CN107148061B

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

Info

Publication number: CN107148061B
Application number: CN201710453451.4A
Authority: CN
Inventors: 赵国锋; 黎军; 徐川; 王新恒
Original assignee: Chongqing University of Post and Telecommunications
Current assignee: Chongqing University of Post and Telecommunications
Priority date: 2017-06-15
Filing date: 2017-06-15
Publication date: 2020-09-29
Anticipated expiration: 2037-06-15
Also published as: CN107148061A

Abstract

The invention requests to protect an LTE and WLAN heterogeneous network switching method based on an SDN. Specifically, a wireless access gateway WAG is applied in the WLAN, and the WAG is used as an interface for accessing the WLAN to the LTE, and can also be used as a communication interface from the LTE to the WLAN, and is connected with a packet data gateway PGW in the LTE through a tunneling protocol. The WAG and the PGW are controlled by a controller based on the SDN, the switching between the LTE and the WLAN is realized through a switching decision, the controller makes a corresponding switching decision rule by gathering user related information from a bottom layer, and sends the information to the PGW or the WAG, and the PGW or the WAG forwards a data packet according to the information. The invention simplifies the complexity of PGW, can realize seamless switching between WLAN and LTE, meets the requirement of service quality, reduces the time delay caused by system switching and ensures the system performance.

Description

LTE and WLAN heterogeneous network switching system and method based on SDN

Technical Field

The invention belongs to the field of fusion, data session maintenance and vertical handover control under different wireless access technologies, and particularly relates to the fusion of an LTE (3GPP Long term evolution system) and a WLAN (wireless local area network) and a method for maintaining seamless handover of UE (user equipment) between the two access technologies under the fusion system.

Background

With the rapid development of mobile communication technology and the increasing demand of user services, especially for video streams and audio streams, the coexistence and integration of various networks becomes a necessary trend for the development of next-generation mobile communication. The concrete points are as follows: 1. the existing switching method of the heterogeneous network has large time delay, when a user changes from one network to another network, the user session is easy to interrupt, and the QoS of the user cannot be ensured; 2. at present, traffic generated by a user is mainly audio stream or video stream, and the data is characterized by high network bandwidth, which cannot be supported by the conventional LTE, and a widely deployed WLAN network has high network bandwidth and high access rate, and can provide a faster network access speed for a mobile user.

Based on the above 2 points, the LTE and the WLAN are integrated, and the characteristics of high access rate, large bandwidth and high access rate of the WLAN are utilized to make up for the defects of the current LTE, so as to provide better service for users. Aiming at the fusion of different access networks, the biggest problem is that when a user roams among different networks, a larger time delay is generated, so that the user service cannot be normally carried out. Therefore, a heterogeneous network handover method based on the SDN is provided herein, which reduces handover delay and ensures system performance.

Disclosure of Invention

The present invention is directed to solving the above problems of the prior art. The SDN-based LTE and WLAN heterogeneous network switching system and method can reduce time delay caused by switching between LTE and WLAN and ensure system performance. The technical scheme of the invention is as follows:

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 datato WAG instruction, and after the PGW receives the instruction, the controller establishes a tunnel from the PGW to the WAG; 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.

Further, the wireless access gateway WAG is mainly used as an interface for accessing the WLAN to the 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.

An LTE and WLAN heterogeneous network switching method based on the system comprises 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. The invention has the following advantages and beneficial effects:

the invention provides a fusion framework of LTE and WLAN based on SDN, which can relieve the workload of PGW, simplify the design of PGW, ensure that the PGW is only responsible for fast routing forwarding of data, and simultaneously reduce the complexity of EPC of LTE in an edge network. In order to solve the problems of user data loss and the like caused by switching and ensure seamless switching, the invention provides that a Controller is used for controlling a PGW and a WAG, an IP tunnel is established between the PGW and the WAG, and the seamless migration of data flow in an IP network layer is realized, namely the user UE realizes quick switching under different access networks. The data integrity in the user roaming process is ensured, the user speed is improved, and the user experience is ensured.

Drawings

Fig. 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 a UE access LTE process;

FIG. 3 is a diagram illustrating a process for accessing a WLAN by a UE;

FIG. 4 is a schematic diagram of a tunnel establishment procedure;

fig. 5 is a schematic diagram of an LTE-to-WLAN handover procedure;

fig. 6 is a schematic diagram of a WLAN to LTE handover procedure.

Detailed Description

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

The technical scheme for solving the technical problems is as follows:

the invention introduces a PMIPv 6-based technology, introduces a wireless access gateway WAG in a WLAN, and uses the wireless access gateway as an intercommunication interface of LTE and the WLAN, so that user equipment UE with a plurality of network interfaces can realize seamless switching under two access technologies of the LTE and the WLAN.

As shown in fig. 1, the LTE system mainly includes 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 S5/S8 in LTE, and mainly completes the distribution of the IP address of the UE and the related routing function; the SGW is connected with the PGW and the MME through an S5/S8 interface and 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 mobile user equipment UE will maintain communication with the base station by means of radio bearers. Besides, the system also comprises a Controller which is respectively connected with the PGW and the SGW which support Openflow.

In the WLAN, 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 the PGW.

The UE generally has multiple network interfaces, and is generally a terminal intelligent device such as a mobile phone or a computer with LTE and WLAN access capabilities. And the user access internet is provided by the packet data gateway (PGW).

The wireless access gateway WAG is mainly used as an interface for accessing the WLAN to the LTE and exchanges user signaling with the controller FC; 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. And PGW has similar function to WAG.

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 is interrupted, and the IP addresses of different networks must be processed to maintain the session continuity. Here, we use that the network physical interface of the WLAN of LTE is abstracted to form a virtual network interface, and the physical network interface is hidden, so that the same IP address can be configured for the virtual interface, i.e. the address from LTE to WLAN remains unchanged. I.e., the IP addresses assigned by the PGW and WAG to the user are the same.

Users begin to associate with enbs in LTE, and we do not draw some components not involved in the architecture, such as MME, SGW, AP, etc., here for the sake of simplicity in fig. 2, 3 and 4. As shown in fig. 2, the UE firstly connects via a layer 2, and then the PGW acquires identity information of the UE via a layer two signaling, such as number 1 in the figure, including a user identification code UE _ ID, etc.; if the PGW receives the user request and provides service for the user request, the PGW sends a user binding update message UB _ update to the Controller, as denoted by reference numeral 2 in the figure; after receiving the UB _ update, the Controller will maintain the table entry for establishing the UE information, and send UB _ ACK, which is denoted by reference numeral 3 in the figure; after receiving the UB _ ACK, the PGW allocates an IP to the UE, and sends a route advertisement message RA, which is denoted by reference numeral 4 in the drawing. After receiving the RA, the UE configures the relevant information to realize accessing to the Internet.

As shown in fig. 3, when the UE sends an association request, a WIFI signal is detected, which is denoted by reference numeral 1 in the figure; after receiving the request, the PGW sends a handover request message to the Controller, where the request message includes LTE network state information, which is denoted by reference numeral 2 in the figure; and after receiving the request, the Controller acquires the state of the WLAN, makes a comprehensive decision, and sends HD _ ACK to the PGW, the UE completes the access process with the AP, meanwhile, the WAG sends binding update information to the FC, newly establishes a user information maintenance table entry in the FC, and replies UB _ ACK with the numbers 4 and 5 in the figure.

As shown in fig. 4, after the UE completes the association process with the AP, the Controller may send a move data to WAG instruction, and after receiving the move data to WAG instruction, the PGW may establish a tunnel from the PGW to the WAG; meanwhile, the Controller sends receivedata, the WAG establishes a tunnel from the WAG to the PGW after receiving the receivedata, so that a bidirectional tunnel between the PGWs is established, and data pre-stored in the PGW can be transmitted to a user through the tunnel and is unpacked.

To explain 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 in the coverage of LTE, the base station connected with the UE is responsible for the Internet access of the UE and the roaming mobility management between the base stations. The method specifically comprises the following steps: 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, an EPS default bearer is established, a user binding update message UB _ update is sent to a Controller, a Controller checks a local cache, if no UE related information exists, an entry is created, and meanwhile, the FC correspondingly replies a UB _ ACK message to confirm that the FC has successfully received the UB _ update.

Step 502: when the UE is located at the edge of the LTE network and detects signals of one or more APs of the WLAN, the UE may send a measurement report to the PGW according to a measurement control requirement sent by the PGW, where the measurement report includes an MN identifier ID, a cell identifier, a received power, a signal quality, and the like. And then the PWG uploads a switching request message to the Controller, the switching request comprises a network condition message of LTE, and the Controller requires the WAG to establish contact with the AP after receiving the switching request message, so as to acquire the WLAN network condition information. And finally, the Controller makes a switching decision and sends a switching 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, whether to satisfy the QoS of the service, and the like. The handover response message includes an allow handover and a reject handover.

Step 503: after receiving the switching response message from the FC, the PGW issues a switching 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 caches data to be sent to the UE terminal, transmission is achieved through a tunnel between the PGW and the WAG, and the WAG receives the data from the PGW and caches the data

Step 504: when the UE completes the WLAN access process, it will send an access completion message to the WAG, which replies an acknowledgement message and allocates an IP address for the UE, and sends a UB _ update message to the FC. The UB _ update includes a change of the UE port, etc., indicating that the data communication port of the UE has changed, and 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 is interrupted, and the IP addresses of different networks must be processed to maintain the continuity of the session. Here, we use that the network physical interface of the WLAN of LTE is abstracted to form a virtual network interface, and the physical network interface is hidden, so that the same IP address can be configured for the virtual interface, i.e. the address from LTE to WLAN remains unchanged.

Step 505: the Controller informs the PGW to forward the buffered user data to the WAG, and also informs the WAG to prepare to receive data from the PGW. Finally, an IP tunnel is established between the PGW and the WAG. The WAG receives the data from the PGW through the tunnel, decapsulates the packet data, converts the data into a format capable of being transmitted on the WLAN, and transmits the data to the corresponding user UE to realize lossless transmission of the data. The UE sends a switching confirmation request to the controller, and the controller receives the switching completion request and informs the eNB to release network resources and remove the related information of the UE.

The handover procedure from WLAN to LTE is shown in fig. 6, and the handover procedure is basically similar to the handover procedure of LTE to WLAN, and includes the following specific steps:

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 WLAN network available state to the WAG according to the measurement requirement and forwards the WLAN network available state to the Controller, and meanwhile, the Controller informs the PGW to report the LTE measurement message. And finally, according to the obtained network state information, the controller can make a switching decision and issue a switching rule to the WAG.

Step 603: and the WAG issues a switching instruction to the UE according to the switching confirmation message, establishes connection with the eNB according to a random access flow of an LTE standard, and simultaneously caches user data in a WAG local cache.

Step 604: after the UE completes the access process with the LTE, the PGW allocates an IP address for the UE and sends UB _ update to the Controller to determine the binding relationship between the UE and the PGW.

Step 605: the Controller informs the WAG to forward the buffered user data to the PGW, and also informs the PGW to prepare to receive data from the WAG. Finally, an IP tunnel is established between the WAG and the PGW. The PGW receives the data from the WAG through the tunnel, decapsulates the packet data, converts the data into a format capable of being transmitted on the LTE, and transmits the data to the corresponding user UE to realize lossless transmission of the data. The UE sends a switching confirmation request channel FC, the FC receives a switching completion request, and then the FC informs the AP to release network resources and remove related information of the UE.

The above examples are to be construed as merely illustrative and not limitative of the remainder of the disclosure. After reading the description of the invention, the skilled person can make various changes or modifications to the invention, and these equivalent changes and modifications also fall into the scope of the invention defined by the claims.

Claims

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 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 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.