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uses a rate adaptation algorithm that adapts the modulation and coding scheme (MCS) according to the quality of the radio channel, and thus the bit rate and robustness of data transmission. The process of link adaptation is a dynamic one and the signal and protocol parameters change as the radio link
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Thus HSDPA adapts to achieve very high bit rates, of the order of 14 megabit/sec, on clear channels using 16-QAM and close to 1/1 coding rate. On noisy channels HSDPA adapts to provide reliable communications using QPSK and 1/3 coding rate but the information bit rate drops to about 2.4 megabit/sec.
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is approximately the same as the channel from the receiver to the transmitter. Alternatively, the channel knowledge can also be directly measured at the receiver, and fed back to the transmitter. Adaptive modulation systems improve
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propagation environments, adaptive modulation systems exhibit great performance enhancements compared to systems that do not exploit channel knowledge at the transmitter.
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due to signals coming from other transmitters, the sensitivity of the receiver, the available transmitter power margin, etc.). For example,
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for clearer channels. The former is more robust and can tolerate higher levels of interference but has lower
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From GSM to LTE: An
Introduction to Mobile Networks and Mobile Broadband
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systems by assuming the channel from the transmitter to the
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Shami, Abdallah; Maier, Martin; Assi, Chadi (2010-01-23).
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This adaptation is performed up to 500 times per second.
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Broadband Access
Networks: Technologies and Deployments
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Energy and spectrum efficient wireless network design
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that is present at the transmitter. Especially over
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Adaptive modulation systems invariably require some
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127:In HSDPA link adaptation is performed by:
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83:(UMTS) this can take place every 2 ms.
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258:Sauter, Martin (2010-12-30).
202:IEEE 802.11ax § Rate set
324:Computer network technology
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294:Cambridge University Press
334:Radio resource management
212:Radio resource management
109:channel state information
88:channel state information
145:forward error correction
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62:(e.g. the
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50:and other
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152:code rate
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181:See also
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96:receiver
64:pathloss
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123:Example
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66:, the
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72:WiMAX
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