28-01-2013, 12:42 PM
Abstract of Wireless Video Service in CDMA Systems
Wireless Video.docx (Size: 26.94 KB / Downloads: 18)
ABSTRACT
Video services are becoming an integral part of future communication systems. Especially for the upcoming 3G-CDMA system wireless networks such as UMTS, video may very well turn out to be the key value addition that achieves the required return of investment. While previous generations of wireless communication systems were primarily designed and used for voice services, next generation systems have to support a broad range of applications in a wide variety of settings. The early market stages were characterized by the needs of early adopters, mostly for professional use. As the market matures from the early adopters to normal users, new services will be demanded. These demands will likely converge toward the demands that exist for wired telecommunications services.
Market research finds that mobile commerce for 3G wireless systems and beyond will be dominated by basic human communication such as messaging, voice, and video communication [1]. Because of its typically large bandwidth requirements, video communication (as opposed to the lower rate voice and the elastic e-mail) is expected to emerge as the dominant type of service in 3G/4G wireless systems. Video services obth real-time services and streaming services are gaining a lot of importance and applications in CDMA systems.
There are three ways to spread the bandwidth of the signal:
• Frequency hopping. The signal is rapidly switched between different frequencies within the hopping bandwidth pseudo-randomly, and the receiver knows beforehand where to find the signal at any given time.
• Time hopping. The signal is transmitted in short bursts pseudo-randomly, and the receiver knows beforehand when to expect the burst.
• Direct sequence. The digital data is directly coded at a much higher frequency. The code is generated pseudo-randomly, the receiver knows how to generate the same code, and correlates the received signal with that code to extract the data.