Radio Resources

Radio Resource Procedures for GSM, GPRS, and EDGE
The general purpose of radio resource procedures is to establish, maintain, and
release radio connections. To be effective, the radio resource procedures are complex
and include the cell selection/reselection and handover procedures.

Radio Resource in Idle Mode
The mobile handset continuously monitors the system information broadcasts on
the broadcast channel, interpreting the information appropriately. This information
contains parameters such as the identity of the serving cell and information on
how to access the network.

Once the cell is selected, the mobile leaves the idle state to register its location with
the network. In the absence of any other activity, it then falls back to the idle mode, to
monitor the paging channel (to identify any incoming calls), updating its location as
required (periodically, or as location area or routing area boundaries are crossed).

Radio resource in idle mode:
Monitor system information broadcast (contains required information)
Cell selection
Cell reselection
Location registration and updating
Monitor paging channel
Radio Resource Connection Establishment

This is instigated from idle mode. The RRC connection request is sent from the
mobile to the network. This may be to make a call, transfer data, or update a location
or routing area. Once the connection is established, a confirmation is sent to
the mobile.

The mobile now moves into the connected state, sending a Radio Resource
Connection Setup Complete indication to the network on the dedicated channel that
has just been assigned.

Paging
For idle mode mobiles, paging is initiated over the required location area, or routing
area for incoming calls, or for session setup in the case of packet services. The
core network node (MSC / VLR or SGSN) initiates the paging procedure.

The paging message is broadcast using Radio Resource procedures on the paging
channel that each idle mode mobile monitors within the cell(s).

Other Radio Resource Procedures
Radio resource procedures are extremely comprehensive and cover a wide range of
requirements. Some of the procedures not dealt with here include:

Power control (uplink and downlink)
Handovers (can be extremely complex in UMTS/W-CDMA)
Connection release
Packet mode procedures
Radio Resource Procedures for UMTS (including HSDPA)

UMTS (Universal Mobile Telecommunication System) procedures follow the
general requirements for GSM and GPRS, except that the radio interface and
channel structure are more complex and therefore require more (and more complex)
procedures. This is also true for HSDPA (High-Speed Downlink Packet
Access), which is a specific implementation of W-CDMA used on the UMTS
radio interface.

The mobility management (MM) and connection management (CM) procedures
are essentially very similar to those discussed above, except that more options
are generally available with UMTS because of the multimedia-capable nature of
the connections. In fact, the procedures for the GSM family of technologies are
contained within a common set of documents (available through the Third Generation
Partnership Project [3GPP] Web site at www.3GPP.org).

The documents are arranged such that all procedures relating to MM and CM
will be in a single document, irrespective of access technology.

Radio resource (RR) management is where the main differences occur between
the technologies and, in this case, the procedures for UMTS (W-CDMA) are separated
from those for GSM, GPRS, and EDGE by the use of different documents
detailing the RR procedures.

First, the radio elements are known as the Node B, which is equivalent to
the BTS in GSM, GPRS, and EDGE, and the radio network controller (RNC),
which is equivalent to the BSC. The term “radio network subsystem” (RNS)
is used in place of the base station subsystem (BSS) used in GSM, GPRS, and
EDGE.

To illustrate just two of the major differences between UMTS (W-CDMA)
and GSM, GPRS, and EDGE, two procedures relating to radio resources (RR) are
described below.