differential space time modulation over frequency selective channels we present herein a new differential space time frequency dstf modulation scheme for systems that are equipped with an arbitrary number of transmit antennas and operate in frequency selective channels the proposed dstf modulator consists of a concatenating spectral encoder and differential encoder that offer full spatio spectral diversity and significant coding gain a unitary structure is imposed on the differential encoder to admit linear decoupled maximum likelihood ml detection in space and time optimum criteria based on pairwise error probability analysis are developed for spectral encoder design we introduce a class of spectral codes namely linear constellation decimation lcd codes which are nonbinary block codes obtained by decimating a phase shift keying psk constellation with a group of decimation factors that are co prime with the constellation size since lcd codes encode across a minimally necessary set of subchannels for full diversity they incur modest decoding complexity among all full diversity codes numerical results are presented to illustrate the performance of the proposed dstf modulation and coding scheme which compares favorably with several existing differential space time schemes in frequency selective channels

on optimal multilayer cyclotomic space time code designs high rate and large diversity product or coding advantage or coding gain or determinant distance or minimum product distance are two of the most important criteria often used for good space time code designs in recent linear lattice based space time code designs more attention is paid to the high rate criterion but less to the large diversity product criterion in this paper we consider these two criteria together for multilayer cyclotomic space time code designs in a previous paper we recently proposed a systematic cyclotomic diagonal space time code design over a general cyclotomic number ring that has infinitely many designs for a fixed number of transmit antennas where diagonal codes correspond to single layer codes in this paper in this paper we first propose a general multilayer cyclotomic space time codes we present a general optimality theorem for these infinitely many cyclotomic diagonal or single layer space time codes over general cyclotomic number rings for a general number of transmit antennas we then present optimal multilayer full rate cyclotomic space time code designs for two and three transmit antennas we also present an optimal two layer cyclotomic space time code design for three and four transmit antennas the optimality here is in the sense that for a fixed mean transmission signal power its diversity product is maximized or equivalently for a fixed diversity product its mean transmission signal power is minimized it should be emphasized that all the optimal multilayer cyclotomic space time codes presented in this paper have the nonvanishing determinant property

space time block codes from orthogonal designs we introduce space time block coding a new paradigm for communication over rayleigh fading channels using multiple transmit antennas data is encoded using a space time block code and the encoded data is split into n streams which are simultaneously transmitted using n transmit antennas the received signal at each receive antenna is a linear superposition of the n transmitted signals perturbed by noise maximum likelihood decoding is achieved in a simple way through decoupling of the signals transmitted from different antennas rather than joint detection this uses the orthogonal structure of the space time block code and gives a maximum likelihood decoding algorithm which is based only on linear processing at the receiver space time block codes are designed to achieve the maximum diversity order for a given number of transmit and receive antennas subject to the constraint of having a simple decoding algorithm the classical mathematical framework of orthogonal designs is applied to construct space time block codes it is shown that space time block codes constructed in this way only exist for few sporadic values of n subsequently a generalization of orthogonal designs is shown to provide space time block codes for both real and complex constellations for any number of transmit antennas these codes achieve the maximum possible transmission rate for any number of transmit antennas using any arbitrary real constellation such as pam for an arbitrary complex constellation such as psk and qam space time block codes are designed that achieve 1 2 of the maximum possible transmission rate for any number of transmit antennas for the specific cases of two three and four transmit antennas space time block codes are designed that achieve respectively all 3 4 and 3 4 of maximum possible transmission rate using arbitrary complex constellations the best tradeoff between the decoding delay and the number of transmit antennas is also computed and it is shown that many of the codes presented here are optimal in this sense as well

on space time code design with a conditional pic group decoding space time code designs based on a partial interference cancellation pic group decoding have been recently proposed the pic group decoding complexity depends on the group size and is between the lowest linear receiver complexity and the highest ml decoding complexity the symbol rate for a space time code achieving full diversity with the pic group decoding is also between those for the linear receivers and the ml decoding in this paper we propose a new decoding called conditional pic group decoding that is between the pic group decoding and the ml decoding with the proposed new decoding we obtain a new design criterion for space time codes to achieve full diversity which is also between the one with the pic group decoding and the one with the ml decoding we then present some designs that satisfy the new criterion and in the meantime have higher symbol rates than that for the pic group decoding

joint mimo channel tracking and symbol decoding using kalman filtering in this paper the problem of channel tracking is considered for multiple input multiple output mimo communication systems where the mimo channel is time varying we consider a class of mimo systems where orthogonal space time block codes are used as the underlying space time coding schemes for such systems a two step mimo channel tracking algorithm is proposed as the first step kalman filtering is used to obtain an initial channel estimate for the current block based on the channel estimates obtained for previous blocks then in the second step the so obtained initial channel estimate is refined using a decision directed iterative method we show that due to specific properties of orthogonal space time block codes both the kalman filter and the decision directed algorithm can be significantly simplified simulation results show that the proposed tracking method can provide results in a symbol error rate performance that is 1 db better than that of the differential receiver

the essential spectrum of neumann laplacians on some bounded singular domains in the present paper we consider neumann laplacians on singular domains of the type rooms and passages or combs and we show that in typical situations the essential spectrum can be determined from the geometric data moreover given an arbitrary closed subset s of the non negative reals we construct domains s such that the essential spectrum of the neumann laplacian on is just this set s

nonclassical eigenvalue asymptotics abstract the leading asymptotics for the growth of the number of eigenvalues of the two dimensional dirichlet laplacian in the regions x y x y 1 and for x y all of which are non weyl because of infinite phase space volumes are computed along the way a general inequality on quantum partition functions computed in a kind of born oppenheimer approximation is proved

trace orthonormal full diversity cyclotomic space time codes in this paper we consider the design of full diversity space time codes for a coherent multiple input multiple output mimo communication system starting from both the information theoretic and detection error viewpoints we first establish that a desirable property for general linear dispersion ld codes is to have an interunitary as well as an intraunitary structure a structure we call trace orthonormality by imposing the trace orthonormal structure on an ld code and applying cyclotomic number theory we establish for an arbitrary number of transmitter and receiver antennas a systematic and simple method to jointly design a unitary cyclotomic matrix the diophantine number and the corresponding constellation for an ld code as a result this enables us to construct full diversity rectangular cyclotomic ld codes with any symbol transmission rate less than or equal to the number of transmitter antennas in addition for the case when the number of transmitter antennas is greater than the number of receiver antennas by taking advantage of the delay we also arrive at the design of a special trace orthonormal full diversity cyclotomic space time block code which for the number of transmitter antenna being equal to 2m can be proved to minimize the worst case pairwise error probability of a maximum likelihood ml detector for a q ary quadrature amplitude modulation qam signal constellation and therefore achieves optimal coding gain computer simulations show that these codes have bit error performance advantages over currently available codes

on the spectrum of the dirichlet laplacian for horn shaped regions in rn with infinite volume abstract an inequality for trace et d is proven where d is the dirichlet laplacian for horn shaped regions d in rn the results of rozenbljum and simon for the leading asymptotics for the growth of the number of eigenvalues of the two dimensional dirichlet laplacian in the regions x y x y 1 0 are easily recovered an example of a horn shaped region in r2 where that asymptotics is exponential is given

exact symbol error probability analysis for orthogonal space time block codes two and higher dimensional constellations cases exact expressions are obtained for the symbol error probability of orthogonal space time block codes at the output of the coherent maximum likelihood decoder in the general case of arbitrary input signal constellation and code such expressions are derived for the cases of both deterministic fixed and random rayleigh ricean fading channels and both the two and higher dimensional constellations

minimum variance linear receivers for multiaccess mimo wireless systems with space time block coding we consider the problem of joint space time decoding and multiaccess interference mai rejection in multiuser multiple input multiple output mimo wireless communication systems we address the case when both the receiver and multiple transmitters are equipped with multiple antennas and when space time block codes stbcs are used to send the data simultaneously from each transmitter to the receiver a new linear receiver structure is developed to decode the data sent from the transmitter of interest while rejecting mai self interference and noise the proposed receivers are designed by minimizing the output power subject to constraints that zero force self interference and or preserve a unity gain for all symbols of the transmitter of interest simulation results show that in multiaccess scenarios the proposed techniques have substantially lower symbol error rates as compared with the matched filter mf receiver which is equivalent to the maximum likelihood ml space time decoder in the point to point mimo communication case

trace properties of the dirichlet laplacian on obtient des bornes superieures et inferieures pour tr exp ht en termes de la fonction r x

optimal transmitter eigen beamforming and space time block coding based on channel mean feedback optimal transmitter designs obeying the water filling principle are well documented they are widely applied when the propagation channel is deterministically known and regularly updated at the transmitter because channel state information is impossible to be known perfectly at the transmitter in practical wireless systems we design in this paper an optimal multiantenna transmitter based on the knowledge of mean values of the underlying channels our optimal transmitter design turns out to be an eigen beamformer with multiple beams pointing to orthogonal directions along the eigenvectors of the correlation matrix of the estimated channel at the transmitter and with proper power loading across beams the optimality pertains to minimizing an upper bound on the symbol error rate which leads to better performance than maximizing the expected signal to noise ratio snr at the receiver coupled with orthogonal space time block codes two directional eigen beamforming emerges as a more attractive choice than conventional one directional beamforming with uniformly improved performance without rate reduction and without essential increase in complexity with multiple receive antennas and reasonably good feedback quality the two directional eigen beamformer is also capable of achieving the best possible performance in a large range of transmit power to noise ratios without a rate penalty

blind ml detection of orthogonal space time block codes identifiability and code construction the blind maximum likelihood ml detection of a general space time block code stbc is considered a challenging implementation problem recent work has revealed that for the orthogonal stbcs ostbcs their special code structures can be exploited to formulate highly effective blind ml based algorithms attracted by this realization merit this paper investigates the blind ml identifiability of ostbcs with an emphasis on the binary psk bpsk and quaternary psk qpsk constellations we find a class of ostbcs called the nonrotatable ostbcs that can be uniquely identified up to a sign uiuts almost surely under a few mild assumptions for example for an independently distributed rayleigh channel with any number of receiver antennas a nonrotatable ostbc can be uiuts with probability 1 while this identifiability looks appealing already we further examine a subclass of nonrotatable ostbcs called the nonintersecting subspace nis ostbcs we prove that nis ostbcs are uiuts for any nonzero channel however nis ostbcs are not available in the existing literature to fill this gap we devise a code construction procedure that can convert any bpsk or qpsk ostbc to an nis ostbc

eigenvalue asymptotics of the neumann laplacian of regions and manifolds with cusps abstract we study the eigenvalue asymptotics of a neumann laplacian n in unbounded regions of r2 with cusps at infinity a typical example is x y r 2 x 1 y x 2 and prove that n e n n e h v e 2 vol where hv is the canonical one dimensional schrodinger operator associated to the problem we establish a similar formula for manifolds with cusps and derive the eigenvalue asymptotics of a dirichlet laplacian d for a class of cusp type regions of infinite volume

spatially modulated orthogonal space time block codes with non vanishing determinants this paper proposes a multiple input multiple output mimo transmission scheme for m ary modulations called spatially modulated orthogonal space time block coding sm ostbc based on the concept of spatial constellation sc codewords introduced by le at el in the proposed scheme transmit codeword matrices are generated by multiplying sc matrices with codewords constructed from orthogonal space time block codes o stbc the maximum spectral efficiency of the proposed scheme is equal to n t 2 log 2 m bpcu where n t is the number of transmit antennas and m is the modulation order the sc matrices provide a means of carrying information bits together with the o stbc codewords and allow the sm ostbc scheme to achieve second order transmit diversity by satisfying the non vanishing determinant property a systematic method to design the sc codewords for an even number of transmit antennas greater than 3 is presented a single stream maximum likelihood ml decoder which requires a low computational complexity thanks to the structure of the sm ostbc codewords and to the orthogonality of the o stbcs and a sphere decoder with further reduced signal processing complexity are developed the bit error rate ber performance of the proposed scheme is studied by using both theoretical union bound analysis and computer simulations finally simulation results are presented in order to compare ber performance energy efficiency and decoding complexity of the proposed scheme with those of several existing mimo transmission schemes

euclidean and space time block codes relationship optimality performance analysis revisited an equivalent model for a multiple input multiple output communication system with space time block codes stbcs is proposed based on a revealed connection between stbcs and euclidean codes examples of distance spectra signal constellations and signal coordinate diagrams of euclidean codes equivalent to simplest orthogonal stbcs are given a new asymptotic upper bound for the symbol error rate ser of stbcs based on the distance spectra of the equivalent euclidean codes is derived and new general design criteria for signal constellations of the optimal code are proposed some bounds relating distance properties dimensionality and cardinality of stbcs with constituent signals of equal energy are given and new signal constellations with cardinalities of 8 and 16 for alamouti s code are designed a general methodology for performance analysis of stbcs is revisited as an example of the application of this methodology an exact evaluation of the ser of an orthogonal stbc is given namely a new expression for the ser of alamouti s code with binary phase shift keying signals is derived

two generalized complex orthogonal space time block codes of rates 7 11 and 3 5 for 5 and 6 transmit antennas space time block codes from orthogonal designs have two advantages namely fast maximum likelihood ml decoding and full diversity rate 1 real pulse amplitude modulation pam space time codes real orthogonal designs for multiple transmit antennas have been constructed from the real hurwitz radon families which also provides the rate 1 2 complex quadrature amplitude modulation qam space time codes complex orthogonal designs for any number of transmit antennas rate 3 4 complex orthogonal designs space time codes for three and four transmit antennas have existed in the literature but no high rate 1 2 complex orthogonal designs for other numbers of transmit antennas exist we present rate 7 11 and rate 3 5 generalized complex orthogonal designs for five and six transmit antennas respectively

space time block codes a maximum snr approach in tarokh et al 1999 space time block codes were introduced to obtain coded diversity for a multiple antenna communication system in this work we cast space time codes in an optimal signal to noise ratio snr framework and show that they achieve the maximum snr and in fact they correspond to a generalized maximal ratio combiner the maximum snr framework also helps in calculating the distribution of the snr and in deriving explicit expressions for bit error rates we bring out the connection between the theory of amicable orthogonal designs and space time codes based on this we give a much simpler proof to one of the main theorems on space time codes for complex symbols we present a rate 1 2 code for complex symbols which has a smaller delay than the code already known we also present another rate 3 4 code which is simpler than the one already known in the sense it does not involve additions or multiplications we also point out the connection between generalized real designs and generalized orthogonal designs

error probability for orthogonal space time block code diversity system using rectangular qam transmission over rayleigh fading channels in this paper theoretical symbol error probability sep expressions are derived for orthogonal space time block code ostbc diversity systems employing arbitrary rectangular m qam transmission over flat rayleigh fading channels independent fading between diversity channels is assumed channel average powers may be distinctive identical or mixed with both the rectangular m qam results are extended to square m qam m pam and binary antipodal signaling all derived expressions are in elementary forms without complicated high order transcendental functions and unevaluated integrals and hence are strictly exact and can be readily simulated by the computer moreover it is shown that mixed rayleigh fading results can be readily extended to various nakagami m fading results a four transmit antenna system with a half rate ostbc for 16 qam signaling is used to demonstrate that the theoretical result is in excellent agreement with the monte carlo simulated result from simulation curves it is shown that under the independent channel fading condition channels with identical powers have better error rate performance than channels with distinctive powers

space time spreading and block coding for correlated fading channels in the presence of interference we consider point to point wireless links with multiple antennas in the presence of interference and exploit channel s spatial correlation and the temporal covariance of the interference to design multiantenna transmitters we develop a space time spreading scheme that maximizes average signal to interference and noise ratio and an optimally power loaded space time beamforming stbf scheme which improves error probability performance in order to increase transmission rates we combine orthogonal space time block coding with stbf optimize power loading across beams and develop low complexity receivers optimal training for least squares error channel estimation and stbf for minimum mean square error channel estimation are also studied our analytical and simulated results corroborate that stbf with optimal power loading can considerably reduce error probability and channel estimation errors

heavy tails and long range dependence in on off processes and associated fluid models on off models are common inputs for a variety of communication network models as well as storage and inventory models a stationary renewal process alternating periods of activity active transmission fluid buildup etc with periods of inactivity silence no transmission inputs off etc induces a stationary indicator process which indicates if the system is active or not heavy tails for the on periods induces a covariance function for the indicator process which decreases slowly at a rate characteristic of long range dependence this has dramatic consequences for fluid models where fluid flows in at constant rate and there is a constant rate of release

closed form blind mimo channel estimation for orthogonal space time block codes in this paper a new computationally simple approach to blind decoding of orthogonal space time block codes ostbcs is proposed using specific properties of ostbcs the authors approach estimates the channel matrix in a closed form and in a fully blind fashion this channel estimate is then used in the maximum likelihood ml receiver to decode the information symbols the proposed estimation technique provides consistent channel estimates and as a result the performance of the authors blind ml receiver approaches that of the coherent ml receiver which exploits the exact channel state information csi simulation results demonstrate the performance improvements achieved by the proposed blind decoding algorithm relative to the popular differential space time modulation scheme

orthogonal space time block codes with sphere packing orthogonal designs have received considerable attention in the development of efficient modulation and coding methods for future multi antenna wireless communication systems due to their special properties in this paper we propose a class of space time block codes constructed by combining orthogonal designs with sphere packing for an arbitrary number of transmit antennas the structure of the orthogonal designs is exploited to guarantee full diversity and sphere packing is used to improve the coding advantage space time block code construction from block orthogonal designs is also considered the full diversity property is ensured by rotating the sphere packing underlying the code and the optimal rotation angle is determined for a class of sphere packing code design examples are provided for two and four transmit antennas and various transmission rates the simulation results show that by jointly designing the symbols in the orthogonal designs the performance of the block codes can be significantly increased

blind ml detection of orthogonal space time block codes efficient high performance implementations orthogonal space time block codes ostbcs have attracted much attention owing to their simple code construction maximal diversity gain and low maximum likelihood ml detection complexity when channel state information csi is available at the receiver this paper addresses the problem of ml ostbc detection with unknown csi focusing on the binary and quaternary psk constellations we show that blind ml ostbc detection can be simplified to a boolean quadratic program bqp from an optimization viewpoint the bqp is still a computationally hard problem and we propose two alternatives for dealing with this inherent complexity first we consider the semidefinite relaxation sdr approach which leads to a suboptimal but accurate blind ml detection algorithm with an affordable worst case computational cost we also consider the sphere decoding approach which leads to an exact blind ml detection algorithm that remains computationally expensive in the worst case but generally incurs a reasonable average computational cost for the two algorithms we study implementation methods that can significantly reduce the computational complexity simulation results indicate that the two blind ml detection algorithms are competitive in that the bit error performance of the two algorithms is almost the same and is noticeably better than that of some other existing blind detectors moreover numerical studies show that the sdr algorithm provides better complexity performance than the sphere decoder in the worst case sense and vice versa in the average sense

iterative detection in block orthogonal and spatially multiplexed multisensor signaling schemes the impact of iterative minimum mean square error mmse detection on multisensor signaling schemes in frequency selective media is considered the suitability of a decision feedback mmse df mmse front end relative to a linear mmse lmmse front end is examined using two case studies namely layered spatial multiplexing and block orthogonal space time signaling iterative mmse detection is observed to afford near optimal performance further in channels with large delay spreads a combination of the lmmse and df mmse front ends seems appropriate the former in earlier iterations and the latter in concluding iterations

group decodable space time block codes with code rate 1 high rate space time block codes stbc with code rate 1 in multi input multi output mimo systems are able to provide both spatial multiplexing gain and diversity gain but have high maximum likelihood ml decoding complexity since group decodable quasi orthogonal code structure can reduce the decoding complexity we present in this paper systematic methods to construct group decodable high rate stbc with full symbol wise diversity gain for arbitrary transmit antenna number and code length we show that the proposed group decodable stbc can achieve high code rate that increases almost linearly with the transmit antenna number and the slope of this near linear dependence increases with the code length comparisons with existing low rate and high rate codes such as orthogonal stbc and algebraic stbc are conducted to show the decoding complexity reduction and good code performance achieved by the proposed codes

on channel orthogonalization using space time block coding with partial feedback orthogonal space time block codes ostbcs yield full diversity gain even while requiring only a linear receiver such full rate rate one orthogonal designs are available for complex symbol constellations only for n 2 transmit antennas in this paper we propose a new family of full rate space time block codes stbcs using a single parameter feedback for communication over rayleigh fading channels for n 3 4 transmit antennas and m receive antennas the proposed rate one codes achieve full diversity and the performance is similar to maximum receiver ratio combining the decoding complexity of these codes are only linear even while performing maximum likelihood decoding the partial channel information is a real phase parameter that is a function of all the channel gains and has a simple closed form expression for n 3 4 this feedback information enables us to derive channel orthogonal designs starting from quasi orthogonal stbcs the feedback complexity is significantly lower than conventional closed loop transmit beamforming we compare the proposed codes with the open loop ostbcs and also with the closed loop equal gain transmission egt scheme which uses equal power loading on all antennas simulated error rate performances indicate that the proposed channel orthogonalized stbcs significantly outperform the open loop orthogonal designs for the same spectral efficiency moreover even with significantly lower feedback and computational complexity the proposed scheme outperforms the egt technique for m n

rank two beamforming and power allocation in multicasting relay networks in this paper we propose a novel single group multicasting relay beamforming scheme we assume a source that transmits common messages via multiple amplify and forward relays to multiple destinations to increase the number of degrees of freedom in the beamforming design the relays process two received signals jointly and transmit the alamouti space time block code over two different beams furthermore in contrast to the existing relay multicasting scheme of the literature we take into account the direct links from the source to the destinations we aim to maximize the lowest received quality of service by choosing the proper relay weights and the ideal distribution of the power resources in the network to solve the corresponding optimization problem we propose an iterative algorithm which solves sequences of convex approximations of the original non convex optimization problem simulation results demonstrate significant performance improvements of the proposed methods as compared with the existing relay multicasting scheme of the literature and an algorithm based on the popular semidefinite relaxation technique

on the blind identifiability of orthogonal space time block codes from second order statistics in this paper the conditions for blind identifiability from second order statistics sos of multiple input multiple output mimo channels under orthogonal space time block coded ostbc transmissions are studied the main contribution of the paper consists in the proof that assuming more than one receive antenna any ostbc with a transmission rate higher than a given threshold which is inversely proportional to the number of transmit antennas permits the blind identification of the mimo channel from sos additionally it has been proven that any real ostbc with an odd number of transmit antennas is identifiable and that any ostbc transmitting an odd number of real symbols permits the blind identification of the mimo channel regardless of the number of receive antennas which extends previous identifiability results and suggests that any nonidentifiable ostbc can be made identifiable by slightly reducing its code rate the implications of these theoretical results include the explanation of previous simulation examples and from a practical point of view they show that the only nonidentifiable ostbcs with practical interest are the alamouti codes and the real square orthogonal design with four transmit antennas simulation examples and further discussion are also provided

leveraging coherent space time codes for noncoherent communication via training training codes are introduced for the multiple antenna noncoherent multiple block rayleigh fading channel in which the fading coefficients which are constant over a fixed number of dimensions coherence interval for each block and then change independently to a new realization are known neither at the transmitter nor at the receiver each codeword of a training code consists of a part known to the receiver used to form a minimum mean squared error mmse estimate of the channel and a part that contains codeword s of a space time block or trellis code designed for the coherent channel in which the receiver has perfect knowledge of the channel the channel estimate is used as if it were error free for decoding the information bearing part of the training codeword training codes are hence easily designed to have high rate and low decoding complexity by choosing the underlying coherent code to have high rate and to be efficiently decodable conditions for which the estimator detector e d receiver is equivalent to the optimal noncoherent receiver are established a key performance analysis result of this paper is that the training codes when decoded with the e d receiver achieve a diversity order of the error probability that is equal to the diversity order of the underlying coherent code in some cases the performance of training codes can be measured relative to coherent reception via training efficiency which is then optimized over the energy allocation between the training and data phases in the limit of increasing block lengths training codes always achieve the performance of coherent reception the examples of training codes provided in this work have polynomial complexity in rate but an error rate comparable to the best performing unitary designs available even though the latter require exponential decoding complexity

upper bounds of rates of complex orthogonal space time block codes we derive some upper bounds of the rates of generalized complex orthogonal space time block codes we first present some new properties of complex orthogonal designs and then show that the rates of complex orthogonal space time block codes for more than two transmit antennas are upper bounded by 3 4 we show that the rates of generalized complex orthogonal space time block codes for more than two transmit antennas are upper bounded by 4 5 where the norms of column vectors may not be necessarily the same we also present another upper bound under a certain condition for a generalized complex orthogonal design its variables are not restricted to any alphabet sets but are on the whole complex plane a generalized complex orthogonal design with variables over some alphabet sets on the complex plane is also considered we obtain a condition on the alphabet sets such that a generalized complex orthogonal design with variables over these alphabet sets is also a conventional generalized complex orthogonal design and therefore the above upper bounds on its rate also hold we show that commonly used quadrature amplitude modulation qam constellations of sizes above 4 satisfy this condition

effects of non identical rayleigh fading on differential unitary space time modulation non identical fading distribution in a multiple input multiple output mimo channel including unequal average channel gains and fade rates often occurs when antennas are not co located in this paper we present an analytical study of the effects of non identical rayleigh fading on the error performance of differential unitary space time modulation dustm the fading processes for different transmit receive antenna pairs are assumed to be independent and time variant we find that the maximum likelihood ml differential detector of dustm over such channels is involved except for differential cyclic group codes the conventional detector is proved to be asymptotically optimal in the limit of high signal to noise ratio snr over static fading channels applying the distribution of quadratic forms of gaussian vectors we then derive closed form expressions for the exact error probabilities of two specific unitary classes namely cyclic group codes and orthogonal codes simple and useful asymptotic bounds on error probabilities are also obtained our analysis leads to the following general findings 1 equal power allocation is asymptotically optimal and 2 non identical channel gain distribution degrades the error performance finally we also introduce a water filling based power allocation to exploit the transmit non identical fading statistics

on full diversity space time block codes with partial interference cancellation group decoding in this paper we propose a partial interference cancellation pic group decoding strategy scheme for linear dispersive space time block codes stbc and a design criterion for the codes to achieve full diversity when the pic group decoding is used at the receiver a pic group decoding decodes the symbols embedded in an stbc by dividing them into several groups and decoding each group separately after a linear pic operation is implemented it can be viewed as an intermediate decoding between the maximum likelihood ml receiver that decodes all the embedded symbols together i e all the embedded symbols are in a single group and the zero forcing zf receiver that decodes all the embedded symbols separately and independently i e each group has and only has one embedded symbol after the zf operation is implemented the pic group decoding provides a framework to adjust the complexity performance tradeoff by choosing the sizes of the information symbol groups our proposed design criterion group independence for the pic group decoding to achieve full diversity is an intermediate condition between the loosest ml full rank criterion of codewords and the strongest zf linear independence condition of the column vectors in the equivalent channel matrix we also propose asymptotic optimal ao group decoding algorithm which is an intermediate decoding between the mmse decoding algorithm and the ml decoding algorithm the design criterion for the pic group decoding can be applied to the ao group decoding algorithm because of its asymptotic optimality it is well known that the symbol rate for a full rank linear stbc can be full i e nt for nt transmit antennas it has been recently shown that its rate is upper bounded by 1 if a code achieves full diversity with a linear receiver the intermediate criterion proposed in this paper provides the possibility for codes of rates between nt and 1 that achieve full diversity with the pic group decoding this therefore provides a complexity performance rate tradeoff some design examples are given

optimal transmitter eigen beamforming and space time block coding based on channel correlations optimal transmitter designs obeying the water filling principle are well documented and widely applied when the propagation channel is deterministically known and regularly updated at the transmitter because channel state information csi may be costly or impossible to acquire in rapidly varying wireless environments we develop in this paper statistical water filling approaches for stationary random fading channels these approaches require only knowledge of the channel correlations that do not necessitate frequent updates and can be easily acquired applied to a multiple transmit antenna paradigm our optimal transmitter design turns out to be an eigen beamformer with multiple beams pointing to orthogonal directions along the eigenvectors of the channel s correlation matrix and with proper power loading across the beams the optimality pertains to minimizing a tight bound on the symbol error rate the resulting loaded eigen beamforming outperforms not only the equal power allocation across all antennas but also the conventional beamformer that transmits the available power along the strongest direction coupled with orthogonal space time block codes two dimensional 2 d eigen beamforming emerges as a more attractive choice than conventional one dimensional 1 d beamforming with uniformly better performance without rate reduction and without complexity increase

robust linear receivers for space time block coded multiaccess mimo systems with imperfect channel state information recently several linear receiver algorithms have been developed for space time block coded multiaccess multiple input multiple output mimo wireless communication systems all these techniques are based on the assumption that the channel state information csi at the receiver side is perfect however in practical situations the available csi may be imperfect because of channel estimation errors and or outdated training in this paper we develop new robust linear receiver techniques for joint space time decoding and interference rejection in multiaccess mimo systems that use orthogonal space time block codes and erroneous csi the proposed receivers are based on worst case performance optimization they are shown to provide a substantially improved robustness against csi mismatches as compared with the existing linear multiaccess mimo receivers

a linear fractional semidefinite relaxation approach to maximum likelihood detection of higher order qam ostbc in unknown channels this paper considers the blind maximum likelihood ml detection problem for orthogonal space time block codes ostbcs in multiple input multiple output flat fading channels while the blind ml detection problem for general space time codes is difficult to solve it has been shown that for ostbcs with constant modulus constellations the blind ml detection problem can be formulated as a discrete quadratic program and then handled by a powerful convex approximation technique known as semidefinite relaxation sdr in this paper we turn our attention to the case of higher order qam ostbcs due to the nonconstant modulus nature of higher order qam signals the blind ml detection problem turns out to be a discrete rayleigh quotient maximization problem and as a result the current sdr technique is no longer directly applicable we propose a linear fractional sdr lfsdr approach to this problem this approach first relaxes the higher order qam blind ml detection problem into a quasi convex problem followed by a simple solution approximation procedure in general quasi convex problems are computationally more complex to solve than convex problems but we show that an optimum solution of our quasi convex problem can be efficiently obtained by solving a convex semidefinite program the approximation accuracy of the proposed approach relative to other possible relaxation approaches is also studied simulation results are presented to demonstrate that the proposed lfsdr based blind ml detector outperforms some existing suboptimal detectors and can yield promising performance even with a small to moderate number of code blocks

a symbol by symbol channel estimation receiver for space time block coded systems and its performance analysis on the nonselective rayleigh fading channel we present a symbol by symbol channel estimation receiver for an orthogonal space time block coded system and derive its analytical performance on a slow nonselective rayleigh fading channel exact closed form expressions for its bit error probability bep performance for m ary phase shift keying modulations are obtained which enable us to theoretically predict the actual performance achievable under practical conditions with channel estimation error our bep expressions show explicitly the dependence of bep on the mean square error of the channel estimates which in turn depend on the channel fading model and the channel estimator used tight upper bounds are presented that show more clearly the dependence of the bep on various system parameters simulation results using various fading models are obtained to demonstrate the validity of the analysis

the theory of quaternion orthogonal designs over the past several years there has been a renewed interest in complex orthogonal designs for their application in space time block coding motivated by the success of this application this paper generalizes the definition of complex orthogonal designs by introducing orthogonal designs over the quaternion domain this paper builds a theory of these novel quaternion orthogonal designs offers examples and provides several construction techniques these theoretical results along with the results of preliminary simulations lay the foundation for developing applications of these designs as orthogonal space time polarization block codes

design of block transceivers with decision feedback detection this paper presents a method for jointly designing the transmitter receiver pair in a block by block communication system that employs intrablock decision feedback detection we provide closed form expressions for transmitter receiver pairs that simultaneously minimize the arithmetic mean squared error mse at the decision point assuming perfect feedback the geometric mse and the bit error rate of a uniformly bit loaded system at moderate to high signal to noise ratios separate expressions apply for the zero forcing and minimum mse mmse decision feedback structures in the mmse case the proposed design also maximizes the gaussian mutual information and suggests that one can approach the capacity of the block transmission system using independent instances of the same gaussian code for each element of the block our simulation studies indicate that the proposed transceivers perform significantly better than standard transceivers and that they retain their performance advantages in the presence of error propagation