CN111082811A - Low-power-consumption Bluetooth Viterbi joint demodulation decoding algorithm with S =8 coding mode - Google Patents

Low-power-consumption Bluetooth Viterbi joint demodulation decoding algorithm with S =8 coding mode Download PDF

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CN111082811A
CN111082811A CN201911383137.9A CN201911383137A CN111082811A CN 111082811 A CN111082811 A CN 111082811A CN 201911383137 A CN201911383137 A CN 201911383137A CN 111082811 A CN111082811 A CN 111082811A
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杜晴鹤
蒋轶
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Fudan University
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
    • H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
    • H03M13/11—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits using multiple parity bits
    • H03M13/1102—Codes on graphs and decoding on graphs, e.g. low-density parity check [LDPC] codes
    • H03M13/1105—Decoding
    • H03M13/1108—Hard decision decoding, e.g. bit flipping, modified or weighted bit flipping
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
    • H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
    • H03M13/11—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits using multiple parity bits
    • H03M13/1102—Codes on graphs and decoding on graphs, e.g. low-density parity check [LDPC] codes
    • H03M13/1105—Decoding
    • H03M13/1111—Soft-decision decoding, e.g. by means of message passing or belief propagation algorithms
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention belongs to the technical field of demodulation and decoding of wireless communication, and particularly relates to a low-power-consumption Bluetooth Viterbi joint demodulation and decoding algorithm in an S-8 coding mode. Aiming at an S-8 coding mode, a Gaussian Frequency Shift Keying (GFSK) process and a low-power consumption Bluetooth coding process are modeled into a finite state machine, and the model is subjected to joint demodulation decoding by utilizing a Viterbi decoding algorithm. The invention considers the practical application scene of the low-power-consumption Bluetooth, has low algorithm complexity, can obviously reduce the error rate and improve the sensitivity of the receiver.

Description

Low-power-consumption Bluetooth Viterbi joint demodulation decoding algorithm with S =8 coding mode
Technical Field
The invention belongs to the technical field of demodulation and decoding of wireless communication, and particularly relates to a low-power-consumption Bluetooth Viterbi joint demodulation and decoding algorithm in an S-8 coding mode.
Background
The Bluetooth low energy technology is one of representative technologies of the Internet of things, and is widely applied to computing devices with low cost and low power consumption and short-distance wireless communication scenes with low data rate and low duty ratio. With the development of the internet of things, in the 2016 release of the bluetooth protocol 5.0, the bluetooth low energy (bt) has an additional coding physical layer and two coding schemes (S ═ 2 and S ═ 8), and the corresponding information transmission rates are 500kb/S and 125kb/S, respectively. The coding physical layer enhances the stability of Bluetooth signal transmission, the transmission distance of the low-power Bluetooth signal can be improved by 4 times at most on the premise of not improving the sending power, and the application field and the development prospect of the low-power Bluetooth in the Internet of things are greatly expanded.
For the S-8 coded physical layer of bluetooth low energy, the receiver uses viterbi joint demodulation decoding, which will greatly improve the sensitivity of the receiver, and is a very practical problem.
Disclosure of Invention
The invention aims to provide a low-power-consumption Bluetooth Viterbi joint demodulation decoding algorithm of an S-8 coding mode with low calculation complexity and low error rate.
The core of the invention is that a Gaussian frequency shift keying modulation (GFSK) process and a low-power consumption Bluetooth coding process are modeled into a finite state machine, and demodulation and decoding are jointly carried out according to a Viterbi decoding algorithm. The invention uses Viterbi decoding algorithm to carry out joint demodulation decoding on the model aiming at the S-8 coding mode. The invention considers the practical application scene of the low-power-consumption Bluetooth, has low algorithm complexity, can obviously reduce the error rate and improve the sensitivity of the receiver.
The invention provides a low-power consumption Bluetooth Viterbi joint demodulation decoding algorithm with an S-8 coding mode.
In the first step, for a transmitted bluetooth signal r (t) passing through an S ═ 8 encoder and a modulator, the phase is:
Figure BDA0002342776900000011
from the GFSK signal model, there are:
Figure BDA0002342776900000012
Figure BDA0002342776900000021
wherein ,
Figure BDA0002342776900000022
q () is a Gaussian Q function, IkE { ±. 1} is the input random bit stream, h is the GFSK modulation index, which is usually taken to be 0.5; BT is the time-bandwidth product, typically taken to be 0.5, and the effective duration of the pulse shaping function q (T) is 2T.
Therefore, there are: when t is<When q (T) is 0 and T is not less than 2T,
Figure BDA0002342776900000023
when t is<When 0 and T are not less than 2T, g (T) is 0;
Figure BDA0002342776900000024
according to the bluetooth low energy 5.0 protocol, bits '1' are mapped to '1100' and '0' is mapped to '0011' after the bitstream is encoded and subjected to mapping extension, and thus IkThe '+ 1' and '-1' pairs in the sequence appear, and thus the above formula can be rewritten as:
Figure BDA0002342776900000025
the first term in the above formula is,
Figure BDA0002342776900000026
thus, it is possible to provide
Figure BDA0002342776900000027
In the above formula IkSince (k ═ n … n +7) is determined only by the convolutional code encoder output, the finite state machine that combines coding and modulation in the S ═ 8 mode can be equivalent to the finite state machine in bit stream coding (convolutional code).
And secondly, decoding the received signals according to a finite state machine modeled in the first step by a Viterbi decoding method so as to achieve joint demodulation and decoding.
The viterbi joint demodulation decoding algorithm used in the second step specifically comprises the following processes:
(1) calculating branch metrics from the output of each state of the finite state machine into which the received signal is modeled in the first step;
(2) calculating a path metric value according to the conversion relation of each state of the finite state machine;
(3) for each state, reserving the arrival path (survival path) with the minimum path metric value calculated in the last step, and deleting the rest arrival paths;
(4) and finding a survival path corresponding to the minimum path metric value, and sequentially outputting decoding bits according to the state conversion relation of the finite state machine.
The phase of the received Bluetooth signal is shown as formula (6);
Figure BDA0002342776900000028
status is represented bykThe value of (k ═ n, n +1 … n +7) is determined because of IkIs obtained by extending two bits of the output of a convolutional code encoder through mappingkThe 8-bit sequence of (1) is formed by only combining sequences '0011' and '1100', and 4 combination cases are total; therefore, the Viterbi decoding algorithm calculates at nT when calculating branch metrics<t<At time (n +8) T, the received signal r (T) and all
Figure BDA0002342776900000031
Of a state
Figure BDA0002342776900000032
(4 state combinations total, i ═ 0 … 3) and the path with the largest correlation metric value is retained, i.e.:
Figure BDA0002342776900000033
in the present invention, the relationship between the input and output of the code modulation joint finite state machine and the state transition in the S-8 coding mode is shown in table 1.
Advantages of the method of the invention
(1) Compared with the traditional decoding method of decoding after demodulation, the method has the advantages that the bit error rate is obviously reduced by combining the Viterbi demodulation decoding algorithm, and the sensitivity of a receiver is improved;
(2) the characteristics of limited computing capability, low power consumption and the like of the low-power-consumption Bluetooth receiver are considered, the algorithm complexity is low, and the implementation is easy.
Drawings
Fig. 1 is a state transition diagram of coding modulation combination in S-8 coding mode.
Fig. 2 is a comparison of the bit error rate performance of the joint demodulation decoding algorithm under the S-8 coding scheme.
Detailed Description
The invention is further illustrated by the following specific examples.
By way of example, the invention simulates the complete process of encoding, modulating, demodulating and decoding the Bluetooth GFSK signal by a computer. In the simulation process, 1000-bit data packets are randomly generated, the GFSK modulation index is 0.5, a coding mode specified by a low-power-consumption Bluetooth protocol is adopted, and 1000 Monte Carlo experiments are performed under a low-power-consumption Bluetooth S-8 coding scheme. The final error rate performance and comparison is shown in fig. 2, where the x-axis is the simulated signal-to-noise ratio and the y-axis is the error rate after decoding at the receiving end.
In the figure, a differential hard demodulation decoding algorithm (a line with diamonds on the upper side) directly takes the optimal phase difference of a received signal, makes hard decisions into 0/1 bits, and then inputs the 0/1 bits into a Viterbi decoder for hard decoding through demapping; the differential soft demodulation soft decoding algorithm (line with triangle at upper side) directly uses the demodulated phase as the input of Viterbi soft decoding after demapping; the Viterbi hard demodulation hard decoding algorithm (line with cross at lower side) demodulates the received signal into 0/1 bits by Viterbi algorithm, and then inputs the signal to Viterbi decoder for hard decoding; the viterbi joint demodulation decoding algorithm (lower dotted line) corresponds to the algorithm of the present invention. The bit error rate performance of the joint demodulation decoding algorithm provided by the invention is improved by 4 dB-6 dB compared with the traditional soft decoding and is improved by 2 dB-3 dB compared with the Viterbi hard demodulation hard decoding.
Table 1, i.e. the relation between input and output of code modulation joint finite state machine and state transition in coding mode 8
Figure BDA0002342776900000041
Reference to the literature
[1]Bo Y,Yang L,Chong C C.Optimized Differential GFSK Demodulator[J].IEEE Transactions on Communications,2011,59(6):1497-1501.
[2]Anderson J B,Aulin T,Sundberg C E.Digital Phase Modulation[J].Applications of Communications Theory,1986:412-412.。

Claims (3)

1. The Bluetooth low energy Viterbi joint demodulation decoding algorithm with the S-8 coding mode is characterized by comprising the following specific steps:
in the first step, for a transmitted bluetooth signal r (t) passing through an S ═ 8 encoder and a modulator, the phase is:
Figure FDA0002342776890000011
from the GFSK signal model, there are:
Figure FDA0002342776890000012
q(t)＝∫0 tg(τ)dτ (3)
wherein ,
Figure FDA0002342776890000013
q () is a Gaussian Q function, IkE { +/-1 } is an input random bit stream, and h is a GFSK modulation index; BT is the time-bandwidth product, and the effective duration of the pulse shaping function q (T) is 2T;
therefore, there are: when t is<When q (T) is 0 and T is not less than 2T,
Figure FDA0002342776890000014
when t is<When 0 and T are not less than 2T, g (T) is 0;
Figure FDA0002342776890000015
according to the bluetooth low energy 5.0 protocol, after the bit stream is encoded in an S-8 manner and subjected to mapping extension, bit '1' is mapped to '1100', bit '0' is mapped to '0011', and IkThe '+ 1' and '-1' pairs in the sequence appear, and the above formula is rewritten as:
Figure FDA0002342776890000016
due to the first term in the above formula,
Figure FDA0002342776890000017
therefore, the method comprises the following steps:
Figure FDA0002342776890000018
in the above formula (6), Ik(k n … n +7) is determined only by the convolutional code encoder output, and thus the finite state machine of the coding-modulation combination in the S8 mode is equivalent to a finite state machine in the case of bit stream coding, i.e., convolutional code;
and secondly, performing joint demodulation and decoding on the received signals according to a Viterbi decoding algorithm according to the finite state machine modeled by the received signals in the first step.
2. The joint demodulation decoding algorithm according to claim 1, wherein in the second step, the joint demodulation decoding is performed on the received signal by using the viterbi decoding algorithm by the following specific procedures:
(1) calculating branch metrics from the output of each state of the finite state machine into which the received signal is modeled in the first step;
(2) calculating a path metric value according to the conversion relation of each state of the finite state machine;
(3) for each state, reserving the arrival path with the minimum path metric value calculated in the last step, surviving the path, and deleting the rest arrival paths;
(4) and finding a survival path corresponding to the minimum path metric value, and sequentially outputting decoding bits according to the state conversion relation of the finite state machine.
3. The joint demodulation decoding algorithm of claim 2 wherein the phase of the received bluetooth signal is:
Figure FDA0002342776890000021
Figure FDA0002342776890000022
status is represented bykThe value of (k ═ n, n +1 … n +7) is determined because of IkIs obtained by extending two bits of the output of a convolutional code encoder through mappingkThe 8-bit sequence of (1) is formed by only combining sequences '0011' and '1100', and 4 combination cases are total; therefore, the Viterbi decoding algorithm calculates at nT when calculating branch metrics<t<At time (n +8) T, the received signal r (T) and all
Figure FDA0002342776890000023
Of a state
Figure FDA0002342776890000024
Correlation metric for a total of 4 state combinations, i-0 … 3; and the path with the largest correlation metric value is retained, i.e.:
Figure FDA0002342776890000025
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