WO2006036093A1

WO2006036093A1 - A method and a device for providing access in a short range communication network

Info

Publication number: WO2006036093A1
Application number: PCT/SE2004/001393
Authority: WO
Inventors: Annika Jonsson; Johan Rune; Mattias Pettersson; Tony Larsson; András MÉHES
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2004-09-30
Filing date: 2004-09-30
Publication date: 2006-04-06
Also published as: GB2432085A; GB0703390D0; GB2432085B

Abstract

The present invention relates to a method and a PAN managing device for providing access to external networks for communication devices in a Personal Area Network (PAN). The method comprises the steps of: discovering external access means (315, 325) of PAN access nodes (112, 114) available in the PAN; selecting a first external access means (315) of a first PAN access node (114) to be used by a PAN device (111) for providing external access; and, instructing the PAN access nodes (112, 114) that the first external access means (315) of the first PAN access node (114) has been selected as the access to be used by the PAN device. The PAN access nodes will then act based on the instructions such that data packets from the PAN device (111) will be routed via the first PAN access node. The steps of discovering, selecting and instructing the PAN access nodes is performed by a PAN managing device (113) which is a PAN device used by the user to control his PAN. By using the invention, all types PAN devices, including legacy devices, can be provided with external access in a controlled manner.

Description

A METHOD AND A DEVICE FOR PROVIDING ACCESS IN A SHORT RANGE

COMMUNICATION NETWORK

FIELD OF THE INVENTION

The present invention relates to methods and devices in a short-range communication network, and more particularly it relates to methods and devices for providing access to an external communication network for a communication device in a personal area network (PAN).

BACKGROUND OF THE INVENTION

Today it is common that a user of a mobile communication network has many different communication devices. For example, a user may have a mobile phone, a laptop and a Personal Digital Assistant (PDA). In addition to that, he may also have, for example, a digital camera and a wireless headset. For the user using one of his communication devices, there may be interesting to gain access to resources belonging to another of his communication devices or to other communication devices in the vicinity of the user. Therefore, some of the communication devices have short- range communication means suitable for this purpose. As an example, a laptop that does not have any external access possibilities by itself to e.g. a mobile communication network can be connected via a short-range communication means to a mobile phone having cellular access possibilities. Thereby, the laptop can take advantage of the cellular access possibilities of the mobile phone to get access to for example an Intranet or to the Internet. A short-range communication means may be for example a short-range radio link, e.g. Bluetooth, or an infrared link or a wire-line connection.

Recent development has suggested to wirelessly connect communication devices being in the vicinity of a user into one short-range communication network, called a personal area network (PAN). The PAN is then constituted of the communication devices that are within short-range communication distance of each other, called PAN devices. The PAN devices may or may not belong to the user. As an example, a PAN may also comprise a printer situated in a room that the user is currently passing. The reach of such a personal area network is typically a couple of meters. A purpose of the

PAN is for a PAN device to gain access to resources belonging to another PAN device, resulting in an enhanced experience for the user compared to the experience given by each device by itself. A user may for instance choose to bring only the necessary devices to perform the desired functionality during a particular time period.

Examples of applications where resources belonging to one PAN device could be shared with other PAN devices to enhance the experience of the user are: Accessing files belonging to one PAN device at any other PAN device, and sharing the external access capabilities (e.g. cellular access) of one PAN device between all PAN devices.

A typical PAN, a method and a protocol for managing devices in a PAN is described in the co-pending PCT-application PCT/ SE2004/001027.

As mentioned above, some PAN devices have at least one interface through which they can get access to an external network, for example the Internet, or a cellular network. Such a PAN device is in this application called a PAN access node, but it may also be called e.g. a Global Access Point (GAP). Examples of a PAN access node and the external network it can get access to are: A mobile phone having access to a cellular network, such as a UMTS network, and a laptop having access to a wireless local area network (WLAN). In a PAN there are also PAN devices with no own external access possibility. Consequently, if these PAN devices should be able to get external access, the access has to be provided to them via the PAN access nodes. In particular, to make the PAN transparent to the user for an optimal performance of the PAN, there is a need to make it possible for a PAN device to get access to the best possible external network for the service the PAN device is currently in need of.

The Dynamic Host Configuration Protocol (DHCP) is a prior art protocol providing a framework for passing configuration information to hosts on a TCP/IP network. DHCP is based on the Bootstrap Protocol and adds the capability of automatic allocation of reusable network addresses and additional configuration options. DHCP is the common protocol used for configuration of IP address, default route, domain name server (DNS) and domain name of a host. DHCP is a standard protocol implemented in most electrical devices that have communication possibilities. DHCP is described in: "The DHCP Handbook", by Droms R. and Lemon T., published October 1999 by Pearson Higher Education, ISBN 1-57870-137-6, or in the Internet standards track protocol for the Internet community, RFC 2131 called "Dynamic Host Configuration Protocol" by Droms, R., published March 1997. If the DHCP according to prior art would be used in a PAN, it would imply problems because DHCP is not made for a system where there are many different access possibilities. Consequently, a PAN device that has implemented DHCP will not be able to choose between the offered accesses. Instead it will choose one access arbitrarily. In all, the model for shared medium networks such as Ethernet-based ones where DHCP typically is used is to reflect a static network with stable address space where there is only one external connection (i.e. to the Internet). Consequently, there is a need for a method for providing a PAN device with the most suitable external access from a number of available accesses in the PAN and to coordinate available accesses in the PAN.

SUMMARY OF THE INVENTION

A Personal Area Network (PAN) is a short-range communication network constituted by a number of PAN devices that are connected via short-range communication means. In such a network, some of the PAN devices may also have external access means for providing access to an external network. The PAN devices having external access means are in this application called PAN access nodes. Also, there are other PAN devices with no own external access means. For such a PAN device to get external access, the access has to be provided to it via the external access means of the PAN access nodes. In addition, some of the PAN devices may be legacy devices, i.e. PAN devices that are not PAN enabled and therefore do not have a particular PAN protocol, instead such devices have a standard/legacy protocol, such as DHCP. Also such PAN devices may need to get external access via the PAN access nodes. For a PAN device it may be necessary to get in contact with a certain external network for the PAN device to e.g. receive a certain service. Therefore, there is a need to create a solution for providing a PAN device with an external access suitable for the needs of the PAN device.

An object of the present invention is thus to create a solution that can provide a PAN device with a suitable external access via an external access means of a PAN access node, which solution is usable for all types of PAN devices, including legacy devices. The above stated object is achieved by means of a method, a PAN controller device and a computer readable program according to the independent claims. Preferred embodiments are set forth in the dependent claims.

The object is achieved by discovering accesses available in the PAN, selecting an access to be used by the PAN device and instructing the PAN access nodes which PAN access node and which external access means of the PAN access node that has been selected as the access to be used by the device. The PAN access nodes will then act based on the instructions such that the traffic from the PAN device will be routed via the selected PAN access node. The steps of discovering, selecting and instructing are preferably made by a PAN managing device.

According to a first aspect of the invention, a method is provided for providing access to external communication networks for a communication device in a personal area network (PAN) where the PAN is constituted by communication devices presently being within short-range communication distance from each other and wherein the communication devices communicates via short-range communication means, and wherein at least one of the communication devices, called a PAN access node, has at least one external access means for accessing at least one external communication network. The method comprises the steps of: discovering in the PAN the at least one external access means of the at least one PAN access node; selecting a first external access means of a first PAN access node as the external access means to be used by the device for providing external access to the device; instructing the at least one PAN access node that data from the device intended for an external network shall be routed via the first external access means of the first PAN access node; and, enforcing data from the device intended for an external communication network such that the data is routed via the first external access means of the first PAN access node.

According to a second aspect of the invention, a PAN controller device is provided in a Personal Area Network (PAN), wherein the PAN controller device is arranged for managing devices in a PAN such that a communication device is provided with access to an external communication network, and where the PAN is constituted by the communication devices presently being within short-range communication distance from each other, and wherein the communication devices are arranged to communicate via short-range communication means. At least one of the communication devices, called a PAN access node, has at least one external access means for accessing at least one external communication network. The PAN controller device comprises a short-range communication means for sending instructions to and receiving information from the at least one PAN access node such that the PAN controller device can discover the at least one external access means of the at least one PAN access node. The PAN controller device further comprises a control unit for processing the received information and for selecting a first external access means of a first PAN access node as the external access means to be used by the device for providing external access to the device, and for compiling instructions to be sent to the at least one PAN access node via the short-range radio communication means instructing the at least one PAN access node that data from the device intended for an external communication network shall be routed via the first external access means of the first PAN access node.

According to a first advantageous embodiment of the invention, the device is enforced in a connection establishment procedure to use the selected external access means of the selected PAN access node as the means for transporting data from the device to an external network.

According to another advantageous embodiment of the invention data is sent from the device to any of the PAN access nodes and from that node, the data is tunnelled or forwarded to the selected PAN access node and further via the selected external access means to the external access network.

An advantage of the present invention is that it makes it possible for all types of PAN devices, including legacy devices, to function in the multi-access environment that the PAN represents.

A further advantage of the invention is that it manages to provide external access to all types of PAN devices, both legacy devices and PAN enabled devices. By letting the PAN managing device and the PAN access nodes do all the steps of the invention, legacy devices can function in the invention and still use their legacy protocols, and not having to know anything about the process behind its access provision.

A still further advantage of the invention is that it makes it possible for the user of the PAN to enforce via its PAN managing device each PAN device to use a specific access. Another advantage is that the present invention makes it possible to control the use of existing external access means by the PAN managing device such that the external resources of the PAN are used in an optimal way.

A still further advantage lies in the possibility to instruct the entire PAN to e.g. use only one access.

An advantage of an embodiment of the invention is that it makes it possible to force a device to use a specific access means of a PAN access node also when the device is already using another access means of another PAN access node.

A still further advantage of the present invention is that each device can use an access independently of what access other devices in the PAN use.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic figure of an exemplary Personal Area Network (PAN) in which the present invention can be used.

Figure 2 shows a message sequence scenario in a PAN when using a prior art protocol.

Figure 3 shows a schematic block diagram of an exemplary PAN with its functional blocks necessary for carrying out the invention.

Figure 4 shows a message sequence scenario in a PAN according to a first embodiment of the invention.

Figure 5 shows a message sequences scenario in a PAN according to a second embodiment of the invention.

DETAILED DESCRIPTION The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements.

Figure 1 shows an example of a small personal area network (PAN) 100, in which the present invention can be used such that PAN devices can get access to external networks via other PAN devices that have external access possibilities (so called PAN access nodes). The figure shows the exemplary PAN 100 with its PAN devices and existing external access possibilities. The PAN 100 covers an area around the user 110, and comprises the following PAN devices: a laptop 112, a digital camera 111, a Personal Digital Assistant (PDA) 113 and a mobile phone 114. All PAN devices have short-range communication means such that they can communicate with other PAN devices. Two of the PAN devices in the PAN 100 also have external access means, and are therefore called PAN access nodes: These are the laptop 112, which can provide external access to a Wireless Local Area Network (WLAN) via a WLAN access point 120; and the mobile phone 114, which can provide external access to a cellular network 121, for example a GPRS network, a CDMA 2000 network, a UMTS network or any other cellular network. Other examples of networks that PAN access nodes may have external access to are e.g. fixed Ethernet, ADSL. According to the invention, the external accesses of the PAN access nodes 112, 114 can be used by other PAN devices to provide them with external access. In the example shown in figure 1, the PDA 113 and the camera 111 do not have any external access possibilities of their own, and, consequently, if they need external access they have to get it via any of the PAN access nodes, i.e. the laptop 112 or the mobile phone 114. In addition, the camera is not PAN enabled and, consequently, does not have a particular PAN protocol, i.e.. the camera is a legacy device communicating via a legacy protocol, such as DHCP. The network functionaliiy in a legacy device may only include e.g. Bluetooth PAN profile, Ethernet, TCP/IP and/ or DHCP (Dynamic Host Configuration Protocol). Other examples of potential legacy PAN devices are digital audio players, headsets and pens.

Figure 2 shows a message sequence scenario when the camera 111 in figure 1, which is a legacy device having DHCP functionality, will try to get external access from any of the PAN access nodes, in figure 1 the laptop 112 and the mobile phone 114, using the DHCP according to prior art. When the camera 111 needs an access it will broadcast a DHCP discover message 201 to all DHCP servers it can get access to. If the PAN access nodes 112, 114 are DHCP servers themselves they will receive and process the DHCP discover messages themselves. If the PAN access nodes are not DHCP servers they will relay the DHCP discover messages to DHCP servers in the external access networks. The DHCP servers will respond by sending a DHCP offer message 202 to the camera 111, comprising an IP address to the DHCP client. The camera has no way of telling from the DHCP offer messages 202 what the difference between the different PAN access nodes is, apart from the IP addresses and domain names. Therefore, the camera will select one DHCP server (PAN access node) arbitrarily. In the example, the camera 111 arbitrarily chooses the laptop 112 as its PAN access node. The camera then sends a DHCP request 203 to the laptop and the laptop answers with a DHCP acknowledgement 204. Thereafter, data packets will be sent on the link from the camera to the laptop and out in the WLAN network.

As shown above, for the prior art method, the PAN device will choose arbitrarily which PAN access node and, consequently, which access network it will get access to and, consequently, it may not receive the type of access it is interested in, and the PAN will not be able to control the use of its different external accesses. Also, if the PAN access node is a DHCP server, then the addresses handed out to a PAN device are the same independently of what access network it wants to connect to. Consequently, when the PAN device starts sending packets to the PAN access node, there is no way for the PAN access node to know towards what access network a specific packet should be routed.

Another possible solution for controlling the access used by a PAN device would be to develop a PAN specific protocol that is to be used by all PAN devices when selecting access, see co-pending application PCT/ SE2004/001027. Although, if such a PAN specific protocol would be used in the PAN, it would be necessary for all PAN devices to be PAN enabled, This implies that if any of the PAN devices is a legacy device, that legacy device will still select access arbitrarily according to its legacy protocol (e.g. DHCP). Consequently, the control of the PAN will not be fully satisfactory as long as there are legacy devices on the market.

Therefore, the present invention aims at creating a method for controlling the external access used by a PAN device in a PAN. This will be achieved by a PAN managing device discovering and selecting access to be used by the PAN device, based on manual input from the user or based on default preferences for the type of the PAN device. The PAN managing device then informs each PAN access node whether the PAN device should have access from the PAN access node in question, and, if the PAN access node has multi-access possibilities, which access network the PAN device will use. When establishing a connection from the PAN device or when sending the packets from the PAN device, the PAN access nodes will act based on the instructions from the PAN managing device such that the packets will be routed via the selected PAN access node.

As mentioned above when describing the method of the invention, a PAN managing device is used for controlling which access a PAN device will be provided with. A PAN managing device is further described in the co-pending PCT-application PCT/ SE2004/001027, dealing with controlling the communication in a PAN. A PAN managing device is a PAN device that is used for managing the PAN and all PAN devices, either automatically via pre-entered commands or by the user via commands currently entered by the user. In the application PCT/ SE2004/001027 a PAN device that can be a candidate for being a PAN managing device is called a PAN controller device. A PAN can have many PAN controller devices but only one of the PAN controller devices at a time can be a PAN managing device. A PAN controller device should have a good user interface with good input/output capabilities. Also, for controlling the PAN according to the invention, it would be necessary if at least one PAN controller device is present in the PAN all the time. Therefore, the mobile phone is a very suitable PAN controller device. Other advantageous characteristics of a PAN controller device are reasonably good memory resources and processing power. Obvious PAN managing device candidates are e.g. laptops, PDAs and mobile phones. In figure 1, the mobile phone 114, the laptop 112 and the PDA 113 are PAN controller devices and can consequently be the PAN managing device.

Figure 3 shows a schematic block diagram of the exemplary PAN 100. In the exemplary PAN, each PAN device is described with its functional blocks necessary for carrying out the invention. The PAN devices, i.e. the camera 111, the laptop 112, the PDA 113 and the mobile phone 114 each comprises a short-range radio communication means 301, 311, 321, 331 for the purpose of communicating with each other within the PAN. The PAN controller devices, i.e. the laptop 112, the PDA 113 and the mobile phone 114, also each comprises a PAN user interface 302, 312, 322 that the user can use to control its PAN. As mentioned before, the role of being the PAN managing device may change between the PAN controller devices, depending on which PAN controller device the user uses for the moment for controlling his PAN. The PAN devices that also are PAN access nodes (the mobile phone 114 and the laptop 112) each have external access means 315, 325 for offering the PAN access to external access networks. Further, the PAN controller devices 112, 113, 114 comprise control units 303, 313, 323 that are used in the invention for controlling the use of external access for the PAN devices. Also, the camera 111, which is not a PAN controller device, has a processing unit 332 for processing messages received and to be sent. At last, each PAN device has a memory 304, 314, 324, 333 for storing information that could be useful for each of the PAN devices for carrying out the method of the invention.

Below is described how the method of the invention is carried out in the exemplary PAN of figure 3. In the example it is assumed that the camera needs access and, for sake of clarity, that the PDA is used as the PAN managing device. Although, any of the other PAN controller devices, i.e. the laptop or the mobile phone may be used as the PAN managing device. As understood, the laptop and the mobile phone may, as well as being PAN access nodes, also be the PAN managing device.

According to the method of the invention, if the camera 111 in figure 3 needs access, the PAN management device, i.e. the PDA 113 in figure 3, would discover the available accesses in the PAN for the camera by requesting information from the PAN access nodes regarding their accesses. Alternatively, the information regarding the available accesses in the PAN may already be present in the PAN management device, via e.g. an earlier access discovery process. Thereafter, an access selection for the camera will be performed by the PAN management device based on the information from the PAN access nodes, which, preferably, is presented for the user such that the user makes a selection via the PAN user interface of the PAN management device. Alternatively, the selection may be made e.g. based on a preconfigured preference for the camera. The next step is for the PAN management device 113 to send instructions to the PAN access nodes, i.e. the laptop 112 and the mobile phone 114, based on the access selection, instructing the laptop 112 and the mobile phone 114 how to behave if the camera 111 wants external access. The access discovery and the communication of the access instructions may be performed by the PAN management device by a PAN specific protocol, for example the PAN Management Protocol described in the co- pending application PCT/SE2004/001027 or by any other service discovery protocol. In the example it is assumed that the PAN management device has selected the mobile phone's external access 315 to be used by the camera 111. Based on the instructions received at the PAN access nodes, when the camera 111 contacts the PAN requesting access to an external network, it will be forced to use the external access of the mobile phone. The step of access enforcement will be described for different scenarios below, either as enforced in a connection establishment process or as enforced on delivered packets. When the camera is enforced in a connection establishment process, it will be enforced when the PAN device (in this case the camera) uses its (legacy) protocol to send a connection establishment request message requesting to establish a connection to an external network before the data packets are sent. Due to the instructions received from the PAN management device 113, only the selected PAN access node, i.e. the mobile phone 114 will answer such a message from the camera. When enforcing on delivered packets, the packets that the camera send to any of the PAN access nodes will be directed to the selected PAN access node, i.e. the mobile phone 114. In this example, if packets are sent to the laptop they will be forwarded or tunnelled to the mobile phone 114.

By such instructions, the PAN access nodes can support multiple PAN devices, including legacy devices, using different accesses via different PAN access nodes such that each PAN device can use an access independently of the other PAN devices. If a PAN access node has multiple external access means, i.e. can provide access to different networks, that PAN access node needs to route the packets based on the source IP-address of the PAN device to be able to handle the case when different PAN devices use different external accesses from the same PAN access node.

The access discovery step, the access selection step and the step of sending of instructions to the PAN access nodes could either take place before an actual access is needed by the camera as shown above, or be triggered by a connection establishment request message sent by the camera. The access discovery step, the access selection step and the step of sending instructions can also be triggered by the camera sending packets to any of the other PAN devices. Although, in this case it is necessary that the IP addresses etc. that has to be used for the communication are already correctly configured.

According to a first embodiment of the invention, the method according to the invention will be implemented in a PAN in a connection establishment procedure using DHCP, i.e. when configuring a PAN device using DHCP for enabling communication with an external network. Most legacy devices on the market have implemented DHCP, why a DHCP-adapted embodiment of the invention would be advantageous. In the first embodiment of the invention, there are three alternatives how to implement DHCP in the PAN, depending on the external networks that the PAN access nodes are offering access to.

The first alternative deals with when a PAN is connected to an external network via a PAN access node and if there is no PAN support in the external network or if IP- addresses are a scarce resource in the external network. In this case the PAN will only be assigned one IP address by the external network. This is the case for most cellular networks because the operators most likely want to preserve their address space, resulting in that each end-user only gets one address. Another example of such a network is a WLAN Internet Service Provider that put restrictions on address acquisition from the clients (e.g. a laptop working as a PAN access node). For the solution according to the invention to function in such a network it will be necessary to place a Network Address Translator (NAT) and a DHCP server in each PAN access node to be able to multiplex traffic from the PAN onto the single address of the PAN access node. A NAT is used to translate between private addresses within the PAN and the only external address provided by the external network. The DHCP server assigns the private addresses to the PAN devices requesting access. It is most preferred that all PAN access nodes function the same, providing addresses from the same address pool. The DHCP servers could then work as backup for each other. The other information in the DHCP configuration, i.e. the information sent from the DHCP server to the DHCP client, i.e. the PAN device, such as default router and name server will change if the PAN device changes access. Default router will only change if the PAN device changes PAN access node, but not when changing access within the PAN access node (i.e. if the PAN access node can provide more than one different external access). Name server will change if the PAN device changes either PAN access node or access. Domain name will change if the PAN device changes either PAN access node or access. Although, if the PAN access node specifies itself as name server in the DHCP messages to the PAN device, the PAN access node can do recursive name lookups on behalf of the PAN device, resulting in that the PAN device does not have to change its name server when changing access within a PAN access node. By taking the measures above, the method according to the invention will function even if the external network only provides one IP address to the PAN. Another advantage is that the PAN access nodes will all function the same. Also, the PAN devices do not have to change their addresses when any of them changes its access.

The second alternative deals with when there is PAN support in the external network. In this case it is possible to assign multiple IP addresses to one PAN. This will be the case e.g. if the operator of a cellular network actively supports PANs. It may be likely if a corporation requires that their corporate VPN (Virtual Private Network) or similar have to support PANs. In case of external networks other than cellular networks, it may well be the case that they can give away more than one IP address to one user. In this second alternative the PAN access node will only be working as a relay, bridging all traffic between the PAN and the external network. In this case the NAT and the DHCP server will reside in the external network and the PAN access node will only relay the messages between the PAN device and the external access network.

The third alternative is like a mix of the first and the second alternative. It deals with the case when the external network can hand out IPv6 addresses. It implies shortly that the PAN access node receives from the external network an IPv6 prefix, which the PAN access node then distributes in the PAN using DHCP or stateless auto configuration. If stateless configuration is used, the PAN device will build an own address based on the prefix that it receives from the PAN access node and on the PAN device's own interface-ID. For DHCP, the PAN access node will give the PAN device an address from the prefix the PAN access node has received. Either the PAN access node has received the prefix to use in its own manner, or it only bridges the prefix that is used in the external network. In practise, it means that the PAN access node will not use a Network Address Translator but that it might very well use a DHCP server.

Figure 4 describes a message sequence scenario according to the first embodiment of the invention. In figure 4, the PAN managing device 512 will instruct all PAN access nodes 513, 514 how to behave if a PAN device 511 wants external access. The PAN managing device 512 discovers available accesses and selects access to be used by the PAN device 511, based on manual input from the user or on preconfigured preferences regarding the type of PAN device. The PAN managing device 512 then informs in an instruction message 501, which could be either unicast, multicast or broadcast, to each PAN access node 513, 514 if the PAN device 511 should have access from the PAN access node in question, and, if the PAN access node has multi¬ access possibilities, which access network it shall use. In this example, the first PAN access node 513 is instructed to give access to the PAN device. The instruction message may actually consist of many messages, one for each PAN access node. As before, these instructions may be sent and access discovery may be done by the PAN managing device using the PAN management Protocol defined in the co-pending patent application PCT/SE2004/001027. When the PAN device broadcasts DHCP discover messages 502, the PAN access nodes will act based on these instructions such that only the PAN access node that has been selected for external access for the PAN device, i.e. the first PAN access node 513 in figure 4, will send a DHCP offer message 503 to the PAN device. The PAN access nodes that have not been selected, i.e. the second PAN access node 514 in figure 4, will filter out the DHCP discover message before the message reaches the DHCP server, and, consequently, the DHCP server will not try to respond to the message. This first embodiment of the invention will work both if the first PAN access node 513 is a DHCP relay and if it works as a DHCP server, according to the two alternatives described above. If the PAN access node is a DHCP relay the DHCP server will reside in the external network and consequently be out of control from the PAN, then the PAN access node will filter the DHCP messages by firewall rules. In cases where the DHCP server is within the PAN, access control lists within the DHCP server can be dynamically modified to achieve the same behaviour. Following the reception of the DHCP offer message 503 received from the first PAN access node 513, the PAN device will send a DHCP request message 504 to the first PAN access node, followed by a DHCP acknowledgement message 505 from the first PAN access node to the PAN device 511. Thereafter, the PAN device can start sending data packets via the first PAN access node. As an alternative, the PAN managing device 512 could make the access selection and send instructions to the PAN access nodes 513, 514 after the PAN device 511 has sent the DHCP discover message 502. In this case, it would be necessary that the PAN is locked for messages from the particular PAN device until instructions have been received from the PAN managing device. Then, the selected PAN access node can start responding to the DHCP discover message. Although, since it is not preferable to have the PAN device wait a long time before any PAN access node replies to its message, it is to prefer that the PAN access nodes have already received instructions when the PAN device sends a DHCP discover message.

A further scenario in a PAN may be that the PAN device (or the user of the PAN device) wants to change external access when the PAN device already has been assigned one access. There may be a problem how to communicate such a request from the PAN managing device to the PAN device, especially if the PAN device is not able to speak any PAN specific protocol. For example, in the first embodiment dealing with the scenario where the PAN device speaks DHCP, there are two alternative suggestions according to the invention how to handle such a request. According to a first suggestion, the PAN device is simply restarted by the user. This is done because if the PAN device is restarted it will send a DHCP discover message by default, and the process described above can be followed again, i.e. only the correct DHCP server (PAN access node) replies to the DHCP discover message based on the instructions received from the PAN managing device.

According to a second suggestion for changing external access, a new option can be used, defined in Network Working Group RPC3203 "DHCP reconfigure extension" by T'Joens et al published December 2001 by The Internet Society. In this publication, a new option is defined for a DHCP server to force a DHCP client to renew its information, in a message called DHCPFORCERENEW. Such a push mechanism was not available prior to this publication. This new mechanism can be used in the present invention by a PAN access node when it has received new instructions from the PAN managing device regarding which access and which PAN access node the PAN device should use. If the PAN device already uses a PAN access node as its DHCP server/ DHCP relay, either the new PAN access node or the old PAN access node can send a DHCPFORCERENEW to the PAN device. The PAN device will then go into a renewing state and unicast a DHCP request to the old PAN access node (i.e. DHCP server or DHCP relay). In order to change PAN access node, the old PAN access node must respond with a DHCPNAK (DHCP not acknowledged). The PAN device will then enter the INIT state (Initiation state) and start the DHCP procedure from scratch by broadcasting a DHCP discover message. Now the new DHCP server takes over and responds with a DHCP offer etc., and the PAN access node serving the PAN device is changed, or the external access means is changed, if the same PAN access node is to be used, but a different external access means of that PAN access node.

According to a second embodiment of the invention, which is an alternative to the first embodiment of the invention, the invention will be implemented in a PAN in a connection establishment procedure using the Address Resolution Protocol (ARP) . The ARP is described in "An Ethernet Address Resolution Protocol or Converting Network Protocol Addresses to 48. bit Ethernet Address for Transmission on

Ethernet Hardware" by Plummer, published November 1982 on the Internet as a Request For Comments 826 (RFC826). The ARP is an Ethernet-protocol, i.e. a layer 2 protocol, that is used to resolve an IP address to a layer 2 address. As an example, if a device wants to send packets to the IP address 1.2.3.4 and it wants to use Ethernet for communication, addressing on layer 2 level is necessary. Since the device does not know the layer 2 address corresponding to the IP address 1.2.3.4, it sends an ARP request. The ARP request is of the type "Who has address 1.2.3.4?" and it is broadcast. The unit that has this address responds with "I have 1.2.3.4", and sends its layer 2 address, implicitly. Then the resolved layer 2 address is the source layer 2 address of the response packet.

The Internet draft "Dynamic Configuration of link-local IPv4 Addresses" version 17, by Cheshire et al, a working document published July 8, 2004 by the IETF, called "zero-conf ', describes how a host may automatically configure an interface with a link-local IPv4 address that is valid for communication with other devices connected to the same physical or logical link. According to "zero-conf all destinations are supposed to be on-link. Also, each unit defines its own link-local address. Each address is tested before it is configured such that the address is not already occupied. This will be tested by each unit sending an ARP request for its own newly defined link-local address. If no other unit answers, the address is vacant, within the scope of the link.

The ARP protocol and the zero-conf is used in the invention for pretending for the PAN device that all destinations are on-link in the PAN. For the ARP solution to work in the invention, the PAN devices cannot have a default route configured (e.g. configured by a DHCP server). Thus, each PAN access node would need an ARP proxy and a NAT.

Figure 5 shows a message sequence scenario for an example of how the method of the invention would work if the ARP protocol would be used for establishing a connection for a PAN device. In figure 5, a PAN device 611 needs external access in a PAN, which except for the PAN device also comprises a PAN managing device 612, a first PAN access node 613 and a second PAN access node 614. For sake of clarity, the roles are divided between all four entities. Although, it should be understood that any of the PAN access nodes may also be the PAN managing device, or that the PAN device is also a PAN access node. In the method, the PAN managing device 612 will instruct all PAN access nodes 613, 614 how to behave if the PAN device 611 wants external access. The PAN managing device 612 first performs access discovery and then selects access to be used by the PAN device 611, based on manual input from the user or on preconfigured preferences regarding the type of PAN device. The PAN managing device 612 then informs in an instruction message 601 each PAN access node 613, 614 if the PAN device 611 should have access from the PAN access node in question, and, if the PAN access node has multi-access possibilities, which access network it shall use. In this example the PAN managing device has decided that the PAN device will use the access of the first PAN access node 613. The instruction message may actually consist of many messages, one for each PAN access node. As before, the instruction messages and the access discovery of the PAN management device may be executed by using the PAN Management Protocol defined in the co-pending patent application PCT/ SE2004/001027.

A PAN device would in most cases by default broadcast a DHCP discover message 602 to get in contact with an external network. In this second embodiment there are no DHCP servers available, and consequently, there will be no reply to the DHCP discover message. The PAN device would then use the ARP protocol and the zero-conf prior art when no reply on the DHCP discover message is received, and instead configure an own link-local address (local IP-address), and try to contact the destination with a broadcast ARP request 605. If the PAN device for example wants to get in contact with the IP address 1.2.3.4, it will broadcast an ARP request 605 requesting to contact the node with the IP address 1.2.3.4. Although, according to ARP prior art, there will be no reply since this IP address is not present in the PAN, but on an external network that is not available to the PAN device. But, according to the invention, the first PAN access node 613 will, according to the instructions 602 from the PAN managing device 612, pretend to be the IP address 1.2.3.4 and act as an ARP proxy such that it replies to the ARP request 605 with an ARP response 606, comprising its link-layer address. All subsequent traffic from the PAN device will be intercepted by the first PAN access node. Before the PAN access node sends the traffic from the PAN device further to the IP address 1.2.3.4 in the external network, the PAN device's link-local address will be replaced in the NAT by the PAN access node's external IP address, and vice versa for traffic in the opposite direction. If the PAN device does not know the IP-address of the destination but only the name address, for example www.ericsson.se in the Internet domain, the PAN device may use Multicast DNS to resolve which IP-address lies behind a certain name address, before it sends an ARP request 605. Multicast DNS is described in the Internet Draft "Linklocal Multicast Name Resolution (LLMNR)", version 36, by Esimov et al, a working document published September 8, 2004 by IETF. The PAN device will then broadcast an LLMNR query 603. The first PAN access node 613 will intercept the request based on source address, and based on the instructions received from the PAN managing device. Then the first PAN access node will act as proxy such that it creates a new request to be sent as an ordinary DNS request to a real name server in the external network. The first PAN access node 613 will receive a response from the external network including the IP address of the requested name address. The first PAN access node 613 then sends an LLMNR response 604 to the PAN device 611, including the IP address for the requested name, in the example above, the IP address 1.2.3.4. For translating between the PAN device's link-local address and the external IP address of the PAN access node, the PAN access node uses a NAT. This way the PAN access node will act as a multicast DNS proxy.

As an alternative, the PAN managing device 612 could make the access selection and send instructions 601 to the PAN access nodes 613, 614 after the PAN device 611 has sent the DHCP discover message, or the LLMNR query or the ARP request. ARP responses from the PAN access node should be unicast towards the correct PAN device, so that two PAN devices can use different PAN access nodes even though the destination IP address is the same.

According to a third embodiment of the invention, the configuration of the PAN devices will not be changed. Instead, the PAN access nodes will have to cover for the behaviour of the PAN devices, based on the instructions they have received from the PAN managing device. This means that if a PAN device sends data packets to a second PAN access node, but, according to the instructions from the PAN managing device, the packets should be sent to a first PAN access node, the second PAN access node will tunnel or forward the packets to the first PAN access node. This assumes that all PAN devices uses the same address space, and that the PAN devices get their IP addresses, default router, i.e. IP address to the default PAN access node and DNS parameters by DHCP or any other similar protocol. This way the configuration is access independent and the camera can change access without changing configuration. Instead, as said above, the PAN access nodes will tunnel or forward the packets to the right PAN access node. For this to work, each PAN access node would need to implement a DHCP server and a NAT. If each PAN access node does not implement a NAT outgoing packets may leave the PAN with an incorrect source address and be dropped at first ingress filtering router. Also, response packets may be routed through another access network. In this case it may also be necessary for the PAN access nodes to act name servers for handling DNS requests from the PAN devices.

As shown in the application, this invention makes it possible for all possible types of PAN devices, including legacy devices, to function in the multi-access environment that the PAN presents. Especially, it makes it possible for the user of the PAN to enforce via his PAN managing device each PAN device to use a specific access. Thereby, each PAN device can use an access independently of the other PAN devices. Also, if the PAN or the user of the PAN so wishes, the entire PAN could be instructed to use only one access.

In the drawings and specification, there have been disclosed preferred embodiments and examples of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation, the scope of the invention being set forth in the following claims.

Claims

1. A method for providing access to external communication networks for a communication device in a personal area network (PAN) (100) where the PAN is constituted by communication devices presently being within short-range communication distance from each other, called PAN devices, and wherein the PAN devices (111, 112, 113, 114) communicates via short-range communication means

(301, 311, 321, 331) and wherein at least one of the PAN devices, called a PAN access node (112, 114), has at least one external access means (315, 325) for accessing at least one external communication network, characterized in that the method comprises the steps of: discovering in the PAN the at least one external access means (315, 325) of the at least one PAN access node (112, 114); selecting a first external access means (315) of a first PAN access node (114) as the external access means to be used by a first PAN device (111) for providing external access to the first PAN device; instructing the at least one PAN access node (112, 114) that data from the first

PAN device (111) intended for an external network shall be routed via the first external access means (315) of the first PAN access node (114); and enforcing data from the first PAN device (111) intended for an external communication network such that the data is routed via the first external access means (315) of the first PAN access node (114).

2. The method according to claim 1 wherein the steps of discovering, selecting and instructing is performed by a PAN managing device (113) which is a PAN device used by a user of the PAN for controlling the PAN.

3. The method according to claim 1 or 2 wherein the step of enforcing is performed by the first PAN access node (114) responding to a message from the first PAN device (111) requesting to establish a connection to an external network, such that the first PAN device is enforced to use the first external access means (315) of the first PAN access node (114) when communicating with an external network.

4. The method according to claim 1 or 2 wherein the step of enforcing is performed by the at least one PAN access node (112, 114) receiving traffic from the first PAN device (111), tunnelling or forwarding the traffic to the first external access means (315) of the first PAN access node (114).

5. The method according to claim 3, wherein the first PAN device (111) is enforced to use the first external access means (315) of the first PAN access node (114) when communicating via the Dynamic Host Configuration Protocol (DHCP).

6. The method according to claim 5, wherein the first PAN access node (114) comprises a Network Address Translator (NAT) and a DHCP server.

7. The method according to claim 3, wherein the first PAN device (111) is enforced to use the first external access means (315) of the first PAN access (114)node when communicating via the Address Resolution Protocol (ARP).

8. The method according to claim 7, wherein the first PAN access node (114) comprises a Network Address Translator (NAT) and an ARP server.

9. The method according to claim 3, further comprising the step of: enforcing data from the first PAN device (111) intended for an external communication network such that the data is routed via an external access means of a second PAN access node (112 ) or via a second external access means of the first

PAN access node (114), after the first PAN device has been enforced to use the first external access means (315) of the first PAN access node (114), wherein the first PAN device is restarted before it is enforced to use the external access means of the second PAN access node (112) or the second external access means of the first PAN access node.

10. The method according to claim 3, further comprising the step of: enforcing data from the first PAN device (111) intended for an external communication network such that the data is routed via an external access means of a second PAN access node (112 ) or via a second external access means of the first

PAN access node (114), after the first PAN device (111) has been enforced to use the first external access means (315) of the first PAN access node (114), wherein any of the at least one PAN access nodes (112, 114) sends a message to the first PAN device forcing the first PAN device to renew its configuration information such that the first

PAN device can be enforced to use the external access means of the second PAN access node (112) or the second external access means of the first PAN access node (114).

11. A PAN controller device (113) in a Personal Area Network (PAN) (100) arranged for managing communication devices in a PAN such that a communication device is provided with access to an external communication network, and where the PAN is constituted by the communication devices presently being within short-range communication distance from each other, called PAN devices, and wherein the PAN devices (111, 112, 113, 114) are arranged to communicate via short-range communication means (301, 311, 321, 331), and wherein at least one of the PAN devices (112, 114), called a PAN access node, has at least one external access means (315, 325) for accessing at least one external communication network, wherein the PAN controller device (113) comprises:

A short-range communication means (301) for sending instructions to and receiving information from the at least one PAN access node (112, 114) such that the PAN controller device can discover the at least one external access means of the at least one PAN access node; characterized in that the PAN controller device further comprises:

A control unit (303) for processing the received information and for selecting a first external access means of a first PAN access node as the external access means to be used by a first PAN device (111) for providing external access to the first PAN device, and for compiling instructions to be sent to the at least one PAN access node (112, 114) via the short-range radio communication means (301) instructing the at least one PAN access node that data from the first PAN device (111) intended for an external communication network shall be routed via the first external access means (315) of the first PAN access node (114).

12. The PAN controller device (113) of claim 11 wherein the at least one PAN access node (112, 114) is instructed by the instructions received from the PAN controller device such that the first PAN access node (114) will respond to a message from the first PAN device (111) requesting to establish a connection to an external network, such that the first PAN device is enforced to use the first external access means (315) of the first PAN access node (114) when communicating with an external network.

13. The PAN controller device (113) of claim 11 wherein the at least one PAN access node (112, 114) is instructed by the instructions received from the PAN controller device such that if data from the first PAN device (111) intended for an external communication network is received at a PAN access node (112) different from the first PAN access node (114), the data will be tunnelled or forwarded to the first external access means (315) of the first PAN access node (114).

14. The PAN controller device (113) of claim 12, wherein the first PAN device (111) is enforced to use the first external access means (315) of the first PAN access node (114) when communicating via the Dynamic Host Configuration Protocol (DHCP).

15. The PAN controller device of claim 14, wherein the first PAN access node (114) comprises a Network Address Translator (NAT) and a DHCP server.

16. The PAN controller device of claim 12, wherein the first PAN device (111) is enforced to use the first external access means (315) of the first PAN access (114) node when communicating via the Access Resolution Protocol (ARP) .

17. The PAN controller device of claim 16, wherein the first PAN access node (114) comprises a Network Address Translator (NAT) and an ARP server.

18. The PAN controller device of claim 11 or 12, wherein the PAN controller device (113) is further arranged to send instructions to the at least one PAN access node (112, 114) instructing the at least one PAN access node that the data from the first PAN device (111) intended for an external network shall be routed via the external access means (325) of a second PAN access node (112) different from the first PAN access node (114) or via a second external access means of the first PAN access node, wherein the first PAN device (111) is restarted before data is sent to the external access means of the second PAN access node (112) or to the second external access means of the first PAN access node.

19. The PAN controller device of claim 11 or 12, wherein the PAN controller device (113) is further arranged to send instructions to the at least one PAN access node (112, 114) instructing the at least one PAN access node that the data from the first PAN device (111) intended for an external network shall be routed via the external access means (325) of a second PAN access node (112) different from the first PAN access node (114) or via a second external access means of the first PAN access node, wherein any of the at least one PAN access node is instructed to send a message to the first PAN device (111) forcing the first PAN device to renew its configuration information such that the first PAN device can be enforced to start sending data to the external access means of the second PAN access node (114) or to the second external access means of the first PAN access node (112).

20. The PAN controller device (113) according to any of claims 11-19, also comprising:

A PAN user interface (302) for presenting information to a user such that the user can select a preferred external access for the first PAN device (111), which preferred external access is communicated to the control unit (303) to be used when selecting the first external access means (315) of the first PAN access node (114) as the external access means to be used by the first PAN device (111) for providing external access to the first PAN device;

21. A computer program product loadable into a memory of a digital computer device residing in each PAN device (111, 112, 113, 114), wherein the computer program product comprises software code portions for performing the method of any of claims 1-10 when the computer program product is run on the computer device.