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。     

A capture-aware access control method for enhanced RFID anti-collision performance

This letter presents a novel anti-collision algorithm for Radio Frequency Identification (RFID) systems that drastically improve throughput performance via an intelligent access control for capture inducement. In order to induce the capture, our protocol attempts to divide tags into multiple groups depending on received signal strength, and allow only a selected pair of groups to join the contention process, in which the outcome of contention is more likely to lead to capture due to a significant difference in their signal strengths. Numerical results show that our proposed algorithm significantly outperforms the existing approaches in terms of throughput.     

捕获效应下树形算法的信道吞吐率及优化

随机多址方式是解决目前信道资源日益紧张问题的一项关键技术，本文基于一个分组无线网中具有捕获效应的信道模型，分析了网址方式 中拓种树形算法的吞吐率，得出结论：在捕获效应下，这三种算法的吞吐率都能得到一定程度的提高，进一步地，在捕获效应的启发下，给出了一种优化树表算法的方法。     

Experimental Study of Capture Effect for Medium Access Control with ALOHA

In this paper, we investigate the capture effect through experiments conducted with Iris nodes equipped with AT86RF230 radio transceivers. It is shown that the first arriving packet in a collision can capture the radio channel for equal power transmissions and may be decoded depending on the amount of overlap. A new 3‐packet‐capture scenario is introduced and implemented. To be able to understand the impact of capture on the throughput performance of wireless sensor networks, we present an analysis of the capture coefficient using our practical results. For real‐world implementations, the throughput of pure ALOHA considering a finite number of users is presented in analytical form. The capture coefficient is then applied to pure ALOHA as a case study. Using analytical and practical implementations of the capture effect on ALOHA, a very good match in channel throughput performance enhancement is demonstrated over the non‐capture effect case. TinyOS‐2.x is used to program the nodes and to observe data exchange on a computer through a base station.     

Fish‐Microarray: A Miniaturized Platform for Single‐Embryo High‐Throughput Screenings

Small molecule high‐throughput screenings are essential for the fields of drug discovery and toxicology. Such screenings performed on whole animals are more physiologically relevant leading to more predictive results. However, due to challenges in automation, high costs and absence of miniaturized solutions for animal‐based experiments, high throughput screenings based on animal models are still in its infancy. Here a platform for miniaturized high throughput whole‐organism screenings is presented. The new platform is based on patterns of hydrophilic spots separated by superhydrophobic borders. The difference in wettability of spots and borders generates the effect of discontinuous dewetting and allows for formation of arrays of microdroplets that incorporate single fish embryos. Due to the flat border‐less nature of the platform, the system is compatible with single‐step collection of embryos and pipetting‐free parallel addition of chemical libraries using the “sandwiching method.” The system is miniaturized and allows for incubation of embryos in volumes as low as 5 µL. Finally, the platform realizes surface tension based immobilization of single embryos inside of each microcompartment and permits high‐throughput microscopic analysis directly on the platform. Thus, this method combines the advantages of microarrays, such as high‐throughput and simplicity, with the power of in vivo experiments.     

Random Signal Levels for Channel Access in Packet Broadcast Networks

In this paper, it is proposed to employ random multiple signal levels for channel access in packet broadcast networks. We present priority-free random access protocols that possess the advantage of capture effect. The presented schemes are applied to the slotted ALOHA, and the performance is analyzed based on a conservative capture model. Closed-form expressions for the system throughput are derived for a general two-signal level system and a generalm-signallevel system. It is shown that the maximum throughput for the twolevel system increases from 0.47 to 0.52 as the separation between the two levels increases. For them-level system, the maximum throughput increases from 0.52 to 0.66 asmincreases from three to infinity. Then a rotary-priority sure-capture random access scheme is presented, which can achieve perfect channel utilization. The time-delay characteristic and the throughput-delay tradeoff are analyzed for the simplest two-level system for which the higher level is double the lower level. The results compare favorably to those of the conventional slotted ALOHA system which employs a single signal level for packet transmission. A number of open problems are addressed.     

Genetic algorithm‐based content distribution strategy for F‐RAN architectures

Fog radio access network (F‐RAN) architectures provide markedly improved performance compared to conventional approaches. In this paper, an efficient genetic algorithm‐based content distribution scheme is proposed that improves the throughput and reduces the transmission delay of a F‐RAN. First, an F‐RAN system model is presented that includes a certain number of randomly distributed fog access points (F‐APs) that cache popular content from cloud and other sources. Second, the problem of efficient content distribution in F‐RANs is described. Third, the details of the proposed optimal genetic algorithm‐based content distribution scheme are presented. Finally, simulation results are presented that show the performance of the proposed algorithm rapidly approaches the optimal throughput. When compared with the performance of existing random and exhaustive algorithms, that of the proposed method is demonstrably superior.     

Enhanced energy-saving anticollision algorithms with improving throughput for RFID system

Tag collision algorithm is a key issue for energy saving and throughput with Radio Frequency IDentification (RFID) system more popular in sensing infrastructure of covering wider area on a large scale. Exploiting low energy consumption strategy would enable longer operational life of tags and reader with battery energy supply. And improving throughput is required on a large scale to preserve the capability of the correct reception. Therefore, this paper proposes an enhanced anti-collision algorithm called Dynamic Slotted with Muting (DSM), which uses multiple slots within a frame per node in a binary tree and takes tag estimation function to optimize the number of slots, and adds a mute command to put identified tags silence. The performance of the proposed algorithm is analytically provided, and simulation results show that DSM saves more than 40% energy consumptions both at reader and tags, and improves more than 35% throughput compared to the existing algorithms. Thus our algorithm is demonstrated to perform efficient energy savings at reader and tags with throughput improvement.     

基于CDMA技术的新型防碰撞算法

标签碰撞是射频识别（RFID）技术的常见问题,该问题影响了RFID系统通信过程中数据传输的完整性.在分析已有防碰撞方法的基础上,根据帧时隙分组ALOHA算法,结合码分多址技术,提出了新型的标签防碰撞算法.该算法能够有效减小标签之间的碰撞概率,缩短读写器操作时间,提高吞吐率,很适合应用于具有较大数量标签的RFID系统中.     

捕获效应下RFID标签的CATPE防冲突协议

在被动式RFID系统中,当多个标签同时向阅读器发射信号时,捕获效应能使阅读器成功接收其中一个标签信号。为提高捕获效应下的识别效率,本文提出一种名为CATPE (capture-aware and tag-population estimation)的RFID标签防冲突协议。该协议可同时估计标签数和捕获效应的发生概率,并在非等长时隙下设置最优帧长。CATPE协议的优点在于不需搜索极值,仅一步计算就能完成估计,从而降低了计算复杂度。计算机仿真显示,该协议与已有协议的识别效率相近,但计算复杂度得到了降低。     

ALOHA with capture over slow and fast fading radio channels withcoding and diversity

The effects of capture on the average system throughput and delay performance of slotted ALOHA were analyzed for slow and fast Rayleigh fading radio channels. A short-range multipoint-to-base station packet radio network is considered. It is shown that larger capture effects and thus improved network performance can be achieved with proper choice of modulation. It is also shown that the use of simple error-correcting codes improves capture. The use of selection diversity also improves the capture effect both for fast and slow fading. It is concluded that the inverse distance variability of the received signal is the main reason for the capture effect. The Rayleigh fading alone yields a very small contribution in terms of throughput; nonetheless, it helps to stabilize the system. Numerical results are presented for a slotted ALOHA system with 50 users. It is found that the maximum average throughput can be increased from about 36% to almost 60% by using channel coding and space diversity     

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.     

Generalized Hardware Post‐processing Technique for Chaos‐Based Pseudorandom Number Generators

This paper presents a generalized post‐processing technique for enhancing the pseudorandomness of digital chaotic oscillators through a nonlinear XOR‐based operation with rotation and feedback. The technique allows full utilization of the chaotic output as pseudorandom number generators and improves throughput without a significant area penalty. Digital design of a third‐order chaotic system with maximum function nonlinearity is presented with verified chaotic dynamics. The proposed post‐processing technique eliminates statistical degradation in all output bits, thus maximizing throughput compared to other processing techniques. Furthermore, the technique is applied to several fully digital chaotic oscillators with performance surpassing previously reported systems in the literature. The enhancement in the randomness is further examined in a simple image encryption application resulting in a better security performance. The system is verified through experiment on a Xilinx Virtex 4 FPGA with throughput up to 15.44 Gbit/s and logic utilization less than 0.84% for 32‐bit implementations.     

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%.     

Conception and Performance Analysis of Efficient CDMA‐Based Full‐Duplex Anti‐collision Scheme

Ultra‐high‐frequency radio‐frequency identification (UHF RFID) is widely applied in different industries. The Frame Slotted ALOHA in EPC C1G2 suffers severe collisions that limit the efficiency of tag recognition. An efficient full‐duplex anti‐collision scheme is proposed to reduce the rate of collision by coordinating the transmitting process of CDMA UWB uplink and UHF downlink. The relevant mathematical models are built to analyze the performance of the proposed scheme. Through simulation, some important findings are gained. The maximum number of identified tags in one slot is g/e (g is the number of PN codes and e is Euler's constant) when the number of tags is equal to mg (m is the number of slots). Unlike the Frame Slotted ALOHA, even if the frame size is small and the number of tags is large, there aren't too many collisions if the number of PN codes is large enough. Our approach with 7‐bit Gold codes, 15‐bit Gold codes, or 31‐bit Gold codes operates 1.4 times, 1.7 times, or 3 times faster than the CDMA Slotted ALOHA, respectively, and 14.5 times, 16.2 times, or 18.5 times faster than the EPC C1 G2 system, respectively. More than 2,000 tags can be processed within 300 ms in our approach.     

Feedback‐based multi‐layered STBC system for MIMO multi‐cellular networks with cochannel interference

A feedback‐based multi‐layered STBC (MLSTBC) system, which is adapted to cochannel interference, is proposed. This system can adjust its transmitter configuration so that the largest throughput for the given SINR is obtained, also, it can use joint beamforming and power control to minimize cochannel interference so that the throughput requirement is satisfied. We propose an iterative algorithm to realize joint beamforming and power control for the feedback‐based MLSTBC system, and in this algorithm, we derive the required SINR and the corresponding transmitter configuration for attaining the throughput requirement. Some properties and simulation results are presented, they show that the proposed algorithm helps the feedback‐based MLSTBC system increase the probability of the success in meeting the throughput requirement, also they show that the feedback‐based MLSTBC system results in larger throughput than MLSTBC (with fixed transmitter configuration), STBC, and V‐BLAST. Copyright © 2010 John Wiley & Sons, Ltd.     

Optical transmission as a fast and non‐destructive tool for determination of ethylene‐co‐vinyl acetate curing state in photovoltaic modules

Poly(ethylene‐co‐vinyl acetate) (EVA) is the primary polymer used for encapsulation of photovoltaic (PV) modules. Its degree of cross‐linking (gel content) is taken as a major quality reference. The EVA gel content is normally measured by Soxhlet extraction and more recently also by Differential Scanning Calorimetry (DSC). The DSC method is proven here to be fast and effective but is, as the Soxhlet extraction method, destructive to the PV module. With the aim of developing a fast and non‐destructive method to determine the gel content, a number of analytical techniques are presented. The most promising method is ultraviolet/visible/near‐infrared (UV/Vis/NIR) optical transmission. The measured diffuse transmission reflects the EVA crystallite size, which is related to the EVA gel content. This opens the possibility to apply an in‐line analysis of every PV module immediately after the lamination step and could significantly contribute to the process quality control that is needed in future high‐throughput production lines of PV modules. Copyright © 2011 John Wiley & Sons, Ltd.     

Dynamic frame-slotted ALOHA anti-collision algorithm in RFID based on non-linear estimation

We propose an RFID tag anti-collision method using adaptive frame length adjustment. Based on the number of tags identified in the first frame, the original tag population can be estimated by solving a non-linear estimating equation. Subsequent frame lengths can be adaptively adjusted according to the number of remaining tags. The simulation results demonstrate the error rate of the proposed method to be less than 5% – superior to that of existing methods. Compared with the widely used dynamic frame slot ALOHA algorithm – adopted by EPC_C1 G2 standard – tag identification throughput performance increased by 50%.     

Engineered Microneedles for Interstitial Fluid Cell‐Free DNA Capture and Sensing Using Iontophoretic Dual‐Extraction Wearable Patch

Interstitial fluid (ISF), as an emerging source of biomarkers, is unmistakably significant for disease diagnosis. Microneedles (MNs) provide a minimally invasive approach for extracting the desired molecules from ISF. However, existing MNs are limited by their capture efficiency and sensitivity, which impedes early disease diagnosis. Herein, an engineered wearable epidermal system is presented with a combination of reverse iontophoresis and MNs for rapid capture and sensing of Epstein‐Barr virus cell‐free DNA (an important biomarker of nasopharyngeal carcinoma). Owing to a dual‐extraction effect demonstrated by reverse iontophoresis and MNs, the engineered wearable platform successfully isolates the cell‐free DNA target from ISF within 10 min, with a threshold of 5 copies per µL and a maximum capture efficiency of 95.4%. The captured cell‐free DNA is also directly used in a recombinase polymerase amplification electrochemical microfluidic biosensor with a detection limit of 1.1 copies per µL (or a single copy). The experimental data from immunodeficient mouse models rationalizes the feasibility and practicality of the wearable system. Collectively, the developed method opens an innovative route for minimally invasive sampling of ISF for cell‐free DNA‐related cancer screening and prognosis.     

基于信息位编码的自适应搜索RFID防碰撞算法研究

无线射频识别（RFID）技术可实现对目标物体的自动识别.为了减少对物体标签识别时间,提出一种基于信息位编码的自适应搜索的防碰撞（AS）算法.读写器充分利用碰撞位信息,要求标签返回碰撞位编码信息,进而自适应地生成有效查询前缀,对标签进行无空闲时隙识别,以减少查询次数,提高算法的性能.此外,AS算法也解决了读写器与标签通信中传输信息冗余等问题.本文通过理论分析证明了该算法的有效性,其中吞吐率的理论值与实验值的误差不超过5%,还从时间复杂度和通信复杂度对该算法进行了详细地分析.仿真结果表明：AS算法不仅提高了系统的性能,而且还降低了标签能量的消耗.特别是当标签数为1000时,该算法的吞吐率仍保持在61%左右,比查询树算法和自适应多叉树算法的系统效率分别提高了72%和20.1%左右.