Abstract:
Various embodiments of the invention describe a format and procedure for a wireless communication device to request a network controller to transmit a synchronization frame so that the device may synchronize its communication activities with the network controller. This operation may be used in various types of wireless networks, such as but not limited to those conforming to IEEE standard 802.11ah.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is derived from U.S. provisional application Ser. No. 61/756,548, filed Jan. 25, 2013, and claims priority to that filing date for all applicable subject matter. 
    
    
     BACKGROUND 
     A wireless communication device that is associated with a wireless network may sometimes go into a low power state to conserve battery power. However, upon transitioning from the low power state back to the awake state, the device may need to re-synchronize its activities with the network controller that schedules communications within the network. Waiting for the next beacon frame may cause an unacceptable delay in such re-synchronizing. The network controller can reduce this delay by sending a synchronization (sync) frame to the device to enable synchronization, but an excessive amount of time may pass before this happens, unless the device requests a sync frame. Current communication protocols don&#39;t define such a request. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the invention may be better understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings: 
         FIG. 1  shows a network, according to an embodiment of the invention. 
         FIG. 2  shows a wireless communication device, according to an embodiment of the invention. 
         FIG. 3  shows a flow diagram of a method of communicating a sync frame, according to an embodiment of the invention. 
         FIG. 4  shows a diagram of a capabilities information element, according to an embodiment of the invention. 
         FIG. 5  shows a diagram of a sync control frame, according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. 
     References to “one embodiment”, “an embodiment”, “example embodiment”, “various embodiments”, etc., indicate that the embodiment(s) of the invention so described may include particular features, structures, or characteristics, but not every embodiment necessarily includes the particular features, structures, or characteristics. Further, some embodiments may have some, all, or none of the features described for other embodiments. 
     In the following description and claims, the terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” is used to indicate that two or more elements are in direct physical or electrical contact with each other. “Coupled” is used to indicate that two or more elements co-operate or interact with each other, but they may or may not have intervening physical or electrical components between them. 
     As used in the claims, unless otherwise specified the use of the ordinal adjectives “first”, “second”, “third”, etc., to describe a common element, merely indicate that different instances of like elements are being referred to, and are not intended to imply that the elements so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. 
     Discussions herein 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. 
     Various labels may be used in describing particular devices, software, functions, etc. These are used for simplicity and convenience, but this should not be interpreted to mean that only items with those labels are covered by the description. Devices, software, functions, etc., that perform in the same manner as the described items, but are labeled with different terminology, should be considered to be equivalent to the described items. 
     Various embodiments of the invention may be implemented fully or partially in software and/or firmware. This software and/or firmware may take the form of instructions contained in or on a non-transitory computer-readable storage medium. Those instructions may then be read and executed by one or more processors to enable performance of the operations described herein. The instructions may be in any suitable form, such as but not limited to source code, compiled code, interpreted code, executable code, static code, dynamic code, and the like. Such a computer-readable medium may include any tangible non-transitory medium for storing information in a form readable by one or more computers, such as but not limited to read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; a flash memory, etc. 
     The term “wireless” may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that communicate data by using modulated electromagnetic radiation through a non-solid medium. A wireless device may comprise at least one antenna, at least one radio, at least one memory, and at least one processor, where the radio(s) transmits signals through the antenna that represent data and receives signals through the antenna that represent data, while the processor(s) may process the data to be transmitted and the data that has been received. The processor(s) may also process other data which is neither transmitted nor received. 
     As used within this document, the term “network controller” is intended to cover a device that schedules and controls, at least partially, wireless communications by other devices in the network. A network controller may also be known as a base station (BS), access point (AP), central point (CP), or any other term that may arise to describe the functionality of a network controller. 
     As used within this document, the term “mobile device” is intended to cover those devices whose wireless communications are at least partially scheduled and controlled by the network controller. A mobile device (MD) may also be known as a mobile station (MS), STA, subscriber station (SS), user equipment (UE), or any other term that may arise to describe the functionality of a mobile device. Mobile devices may move during such communications, but movement is not required. 
     As used within this document, the term “communicate” is intended to include transmitting and/or receiving. This may be particularly useful in claims when describing the organization of data that is being transmitted by one device and received by another, but only the functionality of one of those devices is required to infringe the claim. Similarly, the exchange of data between a network controller and a mobile device (both devices transmit and receive during the exchange) may be described as ‘communicating’, when only the functionality of one of those devices is being claimed. 
     Some embodiments of the invention describe one or more methods of transmitting a request to a network controller for a synchronization (sync) frame. The network controller may then transmit the sync frame, thus permitting the mobile device to synchronize its communication activities with those of the network controller. 
       FIG. 1  shows a network, according to an embodiment of the invention. In network  10 , network controller (NC)  120  may control the overall communications between itself and mobile device (MDI)  131 . NC  120  may also control communication between itself and one or more other mobile devices (MDx)  13   x , shown with a dashed line. The functionality described herein may also apply to those other devices  13   x , but for simplicity the description covers one mobile device communicating with one network controller. 
       FIG. 2  shows a wireless communication device, according to an embodiment of the invention. Although the illustrated wireless communication device is labeled as mobile device  131 , the same general configuration may be applied to network controller  120  or any other feasible wireless communication device. Mobile device  131  is shown with one or more antennas  211 , one or more radios  212 , one or more processors  213 , one or more memories  214 , and one or more user interfaces  215 . These components may be coupled together in any feasible manner. In addition to the physical components shown, device  131  may also be configured into various functional components, such as software, a medium access control (MAC) layer, a physical medium access (PHY) layer, an application layer, and others. These will not be further described in this document unless such a description would increase an understanding of the various embodiments of the invention by a person of ordinary skill in the art. 
       FIG. 3  shows a flow diagram of a method of communicating a sync frame, according to an embodiment of the invention. In flow diagram  300 , at  310  a network controller may transmit its Sync Capable status by transmitting an indication of whether it&#39;s able to transmit a sync frame. This indication may be transmitted in various types of frames, including but not limited to a Beacon frame or a Probe Response frame. Alternately, the network controller may transmit an indication that it is not able to transmit a sync frame, but this flow diagram assumes that it is capable of transmitting a sync frame. The mobile device is shown receiving that status at  315 , and the subsequent operations in  FIG. 3  are based on the assumption that this status does not change; i.e., that the network controller is capable of transmitting a sync frame throughout the operations of  FIG. 3 . 
     Before entering a low power state, the mobile device may want to assure that the network controller transmits a sync frame shortly after the mobile device is scheduled to wake up. (The low power state is described here as a ‘doze’ state, although the embodiments of the invention are not limited to low power states that are described with that term.) Therefore, before entering the low power state, the mobile device may transmit a sync request to the network controller at  345 , requesting that the network controller transmit a sync frame at a predictable time. The mobile device may subsequently enter the doze state at  365 . 
     The network controller may receive the sync request at  350 , and based on that request may determine at  360  when the sync frame is to be transmitted. In some embodiments, this timing may be based on a prearranged assumption. For example, it may be transmitted at the next slot boundary after the mobile device wakes up. This assumes that the mobile device and network controller have communicated enough that they both know when the mobile device will wake up. 
     The mobile device may resume an operational awake state at  365 . Since the mobile device has been dozing and unable to monitor network communications, after awakening it may need to synchronize on the network communications so that it will know when to transmit a frame without causing collisions with other ongoing transmissions. It would be possible to simply wait until a synchronizing event is received, such as a new frame transmitted in the normal course of network communications, but this might require waiting for an unacceptably long period of time. Also, waiting and monitoring may require using additional battery power without the benefit of being able to effectively communicate. 
     Therefore, at  370  the network controller may transmit the sync frame at the designated time, and the mobile device may receive it at  375 , thus permitting the mobile device to synchronize itself on network communications. 
       FIG. 4  shows a diagram of a capabilities information element, according to an embodiment of the invention. As previously described for the beginning of the flow diagram in  FIG. 3 , the network controller may transmit an indication of whether or not it will support a sync frame. In some embodiments, this indication may be made in an information element (IE). Such an IE is shown as the SIG Capabilities IE in  FIG. 4 . This IE may be contained in various types of frames, such as but not limited to a Beacon frame or a Probe Response frame. 
     In the illustrated embodiment, the IE begins with a 1-byte Element ID field, which contains a value to indicate this is a SIG Capabilities IE. The next field may be a 1-byte Length field to indicate the length of the IE. The next field is shown as a SIG Capabilities Info field, which may have any feasible number (n) of bytes, followed by another field of m bytes, which may be reserved for future use. The illustrated SIG Capabilities Info field is shown as consisting of 1 byte, with the first bit being shown as an Uplink Sync Capable field, and the remaining 7 bits being reserved for future use. In some embodiments, the Uplink Sync Capable field will contain a value of ‘1’ to indicate the network controller will support transmitting a sync frame, and a value of ‘0’ to indicate the network controller will not support transmitting a sync frame, but other values may be used instead. 
     Although various field lengths and field names have been shown in this embodiment, other field lengths and other field names may also be used, as long as they perform the same function and indicate the same information. 
       FIG. 5  shows a diagram of a sync control frame, according to an embodiment of the invention. As previously described for the Sync Request in  FIG. 3 , the mobile device may transmit a request to the network controller to transmit a sync frame. An embodiment of such a request is shown as the Sync Control Frame of  FIG. 5 . In some embodiments the Sync Control Frame may be a form of Action Frame. In some embodiments, the SIG Action field may be used to indicate that this is a Sync Control Frame, and the Sync Control field may be used to indicate that this is a request. In the illustrated embodiment, the Sync Control field has a 1-bit Uplink Sync Request field, and a 1-bit Protect Time Slot field. In a particular embodiment, a value of ‘1’ in the Uplink Sync Request field may be used to indicate the mobile device is requesting a sync frame, and a value of ‘0’ may be used to indicate the mobile device does not wish to receive a sync frame. 
     In an alternate embodiment, the mobile device may request a sync frame by transmitting the SIG Capabilities IE of  FIG. 4  to the network controller, with a value of ‘1’ in the Uplink Sync Capable field indicating a request. 
     The Protect Time Slot field, if it is used, may indicate whether the mobile device wants to protect its allocated time slot in a Restricted Access Window or a Target Wake time. In some embodiments, a value of ‘1’ in this field may indicate the mobile device wants to protect its time slot, while a value of ‘0’ may indicate it does not. 
     The foregoing description is intended to be illustrative and not limiting. Variations will occur to those of skill in the art. Those variations are intended to be included in the various embodiments of the invention, which are limited only by the scope of the following claims.