CN100366010C - Mobile IP nonuniform switching detection in Wi-Fi network - Google Patents
Mobile IP nonuniform switching detection in Wi-Fi network Download PDFInfo
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Abstract
The present invention relates to a nonuniform switching detection method of mobile IP in a Wi-Fi network. The present invention apperceives the occurrence of switching by using a method for detecting the change of an MAC address of AP and detects the occurrence of the switching by using a nonuniform interval detection model. After the occurrence of the switching is detected by MN, a new MAC address of the AP is obtained, and through the search of a mapping table, an IP address of the AR in ESS which MN enters and a subnetwork prefix are obtained by the MN. An onward transmission address of the MN is constructed by using an MAC address of the MN and the subnetwork prefix of the ESS near the MN, and the uniqueness authentication and the pre-registration of the AR in the ESS near the MN is carried out. The present invention has the advantages that the detection of the mobility of nodes does not need beacons of link layers or the support of a trigger and is only realized in a network layer, and the detection of the mobility of nodes can be fast applied to a wireless local area network environment widely used at present. The nonuniform detection method is firstly used for the switching of the link layers, the time delay of mobility detection is effectively lowered, and simultaneously, the burden to the mobile nodes is reduced.
Description
Technical Field
The invention relates to a non-uniform switching detection method of a mobile IP in a Wi-Fi network.
Background
With the maturity of wireless technology and the continuous emergence of new services on the Internet, providing multimedia services such as voice and video for mobile terminals has become an inevitable trend in the development of communication technology. Compared with technologies such as 3G, the IEEE 802.11 wireless local area network (Wi-Fi) technology can provide higher channel bandwidth and a flexible networking mode, and the application of the technology in the aspect of Internet wireless access is more and more extensive. In addition, the IETF has recently issued the mobile IPv6 standard (RFC 3775), which will certainly contribute to the popularization of Internet radio access technology.
However, the current Mobile IPv6 protocol (MIPv 6: mobile IPv 6) only solves the problem of maintaining the communication continuity of the Mobile Node (MN: mobile Node) during the moving process, and because the link layer handover and network layer handover processes that the MN passes through during the inter-subnet handover generate a large delay (generally in the order of seconds), MIPv6 cannot provide satisfactory support for time-sensitive voice and video services. Especially in the Wi-Fi infrastructure (infrastructure) mode, the network layer cannot know the handover situation of the link layer in time because the handover process of the link layer does not provide enough information for the network layer, which results in further increase of the time delay of the whole handover process.
At present, the following methods are mainly used for the mobile IP handover process:
1. pre-registration handover, post-registration handover and hybrid handover methods
There are three methods to reduce the handover delay and the data loss rate: pre-registration switching, post-registration switching and hybrid switching methods. These methods assume that the MN can maintain the communication with the original Access Point (oAP: old Access port) during the process of switching to the new Access Point (nAP: new Access Point), and the switching is triggered by the trigger of the link layer.
These methods can effectively improve the handover performance of mobile IP, but in a Wi-Fi environment, one wireless interface of the MN cannot simultaneously establish two link layer connections to the AP, and therefore these methods cannot be applied in the current Wi-Fi network.
2. Simultaneous handover scheme and improvement scheme
The method uses the link layer response request frame to carry the network layer registration information, so that the link layer and the network layer can be switched in parallel. The method of simultaneous switching needs to modify the frame structure of the MAC layer and also destroys the inter-layer independence of the OSI model, which affects the scalability of the protocol.
3. Fast handover
There is a MIPv6 fast handover method (FMIPv 6) that uses a beacon of a link layer to obtain an event that a handover is about to occur, and then sends a fast binding update message to an original Access Router (oAR) or a new Access Router (nAR). In the process of link layer switching and before the nAR receives a quick neighbor advertisement message sent by the MN, the oAR is responsible for forwarding the received data to the nAR, so that the data is not lost during switching.
Research on FMIPv6 shows that FMIPv6 effectively reduces the binding update delay of the MN during the handover process, but does not contribute much to reducing the delay of the entire handover process, since a major part of the handover delay is caused by the discovery process for nAR.
4. Fast handover proxy
Aiming at the defects of FMIPv6, an improved method is provided by a Fast Handover Agent (FHA). The FHA advertises the AR information to the MN through the fast handoff proxy to reduce the delay caused by the MN router discovery process.
The FHA advertisement message is triggered by a link establishment event at the link layer, and thus in Wi-Fi networks, link layer trigger support is also required.
5. Hierarchical mobile IPv6
Hierarchical MIPv6 mobility management (HMIPv 6) is a pure network layer mechanism. HMIPv6 reduces the information interaction quantity between MN and communication opposite terminal (CN: coresponsent Node) and Home Agent (HA: home Agent) by layering the network, and shields the mobility of MN in the network in a small range.
When the MN performs the switching between the subnetworks, HMIPv6 adopts the MIPv6 method, so that the switching delay is not improved.
6. Periodic handover detection
There is another handover mechanism at the network layer in a Wi-Fi environment. The method senses whether the MN is switched or not by periodically detecting the change condition of the MAC address of the MN. After the switching is known to occur, the MN quickly obtains information of the nAR in the new subnet by querying a fixed MAC address. The mechanism effectively reduces the time delay of MN in the process of switching detection and router discovery, and meanwhile, the switching detection does not need the support of a trigger mechanism of a link layer and the change of the link layer.
The drawback of this approach is that periodic MAC address detection burdens the MN. In addition, the discovery process of nAR requires support by the link layer.
Disclosure of Invention
The current MIPv6 fast handover algorithm needs the support of a link layer, so the method cannot be used in the Wi-Fi network environment which is widely applied at present. Aiming at the problem, the invention provides a non-uniform switching detection method of mobile IP in a Wi-Fi network, which does not need to modify the protocol of a link layer and does not need a novel switching detection method supported by a link layer trigger mechanism.
The technical scheme adopted by the invention for solving the technical problem is as follows:
step 1: the invention uses a method for detecting the change of the MAC address of the AP to sense the occurrence of switching;
when the MN is in one ESS, the MAC address of each AP in the ESS is obtained through the AR and cached. During the movement, the MN marks the MAC address of the currently attached AP and checks again at every interval. If the MAC address detected this time is inconsistent with the address marked last time, it indicates that the MN is attached to a new AP. The MN is able to know whether a new ESS is entered by comparison with the MAC address in the cache.
Step 2: detecting by using a non-uniform interval detection model;
the non-uniformly spaced handover detection is described as follows:
Δt＝βA
β＝g(x)＝g(I(x))
in the above formulas, Δ t is a detection interval; a is the maximum detection interval; beta is called interval ratio; g (x) is a function of the detection interval compression characteristic and is a nonlinear function; i (x) is a switching strength function, the switching possibility of the MN at the position x is represented, and the probability of switching the MN is higher when the switching strength is higher; x is the location of the MN during mobility.
And step 3: after MN detects the switching, it needs to obtain the IP address of new access router nAR, AR in one ESS obtains the IP address of AR in neighbor ESS and the MAC address of AP in it through the AR interactive announce message with neighbor ESS, and establishes a one-to-many mapping relation from IP address to MAC address, called as mapping table of ESS, when MN is in one ESS, it can obtain the mapping table of ESS adjacent to the ESS currently located by the attached AR, once MN detects the switching and obtains the MAC address of new AP, through the search of mapping table of ESS, MN obtains the IP address and subnet prefix of AR in ESS where it enters,
and 4, step 4: in the switching detection process, a care-of address pre-registration threshold psi is set, when beta is not more than psi, the MN sends a pre-registration request to an original access router oAR, the original access router oAR adopts a stateless address automatic configuration method of RFC2462, an MAC address of the MN and a subnet prefix of a neighbor ESS of the MN are used for constructing a care-of address of the MN, uniqueness verification and pre-registration are carried out on the AR in the neighbor ESS, if the pre-registration is successful, the original access router oAR sends a pre-registration response message to the MN, the AR in the neighbor ESS marks the care-of address, a pre-registration timing is set, when the MN enters one ESS, the MN uses the MAC address of the MN and the subnet prefix of the currently entering ESS to construct the care-of address, the address is immediately used for establishing connection with the AR in the currently entering ESS, the AR changes the pre-registration address marked by the MN into an occupied state, and informs the original AR of canceling the pre-registration of the care-registration of the MN to the care-of the MN if the original AR is still within the pre-registration timing time of the MN, and informs the neighbor ESS of canceling the registration of the MN to the neighbor.
The remarkable effects of the invention include: the detection of the node mobility does not need the support of a beacon or a trigger of a link layer, is realized only in a network layer, and can be quickly applied to the currently widely used wireless local area network environment; the non-uniform detection method is adopted for the switching of the link layer for the first time, so that the burden on the mobile node is reduced while the mobile detection time delay is effectively reduced, and the wireless link resource for detecting the position of the mobile node is saved; the cached IP address and MAC address mapping mechanism is adopted to acquire the AR address, so that the pre-registration of the care-of address of the mobile node is realized, and the time delay caused by the care-of address configuration in the switching process is reduced.
Drawings
The invention is further illustrated with reference to the following figures and examples.
Fig. 1 is a flow chart of non-uniform handover detection.
Fig. 2 is a mobility detection diagram of a mobile node handoff between ESS.
Fig. 3 is a graph of compression characteristics for non-uniform switching detection.
Detailed Description
Example (b): a specific example of the implementation of the method proposed in the present invention is given below, as shown in the flow chart of fig. 1;
step 1: comparing whether the MAC address of the AP changes. In the case that information about whether the link layer is switched cannot be obtained, the mobile detection of the MN is a passive behavior, and the AR frequently sends an RA message on the wireless port of the AP in a broadcast manner, which also occupies a lot of wireless resources. Since Wi-Fi hardware can provide the network layer with the identity, i.e., MAC address, of the AP to which the MN is currently attached, the present invention senses the occurrence of a handoff using a method of detecting a change in the MAC address of an AP. If the MAC address changes, step 2 is executed, otherwise, step 7 is executed.
And 2, step: when the MN is in one ESS, the MAC address of each AP in the ESS is obtained through the AR and cached.
And step 3: and searching the IP address of the new AP in the cache list according to the MAC address of the new AP. After detecting that the handover occurs, the MN needs to obtain the IP address of the nAR next, and a mechanism for expediting the obtaining of the IP address of the AR through mapping the IP address and the MAC address is provided below. The basic idea of the mechanism is that the AR in one ESS obtains the IP address of the AR in the neighbor ESS and the MAC address of the AP in the neighbor ESS through the AR interaction notification message with the neighbor ESS, and establishes the one-to-many mapping relation from the IP address to the MAC address. When the MN is in one of the ESS, the AR attached thereto can get the mapping table of the ESS adjacent to the current ESS. Once the MN detects that a handoff occurs and obtains the MAC address of the new AP, the MN can immediately obtain the IP address and subnet prefix of the AR in the ESS it entered by looking up the mapping table.
And 4, step 4: the care-of address CoA is constructed and connected to the new AR. The oAR adopts the stateless address automatic configuration method of RFC2462, constructs a care-of address of the MN using the MAC address of the MN and the subnet prefix of its neighbor ESS, and performs uniqueness verification and pre-registration with the AR in its neighbor ESS. If the pre-registration is successful, the oAR sends a pre-registration response message to the MN. The AR in the neighboring ESS marks the care-of address and sets a pre-registration timing. When the MN enters one ESS, the MN uses the MAC address of the MN and the subnet prefix of the current entering ESS to construct a care-of address, and immediately uses the address to establish connection with the AR in the current entering ESS.
And 5: the new AR informs the original AR to cancel the pre-registration through the network. The AR changes the pre-registered address marked for the MN into an occupied state and simultaneously informs the original AR of the MN to cancel the pre-registration of the care-of address of the MN. If the time is still within the pre-registration timing time of the MN, the original AR informs the neighbor ESS to cancel the pre-registration of the MN.
Step 6: turning to step 1.
And 7: x is obtained from the round trip time of the packet.
And step 8: delta t is calculated using a non-uniform handover detection model. Suppose that the MN is in the network environment shown in fig. 2, the distance from the current MN to AP1 is x, and the maximum coverage area of AP1 is d.
Let the detection interval compression characteristic function take the form:
when the compression parameter mu takes different values, the compression effect is as shown in fig. 3.
According to the IEEE 802.11 standard, the condition for the MN to decide whether to perform handover is that the strength or the signal-to-noise ratio of a wireless signal falls to a certain threshold, and under the condition that the wireless signal is not affected by other than the attenuation of the over-the-air transmission, there are:
Pr(x 1 )≥Pr(x 2 )，x 1 ≥x 2 ≥0
where Pr (x) is the probability of a handover occurring when the distance of MN to AP1 is x.
Since the switching strength of the MN is only used for calculating the time interval of the switching detection without affecting the operation process of the actual link layer switching, the variation trend of the switching probability can be approximately described by selecting an appropriate switching strength function. Let L denote the value calculated by the following equation when MN is switched, and let L be the negative exponential distribution of the load:
x is the distance from MN to AP1
The distribution function of L can be obtained:
F L (l)＝1-e -λl ，l＞0
using the distribution function of L as the switching strength, at a given position x * In the above, the handover detection interval of the available MN is:
and step 9: and (3) comparing the delta t with a preset threshold value, and if the delta t is larger than the threshold value, turning to the step 1 after delaying the delta t.
Step 10: and informing the original AR to perform pre-registration, and turning to the step 1 after delaying delta t.
The intervals for comparing the MAC addresses of APs attached to the MN are non-uniform, and the length of the comparison interval is related to the probability of the MN switching at the time of comparison.
Claims (1)
1. A non-uniform switching detection method of mobile IP in Wi-Fi network is characterized in that the following steps are adopted;
step 1: when MN is in an ESS, obtaining MAC address of each AP in the ESS through AR and caching, in the process of moving, MN marks the MAC address of the AP which is currently attached, and detects again at intervals, if the MAC address detected this time is not consistent with the address marked last time, the MN is indicated to be attached to a new AP, through the comparison with the MAC address in the cache, the MN can know whether to enter a new ESS,
and 2, step: detecting by using a non-uniform interval detection model;
the non-uniformly spaced handover detection is described as follows:
Δt＝βA
β＝g(x)＝g(I(x))
in the above formulas, Δ t is a detection interval; a is the maximum detection interval; beta is called interval ratio; g (x) is a function of the detection interval compression characteristic and is a nonlinear function; i (x) is a switching strength function, the switching strength function represents the switching possibility of the MN at the position x, and the higher the switching strength is, the higher the switching probability of the MN is; x is the location of the MN during mobility,
and step 3: after MN detects the switching, next, it needs to obtain the IP address of new access router nAR, AR in one ESS obtains the IP address of AR in neighbor ESS and MAC address of AP in it through AR interaction notification message with neighbor ESS, and establishes one-to-many mapping relation from IP address to MAC address, called as mapping table of ESS, when MN is in one ESS, it can obtain the mapping table of ESS adjacent to the current ESS through its attached AR, once MN detects the switching and obtains MAC address of new AP, MN obtains the IP address and subnet prefix of AR in ESS through searching mapping table of ESS,
and 4, step 4: in the switching detection process, a care-of address pre-registration threshold psi is set, when beta is less than or equal to psi, the MN sends a pre-registration request to an original access router oAR, the original access router oAR adopts a stateless address automatic configuration method of RFC2462, an MAC address of the MN and a subnet prefix of a neighbor ESS are used for constructing a care-of address of the MN, uniqueness verification and pre-registration are carried out on the AR in the neighbor ESS, if the pre-registration is successful, the original access router oAR sends a pre-registration response message to the MN, the AR in the neighbor ESS marks the care-of address, a pre-registration timing is set, when the MN enters one ESS, the MN uses the MAC address of the MN and the subnet prefix of the currently entering ESS to construct the care-of address, and immediately uses the address to establish connection with the AR in the currently entering ESS, the AR changes the pre-registration address marked by the MN into an occupied state, and informs the original AR of canceling the care-of the registration of the MN to the neighbor ESS at the MN, and if the pre-registration timing of the MN is still within the pre-registration timing time of the MN, the original AR of the neighbor ESS, the neighbor ESS informs the neighbor MN of canceling the pre-registration of the neighbor MN.
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| CN101977423B (en) * | 2010-10-19 | 2013-01-30 | 北京航空航天大学 | Method for selecting access point by vehicle-mounted WiFi (Wireless Fidelity) equipment |
| US9253808B2 (en) * | 2011-07-10 | 2016-02-02 | Qualcomm Incorporated | Systems and methods for low-overhead wireless beacons having next full beacon indications |
| US9642171B2 (en) | 2011-07-10 | 2017-05-02 | Qualcomm Incorporated | Systems and methods for low-overhead wireless beacons having compressed network identifiers |
| US8832238B2 (en) * | 2011-09-12 | 2014-09-09 | Microsoft Corporation | Recording stateless IP addresses |
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| WO2003077483A1 (en) * | 2002-03-12 | 2003-09-18 | Koninklijke Philips Electronics N.V. | System and method for performing fast channel switching in a wireless medium |
| CN1518390A (en) * | 2003-01-23 | 2004-08-04 | ���ǵ�����ʽ���� | Switching method in radio local network, insertion point and mobile station for executing switching method |
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| WO2003077483A1 (en) * | 2002-03-12 | 2003-09-18 | Koninklijke Philips Electronics N.V. | System and method for performing fast channel switching in a wireless medium |
| CN1518390A (en) * | 2003-01-23 | 2004-08-04 | ���ǵ�����ʽ���� | Switching method in radio local network, insertion point and mobile station for executing switching method |
Non-Patent Citations (1)
| Title |
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| 802.11无线局域网组网方式与移动性分析. 毛玉明，段景山，杨宁.电信技术，第10期. 2003 * |
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