CN100583728C - Method for determining asynchronous silent period for sensing wireless regional area network system - Google Patents

Abstract

The method includes steps: base station obtains information of distance form each device at client end in active state in this sector relative to base station self; based on the obtained distance information of client end, and requirement of system on sensing channel, the base station calculates parameter, which is in use for determining own silence cycle, of device at client end, and sends the parameter to corresponding device at client end; based on received parameter, device at client end determines own asynchronous silence cycle. Under condition of not increasing system spending, the method raises precision for sensing channel.

Description

Determine the method for asynchronous silent period in a kind of cognitive radio regional network system

Technical field

The present invention relates to WiMAX access technology field, particularly a kind of cognitive radio regional network (Wireless Regional Area Network, WRAN) method of definite asynchronous silent period in the system.

Background technology

The WiMAX access technology is the very popular research topic in the current wireless communications field.Broadband wireless access may select to use the television broadcast band of very high frequency(VHF) (VHF)/hyperfrequency (UHF) of 47MHz～910MHz, this is because the penetration power of TV broadcast channel signal is good, can realize that large tracts of land covers, and is convenient to reduce cost, improve the competitiveness.For this reason, (the Instituteof Electrical and Electronic Engineers of U.S.'s electrical equipment and Electronic Engineering Association, IEEE) set up 802.22WRAN standard operation group, its objective is the development air interface, so that provide broadband wireless access in the zone of reason variously that comprises underpopulated rural area.

Exist such as mandate or unauthorized existing business such as TVs on the frequency range that the WRAN system works, therefore, WRAN equipment must be able to detect the system signal that other use this frequency range, to avoid the mutual interference of signal phase.In the WRAN system, can use cognitive radio (Cognitive Radio, CR) detect the operating position of frequency spectrum, and utilize the idle frequency spectrum that is not taken to use the equipment of CR to set up or maintain a network and be connected, thereby find the frequency range that is not taken to be utilized by the WiMAX access service by existing business with another by existing network.Therefore, designed the silent period that is used for sensing channel in the WRAN system, so-called silent period refers to that all WRAN equipment stop to launch and detecting a period of time of the existing service signal that is not subjected to the WRAN system interference on a particular channel.

According to the difference of implementation, silent period can be divided into:

Synchronous silent period, WRAN equipment all stop time interval of launching on all available channels of system; In this manner, all channels that each WRAN equipment can detecting system.By such detecting, the WRAN system can understand wireless environment on every side more all sidedly.

Asynchronous silent period, the time interval that one or more WRAN equipment stop emission signal on certain shared particular channel; This method can produce a no WRAN signal on specific channel time cycle is used for doing the channel detecting; Each channel can have different asynchronous silent periods, and promptly the zero hour of the silent period of each channel or duration are all different; Each WRAN equipment can only be detected self shared particular channel usually under this mode.

Above-mentioned two kinds of silent periods comparatively speaking, the former is provided with comparatively simple, and the latter has higher flexibility, thereby can utilize system resource more fully.

At Singapore Information And Communication research institute (Institute of Infocomm Research, I2R) in " the System description and operation principles for IEEE 802.22WRANs " motion of Ti Jiaoing, introduced an asynchronous silent period scheme.This scheme is at time division duplex (TimeDivision Dual, TDD) pattern, the asynchronous silent period of insertion regular length in tdd frame.Especially, these silent periods are arranged at the transfer point of downstream-to-upstream.

In the such scheme that I2R submits to, no matter how far client device (CPE) and base station (BS) are separated by, and CPE must have the silent period of a compulsory regular length.For near the CPE the base station, this way can not brought problem; But for the CPE away from the base station, if there is not silent period, up transmission can be in the moment that descending transmission finishes, if still insert silent period, up transmission just has been delayed, and therefore this way can increase the expense of system.

Summary of the invention

In view of this, the objective of the invention is to, propose to determine in a kind of WRAN system method of asynchronous silent period, can reduce overhead.

This method comprises the steps:

A, base station obtain that each is in the range information of the client device of active state with respect to base station itself in this sub-district;

B, base station calculate each client device and are used for determining autoprotection parameter at interval, and the parameter that calculates is sent to clients corresponding equipment according to the client range information that is obtained;

C, client device are determined the protection interval of self according to the parameter of receiving; and with the protection interval of sub-frame of uplink to the descending sub frame transfer point; or descending sub frame is to the protection of sub-frame of uplink transfer point at interval, or sub-frame of uplink to the protection of descending sub frame transfer point at interval with descending sub frame to the protection interval sum of sub-frame of uplink transfer point as asynchronous silent period.

Described parameter comprise sub-frame of uplink to the protection of the transfer point of descending sub frame at interval the initial moment and duration and descending sub frame to the initial moment and duration at the protection interval of sub-frame of uplink transfer point.

Preferably, described step B falls into a trap to calculate and further comprises:

The time delay that B11, measuring-signal come and go to be propagated on this segment distance between client device and the base station according to measured time delay, determines that this client device is in the sub-frame of uplink protection initial moment and duration at interval to the transfer point of descending sub frame;

B12, according to the determined sub-frame of uplink of the step B11 protection initial moment and duration at interval to the transfer point of descending sub frame; and sub-frame of uplink to the protection of descending sub frame transfer point at interval and descending sub frame be the condition that the signal round-trip delay of cell edge is arrived in the base station to the total length at the protection interval of sub-frame of uplink transfer point, determine the initial moment and the duration of descending sub frame to the protection interval of sub-frame of uplink transfer point.

Perhaps, calculating further comprises described in the step B:

B21, measuring-signal come and go the time delay of propagating on this segment distance between client device and the base station, according to measured time delay, determine that this client device is in protection at interval the initial moment and the duration of sub-frame of uplink to the transfer point of descending sub frame;

B22, by optimized Algorithm, and, calculate the slot length of descending sub frame to the sub-frame of uplink transfer point according to the protection initial moment and the duration at interval that step B21 obtains;

Step C is: client device is according to transfer point protection at interval the initial moment and the duration of the sub-frame of uplink of receiving to descending sub frame; and the protection that descending sub frame is determined self to the slot length of sub-frame of uplink transfer point at interval, and protection that will be part or all of interval is as the asynchronous silent period of self.

After described step B22, can further include:

B23, according to the slot length that step B22 obtains, calculate the number of OFDM symbol in the sub-frame of uplink, and the OFDM number of symbols that has more with respect to normal OFDM number of symbols of the OFDM number of symbols that obtains being calculated;

B24, choose sum smaller or equal to the OFDM symbol of the resultant OFDM number of symbols that has more of step B23;

Step C is: client device is according to transfer point protection at interval the initial moment and the duration of the sub-frame of uplink of receiving to descending sub frame; and the protection that descending sub frame is determined self to the slot length of sub-frame of uplink transfer point at interval, and shared time of the selected OFDM symbol of protection that will be part or all of interval and step B24 is as silent period.

Preferably, step B24 is described to be chosen for: from the sub-frame of uplink ending, choose the continuous OFDM symbol of sum smaller or equal to the resulting OFDM number of symbols that has more of step B23.

Preferably, the minimum slot length L that avoid occur inter-signal interference ISI of descending sub frame to the sub-frame of uplink transfer point is set, described optimized Algorithm is:

A1, setting and base station distance are the slot length L1=L of the descending sub frame of 0 client CPE1 to the sub-frame of uplink transfer point;

B1, the sub-frame of uplink that the sub-frame of uplink of arbitrary client CPE2 in the sub-district is corresponding with CPE1 are made symbol level other are synchronous, and minimize L2 at the descending sub frame that satisfies CPE2 under the condition of the slot length L2 〉=L of sub-frame of uplink transfer point.

Perhaps, described optimized Algorithm is:

Arbitrary client CPEi in a2, the base station selected sub-district is provided with the slot length Li=L of the descending sub frame of CPEi to the sub-frame of uplink transfer point;

B2, corresponding with the CPEi respectively sub-frame of uplink of other clients CPEj sub-frame of uplink in the sub-district is carried out symbol level, and other is synchronous, and under the condition of the slot length Lj 〉=L of sub-frame of uplink transfer point, minimize Lj, and the summation of the Lj of interior all clients of calculation plot at the descending sub frame that satisfies CPEj;

All clients repeat above-mentioned a2～b2 in c2, the traversal sub-district, base station, find out wherein minimum summation;

The descending sub frame of d2, use each client in the minimum summation that finds is to the slot length of sub-frame of uplink transfer point.

From above scheme as can be seen, the present invention utilizes GI not need the over-specification silent period as silent period, guarantees channel detecting precision under the situation that does not increase overhead; Further, determine GI by adopting self-adaptive controlled making mechanism, make frame structure more flexible, reduced the overhead that descending sub frame brings to the GI of sub-frame of uplink transfer point, making the original silent period that disperses to merge becomes long silent period; And the time that some OFDM symbols are taken is as silent period, further increased the time of silent period simultaneously at traffic affecting not, thereby improved the detecting precision to channel.

Description of drawings

Fig. 1 is the tdd frame structure chart of the received employing OFDMA mode of CPE;

Fig. 2 is the method flow diagram of the embodiment of the invention one;

Fig. 3 is a tdd frame structure chart of having introduced the received employing OFDMA mode of the CPE of self-adaptive controlled making mechanism;

Fig. 4 is not for adopting the tdd frame structure comparison diagram of self-adaptive controlled making mechanism and the CPE that the has adopted self-adaptive controlled making mechanism employing OFDMA mode received in same place;

Fig. 5 is for determining the algorithm schematic diagram of TDD descending sub frame to sub-frame of uplink transfer point time slot;

Fig. 6 is the embodiment of the invention two method flow diagrams.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, the present invention is further elaborated below in conjunction with accompanying drawing.

The scope of application of the present invention is for adopting TDD and OFDM (Orthogonal FrequencyDivision Multiple Access, OFDMA) the WRAN system of mode.

In the wireless solution of current various high rate data transmission, (OrthogonalFrequency Division Multiplexing is one of the most promising scheme for the multi-carrier modulation technology of representative OFDM) with OFDM.Multi-carrier modulation technology is decomposed into the relatively low sub data flow of several speed with data flow, and the low rate multimode symbol that forms with such low bit rate goes to modulate corresponding subcarrier again, thereby constitutes the transmission system that a plurality of low rate symbol parallels send.In order to resist the intersymbol interference (ISI) that multipath effect causes, the way that the OFDM technology adopts is to insert one section GI before each OFDM symbol.

The inventive method is exactly the GI that makes full use of in the OFDM technology, with its asynchronous silent period as the WRAN system.According to the difference of execution mode, the present invention is divided into three specific embodiments, and wherein embodiment one is: determine GI by measuring between CPE and the base station distance, and use sub-frame of uplink to the GI of descending sub frame transfer point as asynchronous silent period; Embodiment two is: on the basis of measuring distance between CPE and the base station, further adopt adaptive guard mechanism to determine GI, and use sub-frame of uplink to the GI of descending sub frame transfer point as asynchronous silent period; Can also be further with some OFDM symbols as silent period.

Before embodiment is specifically described, at first introduce the existing work of the GI aspect relevant with content of the present invention.A method of remote equipment synchronously in communication system that the patent No. is 6,647,246 U.S. Patent Publication, when using the TDD mode, this method for synchronous will produce GI, so this patented method can be used to produce GI.Method of revising measured signal round trip delay time that the patent No. has been 6,647,246 U.S. Patent Publication, and the round trip delay time of signal can be used for determining the length of GI, so this patent can accurately be determined the length of GI.

According to IEEE 802.16 frame structures specified, one is adopted the tdd frame of OFDMA mode can be divided into two subframes, and each subframe is made up of several OFDM symbols, and one of them subframe is used for downlink transfer, another is used for uplink, is called descending sub frame and sub-frame of uplink.OFDM symbol in the sub-frame of uplink must be synchronous in the base station realization to the GI of sub-frame of uplink transfer point by descending sub frame, and this GI is considered as overhead usually.

Figure 1 shows that the tdd frame structure chart of the employing OFDMA mode that CPE is received, CPE1 be positioned at apart from the base station apart from the d=0 place, CPE2 be positioned at apart from the base station apart from the d=R place, wherein R is the radius of the signal that launches the base station scope that can cover, i.e. radius of society.In other words, CPE1 is positioned near the base station and CPE2 is positioned at cell edge.A tdd frame among Fig. 1 comprises eight OFDM symbols altogether, and wherein preceding four OFDM symbols are formed descending sub frame, and back four OFDM symbols are formed sub-frame of uplink.For CPE1, be 2 τ at descending sub frame to the required GI length of the transfer point of sub-frame of uplink, τ=R/C here, C is the light velocity; This GI manually adds in the synchronous purpose in place, base station for the upward signal that reaches each CPE; For CPE2, GI is positioned at the transfer point from the sub-frame of uplink to the descending sub frame, and the duration also is 2 τ; This GI is because the transmission delay of downstream signal on the distance between CPE2 and the base station causes.If the distance that has CPE3 to be positioned at apart from the base station is 0＜d＜R place, then CPE3 these two transfer points all GI can appear, the total length of two GI of place is 2 τ, and the reason that forms the GI of this two place is identical with the reason that forms above-mentioned corresponding conversion point GI respectively.

For each CPE, in the GI of self, do not have signal emission or arrival, so CPE can utilize GI to detect the channel that self takies.Yet because relevant apart from d between the initial moment of GI and duration and CPE and the base station, so the GI that is in the CPE of different location differs from one another the step, and any CPE can not detect the channel that other CPE occupy in the GI of self.For instance, if CPE1 uses subcarrier 1, CPE2 uses subcarrier 2, so just can guarantee in the GI of CPE2 and in the residing place of CPE2, there is not the WRAN signal on the shared channel subcarrier 2 of CPE2, yet still have here and now from the signal on the shared channel subcarrier 1 of CPE1, so CPE2 can not utilize the shared channel subcarrier 1 of GI detecting CPE1 of self; In like manner CPE1 can not utilize the shared channel subcarrier 2 of GI detecting CPE2 of self.

Just be based on above reason, proposing the embodiment of the invention one, its flow process comprises the steps: as shown in Figure 2

Step 201: the base station obtains each CPE and the range information of self in this sub-district, be that the base station is measured each CPE and the distance of self in the sub-district respectively, it number is 6 that described metering system can be taked aforementioned patent, 647, metering system described in 246 the United States Patent (USP), the present invention does not limit metering system.

Step 202: according to the range information that is obtained, the base station calculates in this sub-district the initial moment and the duration of the GI of each CPE that is in active state.Described computational process can for: at first according to the distance of CPE and base station, calculate since the sub-frame of uplink that the time delay that signal come and go to be propagated on this segment distance between CPE and the base station causes to the initial moment and duration of the GI of the transfer point of descending sub frame; Utilizing the total length of sub-frame of uplink to the GI of descending sub frame transfer point and descending sub frame to the GI of sub-frame of uplink transfer point again is the relation of 2 τ, determines the initial moment and the duration of descending sub frame to the GI of sub-frame of uplink transfer point.

Step 203: the base station notifies the parameter of the GI of each transfer point that is calculated each to be in the CPE of active state by certain down channel, above-mentioned notice can be to adopt broadcast channel each interior CPE of mode while notifying cell with broadcasting, can be selected arbitrarily idle down channel each interior CPE of notifying cell respectively, the present invention limit concrete advice method yet.

Step 204:CPE GI that self is all or part of is as asynchronous silent period, as sub-frame of uplink being arrived the GI of descending sub frame transfer point as asynchronous silent period, or with descending sub frame to the GI of sub-frame of uplink transfer point as asynchronous silent period, or with above-mentioned whole GI as asynchronous silent period.And in the asynchronous silent period scope, open the CR detecting occupy the existing business signal of channel and carry out respective handling.

After execution of step 204, through going to step 201 after the default time interval, repeat above-mentioned flow process, this time interval can be set to zero.

Further, can take self-adaptive controlled making mechanism that descending sub frame is adjusted to the length of the GI of sub-frame of uplink transfer point, make the GI that under the prerequisite that ISI do not occur, shortens this transfer point place as much as possible, make frame structure more flexible, further save overhead.Frame structure as shown in Figure 1, at the transfer point place of descending sub frame to sub-frame of uplink, CPE1 must wait for that CPE2 can be synchronous in base station side with the upward signal that guarantees them; And after having introduced self-adaptive controlled making mechanism, first OFDM symbol of CPE2 sub-frame of uplink needn't keep with first OFDM symbol of CPE1 sub-frame of uplink synchronously, but with some OFDM symbols of CPE1 sub-frame of uplink, for example say that second OFDM symbol keeps synchronously.Like this, CPE1 can launch in advance and can launch more multi-OFDM symbol, more importantly is that the GI length from descending sub frame to the sub-frame of uplink transfer point can reduce.

Figure 3 shows that the tdd frame structure chart of the employing OFDMA mode that the CPE that introduced self-adaptive controlled making mechanism is received, wherein the definition of each symbol is consistent with Fig. 1, to sub-frame of uplink transfer point place, second OFDM symbol of first OFDM symbol of first sub-frame of uplink of CPE2 and CPE1 sub-frame of uplink keeps synchronously at descending sub frame; Label is that 5 OFDM symbol is the many OFDM symbols transmitted of CPE1.

Because the restriction of hardware, the various reasons such as time delay spread of multipath channel, descending sub frame must can not be eliminated greater than some values fully to the GI between the sub-frame of uplink.For example, because the multipath effect of channel, the 4th of CPE2 the descending OFDM symbol lengths will be elongated among Fig. 3, if descending sub frame is 0 or too little to the GI between the sub-frame of uplink so, the afterbody of this OFDM symbol that is elongated may be subjected to the interference from first upgoing O of CPE1 FDM symbol.Here suppose that be that the time slot of L is a minimum length time slot of avoiding ISI at descending sub frame to the transfer point director degree of sub-frame of uplink, the concrete of the length of described L determines that method is not within the scope of the inventive method.

Fig. 4 a and Fig. 4 b show the tdd frame structure that does not adopt self-adaptive controlled making mechanism and the CPE that the has adopted self-adaptive controlled making mechanism employing OFDMA mode received in same place respectively, CPE shown in it and base station distance are 0＜d＜R, and each symbol definition is consistent with Fig. 1.From Fig. 4, can visually see, adopted self-adaptive controlled making mechanism after, descending sub frame has shortened to the GI of sub-frame of uplink transfer point; And since the sub-frame of uplink that causes of signal transmission delay remain unchanged to the GI of descending sub frame transfer point.

To illustrate below and be used for determining descending sub frame, suppose still that here length between descending sub frame and the sub-frame of uplink is that the time slot of L is a time slot of avoiding the ISI minimum length to two kinds of algorithms that sub-frame of uplink transfer point place time slot may adopt.Fig. 5 a has showed that using algorithm example of frame structure for the moment, CPE1 is the CPE of close base station, i.e. d=0; CPE2 is any one CPE in the sub-district of base station, 0＜d＜R; L1 and L2 represent that respectively CPE1 and CPE2 are at the slot length of descending sub frame to the sub-frame of uplink transfer point.

Algorithm one comprises the steps:

The descending sub frame of a1, CPE1 is set to L to the slot length L1 of sub-frame of uplink transfer point, make with base station distance be that the fast as far as possible of 0 CPE is converted to sub-frame of uplink from descending sub frame;

B1, the synchronous sub-frame of uplink sub-frame of uplink corresponding of CPE2 with CPE1, described synchronous be symbol level other is synchronous, and minimize L2 satisfying under the condition of L2 〉=L; First OFDM symbol of handling the sub-frame of uplink of the resultant CPE2 as a result in back keeps synchronously with certain OFDM symbol of the corresponding sub-frame of uplink of CPE1, specifically is with which OFDM sign synchronization to be decided by the concrete value of each amount in the described condition.

L1=L among Fig. 5 a; Owing to must satisfy this condition of L2 〉=L, suppose CPE2 in this example first upgoing O FDM symbol can only with the 3rd the upgoing O FDM sign synchronization of CPE1.

Algorithm two minimizes slot length total in the sub-district.If total n client in the sub-district represents that with CPEi client in the sub-district, Li are this client and arrive the slot length of sub-frame of uplink transfer point at descending sub frame, i=1,2,3 ..., n; Algorithm two is promptly satisfying the time slot sum that minimizes each CPE under the condition of Li 〉=L $T=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{Li};$ Specifically comprise the steps:

A2, base station selected CPE1, L1 is set to L, promptly make CPE1 fast as far as possible be converted to sub-frame of uplink from descending sub frame;

B2, other CPE in the sub-district are carried out symbol level with CPE1 respectively, and other is synchronous, and minimizes Li satisfying under the condition of Li 〉=L, and described method for synchronous is identical with step b1 in the algorithm one, and calculates

C2, base station select successively CPE2, CPE3 ... CPEn repeats above-mentioned a2～b2, finds out wherein minimum CPE time slot sum $T_{\min }=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{Li};$

The T that d2, use are found _MinIn the slot length of each CPE.

Fig. 5 b has showed an example of frame structure when using algorithm two, because algorithm two is that global optimization is carried out in whole sub-district, total slot length of each CPE is littler in the sub-district, makes second up sign synchronization of first upgoing O FDM symbol and the CPE1 of CPE2 under identical condition.

After having adopted self-adaptive controlled making mechanism, compare with primitive frame structure shown in Figure 1, because silent period can be distributed according to need and be made the flexibility of frame structure be enhanced, and the silent period that disperses in the primitive frame structure can put together the silent period that forms than long.In order to guarantee the enough detecting time, can also remove some OFDM symbols further, and the time that these OFDM symbols are shared is as silent period.For example, if be silent period with the 5th OFDM symbolic substitution in the sub-frame of uplink among Fig. 4 b, just can obtain a longer silent period and make the detecting precision rise; This does not reduce with the primitive frame structure ratio shown in Fig. 4 a, upgoing O FDM number of symbols yet.

The embodiment of the invention two is proposed for these reasons, its main contents are in the WRAN system, adopt self-adaptive controlled making mechanism to obtain to adopt the GI of the tdd frame of OFDMA mode, and with this GI as asynchronous silent period, be silent period with some OFDM symbolic substitution simultaneously; Detect the existing business signal with determined silent period,

The flow process of embodiment two comprises the steps: as shown in Figure 6

Step 601: the base station obtains each CPE and the range information of self in this sub-district, be that the base station is measured each CPE and the distance of self in the sub-district respectively, it number is 6 that described metering system can be taked aforementioned patent, 647, metering system described in 246 the United States Patent (USP), the present invention does not limit metering system.

Step 602: according to the requirement to the channel detecting of the range information that is obtained and system, following operation is done for the CPE that each is in active state in the base station:

602a, according to range information, calculate the initial moment and the duration of sub-frame of uplink to the GI of descending sub frame transfer point;

602b, according to the GI that obtains among certain algorithm and the step 602a, calculate and be positioned at the slot length of descending sub frame to the sub-frame of uplink transfer point;

602c, according to described slot length, further obtain the number of OFDM symbol in the sub-frame of uplink;

602d, determine which OFDM symbol can be replaced by silent period in the sub-frame of uplink.Described definite mode is: select in the sub-frame of uplink because all or part of OFDM symbol in the additional OFDM symbol of self-adaptive controlled making mechanism, and normally choose continuously from the afterbody of sub-frame of uplink.

Step 603: the base station is in each parameter broadcast announcement that obtains in the step 603 by certain down channel the CPE of active state.Above-mentioned notice can be to adopt broadcast channel each interior CPE of mode while notifying cell with broadcasting, also can be selected arbitrarily idle each interior CPE of down channel difference notifying cell, and the present invention does not limit concrete advice method.

Step 604:CPE determines self silent period, the shared time of OFDM symbol that this silent period comprises all or part of GI and is replaced according to the parameter of being received.Described all or part of GI can be the GI of sub-frame of uplink to the descending sub frame transfer point, or descending sub frame is to the slot length of sub-frame of uplink transfer point, or the slot length of sub-frame of uplink to the GI of descending sub frame transfer point and descending sub frame to the sub-frame of uplink transfer point.

After execution of step 604, through going to step 601 after the default time interval, repeat above-mentioned flow process, this time interval can be set to zero.

If stipulate that first OFDM symbol of each CPE sub-frame of uplink must be synchronized with each other, then embodiment two determined silent periods are just identical with embodiment one determined silent period.

Below illustrate the beneficial effect that the present invention can bring.Suppose that a radius of society is 33 kilometers, the length of frame is 5ms.Time delay is approximately 0.22ms back and forth, and the overhead that is brought by GI approximately is 4.4%.In other words, about at least 4.4% system bandwidth can be used for channel monitoring.For the CPE of standby with can measure the CPE of other channel beyond self busy channel, asynchronous silent time that this is extra even allow these equipment sensings not by they self shared channel, this and the original only way of sensing channel comparison in service process, the system resource that is used for sensing channel obviously rises, and does not but increase overhead.Therefore, the inventive method can improve precision for sensing channel under the situation that does not increase overhead; When existing other business are seized channel suddenly, the system response ability also will improve in addition.

The above only is preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of being done within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims (8)

1, determines the method for asynchronous silent period in a kind of cognitive radio regional network WRAN system, it is characterized in that this method comprises the steps:

A, base station obtain that each is in the range information of the client device of active state with respect to base station itself in this sub-district;

B, base station calculate each client device and are used for determining autoprotection parameter at interval, and the parameter that calculates is sent to clients corresponding equipment according to the client range information that is obtained;

C, client device are determined the protection interval of self according to the parameter of receiving; and with the protection interval of sub-frame of uplink to the descending sub frame transfer point; or descending sub frame is to the protection of sub-frame of uplink transfer point at interval, or sub-frame of uplink to the protection of descending sub frame transfer point at interval with descending sub frame to the protection interval sum of sub-frame of uplink transfer point as asynchronous silent period.

2, method according to claim 1; it is characterized in that, described parameter comprise sub-frame of uplink to the protection of the transfer point of descending sub frame at interval the initial moment and duration and descending sub frame to the initial moment and duration at the protection interval of sub-frame of uplink transfer point.

3, method according to claim 1 and 2 is characterized in that, described step B falls into a trap to calculate and further comprises:

The time delay that B11, measuring-signal come and go to be propagated on this segment distance between client device and the base station according to measured time delay, determines that this client device is in the sub-frame of uplink protection initial moment and duration at interval to the transfer point of descending sub frame;

B12, according to the determined sub-frame of uplink of the step B11 protection initial moment and duration at interval to the transfer point of descending sub frame; and sub-frame of uplink to the protection of descending sub frame transfer point at interval and descending sub frame be the condition that the signal round-trip delay of cell edge is arrived in the base station to the total length at the protection interval of sub-frame of uplink transfer point, determine the initial moment and the duration of descending sub frame to the protection interval of sub-frame of uplink transfer point.

4, method according to claim 1 and 2 is characterized in that, calculates described in the step B further to comprise:

B21, measuring-signal come and go the time delay of propagating on this segment distance between client device and the base station, according to measured time delay, determine that this client device is in protection at interval the initial moment and the duration of sub-frame of uplink to the transfer point of descending sub frame;

B22, by optimized Algorithm, and, calculate the slot length of descending sub frame to the sub-frame of uplink transfer point according to the protection initial moment and the duration at interval that step B21 obtains;

Step C is: client device is according to transfer point protection at interval the initial moment and the duration of the sub-frame of uplink of receiving to descending sub frame; and the protection that descending sub frame is determined self to the slot length of sub-frame of uplink transfer point at interval, and protection that will be part or all of interval is as the asynchronous silent period of self.

5, method according to claim 4 is characterized in that, in the described calculating of step B, further comprises after described step B22:

B23, according to the slot length that step B22 obtains, calculate the number of OFDM symbol in the sub-frame of uplink, and the OFDM number of symbols that has more with respect to normal OFDM number of symbols of the OFDM number of symbols that obtains being calculated;

B24, choose sum smaller or equal to the OFDM symbol of the resultant OFDM number of symbols that has more of step B23;

Step C is: client device is according to transfer point protection at interval the initial moment and the duration of the sub-frame of uplink of receiving to descending sub frame; and the protection that descending sub frame is determined self to the slot length of sub-frame of uplink transfer point at interval, and shared time of the selected OFDM symbol of protection that will be part or all of interval and step B24 is as silent period.

6, method according to claim 5 is characterized in that, step B24 is described to be chosen for: from the sub-frame of uplink ending, choose the continuous OFDM symbol of sum smaller or equal to the resulting OFDM number of symbols that has more of step B23.

7, method according to claim 4 is characterized in that, the minimum slot length L that avoid occur inter-signal interference ISI of descending sub frame to the sub-frame of uplink transfer point is set, and described optimized Algorithm is:

A1, setting and base station distance are the slot length L1=L of the descending sub frame of 0 client CPE1 to the sub-frame of uplink transfer point;

B1, the sub-frame of uplink that the sub-frame of uplink of arbitrary client CPE2 in the sub-district is corresponding with CPE1 are made symbol level other are synchronous, and minimize L2 at the descending sub frame that satisfies CPE2 under the condition of the slot length L2 〉=L of sub-frame of uplink transfer point.

8, method according to claim 4 is characterized in that, the minimum slot length L that avoid occur ISI of descending sub frame to the sub-frame of uplink transfer point is set, and described optimized Algorithm is:

Arbitrary client CPEi in a2, the base station selected sub-district is provided with the slot length Li=L of the descending sub frame of CPEi to the sub-frame of uplink transfer point;

B2, corresponding with the CPEi respectively sub-frame of uplink of other clients CPEj sub-frame of uplink in the sub-district is carried out symbol level, and other is synchronous, and under the condition of the slot length Lj 〉=L of sub-frame of uplink transfer point, minimize Lj, and the summation of the Lj of interior all clients of calculation plot at the descending sub frame that satisfies CPEj;

All clients repeat above-mentioned a2～b2 in c2, the traversal sub-district, base station, find out wherein minimum summation;

The descending sub frame of d2, use each client in the minimum summation that finds is to the slot length of sub-frame of uplink transfer point.

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