TWI531171B - Window stop method for turbo decoding - Google Patents

Description

Window stop method for turbo decoding

The present invention relates to a window stop method for turbo decoding, and more particularly to a turbo decoding algorithm for reducing the amount of computation of the internal window of each iteration of the turbo decoding, saving unnecessary operations and reducing power consumption.

In today's communication systems, the Forward Error Correction (FEC) plays an important role in the system, and its main purpose is to protect data. Once the data is encoded by the error correction code module, even if it is interfered by the noise in the transmission channel during the transmission process, the message to be transmitted can be received correctly after the decoding process through the decoding process; (Turbo Code, TC) is one of the feedforward error correction codes with better correction ability. The turbo code is the iterative operation of two soft input soft output decoders, and the exchange rate information of each other makes its coding gain close to Xue. Shannon Limit, also because of its excellent performance, turbo code is also widely used in various wireless communication standards, such as DVB, WCDMA, LTE, WiMAX, etc., can also be applied to power line transmission systems. For example: HomePlug.

Turbo code decoding is performed by the Soft-input Soft-output algorithm decoder and the interleaver to exchange information with each other for the iterative operation, which can be subjected to multiple Iterative operations and exchanged with each other. Information to improve error correction capabilities. The current turbo decoder (Turbo Decoder) design mostly uses window decoding to save a lot of turbo decoding delay and improve turbo code throughput. However, as the number of turbo decoders is increased, the power consumed is increased. It also increases linearly, which in turn shortens the time it takes to use the mobile device; In order to solve the above problems, many studies have proposed a variety of Early Termination Techniques, and the early iterative termination technique is a technique for effectively detecting the number of superpositions, which can stop the turbo decoding that has already converged. And maintain the overall decoding performance of the turbo code. However, the early iterative termination technique stops the iterative operation of the entire turbo decoder only for the convergence of the entire information framework. Therefore, the turbo decoding cannot further stop the internal decoding operation until the early iteration termination technology condition is reached. It is not possible to detect internal information and stop its operation.

Therefore, in order to reduce the amount of computation of the internal window of each iteration of the turbo decoding, unnecessary operations are saved to reduce power consumption. In the turbo decoding, the window detection is performed after the soft input soft output decoding, to detect and record the convergence of the windows in the decoded information, so that the iterative operation can be performed in the future, and the internal window is stopped for the converged window. The operation thus achieves the goal of low power turbo decoding, which should be an optimal solution.

The invention provides a window stopping method for turbo decoding, which can perform window detection after decoding the soft input soft output of the turbo decoding, so as to detect and record the convergence state of each window in the decoded information, so in the future The iterative operation can stop its internal operations for the converged window to reduce the amount of computation of the internal window of each iteration of the turbo decoding, saving unnecessary operations and reducing power consumption.

The window stop method for turbo decoding which can achieve the above object is a window for decoding information when the soft input soft output decoder performs turbo decoding after performing turbo decoding in each iteration operation. Detect to detect and record the convergence of the windows in the decoded information.

More specifically, the soft input soft output decoder can generate soft or hard information of the decoding bit in the window after performing soft input soft output decoding, and the window detector is to decode the bit in the window. Soft or hard information is compared to detect the convergence of each window.

More specifically, when the window detector determines that the entire window has reached convergence, the window is recorded as a window of convergence, and in the subsequent iterative operation, the operation of the converged window is stopped.

More specifically, the operation of stopping the converged window can use a reliable information as an exchange of external information to provide a soft input. The soft output decoding can continue to operate normally and maintain its error correction capability under the stop part operation. .

More specifically, the operation of stopping the converged window can temporarily store external information using a memory to provide soft input soft output decoding under the stop part operation, and continue to operate normally and maintain its error correction capability.

More specifically, the decoding information has a plurality of parallel decoding cores, and when the window detector determines that all the windows in a parallel decoding core converge, the decoding core can be defined as a convergence core, and the convergence core The operation will be stopped in the subsequent iterative operation, and the operation of one convergence core stops equivalent to stopping all operations in the convergence core.

More specifically, the operation of stopping the convergence core can use a reliable information as an exchange of external information to provide soft input soft output decoding, which can continue to operate normally and maintain its error correction capability under the stop part operation.

More specifically, the operation of stopping the convergence core can use a memory to temporarily store external information to provide soft input. The soft output decoding can continue to operate normally and maintain its error correction capability under the stop part operation.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Please refer to FIG. 1 , which is a schematic diagram of a main structure of a window stop method for turbo decoding according to the present invention. As can be seen from the figure, the present invention proposes a window-stopped technique (Window-stopped, WS), in order to effectively detect each element. Convergence, after the Soft-input Soft-output (SISO) decoder 1 is inserted into the Window-based Detector (WBD) to detect the maximum probability of each point in a single window. Whether the value is greater than a preset threshold value, and the maximum event probability value is greater than a certain threshold value, it can be assumed that the decoded information is correct, and the judgment is convergence; and the window detector 2 can run the window operation stop technology and The core operation stops the technique; while the WBD will record the window as a convergence window when the entire window is converged in the subsequent iteration operation, and in the subsequent iterative operation, the operation of the converged window is stopped. Reduce power consumption.

In the turbo decoding process, a forward recursive operation unit can calculate and store the last bit in each parallel decoding frame to wait for the next iteration operation and read it to the iterative operation. The forward recursive computing unit initially uses the value; and a backward recursive computing unit can calculate and store the last bit in each window to wait for the next iteration, read the last stack The last bit data in the generation operation is used as the initial value for the backward recursive operation unit; however, the simple window stops the operation and does not stop the forward recursive operation unit, and the forward operation unit still needs to continue to calculate to provide Give the next window a reliable initial value; therefore, the present invention is based on the windowed operation stop technique, extending the core operation stop (Kernel-stopped, KS), if all the windows in a MAP decoding core (Concoding Kernel) converge, the decoding core can be defined as a convergence core, which will stop the operation in the subsequent iteration operation, and one The core operation stops as if all the operations in the core are stopped, including all the operations in the window and the forward recursive operation unit; as shown in Figure 2, if there are two MAP decoding cores in the turbo decoder (MAP0, MAP1) Each MAP decoding core has two windows (Window 0, 1 and Window 2, 3), while MAP0 has a convergence window (Window 0) and an unconverged window (Window 1), and MAP1 has two Convergence window (Window 2, Window 3), so it can define MAP1 as a convergent decoding core; and in the iterative operation of turbo code, as shown in Figure 3, enter this soft input soft output decoding operation 301, according to The convergence window and the convergence core of the last record stop its operation 302, and then use the window operation stop technique to detect the converged window 303. If it is determined that there is convergence, the window convergence condition 304 is recorded, and then used. The core operation stop technology detects the converged core 305. If the convergence is determined, the core convergence status 306 is recorded, and the next soft input soft output decoding operation 307 is entered again; if it is determined that the window is not converged or the core is not converged, Then enter the soft input soft output decoding operation 307; in addition, for the window or core of the stop operation, the present invention also proposes to utilize the external memory due to the lack of external information (Extrinsic Information) for the soft input decoding exchange with the next soft input. Temporary exchange of external information or a reliable information as an exchange of external information to provide soft input soft output decoding can continue to operate normally and maintain its error correction capability under the stop part of the operation.

The present invention provides two turbo code mechanisms of WiMAX and HomePlug as an embodiment. The first embodiment is based on the WiMAX turbo code mechanism and uses a single decoding core to detect the state of window convergence. The decoder adopts the WiMAX communication standard. Turbo code standard, under the 1920-bit information frame, the maximum number of iterations is 8 times, and the additive Gaussian white noise channel is used as the simulation condition. In hardware implementation, this technology uses TSMC 90 nanometer process for synthetic simulation verification. At the operating frequency of 250 MHz, after analyzing the power consumption by Synopsys Design Vision software synthesis and Synopsys Prime Power, the area and power consumption analysis is shown in Figure 4 and Figure 5. The SISO logic in Figure 5 is the soft input soft output logic. Unit, the soft input soft output logic unit includes a forward operation recursive unit, a backward recursive operation unit, and a post-event probability operation unit; as shown in FIG. 5 and FIG. 6, after adopting the technology, for the converged window It can reduce the power consumption by about 57%. It can be seen from Figure 6 that after E _b /N ₀ 0.4 dB, the power consumption saved can be greater than the increased power cost.

The second embodiment of the present invention uses a multi-decoding core to detect core convergence and window convergence under the HomePlug turbo code mechanism. The decoder uses the HomePlug communication standard turbo code standard, in which the information frame length is used. 128, 1088, 4160, the maximum number of iterations is 8 times, and the additive Gaussian white noise channel is used as the simulation condition. As shown in Figure 7, the number of parallel decoding cores used in each information frame and the windows included in the core are shown. The number and the length of the window are different. As can be seen from the figure, the number of windows in the core is determined by the length of the window and the number of parallel decoding cores, and the length of the window determines the difficulty of achieving the stop condition of the window operation. The number of windows also determines the difficulty of reaching the core operation stop condition.

In order to calculate the amount of computation saved by the converged window and the core, the present invention defines a window reduction rate (WRR) and a core stop reduction rate (KRR), and a total stop rate ( Total Reduction Rate, TRR) is WRR The sum of KRR and KRR is known from Figure 8. The window stopped by WRR and KRR is not repeated, and the window stop rate and core stop rate under each signal-to-noise ratio (Eb/N0) are shown in the figure; In order to analyze the turbo decoder, the invention is made of TSMC 90nm, Synopsys Design Vision frequency is operated at 250MHz, and in order to save more energy consumption, we combine window operation stop technology, core operation stop technology and early iteration termination. Technology, in which the early iterative termination technique detects the converged iterative operation and stops the entire turbo decoding operation, and in the unconverged iterative operation, the core is stopped by using the core computation stop technique to stop the convergence. Core computing; however, in the unconverged core, by using the windowed operation stop technique to detect the converged window and stop the operation of the convergence window, the converged window and core do not overlap; please refer to Figure IX, and sorted out The actual power saved by the computational unit that was stopped after verification, where the unconverged window, the convergence window, and the convergence core were measured using Synopsys PrimePower. Rate, including other soft input soft output logic unit (SISO logic), forward recursive operation unit, backward recursive operation unit, after-the-fact probability unit, branch memory (BMC), forward memory (SMM) The entire decoding core (SISO), the overall power, and the SISO logic system includes the branch operation unit, the register and the control signal, wherein the other soft input soft output logic unit (SISO logic) does not include the forward operation recursive unit The backward recursive arithmetic unit and the after-the-fact probability computing unit only contain the remaining control units, so it is different from the SISO logic (soft input soft output logic unit) of FIG. 5; the final test result is known from FIG. 9 , the convergence window and The unconverged window can save about 64% of the power, and the convergence core proposed by the present invention can save 96.6% of the power.

A window stop method for turbo decoding provided by the present invention, and other conventional technologies When comparing with each other, it has the following advantages:

1. The invention can reduce the calculation amount of the internal window of each iteration operation of the turbo decoding, and save unnecessary calculations to reduce power consumption. In the turbo decoding, the window detection is performed after the soft input soft output decoding, to detect Measure and record the convergence of each window in the decoded information, so it can be used in the subsequent iterations to stop the internal operation of the closed window and achieve low-power turbo decoding.

2. The present invention differs from the early iterative termination technique in that the early iterative termination technique can stop the entire iterative operation. However, before the early iterative termination technique condition is reached, the turbo decoding cannot further stop the internal decoding operation; The window-based operation stop technology and the core operation stop technology are proposed. By detecting the information obtained by the soft input soft output decoding, the convergence state of the window and the convergence core is determined, and when convergence is reached, the operation of the window and the convergence core is stopped to reduce Power consumption, so that the partial convergence window can be detected and the operation can be stopped before the entire information frame converges to achieve low power turbo code design.

3. The detected convergence window and the converged core of the present invention do not overlap each other, so the present invention is different from the early iteration termination technology, and can additionally detect a partial convergence window before the entire information frame converges, and Stop its operation to achieve a low power design.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed.

1‧‧‧Soft Input Soft Output Decoder

2‧‧‧Window Detector

FIG. 1 is a schematic diagram of a main structure of a window stop method for turbo decoding according to the present invention; FIG. 2 is a schematic diagram of a convergence window and a convergence core of a window stop method for turbo decoding according to the present invention; FIG. 3 is a window for turbo decoding according to the present invention; FIG. 4 is a schematic diagram of a turbo decoder area comparison of a first embodiment of a window stop method for turbo decoding according to the present invention; FIG. 5 is a diagram of a window stop method for turbo decoding according to the present invention. FIG. 6 is a schematic diagram of a window convergence stop ratio of a first embodiment of a window stop method for turbo decoding according to the present invention; FIG. 7 is a second diagram of a window stop method for turbo decoding according to the present invention. A schematic diagram of the number of parallel decoding cores and the number of windows in the information frame of the embodiment; FIG. 8 is a schematic diagram of the symbol standard used in the WRR and KRR of the second embodiment of the window stop method for turbo decoding according to the present invention; FIG. 9 is an unconvergent window, convergence window and a second embodiment of a window stop method for turbo decoding according to the present invention; FIG. The core of the comparative diagram of power grabbing.

Claims (7)

A window stop method for turbo decoding is performed when turbo decoding is performed in each iterative operation, and when the soft input soft output decoder performs turbo decoding, the window detector is used to perform window detection on the decoded information to detect Measure and record the convergence of the windows in the decoded information. When the window detector determines that the entire window has reached convergence, the window is recorded as a convergence window, and the operation of the converged window is stopped in the subsequent iterative operation, but When the operation of the converged window is stopped, a forward reciprocating unit is not stopped, and the forward unit still needs to continue to calculate to provide a reliable initial value for the next window. The window stop method for turbo decoding according to claim 1, wherein the soft input soft output decoder can generate soft or hard information of the decoding bit in the window after performing soft input soft output decoding. The window detector compares the soft or hard information of the decoding bits in the window to detect the convergence of each window. The window stop method for turbo decoding according to claim 1, wherein the operation of stopping the converged window without stopping a forward reciprocating operation unit can use a reliable information as an exchange. External information to provide soft input soft output decoding can continue to operate normally and maintain its error correction capability under the stop part of the operation. The window stop method for turbo decoding according to claim 1, wherein the memory can be temporarily stored using a memory without stopping a forward reciprocating unit and stopping the operation of the converged window. In order to provide soft input soft output decoding under the stop part of the operation, continue to operate normally and maintain its error correction capability. The window stop method for turbo decoding according to claim 2, wherein the decoding information has a plurality of parallel decoding cores, and the window detector determines a parallel solution. When all the windows in the code core converge, the decoding core can be defined as a convergence core, which will stop the operation in the subsequent iterative operation, and the operation of a convergence core stops is equivalent to stopping all operations in the convergence core. . The window stop method for turbo decoding according to claim 5, wherein the operation of stopping the convergence core can use a reliable information as an exchange of external information to provide a soft input soft output decoding capable of stopping part of the operation. , continue to operate normally and maintain its ability to correct errors. The window stop method for turbo decoding according to claim 5, wherein the operation of stopping the convergence core can use a memory to temporarily store external information to provide soft input. The soft output decoding can still be performed under the stop part operation. Continue to function properly and maintain its ability to correct errors.