An Adaptive Modulation Method

Abstract

The invention provides a self-adaptive modulating method which comprises the following steps: a. obtaining a current channel state by a transmitting end according to channel measurement and estimation, and according to an available transmission power and an available channel resource, under a precondition that a user requirement is satisfied and the current channel state is adapted, deciding to start a high-grade modulation manner on condition that the transmission power is enough; b. before starting the high-grade modulation manner by the transmitting end, transmitting a power which is required by the high-grade modulation manner, operating in a secondary low-grade modulation manner, and detecting a receiving signal-to-noise ratio of the receiving end, and if an average receiving signal-to-noise ratio in a detecting period is larger than or equal with a signal-to-noise ratio threshold in a detecting period, starting the high-grade modulation manner for operating, and otherwise, transmitting the power which is required by the secondary low-grade modulation manner, and operating in the secondary low-grade modulation manner. According to the self-adaptive modulating manner, when the high-grade modulation manner is to be started, whether the channel condition is suitable for the high-grade modulation manner is detected in the detecting period, thereby preventing communication quality reduction caused by transmission non-linearity.

Description

technical field [0001] The invention relates to the field of wireless mobile communication, in particular to an adaptive modulation method. Background technique [0002] At present, in the field of mobile communication, most mobile communication systems are OFDM systems (such as TD-SCDMA, WiMAX, McWiLL, etc.), which use multi-carrier modulation technology to divide the channel into multiple orthogonal sub-channels, and each sub-channel can independently perform sub-carrier modulation. , and each sub-carrier is transmitted in parallel, so in the OFDM system, users can use multiple mixed modulation methods at the same time for uplink and downlink, and can adopt adaptive modulation methods according to the channel conditions estimated by channel measurement, that is, when the channel conditions are good and the received signal When the noise ratio is high, the user can use a higher-order modulation method (such as QAM64) to obtain the maximum spectral efficiency, and can reduce...

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Problems solved by technology

[0003] However, the inventors have found that there are at least the following problems in the implementation of the above-mentioned prior art: the OFDM system usually adopts an adaptive modulation method based on the channel conditions estimated by channel measurement, but in practical applications, there are also third-order The non-linear phenomenon of transmission caused by intermodulation, that is, when the channel condition is good and the interference is small, the transmitting end linearly increases the transmitting power, and the receiving signal-to-noise ratio of the receiving end does not increase linearly as expected but decreases slowly. If this phenomenon occurs, It is not possible to let the transmitting end know through channel measurement and estimation. The channel condition obtained by the transmitting end according to the measurement and estimation is that the channel condition is better at this time and the interference is small. The transmitting end will adaptively adopt a higher-order modulation method. The required receiving signal-to-noise ratio threshold is relatively high, so the transmitter needs to transmit higher power. Due to the existence of the nonlinear phenomenon of transmitting, the transmitting terminal transmits higher power into the transmitting nonlinear region, and the user does not actually obtain a higher receiving signal-to-noise ratio. , which is not enough to meet the SNR threshold of the higher-order modulation mode, and the user is still working in the higher-order modulation mode, resulting in an increase in the bit error rate during transmission and a decrease in communication quality

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