APN - Access Point Name

• It is a setting that enables you to access data (internet service) on your mobile [common man meaning]
• It identifies an access point on the far side of a GGSN, it acts as a reference to GGSN [technical meaning]

In addition to identifying a Packet Data Network, an APN may also be used to define the type of service (e.g. connection to WAP server, MMS) that is provided by the PDN

An APN resembles to a DNS name of a GGSN and has a maximum length of 100 octets. An APN consists of one more labels. 

Structure of APN

Network Identifier 

• Defines to which external network the GGSN is connected to. [required field]
• It will contain atleast one label and have a maximum length of 63 octets. 
• It will not start with the strings 'rac' 'lac' or 'sgsn'; not end in '.gprs' and not take the value '*'.

Operator Identifier 

• Defines in which PLMN GPRS backbone the GGSN is located
• It is composed of three labels. The last label be 'gprs'. The first two labels together identify the GPRS PLMN. 
• For each service provider (operator), there is a default Operator Identifier that is derived from IMSI 
• mnc<MNC>.mcc<MCC>.gprs
• 
  

NOTE - To support inter-PLMN roaming, the internal GPRS DNS functionality is used to translate the APN into the IP address of the GGSN.

How to configure APN manually ?? [DIY]

Go to Settings --> Wireless & Networks --> Mobile Networks --> Access Point Names --> Create New APN and Edit the fields you get from the service provider

Look !! how i did in my mobile

** You just need to set Name and APN fields only **

• Proxy, Port, Username, Password & Server not required to be set
• MMSC, MMS Proxy and MMS Port are related to MMS functionality
• MCC & MNC will already be set when you create a new APN (depending on your operator)
• Authentication Type is not needed to be set, but you can check about the two types here
• APN Type can be set as default or not needed to be set
• APN & APN roaming protocol is also set as IPv4 once you create a new APN
• Bearer field must by set Unspecified
• MVNO - Mobile Virtual Network Operator 
• It is the network operator who doesn't have the frequency spectrum or infrastructure to provide internet service. 
• Three types are SPN (Service Provider Name); IMSI (International Mobile Subscriber Identity & GID (Group Identifier).
• So, MVNO type and value are not needed to be set. You can try if you wish to know the SPN, IMSI and GID of your mobile

After you set the APN, just restart your phone and surf internet.

OR

Call your operator's customer care and tell him to send internet settings for your phone. Once received, just save it and make it as default settings

Example:

internet.mnc852.mcc405.gprs ; Set APN as internet and Name as specified by your operator

** Now-a-days, service providers are using star APN or default APN, you must save the settings sent by them. Rest you can make any changes in name or other fields but data surfing wont get affected **

Add-ons

• Watch this 2 minute video if you face any difficulty in setting APN
• List of APNs of leading service operators in India - Check this link
• Find APN list for US, Canada, UK & Australia here

--

Satya Sravan

All about IMEI

International Mobile Station Equipment Identity

(Here Mobile Station means the handset + SIM) 

• It is a unique number to identify mobile phones.
• mobile phones  i.e.,  3GPP (i.e., GSM, UMTS and LTE) and iDEN mobile phones, as well as some satellite phones.
• One can find the IMEI number in different ways, this link here provides you with the ways to find the IMEI number for different handsets. (I dialed *#06# and checked) 
• It is related to the device only, not to the subscriber who is using it. 
• These IMEIs are allocated by BABT
• It includes information on the origin, model and serial number of the device (note - this serial no. is different to the one which we get while we buy a phone)

Structure of IMEI Number

AA	-	BB	BB	BB	-	CC	CC	CC	D or EE

AA - BB BB BB : TAC (Type Allocation Code) 

• These represent the origin and the particular model of the device
• The first two digits are the RBI and the rest makes up the allocation number
• Reporting Body Identifier - indicates the GSMA-approved organization that allocated TAC 
• find the list of RBIs in the Annex A (page 19) of the doc stated at the end
• Earlier TAC used to be only six digits followed by FAC
• Final Assembly Code 
• was a manufacturer-specific code indicating the location of the device's construction (prior 2002) 
• was 00 (January 1, 2003 until that April 1, 2004 = transition period)
• are terminated to make TAC a 8 digit code (after April 1, 2004)
• Go through few TAC examples given here

CC CC CC : SNR

• Serial Number that distinctively identifies the unit of a model 

D or EE : Luhn check digit / checksum

• For the meaning of checksum, follow this link
• used to validate the IMEI number. 

Luhn Algorithm:

• It is used to validate a variety of identification numbers, such as bank account numbers, credit and debit card numbers, IMEI numbers etc. 
• Steps to calculate the number
• Moving from rightmost digit to leftmost, double the value of every second digit; if the product of this doubling operation is greater than 9 (e.g., 6 × 3 = 18), then sum the digits of the products (i.e., 1 + 8 = 9)
• Compute the sum of the digits
• Take the units digit
• Subtracting it from 10 results in the check digit.
• The above mentioned method is the easiest way, one can also verify the checksum by checking whether the total modulo 10 of the sum of the digits is equal to 0 or not. 

EE represents the Software Version Number identifying the revision of the software installed on the phone. The number sounds IMEISV in this case.

Theory done !! Practical part now !! 

I dialed *#06# on my phone

I will take the first one

352251065012588
TAC	35 - 22 51 06
RBI	35
SNR	50 12 58
Checksum	8

  

Now the verification of the checksum (Luhn algorithm)

Taking the first 14 digits = 3522510651258

3	5	2	2	5	1	0	6	5	0	1	2	5	8
3	10	2	4	5	2	0	12	5	0	1	4	5	16
3	1	2	4	5	2	0	3	5	0	1	4	5	7

The sum of digits equals 3 + 1 + 2 + 4 + 5 + 2 + 0 + 3 + 5 + 0 + 1 + 4 + 5 + 7 = 42

Unit digit number - 2 

So, the check digit is 10 - 2 = 8 (here it is) 

*** Interesting thing ***

Know the quality of your phone using the IMEI number

• Look at 7th and 8th digit, these will tell your handset quality
• Check this table

7th & 8th Digit	Manufactured at	Quality
00	Original Factory	Best
01/10	Finland	High
13	Azerbaijan	Too bad
02/20	UAE	Very Poor
03/30 & 04/40	China	Better
05/50	Brazil/Finland/USA	Good
06/60	China/Hong Kong/Mexico	OK
08/80	Germany	Fair

I am not sure about how much true it is but found this information in many websites so i included it.

Blocking IMEI Number

People ask the operator to block the SIM card once their mobile is stolen. What do they do exactly is blacklist the IMEI number. Before i write further i wish to say one thing i.e., IMEI is handset specific it becomes active once SIM is inserted.

Blocking of IMEI number makes the handset unfit to use particular operator's SIM which means one cannot put the same operator's SIM, they can try using other operator's SIM card in same state or other state also.

So when a person lodges a complaint that his mobile is stolen, what police does is that he provides the IMEI number to all the service providers throughout the nation and tell to check to which VLR is it latched to, from this he can identify under which BTS he is and go and catch him. It is also used to trace a particular MS.

NOTE: For CDMA handsets the counterpart is MEID

That is it, it sums up all the info i gathered about IMEI. Please refer this doc to read more

--

Satya Sravan

Why Telecom Guide ??

I started this blog to post about all the terms related to our basic daily need - MOBILE

I will try to cover all the aspects related to GSM right from grass root level making one or two posts a day. All the information i write here is gathered from various sources and from experts in the respective fields.

Happy reading !!

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Satya Sravan