Orthogonal frequency division multiplexing (OFDM) system with channel transfer function prediction
First Claim
1. A method for an adaptive subcarrier loading for a mobile receiver in a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM), the method applied to predict a frequency-selective distortion of a second channel transfer function for a multipath propagation channel impaired by attenuation fades and a time-variant behavior when said mobile receiver is moved, the method comprising:
- estimating a first and second channel transfer functions for a received signal;
assigning a subcarrier to the mobile receiver based on the estimated first and second channel transfer functions; and
assigning a modulation scheme to the subcarrier by estimating a subsequent channel transfer function for a subsequent received signal, wherein the estimating the subsequent channel transfer function includes predicting a movement of a plurality of zero points based on the estimated first and second channel transfer functions.
2 Assignments
0 Petitions
Accused Products
Abstract
Wireless communication systems are provided with an adaptive subcarrier loading function for a mobile receiver in a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM) that can advantageously be applied to predict the channel transfer function of a multipath propagation channel being severely impaired by frequency-selective fading and an extremely time-variant behavior by detecting the position and/or movement of zero points of the transfer function, thereby reducing the probability of incorrect assignment of the modulation scheme for each subcarrier caused by mobile terminals moving at high velocity. The zero points of the estimated channel transfer function are determined by detecting the position of deep notches on the associated amplitude response of the measured channel transfer function caused by frequency-selective fading whose depths are larger than a predefined threshold.
66 Citations
9 Claims
-
1. A method for an adaptive subcarrier loading for a mobile receiver in a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM), the method applied to predict a frequency-selective distortion of a second channel transfer function for a multipath propagation channel impaired by attenuation fades and a time-variant behavior when said mobile receiver is moved, the method comprising:
-
estimating a first and second channel transfer functions for a received signal; assigning a subcarrier to the mobile receiver based on the estimated first and second channel transfer functions; and assigning a modulation scheme to the subcarrier by estimating a subsequent channel transfer function for a subsequent received signal, wherein the estimating the subsequent channel transfer function includes predicting a movement of a plurality of zero points based on the estimated first and second channel transfer functions. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. A method for determining a modulation scheme for a mobile transmitter in a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM) in combination with an adaptive subcarrier loading technique which can be applied to predict a frequency-selective distortion of a channel transfer function for a multipath propagation channel impaired by attenuation fades and a time-variant behavior comprising a mobile receiver that includes each downlink signal burst, the method comprising:
-
performing a first channel estimation with a first preamble frame that serves as a pilot pattern for a current downlink signal burst, and finding a plurality of zero points of an estimated channel transfer function by detecting a position of notches on an associated amplitude response characteristic of the estimated channel transfer function, performing a second channel estimation with a second preamble frame that serves as a pilot pattern for a succeeding downlink signal burst, and finding said plurality of zero points of a newly estimated channel transfer function by detecting a position of notches on an associated amplitude response characteristic of the newly estimated channel transfer function, predicting a movement of said plurality of zero points of said channel transfer function with results obtained from the first and second channel estimations, and assigning a modulation scheme based on a position and movement of said plurality of zero points of the estimated channel transfer function. - View Dependent Claims (8)
-
-
9. A mobile receiver for wireless communication over a mobile radio channel using Orthogonal Frequency Division Multiplexing (OFDM) systems, the mobile receiver comprising:
-
a modulator/demodulator unit configured to perform an OFDM multi-carrier modulation and/or an OFDM multi-carrier demodulation, a channel estimation unit configured to perform a channel estimation, a channel equalization/synchronization unit configured to perform a channel equalization and/or a synchronization on the basis of at least one part of the received signal, a receiver subunit configured to perform an adaptive subcarrier loading technique of adaptively assigning a subcarrier to the mobile receiver to increase usage capacity of the underlying multipath propagation channel, the technique including, predicting a frequency-selective distortion of the channel transfer function for the underlying multipath propagation channel being severely impaired by attenuation fades and a time-variant behavior when the mobile receiver is moved, and an estimation unit configured to calculate an estimation of said channel transfer function by evaluating a position of a plurality of zero points of the channel transfer function, wherein, for each downlink signal burst, a first estimating unit configured to perform a first channel estimation with a first preamble frame that serves as a pilot pattern for a current downlink signal burst, and find said plurality of zero points of the estimated channel transfer function by detecting a position of notches on an associated amplitude response characteristic of the estimated channel transfer function, a second estimating unit configured to perform a second channel estimation with a second preamble frame that serves as a pilot pattern for a succeeding downlink signal burst, and find said plurality of zero points of a newly estimated channel transfer function by detecting a position of notches on an associated amplitude response characteristic of the newly estimated channel transfer function, a predicting unit configured to predict a movement of said plurality of zero points of said channel transfer function with results obtained from the first and second estimating units, and a modulator configured to assign a modulation scheme based on the position and movement of said plurality of zero points of the estimated channel transfer function.
-
Specification