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Service aspects

 

The introduction of EGPRS enables bit rates that are

approximately three times higher than standard GPRS

bit rates. Within the EDGE work item, this was simply

handled by reusing the GPRS quality of service (QoS)

profiles and extending the parameter range to reflect

the higher bit rates, or in other words, introducing

higher throughput values.

 

 

Architecture

 

EGPRS does not bring about any direct architecture

impacts (see GSM 03.60). The packet control unit may

still be placed either in the base station, the base

station controller or the GPRS support node, and the

central control unit is always placed in the base

station. However, since the radio link control automatic

repeat request function on the network side is located

in the packet control unit, any delay introduced

between the PCU and the radio interface will directly

affect the radio link control acknowledged/

unacknowledged round-trip times. This, in turn, results

in a higher risk of stalling the radio link control

protocol. To mitigate this risk and to allow the operator

to optimize network behavior, the maximum radio link

control automatic repeat request window size has

been extended for EGPRS.

 

 

 

 

User plane protocols

 

The transmission plane protocol structure for GPRS

is shown in Figure 11. The protocols that are

influenced by the introduction of EDGE are shaded.

The protocols closest to the physical layer (the radio

link control and mobile allocation channel) are most

affected by EDGE (see GSM 04.60). There also are

some minor modifications to the base station system

GPRS protocol. Apart from these changes, the rest of

the protocol stack remains intact after the introduction

of EDGE.

 

Control plane protocols and channels

 

The introduction of EGPRS also has an impact on

these control plane layers: mobility management and

radio resource management. There is no impact on

session management.

The mobility management modifications are related

to introducing information on EGPRS capabilities in

the mobile station radio access capabilities information

element. These capabilities include the EGPRS

multislot class, the EDGE modulation capability and

the 8PSK power class.

On the radio resource management layer, support for

setting up and maintaining EGPRS temporary block

flows is introduced as opposed to standard GPRS

temporary block flows. Signaling supporting the radio

link control, link quality control and measurement

procedures is also introduced (see GSM 03.64, 04.18,

04.60).

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