IIIIIIIIIIIIIIIIIIIIII US009960831B2

( 12 ) United States Patent Basar

( 10 ) Patent No . : ( 45 ) Date of Patent :

US 9 , 960 , 831 B2 May 1 , 2018

( 58 ) ( 54 ) MULTIPLE INPUT MULTIPLE OUTPUT ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING WITH INDEX MODULATION , MIMO - OFDM - IM , COMMUNICATIONS SYSTEM

Field of Classification Search CPC . . H04B 7 / 0854 ; H04B 7 / 0417 ; H04B 7 / 0452 ;

H04B 7 / 0495 ; H04B 7 / 0617 ; H04B 7 / 0619 ; H04B 7 / 0671 ; H04B 7 / 0894

See application file for complete search history .

( 56 ) References Cited ( 71 ) Applicant : ISTANBUL TEKNIK UNIVERSITESI REKTORLUGU , Istanbul ( TR ) U . S . PATENT DOCUMENTS

( 72 ) Inventor : Ertugrul Basar , Istanbul ( TR ) 9 , 209 , 870 B1 * 12 / 2015 Nammi . . . . . . . . . . . . . . . H04B 7 / 0417 9 , 319 , 114 B2 * 4 / 2016 Ling . . . . . . . . . . . . . . . . . . . . H04B 7 / 0417

2005 / 0052991 A1 * 3 / 2005 Kadous . . . . . . . . . . . . . . . . . HO3M 13 / 33 370 / 216 ( 73 ) Assignee : ISTANBUL TEKNIK

UNIVERSITESI REKTORLUGU , Istanbul ( TR ) OTHER PUBLICATIONS

( * ) Notice : Subject to any disclaimer , the term of this patent is extended or adjusted under 35 U . S . C . 154 ( b ) by 0 days . days .

Hui Rong Bai et al : “ MIMO - OFDM with interleaved subcar rierindex modulation ” , 10th International conference on wireless communications , Networking and mobile computing ( WICOM 2014 ) , Sep . 26 , 2014 , pp . 35 - 37 .

( Continued ) ( 21 ) Appl . No . : 15 / 408 , 432 ( 22 ) Filed : Jan . 18 , 2017 Primary Examiner — Janice Tieu

( 74 ) Attorney , Agent , or Firm — Gokalp Bayramoglu ( 65 ) Prior Publication Data

US 2017 / 0180032 A1 Jun . 22 , 2017 Related U . S . Application Data

( 63 ) Continuation - in - part of application PCT / TR2016 / 050268 , filed on Aug . 5 , 2016 .

No .

( 30 ) Foreign Application Priority Data Aug . 12 , 2015 ( TR ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a 2015 / 09964

( 57 ) ABSTRACT A communication system for the next generation wireless communications technology standards . The communication system architecture is created by the combination of the index modulation technique and the multiple input multiple output orthogonal frequency division multiplexing which eliminates the need to utilize complex equalizers by parsing high speed data strings and transmitting them over multiple orthogonal subcarriers , and allows the bits to be transmitted via active subcarrier indices . The OFDM - IM and multiple input multiple output communication techniques are used in tandem . The communication system can be used in future generation mobile communication systems and standards ( 5G and beyond ) , Local Area Network system and stan dards , terrestrial digital TV system and standards , multi carrier communication systems and broadband digital com munication systems

( 51 ) Int . Ci . H04B 7708 ( 2006 . 01 ) H04B 7 / 0495 ( 2017 . 01 )

( Continued ) ( 52 ) U . S . CI .

CPC . . . . . . . . . H04B 770854 ( 2013 . 01 ) ; H04B 770417 ( 2013 . 01 ) ; H04B 770452 ( 2013 . 01 ) ; ( Continued ) 3 Claims , 6 Drawing Sheets

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( 51 ) Int . Cl . H04B 7 / 0452 ( 2017 . 01 ) H04B 7 / 0417 ( 2017 . 01 ) H04B 7 / 06 ( 2006 . 01 )

( 52 ) U . S . CI . CPC . . . . . . . . . H04B 770495 ( 2013 . 01 ) ; H04B 770617

( 2013 . 01 ) ; H04B 770619 ( 2013 . 01 ) ; H04B 770671 ( 2013 . 01 ) ; H04B 7 / 0894 ( 2013 . 01 )

( 56 ) References Cited

OTHER PUBLICATIONS Basar Ertugrul et al : “ Orthogonal frequency division multiplexing with index modulation in the presence of high mobility ” , IEEE First International Black Sea Conference on Communications and Net working ( Blackseacom 2013 ) , Jul . 3 , 2013 , pp . 147 - 151 . Xiao Yue et al : “ OFDM With Interleaved Subcarrier - Index Modu lation ” , IEEE Communications Letters , vol . 18 , No . 8 , Aug . 1 , 2014 , pp . 1447 - 1450 , XPO11555716 , NJ , US . Ertugrul Basar et al : “ Orthnogonal frequency division multiplexing with index modulation ” , IEEE Global Communications Conference ( Globecom 2012 ) , Dec . 3 , 2012 , pp . 4741 - 4746 .

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US 9 , 960 , 831 B2

MULTIPLE INPUT MULTIPLE OUTPUT channels are removed and the desired decrease in signal to ORTHOGONAL FREQUENCY DIVISION noise ratios necessary for reaching the target bit error ratios

MULTIPLEXING WITH INDEX are not achieved . MODULATION , MIMO - OFDM - IM , Thus , these type of multiple input multiple output COMMUNICATIONS SYSTEM 5 orthogonal frequency division multiplexing ( MIMO

OFDM ) systems are not able to fully utilize the communi CROSS - REFERENCE TO RELATED cation characteristics of multiple input multiple output

APPLICATIONS ( MIMO ) channels . Due to not having the flexibility and dynamic working structure which may be necessary in 5G

This application is a Continuation - in - Part of International networks and due to the fact that information can only be Application PCT / TR2016 / 050268 filed on Aug . 5 , 2016 transferred in modulated symbols in subcarriers , it cannot which claims priority from a Turkish patent Application No . provide a trade - off between spectral efficiency and error TR 2015 / 09964 filed on Aug . 12 , 2015 . performance . Multiple input multiple output ( MIMO ) and

16 orthogonal frequency division multiplexing with index TECHNICAL FIELD OF THE INVENTION modulation ( OFDM - IM ) techniques are not used in tandem

for 5G networks . The present invention relates to a communication system The studies that can be relevant to the invention can be

to be applied for the next generation ( 5G ) wireless commu summarized as follows . Document D1 considers a similar nications technology standards . The communication system 20 design issue combining MIMO communications systems architecture , created by the combination of the index modu - with OFDM - IM . However , only a single mapping scheme lation ( IM ) technique and the multiple input multiple output was proposed in D1 that can achieve a very limited spectral orthogonal frequency division multiplexing ( MIMO - efficiency . Furthermore , the minimum mean squared error OFDM ) which eliminates the need to utilize complex equal ( MMSE ) based detector of D1 does not consider the statis izers by parsing high speed data strings and transmitting 25 tics of the MMSE filtered signals and detects the active them over multiple orthogonal subcarriers , allows the bits to subcarriers by the measured subcarrier powers indepen be transmitted via active subcarrier indices . The present dently from the data symbols carried over the active sub communication system relates to a particular system carriers ; as a result , it provides a suboptimal solution . wherein the orthogonal frequency division multiplexing Despite the fact that both the detector of D1 and the with index modulation ( OFDM - IM ) and multiple input 30 proposed two detectors of the invention are based on MMSE multiple output ( MIMO ) communication techniques , which equalizations , their operation principles are considerably form the basis of the recommended invention , are used in different and these different detectors can provide different tandem and it further relates to a system covering the system performances . Document D2 considers a single input technical field regarding future generation mobile commu - of single output ( SISO ) OFDM - IM scheme for frequency nication system and standards ( 5G and beyond ) , Local Area selective fading channels in the presence of high mobility . Network ( LAN ) system and standards ( IEEE 802 . 11n ) , MMSE equalization is used to eliminate the interference terrestrial digital TV system and standards ( Digital Video between different subcarriers due to mobility and LLR Broadcasting , DVB ) , multi - carrier communication systems calculation is used to detect the active indices . Document D3 and broadband digital communication systems . 40 considers block interleaving of subcarriers for SISO type

OFDM - IM . Document D4 is the landmark study that is also BACKGROUND OF THE INVENTION performed by the Inventor and proposed OFDM - IM for

SISO frequency selective fading systems by considering In the known state of the art , modern wireless commu maximum likelihood and log - likelihood ratio ( LLR ) detec nication systems depend on multiple input multiple output 45 tion .

( MIMO ) communication systems which allow for signifi cant improvements in channel capacity and error perfor SUMMARY OF THE INVENTION mance compared to single transmit and single receive antenna systems . Use of multiple input multiple output A novel communication system is recommended for the ( MIMO ) communication systems allow for the improve - 50 next generation ( 5G and beyond ) wireless networks with the ment of capacity and reliability . In multicarrier communi - present invention that is related to a system wherein index cation , orthogonal frequency division multiplexing ( OFDM ) modulation ( IM ) , orthogonal frequency division multiplex systems eliminate the need to utilize complex equalizers by ing ( OFDM ) and multiple input multiple output ( MIMO ) parsing high speed data strings and transmit them over communication systems are used together . The main objec multiple orthogonal subcarriers . Due to being able to cope 55 tives of utilizing the present system are to achieve a higher with inter - symbol interference efficiently and to minimize energy efficiency , to have the potential to achieve a better the distorting effects of the channel , the orthogonal fre error performance in case of utilizing a multiple input quency division multiplexing ( OFDM ) technology is used in multiple output ( MIMO ) system with less transmit and integration with the multiple input multiple output ( MIMO ) receive antennas and to provide a trade - off between spectral technology within the current wireless communication stan - 60 efficiency and error performance through communicating in dards . Multiple input multiple output orthogonal frequency a dynamic and flexible structure . division multiplexing ( MIMO - OFDM ) systems utilize spa tial multiplexing ( V - BLAST ) techniques in order to reach BRIEF DESCRIPTION OF THE DRAWINGS high data speeds . However , due to the use of linear filtering methods with low complexity , such as zero forcing ( ZF ) or 65 The drawings and the related descriptions , which are used minimum mean square error ( MMSE ) estimator , the diver - for the better explanation of the multiple input multiple sity effect of the multiple input multiple output ( MIMO ) output orthogonal frequency division multiplexing with

US 9 , 960 , 831 B2

index modulation , MIMO - OFDM - IM , communications sys considered M - ary signal constellation ( 2 ) . Active subcarrier tem developed with the present invention , are provided index selection is performed by the reference look - up tables below . at OFDM index modulators ( 2 ) of the transmitter ( 14 ) for

FIG . 1 : Transmitter / Receiver Structure of the MIMO smaller N and K values . The considered reference look - up OFDM - IM System 5 tables for N = 4 , K = 2 and N = 4 , K = 3 are given in FIGS . 6 and

FIG . 2 : Block Scheme of the OFDM Index Modulator 7 , respectively , where s ES for k = 1 , 2 , . . . K . For higher and FIG . 3 : BER performance of the MIMO - OFDM - IM sys - K values , a combinatorial method based index selection

tem for BPSK modulation algorithm is employed . FIG . 4 : BER performance of the MIMO - OFDM - IM sys The OFDM index modulate ( 2 ) in each branch of the

tem for QPSK modulation 10 transmitter obtain the OFDM - IM subblocks first and then FIG . 5 : BER performance of the MIMO - OFDM - IM sys concatenate these G subblocks to form the main OFDM

tem for 16 - QAM modulation blocks Xq , t = 1 , 2 , . . . , T . In order to transmit the elements of FIG . 6 : Reference Active Indices Selection Table 1 the subblocks from uncorrelated channels , GxN block inter FIG . 7 : Reference Active Indices Selection Table 2 leavers ( II ) ( 3 ) are employed at the transmitter . The block

15 interleaved OFDM - IM frames ž? , t = 1 , 2 , . . . , T are processed DEFINITIONS OF THE by the inverse FFT ( IFFT ) operators ( 4 ) to obtain ã , t =

ELEMENTS / SECTIONS / PARTS FORMING THE 1 , 2 , . . . , T . After the addition of cyclic prefix of C , samples , INVENTION parallel - to - serial and digital - to - analog conversions ( 5 ) , the

resulting signals sent simultaneously from T transmit anten The parts and sections , which are presented in the draw - 20 nas ( 6 ) over a frequency selective Rayleigh fading MIMO

ings for a better explanation of the wireless communication channel , where g , EC1 * 1 represents the L - tap wireless system developed with the present invention , have been channel between the transmit antenna t and the receive enumerated and the counterpart of each number is presented antenna r . Assuming the wireless channels remain constant below . during the transmission of a MIMO - OFDM - IM frame and

1 . Multiple input multiple output orthogonal frequency 25 Cp > L , after removal of the cyclic prefix ( 8 ) and performing division multiplexing with index modulation , MIMO - FFT operations in each branch of the receiver ( 9 ) , the OFDM - IM , communications system input - output relationship of the MIMO - OFDM - IM scheme

2 . Orthogonal frequency division multiplexing with index in the frequency domain is obtained as ( 13 ) modulation ( OFDM - IM ) blocks

3 . Block interleaver ( II ) 30 = & = 1 " diag ( ? . ) hy , + w , 4 . Inverse fast . Fourier transform ( IFFT ) for r = 1 , 2 , . . . , R , where ? = [ ? , ( 1 ) ? , ( 2 ) . . . ? , ( NP ) ] * is the 5 . Cyclic prefix ( CP ) addition vector of the received signals for receive antenna r ( 13 ) , 6 . Transmit antennas h . , , EC N * l represents the frequency response of the wire 7 . Receive antennas less channel between the transmit antenna t and receive 8 . Cyclic prefix ( CP ) subtraction antenna r , and w , EC NEX1 is the vector of noise samples . The 9 . Fast Fourier transform ( FFT ) elements of h , and w , follow CN ( 0 , 1 ) and CN ( 0 , N . ) 10 . Block deinterleaver ( 11 ~ - ) distributions , respectively , where NoF denotes the variance 11 . Successive minimum mean square error ( MMSE ) of the noise samples in the frequency domain . We define the

detector signal - to - noise ratio ( SNR ) as SNR = E , / N . . . where E , = ( N + 12 . Log - likelihood ratio ( LLR ) calculator 40 Cp ) / m [ joules / bit ] is the average transmitted energy per bit . 13 . The Receiver After block deinterlaving ( 10 ) in each branch of the 14 . The Transmitter receiver ( 13 ) , the received signals are obtained for receive

antenna r as DETAILED DESCRIPTION OF THE

INVENTION y , = ? – 1 " diag ( x , ) } , + , A MIMO system employing transmit and R receive Where Ñ , , , and w , are deinterleaved versions of hy , and

antennas is considered . For the transmission of each frame , W , , respectively . The detection of the MIMO - OFDM - IM a total of riff bits enter the transmitter ( 14 ) and first split into scheme can be performed by the separation of the received groups ( 14 ) and the corresponding rte bits are processed in 50 518 so signals for each subblock g = 1 , 2 , . . . , G as follows each branch of the transmitter by the OFDM index modu lators ( 2 ) . The incoming in information bits are used to form y ; 8 = 2 – 1 " diag ( x , 8 ) , 8 + ve the N * 1 OFDM - IM block x : = [ x ; ( 1 ) x ( 2 ) . . . X ( N2 ) ] ? , for r = 1 , 2 , . . . , R , where y , 8 = [ y , % ( 1 ) y , ( 2 ) . . . y , % ( N ) ] ” is t = 1 , 2 , . . . , T in each branch of the transmitter ( 2 ) , where N , the vector of the received signals at receive antenna r ( 13 ) is the size of the fast Fourier transform ( FFT ) ( 4 ) and 55 for subbblock g? x8 = [ x ( 1 ) X ( 2 ) . . . x ( N ) ] ” is the x ( ) E 0 , S } , n = 1 , 2 , . . . , Ny and S represents the signal OFDM - IM subblock g for transmit antenna t ( 14 ) , constellation . According to the OFDM - IM principle ( 2 ) , and h , = [ h , . $ ( 1 ) h , 19 ( 2 ) . . . h , , , ! ( N ) ] ? and w , 8 = [ , $ ( 1 ) which is carried out simultaneously in each branch of the , 8 ( 2 ) . . . Ñ , 8 ( M ) ] T . The use of the block interleaving ( 10 ) transmitter , these bits are split into G groups each containing ensures the subcarriers in a subblock are affected from p = p , + p , bits , which are used to form OFDM - IM subblocks 60 uncorrelated wireless fading channels for practical values of x8 = [ x ( 1 ) XS ( 2 ) . . . x ( N ) ] , g = 1 , 2 , . . . , G of length NE N = N / G , where x ( n ) E { 0 , S } , n = 1 , 2 , . . . , N . According to For the detection of the corresponding OFDM - IM sub the corresponding p , = log , ( C ( N , K ) ) bits , only K out of N blocks of different transmit antennas ( 14 ) , the following available subcarriers are selected as active by the index MIMO signal model is obtained for subcarrier n of subblock selector ( 2 ) at each subblock g , while the remaining N - K 65 g : subcarriers are inactive and set to zero . On the other hand , the remaining pz = K log2 ( M ) bits are mapped onto the 7n8 = H , 87 , 8 + w ,

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US 9 , 960 , 831 B2

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for n = 1 , 2 , . . . , N and g = 1 , 2 , . . . , G , where y , is the received Then , the conditional mean and variance of $ , $ ( n ) are signal vector , H , 5 is the corresponding channel matrix which obtained as contains the channel coefficients between transmit ( 6 ) and receive antennas ( 7 ) and assumed to be perfectly known at E { 8 } ( ) } = ( W , $ 4 , 9 * ( n ) , var ( €f ( n ) ) = ( cov ( 2 , 3 ) the receiver , x . 8 is the data vector which contains the 5 Using the above found statistics of the MMSE filtered simultaneously transmitted symbols from all transmit anten - signals , the LLR for the nth subcarrier of t th transmitter for nas ( 6 ) and can have zero terms due to index selection in subblock g can be calculated as ( 12 ) each branch of the transmitter and w , is the noise vector . Due to the index information carried by the subblocks of the proposed scheme , it is not possible to detect the transmitted 10 M 18 ( n ) – ( W , X H ) 15ml ) . Letif ( n ) ? symbols by only processing ynk for a given subcarrier n in ( n ) = In > " 2 ( cov ( zh ) * ( cov ( zk ) , the MIMO - OFDM - IM scheme . Therefore , N successive MMSE detections ( 11 ) are performed for the proposed scheme using the MMSE filtering matrix for n = 1 , 2 , . . . , N , t = 1 , 2 , . . . , T and g = 1 , 2 , . . . , G . After the

calculation of N LLR values for a given subblock g and transmit antenna t , which results a linear decoding complex ity of ~ O ( M ) per subcarrier as in classical MIMO - OFDM , in order to determine the indices of the active subcarriers , the LLR detector ( 12 ) calculates the following LLR sums for

for n = 1 , 2 , . . . , N , where p = 0 , 2 / N . F , 0 , 2 = K / N and E { 8 , 8 ( c = 1 , 2 , . . . , C according to the look - up table as 0 % ( c ) = X , g ) H } = 0 , 217 . By the left multiplication of y , 8 with W , Ek = 1 , 9 ( ix ) , where Iº = { 1 , ° , izº , . . . , ik® } denotes the possible MMSE detection ( 11 ) is performed as active subcarrier index combinations . The LLR

detector determines the active subcarriers for a given sub 2 , 8 = W , 85 , 8 = w , £1 , 87 , 8 + W , 8w , 8 block g and transmit antenna t as ? = arg max d ' ( c ) and

1 , 8 = { i º , i2 , . . . , } . The M - ary symbols transmitted by the where 28 = [ z , 8 ( 1 ) 2 , 8 ( 2 ) . . . 2 , 8 ( T ) ] " is the MMSE active subcarriers are determined with ML detection a estimate of 1 , 9 . The MMSE estimate of MIMO - OFDM - IM subblocks 88 = [ 8 , 3 ( 1 ) ^ , ( 2 ) . . . Ñ 8 ( N ) ] can be obtained by $ { ( k ) = argmin , mesli , ( ix ) - ( Wife H , 889 ) ml ? rearranging the elements of z , % , n = 1 , 2 , . . . , N as , 9 = [ z , 8 ( t ) for k = 1 , 2 , . . . , K , , where these metrics were calculated for z ( t ) . . . Zv $ ( t ) ] * for t = 1 , 2 , . . . , T and g = 1 , 2 , . . . , G . As 30 the LLR values calculated earlier and do not increase the mentioned earlier , Â contains some zero terms , whose decoding complexity . After this point , index selecting p , bits positions carry information ; therefore , independent detec are recovered from the look - up table and M - ary symbols are tion of the data symbols in E ( with linear decoding com demodulated to obtain the corresponding P2 information plexity ) is not a straightforward problem for the proposed scheme . As an example , rounding off individually the ele - 35 In FIG . 3 , we compare the bit error rate ( BER ) perfor ments of â to the closest constellation points ( the elements mance of the invention for N = 4 , K = 2 with classical MIMO of { 0 , } for the proposed scheme ) as in classical MIMO OFDM for M = 2 at same spectral efficiency values . As seen OFDM may result a catastrophic active index combination from FIG . 3 , the proposed scheme provides significant BER that is not included in the reference look - up table , which performance improvement compared to classical MIMO makes the recovery of index selecting n bits impossible . 40 OFDM , which increases with higher order MIMO systems . In order to determine the active subcarriers in , , the LLR K As an example , the MIMO - OFDM - IM scheme achieves detector ( 12 ) of the proposed scheme calculates the follow approximately 10 . 4 dB better BER performance than clas ing ratio which provides information on the active status of sical MIMO - OFDM at a BER value of 10 - s for the 8x8 the corresponding subcarrier index n of transmit antenna t : MIMO system .

In FIG . 4 and FIG . 5 , we extend our simulations to higher spectral efficiency values and compare the BER perfor

? PC ? ( N ) | xf ( n ) = sm ) mance of the proposed MIMO - OFDM - IM scheme ( N = 4 , K = 3 ) with classical MIMO - OFDM for M = 4 and 16 , respec

* P ( ( n ) | x ( n ) = 0 ) tively . As seen from FIG . 4 and FIG . 5 , the proposed scheme still maintains its advantage over classical MIMO - OFDM in all considered configurations . It is interesting to note that the

for n = 1 , 2 , . . . , N , where smES . This calculation requires proposed scheme has the potential to achieve close or better the conditional statistics of x , & ( n ) ( 2 % ( t ) ) . However , due to BER performance than the reference scheme , even using a successive MMSE detection ( 11 ) , the elements of gs are still lower order MIMO system in most cases . Gaussian distributed but have different mean and variance » We claim : values . Let us consider the mean vector and covariance 1 . A multiple input multiple output orthogonal frequency matrix of Z conditioned on x ( n ) E { 0 , S } , which are given division multiplexing with index modulation ( MIMO as OFDM - IM ) communications system , comprising :

60 at least two transmit antennas in a transmitter side for E { 2 , 8 } = w , 5H , $ E { 1 , 5 } = ( W , $ 1 , 99xf ( n ) transmitting signals obtained after orthogonal fre quency division multiplexing with index modulation ,

cov ( 2 , 8 ) = w , H , cov ( 3 , ) ( wherein each transmit antenna transmits OFDM - IM HO ) ( W29 ) 4 + NOFW , 8 ) ( W , g ) H frames ;

where E { x , 3 } is an all - zero vector except its t th element 65 at least two receive antennas in a receiver side for is xf ( n ) , and cov ( x3 ) = diag ( [ 0 2 . . . 02 0 . 02 . . . 0 _ 21 ) receiving the signals transmitted from the transmit is a diagonal matrix whose t th diagonal element is zero . antennas for detection and demodulation ;

de ele . 35 bits .

1 ; ( n ) = In m = 1 50

US 9 , 960 , 831 B2

a block interleaver in the transmitter side , wherein said whether the corresponding subcarrier of a given trans block interleaver interleaves the OFDM - IM frames to mit antenna is active or not ; minimize the correlation between channel coefficients a block deinterleaver in the receiver side which deinter corresponding to different OFDM - IM subcarriers ; leaves the OFDM - IM frames ;

a successive minimum mean square error ( MMSE ) detec - 5 wherein each branch of the transmitter side uses reference tor followed by a plurality of log - likelihood ratio ( LLR ) look - up tables or combinatorial number theory for detectors in the receiver side to detect and demodulate selection of indices of active subcarriers according to the OFDM - IM frames transmitted from said each trans index selection data bits ; mit antenna , wherein the successive minimum mean wherein a cyclic prefix addition is performed after an square error ( MMSE ) detector in the receiver side is 10 inverse fast Fourier transform ( IFFT ) process on the configured to eliminate interference between OFDM signals in the transmitter section and a cyclic prefix IM frames transmitted from said each transmit antenna subtraction is performed after the signals are received by performing a filtering process , wherein the succes at the receive antennas followed by a fast Fourier sive MMSE detector in the receiver side is configured transform process for the decoupling of the received to have an enhanced operation mode based on ordered 15 signals without inter - carrier interference . successive interference cancellation ( OSIC ) algorithm 2 . The multiple input multiple output orthogonal fre and calculates a quality measure for each transmit quency division multiplexing with index modulation antenna and starts the detection from the one that has a ( MIMO - OFDM - IM ) communications system according to maximum signal - to - noise ratio ; claim 1 , wherein the system is configured to adjust the

a wherein a plurality of outputs from the successive 201 ive 20 number of active subcarriers . MMSE detector are provided as inputs to the plurality 3 . The multiple input multiple output orthogonal fre

of log - likelihood ratio ( LLR ) detector in the receiver quency division multiplexing with index modulation , side to perform a search over possible realizations of MIMO - OFDM - IM communications system according to data symbols for said each subcarriers to calculate a claim 1 , wherein the system is configured to operate for posterior probability ratio , wherein the posterior prob - - - 25 different multiple input multiple output systems . ability ratio is used as a benchmark for determining *