KR100270279B1 - An adaptive synchronous cdma communication system - Google Patents

Abstract

The base station measures the propagation delay time caused by the distance between the base station and the terminal and transmits the delay time information to the terminal. The terminal delays the transmission time of the data by using the delay time information, and then transmits the data to the base station. If this method is applied to all terminals in the base station, the data transmitted from each terminal can be synchronized with the reference signal of the base station. The present invention relates to an adaptive synchronization code division multiple access communication system having improved performance through such propagation delay time measurement and data transmission delay.

Description

Adaptive Synchronous Code Division Multiple Access Communication System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a code division multiple access (CDMA) system. In particular, the present invention relates to an adaptive synchronous that compensates a time delay between a base station and a terminal and synchronizes the base station and a terminal. It relates to a CDMA system.

A base station of a CDMA communication system communicates with terminals within an area up to a certain distance. In this case, if all the terminals are located at a certain distance from the base station and transmit data to the base station at the same time, the signals received at the base station do not interfere with each other in coincidence with the start point of all data, thereby improving the performance of the communication system. have.

However, in the actual communication system, since the terminals existing in one base station are located at arbitrary positions, the propagation time to the base station is different for each terminal. Therefore, even when all the terminals transmit data at the same time, each terminal signal received by the base station does not coincide with the starting point of the data, resulting in a problem of degrading system performance.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and to improve the performance of a CDMA system by measuring the propagation delay time between the base station and the terminal and correcting the propagation delay time to transmit data from the terminal to the base station.

1 is a diagram showing an apparatus for measuring propagation delay time according to a first embodiment of the present invention.

2 is a flowchart showing generation of delay time information in a base station.

3 is a diagram illustrating a data transmission delay device using a PN seed.

4 is a diagram illustrating a data transmission delay device using a PN mask.

5 is a diagram illustrating a data transmission delay apparatus using a variable clock of a PN generator.

6 is a diagram illustrating a data transmission delay device using a variable delay circuit.

Propagation delay time measuring apparatus of the present invention for achieving the above object

A rake receiver sequentially delaying the data transmitted from the terminal using a plurality of delay elements connected in series and despreading the delayed data output from the plurality of delay elements with a pseudo noise code, and each delay element of the rake receiver. An energy detector for detecting the energy of the output delayed data, and a central processing unit for measuring the propagation delay time between the base station and the terminal using the detection result of the energy detector.

Here, it is preferable that the CPU calculates a propagation delay time by using a position of a delay element having a largest reception power of the delayed data among the reception power of the delay data detected by the energy detector.

In this case, the propagation delay time may be obtained by dividing the number of delay elements of the rake receiver by the delay clock frequency of the rake receiver.

In addition, the central processing unit may use the propagation delay time to generate delay time information such that the received power of signals transmitted from a plurality of terminals to a base station is maximized in a specific delay element of the rake receiver. In this case, it is preferable that the specific delay element is a delay element which is the last of the delay elements having the maximum reception power of the signal transmitted from each terminal.

On the other hand, the data transmission delay apparatus according to an aspect of the present invention

The start point of the pseudo noise code is adjusted according to the delay time information transmitted from the base station using a pseudo noise generator that synchronizes the input data signal with the PN clock to generate a pseudo noise code.

Here, the pseudo noise generator may adjust the starting point of the pseudo noise code according to the PN seed value in consideration of the delay time information.

The data transmission delay apparatus may further include a logical AND circuit for performing an AND operation on the output of the pseudo-noise generator and the PN mask value, and the start point of the pseudo-noise code according to the PN mask value in consideration of the delay time information. I can regulate it.

In addition, the data transmission delay apparatus may adjust the starting point of the pseudo noise code by varying the PN clock according to the delay time information.

On the other hand, the data transmission delay apparatus according to another aspect of the present invention

A modulator for receiving a digital data signal and modulating the digital signal into a digital signal suitable for a CDMA communication method, a variable delay circuit receiving the modulated signal and delaying the modulated signal to synchronize with a base station, and an output of the variable delay circuit. And a digital to analog converter for converting the signal into an analog signal, and a high frequency converter for converting the output of the digital / analog converter into a high frequency signal.

Here, the variable delay circuit

A counter for increasing / decreasing the output value according to the delay time information, and an output terminal of the counter as an input and having n output terminals, and only an output terminal corresponding to the output value of the counter outputs the first state and the rest The terminal includes a decoder for outputting a second state, n multiplexers in which input data is commonly input to the first input terminal, and output terminals of the decoder are respectively input to a set terminal, and are located between the n multiplexers, respectively. And n flip-flops for receiving the output value of the multiplexer and delaying them, and outputting them to the second input terminal of the next multiplexer. The input data of the first flip-flop among the n flip-flops is included in the input data. It is preferable to be input.

At this time, when the value of the second state is input to the set terminal of the multiplexer, the output of the flip-flop of the previous stage is transferred to the flip-flop of the next stage. When the value of the first state is input to the set terminal, the input data is next. It is delivered to the flip-flop of the stage.

On the other hand, the propagation delay time measurement method according to an aspect of the present invention

A base station and a terminal promising a specific type of signal, the base station transmitting the specific type of signal to the terminal, and the terminal transmitting a response signal to the base station to the base station And measuring a response time, which is a time from when the specific type of signal is transmitted to when the response signal is received, and the time required for interpreting the specific signal by the base station or the terminal in the response time. And measuring the propagation delay time between the base station and the terminal.

Hereinafter, with reference to the drawings will be described an embodiment of the present invention;

In the CDMA system of the present invention, the base station first measures propagation delay times of all terminals in the base station and transmits this information to each terminal, and each terminal corrects the propagation delay time to transmit data to the base station and receives the data from the base station. Match the starting point of the data being generated.

To this end, the communication system of the present invention implements a method for measuring the propagation delay time to the base station and a method for correcting the delay time in the terminal.

1 is a diagram illustrating an apparatus for measuring propagation delay time according to a first embodiment of the present invention using a rake receiver.

As shown in FIG. 1, the propagation delay time measuring apparatus according to the first embodiment of the present invention includes a rake receiver 10, an energy detector 20, and a CPU 30.

In a CDMA system, a rake receiver is for distinguishing and combining multipath components between a base station and a terminal to reduce the fading of signals due to the multipath. That is, the rake receiver uses the multipath time delay in the radio channel to combine the waveforms of the same transmitted signals with time difference to improve the performance of the link.

In FIG. 1, the rake receiver 10 of the base station sequentially delays data transmitted from the terminal using a plurality of delay elements (not shown) connected in series, and delays the delayed data output from the plurality of delay elements, respectively. Despread with pseudo noise (PN) codes.

The energy detector 20 calculates energy (hereinafter, referred to as 'receive power') of delayed data output from the respective delay elements of the rake receiver 10.

The CPU 30 measures the propagation delay time and distance between the base station and the terminal using the detection result of the energy detector 20 and generates delay time information.

First, the CPU 30 measures the propagation delay time using the position of the delay element having the largest value of the received power of the delayed data among the received powers of the delayed data detected by the energy detector 20.

That is, since the position of the delay element having the maximum reception power of each terminal in the rake receiver 10 of the base station is proportional to the delay time of the base station and the terminal, the CPU 30 uses the following equation (1) between the base station and the terminal. Find the propagation delay time of.

In addition, by using the propagation delay time, an approximate propagation propagation distance between the base station and the terminal can be obtained by the following equation.

Radio wave propagation distance = (Td-Ts) × C ÷ 2

Here, Td and Ts represent the propagation delay time and the data processing time of the system, respectively, and C represents the luminous flux.

The CPU 30 then calculates the delay time information using the calculated propagation delay time so that the received power of the signal transmitted from each terminal to the base station is maximized at the specific delay element of the rake receiver. In the present invention, the position of the delay element which is the rearmost of the position of the delay element at which the signal received from each terminal is maximum is set to the position of the specific delay element.

The delay time information calculated from the CPU 30 is transmitted to each terminal, and each terminal uses the delay time information to delay or advance the data transmission time and then transmit the data to the base station.

At this time, when the received power of the signal transmitted from any one terminal does not match the specific position of the rake receiver, the CPU 30 generates delay time information so that the received power of the rake receiver is set to the specific delay element. Maximize the position.

This will be described in more detail with reference to FIG. 2.

First, the energy (received power) received by the rake receiver from any terminal is calculated (S10).

The CPU then determines whether the position of the maximum value of the received power of the rake receiver is a particular position. (S20)

At this time, if the maximum value of the received power received from any terminal lags behind a specific position of the rake, the CPU generates delay time information that causes the terminal to transmit data with a smaller time delay (S30). If the maximum value of is ahead of a certain position in the rake, the CPU generates information that causes the data to be transferred with a larger time delay. (S50)

Then, the delay time information generated in the CPU is transmitted to the arbitrary terminal (S60), and the terminal transmits a delay or advances the signal to the base station by using the delay time information.

On the other hand, instead of using the measuring apparatus shown in Fig. 1, the propagation delay time can be measured by the following method.

First, the base station and the terminal promise a specific type of signal or message. Then, the base station (terminal) transmits the specific type of signal to the terminal (base station) and the terminal (base station) transmits a response signal thereto to the base station (terminal).

Then, the base station (terminal) measures the time from the time of transmitting a specific type of signal of the terminal until the response signal is received (hereinafter referred to as a "response time").

The response time measured in this way includes the propagation delay time by the distance between the base station and the terminal and the time required for the system to interpret the specific type of signal or message. By subtracting the time, the pure propagation delay time can be measured.

Such propagation delay time can be measured at the base station and can also be measured in the same way at the terminal.

When the propagation delay time is measured by the base station and transmitted to the terminal or measured by the terminal using the method described above, the terminal applies this information to delay or accelerate the transmission of data.

Next, a method of delaying or advancing data transmission in the terminal will be described.

The data transmission time delay apparatus according to the first embodiment of the present invention can be simply implemented using a conventional pseudo noise (PN) generator.

In general, the PN generator is divided into a method using a PN seed and a method using a PN mask, as shown in FIGS. 3 and 4. In the first embodiment of the present invention, the PN generator uses data of each method. Implemented transmission time delay device.

In Fig. 3, PN generator 40 generates a PN code in synchronization with the PN clock, where the starting point of the PN code is determined by the PN seed. Therefore, after determining the PN seed value in consideration of the delay time information transmitted from the base station, and generating the value of the register of the PN generator 40 with the determined PN seed value, the PN generator delays the desired time and then decodes the PN code. Generate.

In Fig. 4, the register value and the PN mask value of the PN generator 50, which are output in synchronization with the PN clock, are input to the AND circuit 60 and output as PN code values, where the starting point of the PN code is the PN mask. Determined by the value. Therefore, after determining the PN mask value in consideration of the delay time information transmitted from the base station, if the AND operation with the value of the register of the PN generator 50 with the determined PN mask value is delayed by a desired time PN code can be generated.

Meanwhile, in FIG. 3 and FIG. 4, the PN code may be output after delaying a desired time by simply adjusting the PN clock without changing the PN seed or PN mask value.

This will be described with reference to FIG. 5.

In FIG. 5, the CPU 70 of the terminal analyzes the measured delay time information to control the clock generator 80. The clock generator 80 adjusts the PN clock input to the PN generator 90 under the control of the CPU 70. Therefore, when the delay time information further delays the time, the CPU 70 controls the clock generator 80 to slow down the clock so that the PN generator 90 outputs the PN code later than normal. do. In contrast, when the delay information delays the time less, the CPU 70 controls the clock generator 80 to generate the clock speed faster, so that the PN generator 90 outputs the PN code faster than normal. do.

Next, a data transmission time delay apparatus according to a second embodiment of the present invention will be described.

6 is a diagram illustrating a configuration of a terminal to which a data transmission time delay device according to a second embodiment is applied.

In FIG. 6, the baseband digital signal is input to the modulator 100 and modulated into a digital signal suitable for the CDMA communication method. The modulated signal is input to the variable delay circuit 200. The variable delay circuit 200 delays the modulated data signal in consideration of delay time information to synchronize with the base station. The delayed data signal is converted into an analog signal through the D / A converter 300 and the high frequency converter 400, respectively, and is converted into a signal of a high frequency band and transmitted to the base station.

The variable delay circuit 200 of FIG. 6 will now be described in detail.

As shown in Fig. 6, the variable delay circuit 200 includes a counter 210, a decoder 220, and m flip-flop and multiplexer pairs (FF1, MX1) (FF2, MX2), ..., (FFm). , MXm).

In Fig. 6, the output signals Q1, Q2, ..., Qn of the counter 210 are input to the input terminals i0, i1, ..., in of the decoder 220, respectively, and the decoder 220 The output signals Q1, Q2, ..., Qm are respectively input to the set terminal S of each multiplexer.

Input data is input to the first terminal i1 of the multiplexer MXi, an output value of the flip-flop FFi is input to the second terminal i0, and an output value of the multiplexer MXi is the next pair of flip-flops (i). It is input to the second terminal i0 of FFi + 1. Input data is also input to the second terminal i0 of the first flip-flop FF1.

The flip-flop FFi delays the output values of the previous pair of multiplexers MXi-1 and outputs the delayed values to the multiplexer MXi.

The CPU (not shown) analyzes the delay time information and outputs an increase / decrease signal and a clock signal to the counter 210. The output value according to the increase / count signal of the counter 210 is input to the decoder 220, and the decoder 220 selects only the output value corresponding to the output value of the counter as "1" and the rest to "0". Choose. The output of such a decoder is input to the set terminal of each multiplexer.

When the set terminal of the multiplexer MXi becomes "0", the output of the flip-flop FFi is transferred to the current flip-flop FFi + 1, and when the set terminal is "1", the input data is flip-flop FF + Delivered to 1).

Therefore, by appropriately adjusting the output of the decoder, it is possible to output the data after delaying by a desired time, and the output value of the decoder is adjusted by the counter.

The embodiments of the present invention described above are merely exemplary embodiments, and the present invention is not limited to the above embodiments, and various other modifications and changes are, of course, possible.

As described above, according to the present invention, by measuring the propagation delay time between the base station and the terminal, correcting the propagation delay time, and transmitting data in synchronization with the signal between the terminal and the base station, it is possible to improve the performance of the CDMA system. .

Claims (7)

A rake receiver having a plurality of delay elements connected in series and sequentially delaying data transmitted from the terminal using the plurality of delay elements, and despreading the delayed data output from the plurality of delay elements with a similar noise code; An energy detector for detecting energy of delayed data output from each delay element of the rake receiver; A propagation delay time measuring device comprising a central processing unit for measuring a propagation delay time between a base station and a terminal by using the detection result of the energy detector; And a pseudo noise generator for synchronizing the input data signal with a PN clock to generate a pseudo noise code, and including a data transmission delay device for adjusting and outputting a starting point of the pseudo noise code according to delay time information transmitted from a base station. Adaptive Synchronous Code Division Multiple Access Communication System The method of claim 1 or 2, The central processing unit, Adaptive synchronous code division multiple access communication system characterized by calculating the propagation delay time by dividing the number of delay elements of the rake receiver by the delay clock frequency of the rake receiver In claim 1, The data transmission delay device Adaptive synchronization code division multiple access communication system, characterized in that for adjusting the starting point of the pseudo noise code according to the PN seed value in consideration of the delay time information. In claim 1, The data transmission delay device And a starting point of the pseudo noise code is adjusted by varying the PN clock according to the delay time information. In claim 1, The data transmission delay device A logical AND circuit for logical ANDing the output of the pseudo-noise generator and the PN mask value, Adaptive synchronous code division multiple access communication system for controlling the starting point of the pseudo noise code according to the PN mask value considering the delay time information A rake receiver having a plurality of delay elements connected in series and sequentially delaying data transmitted from the terminal using the plurality of delay elements, and despreading the delayed data output from the plurality of delay elements with a similar noise code; An energy detector for detecting energy of delayed data output from each delay element of the rake receiver; A propagation delay time measuring device comprising a central processing unit for measuring a propagation delay time between a base station and a terminal by using the detection result of the energy detector; A modulator for receiving a digital data signal and modulating the digital data signal into a digital signal suitable for a code division multiple access communication method; Receives the modulated signal, and modulates the modulated signal to synchronize with a base station A variable delay circuit for delaying, A digital / analog converter for converting an output of the variable delay circuit into an analog signal; Adaptive synchronous code division multiple access communication system including a data transmission delay device including a high frequency conversion unit for converting the output of the digital to analog converter into a high frequency signal In claim 6, The variable delay circuit A counter for increasing / decreasing an output value according to delay time information; A decoder for inputting an output value of the counter and having m output terminals, outputting only a first output terminal corresponding to the output value of the counter, and a second terminal outputting a second state; M multiplexers, in which input data is commonly input to a first input terminal, and output terminals of the decoder are respectively input to a set terminal of a flip-flop; Located between the n multiplexers, output digital data of the modulator is input to the input terminal of the first flip-flop, and after the second flip-flop, the output value of the multiplexer of the previous stage is input and delayed, and then the multiplexer of the next stage is multiplexed. An adaptive synchronous code division multiple access communication system comprising m flip-flops output to a second input terminal of the terminal.