CN105743617A - Hybrid spatial modulation method based on Euclidean distance and antenna selection - Google Patents

Abstract

The invention discloses a hybrid spatial modulation method based on Euclidean distance and antenna selection, and the method comprises the steps: supposing that a transmitting end is provided with Ns transmitting antennas, selecting Nt transmitting antennas to transmit data, and enabling a receiving end to have Nr receiving antennas, wherein the receiving end employs a maximum likelihood method to detect a received symbol y; enabling an antenna selection method based on system capacity or an antenna selection method based on Euclidean distance to be applied to an ESM, so as to increase the minimum Euclidean distance; enabling the receiving end to detect the state of a channel before each transmission of information, calculating the minimum square Euclidean distances when the SM and ESM schemes are used for data transmission, and selecting the scheme with the larger minimum square Euclidean distance to actually transmit the symbol. The method provided by the invention enables the number of transmitting antennas not to be limited through the absorption of the advantages of SM and ESM, and avoids the interference with the antennas. In particular, a channel adaptive method can enable a system to adapt to the continuous change of a channel better.

Description

Blending space modulator approach based on Euclidean distance and sky line options

Technical field

The invention belongs to radio communication modulation and coding field, particularly to blending space modulator approach based on Euclidean distance and sky line options in a kind of mimo system.

Background technology

Spatial modulation (SM) technology, as a kind of novel MIMO technology, has just become one of hot research field since proposing.In Traditional Space modulation technique, arbitrary time slot only has that transmitting antenna is in running order transmits data, all the other transmitting antennas are mourned in silence, and an information bit part for transmission is mapped on traditional digital modulation planisphere, and remaining bit is mapped in the space dimension that antenna serial number generates.Thus, SM completely avoid interchannel interference, it is not necessary to synchronicity requirement higher between transmitting antenna, and arbitrary time slot has only to a radio frequency link, greatly reduces system cost.

But traditional SM technology must assure that transmitting antenna number is the power side of 2, which results in when system spectral efficiency is higher, transmitting antenna number is required also very big.In order to solve problem above, J.M.Luna-Rivera et al. proposes the space-modulation technique (ExtendedSpatialModulation is called for short ESM) of a kind of extension, this technology allows all antennas to send data at same time slot, make between transmission antenna sum and spectrum efficiency linear, greatly reduce the requirement to transmission antenna number.But simultaneously as many antennas send data simultaneously, the interference between antenna will certainly be caused.

Summary of the invention

The purpose of the present invention is contemplated to solve the problems referred to above, propose a kind of blending space modulator approach based on Euclidean distance and sky line options, the method combines SM and avoids inter-antenna interference and ESM transmission antenna number can be the advantage of arbitrary integer and can better adapt to being continually changing of channel, reduces the bit error rate of ADAPTIVE MIXED spatial modulation system further.

To achieve these goals, the present invention adopts the following technical scheme that

A kind of blending space modulator approach based on Euclidean distance and sky line options, comprises the following steps:

(1) transmitting terminal always total N is assumed_sRoot transmission antenna, therefrom selects N_tRoot sends data, and receiving terminal has N_rRoot reception antenna, then at receiving terminal, receive signal y=Hx+n, wherein,Represent and send symbol,It it is independent identically distributed standard gaussian channelIt is obeyThe white Gaussian noise of distribution；

(2) receiving terminal adopts method of maximum likelihood that the symbol y received is detected, it is judged that the transmission symbol of its correspondence

(3) the sky line options HSM-COAS method based on power system capacity or the sky line options HSM-EDAS method based on Euclidean distance are applied in ESM, to increase its minimum euclidean distance；

(4) before each information sends, receiving terminal detection channel status, calculating the least square Euclidean distance during ESM scheme transmission data adopted in SM and step (3) respectively, the scheme selecting least square Euclidean distance bigger sends symbol for reality.

In described step (1), the method for receiving terminal employing method of maximum likelihood detection is:

$\hat{x}=\underset{x_i\∈\mathrm{\Λ}}{\arg \max }{p}_Y\left(y\right|x_i,H)=\underset{x_i\∈\mathrm{\Λ}}{\arg \min }{\left|\right|y-{\mathrm{Hx}}_i\left|\right|}_F^2$

Wherein,Represent the transmission symbol detected；Λ is the set likely sending symbol；x_iRepresent certain possible transmission symbol,m_bRepresent spectrum efficiency；p_Y(y|x_i, H) and represent the conditional probability density function of receiving terminal.

Described step (2), is applied in ESM by the sky line options HSM-COAS method based on power system capacity method particularly includes:

For given channel status and signal to noise ratio snr, the capacity of ESM is represented by

C_ESM≥γ

Wherein

$\mathrm{\γ}=\frac{1}{N_t}\underset{p=1}{\overset{N_t}{\mathrm{\Σ}}}{\log }_2(1+\frac{E_s}{N_0}{\left|\right|h_p^{\left(l\right)}\left|\right|}_F^2)$

E_sRepresent that ESM sends the mean power of symbol, N₀Represent noise power, N_tRepresent transmission antenna number,Represent and l, two norms of channel H pth column element are combined for given transmission antenna；

By the N from channel H_sRow are selected the front N that two norms are maximum_tThe antenna serial number that row are corresponding increases the value of γ as optimal antenna combination, then the optimal antenna selected combination is returned to transmitting terminal.

Described optimal antenna combination table is shown asMeet

${\left|\right|h_{p1}\left|\right|}_F^2>{\left|\right|h_{p2}\left|\right|}_F^2>...>{\left|\right|h_{p_{N_t}}\left|\right|}_F^2>...>{\left|\right|h_{p_{N_s}}\left|\right|}_F^2$

Wherein,Represent two norms of channel H the i-th column element.

When spectrum efficiency is certain, from each channel H, select the front N that two norms are maximum_tThe N that row composition is new_rRow N_tThe sub-channel of rowThe minimum euclidean distance of ESM and the minimum euclidean distance of SM is calculated respectively according to this channel.

Sky line options HSM-EDAS method based on Euclidean distance is applied in ESM by described step (2) method particularly includes:

Selection criterion based on the sky line options HSM-EDAS of Euclidean distance is as follows:

$l_{\mathrm{selected}}=\underset{l\∈\mathrm{\Γ}}{\arg \max }\left\{\underset{x_i\≠x_j\∈\mathrm{\Λ}}{\min }{\left|\right|H^{\left(l\right)}(x_i-x_j)\left|\right|}_F^2\right\}$

Wherein, Γ represents all possible $n=\left(\begin{array}{c}{N}_s\\ N_t\end{array}\right)$ The set of individual antenna combination, Λ represents that all possible ESM sends the set of symbol, x_i, x_jRepresent and send symbol,Represent N corresponding to antenna combination l_tArrange sub-channel；The optimal antenna selected combination is returned to transmitting terminal.

To each channel status, the optimal antenna combination according to selecting obtains the sub-channel that optimal antenna combination is correspondingThe minimum euclidean distance of ESM and the minimum euclidean distance of SM is calculated respectively according to this channel.

The computational methods of described minimum euclidean distance are:

$d_{\min }^2\left(H\right)=\underset{\underset{x_i\≠x_j}{x_i,x_j\∈\mathrm{\Λ}}}{\arg \min }{\left|\right|H(x_i-x_j)\left|\right|}_F^2$

Wherein, x_i, x_jRepresenting and send symbol, Λ represents that all possible ESM sends the set of symbol,It it is independent identically distributed standard gaussian channel

The invention has the beneficial effects as follows:

In traditional space-modulation technique (SM), spectrum efficiency is expressed as η_SM=log₂N_t+log₂M, wherein Nt represents transmission antenna number, and M represents order of modulation, the visible Nt of above formula must be the power exponent power of 2 and activate an antenna every time only and avoid inter-antenna interference.And its spectrum efficiency is expressed as in the space-modulation technique (ESM) of extensionWith the linear growth of transmission antenna number and every time can by many antenna transmission symbols.The blending space modulator approach (being called for short HSM) that the present invention proposes the as can be seen here advantage by absorbing SM and ESM, making the interference that transmission antenna number is no longer restricted and avoids between antenna, especially the method for its channel self-adapting enables the system to better adapt to being continually changing of channel.

It addition, ADAPTIVE MIXED modulating method is combined by the present invention with sky line options, reduce the bit error rate of ADAPTIVE MIXED spatial modulation system further.

Accompanying drawing explanation

Fig. 1 is the system block diagram of the adaptive space modulation scheme that the present invention proposes；

Fig. 2 is spectrum efficiency is 3bit/s/Hz, from 4 transmission antennas select 2 to be transmitted time difference mixing spatial modulation scheme and tradition SM, ESM scheme comparison；

Fig. 3 is spectrum efficiency is 6bit/s/Hz, from 6 transmission antennas select 4 to be transmitted time difference mixing spatial modulation scheme and tradition SM, ESM scheme comparison.

Detailed description of the invention:

Below in conjunction with accompanying drawing, the present invention will be further described with embodiment:

Assume that transmitting terminal adopts N_tRoot transmission antenna, receiving terminal has N_rRoot reception antenna, system model is as it is shown in figure 1, b is the information bit sent, and a portion is mapped on traditional digital modulation planisphere, and remaining bit is mapped in the space dimension that antenna serial number generates.Because mono-time slot of SM only selects an antenna to send data, then sending only one of which element in symbol x is non-zero.And ESM allows many antennas to send data, therefore it sends more than one element non-zero in symbol.SM, ESM information bit and mapping relations such as table 2 sending symbol, its spectrum efficiency is 3bit/s/Hz.

At receiving terminal, receive signal y and be represented by

Y=Hx+n (1)

Represent and send symbol,It it is independent identically distributed standard gaussian channelIt is obeyThe white Gaussian noise of distribution.

Receiving terminal adopts method of maximum likelihood detection that the symbol y received is detected, it is judged that the transmission symbol of its correspondenceBy compare x withDraw the bit error rate and corresponding bit error rate, and bit error rate determines reliability and the systematic function of transmission.

$\hat{x}=\underset{x_i\∈\mathrm{\Λ}}{\arg \max }{p}_Y\left(y\right|x_i,H)=\underset{x_i\∈\mathrm{\Λ}}{\arg \min }{\left|\right|y-{\mathrm{Hx}}_i\left|\right|}_F^2---\left(2\right)$

Representing the transmission symbol detected, Λ is the set likely sending symbol,m^bRepresent spectrum efficiency) represent certain possible transmission symbol, p_Y(y|x_i, H) and represent the conditional probability density function of receiving terminal.

When signal to noise ratio is higher, the pair-wise error probability of Maximum Likelihood Detection is represented by

$P(x_i\→x_j|H)\≈\mathrm{\λ}\·Q\left(\sqrt{\frac{1}{{2N}_0}{d}_{\min }^2\left(H\right)}\right)---\left(3\right)$

P(x_i→x_j| H) represent x_iIt is mistaken for x_jConditional probability, whereinλ is the number of adjacent space constellation point.

By formula (3) it can be seen that pair-wise error probability and least square Euclidean distanceIt is inversely proportional to.Therefore, it can reduce receiving terminal probability of miscarriage of justice by the method for increase minimum euclidean distance.

Least square Euclidean distanceIt is defined as

$d_{\min }^2\left(H\right)=\underset{\underset{x_i\≠x_j}{x_i,x_j\∈\mathrm{\Λ}}}{\arg \min }{\left|\right|H(x_i-x_j)\left|\right|}_F^2---\left(4\right)$

By formula (4) it can be seen that system minimum euclidean distance is together decided on by channel status H and transmission symbol x.When channel status and spectrum efficiency one timing, owing to the transmission symbol of SM and ESM two schemes is different, its minimum euclidean distance is also different, and the scheme that therefore can pass through to switch between two kinds of delivery plans of SM and ESM reduces system bit error rate.

Assume that channel variation is slow and spectrum efficiency is certain, the message transmitting procedure of the blending space modulator approach that the present invention proposes is: before each information sends, receiving terminal detection channel status, calculate least square Euclidean distance when adopting SM and ESM scheme transmission data respectively according to formula (4), the scheme selecting least square Euclidean distance bigger sends symbol for reality.It is formulated as

$\mathrm{HSM}=\left\{\begin{array}{c}\mathrm{SM},d_{\min ,\mathrm{SM}}^2\left(H\right)>d_{\min ,\mathrm{ESM}}^2\left(H\right)\\ \mathrm{ESM},d_{\min ,\mathrm{SM}}^2\left(H\right)\≤d_{\min ,\mathrm{ESM}}^2\left(H\right)\end{array}\right.---\left(5\right)$

By calculating it can be seen that the minimum euclidean distance of ESM is generally below SM, therefore sky line options is applied in ESM by the present invention, increases its minimum euclidean distance with this, thus reducing the bit error rate of whole HSM system.

1. based on the sky line options (HSM-EDAS) of Euclidean distance

Assume transmitting terminal always total N_sRoot transmission antenna, therefrom selects N_tRoot sends data.Then selection criterion is expressed as

$l_{\mathrm{selected}}=\underset{l\∈\mathrm{\Γ}}{\arg \max }\left\{\underset{x_i\≠x_j\∈\mathrm{\Λ}}{\min }{\left|\right|H^{\left(l\right)}(x_i-x_j)\left|\right|}_F^2\right\}---\left(6\right)$

Γ represents all possible $n=\left(\begin{array}{c}{N}_s\\ N_t\end{array}\right)$ The set of individual antenna combination, Λ represents that all possible ESM sends the set of symbol, x_i, x_jRepresent and send symbol,Represent N corresponding to antenna combination l_tArrange sub-channel.

Based on the principle of above ESM days line options, HSM-EDAS can be summarized as: to each channel status, combines corresponding sub-channel according to the optimal antenna combination that (6) are selected with optimal antennaThe Euclidean distance formula (4) that this sub-channel enters ESM calculates its minimum euclidean distance, calculates SM scheme minimum euclidean distance further according to formula (4), compares and show that the maximum scheme of minimum euclidean distance is for sending data.

2. based on the sky line options (HSM-COAS) of power system capacity

By formula (6) it can be seen that the complexity of HSM-EDAS is significantly high, it is together decided on by constellation size and total transmission antenna number.Such as, when needs are from N_sN selected by root antenna_tWhen root sends data, to each channel status in order to select the antenna combination of the best, it is necessary to calculate $n=\left(\begin{array}{c}{N}_s\\ N_t\end{array}\right)$ Secondary formula (4), and n is along with N_sIncrease and increase, in order to reduce the complexity of calculating, the present invention proposes a kind of low complexity algorithm HSM-COAS based on power system capacity.

Capacity for given channel status and signal to noise ratio snr (signal-to-noiseratio) ESM system is represented by

C_ESM≥γ(7)

Wherein

$\mathrm{\γ}=\frac{1}{N_t}\underset{p=1}{\overset{N_t}{\mathrm{\Σ}}}{\log }_2(1+\frac{E_s}{N_0}{\left|\right|h_p^{\left(l\right)}\left|\right|}_F^2)---\left(8\right)$

E_sRepresent that ESM sends the mean power of symbol, N₀Represent noise power. by (8) it can be seen that namely the value increasing γ adds system appearance.Therefore, it can by the N from channel H_sRow are selected the front N that two norms are maximum_tThe antenna serial number that row are corresponding increases the value of γ as optimal antenna combination, then the optimal antenna selected combination is returned to transmitting terminal.Optimal antenna combination table is shown as $l_{\mathrm{selected}}=\{p_1,p_2,\·\·\·,p_{N_t}\},$ Meet

${\left|\right|h_{p1}\left|\right|}_F^2>{\left|\right|h_{p2}\left|\right|}_F^2>...>{\left|\right|h_{p_{N_t}}\left|\right|}_F^2>...>{\left|\right|h_{p_{N_s}}\left|\right|}_F^2---\left(9\right)$

Therefore, HSM-COAS can be summarized as: when spectrum efficiency is certain, selects the front N that two norms are maximum from each channel H_tThe N that row composition is new_rRow N_tThe sub-channel of rowMinimum euclidean distance according to this channel calculation ESM and the minimum euclidean distance of SM, select the scheme that minimum euclidean distance is bigger to send data.

Table 2 is 3bit/s/Hz, ESM and SM information bit and the mapping sending symbol for spectrum efficiency；

Table 2

The transmission antenna number of SM and ESM is 2, SM employings quadrature amplitude modulation (QAM), and ESM adopts binary phase shift keying modulation (BPSK).

In SM, front log₂N_tIndividual bit determines the sequence number of transmission antenna, when first bit is 0 in this example, adopts first antenna to send；When being 1, adopting second antenna to send, symbol corresponding on other antennas sets to 0.Then log₂M bit determines the symbol mapped on transmission antenna, and example is when adopting QAM modulation (M=4), and latter two bit is 00 is the corresponding 1-j of corresponding symbol 1+j, 01 correspondence-1+j, 10 correspondence-1-j, 11.

And in ESM, front N_tIndividual bit determines transmission antenna sequence number, second antenna transmission of employing when front 2 bits are 01 in this example is 10 is adopt first transmission, adopts the one or two and send simultaneously when being 11, and adopt the one or two and send simultaneously to improve Euclidean distance when being 00, but send when symbol is different from 11.Then log₂M bit determines the symbol mapped, and example is when adopting BPSK modulation (M=2), and latter bit is mapped to symbol-1 when being 0, is mapped to-1 when being 1.

Fig. 2 is spectrum efficiency is 3bit/s/Hz, from 4 transmission antennas select 2 to be transmitted time difference mixing spatial modulation scheme and tradition SM, ESM scheme comparison；When spectrum efficiency is certain and when be 3bit/s/Hz, SM adopts quadrature amplitude modulation (QAM), ESM employing binary phase shift keying promoting or transferring system (BPSK).

Fig. 3 is spectrum efficiency is 6bit/s/Hz, from 6 transmission antennas select 4 to be transmitted time difference mixing spatial modulation scheme and tradition SM, ESM scheme comparison.When spectrum efficiency certain (for 6bit/s/Hz), SM adopts 16 orthogonal dimension amplitude modulation(PAM)s (16QAM), and ESM adopts 4 orthogonal dimension amplitude modulation(PAM)s (4QAM).

As seen from the figure, tri-kinds of scheme bit error rates (BER) of HSM, HSM-EDAS, HSM-COAS that the present invention proposes are below traditional SM and ESM scheme, and compared with HSM-EDAS, HSM-COAS reduces system algorithm complexity with bit error rate for cost, and has reached the balance between systematic function and capacity.

The systematic function (BER) that Fig. 2 compares Fig. 3 is lower slightly, and the increase being primarily due to order of modulation adds the probability of error detection.

In a word, the blending space modulator approach (being called for short HSM) that the present invention proposes, by absorbing the advantage of SM and ESM, making the interference that transmission antenna number is no longer restricted and avoids between antenna, especially the method for its channel self-adapting enables the system to better adapt to being continually changing of channel.It addition, ADAPTIVE MIXED modulating method is combined by the present invention with sky line options, reduce the bit error rate of ADAPTIVE MIXED spatial modulation system further.

The specific embodiment of the present invention is described in conjunction with accompanying drawing although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme, those skilled in the art need not pay various amendments or deformation that creative work can make still within protection scope of the present invention.

Claims (8)

1., based on a blending space modulator approach for Euclidean distance and sky line options, it is characterized in that, comprise the following steps:

(1) transmitting terminal always total N is assumed_sRoot transmission antenna, therefrom selects N_tRoot sends data, and receiving terminal has N_rRoot reception antenna, then at receiving terminal, receive signal y=Hx+n, wherein,Represent and send symbol,It it is independent identically distributed standard gaussian channel It is obeyThe white Gaussian noise of distribution；

(2) receiving terminal adopts method of maximum likelihood that the symbol y received is detected, it is judged that the transmission symbol of its correspondence

(3) the sky line options HSM-COAS method based on power system capacity or the sky line options HSM-EDAS method based on Euclidean distance are applied in ESM, to increase its minimum euclidean distance；

(4) before each information sends, receiving terminal detection channel status, calculating the least square Euclidean distance during ESM scheme transmission data adopted in SM and step (3) respectively, the scheme selecting least square Euclidean distance bigger sends symbol for reality.

2. a kind of blending space modulator approach based on Euclidean distance and sky line options as claimed in claim 1, is characterized in that, in described step (1), receiving terminal adopts the method for method of maximum likelihood detection to be:

$\hat{x}=\underset{x_i\∈\mathrm{\Λ}}{\arg \max }{p}_Y\left(y\right|x_i,H)=\underset{x_i\∈\mathrm{\Λ}}{\arg \min }{\left|\right|y-{\mathrm{Hx}}_i\left|\right|}_F^2$

Wherein,Represent the transmission symbol detected；Λ is the set likely sending symbol；x_iRepresent certain possible transmission symbol,m_bRepresent spectrum efficiency；p_Y(y|x_i, H) and represent the conditional probability density function of receiving terminal.

3. a kind of blending space modulator approach based on Euclidean distance and sky line options as claimed in claim 1, is characterized in that, described step (2), is applied in ESM by the sky line options HSM-COAS method based on power system capacity method particularly includes:

For given channel status and signal to noise ratio snr, the capacity of ESM is represented by

C_ESM≥γ

Wherein

$\mathrm{\γ}=\frac{1}{N_t}\underset{p=1}{\overset{N_t}{\mathrm{\Σ}}}{\log }_2(1+\frac{E_s}{N_0}{\left|\right|h_p^{\left(l\right)}\left|\right|}_F^2)$

E_sRepresent that ESM sends the mean power of symbol, N₀Represent noise power, N_tRepresent transmission antenna number,Represent and l, two norms of channel H pth column element are combined for given transmission antenna；

By the N from channel H_sRow are selected the front N that two norms are maximum_tThe antenna serial number that row are corresponding increases the value of γ as optimal antenna combination, then the optimal antenna selected combination is returned to transmitting terminal.

4. a kind of blending space modulator approach based on Euclidean distance and sky line options as claimed in claim 3, is characterized in that, described optimal antenna combination table is shown asMeet

${\left|\right|h_{p_1}\left|\right|}_F^2>{\left|\right|h_{p_2}\left|\right|}_F^2>...>{\left|\right|h_{p_{N_t}}\left|\right|}_F^2>...>{\left|\right|h_{p_{N_s}}\left|\right|}_F^2$

Wherein,Represent two norms of channel H the i-th column element.

5. a kind of blending space modulator approach based on Euclidean distance and sky line options as claimed in claim 3, is characterized in that,

When spectrum efficiency is certain, from each channel H, select the front N that two norms are maximum_tThe N that row composition is new_rRow N_tThe sub-channel of rowThe minimum euclidean distance of ESM and the minimum euclidean distance of SM is calculated respectively according to this channel.

6. a kind of blending space modulator approach based on Euclidean distance and sky line options as claimed in claim 1, it is characterized in that, the sky line options HSM-EDAS method based on Euclidean distance is applied in ESM by described step (2) method particularly includes: the selection criterion based on the sky line options HSM-EDAS of Euclidean distance is as follows:

$l_{\mathrm{selected}}=\underset{l\∈\mathrm{\Γ}}{\arg \max }\left\{\underset{x_i\≠x_j\∈\mathrm{\Λ}}{\min }{\left|\right|H^{\left(l\right)}(x_i-x_j)\left|\right|}_F^2\right\}$

Wherein, Γ represents all possible $n=\left(\begin{array}{c}{N}_s\\ N_t\end{array}\right)$ The set of individual antenna combination, Λ represents that all possible ESM sends the set of symbol, x_i, x_jRepresent and send symbol,Represent N corresponding to antenna combination l_tArrange sub-channel；The optimal antenna selected combination is returned to transmitting terminal.

7. a kind of blending space modulator approach based on Euclidean distance and sky line options as claimed in claim 6, is characterized in that,

To each channel status, the optimal antenna combination according to selecting obtains the sub-channel that optimal antenna combination is correspondingThe minimum euclidean distance of ESM and the minimum euclidean distance of SM is calculated respectively according to this channel.

8. a kind of blending space modulator approach based on Euclidean distance and sky line options as described in claim 5 or 7, is characterized in that, the computational methods of described minimum euclidean distance are:

$d_{\min }^2\left(H\right)=\underset{\underset{x_i\≠x_j}{x_i,x_j\∈\mathrm{\Λ}}}{\arg \min }{\left|\right|H(x_i-x_j)\left|\right|}_F^2$

Wherein, x_i, x_jRepresenting and send symbol, Λ represents that all possible ESM sends the set of symbol,It it is independent identically distributed standard gaussian channel