CN100373981C - Realization method for mixed network structure in cognitive radio - Google Patents

Abstract

The present invention relates to a realization method for mixed network structure in a cognitive radio system, which belongs to the technical field of wireless communication, particularly to a frequency spectrum use method of a cognitive radio system and the realization of a physical transmission medium of the mixed network structure of a cognitive radio system. The present invention comprises the steps: the allowed maximum receiving power of a receiver at the time is calculated according to an interference temperature model; actual transmission power on a transmission terminal is calculated; the set of two kinds of effective frequency spectra is calculated; point to multipoint topology and mesh topology in mixed structure are realized, etc. A graded frequency spectrum sharing method suggested by the present invention realizes the mixed structure which simultaneously supports point to multipoint topology and mesh topology, widens the set of usable frequency spectra, increases the capacity of a system, enlarges the coverage range of housing estates and can provide strong and flexible communication.

Description

A kind of implementation method of mixed network structure in the cognitive radio

Technical field

A kind of implementation method of mixed network structure in the cognitive radio, belong to wireless communication technology field, be particularly related to the frequency spectrum occupation mode of cognitive radio (Cognitive Radio) system, and to the realization of the physical transfer media of cognitive radio mixed network structure.

Background technology

Cognitive radio system is an intelligent radio communication system, and it can perception, the study surrounding environment, adjusts own parameter (as modulation system, communication band etc.) of communicating by letter and adapts to environmental change on every side.Cognitive radio is mainly used to solve the problem in short supply of radio communication intermediate frequency spectrum resource at present.Utilize the intelligent perception of cognitive radio, unauthorized (unlicensed) user can be when authorizing (licensed) user not use the licensed frequency spectrum resource, authorized user is not being caused under the situation of interference, using the frequency spectrum resource of distributing to authorized user originally.The cognitive radio of below mentioning (CR) user as special declaration not, all refers to unauthorized user.

In order to weigh and manage of the interference of undelegated cognitive radio system to authoring system, (the Federal Communications Commission of FCC, FCC) interference temperature model (interference temperaturemodel) has been proposed, as shown in Figure 1.As long as when sharing the frequency band of authorizing, the interference that the CR system introduces is no more than interference temperature limit (interference temperature limit), and the CR system allows the use of this frequency band so.FCC has provided the definition of interference temperature:

$T_I=\frac{P_I}{\mathrm{kB}}---\left(1\right)$

In the formula, T _IBe the interference temperature of receiver radio frequency perception, unit is Kelvin degree (Kelvin degree), P _IBe interference power, B is a bandwidth, and K is Bo Ziman (Boltzmnn) constant, equals 1.38 * 10 ^-23Joule/Kelvin degree.When being tending towards infinitesimal, bandwidth can obtain the function of interference temperature to frequency.In fact to be multiplied by Boltzmann's constant be exactly the interference power spectrum density to interference temperature, and the interference power on certain frequency band m can be obtained by following formula:

$P_{I,m}=\underset{\mathrm{Bm}}{\∫}k{T}_I\left(f\right)\mathrm{df}---\left(2\right)$

In like manner, the interference power restriction can be limit by interference temperature and calculate, the interference power limit P on certain frequency band m _{L, m}Can obtain by following formula:

$P_{L,m}=\underset{\mathrm{Bm}}{\∫}k{T}_L\left(f\right)\mathrm{df}---\left(3\right)$

Other explanations about interference temperature see Federal Communications Commission for details, " Establishment ofinterference temperature metric to quantify and manage interference and to expand availableunlicensed operation in certain fixed mobile and satellite frequency bands; " ET Docket 03-289, Notice ot Inquiry and Proposed Rulemaking, 2003.

Now people are promoting the application of cognitive radio (CR) technology in the centralized control formula network that Da Qu covers, WRAN (the Wireless Regional Area Network) standard of formulating such as IEEE802.22.In the cognitive radio networks of the big regional centralized control formula that covers, adopt the star topology structure of point to multiple spot, unauthorized CR cognition wireless electric terminals (Cognitive Radio Service Access Point, all must and transmit by CR base station (CR-BS) control by communication CR-SAP).There are following shortcomings in this structure: first, because coverage is big, the CR-SAP at coverage cell edge and CR-BS distance are far away, the emitted power level of wanting also requires than higher, this makes its easier interference temperature that surpasses limit, so it is less to can be used for the number of frequency bands of CR-SAP and CR-BS direct communication.Second, because the overlay area is wide, the zone that some and authoring system overlap mutually may appear in the overlay area of CR-BS, when authoring system is communicated by letter, these zones will become the communication blind district of CR system, and because the when and where of the appearance of authoring system can't be predicted by the CR system, the appearance of communication blind district will present randomness and polytropy, thereby make the coverage of CR sub-district become changeable and irregular, the communication continuity in the sub-district may be destroyed.The cognitive radio system of putting now under the structure of multiple spot adopts the mode of sharing a plurality of authorized frequency bands to solve this problem, when a frequency band is authorized to the user when using, switches to the frequency band that other uncommitted users use; And can further adopt directional antenna to improve the space availability ratio and the continuity of keeping cell communication of frequency spectrum.But this can not solve the problem of communication blind district fully.Suppose that the CR system can share two authorized frequency bands (F1 and F2), use these two frequency bands two authoring systems covering as shown in Figure 2, then under the prerequisite that does not change transmitting power, even employing directional antenna, also can only overlay area D1, become communication blind district (shade sector part among Fig. 2) for 2 of region D.The 3rd, put the big regional overlay network of multiple spot because long Distance Transmission causes transmission rate limited, can not satisfy the requirement of high-rate service transmission, and in fact not all business all must insert forwarding by CR-BS, does not just have this necessity as the local service in the area of coverage.

(Wireless Mesh Network WMN) is a kind of specific form of mobile Ad Hoc network to wireless mesh network, and its early stage research all comes from the research and development of mobile Ad Hoc network.In WMN, terminal use/equipment (Client) has both main frame and two kinds of roles of router.On the one hand, node is as the relevant application program of main frame operation; On the other hand, node need move relevant Routing Protocol as router, participates in common routing operations such as route discovery, route maintenance.WMN has 2 kinds of typical implementation patterns: terminal use mesh pattern (client meshing) and infrastructure mesh pattern (infrastructuremeshing).First kind of pattern is typical A d Hoc network, and second kind of pattern can combine with multiple existing network, such as present Wi-Fi WLAN (wireless local area network), WiMax and wireless MAN.

Summary of the invention

The purpose of this invention is to provide in a kind of cognitive radio simultaneously support point to the implementation method of the mixed structure of multiple spot (PMP) topology and netted (Mesh) topology---based on graded frequency spectra shared (hierarchical spectrum sharing, HSS) implementation method.Graded frequency spectra share be unauthorized user should the period can with the effective band set be divided into two classes, the first kind (TYPEI) is the direct communication that is used for CR-SAP and CR-BS, second class (TYPE II) is the direct communication that is used between CR-SAP.The cognitive radio system of exempting from license that adopts the inventive method to realize, can be in conjunction with the advantage of cognitive radio technology and mesh network, realize single-hop and the multi-hop communication of unauthorized user on authorized frequency bands, when improving the sub-district covering, increase capability of communication system greatly and communication mode more flexibly is provided.

Technical solution of the present invention is:

A kind of implementation method of mixed network structure in the cognitive radio, form by following step:

Step 1: obtain the maximal received power that this moment receiving terminal allows according to interference temperature model.

Consider a sub-district of exempting from the license cognitive radio system, form by a N cognition wireless electric terminals CR-SAP (index bound from 1 to N) and a cognitive radio base station CR-BS (with subscript 0 expression), the spectrum division that the radio frequency end can be supported is a M frequency band, index bound from 1 to M.We can obtain the set of receiving terminal Power Limitation by interference temperature model

P _L＝{pl _s，k，m，0≤s，k≤N，1≤m≤M} _{(N+1)×(N+1)×M} (4)

Wherein

${\mathrm{pl}}_{s,k,m}=\{\begin{array}{c}\underset{\mathrm{Bm}}{\∫}(k\·T_{L,k}\left(f\right)-k\·T_{I,k}\left(f\right)-N_k\left(f\right))\mathrm{df},\\ 0,k=s\end{array}$ k≠s

T _{L, k}(f), T _{I, k}(f) and N _k(f) be interference temperature and the background noise spectrum density that receiving terminal k interference temperature is limit and perceived respectively, pl _{S, k, m}Expression launch terminal s is when frequency band m transmission signals is given receiving terminal k, and the received power of receiving terminal k limits.

Step 2: the actual emission power set of calculating launch terminal.

The set of definition transfer function is

H＝{h _s，k，m，0≤s，k≤N，1≤m≤M} _{(N+1)×(N+1)×M} (5)

Wherein, h _{S, k, m}=0, if k=s

h _{S, k, m}Represent launch terminal s to the channel conditions of receiving terminal k on frequency band m, | h _{S, k, m}| ²The decay factor of then representing power.Then allow emitted power to be restricted at launch terminal s

α _kBe adjustable integral coefficient, be used to leave and take the certain power redundancy, span be (0,1], this be for more reliable assurance unauthorized user to the interference of authorized user in the scope that authorized user can bear.α _kValue relevant with accuracy to the estimation of interference temperature.

Suppose that launch terminal s is P at the maximum transmission power of frequency band m _{Max, s, m}, then launch terminal s at the actual emission power of frequency band m is

$p_{s,m}=\mathrm{Min}\{p_{\mathrm{Max},s,m},{\mathrm{\α}}_0\·\frac{{\mathrm{pl}}_{s,0,m}}{{\left|h_{s,0,m}\right|}^2},\·\·\·{,\mathrm{\α}}_k\·\frac{{\mathrm{pl}}_{s,k,m}}{{\left|h_{s,k,m}\right|}^2},\·\·\·{,\mathrm{\α}}_N\·\frac{{\mathrm{pl}}_{s,N,m}}{{\left|h_{s,N,m}\right|}^2}\}---\left(6\right)$

Step 3: the set of calculating two class effective spectrums

The set of definition environment noise is

N _R＝{n _s，k，m，0≤s，k≤N，1≤m≤M} _{(N+1)×(N+1)×M} (7)

Wherein

n _{S, k, m}=0, when k=s

n _{S, k, m}Expression launch terminal s is when frequency band m sends a signal to receiving terminal k, and the minimum signal to noise ratio set that the ambient noise size definition reliable transmission of receiving terminal k requires is

SNR _MIN＝{r _s，k，m，0≤s，k≤N，1≤m≤M} _{(N+1)×(N+1)×M} (8)

Wherein

r _{S, k, m}=0, when k=s

r _{S, k, m}Represent launch terminal s when frequency band m sends a signal to receiving terminal k, the signal to noise ratio of receiving terminal k energy reliable reception signal.

The set of definition effective spectrum is

V＝{v _s，k，m，0≤s，k≤N，1≤m≤M} _{(N+1)×(N+1)×M} (9)

Wherein

v _{S, k, m}=0, when k=s

So, according to the requirement of interference temperature model and reliable transmission, can be by the signal to noise ratio that relatively can reach and the minimum signal to noise ratio r of reliable reception signal _{S, k, m}, judge whether frequency band m can be used for transmitting launch terminal s to the data between the receiving terminal k.

v _{S, k, m}=0 expression launch terminal s does not allow to give receiving terminal k, v at frequency band m transmission signals _{S, k, m}≠ 0 expression frequency band m can be used for communicating by letter of launch terminal s and receiving terminal k, and promptly frequency band m is effectively to launch terminal s with communicating by letter of receiving terminal k, and v _{A, k, M}Also characterized the channel quality between launch terminal s and the receiving terminal seven.Thus, can obtain the available information of two class frequency spectrums, be expressed as with matrix form:

V ₀＝{v _0，k，m1≤k≤N，1≤m≤M} _N×M，V ₀′＝{v _k，0，m1≤k≤N，1≤m≤M} _N×M

V _s＝{v _s，k，m，1≤k≤N，1≤m≤M} _N×M，s＝1...N

By the spectrum efficiency analysis, can draw two class available spectrum.In the effective spectrum set, matrix v ₀, v ₀' characterized the available information that is used for the TYPE I frequency band of communicating by letter between CR-BS and the CR-SAP (v wherein ₀Expression is used for downstream bands information, V ₀' expression is used for up band information), matrix v _l... v _sV _NCharacterized the available information of the TYPEII frequency band that is used for direct communication between the CR-SAP.

Step 4 realizes PMP and the Mesh topology under the mixed structure

If in the cognitive radio system, network is divided into one or more sub-district (cell), and each sub-district is made up of a CR-BS and a plurality of CR-SAP.CR-BS is as the forwarding and the access point of communicating by letter outside the master controller of sub-district and the sub-district.CR-SAP can use TYPE I frequency band and CR-BS direct communication, uses in TYPE II frequency band and the same sub-district " neighbours " direct communication.If definition v _{S, k, m}≠ 0 (then CR-SAP K is the neighbours (Neighbor) that CR-SAP s can link to each other with frequency band m for 1≤s, k≤N).

1.PMP the realization of topology

Obtain matrix V by step 3 ₀, V ₀The available information of ' TYPE I the frequency band that characterizes, CR-SAP directly is connected with CR-BS by TYPE I frequency band, CR-BS by TYPE I frequency band and CR-SAP point to the communicating by letter of multiple spot, shown in accompanying drawing 3d.

2.Mesh the realization of topology

Obtain matrix V by step 3 _l, V _sV _NThe available information of the TYPE II frequency band that characterizes directly is connected by TYPE II frequency band realization point-to-point between CR-SAP and its neighbours.The multi-hop and whether insert CR-BS and be divided into 3 kinds of situations according to whether:

1. the single-hop communication of point-to-point between CR-SAP and its neighbours is shown in Fig. 3 a

2. the multi-hop mode between CR-SAP is without CR-BS.This is first kind of pattern---the terminal use mesh pattern that the WMN that introduces in the background of front realizes, is a kind of typical A d-hoc mode, and all CR-SAP in the sub-district have routing function, can be used as relaying, shown in Fig. 3 b.

3. CR-SAP is connected to CR-BS by multi-hop, transmits or inserts by CR-BS again, shown in Fig. 3 c.This is second kind of pattern---the infrastructure mesh pattern that the WMN that introduces in the background of front realizes.Under this pattern, all CR-SAP in the sub-district all may interconnect with TYPE II frequency band between CR-SAP as router.Source node (source node, SN) search for constantly route until last CR-SAP of route can with CR-BS with the direct communication of TYPE I frequency band.

By above step, just can realize supporting simultaneously in the cognitive radio system mixed network structure of PMP and Mesh topology, as shown in Figure 4.

Core of the present invention innovation is that the structure of wireless mesh network is introduced in the cognitive radio system, thereby supports the network configuration of PMP and Mesh topology when constituting a kind of mixing, and a kind of implementation method of sharing based on graded frequency spectra is provided.Concretism is: unauthorized user is by the environment around the cognitive radio technology perception intelligently, requirement according to interference temperature model and reliable transmission, calculate the usable spectrum resource that authorized user is not produced insufferable interference, and effective band set classified, the first kind (TYPE I) is the direct communication that is used for CR-SAP and CR-BS, and second class (TYPE II) is the direct communication that is used between CR-SAP.Can be by introducing at the TYPE of share spectrum resources under low power level II frequency band, for the direct communication between cancellated CR-SAP and multi-hop communication provide physical means.

The invention has the beneficial effects as follows:

1, adopt the cognitive radio system of the mixed structure of the inventive method realization to compare with the big regional covering system of the centralized control of PMP structure, having introduced can be at the TYPE of share spectrum resources under low power level II frequency band, increased the quantity of available band, expand the available band set, increased the capacity of system.In the cognitive radio networks of the big regional centralized control formula that covers, the communication of user terminal all must and be transmitted by CR-BS control, and because coverage is big, CR-SAP and CR-BS distance are far away, the emitted power level of wanting also requires than higher, and the high-power easier interference temperature restriction that surpasses, so it is less to can be used for the number of frequency bands of direct communication of CR-SAP and CR-BS.But the frequency band that can not be used for the direct communication of CR-SAP and CR-BS not necessarily can not be used for lower powered channeling.Position when between adjacent C R-SAP is closer, can communicate and when authorized user not being caused insufferable interference, low-power is multiplexing to be feasible with low-power between the two.

2, the cognitive radio system of the mixed structure of employing the inventive method realization can also enlarge the coverage of sub-district.Utilize the unauthorized user of cognitive radio technology, the use strictness of authorized frequency bands is subjected to the restriction of the situation of authorized user use authority frequency band.Adopt the network configuration of similar cellular cell, must in the period of using certain authorized frequency bands, guarantee in the sub-district, not have authorized user to use this frequency band.Because the randomness and the time variation of authorized user service band, the cell coverage area of exempting from the cognitive radio system of license also may present randomization and the time change.Adopt the method for low-power frequency spectrum share of the second class frequency band and the mode of mesh network multi-hop, can enlarge cell coverage area and avoid authorized user to resume the acute variation that frequency band causes coverage as much as possible.As shown in Figure 5, when authoring system LS is working, adopt PMP structure cognitive radio cell coverage area can only reach C3, the CR-BS of sub-district can not with user SAP1 direct communication, and the cognitive radio system of the mixed structure that employing the present invention realizes, the CR-BS of sub-district communicates by letter with SAP1 by the mode of multi-hop, makes communication path get around authoring system LS, both avoided interference, enlarged coverage again authoring system LS.Fig. 5 has also represented other one deck implication, be exactly the coverage of exempting from license cognitive radio sub-district originally be C4, but when certain period, authoring system LS resumed frequency band, the sub-district under the PMP structure must be retracted to C3 to coverage for fear of the interference to LS.Even the employing directional antenna in the sector coverage area territory of LS one side, such as user SAP1, still can become communication blind district.And because the randomness and the time variation of authorized user service band, the appearance of blind area may be irregular, and this can cause the instability of cell coverage area.The mode of the multi-hop that employing the present invention realizes then can be avoided the appearance of this communication blind district.

2, in the cognitive radio system of the mixed structure that the present invention realizes, support PMP and Mesh structure simultaneously, thereby provide communication mode more flexibly, a CR-SAP can communicate connection with multiple mode, when a connection is invalid (having authoring system to restart work on such as path) in this connection, also have other connected modes can keep original communication, thereby make network service have more robustness.And, can also select different communication modes with characteristic according to the requirement of business, thereby under the prerequisite that guarantees service quality, improve the availability of frequency spectrum of system.

Description of drawings

Fig. 1 is the interference temperature model schematic diagram of cognitive radio.

Bottom dot-hatched partly is the background noise spectrum density, and middle one deck diagonal line hatches partly is existing interference power spectrum density to authorized user, and uppermost stair-stepping straight line is that the interference temperature limit derives next interference power restriction.1-13 represents frequency band.

Fig. 2 is the schematic diagram of a kind of communication blind district under the PMP structure.

Cognitive radio system can be shared the F1 and the F2 frequency band of authoring system among the figure, C1 and C2 are to use the coverage of the authoring system of F1 and F2 frequency band respectively, C0 is the coverage of cognitive radio system, the shade sector zone of D2 is when two authoring systems all just in working order the time, the communication blind district of cognitive radio system, the zone that D1 adopts directional antenna to communicate by letter for this moment.

Fig. 3 is that the PMP and the Mesh topology of cognitive radio mixed network structure of the present invention shared the schematic diagram of realizing based on graded frequency spectra.

Subgraph a-c has represented 3 kinds of situations of the Mesh topology of point-to-point respectively among the figure, and subgraph d is the schematic diagram of the realization of PMP structure.SAP1-SAP7 is the cognition wireless electric terminals, and CR-BS1 and CR-BS2 are the base stations of cognitive radio system, and B6 and B7 are first kind frequency spectrum resources, and B1-B5 is the second class frequency spectrum resource.

Fig. 4 is the schematic diagram of a sub-district of cognitive radio mixed network structure of the present invention, characterized PMP and Mesh topology with and the implementation that is connected.

20 is base stations (CR-BS) of the netted net of cognition wireless among the figure, 21-31 is cognition wireless electric terminals (CR-SAP), B11-B13 is used for the first kind frequency spectrum resource (TYPE I) that CR-SAP communicates by letter with CR-BS, and B14-B18 is used between CR-SAP directly and the second class frequency spectrum resource (TYPE II) of multi-hop communication.

Fig. 5 is the covering schematic diagram of a sub-district of the cognitive radio system of mixed structure of the present invention.

CR-BS is the cell base station of cognitive radio, and SAP1-SAP4 is the cognition wireless electric terminals, and LS is an authoring system, and C3 is the coverage of cognitive radio sub-district under the PMP structure, and C4 is the coverage of cognitive radio system sub-district under the mixed structure of the present invention.

Embodiment

Support the mixed structure of PMP and Mesh topology to adopt graded frequency spectra to share realization in the cognitive radio of the present invention simultaneously.Consider a sub-district of exempting from the license cognitive radio system, form that the spectrum division that the radio frequency end can be supported is a M frequency band by a N CR-SAP (index bound from 1 to N) and a CR-BS (with subscript 0 expression), index bound from 1 to M.The implementation method that graded frequency spectra provided by the invention is shared is divided into following step:

Step 1: obtain the maximal received power that this moment receiving terminal allows according to interference temperature model.

P _L＝{pl _s，k，m，0≤s，k≤N，1≤m≤M} _{(N+1)×(N+1)×M}

Wherein

${\mathrm{pl}}_{s,k,m}=\{\begin{array}{}\end{array}\begin{array}{c}\underset{\mathrm{Bm}}{\∫}(k\·T_{L,k}\left(f\right)-k\·T_{I,k}\left(f\right)-N_k\left(f\right))\mathrm{df},\\ 0,k=s\end{array}$ k≠s

T _{L, k}(f), T _{I, k}(f) and N _k(f) be interference temperature and the background noise spectrum density that receiving terminal k interference temperature is limit and perceived respectively.Pl _{S, k, m}Expression launch terminal s is when frequency band m transmission signals is given receiving terminal k, and the received power of receiving terminal k limits.

Step 2: the actual emission power that calculates launch terminal.

$p_{s,m}=\mathrm{Min}\{p_{\mathrm{Max},s,m},{\mathrm{\α}}_0\·\frac{{\mathrm{pl}}_{s,0,m}}{{\left|h_{s,0,m}\right|}^2},\·\·\·{,\mathrm{\α}}_k\·\·\·,\frac{{\mathrm{pl}}_{s,k,m}}{{\left|h_{s,k,m}\right|}^2},\·\·\·,{\mathrm{\α}}_N\frac{{\mathrm{pl}}_{s,N,m}}{{\left|h_{s,N,m}\right|}^2}\}$

p _{Max, s, m}Be the maximum transmission power of launch terminal s at frequency band m, Allow emitted power restriction, h for what derive at launch terminal s by interference temperature model _{S, k, m}Represent launch terminal s to the channel conditions of receiving terminal k on frequency band m, | h _{S, k, m}| ²The decay factor of expression power, α _kBe adjustable integral coefficient, be used to leave and take the certain power redundancy, span be (0,1].

Step 3: the set of calculating two class effective spectrums

V ₀＝{v _0，k，m，1≤k≤N，1≤m≤M} _N×M，V ₀＇＝{v _k，0，m，1≤k≤N，1≤m≤M} _N×M

V _s＝{v _s，k，m，1≤k≤N，1≤m≤M} _N×M，s＝1…N

Matrix V ₀, V ₀＇ has characterized the available information that is used for the TYPE I frequency band of communicating by letter between CR-BS and the CR-SAP (V wherein ₀Expression is used for downstream bands information, V ₀＇ represents to be used for up band information), matrix V _l... V _sV _NCharacterized the available information of the TYPE II frequency band that is used for direct communication between the CR-SAP.v _{S, k, m}≠ 0 expression frequency band m can be used for communicating by letter of launch terminal s and receiving terminal k.

n _{S, k, m}And r _{S, k, m}Represent launch terminal s respectively when frequency band m sends a signal to receiving terminal k, the signal to noise ratio of the ambient noise of receiving terminal k size and reliable reception signal.

Step 4 is according to PMP and Mesh topology under the two class frequency spectrums set realization mixed structure

In the cognitive radio system of mixed network structure of the present invention, network is divided into one or more sub-district (cell), and each sub-district is made up of a CR-BS and a plurality of CR-SAP.CR-BS is as the forwarding and the access point of communicating by letter outside the master controller of sub-district and the sub-district.CR-SAP can use TYPE I frequency band and CR-BS direct communication, with " neighbours " direct communication in TYPE II frequency band and the same sub-district.

1.PMP the realization of topology

Obtain matrix V by step 3 ₀, V ₀The available information of the TYPE I frequency band that ＇ characterizes, CR-SAP directly is connected with CR-BS by TYPE I frequency band, shown in accompanying drawing 3d.

2.Mesh the realization of topology

Obtain matrix V by step 3 _l... V _sV _NThe available information of the TYPE II frequency band that characterizes directly is connected by TYPE II frequency band realization point-to-point between CR-SAP and its neighbours.The multi-hop and whether insert CR-BS and be divided into 3 kinds of situations according to whether:

1. the single-hop communication of point-to-point between CR-SAP and its neighbours is shown in Fig. 3 a

2. the multi-hop mode between CR-SAP is without CR-BS.All CR-SAP in the sub-district have routing function, can be used as relaying, shown in Fig. 3 b.

3. CR-SAP is connected to CR-BS by multi-hop, transmits or inserts by CR-BS again, shown in Fig. 3 c.In this case, all CR-SAP in the sub-district all may interconnect with TYPE II frequency band between CR-SAP as router.Source node (source node, SN) search for constantly route until last CR-SAP of route can with CR-BS with the direct communication of TYPE I frequency band.

By above step, just can realize supporting simultaneously in the cognitive radio system mixed network structure of PMP and Mesh topology.

Claims (1)

1. a kind of implementation method of mixed network structure in the cognitive radio, suppose in the sub-district of a cognitive radio system, form by N cognition wireless electric terminals and a cognitive radio base station, the spectrum division that the radio frequency end can be supported is a M frequency band, it is characterized in that, form by following step:

Step 1: obtain the maximal received power that this moment receiving terminal allows according to interference temperature model

P _L＝{pl _s，k，m，0≤s，k≤N，1≤m≤M} _{(N+1)×(N+1)×M}

Wherein

${\mathrm{pl}}_{s,k,m}=\left\{\begin{array}{cc}\underset{\mathrm{Bm}}{\∫}(k\·T_{L,k}\left(f\right)-k\·T_{l,k}\left(f\right)-N_k\left(f\right))\mathrm{df},& k\≠s\\ 0,& k=s\end{array}\right.$

T _{L, k}(f), T _{I, k}(f) and N _k(f) be interference temperature and the background noise spectrum density that receiving terminal k interference temperature is limit and perceived respectively, pl _{S, k, m}Expression launch terminal s is when frequency band m transmission signals is given receiving terminal k, and the received power of receiving terminal k limits;

Step 2: the actual emission power that calculates launch terminal

$p_{s,m}=\mathrm{Min}\{p_{\mathrm{Max},s,m},{\mathrm{\α}}_0\·\frac{{\mathrm{pl}}_{s,0,m}}{|h_{s,0,m}{|}^2},...,{\mathrm{\α}}_k\·\frac{{\mathrm{pl}}_{s,k,m}}{|h_{s,k,m}{|}^2},...,{\mathrm{\α}}_N\·\frac{{\mathrm{pl}}_{s,N,m}}{|h_{s,N,m}{|}^2}\}$

p _{Max, s, m}Be the maximum transmission power of launch terminal s at frequency band m,

Allow emitted power restriction, h for what derive at launch terminal s by interference temperature model _{S, k, m}Represent launch terminal s to the channel conditions of receiving terminal k on frequency band m, | h _{S, k, m}| ²The decay factor of expression power, α _kBe adjustable integral coefficient, be used to leave and take the certain power redundancy, span be (0,1];

Step 3: the set of calculating two class effective spectrums

v ₀＝{v _0，k，m，1≤k≤N，1≤m≤M} _N×M，v ₀′＝{v _k，0，m，1≤k≤N，1≤m≤M} _N×M

v _s＝{v _s，k，m，1≤k≤N，1≤m≤M} _N×M，s＝1…N

Matrix v ₀, v ₀' characterized the available information that is used for the TYPE I frequency band of communicating by letter between cognitive radio base station and the cognition wireless electric terminals, wherein v ₀Expression is used for downstream spectrum information, V ₀' expression is used for up spectrum information; Matrix v ₁... v _sV _NCharacterized the available information of the TYPE II frequency band that is used for direct communication between the cognition wireless electric terminals; v _{S, k}, m ≠ 0 expression frequency band m can be used for communicating by letter of launch terminal s and receiving terminal k;

n _{S, k, m}And r _{S, k, m}Represent launch terminal s respectively when frequency band m sends a signal to receiving terminal k, the signal to noise ratio of the ambient noise of receiving terminal k size and reliable reception signal;

Step 4 realizes PMP and the Mesh topology under the mixed structure

If in the cognitive radio system, network is divided into one or more sub-district, and each sub-district is made up of with a plurality of cognitive radio terminals a cognitive radio base station: the cognitive radio base station is as the forwarding and the access point of communicating by letter outside the master controller of sub-district and the sub-district; The cognition wireless electric terminals can be used TYPE I frequency band and the direct communication of cognitive radio base station, with " neighbours " direct communication in TYPE II frequency band and the same sub-district; If definition v _{S, k, m}≠ 0 (1≤s, k≤N), then launch terminal k is that receiving terminal s can be with the continuous neighbours of frequency band m;

1) realization of .PMP topology

Obtain matrix v by step 3 ₀, v ₀The available information of the TYPE I frequency band of ' sign, the cognition wireless electric terminals directly is connected with the cognitive radio base station by TYPE I frequency band, and the cognitive radio base station is put communicating by letter of multiple spot by TYPE I frequency band with the cognition wireless electric terminals;

2) realization of .Mesh topology

Obtain matrix V by step 3 ₁... v _sV _NThe available information of the TYPE II frequency band that characterizes directly is connected by TYPE II frequency band realization point-to-point between cognition wireless electric terminals and its neighbours, the multi-hop and whether insert the cognitive radio base station and be divided into 3 kinds of situations according to whether:

1. the single-hop communication of point-to-point between cognition wireless electric terminals and its neighbours;

2. the multi-hop mode of cognitive radio terminal room is without the cognitive radio base station; This is a terminal use mesh pattern, is a kind of typical A d-hoc mode, and all the cognition wireless electric terminals in the sub-district all have routing function, can be used as relaying;

3. the cognition wireless electric terminals is connected to the cognitive radio base station by multi-hop, transmits or inserts by the cognitive radio base station again, and this is an infrastructure mesh pattern; Under this pattern, all the cognition wireless electric terminals in the sub-district all may be as router, and the cognitive radio terminal room interconnects with TYPE II frequency band; Source node search for constantly route until last cognition wireless electric terminals of route can with the cognitive radio base station with the direct communication of TYPE I frequency band;

By above step, just can realize supporting simultaneously in the cognitive radio system mixed network structure of PMP and Mesh topology.

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