This is an acronym for General Packet Radio Service which can be approach as a second generation of wireless networks. This version of wireless networks can be claimed to have cropped from the former GSM (global service for mobile communications). Researchers found that GSM is best suited for wireless voice transfer but was (GSM) very slow in transferring data (digital data) from one mobile device to the next (Christian, 1999).
Therefore, GPRS is a new bearer of data transfer between mobile GSM stations and external networks. The main advantages of GPRS over GSM include speed, capacity and flexibility since it is more of a transition generation between the second and third generations in data communications.
GPRS is packet switched wireless network thus does not have to use a dedicated line. This makes it be flexible and have high data capacity. This is due to the varieties of routes that data can take while being transmitted from the source to the destination. This makes the access speed of GPRS much great compared to GSM and at times makes it up to tens of kbps. Another advantage of GPRS being packet switched is the ease in billing. This is because the connection is made only when a person is need of accessing data unlike in circuit switched networks which offer access all the time but at very high costs (Christian, 1999).
Architecture
The architecture of GPRS is based on the architecture of GSM. GSM has several unique identifiers on any mobile telecommunications device. These identifiers include: IMEI (international mobile equipment identity) which uniquely indentifies any telecommunications device. It is given by the manufacturer and cannot be identical for any device. The other is SIM number which in GSM is closely related to the telephone number of a person (Christian, 1999).
The architecture of GPRS is based upon these two for its operation but has added aspects know as network node (GPRS support nodes (GSN)). The GSNs are the ones responsible for packet switching of data between the mobile stations (equipment) and the external packet switched networks.
Serving GSN is responsible for delivery of data to and from the mobile devices or stations within its area of service. Its main tasks include: packet routing and transfer, mobility management (attach or detach a location management), logical link management and authentication and charging management (payload).
Gateway GSN is the interface between the GPRS backbone network and external data packet networks. Its main function is to convert any data released from the serving SGN intended for external transfer into an appropriate format for transmission in the public network. It also decodes any incoming addresses and helps in routing the data to the respective serving GSN for further transmission to the respective GPRS user (Christian, 1999).
All GSNs are interconnected using IP based addressed in the backbone of the GPRS system. The SGSNs and GGSNs communicate through interfaces which are either GB or GP. This helps create a large interconnected network of intermediate wireless devices with efficient data flow. Within the backbone, data is encapsulated by GSNs into PDN (packet data networks) packets and channeled into GPRS tunneling protocol (GTP) (Christian, 1999).
Two types of GPRS backbones exist:
Intra-PLMN backbone: connects GSNs of the same PLMN hence they are used for private IP-based networks.
Inter-PLMN backbone: in this backbone, GSNs connect to different PLMNs thus roaming is possible. To make this backbone more effective, some agreements must be made and adhered to.
Services offered by GPRS
- End to end services in packet switched data transfer. This makes the connection to be reliable since many routes can be used to transmit the data from the source to the destination with minimal delays. Point to point transfer is so far the successful but future versions of GPRS aim at implementing point to multi-point transfer.
- Selective data transfer. This is mainly achieved when the mobile communications device or server sends specific data only to a certain region this means that all data pertaining to a certain event is switched towards a certain set of GSNs.
- Other services. These may vary from browsing to multimedia messaging. In some new GPRS versions, this may include internet based telephone services. (Christian, 1999)
Features of GPRS
Data routing
Data routing is done more like in any other network whereby the packets to be routed are encapsulated and formatted by the gateway GSNs into the appropriate frames for relay to the destination. Upon reception, these packets are decoded by the gateway GSN and routed to the SGSN to which the specific mobile device which is the destination is located (James, 2008).
Tracking
Transmission techniques and multiple access methods
GSM is able to operate on TMDA and FDMA. Since GPRS is an improvement of GSM, it has enhanced capabilities thus it can transmit using multiple time slots in TDMA. This allows for very flexible channel allocation while transmitting data. GSM allows or allocates only one channel during an entire call but for GPRS, there are alternative channels which are allocated depending on which is available and more effective.
Data encoding
This is done to protect data from destruction due to errors in case the channel used introduces some errors in timing. The techniques used are the four employed in GSM but has higher security. This keeps the data secure and safe in case an error is introduced in the system. This introduces an element of ciphering whereby the data transmitted is in a means that only the sender and receiver can decode the message (James, 2008).
Multiple broadcasts
This is another feature of GPRS that allows a person on one end to send information to a very high number of recipients. This allows for the receiver to access the information without having to know the sender.
Non-voice graphical files transfer
This is mostly employed for sending graphical tools mostly when working outside the office or remotely from where the file is wanted. GPRS through one its features known as multimedia allow the transfer of the files to the recipient (James, 2008).
Principle of GPRS
The basic operation principle of GPRS as earlier discussed is packet switching. This means that data is broken down into smaller chunks and encapsulated into proper formats to for transmission. This however means that data sent can follow different routes to the destination. This is guided by presence of addressing showing the origin and destination of the data packets. This allows for fast data transfer since if any route is congested, others might have less traffic and hence data can be re-routed. This is made possible by the TCP/IP like model in data transfer within the network (James, 2008).
Internetworking with IP networks
GPRS is able to interconnect with other networks like intranet and internet. It supports both IP versions 4 and 6 hence easily communicates with the TCP/IP based network architectures. Upon configuring the GPRS to work or communicate with the internet, it operates as an extension of the internet. The DHCIP server in the internet allocates the GPRS service provider an IP address which is used by almost all GPRS clients. DNS is managed by the mobile operator (James, 2008).
References
Christian B. 1999. IEEE communication surveys: General Packet Radio Service: architecture, protocols and air interface.
James G. 2008. Understanding GPRS: the GSM Packet Radio Service, Retrieved from http://cserg0.site.uottawa.ca/ftp/pub/Lotos/Papers/GPRS_Tutorial.pdf
