CN103401821A - Adaptive equalizer of Bluetooth 4.0 low-power receiver and implementation method of adaptive equalizer - Google Patents

Abstract

The invention relates to an adaptive equalizer of BT4.0 (Bluetooth 4.0) low-power receiver and an implementation method of the adaptive equalizer. A feed-forward equalizer (FFE) is connected with a decision device by a summator; the output end of the decision device is connected with a feed-backward equalizer (FBE); the input end of an error generator is connected with the input end and the output end of the decision device; the output end of the error generator is connected with the input end of a first tap coefficient updater and the input end of a second tap coefficient updater; the output end of the first tap coefficient updater is connected with the FFE; the output end of the second tap coefficient updater is connected with the FBE; the output end of the FBE is connected with the summator. The optimization and the improvement are made in the aspects of eliminating ISI (inter symbol interference) and tolerating symbol timing phase errors, and the ascertained ISI introduced by originating is eliminated by using a decision feedback equalizer of symbol intervals, and therefore, PER can be favorably reduced by a BT 4.0 signal receiving end, and the stability of the receiver is improved.

Description

Bluetooth 4.0 low-power consumption receiver adaptive equalizer and its implementation

Technical field

The present invention relates to a kind of bluetooth 4.0 low-power consumption receiver adaptive equalizer and its implementation, belong to the WLAN (wireless local area network) transmission technique field.

Background technology

In December, 2009, bluetooth sig (Bluetooth Special Interest Group, SIG) release in advance for the first time bluetooth 4.0 versions, and in the end of the year 2010, formally announce the related data of bluetooth core specification 4.0 versions in Seattle, bluetooth 4.0 versions will be pass by three kinds of bluetooth compliants and be comprised that three kinds of specifications such as traditional bluetooth technology, bluetooth Low-power Technology and blue teeth high speed technology integrate.

Low-power Technology can say the important breakthrough of bluetooth 4.0 versions, possesses ultralow peak value (Peak), mean value and stand-by power consumption, and seeing through the standard button cell is enough to use the several years, supports the compatibility between plurality of devices, and strengthens range.Support very short data packet, 8octet to 27octet, its transmission speed is up to 1Mbps.The Bluetooth technology of bluetooth Low-power Technology and other versions is the same is all to use AFH, to reduce the interference of 2.4GHz ISM wave band other technologies as far as possible.The bluetooth low power dissipation design mainly provides 3 kinds of application schemes: independent operating mode (Stand-alone), dual-mode of operation pattern (Dual Mode) and integration mode.In the bimodulus application, the function of bluetooth low-power consumption can be integrated in existing traditional bluetooth controller, shares existing radio frequency and the function of traditional bluetooth technology, and the cost that increases compared to traditional Bluetooth technology is less.In addition, manufacturer can utilize the storehouse of upgrade version bluetooth Low-power Technology, integrates traditional bluetooth chipset such as present bluetooth 3.0 high speed versions or 2.1+EDR, promotes the new usefulness of traditional blue-tooth device.In addition, the independent running chipset of low-power consumption is a highly integrated device, the link layer (Link Layer) that possesses light weight, can under the prerequisite of least cost, support the standby mode of low-power consumption, easy device discovery, the transfer of data of reliable point-to-multipoint, the encryption link of safety etc.; Be arranged in the link layer of above-mentioned controller, be applicable to the network connecting sensor, and guarantee in wireless transmission, all can be by bluetooth low-power consumption transmission.

BT4.0LE(bluetooth 4.0 Low-power Technology) in, the GFSK of physical layer use h=0.5 is its modulation system, and combining adaptive frequency hopping (AFH) makes its random frequency hopping on 40 possible channels.Its frame structure has the characteristics of physical layer frame structure in the general communication technology, and frame is initial by the lead code (Preamble) of a 8bit, and back, followed by the access address (Access Address) of 32bit, is PDU and CRC byte afterwards.Preamble and Access Address can be by scramblings in transmitting procedure.Because BT4.0LE is the GFSK modulation, so all being contained in, all transmission informations receive in the signal transient frequency, in order to be that the frequency spectrum that transmits is compacter, the FM signal of GFSK has been passed through Gassian low-pass filter and has been treated the high fdrequency component of tonal signal with minimizing before carrying out frequency modulation.The side effect of such way is to have introduced intersymbol interference (ISI), and ISI has vital impact to receptivity in communication.

Reception to physical frame in BT4.0LE is the non-coherent demodulation method that uses frequency detection mode, signal after demodulation according to sign synchronization estimate the sampling phase obtain to frequency discriminator output carry out direct sampling and obtain restituted signal with the symbol rate sampling, and directly hard decision obtains information bit.The impact of the intersymbol interference (ISI) of introducing due to the existence of additive noise and gaussian filtering, make in the output bit that this moment, directly hard decision produced and easily produce error code, always can there be certain error in the sampling phase that the while sign synchronization obtains, this phase place has further been introduced intersymbol interference, and this intersymbol interference is unpredictable, therefore the existence of sign synchronization phase error makes the output error performance of direct hard decision sharply descend, and these error codes are not eliminated specially and reduced in existing technology chance.

Summary of the invention

The objective of the invention is to overcome the deficiency that prior art exists, a kind of bluetooth 4.0 low-power consumption receiver adaptive equalizer and its implementation are provided.

Purpose of the present invention is achieved through the following technical solutions:

bluetooth 4.0 low-power consumption receiver adaptive equalizers, characteristics are: comprise forward equalizer FFE, backward equalizer FBE, the first tap coefficient renovator, the second tap coefficient renovator, decision device and error generator, forward equalizer FFE is connected with decision device through adder, the output of decision device connects backward equalizer FBE, the input of error generator is connected with output with the input of decision device, the output of error generator is connected with the input of the second tap coefficient renovator with the input of the first tap coefficient renovator, the output of the first tap coefficient renovator connects forward equalizer FFE, the output of the second tap coefficient renovator connects backward equalizer FBE, the output of backward equalizer FBE is connected with adder,

Signal inputs to forward equalizer FFE, the output signal of decision device is given backward equalizer FBE, the error generator adopts the input signal of decision device and output signal to produce to be used for carrying out the error component that tap coefficient upgrades, and the first tap coefficient renovator, the second tap coefficient renovator upgrade each tap coefficient of equalizer according to the input value adjustment of the output of error generator and current equalizer.

Further, above-mentioned bluetooth 4.0 low-power consumption receiver adaptive equalizers, described forward equalizer FFE is the FFE equalizer on ffe_N rank, described ffe_N is the integer greater than 1; The FBE equalizer that described backward equalizer FBE is the fbe_N rank, described fbe_N is the integer greater than 1.

Further, above-mentioned bluetooth 4.0 low-power consumption receiver adaptive equalizers, described forward equalizer FFE and backward equalizer FBE are the FIR finite impulse response filter.

Further, above-mentioned bluetooth 4.0 low-power consumption receiver adaptive equalizers, described forward equalizer FFE and backward equalizer FBE are transversal filter or transposed form filter.

the present invention realizes the method for adaptive equalization, the baseband sampling signal rx(n that receives) after low pass filter will be with outer interference and noise to suppress by the frequency discriminator computing, it is output as FD(n), after the sign synchronization estimation module of receiver is judged the Symbol Timing phase place, FD(n) obtain FD(OSR*n+offset from initial sampling rate is down-sampled to character rate) and send into adaptive equalizer, wherein integer offset represents the symbol sampling phase, determined by the Symbol Timing module, OSR is positive integer, the ratio that represents initial sample rate and symbol rate, 0＜offset＜OSR,

In adaptive equalizer when work,, in each mark space, the input of forward equalizer FFE has a new frequency discriminator output valve FD(OSR*n+offset) enter forward equalizer FFE; FFE_out (n) is the output valve of FFE in n mark space, and FBE_out (n) is the output valve of backward equalizer FBE in n mark space, and EQ_out (n) is the input value of decision device in n mark space; Above each value computing in each symbol period is calculated by following formula, wherein, ffe_coef(k, n) and fbe_coef (k, n) represent that respectively forward equalizer FFE and backward equalizer FBE are at n k the tap coefficient in the moment;

$\mathrm{FFE}\_\mathrm{out}\left(n\right)=\underset{k=0}{\overset{\mathrm{ffe}\_N-1}{\mathrm{\Σ}}}\mathrm{FD}\[\mathrm{OSR}(n-k)+\mathrm{offset}\]\·\mathrm{ffe}\_\mathrm{coef}(k,n)$

$\mathrm{FBE}\_\mathrm{out}\left(n\right)=\underset{k=0}{\overset{\mathrm{fbe}\_N-1}{\mathrm{\Σ}}}\mathrm{sign}\[\mathrm{EQ}\_\mathrm{out}(n-k)\]\·\mathrm{fbe}\_\mathrm{coef}(k,n)$

EQ_out(n)=FFE_out(n)+FBE_out(n)

Tap coefficient upgrades according to following more new formula iteration in each symbol period simultaneously:

ffe(k,n+1)=ffe(k,n)+μ·err(n)·FD[OSR(n-k)+offset]

fbe(k,n+1)=fbe(k,n)+μ·err(n)·sign[EQ_out(n-k)]

err(n)=sign[EQ_out(n)]-EQ_out(n)

Wherein err (n) produces in each symbol period for the error generator is used for the error signal that tap coefficient is adjusted; μ is for adjusting step-length; Sign () is for getting symbolic operation, and EQ_out (n) is the input of decision device, sign[EQ_out (n)] be the output of decision device;

The output sign[EQ_out (n) of decision device] send into the next stage module of receiver in order to recover the information that receives as the final effectively output of adaptive equalizer.

The substantive distinguishing features that technical solution of the present invention is outstanding and significant progressive being mainly reflected in:

1. process using sef-adapting filter to carry out signal in receiver before the signal after frequency demodulation carrying out hard decision, eliminate between the symbol (bit) of being introduced by the Gaussian filter of transmitting terminal and disturb the tolerance that has enlarged simultaneously the sampling phase deviation; The forward taps that part FIR structure is also arranged due to filter, therefore this sef-adapting filter has the effect of self adaptation adjustment sampling phase, filter can self adaptation be adjusted wrong sampling phase to the optimum sampling phase place when there is certain phase error constantly in sign synchronization, thereby reaches the effect that improves the receiver error performance;

2. relative prior art is making and is optimizing and improve aspect elimination ISI and tolerance Symbol Timing phase error, eliminate the intersymbol interference that knows of making a start and introducing with the DFF of mark space, make equalizer can correct Symbol Timing phase error in certain limit by the adaptive algorithm of specially selecting simultaneously, therefore being conducive to the BT4.0LE signal receiving end reduces PER, improves the stability of receiver.

Description of drawings

Below in conjunction with accompanying drawing, technical solution of the present invention is described further:

Fig. 1: the structural representation of equalizer of the present invention;

Fig. 2: equalizer application schematic diagram.

Embodiment

as shown in Figure 1, bluetooth 4.0 low-power consumption receiver adaptive equalizers, comprise forward equalizer FFE1, backward equalizer FBE6, the first tap coefficient renovator 4, the second tap coefficient renovator 7, decision device 3 and error generator 5, forward equalizer FFE1 is connected with decision device 3 through adder 2, the output of decision device 3 connects backward equalizer FBE6, the input of error generator 5 is connected with output with the input of decision device 3, the output of error generator 5 is connected with the input of the second tap coefficient renovator 7 with the input of the first tap coefficient renovator 4, the output of the first tap coefficient renovator 4 connects forward equalizer FFE1, the output of the second tap coefficient renovator 7 connects backward equalizer FBE6, the output of backward equalizer FBE6 is connected with adder 2,

Signal inputs to forward equalizer FFE1, the output signal of decision device 3 is given backward equalizer FBE6, error generator 5 adopts the input signal of decision devices 3 and output signal to produce to be used for carrying out the error component that tap coefficient upgrades, and the first tap coefficient renovator 4, the second tap coefficient renovator 7 upgrade each tap coefficient of equalizer according to the input value adjustment of the output of error generator 5 and current equalizer.

Wherein, forward equalizer FFE1 is the FFE equalizer on ffe_N rank, and ffe_N is the integer greater than 1; The FBE equalizer that backward equalizer FBE6 is the fbe_N rank, fbe_N are the integer greater than 1.Forward equalizer FFE1 and backward equalizer FBE6 are the FIR finite impulse response filter.Forward equalizer FFE1 and backward equalizer FBE6 are transversal filter or transposed form filter, and its filter coefficient is provided by two tap coefficient renovators of correspondence respectively.

during concrete application, as shown in Figure 2, the baseband sampling signal rx(n that receives) after being with outer interference and noise to suppress, low pass filter carries out the frequency discriminator computing, it is output as FD(n), after the sign synchronization estimation module of receiver is judged the Symbol Timing phase place, FD(n) obtain FD(OSR*n+offset from initial sampling rate is down-sampled to character rate) and send into adaptive equalizer, wherein integer offset represents the symbol sampling phase, determined by the Symbol Timing module, OSR is positive integer, the ratio that represents initial sample rate and symbol rate, 0＜offset＜OSR,

In adaptive equalizer when work,, in each mark space, the input of forward equalizer FFE has a new frequency discriminator output valve FD(OSR*n+offset) enter forward equalizer FFE; FFE_out (n) is the output valve of FFE in n mark space, and FBE_out (n) is the output valve of backward equalizer FBE in n mark space, and EQ_out (n) is the input value of decision device in n mark space; Above each value computing in each symbol period is calculated by following formula, wherein, ffe_coef(k, n) and fbe_coef (k, n) represent that respectively forward equalizer FFE and backward equalizer FBE are at n k the tap coefficient in the moment;

$\mathrm{FFE}\_\mathrm{out}\left(n\right)=\underset{k=0}{\overset{\mathrm{ffe}\_N-1}{\mathrm{\Σ}}}\mathrm{FD}\[\mathrm{OSR}(n-k)+\mathrm{offset}\]\·\mathrm{ffe}\_\mathrm{coef}(k,n)$

$\mathrm{FBE}\_\mathrm{out}\left(n\right)=\underset{k=0}{\overset{\mathrm{fbe}\_N-1}{\mathrm{\Σ}}}\mathrm{sign}\[\mathrm{EQ}\_\mathrm{out}(n-k)\]\·\mathrm{fbe}\_\mathrm{coef}(k,n)$

EQ_out(n)=FFE_out(n)+FBE_out(n)

Tap coefficient upgrades according to following more new formula iteration in each symbol period simultaneously:

ffe(k,n+1)=ffe(k,n)+μ·err(n)·FD[OSR(n-k)+offset]

fbe(k,n+1)=fbe(k,n)+μ·err(n)·sign[EQ_out(n-k)]

err(n)=sign[EQ_out(n)]-EQ_out(n)

Wherein err (n) produces in each symbol period for the error generator is used for the error signal that tap coefficient is adjusted; μ is for adjusting step-length; Sign () is for getting symbolic operation, and EQ_out (n) is the input of decision device, sign[EQ_out (n)] be the output of decision device;

The output sign[EQ_out (n) of decision device] send into the next stage module of receiver in order to recover the information that receives as the final effectively output of adaptive equalizer.

In sum, the present invention processes using sef-adapting filter to carry out signal in receiver before the signal after frequency demodulation carrying out hard decision, eliminates between the symbol (bit) of being introduced by the Gaussian filter of transmitting terminal and disturbs the tolerance that has enlarged simultaneously the sampling phase deviation.Because the Gaussian filter of making a start response knows, thus the intersymbol interference that causes also know, the filter of therefore according to the response of Gaussian filter, designing a mark space decision-feedback structure is eliminated intersymbol interference.The forward taps that part FIR structure is also arranged due to filter, therefore this sef-adapting filter has the effect of self adaptation adjustment sampling phase, filter can self adaptation be adjusted wrong sampling phase to the optimum sampling phase place when there is certain phase error constantly in sign synchronization, thereby reaches the effect that improves the receiver error performance.

Optimizing and improvement eliminating aspect ISI and tolerance Symbol Timing phase error making of the relative prior art of the present invention.Eliminate the intersymbol interference that knows of making a start and introducing with the DFF of mark space, make this equalizer can correct Symbol Timing phase error in certain limit by the adaptive algorithm of specially selecting simultaneously, therefore being conducive to the BT4.0LE signal receiving end reduces PER, improves the stability of receiver.

Eliminate the intersymbol interference that knows of making a start and introducing with the adaptive decision feedback equalizer of a mark space, make this equalizer can correct Symbol Timing phase error in certain limit by the adaptive algorithm of specially selecting simultaneously.

Equalizer consists of feed forward equalizer (FFE) and feedback equalizer (FBE), and main tapping is positioned at feed forward equalizer and register configuration can be passed through in its position; The input of feed forward equalizer is the frequency discriminator output through Symbol Timing, and the input of feedback equalizer is the output decision value (2 level) of whole equalizer.Adaptive equalization algorithm is used " decision-directed least mean-square error " algorithm (DD-LMS).

What need to understand is: the above is only the preferred embodiment of the present invention; for those skilled in the art; under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (8)

1. bluetooth 4.0 low-power consumption receiver adaptive equalizers, it is characterized in that: comprise forward equalizer FFE(1), backward equalizer FBE(6), the first tap coefficient renovator (4), the second tap coefficient renovator (7), decision device (3) and error generator (5), forward equalizer FFE(1) be connected with decision device (3) through adder (2), the output of decision device (3) connects backward equalizer FBE(6), the input of error generator (5) is connected with output with the input of decision device (3), the output of error generator (5) is connected with the input of the second tap coefficient renovator (7) with the input of the first tap coefficient renovator (4), the output of the first tap coefficient renovator (4) connects forward equalizer FFE(1), the output of the second tap coefficient renovator (7) connects backward equalizer FBE(6), backward equalizer FBE(6) output is connected with adder (2),

Signal inputs to forward equalizer FFE(1), the output signal of decision device (3) is given backward equalizer FBE(6), error generator (5) adopts the input signal of decision device (3) and output signal to produce to be used for carrying out the error component that tap coefficient upgrades, and the first tap coefficient renovator (4), the second tap coefficient renovator (7) upgrade each tap coefficient of equalizer according to the input value adjustment of the output of error generator (5) and current equalizer.

2. bluetooth 4.0 low-power consumption receiver adaptive equalizers according to claim 1, is characterized in that: described forward equalizer FFE(1) be the FFE equalizer on ffe_N rank.

3. bluetooth 4.0 low-power consumption receiver adaptive equalizers according to claim 2 is characterized in that: described ffe_N is the integer greater than 1.

4. bluetooth 4.0 low-power consumption receiver adaptive equalizers according to claim 1, is characterized in that: described backward equalizer FBE(6) be the FBE equalizer on fbe_N rank.

5. bluetooth 4.0 low-power consumption receiver adaptive equalizers according to claim 4 is characterized in that: described fbe_N is the integer greater than 1.

6. bluetooth 4.0 low-power consumption receiver adaptive equalizers according to claim 1 is characterized in that: described forward equalizer FFE(1) and backward equalizer FBE(6) be the FIR finite impulse response filter.

7. bluetooth 4.0 low-power consumption receiver adaptive equalizers according to claim 1 is characterized in that: described forward equalizer FFE(1) and backward equalizer FBE(6) be transversal filter or transposed form filter.

8. utilize the described equalizer of claim 1 to realize the method for adaptive equalization, it is characterized in that: the baseband sampling signal rx(n of reception) through low pass filter will be with outer disturb and noise suppress after by the frequency discriminator computing, it is output as FD(n), after the sign synchronization estimation module of receiver is judged the Symbol Timing phase place, FD(n) obtain FD(OSR*n+offset from initial sampling rate is down-sampled to character rate) and send into adaptive equalizer, wherein integer offset represents the symbol sampling phase, determined by the Symbol Timing module, OSR is positive integer, the ratio that represents initial sample rate and symbol rate, 0＜offset＜OSR,

In adaptive equalizer when work,, in each mark space, the input of forward equalizer FFE has a new frequency discriminator output valve FD(OSR*n+offset) enter forward equalizer FFE; FFE_out (n) is the output valve of FFE in n mark space, and FBE_out (n) is the output valve of backward equalizer FBE in n mark space, and EQ_out (n) is the input value of decision device in n mark space; Above each value computing in each symbol period is calculated by following formula, wherein, ffe_coef(k, n) and fbe_coef (k, n) represent that respectively forward equalizer FFE and backward equalizer FBE are at n k the tap coefficient in the moment;

$\mathrm{FFE}\_\mathrm{out}\left(n\right)=\underset{k=0}{\overset{\mathrm{ffe}\_N-1}{\mathrm{\Σ}}}\mathrm{FD}\[\mathrm{OSR}(n-k)+\mathrm{offset}\]\·\mathrm{ffe}\_\mathrm{coef}(k,n)$

$\mathrm{FBE}\_\mathrm{out}\left(n\right)=\underset{k=0}{\overset{\mathrm{fbe}\_N-1}{\mathrm{\Σ}}}\mathrm{sign}\[\mathrm{EQ}\_\mathrm{out}(n-k)\]\·\mathrm{fbe}\_\mathrm{coef}(k,n)$

EQ_out(n)=FFE_out(n)+FBE_out(n)

Tap coefficient upgrades according to following more new formula iteration in each symbol period simultaneously:

ffe(k,n+1)=ffe(k,n)+μ·err(n)·FD[OSR(n-k)+offset]

fbe(k,n+1)=fbe(k,n)+μ·err(n)·sign[EQ_out(n-k)]

err(n)=sign[EQ_out(n)]-EQ_out(n)

Wherein err (n) produces in each symbol period for the error generator is used for the error signal that tap coefficient is adjusted; μ is for adjusting step-length; Sign () is for getting symbolic operation, and EQ_out (n) is the input of decision device, sign[EQ_out (n)] be the output of decision device;

The output sign[EQ_out (n) of decision device] send into the next stage module of receiver in order to recover the information that receives as the final effectively output of adaptive equalizer.

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