NDA-EVM Based Channel Quality Evaluation Method In D2D Communication

With the rapid development of communication technology,the contradiction between the explosive growth of data traffic and the scarce spectrum resources starts to draw more attention.D2 D communication technology allows the terminal equipment to communicate with each other directly.D2 D technology can reuse the spectrum resources in a short distance,thus reducing cell load pressure and improving spectrum utilization.This transmission scheme with short distance and low power is an effective way to solve the contradiction mentioned above.However,due to the reuse of spectrum resources,D2 D technology not only brings considerable benefits to the system,but also inevitably introduces a lot of co-channel interference to the cellular network,therefore,mode selection,power control,resource allocation and other technologies are applied to effectively coordinate the communication between D2 D users and cellular users,reduce the co-channel interference.The design of the above technologies depends on accurate channel state information CSI.The real-time and accuracy of CSI are important factors that determine the rationality of the above kinds of interference control technologies.Therefore,it is necessary to evaluate the channel quality in D2 D communication to obtain accurate CSI.However,the diversity of D2 D communication scenes and the complexity of interference scenes greatly increase the difficulty of interference detection in the communication channel.By using reliable and accurate channel state information,the quality of channel can be accurately detected,which is the key of interference detection technology.In this paper,a new method based on nondate-aided error vector magnitude is proposed to estimate channel quality,providing a more accurate and immediate channel evaluation,so as to provide a reference index for interference control technology in D2 D.This paper mainly studies the estimation of channel quality in D2 D communication for cellular networks.The main research contents are divided into the following two parts:(1)To solve the problem that traditional channel evaluation parameters fail to provide real-time and accurate channel state information effectively,this paper proposes to use NDA-EVM evaluation parameter to evaluate the link state of D2 D communication.By giving the general NDA-EVM upper bound expression of M-QAM signal,the worst possible performance of the transmission channel under the current conditions can be predicted,which provides specific parameters for the evaluation of channel quality in D2 D communication system.In this paper,the accuracy of the performance upper bound evaluation is analyzed by solving the minimum root mean square error of the NDA-EVM performance upper bound.The sensitivity of the NDA-EVM performance upper limit to the channel fading factor is calculated,quantifying the sensitivity of the proposed evaluation algorithm to channel change.In addition,the time complexity of the upper bound algorithm is compared with that of the traditional algorithm.The theoretical analysis and simulation results show that the NDA-EVM upper bound can reduce the time complexity of the algorithm while maintaining the accuracy of the evaluation,and is sensitive to channel changes,which can provide real-time and accurate channel quality evaluation for D2 D communication.(2)Aiming at the problem that the traditional channel quality estimation algorithm fails to predict the channel quality under the influence of co-channel interference,this paper proposes a link quality estimation algorithm based on NDA-EVM under the influence of co-channel interference.The algorithm takes NDA-EVM as the channel quality evaluation parameter,uses the channel gain influenced by interferences as the intermediate variable,establishes the model of NDA-EVM under the influence of cochannel interference,deduces the upper limit of NDA-EVM under the influence of cochannel interference,determine the worst performance of a transmission channel under co-channel interference.The simulation results show that the proposed method based on NDA-EVM can reflect the change of the co-channel interference correctly.The derived upper bound closely matches with the theoretical value,especially at low SNR and low modulation order,thus can provide consistent channel quality estimation function even under the condition of bad channel.