Strategy Study On Space-Time Coding For MIMO Power Line Communication System

Smart grid has attracted much attention lately due to its convenient structure that can make power supply to achieve energy conservation,reduce losses and enhance reliability.Nevertheless,the implementation of smart grid function rely on real-time operation,which makes the fast and reliable communication between terminals as a key factor in its success.As the Multi-Input Multiple-Output Power Line Communication(MIMO-PLC)system can achieve full coverage of the power network with the original power grid infrastructure,doubling the system capacity and spectrum utilization,and space-time coding is the main technology to achieve MIMO diversity.To this end,researches are extended focuses on the application of manifold differential unitary space-time code for MIMO-PLC system in this paper.And combined with the simulation,the performance of these schemes are analyzed and compared likewise.Firstly,in the light of the C hannel Transfer Function(C TF)and the noise distribution model of MIMO-PLC system,the construction of applying unitary space-time codes that without knowing channel status information was proposed in this paper.Above all,the scheme first maps the information data to the constellations with diagonal block unitary matrices which satisfying the diversity product criterion,and the unitary space-time codes are formed in a differential manner subsequently,the corresponding codeword is connected via a digital-to-analog converter module and then coupled to a different power line port via a power line channel.Finally,the receiver uses the maximum likelihood(ML)decoding to get the estimated value of the transmitted message.The simulation results show that the CTF and the noise distribution model are consistent with the mea sured results.In addition,in the MIMO-PLC system with low transmission rate requirements,the differential unitary space-time code can significantly improve the performance of the system,especially for a PLC system with high impulse noise amplitude.Secondly,in view of that the unitary matrix satisfying the diversity criterion is difficult to construct and the data transmission rate is low,clustering with Cayley differential unitary space-time code to the MIMO-PLC system was presented Firstly,the codes maps the highly nonlinear Stiefel manifold of unitary matrices to the linear space of skew-Hermitian matrices.This transformation leads to a simple linear constellation structure in the Cayley transform domain and to an information-theoretic design criterion based on emulating a Cauchy random matrix.Moreover,the resulting Cayley codes allow polynomial-time ML decoding.Simulation results demonstrate that,although the Cayley difference unitary space-time code will improve the system error rate to a certain extent,it is also very important for the MIMO-PLC environment with higher demand of the data transmission rate.Subsequently,in terms of the the problem that for the high speed data transmission in the MIMO-PLC system,the multipath environment makes the MIMO channel a frequency selective fading channel,clustering with improved propose to apply orthogonal frequency division multiplexing(OFDM)modulation to broadband PLC system was explored.The scheme converts the frequency selective channel into an equivalent set of multiple flat fading subchannels,combining the orthogonal 43 ? space-time block codes so that each of the carrier time-space symbols for each OFDM packet is transmitted.And subcarriers can be considered to be transmitted in a flat fading channel.Simulation results indicate that,with the increase of the number of subcarriers,the performance of the system is improved significantly.Finally,in order to solve the problem that it is difficult to construct the unitary matrix constellation caused by nonlinearity of the matrix Stiefel manifold and the nonconvexity of the signal set and the cost function,the differential space-time codes based on the special Lie group SP(1),SU(3)were applied to MIMO-OFDM-PLC systems.The above coding scheme is used to induce the linear unitary matrix constellation satisfying the criterion of the product in the nonlinear special Lie group by relaxing the constraint condition of the fixed point group which can reach the full diversity.Then,further simplifyed the structure by abandoning the restriction that both the matrices have unit determinan,two AB group difference unitary space-time code were proposed.S imulation results make known that the proposed coding scheme can provide higher data transmission rate and obtain higher diversity product without sacrificing the performance of the system.With the increase of the number of subcarriers,the bit error rate of SP(1)differential unitary space time code is significantly reduced,and the latter three kinds of coding will be improved to some extent.