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Introduction

Historical Background

GSM

EDGE

  The Evolution of the GSM Network

High Speed Circuit Switched Data (HSCSD)

General Packet Radio Service (GPRS)

System Overview

Traffic Cases

- IMSI attach

- GPRS Attach

 -Combined GPRS/IMSI Attach

- PDP Context Activation and Deactivation

GPRS Air Interface

Logical Channels

PDCH Allocation

Dedicated PDCH

On-demand PDCH

Master PDCH

Cell Selection and Reselection

GPRS Support Node (GSN)

Interconnection Principles

GPRS IP Connectivity

The users IP communication

EDGE Summary and Key Points

WCDMA

UMTS

The Future

Final Thoughts

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PDCH Allocation

The following section will explain how the PDCH is allocated. Traffic Channels and packet data channels basically create a common pool of resources, utilizing the existing resources in an efficient way. See Figure 26

Figure 26 Common Recourse Pool

 

The PDCHs are allocated to the PCU, the PCU is responsible for assigning channels to different GPRS MSs. The PDCHs can be allocated in different ways:

Dedicated PDCHs are allocated and released by operator command.

On-demand PDCHs, serving as temporary dynamic GPRS recourses, are allocated and released depending on GPRS traffic demand.

The channels that are allocated for GPRS (PDCH) are allocated in sets of maximum four consecutive time slots, such a set is called a PEST (Shown in Figure 27), a PEST can consist of both dedicated and on demand PDCH. All PESTS are on the same frequency or hop the same frequency hopping set. An MS can only be assigned PDCHs from one PEST, at present this limits the maximum number of assigned time slots to four, there is no additional limit on the number of PDCHs that can be allocated in a cell, except the number of available TCHs.

Figure 27 Channel Reservation (PESTs)

 

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