KR20030008603A - Decoding Apparatus and Method for supporting variable data rates - Google Patents

Abstract

PURPOSE: A device for demodulating variable rate data and a method therefor are provided to obtain the minimum error probability of a receiving frame and reduce power consumption by estimating the most probable rate among probable rates and by decoding the estimated rate. CONSTITUTION: An SEA(Symbol Energy Accumulation) unit(10) accumulates each symbol energy for all probable data rates. An IEA(Interval Energy Accumulator)(20) accumulates the accumulated symbol energies at certain intervals. A TC(Threshold Comparator)(30) compares each interval energy-accumulated value with threshold values of all probable rates. A DC(Differential Comparator)(40) compares differences between interval energy values for a low and a high rate with each differential threshold value among probable rates passing through the TC(30). A likelihood checker(50) selects a probable rate. A decoder(60) decodes the selected probable rate.

Description

Decoding Apparatus and Method for supporting variable data rates

The present invention relates to a channel having a variable data rate in an IMT-2000 system, and more particularly, to a variable rate data demodulation device and a method for estimating a data rate for a data channel having a variable rate.

Next generation CDMA mobile communication, IMT-2000 system should support data channel with variable data rate for flexible service.

At this time, if the sender freely converts the data rate in a timely manner, the receiver must know the converted data rate. However, since the sender cannot inform the receiver in advance of the change in the data rate, the receiver must attempt to receive all possible rates. will be.

Attempting to receive for all possible data rates will eventually increase the complexity of the receiver and thereby increase power consumption in proportion to the number of rates that can be varied.

Conventional mobile communication systems do not support data channels with variable data rates.

However, the IMT-2000 system is proceeding to support data channels with variable data rates, and accordingly, these specifications are specified in the specification, but at this stage, there is no mention of the implementation method, but only for all possible variable data rates. There is only a basic principle that demodulation should be performed.

Accordingly, an object of the present invention is to provide a variable rate data demodulation apparatus and method capable of minimizing a load at a receiving end by estimating and decoding a data rate for a variable rate data channel at a receiving side.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the structure of a data demodulator of variable rate according to the present invention.

2A is a table illustrating an example of threshold operation of a threshold comparator.

2B is a table illustrating an example of threshold operation of a differential comparator.

3 is a block diagram illustrating an embodiment according to the present invention.

In order to achieve the above object, there is provided a symbol first energy accumulator for accumulating symbol energy for all possible data rates;

A second energy accumulator for accumulating the accumulated symbol energy for a predetermined period;

A threshold comparator for comparing each interval energy accumulation value with a threshold for each of all possible data rates;

A differential comparator for comparing the difference between the interval energy value for the low rate and the interval energy value for the high rate among the possible transmission rates passing through the threshold comparator with respective differential thresholds;

A Likelihood checker for selecting a possible rate of transmission of the differential comparator;

And a decoder that performs decoding on the possible data rate selected by the likelihood checker.

In addition, the present invention further comprises a symbol energy accumulation step of accumulating symbol energy for each possible data rate;

Accumulating the accumulated symbol energy for a predetermined period;

A threshold comparison step of comparing each interval energy accumulation value with a threshold value of each of all possible transmission rates;

A differential comparison step of comparing the difference between the interval energy value for the low transmission rate and the interval energy value for the high transmission rate with each differential threshold value among possible transmission rates as a result of the threshold comparison;

A Likelihood check step of selecting a possible data rate as a result of the differential comparison step;

And decoding the selected possible data rate as a result of the Likelihood check.

Further, in the present invention, the interval energy accumulation accumulates the symbol energy for a predetermined interval for all possible transmission rates, and the predetermined interval is an integer multiple of the encoded symbol interval for the lowest transmission rate among all possible transmission rates. .

In the present invention, if the likelihood check results in two or more remaining available rates, the symbol energy accumulation steps to the Likelihood check step are repeated for the possible rates.

In the present invention, the decoding is characterized in that if one or more possible data rates remain until the end of each frame, decoding for the lowest data rate among them is performed first.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

1 is a block diagram illustrating a structure of a data demodulator of a variable data rate according to the present invention, FIG. 2A is a table illustrating an example of threshold operation of a threshold comparator, and FIG. 2B is a table illustrating an example of threshold operation of a differential comparator. 3 is a block diagram showing an embodiment according to the present invention.

The next generation mobile communication system, IMT-2000, must support data channels with variable data rates.

At this point, it would be nice if the sender could keep the receiver informed of the change in the data rate of the data channel.

Therefore, the receiver should assume all possible variable rates and perform demodulation.

In an IMT-2000 system based on CDMA, channels are classified using Walsh sequences having different lengths according to data rates.

It is well known that selecting a Walsh sequence having a length equal to the length of an encoded symbol is optimal in terms of Walsh resource utilization in assigning Walsh sequences to channels having a fixed bit rate.

However, in a variable bit rate channel, it is necessary to allocate a Walsh channel that can always be used for all possible bit rates because it does not know at what moment the data rate will be transmitted. This will be a Walsh sequence suitable for the channel that assumes the highest bit rate. .

Hereinafter, the highest predictable data rate will be referred to as a reference data rate.

If the sender wants to send data with a lower rate than the reference rate, it can generate the same rate as the reference rate by properly repeating the channel interleaved symbols.

This will result in different rates for the original data, but will always be constant for the encoded and interleaved signals.

The present invention proposes a method for effectively demodulating transmission data at the receiving side under the above assumption.

First, all possible transmission rates are called RH (Rate Hypothesis), and each transmission rate can be expressed as R1, R2, R3, ..., Rn.

That is, rate group ,

1 is a block diagram illustrating a structure of a data demodulator of a variable data rate according to the present invention.

As shown in FIG. 1, a variable data rate demodulator includes a symbol energy accumulator (SEA) 10, an interval energy accumulator (IEA) 20, and a threshold comparator (TC). Comparator 30, a differential comparator (DC) 40, a Likelihood checker 50, and a decoder 60.

The variable rate data demodulator has a symbol energy accumulator (SEA) 10 for every rate (RH), each symbol energy accumulator (10) having a number of repeated interleaved symbols assuming that data rate. The symbol energy accumulation is performed as much as the repeated information.

If the hypothesized data rate is lower than the actual data rate, since the code of the received symbol is randomized by interleaving for the cumulative period, the accumulated amount will be considerably smaller than the case where the hypothesized data rate matches the actual data rate.

The next stage energy accumulator (IEA) 20 accumulates the result of the symbol energy accumulator 10 for a predetermined time (T). When comparing the results, the value is assumed to be lower than the actual data rate. It is more likely to be much smaller than in these other cases (assuming that the rate is greater than and equal to the actual rate).

At this time, the accumulation time T should be equally applied to all transmission rates (RH).

The next stage is the threshold comparator (TC) 30, which shows the result of the interval energy accumulator 20 for each transmission rate (RH) for a given target Eb / No (energy to noise / noise power density ratio). Check the likelihood that the RH will match the actual rate against the threshold.

If the result of the section energy accumulator 20 of the corresponding data rate (RH) is lower than the threshold value, the RH is excluded from the demodulation item for the current frame.

The next stage is the differential comparator (DC) 40, which compares the low rate RH and the higher rate RH among the rate (RH) that passed the threshold of the threshold comparator 30 so that the difference is If it is not greater than the threshold of the comparator, the high rate RH is excluded from the demodulation.

In other words, under the following conditions, high data rates are excluded from the possibility of data rates.

Conditions for Excluding Demodulation: (Section Energy Accumulation for Higher Rates-Interval Energy Accumulation for Lower Rates) <Threshold.

Likelihood checker 50 selects a possible data rate that satisfies the condition from the result of the differential comparator 40, and if there is only one possible data rate, it ends the rate estimation in the frame.

If the number of remaining data rates (RH) through the differential comparator 40 is one, the data rate is already determined, and thus may be the same as processing a data frame having one fixed data rate.

In addition, if the number of RHs remaining through the differential comparator 40 is two or more, the operation from the symbol energy accumulation to the Likelihood check is repeated for the corresponding RHs during the next T period.

At this time, the result is accumulated during the previous T section.

If one or more RHs remain until the end of the frame, decoding of the RHs should be performed independently.

The decoding order is performed by first performing the lowest data rate among the corresponding RHs, and then performing a higher data rate RH.

If the CRC (Cyclic Redundancy Check) check succeeds or can no longer perform decoding due to the decoder's performance limitation, demodulation for the frame is terminated and the result is returned to the receiving frame processor.

If the cumulative interval T of the section energy accumulator 20 is too small, the probability of an incorrect rate determination is increased, so that T must be somewhat large.

2A is a table illustrating an example of threshold operation of a threshold comparator, and FIG. 2B is a table illustrating an example of threshold operation of a differential comparator.

As shown in FIG. 2A, for example, when the reception Eb / No is 4 dB, the threshold of the threshold comparator is as follows.

The data rate is 9.6kbps, 1000, the data rate 19.2kbps is 1800, and the data rate 38.4kbps is 3000.

However, the thresholds do not mean optimal values.

In addition, the threshold of the differential threshold is as shown in Fig. 2b.

A low threshold of 9.6 kbps and a high bit rate of 19.2 kbps have a differential threshold of 200, a high bit rate of 38.4 kbps, a low bit rate of 9.6 kbps, a differential threshold of 400, a high bit rate of 38.4 kbps, and a low bit rate of 19.2 kbps. In the case of kbps, the differential threshold is 200.

The differential thresholds are also expressed by way of example only, and do not mean optimal values.

3 is a block diagram illustrating an embodiment according to the present invention.

As shown in FIG. 3, a case in which possible transmission rates (RH) are 9.6 kbps, 19.2 kbps, and 38.4 kbps will be described.

In this case, K means a number of times of interleaving and repeating data having a low data rate to increase a data rate.

The transmission rate and the number of repetitions are inversely proportional.

The accumulation section T of the section energy accumulator 200 is 1.25 msec, and the target Eb / No is 4 dB.

As shown in the tables of FIGS. 2A and 2B, the thresholds of the threshold comparator 300 may be named TC 1, TC 2, and TC 3, respectively, in order of low data rate to high data rate, and their respective values. Is 1000, 1800, 3000 according to the table of FIG.

In addition, the threshold of the differential comparator 400 may be referred to as the DC 2_1 threshold value of the second data rate (19.2kbps) and the first data rate (9.6kbps), the value is 200 according to the table of FIG.

The threshold of the third data rate (38.4 kbps) and the first data rate (9.6 kbps) may be named DC 3_1, and the value is 400 according to the table of FIG. 2B.

The threshold of the third data rate (38.4 kbps) and the second data rate (19.2 kbps) may be named DC 3_2, and the value is 200 according to the table of FIG. 2B.

First, when each symbol energy accumulator 100 assumes a corresponding data rate, symbol energy accumulate as much as it is repeated using information on how much the interleaved symbols have been repeated.

Then, the result of the symbol energy accumulator 100 is accumulated in a section energy accumulator (IEA) 200 for a predetermined time (T = 1.25 msec).

At this time, the accumulation time T is equally applied to all the data rates (RH).

The threshold comparator 300 compares the result of the interval energy accumulator 200 for each transmission rate RH with a respective threshold value for a given target Eb / No = 4 dB.

In the case of the first possible data rate, the interval energy accumulator 200 has a value of 300 but the threshold of the comparator 300 has a threshold value of 1000 and thus cannot exceed a threshold.

Therefore, the first possible rate (9.6kbps) is excluded from the rate estimate.

In the case of the second possible data rate, since the value of the interval energy accumulator 200 is 3000 and the threshold of the threshold comparator 300 is 1800, the threshold is sufficiently satisfied.

So the second possible bit rate (19.2 kbps) continues to the next stage.

In the case of the last third possible data rate, since the value of the interval energy accumulator 200 is 3100 and the threshold of the threshold comparator 300 is 3000, the third possible data rate (38.4 kbps) is also passed to the next stage by satisfying the threshold.

The differential comparator (DC) 400 compares a low bit rate with a high bit rate among the bit rates (19.2 kbps and 38.4 kbps) that have passed the threshold of the threshold comparator 300. Exclude from demodulation items.

First, the difference between the interval energy accumulation value of the second transmission rate (19.2 kbps) and the interval energy accumulation value of the first transmission rate (9.6 kbps) is compared with the threshold DC 2_1 of the differential comparator 400 for the possible transmission rate 19.2 kbps.

Since the difference between the interval energy accumulation value between the second data rate and the first data rate is 2700, the threshold value DC 2_1 = 200 is satisfied.

Therefore, the next Likelihood check stage 500 may estimate the second possible rate as the actual rate and decode the data at this rate (19.2 kbps).

For the third data rate (38.4 kbps), the differential comparator 400 may compare the thresholds for the two cases.

First, the difference between the interval energy accumulation values of the first possible data rate (9.6 kbps) and the third possible data rate (38.4 kbps) is compared with the threshold DC 3_1 of the differential comparator 400.

Since the difference between the interval energy accumulation values between the first rate and the third rate is 2800, the threshold value DC 3_1 = 400 is satisfied.

Secondly, the difference between the interval energy accumulation values of the second possible rate (19.2 kbps) and the third possible rate (38.4 kbps) is compared with the threshold DC 3_2 of the differential comparator 400.

The difference between the interval energy accumulation values of the second data rate and the third data rate is 100, which is less than the threshold value DC 3_2 = 200, and thus the threshold value is not satisfied.

Therefore, even the third possible data rate (38.4 kbps) is difficult to estimate as the actual data rate.

In the above embodiment, since the number of possible data rates remaining after passing through the differential comparator 400 is determined as one, the same process as the processing of a data frame having one fixed data rate may be performed.

If the number of possible transmission rates remaining through the differential comparator 400 is two or more, the operation from the symbol energy accumulation to the Likelihood check is repeated for the corresponding transmission rates for the next T interval.

If one or more possible data rates (RHs) remain until the end of the frame, decoding of the RHs is performed in order from the lowest data rate to the highest data rate.

As described above, the apparatus and method for variable data rate demodulation according to the present invention is to calculate the interval energy accumulation value of each data rate for the data channel of variable rate at the receiving end when the data rate of the transmitting end is changed from time to time. It can be seen that the performance of the receiving terminal is improved by finding a data rate that meets the threshold compared to the threshold value, estimating the actual data rate, and decoding the data.

As described above, the present invention relates to an effective demodulation apparatus and method for a data service having a variable data rate in an IMT-2000 system based on CDMA. The present invention relates to a CRC check after decoding and accumulates symbol energy during demodulation. Appropriate use can reduce the load on the receiver and, consequently, reduce the power consumption of the receiver.

The present invention estimates the most likely transmission rate among the possible transmission rates and performs decoding so that a minimum received frame error probability can be obtained at a given terminal performance and the power consumption of the terminal can be reduced.

Claims (5)

A symbol first energy accumulator, each accumulating symbol energy for all possible data rates; A second energy accumulator for accumulating the accumulated symbol energy for a predetermined period; A threshold comparator for comparing each interval energy accumulation value with a threshold for each of all possible data rates; A differential comparator for comparing the difference between the interval energy value for the low rate and the interval energy value for the high rate among the possible transmission rates passing through the threshold comparator with respective differential thresholds; A Likelihood checker for selecting a possible rate of transmission of the differential comparator; And a decoder configured to perform decoding on a possible data rate selected by the likelihood checker. A symbol energy accumulating step of accumulating symbol energy for each possible data rate; Accumulating the accumulated symbol energy for a predetermined period; A threshold comparison step of comparing each interval energy accumulation value with a threshold value of each of all possible transmission rates; A differential comparison step of comparing the difference between the interval energy value for the low transmission rate and the interval energy value for the high transmission rate with each differential threshold value among possible transmission rates as a result of the threshold comparison; A Likelihood check step of selecting a possible data rate as a result of the differential comparison step; And decoding the selected possible data rate as a result of the Likelihood check. The method of claim 2, wherein the interval energy accumulation, Accumulating the symbol energy over a period of time for all possible data rates, wherein the time interval is an integer multiple of the encoded symbol interval for the lowest rate of all possible data rates. The method of claim 2, And repeating the symbol energy accumulation step to the Likelihood check step for the possible transmission rates when there are two or more possible transmission rates as a result of the Likelihood check. The method of claim 2, wherein the decoding is, And if more than one possible data rate remains until the end of every frame, decoding for the lowest data rate among them is performed first.