Journal of Communications and Information Networks
Print ISSN 2096-1081 CN 10-1375/TN
Editor-in-Chief: Wei Zhang
Abstract—This paper investigates the power allocation problem in non-orthogonal multiple access (NOMA)integrated unmanned aerial vehicle (UAV) communication systems.In particular, we propose a novel resource allocation scheme to increase the transmission rate of the users that have relatively worse channel state information, while reducing the sum rate loss.To solve this problem efficiently, we decouple the optimization problem into three subproblems.First, we solve the problem of user pairing and subchannel allocation.Second,the optimum power proportional factor is derived to allocate transmit power among different users on the same subchannel.At last,different subchannels are allocated with appropriate power to improve the performance of the subchannels.Simulation results show that the proposed scheme can enjoy a better performance than the benchmark methods since it can achieve a proper trade-off between the system sum rate and the proportional fairness.
基于用户公平性的UAV-NOMA通信系统资源分配
本文研究了非正交多址技术在无人机通信系统中应用的功率分配问题。特别地，本文提出了一种新的资源分配方案来提高信道状态信息相对较差的用户的传输速率，同时将系统和速率的损失最小化。为了有效地解决这一问题，本文将优化问题分解为三个子问题。首先，我们优化了用户配对和子信道分配问题。其次，推导出在同一子信道上不同用户间分配发射功率的最优功率比例因子。最后，为不同的子信道分配适当的功率，以提高子信道的性能。仿真结果表明，该方案能够在系统和速率和用户公平性之间取得适当的平衡，因而比基准方案具有更好的性能。
Abstract—The performance of conventional direction of arrival (DOA) method is greatly affected by the uncertainty of wave velocity in underwater environment.To solve this problem, an acoustic velocity-independent method is proposed to estimate the underwater DOA using two arbitrary intersecting uniform linear arrays in this study.By introducing the additional array compared to the conventional DOA methods,the proposed algorithm can make its performance independent of the acoustic velocity through the geometric relationship between those two arrays.The simulation results demonstrate that the proposed method is more accurate and robust than other methods in an unknown sound velocity.
基于任意一维阵列的声速独立的DOA估计方法
水下环境中波速的不确定性极大地影响了传统到达角（Direction of Arrival，DOA）估计方法的性能。为了解决这个问题，本文提出了一种利用两个任意相交均匀线性阵列的声速独立DOA估计方法。与传统的DOA估计方法相比，提出的算法通过引入一个额外的阵列，并且利用两个阵列之间的几何关系来获得与声速无关的DOA估计算法。仿真结果表明，本文提出的方法在未知声速的情况下比其他方法更加准确、稳健。
Abstract—Direction-of-arrival (DOA) estimation is an important task in many unmanned aerial vehicle (UAV) applications.However, the complicated electromagnetic wave propagation in urban environments substantially deteriorates the performance of many conventional model-driven DOA estimation approaches.To alleviate this, a deep learning based DOA estimation approach is proposed in this paper.Specifically, a complex-valued convolutional neural network (CCNN) is designed to fit the electromagnetic UAV signal with complex envelope better.In the CCNN design,we construct some mapping functions using quantum probabilities, and further analyze some factors which may impact the convergence of complex-valued neural networks.Numerical simulations show that the proposed CCNN converges faster than the real convolutional neural network, and the DOA estimation result is more accurate and robust.
复卷积神经网络设计及其在城市环境下无人机方向估计中的应用
DOA估计是无人机应用中的一个重要任务。然而，城市复杂的电磁传播环境会降低传统基于模型驱动的DOA估计方法的性能。为了减轻环境影响，提出一种基于深度学习的DOA估计方法。具体而言，该方法采用复值卷积神经网络，以便更好的表征无人机无线信号的复包络特性。本文使用复数域概率来构建复值卷积神经网络映射函数，并进一步分析了影响复值卷积神经网络收敛性的因素。数值仿真的结果表明，针对DOA估计任务，复值卷积神经网络在收敛速度、准确性和鲁棒性等方面都优于传统的实值卷积神经网络。
Abstract—This paper investigates a simple design of intelligent reflecting surface (IRS) based unmanned aerial vehicles(UAV)assisted multiple-input single-output nonorthogonal multiple access (NOMA) downlink network.The aim of this paper is to maximize the rate of the strong user while guaranteeing the target rate of the weak user given by the optimized UAV horizontal position.We first optimize the location of IRS-UAV.Then we propose an iterative algorithm to optimize the transmit beamforming and phase shift of IRS alternatively.For the beamforming optimization, the closed-form expressions of the optimal beamforming vectors are derived.Then, given by the obtained beamforming, we propose two methods to obtain the optimal phase shifting of IRS.One is the semidefinite relaxation based iteration algorithm which provides high data rate and the other one is based on successive convex approximation technique which has low complexity.Finally, simulation results are provided to show that the performance of the two proposed algorithms are significantly better than using random phase shifting scenario and IRS based UAV-assisted orthogonal frequency-division multiple access scheme.
IRS辅助的NOMA下行UAV网络中的联合波束成形和相移设计
本文研究了一种基于智能反射表面（Intelligent Reflecting Surface，IRS）与无人机（Unmanned Aerial Vehicles，UAV）的多输入单输出非正交多址（Nonorthogonal Multiple Access，NOMA）下行传输网络的简单设计。论文研究的目的是在给定UAV最优水平位置、以及保证弱用户数据速率需求的前提下，最大化强用户的数据传输速率。论文首先对挂载IRS的UAV位置进行了优化，进而提出了一种迭代算法以交替优化IRS的发射波束与相移参数。针对波束成形优化，论文推导获得了最优波束成形矢量的闭式表达。以此为基础，设计提出了两种获得IRS最优相移的方法，即基于半定松弛的迭代算法与基于连续凸逼近技术的算法。其中前者可以提供高数据速率，后者具有较低复杂度。仿真结果表明，论文所提两类算法的性能皆明显优于随机相移方案，以及IRS-UAV正交分频多址方案。
Abstract—Since mobile nodes such as autonomous underwater vehicles can effectively expand network coverage, underwater acoustic networks with mobile nodes have attracted more and more attention in recent years.To ensure the timely access of a mobile node without disturbing the normal transmission of data packets from static nodes, a sequence-scheduled and query-based medium access control protocol is proposed in this paper.The underwater nodes with data packets to be transmitted reply with a control packet for channel reservation after receiving the broadcast control packet of the buoy, then the reserved nodes transmit their data packets as the order calculated by the buoy.We develop a mechanism to adjust the transmission order of the control packets sent by the underwater nodes in the handshake phase to reduce the collision and guarantee the success rate of reservation, and a query is initiated when the reserved control packet of the mobile node is not received by the buoy in the handshake to respond to the data transmission request of the mobile node in time.Simulations show that the maximum nodal throughput of the proposed MAC protocol increases by at least 20% and the access delay of the mobile node decreases by about 90%,compared to the two reference protocols.Besides, the average access probability of the mobile node in the proposed protocol is more than 90%.
基于顺序调度与查询机制的水声网络移动节点接入协议
由于无人潜航器、自主水下航行器等移动节点可有效扩展网络覆盖范围，近年来带移动节点的水声网络得到了越来越多的关注。为了在不影响固定节点数据包正常传输的同时，保证移动节点的及时接入，本文提出了基于顺序调度与查询机制的MAC协议。有数据包需要传输的节点在收到浮标（接收端）广播的控制包后回复相应的控制包完成预约，并根据浮标规划的数据包传输顺序发送缓存空间中的数据包。为保证预约成功率，我们提出了控制包发送顺序的调整机制，并在浮标未接收到移动节点的预约控制包时，启动查询机制，为移动节点分配更高的接入优先级，及时响应移动传输。仿真结果表明，提出协议的固定节点最大吞吐量较其他两种对比协议至少增加了20%，移动节点的接入时延最多减少90%，且移动接入成功率始终大于90%。
Abstract—Recently, battery capacity and charging speed have been the bottlenecks of mobile communication networks.Energy harvesting (EH) relaying has become a promising solution for green 5th generation mobile communication with the advancement of wireless power transfer technology.In this paper, we investigate EH relaying in vehicular networks and adopt distributed beamforming(DB)to enhance the reliability and capacity of EH relaying.To be more specific, we propose a DB solution based on the joint optimization of power-splitting (PS)factors.For amplify-and-forward relaying,to transform the optimization problem into a quasi-convex one, we apply the semidefinite relaxation(SDR)method so that we can effectively attain the global optimal solution,while the suboptimal DB solution with distributed optimal PS factor which only requires local channel state information is also proposed.For decode-and-forward relaying, to get the optimal PS factors, we set a signal-to-noise ratio threshold at the relays,which can reduce the system error rate caused by the poor transmission link.Simulation results demonstrate the efficiency of our proposed DB-based EH relaying scheme in vehicular networks.
车联网中基于能量采集中继的分布式波束成形传输
近年来，电池容量和充电速度成为移动通信网络发展的重要约束。随着无线能量传输技术的发展，能量采集（Energy Harvesting，EH）中继已经成为5G绿色通信的一种有前景的解决方案。在本文中，我们研究了车联网中的EH中继，并采用分布式波束成形（Distributed Beamforming，DB）方案来提高EH中继传输的可靠性和传输容量。更具体地说，我们提出了一种基于功率分配（Power-Splitting，PS）因子联合优化的DB策略。对于放大–转发（Amplify-and-Forward，AF）中继，为了将优化问题转化为一个准凸优化问题，我们应用了半定松弛（Semidefinite Relaxation，SDR）方法，以便可以有效地获得全局最优解，同时还给出了只需要本地信道状态信息的具有分布最优PS因子的次优DB解。对于解码–转发（Decode-and-Forward，DF）中继，为了获得最优PS因子，我们在中继处预设了一定的信噪比阈值，可以有效降低由于传输链路不良而导致的系统误码率。仿真结果证明了我们在车联网中提出的基于DB的EH中继方案的有效性。
Abstract—In this paper, we consider the problem of Doppler tracking and compensation for a direct sequence spread spectrum (DSSS) signal in underwater acoustic (UWA) communication.Since the dynamic property of the UWA channel and the long duration of DSSS signals result in significant Doppler spread that severely distorts the propagated signal, Doppler tracking and compensation are required.Based on the ultra-wideband property of UWA signal, the Doppler spread not only results in the frequency shift,but also changes the signal duration.Therefore,the accurate estimation of the signal expansion/compression in the time domain can reflect the Doppler spread.Accordingly, we present a Doppler tracking and compensation algorithm for a DSSS signal operating on the correlation output of passband signal at a symbol-by-symbol basis.Note that the carrier frequency of UWA communication is around several kilohertz, and thus the time delay estimation can be performed on the passband to improve the accuracy.Furthermore, the prior information of Doppler limit is used to refine the resolution of delay estimation and achieve sequential estimation.To compensate the correlation magnitude distortion induced by the velocity variation, the local reference signal is selected adaptively based on the filtered Doppler factor.Simulation results demonstrate that the proposed passband Doppler tracking algorithm achieves a superior performance compared with the conventional receiver.
一种适用于水声直扩通信的符号级通带多普勒跟踪及补偿算法
本文主要研究水声通信中适用于直接序列扩频信号的多普勒跟踪及补偿的方法。由于水声信道的动态特性以及直扩信号的持续时间长的特点，导致极其明显的多普勒扩展现象，使得水下传播的通信信号存在严重衰减，继而影响通信性能，因此针对直扩信号的多普勒跟踪以及补偿方法显得尤为重要。由于水声信号的超宽带特性，多普勒扩展不仅表现为频率偏移，还会导致信号脉宽产生相应的变化。因此，可以利用高精度的时间估计来计算对应的频率偏移以及多普勒因子。基于此特性，本文提出了一种适用于水声直扩通信的多普勒跟踪以及补偿算法。该算法以符号间隔为处理步长进行序贯处理，并且以通带匹配相关的输出作为输入而不是以解调后的基带信号作为输入。基于通带相关输出信号的时延估计精度远高于基带时延估计。注意到水声通信的载波频率通常低于几十千赫兹，因此对通信信号直接进行匹配相关的复杂度是可以接受的。为了进一步提高时延估计精度，将多普勒容限以及前一符号的时延估计结果作为先验信息以估计当前符号的时延。为了补偿导致的相关幅度衰减，本地参考信号根据时延估计结果计算的多普勒因子进行动态调整。为了提高该算法的抗噪声性能，对多普勒因子进行平滑滤波以防止本地参考信号的突变。仿真结果验证了该算法的可行性，并且性能远好于传统的直扩接收机算法。
Abstract—Wireless backhaul is considered to be the key part of the future wireless network with dense small cell traffic and high capacity demand.In this paper,we focus on the design of a high spectral efficiency line-of-sight (LoS)multiple-input multiple-output(MIMO)system for millimeter wave backhaul using dual-polarized frequency division duplex (FDD).High spectral efficiency is very challenging to achieve for the system due to various physical impairments such as phase noise(PHN),timing offset (TO) as well as the poor condition number of the LoS MIMO.In this paper, we propose a holistic solution containing TO compensation, PHN estimation, precoder/decorrelator optimization of the LoS MIMO for wireless backhaul,and the interleaving of each part.We show that the proposed solution has a robust performance with end-to-end spectral efficiency of 60 bit/s/Hz for 8×8 MIMO.
频分双工LoS MIMO系统中的高容量毫米波回传技术
无线回传是未来无线网络的关键部分，对于密集的小蜂窝系统以及高容量的通信需求更是尤为重要。在本文中，我们对基于频分双工LoS MIMO的高容量毫米波回传进行了系统级的设计。我们考虑了高频率传输中各种非理想物理条件带来的影响，例如：相位噪声（PHN）、时钟偏移（TO）以及LoS MIMO的病态信道。这些非理想物理条件使得在高频率波段实现高频谱效率非常具有挑战性。文中，我们提出了一个系统级的解决方案，其中包括TO补偿、PHN估计、LoS MIMO毫米波无线回传的预编码器/解相关器优化设计以及各个部分的协同。实验表明，文中所提出的解决方案可以实现较高的频谱效率：对于8x8双极化MIMO系统，端到端的频谱效率可达60 bit/s/Hz。
Abstract—With a given communication protocol, performance optimization of a multiple-input multipleoutput(MIMO)wireless system mainly lies on the design of the radio frequency (RF) front end.Currently, the optimization is mainly achieved based on experiences, such as promoting the multiple antenna gains and reducing their correlations.This experience-based method works to a certain extent,but is inefficient since the final performance impact by each sub-system is not quantified.The challenge lies on how to find the most limiting factor that restricts the overall communication throughput.This paper presents an analytical model for throughput calculations of 2 × 2 MIMO wireless system, which is built on a first step of maximum rate calculated under the chosen protocol and channel, followed by a second step of throughput baseline measurement,and continued with the third step of throughput calculations of the overall system according to the actual settings of subsystems.The model can provide a detailed diagnostic report of each RF factor,which will directly point out the imperfections and make the troubleshooting and debugging much more effective.Besides,throughput is analyzed in a mathematical approach that allows the performance more predictable during the design phase.
用于RF前端优化的2×2MIMO吞吐量分析模型
在固定的通信协议下，多输入多输出（Multiple-Input Multiple-Output，MIMO）无线系统的性能优化主要取决于射频（Radio Frequency，RF）前端的设计。目前，RF性能优化方法主要是基于经验指导，例如，提高天线增益和降低天线相关性是公认的可以提升RF性能的方法。这种基于经验的方法在一定程度上有效，但是其效率低下，因为每个子系统对最终性能的影响无法量化。那么如何找到限制整个通信吞吐量性能的最大短板是一个问题。本文提出了一种用于2×2MIMO无线系统吞吐量计算的分析模型，该模型首先根据所选通信制式和信道计算出吞吐率上限值，再进行吞吐量基准曲线测量，最后根据子系统的实际RF性能指标计算整个系统的吞吐量。该模型可以提供每个RF因子对吞吐率影响的详细诊断报告，该报告将直接指出系统设计缺陷，提升系统故障排除和调试效率。此外，该模型通过数学方法来分析吞吐量，可以研发在设计阶段就能预知产品性能。
Abstract—Wireless body area networks (WBANs) would benefit reasonably after the introduction of mmWaves in the communication.The characteristics like high data rate and reduced antenna size are crucial benefits.However,the drawbacks of mmWaves like high pathloss and high interference can be reduced by use of spectrum switching.The paper proposes a method of spectrum switching for indoor applications over the frequency range of 5 GHz to 60 GHz based on SNR as a threshold.This helps to maximize the throughput and minimize the pathloss over varied distance between the transreceivers.The paper further discusses the effects of this frequency on beamforming.The accuracy of the object tracking during the beam alignment despite of the narrow bandwidth is maintained due to prediction of the mobile user equipment by Kalman filter.The results are supported by Matlab simulation of a mobile UE over a range of 100 m and the corresponding spectrum switching and beam alignment results are discussed.The object tracking model is built with the help of Gaussian random walk and the results show an error margin of less than 1 m which is within the threshold designed for the system.The paper also presents the challenges reflected on secondary parameters like directivity, energy consumption, and beamforming array structures.
Abstract—As the rapid growth of mobile social networks, mobile peer-to-peer (P2P) communications and mobile edge computing (MEC) have been developed to reduce the traffic load and improve the computation capacity of cellular networks.However, the stability of social network is largely ignored in the advances of P2P and MEC, which is related to the social relations between users.It plays a vital role in improving the efficiency and reliability of traffic offloading service.In this paper, we integrate an edge node and the nearby P2P users as a mobile P2P social network and introduce the problem of adaptive anchored(k,r)-core to maintain the stability of multiple mobile P2P networks.It aims to adaptively select and retain a set of critical users for each network,whose participation is critical to overall stability of the network,and allocate certain resource for them so that the maximum number of users of all networks will remain engaged and the traffic of cellular network can be minimized.We called the retained users as anchor vertices.To address it, we devise a peer-edge-cloud framework to achieve the adaptive allocation of resources.We also develop a similarity based onion layers anchored (k,r)-core (S-OLAK) algorithm to explore the anchor vertices.Experimental results based on a real large-scale mobile P2P data set demonstrate the effectiveness of our method.
边缘支持的移动P2P社交网络中为提高流量卸载服务可靠性的锚点选择
随着移动社交网络的快速发展，移动点对点通信（Peer-to-Peer，P2P）和移动边缘计算（Mobile Edge Computing，MEC）在减少流量负载、提高蜂窝网络的计算能力方面做出了相应贡献。然而，P2P和MEC的发展很大程度上忽略了社交网络的稳定性，这也与用户之间的社交关联有关。网络稳定性在提高流量卸载服务的效率和可靠性方面起着至关重要的作用。在本文中，我们将网络边缘节点和其覆盖下的P2P用户称为一个移动P2P社交网络，并引入了自适应的锚定(k,r)-core问题，以维护移动P2P网络群组的稳定性。它旨在自适应地为每个移动P2P网络选中并留存住一组对于网络的整体稳定起至关重要作用的关键用户，并为其分配一定的资源，从而使网络群组能够有最大数量的用户留存下来，并最小化流量负载。我们将这些被选中的关键用户称为锚点。为了解决这个问题，我们设计了一个“端–边–云”协同架构来实现资源的自适应分配。此外，我们还提出了一个基于相似度的锚点选取算法。我们基于一个真实的大规模移动P2P数据集进行了多重实验，其结果证明了我们提出的方法的有效性和可行性。
Abstract—Non-orthogonal multiple access (NOMA) has emerged as one important enabling technology for future wireless communications and services, including machine type communication (MTC).Unfortunately, supporting diverse MTC services and massive connectivity is still challenging due to the very different service requirements, scarce radio resources, limited battery capacity of MTC devices, as well as rapidly changing network conditions.In this paper, a hybrid-multipleaccess (HMA) scheme for service-oriented resource allocation scheme is proposed in supporting diverse MTC services for resource constrained devices and networks.In the proposed scheme, HMA allows MTC devices to choose a suitable type of multiple access technique according to their channel conditions,power constraints, and quality of service (QoS) requirements.To support service-oriented resource allocation,the physical network is firstly sliced into several virtualized networks based on QoS requirements and hardware conditions of MTC devices.A novel utility function integrating network performance and the power consumption in MTC devices is proposed.Furthermore,the resource allocation problem is formulated as an optimization problem to maximize the different utility functions under constraints of user QoS requirements and maximum transmitted power.To improve computational capacity as well as reduce the operational latency, a cloud-edge collaborative scheme is further designed to share the computation loads between the cloud and edge.Simulation results demonstrate the proposed service-oriented resource allocation scheme is effective and illustrate that the proposed hybrid multiple access method provides better performance than NOMA in terms of effective energy efficiency.
异构机器类通信中面向服务质量保障的混合多址技术和资源分配方案
非正交多址接入（Non-Orthogonal Multiple Access，NOMA）作为5G的关键技术，可用于未来高效率的无线通信网络和业务，包括机器类型通信（Machine Type Communication，MTC）。然而，由于机器类通信业务类型众多，机器类通信设备的硬件资源、电池容量有限以及网络条件瞬息万变，仅用非正交多址技术支持多样化的业务和大规模的机器类通信仍面临严峻的挑战。为了有效支持MTC网络中各种业务类型和资源受限的MTC设备，本文提出了一种面向多业务应用的混合多址接入（Hybrid Multiple Access，HMA）技术和资源分配方案。在提出的方案中，HMA允许MTC设备根据其信道条件、功率限制条件和服务质量（Quality of Service，QoS）要求选择合适类型的多址接入技术，其中包括非正交及正交多址接入。为了实现面向服务的资源分配，首先根据QoS要求和MTC设备的硬件条件，将物理网络划分成多个虚拟化的网络。本文同时提出了一种基于网络性能和MTC设备功耗的新型效用函数，此效用函数会根据每个虚拟网络里不同的性能要求调整其相应的权重因子。然后在满足每个用户QoS要求和基站最大发射功率约束条件下，将资源分配问题建模为以最大化效用函数为目标的优化问题。为了提高计算能力和减少时延，本文还设计了一种“云–边”（cloud-edge）协同方案让云计算和边缘计算去分摊资源分配的计算负载。仿真结果表明本文所提出的面向业务的资源分配方案对解决6G大规模异构机器类通信中的各种技术挑战十分有效，而且所提出的混合多址接入技术比非正交多址技术能达到更好的能效。
