Evaluating the energy consumption of the RFID tag collision resolution protocols

RFID technology acts as a bridge to connect the physical world with the digital space, and RFID system is pervading our daily life in the last few years. The energy consumed by the reader and a tag in resolving the collisions caused by multiple tags is a key issue that affects life time of mobile reader and active tags, as well as the identification accuracy of passive tags. In this paper, the energy consumed by the reader and a tag in resolving the tag collision is examined for the commonly used RFID tag collision resolution protocols, including the frame slotted ALOHA based and the binary query tree based protocols. Numeric evaluation is also performed and the result verifies that regarding to energy consumption, the dynamic frame slotted ALOHA protocol for the Class-1 RFID system performs best among the frame slotted ALOHA protocols, and the modified binary query tree protocol also performs better than the standard binary query tree protocols.     

分组自适应分配时隙的RFID防碰撞算法研究

为了解决射频识别(Radio Frequency IDentification,RFID)系统中的多标签防碰撞问题,在分析帧时隙ALOHA算法的基础上,提出一种基于分组自适应分配时隙的RFID防碰撞算法(GAAS).首先让阅读器对标签随机所选的时隙进行扫描统计,并将其发送给每一个标签,标签再进行相应地时隙调整,使阅读器跳过空闲时隙和碰撞时隙,自适应地分配有效时隙,进而对标签进行快速识别.当未识别标签数比较大时,算法采用分组以及动态调整帧长等策略,以减少时隙处理的时间.仿真结果表明:GAAS算法提高了系统的识别效率和稳定性,降低了传输开销.特别是当标签数超过1000时,该算法的吞吐率仍保持在71%以上,比传统的帧时隙ALOHA-256算法和分组动态帧时隙ALOHA算法的系统效率分别提高了300%和97.2%.     

A new anti‐collision protocol based on information of collided tags in RFID systems

Radio frequency identification (RFID) technology has recently become an integral part of a wide range of applications. One of the challenges in RFID systems is the tag anti‐collision issue, for which several anti‐collision tag identification protocols have been proposed. This paper proposes a novel slotted ALOHA‐based RFID tag anti‐collision algorithm which can be employed for tag identification. The main idea of this algorithm is to use the information available in collision slots, called collided data, to identify tags uniquely. For this purpose, the collision slots that include only two tags are selected. Then, the non‐conflict bits in these slots are used to possibly identifying the tags. Because in the proposed algorithm readers use both single slots and also the collision slots for tag identification, the performance is increased significantly compared with other protocols. Results of the study indicate that in the proposed algorithm, the optimal frame size for an individual tag number is equal to the half of tags number and the efficiency of the proposed protocol is improved to about 73%. Copyright © 2015 John Wiley & Sons, Ltd.     

改进型帧时隙ALOHA防碰撞算法研究

为进一步提高RFID系统中电子标签防碰撞算法的识别效率,对帧时隙ALOHA防碰撞算法的性能进行分析,提出一种结合精确标签估计和二进制搜索的改进型帧时隙ALOHA算法.将识别过程分为标签估计和标签识别两个阶段,在标签估计算法中引入碰撞概率上、下限参数,并精确估计标签数量对初始帧时隙大小进行优化;在标签识别阶段,利用二进制搜索算法对时隙内的碰撞标签进行快速识别.通过对识别过程进行仿真结果表明:改进的算法改善了防碰撞性能,提高了RFID系统的标签识别效率.     

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。     

Novel tag estimation method by use of Manchester coding in RFID systems

Radio frequency identification suffers from tag collision issue. ALOHA‐based algorithms are useful and practical groups of tag anti‐collision algorithm among others. Some standards such as EPCglobal Class‐1 Generation‐2 use some kind of dynamic framed slotted ALOHA (DFSA) to cope with tag collision. DFSA efficiency depends on estimating the number of unidentified tags in each identification cycle accurately. So tag estimation is one of the challenging issues in DFSA. In this paper, we use Manchester coding to compute the lower bound of collided tags in a frame and then add α as an additional value to computed value according to the difference between optimal number of collision slots and calculated number of collision slots. Then, we evaluate and compare our method with other proposed methods.     

Split-aloha algorithm for radio frequency identification system

Anti-Collision algorithm is one of the most important components of radio frequency identification (RFID) technology, which possesses a key position in the performance of the whole system. ALOHA algorithm is one of the most popular methods to solve the collision problem because of its efficiency and practicability. The grouping method has been developed for enhancing the performance of conventional ALOHA when there are thousands of tags. However, the existing grouping method has limitations in applications due to its rigorous requirements for the estimation of the number of backlog tags or the admirable characteristics of the tags' ID number. Working on the improvement of the grouping methods, we proposed an algorithm named split-ALOHA with a novel grouping method that split tags as a binary tree. The novel grouping method makes it more practicable than the existing grouping methods due to the simplified requirements for tags. Simulations of the proposed algorithm show the superior performance of a linearly increasing of the number of consumed time slots while the number of tags increases. The algorithm performance analysis between split-ALOHA and ALOHA algorithms with other grouping methods has been implemented in a proper way.     

Pereormance analysis of slotted ALOHA for land mobile satellite networks

The ALOHA protocol has been proposed for accessing reservation channels in demand-assigned channel access protocols for land mobile satellite communications networks. This paper provides a rigorous performance analysis of both the slotted ALOHA protocol and two-packet replication ALOHA protocol taking into account the effects of the fading multipath communications environment. Throughput, delay and stability of these two protocols are determined using a Gilbert channel error model with memory. Comparison of slotted ALOHA and two-packet replication ALOHA shows that a smaller average delay can be achieved by replication. Moreover average throughput is improved in some cases. However replication reduces stability.     

基于EPC-C1G2协议的多标签识别性能分析

EPC-C1G2协议属于EPCglobal组织发布的第二代超高频射频识别空中接口协议,该协议采用时槽ALOHA算法解决多标签识别时产生的碰撞问题.首先介绍了该协议多标签碰撞解决所需的参数和命令,协议中的Q值决定了解决碰撞时所用的时槽数.时槽数越多,标签越不容易碰撞,但识别时间却越长,因此,恰当地选择Q值可以在标签识别时间和识别标签数之间找到最佳平衡点.给出了两种碰撞解决流程,一种是固定Q值算法,另一种是递减Q值算法,并仿真分析了这两种多标签识别流程的性能.     

可并行识别的分组动态帧时隙ALOHA标签防碰撞算法

该文针对现有动态帧时隙ALOHA标签防碰撞算法的系统吞吐率低、算法效率低等问题,提出一种可并行识别的分组动态帧时隙ALOHA(PIGDFSA)标签防碰撞算法。该文以实验为基础,探索了待识别标签数、标签分组数、帧长对系统吞吐率与标签碰撞率的影响,研究了提升系统吞吐率与降低标签碰撞率的策略与方法。结合射频识别(RFID)的多天线系统,引入FastICA技术,从而实现碰撞时隙重新定义,并以此为基础,利用未识别标签数目自适应确定分组数与帧长。仿真结果表明:PIGDFSA算法在标签数达到2000时,算法吞吐率仍能稳定在92%以上,与FSA-256, GDFSA, BSDBG等算法相比具有更高的算法吞吐率,更少的空隙时隙,更高的算法效率。     

Analysis of Channel-aware Multichannel ALOHA in OFDMA Wireless Networks

Orthogonal frequency division multiple access (OFDMA) systems provide multiple channels that can be accessed via random access schemes. In this paper a channel-aware multichannel random access, based on local channel state information (CSI), was investigated and a multichannel slotted ALOHA scheme was proposed accordingly. Also an analytical investigation of total system throughput and the queue state evolution of generic node in the network were present by assuming the channel has been modeled by means of a two state Markov chain. Through the theoretical model and simulation results, we confi rm that the proposed algorithm has the advantage of high throughput and low access delay.     

A model for local/mobile radio communications with correct packetcapture

The performance of a local/mobile radio communications system utilizing the slotted ALOHA multiple random access protocol is analyzed. The probability of correct packet capture is evaluated for a local/mobile packet radio system using ideal coherent binary phase-shift keying (BPSK) modulation. Both the near/far effect and the effect of Rayleigh fading on the probability of correct packet capture are taken into account, but the effect of thermal noise is neglected since the interference due to competing packets is dominant in practical systems. The probability of correct packet reception is evaluated for a system using spatial diversity. In addition, the effect on system performance of either convolutional coding with hard decision Viterbi decoding or binary linear block coding with hard decision decoding is evaluated. The pseudo-Bayesian algorithm that has been developed to stabilize a packet system based on the slotted ALOHA protocol at maximum channel throughput is found to be adaptable to the local mobile operating environment. For the system considered here, channel throughputs as high as 0.66 can be obtained     

基于碰撞预检测的分组动态帧时隙ALOHA防碰撞算法

本文在分析传统 ALOHA 算法的基础上,提出了一种基于碰撞预检测的分组动态帧时隙 ALOHA 防碰撞算法。该算法通过分组限制响应的标签数量,并且在组内预先发送一个短暂的碰撞检测帧去检测帧内的情况,达到在阅读器与标签之间建立一个完全无碰撞信道的目的。仿真结果表明,当标签数量较大时,该算法能有效减少总数据传输量,提高识别效率。     

A rural messaging network using spread ALOHA access with VSAT satellite terminals

This paper underlines the characteristics of a proposed mesh network for messaging applications in C-band using spread ALOHA protocol. A simulation program has been developed for studying the behaviour of large networks employing ALOHA access or its variants. It is a simulation for a large population network consisting of thin traffic small messaging terminals (SMTs), and models an infinite user population which employs fixed length data packets. The program is general and allows for the study of either the mesh or the star connected networks. Certain variations of the classical ALOHA schemes, such as slotted ALOHA (with user selectable slot length) and spread ALOHA, have been studied for network operation. In the case of spread ALOHA access, the program can be run with Barker, pseudorandom, Ping Fai Li or any other spreading sequence. The results of the simulation have confirmed the utility of spread ALOHA as an access protocol for MESCOMNET. It has identified an operating point on the throughput-traffic curve at which spread advantage is available for power reduction of SMTs.     

Probabilistic Dynamic Framed Slotted ALOHA for RFID Tag Identification

In this paper, we study radio frequency identification tag identification problems using framed slotted ALOHA protocol. Each tag will be assumed to participate in the contention with a certain probability. Then, the frame size and the probability will be dynamically controlled by the reader in every reading round so that all the tags can be detected in a short period of time. Moreover, we propose a practical way of controlling the probability in terms of transmit power control, assuming Additive White Gaussian Noise channel or flat Rayleigh fading channel. Computer simulation results demonstrate the effectiveness of the proposed method.     

Multichannel random access protocol for multihop cellular systems

A stabilised multichannel random-access protocol based on slotted ALOHA for multihop cellular systems is proposed. The fundamental contribution is a mathematical formula for an optimal partition ratio of shared random access channels between a base station and a relay station. Numerical results show that the proposed protocol can guarantee the required utilisation or delay even if the offered load is higher than the threshold, which otherwise can cause the bistable problem of slotted ALOHA.     

Gen2‐Based Tag Anti‐collision Algorithms Using Chebyshev's Inequality and Adjustable Frame Size

Arbitration of tag collision is a significant issue for fast tag identification in RFID systems. A good tag anti‐collision algorithm can reduce collisions and increase the efficiency of tag identification. EPCglobal Generation‐2 (Gen2) for passive RFID systems uses probabilistic slotted ALOHA with a Q algorithm, which is a kind of dynamic framed slotted ALOHA (DFSA), as the tag anti‐collision algorithm. In this paper, we analyze the performance of the Q algorithm used in Gen2, and analyze the methods for estimating the number of slots and tags for DFSA. To increase the efficiency of tag identification, we propose new tag anti‐collision algorithms, namely, Chebyshev's inequality, fixed adjustable framed Q, adaptive adjustable framed Q, and hybrid Q. The simulation results show that all the proposed algorithms outperform the conventional Q algorithm used in Gen2. Of all the proposed algorithms, AAFQ provides the best performance in terms of identification time and collision ratio and maximizes throughput and system efficiency. However, there is a tradeoff of complexity and performance between the CHI and AAFQ algorithms.     

Slotted ALOHA performance for FU‐FB in frequency selective fading environment

Slotted ALOHA is a simple and straightforward random multiple access technique, which has been used extensively in data and cellular networks as the protocol for random access. The complexity of state space‐based analysis methods for finite user finite buffer systems increases exponentially with buffer size and number of users. The presence of multipath frequency selective fading channel further adds to the complexity, making the analysis practically intractable. This paper uses an approximate analysis technique called tagged user analysis (TUA) to analyze the performance parameters of slotted ALOHA over multipath and frequency selective fading channels for finite user finite buffer systems. In TUA, the steady state system performance is evaluated from the analysis of a single user. Moreover, the state flow graph of TUA has just four states, thus reducing the complexity of the analysis. Simulation results confirm the validity of the TUA analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

A Reliable Pipeline Protocol for the Message Service of a Land Mobile Satellite Experiment

This paper describes and analyzes a pipeline protocol for the data message communications of MSAT-X, a proposed experimental satellite-based mobile communications network. A demand-assigned multiple access protocol using pure ALOHA for making reservation requests has been developed for MSAT-X under error-free assumptions. Preliminary propagation studies indicate that the shortterm bit error rate of satellite channels in a mobile environment can be as high as 10^-3. Therefore, error-control schemes must be developed to ensure reliable transmissions. In this paper, we propose a retransmission scheme using selective repeat to minimize the end-to-end delay. We also use slotted ALOHA for making reservation requests to increase the overall system throughput. Since the number of channels available for reservation and data channels is essentially fixed for a given voice call blocking probability and a fixed call arrival rate, the analysis presented in this paper is also applicable to the integrated voice and data services of MSAT-X. Various operational scenarios have been investigated.     

Performance analysis of a slotted CDMA ALOHA network

ALOHA is a simple and efficient way of allowing many machines with bursty data streams to communicate with a central computer. For cases where machines are equally likely to transmit to one another, CDMA ALOHA, which allows for full connectivity, may be a better multiple access protocol than slotted ALOHA through a central machine. This paper first describes a model for a fully connected, full duplex, and slotted CDMA ALOHA network where the receiver-based code access protocol is used. The stations can send data to, and receive data from, different stations simultaneously. The model is analyzed using discrete-time Markov chain, and some numerical results are presented. For a system with a large number of users where Markov analysis is impractical, equilibrium point analysis is used to predict the stability of the system and determine the throughput as well as the delay performance of the system when it is stable. It is shown that a CDMA slotted ALOHA network has a much better performance compared to simple slotted ALOHA networks.