Max-Min Fair RIS-Aided Rate-Splitting Multiple Access for Multigroup Multicast Communications

Rate-splitting multiple access(RSMA)can cope with a wide range of propagation conditions in multigroup multicast communications through rate splitting optimization.To breakthrough the grouprate limited bottleneck,reconfigurable intelligent surface(RIS)technique can be introduced to assist wireless communications through enhancing the channel quality.In RIS-aided RSMA multigroup multicasting,how to provide fair and high-quality multiuser service under power and spectrum constraints is essential.In this paper,we propose a max-min fair RIS-aided rate-splitting multiple access(MMF-RISRSMA)scheme for multigroup multicast communications,where the rate fairness is obtained by maximizing the minimum group-rate.In doing so,we jointly optimize the beamformers,the rate splitting vector at the transmitter,as well as the phase shifts at RIS.To solve it,we divide the original optimization problem into two subproblems and alternately optimize the variables.The beamforming and rate splitting optimization subproblem is solved by using the successive convex approximation technique.The phase shift optimization subproblem is solved through the penalty function method to achieve a rank-one locally optimal solution.Simulations demonstrate that the proposed MMF-RIS-RSMA scheme can obtain significant performance gain in terms of the minimum group-rate.

Information Freshness-Oriented Trajectory Planning and Resource Allocation for UAV-Assisted Vehicular Networks

In this paper,multi-UAV trajectory planning and resource allocation are jointly investigated to improve the information freshness for vehicular networks,where the vehicles collect time-critical traffic information by on-board sensors and upload to the UAVs through their allocated spectrum resource.We adopt the expected sum age of information(ESAoI)to measure the network-wide information freshness.ESAoI is jointly affected by both the UAVs trajectory and the resource allocation,which are coupled with each other and make the analysis of ESAoI challenging.To tackle this challenge,we introduce a joint trajectory planning and resource allocation procedure,where the UAVs firstly fly to their destinations and then hover to allocate resource blocks(RBs)during a time-slot.Based on this procedure,we formulate a trajectory planning and resource allocation problem for ESAoI minimization.To solve the mixed integer nonlinear programming(MINLP)problem with hybrid decision variables,we propose a TD3 trajectory planning and Round-robin resource allocation(TTPRRA).Specifically,we exploit the exploration and learning ability of the twin delayed deep deterministic policy gradient algorithm(TD3)for UAVs trajectory planning,and utilize Round Robin rule for the optimal resource allocation.With TTP-RRA,the UAVs obtain their flight velocities by sensing the locations and the age of information(AoI)of the vehicles,then allocate the RBs to the vehicles in a descending order of AoI until the remaining RBs are not sufficient to support another successful uploading.Simulation results demonstrate that TTP-RRA outperforms the baseline approaches in terms of ESAoI and average AoI(AAoI).

Design and Analysis of Spatial Modulation Based Orthogonal Time Frequency Space System

In this paper,we design a spatial modulation based orthogonal time frequency space(SMOTFS)system to achieve improved transmission reliability and meet the high transmission rate and highspeed demands of future mobile communications,which fully utilizes the characteristics of spatial modulation(SM)and orthogonal time frequency space(OTFS)transmission.The detailed system design and signal processing of the SM-OTFS system have been presented.The closed-form expressions of the average symbol error rate(ASER)and average bit error rate(ABER)of the SM-OTFS system have been derived over the delay-Doppler channel with the help of the union bounding technique and moment-generating function(MGF).Meanwhile,the system complexity has been evaluated.Numerical results verify the correctness of the theoretical ASER and ABER analysis of the SM-OTFS system in the high signal-to-noise ratio(SNR)regions and also show that the SM-OTFS system outperforms the traditional SM based orthogonal frequency division multiplexing(SM-OFDM)system with limited complexity increase under mobile conditions,especially in high mobility scenarios.

Analysis of Lifetime of Large Wireless Sensor Networks Based on Multiple Battery Levels

Due to the limited transmission range, data sensed by each sensor has to be forwarded in a multi-hop fashion before being delivered to the sink. The sensors closer to the sink have to forward comparatively more messages than sensors at the periphery of the network,and will deplete their batteries earlier. Besides the loss of the sensing capabilities of the nodes close to the sink, a more serious consequence of the death of the first tier of sensor nodes is the loss of connectivity between the nodes at the periphery of the network and the sink;it makes the wireless networks expire. To alleviate this undesired effect and maximize the useful lifetime of the network, we investigate the energy consumption of different tiers and the effect of multiple battery levels, and demonstrate an attractively simple scheme to redistribute the total energy budget in multiple battery levels by data traffic load. We show by theoretical analysis, as well as simulation, that this substantially improves the network lifetime.

Perioperative toripalimab plus neoadjuvant chemotherapy might improve outcomes in resectable esophageal cancer:an interim analysis of a phase Ⅲ randomized clinical trial

Background:In the era of immunotherapy,neoadjuvant immunochemotherapy(NAIC)for the treatment of locally advanced esophageal squamous cell carcinoma(ESCC)is used clinically but lacks of high-level clinical evidence.This study aimed to compare the safety and long-term efficacy of NAIC followed byminimally invasive esophagectomy(MIE)with those of neoadjuvant chemotherapy(NAC)followed by MIE.Methods:A prospective,single-center,open-label,randomized phase Ⅲ clinical trial was conducted at Henan Cancer Hospital,Zhengzhou,China.Patients were randomly assigned to receive either neoadjuvant toripalimab(240mg)plus paclitaxel(175 mg/m^(2))+cisplatin(75 mg/m^(2))(toripalimab group)or paclitaxel+cisplatin alone(chemotherapy group)every 3 weeks for 2 cycles.After surgery,the toripalimab group received toripalimab(240 mg every 3 weeks for up to 6 months).The primary endpoint was event-free survival(EFS).The pathological complete response(pCR)and overall survival(OS)were key secondary endpoints.Adverse events(AEs)and quality of life were also assessed.Results:Between May 15,2020 and August 13,2021,252 ESCC patients ranging fromT1N1-3M0 to T2-3N0-3M0were enrolled for interim analysis,with 127 in the toripalimab group and 125 in the chemotherapy group.The 1-year EFS rate was 77.9%in the toripalimab group compared to 64.3%in the chemotherapy group(hazard ratio[HR]=0.62;95%confidence interval[CI]=0.39 to 1.00;P=0.05).The 1-year OS rates were 94.1%and 83.0%in the toripalimab and chemotherapy groups,respectively(HR=0.48;95%CI=0.24 to 0.97;P=0.037).The patients in the toripalimab group had a higher pCR rate(18.6%vs.4.6%;P=0.001).The rates of postoperative Clavien-Dindo grade Ⅲb or higher morbidity were 9.8%in the toripalimab group and 6.8%in the chemotherapy group,with no significant difference observed(P=0.460).The rates of grade 3 or 4 treatment-related AEs did not differ between the two groups(12.5%versus 12.4%).Conclusions:The interim results of this ongoing trial showed that in resectable ESCC,the addition of perioperative toripalimab to NAC is safe,may improve OS and might change the standard treatment in the future.