CN1720701A - Method, system and apparatus for acquiring received pulsed radio signals - Google Patents

Abstract

The present invention discloses a method and system for acquiring received impulse radio signals, which acquires received impulse radio signals by first searching an area of the impulse radio signal using a first template signal for time to locate a block including the signal area, and then searching the block using a second template signal for time to locate the signal cell.

Description

Obtain the mthods, systems and devices of the impulse radio signal that receives

Technical field

The present invention relates generally to impulse radio signal, relate in particular to and obtain ultra wide bandwidth signals.

Background technology

Between ultra wide bandwidth (UWB) signal that can demodulate reception arrives, template signal must be aimed at the signal that receives.The purpose of aiming at is to determine the signal that the receives relative delay with respect to template signal.This process is called as signal capture.

Routinely, by carrying out aligning the possible time of delay of sub-district in the serial search uncertain region, see people's such as Simon " Spread Spectrum CommunicationsHandbook ", McGraw-Hill, New York, 1994.Each different searching position about the time i.e. the time interval, are called as the sub-district.If signal exists in the delay position, that sub-district is called as signal cell so.In this method, the signal that receives is relevant with template signal, and the output that will be correlated with and threshold ratio are.If output is lower than threshold value, then template signal is offset the time of certain amount.The time of skew is usually corresponding to distinguishable route interval.Then, this information is used to repeat to be correlated with, and surpasses threshold value up to output.

If relevant output is the situation that comes from signal path and template signal aligning, then be called as signal cell output, otherwise, be called as non-signal cell output.When non-signal cell output surpassed threshold value, warning made a mistake.In this case, elapsed time t _p, recover up to search.This time is called as the punishment of false alarm.

Because the short time resolution of UWB signal is so all delay positions of serial search may need long time.Therefore, alignment methods must be very fast, makes to distribute to the time decreased of catching the UWB signal.

For big N value, serial search mean acquisition time directly and in the uncertain region number of cells N proportional, see people such as Polydoros " A unified approach to serialsearch spread-spectrum code acquisition-Part I:General Theory ", IEEE Trans.Comm., Vol.COM-32, pp.542-549, May 1984.Fig. 3 has represented to have the basic operation of prior art serial cell search of the uncertain region 300 of template 301 with common form.

Therefore, need a kind of method and system, can obtain the UWB signal in the short time than known systems serial search technology.

Summary of the invention

In impulse radio communication systems, for example in ultra wide bandwidth (UWB) communication, must be able to obtain the radio signal that receives before the restituted signal.Because the very short temporal resolution of the burst pulse of UWB signal, thus must the considerable possible signal location of search, promptly postpone, so that obtain the signal that receives.Therefore, rapid signal acquisition is extremely important for impulse radio communications.

According to sequential block search method of the present invention (SBS) at first use the signal cell that receives that first template signal determines wherein may to exist, for little zone of time.Then, the accurate delay of signal is found out to use second template signal in this zone of detailed search.

The signal that receives is exported with relevant some sub-districts of having added effectively of first template signal.Then, the result is used as the standard whether definite that zone comprises signal cell usually.

If the relevant output in zone surpasses specified threshold value, then use second template signal serial search piece at length.

The related interval of sequential block search and serial cell search step is not must be identical.In fact, the related interval of block search is selected as longer usually, so that can find correct piecemeal with high probability.

In strong (harsh) non-sight line (NLOS:non-line-of-sight) condition, there are a plurality of multipaths, it makes signal capture more complicated.Under such condition, obtain first path or minority first path if desired, then use according to average block search method of the present invention.In this method, the output of a plurality of serial search is by average, and the recruitment between the mean value in succession and threshold ratio are, the beginning edge of the signal that receives with detection.

If significant increase is arranged in the mean value, so further search causes the output of the sub-district that increases, with first path of the signal determining to receive.

Description of drawings

Fig. 1 is the block diagram according to sequential block search method of the present invention and system; And

Fig. 2 is the block diagram according to average block search method of the present invention and system.

Embodiment

When binary phase shift keying is jumped at random in pulse radio (TH-IR) system, can represent the signal launched in order to drag:

Wherein, w _TrBe the unit energy pulse of emission, T _fBe the average pulse repetition time, N _fBe the number of pulses of an information symbol of expression, b is the information symbol of emission, promptly 0 or 1.

In order to allow a plurality of users to use channel and to avoid serious conflict, for each user distributes pseudo random sequence { c _j(TH) sequence when this sequence is called as jumping.The TH sequence provides additional c for j pulse of signal _jT _cTime shift, wherein T _cSometimes become chip-spaced.In order to prevent pulse overlap, select chip-spaced to satisfy T _c≤ T _f/ N _c

Consider the IR system of coding, wherein d _jBe the binary system stochastic variable, for i ≠ j, d _iAnd d _jBe independently, get each value ± 1, see people's such as Fishler " On thetradeoff between two types of processing gain ", 40 with 1/2 probability ^ThAnnual AllertonConference on Communication, Control, and Computing, 2002.This system can be regarded as T _f=T _cThe radio signal of code division multiple access at random (RCDMA) system.In this case, N _fAlso expression is handled.

Defined nucleotide sequence { s _jAs follows:

So T is supposed on the ground that is without loss of generality _f/ T _c=N _c, equation (1) can be expressed as:

Suppose, do not carry out data-modulated at acquisition phase, promptly $b_{j/N_f{N}_c}^k=1\∀j.$ In this case, the signal that receives on the flat fading channel in the unique user system can be represented as:

$r\left(t\right)=\underset{j=-\∞}{\overset{\∞}{\mathrm{\Σ}}}{s}_f{w}_{\mathrm{rec}}(t-j{T}_c-\mathrm{\τ})+{\mathrm{\σ}}_{n}n\left(t\right),---\left(4\right)$

W wherein _Rec(t) be the UWB pulse that receives, and n (t) is the white Gauss noise with unit power spectrum density.This model approximation ground expression has sight line (LOS:line-of-sight) situation of strong first component.

Get that number of cells is N=N in the uncertain region _fN _cA sub-district in these sub-districts is a signal cell, and other sub-districts are non-signal cell.

Template signal

Suppose to be not used in the data-modulated of catching purpose, be used for then that employed template signal can be expressed as follows in the serial search signal of equation (3) signal model:

$s_{m_2}^{\left(c\right)}\left(t\right)=\underset{n=j{N}_c}{\overset{(j+m_2)N_c-1}{\mathrm{\Σ}}}{s}_n{w}_{\mathrm{rec}}(t-n{T}_c),---\left(5\right)$

Wherein, m ₂Be quantity to its pulse of being correlated with.

Sequential block search

For sequential block search according to the present invention (SBS), there are two different template signals.First template signal is used for the search cell piece, and the template signal that uses in second template signal and the serial search is similar.

First template signal that is used for signal model described in the equation (3) can be expressed as follows:

$s_{m_1}^{\left(b\right)}\left(t\right)=\underset{i=0}{\overset{K-1}{\mathrm{\Σ}}}\underset{n=j{N}_c}{\overset{(j+m_1)N_c-1}{\mathrm{\Σ}}}{s}_n{w}_{\mathrm{rec}}(t-n{T}_c-i{T}_c-(b-1)K{T}_c),---\left(6\right)$

Wherein, B is the quantity of piece in the uncertain region, and each piece comprises K sub-district, and m ₁Be quantity to its pulse of being correlated with.In order to simplify, suppose that the total quantity of uncertain sub-district can be expressed as N=KB.To be worth T _cBe taken as minimum distinguishable route interval.

Whether the relevant output of first template signal comprises signal cell as test fast to check whole in the signal that receives and the equation (6).Then, the signal that receives and the relevant output of second template signal are used for the detailed search of piece.

Current is being b at the index of searched piecemeal just, and initial b=1.So the SBS method can be described below:

1) uses first template signal Check b piece.

2) if the output of b piece is not higher than block threshold value, τ _b, then jump to step 6.

3) if the output of b piece is higher than block threshold value, τ _b, then search block is in more detail promptly used second template signal With ground, a sub-district, sub-district of signal threshold value τ s serial search.

4) if in piece, do not detect signal cell, then jump to step 6.

5), finish if in piece, detect signal cell.

6) establish b=(bmodB)+1, and jump to step 1.

If in serial search part, false alarm (FA) occurs, after C chronomere, restart to search for next sub-district as the Penalty time of frame time.

In step 5, the output of " detection signal sub-district " expression signal cell surpasses signal threshold value τ _sSimilarly, in the step 4, " not detecting signal cell " expression signal cell is not in piece, even perhaps the sub-district is in piece, sub-district output is lower than signal threshold value τ _s

Fig. 1 represents the SBS method.The signal 101 that receives is relevant with first template signal of equation (6), and export 111 with block threshold value τ _bCompare 120.

If be no more than block threshold value 121, then identifying unit makes lock unit 130 adjust the delay of 131 first template signals, and carry out with the signal that receives another relevant 110.

When piece output 111 is higher than block threshold value τ _b, then use second template signal in the equation (5), and the sub-district in the search block serially.In other words, identifying unit 120 is relatively exported and threshold value, and judges whether detect signal 122, or does not detect 121, and lock unit 130 is adjusted the delay of 131 template signals, and sends phase delay to correlation unit.

Average block search

Average block search method is suitable in strong NLOS condition.The basic ideas of this method are to use the mean value of the relevant output of a plurality of serials, to see increase big in the output valve.This increases the beginning of expression signal cell.The signal indication that receives in this situation is:

$r\left(t\right)=\underset{j=\∞}{\overset{\∞}{\mathrm{\Σ}}}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{\α}}_l{s}_j{w}_{\mathrm{rec}}(t-j{T}_c-{\mathrm{\τ}}_1)+{\mathrm{\σ}}_n\left(t\right),---\left(7\right)$

α wherein _lBe range coefficient, and τ _lIt is the delay of l multipath component.

The signal output relevant that consideration receives with following template signal:

$s_m^{\left(c\right)}\left(t\right)=\underset{n=j{N}_c}{\overset{(j+m)N_c-1}{\mathrm{\Σ}}}{s}_n{w}_{\mathrm{rec}}(t-n{T}_c)---\left(8\right)$

If the result's that this is relevant absolute value is z ₁..., z _N, then can define

$w_i=\frac{1}{K}\underset{j=\mathrm{iK}+1}{\overset{(i+1)K}{\mathrm{\Σ}}}{z}_j,---\left(9\right)$

Wherein suppose N=KB.

If i is present just at the index of searched average piecemeal, initial i=0.So the ABS method can be described below:

1) the poor w between the check consecutive mean _iModB-w _(i-1)ModB.

2) if difference is not higher than first threshold τ _a, jump to step 6.

3) if difference is higher than first threshold τ _a, by with second threshold tau _cRelatively, check z serially _{(imod B) K+1}..., z _{(imod B)+1) K}

4) if do not detect signal cell, jump to step 6.

5), finish if detect signal cell.

6) establish i=(i+1) mod B, and jump to step 1.

Fig. 2 represents ABS method and system 200.In this embodiment, parallel a plurality of correlators 210, the averaging unit 215 used.The signal r (t) 201 that receives at first is correlated with 210 with first template signal with different delays.Then, these relevant absolute values are by average 220, and by identifying unit 230 and previous mean value relatively.Increase if mean value exists obviously, and if in the relevant block any one in the serial search output surpass threshold value, then detection signal 231.

If do not detect 232, then lock unit 240 is adjusted the delay of template signal, and is carrying out same steps as.

Note, though the situation of a block representation K correlator and averaging unit, but this method and system also can be only with correlator job.Under these circumstances, identifying unit can be exported by the single correlator of storing predetermined quantity and carry out average and comparison task.

Effect of the present invention

Serial block search according to the present invention provides a kind of method of signal cell position of quick discovery UWB signal.At first, method determine fast to exist signal cell than the zonule.Then, that zone of detailed search is to find the accurate position of signal.By this way, can obviously reduce to obtain the time of UWB signal.In fact, the mean acquisition time of SBS method is proportional with the square root of the N of big signal to noise ratio.On the contrary, the mean acquisition time of the serial search of prior art directly and in the uncertain region number of cells proportional.For actual value, the capture time of use SBS is approximately half of serial search mean acquisition time.

In strong multipath conditions, average block search has reduced capture time, because more reliable during the beginning of mean value signal in some NLOS conditions of detection of serial search output.By this way, the instantaneous increase of single output is smoothed, the feasible frequency that reduces false alarm.Should be noted that the present invention also can be used for direct sequence-code division multiple access (DS-CDMA) system.

Although described the present invention, should be appreciated that and to carry out multiple other changes and modification within the spirit and scope of the present invention in the mode of preferred embodiment.Therefore, claims cover all such variations and the modification that occurs in true spirit of the present invention and the scope.

Claims (13)

1. A method for acquiring received pulsed radio signals comprising: searching the area of the impulsive radio signal using the first template signal with respect to time to locate a segment comprising a cell of the signal; and The segment is searched with respect to time using a second template signal to locate the signal cell for obtaining the received pulsed radio signal. 2. The method according to claim 1, wherein said impulsive radio signal is a random code division multiple access radio signal. 3. The method of claim 1, wherein the impulsive radio signal is an ultra-wide bandwidth radio signal. 4. The method according to claim 1, wherein said impulsive radio signal is a direct sequence-code division multiple access radio signal. 5. The method according to claim 1, wherein said impulsive radio signal is a direct binary phase shift keyed random time hopping radio signal. 6. The method according to claim 1, further comprising: wherein a first correlation interval associated with said first template signal is substantially longer than a second correlation interval associated with said second template signal. 7. The method of claim 5, wherein said searching further comprises: time shifting said first and second template signals while searching; correlating said shifted first and second template signals over said first and second correlation intervals to determine first and second outputs, respectively; and The first and second outputs are compared to first and second thresholds to locate the segments and signal cells, respectively. 8. The method according to claim 1 , wherein the transmitted pulsed radio signal corresponding to said received pulsed radio signal is denoted as where w _tr is the transmitted unit energy pulse, T _f is the average pulse repetition time, N _f is the number of pulses representing one information symbol, and b is the transmitted information symbol, 0 or 1, and for each pulse radio signal user Assign a pseudo-random sequence {c _j } to provide an additional c _j T _c second time shift to the jth pulse of the impulsive radio signal, where T _c is the chip interval and T _c ≤ T _f /N _c , and d _j is a binary random variable, d _i and d _j are independent and take each value ± 1 with probability 1/2, and the sequence {c _j } is defined as follows

So that when T _f /T _c =N _c , the transmitted pulsed radio signal is expressed as

so that the received impulsive radio signal is denoted as $\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; rec</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$ where w _rec (t) is the received pulse, and σ _n n (t) is white Gaussian noise with unit power spectral density, and $b_{j/N_f{N}_c}^k=1\&ForAll;j,$ And the number of cells in the area is N=N _f N _c , and T _c is the minimum resolvable path spacing. 9. The method according to claim 8, wherein said first template signal is expressed as ${\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{\overset{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; rec</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; K</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$ where m ₁ is the number of pulses on the first correlation interval associated with the region, B is the total number of blocks in the region, each block includes K cells, and the number of cells is N=KB. 10. The method according to claim 8, wherein said second template signal is expressed as ${\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{\overset{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; rec</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$ where _m2 is the number of pulses on the second correlation interval associated with the block. 11. The method of claim 1, wherein said search region uses a block threshold, _τb , and said search block uses a signal threshold _τs . 12. A system for acquiring received pulsed radio signals comprising: a first unit for searching, with respect to time, an area of said impulsive radio signal using a first template signal to locate a segment comprising a cell of the signal; and A second unit is configured to search the segment using a second template signal with respect to time to locate the signal cell to obtain the received pulsed radio signal. 13. An apparatus for acquiring pulsed radio signals comprising: a correlation unit configured to search, with respect to time, the region of the impulsive radio signal using a first template signal to locate a segment comprising a cell of the signal, and to search the segment with respect to time, using a second template signal to locating said signal cell, thereby acquiring said received pulsed radio signal; a synchronization unit for time-shifting said first and second template signals during a search; and A decision unit for comparing the first and second outputs of said correlation unit with first and second thresholds during searching said region and block, respectively.

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