CN107148061B - LTE and WLAN heterogeneous network switching system and method based on SDN - Google Patents

Abstract

The present invention claims to protect a SDN-based LTE and WLAN heterogeneous network handover method, which adopts SDN as a centralized controller in LTE and WLAN to realize heterogeneous network handover. Specifically, the wireless access gateway WAG is used in the WLAN. The WAG will be used as the interface for WLAN access to LTE, and it can also be used as the communication interface from LTE to WLAN, and is connected to the packet data gateway PGW in LTE through tunneling protocol. The WAG and PGW are controlled by the SDN-based controller, and the handover between LTE and WLAN is realized through the handover decision. The controller aggregates user-related information from the bottom layer, makes corresponding handover decision rules, and delivers the information. To the PGW or WAG, the PGW or WAG forwards the data packet according to the information. The present invention simplifies the complexity of the PGW, can realize seamless handover between WLAN and LTE, meet the requirements for service quality, reduce time delay caused by system handover, and ensure system performance.

Description

A SDN-based LTE and WLAN heterogeneous network switching system and method

technical field

The present invention belongs to the fusion of different wireless access technologies, data session maintenance and vertical handover control, and in particular, to the fusion of LTE (3GPP Long Term Evolution) and WLAN (Wireless Local Area Network) and keeping UE in the two systems under this fusion system. A method for seamless handover between access technologies.

Background technique

With the rapid development of mobile communication technology and the continuous improvement of user service requirements, especially the continuous increase of video streams and audio streams, the coexistence and integration of various different networks has become an inevitable trend in the development of next-generation mobile communications. The specific manifestations are: 1. The current switching method of heterogeneous networks has a large delay. When a user switches from one network to another, the user session is easily interrupted, and user QoS cannot be guaranteed; 2. Currently, the traffic generated by users is mainly audio streams. Or video streams, and the characteristics of these data are that they require high network bandwidth, and traditional LTE cannot support this demand, while the widely deployed WLAN network has large network bandwidth and high access rate, which can provide mobile users with Faster internet speed.

Based on the above two points, LTE and WLAN are integrated together, and the characteristics of high access rate, large bandwidth and high access rate of WLAN are used to make up for the shortcomings of current LTE and provide better services for users. For the integration of existing different access networks, the biggest problem is that when a user roams between different networks, a large delay is generated, so that user services cannot be performed normally. Therefore, this paper will provide an SDN-based heterogeneous network switching method to reduce the switching delay and ensure system performance.

SUMMARY OF THE INVENTION

The present invention aims to solve the above problems of the prior art. An SDN-based LTE and WLAN heterogeneous network handover system and method are proposed, which can reduce the time delay caused by handover between LTE and WLAN and ensure system performance. The technical scheme of the present invention is as follows:

An SDN-based LTE and WLAN heterogeneous network switching system. The LTE system is mainly composed of a packet data gateway PGW, a service gateway SGW, an LTE base station eNB and a mobility management entity MME. The PGW is connected to the SGW through a standard protocol interface in LTE. It mainly completes the allocation of the UE's IP address and related routing functions; the SGW uses the S5/S8 interface to connect with the PGW, and the S11 interface is used to connect with the MME; finally, each eNB will use the S1-MME and S1-U interfaces to connect with the MME and the MME respectively. The SGWs are directly connected to each other; the mobile user equipment UE will maintain communication with the base station by means of wireless bearers. In the WLAN, it is mainly composed of a wireless access gateway WAG and a wireless access point AP. The WAG is directly connected to the AP, and the WAG passes The IP tunnel established between the PGW performs data and signaling forwarding, and it is characterized in that it also includes an SDN-based controller. The data flow control function is separated and transferred to the SDN-based controller, using the whole network characteristics of the controller to do data flow forwarding control; establish an IP tunnel between the packet data gateway PGW and the wireless access gateway WAG to realize LTE and WLAN The data or signaling interaction between them; when the LTE to WLAN handover is triggered, the controller makes a handover decision based on the network status information and comprehensive information, the UE implements the handover according to the handover command issued, and the corresponding IP tunnel will be established. , to ensure the integrity of data migration;

The process that the UE associates with the eNB is as follows: the UE first connects through Layer 2, and then the PGW obtains the identity information of the UE through Layer 2 signaling. If the PGW receives the user request and provides services for it, the PGW will send a user binding update message. UB_update is sent to the controller. After receiving the UB_update, the controller establishes the UE information maintenance table, sends UB_ACK to the PGW, assigns an IP to the UE, and sends a route advertisement message RA. After receiving the RA, the UE configures relevant information to realize access Internet access;

After the IP tunnel between the packet data gateway PGW and the wireless access gateway WAG is established, the physical network interface of the LTE WLAN is abstracted to form a virtual network interface, and the physical network interface is hidden, so that the virtual interface can be configured The same IP address, that is, the address from LTE to WLAN remains unchanged, that is, the IP address assigned to the user by the PGW and WAG is the same;

The specific IP tunnel establishment process is as follows: when the UE completes the association process with the AP, the controller will send the move data to WAG command, and after the PGW receives it, it will establish a PGW-WAG tunnel; at the same time, the controller sends the receive data, and the WAG receives it. Afterwards, the tunnel from WAG to PGW will be established. So far, the bidirectional tunnel between PGW and WAG is established. The data stored in PGW in advance can be transmitted through the tunnel, and sent to the user after decapsulation.

Further, the wireless access gateway WAG is mainly used as an interface for WLAN access to LTE, and exchanges user signaling with the controller; it mainly provides Internet access services for the UE, assigns an IP address to the UE, and is responsible for the UE's access to the WLAN under the WLAN. Mobility management for roaming between different APs; when handover occurs between LTE and WLAN, WAG will notify AP to report measurement information, and forward it to the controller through WAG for handover decision and user cache data from PGW for data transfer Format conversion, converted into a format that can be transmitted on the WLAN.

A method for handover between LTE and WLAN heterogeneous networks based on the system, comprising the following steps:

The specific steps for user UE roaming from LTE to WLAN are as follows:

Step A1, when the UE is within the coverage of LTE, the base station connected to it is responsible for the UE's Internet access and roaming mobility management between the base stations, specifically: the eNB uploads the association request from the UE to the PGW, and the PGW receives it. After the association request, an IP address will be allocated to the UE, an EPS default bearer will be established, and a user binding update message UB_update will be sent to the controller, and the controller will reply a UB_ACK message correspondingly to confirm that the controller has successfully received UB_update;

Step A2: When the mobile user UE roams to the edge of the LTE network and detects the signal of one or more APs of the WLAN, the UE will send a measurement report to the PGW according to the measurement control request sent by the PGW, including the mobile node MN identification ID and information including signal quality;

Step A3, the PGW uploads the handover request message to the controller, the controller forwards the handover request message to the WAG, and after receiving the handover request message, the WAG establishes a connection with the AP to obtain the available resource information and load of the WLAN access point The information is used as access control measurement information. After the WAG receives the access control measurement information, it reports the information to the controller for processing;

Step A4, the controller makes a corresponding handover control decision according to the measurement report information from LTE and WLAN, and sends a handover request response to the PGW. Enter step A5, otherwise the handover process is not executed;

Step A5, after the controller sends a handover request response to the PGW in the LTE, the base station eNB sends a handover instruction to the UE according to the handover request response message, and the handover request response message includes allowing the handover or rejecting the handover;

Step A6, when the UE obtains permission to handover, the UE performs the standard authentication and related operations defined in the WLAN protocol with a suitable AP in the WLAN, and the PGW buffers the data to be sent to the UE terminal, and then passes the data between the PGW and the WAG. The tunnel realizes the transmission, and the WAG receives the data from the PGW and buffers it;

Step A7, when the UE completes the WLAN access process, it will send an access completion message to the WAG, the WAG replies with a confirmation message and assigns an IP address to the UE, and sends UB_update to the controller;

Step A8: The controller informs the WAG to decapsulate the data received from the PGW, and transmits it to the corresponding user UE to achieve lossless data transmission. The UE sends a handover confirmation request to the controller, and the controller receives the handover completion request, and then controls The UE will notify the eNB to release network resources and remove UE related information. The advantages and beneficial effects of the present invention are as follows:

The invention provides an SDN-based LTE and WLAN fusion architecture, which can relieve the workload of the PGW, simplify the design of the PGW so that it is only responsible for fast routing and forwarding of data, and at the same time reduce the complexity of the LTE EPC in the edge network. In order to solve the problems of user data loss caused by handover and ensure seamless handover, the present invention proposes to control the PGW and the WAG through the Controller, and establish an IP tunnel between the PGW and the WAG, so as to realize the seamless migration of the data flow at the IP network layer, That is, the user UE implements fast handover under different access networks. This ensures data integrity during user roaming, improves user speed, and ensures user experience.

Description of drawings

1 is a schematic diagram of a preferred embodiment LTE and WLAN converged network architecture provided by the present invention;

FIG. 2 is a schematic diagram of UE access LTE process;

3 is a schematic diagram of a UE accessing a WLAN;

4 is a schematic diagram of a tunnel establishment process;

5 is a schematic diagram of an LTE to WLAN handover process;

FIG. 6 is a schematic diagram of a WLAN to LTE handover process.

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and in detail below with reference to the accompanying drawings in the embodiments of the present invention. The described embodiments are only some of the embodiments of the invention.

The technical scheme that the present invention solves the above-mentioned technical problems is:

The present invention introduces the PMIPv6-based technology, introduces the wireless access gateway WAG into the WLAN, and uses the wireless access gateway as the intercommunication interface between LTE and WLAN, so that the user equipment UE with multiple network interfaces can be used in both LTE and WLAN. Seamless handover is achieved under the access technology.

As shown in FIG. 1 , the LTE system is mainly composed of a packet data gateway PGW, a serving gateway SGW, an LTE base station eNB and a mobility management entity MME. The PGW is connected to the SGW through the standard protocol interface S5/S8 in LTE, and mainly completes the allocation of the UE's IP address and related routing functions; the SGW uses the S5/S8 interface to connect to the PGW and the S11 interface to connect to the MME; finally, each eNB will The S1-MME and S1-U interfaces are used to directly connect with the MME and the SGW respectively; the mobile user equipment UE maintains communication with the base station by means of a radio bearer. In addition, it also includes Controller, which is connected to PGW and SGW supporting Openflow respectively.

In WLAN, it is mainly composed of wireless access gateway WAG and wireless access point AP. The WAG is directly connected to the AP, and the WAG forwards data and signaling through the IP tunnel established with the PGW.

The user equipment UE generally has multiple network interfaces, and is generally a terminal smart device such as a mobile phone or a computer with LTE and WLAN access capabilities. The user's access to the Internet is provided by the packet data gateway PGW.

The wireless access gateway WAG is mainly used as the interface for WLAN access to LTE, and exchanges user signaling with the controller FC; it mainly provides Internet access services for the UE, assigns an IP address to the UE, and is responsible for the communication between different APs of the UE under the WLAN. Mobility management for inter-roaming; when a handover occurs between LTE and WLAN, WAG will notify AP to report measurement information, and forward it to the controller through WAG for handover decision-making and data format conversion of user cache data from PGW. into a format that can be transmitted over WLAN. The PGW and WAG have similar functions.

When the user session is converted from the LTE interface to the WLAN interface or from the WLAN to the LTE, the original IP session will be interrupted. In order to maintain the continuity of the session, related processing must be performed on the IP addresses of different networks. What we use here is to abstract the network physical interface of LTE WLAN to form a virtual network interface, while the physical network interface is hidden, so that the same IP address can be configured for the virtual interface, that is, the address from LTE to WLAN remains unchanged. Change. That is, the IP addresses assigned to users by the PGW and the WAG are the same.

The user begins to associate with the eNB in LTE. Here we do not draw some components that are not involved in the architecture, such as MME, SGW, AP, etc. The process of UE associating with eNB is shown in Figure 2. The UE first connects through Layer 2, and then the PGW obtains the UE's identity information through Layer 2 signaling, as shown in Figure 1, including the user identification code UE_ID, etc.; if the PGW receives the user request, and provide services for it, the PGW will send the user binding update message UB_update to the Controller, as shown in the figure 2; after the Controller receives the UB_update, it will maintain the entry for the establishment of UE information, and send UB_ACK, in the figure 3; PGW After receiving the UB_ACK, assign an IP to the UE, and send a route advertisement message RA, marked with 4 in the figure. After receiving the RA, the UE configures relevant information to achieve access to the Internet.

The process of UE association with WAG is shown in Figure 3. When the UE sends an association request and detects a WIFI signal, the number 1 in the figure; after the PGW receives it, it sends a handover request message to the Controller. The request message contains the LTE network status information, which is numbered in the figure. 2; After the Controller receives the request, it obtains the WLAN network status, makes a comprehensive decision, and sends HD_ACK to the PGW. The UE completes the access process with the AP. At the same time, the WAG sends the binding update information to the FC, and maintains the new user information in the FC. Table entry, reply UB_ACK, numbered 4 and 5 in the figure.

The specific tunnel establishment process is shown in Figure 4. After the UE completes the association process with the AP, the Controller will send the move data to WAG command. After the PGW receives it, it will establish the PGW to WAG tunnel; at the same time, the Controller sends the receive data, and the WAG receives After that, the tunnel from WAG to PGW will be established. At this point, the bidirectional tunnel of WAG between PGWs is established. The data stored in PGW in advance can be transmitted through the tunnel and sent to the user after decapsulation.

In order to illustrate the present invention in detail, the handover process from LTE to WLAN is shown in FIG. 5 , and the specific steps of the handover process are as follows:

Step 501: When the UE is within the coverage of LTE, the base station connected to the UE is responsible for the UE's Internet access and roaming mobility management between base stations. Specifically, the eNB uploads the association request from the UE to the PGW. After receiving the association request, the PGW will assign an IP address to the UE, establish an EPS default bearer, and send the user bundle update message UB_update to the Controller. The controller will check the local cache. If there is no UE-related information, a new entry will be created, and the FC will reply a UB_ACK message correspondingly to confirm that the FC has successfully received the UB_update.

Step 502: When the UE is at the edge of the LTE network and detects the signal of one or more APs of the WLAN, the UE will send a measurement report to the PGW according to the measurement control request sent by the PGW, including the mobile node MN ID, cell ID , received power and signal quality, etc. After that, the PWG uploads the handover request message to the controller. The handover request includes the LTE network status message. After the Controller receives the handover request message, it will request the WAG to establish contact with the AP to obtain the WLAN network status information. Finally, the Controller will make a handover decision and send a handover response message to the PGW. Specifically, the controller determines whether to allow the user UE to access the WLAN network by using the obtained number of network users, available resources and whether the service QoS is satisfied. Handover response messages include handover permission and handover rejection.

Step 503: After receiving the handover response message from the FC, the PGW will issue a handover instruction to the UE. When the UE obtains permission to handover, the UE will perform standard authentication and related operations defined in the WLAN protocol with a suitable AP in the WLAN. The PGW will buffer the data to be sent to the UE terminal, and then transmit it through the tunnel between the PGW and the WAG, and the WAG will receive the data from the PGW and buffer it

Step 504: After the UE completes the WLAN access process, it will send an access completion message to the WAG, the WAG will reply with a confirmation message and assign an IP address to the UE, and send a UB_update update message to the FC. UB_update includes the change of the UE port, etc., indicating that the data communication port of the UE has changed. Through this message, the UE completes the binding relationship with the PGW. However, when the LTE interface is converted to the WLAN interface, the original IP session will be interrupted. In order to maintain the continuity of the session, the IP addresses of different networks must be processed. What we use here is to abstract the network physical interface of LTE WLAN to form a virtual network interface, while the physical network interface is hidden, so that the same IP address can be configured for the virtual interface, that is, the address from LTE to WLAN remains unchanged. Change.

Step 505: The Controller notifies the PGW to forward the cached user data to the WAG, and also notifies the WAG to prepare to receive data from the PGW. Finally, an IP tunnel is established between the PGW and the WAG. The WAG accepts the data from the PGW through the tunnel, decapsulates the packet data, converts it into a format that can be transmitted on the WLAN, and transmits it to the corresponding user UE to realize lossless data transmission. The UE sends a handover confirmation request to the controller, and the controller receives the handover completion request, and notifies the eNB to release network resources and remove the relevant information of the UE.

The handover process from WLAN to LTE is shown in Figure 6. The handover process is basically similar to the handover process from LTE to WLAN. The specific steps are as follows:

Step 601: The UE associates with the AP, and sends a user binding update message UB_update to the controller to establish a binding relationship between the PGW and the UE.

Step 602: The UE detects the signal in the LTE, reports the available state of the WLAN network to the WAG according to the measurement requirement and forwards it to the Controller, and the controller notifies the PGW to report the LTE measurement message. Finally, based on the obtained network status information, the controller will make a switching decision and issue a switching rule to the WAG.

Step 603: The WAG sends a handover instruction to the UE according to the handover confirmation message, establishes a connection with the eNB according to the random access procedure of the LTE standard, and at the same time, the WAG caches the user data in the WAG local cache.

Step 604: After the UE completes the access process with the LTE, the PGW will assign an IP address to the UE, and send UB_update to the Controller to determine the binding relationship between the UE and the PGW.

Step 605: The Controller notifies the WAG to forward the buffered user data to the PGW, and also notifies the PGW to prepare to receive data from the WAG. Finally, an IP tunnel is established between the WAG and the PGW. The PGW accepts the data from the WAG through the tunnel, decapsulates the packet data, converts it into a format that can be transmitted over LTE, and transmits it to the corresponding user UE to realize lossless data transmission. The UE sends a handover confirmation request to the FC, the FC receives the handover completion request, and then the FC notifies the AP to release network resources and remove the relevant information of the UE.

The above embodiments should be understood as only for illustrating the present invention and not for limiting the protection scope of the present invention. After reading the contents of the description of the present invention, the skilled person can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims (3)

1. An LTE and WLAN heterogeneous network switching system based on SDN is disclosed, wherein the LTE system mainly comprises a packet data gateway (PGW), a Serving Gateway (SGW), an LTE base station eNB and a Mobility Management Entity (MME), the PGW is connected with the SGW through a standard protocol interface in the LTE, and the distribution of an IP address of UE and a related routing function are mainly completed; the SGW is connected with the PGW by adopting an S5/S8 interface and connected with the MME by adopting an S11 interface respectively; finally, each eNB is directly connected with the MME and the SGW respectively by utilizing S1-MME and S1-U interfaces; the method comprises the steps that the mobile User Equipment (UE) can keep communication with a base station in a wireless bearing mode, the WLAN mainly comprises a Wireless Access Gateway (WAG) and a wireless Access Point (AP), the WAG is directly connected with the AP, and the WAG forwards data and signaling through an IP tunnel established between the WAG and a packet data gateway (PGW), and is characterized by further comprising a controller based on an SDN (software defined network), wherein the controller is respectively connected with the PGW and an SGW supporting the Openflow, separates the data flow control function of the PGW in the packet data gateway in the LTE and transfers the data flow control function to the controller based on the SDN, and the whole network characteristic of the controller is utilized to carry out data flow forwarding control; an IP tunnel is established between a packet data gateway (PGW) and a Wireless Access Gateway (WAG), so that the interaction of data or signaling between the LTE and the WLAN is realized; when the LTE is switched to the WLAN, the controller makes a switching decision according to the network condition information and the comprehensive information, the UE realizes switching according to the issued switching instruction, and a corresponding IP tunnel is established to ensure the integrity of data during the migration;

the process of associating the UE with the eNB comprises the following steps: UE connects through 2 layers at first, then PGW obtains the identity information of UE through two layers of signaling, if PGW receives the user request, and provide service for it, PGW will send the user to bind the renewal message UB _ update to the controller, after the controller receives UB _ update, set up UE information maintenance table entry, and send UB _ ACK to PGW, distribute IP for UE, and send the route and announce message RA, after UE receives RA, dispose the relevant information, realize and insert the online;

after an IP tunnel between the PGW and the WAG is established, abstracting a physical network interface of the LTE WLAN to form a virtual network interface, and hiding the physical network interface, so that the same IP address can be configured for the virtual interface, namely the address from the LTE to the WLAN is kept unchanged, namely the IP addresses allocated by the PGW and the WAG for the user are the same;

the specific IP tunnel establishment process comprises the following steps: after the UE completes the association process with the AP, the controller sends a move data toWAG instruction, and after the PGW receives the move data toWAG instruction, a tunnel from the PGW to the WAG is established; meanwhile, the controller sends the receive data, the WAG establishes a tunnel from the WAG to the PGW after receiving the receive data, so that a bidirectional tunnel between the PGW and the WAG is established, and the data pre-stored in the PGW can be transmitted to the user through the tunnel transmission and after being unpacked.

2. The SDN-based LTE and WLAN heterogeneous network handover system according to claim 1, wherein the wireless access gateway WAG mainly serves as an interface for WLAN access to LTE, and exchanges user signaling with the controller; the method mainly provides internet access service for the UE, allocates an IP address for the UE and is responsible for mobility management of roaming of the UE among different APs under the WLAN; when the LTE and the WLAN are switched, the WAG informs the AP of reporting the measurement information, and the measurement information is forwarded to the controller through the WAG to make a switching decision and perform data format conversion on user cache data from the PGW, so that the data format is converted into a format capable of being transmitted on the WLAN.

3. An LTE and WLAN heterogeneous network handover method based on the system of claim 1, comprising the following steps:

the specific steps of roaming the user UE from LTE to WLAN are as follows:

step a1, when the UE is in the coverage of LTE, the base station connected to the UE is responsible for the internet access of the UE and the roaming mobility management between the base stations, which specifically includes: the eNB uploads an association request from the UE to the PGW, the PGW allocates an IP address for the UE after receiving the association request, establishes an EPS default bearer, and sends a user binding update message UB _ update to the controller, and the controller correspondingly replies a UB _ ACK message to confirm that the controller has successfully received the UB _ update;

step A2, when the UE roams to the edge of LTE network and detects the signals of one or more APs of WLAN, the UE will send the measurement report to the PGW according to the measurement control requirement sent by the PGW, including the information of MN ID and signal quality;

step A3, the PGW uploads the switching request message to the controller, the controller forwards the switching request message to the WAG, the WAG establishes the contact with the AP after receiving the switching request message, obtains the available resource information and the load information of the WLAN access point as the access control measurement information, and the WAG reports the information to the controller for processing after receiving the access control measurement information;

step A4, the controller makes a corresponding switching control decision according to the measurement report information from LTE and WLAN, sends a switching request response to the PGW, if the controller makes a decision that the UE is switched to the WLAN, the relevant switching operation is executed, and then step A5 is executed, otherwise, the switching process is not executed;

step A5, after the controller sends a handover request response to the PGW in LTE, the base station eNB sends a handover instruction to the UE according to the handover request response message, wherein the handover request response message includes permission of handover or rejection of handover;

step A6, when UE obtains permission to switch, UE and some proper AP in WLAN carry out standard authentication and related operation defined in WLAN protocol, PGW caches data to be sent to UE terminal, then realizes transmission through tunnel between PGW and WAG, WAG receives data from PGW and caches;

step A7, after the UE completes the WLAN access process, it will send the access completion message to the WAG, which replies the confirmation message and allocates IP address for the UE, and sends UB _ update to the controller;

step A8, the controller notifies the WAG to decapsulate the data received from the PGW and transmit the decapsulated data to the corresponding user UE, so as to implement lossless transmission of the data, the UE sends a handover confirmation request to the controller, the controller receives the handover completion request, and then the controller notifies the eNB to release the network resource and remove the related information of the UE.

Images