full rate, to 12.2 kbit / s for extended full rate (EFR) or 5.6 kbit / s for Half-rate transmission responsible. The language is broken down into 20 ms long language packets. The Packet Control Unit also inserts radio-specific control data into these TRAU frames and then forwards them to the base station via the Abis interface.

The GPRS architecture allows the Packet Control Unit to be positioned at different points in the network. The position of the packet control unit depends primarily on the placement of the transcoder and rate adaptation unit within the line-oriented part of the cellular network. The Packet Control Unit should be adapted to this location, as it should process the same frame format as the TRAU so that the PCU frames can be routed transparently through the Base Station Controller . The packet control unit is usually set up between the base station controller and the SGSN.

Individual evidence

  1. a b 3GPP TS 23.060: General Packet Radio Service (GPRS); Service description; Stage 2; Cape. 12.8 Abis Interface (A / Gb mode) ( English , ZIP / DOC; 5.2 MB) September 29, 2009. Accessed December 2, 2009.