Research On Non-orthogonal Multiple Access Technology For B5G Internet Of Vehicles

With the development of intelligent transportation,various computation-intensive and latency-sensitive applications are emerging in the Internet of Vehicles(IoV).The IoV network in the beyond 5G(B5G)era has the characteristics of ultra-low latency and massive connections.However,for future Vehicle-to-everything(V2X)networks,traditional orthogonal multiple ac-cess(OMA)-based networks will face congestion issues.Due to the low access efficiency of OMA,this will lead to significant access latency and pose significant challenges to safety-critical applications.Compared with OMA,non-orthogonal multiple access(NOMA)allows different users to share the same time/frequency/code domain resources,thereby achieving higher spec-trum efficiency,supporting large-scale user access,ensuring user fairness,and reducing trans-mission latency and signaling overhead.Therefore,NOMA technology has been recognized as one of the effective solution to the problems currently faced by IoV.This paper mainly discusses several key applications of NOMA in the IoV network.Specifically,the work of this paper can be summarized as follows:1.A novel NOMA scheme that can further improve the IoV performance is proposed.In conventional power-domain NOMA,multiple users are multiplexed in the same time and frequency band with different preset power levels,which,however,may limit the spectral effi-ciency under practical finite alphabet inputs.Inspired by the concept of spatial modulation,we propose to solve this problem by encoding extra information bits into the power levels,and ex-ploiting different signal constellations to help the receiver distinguish between them.To convey this idea,termed power selection(PS)-NOMA,clearly,we consider a simple downlink two-user NOMA system with finite input constellations.Assuming maximum-likelihood detection,we derive closed-form approximate bit error ratio(BER)expressions for both users.Moreover,the two-user achievable rate region is also characterized.Simulation results verify the analysis and show that the proposed PS-NOMA can outperform conventional NOMA in terms of BER and achievable rate.2.The design of cooperative direct transmission and relay transmission system in IoV is deeply discussed.Considering the large number of vehicles in IoV,this paper firstly analyzes the situation where there are multiple edge vehicle users in a cell.Assuming that the mutual interference cancellation between users is imperfect and the relay adopts the decode-and-forward(DF)mode,This paper specifically discusses two different scenario where the relay utilizes two different protocols,i.e.,full-duplex(Full-duplex,FD)and half-duplex(Half-duplex,HD).Both the exact analytical expression of outage probability and an approximate expression of the ergodic sum rate at high signal-to-noise ratio(SNR)are derived.In addition,this paper also analyzes the specific characteristics of various performance indicators in the case of high and low SNR.3.A NOMA-based pervasive edge computing(Pervasive Edge Computing,PEC)power allocation framework in IoV is constructed.In order to meet the security and system delay re-quirements of IoV in the B5 G era,after considering factors such as eavesdroppers,server queu-ing model,imperfect channel state information and vehicle moving speed,this paper proposes a resource allocation algorithm that minimizes system delay.Furthermore,this paper considers the lower bound of the objective function and derives a suboptimal closed-form solution for the power distribution coefficient.Simulation results illustrate the superior performance of the proposed NOMA scheme.4.A NOMA-based caching framework in IoV is designed,and a hybrid multicast/unicast scheme is proposed in the face of fast fluctuating vehicular wireless channels.Considering a more practical situation,imperfect channel state information is taking into account.In this paper,we formulate an optimization problem to maximize the unicast sum rate under the constraints of the peak power,the peak backhaul,the minimum unicast rate,and the maximum multicast outage probability.To solve the formulated non-convex problem,a lower bound relaxation method is proposed,which enables a division of the original problem into two convex sub-problems.Computer simulations show that the proposed caching-aided NOMA is superior to the orthogonal multiple access counterpart.