CN102098059A - Low-density parity check code-based decoding method and implementation device thereof - Google Patents

Abstract

The invention discloses a low-density parity check code-based decoding method, which comprises the following steps of: initializing iteration information and control quantity parameters, performing open mobile system (OMS) check node computation, OMS variable node computation and hard decision decoding to acquire the check result of each check expression, meanwhile, recording the total number of check bit errors, accumulating iterations, repeating the contents till satisfying the normal iteration judgment ending condition or the advanced iteration judgment ending condition, and ending the decoding iteration. The invention also discloses a low-density parity check code-based decoding device, which comprises computing units, an iteration ending control unit, a hard code decision unit and a switching network. The computing units comprise an OMS variable node computing unit and an OMS check node computing unit. The method and the device can effectively reduce the decoding computation quantity in the decoding process, reduce the computing complexity, and meanwhile, reduce the decoding delay time on the premise of keeping the computing performance.

Description

A kind of based on low density parity check code decoding method and implement device thereof

Technical field

The present invention relates to interpretation method and device thereof in a kind of field of wireless communication, relate in particular to a kind of based on low-density checksum interpretation method and implement device thereof.

Background technology

In wireless communication system,, will inevitably introduce distortion and signal decision mistake to the transmission data because transmission channel exists noise, decline, multipath.The signal error that takes place in the transmission is found, corrected to channel coding technology by add redundancy symbol in information sequence, thereby improve the reliability of system.

Low density parity check code (being called for short " LDPC sign indicating number ") decoding is that a kind of performance of Shannon (Shannon) limit of can approaching is than more excellent channel coding/decoding method.The standard Soft decision decoding of LDPC sign indicating number adopts a kind of belief propagation algorithm, is referred to as sum-product algorithm (being called for short " SPA ").Sum-product algorithm makes the LDPC sign indicating number obtain optimum decoding performance, but the hardware implementation complexity of the hyperbolic cotangent function algorithm in the check node calculation is very high.Minimum-sum algorithm (being called for short " MS ") has replaced complicated hyperbolic cotangent function with minimum value function, greatly reduce the decoding algorithm complexity, but performance has bigger loss.Offset (side-play amount) minimum-sum algorithm (be called for short " OMS ") on the basis of MS algorithm, the performance loss of MS algorithm of in check node calculation, having introduced the Offset compensation factors.It has only increased very little implementation complexity and has obtained the performance approaching with the SPA algorithm.

Under AWGN (Additive White Gaussian Noise additive white Gaussian noise) channel, when adopting BPSK (Binary Phase Shift Key binary phase shift keying) modulation, make signal-noise ratio threshold value Y=[y ₁, y ₂... y _N] be the soft-decision receiving sequence of receiving terminal matched filter output.The OMS decoding algorithm of LDPC sign indicating number is as follows:

(1) initialization:

$L\left(q_{\mathrm{ji}}^0\right)=L\left(P_i\right)=y_i$ And iterations k=1 is set.

Wherein, L (q _Ji) be the external information from the variable node to the verification, L (P _i) be initial channel information.

(2) the calculation check node is to the external information of variable node:

$L\left(r_{\mathrm{ji}}^k\right)=\left(\underset{i^{\′}\∈R_j\backslash i}{\mathrm{\Π}}{\mathrm{\α}}_{i^{\′}j}^{k-1}\right)\·\max (\underset{i^{\′}\∈R_j\backslash i}{\min }\left({\mathrm{\β}}_{i^{\′}j}^{k-1}\right)-\mathrm{\β},0)$

L (r wherein _Ji ^k) be the external information from the check-node to the variable on the log-domain, β is a displacement factor, and satisfies: β＞0.

(3) calculate the external information of variable node to check-node:

$L\left(q_{\mathrm{ji}}^k\right)=L\left(P_i\right)+\underset{j^{\′}\∈C_i\backslash j}{\mathrm{\Σ}}L\left(r_{j^{\′}i}^k\right)$

(4) for all i, ask posterior probability:

$L\left(Q_i^k\right)=L\left(P_i\right)+\underset{j\∈C_i}{\mathrm{\Σ}}L\left(r_{\mathrm{ji}}^k\right)$

L (Q _i ^k) be the posterior probability on the log-domain.

(5) for all i, carry out hard decision, produce decode results:

${\hat{c}}_i=\left\{\begin{array}{cc}1& \mathrm{ifL}\left(Q_i^k\left(1\right)\right)<0\\ 0& \mathrm{else}\end{array}\right.$

(6) repeating step (2) is to (5), k=k+1.Up to $\hat{c}{H}^T=0$ Perhaps reach maximum iteration time, finishing iteration decoding, and select whether to export decode results.

OMS algorithm essence is a kind of iterative decoding algorithm, and message is transmitted between variable node and check-node back and forth, thereby brings in constant renewal in.The iteration stopping condition is in the present OMS decoding algorithm: when iterations reaches maximum iteration time, perhaps know decoding correctly the time by judgement, finishing iteration decoding is the output decode results also.But in some decode procedure, though the decoding iterations reach maximum iteration time can not correct decoding, need a lot of useless decoding computings on the contrary, the problem that causes the hardware power consumption to increase.

Summary of the invention

At the problems referred to above, the present invention proposes a kind of based on low density parity check code decoding method and implement device thereof, can effectively be reduced in the decoding operand in the decode procedure, reduces computational complexity, can under the prerequisite that does not influence operational performance, reduce and decipher time of delay simultaneously.

It is a kind of based on low density parity check code decoding method that the present invention proposes, and comprises following content:

(1), iteration information, controlled quentity controlled variable parameter are carried out initialization;

(2), carry out the computing of OMS check-node, the computing of OMS variable node, Hard decision decoding, obtain the check results of each verification formula, write down the total number of check digit mistake simultaneously, iterations adds up;

(3), repeating step (2), up to satisfying normal termination iteration judgment condition or in advance during the finishing iteration judgment condition, finishing the decoding iteration.

In the step (1), the iteration information initializing is to L (q _Ji ⁰) _iAnd L (P _i) carry out initialization, controlled quentity controlled variable parameter initialization content comprises iteration count k, maximum iteration time N, time span parameter S pan_1, Span_2 (wherein Span_1＜Span_2＜N), iterations decision parameter Delta_1, Delta_2 and effective judging threshold Threshold.

In the step (2), iterative decoding process comprise adopt OMS method calculation check node to the external information of variable node, adopt the OMS method calculate variable node to the external information of check-node, ask posterior probability, carry out the hard decision generation decode results and the iterations that adds up.In the process of carrying out hard decision generation decode results, obtain the check results of each verification formula, write down the total number T_err (k) of check digit mistake simultaneously.The calculating formula of iterations of adding up is k=k+1.

In the step (3), normal termination iteration judgment condition is $\hat{c}{H}^T=0$ Perhaps reach maximum iteration time.In advance the finishing iteration judgment condition if the number T_err (k) of check digit mistake satisfies certain judgement of finishing iteration in advance, then finishes to decipher iteration for when Span_2＜k≤N in advance.Certain finishing iteration judgment condition in advance that T_err (k) is satisfied need meet the following conditions simultaneously:

①T_err(k)＞T_err(k-Span_1)+Delta_1；

②T_err(k)＞T_err(k-Span_2)+Delta_2；

③T_err(k)＞Threshold；

It is a kind of based on low density parity check code realization of decoding device that the present invention also provides simultaneously, comprises arithmetic element, iteration finishing control unit, decoding hard decision unit and switching network.Wherein, arithmetic element comprises OMS variable node arithmetic element and OMS check-node arithmetic element.

OMS variable node arithmetic element, the OMS variable node of finishing in the decoding algorithm upgrades.

OMS check-node arithmetic element, the OMS check-node of finishing in the decoding algorithm upgrades.

Iteration finishing control unit, whether the iterations in the control decode procedure finishes according to the judgement of normal termination iteration and two conditional decision decodings of finishing iteration judgement in advance.

Decoding hard decision unit carries out hard decision to the message in each iterative process, produces decode results, obtains the check results of each verification formula simultaneously, the total number of calculation check bit-errors.

Switching network, the renewal result of OMS variable node arithmetic element and OMS check-node arithmetic element exchanges mutually by switching network.

According to provided by the invention based on low density parity check code decoding method and implement device thereof, iteration can predict in early days can not correct decoding situation and finishing iteration in advance.This technical method complexity is low and be easy to hardware and realize.Can under the prerequisite that does not influence performance, reduce the decoding operand, and reduce to decipher time of delay.

Description of drawings

Fig. 1 is a kind of based on the low density parity check code decoding method basic flow sheet

A kind of structural representation of Fig. 2 based on the low density parity check code code translator

Fig. 3 is based on the ber curve figure of the embodiment of low density parity check code decoding method

Fig. 4 adopts the iterations correlation curve figure of standard OMS algorithm and embodiment of the present invention

Specific embodiments

Below in conjunction with each accompanying drawing to a kind ofly being described in detail of proposing in the content of the present invention based on low density parity check code decoding method and implement device thereof:

Fig. 1 is the flow chart based on low density parity check code decoding method, and its concrete implementation step is:

At first, iteration information and controlled quentity controlled variable parameter etc. is carried out initialization, iteration information is to L (q _Ji ⁰) _iAnd L (P _i).The controlled quentity controlled variable parameter comprises iteration count k, maximum iteration time N, time span parameter S pan_1, Span_2 (wherein Span_1＜Span_2＜N), iterations decision parameter Delta_1, Delta_2 and effective judging threshold Threshold.

Secondly, carry out the computing of OMS check-node, the computing of OMS variable node, Hard decision decoding, obtain the check results of each verification formula, write down the total number of check digit mistake simultaneously, iterations adds up.Iterative decoding process comprise adopt OMS method calculation check node to the external information of variable node, adopt the OMS method calculate variable node to the external information of check-node, ask posterior probability, carry out the hard decision generation decode results and the iterations that adds up.In the process of carrying out hard decision generation decode results, obtain the check results of each verification formula, write down the total number T_err (k) of check digit mistake simultaneously.The calculating formula of iterations of adding up is k=k+1.

The iteration decoding treatment process when satisfying normal termination iteration judgment condition or shifting to an earlier date the finishing iteration judgment condition, finishes the decoding iteration.

In the device that adopts above-mentioned implementation method, as Fig. 2 based on as shown in the low density parity check code realization of decoding structure drawing of device, the OMS variable node that the variable node arithmetic element is finished in the decoding algorithm upgrades, and the check-node that OMS check-node arithmetic element is finished in the decoding algorithm upgrades.The renewal result of the two exchanges mutually by switching network.Decoding hard decision unit carries out hard decision to the message in each iterative process, produces decode results, obtains the check results of each verification formula simultaneously, the total number of calculation check bit-errors.Iterations in the decode procedure is by iteration finishing control unit controls, determines according to the judgement of normal termination iteration and two conditions of finishing iteration judgement in advance whether decoding finishes or proceed.

Fig. 3 has provided a kind of ber curve figure based on an embodiment who hangs down the operand low density parity check code decoding method provided by the invention, has listed file names with the ber curve that adopts standard OMS algorithm among the figure.In this embodiment, the code length of LDPC sign indicating number is 2304, adopt the decoding of OMS algorithm, the offset factor of OMS algorithm is 0.1, and initiation parameter is: maximum iteration time: N=30, time span parameter: Span_1=3, Span_2=6, iterations decision parameter: Delta_1=15, Delta_2=15, effectively judging threshold: Threshold=180.As can be seen from Figure 3, provided by the inventionly a kind ofly do not influence decoding performance substantially based on low operand low density parity check code decoding method.

Fig. 4 is the average iterations curve of embodiment among Fig. 3, has provided the average iterations curve that adopts standard OMS algorithm among Fig. 4 simultaneously.As can be seen from Figure 4, provided by the inventionly a kind ofly effectively reduced the interative computation number of times, reduced the decoding operand, had the technique effect of highly significant based on low operand low density parity check code decoding method.

Claims (9)

1. one kind based on low density parity check code decoding method, it is characterized in that comprising following content:

(1), iteration information, controlled quentity controlled variable parameter are carried out initialization;

(2), carry out the computing of OMS check-node, the computing of OMS variable node, Hard decision decoding, obtain the check results of each verification formula, write down the total number of check digit mistake simultaneously, iterations adds up;

(3), repeating step (2), up to satisfying normal termination iteration judgment condition or in advance during the finishing iteration judgment condition, finishing the decoding iteration.

2. as claimed in claim 1 a kind of based on low density parity check code decoding method, it is characterized in that: described iteration information initializing is to L (q _Ji ⁰) i and L (P _i) carry out initialization.

3. as claimed in claim 1 a kind of based on low density parity check code decoding method, it is characterized in that: described controlled quentity controlled variable parameter initialization content comprises iteration count k, maximum iteration time N, time span parameter S pan_1, Span_2 (wherein Span_1＜Span_2＜N), iterations decision parameter Delta_1, Delta_2 and effectively judging threshold Threshold.

4. as claim 1 or 3 described a kind of based on low density parity check code decoding method, it is characterized in that: described time span parameter S pan_1, Span_2 is Span_1＜Span_2＜N.

5. as claimed in claim 1 a kind of based on low density parity check code decoding method, it is characterized in that: in the process of carrying out hard decision generation decode results, obtain the check results of each verification formula, write down the total number T_err (k) of check digit mistake simultaneously.

6. as claimed in claim 1 a kind of based on low density parity check code decoding method, it is characterized in that: the calculating formula of the iterations that adds up is k=k+1.

7. as claimed in claim 1 a kind of based on low density parity check code decoding method, it is characterized in that: normal termination iteration judgment condition is $\hat{c}{H}^T=0$ Perhaps reach maximum iteration time.

8. as claimed in claim 1 a kind of based on low density parity check code decoding method, it is characterized in that: the finishing iteration judgment condition is Span_2＜k≤N in advance, the number T_err (k) of check digit mistake meets the following conditions simultaneously simultaneously, then finishes the decoding iteration in advance:

T_err(k)＞T_err(k-Span_1)+Delta_1；

T_err(k)＞T_err(k-Span_2)+Delta_2；

T_err(k)＞Threshold。

9. one kind based on low density parity check code realization of decoding device, comprise arithmetic element, iteration finishing control unit, decoding hard decision unit and switching network, it is characterized in that: described arithmetic element comprises OMS variable node arithmetic element and OMS check-node arithmetic element.

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