WO2017139936A1

WO2017139936A1 - Method for transmitting traffic, terminal device and network node

Info

Publication number: WO2017139936A1
Application number: PCT/CN2016/073970
Authority: WO
Inventors: Yi Shi; Konstantinos KATSAROS; Mehrdad DIANATI; Xiao Xiao
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2016-02-17
Filing date: 2016-02-17
Publication date: 2017-08-24

Abstract

The present invention provides a method for transmitting traffic, a terminal device and a network node. The method comprises : receiving, by a first terminal device, a network usage policy from a network node, wherein the network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time, and the network usage policy depends on a network provider's revenue received from providing traffic and a net-utility of a user of the first terminal device using traffic; determining, by the first terminal device, at least one available access network among the plurality of access networks according to the network usage policy; selecting, by the first terminal device, an access network from the at least one available access network; transmitting, by the first terminal device, traffic to the second terminal device through the selected access network.

Description

METHOD FOR TRANSMITTING TRAFFIC, TERMINAL DEVICE AND NETWORK NODE

Field of Invention

The embodiments of the present invention relate to the field of communication technologies, and particularly, to a method for transmitting traffic, a terminal device and a network node.

Background of the Invention

A variety of applications are expected to be designed to improve safety of future transport systems and provide many industrial and entertainment services. Dedicated Short Range Communication (DSRC) is proposed as the main communication technology to enable vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications to implement such applications.

Connected vehicles may be promoted with the use of different communication technologies for diverse applications. DSRC and cellular access technologies are predominantly used for V2V and V2I communications. In general, safety related applications have low latency requirements, high priority and small coverage range. DSRC is proposed as the main technology that can support these applications. On the other hand, comfort and infotainment applications require longer range, higher data rates and may have higher tolerance on latency.

Therefore, hybrid network architectures (HNA) will be required to ensure efficient data dissemination in typical vehicular environments. In such environments, a node equipped with multiple network interfaces and connected to multiple access networks is referred to as a multi-homed node. A Stream Control Transmission Protocol (SCTP) supports multi-homing. However, original SCTP multi-homing functionality is only used when the primary interface becomes unavailable.

A solution proposes the integration of cellular networks in intelligent transport systems (ITS) . However, in this solution, DSRC and cellular networks are not designed to be used simultaneously for the same traffic, e.g. for load balancing purposes. 3GPP (3rd Generation Partnership Project) has specifies how a user equipment (UE) establishes a connection to access networks and the procedures to switch traffic from one network to the other based on either network or user initiation. Nevertheless, the selection of the access network is only based on Quality-of-Service (QoS) metrics.

Another solution utilizing the SCTP allows to simultaneously use all available access networks to transmit traffic. During establishment of a SCTP association between two end points, the two end points exchange information on available interfaces, which can be used for the data exchange phase. Then, during data exchange, traffic packets are transmitted on each of the available interfaces in a Round Robin manner.

However, none of the above solutions considers the cost of using each access network. Thus, traffic packets cannot be cost-efficiently transmitted when traffic flow is split between the access networks.

Summary of the Invention

Embodiments of the present invention provide a method for transmitting traffic, a terminal device, and a network node which can cost-efficiently transmit traffic.

In a first aspect, the present application provides a method for transmitting traffic. The first terminal device receives a network usage policy from a network node, determines at least one available access network among the plurality of access networks according to the network usage policy, select an access network from the at least one available access network, and transmit traffic to the second terminal device through the selected access network. The network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time, and the network usage policy depends on a network provider’s revenue received from providing traffic and a net-utility of a user of the first terminal device using traffic.

According to the solution of the present application, the terminal device may determine available access networks according to a network usage policy which depends on a network provider’s revenue and a user’s net-utility and selects an access network from the available access networks for transmitting traffic so as to cost-efficiently transmit traffic, therefore having economic benefit for both consumers and the network provider.

According to a first implementation of the method according to the first aspect, the first terminal device further monitors QoS which the at least one available access network is capable of providing for the first terminal device to transmit traffic to a second terminal device respectively. The first terminal device selects an access network with the best QoS from the at least one available access network according to the monitored QoS.

According to the solution of the present application, the available access networks (or paths) for each terminal device may be restricted by the guidelines of the network operator, and QoS for each terminal device may be maintained by selecting the best path according to a QoS metric. Since the terminal device may dynamically select available access networks according to a network usage policy determined by the network provider to cost-efficiently transmit packets of traffic, the network provider can influence the behaviour of a user of the terminal device, in terms of network selection, in order to balance between QoS for the user and the operation costs of the network provider.

According to a second implementation of the method according to the first implementation, when monitoring QoS, the first terminal device sends at least one heartbeat message to the second terminal device through the at least one available access network, respectively, receives at least one heartbeat response message from the second terminal device through the at least one available access network, respectively, and determines the QoS according to the at least one heartbeat response, respectively.

According to a third implementation of the method according to any preceding implementation of the first aspect or the first aspect as such, the first terminal device further establishes an association for the traffic between the first terminal device and second terminal device through a SCTP, and sends a request message to the network node. The request message carries price sensitivity parameter of the traffic, and the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic. The first terminal device receives a response message from the network node and the response message carries the network usage policy. Since the price sensitivity for different types of traffic is considered, the network usage policy may be determined more accurately and availably. In addition, the terminal device may contact the network node during a SCTP connection establishment based on the connection requirements or other service-level agreements (SLAs) so as to obtain the most recent off-loading indicator for cost-efficient data transmission.

According to a fourth implementation of the method according to any preceding implementation of the first aspect or the first aspect as such, the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one available access network. The first terminal device determines at least one available access network excluding the paid access network when the ratio is not less than the offloading ratio threshold.

According to a third implementation of the method according to the fourth implementation of the first aspect, the offloading ratio threshold is determined by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks.

In a second aspect, the present application provides a method for transmitting traffic. A network node determines a network usage policy according to a network provider’s revenue received from providing traffic and a net-utility of a user of a first terminal device using traffic, and sends the network usage policy to the first terminal device, so that the first terminal device determines at least one available access network among the plurality of access networks according to the network usage policy. The network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time.

According to a second implementation of the method according to the second aspect, the network node further receives a request message from the first terminal device. The request message carries price sensitivity parameter of the traffic, and the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic. The network node sends a response message to the first terminal device, and the response message carries the network usage policy.

According to a second implementation of the method according to the first implementation or the first aspect, the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one free access network. The network node determines the offloading ratio threshold by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks.

In a third aspect, the present application provides a terminal device. The terminal device includes units for performing the method of the first aspect.

In a fourth aspect, the present application provides a network node. The network node includes units for performing the method of the second aspect.

In a fifth aspect, the present application provides a terminal device. The terminal device includes a memory unit, a communication interface and a processor coupled with the memory unit and the communication interface. The memory unit is configured to store instructions, the processor is configured to execute the instructions and the communication interface is configured to communicate with a network node under control of the processor. The instructions, when executed by the processor, cause the processor to perform the method of the first aspect.

In a six aspect, the present application provides a network node. The network node includes a memory unit, a communication interface and a processor coupled with the memory unit and the communication interface. The memory unit is configured to store instructions, the processor is configured to execute the instructions and the communication interface is configured to communicate with a network node under control of the processor. The instructions, when executed by the processor, cause the processor to perform the method of the second aspect.

In seventh aspect, the present application provides a computer readable medium, which stores program codes for execution by a terminal device. The program codes comprise instructions for performing the method of the first aspect.

In seventh aspect, the present application provides a computer readable medium, which stores program codes for execution by a network node. The program codes comprise instructions for performing the method of the second aspect.

In some implementations, the at least one profile comprises at least one of the following parameters: willingness to pay, traffic demand, delay profile, and probability that the user uses the at least one free access network.

In some implementations, the paid access network comprises a cellular access network, and the at least one free access network comprises at least one of a Wireless Fidelity WiFi access network, a Dedicated Short Range Communications DSRC access network, a Wireless Local Area Network WLAN access network and a Worldwide Interoperability for Microwave Access WiMAX access network.

Brief Description of the Drawings

To illustrate the technical solutions in the embodiments of the present invention more clearly, a brief introduction on the accompanying drawings which are needed in the description of the embodiments or the prior art is given below. Apparently, the accompanying drawings in the description below are merely some of the embodiments of the present invention, based on which other drawings can be acquired by the persons of ordinary skill in the art without any inventive effort.

FIG. 1 is a schematic architecture diagram of a communication system in accordance with an embodiment of the present invention；

FIG. 2 is a schematic block diagram illustrating a relationship between an HTLS and other entities within the EPC according to an embodiment of the present invention；

FIG. 3 is a schematic diagram of functional entities of a communication system in accordance with an embodiment of the present invention；

FIG. 4 is a schematic flowchart of a method for transmitting traffic in accordance with an embodiment of the present invention；

FIG. 5 is a schematic flowchart of a process for transmitting traffic in accordance with another embodiment of the present invention；

FIG. 6 illustrates a format of an OTR chunk according to embodiments of the present invention；

FIG. 7 illustrates a format to carry application characteristics in FIG. 6；

FIG. 8 illustrates a format of an OTA chunk according to embodiments of the present invention；

FIG. 9 is a simplified block diagram of a terminal device according to an embodiment of the present invention；

FIG. 10 is a simplified block diagram of a network node according to another embodiment of the present invention；

FIG. 11 is a simplified block diagram of the computing device according to another embodiment of the present invention.

Embodiments of the Invention

The technical solutions in the embodiments of the present invention will be described clearly and completely hereinafter with reference to the accompanying drawings in the embodiments of the present invention. Evidently, the described embodiments are merely part, but not all, of the embodiments of the present invention. All other embodiments, which can be derived by persons of ordinary skills in the art based on the embodiments of the present invention without any inventive efforts, shall fall into the protection scope of the present invention.

It should be understood that the technical solutions of the present invention may be applied to various communication systems, for example, a Global System of Mobile communication (GSM) , a Code Division Multiple Access (CDMA) system, a Wideband Code Division Multiple Access (WCDMA) system, a General Packet Radio Service (GPRS) , an LTE system, an Advanced long term evolution (LTE-A) system, a Universal Mobile Telecommunication System (UMTS) , and so on.

It should also be understood that, in the embodiments of the present invention, a terminal device includes but is not limited to a user equipment (UE) , a mobile telephone (or called a "cellular" phone) , a computer with a wireless communication function, the terminal device may also be a portable mobile apparatus, a pocket-sized mobile apparatus, a handheld mobile apparatus, a computer built-in mobile apparatus, a On Board Unit (OBU) or a vehicle-mounted mobile apparatus, and the like, and the terminal device may communicate through one or more access networks, for example, a radio access network (Radio Access Network, RAN) , a Wireless Fidelity (WiFi) access network, a Wireless Local Area Network (WLAN) access network, a Dedicated Short Range Communications (DSRC) access network, a Worldwide Interoperability for Microwave Access (WiMAX) access network, and so on.

The main objective of this invention is to propose a new cost effective technique for utilization of network resources in a loosely coupled HNA, where each node is simultaneously connected to at least two networks (e.g. DSRC, LTE) . The proposed mechanism may consider both the Quality of Service (QoS) requirements of the application, as well as the potential cost of using individual networks. The overall objective is to increase cost-efficiency of the network provider by controlling the off-loading ratio of individual traffic flows.

FIG. 1 is a schematic architecture diagram of a communication system 100 in accordance with an embodiment of the present invention.

Embodiments of the present invention utilize a conceptual hybrid network architecture (HNA) in which multi-homed terminal devices may dynamically determine available access networks according to a network usage policy and select an access network from available access networks to cost-efficiently transmit packets of traffic, which allows a network provider to influence the behaviour of a user in terms of network selection.

The Communication system 100 may be provided with multiple access networks, for example, a paid access network, e.g., a cellular access network, and at least one free access network, e.g., a wireless access network. The terminal device is typically guaranteed to be under the coverage of a base station in a paid cellular access network, but not necessarily of access point in a free wireless access network. Taking the combination of E-UTRAN (acellular access network) and WiFi (a wireless access network) as an example, the communication system 100 may include network node 110 in an Evolved Packet Core (EPC) , base station 150, access point 160 and terminal device 130 (for example, a vehicle) . It is to be understood that the naming of these network nodes in the communication system 100 is for the identification purpose only, and it should not be interpreted as a limitation.

Terminal device 130 may communicate with another terminal device through access devices of multiple access networks, for example, through base station 150 and WiFi AP 160. Embodiments of the present invention are not limited thereto, for example, terminal device 130 may also communicate with remote host 120 through the base station 150 and WiFi AP 160 via Internet 140. Accordingly, terminal device 130 may be called a multi-homed terminal device.

Network node 110 may implement two main functionalities. The first is to monitor the traffic on the cellular access network and the wireless access networks and the second is to calculate and provide a network usage policy according to a cost model implemented by a network provider. Accordingly, network node 110 may also be called a monitoring server. The network usage policy may include an offloading ratio indicator which may be used for indicating an offloading ratio threshold of an access network, for example, an offloading ratio threshold of the paid access network. In order to be able to monitor traffic and provide an advice on the network usage policy, the monitoring server may provide interfaces to the EPC, including: (a) a RESTful API interface to a terminal device for requesting an offloading ratio threshold, (b) an interface to underlying networks for obtaining network traffic information, (c) an HSS/SPR interface for subscriber-specific information that may influence policy decisions.

It should be understood that, the available access networks for the multi-homed terminal device corresponds to available interfaces or communication paths for the multi-homed terminal device. At the mention of an available access network, they also refer to an available interface or communication path.

FIG. 2 is a schematic block diagram illustrating a relationship between an HTLS and other entities within the EPC according to an embodiment of the present invention. The HTLS is an example of network node 110 in FIG. 1.

Referring to FIG. 2, the EPC may include User Data Repository (UDR) 210, Application Function (AF) 220, Subscription Profile repository (SPR) 230, Hybrid Transport Layer Support (HTLS) 240, Policy &Charging Rule Function (PCRF) 250, Online Charging System (OCS) 260, (Bearer Binding and Event Reporting Function) BBERF 270, and Policy and Charging Enforcement Function (PCEF) 280. PCRF 250 may communicate with UDR 210, AF 220, SPR 230, HTLS 240, OCS 260, BBERF 270, PCEF 280 via interfaces Ud, Rx, Sp, Rh, Gy, Gxx, and Gx respectively.

Accordingly, HTLS 240 may connect to PCRF 250, through which it has access to SPR 230 and AF 220 in order to obtain information for evaluating a cost model and an advice for the network usage policy.

FIG. 3 is a schematic diagram of functional entities of the communication system in accordance with an embodiment of the present invention. The HTLS in FIG. 3 is an example of network node 110 in FIG. 1. The terminal device in FIG. 3 is an example of terminal device 130 in FIG. 1

Embodiments of the present invention may involve a cost efficient extension for a SCTP that is implemented in terminal devices or end hosts (vehicles, RSUs or remote hosts) of an HNA, as well as an HTLS server. A multi-homed terminal device has multiple network interfaces and a single-homed terminal device has a single network interface. In embodiments of the present invention, the conventional transport layer protocol may be replaced by a cost-efficient transport protocol based on SCTP, named CE-SCTP, for hybrid vehicular networks.

Referring to FIG. 3, HTLS server 310 hosts the functionality of determining a cost model and monitoring traffic transmitted through the multiple access networks. The HTLS server 310 may communicate with other entities in the EPC via an Internet interface. Multi-homed terminal device 320 is provided with a CE-SCTP protocol stack. For example, when multi-homed terminal device 320 is capable of transmitting traffic through an LTE access network and a DSRC access network, the CE-SCTP protocol stack may include an Internet Protocol (IP) layer which has Internet Protocol (IP) 1 and IP2 as well as an MAC/PHY layer which has a DSRC MAC/PHY interface and an LTE MAC/PHY interface respectively. In addition, for single-homed end user 330, the protocol stack may include a CE-SCTP which has an IP and an MAC/PHY interface.

FIG. 4 is a schematic flowchart of a method for transmitting traffic in accordance with an embodiment of the present invention. The method of FIG. 4 may be executed by network node 110 and terminal device 130 in FIG. 1.

410, The network node determines a network usage policy according to a network provider’s revenue received from providing traffic and a net-utility of a user of a first terminal device using traffic. The network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time.

For example, the network usage policy may indicate the offloading ratio threshold for different access networks, i.e., threshold of the proportion of traffic transmitted among different access networks.

420, The network node sends the network usage policy to a first terminal device.

For example, the network work node may send the network usage policy to the first terminal device as a response to a request received from the first terminal device. Embodiments of the present invention are not limited thereto, for example, the network node may also periodically send the network usage policy to the first terminal device by carrying the network usage policy in a high-layer signaling.

430, After receiving the network usage policy, the first terminal device determines at least one available access network among the plurality of access networks according to the network usage policy.

In other words, a plurality of available communication paths may be established between the first terminal device and a second terminal device through the plurality of access networks, and the first terminal device may determine at least one available communication paths among the plurality of communication paths according to the network usage policy. For example, when an offloading ratio of a communication path reaches or exceeds an offloading ratio threshold indicated by the network usage policy, the communication path shall be excluded from the available communication paths.

440, The first terminal device selects an access network from the at least one available access network.

For example, the first terminal device may select an access network (or communication path) from the available access networks (or communication paths) according to QoS metric of the available access networks (or communication paths) . Embodiments of the present invention are not limited thereto, for example, the first terminal device may also select an access network from the available access networks in a Random or Round Robin manner. It should be understood that the first terminal device may select one or more access networks to transmit traffic. For example, when using a concurrent multipath transfer SCTP, the first terminal device may select multiple paths to transmit traffic concurrently.

450, The first terminal device transmits traffic to the second terminal device through the selected access network.

For example, the traffic may include at least one of the following: 1) media download/stream from remote server, e.g. video download； 2) web-radio Internet/Cloud connectivity, e.g. personal data synchronization； 3) VoIP services for vehicles； 4) Co-operative local services, e.g. local electronic commerce； 5) vehicle relation management； 6) Internet-of-Things services, e.g. eco-driving assistance, remote-diagnosis.

According to embodiments of the present invention, the terminal device may determines available access networks according to a network usage policy which depends on a network provider’s revenue and a user’s net-utility and selects an access network from the available access networks for transmitting traffic so as to cost-efficiently transmit traffic, therefore having economic benefit for both consumers and provider.

According to embodiments of the present invention, the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one available access network. In 430, the first terminal device determines at least one available access network excluding the paid access network when the ratio is not less than (i.e. reaches or exceeds) the offloading ratio threshold. An operating system (OS) running on the terminal device may provide information on the amount of traffic transmitted on each network interface, i.e., the amount of traffic (in bytes) transferred on that particular network interface card (NIC) . For example, Android OS gives that information through a public API (TrafficStats) . In addition, the total amount of traffic may refer to the traffic demand of the user in a preset period of time or an estimated amount of traffic transmitted through the at least one available access network.

Alternatively, as another embodiment, the offloading ratio threshold may indicate a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one free access network.

In 410, the network node determines the offloading ratio threshold by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks. For example, the at least one profile comprises at least one of the following parameters: willingness to pay, traffic demand, delay profile, and probability that the user uses the at least one free access network.

According to the embodiments of the present invention, the paid access network comprises a cellular access network, and the at least one free access network comprises at least one of wireless access network, such as a WiFi access network, a WLAN access network, a DSRC access network, and a WiMAX access network.

Optionally, as another embodiment, the method of FIG. 1 further comprises: the first terminal device monitors QoS which the at least one available access network is capable of providing for the first terminal device to transmit traffic to a second terminal device respectively. In 440, the first terminal device selects an access network with the best QoS from the at least one available access network according to the monitored QoS.

According to embodiments of the present invention, the available access networks (or paths) for each terminal device may be restricted by the guidelines of the network operator, and QoS for each terminal device may be maintained by selecting the best path according to a QoS metric, e.g. minimum RTT (Round-Trip Time) , maximum available bandwidth, etc. Since the terminal device may dynamically select available access networks according to a network usage policy determined by the network provider to cost-efficiently transmit packets of traffic, the network provider can influence the behaviour of a user of the terminal device, in terms of network selection, in order to balance between QoS for the user and the operation costs of the network provider.

Specifically, when monitoring Quality of Service QoS, the first terminal device sends at least one heartbeat message to the second terminal device through the at least one available access network (or corresponding interface) , respectively, receives at least one heartbeat response message from the second terminal device through the at least one available access network, respectively, and determines the QoS according to the at least one heartbeat response, respectively. For example, when using a CE-SCTP, a Heartbeat (HB) chunk and a Heartbeat acknowledgments (HB-ACK) chunk are sent periodically (e.g., 10sec) on each interface to monitor status (e.g., interface availability and QoS metric) .

Alternatively, as another embodiment, when traffic is transmitted through an access network, the QoS may be determined according to the traffic data transmitted between the first terminal device and the second terminal device through this access network. For example, when a cellular access network is selected to transmit traffic, the QoS for the communication path through the cellular access network is determined according the traffic packets transmitted through the cellular access network.

Optionally, as another embodiment, the method of FIG. 1 further comprising: the first terminal device establishes an association for the traffic between the first terminal device and second terminal device through a SCTP, sends a request message to the network node, wherein the request message carries price sensitivity parameter of the traffic, wherein the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic. Specifically, the first terminal device receives a response message from the network node, wherein the response message carries the network usage policy.

For example, when a new CE-SCTP association is initialized, the first terminal device will send an offloading Ratio threshold request (OTR) chunk to network node (i.e., an HTLS server) , which will contain the characteristics of the association (e.g., the association for a video stream service) , price sensitivity parameter θ. The HTLS server uses this information and other information which it has for the user, e.g. contract information, mobility information to calculate the network usage policy for this association. The network usage policy is passed back to the user with an offloading Ratio threshold acknowledge (OTA) chunk. After the association is established, a plurality of communication paths are established between the first terminal device and the second terminal device through a plurality of available access networks and data transfer can begin, e.g. actual video download. Traffic packets may be transmitted on at least one interface corresponding to at least one communication paths according to a path selection algorithm.

Since the price sensitivity for different types of traffic is considered, the network usage policy may be determined more accurately and availably. In addition, the terminal device may contact the network node during a SCTP connection establishment based on the connection requirements or other service-level agreements (SLAs) so as to obtain the most recent off-loading indicator for cost-efficient data transmission.

FIG. 5 is a schematic flowchart of a process for transmitting traffic in accordance with another embodiment of the present invention. The method of FIG. 5 is an example of the method of FIG. 4. The HTLS server is an example of the network node in FIG. 1.

The present embodiment is related to a transport layer protocol and specifically to the modification of the standard SCTP on terminal devices, for example, onboard units (OBUs) or remote hosts in a DSRC scenario.

510. The first terminal device identifies available interfaces and mark one as a primary interface.

The first terminal device as a sender identifies available interfaces and selects one as a primary interface which will be used for establishment of an association for traffic to be transmitted from the first terminal device to the second terminal device. The selection of the primary interface may be based on a QoS metric such as received signal strength indicator (RSSI) .

The association establishment procedure is performed in the following steps in which a 4-way standard SCTP association establishment handshake is extended with the exchange of control chunks such as an OTR and an OTA.

515, The first terminal device sends an INIT message to the second terminal device.

520, The second terminal device responds an ACK message to the first terminal device.

525, The first terminal device sends a COOKIE-ECHO to the second terminal device.

530, The second terminal device responds a COOKIE-ACK to the first terminal device.

The above 4-way SCTP association establishment handshake is performed through the primary interface. After receiving the COOKIE-ACK, the first terminal device determines that the association is established between the first terminal device and the second terminal device. Accordingly, the multiple communication paths can be formed between the first terminal device and the second terminal device through multiple available access networks (or interfaces) , respectively, for example, a cellular access network and a wireless access network.

540, The HTLS server monitors traffic offloaded by access networks.

In order to calculate the offloading indicator indicated by the network usage policy, the network provider (e.g., mobile operator) may keep track of all traffic in its cellular access network and offloaded traffic through the wireless access network, for example, in a period of one month. The HTLS server may provide an HTLS function in a RESTful manner, interacting with the underlying cellular and wireless networks, as well as external hosts.

545, The first terminal device sends an OTR to the HTLS server.

FIG. 6 illustrates a format of an OTR chunk according to embodiments of the present invention. Referring to FIG. 6, the OTR chunk includes a Type field, a Chunk flags field, a Length field and an Application characteristics (Variable) field.

FIG. 7 illustrates a format to carry Application characteristics in FIG. 6. Referring to FIG. 7, the format to carry Application characteristics follows SCTP standard representation of optional/variable-length parameter, which includes Parameter Type field, a Parameter Length field and a Parameter Value field. A price sensitivity parameter for the traffic to be transmitted through the association may be carried in the OTR, for example, contained in the Parameter Value field.

550， The HTLS determines a network usage policy.

Network providers can implement different cost models according to their requirements, and the network usage policy may be determined based on a cost model. For example, an IEEE document (Joohyne Lee et al., “Economics of WiFi Offloading: Trading Delay for cellular Capacity” ) recites how to calculate the offloading ratio threshold κ_avg. It will be briefly described as follow.

In order to facilitate the description of how to determine a network usage policy, it is assumed in the present embodiment that the first terminal device may transmit traffic through cellular base stations, for example, eNodeBs in LTE and WiFi APs, where N users are served by the cellular network provider.

The users may be modelled with four attributes: (i) how much money they can pay (willingness to pay, γ) , (ii) how many data they want to use,

) , (iii) how long their data can tolerate (delay profile, α) , and (iv) how they move (WiFi contact probability, e) . It is assumed that the network provider knows users'a ttributes, i.e. the user profiles, a prior. For example, this information can be available to the cellular network provider through its UDR, SPR and HSS functional entities.

For example, a day may be divided into equal time slots t∈ {1, 2, ... , T} , where T is the last index of one day. C is the capacity (in volume per time slot) provided by a base station. During each day, users move among BSs as well as APs.

is the probability that user i meets any WiFi AP within deadline d at time slot t. It is assumed that the cost from data offloaded via WiFi AP connected to a wired network is ignored. It is assumed that the user i has the average daily traffic demand Φ_i, LTE+WiFi traffic vector x_i＝ (x (t) : t∈T) , and LTE traffic vector y_i (x_i) ＝ (y (t) : t∈T) . The daily traffic demand Φ_i is temporally split into φ_i＝ (φ_i (t) : t∈T) , where φ_i (t) is the traffic demand at slot t. α denotes delay profile which models per-user delay-tolerance of traffic.

The market for the traffic may be modelled based on a two-stage sequential game (e.g. Stackelberg game) . At the first stage, the provider decides on the pricing parameters (p) as a leader, and at the second stage, each user is a price-taker as a follower and chooses its LTE+WiFi traffic volume x. The analysis results are carried out based on the equilibrium of this game assuming N total users. The user's net-utility is defined as U (x) and the provider's revenue as R (p) :

where θ∈ (0, 1) is the price sensitivity parameter, m (p, y (x) ) is the daily payment charge for usage of LTE network, and

where c (y_i) ＝η∑_t∈Ty_i (t) is the network cost to handle the traffic with η being the cost per unit of data. Given the traffic demand φ_i, mobility pattern

willingness to pay γdelay profile

and a pricing function, each user i choose

to maximize the user’s net-utility. Under a given pricing scheme, the network provider decides on the price to maximize its expected revenue.

The offloading indicator quantifies how much LTE data is offloaded, (i) aggregate LTE traffic ratio κ_avg, and (ii) peak LTE traffic ratio κ_peak.

where the transmitted total traffic and LTE traffic over a cell at time t, X (t) , Y (t) are:

where,

is the portion of the traffic generated at time t which is transmitted through LTE at time t+d.

denotes the number of users in the cell. It is also assumed that the heterogeneity of users in a cell only comes from traffic demand, and for simplicity, in formulae (5) and (6) , the subscript i is omitted and subscript Φ is used to represent the user variables with traffic demand Φ, for example, x_Φ (t) denotes the traffic volume of the user with traffic demand Φ at time slot t.

The network provider may provide a plurality of pricing scheme, for example, including a flat pricing in which the network provider may offers unlimited service for users who pay a subscription fee, a two-tier pricing in which multiple prices are provided, and a volume pricing in which a user is charged to pay a price for the unit LTE traffic volume, and so on.

Taking flat pricing as an example, if the cost of the unit volume of the LTE traffic ,

then the net-utilities of all subscribers increase and the provider's revenue at equilibrium increases as (i) κ_peak decreases in the opt-saturated case, and (ii) as κ_avg decreases in the opt-unsaturated case. The economic benefits of both provider and users are increased as κ_avg decreases and

If the inequality does not hold, provider has loses, so for a given η, Φ_max and θ, which can be seen as system parameters, there is a threshold on the offloading ratio, below which the provider is profitable and the end-user has economic benefits as well. For example, for a given η＝0.1$/MB, the offloading ratio threshold for aggregate LTE traffic is 0.7 and 0.31 for a maximum daily demand of 200MB and 1GB assuming θ＝0.5, while it lowered to 0.24 and 0.08 for θ＝0.3, respectively.

555, The first terminal device sends an OTA to the second terminal device.

FIG. 8 illustrates a format of an OTA chunk according to embodiments of the present invention. The offloading Ratio threshold field may be carried in the OTR. Referring to FIG. 8, the OTR Chunk may includes Type field, Chunk flags field, Length field and offloading Ratio threshold field.

557, The first terminal device determines available communication paths according to the network usage policy.

Before the offloading ratio of traffic through the cellular access network reaches or exceeds the offloading ratio threshold, all interfaces of the first terminal device can be available for data exchange. When the offloading ratio of traffic through the cellular access network reaches or exceeds the offloading ratio threshold, the communication path through cellular access network is excluded from the available communication paths.

560， The first terminal device sends HEARTBEAT messages to the second terminal device on all available communication paths, respectively.

565， The second terminal device responds HEARTBEAT-ACK messages to the first terminal device on all available communication paths, respectively.

567, The first terminal device determine the QoS of each available communication path according to the HEARTBEAT-ACK responded through the available communication path.

In order to select the best communication path according to QoS metric, the first terminal device sends a HEARTBEAT to the second terminal through each available access network, and determines the QoS of the corresponding communication path. Two QoS metrics, for example, minimum RTT and maximum available bandwidth may be used for selecting a communication path. These metrics may be calculated from the received ACK messages.

In addition, HEARBEAT packets may be send on all interfaces periodically (every 10 sec) in order to check their availability and potentially update the QoS metric for a communication path that has not been selected during the previous time interval.

570， The first terminal device selects a communication path with best QoS from the available communication paths.

575， The first terminal device sends traffic to the second terminal device on the selected communication path.

580， The first terminal device updates the offloading ratio.

The offloading ratio may refer to a ratio of amount of traffic transmitted through an LTE access network to total amount of traffic transmitted through the LTE access network and the wireless access network. For example, the total amount of traffic may refer to the traffic demand of the user in a preset period of time.

585， The first terminal device determines whether the offloading ratio reaches or exceeds an offloading ratio threshold. If the offloading ratio reaches or exceeds the offloading ratio threshold, continue to execute step 590； otherwise, continue to execute 557.

590， The first terminal device updates available communication paths, and continue to execute step 557.

For example, traffic transmission starts on the primary interface (e.g., an LTE interface) . Traffic data and acknowledgments follow the same communication path. Meanwhile, the terminal device may keep track of traffic data on each interface and upon receipt of a SACK, QoS metric for the communication path is updated. During path selection, the ‘best’ communication path is selected according to QoS metric. If the DSRC interface has better QoS, traffic is switched to the DSRC interface. When the offloading ratio gets greater than the enforced offloading ratio threshold (e.g. the offloading ratio > 0.31) , LTE interface cannot be selected, even though it has better QoS, and then, data is switched to the DSRC interface. In addition, after the offloading ratio is below the enforced offloading ratio threshold, data can be sent again over the LTE interface (as long as it still has better QoS) . For a CMT-enabled CE-SCTP, where both interfaces can be used simultaneously, when the offloading ratio exceeds the enforced offloading ratio threshold (e.g. ratio > 0.31) , LTE interface cannot be selected. After the offloading ratio lowers below the enforced offloading ratio threshold, data can be sent again over the LTE interface.

The above discussed processes may be performed by units in apparatuses or software modules in computing devices. These apparatuses and computing devices will be described in the following part of application.

FIG. 9 is a simplified block diagram of a terminal device 900 according to an embodiment of the present invention.

The terminal device includes a receiving unit 910, a determining unit 920, a selecting unit 930 and a transmitting unit 940.

The receiving unit 910 is configured to receive a network usage policy from a network node. The network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time, and the network usage policy depends on a network provider’s revenue received from providing traffic and a net-utility of a user of the first terminal device using traffic.

The determining unit 920 is configured to determine at least one available access network among the plurality of access networks according to the network usage policy.

The selecting unit 930 is configured to select an access network from the at least one available access network.

The transmitting unit 940 is configured to transmit traffic to the second terminal device through the selected access network.

Optionally, the terminal device 900 further includes a monitoring unit 950. The monitoring unit 950 is configured to monitor QoS which the at least one available access network is capable of providing for the first terminal device to transmit traffic to a second terminal device respectively. The selecting unit selects an access network with the best QoS from the at least one available access network according to the monitored QoS.

According to embodiments of the present invention, the monitoring unit 950 sends at least one heartbeat message to the second terminal device through the at least one available access network, respectively, receives at least one heartbeat response message from the second terminal device through the at least one available access network, respectively, and determines the QoS according to the at least one heartbeat response, respectively.

Optionally, the terminal device 900 further includes a establishing unit 960, which is configured to establish an association for the traffic between the first terminal device and second terminal device through a Stream Control Transport Protocol SCTP. The transmitting unit 940 is further configured to send a request message to the network node, wherein the request message carries price sensitivity parameter of the traffic, wherein the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic, the receiving unit receives a response message from the network node, wherein the response message carries the network usage policy.

FIG. 10 is a simplified block diagram of a network node 1000 according to an embodiment of the present invention. The network node 1000 includes a determining unit 1010 and a sending unit 1020.

The determining unit is configured to determine a network usage policy according to a network provider’s revenue received from providing traffic and a net-utility of a user of a first terminal device using traffic. The network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time.

The sending unit is configured to sending the network usage policy to the first terminal device, so that the first terminal device determines at least one available access network among the plurality of access networks according to the network usage policy.

Optionally, the network node 1000 further includes a receiving unit 1030, which is configured to receive a request message from the first terminal device. The request message carries price sensitivity parameter of the traffic, the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic, the sending unit sends a response message to the first terminal device, and the response message carries the network usage policy.

According to embodiments of the present invention, the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one free access network. The determining unit determines the offloading ratio threshold by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks.

FIG. 11 is a simplified block diagram of the computing device 1100 according to another embodiment of the present invention. The computing device includes a processor 1110, which is coupled with one or more data storage means. The data storage means may include a storage medium 1150 and a memory unit 1120. The storage medium 1150 may be read-only, like a read-only memory (ROM) , or readable/writeable, like a hard disk or a flash memory. The memory unit 1120 may be a random access memory (RAM) . The memory unit 1120 may be either physically integrated with or within the processor or constructed in a stand-alone unit or units.

The processor 1110 provides sequencing and processing facilities for executing instructions, performing interruption actions, providing timing functions and may other functions. Optionally, the processor 1110 includes one or multiple central processing units (CPUs) . Optionally, the computing device 1100 includes more than one processor. The term “processor” refers to one or more devices, circuits and/or processing cores configured to process data, such as computer program instructions.

Program codes to be executed by the processor 1110 may be stored in the memory unit 1120 or storage medium 1150. Optionally, program codes stored in the storage medium 1150 may be copied into the memory unit for the processor 1110 to execute.

The computing device 1100 further includes a communication interface 1160 for communication with another device or system directly or via an external network. Optionally, the computing device 1100 further includes an output device 1130 and an input device 1140. The output device 1130 is coupled with the processor 1110, and capable of displaying information in one or more ways. The input device 1140 is also coupled with the processor 1110, capable of receiving an input from a user of the computing device 1100 in one or more ways.

The above elements of the computing device 1100 may be coupled with each other by a bus.

The computing device 1100 can be a general-purpose computing device or an application-specific computing device. As practical examples, the above-described computing device may be a desktop computer, a laptop computer, a network server, a personal digital assistant (PDA) , a mobile phone, a tablet computer, a wireless terminal device, a telecommunication device, an embedded system or any other devices having similar structure as show in FIG. 11. However, the present application is certainly not limited by any particular types of the computing device.

As another embodiment, the present application provides a terminal device. The functions of the terminal device may be implemented by the computing device described in FIG. 11.

The terminal device includes: a memory unit storing computer executable program codes； a communication interface； and a processor, coupled with the memory unit and the communication interface, wherein the program codes includes instructions which, when executed by processor, cause the processor to: receive a network usage policy from a network node, determines at least one available access network among the plurality of access networks according to the network usage policy, select an access network from the at least one available access network and transmit traffic to the second terminal device through the selected access network, wherein the network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time, and the network usage policy depends on a network provider’s revenue received from providing traffic and a net-utility of a user of the first terminal device using traffic.

Optionally, the processor further monitors QoS which the at least one available access network is capable of providing for the first terminal device to transmit traffic to a second terminal device respectively, wherein the processor selects an access network with the best QoS from the at least one available access network according to the monitored QoS.

Optionally, when monitoring QoS, the processor sends at least one heartbeat message to the second terminal device through the at least one available access network, respectively, receives at least one heartbeat response message from the second terminal device through the at least one available access network, respectively, and determines the QoS according to the at least one heartbeat response, respectively.

Optionally, the processor further establishes an association for the traffic between the first terminal device and second terminal device through a SCTP and sends a request message to the network node. The processor receives a response message from the network node, the response message carries the network usage policy and the request message carries price sensitivity parameter of the traffic, and the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic.

According to embodiment of the present invention, the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one available access network. The processor determines at least one available access network excluding the paid access network when the ratio is not less than the offloading ratio threshold.

As another embodiment, the present application provides a network node. The functions of the network node may be implemented by the computing device described in FIG. 11.

The network node includes: a memory unit storing computer executable program codes； a communication interface； and a processor, coupled with the memory unit and the communication interface. The program codes includes instructions which, when executed by processor, cause the processor to: determine a network usage policy according to a network provider’s revenue received from providing traffic and a net-utility of a user of a first terminal device using traffic, and send the network usage policy to the first terminal device, so that the first terminal device determines at least one available access network among the plurality of access networks according to the network usage policy. The network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time.

Optionally, the processor receives a request message from the first terminal device. The processor sends a response message to the first terminal device, the response message carries the network usage policy, the request message carries price sensitivity parameter of the traffic, and the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic.

Optionally, the at least one available access network comprises a paid access network and at least one free access network, the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one free access network, and the processor determines the offloading ratio threshold by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks.

In the above embodiments of the present invention, the offloading ratio threshold is determined by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks. The at least one profile comprises at least one of the following parameters: willingness to pay, traffic demand, delay profile, and probability that the user uses the at least one free access network. The paid access network comprises a cellular access network, and the at least one free access network comprises at least one of a WiFi access network, a DSRC access network, a WLAN access network and a WiMAX access network.

The persons of ordinary skills in the art may realize that the units and steps of algorithm of the respective examples, described with reference to the embodiments disclosed in the text, can be accomplished by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed by means of hardware or software depends on a specific application and a design constraint condition of the technical solutions. Professional technical personnel may accomplish the described functions by adopting a different method for each specific application, but this kind of accomplishment shall not go beyond the scope of the present invention.

Those skilled in the art may understand clearly that, for convenience and simplicity of description, specific working processes of the above-described systems, apparatus and units may be referred to corresponding processes in the aforementioned embodiments of the methods, and will not be described repeatedly herein.

In several embodiments provided by the present application, it shall be understood that disclosed systems, apparatus and methods may be implemented by other manners. For example, the embodiments of the apparatus described above are just illustrative. For example, division of the units is just a kind of division according to logical functions, and there may be other division manners for practical implementations. For example, a plurality of units or components may be combined or integrated into another system, or some features may be neglected or may not be performed. In addition, the shown or discussed mutual coupling or direct coupling or communication link may be an indirect coupling or communication link through some interfaces, apparatus or units, which may be in an electrical form, a mechanical form or in other forms.

The units described as separated parts may be, or may not be, physically separated, and the parts shown as units may be, or may not be, physical units, which may be located in one place or distributed to a plurality of network elements. Part or all units therein may be selected, according to an actual need, to implement the objective of solutions provided in the present invention.

In addition, the respective functional units in the respective embodiments of the present invention may be integrated into one processing unit, or the respective units may exist separately and physically, or, two or more units may be integrated into one unit.

If the function is implemented in the form of a software functional unit and is sold or used as an independent product, the function may be stored in a computer readable storage medium. Based on this understanding, the spirit, or the parts that make contributions to the prior art, of the technical solution in the present invention may be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes a number of instructions that enable a computer device (may be a personal computer, a server, or a network device) to execute all or part of steps of the method described in the respective embodiments of the present invention. The preceding storage mediums includes various mediums that can store program codes, such as, a U disk, a removable hard disk, a read-only memory (Read-Only Memory, ROM) , a random access memory (Random Access Memory, RAM) , a magnetic disk, an optical disk, or the like.

The foregoing descriptions are merely specific embodiments of the invention, rather than limiting the protection scope of the invention. It is easy for any one skilled in the art to conceive changes or substitutions within the technical scope disclosed by the invention, and the changes or substitutions shall fall in the protection scope of the invention. Therefore, the protection scope of the present invention shall be defined by the claims.

Claims

A method for transmitting traffic, comprising:

receiving, by a first terminal device, a network usage policy from a network node, wherein the network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time, and the network usage policy depends on a network provider’s revenue received from providing traffic and a net-utility of a user of the first terminal device using traffic；

determining, by the first terminal device, at least one available access network among the plurality of access networks according to the network usage policy；

selecting, by the first terminal device, an access network from the at least one available access network；

transmitting, by the first terminal device, traffic to the second terminal device through the selected access network.
The method according to claim 1, further comprising:

monitoring, by the first terminal device, Quality of Service QoS which the at least one available access network is capable of providing for the first terminal device to transmit traffic to a second terminal device respectively,

wherein the selecting, by the first terminal device, an access network from the at least one available access network, comprises:

selecting, by the first terminal device, an access network with the best QoS from the at least one available access network according to the monitored QoS.
The method according to claim 2, wherein the monitoring, by the first terminal device, Quality of Service QoS which the at least one available access network is capable of providing for the first terminal device to transmit traffic to a second terminal device respectively, comprises:

sending, by the first terminal device, at least one heartbeat message to the second terminal device through the at least one available access network, respectively；

receiving, by the first terminal device, at least one heartbeat response message from the second terminal device through the at least one available access network, respectively；

determining, by the first terminal device, the QoS according to the at least one heartbeat response, respectively.
The method according to any of claims 1-3, further comprising:

establishing, by the first terminal device, an association for the traffic between the first terminal device and second terminal device through a Stream Control Transport Protocol SCTP；

sending, by the first terminal device, a request message to the network node, wherein the request message carries price sensitivity parameter of the traffic, and the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic,

wherein receiving, by a first terminal device, a network usage policy from a network node, comprises:

receiving, by the first terminal device a response message from the network node, wherein the response message carries the network usage policy.
The method according to any of claims 1-4, wherein the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one available access network,

wherein the determining, by the first terminal device, at least one available access network among the plurality of access networks according to the network usage policy, comprises:

determining, by the first terminal device, at least one available access network excluding the paid access network when the ratio is not less than the offloading ratio threshold.
The method according to claim 5, wherein the offloading ratio threshold is determined by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks.
The method according to claim 6, wherein the at least one profile comprises at least one of the following parameters: willingness to pay, traffic demand, delay profile, and probability that the user uses the at least one free access network.
The method according to any of claims 5-7, wherein the paid access network comprises a cellular access network, and the at least one free access network comprises at least one of a Wireless Fidelity WiFi access network, a Dedicated Short Range Communications DSRC access network, a Wireless Local Area Network WLAN access network and a Worldwide Interoperability for Microwave Access WiMAX access network.
An method for transmitting traffic, comprising:

determining, by a network node, a network usage policy according to a network provider’s revenue received from providing traffic and a net-utility of a user of a first terminal device using traffic, wherein the network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time；

sending, by the network node, the network usage policy to the first terminal device, so that the first terminal device determines at least one available access network among the plurality of access networks according to the network usage policy.
The method according to claim 9, further comprises

receiving, by a network node, a request message from the first terminal device, wherein the request message carries price sensitivity parameter of the traffic, and the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic,

wherein sending, by the network node, the network usage policy to the first terminal device, comprises:

sending, by the network node, a response message to the first terminal device, wherein the response message carries the network usage policy.
The method according to claim 9 or 10, wherein the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one free access network,

wherein the determining, by a network node, a network usage policy according to a network provider’s revenue received from providing traffic and a net-utility of a user of a first terminal device using traffic, comprises:

determining, by the network node, the offloading ratio threshold by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks.
The method according to claim 11, wherein the at least one profile comprises at least one of the following parameters: willingness to pay, traffic demand, delay profile, and probability that the user uses the at least one free access network.
The method according to claim 11 or 12, wherein the paid access network comprises a cellular access network, and the at least one free access network comprises at least one of a Wireless Fidelity WiFi access network, a Dedicated Short Range Communications DSRC access network, a Wireless Local Area Network WLAN access network and a Worldwide Interoperability for Microwave Access WiMAX access network.
A terminal device, comprising:

a receiving unit, configured to receive a network usage policy from a network node, wherein the network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time, and the network usage policy depends on a network provider’s revenue received from providing traffic and a net-utility of a user of the first terminal device using traffic；

a determining unit, configured to determine at least one available access network among the plurality of access networks according to the network usage policy；

a selecting unit, configured to select an access network from the at least one available access network；

a transmitting unit, configured to transmit traffic to the second terminal device through the selected access network.
The terminal device according to claim 14, further comprising:

a monitoring unit, configured to monitor Quality of Service QoS which the at least one available access network is capable of providing for the first terminal device to transmit traffic to a second terminal device respectively, wherein the selecting unit selects an access network with the best QoS from the at least one available access network according to the monitored QoS.
The terminal device according to claim 15, wherein the monitoring unit sends at least one heartbeat message to the second terminal device through the at least one available access network, respectively, receives at least one heartbeat response message from the second terminal device through the at least one available access network, respectively, and determines the QoS according to the at least one heartbeat response, respectively.
The terminal device according to any of claims 14-16, further comprising:

a establishing unit, configured to establish an association for the traffic between the first terminal device and second terminal device through a Stream Control Transport Protocol SCTP, wherein the transmitting unit is further configured to send a request message to the network node, the request message carries price sensitivity parameter of the traffic, the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic, the receiving unit receives a response message from the network node, and the response message carries the network usage policy.
The terminal device according to any of claims 14-17, wherein the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one available access network, and the determining unit determines at least one available access network excluding the paid access network when the ratio is not less than the offloading ratio threshold.
The terminal device according to claim 18, wherein the offloading ratio threshold is determined by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks.
The terminal device according to claim 19, wherein the at least one profile comprises at least one of the following parameters: willingness to pay, traffic demand, delay profile, and probability that the user uses the at least one free access network.
The terminal device according to any of claims 18-20, wherein the paid access network comprises a cellular access network, and the at least one of a Wireless Fidelity WiFi access network, a Dedicated Short Range Communications DSRC access network, a Wireless Local Area Network WLAN access network and a Worldwide Interoperability for Microwave Access WiMAX access network.
An network node, comprising:

a determining unit, configured to determine a network usage policy according to a network provider’s revenue received from providing traffic and a net-utility of a user of a first terminal device using traffic, wherein the network usage policy is used for indicating a policy for the first terminal device to use a plurality of access networks to transmit traffic in a preset period of time；

a sending unit, configured to sending the network usage policy to the first terminal device, so that the first terminal device determines at least one available access network among the plurality of access networks according to the network usage policy.
The network node according to claim 22, further comprises

a receiving unit, configure to receive a request message from the first terminal device, wherein the request message carries price sensitivity parameter of the traffic, the network usage policy depends on the revenue, the net-utility and the price sensitivity parameter of the traffic, the sending unit sends a response message to the first terminal device, and the response message carries the network usage policy.
The network node according to claim 22 or 23, wherein the at least one available access network comprises a paid access network and at least one free access network, and the network usage policy comprises an offloading ratio threshold which indicates a threshold for a ratio of amount of traffic transmitted through a paid access network to total amount of traffic transmitted through the at least one free access network, wherein the determining unit determines the offloading ratio threshold by maximizing the revenue and the net utility in a cost model which is determined based on a pricing scheme for using the paid access network provided by the network provider and at least one profile of the user when using the plurality of access networks.
The network node according to claim 24, wherein the at least one profile comprises at least one of the following parameters: willingness to pay, traffic demand, delay profile, and probability that the user uses the at least one free access network.
The network node according to claim 24 or 25, wherein the paid access network comprises a cellular access network, and the at least one free access network comprises at least one of a Wireless Fidelity WiFi access network, a Dedicated Short Range Communications DSRC access network, a Wireless Local Area Network WLAN access network and a Worldwide Interoperability for Microwave Access WiMAX access network.