GPRS PCU implementation for Open BTS Ivan Kluchnikov

GPRS PCU implementation for Open. BTS Ivan Kluchnikov Ivan. Kluchnikov@fairwaves. ru

GPRS architecture CCU - Channel Codec Unit PCU - Packet Control Unit SGSN - Serving GPRS Support Node GGSN - Gateway GPRS Support Node

GPRS Core Network SGSN Serving GPRS Support Node Mobility management Control of network access Osmo. SGSN Ciphering and authentication Gateway GPRS Support Node GGSN Interface to external packet data networks Routing functions Firewall Open. GGSN

GPRS Base Station Subsystem Channel Codec Unit CCU Channel coding (CS-1 until CS-4) Forward Error Correction Interleaving. Measuring of the radio parameters, signal level and quality PCU Packet Control Unit Radio resource assignment Radio channel management Segmentation and reassembly of LLC frames Transfer of RLC blocks

GPRS Packet Control Unit (PCU)

GPRS Transmission Plane

GPRS Radio Interface GPRS physical layer is based on that of the GSM: Access scheme: TDMA Transportation unit for data: Normal Burst Modulation: GMSK Packet data channel (PDCH): dynamically allocated in the cell by the network mapped on a 52 -multiframe

GPRS Additional Logical Channels

GPRS Capacity on Demand TS 7 Packet switched channels PDCH 6 5 4 3 Circuit switched channels 2 1 Signalling BCCH+FCCH+SCH+CCCH 0 time

GPRS Allocation of physical resource

GPRS Dynamic Assignment

GPRS RLC/MAC Layer

RLC/MAC Block Structure Differences in Block Structure

GPRS Temporary Block Flow (TBF)

GPRS implementation for Open. BTS Implemented features Open BTS side Handling of BCCH, RACH and AGCH for GPRS support. 52 -GPRS multiframe. Logical Channels: PACCH, PDTCH. Channel coding using Coding Scheme 1. Channel access control functions, including access requests and grants.

GPRS implementation for Open. BTS Implemented features PCU side Segmentation of LLC PDUs into RLC data blocks and re-assembly of RLC data blocks into LLC PDUs. Segmentation of RLC/MAC control messages into RLC/MAC control blocks and re-assembly of RLC/MAC control messages from RLC/MAC control blocks. Minimal BSSGP protocol implementation for integration with SGSN. Uplink TBF Establishment on CCCH. Downlink TBF Establishment on CCCH.

GPRS implementation for Open. BTS To be done L 1 interface between PCU and Open. BTS for communication. GPRS Attach procedure

GPRS implementation for Open. BTS Next steps TBF Uplink/Downlink management with multiple mobiles Backward Error Correction (BEC) procedures enabling the selective retransmission of RLC data blocks. PDCH scheduling functions for UL and DL data transmission. TFI (Temporary Flow Identity) management. Medium Access modes (Dynamic Allocation). USF (Uplink State Flag) management. Contention Resolution Procedure. Paging procedures using paging subchannel on CCCH. Improved BSSGP (SGSN integration).

Sizeof RLC/MAC control message structures (Rlc. Mac. Uplink and Rlc. Mac. Downlink union) in bytes. Rlc. Mac. Uplink 1380 ===================== Packet Cell Change Failure 92 Packet Control Acknowledgement 28 Packet Downlink Ack Nack 60 EGPRS PD Ack. Nack 288 Packet Uplink Dummy Control Block 8 Packet Measurement Report 212 Packet Resource Request 400 Packet Mobile. BF Status 9 Packet PSI Status 40 Packet Enh Measurement Report 1376 Packet Cell Change Notification 140 Packet SI Status 70 Additional MS Rad Access Cap 136 Packet Pause 16 =====================

Rlc. Mac. Downlink 67340 ===================== Packet Access Reject 64 Packet Cell Change Order 67336 Packet Downlink Assignment 184 Packet Measurement Order Reduced 12 Packet Neighbour Cell Data 30 Packet Serving Cell Data 25 Packet Paging Request 85 Packet PDCH Release 3 Packet Polling Request 16 Packet Power Controliming Advance 42 Packet PRACH Parameters 15 Packet Queueing Notification 8 Packetimeslot Reconfigure 160 Packet. BF Release 7 Packet Uplink Ack Nack 148 Packet Uplink Assignment 184 Packet Cell Change Continue 10 Packet Handover Command 340 Packet Physical. Information 5 Packet Downlink Dummy Control Block 7 PSI 1 64 PSI 2 556 PSI 3 15936 PSI 3 BIS 11528 PSI 4 56 PSI 13 84 PSI 5 80