General Packet Radio Service

GPRS (General Packet Radio Services) is a packet-based wireless communication service that, when available in late 2000, promises data rates from 56 up to 114 Kbps and continuous connection to the Internet for mobile phone and computer users. The reality will be around 33 Kbps (2+1 or 3+1 @ CS2, 4+1 for fixed modem). GPRS is based on "regular" GSM (with the same modulation) and will complement existing services such circuit-switched cellular phone connections such as SMS or cell broadcast. Voice over Ip over GPRS is also explored.

In theory, GPRS packet-based service should cost users less than circuit-switched services since communication channels are being used on a shared-use, as-packets-are-needed basis rather than dedicated only to one user at a time. It should also be easier to make applications available to mobile users and Wap or i-mode should far more attractive for the user. In addition to the Internet Protocol GPRS supports X.25, a packet-based protocol that is used mainly in Europe. 

Operator should deploy GPRS very fast as most of the interoperability test between the network and the Handset are now finished (September'00) and because GPRS is mainly a software upgrade for the BTS, BSC and servers.GPRS avec different coding schemes. We may just see CS2 in the market.

Table of rate per slot according to coding schemes 

CS1 : 9,05 kbit/s
CS2 : 13,4 kbit/s
CS3 : 15,6 kbit/s
CS4 : 21,4 kbit/s
Net rate: -  10 %

 

SPECTRUM EFFICIENCY Packet switching means that GPRS radio resources are used only when users are actually sending or receiving data. Rather than dedicating a radio channel to a mobile data user for a fixed period of time, the available radio resource can be concurrently shared between several users. This efficient use of scarce radio  resources means that large numbers of GPRS users can potentially share the

same bandwidth and be served from a single cell. The actual number of users supported depends on the application being used and how much data is being transferred. Because of the spectrum efficiency of GPRS, there is less need to build in idle capacity that is only used in peak hours. GPRS therefore lets network operators maximize the use of their network resources in a dynamic and flexible way, along with user access to resources and revenues.

GPRS should improve the peak time capacity of a GSM network since it simultaneously:

• allocates scarce radio resources more efficiently by supporting virtual connectivity

• immigrates traffic that was previously sent using Circuit Switched Data to GPRS instead, and reduces SMS Center and signaling channel loading by migrating some traffic that previously was sent using SMS to GPRS instead using the GPRS/ SMS interconnect that is supported by the GPRS standards.

Relatively high mobile data speeds may not be available to individual mobile users until Enhanced Data rates for GSM Evolution (EDGE) or Universal Mobile Telephone System (UMTS) are introduced.

GPRS Class Type

The class of the device determines the speed at which GPRS can be used.

For example, the majority of GPRS terminals will be able to download data at speeds of up to 24Kbps (kilobytes per second). At the higher end, speeds are theoretically possible up to 171.2 kbit/sec when 8 slots are assigned at the same time to a single user. In reality 40-50Kbps.

PC cards capable of GPRS will send data up to speeds of 48Kbps.

GPRS Multislot Classes

Multislot classes are product dependant, and determine the maximum achievable data rates in both the uplink and downlink directions.

Written as (for example) 3+1 or 2+2, the first number indicates the amount of downlink timeslots (what the mobile phone is able to receive from the network).
The second number indicates the amount of uplink timeslots (how many timeslots the mobile phone is able to transmit).

The active slots determine the total number of slots the GPRS device can use simultaneously for both uplink and downlink communications.

Futher Examples: