CN100563144C - A kind of demodulation method of multi-user mapping signal - Google Patents

Abstract

The invention discloses a kind of demodulation method of multi-user mapping signal.The process of this method comprises: each user's that transmitting terminal comprises in multi-user's mapping receiving terminal sends modulation parameter information and multi-user mapping signal, and receiving terminal generates multi-user's mapped constellation table according to the multiple user signals modulator approach of modulation parameter information that receives and preservation in advance; Each user's who comprises in the multi-user mapping receiving terminal determines and the immediate constellation point of multi-user mapping signal that receives according to multi-user's mapped constellation table, and from choose the information bit that self takies the information bit of definite constellation point correspondence.This method of the present invention realizes simple, can be applied in the cellular system based on OFDM modulation and multiuser multiplexing, for multi-user's mapping provides a kind of general demodulation method.

Description

A kind of demodulation method of multi-user mapping signal

Technical field

The present invention relates to the signal demodulating method in the cellular communication system, refer to a kind of demodulation method of multi-user mapping signal especially.

Background technology

The down link of cellular communication system adopts the broadcast channel model of point-to-multipoint, and a plurality of users' signal is in transmitting terminal multiplexing back emission, and this multiplexing general employing orthogonal multiplex realizes, such as the time-frequency multiplex technique etc.But the spectrum efficiency of orthogonal multiplex system is subjected to low signal-to-noise ratio user's influence easily, and the low signal-to-noise ratio number of users in the system is many more, or the data rate of low signal-to-noise ratio customer requirements is high more, and the spectrum efficiency of whole system is just low more.

In order to overcome the problems referred to above, a kind of nonopiate multiplex technique is proposed again, promptly two or more users' information bit is mapped on the same data symbol and sends, to improve the spectrum efficiency of orthogonal multiplex system at transmitting terminal.

In the prior art, at transmitting terminal a plurality of users' information bit being mapped to the method that same data symbol sends has multiple.Shown in Figure 1 is exactly wherein a kind of method, and this method realizes that by stack the multi-user shines upon, so be called multi-user's mapping algorithm that superposes.Suppose to have two users' the information bit need be by multi-user's mapping method that superposes, be mapped on the same data symbol, and among these two users, user 1 information bit has two, user 2 information bit has one, and then this data symbol has three bit c1, c2 and c3.Suppose that front two c1 and c2 are user 1 information bits, the 3rd c3 is user 2 information bit, and method detailed process then shown in Figure 1 is as follows:

At first, the information bit with user 1 and user 2 carries out independent mapping according to its modulation algorithm separately.Wherein, what user 1 adopted is the QPSK modulator approach, and the planisphere of QPSK modulation is shown in Fig. 2 a, and transverse axis is that real part, the longitudinal axis are on the complex plane of imaginary part four constellation point to be arranged, respectively the information bit 00,10,11 and 01 of respective user 1.What user 2 adopted is the BPSK modulator approach, and the planisphere of BPSK modulation has two constellation point shown in Fig. 2 b, respectively the information bit 0 and 1 of respective user 2.

Then, adopt amplitude d1 and d2 to amplify respectively through the signal that independent mapping back obtains user 1 and user 2, again amplifying signal is superimposed as a data symbol and sends.Wherein, amplitude d1 and d2 are respectively user 1 and user's 2 signal enlargement ranges.

In this step, the data symbol that the stack back obtains has three bits, and corresponding planisphere has eight constellation point as shown in Figure 3, difference corresponding 000,001,100,101,111,110,011 and 010.

Among the application, the information bit of supposing user 1 is 10, and user 2 information bit is 1, and after the process multi-user superposeed and shines upon, what transmitting terminal sent was the data symbol of constellation point 101 correspondences.User 1 and user's 2 receiving terminal demodulates information bit separately respectively after receiving the data symbol that transmitting terminal sends.

Wherein, to demodulate user 1 the method for information bit as follows for user 1 receiving terminal: the planisphere of preserving user 1 at user 1 receiving terminal in advance; After user 1 receiving terminal receives data symbol, search the constellation point of described received signal most probable correspondence on planisphere, then the information bit of this constellation point correspondence is exactly the information bit that user 1 is sent.

In this method, receiving terminal employing maximal possibility estimation algorithm is searched for and the nearest constellation point of received signal in user 1 planisphere, thereby determines the constellation point of most probable correspondence, and this process is used as user 2 signal as noise and is handled.

The method of information bit that user 2 receiving terminal demodulates user 2 is as follows:

At first, user 2 receiving terminal is searched the constellation point of described received signal most probable correspondence according to the user's 1 who preserves in advance planisphere on user 1 planisphere, determine user 1 transmission signal according to the information bit of constellation point correspondence.

Then, in received signal, deduct user 1 transmission signal, to obtain user 2 transmission signal.

At last, user 2 receiving terminal is searched the constellation point of user 2 transmission signal most probable correspondence according to the user's 2 who preserves in advance planisphere on user 2 planisphere, and then the information bit of this constellation point correspondence is exactly the information bit that user 2 is sent.

Because the signal that each user's receiving terminal receives all is to send after the transmitting terminal process multi-user mapping, so the received signal of receiving terminal is called multi-user mapping signal.

Two above users also can adopt multi-user's mapping algorithm that superposes to modulate simultaneously, and this method and two users' modulator approach is similar.Similarly, two above users' demodulation method is also similar with two users' demodulation method.

When adopting stacking method to realize that the multi-user is shone upon, each user has self independently planisphere, so receiving terminal can demodulate the self information bit by above-mentioned demodulation method from received signal.But there is following shortcoming in this demodulation method:

(1) at user 2 receiving terminal, to obtain by demodulation earlier user 1 transmission signal, could utilize received signal and user's 1 transmission signal to obtain the information bit that user 2 is sent, i.e. user 1 and user's 2 signal demodulation has correlation.If mistake appears in user 1 demodulation, user 2 signal demodulation also can make a mistake, thereby reduces the accuracy of signal demodulation.

(2) separate timing to received signal, user 1 needs to adopt different demodulation methods with user 2, causes the receiving algorithm disunity of different user.

In addition, for other multi-user's mapping method, if there is not independently planisphere in unique user, this method will be no longer suitable.

Summary of the invention

In view of this, main purpose of the present invention is to provide a kind of demodulation method of multi-user mapping signal, makes receiving terminal can adopt unification, method in common to demodulate self signal from multi-user mapping signal, improves the accuracy of signal demodulation.

For achieving the above object, technical scheme of the present invention specifically is achieved in that

A kind of demodulation method of multi-user mapping signal is characterized in that, this method may further comprise the steps:

Each user's that a, transmitting terminal comprise in multi-user's mapping receiving terminal sends modulation parameter information and multi-user mapping signal, and receiving terminal generates multi-user's mapped constellation table according to the multiple user signals modulator approach of modulation parameter information that receives and preservation in advance;

Each user's who comprises in b, the multi-user mapping receiving terminal determines and the immediate constellation point of multi-user mapping signal that receives according to multi-user's mapped constellation table, and from choose the information bit that self takies the information bit of definite constellation point correspondence,

Wherein, described modulation parameter information comprises: the bit of each CU that comprises in multi-user's mapping and each user's signal enlargement range, and the method that the described receiving terminal of step a generates multi-user's mapped constellation table is:

A1, receiving terminal are determined the number of constellation points on the planisphere of multiple user signals modulator approach correspondence according to the bit of all CUs;

A2, receiving terminal are according to multiple user signals modulator approach and each user's signal enlargement range, determine the position of each constellation point on planisphere, and calculate the real part and the imaginary part coordinate figure of each constellation point, all coordinate figures are saved as multi-user's mapped constellation table

The method that the described receiving terminal of step b is chosen the information bit that self takies is: receiving terminal is preserved the corresponding relation of Customs Assigned Number and the shared bit of this user in advance, and after definite and the immediate constellation point of multi-user mapping signal, search the bit of the Customs Assigned Number correspondence of self, from the information bit of described constellation point correspondence, select the bit of self.

Described multiple user signals modulator approach is multi-user's mapping algorithm that superposes.

Described multiple user signals modulator approach is the multi-user association mapping algorithm.

Further, the method for the described immediate constellation point of multi-user mapping signal of determining and receiving of step b is: the square distance value of all constellation point in the multi-user mapping signal that calculating receives and the multi-user's mapped constellation table; Select the constellation point of the minimum value correspondence in all square distance values.

As seen from the above technical solution, in the demodulation method of this multi-user mapping signal of the present invention, each user's that multi-user's mapping comprises receiving terminal will be according to multi-user's modulation algorithm of preserving in advance, and the modulation parameter information of transmitting terminal transmission, determine multi-user's mapped constellation figure, select the nearest constellation point of constellation map range received signal according to maximum-likelihood criterion then, obtain the information bit of this constellation point correspondence, and from above-mentioned information bit, take out the bit of self.The independence of this method restituted signal is strong, can not influence the correctness of other user's demodulation because of certain user's signal demodulation mistake, thereby improves the accuracy of signal demodulation.

In addition, the method that adopts when restituted signal of each user's receiving terminal all is identical.The user can directly obtain the information bit of self correspondence after obtaining restituted signal.And, this method needn't use each user self independently planisphere carry out demodulation, so highly versatile can be widely used in the cellular system based on OFDM modulation and multiuser multiplexing.

Description of drawings

Fig. 1 is the superpose realization block diagram of mapping algorithm of multi-user in the prior art;

Fig. 2 a is the planisphere of QPSK modulator approach in the prior art;

Fig. 2 b is the planisphere of BPSK modulator approach in the prior art;

Fig. 3 realizes the planisphere of modulation for two users in the prior art adopt multi-user's mapping algorithm that superposes;

Fig. 4 is the demodulation method flow chart of first embodiment of the invention;

Fig. 5 is the realization block diagram of multi-user association mapping algorithm in the second embodiment of the invention;

Fig. 6 adopts the multi-user association mapping algorithm to realize the planisphere of modulation for two users in the second embodiment of the invention.

Embodiment

For making purpose of the present invention, technical scheme and advantage clearer, below with reference to the accompanying drawing embodiment that develops simultaneously, the present invention is described in more detail.

Embodiment one,

In the present embodiment, transmitting terminal adopts stacking method to carry out multi-user's mapping, and each user's who comprises in multi-user's mapping receiving terminal is preserved multi-user's superposition modulated algorithm in advance, is used to carry out the demodulation of received signal.Described multi-user's superposition modulated algorithm refers to the algorithm that uses in the modulated process of Fig. 1.

Supposing to comprise two users in the multi-user mapping, is respectively user 1 and user 2, concrete demodulating process as shown in Figure 4:

Step 401, each user's receiving terminal generates multi-user's mapped constellation table of transmitting terminal according to multi-user's superposition modulated algorithm of modulation parameter information that receives and preservation in advance after obtaining the modulation parameter information of transmitting terminal by the control channel transmission.

In this step, the modulation parameter information that transmitting terminal sends comprises: the bit b2 that the bit b1 that user 1 takies, user 2 take, and user 1 and user's 2 signal enlargement range d1 and d2.

Receiving terminal is as follows according to the detailed process of multi-user's superposition modulated algorithm and above-mentioned modulation parameter information generation multi-user mapped constellation table:

1) bit that takies according to user 1 and user 2 is determined to count number of constellation points=2 on the planisphere of multi-user's superposition modulated algorithm correspondence ^B1+b2During such as b1=2, b2=1, described planisphere has 2 ³Individual constellation point.

2) according to multi-user's superposition modulated algorithm and user 1, user's 2 signal enlargement range d1, d2, determine the position of each constellation point on planisphere, and calculate the real part and the imaginary part coordinate figure of each constellation point, be kept in multi-user's mapped constellation table.

Shown in the table one is multi-user's mapped constellation table of each constellation point coordinate figure in the record planisphere shown in Figure 3.

Label	Bit words	Real part	Imaginary part
				s 0	000	(d 1+d 2)/2	d 1/2
s 1	001	(d 1-d 2)/2	d 1/2
				s 2	010	(d 1+d 2)/2	-d 1/2
s 3	011	(d 1-d 2)/2	-d 1/2
				s 4	100	-(d 1-d 2)/2	d 1/2
s 5	101	-(d 1+d 2)/2	d 1/2
				s 6	110	-(d 1-d 2)/2	-d 1/2
s 7	111	-(d 1+d 2)/2	-d 1/2

Table one

Step 402, each user's receiving terminal receives input signal y _k ⁽ⁱ⁾After, calculate apart from input signal y according to multi-user's mapped constellation table _k ⁽ⁱ⁾Constellation point with least square Euclidean distance

And find this constellation point

Pairing information bit.

In ofdm system, need carry out equilibrium to baseband receiving signals according to formula (1), to obtain input signal y _k ⁽ⁱ⁾

$y_k^{\left(i\right)}={\tilde{y}}_k^{\left(i\right)}/h_k^{\left(i\right)}---\left(1\right)$

Wherein,

Be the baseband receiving signals of i user on k carrier wave, h _k ⁽ⁱ⁾Be the channel coefficients of this user on current carrier wave, i=1,2 represent to participate in two multiplexing users respectively.For ease of explanation, can be with input signal y _k ⁽ⁱ⁾Brief note is y after omitting subscript k ⁽ⁱ⁾

Because the signal after the equilibrium only is subjected to the interference of additive noise, so input signal y ⁽ⁱ⁾Can be expressed as y ⁽ⁱ⁾=s+v ⁽ⁱ⁾, i=1,2.Wherein, s represents to shine upon the actual data symbol that sends in back through the multi-user of transmitting terminal, and it receives the user to two is identical; v ⁽ⁱ⁾Represent the additive white Gaussian noise that i user receives.

In this step, can calculate constellation point according to formula (2) with least square Euclidean distance

${\hat{s}}^{\left(i\right)}=\arg \underset{\tilde{s}\∈S}{\min }{|y^{\left(i\right)}-\tilde{s}|}^2,i=\mathrm{1,2}---\left(2\right)$

Wherein, y ⁽¹⁾Expression user's 1 received signal; S represents the set of all constellation point, i.e. S={s ₀, s ₁..., s ₇, then ${\hat{s}}^{\left(i\right)}=\arg \underset{\tilde{s}\∈S}{\min }{|y^{\left(i\right)}-\tilde{s}|}^2$ Expression user's 1 receiving terminal calculates the square distance value of received signal and all constellation point respectively, and chooses the constellation point conduct of the minimum value correspondence in the above-mentioned square distance value Suppose ${\hat{s}}^{\left(1\right)}=s_3,$ Find out that from table one corresponding bit words is 011, comprise user 1 information bit and user 2 information bit in this bit words.

Similarly, y ⁽²⁾The signal that expression user 2 receives;

Be illustrated in the data symbol that user 2 receiving terminal demodulates, comprise user 1 information bit and user 2 information bit in this symbol.

Can also calculate constellation point according to formula (3) with least square Euclidean distance

A be one greater than 0 coefficient.

${\hat{s}}^{\left(i\right)}=\arg \underset{\tilde{s}\∈S}{\min }a\×{|y^{\left(i\right)}-\tilde{s}|}^2,a>0---\left(3\right)$

Step 403, each user's receiving terminal is selected the bit of self according to the Customs Assigned Number of self preserving and the corresponding relation of the shared bit of this user from the information bit that step 402 demodulates.

In this step, the corresponding relation of Customs Assigned Number and the shared bit of this user can save as bit map, and then receiving terminal is by searching the bit that bit map is selected self.

Suppose that the bit words that obtains after user's 1 demodulation is 011, searching what determine that user 1 takies after the bit map is preceding two bits, will be abandoned by user 1 so user 1 effective information bit is 01, the three bit 1.

Similarly, user 2 obtains bit words 011 through demodulation, is the 3rd bit by what search that bit map determines that user 2 takies, so user 2 effective information bit is 1, preceding two bits 01 will be abandoned by user 2.

If comprise two above users in the multi-user of the transmitting terminal mapping, transmitting terminal comprises by the modulation parameter information that control channel sends to each user: the bit of each CU and each user's signal enlargement range.

Embodiment two,

The applicant has also proposed a kind of method of multi-user association mapping, and described multi-user association mapping method is united mapping to two or more users' information bit as shown in Figure 5, and output is through the data symbol of the planisphere correspondence of optimal design.With the multi-user superpose mapping method different be that above-mentioned multi-user association mapping method carries out the integral body mapping with two or more users' information bit, go on foot map operation so only need to carry out one.

Suppose to comprise two users in the multi-user association mapping, user 1 has two information bits, user 2 has an information bit, then adopt planisphere that the multi-user association mapping algorithm generates as shown in Figure 6, comprise eight constellation point, be respectively 000,001,100,101,111,110,011 and 010.

Planisphere shown in Figure 6 designs according to following rule:

1) this planisphere is an octagon, and the distance between each constellation point and adjacent two constellation point is respectively d1 and d2.For example, the distance between constellation point 000 and the constellation point 100 is d1, and the distance between constellation point 000 and the constellation point 001 is d2.

2) all constellation point are 1 to the square distance value sum of initial point divided by the merchant of constellation point number.

The demodulating process and the embodiment one of the received signal of employing multi-user association mapping are similar.

At first, each user's of comprising in the multi-user mapping receiving terminal preserves the multi-user association mapping algorithm in advance, receiving terminal can be according to modulation parameter information and the multi-user association mapping algorithm of preserving in advance generation multi-user's mapped constellation table as shown in Table 2.

The method that adopts among the method for above-mentioned generation multi-user mapped constellation table and the embodiment one is similar, does not give unnecessary details herein.

Table two

Then, find out the constellation point that has the least square Euclidean distance with received signal, determine the pairing information bit of each user according to multi-user's mapped constellation table.

Suppose that received signal is positioned at an A in planisphere shown in Figure 6, then the constellation point that has a least square Euclidean distance with an A is 001.

When adopting the multi-user association mapping algorithm that a plurality of users' information bit is shone upon simultaneously, there is not independently planisphere in unique user.Demodulation method of the present invention does not need to use the independent planisphere of unique user, so can carry out demodulation to the signal that the multi-user association mapping obtains.

By the above embodiments as seen, the demodulation method of this multi-user mapping signal of the present invention needn't use independently planisphere of each user self, so highly versatile.In addition, the method that each user adopts when restituted signal is all identical, can not influence the correctness of other user's demodulation because of certain user's signal demodulation mistake.The user can directly obtain the information bit of self correspondence after obtaining restituted signal, so that this method realizes is simple, can be applied in the cellular system based on OFDM modulation and multiuser multiplexing, and shining upon for the multi-user provides a kind of general demodulation method.

Claims (4)

1, a kind of demodulation method of multi-user mapping signal is characterized in that, this method may further comprise the steps:

Each user's that a, transmitting terminal comprise in multi-user's mapping receiving terminal sends modulation parameter information and multi-user mapping signal, and receiving terminal generates multi-user's mapped constellation table according to the multiple user signals modulator approach of modulation parameter information that receives and preservation in advance;

Each user's who comprises in b, the multi-user mapping receiving terminal determines and the immediate constellation point of multi-user mapping signal that receives according to multi-user's mapped constellation table, and from choose the information bit that self takies the information bit of definite constellation point correspondence,

Wherein, described modulation parameter information comprises: the bit of each CU that comprises in multi-user's mapping and each user's signal enlargement range, and the method that the described receiving terminal of step a generates multi-user's mapped constellation table is:

A1, receiving terminal are determined the number of constellation points on the planisphere of multiple user signals modulator approach correspondence according to the bit of all CUs;

A2, receiving terminal are according to multiple user signals modulator approach and each user's signal enlargement range, determine the position of each constellation point on planisphere, and calculate the real part and the imaginary part coordinate figure of each constellation point, all coordinate figures are saved as multi-user's mapped constellation table

The method that the described receiving terminal of step b is chosen the information bit that self takies is: receiving terminal is preserved the corresponding relation of Customs Assigned Number and the shared bit of this user in advance, and after definite and the immediate constellation point of multi-user mapping signal, search the bit of the Customs Assigned Number correspondence of self, from the information bit of described constellation point correspondence, select the bit of self.

2, method according to claim 1 is characterized in that, described multiple user signals modulator approach is multi-user's mapping algorithm that superposes.

3, method according to claim 1 is characterized in that, described multiple user signals modulator approach is the multi-user association mapping algorithm.

4, method according to claim 1, it is characterized in that the method for the described immediate constellation point of multi-user mapping signal of determining and receiving of step b is: the square distance value of all constellation point in the multi-user mapping signal that calculating receives and the multi-user's mapped constellation table; Select the constellation point of the minimum value correspondence in all square distance values.

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