CN100448231C - Service quality assuring method in wireless mesh network - Google Patents
Service quality assuring method in wireless mesh network Download PDFInfo
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Abstract
The present invention provides a method for guaranteeing service quality in a wireless mesh network, which comprises following procedures: a. when a data packet is received by a wireless router, if priority information is not carried in an IP packet header, the priority information in an MAC packet header is stored into the IP packet header at an MAC layer and is transmitted to an IP layer; b. the priority information is read in the IP packet header of the data packet at the IP layer, the priority information is written into the MAC packet header and the data packet is forwarded. The business distinction of the wireless mesh network is realized and service quality is guaranteed by the method for guaranteeing service quality in a wireless mesh network, and the service quality is further enhanced by the call admission control of the method for guaranteeing service quality in a wireless mesh network.
Description
Technical field
The present invention relates to wireless local area network technology, relate in particular to wireless mesh network, the method for ensuring service quality that concrete is in a kind of wireless mesh network.
Background technology
Over past ten years, wireless communication technology has obtained paying close attention to widely and develop rapidly.Be very easy to people's contact and communication mode based on the digital mobile phone of global system for mobile communications (GSM) technology, and infiltration and have influence on fields of society.Meanwhile, the develop rapidly of wireless local area network technology makes this market rapidly grow in strength and has attracted the ` of a large amount of academias, scientific and technological circle.Current, wireless local area network technology can provide the speed up to 54,000,000 per seconds (Mbps), can satisfy people's data services such as surfing on the net basically; WLAN (wireless local area network) physical-layer techniques just under study for action then can provide the speed above 100Mbps, is linked into the Internet by wireless local area network technology like this and carries out professional being easy to get of becoming of various data communications.And the WLAN devices manufacturing cost is more and more lower to make that WLAN devices on the market is more and more cheap, and like this, people can enjoy the facility that WLAN (wireless local area network) is brought more.But probably about hundred meters, this has greatly retrained the development of WLAN (wireless local area network) and the facility that it brings to people to the communication range of current wireless local area network technology.Thereby communication range how to expand WLAN (wireless local area network) effectively becomes current focus.And a kind of new technology, wireless mesh network is then expanded the effective means of wireless LAN communication scope just.
Wireless mesh technology has self-organizing, self-healing plurality of advantages.In a wireless mesh network, the main node that has two types: based on the client and the wireless router of wireless local area network technology.Communicate the backbone network of forming in the similar cable network (Backbone) between the wireless router; And client is by being connected to wireless router and utilizing wireless trunk net and outside to communicate, as shown in Figure 1.Like this, a client is when communicating with the outside, and the centre might be transmitted through several wireless routers.Thereby wireless mesh network is the wireless communication networks of a multi-hop.Wireless local area network technology is defined by IEEE 802.11 series standards; Its medium access control (MAC) layer access technology mainly avoided (CSMA/CA) mechanism based on carrier sense/collision.But CSMA/CA mechanism is designed at the WLAN (wireless local area network) of single-hop, thus it and be not suitable for the wireless mesh network of multi-hop.Be based on the CAMA/CA technology and service quality strengthens machine-processed IEEE 802.11e, so it is not suitable for wireless mesh network equally.
Though IEEE802.11e has carried out traffic differentiation by the formation that four different priorities are provided, but this traffic differentiation only is confined to a wireless local network connecting point (AP:access point) scope and so on.(as Fig. 2 a), WLAN (wireless local area network) only is that one on the whole data transfer path jumped (first jumps or final jump) from whole network configuration.Like this, only utilize the traffic differentiation mechanism of MAC layer, i.e. IEEE 802.11e just can guarantee the traffic differentiation of WLAN (wireless local area network).But for wireless mesh network, thing is really not so, and this mainly is because wireless mesh network has the feature of multi-hop.As Fig. 2 b, for data flow 2 (Flow 2), iff the traffic differentiation mechanism that MAC is arranged, on the whole transfer path of this stream, it can not obtain unified consistent priority, does not just obtain traffic differentiation so.
Utilize the data flow 2 among Fig. 2 b to illustrate why IEEE 802.11e can not carry out traffic differentiation in wireless mesh network below.The source end client of tentation data stream 2 had been distributed a priority to it before sending its packet, just it has been carried out traffic differentiation.Since client has been assembled the IEEE802.11e radio, so the data flow that it can send itself be carried out traffic differentiation, thereby this hypothesis is also just always set up.So, between client and first wireless router (Mesh router 1), data flow can both be by traffic differentiation.Next, what can take place in the time of can looking to transmit data between first and second wireless router.After first wireless router received the packet with priority that client sends, it need be delivered to the IP layer so that carry out Path selection from the MAC layer with these packets.And the precedence information of MAC layer only is stored in MAC packet header the inside, give the IP layer on upper strata when packet data delivery after, MAC packet header is with disallowable, the packet that is to say the IP layer is not comprise any precedence information.After executing Path selection, the MAC layer that packet can be sent to lower floor once more sends.And this moment since the IP layer without any precedence information, the IEEE 802.11e of MAC layer cannot know that this packet is to belong to which kind of priority, thereby they can not be carried out traffic differentiation.Therefore, when first wireless router is transmitted the packet of data flow 2, they are not carried out traffic differentiation, can they be sent according to the priority of acquiescence; And then can push away it, and in ensuing all paths, in Fig. 2 b wireless router 2,3, all data flow 2 is not carried out traffic differentiation.Beginning most of entire path, data flow 2 has been carried out traffic differentiation by IEEE 802.11e, but owing to IEEE802.11e only works at the MAC layer, to such an extent as to data flow 2 can not be carried out uniform traffic differentiation when transmitting on wireless mesh network.Thereby, need a kind of new mechanism of design to realize the traffic differentiation of wireless mesh network.
In addition, current IP layer service quality guarantees that mechanism also is not suitable for wireless mesh network.Can see by top analysis,, distinguish just can realize the data service of whole network if traffic differentiation mechanism is arranged at the IP layer.At present, on the internet, most popular two I P layer quality-of-service mechanisms are: Differentiated Services (Diffserv:Differentiated Services) mechanism and integrated service (Interserv:Integrated Services) mechanism.Obviously, Interserv also is not suitable as the IP layer quality-of-service mechanisms of wireless mesh network, and this mainly is because its extensibility is too poor.For the wireless mesh network that a network topology structure often changes, Interserv is unavailable basically.Equally, Diffserv is not suitable in the wireless mesh network yet, this mainly be because:
1) it does not utilize the traffic differentiation mechanism of the MAC of lower floor layer, so just can not can communicate with the client of IEEE 802.11e.If need and to communicate by letter, then need to design a mechanism and can shine upon precedence information between Diffserv and the IEEE 802.11e.
2) practical operation of Diffserv also is difficult to realize in wireless mesh network.The veteran engineer of needs is familiar with and understands whole network state, and need all be configured on each router.The more important thing is that Diffserv has an important hypothesis, is exactly to transmit (EF:ExpeditedForwarding) stream for accelerating type, they the arrival rate of a node should guarantee to be lower than this node the bandwidth that can use.This guarantees to become difficult to achieve for the wireless channel that may change at any time.
Therefore, for wireless mesh network, just be necessary to design new service quality controlling mechanism and guarantee that various data services are to performance demands such as throughput, delays.In general, provide service quality to guarantee that technology has following two considerations in the digital communication technology:
1. in wireless mesh network, the data traffic flow of number of different types is arranged.They have nothing in common with each other to performance demands such as throughput, delay, delay jitters.In order to satisfy demand separately, at first just have and to carry out traffic differentiation to them, so that make relative measures.Further, for Virtual network operator, they need be for the more client that pays provides better network service, thereby also needs to carry out traffic differentiation.
2. for some data service, particularly multimedia service flows, for example voice communication, and they need a kind mechanism and control its time delay that is experienced, shake, loss rate etc. when transmission over networks.If neither one mechanism is controlled these performances, these data services just can't communicate.So second aspect of service quality control is exactly to carry out the assurance of service quality.
Because IEEE 802.11e is not suitable for the wireless mesh network of multi-hop, based on above 2 considerations, so at first need to provide the mechanism of a traffic differentiation to distinguish the online various dissimilar business of wireless mesh.Secondly, under the wireless communications environment of a multi-hop, how to guarantee that performance of services is faced with great challenge.For the VoIP speech business, it need be controlled the delay and jitter of each jumping and guarantee to postpone end to end, shake the requirement that can meet a Speech Communication especially.
Summary of the invention
In view of this, the object of the present invention is to provide the method for ensuring service quality in a kind of wireless mesh network, provide service quality Differentiated Services consistent in the whole wireless mesh network by exchange precedence information between MAC packet header and IP packet header, for example utilize the ToS territory (or DS territory) in IP packet header and the QoS control domain in MAC packet header, when a router receives a packet, the precedence information in the QoS control domain of MAC packet header is saved in ToS (the Type of Service) territory in IP packet header at the MAC layer; And when it will transmit a packet, at the IP layer precedence information in IP packet header is taken out and to be stored in the QoS control domain in MAC packet header, provide unified traffic differentiation thereby be implemented in the wireless mesh network of multi-hop; Simultaneously, the present invention also considers exclusive characteristics such as the roaming characteristic, backbone network bandwidth of wireless mesh network, realizes Admission Control in the wireless mesh network by setting Control Parameter.
To achieve these goals, technical scheme of the present invention is:
Method for ensuring service quality in a kind of wireless mesh network is characterized in that comprising the steps:
When a. wireless router receives packet, if do not carry precedence information in the IP packet header, then the precedence information in the MAC packet header is saved in the IP packet header, and transfers to the IP layer at the MAC layer;
B. from the IP packet header of described packet, read precedence information at the IP layer, this precedence information is written in the MAC packet header, and transmit described packet.
Among the described step a: described precedence information writes the COS territory or the different service domains in IP packet header.
Among the step b: described precedence information is written in the QoS control domain in MAC packet header.
Described method also comprises: when gateway sent packet to this wireless mesh network inside, if having precedence information in the IP packet header of this packet, then the precedence information with this IP layer was saved in the MAC layer.After described MAC layer is preserved precedence information, new MAC layer priority is set in IP packet header.
If do not have precedence information in the IP packet header of packet, then directly give MAC layer with packet data delivery.
The Differentiated Services code-point DSCP that is provided with in the COS territory in IP packet header or the different service domains is mapped as the priority of MAC layer.
Described method also comprises:
C. when gateway was forwarded to external network (as the Internet) with the packet of this wireless mesh network, the COS territory in the IP packet header or the value of different service domains were set to 0.
Described method also comprises:
D1. when a VoIP request added this wireless mesh network, access point radio (radio) and the wireless also open ended voip call quantity of backbone network according to calculating judged whether to admit this calling;
If d2. at least one in the wireless also open ended voip call quantity of access point radio and backbone network is not more than 0, then exclude the calling of this VoIP.
If the wireless also open ended voip call quantity of access point radio and backbone network is all greater than 0, and wireless packet loss is admitted this voip call when being not more than its maximum packet loss FraLossRatio.
The wireless also open ended voip call quantity AllowNum of described access point radio and backbone network is calculated by following formula:
AllowNum＝MaxNum-CurrentNum-RoamNum，
Wherein, MaxNum is the maximum concurrent voip call quantity that a radio can hold, and CurrentNum is the quantity of the voip call of current existence in the radio, and RoamNum is the VoIP quantity that a radio is reserved.
Beneficial effect of the present invention is that the present invention has realized the traffic differentiation of wireless mesh network, has guaranteed service quality, and has further improved service quality by Admission Control of the present invention.Simultaneously, the present invention also has the following advantages: (1) distinguishes machine-processed IEEE 802.11e based on existing MAC layer.Can be fully compatible current WLAN devices; (2) realize easily.In case wireless mesh network is set up, just can guarantee the traffic differentiation of end-to-end unification, unanimity, and need not unnecessary configuration and setting.This is even more important for the wireless mesh network that topological structure often changes, sets up temporarily.(3) extensibility is good, and the user need not to adding in the wireless mesh network into safeguarding, reshuffle work after the wireless router; (4) introduce the self-designed IP layer of user mechanism easily, make things convenient for equipment supplier or operators to provide machine-processed according to the service quality that own demand designs oneself.
Description of drawings
Fig. 1 is a typical wireless mesh network schematic diagram;
Fig. 2 a is WLAN (wireless local area network) shared position view in the whole network equipment;
Fig. 2 b is wireless mesh network shared position view in whole network topology;
Fig. 3 a is a MAC packet header schematic diagram;
Fig. 3 b is an IP head-coating structure schematic diagram;
The flow chart that Fig. 4 carries out on wireless router for traffic differentiation mechanism of the present invention;
The flow chart that Fig. 5 carries out on radio network gateway for traffic differentiation mechanism of the present invention.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, specific embodiments of the invention are elaborated below in conjunction with accompanying drawing.
The present invention is applicable to the described network topology structure of Fig. 1.In a wireless mesh network, wireless router (Mesh router) is its topmost element.Except the access point (AP:AccessPoint) as client, wireless router is also born the wireless trunk net of setting up between the wireless router.In addition, be connected to external network if desired, also should have a radio network gateway in the wireless mesh network at least, they are connected to the correspondence with foreign country that whole wireless mesh network is responsible for transmitting in the Internet by cable.
The present invention herein needs special declaration once.The wireless mesh network that the inventive method was suitable for uses existing WLAN (wireless local area network) physical layer and the MAC layer technology except continuing, and also needs to use IP layer technology, and this is because when carrying out need utilizing the IP layer to carry out Path selection when packet is transmitted.In other words, be exactly that the inventive method is applicable to that those have adopted IP layer, MAC layer and physical layer, and be based on the wireless mesh network of wireless local area network technology.In addition, wireless mesh network has many networking models at present, that is to say according to the employed radio of each router (Radio) number and channel (channel) quantity, has multiple different networking structure.Usually have four types: single radio-single channel, multi radio-single channel, single radio-multichannel, multi radio-multichannel.It is pointed out that equally the inventive method is applicable to above various networking mode, is not subjected to radio number and number of channel quantitative limitation.In a word, this method only is not suitable for those wireless mesh networks that does not adopt wireless local area network technology or do not relate to IP layer technology, all is suitable for for other wireless mesh network networking technology, mode.
Current, the service quality control of MAC layer can be provided for WLAN devices by IEEE 802.11e.So, the most basic condition is exactly the new method that designs can compatible existing IEEE 802.11e agreement.In fact, because the existence of IEEE 802.11e, only there is the data flow of jumping can be by traffic differentiation.And unified traffic differentiation is provided in the wireless mesh network of multi-hop, shortage be a tie, this tie can connect the priority that every jumping has.And the realization of this tie can realize by the precedence information in exchange MAC packet header and the IP packet header.
The basic principle of method for ensuring service quality of the present invention is exactly to utilize the QoS control domain (QoS Control) in the ToS territory and the MAC packet header in IP packet header.Shown in Fig. 3 a, the QoS control domain in MAC packet header is the structure of one 16 bit long, and it has comprised priority of data packets information and some other information about the service quality aspect, wherein preceding 3 bits, be bit0-bit2, what comprise is this priority of data packets information.And the ToS territory in IP packet header is the structure (Fig. 3 b) of 8 bit long, is used to refer to the COS that IP layer data bag belongs to.Wherein, preceding 6 bits in ToS territory, i.e. bit0-bit5, what comprise is the COS of packet; Last two bit6-bit7 then are reserved.It should be noted that the packet header of only mentioning IPv4 herein.In fact for IPv6, it equally also has the DS territory of 8 bit long.This DS territory also is to be used for comprising the affiliated COS of packet.So, equally also be applicable to the IPv6 packet in fact for institute of the present invention extracting method.In the practical operation, as biconditional operation IPv4 packet, only need that operand is become the DS territory from the ToS territory and get final product.So the present invention only describes the operation of IPv4 with the lower part, these operations are suitable equally to IPv6.
In order to guarantee to obtain unified traffic differentiation, on the contrary method of the present invention the precedence information in MAC packet header can be passed to IP packet header or.When a router receives a packet, the precedence information in the QoS control domain of MAC packet header is saved in the ToS territory in IP packet header at the MAC layer; And when it will transmit a packet, be stored in the QoS control domain in MAC packet header in the precedence information taking-up of IP layer with IP packet header.
In the wireless mesh network, a wireless router should have the function of wireless local network connecting point, has the packet forwarding capability again.But for the gateway in the wireless mesh network, it also needs to transmit the data flow of discrepancy wireless mesh network.Because wireless router has different effects with gateway in wireless mesh network, thereby their performed actions are also inequality.Reach the action that to carry out on the radio network gateway on the wireless router with being described in respectively below.
I. the action of carrying out on the wireless router
The flow chart that Fig. 4 carries out on wireless router for traffic differentiation mechanism of the present invention.As shown in Figure 4, when wireless router received packet from the MAC layer, to the IP layer, it should carry out following action at the MAC layer at the data delivery bag:
1) at first, checks that whether the value (value of bit0-bit5) of the COS in the ToS territory, IP packet header is greater than 0.If greater than 0, show this packet at the existing precedence information of IP layer, need not again the priority of MAC is passed to the IP layer, so Xia Mian action then need not to remake.If but be 0, then this packet may also need to carry out traffic differentiation, the action below continuing so.
2) need from the QoS control domain in MAC packet header, read out this priority of data packets information, as the MAC precedence information being read to MAC priority variable mac_prio.Herein, the packet of always supposing the MAC layer all has precedence information.If this packet is from the client that has been equipped with IEEE 802.11e network interface card, it should have precedence information certainly; If this packet is from other wireless router, under the use of new mechanism of the present invention, it should also have precedence information.Thereby this hypothesis is always set up.
3) MAC layer precedence information is written in the ToS territory in IP packet header.Since IEEE802.11e has only defined 8 priority, can be only at mac_prio greater than 0 and gave the bit0-bit2 in the ToS territory in IP packet header with the value assignment of variable mac_prio less than 7 o'clock, thereby only preceding 3 bits (bit0-bit2) in ToS territory are used.Simultaneously, recomputate the verification in IP packet header and (checksum).
Pseudo-code when wireless router of the present invention receives packet is as shown in table 1, but is not limited to this.
Pseudo-code when table 1. wireless router receives packet
When wireless router sent a packet, to the MAC layer, it should carry out following action at the IP layer at the data delivery bag:
1) whether the value of judging ToS territory, IP packet header is 0.If be 0, illustrating in the IP packet header does not have precedence information, does not therefore move and directly is sent to the MAC layer;
2), then from preceding 3 bits in ToS territory, IP packet header, read precedence information if be not 0.
3) precedence information that reads out is written in the QoS control domain in MAC packet header.The precedence information in IP packet header can be read out to a ToS priority variable (tos_prio), and can be only at this variable greater than 0 and less than 7 o'clock, assignment is given preceding 3 bits (0-2bit) of MAC packet header QoS control domain.
Pseudo-code when wireless router of the present invention sends packet is as shown in table 2, but is not limited to this.
Pseudo-code when table 2. wireless router sends packet
II. when receiving equipment is wireless mesh network gateway, performed action on the gateway of this wireless mesh network:
Because this gateway need be connected to outside the Internet, thereby when carrying out traffic differentiation, it needs packet of correct differentiation is to be forwarded to wireless mesh network inside, still is sent to the Internet, and need takes corresponding action according to the whereabouts of packet.
When wireless mesh network gateway sent packet from the IP layer, to the MAC layer, it should carry out following action (as shown in Figure 5) at the IP layer at the data delivery bag:
1) at first, checks that this packet is will be forwarded to wireless mesh network inside or be forwarded to outside the Internet.If it is the packet that sends to wireless mesh network from external the Internet, then execution in step 2); Otherwise then execution in step 3).
2), check then whether the priority value in ToS territory, IP packet header is 0 if packet sends to wireless mesh network from external the Internet.If this value is not 0, show that this packet was carried out traffic differentiation by the service quality controlling mechanism of the IP layer on the Internet.Thereby, the precedence information of IP layer should be saved in the MAC layer, promptly be mapped as the priority mac_prio of MAC layer, and the bit0-bit2 of MAC packet header QoS control domain is set to mac_prio.Since the Diffserv mechanism most widely used IP layer service quality controlling mechanism that is current internet can always suppose that then the ToS territory is set to the DSCP value of Diffserv definition.The priority that as for how the DSCP value is mapped as the MAC layer then be part very flexibly and the thing that realizes easily.Can adopt any mapping relations among the present invention.In table 3a and table 3b, provide the example of two mapping relations herein.Simultaneously, after the MAC layer is preserved precedence information, the value in ToS territory, IP packet header need be rewritten as new MAC layer priority, and recomputate IP packet header verification and.Need to prove that the present invention also is applicable to other IP layer service quality controlling mechanism, the user also can be according to the new mapping relations of needs definition of oneself.If the original ToS thresholding in IP packet header equals 0, show that this packet need not to carry out traffic differentiation, just it is not submitted to the MAC layer so do not need to move.
Table 3a. is mapped as the DSCP value example of MAC priority
| Diffserv(DSCP) | |
| CS7 | |
| 7 | |
| EF， |
6 |
| CS5 | 5 |
| AF4x’， |
4 |
| AF3x’，CS3 | 3 |
| DE，CS0 | 0 |
| AF2x’， |
2 |
| AF1x’，CS1 | 1 |
Table 3b. is mapped as the DSCP value another example of MAC priority
| Diffserv(DSCP) | MAC priority |
| EF， |
7 |
| |
6 |
| AF4x’，CS5 | 5 |
| AF3x’， |
4 |
| CS3 | 3 |
| DE，CS0 | 0 |
| AF2x’， |
2 |
| AF1x’，CS1 | 1 |
3) if this packet from wireless mesh network inside, need be forwarded on the Internet, the value in its ToS territory, IP packet header should be changed to 0.Since the value in the ToS territory, IP packet header of this moment is only in the inner use of wireless mesh network, so when packet was sent to the Internet, these precedence informations did not have meaning.And, if adopted other IP layer service quality controlling mechanism, then can reset the ToS territory in IP packet header on the Internet.
Table 4 is a wireless mesh network gateway of the present invention pseudo-code when sending packet, but the present invention is not limited to this.
Pseudo-code when table 4. wireless mesh network gateway sends packet
When gateway received a packet, it need not carry out any action.If this packet from wireless mesh network, need be forwarded on the Internet, the precedence information that does not need to preserve any MAC layer is to the IP layer, this is that current precedence information is effect not owing to can adopt no service quality controlling mechanism on the Internet.If this packet comes from the Internet, do not need to preserve the precedence information of any MAC layer equally.Therefore, gateway need not to do any action when receiving a packet.
As mentioned above, the present invention provides service quality Differentiated Services consistent in the whole wireless mesh network by exchange precedence information between MAC packet header and IP packet header; Strong and the easily realization of this method extensibility, be highly suitable under the wireless mesh network environment and use, and its is fully compatible and made full use of the service quality standard IEEE 802.11e of current MAC layer, makes any terminal equipment provider need not to consider compatibility issue.And this method only needs to carry out in wireless mesh network equipment, and allows the equipment supplier to design the IP layer quality-of-service mechanisms of oneself.
Further describe the Admission Control mechanism on service quality Differentiated Services of the present invention basis below.Based on above-mentioned voice communication VoIP business based on the IP layer will be one of main applied business of following wireless mesh network.In order to provide gratifying voice quality on the net at wireless mesh, calling out mechanism of permitting the entrance is one of key element.Existing studies show that, a WLAN (wireless local area network) the VoIP quantity that can support simultaneously be certain.When the VoIP quantity in the system surpassed certain numerical value, the VoIP that not only newly enters connects can't obtain satisfied speech quality, and already present VoIP connection also can be destroyed.Thereby, just must have one to call out mechanism of permitting the entrance, thereby its can be refused new calling according to current network conditions and guarantee existing VoIP conversation.
Than WLAN (wireless local area network), in wireless mesh network, provide and call out mechanism of permitting the entrance and can be subjected to the more resources restriction, the wide restriction of for example restriction of WAP (wireless access point), wireless trunk guipure, the roaming characteristic that terminal mobility causes etc.Consider the characteristic that these are new, propose a calling mechanism of permitting the entrance that is suitable for wireless mesh network simply among the present invention.Its detailed operating process is described below:
I. each wireless router (comprising gateway) all can be provided with following four parameters in advance.This Several Parameters is used for judging whether new voip call of this admittance.
First parameter is MaxNum.It represents the maximum concurrent voip call quantity that radio can hold.In fact this value is exactly a theoretic limiting value.Concurrent voip call has surpassed this value, and the voip call quality in the system can significantly descend.The acquisition of MaxNum then depends on the physical-layer techniques of radio adaptation.Recent some theoretical researches and experimental result show that for the 802.11b radio of a 11Mbps, it can hold the voip call of 6 G711 codings at most; The 802.11a radio of a 54Mbps then can hold the voip call of 30 G711 codings.Thereby, when the MaxNum value of a router is set, then need correspondingly to be provided with according to the operated physical-layer techniques of each radio
It should be noted that current wireless router all can be equipped with a plurality of radio basically, so MaxNum should be set at each radio.For radio, their MaxNum value just can be set directly according to existing result of study as WAP (wireless access point).But for the radio as the wireless trunk net, the MaxNum value is then slightly different, and this mainly is that the MAC layer is caused.Because the frequency range of backbone network radio adaptation generally all can be different from the frequency range of access point, the interference that does not just have too many client's section enters.Thereby the caused collision probability of these wireless MAC layers then can reduce greatly, and the wireless MaxNum of backbone network can be bigger slightly than the wireless value of access point so.And for the backbone network radio, the calculating principle of its MaxNum value is wireless the same with access point; Unique different place be that the collision back-off time value that the MAC layer need be consumed changes minimum contention window value into half get final product.The current theoretical calculation formula that utilizes (can referring to document [1]), some differences mentioned above considering again just can obtain the wireless MaxNum value of backbone network.In practical operation, except the reference theoretical value, the user can also be provided with MaxNum according to the needs of oneself.
Second parameter is CurrentNum.The quantity of the voip call of current existence in radio of its expression.Consider the mobility of terminal, thereby to have some voip calls may be by other local roamings, the voip call so this value must comprise these roamings.The calculating of this value is carried out separately by each radio, stores separately.Whenever a new calling is admitted or voip call roaming, this value then increases by 1; And call out to stop or roaming and walking when one, this value then subtracts 1.
The 3rd parameter is RoamNum.This parameter is to aim at wireless mesh network and design, and is used for representing that a radio reserves the VoIP quantity of coming out in advance, and roaming is only served and the voip call that comes in the space of these reservations.In order to keep a continuity in the voip call process, when terminal was carried out mobile roaming, this VoIP should from start to finish keep connecting and terminal not.So just be necessary on each radio, to reserve in advance the voip call of some to roaming.The user is depended in the setting of this value.We advise that the access point radio is set to 1-2 and gets final product, and backbone network then can be provided with big owing to will admit more roaming call a little.
The 4th parameter is FraLossRatio.A voip call of its expression the maximum packet loss that can tolerate.After packet loss surpassed this value, the both call sides the other side that can not hear clearly basically was said.The setting of this value can be with reference to the quality of service requirement of voip call.In system's running, wireless router can detect each wireless packet loss in time and upgrade them.
Before providing detailed operating procedure, express for convenience, define two abbreviations herein.One is APRadio, is used for representing asking the access point radio that voip call connected that adds.Another one is BKRadio, and it represents a backbone network radio, and the transmission path of this new voip call can be via this radio.When a new voip call request adds fashionablely, can be easy to determine APRadio; And for BKRadio, it then can be determined by the destination address of this VoIP and the routing table in the router.
II. add fashionablely when new voip call request, utilize above-mentioned four parameters, no circuit has device execution following steps to judge whether that this admits this voip call:
1) checks the destination address of this voip call, and determine BKRadio according to routing table.
2), calculate also open ended voip call quantity (AllowNum) respectively for APRadio and BKRadio.Calculate by following formula AllowNum=MaxNum-CurrentNum-RoamNum.
3) AllowNum of inspection APRadio and BKRadio.If have at least one AllowNum to be not more than 0 in them, then refuse this voip call; Otherwise, carry out following steps.
4) obtain the packet loss of APRadio and BKRadio.If have the FraLossRatio of a wireless packet loss at least, then refuse this voip call greater than it; Otherwise, admit this calling.
The pseudo-code that realizes Admission Control of the present invention can be as shown in table 5, but be not limited to this.
The pseudo-code of table 5. Admission Control mechanism
By Admission Control of the present invention, further improved the service quality of speech business in the wireless mesh network.
In sum, realized having guaranteed the traffic differentiation of wireless mesh network service quality, and further improved service quality by method of the present invention by Admission Control of the present invention.Simultaneously, the present invention also has the following advantages: (1) distinguishes machine-processed IEEE 802.11e based on existing MAC layer.Can be fully compatible current WLAN devices; (2) realize easily.In case wireless mesh network is set up, just can guarantee the traffic differentiation of end-to-end unification, unanimity, and need not unnecessary configuration and setting.This is even more important for the wireless mesh network that topological structure often changes, sets up temporarily.(3) extensibility is good, and the user need not to adding in the wireless mesh network into safeguarding, reshuffle work after the wireless router; (4) introduce the self-designed IP layer of user mechanism easily, make things convenient for equipment supplier or operators to provide machine-processed according to the service quality that own demand designs oneself.
Above embodiment only is used to illustrate the present invention, but not is used to limit the present invention.Within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
List of references
[1]Sachin?Garg?and?Martin?Kappes，“Can?I?add?a?VoIP?call？”，IEEE?ICCconference，pp.779-783，2003.
Claims (9)
1. the method for ensuring service quality in the wireless mesh network is characterized in that comprising the steps:
When a. wireless router receives packet,, then the precedence information in the MAC packet header is saved in the COS territory or different service domains in IP packet header, and transfers to the IP layer at the MAC layer if do not carry precedence information in the IP packet header;
B. from the IP packet header of described packet, read precedence information at the IP layer, this precedence information is written in the QoS control domain in MAC packet header, and transmit described packet.
2. method according to claim 1 is characterized in that also comprising:
When gateway sent packet to this wireless mesh network inside, if having precedence information in the I P packet header of this packet, then the precedence information with this IP layer was saved in the MAC layer.
3. method according to claim 2 is characterized in that also comprising:
After described MAC layer is preserved precedence information, new MAC layer priority is set in IP packet header.
4. method according to claim 2 is characterized in that:
If do not have precedence information in the IP packet header of packet, then directly give MAC layer with packet data delivery.
5. method according to claim 2 is characterized in that:
The Differentiated Services code-point DSCP that is provided with in the COS territory in IP packet header or the different service domains is mapped as the priority of MAC layer.
6. method according to claim 1 is characterized in that, also comprises:
C. when gateway was forwarded to external network with the packet of this wireless mesh network, the COS territory in the IP packet header or the value of different service domains were set to 0.
7. according to any described method among the claim 1-6, it is characterized in that also comprising:
D1. when a VoIP request added this wireless mesh network, access point radio and the wireless also open ended voip call quantity of backbone network according to calculating judged whether to admit this calling;
If d2. at least one in the wireless also open ended voip call quantity of access point radio and backbone network is not more than 0, then exclude the calling of this VoIP.
8. method according to claim 7 is characterized in that:
If the wireless also open ended voip call quantity of access point radio and backbone network is all greater than 0, and wireless packet loss is admitted this voip call when being not more than its maximum packet loss FraLossRatio.
9. method according to claim 7 is characterized in that, in the steps d 1:
The wireless also open ended voip call quantity AllowNum of described access point radio and backbone network is calculated by following formula:
AllowNum＝MaxNum-CurrentNum-RoamNum，
Wherein, MaxNum is the maximum concurrent voip call quantity that a radio can hold, and CurrentNum is the quantity of the voip call of current existence in the radio, and RoamNum is the VoIP quantity that a radio is reserved.
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