Covert Communication with a Spectrum Sharing Relay in the Finite Blocklength Regime

In this paper,we investigate the feasibility and performance of the covert communication with a spectrum sharing relay in the finite blocklength regime.Specifically,the relay opportunistically forwards the source's messages to the primary receiver or conveys the covert messages to its own receiver via the sharing spectrum,while the warden attempts to detect the transmission.First,we derive a lower bound on the covertness constraint,and the analytical expressions of both the primary average effective covert throughput(AECT)and sum AECT are presented by considering the overall decoding error performance.Then,we formulate two optimization problems to maximize the primary and sum AECT respectively by optimizing the blocklength and the transmit power at the source and the relay.Our examinations show that there exists an optimal blocklength to maximize the primary and sum AECT.Besides,it is revealed that,to maximize the primary AECT,the optimal transmit power of each hop increases as its channel quality deteriorates.Furthermore,in the optimization for maximizing the sum AECT,the optimal transmit power at the source equals to zero when the channel quality from relay to the secondary receiver is not weaker than that from relay to the primary receiver.

Resource Allocation for Massive Machine Type Communications in the Finite Blocklength Regime

Massive machine type communications(mMTC)have been regarded as promising applications in the future.One main feature of mMTC is short packet communication.Different from traditional long packet communication,short packet communication suffers from transmission rate degradation and a significant error rate is introduced.In this case,traditional resource allocation scheme for mMTC is no longer applicable.In this paper,we explore resource allocation for cellular-based mMTC in the finite blocklength regime.First,to mitigate the load of the base station(BS),we establish a framework for cellularbased mMTC,where MTCGs reuse the resources of cellular users(CUs),aggregate the packets generated by MTCDs,and forward them to the BS.Next,we adopt short packet theory to obtain the minimum required blocklength of a packet that transmits a certain amount of information.Then,by modeling the process of MTCGs-assisted communication as a queuing process,we derive the closed-form expression of the average delay of all MTCDs.Guided by this,we propose a joint power allocation and spectrum sharing scheme to minimize the average delay.Finally,the simulation results verify the correctness of the theoretical results and show that the proposed scheme can reduce the average delay efficiently.

Channel Coding at Finite Blocklength and Its Application in 6G URLLC

To support mission-critical applications, such as factory automation and autonomous driving, the ultra-reliable low latency communications (URLLC) is adopted in the fifth generation (5G) mobile communications network, which requires high level of reliability and low latency. Naturally, URLLC in the future 6G is expected to have a better capability than its 5G version which poses an unprecedented challenge to us. Fortunately, the potential solution can still be found in the well-known classical Shannon information theory. Since the latency constraint can be represented equivalently by blocklength, channel coding at finite blocklength plays an important role in the theoretic analysis of URLLC. Applying these achievements in rapidly development of massive MIMO techniques gives rise to a new theory on space time exchanging. It tells us that channel coding can also be performed in space domain, since it is capable of providing the same coding rate as that in time domain. This space time exchanging theory points out an exciting and feasible direction for us to further reduce latency in 6G URLLC. .

Effective Capacity of URLLC over Parallel Fading Channels with Imperfect Channel State Information

This paper investigates the effective capacity of a point-to-point ultra-reliable low latency communication(URLLC)transmission over multiple parallel sub-channels at finite blocklength(FBL)with imperfect channel state information(CSI).Based on reasonable assumptions and approximations,we derive the effective capacity as a function of the pilot length,decoding error probability,transmit power and the sub-channel number.Then we reveal significant impact of the above parameters on the effective capacity.A closed-form lower bound of the effective capacity is derived and an alternating optimization based algorithm is proposed to find the optimal pilot length and decoding error probability.Simulation results validate our theoretical analysis and show that the closedform lower bound is very tight.In addition,through the simulations of the optimized effective capacity,insights for pilot length and decoding error probability optimization are provided to evaluate the optimal parameters in realistic systems.

Secure Transmission Scheme for Blocks in Blockchain-Based Unmanned Aerial Vehicle Communication Systems

In blockchain-based unmanned aerial vehicle(UAV)communication systems,the length of a block affects the performance of the blockchain.The transmission performance of blocks in the form of finite character segments is also affected by the block length.Therefore,it is crucial to balance the transmission performance and blockchain performance of blockchain communication systems,especially in wireless environments involving UAVs.This paper investigates a secure transmission scheme for blocks in blockchain-based UAV communication systems to prevent the information contained in blocks from being completely eavesdropped during transmission.In our scheme,using a friendly jamming UAV to emit jamming signals diminishes the quality of the eavesdropping channel,thus enhancing the communication security performance of the source UAV.Under the constraints of maneuverability and transmission power of the UAV,the joint design of UAV trajectories,transmission power,and block length are proposed to maximize the average minimum secrecy rate(AMSR).Since the optimization problem is non-convex and difficult to solve directly,we first decompose the optimization problem into subproblems of trajectory optimization,transmission power optimization,and block length optimization.Then,based on firstorder approximation techniques,these subproblems are reformulated as convex optimization problems.Finally,we utilize an alternating iteration algorithm based on the successive convex approximation(SCA)technique to solve these subproblems iteratively.The simulation results demonstrate that our proposed scheme can achieve secure transmission for blocks while maintaining the performance of the blockchain.

共享码本随机接入有限块长信息理论极限分析

超大规模机器通信(umMTC)是6G移动通信网络的典型应用场景。针对umMTC场景中的共享码本随机接入问题展开信息理论研究,在给定基站天线数、码长、用户载荷和发送功率的情况下,推导了平均每用户误差概率的非渐近可达界和逆定理。仿真结果证实了可达界和逆定理的紧致性,并且证明了当用户数低于某一门限时存在多用户干扰消除效应。基站配置多天线能够显著降低平均每用户误差概率,这对支持大量用户可靠接入具有重要意义。此外,与独立码本随机接入相比,共享码本随机接入在能效性方面更具优势。

醇-可聚合表面活性剂混合胶束法合成微嵌段缔合聚合物及其流变性

低碳醇与可聚合表面活性剂(surfmer)可以形成混合胶束,本文通过稳态荧光猝灭法(SSFQ)测定了该混合胶束中可聚合表面活性剂的聚集数,并通过绝热聚合和后水解工艺合成出不同微嵌段长度的较高分子量(Mw)缔合聚合物聚(丙烯酰胺-丙烯酸钠-十六烷基二甲基烯丙基氯化铵)[P(AM-NaAA-C16DMAAC)].聚合物结构经傅里叶变换-红外(FT-IR)光谱和核磁共振碳谱(13CNMR)表征证实,并通过流变性实验研究了微嵌段长度对增粘性能、抗盐性能、粘弹性能的影响规律.实验结果表明:该方法可以有效调节缔合聚合物中微嵌段的长度,随着微嵌段长度增加,临界缔合浓度(CAC)逐渐降低,增粘性能、粘弹性能先逐步增加后逐步降低,并且发现其对聚合物的性能的影响规律中存在最佳嵌段长度.

上行-下行联合优化的uRLLC传输

考虑有界信道状态信息(CSI)误差的影响,解决了上下行联合设计的高可靠低时延通信(uRLLC)传输问题,以保障最差情况下物理层空口传输的端到端可靠性。利用有限码长容量公式近似刻画传输速率、时延和可靠性之间的关系,在信道估计误差、最大功率和传输可靠性的约束条件下,最小化上下行所需的传输时延。通过分析目标函数的单调性和凸性,对优化问题进行等价转化,并提出了有效的交替优化算法来求解该问题。仿真结果分析了信道估计误差、发送功率、可靠性对传输时延的影响,清晰地表明了系统参数之间的折中关系。

铁路远动信道信息传输差错控制特性分析

本文就电气化铁道牵引变电所远动监控系统中信道的信息传输问题，在其可靠性、吞吐率及最佳码长等方面进行了分析，并分别推导出其数学模型，它直接关系到远动系统信息传输协议的制定及通信方式的选择。

Statistical QoS Provisioning Architecture for 6G Satellite-Terrestrial Integrated Networks

The emergence of massive ultra-reliable and low latency communications (mURLLC) as a category of age/time/reliability-sensitive service over 6G wireless networks has received considerable research attention, which has presented unprecedented challenges. As one of the key enablers for 6G,satellite-terrestrial integrated networks (STIN) have been developed to offer more expansive connectivity and comprehensive 3D coverage in space-aerial-terrestrial domains for supporting 6G mission-critical mURLLC applications while fulfilling diverse and rigorous quality of service (QoS) requirements. In the context of these mURLLC-driven satellite services, data freshness assumes paramount importance, as outdated data may engender unpredictable or catastrophic outcomes.To effectively measure data freshness in satellite-terrestrial integrated communications,age of information(AoI)has recently surfaced as a new dimension of QoS metric to support time-sensitive applications. It is crucial to design new analytical models that ensure stringent and diverse QoS metrics bounded by different key parameters,including AoI,delay,and reliability,over 6G satellite-terrestrial integrated networks. However,due to the complicated and dynamic nature of satellite-terrestrial integrated network environments, the research on efficiently defining new statistical QoS provisioning schemes while taking into account varying degrees of freedom has still been in their infancy. To remedy these deficiencies, in this paper we develop statistical QoS provisioning schemes over 6G satellite-terrestrial integrated networks in the finite blocklength regime. Particularly, we firstly introduce and review key technologies for supporting mURLLC.Secondly,we formulate a number of novel fundamental statistical-QoS metrics in the finite blocklength regime.Finally,we conduct a set of simulations to validate and evaluate our developed statistical QoS provisioning schemes over satellite-terrestrial integrated networks.

面向超可靠低时延通信的有限块长MIMO传输理论与技术

超可靠低时延通信是5G及未来6G无线通信系统的重要组成部分.针对该类通信场景,如何从MIMO传输的角度实现时延和可靠性的最佳折中,是近年来备受关注的一项研究课题.由于现有基于长包假设的经典MIMO传输体系难以满足系统对于时延和可靠性的严苛要求,亟需研究更具挑战性的有限块长MIMO传输理论和技术.本文围绕有限块长MIMO信息论、发射机以及接收机设计的已有研究工作进行全面总结,并重点介绍二维空时信道编码以及MIMO一体化接收机等新型技术,为显著提升超可靠低时延通信的性能提供指导.另外,本文简要介绍了作者所在课题组搭建的MIMO超可靠低时延试验验证平台,为后续相关理论与算法的验证奠定试验基础.