基于区块链的频谱设备网络中防御拜占庭攻击的分布式共识机制

针对大规模、超密集部署移动互联网和物联网引发的精确频谱共享需求,基于区块链技术提出联网海量个人无线设备构成频谱设备网络:频谱管理服务器、移动基站、个人无线设备形成云计算与边缘计算相结合的频谱设备网络架构,以频谱数据获取、频谱区块添加、频谱数据传输、频谱数据采集的激励构成了基于区块链的频谱设备网络的基本运行机制,通过感知节点共识融合、验证节点共识验证、簇头节点共识确认,在一定置信度下的假设检验判断是否有恶意感知节点发动伪造频谱数据的拜占庭攻击。仿真结果表明分布式共识机制在防御恶意感知节点伪造频谱数据的拜占庭攻击上的有效性和可靠性。     

区块链赋能的6G频谱共享技术

6G无线网络将呈现资源协同化趋势,全频谱统一接入无蜂窝技术已成为6G的关键技术之一。然而密集部署的无蜂窝基站在频谱共享时将产生严重的干扰。针对这一问题,提出了一种基于联盟链的多基站协同功率控制方法。各基站共同组成一个联盟链网络,并基于区块链共识机制实现基站间功率协调控制,以降低因频谱共用而产生的干扰。以最大化系统的总吞吐量为目标,优化各基站的发射功率,并提出了一种等效转换方法以求解该非凸问题。仿真结果表明,所提算法相较于最大功率分配和正交频分复用策略能显著减少基站的发射功率开销,提升系统吞吐量。     

一种基于认知无线电的动态频谱接入MAC方案

在传统的无线通信系统中,频谱的分配是固定的。但是由于通信过程的突发性,这些频谱的使用率很低。另一方面,随着无线通信和多媒体的高速发展和广泛应用,无线频谱资源日趋紧张。如何提高频谱利用率已经成为迫切需要解决的问题。一种可行的思路是把这些授权频谱向未授权用户开放,未授权用户采用动态频谱接入技术,在不对授权用户造成干扰的前提下使用频谱。本文以认知无线电技术(Cognitive Radio,CR)为基础,提出了一种基于CR的动态频谱接入MAC方案(CR-Ad Hoc-MAC)。该方案允许未授权用户自适应地选取可用带宽,实现了动态频谱接入,有效地提高了频谱利用率。     

面向实时业务的认知无线网络 MAC 层频谱接入方案

摘 要：为满足认知无线网络中宽带业务实时传输的需求,提出低延迟的MAC层频谱接入方案,包括频谱感知调度与信道接入竞争两部分。在频谱感知阶段,认知用户选取最佳可用信道数实现感知与传输的延迟最小化;在信道接入竞争阶段,协议考虑频谱资源动态变化的特点,通过设计数据帧格式以及邻居节点协同侦听机制,减小信道冲突与“聋终端”的影响。理论与实验结果表明,与传统的认知无线网络MAC层协议相比,提出的接入方案数据传输延迟更短,同时在授权信道空闲率较大时吞吐量性能略优。     

一种基于信誉值拍卖的区块链下的感知收益分配机制

实现频谱共享,需要以实时准确地掌握主用户的频谱占用情况以及频谱交易信息为前提.为此,在利用群智感知以及区块链的前提下,提出了三层式的基于区块链的认知无线电系统,即物理层、传输层以及应用层.其中区块链网络位于传输层,用以记录交易信息,并利用区块链的去中心化以及去信任化特性以保证交易的安全性与可靠性.特别地,为了激励系统中...     

认知无线电网络的MAC层关键技术

认知无线电作为一种智能的频谱共享技术,已成为无线通信领域的研究热点。为达到在不干扰授权用户的条件下有效地实现机会式频谱利用,认知无线电网络的媒体接入控制（MAC）层不仅需要提供传统的服务,还要求能支持一套全新的功能。频谱检测管理通过对检测模式的选取、检测周期及检测时长的设置、检测信道的选取和检测静默期的设置等实现检测策略和参数的选取及优化。接入控制主要采用与授权用户协调接入和透明接入两种方式避免与授权用户的接入产生碰撞。动态频谱分配针对二进制干扰模型和累积干扰模型进行不确定频谱资源的优化分配。安全机制通过增加MAC帧的认证和保密以防御MAC层的安全攻击。跨层设计结合物理层和网络层、传输层等上层信息设计和实现全局优化的MAC层技术。     

感知不确定下卫星认知无线网络多频谱接入优化策略

针对卫星认知无线网络频谱感知不确定性较大导致传统频谱接入机制效率降低的问题,该文提出一种基于动态多频谱感知的信道接入优化策略。认知LEO卫星根据频谱检测概率与授权用户干扰门限之间的关系,实时调整不同频谱感知结果下的信道接入概率。在此基础上以系统吞吐量最大化为目标,设计了一种基于频谱检测概率和虚警概率联合优化的判决门限选取策略,并推导了最佳感知频谱数量。仿真结果表明,认知用户能够在不大于授权用户最大干扰门限的前提下,根据授权信道空闲状态动态选择最佳频谱感知策略,且在检测信号信噪比较低时以更加积极的方式接入授权频谱,降低了频谱感知不确定性对信道接入效率的影响,提高了认知系统吞吐量。     

认知无线电中的频谱接入技术

认知无线电是一种基于软件无线电的智能通信系统,它能够认知周围环境,并能通过一定的方法相应地改变某些工作参数来实时地适应环境,从而达到提高频谱利用率、缓解频谱资源紧张的目的.授权频段的频谱利用问题是认知无线电实现的关键技术之一.研究了授权频段的两种频谱利用方法:动态频谱接入和基于动态频谱接入模型之一的机会频谱接入.     

物联网距离和业务特征结合的频谱接入方法

针对物联网应用中的频谱使用特性提出一种距离和业务结合的频谱接入方法。首先根据非系统用户与系统用户的距离关系构建用于标识系统用户信道可用度的列表,以此提供非系统用户间的资源分配等级。其次,根据非系统用户和系统用户对信道使用特性建立业务匹配关系式,在可用度列表和业务匹配关系式的基础上,构建干扰驱动效用函数,从跨层优化角度设计频谱接入方法。结果证明该方案既能够抑制非系统用户对系统用户干扰,又能够确保物联网应用的服务质量的资源共享。     

不同优先级非授权用户的频谱接入方案探讨

认知无线网络是解决有限的频谱资源与日益剧增的无线接入需求之间矛盾的有效方案之一,也是提高未来无线通信系统频谱效率的有力手段。本文分析了无优先级非授权用户的认知无线网络中各种频谱接入方案的特点,在此基础上提出了不同优先级非授权用户共存环境下的两种频谱接入方案。     

基于稳定匹配的认知无线网络协作物理层安全机制

在Underlay认知无线网络中,次用户被允许在主用户进行数据发送时接入主用户的频谱.此时,主用户将对次用户和窃听者造成干扰.利用协作干扰技术,主用户产生的干扰可以被用来改善次用户的物理层安全.基于此,本文针对包含多个主次用户的Underlay认知无线网络,提出了一种新的协作物理层安全机制.为了在保证主用户通信质量的前提下,最大化网络中次用户的总的安全容量,该机制将对次用户进行合理的频谱接入选择和功率控制.另外,考虑到个体理性和自私性对于频谱接入稳定性的影响,该机制利用稳定匹配理论将频谱接入选择问题建模为一对一的双边匹配问题,通过构建主次用户之间的稳定匹配来保证频谱接入的稳定性.仿真结果表明,使用本文所提安全机制,可以在保证主用户通信质量的前提下,稳定而又有效地改善网络中次用户获得的总的安全容量.     

An Optimal Stability Matching Algorithm for DAG Blockchain Based on Matching Theory

IOTA is a typical blockchain designed for IoT applications. The Markov chain monte carlo algorithm (MCMC) used in IOTA may lead to a large number of unverified blocks, which increases transaction delay to a certain extent. We propose a Stable matching algorithm (SMA) based on matching theory to stimulate nodes to verify blocks, thereby reducing the number of unverified blocks and the consensus delay. The structure of our IoT blockchain uses the Directed acyc1ic graph (DAG) to improve the transaction processing capability. The nodes in the network are abstracted as transaction issuers and transaction verifiers. A verification service scheduling system is used to assign transactions to the verifiers and achieve the optimal matching. We designed a trust evaluation mechanism which offers verifiers references and awards to check transactions. The simulation results show that SMA can significantly reduce the number of orphan blocks and improve the transaction throughput, which helps to improve the reliability of the IoT blockchain.     

Blockchain‐based access control for enterprise blockchain applications

Access control is one of the fundamental security mechanisms of IT systems. Most existing access control schemes rely on a centralized party to manage and enforce access control policies. As blockchain technologies, especially permissioned networks, find more applicability beyond cryptocurrencies in enterprise solutions, it is expected that the security requirements will increase. Therefore, it is necessary to develop an access control system that works in a decentralized environment without compromising the unique features of a blockchain. A straightforward method to support access control is to deploy a firewall in front of the enterprise blockchain application. However, this approach does not take advantage of the desirable features of blockchain. In order to address these concerns, we propose a novel blockchain‐based access control scheme, which keeps the decentralization feature for access control–related operations. The newly proposed system also provides the capability to protect user's privacy by leveraging ring signature. We implement a prototype of the scheme using Hyperledger Fabric and assess its performance to show that it is practical for real‐world applications.     

无人机协作通信系统中基于区块链的频谱共享机制

为解决无人机与蜂窝网络在协作频谱共享中的激励与安全问题,提出了一种基于区块链的频谱共享机制。首先,为保证无人机在协作过程中的可靠性和真实性,采用基于信誉的赢家判决方法和维克里（Vickery）拍卖的付款规则,在保证无人机通信最小速率前提下提出最大化蜂窝网络传输容量的优化方案。其次,为避免集中机构带来隐私泄露等危险,提出基于区块链的拍卖框架,使用区块链存储并更新无人机的信誉值,并使用智能合约功能来验证和执行拍卖。最后,通过仿真验证区块链的防篡改性,表明所提机制具有激励兼容性并能提升蜂窝网络的传输容量,且与其他方案相比具有较低的协作中断百分比和较好的公平性。     

An improved cooperative spectrum sensing of femtocells with hybrid TDD access scheme in massive MIMO system

To improve the sensing performance and achieve higher throughput of the femtocells (FCs) while alleviating the influence to the macrocell in the cognitive massive multiple‐input and multiple‐output system (MIMO), we propose in this paper a hybrid time‐division duplex (TDD) access scheme of the FCs with confidence factor–based weighted cooperative spectrum sensing (CSS). A first, we present an efficient hybrid TDD access scheme for better spectrum reuse of the FCs based on the typical TDD and reversed TDD schemes. Furthermore, confidence factor–based weighted CSS has been used for better spectrum sensing and interference alleviation. In the cognitive massive MIMO system, FC base stations will form dynamical clustering based on the channel conditions, sense the spectrum through cooperative scheme, and decide whether to access the spectrum or not. After information exchange within each FC cluster, the FC base stations can obtain and update their confidence factors and weight factors based on the sensing results and reliability. Numerical results and theoretical analysis show that the proposed scheme can get more accurate sensing results, increase the throughput and the spectrum access opportunity of the FCs, and efficiently alleviate the interference to the macrocell tier.     

A Double Auction Mechanism for Heterogeneous Multi-unit Spectrum Trading

The last decade has witnessed a rapid growth in wireless communications technology,and as a result the demand for spectrum resources increased rapidly.Unfortunately,many new wireless demanders cannot access the limited wireless licenses in time while large chunks of spectrum are idle.To solve this,we design a multiunit double auction mechanism for heterogeneous spectrum channels,which take the spatial and temporal reuse into consideration.The proposed scheme first introduces the multi-participants multi-heterogeneous-spectrum trading double auction to illustrate the system model.Some techniques such as spectrum categorize,virtual sellers and buyers' conflict graph construction,and reconstruction of buyer groups are adopted to achieve a high efficiency of the algorithm.Then,we also prove the truthfulness,individual rationality,and budget balance of the proposed scheme.Finally,the simulation results show that the practical performance of the proposed scheme can efficiently improve the spectrum transaction ratio,reuse ratio,and the buyer's satisfactory ratio.     

卫星物联网混合随机接入技术

在卫星物联网(IoT)场景中,随着终端数量不断增加,频谱资源日益紧张。传统的随机接入技术频谱利用率较低,使得传统随机接入协议不适用于未来卫星IoT的高并发业务需求。同时,卫星通信链路长,开放性强,难以保证特种终端信号的安全性。对此,本文提出一种适用于卫星IoT的混合随机接入方案。该方案引入重叠传输的容量提升与安全性优势,利用扩频码对瞬时功率谱密度的控制能力,构造功率域非正交接入条件,并通过接收端的迭代分离实现稳健接收。对本文所提方案的吞吐量性能进行闭式解推导分析与计算机仿真,结果表明,与传统的随机接入协议相比,所提方案可提高系统吞吐量。同时,相较于常用信号隐藏方法,所提方法利用常规接入数据包的功率优势,强化了波形隐藏效果,提升了特种信息接入的安全性。     

基于属性密码体制的区块链安全技术研究进展

区块链是一种集合了分布式存储、点对点传输、共识机制、密码学算法和智能合约等关键技术的分布式账本,具有去中心化、不可篡改、透明化等特性.近年来区块链技术的安全性问题逐渐显露,阻碍了区块链应用的发展.本文介绍了区块链的基本概念与安全模型,分析了区块链的安全性问题;然后,基于属性密码体制,从访问控制、密钥管理、数据隐私保护这...     

Joint Opportunistic Spectrum Sharing and Dynamic Full Frequency Reuse in OFDMA Cellular Relay Networks

This paper considers the problem of spectrum sharing in orthogonal frequency division multiple access cellular relay networks. Firstly, a novel dynamic full frequency reuse scheme is proposed to improve the spectral efficiency. Different from the conventional full frequency reuse scheme which only allows the base station (BS) reusing the subcarriers in the specific regions, an improved full frequency reuse scheme is proposed to allow the BS reusing all the subcarriers in the whole BS coverage region to exploit additional multiuser diversity gain. In order to dynamically reuse the frequency resource among the BS and relay stations (RSs) to further improve the spectral efficiency, the adaptive subcarrier scheduling is introduced into the improved full frequency reuse scheme to obtain more multi-user diversity gain, which forms the proposed novel dynamic full frequency reuse scheme. Secondly, in order to further increase the system throughput, the opportunistic spectrum sharing scheme is introduced to allow the RSs selectively reusing the subcarriers among each other, which joint with the proposed dynamic full frequency reuse scheme to intelligently allocates the subcarriers originally reused by the BS and a RS to another suitable RS which can best improve the system performance after considering the additional interference. Thirdly, in order to select The optimal reusing combination scheme of BS and RSs to exploit more potential system performance, a heuristic approach based on genetic algorithm is proposed to search the optimal BS and RSs combination to opportunistically share the frequency resource. Simulation results show that the proposed dynamic full frequency reuse scheme can obtain high spectral efficiency, fine fairness and low outage probability compared to the conventional full frequency reuse scheme. Furthermore, the system performance can be improved when considering the opportunistic spectrum sharing among RSs. Finally, after adopting the genetic algorithm, the system performance can be greatly improved by the frequency reusing among the optimal BS and RSs combination.