RFID系统防碰撞算法的研究及其改进

射频识别技术中,防碰撞问题是提高系统读取效率的关键问题。文章在传统防碰撞算法的基础上,提出一种优化的基于动态帧时隙ALOHA的防碰撞（Improved dynamic framed slotted ALOHA,IDFSA）算法。实验结果表明：IDFSA算法大幅度地提高了系统的时隙利用率和读取效率。     

Throughput and delay analysis of multi-channel wireless infrastructure networks

Wireless infrastructure networks (WINs) provide ubiquitous connectivity to mobile nodes in metro areas. The nodes in such backbone networks are often equipped with multiple transceivers to allow for concurrent transmissions in multiple orthogonal channels. In this study, we develop an analytical model for the estimation of the delay and throughput performance of wireless infrastructure networks employing slotted ALOHA channel access and slotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) over multiple channels. The analytical model, which takes into account the correlation due to multi-hop transmissions, approximates the performance observed through simulations accurately.     

食品质量追溯中RFID多标签识别防碰撞算法

针对食品质量追溯中批量标签识别存在的标签碰撞问题,结合帧时隙ALOHA算法和最小均方误差预编码技术提出了一种RFID多标签识别防碰撞算法。该算法在进行多标签识别前,先通过预编码技术对待识别标签进行分组,有效降低多标签间的碰撞。仿真试验表明,改进算法有效提升了RFID多标签识别性能,具有一定的实用价值。     

Delay‐insensitive identification of neighbors using unslotted and slotted protocols

For many applications, it is desirable for a node to be able to identify the neighbor nodes currently within range. However, the identification procedures for terrestrial communication networks (TCNs) are inefficient when implemented in long‐delay networks (LDNs) such as underwater acoustic networks or satellite networks, where the propagation time of a packet cannot be neglected. Here, we propose a time‐efficient and power‐efficient procedure, which is insensitive to propagation delay, for identifying neighbors in an LDN by optimizing the network offered load using either unslotted or slotted protocols. The procedure is adapted to the scenario when node cardinality and distribution are either known or unknown in advance. We achieve improvements as high as 80% in time and 45% in power consumption for our proposed approach compared with approaches developed previously for TCN. Furthermore, we analyze our proposed approach with the inclusion of the capture effect and packet receive time variations. We also provide a closed form formula for finding the optimum guard time and a procedure to estimate the packet receive time variations. Copyright © 2012 John Wiley & Sons, Ltd.     

基于分组动态帧时隙ALOHA防碰撞算法研究

为解决射频识别系统中多标签防碰撞问题,在现有ALOHA算法的基础上提出了一种改进的分组动态帧时隙ALOHA算法。当大量标签同时进入阅读器识别范围内时,算法通过设置一个阈值把要响应的标签分成两组,符合条件的一组去响应阅读器,不符合条件的暂时不响应,该算法通过分组限制响应标签数量达到较高的识别效率。仿真结果表明,该算法在标签数大于256甚至更多时识别效率也能维持在相对较高的数值。     

一种提供良好QoS保障的Ad Hoc网络MAC协议

为有效减小Ad Hoc网络实时业务节点的信道接入时延,提升对多媒体业务的服务质量(QoS)保障,在研究时隙分配类多址协议的基础上,设计了一种新的基于时隙重构的分组预约协议。新协议时隙结构简单,具有较好的冲突化解能力,通过对空闲数据时隙的重构利用以及层级式的接入控制,取得了较好的时延保障性能。     

智能包装中的RFID标签防碰撞算法研究

目的 解决目前物流系统中智能包装RFID标签冲突的问题。方法 在研究已有防碰撞算法的性能和缺点基础上,针对大量标签场景设计一种分组动态帧时隙的混合查询树（GDFSA-HQT）算法。该算法在每一轮识别之后估计还没有识别的标签数量,如果还没有识别的标签数量小于或等于354个,则先采用动态帧时隙ALOHA（DFSA）算法对标签进行识别,再采用混合树查询算法（HQT）进行标签识别;若未被识别标签数大于354个,则先对标签进行分组处理,再分别采用DFSA和HQT进行标签识别。结果 仿真实验表明,GDFSA-HQT算法的吞吐率能够保持在0.82左右。结论 GDFSA-HQT算法解决了标签碰撞问题,在大量智能包装的物流系统中具有良好的应用前景。     

具有多重码的预约Slotted ALOHA协议性能分析

本文对具有多重码的预约Slotted ALOHA协议进行了性能分析。它是基于帧的协议且在一个时隙内有多重码可用来传输分组信息。文中利用离散时间,离散状态和Markov链来分析一个小区上行链路的话音分组吞吐量和数据分组延时性能,并提出了两种改进碰撞解决的方法,得到了较好的系统特性。     

SAMA技术及其与扩频CDMA的性能比较

在阐述SAMAC (扩展ALOHA多址)技术原理的基础上,分析了其性能,并与扩频CDMA进行了比较,讨论了其广阔的应用前景。     

一种动态利用码资源的CDMA系统性能研究

本文提出了一种基于随机预约ALOHA访问方式,能支持话音和数据业务的动态使用码资源的码分多址访问协议。在该协议中,话音终端采用预约请求排队访问方式。数据终端采用时隙ALOHA方式传输数据分组。理论分析和计算机仿真结果表明,该协议能有效地提高系统码资源的利用率。在系统处于重负载情况下该协议能优先保证话音业务服务质量,而处于轻负载下系统码资源能为数据业务充分使用。