KR20130073333A - Apparatus and method of traceback having minimized decoding delay time - Google Patents

Abstract

PURPOSE: A reverse tracking device with a minimized decoding delay time and a method thereof are provided to be able to use minimum memories without using many operation quantities, and to be able to minimize the decoding delay time. CONSTITUTION: A reverse tracking device stores data in a first trace back memory (TBM) which is one of multiple TBMs comprising the reverse tracking device (S800). The reverse tracking device performs a decoding operation which extracts the decoding information of data stored in a previous TBM of the TBM performing the reverse tracking simultaneously with or immediately after that the reverse tracking is performed (S810). Data are stored in the following TBM of the first TBM (S820) in case that the reverse tracking needs to continue after the reverse tracking device completed the storage of data (S815). [Reference numerals] (8S15) Determining whether reverse tracking is continued or not; (AA) Start; (BB) End; (S800) Start data storage; (S805) Start reverse tracking; (S810) Extracting decoded information; (S820) Move to next TBM

Description

Backtracking apparatus and method with minimized decoding delay time {APPARATUS AND METHOD OF TRACEBACK HAVING MINIMIZED DECODING DELAY TIME}

The present invention relates to a backtracking apparatus and method, and more particularly, to a backtracking apparatus and method for minimizing decoding delay time.

In general, it is desirable that the Viterbi decoder maintain the power consumption while keeping the performance of the circuit at or above the desired level. Accordingly, there is a need for an energy efficient method and structure for implementing Viterbi decoders.

Viterbi decoders have many applications. For example, the Viterbi decoder can determine the symbol stream most considered to have been transmitted by the remote transmitter based on the symbol stream received by the receiver in the communication system. Or other applications exist in data storage systems and disk drives.

A wireless communication system for transmitting data using a convolutional encoder uses a Viterbi decoder to recover. In order to find similar decoding strings, a wireless communication system has a memory for storing selected data in various states of progress using received information. These memories store information because they are tracked over a period of time.

Various methods for efficiently managing memory have been implemented, but in consideration of time efficiency, information storage and extraction operations are performed in multiple memories. Some use a method of updating the information of all data every hour to use the least amount of memory, but this requires too much computation. In addition, there is a method of performing the reverse tracking faster than the write clock while decoding to the shift register and decoding and shifting the memory in the opposite direction to perform the reverse tracking and decoding, but it is inconvenient to shift the memory for the reverse tracking.

There is a need for an efficient backtracking device and a backtracking method that use memory effectively and complete backtracking and decoding using the same clock, and do not shift the memory.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a backtracking method and a memory in which a large amount of computation is not required while using a minimum memory.

Another technical problem of the present invention is to provide a method for optimally dividing a backtracking memory and variously operating the divided memory simultaneously.

Another technical problem of the present invention is to provide an efficient memory structure having a minimum decoding delay time for tracking back a decoding sequence.

According to an aspect of the present invention, a method for backtracking data in a communication system includes initiating storage of data in a first TBM, which is one of a plurality of Trace Back Memorys (TBMs) constituting a memory. Performing backtracking for a preset backtracking length from a previous TBM of the first TBM, and performing a decoding operation of extracting decoding information of data stored in the previous TBM of the TBM on which the backtracking is performed; And after storing the data in the first TBM, initiating the storing of the data in the second TBM which is the TBM from which the decoding information is extracted.

The size or number of each of the plurality of TBMs may be determined in consideration of the time of storing a survival path in the memory and the time of performing backtracking in one TBM.

Each size N of the plurality of TBMs may be determined as the smallest integer value among integer values satisfying "N≥T / N + 1" based on the backtracking length T.

The method may further include performing a second traceback during the traceback length forward from the previous TBM of the second TBM.

The method may further include performing a decoding operation of extracting decoding information of data stored in the previous TBM of the section in which the second traceback is performed.

Performing the backtracking may be performed in a plurality of TBMs based on the backtracking length and the size of each of the plurality of TBMs.

If the traceback length is greater than the sum of the sizes of previous TBMs of the first TBM, performing the traceback may be performed backward from the end of the memory after performing the traceback to the front of the memory. Backtracking may then be performed.

Initiating storage of the data may be performed simultaneously with performing the backtracking.

Initiating storage of the data may be performed simultaneously with performing the decoding operation.

The communication system may be a WLAN system using a 5/6 code rate.

Initiating storage of the data may include selecting one survival path of all states of survival stored in the memory, storing the survival paths of all states in the first TBM, and according to the selected one survival path. The data including the tracking path may be updated at each preset update timing.

Initiating the storing of the data includes storing only selected survival paths in all the survival paths stored in the memory in the first TBM, and including a tracking path for the traceback length for each preset update timing according to the selected survival path. May be to update data.

According to another aspect of the present invention, a backtracking device initiates storage of data in a first TBM, which is one of a plurality of TraceBack Memory (TBMs) constituting a memory, and starts forward from the previous TBM of the first TBM. Performing a backtracking for a predetermined backtracking length, extracting decoded information of the data stored in the TBM before the backtracking, and performing the decoding after the data storage is completed in the first TBM. And a backtracking unit which starts storing data in the second TBM which is the TBM from which the information is extracted.

According to another aspect of the present invention, a Viterbi decoder comprises a branch value calculation unit for receiving encoded data and pre-calculating branch values in all cases, a path selection unit for performing calculations with the calculated branch values, and a memory. Storing the selected path through the operation of the path selector in the first TBM, which is one of a plurality of traceback memories (TBMs), and backtracking for a predetermined backward tracking length forward from the previous TBM of the first TBM. Perform a decoding operation of extracting the decoding information of the data stored in the TBM before the back-tracking TBM, and storing the selected path through the operation of the path selection unit in the first TBM after the decoding is completed. And a traceback unit for starting to store another path selected through the operation of the path selector in the second TBM which is the extracted TBM.

The apparatus may further include a first-in-last-out (FILO) buffer unit or a last-in-first-out (LIFO) buffer unit for changing the order of the traced information.

The path selector may include a parallel add compare select (ACS) using radix-4.

The path selector may include a parallel Add Compare Select (ACS) using Radix-16.

According to the present invention, in a system using a Viterbi decoder, the memory necessary for backtracking is optimally configured, so that the minimum memory can be used without using a large amount of computation and the decoding delay time can be minimized.

In addition, according to the present invention, the backtracking can be performed at the same clock speed while writing to the memory, and the backtracking can be performed by finding previous state information based on the contents of the memory without shifting the memory.

1 is a flowchart illustrating an example of a method for receiving and decoding a signal at a receiving end of a communication system to which the present invention is applied.
2 shows an example of a Viterbi decoder to which the present invention is applied.
3 relates to a Radix-4 structure to which the present invention is applied.
4 relates to a Radix-16 structure to which the present invention is applied.
5 illustrates an example of storing a survival path value to perform backtracking and outputting decoded data.
6 shows an example of a traceback memory to which the present invention is applied.
7 shows an example of a traceback memory to which the traceback method according to the present invention is applied.
8 is a flowchart illustrating an operation of a backtracking apparatus for performing backtrace in the backtracking memory of FIG. 7 according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Also, in order to clearly illustrate the present invention in the drawings, portions not related to the present invention are omitted, and the same or similar reference numerals denote the same or similar components.

1 is a flowchart illustrating an example of a method for receiving and decoding a signal at a receiving end of a communication system to which the present invention is applied.

The receiving end receives the data encoded by the generated polynomial from the transmitting end of the system (S100).

The decoder included in the receiver (eg, Viterbi decoder) generates the received data, selects an optimal path among all possible paths based on the polynomial (S105), and selects the optimal path information of a predetermined size or more in advance in all states ( state) and recovers the data by selecting one of them through backtracking (S115).

2 shows an example of a Viterbi decoder to which the present invention is applied.

Referring to FIG. 2, the Viterbi decoder includes a branch metric unit (BMU), a path metric unit (PMU), and a trace back unit (TBU). The apparatus may further include a first-in-last-out (FILO) buffer unit or a last-in-first-out (LIFO) buffer unit for changing the order of the traced information. The apparatus may further include a backtracking memory on which the backtracking is performed.

The branch value calculating unit receives the encoded data and calculates the branch values in all cases in advance. The branch value when calculated depends on the number of data input. For example, when k coded data is input, 2 ^k branch values are calculated. That is, when the input coded data is four, a total of 16 (2 ⁴ ) branch values are calculated.

The path selector may perform an operation based on the calculated branch value, and may include an add compare select (ACS) unit. 3 or 4 may be a Radix-4 or Radix-16 structure. Computation is performed based on the generated polynomial used in the encoding process. If the constraint length is C, the operation is performed on 2 ^C-1 states. The branch value is added to the path value of the previous state to compare and select for all branches that may be present.

The comparison and selected value is updated with the path value of the current state in the backtracking memory. The current state is the number of 2 ^C-1 cases, and each state is updated each time according to the input. If the state to be updated is called the current state, the path value of the previous state that can be updated to the current state and the branch value coming from the previous state to the current state are calculated for all possible previous states, and compared with each other to select the minimum value. do. The selected minimum value is updated with the path value of the current state.

3 relates to a Radix-4 structure to which the present invention is applied. This is the case when the restriction is 3, and the state is 4 (= 2 ^3-1 ).

Referring to FIG. 3, in the case of having a Radix 4-structure, if the current state is "X00", the previous states "00X", "01X", "10X", and "11X" may be "X00". Add the branch values when the state changes to the path values of the previous state. Then, the one with the smallest path value among four paths is selected. This is because it indicates that a similar sequence has a high probability that the difference between the input coded data and the expected coded value due to the state transition is small.

4 relates to a Radix-16 structure to which the present invention is applied. This is the case when the restriction is 5 and the state is 16 (= 2 ^5-1 ).

Referring to Fig. 4, in the case of having a Radix-16 structure, if the current state is "X0000", the 16 previous states "0000X", "0001X",... Add the branch value when the state changes from "1111X" to "X0000" with the path value of the previous state, respectively. Then, the one with the smallest path value among 16 paths is selected.

As such, the minimum path value selected by the path selector is stored in the backtracking memory for each state.

On the other hand, the traceback unit finds the most similar decoding sequence in the traceback memory through traceback.

There are two ways to perform backtracking while storing survival path values in the backtracker, and decoded data can be output by performing backtracking. Here, the survival path value means the minimum path value selected by the path selection unit.

First, there is a method of selecting a selected survival path of all states at every time point and storing the selected survival path in the traceback memory and updating previous information according to the path selected by the path selection unit.

5 illustrates an example of storing a survival path value to perform backtracking and outputting decoded data.

Referring to FIG. 5, after a certain time, one state may be read to simply determine the state at time "t-T". Here, "t" refers to time instant and "T" refers to backtracking depth.

The path information of all states is updated with new path information, and information stored at the time point "tT" among the path information of the previous state is output as decoded data according to the selected path. At this time, the size of the traceback memory required is (state index (2 ^C-1 ) * T). Also, it has a minimum demodulation delay time for demodulation upon input after a certain traceback length. However, the hardware complexity is high and the power consumption is large in the process of updating the survival paths of all memories at each time point.

Second, it stores only the selected survival paths of all states at every point in time, and after a certain time, traces the previous state through the stored survival path values in one state and traces back the previous state again by T step in order to decode There is a way to get the data. In this case, since it is not necessary to update all the information at every time point, the hardware complexity is low and the power consumption is also reduced. The demodulation delay is more than doubled in the process of storing the selected survival path in the traceback memory and in the traceback process.

In this case, since backtracking is performed using the survival path value obtained from the information input at each time point, the memory is stored using multiple read multiple pointers with a backtracking memory larger than the backtracking length for time efficiency. It can be operated. In this case, the read multiple pointer refers to a pointer that allows a read operation to be simultaneously performed in a plurality of memory spaces using a plurality of read pointers. Next, in FIG. 6, it can be seen that read operations are simultaneously performed at three points.

6 shows an example of a traceback memory to which the present invention is applied.

Referring to FIG. 6, when the traceback length is T, a plurality of read pointers (three in FIG. 6) are placed, and data is continuously stored (Write: WR) after a predetermined time. Backtrack (TakeBack: TB) to configure.

The storage memory is divided into (2 * number of read pointers), which is 2 * 3 in FIG.

The size of each storage memory is T / (lead pointer number -1), and T / (3-1) in FIG.

Since the total memory size is (2 * number of lead pointers) * T / (number of lead pointers ^-1 ) * 2 ^C-1 , in the case of FIG. 6, (2 * 3) * T / (3-1) * 2 ^{C- 1} The magnitude (C) value of the constraint field is variable. It is desirable to use enough memory for smooth storage and decoding.

7 shows an example of a traceback memory to which the traceback method according to the present invention is applied.

Referring to FIG. 7, the backtracking memory is divided into a plurality of TBMs (TBM ₁ ,..., TBN _{n +2 in} FIG. 7). The size of each TBM is N, where N is the time required to fill one TBM in terms of time.

Each TBM updates all route information at each time point. Update the new route information selected in the previous state and the trace route information accordingly. At this time, updating the tracking path information means not only updating the selected new path information but also updating all path information necessary for the backtracking of the previous state. However, this update is performed in one TBM.

When the update of the path information for one TBM is completed, the path information is updated in the same manner for the next TBM. While performing the update operation for the next TBM, the previous TBM no longer performs the update operation. That is, the update operation is performed for all states only for one TBM at a time.

The size of the total backtracking memory of FIG. 7 is (size of one TBM) * (2 ^C-1 ) * (n + 2), and if T is n * N, it is (T * 2 ^{C− 1} ) + (size of one TBM) * (2 ^C-1 ) * (2)

When the size of one TBM is N, the time it takes for data to be stored in one TBM is at least N clocks, and backtracking is performed in the other TBMs during the N clocks stored in the TBM. Update the path information in one clock to read the next TBM.

In this manner, n TBM information is read with one read pointer to perform backtracking for n clocks, and the next clock is decoded to obtain decoded data.

The product of the size of TBM and the number of TBMs (N * n) must be longer or equal to the backtracking length T. This will allow you to perform backtracking properly. If T / N is an integer, the TBM number n required for backtracking is selected as T / N. If T / N is not an integer, n is greater than T / N and selected as the nearest integer.

For example, the criterion for dividing the backtracking length (T) into n TBMs and determining the size (N) of one TBM is based on the time required to store the survival path in the memory and the backtracking time. Decide on

The backtracking method is to obtain the path information of the corresponding state by reading the information of the TBM, find the next TBM corresponding to the next state by obtaining the next state information therefrom, and obtain the path information of the next TBM.

When the minimum value of N satisfying the condition of Equation 1 is found and the memory is efficiently divided and used in the traceback process, the decoding delay time can be minimized. If N is too large, power consumption may be high because a lot of path information needs to be updated in one TBM.

The present invention can also be applied to a case in which a long traceback length is required, such as a system using a 5/6 code rate in a WLAN system (for example, an IEEE 802.11n system).

When the backtracking length T is 90 in Equation 1, the size N of the TBM is 10. That is, when N is 10, it satisfies the condition of Equation 1 and has a minimum total memory size and a minimum delay time.

In this case, one TBM size is 10 * 2 ^C-1 , T is 90, the number n of TBMs for backtracking is 9, and the total memory size is 10 * 2 ^{C-1 *} (9 + 2).

On the other hand, when T is 100, the minimum value of N satisfying the condition of Equation 1 is 11. In this case, since one TBM size is not divided by an integer by T / N, a proximity integer is used. Since the size of N * n must be greater than or equal to 100, the backtracking length (T), the number of TBMs for backtracking (n) is 10 and the total memory size is 11 * 2 ^C-1 * (10 + 2) to be.

If T is 100 and N is 12, when using a near-integer for the number n of TBMs for backtracking, n is 9, so the total memory size is 12 * 2 ^C-1 * (9 + 2) to be.

In addition, if T is 100 and N is 13, when the proximity integer is used for the number n of TBMs for backtracking, n is 8, so the total memory size is 13 * 2 ^C-1 * (8 + 2). to be.

Herein, when N is 11 and N is 12, the total memory size is the same, and when N is 13, the total memory size is smaller than when N is 11 or 12. However, when N is 11 for memory update of TBM, it may be advantageous because less hardware is used when N is 12 or 13.

8 is a flowchart illustrating an operation of a backtracking apparatus for performing backtrace in the backtracking memory of FIG. 7 according to the present invention. When the data is stored in the backtracking memory, the backtracking device decodes the stored data and reuses the memory, thereby reducing the decoding delay and efficiently reusing the memory.

The backtracking device starts storing data in the first TBM, which is one of a plurality of TBMs constituting the backtracking memory (S800). At the same time or immediately after, the backtracking is performed in the previous TBM of the first TBM (S805). Backtracking can be performed in multiple TBMs depending on the size (N) and backtracking length (T) values of the TBM. If the backtracking length is larger than the size of the previous TBM of the first TBM, the backtracking is continued continuously from the end of the backtracking memory.

Simultaneously or immediately after the backtracking is performed, a decoding operation of extracting the decoding information of the data stored in the TBM before the backtracking is performed (S810). That is, backtracking and decoding operations are performed in different TBMs at the same time (or immediately after) the data is stored.

After the storage of the data is completed, if the traceback device continues to trace back (S815), the storage of the data is started in the next TBM (second TBM) of the first TBM (S820). The second TBM may be a TBM from which decoding information is extracted in a previous traceback operation. That is, the data is stored in the memory in which the decoding was performed in the previous traceback operation. Since data is obtained through decoding, it can be reused as a memory for storing data.

Like the previous traceback operation, the traceback is performed in the previous TBM of the second TBM, and the traceback may be performed in the plurality of TBMs according to the traceback length T value. If the size of the previous TBM of the first TBM is smaller than the backtracking length, the backtracking is continuously performed from the end of the backtracking memory.

Starting from TBM where data was saved in the previous traceback operation, the traceback is performed by the size corresponding to the traceback length. Also, a decoding operation of extracting decoding information of data stored in a previous TBM of a section in which backtracking is performed is performed. The TBM performing the decoding operation is the last TBM in which the backtracking is performed among the plurality of TBMs performing the backtracking in the previous backtracking operation.

As an example, assuming that the backtracking memory consists of a total of n + 2 TBMs, the backtracking device starts storing data at the n + 2th TBM. The storage of data may be updating the path information or updating the survivor transition information. At the same time (or after the start of storage of data), backtracking is performed in the second TBM to n + 1th TBM, which are a plurality of TBMs before the n + 2th TBM. Backtracking is performed on a total of n TBMs, and the magnitude of the product of each TBM size (N) and the number (n) of TBMs is equal to or longer than the backtracking length (T). The backtracking device extracts the decoding information from the first TBM before completing the storage of data in the n + 2th TBM. The delay is reduced because decoding and data storage and backtracking are performed simultaneously.

In case of continuing to trace back, after the data storage is completed in the n + 2 th TBM, the data storage is started in the first TBM from which the decoded information was extracted. At the same time (or after the start of storage of data), backtracking is performed in the 3rd TBM to n + 2th TBM. Again, backtracking is performed on a total of n TBMs. In addition, the backtracking device extracts the decoding information from the second TBM before completing the storage of the data in the first TBM.

The above embodiment can be applied to the backtracking memory of FIG. 7. First to (n + 1) * N clock after the data n + 1 of the TBM is stored for, and, while storing data on the TBM _{n +2} starting traceback from the TMB to TBM _{2 n +1.} Decoding information is extracted from TBM ₁ before data storage is completed in TBM _{n +2} . When the data is stored in TMB _{n +2} , the memory moves to TBM ₁ and starts storing data for the next N clocks. Hayeoteumeuro immediately extract the decoded information from the TBM ₁ for the previous N is clock data is stored in the TBM _{n +2} for, performing a storage of the data back from the decoded information extracted TBM ₁ to re-use the memory.

Similarly, after the storage of data in TMB ₁ is completed, the memory transfers the storage space to TBM ₂ to start storing data for the next N clocks. Hayeoteumeuro extracts the decoded information from the TBM ₂ during the immediately preceding clock is N ₁ stored for TBM, The Save in TBM ₂ to re-use the memory.

In sequential order, when the storage is completed in TMB ₂ , the memory is moved to TBM ₃ to start the storage. Decoding information is extracted from TBM ₃ while TBM ₂ is stored during the previous N clocks, so storing in TBM ₂ is reusing the memory.

This process includes TMB ₄ , TMB ₅ ,. Repeat on. In this way, the memory can be efficiently used and the decoding delay time can be reduced by storing in the decoded memory.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

Claims (20)

In a method for backtracking data in a communication system,
Initiating storage of data in a first TBM, one of a plurality of Trace Back Memorys (TBMs) constituting a memory;
Performing backtracking for a preset backtracking length backward from a previous TBM of the first TBM;
Performing a decoding operation of extracting decoding information of data stored in a previous TBM of the TBM on which the backtracking is performed; And
And after the storage of the data in the first TBM is completed, initiating storage of the data in the second TBM which is the TBM from which the decoding information is extracted. The method of claim 1,
The size or number of each of the plurality of TBMs is determined in consideration of the time of storing a survival path in the memory and the time of performing backtracking in one TBM. The method of claim 1,
Each size N of the plurality of TBMs uses the backtracking length T,
And a smallest integer value among integer values satisfying "N≥T / N + 1". The method of claim 1,
And performing a second backtrace during the backtracking length forward from the previous TBM of the second TBM. The method of claim 4, wherein
And performing a decoding operation of extracting decoding information of data stored in a previous TBM of a section in which the second traceback is performed. The method of claim 1,
Performing the backtracking;
And a plurality of TBMs based on the traceback length and the size of each of the plurality of TBMs. The method of claim 1,
If the traceback length is greater than the sum of the sizes of previous TBMs of the first TBM,
The performing the backtracking may include performing backtracking up to the front of the memory and then performing backward backtracking from the end of the memory. The method of claim 1,
Initiating storage of the data is performed simultaneously with performing the backtracking. The method of claim 1,
Initiating storage of the data is performed simultaneously with performing the decoding operation. The method of claim 1,
The communication system,
Backtracking method characterized in that the wireless LAN system using a 5/6 code rate. The method of claim 1,
Initiating the storage of the data,
Select one survival path among all survival paths stored in the memory,
Storing all of the survival paths in the first TBM,
And updating the data including the tracking path at each preset update timing according to the selected one survival path. The method of claim 1,
Initiating the storage of the data,
Only the selected survival paths among all the survival paths stored in the memory are stored in the first TBM,
And updating the data including the tracking path during the backtracking length at every preset update timing in accordance with the selected survival path. Initiate storage of data in the first TBM, one of a plurality of TraceBack Memory (TBMs) constituting the memory, and perform backtracking for a predetermined backtracking length forward from the previous TBM of the first TBM. And performing decoding operation for extracting decoding information of data stored in the TBM before the backtracking, and storing the data in the second TBM which is the TBM from which the decoding information is extracted after the data is stored in the first TBM. A backtracking device comprising a backtracking portion for initiating. The method of claim 13,
The size or number of each of the plurality of TBMs is determined in consideration of the time to store the survival path in the memory and the time to perform backtracking in one TBM. The method of claim 13,
The backtracking unit,
And performing a second backtrace during the backtracking length forward from the previous TBM of the second TBM. The method of claim 15,
The backtracking unit,
And a decoding operation of extracting decoding information of data stored in a previous TBM of a section in which the second traceback is performed. A branch value calculator which receives the encoded data and calculates branch values in all cases in advance;
A path selector for performing an operation on the calculated branch value; And
Stores the selected path through the operation of the path selector in the first TBM, which is one of a plurality of traceback memories (TBMs) constituting a memory, and has a predetermined backward tracking length forward from the previous TBM of the first TBM. While performing a backtracking operation, performing a decoding operation of extracting decoding information of data stored in a previous TBM of the backtracking TBM, and storing the selected path through the operation of the path selection unit in the first TBM. And a tracer for starting to store another path selected through the operation of the path selector in a second TBM, which is the TBM from which the decoding information is extracted. The method of claim 17,
A Viterbi decoder further comprising a first-in-last-out (FILO) buffer unit or a last-in-first-out (LIFO) buffer unit for changing the order of the traced information. The method of claim 17,
The path selector,
Viterbi decoder comprising parallel Add Compare Select (ACS) using Radix-4. The method of claim 17,
The path selector,
Viterbi decoder featuring parallel Add Compare Select (ACS) using Radix-16.

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