WO2017028030A1

WO2017028030A1 - Network assisted message forwarding

Info

Publication number: WO2017028030A1
Application number: PCT/CN2015/087031
Authority: WO
Inventors: Qianxi Lu; Hieu DO
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-08-14
Filing date: 2015-08-14
Publication date: 2017-02-23

Abstract

The embodiments disclose a method for a wireless device to transmit a message, the wireless device being enabled to transmit the message to a wireless network via a first interface and to one or more other wireless device via a second interface, the method comprising: obtaining the message to be transmitted; determining whether the wireless device is within coverage of the wireless network; in response to determining that the wireless device is within coverage of the wireless network, transmitting the message to the wireless network via the first interface and transmitting the message to the one or more other wireless devices via the second interface; and in response to determining that the wireless device is not within coverage of the wireless network, transmitting the message to the one or more other wireless devices via the second interface. The embodiments also disclose the wireless device thereof.

Description

NETWORK ASSISTED MESSAGE FORWARDING

TECHNICAL FIELD

The present technology relates generally to radio communication networks, particularly to a method for network assisted message forwarding in D2D communication and the device thereof.

BACKGROUND

During Release 12, the 3GPP (Third Generation Partnership Project) LTE (Long-Term Evolution) standard has been extended with support of device to device (D2D) (specified as “sidelink” ) features targeting both commercial and Public Safety applications. Some functionalities enabled by Rel-12 LTE comprise device discovery, where devices are able to sense the proximity of another device and associated application by broadcasting and detecting discovery messages that carry device and application identities. Other functionalities comprise direct communication based on physical channels terminated directly between devices.

One of the potential extensions for the device to device work comprises support of V2X (vehicle-to-anything-you-can-imagine) communication, which includes any combination of direct communication between vehicles, pedestrians and infrastructure.

SUMMARY

V2X communication may take advantage of a network infrastructure, when available, but at least basic V2X connectivity should be possible even in case of lack of coverage. Providing an LTE-based V2X interface may be economically advantageous because of the LTE economies of scale and it may enable tighter integration between V2I/V2N (vehicle-to-infrastructure/network) communications, and V2P (vehicle-to-pedestrian) and V2V (vehicle-to-vehicle) communications, as compared to using a dedicated V2X technology.

Figure 1 shows V2X scenarios for an LTE-based network. The scenarios comprise V2V communications which cover communications between vehicles, V2P communications which cover communications between a vehicle and a device carried by an individual (e.g. handheld terminal carried by a pedestrian, cyclist, driver or passenger) , and V2I/N communications which cover communications between a vehicle and a roadside (RSU) unit or network. An RSU is a transportation infrastructure entity acts similarly to a wireless LAN access point or implemented in an eNodeB or a stationary UE, and can provide communications with underlying infrastructure. In some existing use cases, roadside units can provide drivers with information which help them in controlling the vehicle, e.g., parking a vehicle, cruise control, lane keeping assistance and road sign recognition.

V2X communications may carry both non-safety and safety information.

LTE-based V2X study is urgently desired due to rapid changes in technology and market for V2X communication. There are many research projects and field tests of connected vehicles taking place around the world, mainly in US, Europe, Japan and Korea. In China, CCSA has finished the feasibility study for vehicle safety application based on TD-LTE in 2014 and began the series of industrial standard of communication based on LTE for vehicle application. Further, in March 2015, the study on radio spectrum for V2X also started in CCSA and some vehicular industrial alliances in China. Based on the study, National Regulatory Authority in China will allocate the spectrum for connected vehicles.

In order to respond to this situation, 3GPP SA1#69 recently agreed a new Rel-14 study (S1-150284/SP-150051) on LTE support for V2X services to investigate the essential use cases and requirements for V2V, V2P and V2I/N.

The SA1 study considers both safety services and non-safety services and the possibility of using existing LTE technologies for unicast, multicast and/or broadcast communication.

More recently a Rel-13 RAN SI has been approved with the objectives to evaluate new functionalities needed to operate LTE-based V2X (V2V, V2I/N, and V2P) , and to investigate potential enhancements for vehicular services defined in SA1 TR 22.885.

The current SA1 TR (which has not been completed yet) mainly focuses on a single hop of message delivery, i.e., a message is delivered from a vehicle A to an immediate vehicle B as shown in Figure 2. However, it would be beneficial to extend it to multi-hop/relay scenario, i.e., a message is delivered from vehicle A to vehicle B, and further forwarded from vehicle B to vehicle C as shown in Figure 2. Such a scenario is crucial in use cases such as accident or roadblock warnings, where vehicle B needs to warn its following vehicles as vehicle A does.

One problem in such a multi-hop/relay scenario may be the limited communication range per hop and the latency to reach faraway vehicles if using multi-hop. Besides, not all devices can support D2D communications and thus communications relying on D2D have limited coverage. Another problem in such a multi-hop/relay scenario may be the message flooding, which means that one message (from vehicle A in Figure 2) would generate a flood of forwarded messages in the proximity, causing high network load and thus lowering packet delivery rate, which in turn further undermines the message forwarding from vehicle A to the faraway vehicles.

Therefore, it is an object to speed up, and/or to extend the message forwarding and/or alleviate the message flooding.

According to one aspect of the embodiments, there is provided a method for a wireless device to transmit a message, the wireless device being enabled to transmit the message to a wireless network via a first interface and to one or more other wireless devices via a second interface, the method comprising: obtaining the message to be transmitted； determining whether the wireless device is within coverage of the wireless network； in response to determining that the wireless device is within coverage of the wireless network, transmitting the message to the wireless network via the first interface and transmitting the message to the one or more other wireless devices via the second interface ； and in response to determining that the wireless device is not within coverage of the wireless network, transmitting the message to the one or more other wireless devices via the second interface.

According to another aspect of the embodiments, there is provided a wireless device for transmitting a message, comprising a first interface and a second interface, the wireless device being enabled to transmit the message to a wireless network via a first interface and to one or more other wireless devices via a second interface, the method further comprising: a memory, adapted to store data and instructions therein； a processing system, adapted to perform the following steps: obtaining the message to be transmitted； determining whether the wireless device is within coverage of the wireless network； in response to determining that wireless device is within coverage of the wireless network, transmitting the message to the wireless network via the first interface and transmitting the message to the one or more other wireless devices via the second interface； and in response to determining that wireless device is not within coverage of the wireless network, transmitting the message to the one or more other wireless devices via the second interface.

According to a further aspect of the embodiments, there is provided a computer program product, which comprises the instructions for implementing the steps of the methods as described above.

According to a still further aspect of the embodiments, there is provided a recording medium which stores instructions for implementing the steps of the methods as described above.

As a whole or by scenario, it is advantageous to apply network-assisted forwarding when possible, as it helps to extend the communication range of certain important messages through powerful and widely covered wireless network when possible and speed up message forwarding to a faraway receiver. Further in combination with message redundancy check or D2D forwarding hops or forwarding distance limiting, network flooding can be greatly alleviated as the packet forwarding load in the direct device-to-device interface is greatly reduced, which in turn further improves packet delivery rate.

BRIEF DESCRIPTION OF THE DRAWINGS

The technology will now be described, by way of example, based on embodiments with reference to the accompanying drawings, wherein:

FIG. 1 illustrates V2X scenarios for an LTE-based network in which embodiments are implemented；

FIG. 2 illustrates an example of a multi-hop V2X scenario in accordance with embodiments of the present invention；

FIG. 3 illustrates a flowchart of a method performed in a wireless device in accordance with embodiments of the present invention；

FIG. 4 illustrates a flowchart of a method performed in the wireless device in accordance with embodiments of the present invention；

FIG. 5 illustrates a block diagram of a wireless device in accordance with embodiments of the present invention.

DETAILED DESCRIPTION

Embodiments herein will be described in detail hereinafter with reference to the accompanying drawings, in which embodiments are shown. These embodiments herein may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. The elements of the drawings are not necessarily to scale relative to each other. Like numbers refer to like elements throughout.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a" , "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" "comprising, " "includes" and/or "including" when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meanings as commonly understood. It will be further understood that a term used herein should be interpreted as having a meaning consistent with its meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The present technology is described below with reference to block diagrams and/or flowchart illustrations of methods, apparatus (systems) and/or computer program products according to the present embodiments. It is understood that blocks of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, may be implemented by computer program instructions. These computer program instructions may be provided to a processor, controller or controlling unit of a general purpose computer, special purpose computer, and/or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer and/or other programmable data processing apparatus, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks.

Accordingly, the present technology may be embodied in hardware and/or in software (including firmware, resident software, micro-code, etc. ) . Furthermore, the present technology may take the form of a computer program product on a computer-usable or computer-readable storage medium having computer-usable or computer-readable program code embodied in the medium for use by or in connection with an instruction execution system. In the context of this document, a computer-usable or computer-readable medium may be any medium that may contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.

Hereinafter, the embodiments may be described in the context of V2X systems deployed in combination with LTE network. However, such description is only exemplary, rather than restrictive, and the embodiments could be generalized to any D2D systems deployed in combination with any wireless networks including for example WLAN and 5G networks.

As shown in FIG. 2, in the example multi-hop V2X scenario there is a message originator, vehicle A, and three message forwarders, vehicle B and C, handheld terminal carried by a pedestrian D, a message receiver vehicle E and a base station S1 and a base station S2. The base station S1 and the base station S2 may belong to the same PLMN (Public Land Mobile Network) or different PLMNs.

Further, those skilled in the art will appreciate that the base station S1 or the base station S2 is sometimes also referred to in the art as a macro base station, a node B, or B-node, an eNodeB (eNB) , and is sometimes also referred to in the art as a micro/femto/pico base stations, a micro/femto/pico node B, or micro/femto/pico B-node, a micro/femto/pico eNodeB (eNB) , etc..

For simplicity and clarity, only 4 vehicles and a handheld terminal carried by a pedestrian are shown. Further, a roadside unit /network may also be included. Any of the vehicles, pedestrian terminals and a roadside unit/network can support D2D communications, and any of them at the meantime can support wireless communications with base stations S1 and S2.It will be appreciated that different numbers of vehicles and pedestrian terminals and RSUs may be included in such a scenario. And it will also be appreciated that all wireless devices could be vehicles only, or could be pedestrian terminals only, or RSUs only, or any combination thereof. For sake of simplicity, they are all referred to as V2X devices hereinafter.

It will be appreciated by one skilled in the art that the following scenario is also included. As RSUs may also have their own networks, referred to as RSU networks herein, such RSU networks may also take the role of assisting network. In such a scenario, an RSU will take place of the base station and unicast, multicast or broadcast the message in RSU networks. A typical use scenario is that all the V2X devices are vehicles, and all the vehicles are able to communicate with each other via V2V communications and to communicate with RSUs within an underlying RSU network via V2I/N communications. As the RSU can communicate with the V2V devices in a wireless way, thus the RSU network may also be regarded as a wireless network. Therefore the embodiments comprise V2V systems deployed in combination with RSU networks.

With reference to FIG. 3, a general flowchart of network assisted D2D communications is described as follows. At step 301, a V2X device obtains a message, either by receiving or originating, in case of, for example, a car accident warning. At step 302, the V2X device determines for itself whether it is in coverage of the assisting wireless network, for example, whether it is in coverage of any base station. If the answer is no, then the V2X device can not forward the message through any assisting wireless network. In that case, a first interface for communications with the base station is not enabled, a second interface for communication with another V2X device is enabled and the message could be forwarded to another V2X device via the second interface (step 309) .

Otherwise, if it is determined that the V2X device is within coverage of some base station, for example base station S1 in Figure 2, then the message could be forwarded to both the base station S1 via the first interface, for example, Uu forwarding interface (step 305) and another V2X device via the second interface, for example, PC5 forwarding interface (step 309) .

Additionally or alternatively, if the message is obtained by receiving rather than originating by the present wireless device, then a redundancy check (now shown in Figure 3) of the message can be performed once received, to make sure the V2X device has not received the same message before. It is advantageous to perform such a redundancy check of the message, as message looping will be prevented.

Additionally or alternatively, if the message is received from a base station, then the message may need no transmitting either via the first interface or via the second interface, as broadcast, unicast or multicast is through the assisting network is already done and thus a wide range of devices may have received the message, .

Additionally or alternatively, before forwarding the message to base station S1 (305) , a check of whether the message has been transmitted through any PLMN could be made at step 303, as previous forwarder (s) may be in coverage of any PLMN and thus may have already transmitted the message to the assisting wireless network. The check can be made by reading related information comprised in the message, for example, comprised in a "NW transmitted" field in the message, with the value of 0 representing the message has not been transmitted through any PLMN, or 1 representing the message has been transmitted through any PLMN respectively. If the message has not been transmitted through any PLMN, then accordingly, before step 305 is performed, additionally or alternatively, the "NW transmitted" field should be updated to, for example, value 1, at step 304. It is advantageous to introduce

steps

303 and 304, as any message receiver can determine whether to transmit the message to the assisting wireless network, for example, LTE networks, based on the related information, for example "NW transmitted" field comprised in the message. Accordingly, repeated transmission load of such a message may not occur in the assisting wireless network, for example, LTE network.

It is noted that the message is forwarded one to one from vehicle A till vehicle E shown in Figure 2, however, it will be appreciated by one skilled in the art that any number of V2X devices could be existing in the proximity of any of the V2X devices shown in Figure 2. Accordingly, the V2X device shown in Figure 2 will forward the message to all the V2X devices in its proximity, or part of the V2X devices in its proximity, depending on its strategy. That specific strategy is not part of our invention.

It is also noted that the message can be further transmitted in the assisting wireless network by way of multicast, unicast or broadcast, depending on a strategy. Detailed discussion of such a strategy is not part of our invention.

Additionally or alternatively, a forwarding distance limit or forwarding hop limit of V2X communications could be introduced. The forwarding distance may herein refer to current distance between the message originator where the message is originated and current message receiver. The forwarding hops may herein refer to the hops that the message has gone through. Accordingly, some information indicating current status relating to forwarding hops or forwarding distance could be comprised in the message, and a threshold of forwarding hops or forwarding distance should be set. Then before forwarding the message to one or more other V2X device (s) at step 309, a determination of whether a metric, for example, forwarding hop number or forwarding distance associated with the message has reached the threshold should be made (step 308) . If the threshold has been reached, then the message will not be forwarded any longer. If the threshold has not been reached, then the message will be forwarded to one or more other V2X devices via the second interface at step 309.

Such a forwarding distance limit or forwarding hop limit scheme requires information indicating current status relating to forwarding hops or forwarding distance comprised in the message to be updated at every forwarding V2X device. The updating may be needed at

steps

306 and 307 before the message is forwarded to one or more other devices. Details of the updating are described as follows.

In one embodiment, the information indicating current status relating to forwarding hops is a forwarding hop number. In one example, the forwarding hops number starts from 0, and is incremented by 1 for each V2X forwarding operation until the threshold. In another example, the forwarding hop number starts from the threshold, and is decreased by 1 for each V2X forwarding operation until 0.

In yet another embodiment, a forwarding distance limit may be introduced. In one example, original geographical position of the message originator is comprised in the message, and current geographical position of the message forwarder can be easily known by the forwarder, however, the message originator is generally moving, especially in the scenario of V2V communications, rather than being still, so current position of the message originator can only be approximated, based on information such as message transmitting time and velocity information of the message originator, which could be comprised in the message, or obtained from other messages such as Cooperative Awareness Message (CAM) or Decentralized Environmental Notification Message (DENM) . In one example, the moving distance of the message originator could be estimated by firstly determining the time cost from transmitting by the message originator to receiving by the current forwarder, and then multiplying the time cost by the velocity. Specific ways of estimation of current position of the message originator is not part of our invention. The information indicating current status relating to distance could be original geographical position of the message originator, or additionally time and velocity information of the message originator. In one example, the distance between the current location of the message originator and location of current message forwarder is calculated based on information comprised in the message and then compared with threshold of distance to determine whether the distance threshold has been reached at step 309. While the fields in the message indicate information of the message originator, updating of the fields is not needed at each forwarding operation.

It is advantageous to introduce such a forwarding distance limit or forwarding hop limit of V2X communications, as the load in the V2X communications could be greatly saved. It is noted only redundancy check or D2D transmission limiting has limited capability of flood avoiding, given a designated range , but either of them in combination with wireless network assisted forwarding can greatly avoid flooding, and make a leverage between prompt transmission to the devices near around and transmission in a wider area.

Additionally or alternatively, the threshold of forwarding distance or forwarding hops may stay the same and subject to changes based on different conditions, and therefore setting of the threshold of forwarding distance or forwarding hops might be performed at step 306 and/or 307 before the message is forwarded to one or more other devices at step 309.

Further details of the threshold setting will be described with reference to Figure 4. Several elements are considered when determining the threshold—being in coverage of the assisting wireless network or not, been transmitted through the assisting wireless network or not, and/or current assisting wireless network being of the same service provider as the message originator or not.

At step 401, the V2X device will determine for itself whether it is in coverage of an assisting wireless network, for example, whether it is in coverage of any base station. Further, the V2X device will determine whether the obtained message from step 301 has been transmitted over the assisting wireless network at both

steps

402 and 403. Similar steps in Figure 3 and 4 may corresponds to each other, such as step 401 corresponding to step 302, or may not corresponds to each other, such as step 402 in Figure 4 not corresponding to step 303 in Figure 3, as Figure 3 and Figure 4 illustrate embodiments from different aspects, with Figure 3 focusing on transmitting via different interfaces and Figure 4 focusing on threshold setting.

In response to determining that the V2X device is not in coverage of the assisting wireless network, and the obtained message has not been transmitted over the assisting wireless network, the V2X device has to rely on V2X communications to forward the message, even to the faraway V2X devices. In that case, a larger threshold of Y will be set for the present at step 404. Detailed value of Y could depend on many factors, and how these factors work for value Y is not part of our invention.

In response to determining that the V2X device is not in coverage of the assisting wireless network, and the obtained message has been transmitted over the assisting wireless network, the threshold will be maintained and not require any new setting.

In response to determining that the V2X device is in coverage of the assisting wireless network, and the obtained message has been transmitted over the assisting wireless network, the threshold will be maintained and not require any new setting.

In response to determining that the V2X device is in coverage of the assisting wireless network, and the obtained message has not been transmitted over the assisting wireless network, the message will be transmitted through both the assisting wireless network and V2X communications. As the assisting wireless network can help transmit the message to faraway devices, a smaller threshold of X will be set for the present (step 406 and 407) .

Additionally or alternatively, considering the assisting wireless network forwarding would undergo larger latency for inter-PLMN case (transmitting to different PLMN (s) ) than for intra-PLMN case (transmitting within the same PLMN) , we may differentiate the thresholds for inter-PLMN case and for intra-PLMN case. In one example, as the transmission over the assisting wireless network covers a larger area than the limited V2X communications, if the PLMN of the current V2X device is different than PLMN of the originator, then the transmission over the assisting wireless network will obviously cover different PLMN (s) . Therefore, we can determine inter-PLMN case and intra-PLMN case by comparing PLMN of the originator and PLMN of the forwarding V2X device at step 405. This requires PLMN of the message originator is known to the forwarding V2X device, for example, comprised in the message. In another example, as running PLMNs are known and limited, for example, we have 3 PLMNs of China Mobile, China Unicom and China Telecom, thus we can indicate in the message whether any of the V2X device belong to any of the 3 PLMNs. If 2 or 3 PLMNs are indicated, then we can determine it is inter-PLMN case, otherwise, it is intra-PLMN case. It is noted that a PLMN can be regarded as a service provider or an operator. The threshold is set to X2 for inter-PLMN case at step 406 and set to X1 for intra-PLMN case at step 407, wherein X1 is smaller than X2.

The value of X1 and X2 is determined considering the assisting wireless network transmitting time. For example, as is shown in Figure 2, if the message transmitting from vehicle A to vehicle E via base station S1 and base station S2 takes 400ms (actually such transmission time is basically determined by the wireless network, regardless of geographical location of the receiving devices) , and if average transmitting time of one hop of V2X transmission is 100ms, then forwarding hop threshold is 4. Assuming base station S1 can cover all the V2X devices, this time the message transmitting from vehicle A to vehicle E via base station S1 may take less than 400ms, for example 300ms, and if average transmitting time of one hop of V2X transmission is still 100ms, then forwarding hop threshold is 3, which is obviously smaller than 4.

In one example, the undergone forwarding hop number and forwarding hop number threshold are both comprised in the message, and then the forwarding hop number threshold is simply updated according to the newly set threshold. In another example, the left forwarding hop number and the forwarding hop number threshold are comprised in the message, and then the left forwarding hop number needs recalculation considering difference of the old threshold and new threshold. For example, if left forwarding hop number updated in the last transmitting device is H, the old forwarding hop number threshold is Y and new forwarding hop number threshold is X, then the updated H's hould be calculated as follows:

H'＝H-1- (Y-X) .

It is advantageous to differentiate inter-PLMN case and intra-PLMN case, so that the system load can be further reduced for intra-PLMN case, and thus resource efficiency can be further improved.

FIG. 5 illustrates a block diagram showing example physical components of a V2X device in accordance with embodiments of the present invention. It should be appreciated that the V2X device can be implemented using components other than those illustrated in the example of Figure 5.

In the example of FIG. 5, the V2X device 500 comprises a memory 501, a processing system 502, a first interface 503 and a second interface 504. The memory 501 includes one or more than one computer-usable or computer-readable storage medium capable of storing data and/or computer-executable instructions. Is should be appreciated that the storage medium is preferably a non-transitory storage medium.

The processing system 502 includes one or more than one processing unit. A processing unit is a physical device or article of manufacture comprising one or more integrated circuits that read data and instructions from computer readable media, such as the memory 501, and selectively execute the instructions. In various embodiments, the processing system 502 is implemented in various ways. For example, the processing system 502 can be implemented as one or more than one processing core. In another example, the processing system 502 can comprise one or more than one separate microprocessor. In yet another example embodiment, the processing system 502 can comprise an application-specific integrated circuit (ASIC) that provides specific functionality. In yet another example, the processing system 502 provides specific functionality by using an ASIC and by executing computer-executable instructions.

The first network interface 503 is a device or article of manufacture that enables the V2X device 500 to send data to or receive data from a wireless network, such LTE. In different embodiments, the first interface 503 is implemented in different ways. For example, the first interface 503 can be implemented as a Uu forwarding interface in case the wireless network is LTE network.

The second network interface 504 is a device or article of manufacture that enables the wireless device 500 to send data to or receive data from other wireless devices directly through for example V2X communications. In different embodiments, the second interface 504 is implemented in different ways. For example, the second interface 504 can be implemented as a PC5 forwarding interface in case V2X communications.

The memory 501 stores various types of data and/or software instructions. For instance, in the example of Figure 5, the instructions in the memory 501 can include those that when executed in the processing system 502, cause the wireless device 500 to implement the methods described herein.

While the embodiments have been illustrated and described herein, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present technology. In addition, many modifications may be made to adapt to a particular situation and the teaching herein without departing from its central scope. Therefore it is intended that the present embodiments not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present technology, but that the present embodiments include all embodiments falling within the scope of the appended claims.

Claims

A method for a wireless device to transmit a message, the wireless device being enabled to transmit the message to a wireless network via a first interface and to one or more other wireless devices via a second interface, the method comprising:

-obtaining the message to be transmitted (301) ；

-determining whether the wireless device is within coverage of the wireless network (302, 401) ；

-in response to determining that the wireless device is within coverage of the wireless network, transmitting the message to the wireless network via the first interface (305) and transmitting the message to the one or more other wireless devices via the second interface (309) ； and

-in response to determining that the wireless device is not within coverage of the wireless network, transmitting the message to the one or more other wireless devices via the second interface (309) .
The method of Claim 1, further comprising:

-determining whether the message has been transmitted over the wireless network (303, 402, 403) ；

-in response to determining that the message has not been transmitted over the wireless network, transmitting the message to the wireless network via the first interface (305) ；

-determining whether a metric associated with the message has reached a threshold； and

-in response to determining that the metric associated with the message has not reached the threshold, transmitting the message to the one or more other wireless devices via the second interface (309) .
The method of Claim 2, further comprising:

-in response to determining that wireless device is within coverage of the wireless network or the message has been transmitted over the wireless network, setting the threshold to a first threshold (307, 406, 407) ；

-in response to determining that wireless device is not within coverage of the wireless network and the message has not been transmitted over the wireless network, setting the threshold to a second threshold (306, 404) ；

wherein the first threshold is smaller than the second threshold.
The method of Claim 3, further comprising:

-determining whether service provider of the wireless network of the wireless device is the same as that of the message originator where the message is originated (405) ；

-in response to determining the service provider of the wireless network of the wireless device is the same as that of the message originator, setting the first threshold to X1 (407) ；

-in response to determining the service provider of the wireless network of the wireless device is not the same as that of the message originator, setting the first threshold to X2 (406) ；

wherein X1 is smaller than X2.
The method of Claim 3 or 4, wherein the metric associated with the message comprises the number of hops that the message has gone through via the second interface.
The method of Claim 3 or 4, wherein the metric associated with the message comprises present geographical distance between the wireless device and the message originator.
The method of Claim 2, or 4, wherein whether the metric associated with the message has reached the threshold, whether the message has been transmitted over the wireless network, and whether service provider of the wireless device is the same as that of the message originator are determined based at least on one or more fields comprised in the message, and the one or more fields are updated if changed in the wireless device (306, 307) .
The method of Claim 7, wherein present geographical distance is calculated from geographical location of the message originator comprised in the message, geographical location of the wireless device, in combination with estimation of moving of the message originator.
A wireless device for transmitting a message, comprising a first interface and a second interface, the wireless device being enabled to transmit the message to a wireless network via a first interface (503) and to one or more other wireless devices via a second interface (504) , the method further comprising:

a memory (501) , adapted to store data and instructions therein；

a processing system (502) , adapted to perform the following steps:

obtaining the message to be transmitted；

determining whether the wireless device is within coverage of the wireless network；

in response to determining that wireless device is within coverage of the wireless network, transmitting the message to the wireless network via the first interface and transmitting the message to the one or more other wireless devices via the second interface； and

in response to determining that wireless device is not within coverage of the wireless network, transmitting the message to the one or more other wireless devices via the second interface.
The wireless device of Claim 9, wherein the processing system is further adapted for:

determining whether the message has been transmitted over the wireless network；

in response to determining that the message has not been transmitted over the wireless network, transmitting the message to the wireless network via the first interface；

determining whether a metric associated with the message has reached a threshold； and

in response to determining that the metric associated with the message has not reached the threshold, transmitting the message to the one or more other wireless devices via the second interface.
The wireless device of Claim 10, wherein the processing system is further adapted for:

in response to determining that wireless device is within coverage of the wireless network or the message has been transmitted over the wireless network, setting the threshold to a first threshold；

in response to determining that wireless device is not within coverage of the wireless network and the message has not been transmitted over the wireless network, setting the threshold to a second threshold；

wherein the first threshold is smaller than the second threshold.
The wireless device of Claim 11, wherein the processing system is further adapted for:

determining whether service provider of the wireless network of the wireless device is the same as that of the message originator where the message is originated；

in response to determining the service provider of the wireless network of the wireless device is the same as that of the message originator, setting the first threshold to X1；

in response to determining the service provider of the wireless network of the wireless device is not the same as that of the message originator, setting the first threshold to X2；

wherein X1 is smaller than X2.
The wireless device of Claim 11 or 12, wherein the metric associated with the message comprises the number of hops that the message has gone through via the second interface.
The wireless device of Claim 11 or 12, wherein the metric associated with the message comprises present geographical distance between the wireless device and the message originator.
The wireless device of Claim 10, or 12, wherein whether the metric associated with the message has reached the threshold, whether the message has been transmitted over the wireless network, and whether service provider of the wireless device is the same as that of the message originator are determined based at least on one or more fields comprised in the message, and the one or more fields are updated if changed in the wireless device.
The wireless device of Claim 15, wherein present geographical distance is calculated from geographical location of the message originator comprised in the message, geographical location of the wireless device, in combination with estimation of moving of the message originator.