CN103237001A - Advanced Metering Infrastructure (AMI) system carrier communication module self-adaptive modulation and coding method - Google Patents

Abstract

The invention discloses an advanced metering infrastructure (AMI) system carrier communication module self-adaptive modulation and coding method. The method comprises the following steps of inputting a code stream through a forward error correction coder to a serial-parallel converter; converting the serial data to a parallel code stream through the serial-parallel converter; setting a comparison threshold, and carrying out the threshold comparison between a subcarrier channel estimation value and a threshold comparative value; determining a subchannel modulation mode through a subchannel according to a comparison result; and modulating the subchannel according to the determined subchannel modulation mode. The modulation way of each subchannel is adaptively adjusted according to the signal-to-noise ratio, and corresponding demodulation is carried out on a receiving end; a modulation way with strong robustness is used for the subchannel with severe noise interference so as to improve the interference resistance; a modulation and coding way is determined according to the signal-to-noise ratio of the subchannel, higher transmission power is allocated to the subchannel with a high signal-to-noise ratio, and a modulation way with a high transmission rate is adopted; and the transmission efficiency and the interference resistance of the entire system can be improved.

Description

AMI system carrier communication module adaptive modulation and coding method

Technical field

The present invention relates to modulation and coding method, particularly a kind of AMI system carrier communication module adaptive modulation and coding method.

Background technology

Existing Automatic meter reading system multi-carrier communication module, the realization standard has G3 standard OFDM power-line carrier communication and PRIME standard OFDM power-line carrier communication.PRIME standard physical layer and G3 standard class seemingly, so be the shortcoming that exemplifies example explanation prior art with the G3 standard here.The physical layer of G3 standard adopts the identical modulation system of all subcarriers in transmitting terminal baseband modulation mode, for the serious subchannel of noise jamming, and its error rate height, efficiency of transmission is low.Also need not to judge at receiving terminal, adopt the identical demodulation mode of all subcarriers.Though algorithm operating is simple like this, do not need the pre-estimation of receiving terminal channel conditions, for the serious subchannel of channel disturbance, its information will heavy damage, and perhaps efficiency of transmission is extremely low, and major defect is as follows:

1. its robustness of the subcarrier that noise jamming is bigger will die down, so error of transmission is more serious, efficiency of transmission is low.

2. for the higher subcarrier of signal to noise ratio, adopt the modulation system of low transmission efficient with waste bandwidth.

3. all subcarriers adopt identical modulation and demodulation mode, will reduce efficiency of transmission and the antijamming capability of whole system.

Summary of the invention

The AMI system carrier communication module adaptive modulation and coding method that the purpose of this invention is to provide a kind of efficient and high anti-jamming capacity.

This AMI system carrier communication module adaptive modulation and coding method provided by the invention, this method comprises the steps:

Step 1, input code flow input to serial-parallel converter through forward error correction coder;

Step 2, serial-parallel converter is converted to parallel code stream with serial data;

Step 3 is set up comparison threshold, and sub-carrier channels valuation and this comparison threshold are compared;

Step 4, subchannel is determined the sub-channel modulation pattern according to the comparative result of step 3;

Step 5 is carried out sub-channel modulation according to the sub-channel modulation pattern of determining.

Described sub-carrier channels valuation is used for obtaining the signal to noise ratio of subchannel.

Described comparison threshold comprises-5dB, 0dB, 5dB; When subchannel signal to noise ratio during less than-5dB, determine the modulating mode with ROBO; When subchannel signal to noise ratio during more than or equal to-5dB and less than 0dB, determine the modulation system with DBPSK; When subchannel signal to noise ratio during more than or equal to 0dB and less than 5dB, determine the modulation system with DQPSK; When subchannel signal to noise ratio during more than or equal to 5dB, determine the modulation system with DQPSK.

Constellation point under the described DBPSK pattern distributes, and input bit pattern (X) is mapped as a symbol on the constellation point, and its mapping mode is with existing mapped mode planisphere difference two-phase phase shift, the mapped mode planisphere after being improved; The variation of its output phase is as follows,

When input code flow is 1, its output phase

Output symbol is+1,

When input code flow is-1, its output phase

Output symbol is-1;

Input bit pattern (X) to be carried out mapping code, its input 0 is expressed as-1, input 1 is expressed as+and 1, the modulation formula of then importing bit pattern (X) is: S=cos θ _k+ j * sin θ _k=X.

Constellation point under the described DQPSK pattern distributes, and (X Y) is mapped as a symbol on the constellation point to the input bit pattern, and its mapping mode is with existing mapped mode planisphere difference four phase phase shifts, the mapped mode planisphere after being improved; The variation of its output phase is as follows,

When input code flow is 00, its output phase , output symbol is ,

When input code flow is 01, its output phase

, output symbol is

,

When input code flow is 11, its output phase , output symbol is

,

When input code flow is 10, its output phase

Output symbol is

If initial phase

Signal strength signal intensity is 1; (X Y) carries out mapping code, X input 0 is expressed as+1, and X input 1 is expressed as-1 to the input bit pattern; Y input 0 is expressed as+1, Y input 1 is expressed as-1; (X, modulation formula Y) is: S=cos θ then to import bit pattern _k+ j * sin θ _k=X+j * Y.

Constellation point under the described D8PSK pattern distributes, and (X, Y Z) are mapped as a symbol on the constellation point to the input bit pattern, and its mapping mode is just to have the eight phase phase shifts of mapped mode planisphere difference, the mapped mode planisphere after being improved now; The variation of its output phase is as follows,

When input code flow is 000, its output phase

Output symbol is $(\sqrt{2+\sqrt{2}}+j\×\sqrt{2-\sqrt{2}})/2,$

When input code flow is 001, its output phase

Output symbol is $(\sqrt{2+\sqrt{2}}-j\×\sqrt{2-\sqrt{2}})/2,$

When input code flow is 010, its output phase

Output symbol is $(\sqrt{2-\sqrt{2}}+j\×\sqrt{2+\sqrt{2}})/2,$

When input code flow is 011, its output phase

Output symbol is $(\sqrt{2-\sqrt{2}}-j\×\sqrt{2+\sqrt{2}})/2,$

When input code flow is 100, its output phase

Output symbol is $(-\sqrt{2+\sqrt{2}}+j\×\sqrt{2-\sqrt{2}})/2,$

When input code flow is 101, its output phase Output symbol is $(-\sqrt{2+\sqrt{2}}-j\×\sqrt{2-\sqrt{2}})/2,$

When input code flow is 110, its output phase

Output symbol is $(-\sqrt{2-\sqrt{2}}+j\×\sqrt{2+\sqrt{2}})/2,$

When input code flow is 111, its output phase

Output symbol is $(-\sqrt{2-\sqrt{2}}-j\×\sqrt{2+\sqrt{2}})/2;$

If initial phase

Signal strength signal intensity is 1; When X is 0 and Z when being 0, (X Z) is expressed as+1 the input bit pattern, and when X is 1 and Z when being 1, (X Z) is expressed as-1 to the input bit pattern; Input bit pattern (Y) is 0 to be expressed as π/8, and input bit pattern (Y) is 1 to be expressed as 3 π/8; (modulation formula Z) can be expressed as: S=cos θ for X, Y then to import bit pattern _k+ j * sin θ _k=X * cos (Y)+j * Z * sin (Y).

After the present invention improves, according to signal to noise ratio the modulation system of each subchannel is carried out adaptive adjustment, carry out corresponding demodulation at receiving terminal, solved following problem:

1. adaptive modulation and coding mode adopts the modulation system of strong robustness to the serious subchannel of noise jamming, to strengthen its antijamming capability.

2. determine modulation and coded system according to the signal to noise ratio of subchannel, guarantee that the high subchannel of signal to noise ratio distributes higher transmission power and the modulation system that adopts high transfer rate.

3. adaptive modulation and coding mode has improved efficiency of transmission and the antijamming capability of whole system.

Description of drawings

Fig. 1 is that transmitting terminal of the present invention is formed schematic diagram.

Fig. 2 is that receiving terminal of the present invention is formed schematic diagram.

Fig. 3 is adaptive modulation and coding method block diagram of the present invention.

Fig. 4 is DBPSK pattern planisphere of the present invention.

Fig. 5 is DQPSK pattern planisphere of the present invention.

Fig. 6 is D8PSK pattern planisphere of the present invention.

Embodiment

OFDM power carrier physical layer is directly towards the actual physical medium power line of bearing transfer of data, be the physical connection that a transmission original bit stream is provided for last layer MAC layer on power line, so physical layer is directly faced various interference and the decay of power line.

The invention will be further described below in conjunction with accompanying drawing.

As shown in Figure 1, physical layer transmitting terminal of the present invention comprises forward error controlled encoder and OFDM modulation module.Data to be transmitted is crosstalked earlier, RS coding, and convolutional encoding, interleaving treatment is carried out Adaptive Modulation again and is sent to and do the IFFT conversion.

Part before IFFT is called baseband system.At first the data of input are carried out forward direction error correction and detection (Forward error correction) coding, FEC is made of Reed Solomon coding and convolutional encoding; After the convolutional encoding, it is the interweaving encoding module of a bidimensional.The purpose that interweaves is protection transmission signal, resists two kinds of different interference and decline: a kind of is that burst error is disturbed, and another kind is the frequency deep fade.Data-signal carries out the subcarrier Adaptive Modulation according to test data channel estimating information before after interweaving.

The link baseband architecture of the receiving terminal corresponding with physical layer transmitting terminal of the present invention as shown in Figure 2.This link is just in time opposite with the transmitting terminal link, and the data after the FFT conversion are separated mapping, and the multi-system data bit is become 2 system data code flows, carries out deinterleaving afterwards, Viterbi decoding, and the solution processing of crosstalking obtains the discernible data of MAC layer at last.

The following describes adaptive modulation and coding principle of the present invention.

As shown in Figure 3, the present invention at first carries out serial to parallel conversion to the data after interweaving, and serial data stream is become parallel data flow; According to the descending lead data channel estimation results of previous frame, signal to noise ratio and predefined comparison threshold that subchannel is estimated compare then; Then determine the modulation system of subchannel according to comparative result; Carry out sub-channel modulation at last.

1. the setting of subchannel signal to noise ratio comparison threshold and modulation system are determined

In above-mentioned adaptive modulation and coding process, relatively more crucial is the setting of comparison threshold.General threshold value can be regulated in engineering is used.The comparison threshold that the present invention sets is as shown in table 1.The present invention determines the sub-channel modulation mode according to these comparison thresholds.When subchannel signal to noise ratio during less than-5dB, determine the modulating mode with ROBO; When subchannel signal to noise ratio during more than or equal to-5dB and less than 0dB, determine the modulation system with DBPSK; When subchannel signal to noise ratio during more than or equal to 0dB and less than 5dB, determine the modulation system with DQPSK; When subchannel signal to noise ratio during more than or equal to 5dB, determine the modulation system with DQPSK.

Table 1:

Comparison threshold	<-5dB	〉=-5dB and＜0dB	〉=0dB and＜5dB	≥5dB
					Modulation system	ROBO	DBPSK	DQPSK	D8PSK

2. sub-channel modulation

Subchannel is determined to modulate accordingly after the modulation system and encode.DBPSK, the planisphere of DQPSK and D8PSK is as follows

For simplicity, analyze removal Gray code conversion and absolute code conversion.

The mapping mode of DBPSK pattern as shown in Figure 4, the relation between input code flow and the output phase is as shown in table 2.

Table 2:

If initial phase Signal strength signal intensity is 1, and input bit pattern (X) is carried out mapping code, and its input 0 is expressed as-1, input 1 is expressed as+and 1, the modulation formula of then importing bit pattern (X) is: S=cos θ _k+ j * sin θ _k=X.

At output solution timing, demodulate input code flow according to real part and the imaginary part of S:

bit0=real(S)，

There is certain logical relation in input code flow after the demodulation with the input code flow of reality, and the bit0 that demodulates does not carry out hard decision, directly sends into the Viterbi decoder and carries out soft-decision, can well recover original input code flow.

The mapping mode of DQPSK pattern as shown in Figure 5, the relation between input code flow and the output phase: as shown in table 3.

Table 3:

If initial phase

Signal strength signal intensity is 1; (X Y) carries out mapping code, X input 0 is expressed as+1, and X input 1 is expressed as-1 to the input bit pattern; Y input 0 is expressed as+1, Y input 1 is expressed as-1; (X, modulation formula Y) is: S=cos θ then to import bit pattern _k+ j * sin θ _k=X+j * Y.

At output solution timing, demodulate input code flow according to real part and the imaginary part of S:

bit0=real(S)，

bit1=imag(S)；

There is certain logical relation in input code flow after the demodulation with the input code flow of reality, and the bit0 that demodulates and bit1 do not carry out hard decision, directly send into the Viterbi decoder and carry out soft-decision, can well recover original input code flow.

The mapping mode of D8PSK pattern as shown in Figure 6, the relation between input code flow and the output phase is as shown in table 4.

If initial phase

, signal strength signal intensity is 1; When X is 0 and Z when being 0, (X Z) is expressed as+1 the input bit pattern, and when X is 1 and Z when being 1, (X Z) is expressed as-1 to the input bit pattern; Input bit pattern (Y) is 0 to be expressed as π/8, and input bit pattern (Y) is 1 to be expressed as 3 π/8; (modulation formula Z) can be expressed as: S=cos θ for X, Y then to import bit pattern _k+ j * sin θ _k=X * cos (Y)+j * Z * sin (Y).

At output solution timing, according to real part and the imaginary part demodulation input code flow of S:

bit0=real(S)；

bit1=abs(real(S))-abs(imag(S))；

bit2=imag(S)；

There is certain logical relation in input code flow after the demodulation with the input code flow of reality, and the bit0 that demodulates, bit1 and bit2 all do not carry out hard decision, directly send into the Viterbi decoder and carry out soft-decision, can well recover original input code flow.

Table 4:

The present invention is described further below in conjunction with specific embodiment.

The present invention includes following steps:

Step 1, input code flow be through forward error correction coder, the input value serial-parallel converter;

Step 2, serial-parallel converter is converted to parallel code stream with serial data;

Step 3 is set up comparison threshold, and these comparison threshold values comprise-5dB, 0dB, 5dB;

Step 4 compares the signal to noise ratio of sub-carrier channels valuation gained and the comparison threshold value of step 3; And determine the sub-channel modulation pattern according to this comparative result;

Step 5 is carried out sub-channel modulation according to the sub-channel modulation pattern of determining.

Claims (6)

1. AMI system carrier communication module adaptive modulation and coding method, this method comprises the steps:

Step 1, input code flow input to serial-parallel converter through forward error correction coder;

Step 2, serial-parallel converter is converted to parallel code stream with serial data;

Step 3 is set up comparison threshold, and sub-carrier channels valuation and this comparison threshold are compared;

Step 4, subchannel is determined the sub-channel modulation pattern according to the comparative result of step 3;

Step 5 is carried out sub-channel modulation according to the sub-channel modulation pattern of determining.

2. AMI system carrier communication module adaptive modulation and coding method according to claim 1 is characterized in that, described sub-carrier channels valuation is used for obtaining the signal to noise ratio of subchannel.

3. AMI system carrier communication module adaptive modulation and coding method according to claim 1 is characterized in that, described comparison threshold comprises-and 5dB, 0dB, 5dB; When subchannel signal to noise ratio during less than-5dB, determine the modulating mode with ROBO; When subchannel signal to noise ratio during more than or equal to-5dB and less than 0dB, determine the modulation system with DBPSK; When subchannel signal to noise ratio during more than or equal to 0dB and less than 5dB, determine the modulation system with DQPSK; When subchannel signal to noise ratio during more than or equal to 5dB, determine the modulation system with DQPSK.

4. AMI system carrier communication module adaptive modulation and coding method according to claim 3, it is characterized in that, constellation point under the described DBPSK pattern distributes, input bit pattern (X) is mapped as a symbol on the constellation point, its mapping mode is with existing mapped mode planisphere difference two-phase phase shift, the mapped mode planisphere after being improved; The variation of its output phase is as follows,

When input code flow is 1, its output phase

, output symbol is+1,

When input code flow is-1, its output phase

, output symbol is-1;

Input bit pattern (X) to be carried out mapping code, its input 0 is expressed as-1, input 1 is expressed as+and 1, the modulation formula of then importing bit pattern (X) is: S=cos θ _k+ j * sin θ _k=X.

5. AMI system carrier communication module adaptive modulation and coding method according to claim 3, it is characterized in that, constellation point under the described DQPSK pattern distributes, input bit pattern (X, Y) be mapped as a symbol on the constellation point, its mapping mode is with existing mapped mode planisphere difference four phase phase shifts, the mapped mode planisphere after being improved; The variation of its output phase is as follows,

When input code flow is 00, its output phase

Output symbol is

When input code flow is 01, its output phase

Output symbol is

When input code flow is 11, its output phase

Output symbol is

When input code flow is 10, its output phase

Output symbol is

If initial phase

Signal strength signal intensity is 1; (X Y) carries out mapping code, X input 0 is expressed as+1, and X input 1 is expressed as-1 to the input bit pattern; Y input 0 is expressed as+1, Y input 1 is expressed as-1; (X, modulation formula Y) is: S=cos θ then to import bit pattern _k+ j * sin θ _k=X+j * Y.

6. AMI system carrier communication module adaptive modulation and coding method according to claim 3, it is characterized in that, constellation point under the described D8PSK pattern distributes, input bit pattern (X, Y, Z) be mapped as a symbol on the constellation point, its mapping mode is just to have the eight phase phase shifts of mapped mode planisphere difference, the mapped mode planisphere after being improved now; The variation of its output phase is as follows,

When input code flow is 000, its output phase Output symbol is $(\sqrt{2+\sqrt{2}}+j\×\sqrt{2-\sqrt{2}})/2,$

When input code flow is 001, its output phase

Output symbol is $(\sqrt{2+\sqrt{2}}-j\×\sqrt{2-\sqrt{2}})/2,$

When input code flow is 010, its output phase

Output symbol is $(\sqrt{2-\sqrt{2}}+j\×\sqrt{2+\sqrt{2}})/2,$

When input code flow is 011, its output phase

Output symbol is $(\sqrt{2-\sqrt{2}}-j\×\sqrt{2+\sqrt{2}})/2,$

When input code flow is 100, its output phase

Output symbol is $(-\sqrt{2+\sqrt{2}}+j\×\sqrt{2-\sqrt{2}})/2,$

When input code flow is 101, its output phase Output symbol is $(-\sqrt{2+\sqrt{2}}-j\×\sqrt{2-\sqrt{2}})/2,$

When input code flow is 110, its output phase

Output symbol is $(-\sqrt{2-\sqrt{2}}+j\×\sqrt{2+\sqrt{2}})/2,$

When input code flow is 111, its output phase

Output symbol is $(-\sqrt{2-\sqrt{2}}-j\×\sqrt{2+\sqrt{2}})/2;$

If initial phase

Signal strength signal intensity is 1; When X is 0 and Z when being 0, (X Z) is expressed as+1 the input bit pattern, and when X is 1 and Z when being 1, (X Z) is expressed as-1 to the input bit pattern; Input bit pattern (Y) is 0 to be expressed as π/8, and input bit pattern (Y) is 1 to be expressed as 3 π/8; (modulation formula Z) can be expressed as: S=cos θ for X, Y then to import bit pattern _k+ j * sin θ _k=X * cos (Y)+j * Z * sin (Y).

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