CN101940019A

CN101940019A - Method for allocating bandwidth from radio frequency spectrum in cellular network including set of cells

Info

Publication number: CN101940019A
Application number: CN2009801043425A
Authority: CN
Inventors: 陶志峰; 张坤好; 张佑榕; 毛雪鸿
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2008-02-08
Filing date: 2009-01-28
Publication date: 2011-01-05
Also published as: KR20100113137A; EP2248367A1; WO2009099076A1; JP2010541300A

Abstract

A method allocates bandwidth from a radio frequency spectrum in a cellular network including a set of cells. Each cell includes a base station for serving a set of mobile stations in the cell. An area around each base station is partitioned into a center region and a boundary region. In each base station, bandwidth for use in the center region is reserved according to an inter-cell interference coordination (ICIC) protocol, and bandwidth for use in the boundary region is reserved according to the ICIC protocol and a base station cooperation (BSC) protocol. Then, the bandwidth is allocated to mobile stations as the mobile stations communicate with the base station in the center regions and the boundary regions according to the bandwidth reservations.

Description

In the cellular network that comprises one group of sub-district according to the method for radio-frequency spectrum allocations bandwidth

Technical field

The dynamic radio resource that present invention relates in general in the wireless cellular network distributes, and more specifically, relates to the minimizing presence of intercell interference.

Background technology

OFDMA

OFDM (OFDM:Orthogonal frequency-division multiplexing) is the modulation technique that some wireless networks use in physical layer (PHY:physical layer), for example, according to the network of well-known IEEE 802.11a/g and IEEE 802.16/16e standard design.OFDM (OFDMA:Orthogonal Frequency Division Multiple Access) is based on the multiple access access protocol of OFDM.In OFDMA, many groups of separation orthogonal sub-carriers (subchannel or frequency) and time slot are distributed to a plurality of transceivers or travelling carriage (MS:mobile station) by base station (BS:base station), thereby transceiver can be communicated by letter concomitantly.Because validity and the changeability of OFDMA in allocation of radio resources, it is adopted in such as the cellular network many of future generation based on the network of 3GPP Long Term Evolution (LTE) and IEEE 802.16m standard widely.

The OFDMA resource allocation

Radio frequency (RF:Radio frequency) comes beared information by the combination that changes wave amplitude, frequency and phase place in frequency band.Many governments come the use of control radio spectrum by Frequency Distribution.

As used herein with the definition, bandwidth is represented the part of radio spectrum.For example, IEEE802.11a uses the bandwidth in the 5GHz U-NII frequency band, and 8 not overlapping channels are provided, and 802.g uses the bandwidth in the 2.4GHz frequency band, and is similar with 802.11b, but the transmission plan based on OFDM among the 802.g is identical with 802.11a.IEEE 802.16a is corrected for 802.16 and use bandwidth in the 2-11GHz frequency band, to carry out multi-point, 802.16e use extendible OFDMA data, support 1.25MHz to the channel width between the 20MHz, can reach 2048 subcarriers, and 802.16m expection is operated on 20MHz or the higher RF bandwidth.

Bandwidth and time are two scarce resources in the radio communication, therefore need effective distribution method.Wireless application and user transceiver, that is, increasing rapidly of travelling carriage (MS) needs good RRM (the RRM:Radio resource management) method that can increase network capacity and reduce scheduling overhead.Therefore, significant at OFDMA exploitation efficient radio resource distributorship agreement for radio communication.

Main challenge is the bandwidth of distributing limited available RF spectrum in big geographic area at a large amount of transceiver (being also referred to as user, node or terminal).Usually, base station assigns resource.In other words, identical frequency spectrum can be used in a plurality of geographic areas or sub-district.When the transceiver in the adjacent cell or travelling carriage (MS) use identical frequency spectrum simultaneously, will cause presence of intercell interference (ICI:inter-cell interference) inevitably.In fact, ICI is proved to be the main performance limiting factor of wireless cellular network.

In order to make the spectrum efficiency maximization, in the OFDMA cell scheduling, use 1 as frequency duplex factor as one, that is, identical frequency spectrum is reused by BS and MS simultaneously.It's a pity that this spectral efficient causes ICI inevitably.Therefore, need good ICI management agreement.

At single subdistrict, most of traditional distribution methods are utilized different subchannels so that under the hypothesis of avoiding disturbing in the sub-district power or throughput are optimized at each MS.That is, all MS use disjoint subcarrier to send and received signal in the sub-district.Thereby, can not disturb.

Another important hypothesis in single local resource distributes is the signal to noise ratio (SNR:signal-to-noise ratio) that BS has obtained subchannel.In the down link from BS to MS (DL:downlink) channel, estimate SNR and this SNR is fed back to BS by MS usually.From the uplink channel of MS to BS, BS can be based on the signal direct estimation SNR that receives from BS.

Under many cell scenario, be difficult to obtain Signal Interference and Noise Ratio (SINR:signal-to-interference-and-noise ratio), can be because disturb from BS in a plurality of sub-districts and MS, and depend on multiple factor, such as, the distance of interference source (interferer), position and occupied channel status, and these factors were unknown before resource allocation.This causes with the interdependence of ICI and makes resource allocation problem complicated.Thereby, needing practical many local resources distribution method, it need not comprehensive, the perfect knowledge about SINR.

Inter-Cell Interference Coordination (ICIC)

Inter-Cell Interference Coordination (ICIC:inter-cell interference coordination) is in the zone away from BS relatively of sub-district,, can reduce the agreement of ICI effectively in the zone of cell boarder that is.By to the cell boarder of different cell association near MS distribute disjoint channel resource to realize ICIC.Because border MS is easy to occur high ICI most, so, by between the MS of border, coordinating channel allocation, can reduce total ICI significantly.More specifically, ICIC distributes identical resource to reduce the ICI interference by MS a good distance away on geography, thereby has reduced owing to disturb the path loss that causes.

Yet, purely based on the ICIC of the resource contention of avoiding border MS only for downlink communication provides limited performance gain, because it not have to consider owing in the interference that transmission caused of center of housing estate from BS to MS.

Space division multiple access inserts (SDMA)

Space division multiple access inserts (SDMA:space division multiple access) provides multiuser channel to insert by multiple-input and multiple-output (MIMO) technology that use has precoding and multi-subscriber dispatching.SDMA uses the spatial information of the MS position in the sub-district.Utilize SDMA, the radiation mode of signal is applicable to the highest gain of acquisition on specific direction.This often is called as beam shaping or beam steering.Beam shaping is the signal processing technology that is used for the transmission or the reception of phasing signal.The directivity that changes signal is disturbed in the beam shaping utilization.When sending, the phase place of beam-shaper control signal generates the pattern of growing interference and destructive interference mutually with relative amplitude.When receiving, will combine from the information of different antennae, so that can preferentially observe desired radiation mode.

Support the BS of SDMA to utilize identical resource to send signal simultaneously to a plurality of travelling carriages.SDMA can increase network capacity, because SDMA allows spatial reuse.Yet even use SDMA, ICI remains key issue.

Base station collaboration (BSC)

Base station collaboration (BSC:base station cooperation) allows a plurality of base stations to utilize beam shaping to send signal to single MS simultaneously, and shares identical resource, that is, and and time and frequency.

BSC is used for BS with the SDMA technology, so that send signal collaboratively to MS.BSC specifically is used for the border MS within the transmitting boundary of a plurality of BS.In the case, become the part of useful signal now from the interference signal of another BS.Thereby BSC has two advantages, and space diversity and ICI reduce.

The diversity group

Usually, each MS registers a BS who is called as grappling BS or serving BS broadcasts, and communicates by letter with this BS.Yet, in such as some situations of switching, the concurrent communication with a plurality of BS can take place.In IEEE 802.16e standard, define the diversity group and reached this purpose.Diversity group record grappling BS and the contiguous BS within the communication range of MS.The information of diversity group also obtains at the MS place safeguarding and upgrading.

Grand diversity is switched (MDHO)

During grand diversity was switched (MDHO:macro diversity handover), a plurality of base stations sent identical signal to a single MS who is switching in (HO) zone.Grand diversity increases the signal strength signal intensity that is received and reduces decline in the HO zone.When MS via the frontier district when a sub-district moves to another sub-district, use MDHO.By making BS make and to merge or the diversity merging at the execution RF of MS place, finish conversion from the down link (DL) of BS to MS thereby utilize to a plurality of copies that MS sends identical information.

From the up link (UL:uplink) of MS to BS, finish conversion by making the MS of two or more BS from the HO district receive same signal, thereby select diversity can use " the best " up link.Although use identical resource for the signal that duplicates,, MDHO can reduce ICI.That is, because MS uses from the resource more than a sub-district, so MDHO has wasted resource, otherwise these resources can be utilized by other MS.

Summary of the invention

Embodiments of the present invention provide a kind of and are used in the wireless network method of allocating resources, this method has been integrated the interference management agreement, that is, Inter-Cell Interference Coordination (ICIC:inter-cell interference coordination) and base station collaboration (BSC:base station cooperation).

Cell area is divided into center of housing estate district and cell boarder district.The center of housing estate district is near the base station, and the frontier district is away from the base station.The frontier district further is divided into one group of sector, for example, and three.Suppose that the base station knows the roughly geometry and the position of travelling carriage (MS) in the zone in this zone.

Reserve minimum bandwidth, be used for the allocated bandwidth of the MS in center of housing estate district and cell boarder district.Therefore, avoided consuming all bandwidth, and MS can be by unnecessarily refusal access.Definitely measuring certainly in practical design of the bandwidth of guaranteeing can adjust accordingly.

For the MS of center, use ICIC.For the MS of frontier district, support ICIC and these two kinds of interference management agreements of BSC.For ICIC distributes fixing bandwidth, and be that BSC distributes variable bandwidth.The changeability of BSC bandwidth can adapt to the variation of communication load, that is, and and the quantity of serviced MS.Alternatively, if needs are arranged, the BSC bandwidth can partly or wholly switch to the purposes of ICIC.

Yet, the adaptations of BSC bandwidth may cause in identical BSC the spectrum overlapping in the sector that can not relate to, thereby ICI takes place.Yet, because dividing, the sector in cell boarder district causes this influence minimum in this specific allocation protocol, wherein, the sector in described cell boarder district is divided and is isolated non-BSC cooperation sector.

Description of drawings

Figure 1A is the schematic diagram according to the allocation of radio resources agreement of embodiment of the present invention;

Figure 1B is according to the schematic diagram of embodiment of the present invention in the ICIC spectrum allocation may of adjacent cell realization;

Fig. 1 C is according to the schematic diagram of embodiment of the present invention in the BSC spectrum allocation may of adjacent cell realization;

Fig. 2 A is a schematic diagram of reusing design according to the bandwidth of embodiment of the present invention;

Fig. 2 B is a schematic diagram of reusing design according to the bandwidth of the alternative of embodiment of the present invention;

Fig. 2 C is a schematic diagram of reusing design according to the bandwidth of the alternative of embodiment of the present invention;

Fig. 3 is according to the schematic diagram of embodiment of the present invention at the cellular network with two travelling carriages and two base stations of ICIC situation;

Fig. 4 is according to the schematic diagram of embodiment of the present invention at the cellular network with two travelling carriages and two base stations of BSC agreement;

Fig. 5 is the schematic diagram of dividing according to the sub-district of embodiment of the present invention; And

Fig. 6 is the flow chart according to the resource allocation methods of embodiment of the present invention.

Embodiment

Resource allocation

Figure 1A illustrates the allocation of radio resources structure according to our working of an invention mode.Figure 1A illustrates seven sub-districts 100 of cellular network.For simplifying this figure, be illustrated in the zone of serving in each sub-district with hexagonal shape 100.It should be understood that this is the approximate of small area shape, for example, depend on landform in the sub-district, topological sum building (as, building), also can be other shape.

Approximate center in each sub-district has base station 110.The base station is travelling carriage (MS) 111 services in the sub-district.It should be understood that BS can utilize the trunk of infrastructure 400 or network to cooperate each other, As be well known in the art and shown in Figure 4.

The configuration of Figure 1A can extend to more than seven sub-districts.Here, frequency duplex factor as one is 1.That is, whole bandwidth of distributing to network are used in each sub-district.At sub-district 1 to 7, each cell area is divided into center of housing estate district (D) 101 and cell boarder district 102 geographically.

As defined herein, cell area is about whole sub-district, and the district then is to this dividing region.In the embodiment shown, cell area is divided into center and a plurality of cell boarders district, for example, and three cell boarder districts.Yet, it should be understood that it also can is other division.In this explanation, base station and travelling carriage in being effectively applied to distinguish at the multiple division of allocated bandwidth purpose.

Center of housing estate district 101 is farther from adjacent cell, thereby causes less presence of intercell interference (ICI) to the travelling carriage in the adjacent cell to the emission of the travelling carriage in center of housing estate district.On the contrary, cell boarder district 102 adjoins the frontier district of adjacent cell, thereby can cause and suffer stronger ICI to the emission of the travelling carriage of frontier district.

In other words, the resource allocation of (to travelling carriage) in the regulatory boundary zone more modestly is so that ICI reduces.By in conjunction with the plan of carrying out such as the ICI management agreement of ICIC or base station collaboration (BSC) at the frontier district, can reduce ICI.

Particularly, by (for example, A1, A2 and A3 in the adjacent cell frontier district; Or B1, B6 and B7; Or C1, C4 and C5) in distribute non-overlapped bandwidth resources to realize ICIC to travelling carriage.On behalf of non-overlapped allocated bandwidth, Figure 1B non-overlapped resource is shown with different hatch mark.

By contrast, by distributing identical bandwidth resources to realize BSC to being positioned at the travelling carriage adjacent cell frontier district and that relate to identical BSC operation.This is shown in Fig. 1 C.Notice that our allocation of radio resources agreement allows to use simultaneously ICIC and BSC management agreement.

Allocated bandwidth

Fig. 2 A to Fig. 2 C illustrates the example according to the BAP, Bandwidth Allocation Protocol of embodiment of the present invention.Also define as used herein, bandwidth is represented the part of radio spectrum.In these accompanying drawings, trunnion axis indication available bandwidth, and vertical axis indicating cell center (D) and frontier district (ABC).It should be understood that when we described allocated bandwidth for the district, the allocated bandwidth that we represent to reserve was to base station in each district and the communication between the travelling carriage.

At first, at planning period, the base station can communicate with one another, and determines their geographical relationship and different districts.The bandwidth reserved of determining at this programming phase can be subsequently enters at MS distributes to travelling carriage when withdrawing from different districts.

In each sub-district shown in Fig. 2 A, all the available network bandwidth is divided into two parts: first keeps for the travelling carriage in the center of housing estate 201, and second portion is kept for the travelling carriage in the cell boarder district 202.

This two-part ratio depends on communication load, and can dynamically adjust along with the variation of load.Here, we illustrate the equal bandwidth reserved to cell boarder district and center of housing estate district, make that this ratio is 1: 1.Center of housing estate is for all sub-district utilized bandwidth D.Suppose that center of housing estate separates geographically, make that ICI is not a problem.

Distribution to the travelling carriage in the cell boarder district in different districts zone designs through careful, to realize ICIC or to allow BSC that perhaps the two is all accomplished.

Shown in Fig. 2 A, we allow to use these two agreements to the allocated bandwidth in cell boarder district, that is, and and ICIC (fixing) 203 and BSC (variable) 204.

In Fig. 2 A, the travelling carriage in the district shown in the same row is assigned to identical bandwidth.In order to realize ICIC 203, the travelling carriage in the nearby sectors is assigned to disjoint frequency band, to reduce ICI.For example, district A1 (205), A2 (206) and A3 (207) are physically contiguous districts, and the travelling carriage in these districts is assigned to disjoint frequency band.This also is applicable to district B1, B6, B7 and C1, C4, C5.

In order to realize BSC 204, the travelling carriage in proximity, for example, A1 205, A2 206, A3 207 are assigned to identical bandwidth to allow the BSC agreement.

Shown in Fig. 2 A, in each different district, the size of assignable frequency band can dynamically adapt to communication load.Shown in Fig. 2 B, there be not communication load to use in the egregious cases of BSC, for example the travelling carriage in district A1 (251), A2 (252) and A3 (253) can be converted to ICIC and not influence other district from BSC.This changeability is very gratifying, because the BSC agreement needs a plurality of antennas, ICIC does not then need.Therefore, in this embodiment, ICIC can be considered as the main method of interference management, and BSC be considered as the less important method of interference management.

Fig. 2 C illustrates the another kind of possibility of distributing.With Fig. 2 A be not both ICIC allocated bandwidth to the cell boarder district.Particularly, at first with allocated bandwidth to the cell boarder district, make the sub-district (for example the sub-district 1,2 and 3) of any vicinity have disjoint bandwidth.By doing like this, have the most strongly disturbing travelling carriage (for example, the travelling carriage in district A1 271, A2 272, A3 273) and on disjoint frequency band, communicate by letter.Then, any remaining bandwidth is assigned to center of housing estate district (interior travelling carriage).

The ICIC situation

Fig. 3 illustrates the network that has two BS (301 and 302) and two MS (303 and 304) at the ICIC situation.In Fig. 3, a cell boarder MS 303 communicates by letter with its BS 301, and another cell boarder MS 304 communicates by letter with its BS 302.Because they are approaching, if MS 303 uses identical frequency band simultaneously with MS 304, then will cause disturbing 306 and 307.Therefore, the ICIC agreement is separated two interference signals on different frequency bands, be minimized thereby disturb.

The BSC situation

Fig. 4 illustrates the BSC situation with two MS and two BS.Under non-BSC situation, two cell boarder MS (403 and 404) communicate by letter with its BS (being respectively 401 and 402) individually.Utilize BSC, possible interference signal 405 to 408 becomes useful signal, thereby suppresses ICI by allowing MS side by side to communicate by letter with two BS.

As long as the base station has a plurality of antennas that can support the BSC operation, the network of two MS shown in Fig. 4, two BS may operate on identical time and frequency resource.

The single subdistrict subregion

Fig. 5 illustrates single subdistrict zone 501 and its center of housing estate district 502.The size impact in center of housing estate district 502 shown in Fig. 2 A center of housing estate district 201 and the allocated bandwidth between the cell boarder district 202.

Shown in Figure 1A, be distributed in the sub-district equably if MS is approximate, and each travelling carriage has similar communication load, and the bandwidth ratio (BR) of the center of housing estate district 502 and the whole network bandwidth and center 502 are proportional with the ratio of the size of cell area 501 so.R that some are exemplary and the value of a and resulting BR are listed in the table below among the A.

Table A

r/a	BR
		1/2	0.3023
2/3	0.5374
		3/4	0.6802
4/5	0.7739

The capacity gain that is used for the BSC of the MS in the cell boarder district increases along with the increase of r/a.Fig. 2 A, 2B and 2C use 0.5 BR, roughly equal 2/3 situation corresponding to r/a.

Fig. 6 is illustrated in the step of reserving and distributing the conventional method of bandwidth in the cellular network.

At programming phase, base station 601 utilizes infrastructure 605 to determine the topology of network.

Topology is divided 620 one-tenth zones at each base station, and each zone further is divided into center 621 and frontier district 622.The border can further be divided into one group of sector.

Reserve 630 bandwidth for use according to the ICIC agreement for each center, simultaneously, according to ICIC and BSC agreement, 640 bandwidth are reserved for use in the frontier district.For the bandwidth that ICIC reserves is fixed, and be that the bandwidth that BSC reserves is variable.

After having reserved bandwidth resources 645, when travelling carriage 602 enters the not same district of network, these bandwidth resources 645 can be distributed to travelling carriage 602.Reserved resource 645 can be dynamically updated 660 and redistribute, to adapt to the change to communication load and network topology.

Though the example by preferred implementation has been described the present invention,, should be understood that, can make various other changes and modification within the spirit and scope of the present invention.Therefore, the purpose of claims is to comprise that in real spirit and scope of the present invention all these classes change and modification.

Claims

1. one kind is used in the method for the cellular network that comprises one group of sub-district according to the radio-frequency spectrum allocations bandwidth, and wherein, each sub-district is included as one group of travelling carriage serving base station in this sub-district, and this method may further comprise the steps:

With the area dividing around each base station is center and frontier district;

Bandwidth reserved in each base station is used for distributing in described center according to the Inter-Cell Interference Coordination agreement;

Bandwidth reserved in each base station is used for distributing in described frontier district according to described Inter-Cell Interference Coordination agreement and base station collaboration agreement; And

When the described travelling carriage in the described center and the described travelling carriage in the described frontier district during, distribute the bandwidth of being reserved to described travelling carriage correspondingly with described base station communication.

2. method according to claim 1, wherein, the step of described division is utilized the infrastructure of described network.

3. method according to claim 1, wherein, for described center described bandwidth of reserving and the described bandwidth of reserving for the frontier district are disjoint.

4. method according to claim 1, wherein, the described bandwidth that is used for the described bandwidth of described Inter-Cell Interference Coordination agreement in described frontier district and is used for described base station collaboration agreement in the described frontier district of same sub-district is disjoint.

5. method according to claim 1, wherein, for the center of specific cell described bandwidth of reserving and the described bandwidth of reserving for the border of adjacent cell are disjoint.

6. method according to claim 1 wherein, is the described bandwidth reserved of described Inter-Cell Interference Coordination agreement in the described center of specific cell and be that the described bandwidth reserved of described Inter-Cell Interference Coordination agreement is overlapping in the described frontier district of adjacent cell.

7. method according to claim 1 wherein, is that the described bandwidth that described base station collaboration agreement is reserved also is used to described Inter-Cell Interference Coordination agreement in described frontier district.

8. method according to claim 1, this method is further comprising the steps of:

Each frontier district is divided into one group of sector, and described method is further comprising the steps of:

When described travelling carriage uses described Inter-Cell Interference Coordination agreement, for reserving and distribute disjoint bandwidth in frontier district contiguous in the different districts; And

When described travelling carriage uses described base station collaboration agreement, for reserving and distribute identical bandwidth in frontier district contiguous in the different districts.

9. method according to claim 8, wherein, for the described center of specific cell described bandwidth of reserving and the described bandwidth of reserving for described one group of sector of same sub-district are disjoint.

10. method according to claim 8 wherein, is the described bandwidth reserved of described Inter-Cell Interference Coordination agreement and described one group of sector at same sub-district is that the described bandwidth that described base station collaboration agreement is reserved is disjoint at described one group of sector.

11. method according to claim 8, wherein, for described center described bandwidth of reserving and the described bandwidth of reserving for the described one group of sector in the described frontier district of adjacent cell are disjoint.

12. method according to claim 8 wherein, is the described bandwidth reserved of described Inter-Cell Interference Coordination agreement in described center and be that the described bandwidth reserved of described Inter-Cell Interference Coordination agreement is overlapping in the described frontier district of adjacent cell.

13. method according to claim 8 wherein, is that the described bandwidth that described base station collaboration agreement is reserved also is used for described Inter-Cell Interference Coordination agreement at described one group of sector of described frontier district.

14. method according to claim 1 wherein, for the described bandwidth that described Inter-Cell Interference Coordination agreement is reserved is fixed, and is that the described bandwidth that described base station collaboration agreement is reserved is variable.

15. method according to claim 1, wherein, for described center described bandwidth of reserving and the ratio that is the described bandwidth of described frontier district reservation depend on communication load.

16. method according to claim 15, wherein, described ratio is dynamically adjusted along with the variation of communication load.

17. method according to claim 15, wherein, described ratio depends on the size of described center and described frontier district.

18. method according to claim 1, wherein, described travelling carriage moves between the described center of described one group of sub-district and described frontier district, and described distribution is dynamically upgraded.