Mechanism of Fast Data Retransmission in CU-DU Split Architecture of 5G NRG

The 5G radio access network （RAN） architectm＇e is supposed to be split into the central unit （CU） and the distributed unit （DU） in order to support more flexible transport networks and provide enhanced user experience. However, such functional split may also introduce some new technical issues. In this pa- per, we study the data fast retransmission issue introduced by this functional split in different scenarios and solutions are provided to handle this issue. With the fast data retransmis- sion mechanism proposed in this paper, the retransmitted da- ta packets could be identified and handled with high priority. In this way, the data delivery between the CU and DU in 5G RAN is assured.

Efficient Broadcast Retransmission Based on Network Coding for InterPlaNetary Internet

In traditional wireless broadcast networks,a corrupted packet must be retransmitted even if it has been lost by only one receiver.Obviously,this is not bandwidth-efficient for the receivers that already hold the retransmitted packet.Therefore,it is important to develop a method to realise efficient broadcast transmission.Network coding is a promising technique in this scenario.However,none of the proposed schemes achieves both high transmission efficiency and low computational complexity simultaneously so far.To address this problem,a novel Efficient Opportunistic Network Coding Retransmission(EONCR)scheme is proposed in this paper.This scheme employs a new packet scheduling algorithm which uses a Packet Distribution Matrix(PDM)directly to select the coded packets.The analysis and simulation results indicate that transmission efficiency of EONCR is over 0.1,more than the schemes proposed previously in some simulation conditions,and the computational overhead is reduced substantially.Hence,it has great application prospects in wireless broadcast networks,especially energyand bandwidth-limited systems such as satellite broadcast systems and Planetary Networks(PNs).

AN ADAPTIVE OPPORTUNISTIC RETRANSMISSION CONTROL SCHEME ENVIRONMENT-AWARE-BASED FOR WIRELESS MULTIMEDIA MESH NETWORKS

In this paper, we propose an aware-based adaptive opportunistic retransmission control scheme for wireless multimedia Mesh networks. The proposed scheme provides maximum retransmis-sion count optimization based on environment-aware to improve packet relay probability. The scheme discriminates the types of packet loss in wireless link by means of environment information and selects the retransmission count by taking the IEEE 802.11 wireless channel characteristics into consideration. Furthermore, the maximum retransmission count of MAC is adjusted adaptively. Extensive simulations demonstrate that the proposed scheme significantly reduces packet collision probability and packet loss rate, and thus improves network throughput.

The Overload Reduction in SIP Servers through Exact Regulation of the Retransmission Timer of the Invite Message

To initiate voice, image, instant messaging and general multimedia communication, the Session communication must initiate between two participants. SIP (Session initiation protocol) is an application layer control, which task is creating management, and terminating this kind of Sessions. With regard to the independence of SIP from the Transport layer protocols, the SIP messages can be transferred on a variety of Transport layer protocols such as TCP or UDP. The mechanism of Retransmission, which has been embedded in SIP, is able to compensate the missing Packet loss, if needed. The application of this mechanism is when SIP messages are transmitted on an unreliable transmission layer protocol such as UDP. This mechanism, while facing with SIP proxy with overload, causes excessive filling of proxy queue, delays the increase of other contacts and adds the amount of the proxy overload. We in this article, while using UDP, as the Transport layer protocol, by regulating the Invite Retransmission Timer appropriately (T1), have improved the SIP functionality. Therefore, by proposing an Adaptive Timer of Invite message retransmission, we have tried to improve the time of Session initiation and as a result, improving the performance. The performance of the proposed SIP, by the SIPP software in a real network environment has been implemented and evaluated and its accuracy and performance has been demonstrated.

A New HARQ Scheme for 5G Systems via Interleaved Superposition Retransmission

Within the framework of the 5G new radio(NR),we propose a new hybrid automatic repeat request(HARQ)scheme to improve the throughput performance.The difference between the proposed scheme and the conventional one lies in the first retransmission,where the erroneous coded block group is interleaved and superimposed(XORed)onto a fresh coded block group.At the receiver,an iterative message-passing decoding algorithm can be employed to recover the target erroneous code block group(CBG).Only when the superposed retransmission fails,the conventional incremental redundancy(IR)or repetition redundancy(RR)retransmission is initiated.In any case,since the first retransmission is along with but has negligible effect on the fresh CBG,it costs neither transmitted power nor bandwidth.Monte-Carlo simulation results reveal that the presented HARQ schemes can achieve throughput improvements up to 10%over block fading channels and up to 50%over fast fading channels in comparison with the original 5G CBG-level HARQ scheme but without excessively increasing the implementation complexity.

Optimizing Utility of Cognitive Radio Ad Hoc Networks under the Energy and Retransmission Constraint

In Cognitive radio ad hoc networks （CRAHNs）, the secondary users （SUs） or cognitive radio nodes （CRs） are always equipped with limited energy and have a high error probability of data transmission. To address this issue, we first describe the network utility under energy constraint as a max-min model, where the re-transmission strategy with network coding is employed. Additionally, the expression of retransmission probability is presented in terms of power and bit error rate （BER）. Moreover, since the max-min model is non-convex in both objective and constraints, we use a normal- form game to find a near-optimal solution. The simulation results show that the proposed approach could achieve a higher network utility than the compared approaches.

Adaptive Retransmission Design for Wireless Federated Edge Learning

As a popular distributed machine learning framework,wireless federated edge learning(FEEL)can keep original data local,while uploading model training updates to protect privacy and prevent data silos.However,since wireless channels are usually unreliable,there is no guarantee that the model updates uploaded by local devices are correct,thus greatly degrading the performance of the wireless FEEL.Conventional retransmission schemes designed for wireless systems generally aim to maximize the system throughput or minimize the packet error rate,which is not suitable for the FEEL system.A novel retransmission scheme is proposed for the FEEL system to make a tradeoff between model training accuracy and retransmission latency.In the proposed scheme,a retransmission device selection criterion is first designed based on the channel condition,the number of local data,and the importance of model updates.In addition,we design the air interface signaling under this retransmission scheme to facilitate the implementation of the proposed scheme in practical scenarios.Finally,the effectiveness of the proposed retransmission scheme is validated through simulation experiments.

Enhanced cooperative packet retransmission employing joint cooperative diversity and symbol mapping diversity

A joint cooperation diversity and symbol mapping diversity (SMD) strategy is proposed for cooperative packet retransmission system with high-order modulation such as 16QAM. Substantial SER/BER (symbol error rate/bit error rate) gains result from multiple packet transmissions over independent paths and distinct bit-to-symbol mappings for each packet transmis-sion. The SER/BER performance of relay assisted retransmission system is analyzed. Simulation results show that the joint-diversity strategy can provide more BER gains than other relaying strategies (i.e., decode-and-forward and constellation rearrangement relaying strategies) when no relay makes a decision error; but if some relays make decision errors, the joint-di-versity strategy outperforms other relaying strategies only when the relays are closer to the source than to the destination.

Best-retransmission count selection for environment optimization over wireless heterogeneous networks

This paper proposes an environment-aware best- retransmission count selected optimization control scheme over IEEE 802.11 multi-hop wireless networks. The proposed scheme predicts the wireless resources by using statistical channel state and provides maximum retransmission count optimization based on wireless channel environment state to improve the packet delivery success ratio. The media access control （MAC） layer selects the best-retransmission count by perceiving the types of packet loss in wireless link and using the wireless channel charac- teristics and environment information, and adjusts the packet for- warding adaptively aiming at improving the packet retransmission probability. Simulation results show that the best-retransmission count selected scheme achieves a higher packet successful delivery percentage and a lower packet collision probability than the corresponding traditional MAC transmission control protocols.

基于前导码重传辅助控制的mMTC动态随机接入

为解决海量机器类通信(mMTC,massive machine type communications)场景下,机器类通信设备(MTCD,machine type communication device)采用传统随机接入方案时,往往出现网络严重拥塞,导致大量MTCD无法成功接入网络问题,提出了一种基于前导码重传辅助的动态接入类别限制(PRT-ACB,preamble retransmission access class barring)方案。利用MTCD的前导码重传次数,将每个随机接入机会(RAO,random access opportunity)中尝试发起接入的MTCD划分为高、低优先级,结合每个RAO中负载数估计模型,分别为其设定随每个RAO中的接入负载动态变化的高、低优先级限制因子和可用前导码池,使更多MTCD能在未达到最大前导码传输次数前成功接入网络。仿真结果表明,所提方案能有效提升MTCD的接入成功概率,降低MTCD接入网络所需时延。所提方案可以作为缓解海量通信设备同时接入网络造成拥塞的一种解决方案。

面向工业超高可靠低时延通信的5G网络上行混合重传策略

5G网络支持更细粒度、更灵活的通信资源分配,对于保障工业自动化的可靠、实时无线传输将发挥关键作用.本文提出一种面向工业超高可靠低时延通信的5G网络上行混合重传策略(Hybrid Uplink Retransmission Scheme,HURS).考虑上行周期性工业数据的传输场景,HURS将优势互补的按需重传机制和循环重传机制相结合,基于对两种重传机制的可靠性建模,在线选择最可靠的重传机制;最后,大量仿真验证了HURS的传输可靠性和最坏时延不仅优于其他重传方法,还满足工业URLLC要求.

一种多站雷达协同时空误差配准方法研究

多站雷达协同系统各个节点工作具有异步性,多节点雷达对同一个或多个目标的测量误差不一致,导致在多站雷达协同进行数据融合时将同一目标误认为不同目标,使得融合航迹性能下降,失去多雷达协同的优势。文中研究了一种基于多站协同数据处理的航迹误差校准方法,利用最小二乘滤波对多站雷达航迹进行关联,同时利用多站协同关联的优势剔除转发式干扰航迹,对多站探测到的同一目标航迹进行时间统一。并基于多站协同迭代最近点算法,使用多站协同系统中高精度节点数据对低精度节点数据进行误差配准。仿真结果表明,文中方法在多目标复杂运动场景中具有更高的航迹关联正确率,且具有较好的抗转发干扰能力。与传统空间误差配准算法相比,具有更低的配准均方根误差。

Ultra Reliable Load-Aware Connection Management(LACM)Algorithm in WIA-FA Systems

The increasing demand for industrial automation and intelligence has put forward higher requirements for the reliability of industrial wireless communication technology.As an international standard based on 802.11,Wireless networks for Industrial Automation-Factory Automation(WIA-FA)greatly improves the reliability in factory automation scenarios by Time Division Multiple Access(TDMA).However,in ultra-dense WIA-FA networks with mobile users,the basic connection management mechanism is inefficient.Most of the handover and resource management algorithms are all based on frequency division multiplexing,not suitable for the TDMA in the WIA-FA network.Therefore,we propose Load-aware Connection Management(LACM)algorithm to adjust the linkage and balance the load of access devices to avoid blocking and improve the reliability of the system.And then we simulate the algorithm to find the optimal settings of the parameters.After comparing with other existing algorithms,the result of the simulation proves that LACM is more efficient in reliability and maintains high reliability of more than 99.8%even in the ultra-dense moving scenario with 1500 field devices.Besides,this algorithm ensures that only a few signaling exchanges are required to ensure load bal-ancing,which is no more than 5 times,and less than half of the best state-of-the-art algorithm.

窄带条件下关键数据可靠传输方法

在窄带条件下,存在数据传输速率低、通信易受外界干扰、数据传输中断和通信网络状态不稳定等制约因素,如何更有效地传输数据是当前计算机网络传输协议的研究热点。通过建立数据分类、网络状态探测与状态建立、报文确认和超时重传等机制,提出了一种具备适应窄带条件的关键数据可靠传输方法。试验结果表明,该方法可有效提高窄带下数据传输的可靠性、实时性和高效性,降低了网络负担。

基于UDP超时重传与快速校验的可靠传输设计

基于UDP以太网传输协议实现的应用程序是一种无连接、传输不可靠的通信应用,UDP网络传输过程中经常会出现丢包、错包、乱序等一系列的问题,为提高网络UDP通信中数据传输的正确性和可靠性,提出了基于UDP超时重传与快速校验的可靠传输设计。设计方法对UDP应用层数据增加了传输控制协议内容,主要有信源、信宿、类型、重传次数和数据校验位等数据项,实现对UDP传输的数据包内容进行正确性校验,保证传输过程数据包的顺序性、正确性和可靠性。经实验数据验证,提出的设计方法能够准确无误的实现UDP网络数据的传输,提高UDP网络数据传输的正确性和可靠性,实现实时、可靠UDP数据传输。

Ad Hoc网络中基于DTN机制的队列管理器设计

设计了一种将延迟容忍网络(Delay Tolerance Network,DTN)技术应用于自组织(Ad Hoc)网络的队列管理器(Queue Manager,QM)。该管理器由自由指针QM、多队列消息存储器、DDR3、输入接口状态机、重发接口状态机和输出接口状态机等模块组成,能根据用户需求区分不同业务流,并对指定数据进行基于完整消息的多次重传。具有结构简单、低时延、资源动态共享和便于数据管理的特性。分析了QM的具体结构和工作流程,并进行了仿真验证。QM基于Xilinx xc7z100ffg900-2 FPGA平台实现,采用ModelSim SE-64 10.6d进行仿真分析。结果表明,该队列管理器能满足延迟容忍网络中交换节点对消息管理的需求。

基于网络编码的无线网络广播重传方法

提出了一种适用于无线广播的基于网络编码的重传方法——NCWBR,通过网络编码组合不同的丢失包进行重传。理论分析表明,该方法能保证接收节点的编码可解性,同时重传次数较原方法更优;模拟测试结果表明,与逐个重传的方法相比,NCWBR有效地减少了信息包的平均传输次数,提高了传输效率。

隐藏木马检测技术的研究

在分析了目前Windows系统中采用DLL技术的木马程序的检测技术,并在该基础上,提出了一种检测基于DLL转发机制木马的新技术。

卫星通信中基于网络编码改进的广播重传策略

针对传统卫星广播重传策略、链路高丢包率下的基于网络编码的广播重传策略和最大团策略的问题,提出了一种改进的基于网络编码的广播重传策略。理论分析及模拟测试结果证明了改进的基于网络编码的广播重传策略较好地解决了传统卫星广播重传策略信道占用率较高、重传次数较多的问题,链路高丢包率下的基于网络编码的广播重传策略不能达到重传性能最优的问题,保证了卫星通信中的组播数据的快速、可靠的发布。

蓝牙自适应分组选择策略与选择重传算法研究

为了提高蓝牙抗干扰能力与传输效率,从基带层重传和L2CAP层重传研究了蓝牙的重传机制。基带层提出了利用重传次数估计跟踪信道质量的自适应分组选择策略,根据当前信道的重传次数动态选择使其吞吐量最大的分组。在L2CAP层,针对连续重传需要传送已经准确接收的数据帧的缺点,提出了结合连续重传和流控制2种模式的选择重传算法,无需改变蓝牙协议。仿真与分析表明,算法能有效提高吞吐量与传输效率、降低时延,容易实现。