wirelesscommunicationlecture0102.ppt

*,*,*,TechniTemplate,Test,Test,Test,Test,State Key Lab.On ISN,Xidian University,Announcements,Remember to turn off your cell phone during the class or turn it into silence,Homework for chapter 1 available and it will be due next week,Review Chapter 1 after class,Read Chapter 2 after class,2026/4/13 周一,Lecture Outline,Review of last lecture,Technical Challenges,Current Wireless Systems,Emerging Wireless Systems,Spectrum Regulation,Standards,2026/4/13 周一,Review of Last Lecture,Course Basics,Policies on,attendance,lectures,，,HWs,，,projects,exams,Course Syllabus,The History of Wireless Communications,Wireless Vision,2026/4/13 周一,Wireless Market in USA and the world,Figure 1.1,；,Growth of Wireless Communications Market,2026/4/13 周一,2026/4/13 周一,2026/4/13 周一,2006,年,4,月超过,4.16,亿,2007,年,4,月超过,4.87,亿,2009,年,4,月,24,日超,6.7,亿,2026/4/13 周一,旧闻？,2026/4/13 周一,Design Challenges,Wireless channels are a difficult and capacity-limited broadcast communications medium,Traffic patterns,user locations,and network conditions are constantly changing,Applications are heterogeneous with hard constraints that must be met by the network,Energy and delay constraints change design principles across all layers of the protocol stack,2026/4/13 周一,Multimedia Requirements,Voice,Video,Data,Delay,Packet Loss,BER,Data Rate,Traffic,100,ms,-,100,ms,1%,0,1%,10,-3,10,-6,10,-6,8-32,Kbps,1-100,Mbps,1-20,Mbps,Continuous,Bursty,Continuous,One-size-fits-all protocols and design do not work well,Wired networks use this approach,with poor results,2026/4/13 周一,Wireless Performance Gap,WIDE AREA CIRCUIT SWITCHING,User,Bit-Rate,(,kbps),14.4,digital,cellular,28.8,modem,ISDN,ATM,9.6,modem,2.4,modem,2.4,cellular,32,kbps,PCS,9.6,cellular,wired-wireless,bit-rate gap,1970,2000,1990,1980,YEAR,LOCAL AREA PACKET SWITCHING,User,Bit-Rate,(,kbps),Ethernet,FDDI,ATM,100,M,Ethernet,Polling,Packet,Radio,1,st,gen,WLAN,2,nd,gen,WLAN,wired-wireless,bit-rate gap,1970,2000,1990,1980,.01,.1,1,10,100,1000,10,000,100,000,YEAR,.01,.1,1,10,100,1000,10,000,100,000,2026/4/13 周一,Evolution of Current Systems,Wireless systems today,2G Cellular:30-70 Kbps.,WLANs,:10 Mbps.,On going system:3G Cellular in Commercial testing,Next Generation,3G Cellular:300 Kbps.,WLANs,:70 Mbps.,Technology Enhancements,Hardware:,Better batteries.Better circuits/processors.,Link:,Antennas,modulation,coding,adaptivity,DSP,BW.,Network:,Dynamic resource allocation.Mobility support.,Application:,Soft and adaptive,QoS,.,“,Current Systems on Steroids”,2026/4/13 周一,Future Generations,Rate,Mobility,2,G,3,G,4,G,802.11,b WLAN,2,G Cellular,Other Tradeoffs:,Rate vs.Coverage,Rate vs.Delay,Rate vs.Cost,Rate vs.Energy,Li,Shihes,report,Fundamental Design Breakthroughs Needed,2026/4/13 周一,Crosslayer,Design,Hardware,Link,Access,Network,Application,Delay Constraints,Rate Constraints,Energy Constraints,Adapt across design layers,Reduce uncertainty through scheduling,Provide robustness via diversity,2026/4/13 周一,Current Wireless Systems,Cellular Systems,Wireless LANs,Satellite Systems,Paging Systems,Bluetooth,UWB,RFID,WiMax,Zibee,2026/4/13 周一,Cellular Systems:,Reuse channels to maximize capacity,Geographic region divided into cells,Frequencies/timeslots/codes reused at spatially-separated locations.,Co-channel interference between same color cells.,Base stations/,MTSOs,coordinate handoff and control functions,Shrinking cell size increases capacity,as well as networking burden,BASE,STATION,MTSO,2026/4/13 周一,Cellular Phone Networks,BS,BS,MTSO,PSTN,MTSO,BS,Xian,Beijing,Internet,2026/4/13 周一,3,G Cellular Design:,Voice and Data,Data is,bursty,whereas voice is continuous,Typically require different access and routing strategies,3G“widens the data pipe”:,384 Kbps.,Standard based on wideband CDMA,Packet-based switching for both voice and data,3G cellular struggling in Europe and Asia,Evolution of existing systems(2.5G,2.6798G):,GSM+EDGE,(Enhanced Data Services for GSM Evolution),IS-95(CDMA)+HDR,(high data rate),100 Kbps may be enough?,What is beyond 3G?,The trillion dollar question,2026/4/13 周一,Wireless Local Area Networks(,WLANs,),WLANs,connect“local”computers(100m range),Breaks data into packets,Channel access is shared(random access),Backbone Internet provides best-effort service,Poor performance in some apps(e.g.video),01011011,Internet,Access,Point,0101,1011,2026/4/13 周一,Wireless LAN Standards,802.11,b,(Current Generation),Standard for 2.4GHz ISM band(80 MHz),Frequency hopped spread spectrum,1.6-10 Mbps,500 ft range,802.11a,(Emerging Generation),Standard for 5GHz NII band(300 MHz),OFDM with time division,20-70 Mbps,variable range,Similar to,HiperLAN,in Europe,802.11g,(New Standard),Standard in 2.4 GHz and 5 GHz bands,OFDM,Speeds up to 54 Mbps,In 200?,all WLAN,cards will,have all 3,standards,2026/4/13 周一,Satellite Systems,Cover very large areas,Different orbit heights,GEOs,(39000 Km)versus,LEOs,(2000 Km),Optimized for one-way transmission,Radio(XM,DAB)and movie(,SatTV,)broadcasting,Most two-way systems struggling or bankrupt,Expensive alternative to terrestrial system,A few ambitious systems on the horizon,2026/4/13 周一,Stratosphere Communications,High Attitude Platform Station,50600,的直径,图,1 HAPS,系统示意图,图,2,日本北海道大树试验基地的,HAPS,升空试验,2026/4/13 周一,Deep Space Communication,Very long Distance(e.g.From the earth to the moon),2026/4/13 周一,Paging Systems,Broad coverage for short messaging,Message broadcast from all base stations,Simple terminals,Optimized for 1-way transmission,Answer-back hard,Overtaken by cellular,Still used in USA,2026/4/13 周一,8,C32810.61-Cimini-7/98,Bluetooth,Cable replacement RF technology(low cost),Short range(10m,extendable to 100m),2.4 GHz band(crowded),1 Data(700 Kbps)and 3 voice channels,Widely supported by telecommunications,PC,and consumer electronics companies,Few applications beyond cable replacement,2026/4/13 周一,Emerging Systems,Ad hoc wireless networks,Sensor networks,Distributed control networks,2026/4/13 周一,Ad-Hoc Networks,Peer-to-peer communications.,No backbone infrastructure.,Routing can be,multihop,.,Topology is dynamic.,Fully connected with different link,SINRs,2026/4/13 周一,Design Issues,Ad-hoc networks provide a flexible network infrastructure for many emerging applications.,The capacity of such networks is generally unknown.,Transmission,access,and routing strategies for ad-hoc networks are generally ad-hoc.,Crosslayer,design critical and very challenging.,Energy constraints impose interesting design tradeoffs for communication and networking.,2026/4/13 周一,Sensor,Networks,Energy is the driving constraint,Nodes powered by,nonrechargeable,batteries,Data flows to centralized location.,Low per-node rates but up to 100,000 nodes.,Data highly correlated in time and space.,Nodes can cooperate in transmission,reception,compression,and signal processing.,2026/4/13 周一,Energy-Constrained Nodes,Each node can only send a,finite,number of bits.,Transmit energy minimized by maximizing bit time,Circuit energy consumption increases with bit time,Introduces a delay versus energy tradeoff for each bit,Short-range networks must consider transmit,circuit,and processing energy.,Sophisticated techniques not necessarily energy-efficient.,Sleep modes save energy but complicate networking.,Changes,everything,about the network design:,Bit allocation must be optimized across,all,protocols.,Delay vs.throughput vs.node/network lifetime tradeoffs.,Optimization of node cooperation.,2026/4/13 周一,Cordless Phones,Cordless telephones first appeared in the late 1970s,Cordless phones were originally designed to provide a low-cost low-mobility wireless connection to the PSTN,i.e.a short wireless link to replace the cord connecting a telephone base unit and its handset.,The base units of cordless phones connect to the PSTN in the exact same manner as a landline phone,and thus they impose no added complexity on the telephone network.,the second generation of digital cordless phones,2026/4/13 周一,Cordless Phones-,the second generation and more,phone-points or,telepoints,are mounted in places where people congregate,Cordless phones registered with the,telepoint,provider can place calls whenever they are in range of a,telepoint,.Calls cannot be received from the,telepoint,since the network has no routing support for mobile users,These systems also do not handoff calls if a user moves between different,telepoints,A more advanced cordless telephone system that emerged in Japan is the Personal,Handyphone,System(PHS).(Xi an is the first city to set up it in China),(No profit made up to 2005),2026/4/13 周一,Distributed Control over Wireless Links,Packet loss and/or delays impacts controller performance.,Controller design should be robust to network faults.,Joint application and communication network design.,Automated Vehicles,-Cars,-,UAVs,Unmanned Aerial,Vehicles,-Insect flyers,2026/4/13 周一,Joint Design Challenges,There is no methodology to incorporate random delays or packet losses into control system designs.,The best rate/delay tradeoff for a communication system in distributed control cannot be determined.,Current autonomous vehicle platoon controllers are not string stable with,any,communication delay,Can we make distributed control robust to the network?,Yes,by a radical redesign of the controller,and,the network.,2026/4/13 周一,Spectrum Regulation,Spectral Allocation in US controlled by FCC(commercial)or OSM(defense),FCC auctions spectral blocks for set applications.,Some spectrum set aside for universal use,Worldwide spectrum controlled by ITU-R,China:,国家无线电,管理局,Regulation can stunt innovation,cause economic,disasters,and delay system rollout,2026/4/13 周一,Standards,Interacting systems require standardization,Companies want their systems adopted as standard,Alternatively try for de-facto standards,Standards determined by TIA/CTIA in US,IEEE standards often adopted,Worldwide standards determined by ITU-T,In Europe,ETSI is equivalent of IEEE,Standards process fraught with,inefficiencies and conflicts of interest,2026/4/13 周一,Spectrum Allocation,Regulation can stunt innovation,cause economic,disasters,and delay system rollout,2026/4/13 周一,Spectrum Allocation ISM Band,2026/4/13 周一,Main Points,The wireless vision encompasses many exciting systems and applications,Technical challenges transcend across all layers of the system design,Wireless systems today have limited performance and interoperability,Standards and spectral allocation heavily impact the evolution of wireless technology,2026/4/13 周一,Assignments,1.Describe two technical advantages and disadvantages of wireless systems that use,bursty,data transmission rather than continuous data transmission.,2.Describe three disadvantages of using a wireless LAN instead of a wired LAN.For what applications will these disadvantages be outweighed by the benefits of wireless mobility.For what applications will the disadvantages override the advantages.,3.Cellular systems are migrating to smaller cells to increase system capacity.Name at least three design issues which are complicated by this trend.,4.As storage capability increases,we can store larger and larger amounts of data on smaller and smaller storage devices.Indeed,we can envision microscopic computer chips storing,terraflops,of data.Suppose this data is to be,transfered,over some distance.Discuss the pros and cons of putting a large number of these storage devices in a truck and driving them to their destination rather than sending the data,electronically.,5.Cellular systems are migrating to smaller cells to increase system capacity.Name at least three design issues which are complicated by this trend.,6.Find the round-trip delay of data sent between a satellite and the earth for LEO,MEO,and GEO satellites assuming the speed of light is 3 108,m/s,.If the maximum acceptable delay for a voice system is 30 milliseconds,which of these satellite systems would be acceptable for two-way voice communication?,2026/4/13 周一,