CN1301033C - Cellular network and wireless local area network loose-coupling mobile communication network - Google Patents

Abstract

A mobile communication network in which a cellular network and a wireless local area network are loosely integrated, and is characterized in that: the wireless local area network (2n″) in the field is composed of a wireless access point (2a), a router (2b) connected to the outside, and a loosely coupled server (2c) , wherein a network port of the router (2b) is connected with the network port of the wireless access point (2a), and its other network port is connected with the network port of the loosely coupled server (2c).Compared with the prior art, the present invention's outstanding The advantages are: to establish a new mobile communication solution that loosely integrates the cellular network and the wireless LAN, realizes the virtual home agent and the physical function of the home agent for different mobile users, shortens the switching delay significantly, and solves the triangular routing problem.

Description

Mobile communication network loosely integrated with cellular network and wireless local area network

technical field

The invention relates to the mutual fusion between the general packet wireless cellular network and the wireless local area network, in particular to a mobile communication network in which the cellular network and the wireless local area network are loosely integrated.

Background technique

With the continuous demand of mobile users for high data transmission rate and the increasing situation of wide-area mobile office, the mutual integration of cellular mobile communication network and wireless local area network has become more and more necessary. Efficiently integrating WLAN into the wireless cellular network to provide users with higher-speed and better-quality data communication services in many hot spots (such as offices, airports, railway stations, hotels, etc.) will become a new trend in the wireless communication market. The growth point is that in the industry, some companies are currently developing dual-mode terminals that support both WLAN and GPRS.

On the data transmission rate, the highest in the GPRS cellular mobile communication network is 115/kbits and WLAN can utilize its high-speed data transmission rate as an effective supplement to GPRS. On the other hand, the working coverage of WLAN is several meters to hundreds of meters, and for For GPRS network, the wireless coverage is much higher than that of WLAN, which can reach tens of kilometers. It can be seen that WLAN and GPRS are complementary in these two aspects. Therefore, the intercommunication and integration of WLAN and GPRS network can make full use of the two Complementary capabilities of mobile operators, attracting a large number of user groups, enabling mobile users and operators to obtain greater benefits.

ETSI has specified two network convergence schemes, tightly coupled and loosely coupled.

In the loose coupling mode as shown in Figure 1, GPRS network is made up of two parts of GPRS core network and wireless access network, and wherein core network 4 is supported by GPRS service GPRS node (SGSN) 4a, gateway GPRS support node (GGSN) 4b, The home location register (HLR) 4c is formed, and the base station controller 5 and the base station 6 form the wireless access part. In the loosely coupled mode, mobile IP technology is used to solve its mobility management problem. The wireless local area network 2n is the mobile node 1 The wireless local area network passing through when roaming in other places, 2a wireless access point (AP), 2b is a router or a layer 2 switch connecting the wireless local area network with the outside, and 7n is the home wireless local area network to which the mobile node 1 belongs.

In the loosely coupled solution, the wireless LAN 2n and the GPRS cellular network are independent of each other, and there is no influence on the construction and extension of each other. The WLAN upper layer protocol uses various standard Internet protocols, and there is no need to modify the protocol stack. Its advantage lies in this, that is, the wireless local area network and the cellular wireless network can be deployed independently. However, the traditional mobile IP technology introduces large switching, transmission delay and packet loss rate, and it is not easy to provide seamless roaming switching. This problem has become the key technology to be solved at this stage.

In the tightly coupled scheme, as shown in Figure 2, the wireless local area network 2n ' exists as a wireless access network of the GPRS network, and is connected with the GPRS service support node 4a through the interface. Switching between two independent cells is equivalent to switching between two independent cells. Users can achieve seamless switching between the two networks, ensuring the continuity of sessions before and after switching, and better support for quality of service (QOS). However, the tight coupling scheme It is very difficult to realize the technology, and it is necessary to upgrade and transform the existing network equipment.

At this stage, the development trend is more concentrated on the research on the loosely coupled network structure.

Contents of the invention

The purpose of the present invention is to provide a mobile communication network in which the cellular network and the wireless local area network are loosely integrated, and a loosely coupled server (also called a virtual home agent) is added in the original wireless local area network in other places to complete the mobility management of the roaming mobile users The function can effectively solve the delay, packet loss and triangular routing problems of roaming mobile users in the handover process of the existing cellular network and wireless local area network integration.

A mobile communication network in which the cellular network and the wireless local area network are loosely integrated. As shown in FIG. 3, in the wireless local area network 2n", a virtual home agent 2c is set to solve the problem of the mobile node 1 whose home agent is the wireless local area network 7n during roaming. Mobility management issues.

The currently used mobile IP server is to register mobile users in the wireless local area network or wide area network after entering the network, and as a home agent or foreign agent, complete the process of encapsulation and disassembly of data packets, so as to realize mobile IP function. To complete the integration of wireless local area network and cellular network, a new server is needed to realize the roaming function of mobile nodes between cellular network and wireless local area network. The present invention refers to such a server as a loosely coupled server, and aims at mobile In the case of nodes roaming in other places, the loosely coupled server in the wireless local area network accessed by the mobile node is defined as a virtual home agent VHA (Virtual home Agent), which abandons the concept of foreign agent in traditional mobile IP and replaces it with a new functional entity— —Virtual home agent, in order to realize the mobile IP function of the roaming user in the loosely coupled network. As shown in Figure 3, such a loosely coupled server 2c is set in the wireless local area network 2n ", so that it communicates with the external data network 3 by coordinating the wireless access point 2a and the router 2b, from the mobile node 1 roaming to the field From the point of view, the loosely coupled server 2c in the wireless local area network 2n" plays the role of a virtual home agent, while the loosely coupled server 7 in its home network 7n acts as a home agent.

The goal of the virtual home agent 2c in Fig. 3 has the following two aspects: firstly, it is to solve the mobility management problem of the mobile node 1 under the loosely coupled network structure, and the most important thing is to solve the time delay and delay during the roaming handover process. Packet loss and other problems, to achieve fast and seamless switching, and secondly, to solve the inherent problems of traditional mobile IP such as triangular routing.

The present invention is based on the following preset basis:

1. What we are aiming at is the mobility management of mobile nodes under the overlapping coverage of wireless cellular network and wireless local area network. It should be emphasized that the small area covered by the wireless LAN should also be within the coverage of the large area of the wireless cellular network. This should be taken for granted, and even multiple wireless LANs may have adjacent coverage. ;

2. The mobile node 1 is a multi-mode intelligent terminal that can simultaneously access the wireless cellular network and the wireless local area network. The wireless cellular network and the wireless local area network have negotiated a roaming agreement (using mobile IP) between each other in advance, so that the mobile node can still maintain communication with the other network when performing data transmission with one network, so that the mobile node can use mobile IP. The technology roams freely between wireless cellular networks and wireless LANs;

3. The GPRS cellular network and the wireless local area network are independent of each other, and their respective data transmission rates are quite different, and the mutual integration adopts a loose coupling method.

Shown in Fig. 4 is to combine the network structure of loosely coupled server wireless local area network 2n ", wherein between the RJ45 network port on the loosely coupled server 2c and the RJ45 network port on the router or the two-layer switchboard 2b are directly connected by twisted pair Similarly, the wireless access points 2a and 2b are also directly connected through their respective RJ45 network ports.

A mobile communication network loosely integrated with a cellular network and a wireless local area network, comprising a mobile communication node 1, a foreign wireless local area network 2n, an external data network 3, a core composed of a service supporting GPRS node 4a, a gateway supporting GPRS node 4b, and a home location register 4c Network 4, base station controller 5, base station 6, hometown wireless local area network 7n formed by wireless access point 7a, router 7b connected with the outside, server 7c, communication node 8, it is characterized in that: use new remote local area network 2n " Replacing the original wireless local area network 2n, the new wireless local area network 2n" is composed of a wireless access point 2a, a router 2b connected to the outside, and a loosely coupled server 2c, wherein a network port of the router 2b is connected to a wireless access point 2a. The other network port is connected to the network port of the loosely coupled server 2c; and the original wireless local area network 2n in other places is composed of a wireless access point 2a and a router 2b connected to the outside.

The following describes the three processes of the initial stage, the decision stage and the execution stage of the handover of the mobile node and the two functions that the virtual home agent played by the loosely coupled server needs to realize.

At first for the general situation, when the mobile node 1 is roaming in other places, as shown in Figure 3, the process of the mobile node 1 being switched from the GPRS cellular network to the wireless local area network 2n" (the solid line arrow direction shown in Figure 3), in conjunction with the present invention The network structure and scheme are described in detail.

FIG. 5 is a simplified process of handover of the mobile node 1 from the GPRS cellular network to the WLAN 2n" as shown in FIG. 3 in the present invention.

FIG. 6 is a simplified process of handover of the mobile node 1 from the WLAN 2n" to the GPRS cellular network.

Generally speaking, the system can be encouraged to enter the handover initial state according to the received signal strength (RSS_WLAN) of the mobile node. However, this will cause a "ping-pong effect" in some cases and seriously affect the mobile performance of the system. The switching process between the cellular network and the LAN is even more inappropriate, because the coverage of the wireless LAN is relatively small. If the user speed is fast and the coverage radius of the wireless LAN is relatively small, even if the RSS_WLAN rises to a very high level, it should not Switch to this wireless local area network, because such a situation of mobile nodes passing through the wireless local area network will cause frequent switching, which will definitely reduce the mobility performance of the system significantly.

The switching decision model in the present invention adopts the mathematical model in document [1]. If the system requires reference to the mobile node's moving speed V _n and RSS_WLAN (abbreviated as S _n ) as decision parameters, these are the two most basic and important parameters (should try to choose a smaller parameter to reduce the burden on the system) Then the value of the Cost function is measured by the mathematical model in the following formula.

Cost _n ＝δ _v InV _n +δ _s Ins _n ，(δ _v +δ _s ＝1)____ (1)

In the formula, Cost _n is the value of the cost function to be referred to, and δ _v and δ _s are normalization coefficients, and their magnitudes show how much the system attaches importance to the corresponding items.

Fig. 7 is the flow chart that mobile node is switched to wireless local area network 2n " by GPRS cellular network. Mobile node 1 begins to receive the broadcast message M1 that wireless local area network sends from GPRS cellular network to wireless local area network, detects whether Satisfy the handover initial condition M2, this handover initial condition uses the Cost function mentioned above to make a decision, once Cost _WLAN <Cost _GPRS occurs, that is, the handover initial condition is met, then the mobile node 1 will send to the wireless LAN 2n″ A pre-handover command, enter the initial state of switching, timer 2 starts timing M3, and in the process of timer 2 timing, also need uninterrupted state monitoring Cost _WLAN < Cost _GPRS whether to continue M3 ', if in this process Once Cost _WLAN >Cost _GPRS occurs, timer 2 is immediately cleared, and a revocation notification is sent to the home agent, and the timer starts counting from 0 again when it detects that the switching condition is met next time. Of course, if the above initial handover condition is not satisfied at the beginning, it should continue to detect whether the initial handover condition is met.

After wireless local area network 2n " received this pre-handover order, for mobile node 1 distribution a take care of address CoA _WLAN , then virtual home agent 2b notifies this care address to the home agent of mobile node 1 (at this moment wireless local area network 2n "needn't this The CoA _WLAN notifies the mobile node 1), and after the home agent receives the message, it immediately starts the timer 1 and counts M4 from zero.

Next, if the home agent 7c does not receive the revocation update message from the virtual home agent 2b when the timer 1 reaches τ, that is, when it detects that the timer 1 reaches τ, M5, the home agent 7c immediately updates the CoA The communication node 8 (the relevant information of the communication node 8 is all stored in _the home agent 7c of the mobile node to the communication node 8 that maintains communication with the mobile node and needs to be contacted, because when the communication node sends a message to the initial route of the mobile node, it must go through Home agent, so the HA can store the relevant information of this communication node), so as to complete the handover process M6.

On the other hand, once detection timer 2 counts and reaches δ M5, (then timer 2 restarts clearing counting), that is, the duration of the state of Cost _WLAN >Cost _GPRS has reached the threshold time for switching requirements, then the virtual hometown Proxy 2b then sends this CoA _WLAN to MN 1, which means that MN 1 locks the handover target as this WLAN 2n", and has decided to execute the handover immediately. Then MN 1 passes through this WLAN 2n""Communicate with the external data network 3, thereby completing the entire switching process M6. During the handover process, the virtual home agent 2b is always bound to the home agent 7c of the mobile node 1. From the perspective of the mobile node 1, the virtual home agent 2b plays the same role as the home agent.

For this handover process, from the side of the home agent 7c, when the timer 1 reaches τ, the home agent 7c immediately transmits the CoA _WLAN to the communication node 8, and then the communication node takes this CoA _WLAN as the target address Communicate directly with the mobile node, thus completing the entire handover task.

In fact, fundamentally speaking, the timing process is a judgment process of switching targets. The two timers here: timer 1 and timer 2 are set in the virtual home agent 2b and the mobile node 1 respectively. Using two timers for timing can reduce the handover delay more flexibly and accurately during the handover process, because as long as any one of the timers meets the condition, it indicates that the mobile node 1 performs the handover immediately, and the packet loss rate can be reduced. The timer 2 continues to work after the mobile node 1 switches into the wireless local area network 2n", and whether the timing exceeds T is used as a judgment reference for the system, and the timer 1 is also in the reverse direction when the mobile node is switched from the wireless local area network to the GPRS cellular network It plays the role of timing judgment, which will be mentioned later.

In the following, the solution of the present invention will be further described in detail with the handover process of the mobile node 1 from the wireless local area network 2n" to the GPRS cellular network (as shown in the direction of the dotted arrow in FIG. 3).

Because there are many cases that mobile users only stay in the wireless local area network in other places for a short time after leaving the home network, such as users waiting at the airport, attending temporary meetings in other places, and so on. And these situations are becoming more and more common, so it can be considered that when the user switches from the cellular network to the wireless LAN for a certain period of time, the user's original care address Cost _GPRS in the cellular network is still retained. The specific process is as follows: after the mobile node 1 performs the handover from the GPRS cellular network to the wireless local area network 2n", the mobile node 1 sends and receives data packets through the externally connected link of the wireless local area network 2n", and the mobile node 1 still passes through the GPRS The detection of the Cost _GPRS cycle in the cellular network is connected to the cellular network and timed. At this time, it is defined that the link connected to the cellular network with Cost _GPRS is in the Sleep state.

If the timer 2 exceeds the time T, the mobile node 1 releases the Cost _GPRS automatically. In this way, as long as the mobile node 1 switches into the wireless local area network 2n" and stays there for longer than T, the mobile node 1 will activate the Cost _GPRS (make it in the Active state) when switching out of the cellular network from the wireless local area network 2n", Instead of re-applying for a care address from the cellular network, the original wireless link with the cellular network can be restored directly and simply, so that the communication node can directly communicate with the mobile node, and in this case, in order to avoid increasing the cellular network burden, and take a similar method as before, the virtual home agent cooperates with the home agent to work, and the Cost _GPRS is immediately notified to the communication node, so as to reduce the handover delay and solve the triangular routing problem in the communication process.

And if the time that mobile node 1 stays in wireless local area network 2n " is greater than T, promptly timer 1 timing has surpassed T, then mobile node 1 releases the care address that originally communicated with cellular network. In this case by wireless local area network 2n " The process of switching to the GPRS cellular network is shown in Figure 6. In this process, make full use of the high-speed transmission and broadband features of the wireless LAN, and try to use the wireless LAN to transmit data and command information during the switching process. 100 seconds for Kb/s transmission is better.

When the mobile node moves from the wireless local area to the cellular network, the virtual home agent is still used to work with the home agent to realize the bidirectional link connection in the handover process, which shortens the handover delay and solves the triangular routing problem.

FIG. 8 is a flow chart of a mobile node switching from a wireless local area network to a cellular network. When the mobile node moves in the wireless local area network, it also receives the broadcast message M1 from the cellular network, and checks whether the initial handover condition M2 is met through the model in the above formula (1). If it is found that the initial handover condition is met, the timer 1 starts counting M3 from 0, and detects whether the timer 2 reaches T. On the other hand, monitors in real time whether the state that meets the initial condition continues for M3′. Next, if the timer 2 has not reached T, it indicates that the mobile node is in the wireless network. When staying in the LAN for a relatively short time, activate Cost _GPRS , directly establish a link connection with the cellular network, and complete the switching M4. If the timer 2 has reached T, the mobile node will apply to the cellular network to register M5, and the SGSN will process and allocate a CoA _GPRS for the mobile node, and pass it to the mobile node M6, and the mobile node will notify the CoA _GPRS to the virtual The home agent M7, and then the virtual home agent notifies the care address to the home agent, and the timer starts timing from 0 to M8, and then in the real-time monitoring process of M3, if the timer 1 reaches τ′, the establishment of a cellular network directly via GPRS The two-way link from the mobile node to the correspondent node, thus completing the handover M9.

Compared with the prior art, the present invention has the following outstanding advantages:

(1) Introduce an entity in the network structure—virtual home agent, to coordinate with the original home agent to handle the communication connection between MN and CNs during the handover process;

(2) Establish a new mobility management scheme, so that the mobile node can directly communicate with the corresponding node when the handover is executed, without making the data packet go around the home agent, which will significantly shorten the handover delay and solve the problem of triangle Routing problem;

(3) After being handed over to WLAN by cellular network, adopt the connection strategy that continues to keep and cellular network with care address CoA _GPRS in a pre-set time, this will obtain when mobile node switches out wireless local area network to a certain extent Better switching performance, especially in the future IPv6 network, due to the abundance of IP addresses, such a timing non-discarding strategy is very valuable;

(4) This solution is based on the loosely coupled network structure, so there is no need to make major changes to the existing cellular network and wireless LAN structure, and no structural changes are required for GPRS and WCDMA cellular networks It only needs to add a special server in the WLAN, realize the virtual home agent and the physical function of the home agent for different mobile users, and determine the roaming agreement between the cellular network and the WLAN.

Description of drawings

FIG. 1 is a schematic diagram of an existing loosely coupled network structure.

FIG. 2 is a schematic diagram of an existing tightly coupled network structure.

Fig. 3 is a schematic diagram of the structure of the loosely coupled network of the present invention.

FIG. 4 is a network structure diagram of a wireless local area network including loosely coupled servers in the present invention.

Fig. 5 is a simplified process diagram of handover of a mobile node from a GPRS cellular network to a wireless local area network.

Fig. 6 is a simplified process diagram of the handover of the mobile node from the wireless local area network to the GPRS cellular network.

Fig. 7 is a flow chart of the handover of the mobile node from the GPRS cellular network to the wireless local area network.

FIG. 8 is a flow chart of a mobile node switching from a wireless local area network to a GPRS cellular network.

references

[1]Helen.J.Wang.Randy.H.Katz.Jochen Giese. "Policy-Enabled Handoffs Across Heterogeneous Wireless Networks." 2nd IEEE Workshop on Mobile Computing and Appilcations(WMCSA 99).New Or Ieans.February 1999.

Claims (1)

1. the mobile communications network that merges of cellular network and WLAN (wireless local area network) pine, comprise mobile communication node (1), other places WLAN (wireless local area network) (2n), outer data network (3), by service support GPRS node (4a), gateway is supported GPRS node (4b), the core net (4) that attaching position register (4c) is formed, base station controller (5), base station (6), by WAP (wireless access point) (7a), the router that is connected with the outside (7b), the local WLAN (wireless local area network) (7n) that server (7c) is formed, communication node (8), it is characterized in that: (2n ") replaces original nonlocal WLAN (wireless local area network) (2n); (2n ") is by WAP (wireless access point) (2a) for new nonlocal WLAN (wireless local area network) with new nonlocal WLAN (wireless local area network), the router that is connected with the outside (2b), loose coupling server (2c) is formed, wherein a network interface of router (2b) is connected with the network interface of WAP (wireless access point) (2a), and its another network interface is connected with the network interface of loose coupling server (2c).

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