摘要:
A method and apparatus for predicting channel estimates for non-received signal frequencies provides knowledge of propagation channel characteristics for non-received frequencies. One embodiment predicts uplink (or downlink) channel estimates based on measured downlink (or uplink) channel estimates, which is advantageous in systems having different uplink and downlink frequencies. Another embodiment predicts channel responses for non-received OFDM sub carrier frequencies based on measuring channel responses for received OFDM sub carrier frequencies. Such processing may comprise, for example, measuring channel responses for received OFDM pilot sub carriers, predicting channel responses at frequency intervals corresponding to pilot sub carrier spacing, and interpolating between those values to predict channel responses at data sub carrier frequencies.
摘要:
Methods and apparatus that achieve good channel estimation without using unnecessarily complex interpolation filters are described. Adaptive interpolation filtering of a signal in a receiver includes determining at least one correlation function parameter of the channel and determining a filter configuration based on the correlation function parameter. Interpolation filtering is then performed on the signal using the determined filter configuration. The interpolation may be performed in time, where a Doppler frequency shift can serve as the correlation function parameter, or in frequency, where a root mean square or maximum delay spread can serve as the correlation function parameter, or both. A worst case signal-to-noise ratio may be used in determining the filter configuration, or, optionally, the signal-to-noise ratio can determined in real time. The filter configuration can be determined in real time or selected from one of a plurality of predetermined configurations having different complexities.
摘要:
Methods for calculating a delay spread estimate in an OFDM-receiver are described, along with computer program products and electronic apparatuses for performing the methods. The methods comprise determining a position of an FFT-window in relation to one or more OFDM-symbols of a received OFDM-signal and using the determined position to obtain a first OFDM-symbol from the received OFDM-signal. An FFT is applied to the first OFDM-symbol to produce an FFT-output signal. A frequency dependent phase rotation component of the FFT-output signal is determined and removed from the FFT-output signal. A number of zero-crossings of at least one of a real component and an imaginary component of a transfer function of a channel, over which the received OFDM-signal has been transmitted, derived from the FFT-output signal where the frequency dependent phase rotation component has been removed is determined, and a delay spread estimate is calculated based on the determined number of zero-crossings.
摘要:
A method and apparatus for adjusting the gain of an amplifier (202) in a communication receiver comprising: estimating the power of a time domain signal (307); estimating the power distribution on one or more sub-carriers of a frequency domain signal (309) transformed from the time domain signal; and generating a gain control signal for the amplifier based on the estimated power of the time domain signal and the power distribution on sub-carriers of the frequency domain signal (311).
摘要:
A method and apparatus for predicting channel estimates for non-received signal frequencies provides knowledge of propagation channel characteristics for non-received frequencies. One embodiment predicts uplink (or downlink) channel estimates based on measured downlink (or uplink) channel estimates, which is advantageous in systems having different uplink and downlink frequencies. Another embodiment predicts channel responses for non-received OFDM sub carrier frequencies based on measuring channel responses for received OFDM sub carrier frequencies. Such processing may comprise, for example, measuring channel responses for received OFDM pilot sub carriers, predicting channel responses at frequency intervals corresponding to pilot sub carrier spacing, and interpolating between those values to predict channel responses at data sub carrier frequencies.
摘要:
Methods for calculating a delay spread estimate in an OFDM-receiver are described, along with computer program products and electronic apparatuses for performing the methods. The methods comprise determining a position of an FFT-window in relation to one or more OFDM-symbols of a received OFDM-signal and using the determined position to obtain a first OFDM-symbol from the received OFDM-signal. An FFT is applied to the first OFDM-symbol to produce an FFT-output signal. A frequency dependent phase rotation component of the FFT-output signal is determined and removed from the FFT-output signal. A number of zero-crossings of at least one of a real component and an imaginary component of a transfer function of a channel, over which the received OFDM-signal has been transmitted, derived from the FFT-output signal where the frequency dependent phase rotation component has been removed is determined, and a delay spread estimate is calculated based on the determined number of zero-crossings.
摘要:
Methods and apparatus that achieve good channel estimation without using unnecessarily complex interpolation filters are described. Adaptive interpolation filtering of a signal in a receiver includes determining at least one correlation function parameter of the channel and determining a filter configuration based on the correlation function parameter. Interpolation filtering is then performed on the signal using the determined filter configuration. The interpolation may be performed in time, where a Doppler frequency shift can serve as the correlation function parameter, or in frequency, where a root mean square or maximum delay spread can serve as the correlation function parameter, or both. A worst case signal-to-noise ratio may be used in determining the filter configuration, or, optionally, the signal-to-noise ratio can determined in real time. The filter configuration can be determined in real time or selected from one of a plurality of predetermined configurations having different complexities.
摘要:
Methods and devices for detecting a symbol in a radio channel and for cell identification are disclosed. A signal is received from the radio channel and the signal is filtered by a filter being responsive to the symbol thereby establishing a first signal. A second signal dependent on the noise floor of the received signal is established—whereby a time interval expected to include multi-path components being excluded or suppressed. A third signal being the ratio between the first signal and the noise floor is established, and the presence of the symbol is detected by detecting a peak in the third signal.
摘要:
The automatic frequency correction value applied by a receiver is altered to minimize long-term drift of a path delay profile. In one embodiment, the phase or timing error resulting from constant frequency corrections is accumulated, and an estimated frequency correction value is selectively quantized into an actual frequency correction value in response to the accumulated phase/timing error. The quantized value above or below the estimate is selected to minimize the accumulated phase/timing error that gives rise to path delay profile drift. In another embodiment, a timing circuit measures the instantaneous path delay profile drift incurred with each frequency correction, and integrates the instantaneous drift measurements over time to yield a path delay profile drift. The drift (or its rate of change) is then used to adjust a frequency correction value so as to minimize the drift.
摘要:
A user equipment (UE) in a mobile communications system is operated in a manner that alleviates or avoids an overload condition in the UE. This involves operating a receiver of the UE to receive one or more data blocks via a channel. In response to a user equipment overload condition being detected, a channel quality indicator (CQI) value is reported to a serving base station, wherein the reported CQI value represents a channel quality that is lower than an actual quality of the channel. The UE is then operated in a manner that is consistent with the reported CQI value. UE overload conditions include overheating, and an inability to process received data blocks at the rate at which they are being received.