KR100705899B1 - Cell searcher of asynchronous terminal modem and Method for detecting downlink STTD encoding indicator - Google Patents

Abstract

The present invention relates to an initial cell searcher and a downlink space time transmission diversity encoding identifier detection method of an asynchronous terminal modem that can reduce the influence of the frequency offset in the initial cell searcher of the asynchronous terminal modem.

A method for detecting downlink space time transmission diversity encoding identifier in an initial cell searcher of an asynchronous terminal modem according to the present invention comprises the steps of: receiving consecutive slot signals from a first antenna and a second antenna; Computing using both the synchronization channel and the common pilot channel signal included in the even (i-th) slot of the second antenna signal and the radix (i-1 or i + 1) slot of the second antenna signal Characterized in that comprises a.

According to the configuration of the present invention, it is possible to eliminate the waste of time caused by the downlink space time transmission diversity encoding identifier signal detection process and to solve the frequency offset problem without additional module configuration.

Initial cell searcher, encoding identifier detection, frequency offset, STTD

Description

Cell searcher of asynchronous terminal modem and Method for detecting downlink STTD encoding indicator}

1 is a view for explaining the configuration of a synchronization channel in the case of non-diversity application according to the prior art;

2 is a view for explaining the configuration of a synchronization channel in the case of diversity application according to the prior art;

3 is a diagram illustrating modulation patterns of a common pilot channel in case of applying and not applying diversity;

4 is a block diagram showing the main building blocks according to an embodiment of an initial cell searcher of an asynchronous terminal modem according to the present invention;

5 is a diagram illustrating an embodiment of a method for detecting downlink space time transmission diversity encoding identifier in an initial cell searcher of an asynchronous terminal modem according to the present invention.

<Explanation of symbols for the main parts of the drawings>

420: spreading code generator 430: 8 spreading code correlator

440: second antenna pattern generator 450: multiplier

460: despreader 470: coherent accumulator

The present invention relates to an initial cell searcher and a downlink space time transmission diversity encoding identifier detection method of an asynchronous terminal modem.

In the module configuration for detecting Space Time Transmit Diversity (STTD) encoding identifier bits of an initial cell searcher of an asynchronous terminal modem, a non-coherent detection scheme and Two approaches can be considered, the coherent detection scheme.

 In the case of the non-coherent detection structure, there is an advantage that no additional module configuration is required in the structure of the initial cell searcher of the asynchronous terminal modem. However, this method has a disadvantage in that a false detection probability is increased due to independent channel fading characteristics of the first antenna and the second antenna transmission channel in the diversity case. Therefore, in the design of the initial cell searcher of the asynchronous terminal modem, even if an additional module is added to the basic structure, a coherent detection structure is considered to increase the accurate detection probability of the space time transmission diversity encoding identifier bit.

Meanwhile, the transmission scheme of a synchronization channel (SCH) of an asynchronous base station is divided into two types depending on whether diversity is applied or not.

1 is a view for explaining the configuration of the synchronization channel in the case of non-diversity application according to the prior art, Figure 2 is a view for explaining the configuration of the synchronization channel in the case of diversity application according to the prior art to be.

Referring to FIG. 1, in the case of non-diversity application according to the prior art, a synchronization channel includes a primary synchronization channel (P-SCH) and an additional synchronization channel (Secondary SCH: S-SCH).

Each slot Slot # 0 to Slot # 14 of the primary SCH includes a primary sync channel STTD encoding identifier bit ac _p composed of 256 chips among 2560 chips. In each slot (Slot # 0 to Slot # 14) of the secondary SCH, additional synchronization channel STTD encoding identifier bits ac _s ^1,0 to ac _s ^1,14 each consisting of 256 chips among 2560 chips are added. Included.

In FIG. 1, a represents an STTD encoding identifier symbol for a primary common control physical channel (P-CCPCH), where a = +1 when P-CCPCH is STTD encoded, and P-CCPCH If this is not STTD encoded, then a = -1. C _p represents a primary synchronization code (PSC), and C _s ^{i, k} represents a secondary synchronization code (SSC).

Referring to FIG. 2, the synchronization channel in the case of diversity application according to the prior art includes a corresponding STTD encoding identifier bit signal for a first antenna (Antenna 1) and a second antenna (Antenna). Unlike the case where the assertion is not applied, the corresponding STTD encoded identifier bit signal is included in all slots, but the STTD encoded identifier bit signal is inserted into only odd or even slots for each antenna. do.

As described above, the SCH channel transmits the presence or absence of STTD using a code indicated by the STTD encoding identifier bit (a), in addition to the synchronization code information. Therefore, although accurate detection of the STTD encoding identifier bits is required, a signal entering the receiver through the transmission channel includes a large amount of distortion in the amplitude and phase of the signal due to the fading characteristics of the transmission channel. Therefore, in the coherence detection structure, the distortion of the signal is compensated according to the transmission channel information estimated using the signal of the common pilot channel (CPICH), and then the presence or absence of STTD application is determined by the STTD encoding identifier bit code.

Assuming a single-path channel (Single-path Channel) to represent the initial cell searcher received signal in the case of non-diversity can be represented as the following equation (1).

(Equation 1)

In Equation 1, since it corresponds to the non-diversity case, a = -1, G is a power ratio between the CPICH channel and the P-SCH channel, and C _{cpich, k} and C _{p, k} are each CPICH on a chip basis. A channel signal and a P-SCH channel signal are shown. In addition, h1 _{, k} and _nk represent the sum of noise and interference components modeled as components of the first antenna transmission channel and Additive White Gaussian Noise (AWGN), respectively.

Equation 2 below shows an initial searcher received signal when diversity is applied.

(Equation 2)

Wherein represents the sum of (2) h _{2, k} and n _'k, respectively the second component of the transmission channel of the antenna and the diversity is modeled as an AWGN in the case where the applied noise and interference components, ± sign and h _{The 1, k} or h _{2, k} channel component is the slot number corresponding to the second antenna as shown in FIG. 3, which is a diagram showing the modulation pattern of the common pilot channel in case of diversity application and non-application. Slot number) and symbol position. As can be seen from Equation 2, as a result of the diversity application, the initial searcher received signal can be seen as the sum of several signals received through the multipath.

Meanwhile, there are two types of coherence detection structures according to the prior art. Hereinafter, a method of obtaining a corresponding soft metric according to each coherence detection method according to the prior art will be described.

In case of the first method, in order to obtain a soft metric, first, the values of S _i and P _i for a synchronization channel and a common pilot channel signal are obtained by the following Equation (3).

(Equation 3)

In Equation (3), i is a slot number, N _SCH is the number of chips of a synchronization channel symbol per slot, N _SCH = 256, and N _CPICH is a chip of CPICH symbols accumulated for channel estimation. Considering the case where the Spread Factor (SF) is set to 256 as the number, the multiplier has a multiple of 256.

It uses the following relationships with respect to the S _i and P _i for the synchronization channel and the pilot channel signal to compensate for the phase of the channel.

(Equation 4)

Using Equation 4, the STTD encoding identifier bit is determined as shown in Equation 5 below.

(Equation 5)

Finally, the soft metric to be obtained is accumulated in the NS slot interval with respect to the result as shown in Equation 6 below.

(Equation 6)

In addition, the second method is to obtain a soft metric by using CPICH signals of two consecutive slot intervals. First, a value expressed by Equation 7 below is obtained.

(Equation 7)

S _i , the i th signal of the synchronization channel used in Equation (7), and P _{i, 1} , P _{i, 2} , the i th signal of the first and second slots of the common pilot channel _, are respectively represented by the following equations. appear.

(Equation 8)

(Equation 9)

(Equation 10)

In the above equation, since N _SCH = 256 and a common pilot channel corresponds to two slot intervals, N _CPICH = 512 is used.

Finally, the two cases according to the second method soft metric is accumulated for N _S rescued by slot interval corresponding to the chip number of the sync channel the result is expressed as the following (Equation 12).

(Equation 11)

However, in the case of using the first method according to the related art as described above, when accumulated using odd-numbered slots, correlation components occur in the process of finding h ₁ and h ₂ when a soft metric is obtained. Therefore, to prevent this, only the even-numbered slot of the N _S slot period is used. As such, if only half of the entire slots are used during the NS accumulated slot period, the overall detection process time is long.

In addition, when the second method is used, the above problem does not occur, but when the influence of the frequency offset is overwhelming, the overall detection performance is rapidly degraded.

For example, when a 3ppm oscillator is used, the effect of a 6 kHz frequency offset in the 2 GHz band results in a 144 degree phase shift during the 256 chip period of the CPICH signal. Therefore, a method using coherent summation of at least two symbol intervals is affected by a phase change, and the influence becomes even larger when considering the use of an oscillator up to 10 ppm.

The present invention provides a method for detecting an initial cell searcher and a downlink space time transmission diversity encoding identifier of an asynchronous terminal modem, which can solve a problem of a detection process delay in an initial cell searcher of an asynchronous terminal modem and reduce the influence of a frequency offset. There is that purpose.

The initial cell searcher of the asynchronous terminal modem according to the present invention for achieving the above object is a spreading code generator for generating and outputting a spreading code, the correlation between the output of the spreading code generator and the chip-by-chip output data from the input buffer An eight spreading code correlator for obtaining and outputting a relationship; a second antenna pattern generator for generating and outputting a second antenna pattern; a multiplier for multiplying an output of the eight spreading code correlator and an output of the second antenna pattern generator; And a coherent accumulator for despreading and outputting the output of the multiplier and a coherent accumulator for outputting a signal in a symbol unit by coherently adding up the output of the despreader for a predetermined chip period.

A method for detecting downlink space time transmission diversity encoding identifier in an initial cell searcher of an asynchronous terminal modem according to the present invention for achieving the above object comprises the steps of: receiving consecutive slot signals from a first antenna and a second antenna; Performing arithmetic processing using both a synchronization channel and a common pilot channel signal included in even-numbered (i-th) slots and odd-numbered (i-1st or i + 1th) slots of the first and second antenna signals. Characterized in that comprises a step.

Computing using both the synchronization channel and the common pilot channel signal may include despreading the synchronization channel signal with respect to the i-th slot of the first antenna signal to obtain a coherent cumulative value. Multiplying two antenna patterns and despreading to obtain a first coherent cumulative value (Coherent Sum) for a predetermined chip interval; and despreading a synchronization channel signal for an i + 1th slot of a second antenna signal. Obtaining a coherent cumulative value, multiplying a second antenna pattern with respect to a common pilot channel signal, and despreading to obtain a second coherent cumulative value (Coherent Sum) for a predetermined chip interval, and the first coherent coherence And calculating a sum of the accumulated value and the second coherent accumulated value and taking a real value of the added value.

The predetermined chip interval for obtaining the first and second coherent accumulation values may not exceed 256 chips.

The predetermined chip period for obtaining the first and second coherent accumulation values is characterized by using a synchronization channel and a common pilot channel signal of the first 256 chips of two consecutive slots.

According to the initial cell search and downlink space time transmission diversity encoding identifier detection method of the asynchronous terminal modem according to the present invention configured as described above, by using the synchronization channel and common pilot channel signals of both even-numbered and odd-numbered slots Therefore, the detection process time delay does not occur in the initial cell searcher of the asynchronous terminal modem, and the benefit of the frequency offset is reduced.

Hereinafter, a method for detecting an initial cell searcher and a downlink space time transmission diversity encoding identifier of an asynchronous terminal modem according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 4 is a block diagram illustrating main components of an initial cell searcher of the asynchronous terminal modem of the present invention, and FIG. 5 is a downlink space time transmission diversity in the initial cell searcher of the asynchronous terminal modem of the present invention. A diagram for describing an embodiment of an encoding identifier detection method.

Referring to FIG. 4, an initial cell searcher of an asynchronous terminal modem according to an embodiment of the present invention may include an input buffer 410, a spread code generator 420, an eight spread code correlator 430, and a second antenna. The pattern generator 440 includes a multiplier 450, a despreader 460, and a coherent accumulator 470.

The input buffer 410 receives signals from the first antenna and the second antenna and outputs input signals in chip units.

The spreading code generator 420 generates and outputs spreading codes according to required spreading coefficients.

The 8 spreading code correlator 430 obtains a correlation between the chip unit output data of the input buffer 410 and the output of the spreading code generator 420 and outputs the correlation.

The second antenna pattern generator 440 generates and outputs a second antenna pattern.

The multiplier 450 multiplies the output of the eight spreading code correlators 430 by the output of the second antenna pattern generator 440 and outputs the multiplier.

The despreader 460 despreads the output of the multiplier 450 and outputs the despreader.

The coherent accumulator 470 coherently sums the output of the despreader 460 for a predetermined chip period and outputs a signal in a symbol unit.

An operation of an initial cell searcher and a downlink space time transmission diversity encoding identifier detection method of an asynchronous terminal modem according to the present invention having the above configuration will be described.

Referring to FIG. 5, in order to detect a downlink space time transmission diversity encoding identifier in an initial cell searcher of an asynchronous terminal modem according to the present invention, an input buffer 410 is provided from a first antenna and a second antenna to which diversity is applied. Receives a signal of, and outputs the received signal in units of chips (S510).

Among the signals output in the chip unit, the synchronization channel signal corresponding to the first 256 chips of the i-th slot of the first antenna signal is despread in accordance with a general method to calculate and output a coherent accumulation value. Next, the following steps are performed on the common pilot channel signal corresponding to the first 256 chips of the i th slot and the i + 1 th slot of the second antenna signal among the signals output in the chip unit.

The 8 spreading code correlator 430 obtains a correlation between the signal data output in the chip unit from the input buffer 410 and the spreading code output from the spreading code generator 420 (S520).

The multiplier 450 multiplies the second antenna pattern output from the second antenna pattern generator 440 with respect to the second antenna signal output from the 8 spreading code correlator 430 to output the multiplied antenna (S530). As shown in FIG. 3, the antenna encoding pattern crosses the second antenna pattern in units of even-numbered slots (slots of 0, 2, 4, etc.) and odd-numbered slots (slots of 1, 3, 5, etc.). Alternately have a value of ± 1. For example, in FIG. 3, in the 2A section of slot 0, the second antenna pattern becomes 0 and has a value of a = -1. In the 2B section of slot 1, the second antenna pattern is encoded as 1 and a = + It will have a value of 1.

The second antenna encoding pattern encoded in this manner is multiplied by the corresponding signal in the slot order and output.

Next, the despreader 460 despreads the output of the multiplier 450 and outputs the despreader (S540).

When a signal in a chip unit is despread and output according to the above process, the coherent accumulator 470 sums the output of the despreader 460 for coherent coherence during a predetermined chip period between an i th slot and an i + 1 th slot. By coherent sum, the first and second coherent cumulative values are obtained to output a signal in a symbol unit.

The predetermined chip interval for obtaining the first and second coherent accumulation values may not exceed 256 chips. This is because the frequency offset may be affected by more than 256 chips. In addition, it is preferable that a predetermined chip interval for obtaining the coherent accumulation value matches the diffusion coefficient used. According to an embodiment of the present invention, the predetermined chip interval for obtaining the coherent accumulation value is set to the first 256 chips of the i th slot and the i + 1 th slot.

According to the above process, the synchronization channel signal (S _i ) and the common pilot channel signal (P _i ) output as a signal in symbol units are represented by Equation (12) below.

(Equation 12)

In the above equation, the number of chips of the synchronization channel (N _sch ), the number of chips of the common pilot channel (N _cpich ) and N _sch = N _cpich = 256 are used, and b is the second antenna pattern, as shown in FIG. 3. It has ± value in units of chip intervals.

Thus, for example, in slots 0 and 1, the equation (12) has a value equal to the following equation (13).

(Equation 13)

When the above result is added to two consecutive slot units, the result is as follows.

Therefore, the sum of 2 slot units in the above relation becomes the following (Equation 14).

(Equation 14)

If only the real value is taken from the above result, the influence of noise due to the transmission channel can be ignored (S560).

In conclusion, it is possible to obtain the same result as the second method and the result according to the prior art described above, and the soft metric obtained according to the present invention is the case that the slot number N _s of the common pilot channel is 2, that is, In the case of N _s = 2, the following equation (15) appears.

(Equation 15)

As described above, according to the present invention, by using both a synchronization channel signal and a common pilot signal added to two consecutive slots, it is possible to detect a required signal faster than using only half of the slot according to the prior art. In addition, as compared with (Equation 11), which is a result of using the two slot signals according to Equation 15 and the prior art, the effect of the frequency offset is eliminated.

In the above, the initial cell searcher and the downlink space time transmission diversity encoding identifier detection method of the asynchronous terminal modem according to the present invention have been described in detail. However, the present invention is not limited thereto, and the present invention is included in the present invention even if the present invention is carried out without change and modification without departing from the spirit of the present invention, and the fact will be apparent to those skilled in the art.

According to the initial cell searcher and the downlink space time transmission diversity encoding identifier detection method of the asynchronous terminal modem according to the present invention, a waste of time due to a signal detection process occurring in a scheme of using only half of a slot in accumulating pilot channel slot signals is eliminated. It eliminates the cost and the frequency offset problem caused by the coherent sum of more than 256 chip intervals due to the inability to use an expensive oscillator in the method using two slot signals according to the prior art without additional module configuration. It provides an advantage that can be solved.

Claims (5)

A spreading code generator for generating and outputting a spreading code; An eight spreading code correlator for obtaining and outputting a correlation between the chip unit output data from an input buffer and the output of the spreading code generator; A second antenna pattern generator configured to generate and output a second antenna pattern; A multiplier for multiplying the output of the eight spread code correlators and the output of the second antenna pattern generator; A despreader for despreading and outputting the output of the multiplier and a coherent accumulator for coherently adding up the output of the despreader for a predetermined chip period to output a signal in a symbol unit; To Initial cell searcher of the asynchronous terminal modem, characterized in that it comprises a. delete Receiving consecutive slot signals from the first antenna and the second antenna; Decoupling the sync channel signal with respect to the i-th slot of the first antenna signal to obtain a coherent cumulative value, multiplying the second antenna pattern with respect to the common pilot channel signal, and then despreading the first coherence for a predetermined chip period. Obtaining a coherent sum; Decoupling the sync channel signal with respect to the i + 1th slot of the second antenna signal to obtain a coherent accumulated value, multiplying the second antenna pattern with respect to the common pilot channel signal, and then despreading the second antenna pattern for a predetermined chip period. Obtaining a coherent cumulative value (Coherent Sum); Obtaining an addition value of the first coherent accumulated value and the second coherent accumulated value; And taking a real value of the addition value. The downlink space time transmission diversity encoding identifier detection method of an initial cell searcher of an asynchronous terminal modem. 4. The downlink space time transmission diversity of the initial cell searcher of the asynchronous terminal modem according to claim 3, wherein the predetermined chip interval for obtaining the first and second coherent accumulation values does not exceed 256 chips. Encoding identifier detection method. [4] The asynchronous terminal modem of claim 3, wherein the predetermined chip interval for obtaining the first and second coherent accumulation values uses a synchronization channel and a common pilot channel signal of the first 256 chips of two consecutive slots. A downlink space time transmission diversity encoding identifier detection method in an initial cell searcher.

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