中国电信看智能无线电CognitiveRadioNextBigThing

1、cognitive radio: next big thingpresented by: huifang limay. 26, 2008china telecom corporation ltd.2outlinebasic conceptsapplications and marketskey issuesemerging standardschallenges to wide-scale deploymentchina telecom corporation ltd.3background- current usage of radio resourceaccording to scanni

2、ng portionsof the radio spectrum below3ghzsome frequency bands in thespectrum are largely; unoccupiedmost of the timesome other frequency bands areonly partially occupiedremaining frequency bands areheavily usedfcc reportutilization of the assigned spectrumrange from 15% to 85%the licensed bands are

3、 abundantbut poorly utilizedfig.1 measurements of spectrum occupancy below 3ghzchina telecom corporation ltd.4background-improvements of spectrum utilizationshortage of spectrum management in traditional wayspectrum usage is very low in certain licensed bandsthe scarcity of radio resources is becomi

4、ng a crisis hindering thedevelopment of many wireless applicationsspectrum holeband of frequencies assigned to a primary user and is not being utilizedby that user at a particular time and specific geographic locationways to improve spectrum utilizationmaking it possible for a secondary user (who is

5、 not being serviced) toaccess a spectrum hole unoccupied by the primary user at the rightlocation and timecognitive radio is seen as the solution to the currentlow usage of the radio spectrumchina telecom corporation ltd.5definition and function of cognitive radiocognitive radio (cr)a radio that can

6、 change its transmitter parameters based on interactionwith the environment in which it operatesfunction of cr:spectrum sensingdetermine which portions of the spectrum is availabledetect the presence of licensed usersspectrum managementselect the best available channelspectrum sharingcoordinate acce

7、ss to this channel with other usersspectrum mobilityvacate the channel when a licensed user is detectedchina telecom corporation ltd.6spectrum hole access with crfig.2 usage of spectrum hole with crcr enables the useraccess a spectrum hole unoccupied by the licensed userif this band is further used

8、by a licensed usermoves to another spectrum holestays in the same band, altering its transmission power level or modulation schemeto avoid interferencechina telecom corporation ltd.7awarenessadaptabilityintelligencelearningefficiencycharacteristics of crcognitive radiochina telecom corporation ltd.8

9、outlinebasic conceptsapplications and marketskey issuesemerging standardschallenges to wide-scale deploymentchina telecom corporation ltd.9prominent target applicationcore application with initial trial deployments of crwireless broadband access in rural and remote areasperformance comparable to tho

10、se of existing fixed broadband accesstechnologiesfcc selected the tv bands for providing cr service duetolower spectrum of frequencies features is favorable for propagationcharacteristicsmany tv channels are largely unoccupiedmost households and businesses rely on cable and satellite tv servicesunli

11、censed bands lower costs of electronic deviceschina telecom corporation ltd.10other key marketscr can be used in other settingssingle-family residentialmulti-dwelling unitssmall office/home office (soho)small businessesmulti-tenant buildingspublic and private campusestype of services provided by crd

12、atavoiceaudio and video traffic with appropriate quality-of-service (qos)supportchina telecom corporation ltd.11outlinebasic conceptsapplications and marketskey issuesemerging standardschallenges to wide-scale deploymentchina telecom corporation ltd.12physical architecture of cr- transceivermain com

13、ponents: radio front-end and the baseband processing unitcomponent can be reconfigured to adapt to the time-varying rfenvironmentbaseband processing unit is essentially similar to existingtransceiversrf front-end is a novelty of the crfig.3 transceiver of crchina telecom corporation ltd.13physical a

14、rchitecture of cr- rf front-end of transceivernovel characteristicwideband sensing capabilityrf hardware technologieswideband antenna, power amplifier, adaptive filterspectrum sensing enables real-time measurements of spectruminformation from radio environmentfig.4 rf front-end of transceiver14fig.5

15、 basic cognitive cyclebandwidth of the transmissionchina telecom corporation ltd.cognitive capability- cognitive cyclethree cognitive tasks:1. radio-scene analysisestimation of interference temperaturedetection of spectrum holes2. channel identificationestimation of channel-state informationpredicti

16、on of channel capacity3. transmit-power control and dynamicspectrum managementdata ratetransmission modechina telecom corporation ltd.15cognitive capability- cognitive stepsthree main stepsspectrum sensingmonitors the available spectrum bands, captures their information, detects thespectrum holes.sp

17、ectrum analysisestimate the characteristics of the spectrum holes which are detected throughspectrum sensingspectrum decisionappropriate spectrum band is chosen according to the spectrum characteristicsand user requirementsfig.6 classification of spectrum sensing techniqueschina telecom corporation

18、ltd.16reconfigurabilitycapability of adjusting operating parameters for the transmissionoperating frequencymodulationtransmission powercommunication technologycharacteristics of reconfigurabilityparameters can be reconfigured at any time of a transmissionenables cr to adapt easily to the dynamic rad

19、io environmentenables cr to switch to a different spectrum bandchina telecom corporation ltd.17outlinebasic conceptsapplications and marketskey issuesemerging standardschallenges to wide-scale deploymentchina telecom corporation ltd.18standard work overviewsdr(software defined radio) forum chartered

20、 two groups on crcr working groupstandardizing a definition of cridentifying the enabling technologiescr special interest groupidentifying attractive commercial applicationsieee 1900 group with three subgroups1900.1standardize definitions and terminology1900.2standardizing a process for testing and

21、verifying the operation1900.3standardizing approaches for qualifying software modulesieee 802 community is currently developing two standards802.22intending to provide high bandwidth access in rural areas802.11hfocusing on dynamic frequency selection in wlanchina telecom corporation ltd.19ieee 802.2

22、2 system- topology, entities and relationshipsspecifies a fixed point-to-multipoint wireless air interface:base station (bs)consumer premise equipments (cpes)bs controls the medium access anddownstream transmits to cpessystem follows a strictmasters/slave relationshipbs controls rf characteristics o

23、f cpescpe is not allowed to transmit beforereceiving authorization from bsdistributed sensingbs instructs cpes to perform distributedmeasurement activitiesfig.7 802.22 deployment configurationchina telecom corporation ltd.20ieee 802.22 system- service coverage and capacityservice coveragelarger cove

24、rage range, up to 100 kmhigher powerfavorable propagation characteristicsof tv frequency bandsservice capacitybroad bandoperation frequency 54-862 mhzextended range to 41-910 mhzaccommodate various tv channelbandwidths of 6, 7, 8 mhz0.5 bit/(sec/hz) up to 5 bit/(sec/hz)fig.8 802.22 compared to other

25、 standardschina telecom corporation ltd.21ieee 802.11h- wlan with cognitive functioncognitive tasksobservationestimate channel characteristics such as path loss and link marginorientationdetermine if it is operating in the presence of a radar installation, in abad channel, in band with satellites, o

26、r in the presence of other wlansdecisiondecide to change frequency (dynamic frequency selection), adjust thetransmit power (transmit power control), or in the case of encounteringactionbe able to implement decisionschina telecom corporation ltd.22outlinebasic conceptsapplications and marketskey issu

27、esemerging standardschallenges to wide-scale deploymentchina telecom corporation ltd.23spectrum sensing challengesspectrum sensing enables cr to be aware of changes inits surrounding by detecting spectrum holeschallenges for development of spectrum sensinginterference measurementno practical way to

28、measure the interference at nearby primaryreceiversspectrum sensing in multi-user networksmulti-user environment makes it more difficult to sense theprimary users and to estimate the actual interferencedetection capabilitydesign complexity increases by using of a large number ofcarriers in order to reduce overall detection timechina telecom corporation ltd.24spectrum decision challengesspectrum decision choose appropriate spectrum bandaccording to the spectrum characteristics and userrequirementschallenges for development of spect