A novel low-complexity power allocation algorithm based on the NOMA system in a low-speed environment

For future wireless communication systems,Power Domain Non-Orthogonal Multiple Access(PD-NOMA)using an advanced receiver has been considered as a promising radio access technology candidate.Power allocation plays an important role in the PD-NOMA system because it considerably affects the total throughput and Geometric Mean User Throughput(GMUT)performance.However,most existing studies have not completely accounted for the computational complexity of the power allocation process when the User Terminals(UTs)move in a slow fading channel environment.To resolve such problems,a power allocation method is proposed to considerably reduce the search space of a Full Search Power(FSP)allocation algorithm.The initial power reallocation coefficients will be set to start with former optimal values by the proposed Lemma before searching for optimal power reallocation coefficients based on total throughput performance.Step size and correction granularity will be adjusted within a much narrower power search range while invalid power combinations may be reasonably discarded during the search process.The simulation results show that the proposed power reallocation scheme can greatly reduce computational complexity while the total throughput and GMUT performance loss are not greater than 1.5%compared with the FSP algorithm.

A New SLM Scheme Based on Constellation Rotation for PAPR Reduction

A new selected mapping(SLM)scheme based on constellation rotation is proposed to reduce the peak-to-average power ratio(PAPR)of orthogonal frequency division multiplexing(OFDM)signals.Its core idea is to generate abundant candidate signals by rotating different sub-signals of the original frequency signal with different angles.This new signal generation method can simplify the calculation process of candidate time signals into the linear addition of some intermediate signals,which are generated by the inverse fast Fourier transform(IFFT)operation of the original frequency signal.This feature can effectively reduce the computational complexity of candidate signal generation process.And compared to the traditional SLM scheme,the number of complex multiplication and complex addition of new scheme can separately be decreased by about 99.99% and 91.7% with some specific parameters.Moreover,with the help of the constellation detection mechanism at the receiver,there is no need to carry any side information at the transmitter.The simulation results show that,with the same channel transmission performance,the PAPR reduction performance of new scheme can approach or even exceed the upper bound of the traditional SLM scheme,which uses all the vectors in Hadamard matrix as the phase sequences.

A Secure Visual Secret Sharing Scheme with Authentication Based on QR Code

With the rise of the Internet of Things(IoT),various devices in life and industry are closely linked.Because of its high payload,stable error correction capability,and convenience in reading and writing,Quick Response(QR)code has been widely researched in IoT.However,the security of privacy data in IoT is also a very important issue.At the same time,because IoT is developing towards low-power devices in order to be applied to more fields,the technology protecting the security of private needs to have the characteristics of low computational complexity.Visual Secret Sharing(VSS),with its features of safety and low computational cost,can fully meet the requirements of communication security in IoT.Therefore,a VSS scheme with QR code(VSS-QR)was proposed and has been applied to some extent.In VSS-QR,the secret is shared into a series of shares.These shares are usually common QR codes,which cannot cause the attention of the attacker.However,if there is dishonesty among participants,the secret cannot be recovered,which will lead to VSS-QR cannot be widely used due to its inadequate security.In this paper,we propose a visual secret sharing scheme with authentication based on QR code(VSSA-QR).Both the reconstructed secret QR code and shares can be verified whether they are forged by attackers.The above-mentioned operations conveniently are performed on low-power QR scanning devices.Not only does the proposed scheme prevent some dishonest participants or attackers from cheating,but also prevent all participants from conspiring.In addition,the payload is the QR code itself,which is higher than other schemes.Theoretical analysis and experiments prove that the proposed scheme is effective.