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Decision Feedback Type Equalizer

A technology of decision feedback and equalizer, which is applied in baseband system components, shaping network in transmitter/receiver, etc., can solve problems such as error propagation, performance deterioration of feedback equalizer, and increase of subsequent symbol error rate

Inactive Publication Date: 2012-04-04
KK TOSHIBA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in this type, when an error occurs in the symbol hard decision, not only the inter-symbol interference for the subsequent symbol is not removed, but also a new interference component is generated, which increases the error rate of the subsequent symbol.
This is generally referred to as error propagation, which causes performance degradation of decision feedback equalizers

Method used

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  • Decision Feedback Type Equalizer
  • Decision Feedback Type Equalizer
  • Decision Feedback Type Equalizer

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Experimental program
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no. 1 approach

[0092] The comparative example has been described so far, and the first embodiment will be described below.

[0093] Additionally, error propagation is known to occur in decision feedback equalizers. That is, when the reliability of a certain bit in the output of the equalizer decreases, the ISI may not be correctly removed for the symbol in which the bit was transmitted. This means that a relationship via feedback taps is found between the number of symbols and the reliability of the bits that convey the symbols. In this embodiment, the reliability of the bit is updated by using the relationship, so as to realize repetition balance.

[0094] The first embodiment is described by taking a decision-feedback equalizer that feeds back soft copy as an example.

[0095] figure 1 It is a block diagram showing an example of the decision feedback equalizer of this embodiment.

[0096] Such as figure 1 As shown, the decision feedback equalizer of this embodiment includes: a storage...

no. 2 approach

[0160] Next, a second embodiment will be described.

[0161] In this embodiment, as in the first embodiment, when the soft copy of the symbol in the (i+1)th decision feedback loop is generated, if a reliable If a symbol with a low degree of influence affects the symbol, the influence of error propagation is reduced by reducing the log-likelihood ratio used in the soft copy generation. At this time, in this embodiment, the details will be described later. By introducing a threshold judgment into the LLR attenuation unit 17, even if the bit is designated as an attenuation target bit, if the reliability of the bit is sufficiently high, it will avoid to attenuate the LLR. That is, in a noisy environment, even if inter-symbol interference is well removed, bits with low reliability may be generated due to the influence of noise, and the preceding bits may be designated as attenuation-target bits. In this embodiment, determination of reliability is introduced so that the removal of...

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Abstract

The invention relates to a decision feedback type equalizer, capable of better reducing error dissemination. The decision feedback type equalizer comprises a storage device, a logarithm likelihood ratio calculating part, a logarithm likelihood ratio evaluation part, a decrement calculating part, and a logarithm likelihood ratio attenuation part, wherein the storage device is used for keeping input signals that make the decision responding to multiple signs to be repeatedly operated; the logarithm likelihood ratio calculating part is used for calculating the logarithm likelihood ratio according to the signals obtained by deducting the output of the feedback filter from the input signals kept in the storage device; the logarithm likelihood ratio evaluation part, according to the absolute value of the logarithm likelihood ratio, carries out confirmation over the signals transmitting the bit that is evaluated with low reliability; the decrement calculating part calculates and keeps the logarithm likelihood ratio attenuation amount corresponding to the whole or part of bits of the signals affected by the feedback filter; and the logarithm likelihood ratio attenuation part makes the logarithm likelihood ratio carry out attenuation according to the logarithm likelihood ratio attenuation amount calculated in the previous decision feedback cycle.

Description

[0001] References to related applications such as the priority basic application [0002] This application is based on Japanese Patent Application No. 2010-202098 (filing date: September 9, 2010), and enjoys priority benefits based on this application. This application incorporates the entire content of this application by reference. technical field [0003] Embodiments of the invention relate to decision feedback equalizers. Background technique [0004] In a communication / broadcasting signal receiving device, etc., as a countermeasure technology for inter-symbol interference (ISI) caused by multipath fading, a method of nonlinear equalization that has characteristics superior to linear equalization, that is, is sometimes used. Decision feedback equalizer (decision feedback equalizer) (hereinafter, DFE stands for decision feedback equalizer). [0005] Among typical types of decision feedback equalizers, there is a decision feedback equalizer that operates by feeding back ...

Claims

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Application Information

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IPC IPC(8): H04L25/03
Inventor 中西俊之竹田大辅
Owner KK TOSHIBA
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