Technique for adaptive data rate communication over fading dispersive channels

摘要

In a duplex radio link wherein digital data information from a data interface is transmitted from a local terminal to a remote terminal over fading dispersive channels, a method and transceiver are described that provide for transmission at an adaptive data rate. The transmission is at a constant symbol rate so that the signal bandwidth can be fixed and at the remote terminal receiver the input sampling rate can be fixed. The digital data information is transmitted over a constant data rate interval in accordance with a selected data rate mode that is a function of direct sequence spreading gain, error correction code rate, and signal constellation type. The data rate is adapted by selecting a data rate mode that is a function of the arrival rate of data packets from the data interface and a link quality measure fed back from the remote terminal. The data packet arrival rate is controlled as a function of the link quality measure and the current data packet arrival rate. In systems with multiple transmit diversity channels, independent data is sent over each of the transmit diversity channels. The adaptive data rate technique utilizes both orthogonal transmit diversities such as frequency and troposcatter polarization diversity as well as nonorthogonal transmit diversities in a Multiple-input Multiple-Output (MIMO) configuration. A single antenna troposcatter link using angle diversity and adaptation of data rate by feedback communications is described. In an idealized feedback communication example, the single antenna system in a Ku-band application is shown to have 15.5 times the data rate capability of a conventional two-antenna system at S-band.