Abstract:
An exemplary method is implemented by a radio frequency receiver for synchronizing the recovery of data carried by frames received by a radio frequency communication. An initial carrier frequency estimate is used to initialize the carrier recovery system to synchronize the data unit contained in a first frame. An indication is generated, from error correction applied to the identified data units for each frame, of whether the error control coding in the receiver is capable of correcting all the errors induced by the channel within the frame. If the indication declares that all the errors are corrected, then the carrier frequency estimate associated with the error free frame is saved in memory and will be used to initialize the carrier recovery loop at the beginning of the following frames until such frequency estimate is declared unreliable. A new carrier frequency estimate is available at the end of each frame, and if such estimate is proven to be reliable for future use, the current estimate in memory will be overwritten by the new estimate and the freshness of the frequency estimate is extended.
Abstract:
Pilot logic may determine based upon channel and phase information how to process pilot tones that shift locations every N symbols in an orthogonal frequency division multiplexing (OFDM) packet transmission. Pilot logic may determine a signal-to-noise ratio (SNR) for the channel to determine how to process the shifting pilot tones. Pilot logic may also determine channel and phase information updates such as channel state information and phase correction information from pilot tones. In situations of high SNR, logic may use channel estimates and phase rotations that are obtained from locations of the pilot tones for phase tracking and updating the equalizer. In situations of low SNR, logic may use the phase rotations for phase tracking and not update the equalizer during the OFDM transmission. Logic may also determine the presence or absence of a Doppler effect on the transmission and transmit a selection for N to an access point in response.
Abstract:
A system and method of frequency offset compensation are disclosed for a wireless system between a fast moving radio terminal associated with a locomotive and a stationary radio terminal associated with a base station. The present invention utilizes advanced frequency offset prediction to quickly track Doppler Shift caused by a fast moving locomotive. In one embodiment according to the present invention, the frequency offset prediction is based on a first plurality of coarse frequency offsets, first-order derivatives of the first plurality of coarse frequency offsets, and second-order derivatives of the first plurality of coarse frequency offsets. In another embodiment according to the present invention, the frequency offset prediction is based on a plurality of previous frequency offsets according to a Doppler shift model.
Abstract:
The present invention relates to a method and an apparatus that supports a multi-carrier wireless access system for transmitting and receiving system information. The 1st embodiment of the present invention is a method for controlling a center frequency in a wireless access system comprising the steps of: receiving a control message including a 1st parameter which indicates a configuration of carrier groups and a 2nd parameter which indicates whether the center frequency is controlled from a base station; deriving the center frequency of carriers allocated to a mobile terminal by using the 1st parameter; and controlling the center frequency by using the 2nd parameter.