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Faces of the Wireless World.

© Wai Seto

We have been talking about WAP, but is WAP the only thing happening in the Wireless World? By no mean I am trying to say WAP is not the way to go. In fact, I always think people do not give enough time for WAP. Expectations of WAP are not well educated. WAP is not (yet) for PC type multi-media applications. WAP is for short/quick access of needed information. I believe given time, WAP can achieve at a higher level, but we need to grow with the technology. In this articles, we take a break and look at other wireless technologies. These technologies form a good wireless background.

AMPS (Advanced Mobile Phone Service) This is the analog cellular technology in United State. Analog technology uses FDMA (Frequency Division Multiple Access). It can be easily see that the way this network allow multiple users by dividing a frequency specturm into different slots for users.

CMDA (Code Division Multiple Access) This digital technology provides bigger subscriber numbers and higher transfer rate. The advantage of CDMA is that it uses the who frequency specturm for communications. Each user channel is assigned with a code (ID). Nothing is divided amount user, and hence a large reusability.

CDPD (Cellular Digital Packet Data) Transfer rate can be 9.6Kbps or 19.2Kpbs. This network is generally used for data trasfer, not voice over the air. One can think of this as wireless IP network technology.

FDMA (Frequency Division Multiple Access) Frequency specturm is divided into user channels in this case. Each user uses a channel at a time. AMPS is a FDMA network as we have mentioned above. Since a channel is assigned to one user, channels can be running out relatively easy.

GSM (Global System for Mobile Communication) The most popular network in Europe, Asia, India, and Africa. Data rate is about 14.4Kpbs with encoding. This standard was invented in 1982 in Europe. GSM is a form of TDMA, which divide a frequency into eight slot. The first two slots are used for broadcasting messages (call establishment) and SMS messages.

PCS (Personal Communication Service) refers to CDMA, GSM, TDMA operating in the 1.9GHz band in United Stated.

TDMA (Time Division Multiple Access) is a method of dividing a frequency channel into time slots. Each user owns a slot at certain timeline. The idea is not only frequencies are broken; a single frequency is further broken to allow more user to use the network simultaneously.

GPRS (General Packet Radio Service) currently can supply 70Kpbs data rate. GPRS is design as a subset of the GSM system. Efforts are put in to use GPRS in a CDMA network. Note that GPRS is a way of packet switching; the idea is similar to IP packet switching.

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