ALOHA应用于TD-SCDMA的随机接入过程

分析了TD-SCDMA系统物理层过程中的随机接入过程和ALOHA算法的应用。随机接入过程作为无线通信系统中的一个关键性过程,其在UpPCH公共信道上产生的碰撞问题将直接影响用户接入的成功和无线资源的利用。在系统级仿真软件OPNET中对用户和基站分别进行建模,并在基站侧对在同一时隙接入的用户强度以及由此产生的碰撞进行了仿真分析,得出:当用户的接入强度很大时,碰撞的概率比较大。应用ALOHA算法于具有竞争冲突特性的上行同步信道,经仿真后得出结论,ALOHA算法的应用可以减少碰撞的影响。     

CMOS image sensors for sensor networks

We report on two generations of CMOS image sensors with digital output fabricated in a 0.6 μm CMOS process. The imagers embed an ALOHA MAC interface for unfettered self-timed pixel read-out targeted to energy-aware sensor network applications. Collision on the output is monitored using contention detector circuits. The image sensors present very high dynamic range and ultra-low power operation. This characteristics allow the sensor to operate in different lighting conditions and for years on the sensor network node power budget. Eugenio Culurciello (S’97–M’99) received the Ph.D. degree in Electrical and Computer Engineering in 2004 from Johns Hopkins University, Baltimore, MD. In July 2004 he joined the department of Electrical Engineering at Yale University, where he is currently an assistant professor. He founded and instrumented the E-Lab laboratory in 2004. His research interest is in analog and mixed-mode integrated circuits for biomedical applications, sensors and networks, biological sensors, Silicon on Insulator design and bio-inspired systems. Andreas G. Andreou received his Ph.D. in electrical engineering and computer science in 1986 from Johns Hopkins University. Between 1986 and 1989 he held post-doctoral fellow and associate research scientist positions in the Electrical and Computer engineering department while also a member of the professional staff at the Johns Hopkins Applied Physics Laboratory. Andreou became an assistant professor of Electrical and Computer engineering in 1989, associate professor in 1993 and professor in 1996. He is also a professor of Computer Science and of the Whitaker Biomedical Engineering Institute and director of the Institute’s Fabrication and Lithography Facility in Clark Hall. He is the co-founder of the Johns Hopkins University Center for Language and Speech Processing. Between 2001 and 2003 he was the founding director of the ABET accredited undergraduate Computer Engineering program. In 1996 and 1997 he was a visiting professor of the computation and neural systems program at the California Institute of Technology. In 1989 and 1991 he was awarded the R.W. Hart Prize for his work on mixed analog/digital integrated circuits for space applications. He is the recipient of the 1995 and 1997 Myril B. Reed Best Paper Award and the 2000 IEEE Circuits and Systems Society, Darlington Best Paper Award. During the summer of 2001 he was a visiting professor in the department of systems engineering and machine intelligence at Tohoku University. In 2006, Prof. Andreou was elected as an IEEE Fellow and a distinguished lecturer of the IEEE EDS society. Andreou’s research interests include sensors, micropower electronics, heterogeneous microsystems, and information processing in biological systems. He is a co-editor of the IEEE Press book: Low-Voltage/Low-Power Integrated Circuits and Systems, 1998 (translated in Japanese) and the Kluwer Academic Publishers book: Adaptive Resonance Theory Microchips, 1998. He is an associate editor of IEEE Transactions on Circuits and Systems I.     

基于动态ALOHA算法的RFID反碰撞技术

简述了无源射频识别系统的组成、工作原理及数据碰撞问题。针对射频识别系统的技术要求和应用特点,提出一种基于时分多路的动态ALOHA反碰撞方法,并对其工作原理、可行性及实现过程进行了分析和论证。该方法无需增加硬件开销,应用成本低,适应性强。     

Spectrum Slicing for Multiple Access Channels with Heterogeneous Services

Wireless mobile networks from the fifth generation (5G) and beyond serve as platforms for flexible support of heterogeneous traffic types with diverse performance requirements. In particular, the broadband services aim for the traditional rate optimization, while the time-sensitive services aim for the optimization of latency and reliability, and some novel metrics such as Age of Information (AoI). In such settings, the key question is the one of spectrum slicing: how these services share the same chunk of available spectrum while meeting the heterogeneous requirements. In this work we investigated the two canonical frameworks for spectrum sharing, Orthogonal Multiple Access (OMA) and Non-Orthogonal Multiple Access (NOMA), in a simple, but insightful setup with a single time-slotted shared frequency channel, involving one broadband user, aiming to maximize throughput and using packet-level coding to protect its transmissions from noise and interference, and several intermittent users, aiming to either to improve their latency-reliability performance or to minimize their AoI. We analytically assessed the performances of Time Division Multiple Access (TDMA) and ALOHA-based schemes in both OMA and NOMA frameworks by deriving their Pareto regions and the corresponding optimal values of their parameters. Our results show that NOMA can outperform traditional OMA in latency-reliability oriented systems in most conditions, but OMA performs slightly better in age-oriented systems.     

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.     

低轨卫星移动通信中扩频S—ALOHA协议吞吐性能分析

由于扩频具有良好的抗多径干扰的能力，因此，在地面移动无线系统中被认为是一种较好的多址方式。但在低轨卫星移动系统中，其传播条件恶劣，各种因素对系统的吞吐性能的影响各不一样，本文分析了多径衰落，扩频增益，同步捕获等因素对吞吐性能的影响，得出了解析式，计算了数值曲线并进行了讨论     

基于ALOHA算法的RFID防碰撞技术研究

在RFID系统中,由于多标签引起的冲突一直是影响系统性能的主要问题。ALOHA算法是解决标签碰撞问题最有效的方法之一。当系统中标签数过多时,帧时隙ALOHA算法和动态帧时隙ALOHA算法,都会降低系统效率。因此我们提出一种利用二进制树形分组的时隙ALHOA算法。由于只需要对标签进行简单分组就可以有效的提高ALOHA算法的效率,所以此方法更具有实际意义。     

First Passage Time Analysis in Wireless Sensor Networks for SPR and MPR Systems

In this paper, we study the performance of Slotted ALOHA in an elementary process in wireless sensor networks, in which sensors are activated by rare events and transmit packets to a single sink node within single hop. The time cost of the process can be viewed as a first passage time and we give the expectation of time and energy cost which is dependent on both the size of active nodes and their transmission rate by a first passage time analysis. Meanwhile, given the size of active nodes n, we demonstrated that the optimal transmission rate λ_min(n) by which the first passage time attains its minimum, is nearly . Our result indicates that time cost of the process in which each node transmits packet with transmission rate λ_min(n) increases nearly linearly with n increasing. We present the maximum likelihood estimate (MLE) of the size of active nodes from the viewpoint of sink nodes so that activated nodes can adjust its transmission rate to improve the performance of the process. Energy dissipation and time cost of the procedure in the channel model of Multi Packet Reception (MPR) are considered also. Numerical results indicate that both time cost and energy consumption of the procedure in MPR channel is superior to that in Single Packet Reception (SPR) channel while the transmission rate near or less than the optimal values with which time costs attain their minimum. Otherwise the energy dissipation in MPR channel is more than that in SPR channel although comparison of time cost in the above two channels reveals the superiority of MPR channel.

A fast tag identification anti‐collision algorithm for RFID systems

In this work, we propose a highly efficient binary tree‐based anti‐collision algorithm for radio frequency identification (RFID) tag identification. The proposed binary splitting modified dynamic tree (BS‐MDT) algorithm employs a binary splitting tree to achieve accurate tag estimation and a modified dynamic tree algorithm for rapid tag identification. We mathematically evaluate the performance of the BS‐MDT algorithm in terms of the system efficiency and the time system efficiency based on the ISO/IEC 18000‐6 Type B standard. The derived mathematical model is validated using computer simulations. Numerical results show that the proposed BS‐MDT algorithm can provide the system efficiency of 46% and time system efficiency of 74%, outperforming all other well‐performed algorithms.     

无线Ad Hoc网络中基于活跃节点数预测的时隙ALOHA算法

针对采用时隙ALOHA算法的无线Ad Hoc网络,考虑数据包到达的动态性与数据包传输的随机性,以最大化吞吐量为目标,同时满足数据队列稳定性,构建了关于接纳控制与竞争接入的随机优化问题。由于在时隙ALOHA算法中数据包传输的最优概率取决于无线Ad Hoc网络中数据队列非空的活跃节点数,提出了一种基于活跃节点数预测的时隙ALOHA算法。该算法要求无线Ad Hoc网络中的所有发送节点实时地侦听通信信道的忙闲状态,计算基于信道状态的活跃节点数条件期望,从而动态地预测无线Ad Hoc网络在不同时刻的活跃节点数,达到网络节点依据局部网络状态信息自适应地优化数据包传输概率的目的。仿真结果表明,所提算法能够有效估计无线Ad Hoc网络在每个时隙的活跃节点数,从而显著提升网络吞吐量并且降低数据包的平均排队时延。