| 1. IntroductionRFID(Radio Frequency Identification), namely the radio frequency identifies a techniquen, is a kind of make use of a wireless radio frequency method at read machine and label of the technique that carries on a non- contact's double to deliver to the data to identify by attaining a target to exchange a purpose with data.It is to make use of a radio frequency method to carry on a non- contact's double toward the correspondence and exchange a data to attain to identify a purpose thus.The RFID technique has accuracy , the orientation environment have strong ability and operate fast, service life long, read distance big, the label data can encrypt, saving the data has great capacity etc. many advantages.The radio frequency (RF) identifies a skill development abroad of very quick, RFID the product category is a lot of, such as Texas famous factory house in the worlds, such as appearance, Motoro1 an and Phillips...etc.s all produce a RFID product, and their products Be each to have a characteristics, from become series.Radio frequency 'sF identifying a technique is extensively been applied to industry to automate, business automation, transportation control management etc. numerous realms:The transportations, such as car and train...etc. supervises and controls;The superhighway automatically charges system;The parking lot manages system;The product manages;The flowing water line production automates;The safe discrepancy checks;The warehouse manages;The animal manages;The vehicle guards against theft etc..There is the car number of Chinese railroad in the local RFID successful profession application automatically identifying system.Its radiating a function has already involved the railroad red and outside stalk probes into the hot stalk fixed position, orbit Heng of system and super etc. for being partial to carry examination system.BE planning the applied item of expansion to there is still an electronics ID card, electronics license plate and railroad going to wrap auto track to manage etc., particularly in 2010 will soon World Exposition in Shanghai for convening in Shanghai, its admission ticket all adopts RFID electronics admission ticket.Radio frequency 'sF identifying a technique is becoming a new economic growth to order and spread to open in the global scope, the research development radio frequency identifies a technique to have huge economic efficiency and social meaning.Although the radio frequency identifies a technique to have many advantagest and all have in a lot of realms good of applied foreground, and F through gradually in some realms start extensive application, however still exist many factor check and supervisions RFID technique of expand completely, widespreadly applied and quickly develop.For example RFID the unifying of standard turn complete sex problem etc. that the processing ability problem, safety problem and data of the problem, cost problem and data delivers.Among them, the RFID data delivers of the complete sex problem is check and supervision RFID development of one of the important factors, directly relate to the whole system function of good and bad degree.The influence data delivers integrity to mainly have 2 and on the other hand comes from outside interference and then come from RFID on the other hand system.The RFID interference results in to°from the following reason of:RFID the system work the scope memory is in several reading machines, and their function scopes appear overlap;Or the function scope memory of reading machine is in several labels, and they return to a data to the reading machine in the meantime.The former is called reading machine collision, the latter is called label collision, is also many targets to identify a problem.Because reading machine of the function is much stronger than the label;So, opposite but talk, the collision problem of label is more more difficult than solution. 2. Research ContentThis text mainly is surround RFID the system defend to collide calculate way but launch of research.Pass introduction RFID system structure and the foundation of workflow up, particularly discussed that the RFID key technique-label defends collision calculate way and says towards in common usely keeping conflict project from carrying on all, and analysis more existing two major typeses defend collision calculate way.Analyzed ALOHA further the calculate way of the calculate way and its development, is having been already had of the foundation of random calculate way up take into to improve, put forward a kind of calculate way of improvement, and imitate to really take into to verify through MATLAB.The concrete research contents is included as follows what time:(1)Introduce RFID first constituting of system and each constitute part of functions;Then work from RFID of the affairs model, data deliver principle and data to deliver of make a few aspects, such as way and coding...etc., analyzed RFID the basic work principle of the system;Finally introduced RFID the data of the system complete sex problem, from medium derivation RFID the anti- collision within system and many roads access a problem, and point out to be compared to many usual roads an access problem, RFID many road access problems of the system have it the special.(2)According to RFID the system defend the function evaluation of conflict calculate way standard, defend conflict calculate way to existing two major typeses, namely indetermination calculate way and assurance the calculate way carried on overview and analysis.This text mainly studies last is an indetermination calculate way, indetermination calculate way mainly is take ALOHA calculate way as a lord, but ALOHA the calculate way include again the calculate way of Xi ALOHA, pure ALOHA calculate way and Xi ALOHA calculate way etc..This text with main research ALOHA calculate way, but defend collision to still have 1 kind in the calculate way to RFID is certain sex calculate way, this calculate way we should also understand.The so-called assurance calculate way points of is read machine choice's correspondence according to label sequence number of only one to choose of, is mainly a binary system to search calculate way in the defending of assurance conflict calculate way, the binary system searches calculate way to mainly include binary system to search the calculate way(BS), dynamic state binary system searches a method(DBS) and has never needed a defending of memory collision agreement(QT), press a binary system number calculate way(BBT).(3)This text research of mainly is ALOHA to defend collision calculate way.The ALOHA calculate way of former usage has one the very obvious weakness is their systems to swallow to vomit a rate widespreadly lower, particularly be the label number increases of time the system function will sharply descend.Therefore the calculate way of Xi ALOHA for this text to put forward the dynamic state of a kind of improvement, the dynamic state of this kind of improvement the Xi calculate way is hasing been already had of ALOHA calculate way up formative.(4)The basic thought of this improvement calculate way is:Read and write a machine to grow to send out claim signal with a certain, can count the label that can identify the label book that need to be identified and grow to come to suppose.Certainly the label supposed count uncertain accurate, so need us to adjust long, make thus label number suppose accurate.The adjustment long method is:Swallow to vomit to lead can complete of the biggest value's wanting be bigger than be not identified of the label several, Be long to reduce;Whereas, if swallow and vomit and lead be smaller than the biggest value that can complete be not identified of the label several, make being long to increase.If doing not identify a label amount is too many and far and far outran the biggest value that the system allows, so can be divided into the label some, carry on again to read.Each read period inside, read machines to all adopt the above-mentioned method to estimate to read to be not been easy to identify of label number, make the system good exaltation swallowed to vomit a rate thus.(5)Carried on calculate way to imitate with MATLAB true get conclusion.Pass to relatively imitate really behind get of the sketch can see and fix system in the middle of the calculate way of Xi ALOHA swallows to vomit its label for rate to attain biggest counts to 250 or so, count along with the label after of the increment system swallow to vomit rate and obviously lower.But pass observation diagram and can discover, in the dynamic state in the calculate way of Xi ALOHA, be label number in 250-300, the system swallows to vomit the speed of leading the growth be not soon, but more slow-moving, after along with label number of the swallowing of increment system vomit a rate and gradually incline to a stability.But pass an observation to imitate really can obviously see as a result, in the improved ALOHA calculate way, be label count low at 100, its curve obvious of in the growth, what this curve representative is a system to swallow to vomit a rate, the system swallows to vomit a rate and tends towards a stability after and swallow to vomit to lead about 0.35.(6)For knowing well the advantage of improving the calculate way more, need to be further to compare this a few calculate ways, for the sake of good compare this a few calculate ways, we counted label to increase 1100 of.Can see very easily from the figure 5.3, improve of dynamic state the calculate way of Xi ALOHA have obvious advantage and be a label amount is bigger than to approach 600, improve swallowing of calculate way to vomit rate still in 35%-40% work, and can also see from the diagram, fix of the calculate way of Xi ALOHA its swallow to vomit rate very ignore think, ALOHA of opposite improvement but talk, can say its function is very unsteady.(7)Can see from imitating a true result, along with the continuously increasing of the label amount, improve of ALOHA reading of calculate way label, swallowing to vomit a rate on the contrary will raise, and time used can't increase on the contrary will lower.So say, improve of the calculate way of Xi ALOHA good problem for solving data collision, make it is in the label amount very big develop oneself advantage-since saving time is again labor-saving.3.Conclusion(1)The dynamic state of improvement the calculate way of Xi ALOHA want to surpass a fixed ALOHA of the Xi calculate way.When the calculate way of Xi ALOHA is very big in the label amount while imitating to really show an improved as a result, swallowing to vomit a rate can raise 100%.(2)This text passes to RFID in the technique defend the research of colliding the calculate way, improvement and finally imitate reality with MATLAB now, make oneself get an exaltation in the abilities, such as calculate way analysis and system design...etc., kept the research of conflict calculate way from offering humble effort in the technique realm for RFID. |
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