Patent Application
20080273507
Historically, when following standards established by the Institute of Electrical and Electronic Engineers standard 802.11 (IEEE 802.11) for wireless local area network (WLAN) protocols, client nodes such as mobile devices communicate directly only with a centralized access point (AP). The AP can then forward any data traffic that is ultimately destined for another client device. More recent WLAN standards have permitted direct client-to-client links between two mobile devices being serviced by the same AP (provided the two mobile devices are within range of each other) by using the AP to help set up the direct link through a procedure called Direct Link Setup (DLS). At the time of this writing, DLS was defined in IEEE 802.11-2007. Once the direct link has been set up in this manner, the two client devices may communicate directly with each other for a period of time without using the AP as an intermediary. But using DLS requires that existing AP's be modified to perform this setup procedure. Modifying every existing AP that might be required to participate in this procedure would be very expensive.
Some embodiments of the invention may be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings:
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 be in direct physical or electrical contact.
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.
Various embodiments of the invention may be implemented in one or any combination of hardware, firmware, and software. The invention may also be implemented as instructions contained in or on a machine-readable medium, which may be read and executed by one or more processors to enable performance of the operations described herein. A machine-readable medium may include any mechanism for storing, transmitting, and/or receiving information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium may include a storage medium, such as but not limited to read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; a flash memory device, etc. A machine-readable medium may also include a propagated signal which has been modulated to encode the instructions, such as but not limited to electromagnetic, optical, or acoustical carrier wave signals.
The term “wireless” and its derivatives 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. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. The term “mobile wireless device” is used to describe a wireless device that may be in motion while it is communicating.
Various embodiments of the invention may use the payload section of a conventional wireless local area network (WLAN) frame to establish a direct link between two client devices in that network. By using a standard format and embedding the necessary information in the flexible payload field, the direct link procedure may be implemented without having to modify existing access points.
At 220, STA-B may respond to this request by transmitting a flame destined for STA-A, indicating STA-B's acceptance or rejection of the request. This response may also be routed through the commonly shared AP described for 210. If STA-B rejects the request (not shown), the communications sequence may end, or STA-A may try again, possibly using different criteria for the connection. Assuming STA-B accepts the request, STA-A and STA-B may begin communicating directly with each other at 230, using the STSL connection they have established at 210 and 220. In some embodiments, STA-A and STA-B may begin communicating directly over the STSL once STA-A has received the acceptance from STA-B. In other embodiments, STA-A and STA-B may need to negotiate further details of the STSL connection, through the AP(s), before starting direct communications with each other. Although STA-A and STA-B are able to communicate directly with each other once the STSL connection has been established, in some embodiments they may also send some frames to each other indirectly through the AP while the STSL connection is still established.
If STA-A wishes to terminate the STSL connection at some point, it may do so at 240 by sending a termination frame, which may sometimes be called a tear-down frame, to STA-B, resulting in the STSL being ended at 250. Alternately, STA-B may terminate the STSL connection by sending the termination frame to STA-A, with the same results. The STSL connection may also be terminated based on other things, such as but not limited to: 1) a pre-determined period of time after the connection was established, 2) one device does not receive any communications from the other device over the STSL connection for a pre-determined period of time, 3) the AP or some other device directs termination of the STSL connection, 4) the quality of communication between the two devices deteriorates below a certain threshold (signal too weak, too much interference, error rate is too high, etc.), 5) detection of radar signals on the channel, 6) etc.
The WLAN format may be found in the aforementioned standard IEEE 802.11-2007, but is repeated at the top of
These three addresses may be followed by a Sequence Control section, to help in reconstructing a string of multiple frames that might be routed through different nodes, some of which might have to be retransmitted, and/or might be received out of order by the destination device. A fourth address may optionally follow, but may be unused in this particular implementation. QoS CNTL may be used to indicate that the protocols for Quality of Service communications are being used. This is then followed by the payload section, and then a Frame Checksum section FCS which may be used to detect errors in the received frame.
An expanded view of the payload section is shown in the bottom part of
These addresses may then be followed by the TYPE field, to indicate which of several types of STSL communication is represented in this payload. For example, TYPE may indicate things such as, but not limited to: 1) a request to establish an STSL between two client devices, 2) a response to that request, either accepting or rejecting the request, 3) a notice that the STSL is being terminated, 4) etc. One or more fields, collectively labeled TYPE-DEPENDENT INFO, may follow the TYPE field. The nature and format of these fields may be dependent on what was specified in the TYPE field.
CAPABILITY INFO may include information about the capabilities of the requesting device. For two devices to communicate directly with each other, they must share certain capabilities. These capabilities may be of various types, such as but not limited to: 1) supported communications protocols, formats, etc., 2) types of information that may be processed, 3) etc. The SUPPORTED RATE field may be similar, with the source device indicating which data rate(s) it is capable of handling. In some embodiments this may indicate which data rates the device is capable of using in communication, while in other embodiments it may indicate which rates are feasible under current conditions.
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 spirit and scope of the following claims.
