A new mobile text telephony system based on GPRS communications

Deaf people have had many difficulties to enjoy the advantages of modem telephone technology up to early days. Since Alexandre Graham Bell invented the telephone in 1876, the first text telephones have needed almost a century to appear in the market and to allow deaf people to communicate with others at long distances. In the same way, the design and development of new text telephones using mobile telephony networks have needed time. Nevertheless, nowadays deaf people suffer from a great economical discrimination due to the telephone call cost in many countries. We must consider that a text conversation need much more time if it is compared with voice one and the service rates depended on connection time and not on transmitted data only. The system we present is based on GPRS (2.5 G) data mobile communications which considers only the transmitted information for billing and in the text conversations case, this amount of data is very limited and independent of telephone call duration. The terminals used are PDA (Personal Digital Assistant) with Pocket PC or Palm operative system. All the system has been designed using Internet technology (TCP/IP protocol), so it is possible to communicate with several terminals like mobile telephones with TCP/IP stack or PC. In the last case, a client text telephone program has been implemented. In the first case, a WAP text telephone client has been developed by the Spanish Vodafone Foundation which is able to communicate with the PDA text telephone client.