WO2010020260A1

WO2010020260A1 - Method for enabling communication between communication devices in mobile networks forming mobile ad hoc networks and mobile ad hoc network

Info

Publication number: WO2010020260A1
Application number: PCT/EP2008/006782
Authority: WO
Inventors: Roberto Baldessari; Andreas Festag
Original assignee: Nec Europe Ltd.
Priority date: 2008-08-18
Filing date: 2008-08-18
Publication date: 2010-02-25

Abstract

A method for enabling communication between communication devices - initiator device and target device - in mobile networks forming mobile ad hoc networks, in particular vehicular ad hoc networks (VANETs), wherein said mobile ad hoc network includes a multitude of mobile nodes, wherein at least some of said mobile nodes constitute a network - mobile network - of their own in that they comprise a communication system being designed to allow for the connection of one or more of said communication devices, wherein a routing protocol for packet forwarding within said mobile ad hoc network is implemented that makes forwarding decisions based on the geographical position of a packet's destination, and wherein the target device's local network address is known to the initiator device, is characterized in that for communication establishment the resolution of the mobile network prefix and position of said target device's mobile node is combined into one single query- response-signalling between said initiator device's mobile node and said target device's mobile node. Furthermore, a mobile ad hoc network with communication functionality between communication devices is disclosed.

Description

METHOD FOR ENABLING COMMUNICATION BETWEEN

COMMUNICATION DEVICES IN MOBILE NETWORKS FORMING

MOBILE AD HOC NETWORKS AND MOBILE AD HOC NETWORK

The present invention relates to a method for enabling communication between communication devices - initiator device and target device - in mobile networks forming mobile ad hoc networks, in particular vehicular ad hoc networks (VANETs), wherein said mobile ad hoc network includes a multitude of mobile nodes, wherein at least some of said mobile nodes constitute a network - mobile network - of their own in that they comprise a communication system being designed to allow for the connection of one or more of said communication devices, wherein a routing protocol for packet forwarding within said mobile ad hoc network is implemented that makes forwarding decisions based on the geographical position of a packet's destination, and wherein the target device's local network address is known to the initiator device.

Furthermore, the present invention relates to a mobile ad hoc network, in particular vehicular ad hoc network (VANET), with communication functionality between communication devices - initiator device and target device -, including a multitude of mobile nodes, wherein at least some of said mobile nodes constitute a network - mobile network - of their own in that they comprise a communication system being designed to allow for the connection of one or more of said communication devices, wherein a routing protocol for packet forwarding within said mobile ad hoc network is implemented that makes forwarding decisions based on the geographical position of a packet's destination, and wherein the target device's local network address is known to the initiator device.

During the last couple of years mobile ad hoc networks have become an interesting topic of research. Mobile ad hoc networks are self-organizing networks without a pre- established infrastructure. The networks consist of autonomous mobile nodes that collaborate in order to transport information, wherein the mobile nodes generally act as end systems and as routers at the same time.

Vehicular ad hoc networks (VANETs) are a particular type of mobile ad hoc networks (MANET) where communicating peers are vehicles and a short-range wireless cornrnunication technology is adopted. VANETs are highly dynamic networks with frequent topology changes, in which the motor vehicles that are equipped with so called on-board units act as mobile routers. The functionality of such wireless vehicular ad hoc networks is typically directed to safety, travelling comfort and onboard entertainment applications. By means of a communication between vehicles, for instance, accidents can be avoided or traffic efficiency can be improved. In the field of non-safety applications, internet browsing with point of interest notification, remote diagnostic functionalities and direct vehicle-to-vehicle file exchange or text/video chat are envisioned.

Due to the above-mentioned frequent topology changes, routing in mobile ad hoc networks is a challenging task. In prior art, topology-based routing protocols are known which are based on information about links that exist in the network to perform packet forwarding. Distance-vector routing, dynamic source routing (DSR), ad hoc on-demand distance vector routing (AODV) or zone routing protocol (ZRP), to name just a few, are such topology-based routing protocols. On the other hand, position- based routing protocols exist which are characterized in that they use additional information about the physical geographic position of the mobile nodes. Position information is to be achieved by means of positioning services, like e.g. GPS. Information about the position of other nodes is retrieved by means of location services, which can be employed by mobile nodes that are sending a data packet to determine the position of the destination mobile node and to include it in the packet's destination address.

Mobile nodes of mobile ad hoc networks as described above may constitute a network of their own. In such cases the mobile nodes comprise communication systems to which one or more communication devices may connect. Relying on the VANET, for example, vehicles could offer communication functionalities to nomadic passenger devices that are temporarily or permanently connected to the vehicles communication system. In such scenarios, mobile ad hoc networks may be regarded as networks of mobile (moving) networks (that are called mobile networks or internal networks or in case of VANETs in-vehicular networks). Hence, the communication devices mentioned above are also referred to as mobile network nodes, i.e. as nodes of a mobile network. In a VANET-scenario a vehicle is like a network of devices and, as a network, it is identified by a network prefix (e.g. IPv6 prefix), which is referred to as mobile network prefix. In other words, the mobile network prefix is the (local) network prefix of the mobile network. Although this scenario is deemed as fundamental for market penetration of vehicular communication, the problem of routing of data packets between passenger devices attached to different vehicles is still unsolved.

It is therefore an object of the present invention to improve and further develop a method and a mobile ad hoc network of the initially described type in such a way that a communication between communication devices connected to different mobile networks is enabled. The signalling procedure employed for communication establishment should consume as little resources as possible.

In accordance with the invention, the aforementioned object is accomplished by a method comprising the features of claim 1. According to this claim, such a method is characterized in that for communication establishment the resolution of the mobile network prefix and position of said target device's mobile node is combined into one single query-response-signalling between said initiator device's mobile node and said target device's mobile node.

Furthermore, the aforementioned object is accomplished by a mobile ad hoc network comprising the features of claim 15. According to this claim such a mobile ad hoc network is characterized in that the communication systems are configured to combine the resolution of the mobile network prefix and position of said target device's mobile node into one single query-response-signalling between said initiator device's mobile node and said target device's mobile node.

According to the invention it has been recognised that in order to enable communication between communication devices attached to different mobile networks (e.g. different vehicles in a VANET), mobile nodes' communication systems need to know the network identifier of the mobile node where the correspondent mobile network is located. Moreover, it has been recognized that mobile nodes' network identifiers are not derivable from mobile networks' prefixes as the network identifiers are typically changed over time in order to preserve privacy. In other words, - A -

due to changing network identifiers, a static binding between mobile nodes' network identifiers and mobile network prefixes is impossible.

According to the invention a combined signalling scheme for the resolution of the mobile network prefix together with the current geographic position of the mobile network is applied. Thus, a transparent communication between communication devices of different mobile networks through a mobile ad hoc network is enabled. Transparent means, that the involved parties - initiator device and target device - are not aware of the signalling, i.e. the query and the response are hidden from them.

In VANET applications, the invention allows sets of passenger devices of different cars to communicate with each other directly via the VANET without involving any fixed network infrastructure, e.g. of a telecommunication operator. The invention enables passengers to enjoy the communication facilities of the car with no need for introducing modifications in their communication devices that can be operated as usual, for instance in plane TCP/IPv6. Furthermore, due to the combined resolution of prefix and geographical position into one single query/response signalling, a minimum signalling overhead is produced, thus saving (typically very limited) physical channel bandwidth. The minimum signalling overhead makes the invention particularly suitable for WLAN-based VANETs.

As regards specific routing protocols for packet forwarding which are based on the geographical position of the packets destination and which may be implemented in mobile ad hoc networks according to the present invention, it is to be referred to M. Mauve J. Widmer and H. Hartenstein "A survey on position-based routing ad hoc networks", IEEE Network, November 2001 , S. 30-39, in which several of such routing protocols (position-based routing algorithms) are described in some more detail. It is to be noted that the query-response-signalling can be implemented as an extension of such basic geographic routing protocols and that it does not require being part of the basic geographic signalling.

According to a preferred embodiment a query is broadcasted by the communication system of the initiator device's mobile node upon receipt of data packets sent by the initiator device to the target device. Broadcasted means that the query is flooded into the network so that it may be received by all mobile nodes within the transmission range of the initiator device's mobile node. The query may include at least the mobile network prefix of the target device's mobile node. Furthermore, the query broadcasted by the communication system of the initiator device's mobile node may include its mobile network prefix and/or its current identifier.

Advantageously, the query may include a counter that is set to a specific value indicating the number of intended re-broadcasts of the query. More specifically, it may be provided that each mobile node that receives the query rebroadcasts the query in case that the value of the counter is unequal to zero and does not rebroadcast the query in case the value of the counter is equal to zero. Before rebroadcasting the query, each mobile node may reduce the counter by the value of "1 ". By such counter the number of hops between the initiator device and the target device may be specified. In case the target device is to far away from the initiator device, i.e. the counter is decreased to the value "0" before the query reaches the target device's mobile node (multi-hop), the process of communication establishment may be aborted. The initiator device could be informed about the abortion by means of a respective notification message (e.g. ICMPvθ Destination Unreachable).

According to a further preferred embodiment it may be provided that the communication system of the target device's mobile node, upon receipt of the query, responds to the query by sending a response. The response may be a unicast message directed to the query's originator. The response may include at least the current network identifier and the current geographical position of the target device's mobile node.

In a next step it may be provided that the communication system of a initiator device's mobile node, upon receipt of the response, delivers the data packets sent from the initiator device to the target device to the geographical position of the target device's mobile node indicated in the response by employing the basic geographical routing protocol implemented in the ad hoc network for packet forwarding.

Advantageously, communication systems of mobile nodes include a cache for caching data packets received from initiator devices until the response from the target device's communication system is received. By caching the received packets it is assured, that no data packets get lost during the time period which is needed for communication establishment.

With respect to a high communication quality it may be provided that, once communication between an initiator device and target device is established, geographic positions of the devices are kept updated. To this end the current position information may be included in the protocol headers of exchanged data packets.

As regards the initiator device's knowledge of the target device's local network address, an offline exchange among acquaintances may be provided. For instance, when a passenger device is connected to the communication system of the vehicle, the passenger device may automatically communicate the acquired address to a predefined list of friends immediately by means of another communication means (e.g. SMS) or later, in order to allow for future communication, for example replying on an Internet service.

In VANETs, infrastructure elements which are positioned along the roadside provide for internet access. According to a preferred embodiment the communication between passenger devices via the VANET may by implemented as a complementary solution to an infrastructure-based communication via the Internet. More specifically it may be provided that communication between passenger devices as specified above, which relies solely on the VANET itself, is activated as soon as the connection of the communication system of an initiator device's mobile node to the Internet gets lost. Vice versa, in case the Internet connection is re-established, the type of communication may be changed again.

More specifically, the communication between initiator device and target device may initially taking place through a network infrastructure and, in case the connection of the communication systems of the initiator device's mobile node and/or the target device's mobile node to said network infrastructure gets lost, the communication may be maintained by means of performing mobile network prefix resolution as described above. Similarily, while the communication between initiator device and target device is taking place through a network infrastructure, a resolution of mobile network prefix as described above may be employed to establish a communication between said initiator device's mobile node and said target device's mobile node that does not involve any network infrastructure.

There are several ways how to design and further develop the teaching of the present invention in an advantageous way. To this end, it is to be referred to the patent claims subordinate to patent claims 1 and 15 on the one hand and to the following explanation of preferred embodiments of the invention by way of example, illustrated by the figure on the other hand. In connection with the explanation of the preferred embodiments of the invention by the aid of the figure, generally preferred embodiments and further developments of the teaching will we explained.

In the drawings:

Fig. i is a schematic view of the different domains involved in a typicai

VANET scenario,

Fig. 2 is a schematic view of a protocol stack related to an application of the method according to the invention in a VANET, and

Fig. 3 is a schematic view of a specific application scenario of a method for enabling communication between passenger devices in a VANET according to an embodiment of the present invention.

Fig. 1 illustrates - schematically - a typical VANET scenario supporting both safety and non-safety applications, in which different domains are involved. The particularities of the VANET are the high number of network nodes or mobile nodes (vehicles), high mobility due to the movement of the vehicles as well as cost restrictions to allow for high deployability. The vehicles shown in Fig. 1 each include an on-board unit OBU which provides complete functionality for a communication within the different domains. In particular, the on-board units OBUs include a communication system which allows for sending and receiving data packets and which allows for the attachment of various nomadic passenger devices, like mobile phones, laptops, etc. With respect to the communication of these passenger devices with other passenger devices via ad hoc domains, the communication systems of the vehicles function as gateways (thus also called mobile routers), as will be explained in more detail below.

As can be seen in Fig. 1 , a typical VANET scenario includes an infrastructure domain which provides connectivity for vehicular network nodes to the Internet. The connectivity may be realized, for instance, via dedicated Road Side Units RSUs, public Wireless LAN IEEE 802.11 hot spots PHS or by means of other wireless technologies (like 3G cellular systems, WiMAX₁ etc.).

Further to the infrastructure domain, ad hoc domains are established between the mobile nodes, i.e. the vehicular network nodes, in which single, short-ranged dedicated technology, for instance on the basis of IEEE 802.11 p, may be employed. For ad hoc domain communication purposes a frequency of 5.9 GHz has been reserved for Intelligent Transport Systems (ITS) according to e.g. ISO and ETSI standards. The communication between the vehicles of the ad hoc network is realised as a single hop or multi-hop communication in which nodes relay messages for other nodes. The maximum single hop communication range is typically between 500 and 1000 meters depending on the specific environment (shadowing effects due to buildings, other vehicles, etc.).

Finally, in-vehicle domains are established as result of application units AU being connected to the communication system of a vehicle. In this context, a vehicle, i.e. a mobile node of the mobile ad hoc network, is to be regarded as network itself, which is alternatively called mobile network, internal network or in-vehicle network. Application units AU are also called mobile network nodes in that they are nodes of a mobile network and may include nomadic passenger devices like, for instance, mobile phones, for which the communication system of the vehicle acts as a gateway.

Fig. 2 illustrates conceptual protocol architecture for a specific application scenario of the method according to the invention, which is based on the current C2C-CC protocol stack (Car to Car Communication Consortium). Fig. 2 depicts a total of four vehicles - vehicle A, B, C and D -, which comprise an on-board unit OBU and which are enabled to communicate over wireless multi-hop links with each other. In vehicle A as well as in vehicle D a user device is connected to the on-board unit OBU. The user device of vehicle A functions as initiator device in that it initiates a communication towards the user device of vehicle D, which functions as target device. Although not shown in Fig. 2, vehicle A and vehicle D may comprise more than one user device connected to the on-board unit OBU₁ and also vehicle B and C may have passenger devices connected to their OBUs. The connection of the user devices to the on-board unit of the vehicle may be a wired or a wireless connection and may be realised as an Ethernet, WLAN or Bluetooth connection. The deployment of other technologies is possible and depends on the interfaces provided by the onboard unit on the one hand and by the user device itself on the other hand.

According to the invention a position-based routing protocol is implemented for packet forwarding within the VANET. In the specific embodiment shown in Fig. 2, the position-based routing protocol is labelled as geo-routing and is implemented as sub- IPv6 protocol layer, or more specifically between the layers IEE802.11 p-based MAC and IPv6.

Referring now to Fig. 3, an embodiment of the method according to the invention for enabling communication between communication devices in VANET is shown. The illustrated scenario corresponds to the exemplarily illustrated protocol architecture in Fig. 2 with a total of four mobile nodes, which are vehicle A, B, C and D. In the specific scenario illustrated in Fig. 3 vehicle A includes a communication system which is part of the on-board unit of vehicle A. A mobile phone, a PDA and a laptop of passengers are connected to the communication system of vehicle A. The mobile phone belongs to passenger Alice and functions as initiator device. More specifically, Alice would like to establish a communication with Bob's mobile phone, which is connected to the communication system of vehicle D. In the scenario illustrated in Fig. 3 it is assumed that a geographical routing protocol is in place and that IP version 6 is supported. It is further assumed that the initiator (Alice) knows the expected IPv6 address of the correspondent node (Bob) which is comprised of prefix and interface identifier. This can be achieved for example by means of offline data exchange (e.g. among friends). In a first step, the initiator device starts sending IPv6 packets targeted to the desired target device of Bob. These packets are received by the communication system of vehicle A to which Alice is connected and which acts as a gateway for the car. This system starts caching the packets and simultaneously broadcasts queries including the target IPv6 prefix, the IPv6 prefix of its mobile network (i.e. Alice's device IPv6 prefix) and its current network identifier. In Fig. 3 this process is illustrated as step 2.

The query generated and broadcasted by vehicle A is relayed in a multi-hop fashion by vehicle B and vehicle C to vehicle D. Upon receipt of the query, vehicle D realizes that it is serving the target IPv6 prefix contained in the query and replies to the query including its vehicle identifier and its current geographical position (step 3 in Fig. 3). Again, the response is relayed by vehicle C and vehicle D and finally reaches vehicle A. However, it is to be noted that due to the high degree of mobility it might happen that the response is relayed via different network nodes than the query, without this affprtinπ the> present method.

Upon receiving the response, Alice's communication system in vehicle A delivers the packets to Bob's geographic position using unicast geographical routing. Once the communication is set up, position update information can be included in the headers of the data packets exchanged between Alice's initiator device and Bob's target device. Furthermore, once the communication is established, other devices belonging to the communicating mobile networks (e.g. other Alice's or Bob's devices) can communicate through the VANET without the need for a new communication establishment. This is possible because the IPv6 prefix is common to all devices of a mobile network (e.g. all Allice's devices connected to Alice's OBU have the same IPv6 prefix).

The mechanism described above can be used to complement Network Mobility Basic Support protocol (NEMO BS, IETF RFC 3963). The usage of NEMO BS in VANET is described in detail in R. Baldessari, A. Festag, W. Zhang, and L. Le, "A MANET- centric Solution for the Application of NEMO in VANET Using Geographic Routing", in Proc of TrdentCom, Innsbruck, Austria, March 2008, 7. NEMO provides session continuity and global reachability at a network prefix. The same network prefix aggregated by the NEMO Mobile Router can than be used for communication with other cars in the way described above when Internet is not available. The method according to the invention is complementary but yet totally independent of the NEMO BS protocol. Complementary means that if the method according to the invention is used in a node that also runs NEMO BS, the method according to the invention may be used when NEMO BS is inactive, e.g. when no internet access is available.

Many modifications and other embodiments of the invention set forth herein will come to mind the one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

C l a i m s

1. Method for enabling communication between communication devices - initiator device and target device - in mobile networks forming mobile ad hoc networks, in particular vehicular ad hoc networks (VANETs), wherein said mobile ad hoc network includes a multitude of mobile nodes, wherein at least some of said mobile nodes constitute a network - mobile network - of their own in that they comprise a communication system being designed to allow for the connection of one or more of said communication devices. wherein a routing protocol for packet forwarding within said mobile ad hoc network is implemented that makes forwarding decisions based on the geographical position of a packet's destination, and wherein the target device's local network address is known to the initiator

c h a r a c t e r i z e d i n that for communication establishment the resolution of the mobile network prefix and position of said target device's mobile node is combined into one single query-response-signalling between said initiator device's mobile node and said target device's mobile node.

2. Method according to claim 1 , wherein the communication system of said initiator device's mobile node, upon receipt of data packets sent by said initiator device to said target device, starts broadcasting a query including at least the mobile network prefix of said target device's mobile node.

3. Method according to claim 1 or 2, wherein said query broadcasted by the communication system of said initiator device's mobile node includes its mobile network prefix and/or its current identifier.

4. Method according to any of claims 1 to 3, wherein said query includes a counter that is set to a specific value indicating the number of intended re-broadcasts of said query.

5. Method according to claim 4, wherein each network node that receives said query rebroadcasts said query in case the value of said counter is unequal to zero and does not rebroadcast said query in case the value of said counter is equal to zero.

6. Method according to claim 4 or 5, wherein each mobile node reduces said counter by the value of "1" before rebroadcasting said query.

7. Method according to any of claims 1 to 6, wherein the communication system of said target device's mobile node, upon receipt of said query, responds to said query by sending a response that includes at least the current identifier and the current geographical position of the target device's mobile node.

8. Method according to claim 7, wherein the communication system of said initiator device's mobile node, upon receipt of said response, delivers the data packets sent from said initiator device to said target device to the geographical position of said target device's mobile node indicated in said response by employing said geographical routing protocol.

9. Method according to any of claims 1 to 8, wherein the communication system of said initiator device's mobile node, upon receipt of packets sent by said initiator device to said target device, starts caching the received packets.

10. Method according to any of claims 1 to 9, wherein, once a communication between said initiator device and said target device is established, geographic positions of said devices are updated by means of position information included in the headers of exchanged data packets.

11. Method according to any of claims 1 to 10, wherein the initiator device gains knowledge of the target device's local network address by means of an offline exchange among acquaintances.

12. Method according to any of claims 1 to 11 , wherein said communication between initiator device and target device is deployed complementary to an infrastructure-based method to provide session continuity and global reachability at a network prefix for mobile networks.

13. Method according to any of claims 1 to 12, wherein said communication between initiator device and target device is initially taking place through a network infrastructure and wherein, in case the connection of the communication systems of the initiator device's mobile node and/or the target device's mobile node to said network infrastructure gets lost, said communication is maintained by means of said resolution of mobile network prefix.

14. Method according to any of claims 1 to 13, wherein said communication between initiator device and target device is taking place through a network infrastructure and wherein said resolution of mobile network prefix is employed to establish a communication between said initiator device's mobile node and said target device's mobile node that does not involve any network infrastructure.

15. Mobile ad hoc network, in particular vehicular ad hoc network (VANET), with communication functionality between communication devices - initiator device and target device -, including a multitude of mobile nodes, wherein at least some of said mobile nodes constitute a network - mobile network - of their own in that they comprise a communication system being designed to allow for the connection of one or more of said communication devices, wherein a routing protocol for packet forwarding within said mobile ad hoc network is implemented that makes forwarding decisions based on the geographical position of a packet's destination, and wherein the target device's local network address is known to the initiator device, c h a r a c t e r i z e d i n that the communication systems are configured to combine the resolution of the mobile network prefix and position of said target device's mobile node into one single query-response-signalling between said initiator device's mobile node and said target device's mobile node.

16. Network according to claim 15, wherein a mobile node's communication system is configured to function as gateway for data packets sent by the communication devices connected to said communication system.

17. Network according to claim 15 or 16, wherein the communication system of said initiator device's mobile node is configured, upon receipt of data packets sent by said initiator device to said target device, to start broadcasting a query including at least the mobile network prefix of said target device's mobile node.

18. Network according to any of claims 15 to 17, wherein the communication system of said target device's mobile node is configured, upon receipt of said query, to respond to said query by sending a response that includes at least the mobile node's current identifier and the mobile node's current geographical position.

19. Network according to any of claims 15 to 18, wherein the comrnunicaiioπ system of said initiator device's mobile node includes a cache for caching data packets received from said initiator device until said response from said target device's communication system is received.

20. Network according to any of claims 15 to 19, wherein said communication systems are part of said vehicular network nodes' on-board units (OBU).

21. Network according to any of claims 15 to 20, wherein said communication systems include a mobile router.

22. Network according to any of claims 15 to 21 , wherein said communication systems are configured to provide infrastructure based Internet connectivity.

23. Network according to any of claims 15 to 22, wherein said communication devices include passenger devices like a mobile phone, a laptop, a PDA (Personal Digital Assistant) and/or a smart phone.