Adaptive modulation for wireless networks

Abstract

This invention relates to communication between terminals. Where communication is over an ideal channel then a high throughput modulation scheme can be used. Where the terminals suffer interference or noise, transmission can be modified to a more robust modulation scheme. The modulation scheme for a signal to be transmitted from the terminal is normally selected based up measurements made on a signal received by the terminal. However, the uplink and downlink between two terminals may not be experiencing the same interference and noise. For example, an interfering source may affect one terminal more than another. Under these circumstances, the terminal will not get a good picture of the status of the channel or link over which it is about to transmit. Therefore, the invention provides a system where quality information is passed from the terminal receiving a signal to the terminal which sent the signal to help to determine the most appropriate modulation scheme.

Description

technical field

[0001] The invention relates to the selection and control of the modulation scheme used in a communication channel between two terminals. Background technique

[0002] When two terminals communicate with each other, whether wireless or otherwise, the choice of a modulation scheme for a communication channel can significantly affect the throughput of that channel on the link and the channel's ability to reject noise. In particular, it is advantageous to use a modulation scheme with a high throughput rate and little error correction when the channel quality is good, and relatively speaking, to use a modulation scheme with a lower throughput rate when the channel is affected by noise or interference. But a modulation scheme with better noise immunity. The difficulty in choosing an appropriate modulation scheme is that the environment is so unstable that the noise may be low in one situation and high in another. In these cases, the most reliable and noise-rejec...

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