KR100672414B1 - RAKE combinator of mobile-type broadcasting receiver - Google Patents

Abstract

The present invention relates to a rake synthesizing apparatus of a mobile broadcast receiver for synthesizing and outputting channel delays of CDM symbols of respective paths output through a plurality of fingers. In particular, the present invention can use the circular buffer to compensate for channel delay, thereby eliminating buffer constraints due to delay, and can minimize power consumption. Also, in selecting the reference finger, by considering the time difference between the reference finger used previously and the reference finger to be newly selected, the continuity of the symbol finally output by the synthesizer during handover is not affected.

Channel delay, handover, circular buffer

Description

RAKE combinator of mobile-type broadcasting receiver

1 is a block diagram of a typical satellite DMB receiver

Figure 2 is a block diagram showing an embodiment of a conventional rake synthesizing apparatus

Figure 3 is a block diagram showing an embodiment of a rake synthesizing apparatus according to the present invention

4 is a block diagram showing an example of a detailed structure of the buffer pool generator and synthesizer of FIG.

Explanation of symbols for main parts of the drawings

301: write address generator 302: buffer pool generator

303: circular buffer 304: synthesizer

301 ~ 30n, 321 ~ 32n: Subtractor 311 ~ 31n, 331 ~ 33n: Comparator

340: reference finger selection and synthesizer

The present invention relates to a mobile broadcast receiver, and more particularly, to an apparatus for compensating and synthesizing a delay of a signal received through a multipath in a satellite digital multimedia broadcasting (DMB) broadcast receiver.

Digitalization of broadcasts has made digital multimedia broadcasting (DMB) possible, encompassing data transmission and multimedia services. The DMB is robust against noise and distortion on a transmission channel, has a high transmission efficiency, and has various advantages of enabling various multimedia services.

The satellite DMB adopted and used in Korea is based on the Japanese-style System E system and consists of performance equipment, earth stations, satellites, terrestrial relay equipment and subscriber receivers.

The satellite DMB system transmits multimedia content from the earth station transmission center to the satellite by using a code division multiplexing (CDM) transmission method, and the user directly receives it from the satellite or uses a gap filler in a shaded area where the signal strength is weak. It is received from the ground auxiliary relay facility called Gap Filler.

The transmission channel of the satellite DMB is a wireless mobile reception channel, and the amplitude of the received signal is not only time-varying, but also the Doppler shift of the received signal spectrum occurs due to the movement reception. In consideration of the transmission and reception under such a channel environment, the satellite DMB transmission scheme adopts the CDM scheme, and interleaves the time domain signals to correct errors occurring in the transmission channel.

In the CDM scheme, broadcast programs are independently transmitted from each other using a 64-bit Walsh code, which is an orthogonal code. At this time, the data to be transmitted is multiplied by a 2048-bit Pseudo Noise (PN) signal having a much faster rate than the data, thereby spreading the frequency spread.

Since the CDM method has a signal over a wide band, it has a strong characteristic against narrow band interference and can reduce reception performance due to multiple paths through a receiver having a RAKE structure.

That is, in the satellite DMB transmitter, an error correction code is added to transmission data of a plurality of channels, multiplied by different Walsh codes for each channel, and multiplied by a PN code to generate and transmit a CDM signal.

1 shows a conceptual block diagram of a general satellite DMB receiver for receiving such CDM signal. That is, the tuner 10 tunes only the RF signal of a specific frequency among the RF signals received by the antenna, converts the baseband into baseband, and outputs the result to the Auto Gain Control (AGC) unit 11.

The AGC unit 11 keeps the magnitude of the signal output from the tuner 10 constant and outputs it to the A / D converter 12. To this end, the AGC unit 11 measures the power of the received signal and multiplies the calculated gain by the received signal.

The A / D converter 12 samples the signal having a relatively constant magnitude by the AGC unit 11 and converts the analog signal into a digital signal. The digitized signal is output to a searcher 13 and a tracker of each finger 141 to 14n for demodulation. Each of the fingers 141 to 14n includes a tracking unit and a despreading unit.

In other words, in order to demodulate a signal in the CDM transmission scheme, the acquisition of a Pseudo Noise (PN) signal used for spreading the signal must be prioritized. This process has two kinds of signal acquisition and tracking. Consists of steps.

The division unit of the PN signal is called a chip, and signal acquisition is a process of securing signal synchronization within a half chip at a receiver, and is performed by the acquisition unit 13. The signal tracking refers to finely synchronizing the found signals, and is performed by a tracker of each finger 141 to 14n. The despreading unit of each finger 141 to 14n despreads by multiplying the signal synchronized by the signal acquisition and tracking with the PN signal generated by the receiver, and by multiplying the corresponding WALSH code used to distinguish the CDM channels. The symbol of the desired CDM channel is extracted.

That is, the above-described signal tracking and despreading processes are performed in all the multipaths found by the search unit 13, and each of them is called a finger. In other words, signals received through different paths are assigned to the arbitrary fingers by the search unit 13 and demodulated. In this case, there may be various ways of allocating a finger, and for example, a pilot signal may be used.

The CDM symbols of each path extracted from the fingers 141 to 14n are output to the RAKE synthesizer 16 and to the frequency offset estimator 15 for frequency offset compensation.

The frequency offset estimator 15 estimates the frequency offset for each finger, synthesizes it, and feeds it back to the tuner 10 to compensate for the frequency offset.

The rake synthesizer 16 synthesizes CDM symbols outputted from the fingers 141 to 14n. In this case, the rake synthesizer 16 may take a method of improving reception performance by estimating and receiving channel environment. That is, the rake synthesizer 16 performs rake synthesis on all CDM channels for demodulation.

The signal synthesized by the rake synthesizer 16 is output to the demodulator 17. The demodulator 17 demodulates the pilot channel and the data channel by demodulating corresponding to the digital modulation on the transmitting side. The pilot channel includes information on interleaver size and convolutional coding rate.

2 is a block diagram showing the structure of a general rake synthesizer. The rake synthesizer includes a plurality of channel delay compensators 201 to 20n connected to an output terminal of each finger and a synthesizer 210 for synthesizing the outputs of the channel delay compensators 201 to 20n.

That is, the symbols that undergo WALSH despreading for each finger 140 to 14n are output to the synthesizer 210 after the signal delay is compensated through the channel delay compensators 201 to 20n, respectively. The synthesizer 210 synthesizes the symbols of all fingers whose signal delay is compensated and outputs the final output symbol to the demodulator 17.

In this case, each channel delay compensator 201 to 20n sends signal information for each finger and state information related to delay compensation to the synthesizer 210, so that the synthesizer 210 finds valid fingers and knows when to perform synthesis correctly. To be. That is, the state information includes whether the corresponding finger is valid and whether each channel delay compensator 201-20n is ready to compensate for the signal delay of the finger. In this case, the channel delay compensation process is performed using a symbol buffer, and the range of the channel delay to be compensated for is proportional to the size of the buffer.

Then, the synthesizer 210 synthesizes the information inputted from the respective channel delay compensators 201 to 20n, and generates a control signal informing each channel delay compensator 201 to 20n to output a valid symbol. Output to delay compensators 201 to 20n. That is, the synthesizer 210 generates a read address of a symbol buffer to be used by the channel delay compensator by using the finger as a reference finger when there is at least one finger that is ready for signal delay compensation. )

In addition, the synthesizer 210 selects one reference finger from the state information as a reference finger, and determines the output timing of the synthesized symbol based on the symbol timing of the reference finger.

For example, the synthesizer 210 controls the timing of the output symbol using a finger having a zero channel delay among the valid fingers as a reference finger. If the transmission channel changes and the current reference finger disappears, the synthesizer 210 should select a new valid finger as the reference finger. This process is called finger handover and should not affect the continuity of the synthesized symbols output from the synthesizer 210 at the time of handover.

The existing finger handover structure recognizes the fact through the state information output by the channel delay compensator when the current reference finger disappears, and waits until a valid finger having completed the signal delay compensation is generated as soon as possible. If it is found through the state information that the finger has completed the delay compensation, the synthesizer 210 is handed over to the finger as a new reference finger.

However, in a situation where a channel such as a mobile reception environment changes rapidly, the existing simple handover structure has a disadvantage of inhibiting the continuity of synthesized symbols during handover. In other words, since the handover occurs only in one direction that lags behind the reference finger in the channel delay profile of the channel, when a certain time elapses in the time-varying channel, the reference finger moves to the last profile on the profile. If the corresponding finger disappears, the synthesizer 210 no longer finds the reference finger generated continuously. Therefore, the synthesizer 210 hands over the reference finger for the first time on the profile, and there is a problem that the synthesized symbols of the output of the synthesizer 210 lose continuity at this point. In addition, when the reference finger is selected, it takes a long time to wait until the corresponding buffer becomes full.

In addition, since the conventional channel delay compensator uses a buffer, there is a problem in that the size of the buffer is restricted. In particular, when a symbol buffer is configured using a first input first output (FIFO), power consumption increases because physical data must be moved every clock.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus for efficiently compensating and combining channel delays using a circular buffer.

In order to achieve the above object, the rake synthesizing apparatus of a mobile broadcast receiver according to an embodiment of the present invention stores and outputs CDM symbols of each path output through a plurality of fingers according to a write address and a read address. A channel delay compensator having a circular buffer for compensating signal delay of each CDM symbol and connected to an output terminal of each finger; A write address generator cyclically generating a write address in a circular buffer of each channel delay compensator; A buffer pool generator for checking a state of the circular buffer of each channel delay compensator and generating and outputting a buffer pool signal at the time when the buffer pool occurs; A read address is generated for the circular buffers of the channel delay compensator where the buffer pool is generated and output to the circular buffers of all channel delay compensators corresponding to valid fingers, and the CDM symbols read from the corresponding circular buffers are synthesized and output according to the read address. Characterized in that it comprises a synthesizer.

The buffer pool generator is configured in parallel by the number of channel delay compensators, and each buffer pool generator is determined as a buffer pool when the difference between the write address and read address of the circular buffer of the channel delay compensator is equal to a preset threshold. To output the buffer pool signal. The threshold is set to at least half the size of the circular buffer.

The synthesizer is configured in parallel with the number of channel delay compensators, and subtracts the write address of the corresponding circular buffer from the reference finger write address and outputs the result, and the outputs of the handover controller and the buffer pool generator. In this case, the reference finger is selected at the time of handover, and the reference finger is selected to determine whether the selected reference finger is faster than the existing reference finger in time, and the reference finger selector and synthesizer controls the read / write of the corresponding circular buffer according to the result. It features.

The rake synthesizing apparatus of a mobile broadcast receiver according to another embodiment of the present invention compensates for signal delay of each CDM symbol by storing and outputting CDM symbols of respective paths output through a plurality of fingers according to a write address and a read address. A plurality of channel delay compensators in a parallel configuration having a circular buffer and connected to an output terminal of each finger; A write address generator cyclically generating a write address in a circular buffer of each channel delay compensator; A buffer pool generator configured in parallel with the number of channel delay compensators to check the state of the cyclic buffer of each channel delay compensator and to generate and output a buffer pool signal at the time when the buffer pool is generated; A handover controller configured in parallel with the number of channel delay compensators to subtract the write address of the circular buffer of the channel delay compensator from the reference finger write address and output the result; A read address is generated for the circular buffers of the channel delay compensator where the buffer pool is generated and output to the circular buffers of all channel delay compensators corresponding to valid fingers, and the CDM symbols read from the corresponding circular buffers are synthesized and output according to the read address. At the time of handover, a reference finger is selected according to the outputs of the respective handover controller and the buffer pool generator, and it is determined whether the selected reference finger is earlier in time than the existing reference finger, and then the read / read of the corresponding circular buffer according to the result. And a synthesizer and a reference finger selection to control writing.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described. At this time, the configuration and operation of the present invention shown in the drawings and described by it will be described as at least one embodiment, by which the technical spirit of the present invention and its core configuration and operation is not limited.

The same components as in the related art are denoted by the same names and the same reference numerals for convenience of description, and detailed description thereof will be omitted.

In general, the rake synthesizing apparatus compensates the delays to synchronize the received finger signals with different channel delays so that they are synchronized with each other, and finally, maximizes the signal-to-noise ratio of the symbol synthesized signal output from the rake synthesizing apparatus. It improves performance. Therefore, the accurate operation and efficient structure of the rake synthesizing device greatly influences the performance of the receiver as a whole.

Figure 3 is a block diagram showing an embodiment of a rake synthesizing apparatus according to the present invention.

Referring to FIG. 3, the write address generator 301, the buffer pool generator 302, the circular buffer 303, and the synthesizer 304 are configured.

That is, the input symbol of the n-th finger is stored in the circular buffer 303, where the stored address is generated by the write address generator 301. The write address generator 301 generates an address of the circular buffer 304 cyclically, thereby virtually limiting the buffer space. It also virtually moves the data, not actually moves it, so there is little power consumption.

3 illustrates a circular buffer, a write address generator, and a buffer pool generator of an n-th channel delay compensator.

That is, the write address generator 301 and the buffer pool generator 302 are provided as many as the channel delay compensator. Each channel delay compensator has a circular buffer. Therefore, the write address generator corresponding to each channel delay compensator generates and outputs each write address (finger1 write address to finger n write address) to the corresponding circular buffer and buffer pool generator. In addition, the buffer pool generator corresponding to each channel delay compensator checks the pool state of the corresponding circular buffer and outputs the result (Finger 1 buffer pool to Finger n buffer pool) to the synthesizer 304.

The synthesizer 304 outputs the read address to the circular buffer of each channel delay compensator and at the same time to the buffer pool generator corresponding to each channel delay compensator.

The buffer pool generator 302 observes the state of the circular buffer 303 and generates a buffer pool signal at the time when the buffer pool occurs, and notifies the synthesizer 304 of this.

In this case, the synthesizer 304 generates a read address for the fingers in which the buffer pool occurs among all the fingers.

The read address generated by the synthesizer 304 is used equally for all valid fingers, and finally synthesizes and outputs the output symbols of the read fingers. In this case, the synthesizer 304 controls the output timing of the synthesized symbol by using a finger having a zero channel delay among the valid fingers as a reference finger.

If the current reference finger disappears, the synthesizer should select a new valid finger as the reference finger. This process is called finger handover and should not affect the continuity of output symbols during handover.

In the present invention, the detailed structure of the buffer pool generator and the synthesizer is shown in FIG. 4 in order not to affect the continuity of output symbols during handover.

In Figure 4, the buffer pool generator and the handover controller in the synthesizer are configured in parallel by the number of channel delay compensators.

In this case, the internal structures of all the buffer pool generators corresponding to the respective channel delay compensators and the handover controller are the same.

Therefore, in the embodiment, only the detailed structure of the n-th buffer pool generator and the handover controller will be described.

That is, the n-th buffer pool generator receives a finger n write address and a read address, and compares the subtractor 30n and outputs the difference between the two addresses, and compares the output of the subtractor 30n with a preset threshold and compares the result with the preset threshold. Therefore, a comparator 31n outputs a finger n buffer pool signal.

The n-th handover controller subtracts the finger n write address from the reference finger write address and outputs a result of the subtractor 32n, and determines whether the subtraction result of the subtractor 32n is negative or positive. It consists of a comparator 33n for outputting a result.

At this time, the signals output from each handover controller and the buffer pool generator are input to the reference finger selector and synthesizer 340. The reference finger selector and synthesizer 340 outputs the output signals of each buffer pool generator (Finger 1 buffer pool to the Finger n buffer pool), the output signal of each handover controller, and the output symbols of each channel delay compensator (Finger 1 output symbol ~). A finger n output symbol) is input to generate a read address to a buffer pool generator and a circular buffer corresponding to a valid finger, and generate a reference finger write address to the handover controller. In addition, according to the read address, the output symbols read from the circular buffer of the channel delay compensator corresponding to the valid finger are finally synthesized and output.

In FIG. 4 configured as described above, the subtractor 30n of the nth buffer pool generator calculates a difference between the write address and the read address of the finger n and outputs the difference to the comparator 31n. That is, the write address and read address are the write address and read address of the circular buffer of the n-th channel delay compensator. The comparator 31n compares whether the difference between the two addresses is equal to half of the buffer size. To this end, in the present invention, the threshold value is set to a value corresponding to half the buffer size.

If the difference between the two addresses is equal to half, a finger n buffer pool signal is generated and output to the reference finger selector and synthesizer 340.

This process is performed simultaneously in all buffer pool generators corresponding to each channel delay compensator and the result is output to the reference finger selector and synthesizer 340.

This can compensate for channel delay of the fingers that advance or lag to half the buffer size in time with respect to the reference finger. That is, when the buffer size is referred to as L, the channel delay in the range of (-L / 2) to (+ L / 2-1) is compensated for the reference finger.

In this case, when the current reference finger disappears, the reference finger selector and synthesizer 340 checks the output of each buffer pool generator, and selects the first buffer finger as the new reference finger, and the corresponding reference finger write address. Is output to the multiplier of each handover controller. In addition, a read address is generated based on the reference finger and outputs to a circular buffer and a buffer pool generator of the channel delay compensators 201 to 20n corresponding to the valid finger.

Meanwhile, the reference finger selection and the control regarding the reference finger selection of the synthesizer 340 are performed as follows.

That is, the subtractor 32n of the nth handover controller subtracts the finger n write address from the reference finger write address and outputs the result to the comparator 33n.

The comparator 33n determines whether the result of the subtractor 32n is positive or negative, and outputs the result to the reference finger selection and synthesizer 340.

This process is performed simultaneously in all handover controllers and the result is output to the reference finger selector and synthesizer 340.

The reference finger selector and synthesizer 340 determines whether the reference finger to be newly selected according to the result of each of the comparators 331 to 33n is ahead or behind in time with respect to the existing reference finger. If the result of the subtraction is positive, the reference finger to be newly selected is behind the existing reference finger, and if it is negative, it means that the reference finger is ahead of the existing reference finger.

Therefore, if the subtraction value is positive, the reference finger selector and synthesizer 340 waits without outputting the output symbol until the buffer pool of the corresponding finger is generated and the time delay of the new reference finger becomes zero. If the number is negative, the number of symbols corresponding to the absolute value of the subtraction value is output continuously so that the time delay of the new reference finger becomes zero. If it is negative, the data read speed is faster than the data write to the circular buffer until the buffer pool. For example, data may be read every clock and written every two clocks. Then, when the buffer is full, the write and read speeds are the same.

On the other hand, the terms used in the present invention (terminology) are terms defined in consideration of the functions in the present invention may vary according to the intention or practice of those skilled in the art, the definitions are the overall contents of the present invention It should be based on.

The present invention is not limited to the above-described embodiments, and can be modified by those skilled in the art as can be seen from the appended claims, and such modifications are within the scope of the present invention.

The effects of the rake synthesis apparatus of the mobile satellite broadcast receiver according to the present invention described above are as follows.

First, by using the circular buffer for channel delay compensation, there is an effect to eliminate the buffer constraints due to the delay, and to minimize the power consumption.

Second, by generating the read address of the circular buffer for the fingers with the buffer pool among all the fingers and using the same for all valid fingers, the channel delay can be efficiently compensated.                     

Third, in selecting the reference finger, by considering the time difference between the reference finger used previously and the newly selected reference finger, there is an effect that the continuity of symbols finally output by the synthesizer during handover is not affected.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (8)

In the rake synthesis apparatus of a mobile broadcast receiver for synthesizing the CDM symbols of each path output through a plurality of fingers, A plurality of channel delay compensators having a circular buffer configured to compensate for a signal delay of the corresponding CDM symbol by storing and outputting the CDM symbol of the corresponding finger according to the write address and the read address; A write address generator cyclically generating a write address in a circular buffer of each channel delay compensator; A buffer pool generator for checking a state of the circular buffer of each channel delay compensator and generating and outputting a buffer pool signal at the time when the buffer pool occurs; And A read address is generated for the circular buffers of the channel delay compensator where the buffer pool is generated and output to the circular buffers of all channel delay compensators corresponding to the valid fingers, and the CDM symbols read from the corresponding circular buffers are synthesized and output. Rake synthesis apparatus of a mobile broadcast receiver, characterized in that comprising a synthesizer. The method of claim 1, wherein the buffer pool generator Configured in parallel by the number of channel delay compensators, Each buffer pool generator, if the difference between the write address and read address of the circular buffer of the channel delay compensator is equal to the preset threshold value, the rake synthesis of the mobile broadcast receiver characterized in that the buffer pool outputs a buffer pool signal Device. The method of claim 2, And the threshold is set to half the size of the circular buffer. The method of claim 1, wherein the synthesizer A handover controller configured in parallel with the number of channel delay compensators to subtract a write address of a corresponding circular buffer from a reference finger write address and output a result thereof; The reference finger is selected at the time of handover according to the outputs of the handover controller and the buffer pool generator, and it is determined whether the selected reference finger is faster in time than the existing reference finger, and then the read / write of the corresponding circular buffer is performed according to the result. Rake synthesis apparatus of a mobile broadcast receiver characterized in that it comprises a reference finger selection and synthesizer to control. 5. The method of claim 4, wherein the reference finger selection and synthesizer If the selected new reference finger lags behind the existing reference finger in time, a buffer pool of the cyclic buffer of the corresponding channel delay compensator is generated and waits without sending an output symbol until the time delay of the new reference finger becomes zero. Rake synthesizing apparatus for broadcast receivers. 5. The method of claim 4, wherein the reference finger selection and synthesizer And if the selected new reference finger is ahead of the existing reference finger in time, the read speed of the buffer is set faster than the write speed until a buffer pool of the circular buffer of the channel delay compensator occurs. In the rake synthesis apparatus of a mobile broadcast receiver for synthesizing the CDM symbols of each path output through a plurality of fingers, A plurality of channel delay compensators having a circular buffer configured to compensate for a signal delay of the corresponding CDM symbol by storing and outputting the CDM symbol of the corresponding finger according to the write address and the read address; A write address generator cyclically generating a write address in a circular buffer of each channel delay compensator; A buffer pool generator configured in parallel with the number of channel delay compensators to check the state of the cyclic buffer of each channel delay compensator and to generate and output a buffer pool signal at the time when the buffer pool is generated; A handover controller configured in parallel with the number of channel delay compensators to subtract the write address of the circular buffer of the channel delay compensator from the reference finger write address and output the result; A read address is generated for the circular buffers of the channel delay compensator in which the buffer pool is generated and output to the circular buffers of all channel delay compensators corresponding to the valid fingers, and the CDM symbols read from the corresponding circular buffers are synthesized and output. At the time of handover, the reference finger is selected according to the outputs of the handover controller and the buffer pool generator, and it is determined whether the selected reference finger is faster in time than the existing reference finger, and then the read / write of the corresponding circular buffer is performed according to the result. Rake synthesis apparatus of a mobile broadcast receiver, characterized in that it comprises a reference finger selection and synthesizer for controlling the. 8. The method of claim 7, wherein each buffer pool generator is If the difference between the write address and the read address of the circular buffer of the channel delay compensator is equal to the preset threshold value, the buffer pool signal is determined by the buffer pool, and the threshold value is half the size of the circular buffer. Rake synthesizing apparatus of the mobile broadcast receiver.

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