KR20010027319A - Apparatus for acquisition of synchronization of PN signal using matching filter in digital communication system and method therefor - Google Patents

Abstract

PURPOSE: An apparatus for obtaining a synchronization of a spread signal in a digital communication system is provided to search a position having a maximum correlation energy between a pilot signal and the spread signal within a half chip, by using an N-Tap matched filter, so as to reduce chip occupation areas and consumed power. CONSTITUTION: A synchronization obtaining device(11) of a spread code comprises as follows. A spread code generator(13) sequentially generates spread codes relating to code sets allocated in a base station, according to spread code seeds. An N-Tap matched filter(12) has an N-Tap receiving signal delay buffer and an N-Tap spread code delay buffer for storing I/Q(In-phase/Quadrature) receiving signals and the spread codes. A correlation value/energy detector(14) correlates values stored in the N-Tap receiving signal delay buffer and the N-Tap spread code delay buffer, and finds N correlation values to accumulate the N correlation values, then converts the accumulated N correlation values into energy values. A maximum value sensor(15) sequentially inputs the energy values, and searches a code variable having a maximum energy. A controller(16) outputs a synchronous position of a searched receiving signal.

Description

Apparatus for acquisition of synchronization of PN signal using matching filter in digital communication system and method therefor}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for fast and efficient synchronization acquisition in wireless communication using a code division multiple access (CDMA) scheme. In particular, an apparatus and method for synchronizing a spreading signal using a matched filter are provided. It is about.

In systems such as IS-95A, WLL, and IMT-2000, the receiver performs a synchronous acquisition of a transmitted code using a pilot channel, and then demodulates the received information through synchronous tracking, channel estimation and correction. The synchronization acquisition apparatus can select and implement an appropriate algorithm according to the code allocation method, synchronization acquisition time, and hardware complexity requirements in the base station.

In the case of a method of dividing an initial value (seed) of a code sequence (2 ¹⁵ pieces) into a predetermined displacement (64 chips) like an IS-95A and assigning it to a base station, synchronization acquisition can be performed through a sequential searcher. . However, in the case of the method of dividing the code sequence (232) into a predetermined time (20ms) and assigning the initial value to the base station as in the WLL wireless access standard, a matching filter is performed to perform synchronization acquisition for all possible code sets within a limited time. (matched filter) can be used to achieve synchronous acquisition at high speed. In addition, in the asynchronous IMT-2000, the synchronization acquisition process includes a slot synchronization step, a frame synchronization and code group classification step, and a scrambling code classification step. In the slot synchronization step, a matching filter is inevitable.

The wireless communication terminal station receives information on spreading codes and phases used in the base station through a pilot acquirer through a pilot channel. In general, the synchronous acquisition process is performed before the frequency synchronous acquisition is performed. Therefore, the synchronous acquisition process should be performed at high speed. In particular, the search time becomes a problem when the code set and the search section allocated to the base station to which the terminal station belongs are large.

In general, a matched filter is used when fast synchronization is required or when a large search code set is required and synchronization is acquired within a limited time in a search section. However, as the number of taps increases, the matched filter becomes difficult to implement due to the large occupied area and power consumption of the chip.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a synchronization acquisition device and method capable of efficiently obtaining synchronization of spreading codes within a half chip even using a matching filter having a smaller number of taps in a digital communication system.

1 is a block diagram illustrating a receiver used in a code division multiple access scheme according to the present invention.

2 is a block diagram illustrating a detailed configuration of a synchronization acquisition apparatus according to the present invention.

3 is a flowchart illustrating a method of synchronously acquiring a spread signal through a pilot channel using an N-Tap matched filter according to the present invention.

FIG. 4 is a diagram for describing a first process 32 of acquiring synchronization within 1 chip of FIG. 3.

5 and 6 are diagrams for describing a second process 33 of acquiring synchronization within 1/2 chip of FIG. 3.

FIG. 7 is a diagram for describing a third process 34, which is a verification process in FIG. 3.

In the digital communication system according to the present invention for achieving the above technical problem, the synchronous acquisition device of the spread signal,

An apparatus for acquiring synchronization of a spread signal received at a receiving end in a digital communication system, the apparatus comprising: a spreading code generation unit for sequentially generating a spreading code for a code set assigned to a base station according to a spreading code initial value; An N-Tap matched filter having an N-Tap received signal delay buffer and an N-Tap spread code delay buffer respectively storing the received signal and the spread code; A correlation value and an energy detector for correlating values stored in the N-Tap received signal delay buffer and the N-Tap spread code delay buffer to obtain N correlation values and accumulating them, and converting the accumulated correlation values into energy values; And a maximum value detector which receives the energy values sequentially from the correlation value and the energy detector, finds a code displacement having the maximum energy value, and outputs a phase of the received signal.

The N-Tap matching filter may include an interpolation unit configured to output an interpolated reception signal by interpolating an on-time reception signal and a rate-time reception signal; And a selector for selecting and outputting one of the on-time received signal, the rate-time received signal, and the interpolated received signal, and storing the N signals selected by the selector in the N-Tap received signal delay buffer. ,

The correlation value and energy detector comprises: a complex correlator for generating N correlation values with respect to a value stored in the Tap received signal delay buffer and a value stored in the N-Tap spread code delay buffer every chip period; A first adder that receives an N / 2 correlation value from a first correlation value and adds the second adder to receive an N correlation value from an (N / 2 +1) correlation value and adds the first summation value; And an adder tree configured to output a second sum correlation value; First and second accumulators for accumulating the first summation correlation value and the second summation correlation value a predetermined number of times; And an energy calculator that adds output values of the first and second accumulators to each other and calculates an energy value and a displacement according to the sum value.

Synchronous acquisition method of the spread signal in the digital communication system according to the present invention for achieving the above technical problem,

A method for acquiring synchronization of spread signals received at a receiving end in a digital communication system, the method comprising: (a1) a correlation value according to N spread codes and N spread codes of N on-time received signals and N rate-time received signals; And calculating an energy value; (a2) repeating step (a1) a predetermined number of times; (a3) comparing the accumulated energy value obtained by the steps with an initial energy threshold; And (a4) obtaining a correlation value and energy from an on-time received signal or a rate-time received signal when the obtained cumulative energy value is greater than the initial energy threshold value, and comparing the obtained energy value with a verified energy threshold value to determine the received signal. Acquiring synchronization; otherwise, starting from step (a1) again.

In the step (a4), if the obtained cumulative energy value is larger than the initial energy threshold, (b1) a signal consisting of N / 2 on-time reception signals and N / 2 rate-time reception signals and N spreading codes Calculating cumulative on-time correlation values and rate-time correlation values, respectively; (b2) calculating and accumulating a rate-time correlation value and an on-time correlation value according to a signal consisting of N / 2 rate-time received signals and N / 2 on-time received signals and N spreading codes, respectively; ; (b3) repeating steps (b1) and (b2) a predetermined number of times; (b4) comparing the cumulative on-time correlation value and the cumulative rate-time correlation value obtained by the steps with each other; And (b5) if the cumulative on-time correlation value is greater than the cumulative rate-time correlation value, in accordance with N on-time received signals and N spreading codes, otherwise N rate-time received signals and N spreading codes. Acquiring an energy value according to the method and acquiring synchronization of the received signal;

Step (b5) may include (c1) if the cumulative on-time correlation value is greater than the cumulative rate-time correlation value, according to N on-time received signals and N spreading codes, otherwise N rate-time received signals. And calculating energy values according to N spreading codes; (c2) repeating step (c1) a predetermined number of times; (c3) comparing the cumulative energy value obtained by the steps with a verification energy threshold; And (c4) if the calculated cumulative energy value is less than the verification energy threshold, increases the number of assumptions by one, and if the number of assumptions is smaller than a predetermined number of searches, starts from step (a1) again; Outputting values and displacements.

In particular, the initial energy threshold or the verification energy threshold is preferably estimated by the average energy of the received signal according to the strength of the received pilot channel and set to a predetermined multiple of the estimated average energy.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a block diagram illustrating a receiver used in a code division multiple access scheme according to the present invention. In the present embodiment, a synchronization acquisition process for receiving a signal transmitted from a base station through an antenna and finding a pilot code and a phase of the base station from the I / Q received signal received from the terminal will be described.

The synchronization code acquisition unit 11 of the spreading code generates a spreading code generator 13 which sequentially generates a spreading code for a code set assigned to the base station according to the spreading code seed value, the I / Q received signal and the spreading code. Correlate values stored in an N-Tap matched filter 12, an N-Tap received signal delay buffer, and an N-Tap spread code delay buffer, each having an N-Tap received signal delay buffer and an N-Tap spread code delay buffer. N correlation values are obtained and accumulated, and the energy values are sequentially inputted from the correlation value and the energy detector 14 and the correlation and energy detector 14 which convert the accumulated correlation values into energy values. A maximum value detecting unit 15 for finding the code displacement and a control unit 16 for performing the control operation related to the synchronization acquisition and outputting the synchronization position of the found reception signal. In the synchronous acquisition device 11, the received signal and the PN signal generated at the receiver are synchronously acquired so as to fall within one chip or 1/2 chip, and then in the spread code synchronous tracking unit 17, the phases of the above two signals coincide. Make fine adjustments to make

2 is a block diagram illustrating a detailed configuration of a synchronization acquisition apparatus according to the present invention. The I / Q signal received by the receiver is input into the on-time and the rate-time signals at regular intervals.

The N-Tap matching filter 12 interpolates the on-time received signal and the rate-time received signal and outputs the interpolated received signal, the on-time received signal, the rate-time received signal, and the interpolated signal. A selector 22 for selecting and outputting one of the received signals, an N-Tap received signal delay buffer 23 for sequentially storing N data output from the selector 22 at every chip period, and generating a spreading code The unit 13 includes an N-Tap spreading code delay buffer 24 that sequentially stores N spreading codes generated every chip period.

The correlation value and energy detector 14 stores the value R stored in the N-Tap received signal delay buffer 23 and the value P stored in the N-Tap spread code delay buffer 24 every chip period. N complex correlators 25 generating two correlation values, a first adder tree 26 that receives N / 2 correlation values from the first correlation value, and adds them to output a first sum correlation value, and (N / 2) Accumulating a second adder tree 27, a first summation correlation value and a second summation correlation value, each of which adds the Nth correlation value from the correlation value and adds them to output the second summation correlation value; A predetermined number of times, the sum of the output values of the accumulator 28 and the accumulator 28 and calculates an energy value and a displacement according to the sum of the accumulator 28 and the first summation correlation value and the second summation correlation value, respectively; A correlation value comparator 30 for comparing the magnitude of the correlation value between the on-time received signal and the rate-time received signal according to the output of the accumulator 28 accumulated by ). The correlation value and the result of comparing the energy value and the correlation value, which are the outputs of the energy detector 14, are transmitted to the maximum value detector 15.

3 is a flowchart illustrating a method of synchronously acquiring a spread signal through a pilot channel using an N-Tap matched filter according to the present invention.

The synchronous acquisition method of the present invention interpolates N on-time received signals and N rate-time received signals, calculates correlation and energy using N interpolated signals, and then compares energy with an initial threshold. In a first process 32 of acquiring synchronization within one chip, N / 2 on-time received signals and N / 2 rate-time received signals are alternately inserted into the N-Tap received signal delay buffer and then on-time. A second process 33 for calculating synchronization between the received signal and the rate-time received signal and the spreading code, and comparing them with each other to obtain synchronization within 1/2 chip, and the received signal selected in the second process (on A third process of verifying according to the verification threshold using a time-received signal or a rate-time-received signal, and averaging the calculated energy of the received pilot channel by averaging the energy calculated in the synchronous acquisition procedure. Based on the first It is used as a threshold in the process and the third process.

First, referring to FIGS. 3 and 4, a first process 32 for acquiring synchronization within one chip will be described.

First, the hypothesis number is set to an initial value of zero (31). N-Tap received signal delay buffer 41 is filled with N signals interpolating N on-time received signals and N rate-time received signals, and N spread codes generated by spreading code initial values. Fill the spread code delay buffer 42 (32a). The correlator 43 calculates a correlation value according to the signals stored in the received signal delay buffer 41 and the spreading code delay buffer 42, and the first adder tree 44 calculates an N / 2 correlation value from the first correlation value. And add these to output the first summation value, and the second adder tree 45 receives the Nth correlation value from the (N / 2 +1) correlation value and adds them to output the second summation correlation value. (32b).

The first and second accumulators 46 and 47 accumulate the first and second summation values by a predetermined primary accumulation length K (32c), and then the energy calculator 49 calculates the first and second The energy value of the interpolated received signal is calculated according to the sum correlation. The calculated energy value is compared with the initial energy threshold (32d).

If the calculated energy value is greater than the initial energy threshold, a second process of acquiring synchronization is performed within 1/2 chip. Otherwise, the assumption number is increased by one (35) and the assumption is compared with the search number (36). ). If the assumption number does not reach the search number, the first process is performed again.

Next, referring to FIGS. 3, 5, and 6, a second process 33 for acquiring synchronization within 1/2 chip will be described.

N-Tap received signal delay buffers are filled with N / 2 on-time received signals and N / 2 rate-time received signals, and N-Tap spreading code delay buffers are filled with N spreading codes (33a).

FIG. 5 is a diagram illustrating the configuration of data stored in the N-Tap received signal delay buffer and the N-Tap spread code delay buffer in the second process 33. During time t1, selector 22 selects the on-time I / Q received signal to fill N / 2 51 in the N-Tap received signal delay buffer, and during time t2 selector 22 selects rate-time. The I / Q received signal is selected to fill the remaining N / 2 52 in the N-Tap received signal delay buffer. Meanwhile, the N-Tap spreading code delay buffer 55 is filled by the N spreading codes generated by the spreading code generation unit 13. Next, during time t3, the selector 22 selects the rate-time I / Q received signal to fill N / 2 53 in the N-Tap received signal delay buffer, and during time t4, the selector 22 The on-time I / Q received signal is selected to fill the remaining N / 2 54 in the N-Tap received signal delay buffer. On the other hand, the N-Tap spreading code delay buffer 56 maintains the previous value.

After filling the delayed buffer with the on-time received signal and the rate-time received signal by the above process, the correlation values for the on-time received signal and the rate-time received signal are respectively calculated (33b).

A process of obtaining a correlation value for the on-time received signal and the rate-time received signal will be described with reference to FIG. 6.

The received signal delay buffer includes N / 2 on-time received signals (or N / 2 rate-time received signals) 61 and N / 2 rate-time received signals (or N / 2 on-time received signals). 62 are stored, and N spreading codes 63 are stored in the spreading code delay buffer.

The correlator 64 calculates a correlation value according to the signals stored in the received signal delay buffers 61 and 62 and the spreading code delay buffer 63, and the first adder tree 65 is N / 2 in the first correlation value. The first adder tree 66 receives the correlation values, adds them, and outputs the first summation value. The second adder tree 66 receives the Nth correlation value from the (N / 2 +1) correlation value and adds them to add the second summation correlation value. Output At this time, the on-time received signal and the rate-time received signal are alternately stored in the received signal delay buffer, that is, in the order of the on-time received signal and the rate-time received signal, and then the rate-time received signal and the on-time received signal. -It is stored in order of time received signal. Accordingly, the first and second adder trees 65 and 66 alternately output correlation values for the on-time received signal and the rate-time received signal. Accordingly, switches 67 and 68 are further needed to accumulate correlation values for the on-time received signal and the rate-time received signal in the accumulators 69 and 70, respectively. The switches 67 and 68 determine the direction of their output in accordance with the data order stored in the received signal delay buffers 61 and 62 by the control signal C.

The on-time accumulator 69 and the rate-time accumulator 70 accumulate 33c each of the correlation values for the on-time received signal and the rate-time received signal by the secondary accumulation length L, respectively. The correlation value comparator 71 compares the magnitude of the on-time correlation value with the rate-time correlation value (33d).

When the comparison result of the correlation value is obtained, a third process 34, which is a verification process, is performed. A third process is described with reference to Figs. 3 and 7, wherein if the on-time correlation value is greater than the rate-time correlation value, then according to N on-time received signals and N spread codes, otherwise N rate-times An energy value is obtained according to the received signal and N spreading codes, and the verification process is performed by comparing the energy value with the verification energy threshold.

First, if the on-time correlation value is greater than the rate-time correlation value, the N-Tap received signal delay buffer is filled with N on-time received signals (34a2), otherwise the N-Tap with N rate-time received signals. The received signal delay buffer is filled (34a1), and the N-Tap spreading code delay buffer is filled with N spreading codes. The correlation and energy values are calculated according to the signals stored in the received signal delay buffer 71 and the spreading code delay buffer 72.

The correlator 73 calculates a correlation value according to the signals stored in the received signal delay buffer 71 and the spreading code delay buffer 72, and the first adder tree 74 calculates the N / 2 correlation value from the first correlation value. And add these to output the first summation value, and the second adder tree 75 receives the Nth correlation value from the (N / 2 +1) correlation value and adds them to output the second summation correlation value. (34b1, 34b2).

The first and second accumulators 76 and 77 accumulate the first and second summation values by the third accumulation length M (34c1 and 34c2), and then the energy calculator 79 calculates the first and second. The energy value of the received signal is calculated according to the sum correlation. The calculated energy value is compared with the verification energy threshold (34d).

If the calculated energy value is greater than the verification energy threshold, the energy and displacement of the received signal are stored (37), and the assumption is compared to whether the number is equal to the search number (38). If the assumption number does not reach the search number, the first process is performed again. If the calculated energy value is not greater than the verification energy threshold, the hypothesis is increased by one (35) and the hypothesis is compared with the search number (36). If the assumption number does not reach the search number, the first process is performed again.

The first, second, and third processes are performed until the assumption number and the search number match for all the search code sets, and the maximum energy is detected from the stored energy and displacement according to the result of the third process 34 to synchronize the received signal. Can be obtained.

The initial energy threshold used in the first process 32 is set using an average value of the initial energy generated in each home, and the verification energy threshold used in the third process 34 is an integer of the initial energy threshold. Use the boat As described above, the synchronization acquisition time can be shortened by using the adaptive threshold value by estimating the average energy of the received signal according to the reception strength of the pilot channel and determining the threshold value by a predetermined multiple of the estimated average energy.

As described above, according to the synchronization acquisition apparatus and method according to the present invention, the position having the maximum correlation energy between the pilot signal and the spreading code can be found within 1/2 chip by using the N-Tap matching filter. Power consumption can be reduced, and the time required for synchronization acquisition can be shortened by measuring the received intensity of the pilot channel and using it to select an appropriate energy threshold.

In addition, the synchronous acquisition device according to the present invention can be variously applied to the wireless communication field, such as a wireless subscriber network (WLL), synchronous / asynchronous IMT-2000.

Claims (7)

An apparatus for acquiring synchronization of a spread signal received at a receiving end in a digital communication system, A spreading code generator that sequentially generates spreading codes for a code set assigned to a base station according to a spreading code initial value An N-Tap matched filter having an N-Tap received signal delay buffer and an N-Tap spread code delay buffer respectively storing the received signal and the spread code; A correlation value and an energy detector for correlating values stored in the N-Tap received signal delay buffer and the N-Tap spread code delay buffer to obtain N correlation values and accumulating them, and converting the accumulated correlation values into energy values; And A spreading signal in a digital communication system, comprising: a maximum value sensing unit for receiving an energy value sequentially from the correlation value and the energy detecting unit, finding a code displacement having a maximum energy value, and outputting a phase of the received signal Synchronous acquisition device. The N-Tap matching filter of claim 1, wherein An interpolation unit configured to output an interpolated reception signal by interpolating an on-time reception signal and a rate-time reception signal; And A selector configured to select and output one of the on-time received signal, the rate-time received signal, and the interpolated received signal, And the N-tap received signal delay buffer stores N signals selected by the selector. The method of claim 1, wherein the correlation value and the energy detection unit A complex correlator for generating N correlation values for the value stored in the Tap received signal delay buffer and the value stored in the N-Tap spread code delay buffer every chip period; A first adder that receives an N / 2 correlation value from a first correlation value and adds the second adder to receive an N correlation value from an (N / 2 +1) correlation value and adds the first summation value; And an adder tree configured to output a second sum correlation value; First and second accumulators for accumulating the first summation correlation value and the second summation correlation value a predetermined number of times; And And an energy calculator configured to sum the output values of the first and second accumulators and calculate an energy value and a displacement according to the sum of the output values of the first and second accumulators. A method for acquiring synchronization of a spread signal received at a receiving end in a digital communication system, (a1) calculating correlation values and energy values according to the interpolated signals of the N on-time received signals and the N rate-time received signals and the N spreading codes; (a2) repeating step (a1) a predetermined number of times; (a3) comparing the accumulated energy value obtained by the steps with an initial energy threshold; And (a4) If the calculated cumulative energy value is larger than the initial energy threshold value, the correlation value and energy are obtained from an on-time reception signal or a rate-time reception signal, and the obtained energy value is compared with a verification energy threshold to synchronize the reception signal. And acquiring, otherwise, starting from the step (a1) again. The method of claim 4, wherein step (a4) If the obtained cumulative energy value is greater than the initial energy threshold, (b1) accumulating and calculating the on-time correlation value and the rate-time correlation value according to a signal composed of N / 2 on-time reception signals and N / 2 rate-time reception signals and N spreading codes, respectively; ; (b2) calculating and accumulating a rate-time correlation value and an on-time correlation value according to a signal consisting of N / 2 rate-time received signals and N / 2 on-time received signals and N spreading codes, respectively; ; (b3) repeating steps (b1) and (b2) a predetermined number of times; (b4) comparing the cumulative on-time correlation value and the cumulative rate-time correlation value obtained by the steps with each other; And (b5) if the cumulative on-time correlation value is greater than the cumulative rate-time correlation value, depending on the N on-time received signals and the N spreading codes, otherwise the N on-time received signals and the N spreading codes Acquiring the energy value accordingly to obtain synchronization of the received signal. The method of claim 4, wherein step (b5) (c1) if the cumulative on-time correlation value is greater than the cumulative rate-time correlation value, depending on the N on-time received signals and the N spreading codes, otherwise on the N rate-time received signals and the N spreading codes. Calculating while accumulating energy values accordingly; (c2) repeating step (c1) a predetermined number of times; (c3) comparing the cumulative energy value obtained by the steps with a verification energy threshold; And (c4) If the calculated cumulative energy value is smaller than the verification energy threshold, the number of hypotheses is increased by one; if the number of hypotheses is less than a predetermined search number, the process starts again from the step (a1); And outputting displacements and displacements. 5. The method of claim 4, wherein the initial energy threshold or verify energy threshold is And estimating the average energy of the received signal according to the strength of the received pilot channel and determining the average energy of the received signal as a predetermined multiple of the estimated average energy.