CN110995401B - OFDM-IM carrier activation selection method - Google Patents

Abstract

The invention discloses an OFDM-IM carrier activation selection method, which relates to the field of wireless communication. The method of maximizing the joint gain carrier selection is adopted to realize the adaptive block OFDM-IM system. The joint gain is the weighted product of the system diversity gain and the transmission rate, and the weighted value ω∈[0,1]. In the present invention, the number combination of sub-carriers, the number of sub-activated carriers and the combination of sub-carriers in the OFDM-IM system including G sub-blocks are determined, that is,

(in

is a vector [T ₁ ,T ₂ ,...,T _G ] ^T containing the number of carriers in each sub-block,

is a vector [ _{K 1} , K ₂ , ^.

Description

An OFDM-IM carrier activation selection method

technical field

The present invention relates to the field of wireless communication, and in particular, to an OFDM-IM carrier activation selection method.

Background technique

Whether it is in the past, present or in the future, wireless communication technology with faster transmission rate, higher reliability and lower cost is an inevitable demand for social development, and it is also the core indicator for technicians to continuously seek breakthroughs. The Orthogonal Frequency Division Multiplexing (OFDM-IM) technology based on index modulation proposed in recent years combines the advantages of high-speed transmission of orthogonal modulation while effectively combating ISI and the low sensitivity of index modulation to frequency offset and phase noise, as well as relatively The advantage of low peak-to-average ratio has become one of the current hot research directions.

The core idea of OFDM-IM technology is to introduce the concept of index modulation and sub-carrier block in the frequency domain, and divide the transmission information into two parts, in which the index bit information determines and activates part of the sub-carriers, and the rest of the information is determined by the activated carrier in MPSK constellation. Transmission in the form of modulation symbols. The research shows that OFDM-IM improves the sensitivity of the system to frequency offset, while the bit error rate (BER) performance is better than that of traditional OFDM under the same spectral efficiency.

Compared with the traditional modulation method, OFDM-IM only activates part of the carriers, which may reduce the system spectral efficiency and transmission rate. At the same time, the diversity of carrier activation combinations brings challenges to the determination of the system scheme.

Therefore, those skilled in the art are devoted to developing a technical solution for improving system performance by determining the number of sub-carriers, the number of sub-activated carriers and the selection of sub-carrier combinations in the block OFDM-IM system mode.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to propose a new carrier activation scheme of the block OFDM-IM system to improve the system performance.

In order to achieve the above object, the present invention provides an OFDM-IM carrier activation selection method, which is characterized in that a method of maximizing joint gain carrier selection is adopted to realize an adaptive block OFDM-IM system, and the joint gain is the system Weighted product of diversity gain and transmission rate, weighted ω∈[0,1].

Further, include the following steps:

Step 1. System initialization, set the initial value of the system, including the upper limit of the total number of carriers T _max , given the number of sub-blocks G of the sub-block OFDM-IM system, set the lower limit of the system transmission rate B _min , and set the lower limit of the system diversity gain ν _min , the initial count r is 1;

Step 2: Initialize the sub-block r. For the sub-block _r , set the initial activated carrier number K _r to 1, set the initial maximum diversity gain ν _max , and set the initial value Tr of the carrier number to be T _max /G;

Step 3. Determine the upper bound Sup{K _r } of the number of active carriers in the sub-block r;

Step 4: Calculate the current system transmission rate B _r , if the B _r is greater than the B _min , return the current value of K _r as the minimum number of active carriers K _min , otherwise increment the K _r , repeat step 4, and repeat. calculating the B _r ;

Step 5. Set the K _r value to the Sup{K _r }, calculate the current r sub-block diversity gain ν _r , if the diversity gain ν _r is greater than the lower limit of the system diversity gain ν _min , return the current The value of K _r is taken as the maximum number of activated carriers K _max , and step 7 is performed, otherwise, step 6 is performed;

Step 6. Update the current number of carriers T _r to a value of T _r -ν _r , if the T _r is not greater than (K _r +1)(ν _max +1), decrease the K _r and return to step 5 , calculate the ν _r , otherwise directly return to step 4 to calculate the ν _r ;

Step 7. Set the initial maximum diversity gain value of the system ν _max =ν _min +1, and set the initial activation carrier number K _r =K _max of the sub-block r;

Step 8. Calculate and update the current transmission rate B _r , and calculate the current r sub-block diversity gain ν _r ;

Step 9. If the current number of carriers T _r is greater than or equal to the (K _r +1)(ν _max +1), and the current rate B _r is greater than the B _min , skip to step 11;

Step 10, decrement the initial activation carrier number K _r , if the initial activation carrier number K _r is greater than the minimum activated carrier number K _min , then skip back to step 8, otherwise skip to step 13;

Step 11, judge whether the ν _r is greater than ν _min , if not, update the _Tr value and the _Br value and jump back to step 8;

Step 12, update the ν _max , the maximum joint gain U _max and the combination [T _r , K _r ] according to the calculation result;

其中

为包含各个子块载波数的向量[T₁,T₂,…,T_G]^T，

为包含各个子块载波数的向量[K₁,K₂,…,K_G]^T，并递增子块r的值；Step 13, update and store the best combination of the carriers in the block OFDM-IM system

in

is a vector [T ₁ ,T ₂ ,...,T _G ] ^T containing the number of carriers in each sub-block,

is a vector [K ₁ , K ₂ ,...,K _G ] ^T containing the number of carriers in each sub-block, and increments the value of sub-block r;

Step 14, judge the relationship between the current sub-block r and the sub-block quantity G, and return to step 2 if the sub-block r is not greater than the sub-block quantity G;

Step 15, output the best combination of the carrier

Further, the initial maximum diversity gain ν _max in step 2 is a number larger than 1.

Further, the Sup{K _r } calculation formula described in step 3 is,

Further, the calculation formula of _Br described in step 4 is

Further, the calculation formula of the r sub-block diversity gain ν _r in step 5 is v _r =d _o,r (T _r ,K _r ), where d _o,r is

Further, the calculation formula of _Br described in step 8 is

Further, the calculation formula of the r sub-block diversity gain ν _r in step 8 is v _r =d _o,r (T _r , K _r ).

Further, in step 11, the Tr value is updated, and the formula is _Tr = _Tr - _{ν r ;} the _Br value is updated, and the formula is Br= _Br -1.

所述最大联合增益U_max值取所述联合增益U的最大值。Further, the calculation formula of the joint gain is

The value of the maximum joint gain U _max takes the maximum value of the joint gain U.

The technical effect achieved by the present invention is that the performance of the OFDM-IM system can be improved by determining the sub-carrier number combination, the sub-activated carrier number combination and the sub-carrier combination selection.

The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, characteristics and effects of the present invention.

Description of drawings

Fig. 1 is the flow chart of the present invention;

FIG. 2 is a structural diagram of a transmitting module of a block OFDM-IM system according to an embodiment of the present invention.

Detailed ways

The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, so as to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned herein.

The invention aims to solve the problem of selecting the optimal combination of carrier numbers in the block OFDM-IM system, and improve the system diversity gain or transmission rate according to actual requirements. The example of the present invention assumes that the system is in the block OFDM-IM mode and the block G is known. Of course, it can also be adjusted as needed. The possibility that G is 1 is not excluded. It is assumed that the lower limit of the system transmission rate B _min and the system The lower limit ν _min of the diversity gain is known. Assuming that the total number of carriers in this environment is unknown but has an upper limit N _max , the optimal networking mode based on the requirements of the best transmission rate, the best diversity gain or the best joint gain is now sought.

对于分发器传输到第r个子块的p_r比特位中的前面

位作为索引调制信息决定子块中激活的载波个数及组合，剩下的

位由激活载波调制成星座符号行成子块信号传输，显然有

对于子块r(r＝1,2,3,..,G)，传输的信息x_r(c,p_r)我们可以表示为：As shown in FIG. 1 , the legend shows an application scenario of this embodiment: a transmitter model of a block OFDM-IM system. The transmitter contains N subcarriers in total, divided into G subblocks. Corresponding to the input m-bit information, the system sends Pr(r=1,2,...,G) bit information to the i-th sub-block in sequence, that is, there are

For the first part of the pr bits transmitted by the distributor to the _rth sub-block

The bit is used as the index modulation information to determine the number and combination of active carriers in the sub-block, and the remaining

The bit is modulated into a constellation symbol by an active carrier and is transmitted as a sub-block signal. Obviously, there are

For sub-block r (r=1, 2, 3, .., G), the transmitted information x _r (c, p _r ) can be expressed as:

当子载波静默状态时其值为0，当初与激活状态时为根据输入比特调制后的M阶星座符号。知道了每个子块传输数据，一个OFDM-IM帧传输的信息X即可以表示为：In formula (1), (·) T represents the transposition operation, and T _r represents the number of carriers included in the sub-block r, including activated sub-carriers and muted sub-carriers. for either

When the subcarrier is in the silent state, its value is 0, and when it is in the active state, it is the M-order constellation symbol modulated according to the input bits. Knowing that each sub-block transmits data, the information X transmitted by an OFDM-IM frame can be expressed as:

x(c,b)={X ₁ ,X ₂ ,...,X _G } (2)

The information contained in X corresponds to N-point IFFT. Now consider the relationship between the number of OFDM-IM frame transmission bits and sub-block transmission bits. According to the characteristics of binary transmission, the number of carriers and the number of active carrier combinations must be a power of 2, that is:

表示当在第r个子块中的Tr个子载波中选择其中Kr个用于激活的所有可能组合，

表示不超过x的整数。同样的，上文中提到的Pr也可以用同样的方法计算，即

M代表用于激活子载波传输信息的星座调制阶数(M＝2,4,16,32……)。where Sr represents the number of active carrier combinations in the rth OFDM-IM sub-block under the premise of binary specification,

represents when all possible combinations of which Kr are used for activation are selected among the Tr subcarriers in the rth subblock,

Represents an integer up to x. Similarly, the Pr mentioned above can also be calculated in the same way, namely

M represents the constellation modulation order (M=2, 4, 16, 32 . . . ) used for activating subcarriers to transmit information.

Without loss of generality, after completing the index mapping and constellation mapping, the OFDM-IM system converts the data into parallel/serial, transforms the frequency domain data to the time domain through N-point IFFT, and then adds CP to complete the baseband data processing. At the receiving end, after sampling, discarding the CP, and performing an FFT, we can represent the received OFDM-IM block as:

where Pt is the transmit power, and K is the number of subcarriers activated in the OFDM-IM system.

种，但由于数字传输的特性，实际可选组合有

种，也就是有Δ_r(r＝{1,2,…,G}种选择被丢弃。可以看出，对组合的选择和丢弃方案是不确定性的，为了量化对载波传输性能的选择，我们可以引入OFDM-IM子块r对应的分集增益的概念：For the sub-block r of the OFDM-IM system, the number of activated carriers and the selection of carriers are various. Given the number of active carriers K _r , the available combinations are

However, due to the characteristics of digital transmission, the actual optional combinations are

There are Δr ( _r ={1,2,...,G} choices to be discarded. It can be seen that the selection and discarding scheme of the combination are uncertain, in order to quantify the choice of carrier transmission performance, We can introduce the concept of diversity gain corresponding to OFDM-IM sub-block r:

The transmission rate Br of the OFDM-IM sub-block r is given by:

决定这系统分集增益和传输速率亦或两者的联合增益，同时也影响着系统对频偏敏感性的改善、频谱效率等通信系统关注的问题。From the above analysis, it can be seen that the combination of the system carrier and the active carrier

Determining the system diversity gain and transmission rate, or the combined gain of the two, also affects the system's attention to issues such as the improvement of the system's sensitivity to frequency offset and spectral efficiency.

According to the process shown in FIG. 2, a specific embodiment of carrier selection based on maximizing joint gain in an adaptive block OFDM-IM system is provided, and the process includes the following steps:

Step 1. Assume that the upper limit of the total number of carriers N _max is 64; the number G of sub-blocks in the given block OFDM-IM system is 1; the modulation order M is given as 2; the lower limit of the system transmission rate B _min is set to 85; The lower limit ν _min of the system diversity gain is 1, and the weighted value ω is 0.250. For sub-block r=1, the initial number of active carriers K _r is set to 1. Set the initial maximum diversity gain ν _max =1+ν _min .

确定子块r激活载波数上界Sup{K_r}为31，为设定子块初始激活载波数K_r取值为1；Step 2, T _max assigns N _max , according to

It is determined that the upper bound Sup{K _r } of the number of activated carriers in the sub-block r is 31, and the value of K _r is set to be 1 for the initial activated carrier number of the sub-block;

为7，不大于所设定的最低传输速率，则K_r值更新2；Step 3. Set the initial value of T _r as T _max , and calculate the current transmission rate

is 7, which is not greater than the set minimum transmission rate, then the K _r value is updated by 2;

直到第一次满足传输速率，此时K_r值更新为27，并将当前值赋予K_min，B_r值为86；Step 4. Calculate the current transmission rate sequentially for 2≤K _r ≤Sup{K _r }

Until the transmission rate is met for the first time, at this time, the value of K _r is updated to 27, and the current value is given to K _min , and the value of B _r is 86;

Step 5. Set the initial activation carrier number K _r of the sub-block as Sup{K _r }, calculate the current diversity gain ν=d _{o, r} (T _r , K _r ) is 1; not greater than the set diversity gain lower limit ν _min , then the Tr value is updated to _{Tr -ν} ;

Step 6. Determine the relationship between the current T _r value and (K _r +1)(ν _min +1), if the former is small, then the value of K _r is Sup{K _r }-1=30;

Step 7. T _r takes the value T _max , and calculates the current diversity gain ν=d _{o, r (} T _r , K _r ) is 1; it is not greater than the set diversity gain lower limit ν _min , then the Tr value is updated to Tr _-ν , 63;

Step 8. Determine the relationship between the current Tr value and (K _r +1 ₎ (ν _min +1), the former is not less than the latter, and calculate the current diversity gain ν=d _{o, r} (T _r , K _r ) is 1; is not greater than the set diversity gain lower limit ν _min , then the value of Tr is updated to _{Tr -ν} , 62;

Step 9. Determine the relationship between the current Tr value and (K _r +1 ₎ (ν _min +1), the former is not less than the latter, and calculate the current diversity gain ν=d _{o, r} (T _r , K _r ) is 1; is not greater than the set diversity gain lower limit ν _min , then the value of Tr is updated to _{Tr -ν} , 61;

Step 10: Determine the relationship between the current T _r value and (K _r +1)(ν _min +1), if the former is small, then K _r takes the value of K _r -1=29;

Step 11. T _r takes the value T _max , and calculates the current diversity gain ν=d _{o, r (} T _r , K _r ) is 1; if it is not greater than the set diversity gain lower limit ν _min , then the Tr value is updated to Tr _-ν , 63;

Step 12: Determine the relationship between the current Tr value and (K _r +1 ₎ (ν _min +1), the former is not less than the latter, and calculate the current diversity gain ν=d _{o, r} (T _r , K _r ) is 1; is not greater than the set diversity gain lower limit νmin, then the value of Tr is updated to _{Tr -ν} , 62;

Step 13: Determine the relationship between the current Tr value and (K _r +1 ₎ (ν _min +1), the former is not less than the latter, and calculate the current diversity gain ν=d _{o, r} (T _r , K _r ) is 1; is not greater than the set diversity gain lower limit ν _min , then the value of Tr is updated to _{Tr -ν} , 61;

Step 14: Determine the relationship between the current Tr value and (K _r +1 ₎ (ν _min +1), the former is not less than the latter, and calculate the current diversity gain ν=d _{o, r} (T _r , K _r ) is 1; is not greater than the set diversity gain lower limit ν _min , then the Tr value is updated to _{Tr -ν} , 60;

Step 15: Determine the relationship between the current Tr value and (K _r +1 ₎ (ν _min +1), the former is not less than the latter, and calculate the current diversity gain ν=d _{o, r} (T _r , K _r ) is 1; is not greater than the set diversity gain lower limit ν _min , then the value of Tr is updated to _{Tr -ν} , 59;

Step 16: Determine the relationship between the current T _r value and (K _r +1)(ν _min +1), if the former is small, then the value of K _r is K _r -1=28;

Step 17: T _r takes the value T _max , calculates the current diversity gain ν=d _{o, r} (T _r , K _r ) is 2; if it is greater than the set diversity gain lower limit ν _min , then update the K _max value to the current K _r value, 28;

Step 18. For K _min ≤K _r ≤K _max , that is, 27≤K _r ≤28, perform the following steps:

为87，计算当前联合增益值U_r，更新当前最佳的选择组合[T_r,K_r]，更新当前最大联合增益值U_max；T_r值更新为T_r-ν，62；Step 19, the current K _r value is 28, the T _r value is T _max , and the diversity gain ν is 2; calculate the current system transmission rate

is 87, calculate the current joint gain value U _r , update the current best selection combination [T _r , K _r ], and update the current maximum joint gain value U _{max ; the Tr value is updated to T r -ν} , 62;

Step 20. Determine the relationship between the current Tr value and (K _r +1 ₎ (ν _min +1), the former is not less than the latter, and calculate the current diversity gain ν=d _{o, r} (T _r , K _r ) is 1; is not greater than the set diversity gain lower limit ν _min , then the value of Tr is updated to _{Tr -ν} , 61;

Step 21. Determine the relationship between the current T _r value and (K _r +1)(ν _min +1), the former is not less than the latter, but at this time, it is known from the recursive relationship that the B _r value is 85, which does not satisfy the system’s transmission rate. requirements, the value of K _r is updated to K _r -1; that is, the value of K _min .

Step 22: T _r takes the value T _max , calculates the current diversity gain ν=d _{o, r (} T _r , K _r ) is 1; if it is not greater than the set diversity gain lower limit ν _min , then update the value of Tr to Tr _-ν , 63;

Step 21. From the recursive relationship, it is known that the current B _r value is 85, which does not meet the transmission rate requirement of the system, and exits.

Step 22, update the optimal combination of carriers in the block OFDM-IM system

So far, the example process of the adaptive block OFDM-IM system based on the maximum joint gain carrier selection scheme ends.

The preferred embodiments of the present invention have been described above in detail. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, any technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the prior art according to the concept of the present invention shall fall within the protection scope determined by the claims.

Claims (6)

1. An OFDM-IM carrier activation selection method, characterized in that a method of maximizing joint gain carrier selection is adopted to implement an adaptive block OFDM-IM system, wherein the joint gain is a weighting of system diversity gain and transmission rate product, weighted value ω∈[0,1], It includes the following steps: Step 1. System initialization, set the initial value of the system, including the upper limit of the total number of carriers T _max , given the number of sub-blocks G of the sub-block OFDM-IM system, set the lower limit of the system transmission rate B _min , and set the lower limit of the system diversity gain ν _min , the initial count r is 1; Step 2: Initialize the sub-block r. For the sub-block _r , set the initial activated carrier number K _r to 1, set the initial maximum diversity gain ν _max , and set the initial value Tr of the carrier number to be T _max /G; Step 3. Determine the upper bound Sup{K _r } of the number of active carriers in the sub-block r; Step 4: Calculate the current system transmission rate B _r , if the B _r is greater than the B _min , return the current value of K _r as the minimum number of active carriers K _min , otherwise increment the K _r , repeat step 4, and repeat. calculating the B _r ; Step 5. Set the K _r value to the Sup{K _r }, calculate the current r sub-block diversity gain ν _r , if the diversity gain ν _r is greater than the lower limit of the system diversity gain ν _min , return the current The value of K _r is taken as the maximum number of activated carriers K _max , and step 7 is performed, otherwise, step 6 is performed; Step 6. Update the current number of carriers T _r to a value of T _r -ν _r , if the T _r is not greater than (K _r +1)(ν _max +1), decrease the K _r and return to step 5 , calculate the ν _r , otherwise directly return to step 4 to calculate the ν _r ; Step 7. Set the initial maximum diversity gain value of the system ν _max =ν _min +1, and set the initial activation carrier number K _r =K _max of the sub-block r; Step 8. Calculate and update the current transmission rate B _r , and calculate the current r sub-block diversity gain ν _r ; Step 9. If the current number of carriers T _r is greater than or equal to the (K _r +1)(ν _max +1), and the current rate B _r is greater than the B _min , skip to step 11; Step 10, decrement the initial activation carrier number K _r , if the initial activation carrier number K _r is greater than the minimum activated carrier number K _min , then skip back to step 8, otherwise skip to step 13; Step 11, judge whether the ν _r is greater than ν _min , if not, update the _Tr value and the _Br value and jump back to step 8; Step 12, update the ν _max , the maximum joint gain U _max and the combination [T _r , K _r ] according to the calculation result; Step 13, update and store the best combination of the carriers in the block OFDM-IM system

in

is a vector [T ₁ ,T ₂ ,...,T _G ] ^T containing the number of carriers in each sub-block,

is a vector [K ₁ , K ₂ ,..., T _G ] ^T containing the number of carriers in each sub-block, and increments the value of sub-block r; Step 14, judge the relationship between the current sub-block r and the sub-block quantity G, and return to step 2 if the sub-block r is not greater than the sub-block quantity G; Step 15, output the best combination of the carrier

2 . The OFDM-IM carrier activation selection method according to claim 1 , wherein the initial maximum diversity gain ν _max in step 2 is a number larger than 1. 3 . 3. The OFDM-IM carrier activation selection method according to claim 1, wherein the calculation formula of Sup{K _r } described in step 3 is:

4. The OFDM-IM carrier activation selection method according to claim 1, wherein the calculation formula of B _r in step 4 is:

5. The OFDM-IM carrier activation selection method according to claim 1, wherein the calculation formula of B _r in step 8 is:

6. The OFDM-IM carrier activation selection method according to claim 1, wherein in step 11, the _Tr value is updated, and the formula is Tr= _Tr - _{νr ;} the _Br value is updated, and the formula is is B _r =B _r -1.

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