4 Main Concept

23.0603GPPGeneral Packet Radio Service (GPRS)Release 17Service descriptionStage 2TS

The packet domain uses packet-mode techniques to transfer high-speed and low-speed data and signalling in an efficient manner. The packet domain optimises the use of network and radio resources. Strict separation between the radio subsystem and network subsystem is maintained, allowing the network subsystem to be reused with other radio access technologies.

A common packet domain Core Network is used for both Radio Access Networks (RAN) the GERAN and the UTRAN. This common Core Network provides together with these RANs GPRS services. It is designed to support several quality of service levels to allow efficient transfer of non real-time traffic (e.g. intermittent and bursty data transfers, occasional transmission of large volumes of data) and real-time traffic (e.g. voice, video). Applications based on standard data protocols and SMS are supported, and interworking is defined with IP networks. Charging should be flexible and allow to bill according to the amount of data transferred, the QoS supported, and the duration of the connection.

The Serving GPRS Support Node (SGSN) keeps track of the location of an individual MS and performs security functions and access control. The SGSN is connected to the GERAN base station system through the Gb or Iu interface and/or to the UTRAN through the Iu interface. The SGSN also interfaces via the GPRS Service Switching Function with the GSM Service Control Function for optional CAMEL session and cost control service support.

The Gateway Node (P‑GW/GGSN) provides interworking with packet data networks, and is connected with other core network nodes via an IP-based packet domain PLMN backbone network.

The Serving Gateway is user plane node that provides a common anchor for interoperation between GERAN/UTRAN and E‑UTRAN accesses and when S4 is used it permits Direct Tunnel usage in roaming scenarios.

The Offline Charging System (OFCS) collects charging records from SGSNs, S‑GWs and P‑GW/GGSNs.

The HSS/HLR contains subscriber information.

The SMS‑GMSCs and SMS‑IWMSCs support SMS transmission via the SGSN.

Optionally, the MSC/VLR can be enhanced for more-efficient co-ordination of packet-switched and circuit-switched services and functionality: e.g. combined GPRS and non-GPRS location updates.

In order to use GPRS services, an MS shall first make its presence known to the network by performing a GPRS attach. This makes the MS available for SMS over GPRS and SMS over IMS, paging via the SGSN, and notification of incoming packet data. If the UE is already PS‑attached due to an attach via E‑UTRAN it makes its presence known to an SGSN by a Routeing Area Update.

In order to send and receive packet data by means of GPRS services, the MS shall activate the Packet Data Protocol context that it wants to use. This operation makes the MS known in the corresponding P‑GW/GGSN, and interworking with data networks can commence.

User data are transferred transparently between the MS and the packet data networks with a method known as encapsulation and tunnelling: data packets are equipped with GPRS-specific protocol information and transferred between the MS and the P‑GW/GGSN. This transparent transfer method lessens the requirement for the PLMN to interpret external data protocols, and it enables easy introduction of additional interworking protocols in the future.

Packet Switched (PS) handover is introduced in order to support real-time packet-switched service with strict QoS requirements on low latency and packet loss. PS handover reduces the service interruption of the user plane information at cell change compared to the cell-reselection and enables methods to improve buffer handling of user plane data in order to reduce packet loss at cell-change. PS handover is the handover between GERAN PS and UTRAN PS. The complete specification of the PS handover procedures for A/Gb mode and between Iu mode and A/Gb mode are described in TS 43.129 [87].

Earlier release versions of this specification described a Network Mode Operation III, which is not available for deployment as GERAN specifications forbid deploying Packet Common Control Channels since Release 9 in TS 44.060 [77].