Abstract:
A method and apparatus for communicating slot allocations of nodes in a wireless mesh network that has data exchanges between the nodes occurring during slots. Each node maintains internal tracking of its slot allocation. A node may request a slot allocation of another node, and each node is enabled to report its slot allocation to other nodes. An information element (IE) and management type messages are introduced for tracking and reporting slot allocations among mesh network nodes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/720,580 filed Sep. 26, 2005, which is incorporated by reference as if fully set forth. 
    
    
     FIELD OF INVENTION 
     The present invention is related to a wireless mesh network, (e.g., a wireless local area network (WLAN) mesh), including a plurality of nodes. More particularly, the present invention is related to the sharing of slot allocation schedule information amongst the nodes of a mesh network. 
     BACKGROUND 
     In an IEEE 802.11 mesh network, (e.g., a WLAN mesh), two or more nodes exchange data during periods called slots. The term “slot” implies multi-dimensional information, which may include, but is not limited to, timing information, (e.g., starting time and duration), radio frequency (RF) information, (e.g., the radio and the number of channels used by the node to exchange data), quality of service (QoS) information, (e.g., the QoS required by the data to be exchanged during the slot), peer node information, (e.g., the node identifiers for each node involved in the transmission of data during a particular slot), direction of data exchange, (e.g., unidirectional, bidirectional), or the like. 
     In conventional non-mesh WLANs, optional “scheduling” based on 802.11e HCCA is a one-sided procedure controlled by an AP in a basic service set (BSS). In a WLAN mesh, scheduling should be coordinated among the multiplicity of Mesh Points (MPs) that are providing WLAN mesh services. 
     It would be desirable to incorporate a mechanism in the nodes of a mesh network which allows the nodes to report information regarding their internal slot allocation schedule and to request such schedule information from other nodes. In order to accomplish this new level of coordination, a method and apparatus for exchanging schedule-related information among mesh points in a WLAN mesh is needed. 
     SUMMARY 
     In an IEEE 802.11 mesh network where traffic between nodes is scheduled into allocated slots, an efficient slot allocation across multiple nodes is achieved by allowing the nodes to share their own slot allocation schedule information amongst each other. This provides each node with advance knowledge of the slot availability of other nodes and thereby enables nodes to allocate slot resources in an efficient and non-conflicting manner. 
     The present invention provides a mechanism which allows nodes in a mesh network to report their internal slot allocation schedule to other nodes in the network, and provides a mechanism which allows nodes in the mesh network to request the internal slot allocation schedule the other nodes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more detailed understanding of the invention may be had from the following description, given by way of example and to be understood in conjunction with the accompanying drawings wherein: 
         FIG. 1  shows an information element format for slot allocation; 
         FIG. 2  shows an enhanced information element format according to the present invention; and 
         FIG. 3  shows an exemplary mesh network including two nodes which are configured in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     When referred to hereafter, a node includes but is not limited to a wireless transmit/receive unit (WTRU), a user equipment (UE), a mobile station, a fixed or mobile base station, a fixed or mobile access point (AP), a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. 
     Within a mesh network, each node internally keeps track of the slots it has allocated after previous and mutual agreement with one or more peer nodes. During a particular slot, the node sends and receives data to/from these peer nodes. The internal tracking record is referred hereafter as a “list of allocated slots” and comprises a list of slots. Each node includes an internal memory which stores a list of its allocated slots. 
     A new information element (IE)  100  is required to represent the list of allocated slots.  FIG. 1  shows the preferred format for an IE  100  in accordance with the present invention. The IE  100  includes a one octet element ID field  105 , a one octet length field  110 , and a variable-length element-specific information field  115 . In accordance with the present invention, the ID field  105  indicates that the IE  100  represents a “list of allocated slots” IE. The length field  110  specifies the number of octets in the information field  115 . 
       FIG. 2  shows the new IE  100  in greater detail with respect to the information field  115 . The information field  115  of the list of allocated slots IE  100  comprises a list size subfield  205 , a plurality of information subfields for each slot  210   1 ,  210   2 , . . . ,  210   N , and a slot number list size subfield  215 . Each slot information subfield  210  comprises a timing information field  220 , a radio frequency (RF) information field  225 , a quality of service (QoS) information field  230 , a peer nodes information field  235 , and a direction field  240 . As shown in  FIG. 2 , the subfields shown in greater detail are with respect to slot # 1 . As such, the slot  1  timing information field  220  indicates a starting time and duration of the data exchange for slot # 1 . The RF information field  225  indicates the radio channel and the number of channels used by the node to exchange data. The QoS information field  230  indicates the QoS required by the data to be exchanged during Slot # 1 . The peer nodes information field  235  indicates the node identifiers for each node involved in the data transmission during Slot # 1 . The direction field  240  indicates whether the data exchange is unidirectional, (i.e., from one transmitter to one receiver), or bidirectional, (i.e., to/from all nodes involved), during Slot # 1 . 
     Each node is enabled to request and report its list of allocated slots. This is performed preferably by adding two additional management message types: 1) a “list of allocated slots request message” and 2) a “list of allocated slots response message”. The list of allocated slots response message preferably includes the list of allocated slots IE within its body. 
     The present invention introduces a modification to the existing management “action” frame. A category value “Slot Report” is added to the action frame definition in a medium access control (MAC) entity residing in each mesh node. Slot Report action frames are transmitted by a node to convey its slot allocation information to the other nodes. The Slot Report “category” is used in the management action frame to identify this new category of messages. Within this category, two aforementioned messages, “list request” and “list response”, are defined. Within the “list response” message, a new “list of allocated slots” IE is defined. 
       FIG. 3  shows an exemplary mesh network  300  including two mesh nodes  305  and  310  which are configured in accordance with the present invention. The node  305  includes a transmitter  315 , a receiver  320 , a processor  325 , a memory  330  and an antenna  332 . The node  310  includes a transmitter  335 , a receiver  340 , a processor  345 , a memory  350  and an antenna  352 . The processor  325  in the node  305  is configured to generate a list of allocated slots request message  360 , which is transmitted by the transmitter  315  via the antenna  332  of the node  305 . When node  305  wants to transmit data to node  310 , it has to know when node  310  is free to receive data. Thus, the node  305  requests node  310  to provide its “allocated slots,” (e.g., slots when node  310  is busy). Thus, the node  305  can request the “list of allocated slots” from node  310  to be able to allocate some free slot to exchange data with node  310 . 
     Each memory  330  and  350  keeps track of slot allocation schedule information associated with its respective node  305 ,  310 . 
     The memories  330  and  350  also keep track of the slot allocation information of other nodes besides the node that the respective memory resides in. Thus, each node can keep track of the slot allocation of another node after sending a “list of allocated slots request” and receiving a “list of allocated slots response”. 
     When the receiver  340  in the node  310  receives the list of allocated slots request message  360 , the processor  345  retrieves the IE  100  from the memory  350  and generates a list of allocated slots response message  365  which includes the IE  100 , which is transmitted by the transmitter  335  via the antenna  352  of the node  310 . Each of the processors  325  and  345  include a MAC entity (not shown) which facilitates the generation of the list of allocated slots request message  360  and the list of allocated slots response message  365 . 
     The present invention may be implemented in a data link layer, network layer, as software, hardware, middleware, a future system architecture, radio resource management, or radio resource controller (RRC). The present invention is applicable to, but not limited to, IEEE 802.11, IEEE 802.11s, IEEE 802.15, IEEE 802.15.5, IEEE 802.16 and other relevant mesh technologies. 
     Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone (without the other features and elements of the preferred embodiments) or in various combinations with or without other features and elements of the present invention.