| Analog Service is similar to FM radio in that | | | | resistant to interference from enemy signals. |
| modulating radio signals carry information | | | | Known as spread spectrum technology this |
| such as voice or data. The receiver and | | | | technology was restricted to military use and |
| transmitter must be tuned to the same | | | | top secret during World War 2. In the 1980's |
| frequency within a small band width for the | | | | the commercial use of this technology was |
| receiver to rebuild the signal, amplify it, | | | | realized after a 1976 publication of Spread |
| and send it to the speaker. There are | | | | Spectrum Systems by Robert Dixon was |
| limitations on the number of channels that | | | | published. Previous publications were |
| can be used making this technology soon to be | | | | classified military reports or narrow |
| outlived. Effective February 2008, many | | | | subtopics on academic papers. By 1993 CDMA |
| wireless providers will be discontinuing | | | | was accepted as a standard and went into |
| support of this service. | | | | operation in 1996. CDMA also exists at both |
| | | | the 800 MHz and 1900 MHz band, and is used by |
| Digital Service is a method similar to | | | | the major carriers. |
| computers, in that it uses binary code of Os | | | | |
| and 1s. Most new wireless phones and networks | | | | GSM (Global System for Mobile Communications) |
| use digital technology. The analog signal in | | | | is based upon an improved version of TDMA |
| Digital is converted into binary code and | | | | technology. In 1982, a conference in Europe |
| transmitted as a series of on and off | | | | created a digital standard to allow users to |
| transmissions. There are three digital | | | | roam from country to country in Europe. By |
| wireless technologies, CDMA, TDMA and GSM and | | | | 1987, the GSM standard was created based upon |
| I will explain these three as phones that | | | | both analog and TDMA digital technologies. |
| work with one may not work on another. | | | | Using wider 200 kHz channels instead of the |
| | | | 30 kHz channels TDMA used along with other |
| TDMA (Time Division Multiple Access) was | | | | modifications they were able to speed up the |
| released in 1994; it uses the frequency bands | | | | bit rate with a more natural sounding |
| available to the wireless network and divided | | | | voice-compression algorithm. This also |
| them into time slots with each phone user | | | | enabled GSM to provide such other data |
| having access to one time slot at regular | | | | services as email, fax, internet browsing, |
| intervals. In North America TDMA uses both | | | | and internet/LAN wireless access. The GSM |
| 800 MHz and 1900 MHz bands. Most of the major | | | | standard was accepted in the United States in |
| wireless carriers use TDMA. | | | | 1995 and is the only phone that can be used |
| | | | around the world. This technology will be the |
| CDMA (Code Division Multiple Access) | | | | bases of future growth in the wireless phone |
| technology dates back to the 1940's, when it | | | | industry as it offers the multifunction |
| was developed for military use because it was | | | | capabilities today's users require. |