Patent Publication Number: US-8983468-B2

Title: Communications methods and apparatus using physical attachment point identifiers

Description:
FIELD OF THE INVENTION 
     This invention relates to communications system and, more particularly, to methods and apparatus for routing messages based on physical layer information in wireless, e.g., cellular, communications networks. 
     BACKGROUND OF INVENTION 
     The Open System Interconnection (OSI) reference model is useful in explaining various communications and routing operations. The OSI reference model includes 7 layers with the application layer being the top most layer and the Physical Layer being the lowest layer. The physical layer is the layer which deals with actual physical connections and attributes of the physical connections in the system. Above the physical layer is a Data Link layer, sometimes referred to as the link layer. The link layer (Layer  2  in the OSI model) is sometimes described as a technology specific transfer layer. Above the link layer is the network layer (OSI Layer  3 ) where network routing and relaying is supported. The network layer is sometimes referred to as the packet layer. It is at the network layer that routing of messages/packets through the network is performed, e.g., on one or more paths. Different addressing may be used for directing messages and signals at the different levels. For example, a network address such as an IP address, maybe used for routing messages/packets at the network layer level. MAC addresses maybe use for controlling routing of messages at the data link layer level. At the lowest level of the OSI model, the physical level, one or more physical identifiers have a relationship to an actual physical attribute or characteristic of a source or destination device. An understanding of the different communication layers and different addressing techniques used for each of the layers will facilitate an understanding of the present invention. 
     Communications systems frequently include a plurality of network nodes which are coupled to access nodes through which end nodes, e.g., mobile devices, are coupled to the network. Network nodes may be arranged in a hierarchy. End nodes typically communicate with access nodes directly through connections that have been established with said access nodes. Such systems usually rely on the existence of a bidirectional communications link between an access node and end not to support two way communications between an end node and an access node. Note that in such systems the end node normally does not know the network layer address of a target destination access node but may be cognizant of information that it can receive over broadcast channels which typically can include physical layer identifier that are normally not used in such systems for message routing. This approach results in handoff delays and packet loss when the end node is only able to maintain one single bidirectional communications link at the time. 
     It should then be appreciated that there is a need for methods and apparatus that allows an end node that has no current uplink communications link to a target access node to communicate with said target access node via another access node with which the end node has a current uplink communications link even when said end node does not know the network address of the target access node. 
     In some systems end nodes are capable of maintaining multiple bidirectional communications links with different access nodes at the same time. However, such systems typically require the end nodes to send messages intended for a specific access node, with which an end node has a connection, over the link that is directly connected to that specific access node. This approach, in some cases, is inefficient since links, especially when they are wireless links, tend to fluctuate in terms of quality (e.g., delay and loss characteristics). As a result the link to the target destination access node may not be the best link available to the end node at the time a message to said target destination access node needs to be sent. Typically this limitation is overcome by resorting to network layer communications that can be routed via multiple hops due to the use of network layer addresses (e.g., IP addresses). This approach of using network layer addresses is also inefficient especially when the messaging has to do with link layer specific functions, since network layer messages tend to be much larger than link layer messages in some systems. Such inefficient signaling is not well suited for communications over resource restricted air links. 
     It should then be appreciated that there is also a need for a method that allows an end node to send messages over any of its available wireless communications links independently of the access node the message is intended. It would be desirable is such messages could be sent, at least in some embodiments, without having to resort to inefficient network layer communications, e.g., communications involving the use of network layer addresses, such as IP layer addresses, for routing information to the destination access node. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to methods and apparatus for routing messages between an end node and an access node via another access node. The methods and apparatus of the invention support the use of physical layer identification information when identifying a remote, e.g., adjacent, access node as a message destination. Thus, when a connection identifier based on one or more physical layer identifiers is available to a wireless terminal, e.g., from one or more downlink signals received from a destination access node, the wireless terminal can use the connection identifier corresponding to the destination node to route a message via an access node with which it has an established uplink connection. Such connection identifier information can be used even when other addressing information, e.g., network layer address information, associated with the destination access node, may not be available to the wireless terminal. 
     Various novel features are directed to end node methods of receiving broadcast information from an access node and determining a physical attachment point identifier, for example a connection identifier corresponding to the access node. Other features are directed to the sending of signals to one access node including a connection identifier corresponding to another access node. The connection identifier is based on one or more pieces of information which provide information relating to a physical layer attachment point. Thus, in accordance with the invention physical layer information can be used as a connection identifier. 
     In accordance with the invention, access nodes store information mapping connection identifiers which are based on physical layer identification information to one or more higher level addresses. The mapping information is stored in the access nodes. Access nodes include mapping information for connections identifiers corresponding to physical layer attachment points which are local to the access node in addition to connection identifiers corresponding to physical layer attachment points of other, e.g., neighboring, access nodes. This allows routing between physically adjacent base stations to be performed based on physical layer connection identifiers without the need for a wireless terminal to transmit a link layer or network layer address over the air when sending a message which is to be delivered to a neighboring access node via an existing connection with an access node currently serving the wireless terminal. 
     Thus various features of the invention are directed to end node methods of receiving signals from access nodes indicating an identifier to access node address resolution failure and causing said end node to send neighbor notification messages for the establishment of new access node neighbors. 
     While some features are directed to wireless terminal methods and apparatus, as well as to novel messages of the invention stored in a wireless terminal, other features are directed to novel access node methods and apparatus. The invention is also directed to data storage devices, e.g., memory devices, which store one or more of the novel messages of the present invention. 
     While various embodiments have been discussed in the summary above, it should be appreciated that not necessarily all embodiments include the same features and some of the features described above are not necessary but can be desirable in some embodiments. Numerous additional features, embodiments and benefits of the present invention are discussed in the detailed description which follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a network diagram of an exemplary communications system implemented in accordance with the present invention. 
         FIG. 2  illustrates an exemplary end node implemented in accordance with the present invention. 
         FIG. 3  illustrates an exemplary access node implemented in accordance with the present invention. 
         FIG. 4  illustrates an exemplary Connection Identifier implemented according to this invention. 
         FIG. 5  illustrates an exemplary message using the Connection Identifier of  FIG. 4  implemented according to this invention. 
         FIG. 6  illustrates exemplary signaling performed in accordance with the present invention when an end node maintains a bidirectional connection to one access node and wants to communicate with another access node. 
         FIG. 7  illustrates exemplary signaling performed in accordance with the present invention when an end node maintains bidirectional connections with multiple access nodes. 
         FIG. 8  illustrates exemplary signaling performed in accordance with the present invention when an end node triggers a neighbor discovery process between two access nodes. 
         FIG. 9  illustrates an exemplary PID to higher level address resolution table which may be used for mapping between (to/from) PIDs and corresponding higher level addresses. 
     
    
    
     DETAILED DESCRIPTION 
     The methods and apparatus of the present invention for routing messages based on physical layer information, e.g., physical layer indentifiers, which can be used to support communications sessions with one or more end nodes, e.g., mobile devices. The method and apparatus of the invention can be used with a wide range of communications systems. For example the invention can be used with systems which support mobile communications devices such as notebook computers equipped with modems, PDAs, and a wide variety of other devices which support wireless interfaces in the interests of device mobility. 
       FIG. 1  illustrates an exemplary communication system  100  implemented in accordance with the present invention, e.g., a cellular communication network, which comprises a plurality of nodes interconnected by communications links. Exemplary communications system  100  is, e.g., a multiple access spread spectrum orthogonal frequency division multiplexing (OFDM) wireless communications system. Nodes in the exemplary communication system  100  exchange information using signals, e.g., messages, based on communication protocols, e.g., the Internet Protocol (IP). The communications links of the system  100  may be implemented, for example, using wires, fiber optic cables, and/or wireless communications techniques. The exemplary communication system  100  includes a plurality of end nodes  144 ,  146 ,  144 ′,  146 ′,  144 ″,  146 ″, which access the communication system via a plurality of access nodes  140 ,  140 ′,  140 ″. The end nodes  144 ,  146 ,  144 ′,  146 ′,  144 ″,  146 ″ may be, e.g., wireless communication devices or terminals, and the access nodes  140 ,  140 ′,  140 ″ may be, e.g., base stations. The base stations may be implemeneted as wireless access routers. The exemplary communication system  100  also includes a number of other nodes  104 ,  106 ,  110 , and  112 , used to provide interconnectivity or to provide specific services or functions. Specifically, the exemplary communication system  100  includes a Server  104 , used to support transfer and storage of state pertaining to end nodes. The Server node  104  may be, for example, an AAA server, or it may be a Context Transfer Server, or it may be a server including both AAA server functionality and Context Transfer server functionality. 
     The  FIG. 1  exemplary system  100  depicts a network  102  that includes the Server  104  and the node  106 , which are connected to an intermediate network node  110  by a corresponding network link  105  and  107 , respectively. The intermediate network node  110  in the network  102  also provides interconnectivity to network nodes that are external from the perspective of the network  102  via network link  111 . Network link  111  is connected to another intermediate network node  112 , which provides further connectivity to a plurality of access nodes  140 ,  140 ′,  140 ″ via network links  141 ,  141 ′,  141 ″, respectively. 
     Each access node  140 ,  140 ′,  140 ″ is depicted as providing connectivity to a plurality of N end nodes ( 144 ,  146 ), ( 144 ′,  146 ′), ( 144 ″,  146 ″), respectively, via corresponding access links ( 145 ,  147 ), ( 145 ′,  147 ′), ( 145 ″,  147 ″, respectively. In the exemplary communication system  100 , each access node  140 ,  140 ′,  140 ″ is depicted as using wireless technology, e.g., wireless access links, to provide access. A radio coverage area, e.g., communications cell,  148 ,  148 ′,  148 ″ of each access node  140 ,  140 ′,  140 ″, respectively, is illustrated as a circle surrounding the corresponding access node. 
     The exemplary communication system  100  is subsequently used as a basis for the description of various embodiments of the invention. Alternative embodiments of the invention include various network topologies, where the number and type of network nodes, the number and type of access nodes, the number and type of end nodes, the number and type of Servers and other Agents, the number and type of links, and the interconnectivity between nodes may differ from that of the exemplary communication system  100  depicted in  FIG. 1 . 
     In various embodiments of the present invention some of the functional entities depicted in  FIG. 1  may be omitted or combined. The location or placement of these functional entities in the network may also be varied. 
       FIG. 2  provides a detailed illustration of an exemplary end node  200 , e.g., wireless terminal such as a mobile node, implemented in accordance with the present invention. The exemplary end node  200 , depicted in  FIG. 2 , is a detailed representation of an apparatus that may be used as any one of the end nodes  144 ,  146 ,  144 ′,  146 ′,  144 ″,  146 ″, depicted in  FIG. 1 . In the  FIG. 2  embodiment, the end node  200  includes a processor  204 , a wireless communication interface  230 , a user input/output interface  240  and memory  210  coupled together by bus  206 . Accordingly, via bus  206  the various components of the end node  200  can exchange information, signals and data. The components  204 ,  206 ,  210 ,  230 ,  240  of the end node  200  are located inside a housing  202 . 
     The wireless communication interface  230  provides a mechanism by which the internal components of the end node  200  can send and receive signals to/from external devices and network nodes, e.g., access nodes. The wireless communication interface  230  includes, e.g., a receiver module  232  with a corresponding receiving antenna  236  and a transmitter module  234  with a corresponding transmitting antenna  238  used for coupling the end node  200  to other network nodes, e.g., via wireless communications channels. In some embodiments, the transmitter module  234  includes an orthogonal frequency division multiplexing (OFDM) transmitter. 
     The exemplary end node  200  also includes a user input device  242 , e.g., keypad, and a user output device  244 , e.g., display, which are coupled to bus  206  via the user input/output interface  240 . Thus, user input/output devices  242 ,  244  can exchange information, signals and data with other components of the end node  200  via user input/output interface  240  and bus  206 . The user input/output interface  240  and associated devices  242 ,  244  provide a mechanism by which a user can operate the end node  200  to accomplish various tasks. In particular, the user input device  242  and user output device  244  provide the functionality that allows a user to control the end node  200  and applications, e.g., modules, programs, routines and/or functions, that execute in the memory  210  of the end node  200 . 
     The processor  204  under control of various modules, e.g., routines, included in memory  210  controls operation of the end node  200  to perform various signaling and processing as discussed below. The modules included in memory  210  are executed on startup or as called by other modules. Modules may exchange data, information, and signals when executed. Modules may also share data and information when executed. In the  FIG. 2  embodiment, the memory  210  of end node  200  of the present invention includes a signaling/control module  212  and signaling/control data  214 . 
     The signaling/control module  212  controls processing relating to receiving and sending signals, e.g., messages, for management of state information storage, retrieval, and processing. Signaling/control data  214  includes state information, e.g., parameters, status and/or other information relating to operation of the end node. In particular, the signaling/control data  214  includes configuration information  216 , e.g., end node identification information, and operational information  218 , e.g., information about current processing state, status of pending responses, etc. The module  212  accesses and/or modify the data  214 , e.g., updating the configuration information  216  and/or the operational information  218 . 
     The message generation module  251  is responsible for generating messages for various operations of the end node  200 . Neighbor notification message  280  and signaling message  281  are exemplary messages generated according to this invention. 
     The link selection module  213  is responsible for selecting a link, e.g., the best link, from the plurality of links available to end node  200  for the transmission of the next message ready to be transmitted by end node  200 . The link selection algorithm is based on various link quality parameters including at least some of but not limited to link latency, link channel conditions, link error rate, and link transmission power requirements. 
     The physical layer attachment point identifier (PID) determination module  270  is responsible for determining the PID corresponding to broadcast signals received from an access node. The PID determination module  270  includes a cell identification module  271 , a carrier identification module  272 , and a sector identification module  273 . In some but not all embodiments, a combination of a cell identifier, carrier identifier and sector identifier are used as physical attachment point identifiers. Each of these identifier elements corresponds to physical layer identification information. For example, the cell identifier identifies a physical cell or cell type. The carrier identifier identifies the physical carrier, e.g, the carrier frequency or tone block while the sector identifier identifies a sector in a corresponding cell. Not all of this information need be used to implement a PID and the particular element of a PID may vary depending on the system implementation. For example, in a system which does not use sectorized cells there would be no need for a sector ID. Similarly, in a single carrier system there may be no need for a carrier ID. Making a PID determination, in one exemplary system, includes the steps of operating the cell identification module  271  for the determination of a cell identifier, operating the carrier identification module  272  for the determination of a carrier identifier and operating the sector identification module  273  for the determination of a sector identifier. Thus, it should be appreciated that different signals which pass through a single physical transmitter element, e.g., antenna, can correspond to different physical layer attachment points, e.g., where each of the different physical layer attachment points may be uniquely identified at least within a local area, by a combination of physical identifiers. For example, it should be appreciated that a combination of an antenna or sector identifier in combination with a first carrier identifier might be used to identify a first physical layer attachment point while a second carrier identifier in combination with the same antenna or sector identifier may be used to identify a second physical layer attachment point. 
     The physical layer attachment point identifiers (PIDs) information  260  is a list of PIDs, (PID 1   261 , PID 2   262 ) which are PIDs determined using the PID determination module  260 . One exemplary implementation of a physical layer attachment point identifiers (PDDs) may be a connection identifier (CID) which may be included in messages when sending and/or receiving messages. Particular exemplary CIDs are discussed further below. 
     Memory  210  also includes a neighbor notification module  290 , a message transmission control module  292 , and a link establishment module  294 . The neighbor notification module  290  is used for transmitting a neighbor notification, e.g., a neighbor notification message  280 , to access nodes. Message transmission control module  292  is used for controlling the transmitter module  234 . Link establishment module  294  is used for establishing a wireless communications links with access nodes. 
       FIG. 3  provides a detailed illustration of an exemplary access node  300  implemented in accordance with the present invention. The exemplary access node  300 , depicted in  FIG. 3 , is a detailed representation of an apparatus that may be used as any one of the access nodes  140 ,  140 ′,  140 ″ depicted in  FIG. 1 . In the  FIG. 3  embodiment, the access node  300  includes a processor  304 , memory  310 , a network/internetwork interface  320  and a wireless communication interface  330 , coupled together by bus  306 . Accordingly, via bus  306  the various components of the access node  300  can exchange information, signals and data. The components  304 ,  306 ,  310 ,  320 ,  330  of the access node  300  are located inside a housing  302 . 
     The network/internetwork interface  320  provides a mechanism by which the internal components of the access node  300  can send and receive signals to/from external devices and network nodes. The network/internetwork interface  320  includes, a receiver module  322  and a transmitter module  324  used for coupling the node  300  to other network nodes, e.g., via copper wires or fiber optic lines. The wireless communication interface  330  also provides a mechanism by which the internal components of the access node  300  can send and receive signals to/from external devices and network nodes, e.g., end nodes. The wireless communication interface  330  includes, e.g., a receiver module  332  with a corresponding receiving antenna  336  and a transmitter module  334  with a corresponding transmitting antenna  338 . The interface  330  is used for coupling the access node  300  to other network nodes, e.g., via wireless communication channels. 
     The processor  304  under control of various modules, e.g., routines, included in memory  310  controls operation of the access node  300  to perform various signaling and processing. The modules included in memory  310  are executed on startup or as called by other modules that may be present in memory  310 . Modules may exchange data, information, and signals when executed. Modules may also share data and information when executed. 
     In the  FIG. 3  embodiment, the memory  310  of the access node  300  of the present invention includes a signal generation module  314  for the generation of signals, a packet routing module  350  responsible for the routing of signals and messages, a mapping module  312  that is responsible for mapping PIDs to network layer addresses, an address resolution table  311  including PID to IP address mappings  317 . Memory  310  also includes an end node identification module  351  identifying end nodes with which the access node  300  is in communications with, uplink resource allocation information  340  responsible for allocating uplink resources to end nodes, including resources allocated to an end node X  341  and, downlink resource allocation information  345  responsible for allocating downlink resources to end nodes, including resources allocated to an end node X  346 . 
     Referring now briefly to  FIG. 9 ,  FIG. 9  illustrates an address resolution table  311 ′ which may be used as the address resolution table  311  shown in  FIG. 3 . The address resolution table  311 ′ includes PIDs  902 ,  904 ,  906 ,  908 ,  910 ,  912  and information indicating the corresponding IP addresses  903 ,  905 ,  907 ,  909 ,  911  and  913 , respectively. The PIDs are each unique locally, e.g., the PIDS of immediately adjacent cells are unique from one another. Note that the content of the PIDs may vary depending on the physical characteristics of the access node and number of physical layer attachment points supported by the access node to which the PID corresponds. In the  FIG. 9  example, PIDs  902 ,  904  correspond to a first access node (AN  1 ) which supports two sectors which use the same carrier. Accordingly, in the case of AN  1 , it is sufficient for the PID to include a cell identifier and a sector type identifier to uniquely identify the physical layer attachment points in the cell. PIDs  906 ,  908 ,  910  correspond to a cell which supports multiple carriers and multiple sectors. Accordingly, the PIDs for access node  2  are implemented as CIDs in the same manner as used in various exemplary embodiments discussed further herein. PID  912  corresponds to a third access node which includes a single sector and uses a single carrier. Accordingly, it is sufficient for PID  6  which corresponds to the third access node to include just a cell identifier although additional physical layer identification, e.g., a sector and/or carrier identifier. The inclusion of such additional information may be desirable where, from a processing perspective, consistent PID formats across multiple cells is desirable. 
     Referring now to  FIG. 4 ,  FIG. 4  illustrates an exemplary Connection IDentifier (CID)  400  implemented according to this invention. CID  400  includes a Slope  410 , which is a cell Identifier, a Sector  420  which is a Sector Identifier and a Carrier  430 , which is a carrier frequency identifier also known as tone block identifier. 
     In an exemplary communication system using OFDM technology, in the physical layer, the spectrum is divided into a number of tones and reused in cells and sectors in neighboring geographical areas. In order to improve the interference characteristics, the tones used in each cell/sector hop over time, and different cells and sectors in neighboring geographical areas use different hopping sequences, which specify how the tones shall hop. The hopping sequences are generated using a predetermined function controlled with two input variables, namely, the cell identifier, e.g., slope value, and a sector identifier. The sector identifier may be implemented as a sector type identifier that indicates which of a plurality of possible sector types a particular sector corresponds to. In one embodiment, the slope value is an integer from 1 to 112, and the sector identifier value is an integer from 0 to 5. Neighboring cells and sectors use different pairs of slope and sector identifier so that the generated hopping sequences are different. In one embodiment, all the sectors in a cell use the same slope value but different sector identifiers, and neighboring, e.g., physically adjacent, cells use different slope values. 
     Furthermore, the exemplary OFDM communication system, in some embodiments, uses multiple carriers or tone blocks, so that the available tones are grouped into multiple tone blocks. Tones in a tone block are preferably contiguous. In one exemplary system, hopping of the tones in a given tone block is limited to that tone block. That is, the hopping sequences are such that the tones can hop within the tone block but cannot hop across multiple tone blocks. Tone blocks are indexed with a carrier identifier. In one embodiment, the carrier identifier is an integer 0, 1, or 2. 
     When an end node sets up a connection to get wireless networking services, the entity on the network side is an access node, e.g., a base station in a cell/sector, and the connection is defined with respect to a single tone block. Therefore, in the above exemplary OFDM communication system, a combination of slope, sector identifier and carrier identifier can be used as a locally unique identifier that identifies the connection for the wireless terminal. The combination is thus a connection identifier based on one or more physical layer identifiers. In one embodiment, multiple wireless terminals can have connections with the same base station cell/sector on the same tone block. Those connections normally will share the same connection identifier since they are connected to the same physical layer attachment point as defined by the combination of cell, sector and tone block. The combination of the connecting identifier and a wireless terminal identifier can be used to indicate a communication connection with a particular wireless terminal. 
     In general, the connection identifier is a number or a combination of numbers that locally uniquely identifies a connection. In various embodiments, the number or numbers are physical layer characteristic parameters. In another embodiment, e.g., an exemplary embodiment of a CDMA communication system, the connection identifier can be the combination of a pseudo noise (PN) sequence offset and another parameter, e.g., a carrier identifier if multiple carriers are used. 
       FIG. 5  illustrates an exemplary message  500 , in accordance with the present invention, which uses the Connection Identifier of  FIG. 4 . Exemplary message  500  is a link layer message which includes a CID destination/source address. The CID destination/source address is an optional field in link layer messages in accordance with some embodiments of the present invention. Link layer message  500  includes a Link Layer Control (LLC) Type field  510  identifying the type of Message Body  530  included in the message  500 . CID  520  is a Connection ID in the form of the Connection ID  400  of  FIG. 4 . In one embodiment of this invention the CID field  520  identifies a destination physical attachment point when sent from an end node to an access node in accordance with the invention and identifies a source physical attachment when sent from an access node to an end node in accordance with the invention. 
       FIG. 6  illustrates an exemplary communications method and corresponding signaling performed in accordance with various exemplary embodiments of the invention. In  FIG. 6  end node  630  communicates with access node  620  via access node  610  without a wireless uplink link between end node  630  and access node  620  and without the end node having to know an IP address of the access node  620 . The signaling is illustrated in the context of exemplary system  100  illustrated in  FIG. 1 . Access Nodes  610  and  620  are similar to access nodes  140 ,  140 ′ and  140 ″ of system  100  in  FIG. 1  and they are implemented according to the access node  300  of  FIG. 3 . The End Node  630  is similar to end node  144 ,  146 ,  144 ′,  146 ′,  144 ″ and  146 ″ of system  100  in  FIG. 1 , and it is implemented according to end node  200  in  FIG. 2 . 
     In  FIG. 6 , end node  630  maintains a bidirectional link with access node  610 , which means that it can send messages to and receive message from access node  610 . End node  630  in  FIG. 6 , although inside the transmission range of access node  620 , does not have an uplink with access node  620 . This means that while end node  630  can receive and process broadcast information sent by access node  620  (e.g., broadcast messages  640 ), end node  630  can not send messages to access node  620  over the air and access node  620  can not receive and process messages sent to it by end node  630  over the air interface. In one embodiment of this invention this may be because end node  630  and access node  620  do not have sufficient timing synchronization. Due to certain limitations, e.g., limited hardware capability, end node  630  may not be able to establish an uplink connection with access node  620  while end node  630  currently has a bidirectional connection with access node  610 . In one embodiment, the uplinks used by access node  610  and access node  620  are in different carriers, e.g., the frequency band of the uplink used by access node  610  is different from the frequency band of the uplink used by access node  620 . If end node  630  can only generate uplink signal in one band at a given time, for example, because end node  630  only has one radio frequency (RF) chain due to cost considerations, then end node  630  cannot simultaneously maintain two uplink connections in two separate frequency bands. In another embodiment where the uplinks used by access nodes  610  and  620  are in the same band, the two uplinks may not be time synchronized, because the two access nodes are not time synchronized or because of the difference in the propagation delay for the signal to reach access nodes  610  and  620  from the end node  630 . If end node  630  can generate just one uplink signal according to one timing synchronization scheme at a time, for example, because end node  630  has a single digital processing chain limited to one timing scheme at a time, then end node  630  cannot simultaneously maintain two uplink connections, when the connections are not sufficiently timing synchronized with one another. 
     End node  630  receives broadcast signal(s)  640  which are transmitted by access node  620 . The signal(s)  640 , according to the embodiment of this invention, are sufficient to determine the Connection ID, similar to CID  400  of  FIG. 4 , corresponding to the specific physical attachment of access node  620  that transmits broadcast signal  640 . The signals or signals  640  may include beacon and/or pilot signals which may be transmitted over one or more symbol transmission time periods. 
     End node  630  transmits a message  650  to access node  610 . In an exemplary embodiment of this invention, said message  650  is the same as, or similar to, exemplary message  500  of  FIG. 5 . The CID field, equivalent to CID  520  of  FIG. 5 , of said message  650  is set to the connection identifier that identifies the physical attachment point of access node  620  that broadcasted signal  640 . Said message  650  is thus destined for access node  620  although it is sent to access node  610 . Note that since end node  630 , in the  FIG. 6  example, does not have an uplink with access node  620  it can not send message  650  directly to said access node  620 . 
     Access node  610  receives message  650  and examines the CID field, corresponding to CID  520  of  FIG. 5 , of message  650  and realizes, from the stored CID to link layer identification information that it does not identify one of its own physical attachment points. In such a case, access node  610  searches its memory for said CID of message  650  to find a mapping to a corresponding higher layer identifier for access node  620  (e.g., an IP address). 
     For example, a base station which includes multiple sectors operating under a single link layer controller and/or multiple carriers used under a single link layer controller may have multiple CIDs corresponding to a link layer identifier corresponding to a single link layer controller. In embodiments where separate link layer controllers are used for each sector and/or carrier, different link layer identifiers may be used for each for the different sector and/or carriers. In some embodiments, there is a one to one mapping between physical attachment points and link layers but this is not necessary and there may be several physical attachment points operating under a single link layer. Thus, multiple physical layer identifiers may correspond to the same link layer link identifier but each physical layer identifier connection identifier normally maps to, at most, a single link layer link identifier. 
     Assuming a mapping to a higher layer address is found, access node  610  encapsulates at least part of message  650  into a network layer message  660  which includes a destination address set to the identifier of access node  620  and transmits said message  660  to access node  620 . According to this invention message  660  also includes an end node  630  identifier, said identifier being, depending on the embodiment, one of an end node  630  IP address, end node  630  Network Access Identifier (NAI) and a temporary identifier. Access node  620  receives said message  660  and extracts the encapsulated part of message  650  from it. Access node  620  inspects the CID field of the extracted encapsulated part of message  650  and recognizes that the CID field identifies one of its own physical attachments points. 
     Access node  620  sends message  670  which includes at least part of message  650  received encapsulated in message  660  by access node  620 . Said message  670  also includes an end node  630  identifier similar to the one included in message  660 . Access node  610  then receives message  670  and by examining the end node identifier included determines that the message  670  encapsulates a message  680  destined to end node  630 . Access node  610  then sends message  680  which includes at least part of the message  670 . According to this invention message  680  includes the CID of the physical attachment point of access node  620  that broadcasts signal  640 . 
     End node  630  receives message  680  from access node  610  but by examining the CID field included in said message  680 , e.g., by comparing it to stored CID information, it determines that message  680  is originated from access node  620  in response to message  650  sent to it earlier. 
       FIG. 7  illustrates exemplary signaling performed in accordance with various embodiments of the invention. The signaling is illustrated in the context of exemplary system  100  illustrated in  FIG. 1 . End node  710  is a simplified depiction of end node  200  of  FIG. 2  and it is the same as, or similar to, to the end nodes  144 ,  146 ,  144 ′,  146 ′,  144 ″,  146 ″ of system  100  in  FIG. 1 . Access Nodes  740  and  750  are similar to access nodes  140 ,  140 ′ and  140 ″ of system  100  in  FIG. 1  and they are implemented using access node  300  of  FIG. 3 . In  FIG. 7 , end node  710  includes a message generation module  720  and a link selection module  730 . The message generation module  720  of  FIG. 7 , can be used by applications running in end node  710  to generate messages for their purposes. For example a connection control protocol application maybe included and active in end node  710  allowing the end node  710  to communicate with access nodes for the purpose of creating, disconnecting and/or modifying links between end node  710  and one or both of access nodes  740 ,  750 . Another example is a quality of service (QoS) application which may be included in end node  710 . The QOS application when present can modify QoS characteristics of the various links of end node  710 . Link selection module  730  of  FIG. 7  measures various metrics for the quality of connections including link latency, link channel conditions, link error rate, and link transmission power requirements to determine, e.g., on a message by message basis or at a particular point in time, which of the available links is the most appropriate for the transmission of the next message. 
     The resulting link quality information can, and in various embodiments is, used to determine which of the plurality of simultaneous links to which a message should be transmitted at a particular point in time. 
     In  FIG. 7 , end node  710  maintains bidirectional links with access nodes  740  and  750 , which means that it can send messages to and received message from access node  740  and  750 . In this embodiment of the invention the message generation module  720  of end node  710  generates message  759  with ultimate destination access node  740 . Message  759  is first sent in link selection module  730  of end node  710 . Link selection module  730  selects the link between the links to access nodes  740  and  750  over which the next message is to be transmitted. The link determination function is based on link characteristics including at least one of link latency, link channel conditions, link error rate, and link transmission power requirements. 
     In the exemplary embodiment of this invention depicted in  FIG. 7 , the link selection module  730  selects the link to access node  740  and transmits message  760  over it. Message  760  includes at least some part of message  759  and, in some embodiment of the invention, includes additional fields used for the transmission of a message over the link between end node  710  and access node  740 . For example, the additional fields are, in some embodiments, link framing fields. Since the ultimate destination of message  759  and  760  is access node  740 , access node  740  receives message  760 , processes the received message and responds, e.g., by transmitting message  765  to end node  710 . Message  765  is received by end node  710  and delivered to the message generation module as message  766 . Message generation module  720 , generates a second message  769  with the ultimate destination being the access node  740 . Message  769  is sent to link selection module  730  which selects the link over which message  769  is to be transmitted. In this embodiment of the invention the link to access node  750  is selected and message  770  is transmitted to access node  750 . Message  770  includes at least a part of message  769  and in some embodiments of this invention includes additional fields used for the transmission of the message over the link between end node  710  and  750 . For example, the additional fields are, in some embodiments link framing fields. 
     In one embodiment of this invention the link selection module  730  adds an identifier,e.g., a physical attachment point identifier, of access node  740  together with at least a part of message  769  in comprising message  770 , because the link selected by link selection module  730  for the transmission of message  770  does not correspond to the ultimate destination of message  770 , which is access node  740 . In another embodiment of this invention the link selection module adds the identifier of the ultimate destination of message  760  and  770  before it transmits said messages  760  and  770 , independently from which link is selected for their transmission. In a further embodiment of this invention messages  759 ,  769  include the identifier of their ultimate destination. For example in an example of the exemplary embodiment of  FIG. 7  the identifier of the ultimate destination corresponds to access node  740 . 
     In one exemplary embodiment of this invention, message  770  is implemented according to message  500  of  FIG. 5 , where CID field  520  identifies access node  740 . Access node  750 , receives message  770  and processes it. By examining the ultimate destination of message  770 , e.g., a physical attachment point identifier in the CID field  520  of message  500  of  FIG. 5 , access node  750  determines that message  770  is not intended for itself but for some other node identified by the ultimate destination identifier (e.g., a CID in the CID field). The Access node  750  looks up the physical attachment point identifier (PID) included in message  770  in its address resolution table (see address resolution table  311  in access node  300  of  FIG. 3 ) to find the network address (e.g., IP Address) corresponding to the PID included in message  770 . 
     Access node  750  encapsulates at least a part of message  770  in an appropriate network layer header and transmits message  775  to access node  740 . Message  775  includes at least: a part of message  770 , and at least some of the IP address of access node  740 . In addition the message  775  may ad in various embodiments does include some or all of the following: the IP address of access node  750 , the PID of access node  740  included in message  770 , the PID of access node  750  over which message  770  was received, end node  710  identifier and session identifiers for the encapsulation (also called tunneling) of messages between access node  750  and access node  740 . Access Node  740  receives message  775  which it recognizes as a message intended for itself from the destination PID included in message  775 . 
     In one embodiment of this invention access node  740  responds by transmitting message  780  which includes at least part of message  775 . Access node  750  receives message  780 , which includes end node  710  identifier and sends message  785  to end node  710 . Message  785  includes at least part of message  780 . End node  710  receives message  785  and forwards message  786  to message generation module  720 . 
     In another embodiment of this invention access node  740  responds by transmitting, to endnote  710 , message  780 ′ including at least part of message  775 . Message  780 ′ is transmitted over the direct link between access node  740  and end node  710 . 
       FIG. 8  illustrates exemplary signaling performed in accordance with exemplary embodiments of the invention where an end node is used as part of a neighbor discovery and CID routing information update process. The signaling is illustrated in the context of an exemplary system such as the system  100  illustrated in  FIG. 1 . End node  810  is a simplified depiction of end node  200  of  FIG. 2  and it is the same as or similar to the end nodes  144 ,  146 ,  144 ′,  146 ′,  144 ″,  146 ″ of system  100  in  FIG. 1 . Access Nodes  840  and  850  are the same as or similar to access nodes  140 ,  140 ′ and  140 ″ of system  100  in  FIG. 1  and they may be implemented, e.g., using access nodes of the type illustrated in  FIG. 3 . In the  FIG. 8  example end node  810  has a bidirectional communications link with access node  840 , allowing it to send messages to, and receive message from access node  840 . 
     In  FIG. 8 , end node  810  generates and transmits message  860  to access node  840 . Message  860  includes an identifier that identifies access node  850  as the destination of said message. Access node  840  receives message  860  and attempts to resolve the access node  850  identifier included in said message to a network address, by searching its address resolution table, e.g., address resolution table  311  of access node  300  of  FIG. 3 . In the  FIG. 8  example access node  840  fails to resolve said identifier. Access node  840  then transmits message  865  to end node  810 . Message  865  includes an indication that routing of a message was not possible due to a resolution failure. 
     In one embodiment of this invention end node  810  at this point establishes a bidirectional communications link with access node  850  by exchanging a variety of messages shown as double arrowed message  870  in  FIG. 8 . However, this is not necessary if a bidirectional link already exists with access node  850 . In another example in which the invention is used, end node  810  already has a bidirectional link with access node  850  in addition to the link with access node  840  Using the link with access node  850 , the end node  810  transmits a new neighbor notification message  875  to access node  850 . Message  875  includes at least an identifier of access node  840  and the network layer address of access node  840 . In this way, the access node  850  is supplied with both an identifier, e.g., PID of access node  840  and a corresponding link layer address, e.g., MAC address which the access node  850  can address and store for future resolution of physical layer to network layer identifier. In one embodiment of this invention the access node  840  identifier is a physical attachment point identifier; in another embodiment of this invention it is a link layer identifier. The network layer identifier of access node  840  is known to end node  810  from communication messages  897  communicated to end node  810  during or after the establishment of the link with access node  840 . 
     In an alternative embodiment of this invention end node  810  sends message  875 ′ instead of message  875 . Message  875 ′ has the same or similar message content to message  875  but is sent to access node  850  via access node  840 , instead of access node  850  directly. Access node  840  then routes message  875 ′ as message  875 ″ to access node  850 . Note that unlike message  860 , message  875 ′ is a network layer message including the access node  850  network address as its destination. The network address of access node  850  is known to end node  810  from communication messages  899  communicated during or after the establishment of the link with access node  850 . For this reason, access node  840  can route message  875 ″ to access node  850  using a network address of access node  850  e.g., IP address, without having to perform a CID to address resolution operation. 
     Access node  850  receives message  875  and sends new neighbor creation message  880  to the network address of access node  840 , retrieved from message  875 . Message  880  includes connection identifier to network layer address mappings for access node  850 . In another embodiment of this invention, message  880  includes link layer identifiers to network layer address mappings for access node  850 . In another embodiment of this invention message  880  includes additional neighbor information used for the accommodation of end node handoffs, including but not limited to tunnel address and tunnel session identifiers for packet redirection between access nodes  840  and  850 , access node  850  capabilities with respect to quality of service, loading, protocols, and applications supported. Access node  840  receives message  880  and stores information included in message  880  in its memory e.g., for future use in CID to network address resolution operations. Access node  840  responds with message  882  acknowledging the reception of said information included in message  880 . 
     In one embodiment of this invention access node  840  includes in message  882  some of connection identifier to network layer address mappings for access node  850 , link layer identifiers to network layer address mappings for access node  850 , neighbor information used for the accommodation of end node handoffs, including but not limited to tunnel address and tunnel session identifiers for packet redirection between access nodes  840  and  850 , and or information indicating capabilities of access node  840  with respect to quality of service, loading, protocols, and applications supported. Access node  840  receives message  880  and stores information included in message  880  in its memory, or e.g., for future use in routing messages. In this particular embodiment of the invention messages  883  and  884  are not used. 
     In another embodiment of this invention access node  840  message  882  includes an acknowledgement of the reception of the information included in message  880 . In this embodiment of the invention access node  840  sends message  883  including at least some of connection identifier to network layer address mappings for access node  850 , link layer identifiers to network layer address mappings for access node  850 , neighbor information used for the accommodation of end node handoffs, including but not limited to tunnel address and tunnel session identifiers for packet redirection between access nodes  840  and  850 , access node  840  capabilities with respect to quality of service, loading, protocols, and applications supported. Access node  850  receives message  883  and stores the information included in message  883  in its memory, e.g., for future use. Access node  850  responds with message  884  acknowledging the reception of said information. 
     Following the exchanges of neighboring information and identifier to address mappings between access node  840  and  850  via message  880 ,  882  and optionally  883  and  884 , end node  810  sends message  890  to access node  840 . Like message  860 , in one embodiment of the invention message  890  is also the same as or similar to message  500  of  FIG. 5 . Message  890  identifies as its ultimate destination access node  850 . Access node  840 , receives message  890 , searches its memory for a mapping between the access node  850  identifier and a network address for said node  850  and finds said network address in its address resolution table which was earlier populated by message  880 . Access node  840  encapsulates message  890  according to information in the resolution table and sends it to access node  850  in the form of message  891 . Access node  850  responds with message  892  again using information in its address resolution table and message  891 . Access node  840  sends message  893  to end node  810  including at least part of message  892  received from access node  850  completing the communication exchange between end node  810  and access node  850  via access node  840 . 
     In the above described manner, through the use of messages from end node  810 , access nodes  840  and  850  are provided with address and/or PID information about each other that can be used in routing subsequently received messages. Accordingly, as access nodes are added to the network, end nodes can serve to discover their presence from broadcast signals and notify access nodes of new neighbors. As part of the notification process sufficient address information is distributed to facilitate network PID based routing of messages after the notification process has been completed. 
     In various embodiments nodes described herein are implemented using one or more modules to perform the steps corresponding to one or more methods of the present invention, for example, signal processing, message generation and/or transmission steps. Thus, in some embodiments various features of the present invention are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions, such as software, included in a machine readable medium such as a memory device, e.g., RAM, floppy disk, etc. to control a machine, e.g., general purpose computer with or without additional hardware, to implement all or portions of the above described methods, e.g., in one or more nodes. Accordingly, among other things, the present invention is directed to a machine-readable medium including machine executable instructions for causing a machine, e.g., processor and associated hardware, to perform one or more of the steps of the above-described method(s). 
     Numerous additional variations on the methods and apparatus of the present invention described above will be apparent to those skilled in the art in view of the above description of the invention. Such variations are to be considered within the scope of the invention. The methods and apparatus of the present invention may be, and in various embodiments are, used with CDMA, orthogonal frequency division multiplexing (OFDM), or various other types of communications techniques which may be used to provide wireless communications links between access nodes and mobile nodes. In some embodiments the access nodes are implemented as base stations which establish communications links with mobile nodes using OFDM and/or CDMA. In various embodiments the mobile nodes are implemented as notebook computers, personal data assistants (PDAs), or other portable devices including receiver/transmitter circuits and logic and/or routines, for implementing the methods of the present invention.