多发选收技术白皮书

目录 1概述··························································································································································11.1产生背景··············································································································································· 11.2技术优点··············································································································································· 12多发选收技术实现····································································································································22.1功能介绍··············································································································································· 22.1.1概念介绍···································································································································· 22.1.2组网模型···································································································································· 22.2实现机制··············································································································································· 32.2.1多发选收的报文格式·················································································································· 32.2.2多发选收的数据转发过程··········································································································· 42.3多发选收漫游········································································································································ 63典型组网应用···········································································································································83.1 CPE方案典型组网······························································································································· 83.2 AGV小车典型组网······························································································································· 93.3地铁典型组网········································································································································ 9 1概述 1.1产生背景 随着无线通信技术的日益成熟，其在各行各业的应用已趋于普及与深化。例如： •在仓储、物流及生产制造领域，工业AGV（Automated Guided Vehicle，自动导引运输车）与CPE（Customer Premise Equipment，客户终端设备）的部署实现了自动化远程控制，显著提升了生产线的柔性制造能力。•在轨道交通系统中，高铁与地铁的车地通信系统借助无线技术为高速移动的列车提供了连续、无中断的数据传输服务。•而在矿山等特殊作业环境中，无线控制系统正推动井下作业向少人化、无人化方向发展，有效降低了工作人员的安全风险。 相较于传统有线网络，无线网络以其部署灵活、便于移动的优势获得了广泛应用。然而，无线通信依赖于电磁波在空间中的传播，这一特性也使其在面对复杂环境时更容易受到干扰，从而导致较高的数据丢包率与传输时延。尤其在终端设备密集或无线环境恶劣（如存在大量金属障碍物、电磁干扰源或高速移动场景）的情况下，无线链路的稳定性、时延及可靠性等关键性能指标往往进一步恶化，难以满足上述应用场景中对低时延、高可靠性的严苛要求。 为应对这一挑战，H3C推出了多发选收技术。具体而言，即在通信两端之间建立多条独立的无线链路，同一份数据通过不同链路同时发送。接收端依据“先到先处理”的原则，择优选取最先抵达的数据包进行处理，并对后续到达的重复数据进行过滤与丢弃。这种“多路发送、择优接收”的机制，既通过并行传输降低了单一链路丢包或拥塞对业务的影响，提升了整体可靠性，又通过竞争选择最早到达的数据，有效减少了传输时延。 综上所述，“多发选收”技术的诞生，源于无线网络在复杂工业及移动场景下面临的性能瓶颈，以及市场对无线通信在可靠性、实时性方面不断提升的诉求。它代表了无线通信技术与高可靠网络设计理念相结合的重要发展方向。 1.2技术优点 与单链路传输相比，多发选收技术通过创新的数据传输机制，将“多路发送”与“择优接收”相结合，为现代网络业务提供了两大核心优势： •高可靠性：通过多发机制，即使单条链路发生丢包或故障，数据仍有备份，确保业务不中断，提升整体传输的稳定性和可靠性。•低时延：选收机制实现先到先处理，能够择优利用多条链路资源，减少等待时间，保障业务的低时延需求，提高用户体验。 综上所述，多发选收技术有效结合了冗余保障与快速响应，适合对可靠性和时延要求较高的业务场景。 2多发选收技术实现 2.1功能介绍 2.1.1概念介绍 同一个CPE与接入AP可能会建立多条Mesh链路，但目前多发选收技术仅支持同时通过两条Mesh链路并发传输数据。后续将根据实际需求逐步扩展至更多链路，以进一步增强网络的冗余性和可靠性。 多发选收是一种提升无线网络可靠性的关键技术，通过在无线CPE与AC之间建立两条并发数据链路实现。其核心机制包含“多发”与“选收”两个环节： •多发：发送端（如CPE或AC）将同一份数据复制为两份，通过两条独立链路同时传输，形成冗余路径。•选收：接收端依据“先到先处理”原则，优先解析并转发最先到达的数据包，同时丢弃后到的冗余副本，实现报文的去重与择优处理。 2.1.2组网模型 如图1所示，多发选收基于WLAN Mesh功能，使每台CPE同时与两台接入AP建立Mesh链路，两条Mesh链路发送相同的数据报文，以提升可靠性并降低丢包率。CPE会依据扫描到接入AP的信号强度和负载等因素，择优选择两台接入AP建立Mesh链路。 为了应对双份的数据报文，多发选收使用了报文去重的机制，即无线网络采用集中转发组网，CPE的数据报文将统一发送至AC处理。当AC收到两条链路的重复数据报文时，将丢弃后收到的报文。同理，AC也会向CPE发送双份报文，CPE收到重复报文时同样会丢弃后收到的报文。 2.2实现机制 2.2.1多发选收的报文格式 多发选收机制通过在Mesh报文头中新增序列号Sequence字段，并利用Mesh Flags字段的第二位标识复制报文，实现了在多链路环境下对重复报文的自动去重，有效解决了因多路径转发导致的数据重复处理问题。该机制的优化主要体现为对Mesh Header的扩展与字段的合理复用，从而提升了设备对报文处理的灵活性与控制能力。 1.报文结构概览 报文结构分为两个主要部分： •MAC Header：标准的802.11 MAC层报文头，包含Frame Control、Duration/ID、Address字段等。•Mesh Header：Mesh特定头，包含Mesh Flags、Mesh TTL、Mesh Sequence Number、Mesh Address Extension等字段。 2. Mesh Header优化细节 多发选收对于Mesh Header的优化主要体现在以下两点： •Mesh Flags字段的位重用：借用Mesh Flags字段的第二位来标识该报文为“复制报文”。当第二位被置为1时，接收端知道该报文是通过多发选收机制转发的，需要启用序列号去重功能。•Sequence字段的新增： 在Mesh Header中增加一个4字节的Sequence字段。 该字段用于标识报文的序列号，实现多发选收去重。接收端通过比较当前报文与已处理报文的序列号列表，决定是否丢弃当前报文。如果当前报文序列号是第一次出现，则对当前报文进行正常处理；如果当前报文序列号已存在（说明该报文已处理过），则直接丢弃当前报文，避免重复处理带来的资源浪费。 2.2.2多发选收的数据转发过程 1.上行数据报文转发流程 多发选收上行数据报文转发流程如下： (1)车载设备发送报文车载设备发送802.3业务单播报文。(2)CPE处理与多发a. CPE收到802.3报文后，根据MAC地址表确定该数据需通过Mesh接口向上转发。b. CPE将报文转交至Mesh模块，并转换为802.11s无线报文格式。c.若存在多条链路，Mesh模块会在报头中设置复制标识位，并添加序列号字段，然后将报文复制为双份，分别通过两条链路上传。 (3)FIT AP接收并处理FIT AP接收Mesh报文后不做额外处理，直接通过CAPWAP隧道封装后转发给AC。 (4)AC处理与去重a. AC对CAPWAP报文进行解封装，提取802.11s报文。b.根据复制标识位判断是否为复制报文，然后根据802.11s报文序列号判断是否重复：若未处理过则进行处理；若已处理过则丢弃该报文。c. AC将待处理的802.11s报文转换回802.3报文，并继续转发。 2.下行数据报文转发流程 多发选收下行数据报文转发流程如下： (1)AC接收并封装数据AC从有线端口接收802.3格式的业务单播报文，通过查询MAC地址表确定需通过M