How does the Mobile Phone work? In Africa, this is a gadget that has revolutionalised the way people communicate. Basically, the name “mobile phone” is just a descriptive one, it means, a phone that can be used on the move. In the developed countries of Europe and North America, they had a sort of mobile phones long before our current day mobile phones. What am I trying to say? There are many types of phones that used to be installed in vehicles or hand held that could be used within a short range of say a kilometre or so from the base units, these were a kind of a mobile phone. Most probably, it is these and the “Walk talkies” (Radio Calls) that inspired the inventers of the present day mobile phones. Since the term mobile is somehow misleading, let me switch to another commonly used terminology, the “Cellular Phone” a.k.a. Cell Phone. A Cell Phone in actual sense is a Radio transceiver (transmitter – receiver). The conventional telephone was invented by Graham Bell in the 1870s, where as the radio was invented by a one Nikolai Tesla in the 1880s although it was attributed to an Italian called Marconi. The Cell phone is a combination of the two wonderful technologies. Cell phones employ GSM, CDMA or TDMA. Global System for Mobile communications (GSM) is the international standard used in Europe and many other parts of the world; GSM is the only type of cellular service available. Originally, the GSM stood for Groupe Spécial Mobile, a group formed by the Conference of European Posts and Telegraphs. TDMA stands for “Time Division Multiple Access”, this is a technology employed in transmitting digital wireless service using time-division multiplexing (TDM). TDMA works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way, a single frequency can support multiple, simultaneous data channels. TDMA is used by the GSM digital cellular system. On the other hand, CDMA stand for “Code-Division Multiple Access”, this also a digital cellular technology that uses spread-spectrum techniques. Unlike competing systems, such as GSM, that use TDMA, CDMA does not assign a specific frequency to each user. Instead, every channel uses the full available spectrum. Individual conversations are encoded with a random digital sequence. CDMA consistently provides better capacity for voice and data communications than other commercial mobile technologies, allowing more subscribers to connect at any given time, and it is the common platform on which 3G technologies are built. CDMA was developed in 2nd World War by the English and their allies in a bid to foil German attempts at jamming transmissions. When compared, Cell phones are full duplex as compared to walk talkies that are half duplex. In half duplex, there is only a channel for both parties to communicate that is why we always hear one person telling the other “over” or “roger”, this is to tell him that, I’m done, you can now talk. With the Cell phone, there are two channels and hence, both parties can talk and listen at the same time. Secondly, the mobile phone is capable of using a thousand or more channels as compared to a walk talkie that uses about forty only. Cell phones operate within cells, and can switch cells as they move around. Cells give cell phones unlimited range. If you are using a cell phone, you can travel several kilometres while your conversation is not interrupted because, your phone keeps on automatically switching from one cell to another. eddie@afrowebs.com
