WO2005032058A1

WO2005032058A1 - Method and arrangement for solving identity conflicts in a network

Info

Publication number: WO2005032058A1
Application number: PCT/SE2004/001399
Authority: WO
Inventors: Anders Carlius
Original assignee: Anders Carlius
Priority date: 2003-09-30
Filing date: 2004-09-29
Publication date: 2005-04-07
Also published as: SE526983C2; SE0302607D0; SE0302607L

Abstract

A method and a device to connect a communication apparatus to at least one other node in a network. The device searches for and establishes contact with the at least one other node. The device and the node have locally exchangeable identities. When contact is established, the identity information comprising the current local identity of the device is sent to the at least one other node, identity information comprising at least one current local identity of the at least one other node is received, and it is decided whether an identity conflict between the current local identity of the device and the at least one other node exists. If an identity conflict exists, it is solved so that the first and the at least one other node have locally unique identities.

Description

Method and arrangement for solving identity conflicts in a network Technical Area The present invention generally relates to a method for communicating between nodes in a communication network, and more specifically to a method for adaptively adding nodes to a network. The invention also relates to an apparatus that depending on its position to other nodes can adaptively connect to the network.

Technical Area A number of systems to send information between different nodes that are connected in a network exist. On the one hand there are wire based communication systems and on the other hand there are wireless communication systems. Wire based systems, such as public switched telephone networks or local computer networks, have the disadvantage that they are not flexible, i.e. have fixed nodes, and require expensive investments in infrastructure. To achieve a better flexibility in the communication system there have been for some time wireless communication systems, such as mobile phone communication systems according to a number of standards . These systems are based on a great number of base stations placed in the area where the system should have radio coverage. The mobile terminal and the base station can both be seen as a node in the network but with different tasks. The communication between mobile terminals in the network is always done via a base station. To get such base station based systems to work satisfactory, base stations must be positioned on a mutual distance to obtain coverage of the coverage area of the system. If mobile terminals are positioned on places where radio coverage from a base station is missing, they cannot be used to communicate. Thus, communication systems based on linking via base stations demand large investments to work satisfactory. With still increasing frequency ranges being used by the systems, an even closer placement of the base stations is required. It is not economically possible to construct base station based communication networks in areas with low density of population, since the amount of usage will be too low. Another disadvantage with previously known wireless communication systems are the central control of the communication. In mobile phone communication systems, centrally placed units have control over the identities of the mobile phones and where they are located in the network. This requires large routing tables and many complicated functions to transfer information from one node to another. A further disadvantage with previously known wireless communication systems with central administration is that nodes cannot communicate directly with each other although they are within each other's coverage. This is also true when the comprehensive central system control cannot be reached, for example if there are technical errors.

Summary of the Invention It is an object of the invention to provide a method to communicate between at least two nodes in a network, which does not require an external unit to administrate the connection between the nodes or any base station to forward information between the end nodes. Another object of the invention is to provide a method that enables adaptive and automatic connection of nodes to a network. The above-described objects are achieved by the method according to the invention for connecting a first node to a network with at least one other node. The method comprises searching for and establishing contact with the at least one other node, sending identity information containing the current local identity of the first node to the at least one other node, receiving information containing at least a current local identity for the at least one other node, and deciding whether an identity conflict between the current local identities of the first node and the at least one other node exists. If an identity conflict exist, it is solved so that the first and the at least one other node have locally unique identities. This can be done by either the first and/or the other node, depending on how long they have had their respective identities, which changes its current local identity to a new local identity and informs the other node of its new identity. It is another object of the invention to provide a device to use the method. This object is achieved by a device according to the invention for communicating with at least one node having a local identity in a network. The device comprises a communication unit arranged to search for and establish connection with the at least one other node, and an identity unit. The device has an exchangeable local identity. The communication unit is arranged to send identity information containing the current local identity information of the device to said at least one node and to receive identity information containing the current local identity of said at least one node. The identity unit is arranged to decide whether an identity conflict between the current local identity of the device and said at least one node exists, and if this is the case solve the identity conflict so that the local identities of the device and said at least one node are unique local identities. Further embodiments of the invention are defined in the dependent claims. It is an advantage of the invention that communication between nodes can be achieved without an intermediate base station and that a connection between the nodes can be made automatically when they are within each other's coverage. This makes a network according to the invention much cheaper to build and use then previously known communication systems. It is an advantage of the invention that the communication between the nodes is done within a limited identity list. The unique identities are chosen such that the identity is close to the identities of the surrounding nodes. This entails that the identity lists for the own node for contact with surrounding nodes becomes short and then requires only a few searches to find the right identity. This leads to that only a small amount of processing power is needed to search in the identity lists and thereby the searches by become fast and the energy consumption in the node is limited.

Brief Description of the Drawings. Other objects, features and advantages of the invention will appear from the following description of several embodiments of the invention, wherein different aspects of the invention will be described in further detail with reference to the attached drawings, in which: Fig. 1 is a block diagram of a node according to the invention; Fig. 2 is a block diagram illustrating establishment of a network with two nodes; Fig. 3 is a flow-chart of a first embodiment of the method according to the invention; Figs. 4a-b are block diagrams illustrating establishment of a merged network having one channel; Fig. 4c is a block diagram illustrating a merged network having two channels; Figs. 5a-5b are a block diagrams illustrating two separate networks and an merger thereof; and Figs. 6a-6b are block diagrams illustrating separation of a network; and Fig. 7 is a block diagram illustrating forwarding of information.

Detailed Description of Embodiments The present invention relates to a communication system where two or more nodes adaptively establish a network as more nodes come within the total coverage area of the network. All nodes have self-assigned identities that are unique within the local network. The communication between the nodes is done with the self-assigned unique identities even if the nodes can not communicate directly but through another node that forward the information to the correct receiving node. Furthermore, each node can serve other nodes with services. Each node can be contacted via a globally unique identity or address. If the node is a part of the network, it will answer with its local identity, as will be described below. The nodes can be stationary with a connection to a stationary power source. Alternatively, he nodes can be portable and mobile with a limited amount of power with a battery or a similar power source. The nodes can thus be both stationary and mobile communication devices. The communication between the nodes can be provided with direct sequence or frequency hopping CDMA (Code Division Multiple Access) . One modulation for the implementation is QPSK (Quadrature Phase Shift Keying) . The transferring can be done in the 400MHz band, other frequencies can however be chosen depending on what is most suitable in each specific case. The nodes are described as they decide regarding path or other choices depending on local environment variables. These environmental variables can for example be: traffic load of single nodes, power consumption in the node itself, a shorter path (measured in number of hops) through the local network, historical data of transmissions that have occurred in the network or the data type that is to be transmitted. The nodes can provide services towards other nodes . The services can for example be: give correct local time, distribute media (sound and/or picture) , tell when the next bus leaves the central station, or provide news information. Fig. 1 discloses components comprised in a device or node according to the invention. The device can be stationary or portable. The device according to the invention comprises a communication unit to communicate with other nodes in the network. The communication unit can contain different means for wireless communication, as an antenna 10, a transmitter/receiver 11, a signal decoder 12, a power control unit 13, a signal processor 14, analog digital converter, filter, phase detector, channel search device, etc. An identity unit 15 is arranged to control, and if needed change, the local identity of the device. Furthermore, the identity unit 15 identifies if address conflicts are present, as will be described below. A routing unit 16 can, when information is to be sent to other nodes in the network, decide which way among several possible ways the information is to be sent, for example according to above mentioned criteria. The device also comprises one or several memories, which are shown collectively as memory 17. This can contain both read and write memories. The device also comprises one or more processors, which are shown as processor 18 in fig 1. The processor 18 can be overall responsible for the total function of the device, or be responsible for one or more of the above-mentioned units of the device. Said units can for example be implemented in software and run by said processor 18. Alternatively, the units are implemented as one or several ASICs (Application Specific Integrated Circuit) , logical hardware circuits, or similar. The device can also contain an input interface 20, that comprises a keyboard or a keypad, a mouse or a joystick, or a touch screen. The arrangement can also comprise an output interface with a media processor connected to a display 22, a microphone 23, a speaker 14 and a camera 25. The unique local identity can also be called local address . One and the same address should only by present within one local network. Therefore, when the network is merged each identity conflict in the merged network has to be solved by the changing of identity by one or several nodes, wherein the local identity of each node is unique within its network. Fig. 2a discloses a first and a second node, Node A, Node B. Node A is alone in the network where it is located as far as node A can see. Node B is alone in the network where it is located as far as node B can see. Node A and Node B have chosen their own identity, it can be the same identity as they see this identity as unique in its own network. In Fig. 1, Node A and Node B has the same identity id=l when they are in different networks. When the nodes are getting closer and at the point where their coverage area overlaps, they get contact with each other. If Node A and Node B have chosen there own unique local identity different from the other node, a new network with locally unique identities between the nodes will be established. If Node A and Node B have chosen the same identity, as is shown in Fig. 2a, either one or both Node A, Node B must change to new local identities. The choice of new identity can be done randomly over the total address volume, but should be chosen within the 2 -bit address the application, then the size of the address field, the own address on maximum on 256 bit, stating the size of the time information, then the time since the address of the node was changed max 1024 bits. The packet is sent as soon as possible after contact is established between the nodes. Both nodes can send and receive information at the same time. The above-mentioned values should be seen as example values that can be varied as required. As an example, the channel speed can be 56000 baud. This channel speed can be varied to fit the application by being increased or decreased. The packet for identity transferring could look as follows with 8-bit address space and 8-bit time: [1010101 | 00 I 8 bit own address | 00 | 8 bit time information] . Below, tables with the codes for transferring the address information and transferring of time information, respectively, are shown:

Bit code 2 bit Address information nr of bits 00 8 01 24 10 64 11 256

Bit code 2 bit Time information nr of bits 00 24 01 64 10 256 11 1024

When the contact according to above is done, it is established in step 130 if the respective node has a unique local identity. According to the example in Fig. 2, Node A and Node B see that the other node has the same identity. Then, the node that has had its identity the shortest time chooses to change identity in step 140. Since both nodes in this case have been running for the same time, both chooses to change to a new local identity that is chosen at random without colliding with other known identities. Node A chooses for example identity id=2 and Node B identity id=3. Nodes that have chosen to change there identity sends in step 150 a identity information packet as described above with the new information to the other node. In this case, Node A sends a packet to Node B and Node B sends a packet to Node A. In step 160, it is decided if the identity conflict is solved. If this not the case, the procedure returns to step 140, wherein it is tried to solve the conflict again until no identity conflict is present. The local network for Node A and Node B with the locally unique identities id=2 respectively id=3 is established, wherein the procedure for establishing the new network can be finished. If no new identity conflict is present in step 130, the new local network is established directly and the procedure is ended. Figs. 4a-4b illustrates how a first local network is connected to one other network. Node A and Node B are in the first network where identity conflicts are settled according to Fig. 2a, Fig. 2b and Fig. 3. The other network with Node C is getting closer to the first network. When the first and the second local network get in contact with each other's coverage area and satisfactory signal strength is reached, the networks can be connected. In Figs. 4a-b, Node C reaches the point where Node B can be reached. If Node C has chosen a unique local identity that already is unlike the address of any other node in the first network, a connection between Node B and Node C will commence according to the method in Fig. 3. If Node C and any other node in the first network have chosen the same identity, either one or both nodes changes to new identities. When all nodes in the network, in this case Node A, Node B and Node C, have unique identities the respective node can send information with unique local addressing between them. Connecting the first and the second network is done according to the method of Fig. 3. A Node C that is alone takes a local identity having number 1 at the time T. Node A and Node B is included in the first network established as described above with the unique identities 2 and 3 at the time T. When Node B and Node C gets contact over the radio channel, this is done by scanning of the coverage areas at given time intervals for example every second, i.e. a certain quality of signal to noise ratio is reached, or contact over other media, they connects on OSI level 1, usually called the physical level. When the contact between Node B and Node C is established as described above both nodes sends over their own identity information. This transferring of information with its packet description occurs as described above . When contact between Node B and Node C is established, the nodes sees that they have unique identities, Node B have locally unique identity id=3 and Node C have locally unique identity id=l . Nodes that have chosen to change identity sends an information package according to above with the new information to the other node. If an identity conflict is present where both nodes have the same identity, the conflict is solved as described above . A local network for Node A, B and C with unique local identities id=2 , id=3 and id=l is established. Fig. 4c illustrates how at least two communication channels can be used in the same network according to the invention. The number of channels is not limited to two and can be more depending on requirements. Node A, Node B and Node C are part of a network. Node A has contact with Node B via a first channel. Node B has contact with Node A and Node C via the first channel. Node A and Node C are also directly connected to each other via a direct second channel . When node A and Node C have at least two communication channels they can have contact with each other via the second channel without the involvement of Node B. The communication between node A and Node C can occur either via the first or the second channel . The local identities are not affected since all nodes already are in the local network. Figs. 5a-5b illustrate the connection of a first network with a number of nodes to a second network with a number of nodes. The number of nodes in the first and second network can be the same or different. Node A, Node B and Node C are in the first network with locally unique identities. Node D, Node E and Node F are in the second network with locally unique identities. Initially, the first and the second network have no contact with each other. When two of the nodes, in this case Node C and Node

D, come in contact with each other they establish a connection between themselves with locally unique identities for the two nodes according to the method of Fig. 3. If all nodes in the first and the second network already have unique identities within the merged network, no identities are changed. If two nodes in the merged network have chosen the same identity, one or both nodes change identity to, for the merged network, unique identities. Changing of local identities occurs until all identity conflicts are settled and all nodes have locally unique identities. When all nodes in the network have unique identities, the nodes can send information between themselves using unique addresses. Merging of a first and a second network can occur as follows. Node A, Node B and Node C makes up the first network with the local identities id=2 , id=3 and id=l established at the time T, as described above. Node D, Node E and Node F makes up the second network with the locally unique identities id=3 , id=7 and id=4 established at the time T. Initially, the first and the second network do not have any contact with each other. When two of the nodes, in this case Node C with identity id=l and Node D with identity id=3 , from the first and the second network, respectively, comes in contact with each other they establish a connection between themselves with their unique identities by exchanging identity information. Node C, which has knowledge on the locally unique addresses of the first network, identifies if there are an identity conflict in the joint network between adjacent nodes Node B and Node D, which both have a local identity id=3. Node C sends out identity changing information to both node B and Node D telling them to solve their address conflict. As Node C already have contact with both Node B and Node D, this information is sent over already established links. The identity change packet is coded with information in the following manner: 4 bits indicating that it concerns an identity conflict, indication of the size of the identity information 2 bits, identity conflict address on max 256 bits, statement of the size of the time stamp 2 bits, time since the sending node changed the address max 1024 bit in this case C:s address. In the packet example below, an 8 -bit identity statement is used and an 8bit time stamp. [0010 I 00 I 8 bit conflict identity | 00 | 8 bit time stamp] .

Definition of the four bits that states identity conflict: 0010 Identity conflict

Node B and Node D answers with a identity packet as is done at establishment of a link between two nodes, described in Fig.2, to Node C. The identity package looks like as described above but over established links so only the transferred information is shown: stating the size of address 2 bit, the own address of max 256 bit, a statement of the size of the time stamp 2 bit, time since the address of the node was changed max 1024 bit. The packet can be as follows with an 8-bit address and an 8-bit time stamp: [00 | 8 bit own address | 00 | 8 bit time stamp] . The packet from Node B is transferred by each intermediate node in a signal path to Node D, and the packet from Node D is transferred to Node B. Then, the same address conflict settlement is done as described in Fig. 3. If Node B and Node D have the same time stamp chooses both a new identity. Node B chooses id=5 as new identity and Node D chooses id=6 as new identity. Node B sends an information packet to Node C with the new identity. Node D sends an information packet to Node C with the new identity. The information package is of the same type as the identity conflict packet where the information bits are changed to address change. When Node C does not see any identity conflict any more it does not answer Node B or Node D. After having waited a predetermined time period, for example 20ms, Node B sends the same information packet as it previously has sent to Node C to its neighbor Node A, to which Node B has an previously established link connection. After having waited a predetermined time period, for example 20ms, Node D sends the same information packet as it has sent to Node C to its neighbor Node E, to which Node B has an established link connection. All nodes being adjacent to a Node that has changed local unique identity shall receive an information packet from the changing Node. The time to wait before sending the information packet can be varied depending on local environmental variables, as is described above. In the example below for transferring of new identity an 8 bit address indication and an 8 bit time indication is used. [0001 I 00 I 8 bit new identity | 00 | 8 bit time stamp] . Definition of the four bits that defines address change. 0001 Address change

Figs. 6a-6b illustrate the separation of a network. Nodes A,B,C,D,E and F are part of a network with unique network identities. Node F has only contact with the network through Node E. If Node F gets out of reach from the nearest Node E, no change of the local identities occurs . As soon as there is a possibility to establish a local link between two nodes this will be done. If Node F at a later time, when it still has the unique identity from the moment separation, gets in contact with any node in the network, which Node F was disconnected from, a connection will be established to the network. If for example Node F comes close enough to Node C to establish a connection, Node C will establish a link connection to Node F. As none of the Nodes have had any reason to change local identity there are no address conflicts . Fig. 7 illustrates how information is sent between

Nodes in a network. Node A, B and C is in a network. Node A and Node B, and Node C can send information between themselves, but not Node A directly to Node C. Node A and Node C does not need to know about each others existence. When A want to send information to Node C, but do not know where or whether Node C exists, Node A makes a request by sending out the global identity for Node C to adjacent Nodes, in this case Node B, whether the Node can reach Node C. As Node B can reach Node C, Node B answers Node A with a confirmation on whether and how it reaches Node C. Node A starts to send the information to Node B, which forwards the information to Node C. If Node A had had contact with more nodes, Node A would have contacted those nodes with a request about the path to Node C. The answer from the adjacent nodes on possible paths towards the target node is then received and a path through the network is decided by the local sending node, in this case Node A. The path that is finally chosen is decided by the previously described local environmental variables. For example, the choice can be based on the shortest path through the local network or depending on traffic load by single nodes and their links. If no response on a request is received within a set time, a time that can be decided by the nodes themselves, the network is considered not to containing this target node. The contact for a request to reach a node occurs with a packet having the following structure: 4 bit information indicating a contact request, two bit address size indication, local unique address of the receiving node, local unique address of the sending node, six bits indicating the number of link hops up until now, four bits indicating the data size, raw data having a length in accordance with the previous field. In the packet example below an 8 bit address indication is used and one link hop and the data bits are given by xxx. Node A is transmitting node and Node C is receiving node in the address fields. The data bit and the indication of the size of the data are irrelevant in this example. [0100 I 00 I 0000 0011 I OOOO 0001 I 00 0001 I oooo I xxx ] . Definition of the four bits that indicate contact request 0100 Contact request

Node B, which receives the packet from Node A, forwards the packet to Node C with the changes: The link hop counter is increased by one to '00 0010', the locally unique identity of Node B is written into the data field, the indication of the data size is set to a value in accordance with the amount of data that is to be transferred. Node C processes the request and answers with a contact response packet to Node B. Node C could have chosen to answer another node that would have had a different path to Node A. The contact response packet looks like the contact request packet where the addresses are Node C as a transmitting node and Node A as target node. In the data bits the addresses of the different nodes that have been passed to reach Node C from Node A are indicated. In this case, the locally unique address of node will be indicated in the data field. The data bits and the indication of the size of data are irrelevant in this example. Contact response occurs with a packet having the following structure: 4 bits of information indicating a contact response packet, two bits indicating size of address, local unique address of receiving node, local unique address of sending node, six bits indicating the number of link hops up until now, four bits indicating data size, raw data having a length in accordance with the previous field.

The definition of the four bits indicating contact response 0101 Contact response on request

When Node B receives this contact response packet it is forwarded to Node A with an increase in the link hop counter in the packet . Node A receives the packet and knows that Node C has answered and can see the path to Node C by reviewing the addresses within the packet. If Node A has not received any response within a predetermined time period, for example within 20ms, then the path to Node C would have been regarded as non existent . Node A can now start sending information to Node C by sending information to Node B and get Node B to forward the information to Node C. In addition to voice communication between nodes, different services can also be provided according to the invention. A service request is transmitted from a node to adjacent nodes instead of asking for a specific node. The node that is searching for a service transmits a request on what services that can be provided to the neighbors of the network. The response that is received from the neighbors contains service description and the local unique identity of where that service is provided. Services can for example be: State the correct local time, distribute media (sound and/or picture) , indicate when the next bus leaves the central station, transmit news information, etc. The service request can be transmitted in a network, for example according to Fig. 2. Node A and Node B are in a network where they have the locally unique identities id=l and id=2. If Node A will find out what services Node B can provide, Node A transmits a service request to Node B. Node B responds Node A with a service response package that specifies what services Node B can provide to Node A. The service request and the service response are done with a packet having the following structure: 4 bits of information indicating a service request/response package, locally unique address to receiving Node, locally unique address to sending Node, six bits indicating the number of link hops up until now, four bits indicating data size, data for specifying service having a length in accordance with the previous field. In the packet example below, an 8 bit address indication and 1 link hop and the data bits are given by xxx. Node A is sending node and Node B is receiving node in the address fields. The data bits and the indicated data size are irrelevant in this example. [Service request | Address size | identity of Node A I identity of Node B | data size | data field ] [0111 I 00 I 0000 0010 I OOOO 0001 I 00 0001 I oooo I xxx ] . Definition of the four bits that corresponds to service request/response 0111 Service request/response

The difference between a service request and a service response package is the data in the data field. A service request packet does not need to contain any data. The service response must contain a list on all services that can be provided in the data field together with the locally unique address providing that specific service. To have a global identity, a local identity is associated with a global identity in each single node having a global identity. To find a node via the global identity, a service request with the globally unique address is made to the nodes in the local network. The node having the globally unique identity responds with both its local and globally unique identity. The node transmitting the request can transmit multiple requests without having received a response on the previously transmitted requests. The response on the requests, that contain both the local and the global address, can be associated with the respective requests as both the global and the local unique address are present in the response . If no response is received on a request for a global identity, the Node is assumed to not be in the network. A global request can for example be made if Node A and Node B are in a network with the locally unique identities id=l and id=2. Node A has the globally unique address F55 and Node B has the locally unique address F66. Node A wants to get in contact with the globally unique identity F66. Therefore, Node A transmits an identity request regarding identity F66 to the adjacent node, in this case Node B with id=2. Node B who has the unique global identity F66 responds with the global and local identity, F66 and id=2 , to Node A. The response gives Node A that it can use the locally unique address id=2 to get in contact with F66. GlobalIDrequest and GlobalIDresponse is made with a packet with this structure: 4 bits of information indicating GloballDrequest/response, two bits indicating size of address field, locally unique address to receiving node, locally unique address to sending node, GlobalID to sending node 128 bit, GloballD to node that is requested 128 bit, six bits indicating number of link hops until now, four bits indicating data size, service specific data with length in accordance with the previous field.

In the packet example below an 8 bit address indication is used and one link hop and the data bits are shown as xxx. Node A is transmitting and Node B is receiving in the address fields. The size of the global identities F55 and F66 is seen as 128 bits. The data bits and the specification of the indication of data size are irrelevant in this example. [Service request | Address size | identity of Node A I identity of Node B | GloballD A | GloballD B | Link hop | Data size | Data field ] [0110 I 00 I 0000 0001 I OOOO 0010 I F55 I F66 | 00

0001 I oooo I xxx ] . Definition of the four bits indicating GloballDrequest and GlobalIDresponse :

0110 Global ID request/response

The method according to the invention may be implemented in software, which can be executed by one or more processors in the node in accordance with the invention. The invention also incorporates the implemented computer programs, in particular computer programs on or in a carrier, which is arranged to apply the invention in practice. The program can be in the form of source code, object code or other code that is appropriate code to use at implementation of the method in accordance with the invention. The carrier can be every unit or device that is capable to carry the program. The carrier can for example be a recording medium, computer memory, read memory or an electrical carrier signal . The present invention here has been described above with reference to specific embodiments. Other embodiments than the previously described are still possible within the scope of the invention. Other method steps than previously described, to execute the method with hardware or software can be done within the scope of the invention. The different features of the invention may be combined in other combinations then previously described. The invention is only defined by the appended patent claims.

Claims

PATENT CLAIM 1. Method for connecting a first node (A) to a network with at lest one other node (B) , the method comprising searching for and establishing contact with the at least one other Node, characterized by the steps of: receiving identity information containing at least one current local identity for at the least one other node; deciding if an identity conflict between the current local identity of the first and at least one other node is present ; and if an identity conflict is present solving the identity conflict so that the first and at least one other node have locally unique identities.

2. Method according to claim 1, characterized by the step of sending identity information comprising the current local identity of the first node to the at least one other node ;

3. Method according to claim 2 , characterized in that the sent identity information comprises information regarding how long the node have had its current local identity and the received identity information comprises information regarding how long the at least one other node have had its current local identity.

4. Method according to claim 3, characterized by the steps of : deciding which of the first and the at least one other node have had the current local identity during the longest time period if an identity conflict is present; retaining the current local identity of the first node if the first node has had the identity during the longest time period; otherwise changing the current local identity of the first node if at least one other node has had the local identity during a longer time period.

5. Method according to any of the previous claims, characterized by, if the first and the at least one other node have had its current local identity during the same time period, repeatedly executing, until no identity conflict is present in the local network, the steps of: changing to a new local identity for the first node; sending the new identity of the first node to the at least one other node; receiving at least one new local identity for the at least one other node; and deciding whether an identity conflict between the new local identity of the first and at the least one other node is present .

6. Method according to claim 4 or claim 5, characterized by the steps of: sending the new local identity of the first node to the node for which the identity conflict arose.

7. Method according to any of the previous claims, characterized in that the contact with the first and the at least one other node is established over a first and/or at least a second channel .

8. Method according to any of the previous claims, characterized by the steps of, at a possible identity conflict between the current local identity of the first and at least a third node: receiving identity information comprising at least the current local identity of the third node; deciding whether an identity conflict is present between the current local identity of the first node and the current local identity of the at least third node; and solving the identity conflict between new one of the first node and the current local identity of the at least third node according to any of claims 2-5.

9. Method according to any of the previous claims, characterized by the steps of : asking a question regarding which local unique identity a specific node with a global identity has; receiving information comprising at least one contact path to the specific node; and sending information via the at least one contact path.

10. Method according to claim 9, characterized in that the information comprising the at least one contact path to the specific node contains at least two contact paths, wherein the method comprises the further step of: choosing contact path.

11. Method according to any of the previous claims, characterized by the steps of: sending a service request to receive information regarding which services that are present in the network; and receiving a service response comprising information regarding at least one service that can be provided by at least one specific node in the network and at least one contact path to said specific node.

12. Device for communicating with at least one node (A, B, C,D, E, F) having a local identity in a network, the device comprising a communication unit for searching after and establishing contact with the at least one node (A, B, C, D, E, F) , and a identity unit (15), characterized in that: the device has an exchangeable local identity; the communication unit is arranged to receive identity information comprising a current local identity of said at least one node; the identity unit (15) being arranged to decide whether an identity conflict between the current local identity of the device and said at least one node exists, and if this is the case solve the identity conflict so that the local identity of the device and said at least one node are locally unique identities.

13. Device according to claim 12, characterized in that the communication unit is arranged to send identity information comprising the current local identity of the device to said at least one node.

14. Device according to claim 13, characterized in that the identity unit (15) is arranged to incorporate information regarding for how long the device has possessed the current local identity into the identity information, and in that the identity information received from the at least one other node comprises information regarding for how long said node has possessed its current local identity.

15. Device according to claim 13, characterized in that: the identity unit (15) is arranged to, if an identity conflict exists, determine which of the device and said at least one node have had the current local identity during the longest period of time and keep the current local identity of the device if the device has had the current local identity during the longest time period , otherwise change the current local identity of the device if said at least one node has had the current local identity during the longest time period .

16. Device according to any of the claims 12-15, characterized in that the identity unit (15) , if the device and said at least one node have had the current identity during the same time period, is arranged to, until no identity conflict is present in the local network, repeatedly: change the current local identity of the device to a new local identity; send the new local identity of the device to the at least one node; receive at least one other new local identity of said at least one node; and decide whether an identity conflict between the new local identity of the device and the at least one node is present.

17. The Device according to claim 15 or 16, characterized in that the identity unit (15) is arranged to send the new local identity of the device to the node for which the identity conflict arose.

18. Device according to any of the claims 12-17, characterized in that the communication unit is arranged to establish contact with said at least one node over a first and/or at least a second channel.

19. Device according to any of the claims 12-18, characterized in that the identity unit (15) is arranged to, at a possible identity conflict between the current local identity of the device and at least one other node in the network : receive identity information comprising current local identity of the at least one node; decide whether an identity conflict is present between the local identity of the device and the at least one node ; and solve the identity conflict between local identity of the device and the at least one node according to any of the claims 2-5.

20. Device according to any of the claims 12-19, characterized in that the identity unit (15) is arranged to: make an inquiry regarding what local unique identity a specific node having a global identity has; and receive information comprising the specific local unique identity and at least one contact path to the specific node; the communication unit being arranged to send information via the at least one contact path.

21. Device according to claim 20, characterized by a routing unit (16) being arranged to choose a contact path if the information comprising the at least one contact path to the specific node contains at least two contact paths.

22. Device according to any of the claims 12-21, characterized by a processor (18) being arranged to make a service inquiry to receive information regarding what services are available in the network; and receive a service response comprising information regarding at least one service that can be made available by at least one other specific node in the network and a contact path to said specific node.

23. Computer program comprising a computer program code means configured to execute all the steps according to any of the claims 1-10.

24. Computer program according to claim 23, contained in a computer readable medium.

25. Communication apparatus to communicate with nodes in a network, characterized by the device according to any of the claims 12-22.