CN104540146A - Base station moving track control method based on interference prediction in amorphous cell - Google Patents

Abstract

The invention discloses a base station moving track control method based on interference prediction in an amorphous cell. The method comprises the following steps that an amorphous cell model is created, and at the moment t, a mobile base station MBSi updates an interference region which possibly enters into other mobile base stations by predicting the position of the amorphous cell model at the moment t+T, and defines all mobile base stations in the interference region as an interference base station set Ii; channel rearrangement is carried out on the mobile base stations in the interference base station set Ii to coordinate and process an interference, and meanwhile the interference base station set Ii and the mobile base station MBSi accomplish the channel pre-allocation at the moment t+T for a short-hop link pre-allocation channel at the moment t; the cost of the mobile base station MBSi entering into the interference region is measured according to the change of the call drop rate of the mobile base stations in the interference base station set Ii at the predicted moment t+T; the movement of the mobile base station MBSi is controlled through moving track control strategy. The base station moving track control method based on the interference prediction in the amorphous cell can effectively reduce the possible of the serious performance degradation brought by channel collision in the process of node movement, and the communication serve quality of a mobile user can be guaranteed.

Description

Based on the base station movement method for controlling trajectory of interference prediction in amorphous community

Technical field

The invention belongs to wireless communication field, be specifically related to the base station movement method for controlling trajectory based on interference prediction in amorphous community.

Background technology

Amorphous community (Amorphous cells) technology is an important directions of LTE-Advanced follow-up developments, starts at 3Gpp the rudiment occurring correlation technique.Removable node is that the amorphous community object of feature is to change conventional cell solid shape, plays mobile cooperative node advantage, improves power system capacity, especially adapt to dynamic need and the unbalanced region flow distribution of data business volume, cut operating costs.Moveable low power nodes is supported in amorphous community, and the feature of mobile node is low-power, low antenna gain, low placement, little covering, and more flexible than macro station arrangement, cost is low.Multiple low power nodes can be arranged under a macro station, greatly strengthen covering, and data traffic can be unloaded to low power nodes from macro station, thus improve whole system capacity.But, increase low power nodes and also introduce between more node and disturb, comprise between macro station and low power nodes and low power nodes each other.Meanwhile, along with the introducing of mobile node, channel reuse pattern becomes on-fixed, the cell cluster of common-channel interference can change in time, mobile node also can produce mutual interference in moving process, these features make interference coordination in amorphous community be different from legacy cellular net, are new challenges.Therefore, need the mobility considering node, in conjunction with traditional disturbance coordination method, design the larger interference that effective scheme suppresses mobile node to produce in moving process.

Summary of the invention

The object of the present invention is to provide the base station movement method for controlling trajectory based on interference prediction in amorphous community, the method can effectively reduce the degradation of the performance that channel confliction brings in node motion process, ensures the telecommunication service quality of mobile subscriber.

In order to achieve the above object, the technical solution used in the present invention comprises the following steps:

1) utilize some mobile base stations and some mobile subscribers to build amorphous cell pattern, in amorphous cell pattern, between mobile base station and mobile subscriber, form short-hop link, between two mobile base stations, form backbone link;

2) at moment t, mobile base station MBS _iby predicting its position when moment t+T, to upgrade the interference region that may enter other mobile base stations, all mobile base stations producing this interference region are defined as interference base station collection I _i; Wherein, T is window detection time;

3) interference base station collection I _iin all mobile base stations carry out channel and rearrange, simultaneously according to the request of telex network, interference base station collection I _iwith mobile base station MBS _ibe short-hop link preassignment channel at moment t, to complete the channel preassignment of moment t+T;

4) according to interference base station collection I _imobile base station MBS is weighed in the change of the cutting off rate of prediction moment t+T in interior all mobile base stations _ienter the cost of this interference region; Then motion track control strategy is passed through to mobile base station MBS _imotion control;

Wherein, motion track control strategy is: if mobile base station MBS _ithe cost entering this interference region is greater than threshold gamma, and mobile base station MBS _ithe time adopting broken line motion to arrive required for its point of destination is less than time threshold, then as mobile base station due in t+T, and mobile base station MBS _idirection beyond interference region tangent line, avoids this interference region to mobile base station MBS _ipoint of destination motion; Otherwise, at moment t+T, mobile base station MBS _iadopt rectilinear motion to enter this interference region, and moment t can be used for the result of short-hop link preassignment channel; Wherein, call drop number comprises the call that handoff, channel confliction and user access obstruction first.

Described step 1) in short-hop link the condition that meets be: the distance between mobile base station and mobile subscriber is less than d; The channel multiplexing distance of short-hop link is α × d, α >1; α is the multiplexing factor of short-hop link.

Described step 1) in backbone link the condition that meets be: the distance between two mobile base stations is less than D; And distribute to other any communication for outside the region of channel β × D around two mobile base stations distributed between described two mobile base stations; Wherein, β >1; β is the multiplexing factor of backbone link.

Described step 1) in user in amorphous community meet following movement rule:

User stops and follows it and together moves in a mobile base station, when the time of staying arrives, judges whether the neighbor cell that there is this mobile base station; If have neighbor cell current, then user selects in neighbor cell mobile base station and moves, if in transition process, user is in communication, then a handoff occurs; If current without neighbor cell, then user continues to stay in former mobile base station.

Described step 3) for the method for short-hop link preassignment channel be: first, user calls out this mobile base station MBS _i, this mobile base station MBS _ichecking whether oneself currently exists available channel, if exist, is then short-hop link assignment channel; If do not exist, then mobile base station MBS _isend to neighbor base stations and borrow channel request; Secondly, this mobile base station MBS _ican by the channel set used according to the information calculating that neighbor base stations is replied, mobile base station MBS _ifrom being undertaken using by selecting the channel set used a channel and distribute to short-hop link; If mobile base station self does not exist available channel, and do not have in the feedack of neighbours mobile base station can by the channel used, then mobile base station MBS _ithe call request of refusal user.

In process for short-hop link preassignment channel, a channel can be lent multiple mobile base station with sending by means of channel request by neighbor base stations simultaneously.

Described step 3) for the concrete grammar of short-hop link preassignment channel be:

3-1) upgrade mobile base station MBS _iset of available channels Avai _i, mobile base station MBS _ito interference base station collection I _isend UPDATE signal, interference base station collection I _iin the current channel set B used of mobile base station feedback _j

${\mathrm{Avai}}_i={\mathrm{Allo}}_i-B_{i}U\left(\underset{j\∈I_i}{\mathrm{\Σ}}{B}_j\right)$

Allo _irepresent and distribute to mobile base station MBS _ichannel set;

B _jrepresent mobile base station MBS _jthe current channel set used;

B _irepresent mobile base station MBS _ithe current channel set used;

If 3-2) then mobile base station MBS _ifrom its set of available channels Avai _iin select a channel and distribute;

If then to interference base station collection I _iinterior all base stations send REQUEST signal and use channel;

3-3) interference base station collection I _iin all mobile base station feedback packet containing the feedback information of the channel set Allo distributed and the current channel set B used; Mobile base station MBS _ireceive the feedback information of all mobile base stations, then Allo is stored in Assign set, B is stored in Occupy set;

If 3-4) represent the idle channel that there is neighbor base stations at present and have, then from the idle channel that neighbor base stations has, select an idle channel distribute, meanwhile, this idle channel picked out is added to Allo respectively _iand B _i; Wherein, S represents Whole frequency band channel set;

If and represent that neighbor node exists and distribute to other mobile base stations but current still untapped channel, then from selecting a channel in Assign-Occupy and sending TRANSFER signaling to the mobile base station having this channel; This channel is deleted by the mobile base station receiving TRANSFER signaling from its Allo gathers; Meanwhile, mobile base station MBS _idistribute this channel, and it is added to Allo respectively _iand B _i, complete channel process; Wherein, S represents Whole frequency band channel set.

Described step 4) mobile base station MBS _ithe cost entering this interference region is:

Wherein, η _it () represents mobile base station MBS _iat the cutting off rate of moment t;

η _i' (t) represents mobile base station MBS _icutting off rate after prediction moment t+T enters interference region.

Described step 4) adopt broken line motion to arrive mobile base station MBS _ipoint of destination motion time required run duration adopt following formula to obtain:

${\mathrm{Tcir}}_i\left(t\right)=\frac{\left|\right|l_i^D-l_i(t+T)\left|\right|}{v}+t+T-T_i^S$

Wherein, Tcir _irepresent mobile base station MBS _iadopt the time required for its point of destination of broken line motion arrival at prediction moment t+T, and broken line motion meets:

$\left\{\begin{array}{c}{\∫}_{T_i^s}^{{\mathrm{Tcir}}_i}{v}_i\left(t\right)\·e^{{\mathrm{str}}_i}\mathrm{dt}=\left|\right|l_i^D-l_i^S\left|\right|\\ {\∫}_{T_i^s}^{{\mathrm{Tcir}}_i}{v}_i\left(t\right)\·e_{\⊥}^{{\mathrm{str}}_i}\mathrm{dt}=0\end{array}\right.$

represent mobile base station MBS _ipoint of destination position;

L _i(t+T) mobile base station MBS is represented _iin the position of moment t+T;

represent mobile base station MBS _ihomeposition coordinate;

V=||v _i(t) || represent mobile base station MBS _ivelocity v _ithe modulus value of (t);

T _i ^srepresent mobile base station MBS _iset out the moment;

V _it () represents mobile base station MBS _ispeed.

Compared with prior art, beneficial effect of the present invention is:

The present invention is by predicted interference, and in conjunction with channel pre-allocation process common-channel interference, calculation cost judges whether to perform base station TRAJECTORY CONTROL strategy.In simple terms, the cost caused by interference region that the present invention may be entered by prediction mobile base station, whether decision-making performs TRAJECTORY CONTROL strategy.When cost exceedes certain threshold value, scheme is passed through to select different directions, away from this interference region.That is this technical scheme is extended for cost with what arrive destination time to a certain extent.Simultaneously under not violating mobile subscriber group and arriving the time-constrain of destination, effectively reduce the degradation of the performance that channel confliction brings in node motion process, ensure the telecommunication service quality of mobile subscriber.In addition, the mobility channel multiplexing due to node in the amorphous community of the present invention becomes on-fixed, and the cell cluster of same channel interference can change in time, and based on these difference, the channel allocation algorithm in legacy cellular net will be no longer applicable.And due to the real-time movement of base station, therefore, the present invention not only needs to consider when channel allocation to avoid interference, and also needs to rearrange by channel the problem solving the serious mutual interference brought in the moving process of mobile base station.

Accompanying drawing explanation

Fig. 1 is amorphous cell topology schematic diagram;

Fig. 2 is backbone link and short-hop link link co-channel interference region schematic diagram;

Fig. 3 is interference prediction of the present invention and base station broken line motion schematic diagram;

Fig. 4 accesses blocking rate comparison diagram under different channels number first;

Fig. 5 is that cutting off rate comparison diagram is changed in the incision of different channels number;

Fig. 6 is that difference redistributes number of times comparison diagram to words rate lower channel;

Fig. 7 is the total cutting off rate comparison diagram of system under different thresholding.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further detailed explanation.

As shown in Figure 1, because mobile base station can change position at any time, also need to pass through wireless connections between itself and mobile services switching centre (mobile switch center, MSC).Come in the past few decades, the development of mobile base station network is subject to the restriction of high-speed radio back haul link.When introducing mobile base station, network is one and comprises mesh, the mixed structure of ad hoc and Cellular Networks, and the performance of system can be subject to unstable wireless backhaul capacity limit.Along with tactical information communication network (Tactical InformationCommunication Networks, TICNs) development, wireless backhaul, particularly microwave backhaul link has remarkable progress, so the present invention has realistic meaning for the research of amorphous community introducing mobile base station.

Therefore, first the present invention utilizes some mobile base stations and some mobile subscribers to build amorphous cell pattern; Introduce in conventional cellular cell by mobile base station (mobile base station, MBS), replace fixing macro station, whole network is connected by wireless link.Because base station has mobility, so each moment coverage dynamic change, becomes when from time dimension observation subdistrict topology being.Mobile base station is responsible for allocated channel and is avoided common-channel interference.Have N bar wireless channel in supposing the system, mobile base station has enough Power supplies to make them can with arbitrary neighbor base stations exchange message.Any MBS is by listening to beacon to identify neighbor node and then to identify rapidly the base station entering oneself neighbours region simultaneously.

See Fig. 2, distance between mobile base station and mobile subscriber is less than d, short-hop link could be formed between mobile base station and mobile subscriber in amorphous cell pattern, and, in order to avoid common-channel interference, the channel multiplexing distance of short-hop link is that α × d is (if that is a channel is used, in order to avoid common-channel interference, so identical channel can not use in the scope of this α × d simultaneously), α >1; α is the multiplexing factor of short-hop link.Because base station of the present invention has mobility, be no longer the wired connection in legacy cellular net between base station, but also need to be communicated by wireless, so the allocation of communications channel between also needing to mobile base station; Distance when between two mobile base stations is less than D, could form backbone link; Meanwhile, in order to avoid common-channel interference, distribute to other any communication for outside the region of channel β × D around two mobile base stations distributed between described two mobile base stations; Wherein, β >1; β is the multiplexing factor of backbone link; D, D, α and β depend on the network hardware, through-put power and fading characteristic etc.

The modeling of user mobility is according to as follows: user stops and follows it and together moves in a mobile base station, and the time of staying meets certain probability distribution, when the time of staying arrives, judges whether the neighbor cell that there is this mobile base station; If have neighbor cell current, then user selects in neighbor cell mobile base station and moves, if in transition process, user is in communication, then a handoff occurs; If current without neighbor cell, then user continues to stay in former mobile base station.

2) as shown in Figure 3, because amorphous cell topology is highly dynamic, so the challenge of the severe jamming that base station movement brings faced by needing, the present invention is directed to base station TRAJECTORY CONTROL strategy and combine consideration interference prediction, channel allocation, conflict cost and track regulate, and specifically can be divided into following step:

2-1) when the moment, t started, mobile base station MBS _iby predicting its position when moment t+T, to upgrade the interference region that may enter other base stations, all mobile base stations producing this interference region are defined as interference base station collection; Wherein, T is window detection time;

2-2) then according to the communication request of user, involved mobile base station is coordinated solving channel conflict and is completed the preassignment of t+T moment channel.

In amorphous community, due to the mobility of node, channel multiplexing becomes on-fixed, and the cell cluster of same channel interference can change in time, and based on these difference, the channel allocation algorithm in legacy cellular net will be no longer applicable.Meanwhile, due to the real-time movement of base station, the present invention not only needs to consider when channel allocation to avoid interference, and also needs the problem of the serious mutual interference brought in base station movement process.Common-channel interference can use glitch-free two mobile base stations of same channel initial, produces when to move to each other neighbouring.In this case, the channel confliction that the method that the present invention adopts channel to rearrange produces to avoid serious interference; The process that channel rearranges is: have at least a side to need to stop the communication of current conflict channel, again switch to other channel to avoid serious interference.Only can effective solving channel conflict when offered load is lower but existing channel rearranges scheme, in high load situations, major part channel is used, the probability that channel collides is very high, in this case, channel switching can bring higher cutting off rate frequently, larger access delay and heavier overhead; Therefore, the present invention adopts the movement locus that can regulate mobile base station in subsequent process.

Under the demand of extensibility and reliability, need in amorphous community by a distributed channel distribution mechanism to replace conventional central controller.Mobile base station by with neighbor base stations exchange message, determine the channel allocation situation of oneself service-user completely, main process comprises two parts:

Step1: local distribution: user calls out this mobile base station MBS _i, this mobile base station MBS _ichecking whether oneself currently exists available channel, if exist, is then short-hop link assignment channel; If do not exist, then mobile base station MBS _isend to neighbor base stations and borrow channel request;

Step2: channel: this mobile base station MBS _ithe information of replying according to neighbor base stations calculates can (idle frequency band such as do not had by all neighbor nodes or neighbor base stations have but currently not yet to use by the channel set used, the free channel of common-channel interference can not be caused, it selects a channel and distributes from this set), mobile base station MBS _ifrom being undertaken using by selecting the channel set used a channel and distribute to short-hop link; If mobile base station self does not exist available channel, and do not have in the feedack of neighbours mobile base station can by the channel used, then mobile base station MBS _ithe call request of refusal user.In addition, when not causing interference, in the process for short-hop link preassignment channel, a channel can be lent multiple mobile base station with sending by means of channel request by neighbor base stations simultaneously, can improve the availability of frequency spectrum further like this.Method for channel allocation of the present invention is adopted effectively to avoid common-channel interference and to improve the availability of frequency spectrum to greatest extent.

The method of above-mentioned channel allocation also can be changed and be done following step and state; Wherein, steps A) and the step1 of B) corresponding above-mentioned method for channel allocation, step C) and step D) step2 of corresponding above-mentioned method for channel allocation:

A) mobile base station MBS is upgraded _iset of available channels Avai _i, mobile base station MBS _ito interference base station collection I _isend UPDATE signal, interference base station collection I _iin the current channel set B used of mobile base station feedback _j

${\mathrm{Avai}}_i={\mathrm{Allo}}_i-B_{i}U\left(\underset{j\∈I_i}{\mathrm{\Σ}}{B}_j\right)$

Allo _irepresent and distribute to mobile base station MBS _ichannel set;

B _jrepresent mobile base station MBS _jthe current channel set used;

B _irepresent mobile base station MBS _ithe current channel set used;

B) if then mobile base station MBS _ifrom its set of available channels Avai _iin select a channel and distribute;

If then to interference base station collection I _iinterior all base stations send REQUEST signal and use channel;

C) interference base station collection I _iin all mobile base station feedback packet containing the feedback information of the channel set Allo distributed and the current channel set B used; Mobile base station MBS _ireceive the feedback information of all mobile base stations, then Allo is stored in Assign set, B is stored in Occupy set;

D) if represent the idle channel that there is neighbor base stations at present and have, then from the idle channel that neighbor base stations has, select an idle channel distribute, meanwhile, this idle channel picked out is added to Allo respectively _iand B _i; Wherein, S represents Whole frequency band channel set;

If and represent that neighbor node exists and distribute to other mobile base stations but current still untapped channel, then from selecting a channel in Assign-Occupy and sending TRANSFER signaling to the mobile base station having this channel; This channel is deleted by the mobile base station receiving TRANSFER signaling from its Allo gathers; Meanwhile, mobile base station MBS _idistribute this channel, and it is added to Allo respectively _iand B _i, complete channel process; Wherein, S represents Whole frequency band channel set.

2-3) mobile base station TRAJECTORY CONTROL:

After completing channel preassignment, calculate mobile base station MBS _icutting off rate η ' (t) after prediction moment t+T enters interference region, wherein, call drop number comprises the call that handoff, channel confliction and user access obstruction first.By mobile base station MBS _icutting off rate η ' (t) after prediction moment t+T enters interference region and mobile base station MBS _imobile base station MBS is obtained at cutting off rate η (t) of moment t _ienter the cost of this interference region (namely according to interference base station collection I _imobile base station MBS is weighed in the change of the cutting off rate of prediction moment t+T in interior all mobile base stations _ienter the cost of this interference region), according to interference base station collection I _imobile base station MBS is weighed in the change of the cutting off rate of prediction moment t+T in interior all mobile base stations _ienter the cost of this interference region.

In conjunction with some reality scenes, the movement of base station is modeled as: mobile base station lead served group mobile subscriber linearly constant airspeed to the motion of selected point of destination, if mobile base station MBS _ichange its direction by performing motion track control strategy, so subsequent time still needs to regulate direction, advances to destination with broken line, the mobile base station constant airspeed of this broken line motion, specifically:

For rectilinear movement: served group mobile subscriber is led linearly to the motion of selected point of destination in mobile base station, and base station constant airspeed, so this motion mode has the shortest time of advent, is defined as Tstr _i:

${\mathrm{Tstr}}_i=\frac{\left|\right|l_i^D-l_i^S\left|\right|}{v}$

Wherein, represent MBS _idestination locations, represent the position coordinates that sets out, v=||v _i(t) ||, be velocity v _it the modulus value of (), direction is θ _i(t).

${\mathrm{Tstr}}_i=\frac{\left|\right|l_i^D-l_i^S\left|\right|}{v}$

Wherein, mobile base station MBS _ipoint of destination position; represent mobile base station MBS _ihomeposition coordinate, v=||v _i(t) || represent mobile base station MBS _ivelocity v _it the modulus value of (), direction is θ _i(t).

So, mobile base station MBS _ican be calculated by following formula in the position of moment t+T:

l _i(t+T)＝l _i(t)+v _i(t)T

If MBS _ichange its direction by performing shift strategy, so subsequent time still needs to regulate direction, advances to destination with broken line, mobile base station MBS _ithe timing definition adopting broken line motion to arrive required for its point of destination at prediction moment t+T is Tcir _i(t):

${\mathrm{Tcir}}_i\left(t\right)=\frac{\left|\right|l_i^D-l_i(t+T)\left|\right|}{v}+t+T-T_i^S$

Wherein T _i ^srepresent MBS _iset out the moment.For mobile base station MBS _i, this modeling broken line motion must meet restrictive condition, and the broken line motion of this restrictive condition modeling in order to ensure can arrive point of destination:

$\left\{\begin{array}{c}{\∫}_{T_i^s}^{{\mathrm{Tcir}}_i}{v}_i\left(t\right)\·e^{{\mathrm{str}}_i}\mathrm{dt}=\left|\right|l_i^D-l_i^S\left|\right|\\ {\∫}_{T_i^s}^{{\mathrm{Tcir}}_i}{v}_i\left(t\right)\·e_{\⊥}^{{\mathrm{str}}_i}\mathrm{dt}=0\end{array}\right.$

Wherein, represent mobile base station MBS _ipoint of destination position;

L _i(t+T) mobile base station MBS is represented _iin the position of moment t+T;

represent mobile base station MBS _ihomeposition coordinate;

V=||v _i(t) || represent mobile base station MBS _ivelocity v _ithe modulus value of (t);

T _i ^srepresent mobile base station MBS _iset out the moment;

V _it () represents mobile base station MBS _ispeed.

Wherein, motion track control strategy meets following formula requirement:

$\left\{\begin{array}{c}\underset{j\&Element;I_i}{\mathrm{\&Sigma;}}({\mathrm{\&eta;}}_j^{\&prime;}\left(t\right)-{\mathrm{\&eta;}}_j\left(t\right))>\mathrm{\&gamma;},\\ {\mathrm{Tcir}}_i\left(t\right)/{\mathrm{Tstr}}_i<\mathrm{\&xi;},\end{array}\right.$

η _it () represents mobile base station MBS _iat the cutting off rate of moment t;

η _i' (t) represents mobile base station MBS _icutting off rate after prediction moment t+T enters interference region;

Tcir _it () represents mobile base station MBS _iadopt broken line motion to mobile base station MBS _ipoint of destination motion time required run duration;

γ is threshold value; ξ is time threshold;

That is: if mobile base station MBS _ithe cost entering this interference region is greater than threshold gamma, and mobile base station MBS _ithe time adopting broken line motion to arrive required for its point of destination is less than thresholding, then as mobile base station due in t+T, and mobile base station MBS _idirection beyond interference region tangent line, avoids this interference region to mobile base station MBS _ipoint of destination motion; Otherwise, at moment t+T, mobile base station MBS _iadopt rectilinear motion to enter this interference region, and moment t can be used for the result of short-hop link preassignment channel;

The arranging of γ with ξ of TRAJECTORY CONTROL strategy reacts different system requirements.Such as, when ξ value is enough high, that is we do not need the time restriction considering arrival destination, and so lower γ compares higher value can make the more easy execution in base station TRAJECTORY CONTROL strategy, effectively reduces channel confliction.But thresholding ξ when clamped, select lower γ can before not reaching time threshold frequently switching direction perform shift strategy, avoid interference, and after this, consider time restriction, even if interference implementation strategy can not avoid channel confliction very greatly, this may cause the decline of less desirable systematic function.Therefore need to find suitable threshold value to weigh cost and income.

Fig. 4 ~ 5 be system at different channels number cutting off rate along with system is to the change curve of words rate.Wherein, Fig. 4 accesses blocking rate comparison diagram under being specially different channels number first, and Fig. 5 is that cutting off rate comparison diagram is changed in the incision of different channels number; Emulation is carried out in the square area of 1500m × 1500m, and comprise 10 mobile base stations, time initial, each mobile base station serves 30 group mobile subscribers respectively, and the total family of system is with being 300.All move in all mobile base stations in this square area.When emulating initial, all mobile base stations are randomly dispersed in square area, when entering emulation, each base station is selected at random a bit as the point of destination of oneself in square mesh, and led cluster mobile subscriber is linearly towards its motion, subsequently, reselect new point of destination, and repeat above-mentioned motor pattern, until emulation terminates.In simulation process, mobile subscriber follows serving BS and together moves.In a base station, the time of staying is the exponential distribution of 15 minutes in accordance with average.Meanwhile, a duration of call obeys the exponential distribution that average is 2 minutes.To a given user, the time interval obeys index distribution of two continuous print communication request, is called words rate, and its average is change in simulations.

Emulation terminated after 100000 minutes.Two threshold gamma of TRAJECTORY CONTROL strategy execution condition and ξ value are 0.02 and 1.35.As shown in Figures 4 and 5, traversal call arrival rate, under different channels number, traditional channel redistributes algorithm with comparing in conjunction with the cutting off rate of mobile base station TRAJECTORY CONTROL algorithm after preassignment of proposing.Can find out, certain under words rate, number of available channels is more, and call drop number is lower.Meanwhile, the present invention compares traditional scheme and has lower cutting off rate, and reason is that this programme passes through to perform base station TRAJECTORY CONTROL strategy, and by selecting the suitable direction of motion, that avoids channel collision to bring to a certain extent has a strong impact on.Although can extend the time arriving point of destination, this is in the tolerance that systematic function promotes.

Fig. 6 redistributes number of times comparison diagram at heterogeneous networks to words rate lower channel.As seen from Figure 6, the channel of the scheme proposed redistributes number of times, and to compare traditional scheme low, and reason is that this programme passes through to perform base station TRAJECTORY CONTROL strategy, can avoid channel collision to a certain extent.On the other hand, when rate of arriving calls is lower, the current calling of system is relatively less, and channel collision is lower, therefore, needs again the number of switching channels lower.Along with the increase of rate of arriving calls, two short-hop links adopt identical channel probability greatly to increase, and therefore, channel rearranges number to be increased thereupon.Certain after words rate threshold value when being increased to, present reduction trend.This tendency may have two reasons: one is because higher under words rate, a lot of call when initial access owing to lacking channel and call drop, so leave the potential call that less needs rearrange.Another reason is, under words rate, the link that channel clashes is difficult to successfully find idle channel to switch higher, makes channel redistribute number of times reduction.

The impact of different thresholding on cutting off rate is discussed in the figure 7, shift strategy time threshold is set to ξ=1.25,1.35, traversal cutting off rate thresholding γ.Can find out: under any γ, higher time threshold is compared low threshold and is all had lower cutting off rate.This is because higher time threshold means that we have more chance to perform TRAJECTORY CONTROL strategy, the channel collision brought in moving process to avoid mobile base station.Simultaneously, when ξ=1.25, lower cutting off rate thresholding does not bring good system cutting off rate, reason may be that lower γ can cause in time threshold, perform shift strategy change direction frequently, and after this, even if interference is large again, this mobile base station, due to time restriction, also cannot avoid interference by switching direction.Therefore, under a set time thresholding, low γ can not bring better systematic function.When γ is increased to 0.08, in figure, system cutting off rate reaches minimum value, and after this, cutting off rate increases sharply, this is because thresholding increase makes the condition performing shift strategy be difficult to meet.

Claims (8)

1. in amorphous community based on the base station movement method for controlling trajectory of interference prediction, it is characterized in that, comprise the following steps:

1) utilize some mobile base stations and some mobile subscribers to build amorphous cell pattern, in amorphous cell pattern, between mobile base station and mobile subscriber, form short-hop link, between two mobile base stations, form backbone link;

2) at moment t, mobile base station MBS _iby predicting its position when moment t+T, to upgrade the interference region that may enter other mobile base stations, all mobile base stations producing this interference region are defined as interference base station collection I _i; Wherein, T is window detection time;

3) interference base station collection I _iin all mobile base stations carry out channel and rearrange, simultaneously according to the request of telex network, interference base station collection I _iwith mobile base station MBS _ibe short-hop link preassignment channel at moment t, to complete the channel preassignment of moment t+T;

4) according to interference base station collection I _imobile base station MBS is weighed in the change of the cutting off rate of prediction moment t+T in interior all mobile base stations _ienter the cost of this interference region; Then motion track control strategy is passed through to mobile base station MBS _imotion control;

Wherein, motion track control strategy is: if mobile base station MBS _ithe cost entering this interference region is greater than threshold gamma, and mobile base station MBS _ithe time adopting broken line motion to arrive required for its point of destination is less than time threshold, then as mobile base station due in t+T, and mobile base station MBS _idirection beyond interference region tangent line, avoids this interference region to mobile base station MBS _ipoint of destination motion; Otherwise, at moment t+T, mobile base station MBS _iadopt rectilinear motion to enter this interference region, and moment t can be used for the result of short-hop link preassignment channel; Wherein, call drop number comprises the call that handoff, channel confliction and user access obstruction first.

2. in amorphous community according to claim 1 based on the base station movement method for controlling trajectory of interference prediction, it is characterized in that, described step 1) in short-hop link the condition that meets be: the distance between mobile base station and mobile subscriber is less than d; The channel multiplexing distance of short-hop link is α × d, α >1; α is the multiplexing factor of short-hop link.

3. in amorphous community according to claim 1 and 2 based on the base station movement method for controlling trajectory of interference prediction, it is characterized in that: described step 1) in backbone link the condition that meets be: the distance between two mobile base stations is less than D; And distribute to other any communication for outside the region of channel β × D around two mobile base stations distributed between described two mobile base stations; Wherein, β >1; β is the multiplexing factor of backbone link.

4. in amorphous community according to claim 1 based on the base station movement method for controlling trajectory of interference prediction, it is characterized in that: described step 1) in user in amorphous community meet following movement rule:

User stops and follows it and together moves in a mobile base station, when the time of staying arrives, judges whether the neighbor cell that there is this mobile base station; If have neighbor cell current, then user selects in neighbor cell mobile base station and moves, if in transition process, user is in communication, then a handoff occurs; If current without neighbor cell, then user continues to stay in former mobile base station.

5. in amorphous community according to claim 1 based on the base station movement method for controlling trajectory of interference prediction, it is characterized in that: described step 3) for the method for short-hop link preassignment channel be: first, user calls out this mobile base station MBS _i, this mobile base station MBS _ichecking whether oneself currently exists available channel, if exist, is then short-hop link assignment channel; If do not exist, then mobile base station MBS _isend to neighbor base stations and borrow channel request; Secondly, this mobile base station MBS _ican by the channel set used according to the information calculating that neighbor base stations is replied, mobile base station MBS _ifrom being undertaken using by selecting the channel set used a channel and distribute to short-hop link; If mobile base station self does not exist available channel, and do not have in the feedack of neighbours mobile base station can by the channel used, then mobile base station MBS _ithe call request of refusal user.

6. in amorphous community according to claim 5 based on the base station movement method for controlling trajectory of interference prediction, it is characterized in that: in the process for short-hop link preassignment channel, a channel can be lent multiple mobile base station with sending by means of channel request by neighbor base stations simultaneously.

7. in amorphous community according to claim 5 based on the base station movement method for controlling trajectory of interference prediction, it is characterized in that, described step 3) for the concrete grammar of short-hop link preassignment channel be:

3-1) upgrade mobile base station MBS _iset of available channels Avai _i, mobile base station MBS _ito interference base station collection I _isend UPDATE signal, interference base station collection I _iin the current channel set B used of mobile base station feedback _j

${\mathrm{Avai}}_i={\mathrm{Allo}}_i-B_{i}U\left(\underset{j\&Element;I_i}{\mathrm{\&Sigma;}}{B}_j\right)$

Allo _irepresent and distribute to mobile base station MBS _ichannel set;

B _jrepresent mobile base station MBS _jthe current channel set used;

B _irepresent mobile base station MBS _ithe current channel set used;

If 3-2) then mobile base station MBS _ifrom its set of available channels Avai _iin select a channel and distribute;

If then to interference base station collection I _iinterior all base stations send REQUEST signal and use channel;

3-3) interference base station collection I _iin all mobile base station feedback packet containing the feedback information of the channel set Allo distributed and the current channel set B used; Mobile base station MBS _ireceive the feedback information of all mobile base stations, then Allo is stored in Assign set, B is stored in Occupy set;

If 3-4) represent the idle channel that there is neighbor base stations at present and have, then from the idle channel that neighbor base stations has, select an idle channel distribute, meanwhile, this idle channel picked out is added to Allo respectively _iand B _i; Wherein, S represents Whole frequency band channel set;

If and represent that neighbor node exists and distribute to other mobile base stations but current still untapped channel, then from selecting a channel in Assign-Occupy and sending TRANSFER signaling to the mobile base station having this channel; This channel is deleted by the mobile base station receiving TRANSFER signaling from its Allo gathers; Meanwhile, mobile base station MBS _idistribute this channel, and it is added to Allo respectively _iand B _i, complete channel process; Wherein, S represents Whole frequency band channel set.

8. in described amorphous community according to claim 1 based on the base station movement method for controlling trajectory of interference prediction, it is characterized in that, described step 4) mobile base station MBS _ithe cost entering this interference region is: $\underset{j\&Element;I_i}{\mathrm{\&Sigma;}}({\mathrm{\&eta;}}_j^{\&prime;}\left(t\right)-{\mathrm{\&eta;}}_j\left(t\right));$

Wherein, η _it () represents mobile base station MBS _iat the cutting off rate of moment t;

η _i' (t) represents mobile base station MBS _icutting off rate after prediction moment t+T enters interference region.

Described step 4) adopt broken line motion to arrive mobile base station MBS _ipoint of destination motion time required run duration adopt following formula to obtain:

${\mathrm{Tcir}}_i\left(t\right)=\frac{\left|\right|l_i^D-l_i(t+T)\left|\right|}{v}+t+T-{T_i}^S$

Wherein, Tcir _irepresent mobile base station MBS _iadopt the time required for its point of destination of broken line motion arrival at prediction moment t+T, and broken line motion meets:

$\left\{\begin{array}{c}{\&Integral;}_{T_i^s}^{{\mathrm{Tcir}}_i}{v}_i\left(t\right)\&CenterDot;e^{{\mathrm{str}}_i}\mathrm{dt}=\left|\right|l_i^D-l_i^S\left|\right|\\ {\&Integral;}_{T_i^s}^{{\mathrm{Tcir}}_i}{v}_i\left(t\right)\&CenterDot;e_{\&perp;}^{{\mathrm{str}}_i}\mathrm{dt}=0\end{array}\right.$

represent mobile base station MBS _ipoint of destination position;

L _i(t+T) mobile base station MBS is represented _iin the position of moment t+T;

represent mobile base station MBS _ihomeposition coordinate;

V=||v _i(t) || represent mobile base station MBS _ivelocity v _ithe modulus value of (t);

represent mobile base station MBS _iset out the moment;

V _it () represents mobile base station MBS _ispeed.