KR100382489B1 - Method for recovering symbol in Time Division Multiple Access System - Google Patents

Abstract

The present invention relates to a time division multiple device system, and more particularly, calculates an average symbol period of a preamble extracted by using a time division periodicity, and extracts data using an intermediate value of the average symbol period, and then recovers a symbol. A symbol recovery method in a time division multiple device system comprising: setting a next reference transition time from one reference transition time of a preamble interval of a transmitted frame to one symbol recovery interval; and Setting a plurality of sampling times having a section smaller than the set symbol restoration section, and setting a median transition time of the one symbol restoration section as the average symbol period value of the transmitted frame using the set sampling number. And each data interval transmitted after the preamble interval Restoring a valid symbol value by extracting a digital waveform from the transmitted data by performing symbol restoration at a symbol period position equal to the average value of the average symbol period calculated in the preamble section. Through the present invention, the power consumption of the system can be minimized and the current consumption of the terminal device can be minimized, thereby extending the life of the battery.

Description

Method for recovering symbol in time division multiple access system

The present invention relates to a time division multiple device system, and more particularly, calculates an average symbol interval of a preamble extracted by using a time division periodicity, extracts data using an intermediate value of the average symbol interval period, and then extracts a symbol. The present invention relates to a symbol recovery method in a time division multiple device system for restoring.

A frame in a time division system consists of a preamble, a unique codeword, and data.

For example, the specific codeword may be a synchronization code indicating that the start of data to be transmitted. The preamble is a symbol pattern for identifying a period of a specific frame in the form of '1010'.

1 is a diagram illustrating a time extraction according to a symbol transition according to the prior art.

Referring to FIG. 1, the next input transition time t _i (k + 1) is set as one symbol recovery period from t _i (k), which is an input transition time, and a symbol recovery period is set for the one symbol recovery period. Set a random sampling frequency to a smaller interval.

According to the number of samplings between the input transition time t _i (k) and the next input transition time t _i (k + 1), a transition portion of data existing therebetween is detected each time and the input time value is detected. The symbol is restored by comparing the reference time value, which is an existing time value stored in the ROM, including the symbol interval, the preamble, and the specific codeword.

In other words, in order to extract a symbol for each data, a sampling number for any one symbol is determined, and as the sampling number is determined, a transition portion of the data is detected each time, and for this detection portion, The symbol is restored by comparing the input transition time value t _i (n) with a reference time value of data stored in an existing ROM (Read Only Memory).

However, when restoring the symbol, data distortion may occur due to jitter or ambient noise. In this case, if one or more data transitions occur in any one symbol due to the distortion, The data at the point generated at the transition time t _i (n) closest to the reference value is determined as a symbol value by referring to the reference time stored at.

In this case, a change occurs in the symbol period due to the distortion, and a phase locked loop method is used to correct an error caused by the change.

After the modification is completed, the next symbol value is restored and the data is finally restored in such repeated form.

2 is a flowchart illustrating a symbol reconstruction method according to the prior art.

First, the analog waveform input through the airwave is converted into a digital waveform through a low frequency filter and input.

In order to restore the input digital waveform to a symbol value, a transition time, i.e., t _i (n) detected by sampling the symbol interval in one symbol restoration section is detected.

The t _i (n) is stored in a temporary storage location (RAM or Register).

In addition, it is detected whether a transition point has occurred until a reference time value t _o (k + 1) to be input to the temporary storage place.

Using the reference time value t _o (k) stored in RAM and the next reference time value t _o (k + 1), t _mo (k), which is the intermediate value of the symbol period, is obtained.

Based on the reference time median value, it is determined whether or not the transition time of the input symbol value is less than or equal to the reference time median value t _mo (k).

According to the determination result S14, when the transition time of the input symbol value is smaller than the reference time median value t _mo (k), the input symbol value is determined as noise and the input symbol value is ignored.

And when a transition time t _i (n + j) resulting from distortion of a waveform generated by noise from t _i (n-1) time is adjacent to the reference time intermediate value t _mo (k) according to the input symbol value The t _i (n) value is detected until (S15).

Data corresponding to the transition time at which the value of t _i (n) is detected nearest to the reference time median value t _mo (k) is extracted and decoded to a valid value b (k) (S16).

At this time, since the symbol period is changed due to the distortion of the waveform, the value t _o (k) -t _i (n), that is, the error e _o (k), is calculated.

The error e _o (k) is updated to the reference time t _o (k + 1) of the symbol through a phase locked loop method (S18).

When the update is completed through the correction, the transition time t _i (n + 1) of the next symbol value is detected.

Then, the next symbol value is restored and the data is finally restored in this repeated form.

However, according to the determination result S14, when the transition time of the input symbol value occurs more than the reference time median value t _mo (k), the input symbol value is decoded to the valid value b (k). S20)

However, the algorithm of the prior art increases the amount of computation for identifying a large number of interrupts and data in the DSP (Digital Signal Processing) processor by detecting the transition portion through sampling every symbol. In other words, the need for a fast clock source for performing the task increases the current consumption, shortens the power consumption of the system and the battery life of the terminal.

Accordingly, an object of the present invention has been devised in view of the above-described problems of the prior art, and time division multiplexing is performed so that sampling is not performed for every symbol of data by using an average symbol period calculated in a preamble interval in a data interval. It is to provide a method for symbol recovery in a device system.

According to an aspect of the present invention for achieving the above object, setting the next reference transition time from one reference transition time of the preamble interval of the transmitted frame to one symbol recovery interval, and the set symbol recovery interval Setting a plurality of sampling counts having a section smaller than the set symbol recovery section for the step, and using the set sampling number, a median transition time of the one symbol recovery section as an average symbol period value of the transmitted frame. And performing symbol recovery at a symbol period position equal to the average value of the average symbol period calculated in the preamble period for each symbol recovery period transmitted next to the preamble interval. Extracting the digital waveform restores the effective symbol value.

Other objects, features and advantages of the present invention will become apparent from the detailed description of the embodiments with reference to the accompanying drawings.

1 illustrates time extraction according to a symbol transition according to the prior art.

2 is a flowchart illustrating a symbol restoration method according to the prior art.

3 is a diagram illustrating symbol extraction in a preamble section according to the present invention.

4 illustrates symbol extraction in a data interval using an average symbol period value according to the present invention.

5 is a flowchart illustrating a symbol restoration method according to the present invention.

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

3 is a diagram illustrating symbol extraction in a preamble section according to the present invention.

Referring to FIG. 3, in the present invention, the next reference transition time t _i (k + 1) is set as one symbol recovery period at the reference transition time t _i (k) in the preamble period, and is higher than the one symbol recovery period. The number of random samplings is determined in a small interval, and t _mi (k), which is an intermediate value of the transition time between the reference transition time t _i (k) and the next transition time t _i (k + 1), is obtained.

This transition time intermediate value is an average symbol period value of one frame and serves as a reference for symbols generated in one frame.

FIG. 4 is a diagram illustrating a symbol t _o (k) calculated using an average symbol period value t _av (k) according to the present invention and symbol extraction in a data section at that time.

Referring to FIG. 4, in the present invention, a symbol in a data interval is extracted using the average symbol period value t _mi (k) in the preamble interval calculated in FIG. 3.

Thereafter, t _b (k + m + 1) is extracted from the average symbol period value t _mi (k + 1) in the preamble section of FIG. 3.

A symbol restoration process using the average transition time will be described in detail later with reference to FIG. 5.

5 is a flowchart illustrating a symbol reconstruction method according to the present invention.

First, the analog waveform input through airwaves is converted into a digital waveform through a low frequency filter and input.

In order to restore the input digital waveform to a symbol value, a transition time, i.e., t _i (n) detected by sampling the symbol interval in one symbol restoration section is detected.

The t _i (n) is stored in a temporary storage location (RAM or Register).

In this case, n represents the nth symbol restoring section of the digital waveform, so t _i (n) is the transition time of the nth symbol restoring section (or digital waveform).

The symbol reconstruction specifies a process of determining 0 or 1 at each symbol reconstruction interval of the digital waveform. In addition, the sampling frequency is a predetermined value before the system design, and the sampling frequency is performed any number of times within the interval less than the symbol interval.

It is determined whether the symbol restoring section is the end of the preamble section (S102), if it is not the end of the preamble section, that is, if it corresponds to the preamble section, the reference time value of the next symbol restoring section t _o (k + 1 The symbol recovery interval is continuously performed a predetermined number of times until) to continuously detect the transition time t _i (n) to be input to the storage location (S200).

Using the reference time value t _o (k) stored in the previous memory and the next reference time value t _o (k + 1), t _mo (k), which is the reference time intermediate value of the symbol period, is obtained.

That is, the reference time median value t _mo is calculated at [t _o (k) + t _o (k + 1)] / 2.

Based on the reference time median value t _mo (k), it is determined whether the transition has occurred when the transition time t _i (n) of the symbol restoration interval is less than or equal to the reference time median value t _mo (k) (S202).

The determination result (S202), the digital waveform of the symbol recovery period for the transition corresponding to the time t _i (n) When the transition time t _i (n) of the symbol recovery period is less than or equal to the reference time median t _mo (k) Is determined to be noise.

Therefore, depending on the symbol value, the transition time t _i (n + j) resulting from distortion of the waveform generated by noise from t _i (n-1) time is adjacent to the reference time intermediate value t _mo (k). t _i (n) is detected (S300).

The digital waveform is extracted at the transition time at which the transition time t _i (n) is detected closest to the reference time intermediate value t _mo (k) and decoded to the effective symbol value b (k) (S301).

At this time, since the symbol period is changed due to the distortion of the waveform, the value t _o (k) -t _i (n), that is, the error e _o (k), is calculated.

According to the error e _o (k), the reference time t _o (k + 1) of the symbol is updated through a phase locked loop method (S303).

The intermediate value t _mi (k) is calculated using the transition time t _i (k) and the next transition time t _i (k + 1) stored in the RAM.

That is, it calculates to the transition time intermediate value t _mi (k) = [t _mi (k) + t _mi (k + 1)] / 2 for an input signal.

The average value t _av (k) of the symbol period according to Equation 1 is calculated using the calculated transition time intermediate value t _mi (k) for the input signal (S305).

Here, n represents the number of symbol recovery sections (or the number of digital waveforms), and t _mi (k) represents the median value of each corresponding symbol recovery section.

In addition, k represents an integer increasing from 1 to n.

Then, the transition time t _i (n + 1) for the next symbol recovery interval having t _o (k + 1) as the reference time of the symbol recovery interval is detected (S306).

On the other hand, when the determination result (S202), when the transition time t _i (n) of the symbol recovery interval occurs more than the reference time median value t _mo (k), the digital waveform of the symbol recovery interval to the effective symbol value b (k) Since it is recognized, the digital waveform of the symbol recovery interval corresponding to the transition time t _i (n) is determined as the symbol value of b (k) (S400).

The intermediate value t _mi (k) is calculated using the transition time t _i (k) and the next transition time t _i (k + 1) stored in the RAM.

Thereafter, the average value of the symbol periods for the n symbol recovery intervals is calculated using Equation 1 (S305).

Then, t _i (n + 1), which is a transition time for the next symbol recovery interval having t _o (k + 1) as the reference time of the symbol recovery interval, is detected.

On the other hand, it is determined whether the symbol recovery section is the end of the preamble section (S102), it is determined whether the end of the frame is the end of the preamble section (S500), and if it is the end of the frame, the transition of the next symbol recovery section T _i (n + 1), which is the time elapsed, is detected (S306).

If it is not the end of the frame, a time intermediate value t _b (k) is calculated by multiplying the k value for each symbol reconstruction interval of the corresponding frame by the average symbol period value t _av (k) calculated in the preamble interval. (S501)

The t _b (k) means an intermediate value for one symbol of the data interval.

The digital waveform of the symbol recovery interval at the transition time intermediate value t _b (k) is extracted and decoded into an effective symbol value b (k) (S502).

After the valid symbol value b (k) is obtained, a transition time t _i (n + 1) of the next symbol recovery interval is detected.

In summary, the present invention converts a received analog signal into a digital waveform, and the transition times t _i (n), t _i (n + 1), ... for each symbol recovery interval from the preamble interval of this digital waveform. Extract the data, store the symbol reconstructed data b (k) from the digital waveform corresponding to these transition times, and also calculate the median t _mi (k) from the reference times for the transition times, The average symbol period t _av (k) is calculated and stored from the values.

Then, after the data segment of the digital waveform after using the averaged symbol period value t _av (k) obtaining the intermediate value _{(t b (k) = t} av (k) × k) of the average symbol period, The symbol is decoded from the digital waveform corresponding to the intermediate value in the symbol recovery section.

After symbol reconstruction for one frame is completed, t _av (k) is reinitialized, and t _av (k) is calculated again in the starting preamble section of another frame. The symbol restoration process is repeated as described above.

By repeating the data, data is detected every symbol, and if an error occurs in the symbol, a reference value according to the value generated in the preamble is determined and the restoration routine of the symbol that can be generated can be reduced.

In addition, after extracting the preamble, the data value for the stored average symbol period is returned and the data of the previously stored preamble is initialized to find the average symbol period value to be generated in the next preamble.

As described above, the symbol recovery method in the time division multiple device system according to the present invention takes a median value of a symbol in a preamble section instead of detecting a transition part through sampling, and detects every symbol through the value, which is required by the DSP processor. Reducing the clock source and reducing the interrupt demand reduces the amount of computation required to identify the symbol transition points and reduces the amount of current.

Therefore, system power consumption and terminal battery life can be extended. If the clock source must be applied equally according to the characteristics of the DSP product, other operations such as status information on the monitor or key operation of the terminal can be performed in addition to data processing due to symbol restoration.

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 (5)

Setting a next reference transition time as one symbol reconstruction interval in one reference transition time of the preamble interval of the transmitted frame; Setting a plurality of sampling times having a section less than the set symbol restoration section for the set symbol restoration section; Setting a median transition time of the one symbol reconstruction interval as an average symbol period value of the transmitted frame by using the set sampling number; For the symbol recovery section of each data section transmitted next to the preamble section, symbol restoration is performed at the same symbol period position as the average value of the average symbol period calculated in the preamble section to extract a digital waveform from the transmitted data. Restoring a valid symbol value, symbol recovery method in a time division multiple access system. The method of claim 1, wherein the calculating of the average symbol period comprises: Calculating an intermediate value of a reference time of a symbol period in the set preamble period, and determining whether a transition occurs below the intermediate value of the reference time based on the intermediate value; Determining the transition time of the symbol recovery interval as noise when the transition occurrence is less than or equal to the reference time intermediate value according to the determination, and detecting the reference time intermediate value after the transition time generated by the noise; Extracting and decoding data with respect to the detected reference time intermediate value; Updating the error caused by the noise to a reference time value of a next symbol recovery interval through a phase locked loop method; Calculating an intermediate value between an input transition time and an input transition time of a next symbol reconstruction interval using the updated reference time value; Calculating a transition time average value of a symbol restoration interval based on the calculated input transition time intermediate value; And detecting a transition time of a next symbol recovery interval. The method of claim 2, wherein the determining of the occurrence of a transition below the reference time median value based on the calculated median value comprises: And extracting and decoding data with respect to the detected reference time when the occurrence of the transition is equal to or greater than the reference time intermediate value according to the determination. The method of claim 1, wherein extracting data from an average value of an average symbol period calculated from the preamble period in the data period of the frame, and recovering the symbol comprises: Determining whether the frame is terminated; And detecting a transition time of a next symbol reconstruction interval when the terminal is terminated according to the determination of whether the frame is terminated. The method of claim 4, wherein the determining of whether the frame is terminated comprises: Calculating a median transition time for a bit signal of a data section by multiplying an arbitrary symbol by an average value of an average symbol period calculated from a preamble section according to whether the frame is terminated; And extracting and decoding data with respect to the calculated transition time intermediate value of the bit signal.