Abstract:
An embodiment of the present invention provides a method, comprising notifying of device and piconet controller (PNC) availability in wireless personal area network (WPAN) and/or wireless local area networks (WLAN) at the start of a superframe, wherein whether the PNC will stay awake or go to sleep during a part of the superframe depends on whether or not there are any services to provide in the WPAN and/or WLAN during a given period of time, and wherein the PNC shall stay awake if there are services to provide in the WPAN and/or WLAN to maintain network performance, otherwise the PNC will go to sleep to minimize its energy consumption.

Description:
BACKGROUND 
     Most TDMA based wireless personal area network (WPAN) or wireless local area network (WLAN) technologies divide a fixed time period into contention free periods and contention periods. For example, in the Institute for Electrical and Electronic Engineers (IEEE) 802.15.3c standard, the fixed time period is called superframe (SF), the contention free period is called CTA (channel time allocation) period, and the contention period is called CAP (contention access period). CTAs are scheduled by a central controller called a PNC (piconet controller) and a CTA is exclusively allocated to a pair of devices. CAP periods are also allocated by the PNC, but the difference from the CTA is that any device can access the medium during CAP periods by contending with each other (e.g., through CSMA/CA). A PNC may be also known as an Access Point (AP) and SF may be also known as Beacon Interval (BI) in the IEEE 802.11 standard. Similarly, CAP may be also known as Contention-Based Period (CBP) and CTA may be also known as Service Period (SP). 
     Since a CTA is allocated exclusively to a subset of devices in the network, other devices not involved in the communications in that CTA can go to sleep to minimize their energy consumption. However, during CAPs, all the active devices (i.e., the devices which are not in a sleep state) in the network are required to stay awake and cannot go to sleep because any device may try to communicate with any other device, including the PNC, during the CAPs. Therefore, active devices and PNC cannot save power during CAPs. 
     A similar problem is also present in two other mechanisms. The first is related to CTA truncation and extension. The CTA truncation is a mechanism that releases an unused CTA time period and the CTA extension is a mechanism that extends CTA time if additional time is needed. Since a device that wants to truncate or to extend CTA needs to inform or request to the PNC, the availability of the PNC has to inform the devices. Otherwise, the devices may transmit a CTA truncation or extension messages to the PNC without knowing that the PNC is unavailable. 
     The second is during the polling period for the dynamic bandwidth allocation mechanism. During the polling period of the dynamic bandwidth allocation, the PNC polls associated devices during unused channel time of a superframe to obtain bandwidth requests from the devices for the purpose of dynamic allocation of the unused channel time. For this period, the PNC needs information whether the devices will be available or not (e.g., device may be in power saving mode). Otherwise, the PNC may transmit polling messages to the devices without knowing that the devices are not available. 
     Thus, a strong need exists for techniques for device and piconet controller availability notification in wireless personal area and wireless local area networks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which: 
         FIG. 1  illustrates a Channel Time Request (CTRq) frame format according to one embodiment of the present invention; 
         FIG. 2  illustrates a CTA information element according to one embodiment of the present invention; 
         FIG. 3  illustrates a PNC availability IE format according to one embodiment of the present invention; 
         FIG. 4  illustrates a PNC availability information field format according to one embodiment of the present invention. 
         FIG. 5  illustrates a DEV Availability IE format according to one embodiment of the present invention; 
         FIG. 6  illustrates a DEV availability information field format according to one embodiment of the present invention; and 
         FIG. 7  illustrates a DEV Availability IE format according to one embodiment of the present invention. 
     
    
    
     It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements. 
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the preset invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention. 
     Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, “processing,” “computing,” “calculating,” “determining,” “establishing”, “analyzing”, “checking”, or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulate and/or transform data represented as physical (e.g., electronic) quantities within the computer&#39;s registers and/or memories into other data similarly represented as physical quantities within the computer&#39;s registers and/or memories or other information storage medium that may store instructions to perform operations and/or processes. 
     Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. For example, “a plurality of stations” may include two or more stations. 
     Embodiments of the present invention provide mechanisms and techniques that may provide information whether devices and a PNC will be active during the following periods: 
     1) CAP; 
     2) Dynamic bandwidth allocation; and 
     3) CTA truncation or extension period. 
     In an embodiment of the present invention, this information may be provided on a superframe basis so that the PNC or the devices can go to sleep during these periods without performance degradation. 
     Further, embodiments of the present invention provide a mechanism that enables a PNC to inform the availability of the PNC to associated devices in the network at the start of a superframe. Whether the PNC will stay awake or go to sleep during a part of a superframe depends on whether there are any services to provide in the network or not during that period of time. The PNC shall stay awake if there are services to provide in the network to maintain the network performance; otherwise the PNC will go to sleep to minimize its energy consumption. 
     The information concerning whether the PNC has to be involved in the communications between the devices during a specific superframe may be provided by the devices in the network. For example, if a device wants to communicate with the PNC during a CAP, the device may inform the PNC that during the CAP it will try to communicate with the PNC. With this information from the device, the PNC shall stay awake during the CAP; otherwise it may go to sleep. 
     This can also be applied to the mechanisms such as CTA truncation and extension in a very similar manner. Since the PNC has to be involved in the CTA truncation and extension, if the devices expect their CTAs to be truncated or extended, this information needs be delivered to the PNC when the devices are requesting a CTA allocation. If the device sends a CTA request (bandwidth allocation request) with an indication that it plans to truncate or extend its allocated CTA, the PNC shall stay awake during that CTA; otherwise, the PNC can go to sleep. 
     Turning now to  FIG. 1 , generally as  100 , is an example of the CTA request frame format. As can be seen, a device would indicate to the PNC through the Truncatable and Extensible fields that it plans to truncate or extend this particular CTA. The PNC would then use this information to stay awake or go to sleep during this particular CTA. 
     After a CTA request, the PNC needs to update its scheduling information and broadcast it in its next superframe. The frame format used for this purpose is shown in  FIG. 2  at  200 . As can be seen, the PNC also includes in its schedule the information whether or not a given CTA is truncatable and/or extensible. 
     Once the information is provided by the devices to the PNC, the PNC provides the PNC availability information to the devices. For example, the PNC availability information can be delivered in an information element (IE) (e.g. “PNC Availability IE” (PAIE)) from the PNC to the devices. The availability of the PNC may be specified either for all the CAPs in the superframe or for each CAP separately. For CTAs, the PNC availability will be specified for each CTA implicitly by the CTA IE as shown in  FIG. 2 . If the PNC sets either Truncatable or Extensible bit (shown in  FIG. 2 ) of a CTA block to 1, the PNC shall stay awake during that CTA period; otherwise the PNC may go to sleep during that period. 
     An example of PAIE frame format is shown in  FIG. 3 , generally as  300 , and the PNC availability information field is shown in  FIG. 4 , generally as  400 . If the PNC is available during the CAPs in the superframe, the CAP bit is set to 1; otherwise it is set to 0. 
     Some embodiments of the present invention also provide a mechanism that provides the availability information of the devices to the PNC so that the PNC knows which devices are available during the CAPs or the polling period of the dynamic bandwidth allocation mechanism. 
     Similar to PAIE (PNC Availability IE) provided above, further embodiments of the present invention provide device availability information that may be conveyed in an IE (e.g. “DEV Availability IE” (DAIE)) and delivered from the devices to the PNC. The availability of the devices may be specified either for all the CAPs in the superframe or for each CAP separately. The availability of the devices may be separately specified for the polling period of the dynamic bandwidth allocation. An example of DAIE frame format is shown in  FIG. 5 , generally as  500 , and the DEV availability information field is shown in  FIG. 6 , generally as  600 . If the DEV is available during the CAPs in the next superframe, the CAP bit is set to 1; otherwise it is set to 0. If the DEV is available for the polling, the dynamic bandwidth request bit is set to 1; otherwise it is set to 0. 
     We may also specify the index of the superframe in which a device will be available during the CAPs or for polling by adding another field indicating the index of the superframe as provided generally as  700  of  FIG. 7 . 
     While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.