Temporary Block Flow

Author: Kabeer Ahmed, http://skabeer.ahmed.googlepages.com/ Last Updated: November 27th, 2006

Definition

The main goal of GPRS service is the transfer of Packet Data. Packet data in GPRS is transferred in the form of orderly blocks.

Application data reaches the RLC from LLC. RLC segments this blocks and MAC transfers these blocks across the air interface in an orderly manner. This transfer of the blocks is known as a TBF - Temporary Block Flow.

Description

TBF is of two types. Uplink TBF and Downlink TBF.

Uplink TBF

Uplink TBF for a two phase access is as shown in the picture below

To be continued........

International Mobile Equipment Identity - IMEI

Author: Kabeer Ahmed, http://skabeer.ahmed.googlepages.com/ Last Updated: November 7th, 2006

Definition

IMEIs are usually numbered and approved by an authorised body of the GSMA. The IMEI is numbered as per the below defined procedure. For more information please refer the IMEI Allocation and Approval Guidelines document from the GSMA.

Detailed Information

IMEI is structure as follows:

IMEI = TAC + FAC + SNR + CD

TAC = Type Approval Code (also known as Type Allocation Code) which gives some information on the model and origin of the device. This is usually approved by GSMA for a specific device.

FAC = Final Assembly code which is a manufacturer specific code and can give the location of the device manufacture.

SNR = Serial Number which uniquely identifies the unit of a particular model.

CD = Check Digit which usually indicates the GSM Phase 2 device or higher.

To this, the software version of the device manufacturer might also be added.

In the end LUHN check digit of the entire number is appended. LUHN formula also known as mod 10 algorithm is used to check the accuracy of any algorithmic numbers, say in this case for the correctness of IMEI numbers.