Frame Slotted ALOHA Research Articles

Fast and Accurate Estimation of RFID Tags

Radio frequency identification (RFID) systems have been widely deployed for various applications such as object tracking, 3-D positioning, supply chain management, inventory control, and access control. This paper concerns the fundamental problem of estimating RFID tag population size, which is needed in many applications such as tag identification, warehouse monitoring, and privacy-sensitive RFID systems. In this paper, we propose a new scheme for estimating tag population size called Average Run-based Tag estimation (ART). The technique is based on the average run length of ones in the bit string received using the standardized framed slotted Aloha protocol. ART is significantly faster than prior schemes. For example, given a required confidence interval of 0.1% and a required reliability of 99.9%, ART is consistently 7 times faster than the fastest existing schemes (UPE and EZB) for any tag population size. Furthermore, ART's estimation time is provably independent of the tag population sizes. ART works with multiple readers with overlapping regions and can estimate sizes of arbitrarily large tag populations. ART is easy to deploy because it neither requires modification to tags nor to the communication protocol between tags and readers. ART only needs to be implemented on readers as a software module.

Modeling and Analysis of Reservation Frame Slotted-ALOHA in Wireless Machine-to-Machine Area Networks for Data Collection

Modeling and Analysis of Reservation Frame Slotted-ALOHA in Wireless Machine-to-Machine Area Networks for Data Collection

Energy Analysis of Contention Tree-Based Access Protocols in Dense Machine-to-Machine Area Networks

Machine-to-Machine (M2M) area networks aim at connecting an M2M gateway with a large number of energy-constrained devices that must operate autonomously for years. Therefore, attaining high energy efficiency is essential in the deployment of M2M networks. In this paper, we consider a dense M2M area network composed of hundreds or thousands of devices that periodically transmit data upon request from a gateway or coordinator. We theoretically analyse the devices’ energy consumption using two Medium Access Control (MAC) protocols which are based on a tree-splitting algorithm to resolve collisions among devices: the Contention Tree Algorithm (CTA) and the Distributed Queuing (DQ) access. We have carried out computer-based simulations to validate the accuracy of the theoretical models and to compare the energy performance using DQ, CTA, and Frame Slotted-ALOHA (FSA) in M2M area networks with devices in compliance with the IEEE 802.15.4 physical layer. Results show that the performance of DQ is totally independent of the number of contending devices, and it can reduce the energy consumed per device in more than 35% with respect to CTA and in more than 80% with respect to FSA.

ProTaR: Probabilistic Tag Retardation for Missing Tag Identification in Large-Scale RFID Systems

Radio frequency identification (RFID) technology provides a promising solution to the problem of missing object identification in large-scale systems, such as warehouses and bookstores by employing RFID readers to communicate with numerous RFID tags, each of which is attached to a monitored object. To achieve prompt identification of missing tags/objects, extensive research is carried out while the transmission of expatiatory bits from each tag and the occurrence of substantial tag collisions critically degrade the time efficiency. Therefore, this motivates us to propose ProTaR, a probabilistic tag retardation-based protocol, which addresses the missing tag identification problem in a more time-efficient way than the prior work. Based on an improvement of conventional frame-slotted ALOHA algorithm, ProTaR aims at alleviating the tag collision problem and achieving compact tag transmissions. The novelty of ProTaR is manifested mainly in two aspects. ProTaR leverages a mask at a reader to distill partial bits from 96-bit identifier (ID) of each tag for the characterization of tag uniqueness. In this context, ProTaR averts the transmission of redundant bits from both the tags and reader. A bit vector is constructed by the reader to inform each tag of the transmissions of others. This idea successfully eliminates the tag collisions, and hence makes full utilization of tag responses. Experimental results validate that ProTaR achieves 100% identification accuracy regardless of missing tag ratio. Furthermore, extensive simulations present that ProTaR enables the time efficiency improvement of up to 88% compared with benchmarks while merely degrading the optimum by 15%.

A Review on Highly-Efficient RFID Tag Anti-collision Algorithm

A mixed algorithm based on tag estimation and tag identification is put forward by analyzing the collision problem and the anti-collision algorithm in RFID and combining the advantages of dynamic frame slotted ALOHA algo- rithm and dynamic binary search algorithm.

Analytical Computation of the Mean Number of Tag Identifications During a Time Interval in FSA

We analytically compute the mean number of identifications when $N$ tags contend in a bounded time interval of $T$ seconds in RFID systems using framed slotted aloha. Usually, performance is described in terms of identifications per time-slot. However, slot duration notably varies depending on the event (identification, collision, or empty slot). Moreover, during the reading process, the number of tags contending dynamically changes since identified tags withdraw from the process, and the frame length may vary dynamically as well. These conditions have been included in the model and lead to an accurate analysis of real RFID systems.

Missing Tag HPL Detection Algorithm in Large Scale Active RFID System

To address this issue that the real time monitoring tag of large-scale active RFID tag system, we propose an another missing tag detection algorithm which is based on frame-slotted ALOHA protocol. By reducing the number of bits of the tag reply information, the energy consumption of active tags has been greatly reduced. Compared with that traditional detection algorithm based on tag identification number, experimental results demonstrate that HPL algorithm will reduce an order of magnitude on energy consumption of label, and at the same time, it will reduce the execution time of the algorithm. Meanwhile, compared with the best iteration ID-free protocol detection algorithm currently, HPL algorithm will reduce three orders of magnitude on energy consumption of label, and reduce the execution time of the algorithm.

Exploiting the prefix information to enhance the performance of FSA-based RFID systems

For a radio frequency identification (RFID) system deployed in dense environment, the reader must quickly and reliably extract information from numerous tags. To harmonize the channel access among competing tags and reduce collision probability, conventionally, framed slotted ALOHA (FSA) scheme is employed to resolve the collisions occurring when numerous tags simultaneously respond to the query of the reader. Typically, FSA algorithm consists of two parts: (i) estimating the number of available tags in vicinity, and (ii) base on the estimated value, setting the frame length accordingly. However, in the FSA scheme, when collision happens, it is impossible to estimate how many colliding tags simultaneously reply in a single slot, which, in turn, can lead to inaccuracy of the estimated cardinality and unreasonable setting of the frame length. This will further result in under-utilization of channel resource and the degradation of the system performance. The problem can be aggravated when all slots in the frame are entirely collided under a dense environment, rendering the malfunction of the estimator.To address this problem, in this paper, a prefix assisted approach, namely, PA-FSA, is proposed to enhance the estimation accuracy of the traditional FSA. Specifically, in PA-FSA, each tag appends a prefix in front of RN16 short message. When replying RN16 to the reader, a tag randomly and independently selects one bit in the prefix and sets the bit as active. By synchronizing prefixes of multiple colliding replies and counting the number of active bits in the overlapping prefixes, the reader can more precisely estimate how many tags have collided in a single slot, thus significantly improving the estimation accuracy. Extensive simulation results indicate that, compared with the traditional schemes, PA-FSA can estimate the tag cardinality more accurately and efficiently. Additionally, with PA-FSA adopted, system can reduce the communication overhead for approximately 50% and shorten the tag identification time for about 15%.

Energy Efficient Tag Estimation Method for ALOHA-Based RFID Systems

Radio Frequency Identification (RFID) technology has become an important tool for items identification and tracking. Its rapid deployment in dynamic industry areas enables variety of new applications in behavioural analysis and processes automation. In such systems it is crucial to identify all RFID tags before they leave the interrogation area. To accomplish fast identification, it is necessary to estimate a number of tags which are in the reader interrogation area. In this paper we revisit the problem of tag quantity estimate and adapting frame size of Dynamic Frame Slotted ALOHA (DFSA) widely used as RFID Medium Access Control (MAC) mechanism. The main disadvantage in the implementation of the state-of-art estimation algorithms includes the number of required computations, along with the temporary storage of large numbers which appear before estimation. As a consequence, such algorithms are energy inefficient and may require specific computer architecture to support the calculus. In order to address stated issues, we present Improved Linearized Combinatorial Model (ILCM) algorithm for optimal frame size selection which, due to linear property of the estimator, allows significant reduction in the estimate computation with acceptable trade-off in accuracy. Simulations analyse the required number of slots to identify tag population and the Floating Point Operation (FLOP) costs required to compute estimate. In addition, to emphasize the importance of reducing computational cost, we give a case study which compares energy consumed by the mobile RFID reader processor to compute the estimate and its energy equivalent of the required radio front-end energy to identify tags.

Performance Analysis of RFID Protocols: CDMA Versus the Standard EPC Gen-2

Radio frequency identification (RFID) is a ubiquitous wireless technology which allows objects to be identified automatically. An RFID tag is a small electronic device with an antenna and has a unique identification (ID) number. RFID tags can be categorized into passive and active tags. For passive tags, a standard communication protocol known as EPC-global Generation-2, or briefly EPC Gen-2, is currently in use. RFID systems are prone to transmission collisions due to the shared nature of the wireless channel used by tags. The EPC Gen-2 standard recommends using dynamic framed slotted ALOHA technique to solve the collision issue and to read the tag IDs successfully. Recently, some researchers have suggested to replace the dynamic framed slotted ALOHA technique used in the standard EPC Gen-2 protocol with the code division multiple access (CDMA) technique to reduce the number of collisions and to improve the tag identification procedure. In this paper, the standard EPC Gen-2 protocol and the CDMA-based tag identification schemes are modeled as absorbing Markov chain systems. Using the proposed Markov chain systems, the analytical formulae for the average number of queries and the total number of transmitted bits needed to identify all tags in an RFID system are derived for both the EPC Gen-2 protocol and the CDMA-based tag identification schemes. In the next step, the performance of the EPC Gen-2 protocol is compared with the CDMA-based tag identification schemes and it is shown that the standard EPC Gen-2 protocol outperforms the CDMA-based tag identification schemes in terms of the number of transmitted bits and the average time required to identify all tags in the system.

LPDQ: A self-scheduled TDMA MAC protocol for one-hop dynamic low-power wireless networks

Current Medium Access Control (MAC) protocols for data collection scenarios with a large number of nodes that generate bursty traffic are based on Low-Power Listening (LPL) for network synchronization and Frame Slotted ALOHA (FSA) as the channel access mechanism. However, FSA has an efficiency bounded to 36.8% due to contention effects, which reduces packet throughput and increases energy consumption. In this paper, we target such scenarios by presenting Low-Power Distributed Queuing (LPDQ), a highly efficient and low-power MAC protocol. LPDQ is able to self-schedule data transmissions, acting as a FSA MAC under light traffic and seamlessly converging to a Time Division Multiple Access (TDMA) MAC under congestion. The paper presents the design principles and the implementation details of LPDQ using low-power commercial radio transceivers. Experiments demonstrate an efficiency close to 99% that is independent of the number of nodes and is fair in terms of resource allocation.

Experimental energy consumption of Frame Slotted ALOHA and Distributed Queuing for data collection scenarios.

Data collection is a key scenario for the Internet of Things because it enables gathering sensor data from distributed nodes that use low-power and long-range wireless technologies to communicate in a single-hop approach. In this kind of scenario, the network is composed of one coordinator that covers a particular area and a large number of nodes, typically hundreds or thousands, that transmit data to the coordinator upon request. Considering this scenario, in this paper we experimentally validate the energy consumption of two Medium Access Control (MAC) protocols, Frame Slotted ALOHA (FSA) and Distributed Queuing (DQ). We model both protocols as a state machine and conduct experiments to measure the average energy consumption in each state and the average number of times that a node has to be in each state in order to transmit a data packet to the coordinator. The results show that FSA is more energy efficient than DQ if the number of nodes is known a priori because the number of slots per frame can be adjusted accordingly. However, in such scenarios the number of nodes cannot be easily anticipated, leading to additional packet collisions and a higher energy consumption due to retransmissions. Contrarily, DQ does not require to know the number of nodes in advance because it is able to efficiently construct an ad hoc network schedule for each collection round. This kind of a schedule ensures that there are no packet collisions during data transmission, thus leading to an energy consumption reduction above 10% compared to FSA.

An Improved RFID Tag Collision Algorithm

Tag collision is a very important research direction in the RFID system. Probabilistic solving algorithm is one of the important way to solve the tag collision, dynamic frame slot ALOHA (DFSA) algorithm is more commonly used at present and the probabilistic algorithm with better effect. This paper proposes an Advanced DFSA (ADFSA) which is based on a dynamic frame slot ALOHA algorithm, combined with multiplier factor and grouping thoughts. the algorithm is simple, at the same time, the simulation results show that IDFSA algorithm has better performance.

Experimental Energy Consumption of Frame Slotted ALOHA and Distributed Queuing for Data Collection Scenarios

Experimental Energy Consumption of Frame Slotted ALOHA and Distributed Queuing for Data Collection Scenarios

Research and Implement of an Improved Frame-Slotted ALOHA Anti-Collision Algorithm

The anti-collision algorithm is the key technology of RFID system. Firstly, this paper studied frame-slotted ALOHA anti-collision algorithm, in order to solve the shortcomings of ALOHA algorithm, an improved anti-collision algorithm is proposed based on grouping mechanism, and it also carried out the simulation experiences using the C# language under the .NET platform. The simulation results indicate that the improved algorithms can increase RFID system throughput.

Group improved enhanced dynamic frame slotted ALOHA anti-collision algorithm

With the development of information technology and declining in the cost of tags, radio frequency identification (RFID) system has become more and more popular, which has been widely used in a lot of areas, such as logistics tracking, animals identification, medicine, electronic toll collection, inventory, asset management, manufacturing, etc. However, when we use RFID technology to identify the objects, tag collision is one of the important factors to influence the identification efficiency. Currently, Aloha-based algorithm is one of the popular anti-collision algorithms which performs well when the number of tags is small. But it is not very efficient for cases with large number of tags and some areas which tags' number can be estimated, such as warehouse, supermarket, the production lines of smart factory and so on. So in this paper, we proposed a new anti-collision algorithm called group improved enhanced dynamic frame slotted ALOHA (GroupIEDFSA) by estimating the number of unread tags first, comparing the maximum frame size and dividing tags into groups when the number of tags which are activated is large. What is more, compared with enhanced dynamic frame slotted ALOHA (EDFSA) algorithm in the process of identification, GroupIEDFSA algorithm will combine new group based on the unread tags' number. Simulation results show that the efficiency of GroupIEDFSA algorithm system improves by 20 % in time and over 50 % in rounds than EDFSA algorithm in the standard mode, and increases by 1 % in time when we used fast mode.

A Feasible and Easy-to-Implement Anticollision Algorithm for the EPCglobal UHF Class-1 Generation-2 RFID Protocol

Dynamic frame slotted Aloha (DFSA) has been widely adopted to solve the anticollision problem in a radio frequency identification (RFID) system. In a DFSA procedure, the interrogator needs to continuously estimate tag backlog and select a new frame length for identifying the backlog. Intuitively, the accuracy of the tag estimator will affect the read performance. Hence, a considerable amount of research effort has been invested to improve the accuracy of backlog estimation. The improvement in general comes at the expense of large computation load and may lead to a serious challenge if one needs to implement such a kind of estimators in a real RFID system. This paper analyzes the influence of estimation error on read performance. Based on the analysis, we propose a feasible and easy-to-implement anticollision algorithm. Our proposed algorithm can achieve a normalized throughput of 35% that is very close to the theoretical maximum 36.1% for an EPCglobal UHF Class-1 Generation-2 system. The easy-to-implement advantage of our algorithm comes at the expense of only 1% reduction in normalized throughput as compared with the case where maximum throughput can be obtained. The results obtained are useful in designing fast and efficient interrogators. Note to Practitioners - A fast and efficient anticollision algorithm is required in many applications such as warehouse and supply chain management. Since most RFID interrogators are built with a single-chip microprocessor, whose computation ability or memory is limited. From the implementation point of view, a feasible algorithm should consider the compromise between complexity and performance. In order to easily implement the anticollision algorithm in a real RFID system, the proposed algorithm is based on a simple but sufficiently accurate method rather than complex models. The results obtained can be useful for the industry to develop fast and efficient RFID interrogators.

Design of anti-collision integrated security mechanism based on chaotic sequence in UHF RFID system

Collision and security issues are considered as barriers to RFID applications. In this paper, a parallelizable anti-collision based on chaotic sequence combined dynamic frame slotted aloha to build a high-effciency RFID system is proposed. In the tags parallelizable identification, we design a Discrete Markov process to analyze the success identification rate. Then a mutual authentication security protocol merging chaotic anti-collision is presented. The theoretical analysis and simulation results show that the proposed identifcation scheme has less than 45.1 % of the identifcation time slots compared with the OVSF-system when the length of the chaos sequence is 31. The success identification rate of the proposed chaotic anti-collision can achieve 63% when the number of the tag is 100. We test the energy consumption of the presented authentication protocol, which can simultaneously solve the anti-collision and security of the UHF RFID system.

Standardized Low-Power Wireless Communication Technologies for Distributed Sensing Applications

Recent standardization efforts on low-power wireless communication technologies, including time-slotted channel hopping (TSCH) and DASH7 Alliance Mode (D7AM), are starting to change industrial sensing applications, enabling networks to scale up to thousands of nodes whilst achieving high reliability. Past technologies, such as ZigBee, rooted in IEEE 802.15.4, and ISO 18000-7, rooted in frame-slotted ALOHA (FSA), are based on contention medium access control (MAC) layers and have very poor performance in dense networks, thus preventing the Internet of Things (IoT) paradigm from really taking off. Industrial sensing applications, such as those being deployed in oil refineries, have stringent requirements on data reliability and are being built using new standards. Despite the benefits of these new technologies, industrial shifts are not happening due to the enormous technology development and adoption costs and the fact that new standards are not well-known and completely understood. In this article, we provide a deep analysis of TSCH and D7AM, outlining operational and implementation details with the aim of facilitating the adoption of these technologies to sensor application developers.

Precise-Optimal Frame Length Based Collision Reduction Schemes for Frame Slotted Aloha RFID Systems

An RFID systems employ efficient Anti-Collision Algorithms (ACAs) to enhance the performance in various applications. The EPC-Global G2 RFID system utilizes Frame Slotted Aloha (FSA) as its ACA. One of the common approaches used to maximize the system performance (tag identification efficiency) of FSA-based RFID systems involves finding the optimal value of the frame length relative to the contending population size of the RFID tags. Several analytical models for finding the optimal frame length have been developed; however, they are not perfectly optimized because they lack precise characterization for the timing details of the underlying ACA. In this paper, we investigate this promising direction by precisely characterizing the timing details of the EPC-Global G2 protocol and use it to derive a precise-optimal frame length model. The main objective of the model is to determine the optimal frame length value for the estimated number of tags that maximizes the performance of an RFID system. However, because precise estimation of the contending tags is difficult, we utilize a parametric-heuristic approach to maximize the system performance and propose two simple schemes based on the obtained optimal frame length.namely, Improved Dynamic-Frame Slotted Aloha (ID-FSA) and Exponential Random Partitioning-Frame Slotted Aloha (ERP-FSA). The ID-FSA scheme is based on the tag set estimation and frame size update mechanisms, whereas the ERP-FSA scheme adjusts the contending tag population in such a way that the applied frame size becomes optimal. The results of simulations conducted indicate that the ID-FSA scheme performs better than several well-known schemes in various conditions, while the ERP-FSA scheme performs well when the frame size is small.