With rapid development of radio frequency identification (RFID) technology, ever-increasing research effort has been dedicated to devising various RFID-enabled services. The missing tag identification, which is to identify all missing tags, is one of the most important services in many Internet-of-Things applications such as inventory management. Prior work on missing tag detection all rely on hash functions implemented at individual tags. However, in reality hash functions are not supported by commercial off-the-shelf (COTS) RFID tags. To bridge this gap between theory and practice, this paper is devoted to detecting missing tags with COTS Gen2 devices. We first introduce a point-to-multipoint protocol, named P2M that works in an analog frame slotted Aloha paradigm to interrogate tags and collect their electronic product codes (EPCs). A missing tag will be found if its EPC is not present in the collected ones. To reduce time cost of P2M resulted from tag response collisions, we further present a collision-free point-to-point protocol, named P2P that selectively specifies a tag to reply with its EPC in each slot. If the EPC is not received, this tag is regarded to be missing. We develop two bitmask selection methods to enable the selective query while reducing communication overhead. We implement P2M and P2P with COTS RFID devices and evaluate their performance under diverse settings.

中文翻译：

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COTS RFID 系统中的缺失标签识别：弥合理论与实践之间的差距

随着射频识别 (RFID) 技术的快速发展，越来越多的研究工作致力于设计各种支持 RFID 的服务。缺失标签识别，即识别所有缺失的标签，是库存管理等诸多物联网应用中最重要的服务之一。之前关于缺失标签检测的工作都依赖于在单个标签上实现的哈希函数。然而，实际上商用现货 (COTS) RFID 标签不支持散列函数。为了弥合理论与实践之间的差距，本文致力于使用 COTS Gen2 设备检测丢失的标签。我们首先介绍一种名为 P2M 的点对多点协议，该协议在模拟帧插槽 Aloha 范式中工作，以询问标签并收集其电子产品代码 (EPC)。如果它的 EPC 不存在于收集的标签中，则将找到丢失的标签。为了减少由标签响应冲突导致的 P2M 的时间成本，我们进一步提出了一种无冲突的点对点协议，称为 P2P，它有选择地指定一个标签以在每个时隙中使用其 EPC 进行回复。如果没有收到 EPC，则认为该标签丢失。我们开发了两种位掩码选择方法来启用选择性查询，同时减少通信开销。我们使用 COTS RFID 设备实施 P2M 和 P2P，并评估它们在不同设置下的性能。这个标签被认为是缺失的。我们开发了两种位掩码选择方法来启用选择性查询，同时减少通信开销。我们使用 COTS RFID 设备实施 P2M 和 P2P，并评估它们在不同设置下的性能。这个标签被认为是缺失的。我们开发了两种位掩码选择方法来启用选择性查询，同时减少通信开销。我们使用 COTS RFID 设备实施 P2M 和 P2P，并评估它们在不同设置下的性能。