【導(dǎo)讀】信道，包的產(chǎn)生，碰撞，業(yè)務(wù)量，吞吐量，平均傳輸時(shí)延等名詞概念。在此基礎(chǔ)上重點(diǎn)掌握學(xué)習(xí)。ALOHA協(xié)議，以及協(xié)議評(píng)價(jià)的性能指標(biāo)以及這些指標(biāo)之間的關(guān)系。最后撰寫(xiě)畢業(yè)設(shè)計(jì)論文（應(yīng)包括方案設(shè)計(jì)、比較與論。證、分析與計(jì)算、相關(guān)設(shè)計(jì)文件以及心得體會(huì)等）。1月10日——3月20日：查閱資料，完成外文翻譯原文和開(kāi)題報(bào)告。3月21日——4月20日：完成系統(tǒng)整體框架設(shè)計(jì)，搭建系統(tǒng)，并提交中期檢查報(bào)告。4月21日——5月20日：完成參數(shù)設(shè)計(jì)并仿真，準(zhǔn)備作品驗(yàn)收。[摘要]本文首先介紹了多址接入?yún)f(xié)議的研究背景及其工作原理，對(duì)目前廣泛研究的ALOHA協(xié)議進(jìn)行了詳細(xì)闡。然后根據(jù)協(xié)議的工作過(guò)程，在Matlab平臺(tái)構(gòu)建仿真模。型，對(duì)ALOHA協(xié)議進(jìn)行仿真,并對(duì)所得數(shù)據(jù)進(jìn)行分析，驗(yàn)證了吞吐量與業(yè)務(wù)量及時(shí)延之間的關(guān)系，為提高協(xié)議性能

　　

【正文】 ions。 especially where tag set is dense. We introduce a novel medium access control (MAC) protocol for Radio Frequency Identification (RFID) systems which exploits the statistical information collected at the reader. The protocol, termed Adaptive Slot Adaptive Frame (ASAF) ALOHA protocol, is motivated to significantly improve the total read time performance of the currently suggested MAC protocols for RFID systems by minimizing the collisions of the order to perform this task, ASAF estimates the dynamic tag population and adapts the frame size and number of slots simultaneously in the subsequent round via a simple policy that maximizes an appropriately defined demonstrated that ASAF is better than the current RFID MAC also considered the case where suddenly if the number of tags increases, the running frame with adapted slots gets flushed away and new frame with increased number of slots gets adapted automatically by the system showing the robustness in this case as well. Keywords :ASAF 。ALOHA 。EPC 。RFID 陜西理工學(xué)院畢業(yè)設(shè)計(jì) 第 19 頁(yè) 共 41 頁(yè) 1 Introduction Radio Frequency Identification (RFID) is the most efficient and reliable way to identify an entity and collect data [1,2]. In a system, tags with unique identities municate with an RFID reader using a single multiple access channel [3,4]. This is essentially considered as a derivative of wireless sensor work. In such a work environment, design of an efficient MAC protocol is of utmost importance. There are various factors leading to the performance degradation and the system is said to be operational only if the tags in the range of reader field are successfully identified in a short amount of time. In recent years, many attempts have been made to tackle the tagcollision problem. The methods suggested for RFID systems can be classified into two categories: (a) variants of ALOHA that rely on randomizing the access times of tags to reduce collisions (probabilistic approach) (b) tree search methods that aim to avoid collisions and identify one tag at a time (deterministic approach). STAC, based on slotted ALOHA, has been proposed in [3,5] for Class1Generation1 RFID systems and binary tree search has been proposed for Class0 Generation1 RFID systems [4,6]. In the binary tree search algorithm, one tag is identified at a time without a collision. In contrast, STAC is more likely to lead to severe tag collisions if the frame size is not properly chosen. In order to avoid this severe performance loss, frame size adaptive MAC protocols for RFID system were proposed in [7–11]. Frame size adaptive MAC protocol in [7] uses a simple estimate for the tag population in each round (frame) in order to adaptively adjust the frame size in the subsequent round based on the minimization of the time required to identify all tags with a given level of assurance. In [8,9], the frame size was found to maximize the expected throughput of framed ALOHA. To find the frame size, the probability distribution of the number of tags transmitted is obtained by adopting the Bayesian approach outlined in [12]. Another frame size adaptive MAC protocol for both passive and active RFID tags was developed in [10]. The more recently proposed Class1 Generation2 also provides the option of a variable frame size [11]. Even though these attempts provide a notable performance improvement over fixed frame size RFID MAC protocols, they may still lead to less than acceptable performance for dense RFID systems. EPC Global Class1 Gen2 Specifications: This specification [11] defines the physical and logical requirements for a passiveback scatter,Interrogatortalksfirst (ITF),RadioFrequency Identification (RFID) system operating in the800–960 MHz frequency range. The system prises Interrogators, also known as Readers,and Tags also known as Labels. An Interrogator transmits information to a Tag by modulating an RF signal in the 860–960MHz frequency range. The Tag receives both information and operating energy from this RF signal. Tags are passive, meaning that they receive all of their operating energy from the Interrogator’s RF waveform. An Interrogator receives information from a Tag by transmitting a continuouswave (CW)RF signal to the Tag。 the Tag responds by modulating the reflection coefficient of its antenna,thereby back scattering an information signal to the Interrogator. The system is ITF, meaning that a tag modulates its antenna reflection coefficient with an information signal only after being directed to do so by an interrogator. Interrogators and Tags are not required to talk simultaneously。 rather, munications are halfduplex, meaning that Interrogators talk and Tags listen, or vice versa. Gen2 is a global UHF airinterface protocol standard,where a reader transmits information about a frame with 22bit Query. It notifies the beginning of the frame and the exponent of the frame size to the tags. At the beginning of every slot, the reader transmits 4bit Query Rep to the tags. Then, the tags generate random number ranging from 0 to (frame size1) and count the number of Query Rep. If the counted number matches the generated random number,the tag responds to the query of the reader. To reduce the slot time, the tag transmits16bit temporary ID, RN16, during its slot time. Thereby, it can save the time for collided and empty slots. If a tag successfully transmits its RN16 without error or collision, the reader sends ACK to the tag to receive desired data including 96 or 256bit Electronic Product Code(EPC) and 16bit CRC. In this paper, we propose an intelligent MAC protocol design for improving the performance of an RFID system that has large number of passive tags. This MAC protocol design is inspired by the application of Human Tracking where the 陜西理工學(xué)院畢業(yè)設(shè)計(jì) 第 20