Method and apparatus for connecting a wireless lan to a wired lan

SCOPE OF THE INVENTION

The present invention is concerned with wireless networks in general and means for connecting wireless nodes or wireless local area networks to wired local area networks in particular.

STATE OF THE ART

So far, local area networks (LANs) have consisted of nodes interconnected by physical telecommunication media (such as coaxial cable, dual cable or fiber optic technology). These local networks are called wired networks in the following.

Recently, wireless networks whose nodes are not interconnected by physical media are on the market. These wireless networks communicate using infrared (IR), radio or other signals. One of the advantages of using wireless networks is that no cables are required anymore. This is a particularly useful feature for mobile nodes such as laptop and notebook computers, Personal Digital Assistants (PADs), and the like. If the nodes are equipped with a corresponding wireless adapter (which includes a transceiver and a control card), such as a wireless IR adapter, the nodes can be moved and still remain connected to the network, as long as they are within range ,

A method for implementing a wireless local area network is similar to the system of the mobile telephone network. In this method, wireless nodes do not communicate directly with each other but instead send all the signals to a central base station, which in turn forwards the signals to the destination node.

In certain situations, however, it is advantageous if each wireless node can communicate directly with other nodes, as is the case with most wired networks. In a wireless network where this is possible, the wireless adapter and the control software send data packets that all nodes within the receiving range can receive. The network allows packets to be sent that are received by all nodes, but ignored by those for which the packet is undefined. This corresponds to the packet delivery system using wireless network protocols, such as Ethernet. Therefore, higher-level operating system software for networks such as NETWARE from Novell, which supports such a packet delivery system, may be used in conjunction with such a wireless network (Netware is a registered trademark of Novell). These wireless local area networks are referred to as wireless peer-to-peer networks.

Wireless peer-to-peer networks have a crucial physical property that makes it difficult to create a reliable network compared to a wired local area network. In a wired network, each node is physically connected to the network and thus can access any network traffic. This is not always the case in wireless local area networks. Each node communicates with other nodes by means of a type of electromagnetic signal whose range remains limited. Each node has a coverage area that is limited by factors such as signal type, signal strength, obstacles within the coverage area, and so on. The wireless local area network can not guarantee that each network node, which is believed to be part of the same wireless network, can access all network traffic. For example, if nodes A, B, and C are connected to the same network, A may be able to hear the network data sent from B, but C may not. In this case, C is a "hidden node" opposite A. If C can hear the data from B, but not from A, then A is a hidden node to C

For optimum performance, it is desirable that a wireless local area network can also be connected to a wired local area network. In wireless local area networks operating with a base station, the base station may have this connectivity. However, there must be a system that has services between different networks between peer-to-peer wireless networks and a wired local area network.

There are several problems associated with the wireless network that make it difficult to implement a simple bridge as a means of connecting a wireless local area network to a wired local area network. The primary function of such a device would be to forward hardened network data of a wireless network intended for a wired node on the wired network, and vice versa. Depending on the selected wireless medium, each of these devices has a limited range. In order to ensure a sufficient coverage area, a large number of devices must have overlapping areas. Typically this would result in a duplication of the messages received from nodes within overlapping areas, as well as on the wired local area networks in messages originating from those nodes.

A system is needed that can solve these and similar problems.

The following terms are used in this specification: Services between different networks are called services that allow systems to communicate that could not be otherwise. Typical services between different networks include relaying messages from one wireless node to another, forwarding messages from a wired local area network to a wireless node, and relaying messages from a wireless node to a wired local area network.

The node between different networks that has these services between different networks is called access point (AP). The AP is a physical device capable of performing all of the tasks of a service between different networks via a wired network adapter, as well as a wireless network adapter.

The physical area in which a wireless node must be in order to be within range of the AP is called the Basic Service Area (BSA). If a wireless node is within the BSA of a particular AP, that wireless node is able to receive the transmissions sent by that AP.

Each wireless node also has a limited range within which it can communicate. This range is referred to as the Wireless Node Dynamic Service Area (DSA) in this specification. Other nodes in the DSA of a wireless node are usually capable of receiving transmissions of the wireless node.

If the wireless nodes use the same adapter as the APs, the nodes have the same range as the APs if all other things match. However, there may be differences between the AP's BSA range and the DSA range of a wireless node. First of all, wireless nodes are usually mobile. Therefore, their range may change depending on the obstacles their signals encounter while being moved. In addition, the access points physically connected to a wired local area network are also connected to a power source. Thus, the transmitter used in an AP may be stronger than the battery powered transmitters of a wireless node. In this case, the BSA range of an access point would normally be greater than the BSA range of a wireless node.

In this specification, a distinction is made between the BSA of an AP and the DSA of a wireless node, even if the two ranges should be identical. In this specification, it is assumed that a wireless node can "hear" a second wireless node when it is in the DSA of the second node, so that the signals transmitted by the second node can be received by the first node. Likewise, a wireless node may "hear" an AP when it is in the BSA of the AP, and an AP may "hear" a wireless node when the AP is in the DSA of the node. A "multicast" message is a type of broadcast that a wireless or wired node sends and that is directed to other nodes with the same specific group address. All other wired or wireless nodes ignore this message.

European Patent Application 0 483 544 discloses a communication process in which communication between mobile nodes has to take place via a controller. The mobile node only communicates with the controller. This is a master-slave system where the controller intercepts all communication with the mobile nodes. The controller retrieves the other systems present.

PCT patent application WO 92/19059 discloses another master-slave system in which the communication between mobile nodes has to take place via a controller. The retrieval of the other present stations is performed, and the polling station waits for the response.

Neither of the above two patents disclose a method or means for directly communicating a mobile node with another mobile node.

DISCLOSURE OF THE INVENTION

The invention has a method and means for providing services between different networks to wireless nodes. The invention has a node between different networks, who can either directly convey a message from one wireless node to the other wireless node or indirectly relay such message, by first sending it to another node between different networks, which in turn forwards them to the wireless destination node. The devices between different networks themselves can communicate with each other via the wireless medium. Such devices between different networks are connected as possible by means of a wired local area network.

From the user's point of view, the present invention creates a single logical local area network from a wireless node, such as a wireless local area network, and a wired local area network. The invention enables the integration of wireless nodes with existing wired local area network operating systems and network applications by each wireless node facing other wired network nodes as a wired network node as soon as a wireless node sends data packets to a wired network node. Similarly, in this invention, when a wireless node is part of a wireless local area network, a wired network node also appears to other wireless network nodes as a wireless network node as soon as the wired network node transmits data packets to the wireless node.

The invention has a method and means for using one or more APs as devices between different networks interconnecting a wired local area network and wireless nodes within range of the individual APs and for determining when each AP transmits data between them the wired local area network and wireless node.

The primary functions for each AP are i) the forwarding of data packets from a wireless node to the wired local area network, unless the data packets can reach their destination in any other way (eg if they are intended for a wired node or if they are for a wireless, outside the DSA of the originating node) and ii) forwarding the wireless node dedicated data packets from the wired local area network to the wireless node. In the selected embodiment, the wireless node is part of a wireless local area network. The AP, which has both a wired network adapter and a wireless network adapter, can communicate through both the wired media package delivery system and the wireless media package delivery system. Furthermore, the AP is able to convert a data packet from one system to another.

If possible, the APs will also forward information between two wireless nodes, both of which are within range of the AP, but hidden from each other's nodes. The invention enables this even when the AP is not connected to a wired local area network.

To perform these functions, each AP must be aware of whether a data packet has its destination within its BSA and whether it is responsible for performing the task. The wireless nodes use a method of association to transfer at most one of the APs performing the task. Each wireless node within range of at least one AP allocates itself to a single AP, even if it is within range of more than one AP. Once a node has been assigned to an AP, it will exclusively use that AP to transmit and receive data to and from a wireless node. The AP keeps track of which nodes have been assigned to it and then determines if it is responsible for completing a task.

Each wireless node monitors wireless network traffic and keeps track of which nodes are within its reach, that is, which nodes have recently been heard by it. According to the invention, each wireless node uses this information to determine which wireless nodes, including APs, are within its range.

Each AP sends information about itself to all other nodes as often as possible at regular intervals. In the selected embodiment, this broadcast is in the form of a location signal indicating the network address of the AP. Each wireless node can determine whether it is within the BSA of the AP or not through either the regular data transmissions of the AP or the said location signal. The wireless node tracks APs that it overheard. The node will, if possible, maintain a table of the APs it has recently heard.

If the wireless node is listening to data packets from an AP (either normal traffic or a location signal), it may try to associate with the AP by sending an assignment request to the AP. If the allocation request of a wireless node fails, it will first try to be assigned to another AP currently in its table. If the wireless node is listening to more than one AP or there are multiple APs in its table, the wireless node selects an AP. One embodiment would be for the mobile node to select the AP it most recently overheard.

When a wireless node (the sending node) is to send data packets to a particular node (destination node), it first checks to see if it has recently heard the destination node (assuming the destination node is within range). Each node may optionally issue location signals to assist the other nodes in performing this function.

If the destination node is within range, the sending node transmits the data packet directly to the destination node. If the dispatching node has not overheard the destination node before, the sending node checks to see if it is associated with an AP. Assuming that the sending node is assigned to an AP, the node transmits the data packet to the AP and prompts the AP to forward the data packet to the destination node.

As soon as an AP receives a request for forwarding a data packet from a sending node assigned to it, the AP checks whether the destination node is also assigned to it. If so, the AP transmits the data packet directly to the destination node. If this is not the case, the AP sends the data packet that is still destined for the destination node to the wired network again.

Whenever an AP overhears a data packet, in turn directed to the wired local area network, destined for a wireless node, it checks to see if that node is associated with it. If so, the AP forwards the data packet to the node. Otherwise, the AP ignores the data packet. Similarly, once an AP overhears a broadcast packet on the wired local area network; it transmits the packet to all its associated wireless nodes.

Thus, in the selected embodiment, each wireless node actively selects the AP to which it is assigned and determines whether to send messages using an AP. Each AP keeps track of which wireless nodes it is assigned to and automatically routes data packets addressed to its associated nodes and which the AP has received either over the wired local area network or from another associated wireless node.

An important aspect of the invention is a node for communication in a network, including wireless network adapter for sending data via wireless communication to other nodes in the network and for receiving data via wireless communication from these nodes, and means for monitoring data, which were received via the said wireless adapter, in order to identify, from said data, identification information for identifying the other network nodes, whose data was received, to extract and means for storing the identification information.

Another important aspect of the invention is a method of communication in the network, including transmitting data via wireless communication from a first node in the network to other nodes in the network and receiving data via wireless communication from these nodes and for monitoring data, that were received, in order to identify, from said data, identification information for identifying the other network nodes, whose data was received, to extract and store the identification information.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 schematically illustrates a configuration of wireless nodes around a wired local area network having two APs performing functions as nodes between different networks, with the dotted line DSA for each wireless node;

Figure 2 schematically illustrates the same configuration as in Figure 1, but with the BSA drawn for each AP;

Figure 3 shows schematically the same configuration as Figure 2, as well as the manner in which in the selected embodiment a message is passed from B to A, from A to D and from A to X;

Figure 4 schematically illustrates the same configuration as in Figure 1, as well as the manner in which node A travels from the BSA of AP1 to the BSA of AP2.

DETAILED DESCRIPTION OF THE INVENTION

The selected embodiment will be described and illustrated with reference to an example of its implementation by wireless local infrared (IR) networks and wired Ethernet networks. It should be appreciated that the invention is not limited to wireless IR networks or wired Ethernet networks and may similarly be practiced in other wireless local area networks and / or other wired local area networks.

Both FIG. 1 and FIG. 2 illustrate a configuration of the wireless nodes A, B, C, D and the wired local area network 50, the wired node X and the APs AP1 and AP2. Each AP is a physical device with a wired network adapter and a wireless network adapter. Each AP can read both the protocol of the wired local area network and that of the local area network.

In the selected embodiment, using the international standard terminology ISO / CCITT OSI, the AP behaves as a wire layer that acts as a bridge between the wireless local area network and the wired local area network. It sends data traffic from the wireless local area network to the wired local area network in such a way that the traffic for local area network nodes appears to originate from wired nodes of a wired local area network. It conversely sends traffic from the wired local area network to the wireless local area network in such a way that the traffic on the wireless local area networks appears to originate from wireless nodes of a wireless local area network. Thus, each AP operates as a transparent MAC bridge (where MAC stands for Medium Access Control), which connects the wireless IR nodes to the wired Ethernet network.

In the examples shown in the drawings, the same wireless adapter is used for both the APs and the wireless nodes. Therefore, the BSA of the APs, disregarding the effect of obstacles, and the DSAs of the wireless nodes are identical. As mentioned previously, the AP physically connected to a power source could have a stronger transmitter with an extended BSA range.

Figures 1 and 2 are identical except that Figure 1 illustrates the DSA ranges of the wireless nodes, while Figure 2 illustrates the BSA ranges of the APs. In FIG. 1, the wireless node A has a DSA 10, the wireless node B via a DSA 20, the wireless node C via a DSA 30, the wireless node D via a DSA 40, and the wireless node E via a DSA 45.

In the wireless local IR network, it can not be guaranteed that each network node that is part of the same wireless network can receive all network traffic. In Figure 1, the wireless node E can receive the network data sent from the network node B, but not the wireless node C, because the wireless network node E is within the DSA 20 of the Node B but outside the DSA 30 of the Node C. Similarly, C is a hidden node over E because C is outside DSA 45 of node E.

In some situations, a wireless node may be able to receive data from another wireless node, but not send it to that node. For example, a first node (not shown) would be able to listen to the network data sent by a second node (not shown) while that second node would not be able to receive the data sent from the first node. This situation is called asymmetry.

To compensate for potential errors in wireless transmission, wireless packet delivery systems typically require the receiving nodes to send a specific acknowledgment for each data packet. For example, when a wireless node A sends a data packet to the wireless node B, B sends back a data packet with acknowledgment for the message from A to A. These confirmations are typically not required by parcel delivery systems on wired local area networks due to the low error rate of transmissions using these media.

In Figure 2, the BSA of the AP1 is represented by the circle 60, the BSA of the AP2 by the circle 70. The wireless nodes A, B and E are within the BSA 60 of AP1. The wireless node B is located in the BSA 70 of the AP2, as is the wireless node D. The wireless node C is not within range of any of the APs.

It should be noted that due to the fact that node B is within range of both APs, the wired local area network would receive unwanted duplicate messages if both AP1 and AP2 sent a message from B back to the wired local area network as well Node B would receive unwanted duplicate messages if both AP1 and AP2 returned messages from the wired local area network to B.

To avoid such duplication, the invention provides a switching mechanism to ensure that no more than one AP performs functions for a particular wireless node by checking that each wireless node is not assigned more than one AP.

Each wireless node determines which AP (assuming more than one is within range) is assigned to it. Furthermore, each wireless node determines whether it can send a message directly to its destination node and requests the AP to forward the message if it does not. Each AP determines whether, in turn, a data packet is to be sent from the wired local area network to the wireless node for which the data packet is destined. Each AP monitors the traffic in the wired local area network to find the data packets destined for its associated wireless nodes (ie addressed). When the AP receives such a data packet on the wired local area network, it intercepts the data packet and transmits it to the mobile node.

Each wireless node must keep track of what the other nodes in its environment are doing in order to decide if it can send to it. Therefore, each wireless node monitors the wireless traffic and creates a table of the addresses of all the wireless nodes it has recently overheard. This table is called the DSA table. If one node has heard of another node, the address of the other node is in the DSA table and the first node assumes that it can send to the second node (ie Asymmetry is ignored, at least initially). This table contains all other nodes within whose DSA the monitoring node is located. It is assumed (ignoring asymmetry) that all nodes within the DSAS of the supervising node are listed.

In the selected embodiment, each wireless node relies on listened messages from nearby nodes (including all acknowledgments) to create its DSA table. Optionally, each node can issue location signals, which is automatically heard by all other nodes within its DSA.

Each wireless node also monitors network traffic to look for data packets sent by an AP

Ö were. In order to support wireless nodes (especially currently moving nodes) in the search for near APs, each AP in the selected embodiment of the invention outputs a location signal at regular intervals, eg every 20 seconds the wireless network address of the AP is specified. In the selected embodiment, each wireless node maintains a separate table, called an AP table, which lists the addresses of all APs that have been listened to. This table should preferably save other information, eg which AP last, most, least, etc. was heard. Alternatively, this information can also be stored as part of the DSA table. The wireless node may distinguish between data packets from APs and packets from other wireless nodes, as a portion of its wireless data packet control panel indicates whether a packet originated from an AP. Alternatively, each AP will have a unique network address with a common prefix to connect to one assigned to wireless local network. For example, the network address could be "IRAP001", where IRAP is a common prefix for all wireless network addresses for APs. Only wireless network nodes, which are also APs, are assigned this common prefix.

Each AP is also assigned a wired group network address for its connection to the wired local area network. The group address is used to send "multiple broadcasts". When a "multicast" message, a form of broadcast message, is sent to the AP's group network address in the wired local area network, only APs receive this message. All other wired network nodes ignore this message.

When a wireless node hears an AP, that AP is entered in its AP table. The node also determines which AP in its table it will be assigned to. The following examples of mapping can be cited: assignment with empty table (for example, if the wireless node has just been switched on, or just entered the environment of a wired local area network) or preserving the association with the current AP until the AP can no longer be heard or assigned to the most-owned AP, etc.

If the process indicates that the wireless node is to be assigned to the AP, the wireless node sends a data packet with a mapping request to the AP. If the data packet with the assignment request has been successfully sent to the AP, ie was acknowledged by the AP, the wireless node considered to be assigned to the AP. The association request contains the wireless network address of the wireless node. If possible, the request should also indicate to which AP, if available, the wireless node was previously assigned.

Each AP maintains a table called its Basic Service Set (BSS) table, listing all the wireless nodes associated with the AP. After the allocation request sent by the wireless node has been successfully received, the AP inserts the address of the network node into its BSS table. The AP may be configured to send a data packet to undo the assignment to the previous AP in the event of an indication by the allocation request via a previous assignment of the wireless network node to another AP via the wired local area network, so that it will return the old one Deletes assignment. Alternatively, the wireless node may also instruct the AP to send to the previous AP a request to clear the association once it is associated with the new AP.

Upon receipt of the data packet to undo by the new AP, the old AP deletes the address of the wireless network node from its BSS table.

Optionally, each AP may also maintain a separate BSA table, similar to the DSA table maintained by each wireless node, listing the node addresses of all wireless nodes within its BSA, whether or not they are associated with it.

A wireless node accepts only data packets sent by the AP to which it is associated; all data packets sent by other APs are deleted by him. Of course, it accepts data packets destined for it from other wireless nodes.

As already stated, the selection of which AP is assigned to which wireless node is determined by each individual wireless node. Therefore, each AP accepts all data packets originating from wireless nodes. When the AP receives a data packet directed to it from a wireless node that is not associated with it, the AP considers the data packet as an implicit association request. It adds the address of the wireless node to its BSS table and relays the data packet to the wired local area network.

If the sending of a data packet from a wireless node to its associated AP failed, ie the AP has not sent an acknowledgment of receipt for the data packet, the wireless node considers its wireless connection with the AP to be interrupted. He deletes his assignment to the AP. Then he uses his AP table to check if another AP is available. If so, he tries to get an association with this AP. If there are multiple APs, the wireless node selects the last-heard AP.

Conversely, if the sending of a data packet from the AP to the associated wireless node failed, the AP regards the wireless connection as broken and deletes the node from its BSS table.

During operation, when a wireless node (the sending node) is ready to send a data packet to another network node (destination node), it first determines if the node address of the destination node is in its DSA table. If so, this means that the destination node is another node within the DSA of the sending node. The sending node therefore sends the data packet directly to the other wireless node. If the destination node is not in the DSA table, the sending node sends the data packet to its associated AP and requests the AP to send the data packet to the destination node.

After receiving the data packet, the AP compares the destination of the data packet with its BSS table. If the destination node is in its BSS table (ie if the destination node is also assigned to the AP), the AP sends the data packet directly to the destination node via the wireless medium. Otherwise, the AP will in turn send the data packet to the wired network. If the destination node is another wired node, it receives the data packet directly. If the destination node is on another wireless network connected to the same wired network via another AP (ie the destination node is a wireless node assigned to another AP), the other AP mediates the data packet to that destination node.

Figure 3 illustrates three examples of the function of the selected embodiment. It is assumed that the wireless network node A is entering the BSA of AP1. Furthermore, it is assumed that A has not previously been assigned to any AP. When listening to the AP1 location signals or AP1 traffic to the wireless network node B, node A sends a data packet with an allocation request to AP1. After sending the data packet successfully with the allocation request has completed (ie the acknowledgment sent by AP1 was received), A considers itself assigned as AP1. After successfully receiving the data packet with the allocation request, AP1 adds the node to its BSS table. It also sends a data packet to delete the previous assignment to the wired local area network to notify an AP previously assigned to node A that node A is now assigned to AP1 and that the assignment to the previous node should be deleted. This can be done via the multicast function or via a data packet to the AP previously assigned to A.

It is assumed that A sends a data packet to the wired node X. A first checks his DSA table to see if X is a wireless node in range. Since X is not in the DSA of A, A sends the data packet to AP1 as shown by arrow 1 in FIG. AP1 then checks its BSS table to see if X is an associated node within its BSA. Since X is not listed as such in the table, AP 1 in turn sends the data packet to the wired local area network as indicated by arrow 105.

Furthermore, it is assumed that X sends back a data packet with a response to A after receiving the data packet. AP1 monitors the traffic of the wired local area network and listens to the data packet destined for node A, which in turn is in its BSS table. AP1 intercepts the data packet and sends it over the wireless medium to A.

In another example, it is assumed that the two nodes A and B are connected to AP1, ie that they are both listed in the BSS table of AP1, and that node B should send a data packet to A. Node B examines its DSA to see if A is within range. As shown in Figure 1, neither node B is in DSA 10 of node A, nor is node A in DSA 20 of node B. In other words, the nodes are hidden from each other even though they are both in range of AP 1. Direct wireless communication between the two nodes is therefore not possible. Therefore, B sends a data packet to AP1 to forward the data packet, as indicated by arrow 120 in FIG. AP1 checks its BSS table and finds that A is associated with it. Therefore, AP1 transmits the data packet to A via the wireless medium, as shown by arrow 125. It should be noted that node B is assigned to AP1, even if it is also in the BSA of AP2, and AP2 is therefore not prompted for forwarding.

In another example, it is assumed that node A sends a data packet to node D associated with AP2. Since node D is not in the DSA of node A, A sends the data packet to AP1 as shown by arrow 130. Since node D is not associated with AP1, AP1 in turn sends the packet to the wired local area network as indicated by arrow 130. AP2 listens to this data packet, determines that node D is associated with it, and in turn sends the data packet directly to D, as represented by arrow 140. Node B is in both the BSA of AP1 and AP2. If node B were associated with AP2 (and thus not AP1), and wireless node A sent a data packet to wireless node B, then AP1 would not transmit the data packet directly to node B, but instead send it to the wired local area network. In this case, AP2 would intercept the data packet and forward it to B (because B was in the BSS table of AP2) as it would do to node D.

Figure 4 illustrates how a traveling wireless node can enter and leave the BSAS of the various APs. When a wireless node travels between APs' BSAS, the assignment to one AP is cleared and made to another AP. The data packets sent from the wireless network node to the wired local area network are forwarded by different APs depending on the location of the wireless node and the AP associated with the wireless node. Similarly, the nodes destined for the wireless node are forwarded by different APs, depending on the location of the wireless node and the AP associated with the wireless node. This process is described below.

When a node moves, it may move out of range of all APs in its AP table. The wireless node is then disconnected from the wired local area network until it is within range of another AP and reassigns to the AP. Of course, a migrating node can not be assigned to an AP until it has taken note of the presence of such an AP (ie either the location signal of the AP or a regular transmission has heard). In order to shorten the time between the entry of the wireless node into the BSA of an AP and the detection of an AP, the AP may optionally broadcast its location signal earlier if it has detected a wireless node earlier. For this purpose, in addition to its BSS table, the AP maintains a BSA table as described above. Alternatively, these two tables are combined in an extended BSA table and form an additional column that records whether each listed node is associated with the AP. When an AP hears a wireless node that is not in the BSA table, the AP generates an unplanned beacon signal. The AP detects the existence of the wireless node by listening to a data packet, usually a broadcast packet sent by the wireless node. This broadcast packet is typically generated in response to the higher network layer network operating system trying to determine which other nodes are on the network. The result of this broadcast packet issued by a wireless network node is an early-planned location signal issued by the AP, which in turn initiates the association process.

For example, based on FIG. 4, it is assumed that the wireless node A was originally placed at position 200 and assigned to AP1. It therefore communicates with the wired local node via AP1. If A moves into an area where there is no AP, as shown at position 210, AP1 can not obtain acknowledgments for data packets it sends to X via AP1. He then does not consider himself assigned as AP1 because he can no longer communicate with AP1. When A enters the BSA of AP2, as shown at position 220, it recognizes the presence of AP2 either from the location signals or AP2 traffic. It is possible for AP2 to hear node A before it hears it. In this case, since AP2 would have heard node A at neither position 200 nor 210, AP2 may alternatively assume that node A has not previously been heard by it and will issue its locate signal early. In each of these cases, A initiates an assignment process for AP2. This will reconnect A to the network so that A can communicate with X again. If a whole area is equipped with enough APs, A can move throughout the area and stay connected to the network at the same time.