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Refer to [ 2 ] ch.
Another standard for selectable mode vocoder SMV was in the work but never saw any success in the industry; it based requirements on: SMV was design to offer four modes of operations: The resulting capacity vs. For data systems it is advantageous to take advantage of higher modulation schemes such as 16QAM and 64QAM when the radio link allows it.
Higher modulations are more spectral efficient but prone to more bit error rates and may cause more retransmissions, latency, or jitter. Such systems are sometimes referred to as smart antennas; they can steer a main lobe toward a user, or create a null in the direction of an interferer. Some systems are passive others include active amplification devices.
The main types of smart antenna systems may be described as follows: An array of passive and active elements using multiple power amplifiers on the transmit side, and a low-noise amplifier on the receive side. A fixed array of narrow beams, combined to form various size sectors.
An array of elements offering several degrees of freedom to steer a beam in a certain direction, or create nulls. Array element are sometimes amplified, or attenuated, or are purely passive and utilize phase shift to create the wanted patterns. A sophisticated combination of many adaptive elements.
Smart antenna systems are efficient in dense areas but often costly [ 9 ]. They are now replaced by MIMO systems covered in chapter 9.
Technology advances and standard improvements target an increase in capacity, coverage, data rate, or some other system performance aspect. In many cases however some simple optimization techniques can be used to increase performance: Cell splitting into smaller cells: Repeaters or low-noise amplifiers increase coverage.
Other parameter adjustments power levels, handoff thresholds, etc. These techniques are very important tools used by operators to optimize capacity and coverage. In some cases optimization may be seasonal due to foliage or different usage patterns. In all cases RF network demand constant tweaking to provide optimal performance.
More recently self optimizing networks SON have the ability to continually and automatically optimize these parameters. In most cases, trenching long distances to place communication conduits for fiber or copper is very costly, such as in mountainous areas.
Cellular service is often scarce too in remote areas. Early systems used analog radios to offer voice service over fairly long distances. Newer WLL systems need to be cost-effective, reliable, and compliant with local exchange carrier technical, legal, and regulatory standards.
But the demand for WLL services are generally low, and suppliers consequently treat the opportunity as a fairly low priority. These frequencies however are becoming very rare. In fact, they are in such demand that the FCC recently mandated radio systems to increase their spectral efficiencies, and use only a narrow band of spectrum.
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Chapter 2 Cellular Systems Wireless communications are especially useful for mobile applications, so wireless systems are often designed to cover large areas by splitting them into many smaller cells.
In fact, they are in such demand that the FCC recently mandated radio systems to increase their spectral efficiencies, and use only a narrow.
[PDF]Free Cellular Radio Systems download Book Cellular Radio r-bridal.com Cellular network - Wikipedia Sat, 10 Nov GMT A cellular network or mobile network is a communication network where the last link is wireless.
4G LTE Cellular Security Camera Systems. The receiving radio (also referred to as gateway radio or gateway node) is most often located at a facility that has high-speed internet service, which allows live or recorded video to be accessed from any internet enabled device.
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