CN102387559B - Cross-layer route optimization method and device for wireless Mesh network - Google Patents

Abstract

The invention discloses a cross-layer route optimization method and a cross-layer route optimization device for a wireless Mesh network. The method comprises the following steps of: estimating the channel state of a current network according to the transmission efficiency parameter of a wireless link, judging the major cause of current packet loss according to a packet success ratio and a residual load rate when the channel state is poor, and adjusting the maximum retransmission time according to the packet loss cause; and acquiring the transmission efficiency PTEP of an entire route according to the transmission efficiency parameter of the wireless link, acquiring the residual load rate L-P of the route from which a source node and a target node are removed, computing the effective bandwidth etaB(c) of the route, constructing a route decision function according to the transmission efficiency PTEP of the route, the residual load rate L-P of the route and the effective bandwidth etaB(c) of the route, performing route discovery and route maintenance operation by using the route decision function, and selecting an optical packet transmission route between the source node and the target node. According to the invention, the route quality of an MAC (Media Access Control) layer can be sensed more accurately, and the error judgment times of the route are reduced.

Description

The method of the cross-layer routing optimization of wireless Mesh netword and device

Technical field

The present invention relates to wireless Mesh netword (WMN:Wireless Mesh Network), the method that the cross-layer routing particularly relating to a kind of wireless Mesh netword is optimized and device.

Background technology

To configure and the network coverage that strengthens and network capacity due to lower cost, flexibly, wireless Mesh netword (WMN:Wireless Mesh Network) technology is applied more and more extensive, the performance of its excellence is subject to the favor of academia and industrial circle, has become a kind of novel radio networking technology very with application prospect emerged in next generation wireless network.Wireless Mesh netword is primarily of Mesh terminal and Mesh router composition.Wherein, each Mesh router constitutes network architecture basis and the backbone network of wireless network, and carries out interconnected networking with cable network, together for Mesh terminal provides multi-hop wireless internet to connect.

The protocol model of traditional Web vector graphic layering is transparent each other between different agreement layer.Protocol development and realization are simple and upgradeable processes.But due to the complexity of wireless network, the method for layered protocol design very might not be applicable to wireless network.Such as, the physical channel under wireless environment is change, and capacity and bit error rate etc. are all constantly changes.Adopt the Modulation and Coding Scheme of optimization and error-control schemes can improve the performance of physical channel, but stable capacity, low packet loss ratio and reliable connectivity can not be ensured as desired by more high-rise.Therefore, in the wireless network, upper-layer protocol will inevitably be subject to the impact of physical channel instability.In order to further improve the performance of wireless network, MAC (medium education, Media Access Control), route and host-host protocol must work together with physical layer.In addition, MAC, route and host-host protocol also need to work in coordination, and these need the cross layer design between different layers agreement alternately.By utilizing the co-design between the protocol layers such as physical layer, MAC layer, routing layer to be the effective method of one that wireless multimedia service QoS (service quality, Quality of Service) requires.

In prior art, OLSR (optimized link state route, Optimized Link State Routing) Routing Protocol is a kind of Table Driven agreement based on multiple spot relaying.Each node uses one or more routing table to safeguard full mesh topology, and keep the consistency between routing table information and network topology change by periodically broadcast topology information, as long as node arrives destination node route when sending packet exists, just can obtain the routing iinformation arriving destination node immediately, therefore there is the feature that time delay is little.The optimisation technique of OLSR agreement have employed multiple spot relaying MPR (Multipoint Relay) to provide a kind of selectivity flooding mechanism, and the repetition hop count reducing the identical route test grouping in the same area reduces the quantity of broadcast packe in network.Only have the selected node being multiple spot relaying MPR just can produce link-state information and forward the information of other nodes transmission, decreasing the quantity of network central control message, what the broadcast reducing control packet brought repeats to forward expense.

The problem of OLSR Routing Protocol is, multiple spot relaying MPR select and router-level topology process in, only rely on coverage degree as MPR node selection principle, do not consider that the random mobility of node causes the factors such as link unsteadiness in path and do not consider the processing load of node, the performance parameter such as bandwidth, time delay of network congestion condition and wireless link causes the sensor selection problem of MPR collection inaccurate, cause network congestion, affect network performance.

In prior art, Performance-DSR (P-DSR) cross-layer routing protocol is optimized according to the state information of Link State and node transmission buffer memory DSR (dynamic source routing protocol, Dynamic Source Routing) and improves and propose.P-DSR agreement is by RPV (routing performance value, Route Performance Value) routing mechanism considers the impact of inter-node wireless links state on routing performance, the i.e. outage probability of link, consider again the state of node own to the impact of routing performance simultaneously, namely node sends the probability of cache overflow, build the standard of routing performance value RPV as Route Selection using this, avoid business too to concentrate the decline causing network performance.

P-DSR Routing Protocol adapts to the scene of node high-speed motion, and in the network of node low speed movement, because outage probability and transmission buffer memory well can not reflect the real-time status in path and the congestion condition of network, do not carry out differentiation to the state of channel to treat, cause routing update inaccurate, poor-performing.

Summary of the invention

Technical problem to be solved by this invention is, a kind of method providing cross-layer routing of wireless Mesh netword to optimize and device, exist when solving current cross-layer routing because network state and the problem that routing update is inaccurate and routing performance is poor caused more accurately cannot be obtained.

In order to solve the problem, the present invention proposes a kind of method that cross-layer routing based on channel status is optimized, comprising:

Step 1: according to the channel status of the efficiency of transmission parameter Estimation current network of wireless link, when judging that channel status is transmission performance difference, the reason of current packet loss is judged, according to described packet loss reason adjustment maximum retransmission according to packet success probabilities, remaining load rate;

Step 2: according to the efficiency of transmission PTE in the efficiency of transmission gain of parameter whole piece path of wireless link _p, obtain the remaining load rate L_ in the path after removing source node and destination node _p, calculating path effective bandwidth η _bc (), utilizes the efficiency of transmission PTE in path _p, the remaining load rate L_ in path _p, path effective bandwidth η _bc (), builds routing decision function, utilize described routing decision function to perform route discovery, route maintenance operation, select the best packet transmission path between source node and destination node.

In the step of the channel status of the described efficiency of transmission parameter Estimation current network according to wireless link:

The efficiency of transmission parameter of described wireless link is in the cycle T of broadcast table, the parameter after from node a to transmission success efficiency utilization index weighted moving average algorithm (EWMA) the smoothing process of the Frame of node b; When the efficiency of transmission parameter of described wireless link is less than first threshold Threshold ₁time, judge that channel status is poor as transmission performance.

Describedly judge in the step of the reason of current packet loss according to packet success probabilities, remaining load rate:

Described remaining load rate is in the cycle T of broadcast table, the remaining load rate L_res of path source node _aremaining load rate after utilization index weighted moving average algorithm (EWMA) smoothing process

Utilize path packet success rate PSR _{a, b}with remaining load rate build and for distinguishing the cost function of radio channel state type be:

${\mathrm{COST}}_{a,b}({\mathrm{PSR}}_{a,b},{\stackrel{\‾}{L\_\mathrm{res}}}_a)=\mathrm{\β}\×{\mathrm{PSR}}_{a,b}\·(1-\mathrm{\β})\×\stackrel{\‾}{{L\_\mathrm{res}}_a},$ 0≤β≤1；

When the statistical value of cost function COST is less than Second Threshold Threshold ₂time, the collision packet loss that the reason of current packet loss causes as more serious packet collisions can be judged;

When the statistical value of cost function COST is greater than Second Threshold Threshold ₂time, can judge that the reason of current packet loss is as the higher random error rate of wireless link;

Wherein β is weighted factor, 0 < Threshold ₂< 1.

In the described step according to described packet loss reason adjustment maximum retransmission:

The reason of described packet loss be more serious packet collisions cause collision packet loss time, reduce maximum retransmission C _max; When the reason of described packet loss is wireless link higher random error rate, increase maximum retransmission C _max.

Described maximum retransmission C _maxadjusting range be [0, C _th], the upper limit C of described adjusting range _thjointly calculated by efficiency of transmission parameter, packet success probabilities and remaining load rate to determine.

The efficiency of transmission PTE in the described efficiency of transmission gain of parameter whole piece path according to wireless link _pstep in, described PTE _pbe expressed as:

${\mathrm{PTE}}_p=\underset{\&ForAll;(a,b)\&Element;\mathrm{path}}{\mathrm{\&Pi;}}\stackrel{\&OverBar;}{{\mathrm{FTE}}_{\mathrm{ab}}}\left(i\right)$

The efficiency of transmission parameter of described wireless link be broadcast table cycle T in, the parameter after from node a to transmission success efficiency utilization index weighted moving average algorithm (EWMA) the smoothing process of the Frame of node b, for in multi-hop access path wherein one from node a to the link of node b.

The remaining load rate L_ in described path _pbe expressed as:

${L\_}_p=\underset{a\&NotEqual;s,d}{\min }\left(\stackrel{\&OverBar;}{{L\_\mathrm{res}}_a}\right)$

Described represent the remaining load rate L_res of path source node _aremaining load rate after utilization index weighted moving average algorithm (EWMA) smoothing process.

The structure of described routing decision function is defined as follows:

F _routing(η _B(c)，PTE _p，L_ _p)＝w ₁×η _B(c)+w ₂×PTE _p+w ₃×L_ _p

Wherein, w ₁, w ₂, w ₃be weighted factor, L_ _prepresent the remaining load rate in path, η _bc () is normalization effective bandwidth, namely data flow effective bandwidth accounts for the ratio of total bandwidth, PTE _pfor the efficiency of transmission in path.

Described utilize described routing decision function perform route discovery, route maintenance operation, select in the step of the packet transmission path between source node and destination node, destination node is optimized all path parameter application gray relative analysis methods found, and selects the maximum paths of described routing decision functional value to carry out the transmission of data.

The device that the present invention also provides a kind of cross-layer routing of wireless Mesh netword to optimize, comprising:

For calculating the efficiency of transmission detection module of efficiency of transmission parameter, for calculating the packet success probabilities detection module of packet success probabilities, for the remaining load rate detection module of computing node remaining load rate;

Channel status estimation module, for the channel status according to described efficiency of transmission parameter Estimation current network, for building cost function for judging channel status according to described packet success probabilities, remaining load rate, and channel status is estimated according to described cost function when judging channel status difference, judge packet loss reason;

Maximum retransmission adjusting module, for increasing according to described packet loss reason adjustment or reduce maximum retransmission;

Path remaining load rate detection module, the node remaining load rate for detecting according to remaining load rate detection module obtains the remaining load rate in the path after removing source node and destination node;

Path transmission Efficiency testing module, obtains path transmission efficiency for the efficiency of transmission calculation of parameter obtained according to described efficiency of transmission detection module;

Path effective bandwidth estimation module, for estimating the effective bandwidth in path based on the method for probability statistics;

Routing decision module, for the efficiency of transmission according to path, the remaining load rate in path, path effective bandwidth, build routing decision function, utilize described routing decision function to perform route discovery, route maintenance procedure, select the packet transmission path between source node and destination node.

Described in described routing decision module, the structure of routing decision function is defined as follows:

F _routing(η _B(c)，PTE _p，L_ _p)＝w ₁×η _B(c)+w ₂×PTE _p+w ₃×L_ _p

Wherein, w ₁, w ₂, w ₃be weighted factor, L_ _prepresent the remaining load rate in path, η _bc () is normalization effective bandwidth, namely data flow effective bandwidth accounts for the ratio of total bandwidth, PTE _pfor the efficiency of transmission in path.

When described channel status estimation module judges the reason of current packet loss according to packet success probabilities, remaining load rate:

Described remaining load rate is in the cycle T of broadcast table, the remaining load rate L_res of path source node _aremaining load rate after utilization index weighted moving average algorithm (EWMA) smoothing process

Described channel status estimation module utilizes path packet success rate PSR _{a, b}with remaining load rate what build for distinguishing the cost function of radio channel state type is:

${\mathrm{COST}}_{a,b}({\mathrm{PSR}}_{a,b},{\stackrel{\&OverBar;}{L\_\mathrm{res}}}_a)=\mathrm{\&beta;}\&times;{\mathrm{PSR}}_{a,b}\&CenterDot;(1-\mathrm{\&beta;})\&times;\stackrel{\&OverBar;}{{L\_\mathrm{res}}_a},$ 0≤β≤1；

When the statistical value of cost function COST is less than Second Threshold Threshold ₂time, the collision packet loss that the reason of current packet loss causes as more serious packet collisions can be judged;

When the statistical value of cost function COST is greater than Second Threshold Threshold ₂time, can judge that the reason of current packet loss is as the higher random error rate of wireless link;

Wherein β is weighted factor, 0 < Threshold ₂< 1.

The method of the cross-layer routing optimization of wireless Mesh netword of the present invention and device, by the environmental information of kinetic measurement wireless link, distinguish causing the reason of packet loss, the maximum retransmission of dynamic conditioning MAC layer, optimize the retransmission control scheme of MAC layer, reduce link failure probability, improve successful transmissibility and the network throughput of grouping.Single or measure the inaccurate defect causing routing performance poor for route criterion in WMN, carry out in MAC layer on the basis of packet loss differentiating, propose a kind of didactic multiple target cross-layer routing Optimization Mechanism HEAOR.By cross layer design technology, the state information such as path quality, link available bandwidth of perception MAC layer more exactly, reduces route erroneous judgement number of times, reduces the negative influence that route maintenance expense is brought to network, effectively improve network average throughput, meet the qos requirement of wireless multimedia service.

Accompanying drawing explanation

Fig. 1 is the overview flow chart of the method optimized based on the cross-layer routing of channel status in wireless Mesh netword;

Fig. 2 adjusts channel status and carries out the concrete steps schematic diagram of cross-layer routing optimization in the embodiment of the present invention;

Fig. 3 is for carrying out the module diagram of the device of cross-layer routing optimization in the embodiment of the present invention.

Embodiment

For making the object, technical solutions and advantages of the present invention clearly, below in conjunction with accompanying drawing, the present invention is described in further detail.

In order to overcome the shortcoming that route maintenance in existing cross-layer technology is frequent, resource utilization is lower, solve exist in prior art not to the problem that channel status is distinguished.The method that the cross-layer routing based on channel status of wireless Mesh netword of the present invention is optimized, comprises the Retransmission control optimization of MAC layer and the cross-layer routing optimization of network layer, especially based on wireless network Retransmission control and the joint route optimization of IEEE 802.11.

By dynamic environment perception, carry out adaptive retransmission to causing sending failed packet in MAC layer because of conflict or mistake, by the judgement to channel status, effective sensing optimal number of retransmissions, reduces collision probability, improves throughput of system.

Routing layer passes through the link-state information of heuristic dynamic estimation MAC layer and physical layer to the impact of routing performance, proposes a kind of didactic QoS based on environment sensing (Quality of Service) routing optimality selection algorithm HEAOR (Heuristic Environment-Aware Optimal Routing).This HEAOR algorithm is not increasing on the basis of routing cost substantially, can prediction chains line state more exactly, more effectively selects route.

As shown in Figure 1, a kind of method that cross-layer routing based on channel status is optimized, comprising:

Step 1: according to the channel status of the efficiency of transmission parameter Estimation current network of wireless link, when judging that channel status is transmission performance difference, the reason of current packet loss is judged, according to described packet loss reason adjustment maximum retransmission according to packet success probabilities, remaining load rate;

Step 2: according to the efficiency of transmission PTE in the efficiency of transmission gain of parameter whole piece path of wireless link _p, obtain the remaining load rate L_ in the path after removing source node and destination node _p, calculating path effective bandwidth η _bc (), utilizes the efficiency of transmission PTE in path _p, the remaining load rate L_ in path _p, path effective bandwidth η _bc (), builds routing decision function, utilize described routing decision function to perform route discovery, route maintenance, select the packet transmission path between source node and destination node.

The present invention carries out cross-layer optimizing Path selection based on the self adaptation of channel status, and its key point comprises two: the first, and MAC layer carries out maximum retransmission self-adaptative adjustment based on environment sensing; The second, routing layer carries out routing optimality selection based on channel status.Be described in detail for above-mentioned two key points below.

Because channel status can have a strong impact on Route Selection, thus, first by the statistical analysis to the environmental parameter such as expected transmission times, packet success probabilities, remaining load rate of MAC layer, the main cause telling current packet loss is wrapped caused by collision or wireless link random error, for different packet loss reason self-adaptative adjustment maximum retransmission, conservative control MAC retransmits.

In wireless Mesh netword, MAC layer adopts IEEE 802.11 DCF to carry out channel access, realizes data transmission based on 4 handshake mode of RTS/CTS and competition avoidance mechanism.Sending node first sends request and sends subframe RTS before transmission Frame, and receiving node, after receiving RTS, carries out confirmation reply with control frame CTS to RTS after waiting for the SIFS time interval; Sending node sends packet after receiving the CTS of confirmation, after receiving node receives packet, utilizes ACK to confirm.

When producing packet loss, utilization index avoidance mechanism carries out MAC re-transmission, and what bag number of retransmissions was fixed is set as 4 (packets) or 7 (RTS bags).If message still successfully cannot be sent to down hop through repeatedly retransmitting trial (reaching maximum retransmission) by message, then abandoning this message, being ready for sending next grouping simultaneously.Because this kind of retransmission mechanism is not distinguished the packet loss reason of link, and the best number of retransmissions of physical link is often closely related with packet loss reason, thus cause the unjustness of existing access mechanism, cause unnecessary excessive re-transmission that network performance is sharply declined.

Known according to analysis, cause the reason of packet loss to mainly contain the random error of two kinds: A. wireless link at present; B. caused by network congestion/collision packet loss.Existing based on 802.11 the various algorithms of mac-layer protocol not to causing the true cause of packet loss to judge, cause the burden of routing layer, resource utilization is lower.

First need to judge current network state, well still transmission performance is poor namely to judge network state to know transmission performance by the efficiency of transmission parameter of wireless link, judges its reason further again, retransmit for different reason self-adaptative adjustment when transmission performance is poor.

The maximum retransmission of definition MAC layer is C _max.Because time delay is limited, when number of retransmissions reaches C _maxtime packet still can not correctly receive, then abandon.In network, each node uses the variables A CK_count_Failure in IEEE 802.11MAC_MIB and RTS_count_Failure to represent the actual number of retransmissions of DATA frame and RTS frame respectively.Suppose that the number of retransmissions successfully sending i-th grouping from node a to node b is C _ab(i), C _ab(i) be actually the number of retransmissions of DATA and RTS and (C _ab(i)=ACK_count_Failure (i)+RTS_count_Failure (i)).

In the ideal case, i.e. Successful transmissions one grouping, RTS and DATA should respectively only once transmit.Like this, from node a to the transmission success efficiency FTE of the Frame of node b _abi () can calculate according to formula (1):

${\mathrm{FTE}}_{\mathrm{ab}}\left(i\right)=1-\frac{C_{\mathrm{ab}}\left(i\right)}{C_{\mathrm{ab}}\left(i\right)+2}=\frac{2}{\mathrm{ACK}\_\mathrm{count}\_\mathrm{Failu}{\mathrm{re}}_{\mathrm{ab}}\left(i\right)+\mathrm{RTS}\_\mathrm{count}\_\mathrm{Failur}{e}_{\mathrm{iab}}\left(i\right)+2}---\left(1\right)$

This efficiency of transmission parameter FTE _abi () represents the probability successfully sending RTS and DATA frame, when number of retransmissions is larger, the value of FTE will be less; When not there is LOF, number of retransmissions is 0, FTE _abbe 1, the grouping being namely sent to node b from node a is successfully sent by 100%.

In order to avoid the bursty jitter impact that wireless link transient response is brought to network, in the cycle T of broadcast table, node a passes through exponentially weighted moving average (EWMA) algorithm (EWMA) smoothing process to the Successful transmissions efficiency of link.The mean value of the EWMA calculating of Successful transmissions efficiency is as shown in formula (2).In formula (2) represent the moving average of FTE during transmission the i-th-1 grouping, α ₁for weighted factor, its value depends on the speed of channel variation.

${\stackrel{\&OverBar;}{\mathrm{FTE}}}_{\mathrm{ab}}\left(i\right)={\mathrm{\&alpha;}}_1\&times;{\mathrm{FTE}}_{\mathrm{ab}}\left(i\right)+(1-{\mathrm{\&alpha;}}_1)\&times;{\stackrel{\&OverBar;}{\mathrm{FTE}}}_{\mathrm{ab}}(i-1),$ 0≤α1≤1(2)

Distributed coordination function DCF is the most basic media access method in IEEE 802.11, and namely node first intercepts the busy-idle condition of channel before sending data, if channel idle, illustrate that present channel does not conflict, grouping is transmitted; If channel busy, present channel conflict is described, the interval of a DIFS is waited in the grouping be sent out.Judgement the present invention for channel busy-idle condition adopts following method:

1) the packet success probabilities PSR in path (Packet Success Rate) is utilized to indicate the busy of present physical channel status, suppose the packet error probability PER (a of every bar transmission link, b) (Packet Error Rate) is separate, the packet success probabilities PSR by formula (3) calculating path:

$\mathrm{PSR}\left(\mathrm{path}\right)=\underset{\&ForAll;(a,b)\&Element;\mathrm{path}}{\mathrm{\&Pi;}}(1-\mathrm{PER}(a,b))---\left(3\right)$

Wherein PER (a, b) is the Packet Error Ratio from node a to node b, and the PER (a, b) between each section of transmission range is separate.When decoding end adopts Viterbi decoding, then the PER of link can be gone out by approximate evaluation.

2) judge that another criterion of channel status is the remaining load rate of node a, use L_res _arepresent the remaining load rate of node a, the Congestion Level SPCC of reflection network, defines L_res as Suo Shi formula (4) _afor:

${L\_\mathrm{res}}_a=\frac{{\mathrm{Cap}}_a-{\mathrm{Occup}}_a}{{\mathrm{Cap}}_a}---\left(4\right)$

Wherein, Occup _arepresent the size of data taken in data buffer area, Cap _arepresent the maximum data buffer memory capacity that node a is fixing.L_res _athen can regard as in the data buffer area of node a not yet by the buffer memory ratio used.

L_res can be found out from formula (4) _alarger, illustrate that the available data buffer area of node is larger, the current acceptable load capacity of node is stronger, comparatively speaking, just think that these nodes comparatively " free time ", from justice use Internet resources angle, the route of these nodes participation network business as far as possible should be allowed.In order to reduce error effect, the same remaining load rate of EWMA algorithm to node that adopt is smoothing, and the node remaining load rate after EWMA algorithm process is as shown in formula (5):

${\stackrel{\&OverBar;}{L\_\mathrm{res}}}_a\left(i\right)={\mathrm{\&alpha;}}_2\&times;{L\_\mathrm{res}}_a\left(i\right)+(1-{\mathrm{\&alpha;}}_2)\&times;\stackrel{\&OverBar;}{{L\_\mathrm{res}}_a}(i-1),$ 0≤α ₂≤1(5)

Based on the statistical analysis to packet success probabilities and remaining load rate, can build a cost function can distinguishing radio channel state type is further:

${\mathrm{COST}}_{a,b}({\mathrm{PSR}}_{a,b},{\stackrel{\&OverBar;}{L\_\mathrm{res}}}_a)=\mathrm{\&beta;}\&times;{\mathrm{PSR}}_{a,b}\&CenterDot;(1-\mathrm{\&beta;})\&times;\stackrel{\&OverBar;}{{L\_\mathrm{res}}_a},$ 0≤β≤1，

Wherein β is weighted factor.As less (the COST < Threshold of the statistical value of cost function COST ₂, 0 < Threshold ₂< 1), show that the success rate dividing into groups to send is lower, or remaining load rate is less, then can judge that current radio channel state is as busy further, packet collisions is higher, now excessively increases the deterioration that number of retransmissions can only cause network performance; Otherwise it is higher that grouping sends success rate, and link has more available resources, then judge that present channel is as idle condition.

Based on above-mentioned parameter, as shown in Figure 2, the self-adaptative adjustment process of maximum retransmission is as follows:

The first step, first utilizes the efficiency of transmission parameter FTE of wireless link to estimate the integrality of current network, when the Successful transmissions efficiency through exponentially weighted moving average (EWMA) smoothing processing less ( 0 < Threshold ₁< 1), illustrate that the transmission performance of current ink ab is poor.

The reason of the poor-performing of link ab is caused mainly to comprise: more serious packet collisions or the higher random error rate of wireless link.

In order to distinguish this two kinds of reasons further, distinguish by the value of the wireless link cost function COST built the true cause causing packet loss serious.

When COST is less, (COST < Threshold ₂, 0 < Threshold ₂< 1)), channel is in busy condition, and namely judge that current collision packet loss accounts for major part, packet collisions is serious.Now, retransmit if increase and can only waste valuable channel resource, make congested or conflict more serious; In order to alleviate the congested of network, MAC layer should reduce maximum retransmission C _max, simultaneously in order to avoid the burst of network is fluctuated, carry out from subtracting an operation, i.e. C _max=C _max-1, routing layer correspondingly calls route maintenance strategy.

(the COST > Threshold when COST is larger ₂), when transmission of radio links poor-performing, can infer that current ink random error rate may be higher, wireless channel has more serious error code, now by increasing the maximum retransmission C of MAC layer _max, such as, carry out from adding an operation C _max=C _max+ 1 ability improving channel resist miscode, routing layer avoids route maintenance simultaneously in order to avoid waste channel width.

When the Successful transmissions efficiency through exponentially weighted moving average (EWMA) smoothing processing larger time, illustrate that wireless channel has higher efficiency of transmission, substantially the situation that more serious conflict or the higher error rate appear in channel can be got rid of, in order to improve the performance of network further, H.264 the video encoder of application layer suitably can improve transmission rate, avoid route maintenance, increase network throughput, improve the utilance of Radio Resource.

In order to avoid maximum retransmission C _maxunconfined increase or reduction, improve retransmit adjustment validity, utilize efficiency of transmission parameter FTE, packet success probabilities PSR and remaining load rate L_res to build a C _maxadjustment limiting value as shown in formula (6), the adjusting range of above-mentioned number of retransmissions is [0, C _th].

$C_{\mathrm{th}}=\frac{28}{\mathrm{FTE}+2\&times;\mathrm{PSR}\&times;L\_\mathrm{res}}---\left(6\right)$

Algorithm example based on the Adaptive synthesis mode decision scheme of channel status is as shown in table 1.

Table 1: the algorithm retransmitted based on channel status self-adaptative adjustment

Second step, utilizes the efficiency of transmission PTE in path _p, the remaining load rate L_ in path _p, the effective bandwidth η in path _bc (), builds routing decision function, utilize described routing decision function to perform route discovery, route maintenance, select the routed path between source node and destination node.

According to the MAC layer mechanism in IEEE802.11, for loss or the delay of RTS, CTS of connecting and Frame, timer expiry, mac-layer protocol is all by log-on data frame re-transmission mechanism.The present invention adopts the average transmission efficiency PTE in path (PTE:Path Transmission Efficiency) to reflect quality and the congestion situation of often jumping path, and as one of mixed logic dynamic judgement, expect computational methods (the wherein α of efficiency of transmission according to formula (2) link ₁=0.3), the efficiency of transmission in whole piece path can be obtained further as shown in formula (7), wherein for in multi-hop access path wherein one from node a to the link of node b.

${\mathrm{PTE}}_p=\underset{\&ForAll;(a,b)\&Element;\mathrm{path}}{\mathrm{\&Pi;}}\stackrel{\&OverBar;}{{\mathrm{FTE}}_{\mathrm{ab}}}\left(i\right)---\left(7\right)$

By formula (4) and (5) to the definition of a node remaining load rate, the remaining load rate of a paths can be calculated.After the remaining load rate in path is defined as and this paths removes source node and destination node, the least residue load factor of residue node.The remaining load rate in path can reflect the load capacity of this paths.Suppose there is a path from source node s to destination node d, be designated as P, the remaining load rate of this paths P is designated as L_ _p, can be expressed as shown in formula (8).This paths of the larger explanation of remaining load rate in path is more idle, and acceptable load capacity is stronger, and the probability of success of packet from then on path forwarding data is also larger.

${L\_}_p=\underset{a\&NotEqual;s,d}{\min }\left(\stackrel{\&OverBar;}{{L\_\mathrm{res}}_a}\right)---\left(8\right)$

The present invention adopts the effective bandwidth of bandwidth prediction method to wireless link run counter to based on packetization delay and probability to estimate.The total delay of the method first statistical packet experience, this delay comprises the delay of queue delay and service time, and maximumly deviate from theory by utilizing, as Suo Shi formula (9), packetization delay D exceedes maximum delay scope D _maxprobability can be approximately:

$\mathrm{\&epsiv;}=P_r\{D\&GreaterEqual;D_{\max }\}\&ap;e^{-{\mathrm{\&theta;}}_B{D}_{\max }}---\left(9\right)$

Wherein θ _b=c η _b ^-1(c), and η _bc effective bandwidth that () is data flow, c is the constant service rate of channel, can utilize the available bandwidth of above-mentioned formula (9) approximate calculation channel when known c, and as shown in formula (10), can obtain effective bandwidth is:

${\mathrm{\&eta;}}_B\left(c\right)=\underset{t\&RightArrow;\&infin;}{\lim }\frac{1}{t}\frac{1}{c}{\log }^{E\left[e^{\mathrm{cA}\left(t\right)}\right]}\&ap;\frac{c\&times;D}{{\ln }^{\frac{1}{\mathrm{\&epsiv;}}}},\&ForAll;c>0---\left(10\right)$

Formula (10) meet in certain probable range ensure divide into groups end-to-end delay be less than D _max, and taken into full account delay character.Utilize this statistical property can improve the accuracy of effective bandwidth estimation.

When judging path quality, need to consider various path quality information, as shown in Figure 2, in the HEAOR routing algorithm that the present invention proposes, destination node will be optimized all path application gray relative analysis methods found, and finally selects the maximum paths of routing decision functional value to carry out the transmission of data.

The routing decision function of the present invention's definition is as shown in formula (11):

F _routing(η _B(c)，PTE _p，L_ _p)＝w ₁×η _B(c)+w ₂×PTE _p+w ₃×L_ _p(11)

Wherein, w ₁, w ₂, w ₃be weighted factor; η _bc () is normalization effective bandwidth, namely data flow effective bandwidth accounts for the ratio of total bandwidth.

In order to obtain the correlation between each tolerance and attribute, gray relative analysis method is adopted to calculate weight w ₁, w ₂, w ₃.First metric that is current and buffer memory is utilized to build evaluating matrix A as shown in formula (12), by solving the Maximum characteristic root λ of judgement matrix A _max, obtain corresponding characteristic vector w (w=(w ₁, w ₂, w ₃) ^t), as shown in formula (13), so just can obtain the weight vector needed.

Consider the complexity of solution matrix, just upgrade matrix A when continual data package dropout appears in channel, calculate weights simultaneously, so not only can reduce the complexity of calculating, also ensure that the non-correlation (ensureing the existence of characteristic root) of matrix A simultaneously.

$A=\left[\begin{array}{ccc}{\mathrm{\&eta;}}_B\left(c_1\right)& {\mathrm{PTE}}_p\left(1\right)& {L\_}_p\left(1\right)\\ {\mathrm{\&eta;}}_B\left(c_2\right)& {\mathrm{PTE}}_p\left(2\right)& {L\_}_p\left(2\right)\\ {\mathrm{\&eta;}}_B\left(c_3\right)& {\mathrm{PTE}}_p\left(3\right)& {L\_}_p\left(3\right)\end{array}\right]---\left(12\right)$

$\mathrm{Aw}={\mathrm{\&lambda;}}_{\max }w\&DoubleRightArrow;w=A^{-1}{\mathrm{\&lambda;}}_{\max }w$ Wherein $w=\left[\begin{array}{c}{w}_1\\ w_2\\ w_3\end{array}\right]---\left(13\right)$

After determining routing decision function, this routing decision function can be applied and carry out route discovery and route maintenance.Route selection algorithm is a kind of based on source routing selection algorithm as required, and when certain node needs to obtain the route arriving another node, this node will initiate a route finding process as source node.

First source node sends routing information request (RREQ), and this request comprises the information such as the life cycle TTL (be generally jumping figure restriction) of route requests, bag sequence number and destination address.In addition, the structure of path quality also should be contained in the HEAOR packet header of route requests, and for depositing path quality information, the structure of path quality is as shown in formula (14), and structure comprises the efficiency of transmission PTE in path _p, the remaining load rate L_ in path _p, path effective bandwidth η _bparameters such as (c).

Path_Quality_Struct

(14)

{float η _B(c)；float PTE _p；float L_ _p；}

After intermediate node receives this route requests, first upgrade the structure of path quality entrained by this route requests, then judge whether this node should ignore this route requests.The content judged comprises bag sequence number, path is good and bad, whether node available resources transship and whether TTL expires.

If intermediate node finds the path arriving destination node from buffer memory, then the many criterions routing decision function proposed according to formula (11) judges that whether cache routing is better than the path entrained by route requests, if so, then returns to this path; Otherwise, abandon buffer memory and reply.

After destination node receives route requests, first upgrade the structure of path quality, call routing reply (RREP) process simultaneously and the path of route requests and path quality information (least residue bandwidth, link-quality and network load) are sent to source node.When destination node receives multiple route requests continuously, if verify that the path quality entrained by current route requests is more excellent than the path forwarded by routing decision function (formula (11)), node will carry out routing reply again, otherwise abandon this route requests.

Whether source node obtains the information such as desired path and path quality by routing reply packet and is added in route-caching, check in data buffer storage simultaneously and have data to need to send.In the routing reply stage, if other node receives feedback message, the relevant information in useful path can be extracted and add in the route-caching of self from message.

HEAOR routing algorithm have employed the route maintenance mechanism identical with DSR agreement, and when link failure in path, link upstream node sends routing error grouping (RERR), carries out route maintenance.But unlike node, routing error number maximum in data transmission procedure is judged with DSR, if exceed designated value, then abandon this bag, prevent packet to be recycled forwarding and cause network paralysis.

Searched the path arriving destination node in route maintenance by route-caching, if existed, then use this path to send packet, if do not find, again initiate route request information (RREQ), obtain the route arriving destination node; Meanwhile, node checks in IFQ queue the packet whether having and use this link, judges whether to change original path.

As shown in Figure 3, the device that the cross-layer routing that the present invention gives a kind of wireless Mesh netword is optimized, comprising:

For calculating the efficiency of transmission detection module of efficiency of transmission parameter, for calculating the packet success probabilities detection module of packet success probabilities, for the remaining load rate detection module of computing node remaining load rate;

Channel status estimation module, for the channel status according to described efficiency of transmission parameter Estimation current network, according to described packet success probabilities, the cost function of remaining load rate structure for judging channel status, and channel status is estimated according to described cost function when judging channel status difference, judge packet loss reason;

Maximum retransmission adjusting module, for according to described packet loss reason self-adaptative adjustment maximum retransmission;

Path remaining load rate detection module, the node remaining load rate for detecting according to remaining load rate detection module obtains the remaining load rate in the path after removing source node and destination node;

Path transmission Efficiency testing module, obtains path transmission efficiency for the efficiency of transmission calculation of parameter obtained according to described efficiency of transmission detection module;

Path effective bandwidth estimation module, for estimating the effective bandwidth in path;

Routing decision module, for the efficiency of transmission according to path, the remaining load rate in path, path effective bandwidth, build routing decision function, utilize that described routing decision function performs route discovery, packet transmission path that route maintenance is selected between source node and destination node.

Wherein, described channel status estimation module utilizes the efficiency of transmission parameter FTE of wireless link to estimate the integrality of current network, when the Successful transmissions efficiency through exponentially weighted moving average (EWMA) smoothing processing less ( 0 < Threshold ₁< 1), illustrate that the transmission performance of current ink ab is poor.

Wherein, described channel status estimation module is based on the statistical analysis to packet success probabilities and remaining load rate, and can build a cost function can distinguishing radio channel state type is further:

${\mathrm{COST}}_{a,b}({\mathrm{PSR}}_{a,b},{\stackrel{\&OverBar;}{L\_\mathrm{res}}}_a)=\mathrm{\&beta;}\&times;{\mathrm{PSR}}_{a,b}\&CenterDot;(1-\mathrm{\&beta;})\&times;\stackrel{\&OverBar;}{{L\_\mathrm{res}}_a},$ 0≤β≤1, wherein β is weighted factor.

When COST is less, (COST < Threshold ₂, 0 < Threshold ₂< 1)), channel is in busy condition, and namely judge that current collision packet loss accounts for major part, packet collisions is serious.Now, retransmit if increase and can only waste valuable channel resource, make congested or conflict more serious; In order to alleviate the congested of network, MAC layer should reduce maximum retransmission C _max, simultaneously in order to avoid the burst of network is fluctuated, carry out from subtracting an operation, i.e. C _max=C _max-1, routing layer correspondingly calls route maintenance strategy.

(the COST > Threshold when COST is larger ₂), when transmission of radio links poor-performing, can infer that current ink random error rate may be higher, wireless channel has more serious error code, now by increasing the maximum retransmission C of MAC layer _max, such as, carry out from adding an operation C _max=C _max+ 1 ability improving channel resist miscode, routing layer avoids route maintenance simultaneously in order to avoid waste channel width.

Described device also can comprise further: the limiting value adjusting module of number of retransmissions, for determining the limiting value of maximum retransmission.In order to avoid maximum retransmission C _maxunconfined increase or reduction, improve retransmit adjustment validity, utilize efficiency of transmission parameter FTE, packet success probabilities PSR and remaining load rate L_res to build a C _maxadjustment limiting value as shown in formula (6), the adjusting range of above-mentioned number of retransmissions is [0, C _th].

$C_{\mathrm{th}}=\frac{28}{\mathrm{FTE}+2\&times;\mathrm{PSR}\&times;L\_\mathrm{res}}---\left(6\right)$

The routing decision function of described routing decision module construction is as shown in formula (11):

F _routing(η _B(c)，PTE _p，L_ _p)＝w ₁×η _B(c)+w ₂×PTE _p+w ₃×L_ _p(11)

Wherein, w ₁, w ₂, w ₃be weighted factor; η _bc () is normalization effective bandwidth, namely data flow effective bandwidth accounts for the ratio of total bandwidth.

Routing decision module is when utilizing routing decision function to carry out routing optimality, and can build the structure of a path quality as shown in formula (14), structure comprises the efficiency of transmission PTE in path _p, the remaining load rate L_ in path _p, path effective bandwidth η _bparameters such as (c).

Path_Quality_Struct

(14)

{float η _B(c)；float PTE _p；float L_ _p；}

In routing algorithm, node obtains desired parameters according to structure, destination node will be optimized all path application gray relative analysis methods found, select the maximum paths of routing decision functional value to carry out the transmission of data, thus determine the packet transmission path between source node and destination node.

Method of the present invention and device, by the environmental information of kinetic measurement wireless link, distinguish causing the reason of packet loss, the maximum retransmission of dynamic conditioning MAC layer, optimize the retransmission control scheme of MAC layer, reduce link failure probability, improve successful transmissibility and the network throughput of grouping.Single or measure the inaccurate defect causing routing performance poor for route criterion in WMN, carry out in MAC layer on the basis of packet loss differentiating, propose a kind of didactic multiple target cross-layer routing Optimization Mechanism HEAOR.By cross layer design technology, the state information such as path quality, link available bandwidth of perception MAC layer more exactly, reduces route erroneous judgement number of times, reduces the negative influence that route maintenance expense is brought to network, effectively improve network average throughput, meet the qos requirement of wireless multimedia service.

The foregoing is only embodiments of the invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within right of the present invention.

Claims (11)

1., based on the method that the cross-layer routing of channel status is optimized, comprising:

Step 1: according to the channel status of the efficiency of transmission parameter Estimation current network of wireless link, when judging that channel status is transmission performance difference, the reason of current packet loss is judged, according to described packet loss reason adjustment maximum retransmission C according to packet success probabilities, remaining load rate _max, wherein, described maximum retransmission C _maxadjusting range be [0, C _th], the upper limit C of described adjusting range _thjointly calculated by efficiency of transmission parameter FTE, packet success probabilities PSR and remaining load rate L_res to determine, described upper limit C _thbe expressed as:

$C_{\mathrm{th}}=\frac{28}{\mathrm{FTE}+2\&times;\mathrm{PSR}\&times;L\_\mathrm{res}};$

Step 2: according to the efficiency of transmission PTE in the efficiency of transmission gain of parameter whole piece path of wireless link _p, obtain the remaining load rate L in the path after removing source node and destination node _{_ P}, calculating path effective bandwidth η _bc (), utilizes the efficiency of transmission PTE in path _p, the remaining load rate L in path _{_ P}, path effective bandwidth η _bc (), builds routing decision function, utilize described routing decision function to perform route discovery, route maintenance operation, select the best packet transmission path between source node and destination node.

2. the method for claim 1, is characterized in that, in the step of the channel status of the described efficiency of transmission parameter Estimation current network according to wireless link:

The efficiency of transmission parameter of described wireless link is in the cycle T of broadcast table, the parameter after from node a to transmission success efficiency utilization index weighted moving average algorithm (EWMA) the smoothing process of the Frame of node b; When the efficiency of transmission parameter of described wireless link is less than first threshold Threshold ₁time, judge that channel status is poor as transmission performance.

3. the method for claim 1, is characterized in that, describedly judges in the step of the reason of current packet loss according to packet success probabilities, remaining load rate:

Described remaining load rate is in the cycle T of broadcast table, the remaining load rate L_res of path source node _aremaining load rate after utilization index weighted moving average algorithm (EWMA) smoothing process

Utilize path packet success rate PSR _{a, b}with remaining load rate build and for distinguishing the cost function of radio channel state type be:

${\mathrm{COST}}_{a,b}({\mathrm{PSR}}_{a,b},{\stackrel{\&OverBar;}{L\_\mathrm{res}}}_a)=\mathrm{\&beta;}\&times;{\mathrm{PSR}}_{a,b}\&bull;(1-\mathrm{\&beta;})\&times;\stackrel{\&OverBar;}{{L\_\mathrm{res}}_a},0\&le;\mathrm{\&beta;}\&le;1;$

When the statistical value of cost function COST is less than Second Threshold Threshold ₂time, the collision packet loss that the reason of current packet loss causes as more serious packet collisions can be judged;

When the statistical value of cost function COST is greater than Second Threshold Threshold ₂time, can judge that the reason of current packet loss is as the higher random error rate of wireless link;

Wherein β is weighted factor, 0<Threshold ₂<1.

4. method as claimed in claim 3, is characterized in that, in the described step according to described packet loss reason adjustment maximum retransmission:

The reason of described packet loss be more serious packet collisions cause collision packet loss time, reduce maximum retransmission C _max;

When the reason of described packet loss is wireless link higher random error rate, increase maximum retransmission C _max.

5. the method for claim 1, is characterized in that, the efficiency of transmission PTE in the described efficiency of transmission gain of parameter whole piece path according to wireless link _pstep in, described PTE _pbe expressed as:

${\mathrm{PTE}}_p=\underset{\&ForAll;(a,b)\&Element;\mathrm{path}}{\mathrm{\&Pi;}}\stackrel{\&OverBar;}{{\mathrm{FTE}}_{\mathrm{ab}}}\left(i\right)$

The efficiency of transmission parameter of described wireless link be broadcast table cycle T in, the parameter after from node a to transmission success efficiency utilization index weighted moving average algorithm (EWMA) the smoothing process of the Frame of node b, for in multi-hop access path wherein one from node a to the link of node b.

6. the method for claim 1, is characterized in that,

The remaining load rate L in described path _{_ P}be expressed as:

$L_{-p}=\underset{a\&NotEqual;s,d}{\min }\left(\stackrel{\&OverBar;}{L\_{\mathrm{res}}_a}\right)$

Described represent the remaining load rate L_res of path source node _aremaining load rate after utilization index weighted moving average algorithm (EWMA) smoothing process.

7. the method for claim 1, is characterized in that,

The structure of described routing decision function is defined as follows:

F _routing(η _B(c),PTE _p,L _{_p})＝w ₁×η _B(c)+w ₂×PTE _p+w ₃×L _{_p}

Wherein, w ₁, w ₂, w ₃be weighted factor, L _{_ P}represent the remaining load rate in path, η _bc () is normalization effective bandwidth, namely data flow effective bandwidth accounts for the ratio of total bandwidth, PTE _pfor the efficiency of transmission in path.

8. method as claimed in claim 7, is characterized in that,

Described utilize described routing decision function perform route discovery, route maintenance operation, select in the step of the packet transmission path between source node and destination node, destination node is optimized all path parameter application gray relative analysis methods found, and selects the maximum paths of described routing decision functional value to carry out the transmission of data.

9. a device for the cross-layer routing optimization of wireless Mesh netword, comprising:

For calculating the efficiency of transmission detection module of efficiency of transmission parameter, for calculating the packet success probabilities detection module of packet success probabilities, for the remaining load rate detection module of computing node remaining load rate;

Channel status estimation module, for the channel status according to described efficiency of transmission parameter Estimation current network, for building cost function for judging channel status according to described packet success probabilities, remaining load rate, and channel status is estimated according to described cost function when judging channel status difference, judge packet loss reason;

Maximum retransmission adjusting module, for increasing according to described packet loss reason adjustment or reduce maximum retransmission C _max, wherein, described maximum retransmission C _maxadjusting range be [0, C _th], the upper limit C of described adjusting range _thjointly calculated by efficiency of transmission parameter FTE, packet success probabilities PSR and remaining load rate L_res to determine, described upper limit C _thbe expressed as:

$C_{\mathrm{th}}=\frac{28}{\mathrm{FTE}+2\&times;\mathrm{PSR}\&times;L\_\mathrm{res}};$

Path remaining load rate detection module, the node remaining load rate for detecting according to remaining load rate detection module obtains the remaining load rate in the path after removing source node and destination node;

Path transmission Efficiency testing module, obtains path transmission efficiency for the efficiency of transmission calculation of parameter obtained according to described efficiency of transmission detection module;

Path effective bandwidth estimation module, for estimating the effective bandwidth in path based on the method for probability statistics;

Routing decision module, for the efficiency of transmission according to path, the remaining load rate in path, path effective bandwidth, build routing decision function, utilize described routing decision function to perform route discovery, route maintenance procedure, select the packet transmission path between source node and destination node.

10. device as claimed in claim 9, is characterized in that,

Described in described routing decision module, the structure of routing decision function is defined as follows:

F _routing(η _B(c),PTE _p,L _{_p})＝w ₁×η _B(c)+w ₂×PTE _p+w ₃×L _{_p}

Wherein, w ₁, w ₂, w ₃be weighted factor, L _{_ P}represent the remaining load rate in path, η _bc () is normalization effective bandwidth, namely data flow effective bandwidth accounts for the ratio of total bandwidth, PTE _pfor the efficiency of transmission in path.

11. devices as claimed in claim 9, is characterized in that,

When described channel status estimation module judges the reason of current packet loss according to packet success probabilities, remaining load rate:

Described remaining load rate is in the cycle T of broadcast table, the remaining load rate L_res of path source node _aremaining load rate after utilization index weighted moving average algorithm (EWMA) smoothing process

Described channel status estimation module utilizes path packet success rate PSR _{a, b}with remaining load rate what build for distinguishing the cost function of radio channel state type is:

${\mathrm{COST}}_{a,b}({\mathrm{PSR}}_{a,b},{\stackrel{\&OverBar;}{L\_\mathrm{res}}}_a)=\mathrm{\&beta;}\&times;{\mathrm{PSR}}_{a,b}\&bull;(1-\mathrm{\&beta;})\&times;\stackrel{\&OverBar;}{{L\_\mathrm{res}}_a},0\&le;\mathrm{\&beta;}\&le;1;$

When the statistical value of cost function COST is less than Second Threshold Threshold ₂time, the collision packet loss that the reason of current packet loss causes as more serious packet collisions can be judged;

When the statistical value of cost function COST is greater than Second Threshold Threshold ₂time, can judge that the reason of current packet loss is as the higher random error rate of wireless link;

Wherein β is weighted factor, 0<Threshold ₂<1.