CN100471093C - Chain circuit building method in cognitive radio field - Google Patents
Chain circuit building method in cognitive radio field Download PDFInfo
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- CN100471093C CN100471093C CNB2006100207036A CN200610020703A CN100471093C CN 100471093 C CN100471093 C CN 100471093C CN B2006100207036 A CNB2006100207036 A CN B2006100207036A CN 200610020703 A CN200610020703 A CN 200610020703A CN 100471093 C CN100471093 C CN 100471093C
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Abstract
The present invention refers to a cognitive wireless scene link establishment method, belonging to wireless communication technology field. It contains initial link verifying and frequency spectrum detecting result exchange two steps, wherein in initial link verifying, MS receiving BS transmitted accessing code CAC and demodulating, comparing obtained data with MS accessing code to establish initial link; in frequency spectrum detecting result exchange, MS and BS through frequency spectrum detecting exchange and continuously taking intersection to reduce difference among transmitting/receiving frequency spectrum hood, finally establishing steady link frequency spectrum. Two steps judge link quality through configuring certain threshold value or frequency spectrum detecting exchange times. Said invention Said invention can establish steady communication link in CR scene through frequency spectrum detecting between BS and MS, and matched with relevant link quality evaluate means.
Description
Technical field
Link establishing method in a kind of cognitive radio scene, belong to wireless communication technology field, (content sees S.Haykin for details for Cognitive Radio, CR to be particularly related to cognition wireless, " Cognitive Radio:Brain-Empowered WirelessCommunications; " IEEE JSAC, Feb.2005, vol.23, no2, pp.201-220) technology.
Background technology
The CR technology has become one of a kind of the most attractive technology that improves the frequency spectrum service efficiency, but before the CR technology is extensive use of, needs to solve some technical barriers.For example,, when the frequency spectrum detecting result of sending and receiving end is inconsistent, need a kind of reliable link establishing method, exchange initial control information, comprise frequency spectrum detecting result and frequency spectrum resource distribution instruction in physical layer.Traditional method, (Global PositionSystem GPS) may address this problem on some degree such as the global positioning system of Dedicated Control Channel, local data base and embedding.But these methods can cause the complexity of equipment and the raising of cost, and lack the flexibility of the wireless frequency spectrum environment that adapts to dynamic change.
At this problem, some preliminary results of study have been arranged.Part Study person has proposed a kind of boosting agreement mechanism of signaling in return, selected a kind of simultaneously based on OFDM (Orthogonal Frequency DivisionMultiplexing, OFDM) (content sees for details allocation vector launch scenario as the mechanism of command transmitting, T.Weiss, J.Hillenbrand, A.Krohn, F.K.Jondral, " Efficient Signaling of Spectral Resources in SpectrumPooling Systems; " Proc.of the 10th Symposium on Communications and Vehicular TechnologySCVT 2003, Eindhoven, Netherlands, 2003).But, this article does not provide the method for building up of initial link circuit in the CR scene, and compare with spread spectrum transmission mechanism, when the sending and receiving end frequency spectrum detecting result is inconsistent, can cause serious disturbance more authorized user (Incumbent Users) based on the signalling exchange of OFDM.Other researcher distributes special-purpose logic channel for signaling control channel, and (Ultra-Wide Band, UWB) (content sees for details technology, D. as a kind of signaling transmission mechanism with ultra broadband
, S.M.Mishra, D.Willkomm, R.Brodersen, A.Wolisz, " A CognitiveRadio Approach for Usage of Virtual Unlicensed Spectrum; " 14th IST Mobile and WirelessCommunications Summit, June 2005).In order to solve the usable spectrum that constantly changes in the CR scene, there are some researchers to propose a kind of link maintenance mechanism, but, they do not set forth concrete technology, and (content sees for details, D.Willkomm, J.Gross, and A.Wolisz, " Reliable Link Maintenance in Cognitive RadioSystems; " In Proc.of the IEEE Symposium on New Frontiers in Dynamic Spectrum AccessNetworks (DySPAN 2005), Baltimore (MD), November 2005).
Existing method one (based on the method for boosting agreement and OFDM):
Suppose access point (Access Point, AP) broadcasted pressure frequency spectrum resource allocation vector give all travelling carriages (MobileStation, MS).This method only considers that the situation that new authorized user inserts and original authorized user withdraws from is arranged.
Phase I: collect the testing result stage.
The first step: each travelling carriage is compared the allocation vector of broadcasting after new detected result and the last sense cycle after finishing input.If have in the new authorized user access network, the travelling carriage transmitting power with maximum on the subcarrier that the new user of access inserts that detects new authorized user access is so launched the complex value symbol, such as 1+j1, does not transmit on other subcarrier.
Second step: amplified because the signal of the new authorized user that inserts is detected the travelling carriage of its signal, access point apparatus detects the frequency spectrum that the authorized user of new access takies easily.
The 3rd step: between old subband that has distributed and the subband of free time, do mapping one by one, travelling carriage transmits with maximum transmission power on the idle subband of correspondence allocated subbands, does not transmit on the idle subband of the subband correspondence of the authorized user correspondence that exits network.
The 4th step: access point is known old subband that has distributed and the mapping relations one by one between the idle subband in advance, so it can detect withdrawing from of authorized user.
Second stage: broadcast allocation vector.
The first step: access point apparatus is divided into plurality of sections with allocation vector, and (CyclicRedundancy Checksum CRC) is combined into separately transmission of bag to each section behind the coding with cyclic redundancy check (CRC).Each wraps in and periodically repeats transmission (repeating at least 3 times) on the idle OFDM subcarrier.
Second step: travelling carriage receives the bag of access point broadcasting on the OFDM of free time subcarrier, obtain new spectrum allocation may vector.
The shortcoming of method one:
1, based on the signaling transmission mechanism of OFDM, frequency spectrum detecting result is inconsistent in the sending and receiving end, particularly when having the new authorized user that uses a large amount of subbands to insert, can cause unnecessary interference to authorized user.
2, only consider link maintenance mechanism between access point and the travelling carriage, do not considered the mechanism when travelling carriage initially inserts.
Existing method two (the link maintenance mechanism in a kind of CR system.Mechanism is at D.Willkomm, J.Gross, andA.Wolisz, " Reliable Link Maintenance in Cognitive Radio Systems; " In Proc.of the IEEESymposium on New Frontiers in Dynamic Spectrum Access Networks (DySPAN 2005), Baltimore (MD) mentions among the November 2005, but the author does not provide detailed, concrete implementation method):
Method two adopts CORVUS, and (Cognitive Radio for usage of Virtual Unlicensed Spectrum, content sees R.W.Broderson for details, A.Wolisz, D.
, S.M.Mishra, and D.Willkomm, " CORVUS:Acognitive radio approach for usage of virtual unlicensed spectrum, " White Paper, 2004 and D.
, S.M.Mishra, D.Willkomm, R.W.Broderson, and A.Wolisz, " A cognitive radioapproach for usage of virtual unlicensed spectrum, " in 14
ThIST Mobile Wireless CommunicationsSummit 2005, Dresden, Germany, June 2005) system framework.Wherein, UWB be used as the general controls channel (Universal Control Channel, UCC) and group control channel (Group Control Channel, launch scenario GCC).
The first step: transmitter and receiver detects frequency spectrum, determines which CR user's subchannel to abandon.
Second step: and then on the group control channel, send control information, show which subchannel is authorized to the user and has disturbed.
The 3rd step: if there is subchannel disturbed, in order to keep CR user's link data rates, CR user obtains new subchannel by GCC.
The shortcoming of method two:
1,, can be subjected to the restriction of transmitting range based on the coverage of the GCC of UWB because the power that transmits is very little;
2, need reserve special control channel by coordinating, influence the flexibility of system, cause system complexity to increase with authorized user.
Summary of the invention
In the cognitive radio scene, because the difference of link transmit-receive two ends electromagnetic environment of living in, can cause the available radio spectrum of sending and receiving end and not quite identical, thereby cause the phase mutual interference between the user and the decline of link-quality.In this case, in order to communicate by letter reliably and to avoid authorized user is caused serious disturbance, transmitting-receiving two-end need be set up communication link by exchange both sides available spectrum information.In order to solve the problems of the technologies described above, the present invention proposes the link establishing method in a kind of cognitive radio scene.
Technical solution of the present invention is:
Link establishing method in a kind of cognitive radio scene, precondition is in the hypothesis CR network, a BS (base station, Base Station) is in charge of some MS (travelling carriages, Mobile Station), the frequency spectrum detecting result of BS and MS can reflect the usable spectrum distribution situation of BS and MS end truly, reliably, each BS has unique access code (such as the physical address of BS equipment or the pseudo random sequence of out of phase skew), the MS that any hope inserts the network that this BS manages knows the access code of this BS in advance, it is characterized in that, comprise the steps:
Step 1: initial link circuit checking
Before the link establishment between BS and the MS, BS is by its emission spectrum cover (A
K_BS_Tx), with its its access code of maximum possible transmitting power periodic broadcasting C
ACThe maximum transmission power of BS by it interference temperature limit decision (content sees for details, S.Haykin, " Cognitive Radio:Brain-Empowered Wireless Communications, " IEEE JSAC, Feb.2005, vol.23, no2, pp.201-20).Want to be linked into the received spectrum cover (A of the MS of BS by it
K_MS_Rx) receive the access code C of BS emission
AC, data that demodulation obtains and the access code of MS are compared and are assessed the initial link circuit quality.If link-quality is more than or equal to threshold T
1(threshold T
1Can be signal to noise ratio, its span depends on concrete application scenarios, comprise communication channel condition, the launch scenario that is adopted and type of service etc.), think that so link can be used and MS sends access code to BS, carry out the frequency spectrum detecting result exchange step of step 2 between MS and the BS; If link-quality is less than threshold T
1, MS abandons inserting so, waits for the next broadcast cycle of BS.
Step 2: frequency spectrum detecting result exchange
After the described initial link circuit checking of step 1, set up an available link between MS and the BS, but the transceiving spectral cover (Mask) between MS and the BS is still variant.Exchange the difference that reduces between its transceiving spectral cover (Mask) by frequency spectrum detecting result between MS and the BS, as shown in Figure 3, specifically comprise the steps:
The first step: MS is by its emission spectrum cover (A
K_MS_Tx), launch its frequency spectrum detecting result A
K_MS
Second step: the BS is by its received spectrum cover (A
K_BS_Rx) receive the signal of MS emission, and estimate the usable spectrum resource of MS end by the signal that receives; The result that the BS estimation obtains and the common factor of its local testing result are as the new emission spectrum cover (A of BS
K_BS_Tx) and received spectrum cover (A
K_BS_Rx); The frequency spectrum detecting result A of BS reality
K_BSBy new emission spectrum cover (A
K_BS_Tx) launch.
The 3rd step: MS is by its received spectrum cover (A
K_MS_Rx) receive the signal of BS emission, and estimate the usable spectrum resource of BS end by the signal that receives; The result that the MS estimation obtains and the common factor of its local testing result are as the new emission spectrum cover (A of MS
K_MS_Tx) and received spectrum cover (A
K_MS_Rx); The frequency spectrum detecting result A of MS reality
K_MSBy new emission spectrum cover (A
K_MS_Tx) launch.
The 4th step: after repeatedly exchanging between MS and the BS, if the transceiving spectral cover (Mask) of BS is constantly changing, constantly exchange frequency spectrum detecting result so between MS and the BS, reach the number of times M (M depends on professional requirement to time delay in the different application scene) that maximum can allow up to the exchange number of times.After the exchange number of times surpasses M, if the transceiving spectral cover (Mask) of BS is compared difference greater than threshold T with preceding once exchange
3, abandon this link so; If comparing difference with preceding once exchange, the transceiving spectral cover (Mask) of BS is less than or equal to threshold T
3(threshold T
3Can be the mistake number, its span depends on concrete application scenarios, comprises communication channel condition, the launch scenario that is adopted and type of service etc.), stop exchange so, finish link establishment, carry out transfer of data.
In the such scheme, in described step 1,, need this moment competition to insert between a plurality of MS if there are a plurality of MS to initiate access request simultaneously to same BS.In order to address this problem, the present invention adopts and a kind ofly is similar to carrier sense/collision and avoids (Carrier Sensing Multiple Access/Collision Avoidance, CSMA/CA, content sees K.Pahlavan and P.Krishnamurthy for details, Principles of Wireless Network:A Unified Approach, Prentice Hall, Inc., 2003) algorithm, concrete steps are as follows:
The first step: receive after the access code, wish that the MS that inserts estimates the quality of link by the BS access code that receives.The disabled MS of link withdraws from competition.
Second step: remaining their random counters separately of MS operation, beginning random back.The overdue MS of first counter returns the access code of this BS to BS.Other MS that detects the access code emission stops their counter, waits for the next broadcast cycle of BS.
The 3rd step: if link-quality can be accepted, BS returns an ack signal and gives MS so, carries out the operation of abovementioned steps below one then between MS and the BS, until setting up link; Otherwise, will not have link establishment.
In the technique scheme,, can between frequency spectrum detecting result exchange step and data transmission step, increase the link verification step before the transfer of data if the working environment of system is good inadequately.Concrete steps are: BS is by its emission spectrum cover (A
K_BS_Tx), with its access code of maximum possible transmitting power periodic broadcasting C
ACMS is by its received spectrum cover (A
K_MS_Rx) reception access code signal C
AC, data that demodulation obtains and the access code of MS are compared, and estimate link-quality; If link-quality is more than or equal to threshold T
2(T
2T
1, threshold T
2Can be signal to noise ratio, its span depends on concrete application scenarios, comprise communication channel condition, the launch scenario that is adopted and type of service etc.), think that so link can use, and enter data transfer phase, if link is unavailable, MS abandons inserting so, waits for the next broadcast cycle of BS.
In whole link use, regularly repeating step one and step 2 are to safeguard link.
Beneficial effect of the present invention:
A) the present invention exchanges by the frequency spectrum detection between BS and the MS and is equipped with corresponding link quality evaluation means, can set up communication link stable in the CR scene;
B) complete initial access, multi-user's access and link maintenance method have been proposed;
C) do not need Dedicated Control Channel, adapt to various application scenarioss, the flexibility height.
Description of drawings
Fig. 1 is the link establishing method schematic flow sheet in a kind of cognitive radio scene provided by the invention.
Fig. 2 is the link establishing method schematic flow sheet under the imperfect situation of system works environment provided by the invention.
(a) is link verification operating process schematic diagram among Fig. 3, (b) is frequency spectrum detecting result exchange schematic flow sheet.
Fig. 4 is the sequential schematic diagram that multi-user (MS) competition inserts.
Claims (4)
1, the link establishing method in a kind of cognitive radio scene, precondition is in the hypothesis CR network, a BS is in charge of some MS, the frequency spectrum detecting result of BS and MS can reflect the usable spectrum distribution situation of BS and MS end truly, reliably, each BS has unique access code, the MS that any hope inserts the network that this BS manages knows the access code of this BS in advance, it is characterized in that, comprises the steps:
Step 1: initial link circuit checking
Before the link establishment between BS and the MS, BS is by its emission spectrum cover A
K_BS_Tx, with its its access code of maximum possible transmitting power periodic broadcasting C
ACWant to be linked into the received spectrum cover A of the MS of BS by it
K_MS_RxReceive the access code C of BS emission
AC, data that demodulation obtains and the access code of MS are compared and are assessed the initial link circuit quality; If link-quality is more than or equal to threshold T
1, think that so link can be used and MS sends access code to BS, carry out the frequency spectrum detecting result exchange step of step 2 between MS and the BS; If link-quality is less than threshold T
1, MS abandons inserting so, waits for the next broadcast cycle of BS;
Step 2: frequency spectrum detecting result exchange
After the described initial link circuit checking of step 1, set up an available link between MS and the BS, but the transceiving spectral cover Mask between MS and the BS is still variant; Exchange the difference that reduces between its transceiving spectral cover Mask by frequency spectrum detecting result between MS and the BS, specifically comprise the steps:
The first step: MS is by its emission spectrum cover A
K_MS_Tx, launch its frequency spectrum detecting result A
K_Ms
Second step: the BS is by its received spectrum cover A
K_BS_RxReceive the signal of MS emission, and estimate the usable spectrum resource of MS end by the signal that receives; The result that the BS estimation obtains and the common factor of its local testing result are as the new emission spectrum cover A of BS
K_BS_TxWith received spectrum cover A
K_BS_RxThe frequency spectrum detecting result A of BS reality
K_BSBy new emission spectrum cover A
K_Bs_TxLaunch;
The 3rd step: MS is by its received spectrum cover A
K_MS_RxReceive the signal of BS emission, and estimate the usable spectrum resource of BS end by the signal that receives; The result that the MS estimation obtains and the common factor of its local testing result are as the new emission spectrum cover A of MS
K_Ms_TxWith received spectrum cover A
K_MS_RxThe frequency spectrum detecting result A of MS reality
K_MsBy new emission spectrum cover A
K_Ms_TxLaunch;
The 4th step: after repeatedly exchanging between MS and the BS, if the transceiving spectral cover Mask of BS is constantly changing, constantly exchange frequency spectrum detecting result so between MS and the BS, reach the number of times M that maximum can allow up to the exchange number of times, M depends on professional requirement to time delay in the different application scene; After the exchange number of times surpasses M, if the emission of BS is compared difference greater than threshold T with Mask as a result with preceding once exchange
3, abandon this link so; If comparing difference with preceding once exchange, the transceiving spectral cover Mask of BS is less than or equal to threshold T
3, stop exchange so, finish link establishment, carry out transfer of data.
2, the link establishing method in a kind of cognitive radio scene according to claim 1, it is characterized in that, in the described step 1, if there are a plurality of MS to initiate access request simultaneously to same BS, the access that needs to be at war with between a plurality of MS this moment, concrete steps are as follows:
The first step: receive after the access code, the MS that wish to insert estimates the quality of link by the BS access code that receives, and the disabled MS of link withdraws from competition;
Second step: remaining their random counters separately of MS operation, beginning random back; The access code that the overdue MS of first counter returns this BS is to BS, and other MS that detects the access code emission stops their counter, waits for the next broadcast cycle of BS;
The 3rd step: if link-quality can be accepted, BS returns an ack signal and gives MS so, carries out the following operation of step 1 then between MS and the BS, until setting up link; Otherwise, will not have link establishment.
3, the link establishing method in a kind of cognitive radio scene according to claim 1, it is characterized in that, if the working environment of system is good inadequately, then increase the link verification step before the transfer of data between frequency spectrum detecting result exchange step and data transmission step, concrete steps are: BS is by its emission spectrum cover A
K_BS_Tx, with its access code of maximum possible transmitting power periodic broadcasting C
ACMS is by its received spectrum cover A
K_MS_RxReceive access code signal C
AC, data that demodulation obtains and the access code of MS are compared, and estimate link-quality; If link-quality is more than or equal to threshold T
2, T
2T
1, threshold T
2Span depend on concrete application scenarios, comprise communication channel condition, the launch scenario that is adopted and type of service, think that so link can use, and enter transfer of data, if link is unavailable, MS abandons inserting so, waits for the next broadcast cycle of BS.
4, the link establishing method in a kind of cognitive radio scene according to claim 1 is characterized in that, in whole link use, regularly repeating step one and step 2 are to safeguard link.
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