2. Before you start

To have success in the GPRS world, there are a few requirements to you and your computer. This section also gives you some general information about GPRS to get familiar with that.

2.1 Requirements for you

Before you start using GPRS, make sure you're familiar with the following subjects:

• General networking (routing, DNS)
• Dial-in (like a modem using pppd)
• You should know the GPRS information from you operator, like which APN to connect to and which username/password to use.

2.2 Requirements for your computer

To create a GPRS connection, you need a few things:

• Decent support in your kernel for ppp, ip, and the device you are using.
• The software to create a ppp connection, pppd and optional wvdial or others
• BlueZ if you're using bluetooth

2.3 Some basic GPRS information and terminology

GPRS is an abbreviation for General Packet Radio Service. It started as an addition to the GSM networks. The GPRS service can be delivered via different networks. Like the 2.5G (Generation) GPRS via GSM, but also 3G networks like EDGE, UMTS and it's additions HSDPA/HSUPA.

The maximum speed you can get depends on the network. 2.5G it's about 7 KByte per second download, and 1.5 KByte per second upload. EDGE and UMTS have a download speed of 40 KByte per second, and 7 KByte per second upload. HSDPA can go up to 160 KByte per second down and 40 KByte upload. HSUPA increases the upload speed to 140 KByte per second.
A typical disadvantage for mobile networking is the relatively long round trip time (RTT), which can vary between 120 ms and 700 ms but might also exceed 1200ms. HSDPA on the other side is capable to delivering a 40-60 ms RTT.

There is some terminology used in GPRS which is very specific, so here's a list of commonly used terms:

• APN: Access Point Name. You connect to an APN, and the APN identifies a specific network. For example many operators use "internet" for their internet service. Compare this to the phone number when you use traditional telephony.
• Attach: Like your cell phone has to log on to the network when you turn it on, a GPRS capable phone must do a GPRS attach before it can use any GPRS service.
• PDP-Context: Your data connection. Compare this to calling someone, but instead of really calling, you're setting up a data connection.
• 2.5G network: This was an addition to the existing mobile networks (2G) to enable higher data speeds.
• 3G network: Such a mobile network must at least be capable to give the user a download speed of 384 Kbit per second. If it's lower, it's 2.5G.
• GSM: Groupe Spécial Mobile or General System for Mobile Communications. A 2G network. This only allowed data connections with 9600 (later 14400) Kbit per second. This is not covered in this howto, instead thread your modem like a normal modem. Also a technique called HSCSD (High Speed Circuit Switched Data) is available, while this improves speed, it's not GPRS and is not covered here.
• GPRS: General Packet Radio Service. A service that allows faster data services via different networks. Also called 2.5G.
• UMTS: Universal Mobile Telecommunication System, a 3G network technology.
• HSDPA: High-Speed Downlink Packet Access, an addition to UMTS allowing higher speeds. There are different speeds available like HSDPA 1.8, 3.6 and 7.2 which are speeds in Megabits per second (as a maximum capable speed).
• HSUPA: High-Speed Uplink Packet Access, again an addition to increase speed, this time the uplink speed.

2.4 Basic information on GPRS functioning

When you turn on a GSM/GPRS capable phone, it will first log on to the GSM network, just as a normal GSM phone.

When that succeeds, it will try to make a GPRS attach. This is more or less comparable to the logon it just did on the GSM network. However, this logon is specific for all data related services. This attachment is served in the network by a device called an SGSN (Serving GPRS Support Node). The SGSN however does not know if it should authorize you or not. To know that it's going to ask the HLR (Home Location Register). The HLR is a sort of database which contains all subscription information for subscribers of the network.

After a successful attach, you are able to create a PDP context. In this case the SGSN routes you to the correct GGSN (Gateway GPRS Support Node) which contains the APN (Access Point Name) you choose. When setting up the data connection to the APN/GGSN, this might request other authentication methods like Username/Password. These are the credentials you should provide via your dialer.

For more information see the wikipedia article about GPRS Core Network