Introduction

Cellular phones are usefull for a variety of tasks. Usually only used to talk one might get the idea while sending a short message (sms) that there are other things the expensive little toy can do.

If you drift away from just calling things become a little more complicated whereas the manufacturers of cellular phones contribute a big part of it. What should one imagine of a GSM modem, a GSM softmodem an AT instruction or WAP, HSCSD and GPRS?

Phone features

Let's start with the cellular phone. Not every device is prepared for data transmission. The following graphic shows an overview of the possible featuresets.

GSM-Modem

If the cellular phone is utilized with a GSM modem (upper left of graphics) a connection can be build up with a computer and a special cable which usually isn't that special but only a serial connection (RS232) with a vendor specific plug on one side and sometimes a level converter within this plug. By using this cable the computer can send the commonly used AT commands. These were invented by a company called Hayes and called AT as an abbreviation for "Attention!". An example for such a phone was the Ericsson SH888.

Softmodem

If the cellular phone is prepared for data transmission but lacks a built in modem this is called a softmodem (lower left of graphics). The connection between computer and cellular phone is done by the use of a special cable and a vendor specific software which substitudes the modem. Unfortunately one is in the hands of the vendor according to quality, price and supported computers. While Windows98 systems with Pentium processer are generally available, older PCs with 386/486 CPU or other computers otherwise well equipped like Apple Macintosh, Amiga or PDAs (Personal Digital Assistant) like WinCE or Palm are usually overseen. Too bad, as at least the later ones would be ideal for mobile usage because of their size.

Softmodem with infrared

If an IrDA bus is added to this bundle this is called a Softmodem with Infrared (lower right of graphics). Here the cable is replaced by a transmission via infrared. Everything else is identical. As the infrared bus is not used to transfer the standadized AT-commands but a proprietary protocol a transmission is not possible if the producer of the cellular phone does not submit software for the used computer system. A bad example were Nokias 6110, 6130 & 6150 phones.

GSM-Modem with infrared bus

A cellular phone with GSM modem and infrared bus according to the IrDA standard (upper right of graphics) is todays technical most usefull implementation and highly recommended. Only this permits all devices with IrDA or serial bus (RS232) to build up a data connection with standard software.Usually one can optionally use a cable instead of the IrDA connection for convenient transmission of longer data. Otherwise the connection can be interrupted while the used car or train brakes. Examples for cellular phones with GSM modem and infrared bus are the NOKIA's 88x0, 82x0, 6210 and 7110.
Info about data capabilities of all cellular phones may be found in the overview of GSM & UMTS cellular phones

Computer, PDAs & Co.

That's for the cellular phones and what comes now?

To have a mobile data transmission one usually needs a computer whereas using a notebook or a PDA is the normal choice. Notebooks have about the size of a legal paper and are not much thicker ourdays. They usually feature some PCCARD slots, also formerly known as PCMCIA, an IrDA port, the normal serial port according to the RS232 standard and one or two USB (Universal Serial Bus) ports. The computer can be running Windows, MacOS or Linux. Besides there are also PDAs running Windows Mobile, SymbianOS or PalmOS. Who wants to work on the road like at home has nearly no other choice than buying and carrying a notebook. If only emails have to be received and from time to time sent, rarely faxes and sometimes information from the world wide web PDAs are the better choice.

PCCARDS

A compact an usefull alternative for the connection via data cable or IrDA is the use of a PCCARD Phone. Inserted in the PCCARD slot of a notebook or palmtop this is used for data transfer. Precondition for the use is a support for the card by delivered software drivers which is no problem for Windows computers but leads to problems with other computers. Before buying such a card one should always check the delivered drivers.

Smartphones

Combined PDAs and cellular phones are getting more and more common as carrying only one unit instead of two it simply more practical. The first usable smartphones were the Communitators from Nokia which are running SymbianOS. Ourdays besides these there are also smartphones running Windows Mobile and PalmOS.

Bluetooth

Up to eight units may be wirelessly connected in a micro network. The range is usually up to 10 meters (33 ft). This version is called Pico-Bluetooth and only takes up to 1 mW. Also Mega-Bluetooth with a range of up to 100 meters (330 ft) and a sending power of up to 100  mW is possible. The wireless standard uses the licence free 2,4GHz band and does not need to have a direct view between the units in contrary to infrared. The utilized hardware is very small - the chip only measures 9 mm² (0.014 in²) - and consumes very few energy, ideal premises for PDAs and cellular phones. Other common devices of our everyday life will support this standard, too. The refridgerator tells the pda that there is no more milk for example. The communication is build up on a voice and a data channel. The voice channel supports with 64 Kbit/s ISDN speed and the data channel receives a maximum of 721 Kbit/s and sends up to 56.6 Kbit/s. Thus the cellular phone may rest in the jacket or suitcase while using it.

According to their power Bluetooth devices are classified as follows:

• Class 1
  • 20 dBm
  • 100 mW
  • Range ca. 100 meters
    
    
• Class 2
  • 4 dBm
  • 2,5 mW
  • Range ca. 50 meters
    
    
• Class 3
  • 0 dBm
  • 1 mW
  • Range ca. 10 meters
    
    

To enable Bluetooth devices to communicate with each other they have to support the same profile. An Overview of all Bluetooth profiles can be found here.

The name of this technology was taken from king Harald Blåtand which unified Danmark and Norway in the 10th century.

Speed

The usual data transmission speed of todays GSM networks is 9.6 Kbit/s and really doesn't kick you out of your socks. New standards are thus already standing in line:

HSCSD

High Speed Circuit Switched Data combines several channels and thus allows higher data rates which are dependant of the number of used channels. Standard is 4 timeslots with 14.4 KBit/s each near the transmitter. If the range gets higher the data rate is decreased down to 9.6 KBit/s. The mobile network operator is able to limit the amount of available timeslots per trasmitter. Having a good reception and 4 timeslots would allow 57.6 KBit/s which equals todays normal modem speed. Currently HSCSD is offered in Germany by Vodafone and e-plus.
Cellular phones with HSCSD support may be found in the overview of GSM & UMTS cellular phones

GPRS

General Packet Radio Service is the first step to UMTS. With GPRS data is split in packages and transferred separately. At the recipient they are rejoined. The costs are hereby not calculated by the time span of the transfer but by the amount of transferred data. In addition the simultaneous transfer of data and speech is possible. The data transfer rate is up to 171,2 Kbit/s and thus more than double the speed of ISDN. The possible top speed is depending on the number of used channels. Here uplink and downlink channels may differ with 14,4kbps each. The more channels a phone supports the faster the data transfer. The possible combinations have been put into classes which are shown in the table below:

EDGE

Enhanced Data Rates for GSM Evolution (someone had to think real hard for such a neat abbreviation!) is based on GPRS and allows a data transfer rate of up to 236.8 Kbit/s downlink and up to 118.4 Kbit/s uplink. EDGE represents the last possible level of extension for existing GSM networks.

UMTS

Universal Mobile Telecommunications System is the successor of GSM. In October 2000 the UMTS licenses were auctioned in Germany and since 2003 the first German networks are online. The data transfer rate of up to 236.8 Kbit/s downlink and 53 Kbit/s uplink allowed for the first time fast mobile multimedia applications.

HSDPA

High Speed Downlink Packet Access is based on UMTS and allows a downlink data rate of 3.6 Mbit/s in the beginning and up to 14.4 MBit/s in the final development.

HSUPA

High Speed Uplink Packet Access is based on UMTS and allows an uplink data rate of 1.45 Mbit/s in the beginning and up to 5.8 MBit/s in the final development.

Services

Apart from these new techniques but supported by them are the following services.

SMS

Short Message Service should need no further explanation. This service offers to send short 160 character long texts per message. Desspite unproportional high costs the networks today earn nearly more money by these than by voice calls.

EMS

Enhanced Messaging Service was developed by Alcatel, Ericsson, Motorola and Siemens based on SMS. An open specification should assure the data exchange between cellular phones from different manufacturers. EMS also extends the text based short message service described in the GSM specification with new functions like picture and ringtone transfer already known from Nokia phones. With EMS this will be transferrable between differend brands.

MMS

Multimedia Messaging Service will be realised basicly with GPRS but the main advantages will be introduced with UMTS. Multimedia content like short movies captured by a camera connected to the phone may be transferred for example.

Overview

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