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Next Generation CDMA Technologies - E-bok - Chen Hsiao-Hwa Chen () | Bokus
Future wireless communication systems should be operating mainly, if not completely, on burst data services carrying multimedia traffic. The need to support high-speed burst traffic has already posed a great challenge to all currently available air-link technologies based either on TDMA or CDMA. The first generation CDMA technology has been used in both 2G and 3G mobile cellular standards and it has been suggested that it is not suitable for high-speed burst-type traffic. There are many problems with the first generation CDMA technology, such as its low spreading efficiency, interference-limited capacity and the need for precision power control, etc Addresses various important issues about the next generation CDMA technologies as the major air-link technology for beyond 3G wireless applications.
Covers topics from next generation CDMA system modelling to analytical methodology, starting with the basics and progressing to advanced research topics.
Variable rate coding VRC introduced four rates of transmission, , , , and bits per second bps , allowing a cellular device to throttle the rate of transmission depending on the level speech activity. Overall capacity increased by a factor of 3 with VRC.
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Additionally, the suppression of background noise common in cellular communications at the time greatly improving call quality. CDMA thus created a technology foundation whose benefits have spanned many aspects of society, both economically and socially.
CDMA was the catalyst of this change. As of , there were around 3 billion 3G devices worldwide. Soft Handoff A handoff scheme in which a new cell-site established service while the neighboring cell-site continued to service the call. When the mobile unit was located in the transition region, between the two cell-sites, the call would be switched back and forth between cell-sites as signal strength dictates without call interruption.
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Since the mobile unit was always communicating through at least one cell-site, no disrupting effects to the mobile unit or in service occurred. Once communications were firmly established with the new cell-site, the old cell-site discontinued servicing the call.
The soft handoff was in essence a make-before-break switching function. In contrast, conventional cellular telephone systems were considered a break-before-make switching function.
Next Generation CDMA Technologies for Futuristic Wireless Communications
Variable Rate Vocoder Speech signal compression through variable rate coding of frames of digitized speech samples. The level of speech activity for each frame was determined and an output data packet rate was selected from a set of rates based upon the determined level of frame speech activity.
The lowest rate of the set of rates corresponded to a minimum level of speech activity, such as background noise or pauses in speech, while a highest rate corresponded to a maximum level of speech activity, such as active speech.
Power Control and Pilot A power control system that controlled transmission signal power for each cellular mobile telephone within cellular mobile system. The cell-site transmitted pilot was measured as received at the cellular device. Transmission power is then adjusted at the mobile unit in an opposite manner with respect to increases and decreases in received signal power.
Development of the Next Generation CDMA Technology and Lessons We Learnt from the Past
The cell-site could then transmit a command to the mobile unit to further adjust the mobile unit transmitter power. The feedback scheme was used to further adjust the mobile unit transmitter power so it arrived at the cell-site at a desired power level.
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Jacobs, L. Weaver; priority date: Oct 17, , issued: February 13, Jacobs, W. Gardner, C.