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Phase locked loop for an OFDM system

A communication system and phase technology, applied in the field of data communication, can solve problems such as performance degradation, and achieve the effects of wide loop bandwidth, fast convergence, and short acquisition time

Inactive Publication Date: 2006-10-25
QUALCOMM INC
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  • Abstract
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AI Technical Summary

Problems solved by technology

This performance degradation is especially pronounced for Additive White Gaussian Noise (AWGN) channels (i.e., wireless links with flat fading characteristics)

Method used

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  • Phase locked loop for an OFDM system
  • Phase locked loop for an OFDM system
  • Phase locked loop for an OFDM system

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Embodiment Construction

[0022] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or having advantages over other embodiments or designs.

[0023] figure 1 A block diagram of transmitter system 110 and receiver system 150 in OFDM 100 is shown. At transmitter system 110, a transmit (TX) data processor 120 receives traffic data (eg, information bits) and formats, codes, interleaves, and modulates the traffic data to provide modulation symbols. Said encoding increases the reliability of data transmission. TX data processor 120 may perform error detection coding (eg, CRC coding), forward error correction coding (eg, convolutional coding, turbo coding, and / or block coding), or a combination of the foregoing. The interleaving provides time and / or frequency diversity, which is used to combat adverse path effects. The modulation (eg, symbol mapping) can be ...

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Abstract

Techniques for tracking residual frequency error and phase noise in OFDM systems are provided. At the receiver, each received OFDM symbol is transformed using an FFT to obtain a received modulation symbol, which is serialized. A phase locked loop operates on the serialized receive modulation symbols and provides an independent phase correction value for each receive modulation symbol. Each received modulation symbol is corrected with its own phase correction value to obtain a phase corrected symbol. The phase error in each phase correction symbol is detected to obtain a phase error estimate for that phase correction symbol. The phase error estimate for each phase correction symbol is filtered (eg, with a second order loop filter) to obtain a frequency error estimate, which is accumulated to obtain a phase correction value for another received modulation symbol. Since independent phase correction values ​​are used for the received modulation symbols, the phase correction symbols are not correlated.

Description

[0001] Cross References to Related Applications [0002] This application claims priority to co-pending US Provisional Patent Application No. 60 / 461,169, filed April 7, 2003, entitled "PHASEDLOCKED LOOP FOR AN OFDM SYSTEM," which is hereby incorporated by reference. technical field [0003] The present invention relates generally to data communications and, more particularly, to techniques for tracking residual frequency error and phase noise in Orthogonal Frequency Division Multiplexing (OFDM) communication systems. Background technique [0004] Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and so on. These systems can use OFDM, which is a modulation technique that can provide high performance for some wireless environments. OFDM effectively divides the entire system bandwidth into multiple (N s ) orthogonal subbands, which are also commonly referred to as tones, subcarriers, bins, and frequency su...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03D3/24
Inventor 阿洛克·库马尔·古普塔
Owner QUALCOMM INC
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