CN101605370A - WiMAX method for switching network based on power system capacity - Google Patents

Abstract

The WiMAX method for switching network based on power system capacity in a kind of radio network technique field comprises: the current maximum available capacity of calculation base station; The base station is by each neighbour's of neighbours' broadcast notice portable terminal current idle capacity; Use neighbours' broadcast effective idle capacity of current base station and adjacent base station to be dynamically updated portable terminal as carrier; When current base station and adjacent base station capacity satisfied handover triggering condition, portable terminal started sub-district scanning and switches; Portable terminal is according to decision strategy select target sub-district, sub-district and carry out the sub-district switching.Compared with prior art the present invention can improve the performance of handoffs of portable terminal in the WiMAX network, thereby improves the throughput of whole network, reduces packet loss.

Description

WiMAX method for switching network based on power system capacity

Technical field

What the present invention relates to is the method in a kind of radio network technique field, specifically is a kind of WiMAX method for switching network based on power system capacity.

Background technology

For the research of sub-district handover scheme in the WiMAX network, forefathers have done a large amount of work.Part work is that the sub-district handover scheme of other wireless networks (such as GSM) is applied to the WiMAX network; Some work is called queueing theory+resource reservation scheme, be that the base station keeps the sub-district switching that a part of bandwidth resources are used for terminal, can guarantee switching reject rate lower when switch the sub-district like this, suitably enlarge " handover region " of WiMAX network simultaneously, increase the queuing time of portable terminal, thereby reduce the outage that switches.

Find that through literature search P.Boone etc. have delivered " Strategies for fast scanning and handovers in WiMAX/802.16 " (strategy of searching for and switch fast) on 2008 " InternationalJournal of Communication Networks and Distributed Syste portable terminal " (the international periodical of communication network and distributed system) the 4/5/6th phase of first volume 414-432 page or leaf in WiMAX/802.16 to prior art.This article has proposed two kinds of strategies of search channel and switching, these two kinds of strategies all are based on the historical record of access base station before the portable terminal, the base station of inserting before promptly remembeing and the frequency range of access, the base station and the used frequency range that when needing switching cell, connected before preferential the trial.Its deficiency is, switches and do not mention for when beginning the sub-district.And traditional sub-district handover scheme has following several deficiency: switch according to only being signal strength signal intensity, this may be not enough in the WiMAX network; " ping-pong " and " switching pull(ing) effect ", " ping-pong " are meant that portable terminal switches back and forth two close minizones, and " switching pull(ing) effect " is meant that a lot of portable terminals almost switch simultaneously and enters a sub-district and cause subzone network congested.

Summary of the invention

The present invention is directed to the prior art above shortcomings, a kind of WiMAX method for switching network based on power system capacity is provided, the trigger condition that is proposed among the present invention triggers switching, and with signal power, effectively parameter such as idle capacity is selected as switching input, dynamically switch at last, improve the throughput of whole network, reduce packet loss.

The present invention is achieved by the following technical solutions:

The present invention keeps classical signal quality (RSSI received signal intensity) measured value simultaneously by introducing the base station idle capacity as an important handover measurement value; At the WiMAX physical layer specification, according to the base station available capacity, by current actual flow statistical system idle capacity.Then, by using neighbours' broadcast technology of backbone network base station synchronization and 802.16e standard, portable terminal (mobile subscriber's node) periodically obtains the synchronization message and the idle capacity measured value of current area and neighbor cell.

The present invention includes following steps:

Step 1: the current maximum available capacity of calculation base station: at first add up current idle capacity by current actual flow, obtain the effective idle capacity of current maximum according to statistics then, when current effective idle capacity of base station is lower than mobile phone users demand data flow, and exists to trigger under the situation of at least one neighbours' idle district and switch and carried out for second step.

Described current maximum available capacity is meant: the bandwidth C of transmitting user data between WiMAX base station and the portable terminal _EffectiveAs follows:

$C_{\mathrm{effective}}=\frac{(N_{\mathrm{symbol}}-N_{\mathrm{symbol}\_\mathrm{overhead}})\×N_{\mathrm{bpsymbol}}}{T_{\mathrm{frame}}},$

N _symbol＝T _frame/T _symbol，

Wherein: N _BpsymbolRepresent every symbol significant bit number, T _Symbol, T _FrameRepresent symbol duration and frame length respectively, N _{Symbol_overhead}The expression expense takies symbolic number.

Described every symbol significant bit number is specific as follows:

N _bpsymbol＝(192×Coding_rate×Coding_Efficiency)-8

Wherein: Coding_rate presentation code rate, Coding_Efficiency presentation code efficient.

Described current effective idle capacity is meant: C _Idle=C _Effective-S _Throughput, S wherein _ThroughputIt is the current data flow information that statistics obtains.

Step 2: the base station is by each neighbour's of neighbours' broadcast notice portable terminal current idle capacity; Use neighbours' broadcast effective idle capacity of current base station and adjacent base station to be dynamically updated portable terminal as carrier.

Step 3: when current base station and adjacent base station capacity satisfied handover triggering condition, portable terminal started sub-district scanning and switches;

The scanning switching of described sub-district is meant:

1) triggering cell switches to a chance event under the above-mentioned condition satisfying to establish current mobile terminal, and then the probability that takes place of this chance event should be less than p _Switch, when k constantly satisfies handover triggering condition simultaneously, p is only arranged as n portable terminal _Switch* n portable terminal can trigger base station scans and follow-up handoff procedure.

When following three conditions that 2) and if only if were met, portable terminal triggered base station scans and handoff procedure:

A) C _Idle(current BS)＜MS user's request flow;

b)

C _Idle(BS _k)＞α * MS user's request flow (α 〉=1);

C) P{ triggering cell handover event=true }＜p _Switch(0≤p _Switch≤ 1);

Condition a has defined effective idle capacity minimum threshold of Current Serving BTS, and promptly condition a sets up when the mobile phone users demand volume can't be met.

Condition b avoids portable terminal to do the stricter constraints of invalid base station scans under known adjacent base station can't provide abundant idle capacity situation.Wherein α is an assurance coefficient, and only portable terminal might triggering cell switch when existing adjacent base station that α times user's request flow is provided.

Condition c is described overall controlled condition, is used to regulate portable terminal at each minizone switching frequency.p _SwitchThe portable terminal of representing satisfy condition an a and a condition b triggers the handoff procedure probability.

Step 4: portable terminal is according to the select target sub-district and carry out the sub-district switching.

Described select target sub-district is meant: business demand and the SOT state of termination condition of utilizing network state, user, mobile phone users is linked into the cost that Target cell will pay at current time measures, the cost function expression formula of broad sense is generally as follows:

$D_k=\underset{i=1}{\overset{M}{\mathrm{\Σ}}}{w}_i\×{\cos t}_{i,k}---\left(11\right)$

Wherein: D _kThe expression portable terminal is linked into total cost that Target cell k will pay, and promptly inserts cost, cost _{I, k}Be filial generation valency, w _iBe weight coefficient, M is a policing parameter.

Described policing parameter M is meant: if be cost by i the filial generation valency that policing parameter determined _{I, k}, corresponding with it weight factor is w _iZong then cost is exactly the weighted sum of this M sub-cost.

Described weight factor comprises: base station idle capacity and signal power.

Compared with prior art the present invention can improve the performance of handoffs of portable terminal in the WiMAX network, thereby improves the throughput of whole network, reduces packet loss.

Description of drawings

Fig. 1 is typical 802.16 OFDM frame structures.

Fig. 2 is an adjacent base station idle capacity broadcasting schematic diagram in the New Scheme.

Fig. 3 is the simulating scenes setting of WiMAX sub-district handover scheme.

Fig. 4 is a WiMAX base station saturated capacity simulation result.

Fig. 5 is that effective overall throughput of three kinds of handover schemes changes in time.

Fig. 6 is that the packet loss variation that causes is switched in the sub-district under three kinds of handover schemes.

Fig. 7 is different p _SwitchEffective overall throughput of value changes in time.

Fig. 8 is different p _SwitchThe sub-district of value is switched the packet loss that causes and is changed.

Embodiment

Below embodiments of the invention are elaborated, present embodiment is being to implement under the prerequisite with the technical solution of the present invention, provided detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

Present embodiment is realized by following steps:

Step 1: the current maximum available capacity of calculation base station: at first add up current idle capacity by current actual flow, obtain the effective idle capacity of current maximum according to statistics then, when current effective idle capacity of base station is lower than mobile phone users demand data flow, and exists to trigger under the situation of at least one neighbours' idle district and switch and carried out for second step.

Described current maximum available capacity is meant: the bandwidth of transmitting user data between WiMAX base station and the portable terminal.

As shown in Figure 1, be typical 802.16 OFDM frame structures, comprise a downlink subframe (DLsubframe) and a uplink sub-frames (UL subframe), wherein Preamble is the preamble head, be used for realizing physical layer synchronization, FCH is a frame control head, and DL-MAP is that down link is described, UL-MAP is that up link is described, and is thereafter the bursty data piece of several downlink link.It between downlink subframe and uplink sub-frames transmission transition time slot (TTG).The beginning of uplink sub-frames for range finding competition slot (contention slot for initial ranging) and bandwidth request competition slot (contention slotfor BW requests), is thereafter the bursty data piece of several subscriber stations partly.The uplink sub-frames end is a reception/transmission transition time slot (RTG).Wherein overhead part italics mark comprises preamble head (Preamble), frame control head (FCH), range finding (Ranging) competition slot and bandwidth (BW) application competition slot.

At first calculate the total symbolic number N in the single OFDM frame _Symbol:

T _symbol＝(N _FFT/f _s)×(1+G)????(1)

N _symbol＝T _frame/T _symbol??????(2)

Wherein: N _FFTBe sub-carrier number, f _sBe decimation factor, G is the cyclic prefix CP ratio.T _Symbol, T _FrameRepresent symbol duration and frame length respectively.

The expense of removing as shown in fig. 1 from total symbolic number takies symbol then.802.16d Preamble in the regulation descending sub frame in the standard, FCH adds up to about 3 symbols.The Ranging competition slot is made of at interval the round-trip delay of long preamble head, 2 symbol RNG-REQ (distance measurement request) message and 3 symbols of 2 symbols in the sub-frame of uplink, and BW contention request subsequently is about 2 symbols.Should remove 1 symbol gap that TTG and RTG occupy simultaneously.The length that uplink downlink is described DL-MAP and UL-MAP depends on base station number of connected mobile terminals amount, long (the 64+32*n)/N of DL-MAP _Bpsymbol, long (the 56+48*n)/N of UL-MAP _Bpsymbol, wherein n represents to connect portable terminal quantity, N _BpsymbolRepresent every symbol significant bit number.

To sum up can get expense and take symbolic number N _{Symbol_overhead}:

$N_{\mathrm{symbol}\_\mathrm{overhead}}=13+\frac{120+80\×n}{N_{\mathrm{bpsymbol}}}---\left(3\right)$

Potential in addition overhead comprises MAC PDU encapsulation overhead and periodicity DCD/UCD broadcast.Because these expense generating periods are long or occupied bandwidth is less relatively so ignore.

Calculate every symbol significant bit at last and count N _BpsymbolAnd push away the maximum available capacity C of WiMAX base station _Effective:

N _bpsymbol＝(192×Coding_rate×Coding_Efficiency)-8????(4)

$C_{\mathrm{effective}}=\frac{(N_{\mathrm{symbol}}-N_{\mathrm{symbol}\_\mathrm{overhead}})\×N_{\mathrm{bpsymbol}}}{T_{\mathrm{frame}}}---\left(5\right)$

Coding_rate presentation code rate wherein, Coding_Efficiency presentation code efficient.

In a common 5MHz bandwidth WiMAX PMP network environment, OFDM frame length 4 portable terminals, coded system is 16QAM 3/4, supposes only to have the WiMAX base station to send downlink data to 20 portable terminals, can get according to formula (1)-(5)

N _symbol＝90?????????????(6)

N _{symbol_overhead}＝16????(7)

N _bpsymbol＝578??????????(8)

And estimate the maximum available capacity in base station thus and be:

C _effecitve＝10.198Mbps??(9)

Described current effective idle capacity is meant: C _Idle=C _Effective-S _Throughput, wherein: S _ThroughputIt is the current data flow information that statistics obtains.

Step 2: the base station is by each neighbour's of neighbours' broadcast notice portable terminal current idle capacity; Use neighbours' broadcast effective idle capacity of current base station and adjacent base station to be dynamically updated portable terminal as carrier.

As shown in Figure 2, backbone network is passed through periodically with its effective idle capacity C in each WiMAX base station in the present embodiment _IdleAnd DCD/UCD (descending/the up link descriptor) synchronization message is broadcast to adjacent base station.The own adjacent bast station list of each WiMAX base station stored wherein.Receiving after all current effective idle capacities from adjacent base station upgrade, each base station together is broadcast to portable terminal in the coverage by neighbours' broadcast MOB_NBR_ADV with effective idle capacity of self and all adjacent base stations and DCD/UCD information.

Step 3: current base station and adjacent base station capacity move little domain scanning of starting terminal and switching when satisfying handover triggering condition

By neighbours' broadcasting of effective idle capacity, portable terminal is known current and capacity load situation adjacent base station.The described handover triggering condition of present embodiment regulation is as follows: if the effective idle capacity of current base station is lower than mobile phone users demand data flow, promptly the base station produces system congestion, and exists to trigger under the situation of at least one neighbours' idle district and switch.

In order to eliminate " ping-pong " and " switching pull(ing) effect " as far as possible, present embodiment and prior art another different be exactly the overall switching probability parameter p of introducing an originality _Switch, in order to control the frequency of portable terminal switching cell on a macro scale, concrete sub-district scanning switch step comprises:

1) triggering cell switches to a chance event under the above-mentioned condition satisfying to establish current mobile terminal, and then the probability that takes place of this chance event should be less than p _Switch, when k constantly satisfies handover triggering condition simultaneously, p is only arranged as n portable terminal _Switch* n portable terminal can trigger base station scans and follow-up handoff procedure.

When following three conditions that 2) and if only if were met, portable terminal triggered base station scans and handoff procedure:

A) C _Idle(current BS)＜MS user's request flow;

b)

C _Idle(BS _k)＞α * MS user's request flow (α 〉=1);

C) P{ triggering cell handover event=true }＜p _Switch(0≤p _Switch≤ 1);

Condition a has defined effective idle capacity minimum threshold of Current Serving BTS, and promptly condition a sets up when the mobile phone users demand volume can't be met.

Condition b avoids portable terminal to do the stricter constraints of invalid base station scans under known adjacent base station can't provide abundant idle capacity situation.Wherein α is an assurance coefficient, and only portable terminal might triggering cell switch when existing adjacent base station that α times user's request flow is provided.Factor alpha should be got enough big according to network condition, guarantees that the target adjacent base station can provide abundant idle capacity in a period of time, with compensation because the packet loss loss that causes is switched in base station scans and sub-district.

Condition c is described overall controlled condition, is used to regulate portable terminal at each minizone switching frequency.p _SwitchThe portable terminal of representing satisfy condition an a and a condition b triggers the handoff procedure probability.Work as p _SwitchWhen value was big, the frequent switching cell of portable terminal can make the overweight sub-district of network load be eased very soon like this, but it is congested to cause certain idle district to produce rapidly simultaneously, i.e. " switching pull(ing) effect ", too high in addition p _SwitchValue can produce higher sub-district and switch packet loss; Otherwise, work as p _SwitchValue hour because the portable terminal switching frequency reduces, is switched the packet loss expense that produces by the sub-district and is descended, and can effectively reduce " ping-pong " and " switching pull(ing) effect ", but p _SwitchValue is too small to cause between adjacent cell flow equalization slack-off easily.

Step 4: portable terminal is according to decision strategy select target sub-district, sub-district and carry out the sub-district switching.

After handover triggering condition satisfied, all can connect adjacent base station as candidate base station mobile scanning terminal, and used the Target cell decision strategy to make decision and stay former sub-district or switch to new target cell.The algorithm that the target switching cell is selected has adopted the comprehensive strategic algorithm based on cost function, utilize conditions such as network state, user's business demand and SOT state of termination, mobile phone users is linked into the cost that Target cell will pay at current time measures, the cost function expression formula of broad sense is generally as follows:

$D_k=\underset{i=1}{\overset{M}{\mathrm{\Σ}}}{w}_i\×{\cos t}_{i,k}---\left(11\right)$

Wherein: D _kThe expression portable terminal is linked into total cost that Target cell k will pay, and promptly inserts cost.Cost _{I, k}Be i the filial generation valency that policing parameter determined, w _iBe corresponding weight factor with it.

In the present embodiment, two factors are depended in the selection of Target cell: base station idle capacity and signal power, wherein the base station idle capacity is notified portable terminal by neighbours' broadcast, and signal power strength RSSI is recorded when scanning can connect adjacent base station by portable terminal.By weighting these two factors are formed the decision making algorithm function:

Wherein: P _SignalThe expression signal strength signal intensity.

In formula (12), w ₁And w ₂It is respectively the weight coefficient of candidate base station idle capacity and signal power.According to the decision making algorithm function, portable terminal is chosen D _kThe BS that value is maximum _kSwitch as target BS.

Present embodiment uses the NS-2 network simulator, 802.16 and the mobility protocol support module that utilize NIST to provide, the relevant handover trigger of base station and SS scheduler is judged flow process in the modification source code, and neighbours' broadcast expanded, realized that the WiMAX network that proposes improves the sub-district handover scheme.

The simulating scenes setting of present embodiment WiMAX sub-district handover scheme as shown in Figure 3, simulating area is covered by 4 WiMAX base stations, be respectively WiMAX base station 0, WiMAX base station 1, WiMAX base station 2 and WiMAX base station 3, wherein WiMAX base station 0 is placed in the middle, WiMAX base station 1, WiMAX base station 2 and WiMAX base station 3 are placed in around the WiMAX base station 0, be equilateral triangle, and part is arranged in abutting connection with the overlay area with WiMAX base station 0, to allow the portable terminal autonomous switching cell under the capacity saturated conditions of base station in this zone.60 portable terminals are initial random to be dispersed in 0 overlay area, WiMAX base station and to move at random to complete area during emulation.For the reduced data discharge model, set the fixed bit rate UDP video flowing that each portable terminal demand bandwidth is 0.5Mbps.Shown in the major parameter table 1 of simulating scenes.

Table 1 simulating scenes major parameter

Parameter	Value
		Frequency bandwidth	????5MHz

Mode	????Two?Ray?Ground
		Modulating mode	????16QAM?3/4
The base station covering radius	????1000m
		The received power minimum threshold	????1.27e-13
The OFDM frame length	4 portable terminals
		Antenna model	????Omni?antenna
Contention window size	????5
		Link Going Down coefficient	????1.2
Simulation time	????50s
		Base station number	????4
Portable terminal quantity	????60
		Portable terminal demand data stream	????0.5Mbps

1) base station available capacity estimation simulation result

In order to ensure the accuracy of estimating about WiMAX system available capacity in the New Scheme system model, at first the available capacity computing formula is verified by simulation result.According in the first step for the reckoning of WiMAX base station available capacity, in common 5MHz bandwidth WiMAX PMP network environment, if OFDM frame length 4 portable terminals, coded system is 16QAM 3/4, can estimate to such an extent that the maximum available capacity in base station is:

C _effective＝10.198Mbps????(13)

In NS-2, used the OFDM parameter identical with theoretical calculate, by in single WiMAX base station, dropping into increasing portable terminal (each portable terminal demand data stream is 0.5Mbps) system is reached capacity, and the saturated capacity of register system, the result is as shown in Figure 4.

As can be seen from Figure 4, along with the increase of portable terminal quantity in the sub-district, the WiMAX base station capacity that progressively reaches capacity.The actual maximum saturation capacity that obtains by emulation is 10.132Mbps, with theoretical value maximum 10.198Mbps basically identical.The WiMAX base station saturated capacity that can also observe the emulation from Fig. 4 is lower than theoretical maximum all the time, this trickle difference wherein is by due to some OFDM frame overheads of abridged in the theoretical derivation, for example: MAC PDU encapsulation overhead, padding expense or periodic system broadcast message.

2) overall switching probability parameter p _SwitchInfluence to systematic function

Then use different p _SwitchValue is carried out the simulation result contrast.p _SwitchValue is as follows: p _Switch=0.2,0.5,0.8}.Fig. 7 has showed respectively at different p with Fig. 8 _SwitchEffectively overall throughput over time and because the packet loss variation that causes is switched in the sub-district under the value.

Work as p _SwitchWhen=0.8 value was big, portable terminal frequently switched at each adjacent cell, and the network in general throughput reaches maximum rapidly, and follows some throughput fluctuations (as shown in Figure 7) in transition state.Work as p _Switch=0.5 and 0.2 o'clock, the overall system throughput rises stable but speed is slowed down to some extent.And, adopt the big p of value as the cost that throughput of system rises _SwitchThe time frequent sub-district switch and cause the mass data packet loss, and might cause a large amount of portable terminals to switch to an idle Target cell simultaneously causing congested " switching pull(ing) effect " problem of Target cell.As shown in Figure 8, p during system's transition state _SwitchThe curve of=0.8 correspondence produces instantaneous high packet loss peak value, and this also means the decline that causes QoS of customer QoS; Opposite smaller p _SwitchCan not cause the mass data packet loss that happens suddenly.Generally speaking, by adjusting suitable p _SwitchValue can reach the balance between network traffics optimal speed and the minimum data packet loss.

Compared with prior art, present embodiment has following beneficial effect:

The described improvement of present embodiment sub-district handover scheme is compared with general handover scheme with quick handover scheme, and systematic function is increased dramatically.As shown in Figure 5, present embodiment reached the overall throughput near 30Mbps after 15 seconds, meaning provides in the network the required total data flow of portable terminal substantially in the base station (portable terminal has add up to 60 in the network, the UDP video data stream of each mobile terminal request 0.5Mbps, total flow=60x0.5Mbps=30Mbps).Make discovery from observation 9 seconds to 15 seconds for system is in transition state, a large amount of initial portable terminals that connect base station 0 in this section period because the congested adjacent cell that switches to of base station 0 cell flow.And the WiMAX network of quick handover scheme and conventional cell handover scheme is not owing to use available capacity to estimate and the capacity broadcast technology, portable terminal is switching cell when being in the current base station coverage edge only, effectively overall throughput reached 17Mbps after 33 seconds under same simulating scenes, produced poor-performing under the congestion situation at network.

The described improvement of present embodiment sub-district handover scheme, discovery improves algorithm in 9 seconds to 18 seconds time period data packet loss is higher than the quick handoff algorithms of 802.16g, and this is owing to initiatively be transferred to the switching packet loss that adjacent cell causes at a large amount of portable terminals of system's transition state stage that improve algorithm owing to small area jam; After 20 seconds, system is in stable, improves the algorithm and the packet loss basically identical of handoff algorithms fast, this be since behind the system stability WiMAX network no longer exist congestedly, improve algorithm portable terminal down only owing to self move and cause the sub-district switching.

Claims (9)

1, a kind of WiMAX method for switching network based on power system capacity is characterized in that, by introducing the base station idle capacity as an important handover measurement value, keeps the signal quality measured values of RSSI received signal intensity simultaneously; At the WiMAX physical layer specification, according to the base station available capacity, by current actual flow statistical system idle capacity; Then, by using neighbours' broadcast technology of backbone network base station synchronization and 802.16e standard, mobile terminal period obtains the synchronization message and the idle capacity measured value of current area and neighbor cell.

2, the WiMAX method for switching network based on power system capacity according to claim 1 is characterized in that, may further comprise the steps:

Step 1: the current maximum available capacity of calculation base station: at first add up current idle capacity by current actual flow, obtain the effective idle capacity of current maximum according to statistics then, when current effective idle capacity of base station is lower than mobile phone users demand data flow, and exists to trigger under the situation of at least one neighbours' idle district and switch and carried out for second step;

Step 2: the base station is by each neighbour's of neighbours' broadcast notice portable terminal current idle capacity; Use neighbours' broadcast effective idle capacity of current base station and adjacent base station to be dynamically updated portable terminal as carrier;

Step 3: when current base station and adjacent base station capacity satisfied handover triggering condition, portable terminal started sub-district scanning and switches;

Step 4: portable terminal is according to decision strategy select target sub-district, sub-district and carry out the sub-district switching.

3, the WiMAX method for switching network based on power system capacity according to claim 1 is characterized in that, described current maximum available capacity is meant: the bandwidth C of transmitting user data between WiMAX base station and the portable terminal _EffectiveAs follows:

$C_{\mathrm{effective}}=\frac{(N_{\mathrm{symbol}}-N_{\mathrm{symbol}\_\mathrm{overhead}})\×N_{\mathrm{bpsymbol}}}{T_{\mathrm{frame}}},$

N _symbol＝T _frame/T _symbol，

Wherein: N _BpsymbolRepresent every symbol significant bit number, T _Symbol, T _FrameRepresent symbol duration and frame length respectively, N _{Symbol_overhead}The expression expense takies symbolic number.

4, the WiMAX method for switching network based on power system capacity according to claim 3 is characterized in that, described every symbol significant bit number is specific as follows:

N _bpsymbol＝(192×Coding_rate×Coding_Efficiency)-8，

Wherein: Coding_rate presentation code rate, Coding_Efficiency presentation code efficient.

5, the WiMAX method for switching network based on power system capacity according to claim 2 is characterized in that, described current effective idle capacity is meant: C _Idle=C _Effective-S _Throughput, wherein: S _ThroughputIt is the current data flow information that statistics obtains.

6, the WiMAX method for switching network based on power system capacity according to claim 2 is characterized in that, the scanning switching of described sub-district is meant:

1) triggering cell switches to a chance event under the above-mentioned condition satisfying to establish current mobile terminal, and then the probability that takes place of this chance event should be less than p _Switch, when k constantly satisfies handover triggering condition simultaneously, p is only arranged as n portable terminal _Switch* n portable terminal can trigger base station scans and follow-up handoff procedure;

When following three conditions that 2) and if only if were met, portable terminal triggered base station scans and handoff procedure:

A) C _Idle(current BS)＜MS user's request flow;

b)

C _Idle(BS _k)＞α * MS user's request flow (α 〉=1);

C) P{ triggering cell handover event=true }＜p _Switch(0≤p _Switch≤ 1);

Condition a has defined effective idle capacity minimum threshold of Current Serving BTS, and promptly condition a sets up when the mobile phone users demand volume can't be met;

Condition b avoids portable terminal to do the stricter constraints of invalid base station scans under known adjacent base station can't provide abundant idle capacity situation, wherein α is an assurance coefficient, and only portable terminal might triggering cell switch when existing adjacent base station that α times user's request flow is provided;

Condition c is described overall controlled condition, is used to regulate portable terminal at each minizone switching frequency, p _SwitchThe portable terminal of representing satisfy condition an a and a condition b triggers the handoff procedure probability.

7, the WiMAX method for switching network based on power system capacity according to claim 1, it is characterized in that, described select target sub-district is meant: utilize network state, user's business demand and SOT state of termination condition, mobile phone users is linked into cost that Target cell will pay at current time, and to measure expression formula as follows:

$D_k=\underset{i=1}{\overset{M}{\mathrm{\Σ}}}{w}_i\×{\cos t}_{i,k},$

Wherein: D _kThe expression portable terminal is linked into total cost that Target cell k will pay, and promptly inserts cost, cost _{I, k}Be filial generation valency, w _iBe weight coefficient, M is a policing parameter.

8, the WiMAX method for switching network based on power system capacity according to claim 7 is characterized in that, described policing parameter M is meant: if be cost by i the filial generation valency that policing parameter determined _{I, k}, corresponding with it weight factor is w _iZong then cost is exactly the weighted sum of this M sub-cost.

9, the WiMAX method for switching network based on power system capacity according to claim 7 is characterized in that described weight factor comprises: base station idle capacity and signal power.

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