HK1194898B - Systems, methods, and devices for communicating beacons for wireless communication - Google Patents

Description

Systems, methods, and devices for communicating beacons for wireless communications

Claiming priority pursuant to 35U.S.C. § 119

This patent application claims priority to provisional application No.61/525,353, entitled "beans FOR wireless communication", filed on 19.8.2011, which is assigned to the assignee of the present application and is hereby expressly incorporated herein by reference.

Technical Field

The present application relates generally to wireless communications, and more particularly to systems, methods, and devices for communicating device information between electronic devices in packets having a plurality of different formats.

Background

In many telecommunication systems, communication networks are used to exchange messages between several interacting spatially separated devices. Networks may be classified according to geographic scope (e.g., which may be a city area, a local area, or a personal area). These networks are designated as Wide Area Networks (WANs), Metropolitan Area Networks (MANs), Local Area Networks (LANs), Wireless Local Area Networks (WLANs), or Personal Area Networks (PANs), respectively. The networks also differ according to the switching/routing technology used to interconnect the various network nodes and devices (e.g., circuit-switched versus packet-switched), the type of physical medium used for transmission (e.g., wired versus wireless), and the set of communication protocols used (e.g., internet protocol suite, SONET (synchronous optical network), ethernet, etc.).

Wireless networks are generally preferred when the network elements are mobile and therefore have dynamic connectivity requirements, or if the network architecture is formed in an ad hoc rather than fixed topology. Wireless networks may use electromagnetic waves in the radio, microwave, infrared, or optical frequency bands. Wireless networks advantageously facilitate user mobility and rapid field deployment when compared to fixed, wired networks.

Devices in a wireless network may send/receive information between each other. The information may include packets, which in some aspects may be referred to as data units, data beacons, or beacon messages. These packets may include overhead information (e.g., header information, packet attributes, etc.) that facilitates routing the packet through the network, identifying data in the packet, processing the packet, etc., as well as data (e.g., user data, multimedia content, etc.) that may be carried in the packet's payload.

The access point may also broadcast information to other nodes related to communications in the network. The transmission of such information may require the use of a large amount of bandwidth in the network. Accordingly, improved systems, methods, and devices for transmitting packets are desired.

Disclosure of Invention

Each of the systems, methods, and devices of the embodiments disclosed herein has some aspects, but none of these aspects alone are their desirable attributes. Without limiting the scope of protection of the invention as expressed by the claims which follow, some features are discussed briefly below. After considering this discussion, and particularly after reading the section entitled "detailed description of certain embodiments" one will understand that embodiments within the scope of this invention include systems and methods for transmitting device information between electronic devices using packets having a variety of different formats.

One embodiment is a wireless communication device. The apparatus includes a receiver configured to receive a sequence of beacon messages, wherein the sequence of beacon messages includes a first beacon message and a plurality of subsequent beacon messages. The first beacon message includes at least one of content information and timing information of at least one of the plurality of subsequent beacon messages. Further, the apparatus includes a processor electrically coupled to the receiver, wherein the processor is configured to: decoding a proper subset of the plurality of subsequent beacon messages based on at least one of the content information and the timing information.

Another embodiment is a method of communication. The method comprises the following steps: a sequence of beacon messages is received that includes a first beacon message and a plurality of subsequent beacon messages. The first beacon message includes at least one of content information and timing information of at least one of the plurality of subsequent beacon messages. In addition, the method further comprises: decoding a proper subset of the plurality of subsequent beacon messages based on at least one of the content information and the timing information.

Another embodiment is a wireless communication device. The apparatus comprises: the apparatus includes means for receiving a sequence of beacon messages including a first beacon message and a plurality of subsequent beacon messages. The first beacon message includes at least one of content information and timing information of at least one of the plurality of subsequent beacon messages. Further, the apparatus further comprises: means for decoding a proper subset of the plurality of subsequent beacon messages based on at least one of the content information and the timing information.

Another embodiment provides a computer-readable medium comprising instructions. The instructions, when executed, cause an apparatus to receive a sequence of beacon messages including a first beacon message and a plurality of subsequent beacon messages. The first beacon message includes at least one of content information and timing information of at least one of the plurality of subsequent beacon messages. The instructions, when executed, further cause the apparatus to decode a proper subset of the plurality of subsequent beacon messages based on at least one of the content information and the timing information.

Another embodiment is a method, system, or article of manufacture comprising instructions for transmitting a beacon message in a base station subsystem comprising an access point and an access terminal. The method, system or article of manufacture comprises: transmitting a repeating finite sequence of beacon messages from the access point to the access terminal, the sequence comprising a first beacon message comprising a relative location identifier indicating a timing of a subsequent beacon message in the finite sequence and identifying content contained in the subsequent beacon message, the subsequent beacon message comprising information not contained in the first beacon message. Further, the method, system, or article of manufacture further comprises: decoding, at the access terminal, the first beacon message and a proper subset of a sequence of beacon messages based on the relative location identifier, the access terminal being in a low power state during transmission of a second subset of the sequence of beacon messages, the second subset of beacon messages including beacon messages not in the proper subset and not including the first beacon message.

Another embodiment is a method, system, or article of manufacture comprising instructions for communicating in a base station subsystem. The base station subsystem includes an access point and an access terminal, where the base station subsystem is identified by a BSSID (basic service set identification). The method, system or article of manufacture comprises: transmitting beacon messages from the access point to the access terminal, each beacon message being an instance of a full beacon message type or an instance of a short beacon message type. Further, the method, system, or article of manufacture further comprises: transmitting a beacon message of the short beacon message type at a first time interval and transmitting a full beacon message of the full beacon message type at a second time interval, the second time interval being equal to an integer multiple of the first time interval; wherein each beacon message of the short beacon message type includes a compressed BSSID field having a value indicating a cyclic redundancy check of the BSSID.

Another embodiment is a method, system, or article of manufacture comprising instructions for transmitting a beacon message in a base station subsystem comprising an access point and an access terminal. The method, system or article of manufacture is used to: decoding, by the access terminal, a first beacon message that provides absolute time; and decoding, by the access terminal, a second beacon message subsequent to the first beacon message, the second beacon message including a sequence number relative to the first beacon message and a time offset indicating a time difference between when the second beacon message is scheduled to be transmitted by the access point and when the second beacon message is actually transmitted.

Another embodiment is a method, system, or article of manufacture having instructions for communicating a set of information elements in a base station subsystem that includes an access point and an access terminal. The method, system or article of manufacture is used to: transmitting beacon messages from the access point to the access terminal, each beacon message being an instance of a full beacon message type or an instance of a short beacon message type, wherein each beacon message of the full beacon message type includes the set of information elements; and transmitting a plurality of beacon messages of the short beacon message type, each of the plurality of beacon messages including a proper subset of the set of information elements, wherein the plurality of beacon messages includes the set of information elements.

Another embodiment is a method, system, or article of manufacture having instructions for communicating in a base station subsystem that includes an access point and an access terminal. The method, system or article of manufacture is used to: transmitting beacon messages from the access point to the access terminal, each beacon message being an instance of a full beacon message type or an instance of a short beacon message type; and transmitting a first beacon message including content information specifying content of information contained in a beacon message of the short beacon message type transmitted after the first beacon message.

Another embodiment is a method, system, or article of manufacture having instructions for communicating in a base station subsystem that includes an access point and an access terminal. The method, system or article of manufacture is used to: transmitting beacon messages from the access point to the access terminal, each beacon message being an instance of a full beacon message type or an instance of a short beacon message type; transmitting a plurality of beacon messages of the short beacon message type, each of the plurality of beacon messages comprising a physical layer preamble having a SIG field, the SIG field comprising a length field; and decoding, at the access terminal, the plurality of beacon messages, wherein a beacon message of the plurality of beacon messages is decoded as a synchronization beacon message provided that a length field of the beacon message is set to all zeros.

Drawings

Fig. 1 illustrates an example of a wireless communication system in which aspects of the present disclosure may be used.

Fig. 2 illustrates a functional block diagram of a wireless device that may be used in the wireless communication system of fig. 1.

Fig. 3 illustrates an example of a beacon message that may be used in the wireless communication system of fig. 1.

Fig. 4 illustrates a plurality of beacon messages transmitted by the AP104 to the STAs 106 in the wireless communication system 100 of fig. 1.

Fig. 5A illustrates an example of one form of a shortened beacon message that may be used in the wireless communication system of fig. 1.

Fig. 5B illustrates another example of a beacon message that may be used in the wireless communication system of fig. 1.

Fig. 5C illustrates an example of a physical layer (PHY) preamble including a synchronization beacon that may be used in the wireless communication system of fig. 1.

Fig. 6 illustrates a flow diagram depicting an example process for the wireless device of fig. 2 to obtain a data frame.

Fig. 7 illustrates a flow diagram depicting another example process for the wireless device of fig. 2 generating and transmitting a data frame.

Fig. 8 is a functional block diagram of another exemplary wireless device that may be used in the wireless communication system of fig. 1.

Detailed Description

Various aspects of the novel systems, devices, and methods are described more fully hereinafter with reference to the accompanying drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In light of the present disclosure, those of ordinary skill in the art will appreciate that the scope of the present invention is intended to cover any aspect of the novel systems, apparatus, and methods disclosed herein, whether implemented independently or in combination with any other aspect of the present invention. For example, an apparatus may be implemented or a method may be implemented using any number of the aspects set forth herein. Moreover, the scope of the present disclosure is intended to cover such apparatus or methods, which may be implemented by using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the present disclosure as set forth herein. It should be understood that any aspect disclosed herein may be embodied by one or more components of the present invention.

Although specific aspects are described herein, many variations and permutations of these aspects are possible within the scope of the invention. Although certain benefits and advantages of the preferred aspects have been described, the scope of protection is not limited by particular benefits, uses, or objects. Rather, aspects of the present invention are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and the following description of the preferred aspects. The specification and drawings are accordingly to be regarded in an illustrative rather than a restrictive sense, and the scope of the present invention is defined by the appended claims and their equivalents.

Popular wireless network technologies may include various types of Wireless Local Area Networks (WLANs). WLANs may be used to interconnect nearby devices together using widely used network protocols. The various aspects described herein may be applied to any communication standard, such as a wireless protocol.

In some aspects, wireless signals may be transmitted in sub-gigahertz frequency bands according to the 802.11ah protocol using Orthogonal Frequency Division Multiplexing (OFDM), Direct Sequence Spread Spectrum (DSSS) communications, a combination of OFDM and DSSS communications, or other schemes. Implementations of the 802.11ah protocol may be used for sensors, metering, and smart grids. Advantageously, aspects of certain devices implementing the 802.11ah protocol may consume less power than devices implementing other wireless protocols, and/or may be used to transmit wireless signals over relatively large distances (e.g., about 1 kilometer or more).

In some implementations, a WLAN includes various devices that are components of an access wireless network. For example, there may be two types of devices: an Access Point (AP) and a client. A client may also be referred to as an Access Terminal (AT) or Station (STA). In general, an access point may act as a hub (hub) or base station for a WLAN, while STAs act as users of the WLAN. For example, the STA may be a laptop computer, a Personal Digital Assistant (PDA), a mobile phone, and the like. In one example, the STAs connect to the AP via a wireless link that is WiFi compliant (e.g., IEEE 802.11 protocols such as 802.11ah) to obtain general connectivity to the internet or to other wide area networks. In some implementations, the STA may also be used as an AP.

Further, an Access Point (AP) may also include, be implemented as, or known as a node B, a Radio Network Controller (RNC), an evolved node B (eNodeB), a Base Station Controller (BSC), a Base Transceiver Station (BTS), a Base Station (BS), a Transceiver Function (TF), a wireless router, a wireless transceiver, or some other terminology.

A Station (STA) may also include, be implemented as, or known as an Access Terminal (AT), a subscriber station, a subscriber unit, a mobile station, a remote terminal, a user agent, a user device, user equipment, or some other terminology. In some implementations, an access terminal may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless connection capability, or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or smart phone), a computer (e.g., a laptop), a portable communication device, a headset, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a gaming device or system, a global positioning system device, or any other suitable device configured to communicate over a wireless medium.

As noted above, certain devices described herein may implement, for example, the 802.11ah standard. These devices (whether functioning as STAs or APs or other devices) may be used for smart metering or in smart grids. These devices may provide sensor applications, or for home automation. Alternatively or additionally, these devices may be used in a healthcare context, for example for personal healthcare. These devices may also be used for monitoring, to enable extended range internet connectivity (e.g., for use in a hotspot fashion), or to enable machine-to-machine communication.

Fig. 1 illustrates an example of a wireless communication system 100 in which aspects of the present disclosure may be used. The wireless communication system 100 may operate in accordance with a wireless standard, such as the 802.11ah standard. The wireless communication system 100 may include an AP104, where the AP104 communicates with STAs 106.

Various procedures and methods may be used for transmissions between the AP104 and the STAs 106 in the wireless communication system 100. For example, signals may be transmitted and received between the AP104 and the STAs 106 in accordance with OFDM/OFDMA techniques. If this is the case, the wireless communication system 100 may be referred to as an OFDM/OFDMA system. Alternatively, signals may be transmitted and received between the AP104 and the STAs 106 in accordance with CDMA techniques. If this is the case, the wireless communication system 100 may be referred to as a CDMA system.

The communication link that facilitates transmissions from AP104 to one or more of STAs 106 may be referred to as a Downlink (DL)108, and the communication link that facilitates transmissions from one or more of STAs 106 to AP104 may be referred to as an Uplink (UL) 110. Alternatively, downlink 108 may also be referred to as the forward link or forward channel, and uplink 110 may also be referred to as the reverse link or reverse channel.

The AP104 may act as a base station and provide wireless communication coverage in a Basic Service Area (BSA) 102. The AP104, along with the STAs 106 associated with the AP104 and communicating using the AP104, may be referred to as a Basic Service Set (BSS). It should be noted that the wireless communication system 100 may not have a central AP104, but may instead act as a peer-to-peer network between the STAs 106. Accordingly, the functions of the AP104 described herein may instead be performed by one or more of the STAs 106.

The AP104 may transmit beacon messages (or simply beacons) to other node STAs 106 of the system 100 over a communication link, such as the downlink 108, which may help the other node STAs 106 synchronize their timing with the AP104, or which may provide other information or functionality. Such beacon messages may be transmitted periodically. In one aspect, the period between successive transmissions may be referred to as a superframe. The transmission of beacon messages may be divided into a plurality of groups or time intervals. In one aspect, the beacon message may include, but is not limited to: such as timestamp information for setting a common clock, a peer-to-peer network identifier, a device identifier, capability information, a superframe duration, transmission direction information, reception direction information, a neighbor list, and/or an extended neighbor list, some of which are described in additional detail below. Thus, a beacon message may include information that is common (e.g., shared) among several devices, as well as information that is specific to a given device.

In some aspects, the STA106 may be required to associate with the AP104 in order to send communications to the AP104 and/or receive communications from the AP 104. In one aspect, the information for associating is included in a beacon message broadcast by the AP 104. To receive such beacon messages, the STA106 may, for example, perform an extensive coverage search over the coverage area. The search may also be performed by the STA106 by scanning the coverage area in a lighthouse manner, for example. After receiving the information for associating, the STA106 may send a reference signal (such as an association probe or request) to the AP 104. In some aspects, the AP104 may communicate with a larger network, such as the internet or a Public Switched Telephone Network (PSTN), for example, using backhaul services.

Fig. 2 illustrates various components that may be utilized in a wireless device 202, where the wireless device 202 may be utilized in the wireless communication system 100. The wireless device 202 is an example of a device that may be configured to implement the various methods described herein. For example, the wireless device 202 may include one of the AP104 or the STA 106.

The wireless device 202 may include a processor 204, the processor 204 controlling the operation of the wireless device 202. The processor 204 may also be referred to as a Central Processing Unit (CPU). Memory 206, which may include Read Only Memory (ROM) and Random Access Memory (RAM), may provide instructions and data to processor 204. A portion of the memory 206 may also include non-volatile random access memory (NVRAM). The processor 204 typically performs logical and arithmetic operations based on program instructions stored in the memory 206. The instructions in the memory 206 are executable to implement the methods described herein.

The processor 204 may include or may be a component of a processing system implemented using one or more processors. The one or more processors may be implemented using any combination of the following: general purpose microprocessors, microcontrollers, Digital Signal Processors (DSPs), Field Programmable Gate Arrays (FPGAs), Programmable Logic Devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entity that can perform calculations or other operations on information.

Additionally, the processing system may also include a machine-readable medium for storing the software. Software should be construed broadly to mean any type of instructions, whether referred to as software, firmware, middleware, microcode, hardware description language, or the like. The instructions may include code (e.g., in source code format, binary code format, executable code format, or any other suitable code format). The instructions, when executed by the one or more processors, cause the processing system to perform the various functions described herein.

The wireless device 202 may also include a housing 208, and the housing 208 may include a transmitter 210 and/or a receiver 212 to allow transmission and reception of data between the wireless device 202 and a remote location. The transmitter 210 and receiver 212 may be combined into a transceiver 214. An antenna 216 may be connected to the housing 208 and electrically coupled to the transceiver 214. Wireless device 202 may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers and/or multiple antennas.

The transmitter 210 may be configured to: beacon messages having different beacon message types are wirelessly transmitted. For example, the transmitter 210 may be configured to transmit beacon messages with different types of beacons generated by the processor 204 (discussed above). When the wireless device 202 is implemented as or serves as the STA106, the processor 204 may be configured to process beacon messages of a variety of different beacon message types. For example, the processor 204 may be configured to: the method may further comprise determining the type of beacon message used in the beacon message signal and processing the beacon message and/or fields of the beacon message accordingly. When wireless device 202 is implemented or used as AP104, processor 204 may be further configured to select one of a plurality of beacon message types and generate a beacon message having the beacon message type. For example, the processor 204 may be configured to generate a beacon message including beacon information and determine which type of beacon information to use.

The receiver 212 may be configured to: beacon messages having different beacon message types are received wirelessly. In some aspects, the receiver 212 may be configured to: the type of beacon message used is detected and processed accordingly, as discussed in further detail below.

The wireless device 202 may also include a signal detector 218 that may be used to try to detect and quantify the level of signals received by the transceiver 214. The signal detector 218 may detect signals such as total energy, energy per subcarrier per symbol, power spectral density, and other signals. In addition, the wireless device 202 may also include a Digital Signal Processor (DSP)220 for use in processing signals. DSP 220 may be configured to generate packets for transmission. In some aspects, the packet may include a physical layer data unit (PPDU).

Further, in some aspects, the wireless device 202 may also include a user interface 222. The user interface 222 may include a keypad, a microphone, a speaker, and/or a display. User interface 222 may include any component or component that conveys information to a user of wireless device 202 and/or receives input from the user.

The various components of the wireless device 202 may be coupled together by a bus system 226. For example, the bus system 226 may include a data bus, and may include a power bus, a control signal bus, and a status signal bus in addition to the data bus. The components of wireless device 202 may be coupled together or may use some other mechanism to accept or provide inputs to each other.

Although illustrated in fig. 2 as separate components, one or more of the components may be combined or implemented together. For example, the processor 204 may be used to implement not only the functions described above with respect to the processor 204, but also the functions described above with respect to the signal detector 218 and/or the DSP 220. Further, each of the components shown in FIG. 2 may be implemented using a plurality of separate elements.

The wireless device 202 may comprise an AP104 or STA106 and may be configured to transmit and/or receive communications including beacon messages. That is, the AP104 or the STA106 may act as a transmitter device or a receiver device for the beacon information. Such communication may be initiated upon receipt of a message from a transmitter device to a receiver device. Certain aspects contemplate the use of the signal detector 218 by software running on the memory 206 and processor 204 to detect the presence of a transmitter or receiver.

To ensure proper communication between the AP104 and the STA106 devices, the STA106 may need information about the characteristics of the AP 104. For example, the STA106 may need timing information about the AP104 in order to synchronize the timing of communications between the STA106 and the AP 104. Additionally or alternatively, the STAs 106 may need other information such as a Medium Access Control (MAC) address of the AP104, an identifier of a Basic Service Set (BSS) served by the AP104, and the like. The types of information that may be needed by the STA106 are discussed in further detail below. The STA106 may independently determine whether it needs such information, such as by using the memory 206 and software running on the processor 204.

In certain aspects, the AP104 may use the transmitter 210 to transmit a beacon message that includes all desired information. In one aspect, the AP104 periodically sends beacon messages to synchronize the network and provide basic information to the STAs 106. For example, the beacon message structure may be determined by the AP104 and repeatedly transmitted to the STAs 106 at regular intervals. These beacon messages may be relatively large, as depicted in fig. 3. Further, these beacon messages may be sent at a very low rate. Therefore, there may be considerable overhead in managing these frames.

Fig. 3 illustrates an example of a beacon message frame 300 used in some communication systems such as that depicted in fig. 1. As shown, the beacon message 300 includes a Media Access Control (MAC) header 302, a frame body 304, and a Frame Control Sequence (FCS) 306. As shown in this example, the MAC header 302 is 24 bytes long, the frame body 304 has a variable length, and the FCS 306 is 4 bytes long.

The MAC header 302 is used to provide basic routing information for the beacon message 300. In the illustrated aspect, the MAC header 302 includes a Frame Control (FC) field 308, a duration field 310, a Destination Address (DA) field 312, a Source Address (SA) field 314, a Basic Service Set Identification (BSSID) field 316, and a sequence control field 318. As shown, the FC field 308 is 2 bytes long, the duration field 310 is 2 bytes long, the DA field 312 is 6 bytes long, the SA field 314 is 6 bytes long, the BSSID field 316 is 6 bytes long, and the sequence control field 318 is 2 bytes long.

The frame body 304 is used to provide detailed information about the transmitting node. In the illustrated aspect, the frame body 304 includes a timestamp field 320, a beacon interval field 322, a capability information field 324, a Service Set Identifier (SSID) field 326, a supported rate field 328, a Frequency Hopping (FH) parameter set 330, a direct sequence parameter set 322, a contention free parameter set 334, an Independent Basic Service Set (IBSS) parameter set 336, a country information field 338, an FH hopping parameter field 340, an FH pattern table 342, a power constraint field 344, a channel switch announcement field 346, a silence field 348, an IBSS Direct Frequency Selection (DFS) field 350, a Transmit Power Control (TPC) field 352, an Effective Radiated Power (ERP) information field 354, an extended supported rate field 356, and a Robust Security Network (RSN) field 358.

As shown in fig. 3, the timestamp field 320 is 8 bytes long, the beacon interval field 322 is 2 bytes long, the capability information field 324 is 2 bytes long, the Service Set Identifier (SSID) field 326 is variable length, the supported rate field 328 is variable length, the Frequency Hopping (FH) parameter set 330 is 7 bytes long, the direct sequence parameter set 322 is 2 bytes long, the contention free parameter set 334 is 8 bytes long, the Independent Basic Service Set (IBSS) parameter set 336 is 4 bytes long, the country information field 338 is variable length, the FH hopping parameter field 340 is 4 bytes long, the FH pattern table 342 is variable length, the power constraint field 344 is 3 bytes long, the channel switch announcement field 346 is 6 bytes long, the silence field 348 is 8 bytes long, the IBSS Direct Frequency Selection (DFS) field 350 is variable length, the transmit power control (ERP) field 352 is 4 bytes long, the Effective Radiated Power (ERP) information field 354 is 3 bytes long, the extended supported rate field 356 is of variable length and the Robust Secure Network (RSN) field 358 is of variable length.

The beacon message 300 may include all information required by the STA 106. Thus, the STA106 need only listen to the full beacon message to obtain all the information required by the STA 106. However, the STA106 may not need all the information included in the beacon message. For example, the beacon message may contain information that the STA106 already has, or information related to another STA but not related to the STA 106. Thus, the STA106 is required to listen to or decode additional information in the beacon message in order to obtain the information it needs. This requires the STA106 to spend additional processing power and time in the awake state to decode the entire beacon message.

The STA106 may have multiple modes of operation. For example, the STA106 may have a first mode of operation referred to as an active mode. In the active mode, the STA106 may be in an awake state or an awake state at all times and actively transmit/receive data with the AP 104. Further, the STA106 may have a second mode of operation referred to as a power save mode. In the power save mode, the STA106 may be in an awake state, or a sleep or sleep state, in which the STA106 is not actively transmitting/receiving data with the AP 104. For example, the receiver 212 and possibly the DSP 220 and signal detector 218 of the STA106 may operate in a sleep state with reduced power consumption. Further, as described above, the STA106 needs to remain in the awake state to receive the beacon message. Thus, if the beacon message is longer, the STA106 needs to stay in the awake state for a longer period of time and thus consumes more power.

For example, although the beacon message 300 has a variable length, it may be at least 89 bytes long, which requires the STA106 to spend a significant amount of time in the awake state. However, in various radio environments, most of the information contained in the beacon message 300 may be used little or not at all. Therefore, in a low power radio environment, it may be desirable to reduce the length of the beacon message 300 in order to reduce power consumption. Furthermore, some radio environments use low data rates. For example, an access point implementing the 802.11ah standard may take a relatively long time to transmit the beacon message 300 due to a relatively slow data transmission rate. Accordingly, it may be desirable to reduce the length of the beacon message 300 in order to shorten the amount of time it takes to transmit the beacon message 300.

There are a number of ways in which the beacon message 300 may be shortened or compressed. In an aspect, one or more fields of the beacon message 300 may be omitted. In another aspect, one or more fields of the beacon message 300 may be reduced in size, for example, by using a different encoding scheme or by accepting less information content. In one aspect, the wireless system may allow a STA to query the AP for information omitted from the beacon message. For example, the STA may request information omitted from the beacon message through a probe request. In an aspect, a full beacon message may be sent periodically or at dynamically selected times.

Thus, in certain aspects, the AP104 may transmit one or more shortened beacon messages. These shortened beacon messages may allow the STA106 to listen only to specific beacon messages and only obtain specific information needed by the STA 106. Thus, the STA106 remains in the awake state for a shortened period of time and thus improves power efficiency. Aspects of the shortened beacon message are described with reference to fig. 4, 5A, and 5B.

Certain aspects contemplate mechanisms for transmitting multiple different types of shortened beacons from the AP104 to the STA106 in a particular network. In particular, certain aspects contemplate transmitting a sequence of multiple short beacon messages carrying different information in different beacon messages. The AP104 may determine, using the processor 204 running the software, a plurality of transmission time intervals for transmitting a plurality of beacon messages. The AP104 may then transmit the beacon messages at the determined time intervals using the transmitter 210. Each beacon message may include a (partially) different set of information than its neighbors. The information may include Information Elements (IEs) associated with the transmitting device, information about the network, data, and the like. The transmission time interval may be fixed and repeated.

Fig. 4 illustrates a plurality of beacon messages transmitted by the AP104 to the STAs 106 in the wireless communication system 100 of fig. 1. The STAs 106 may use the processor 204 running software to receive these beacon messages via the receiver 212 and reorganize the transmitted information into its original form. Each of these beacon messages may include partial information that differs from one another. For example, as discussed in connection with fig. 5B, one beacon message may include specific information regarding transmit power constraints. Another beacon message may include bandwidth-specific information for a particular STA 106. These shorter beacon messages facilitate more efficient and selective reception and decoding by the STAs 106. Thus, unlike the network described above, this arrangement will more efficiently communicate information since the STA106 may be more selective in how it obtains information. Thus, the STA106 need only listen or decode beacon messages that include information (e.g., IEs) needed by the STA106 in multiple beacon messages.

In certain aspects, the STA106 may poll the AP104 for certain information using the shortened beacon message format. Generally, using reciprocal "polling" and "encapsulation" messages, the STA106 is able to respond to the shortened beacon message and request specific characteristics about the AP104, other STAs 106, or the network. Thus, certain aspects contemplate a form of polling short beacon message by which the STA106 can request more information, and a plurality of encapsulated short beacons that will respond with the desired information. This arrangement facilitates the STA106 requesting additional characteristics individually from the AP104 (the AP or STA) without the need to receive a large block of information in a single transmission.

The STA106 may implement such polling using software running on the processor 204 and memory 206 that directs the operation of the transmitter 210 and receiver 212 and the DSP 220. Similarly, the AP104 may receive the polling message via the receiver 212 and, through software running on the memory 206 and processor 204, determine the appropriate encapsulated message content to transmit through the transmitter 210.

In some aspects, these individual characteristics are referred to as Information Elements (IEs). These characteristics may include time intervals between beacon message transmissions, supported data rates, power constraint information, bandwidth constraint information, possible network operations, and the like. Since the IE value is not included in the original shortened beacon message sent by the AP104, the STA106 may request the IE value. The STA106 may also request IE values on its own initiative. Further, in some aspects, the STA106 may selectively request IE values from the AP104 individually as part of a more elaborate request procedure. These aspects allow the STA106 to control the transmission of IE values rather than relying on the AP 104.

In some aspects, the first beacon message in the sequence may be special in that: which provides basic information when the STA106 expects to receive supplemental beacon messages. This information may include a relative location identifier or index that indicates the timing at which future beacon messages will arrive and what it may possess. This information may be communicated explicitly or implicitly, as described in further detail below. By taking this information into account, the STA106 may decide to decode only a subset of the transmitted beacon messages, while sleeping the rest of the time.

In some aspects, the processor 204 running software on the STA106 and the processor 204 running software on the AP104 may communicate via their respective transceivers 214 and negotiate which beacon messages will carry the information of interest. The STA106 may then activate its transceiver 214 only when these beacon messages are transmitted. In some aspects, information regarding the timing of transmitting particular beacon messages (e.g., a repeating time interval regarding transmission such as a first beacon) may be transmitted to each of the STAs 106 and the AP104 during initialization of the AP104 and each of the STAs 106 (e.g., at the time of manufacture of the STAs 106 and the AP104, at the first run of the STAs 106 and the AP104, when the STAs 106 join a new wireless network such as the wireless communication system 100, etc.), and the beacons may communicate the included information to each of the STAs 106 and the AP 104. In some aspects, this information may be communicated or otherwise additionally modified, such as through communication with other devices in the wireless communication system 100. This information may be exchanged between the AP104 and the STA106 during an association procedure, such as according to an 802.11 protocol (e.g., 802.11ah), for example. In some aspects, the information may indicate: the first beacon in the sequence carries information about the network bandwidth. In some aspects, the information may indicate: the second beacon in the sequence carries information about the capabilities of the AP104, such as the number of antennas included by the AP 104.

For example, the information may indicate a sequence in which the beacon message is transmitted. For example, the information may be transmitted by the AP104 in a sequence of beacon messages, each separated by a time interval. For example, the sequence may be beacon messages 1, 2, 3, 4, and 5. The AP104 and the STA106 may have information about the type of information included in each of the beacon messages 1, 2, 3, 4, and 5. Thus, as long as the STA106 has information about which beacon messages to send at what time, the STA106 may only listen for beacon messages having information about that STA 106. For example, if the STA106 has information about when to transmit beacon message 1 from the AP104, the STA106 may determine when the next beacon message will be transmitted from the AP 104. Specifically, the STA106 simply adds the interval time between beacon messages (or multiples of this interval time as needed) to the time at which beacon message 1 is transmitted to determine when other beacon messages will be transmitted. Information about the timing of the transmission of any of these beacon messages (not just beacon message 1) can be used to determine when all beacon messages will be sent.

Each beacon message may include: an identifier indicating that it is a beacon message distinguished from a normal frame. The beacon message may also include an identifier of the base station BSS so that the STA106 may discard Overlapping BSS (OBSS) beacon messages. The beacon message may also convey the MAC address of the AP 104.

Each beacon message may also include a relative location identifier in the form of a sequence number. These identifiers help the STA wake up to read any beacon messages and synchronize with the remaining sequence. The sequence may include the number of beacon messages before the next first (or restarted) beacon message. The next first (or restarted) beacon message may itself include a special identifier that also identifies itself. Alternatively, if the total number of beacon messages in the sequence is known, the last beacon message in the sequence may be used instead as a reference.

Certain aspects also consider indicating the time between two beacon messages. Alternatively, the time between beacon messages may be fixed and may be expressed in multiples of microseconds. It may also include a list of information elements, or only those IEs that have changed since the previous transmission. The synchronization beacon message as described below may have a PHY structure to allow it to be very short.

Fig. 5A illustrates an example of one form of shortened beacon message that may be used in certain aspects of the present invention. The short beacon message 500a of this aspect may include 10 components. The short beacon message 500a may include a Frame Control (FC)501 having 2 bytes, a duration field 502 having 2 bytes, a Source Address (SA) field 503 having 6 bytes, a sequence control field 504 having 2 bytes, and an SSID hash value 505 having a single byte. The short beacon message 500a may also include a timestamp 506 having 4 bytes, a field 507 indicating a beacon interval having 2 bytes, and a capability field 508 indicating transmitter capabilities having 1 byte. The short beacon message 500a may also include an indication of channel information 509 having 2 bytes and a CRC check 410 having 4 bytes.

The capability information field 508 may be used to provide information on the wireless capabilities of the transmitting AP. In the illustrated aspect, the capability information field 508 is shorter than the capability information field 324 described above with reference to FIG. 3. Specifically, the capability information field 508 is only 1 byte long, while the capability information field 324 is 2 bytes long.

Fig. 5B illustrates another example of a beacon message format that may be used in the wireless communication system of fig. 1. As described above, the transmit power channel can be divided into more tiny components. Similarly, the beacon information block may be broken down into more tiny components. Such a low overhead beacon 500b may include only 16 bytes.

As shown, the beacon 500b includes a FC field 511 having 2 bytes (which is also referred to as octets), followed by a SA field 512 having 2 bytes, followed by a SSID field 513 having 1 byte, followed by a timestamp field 514 having 4 bytes, followed by a transmit power and channel field 515 having 2 bytes, followed by a beacon information field 516 having 1 byte, and followed by a Cyclic Redundancy Check (CRC) field 517 having 4 bytes.

In describing the individual details of the transmit power and channel field 515, the transmit power and channel field 515 includes a transmit power constraint field 552 having 5 bits, followed by a primary channel offset field 554 having 4 bits, followed by a bandwidth field 556 having 4 bits, followed by a primary channel indicator field 558 having 4 bits, and followed by a reserved field 560 having 3 bits.

In describing the individual details of the beacon information field 516, the beacon information field 516 includes a Traffic Indication Map (TIM) following field 572 having 1 bit, followed by a full beacon following field 574 having 1 bit, followed by an Extended Service Set (ESS) field 576 having 1 bit, followed by an IBSS field 578 having 1 bit, and followed by a reserved field 580 having 4 bits.

In some aspects, such shortened beacon messages may not accommodate all of the characteristic values of interest. Further, as described above, it may be desirable for the STA106 to selectively poll the AP104 for certain characteristics of interest. In the example of fig. 5B, the shortened beacon provides information specifically related to transmit power constraints at the AP 104. STAs 106 interested in this information may optionally request this information using polling messages as described above. In some aspects, the AP104 may periodically transmit the short beacon message, and the STA106 may instead receive the beacon message of fig. 5B by synchronizing its reception with the transmission from the AP 104. In certain aspects, the STA106 may synchronize its reception with transmissions from the AP104 by using a synchronization beacon transmitted by the AP 104. The synchronization beacon may be of the shortened beacon message type and is typically transmitted according to the same methods as those discussed above with reference to the shortened beacon message. The STA106 may also aggregate information received over multiple periods in a periodically transmitted short beacon message to obtain complete network configuration information.

The synchronization beacon may include one or more of the following: a hash value of the BSSID served by the AP104, and additional information that allows the STA106 to determine the position in time of the next beacon to be transmitted from the AP 104. The hash value of the BSSID allows the STA106 to determine that the synchronization beacon is from the AP104, and not from some other AP with which the STA106 is not associated. Thus, in some aspects, the STA106 need only decode the synchronization beacon if it contains a hash of the BSSID used by the AP 104. Further, the additional information allows the STA106 to synchronize timing with the AP104 for communication. For example, the additional information may include an absolute time at which a beacon was transmitted by the AP 104. The STA106 may also have information related to the time period between transmission of beacons. Thus, the STA106 may synchronize to the absolute time transmitted in the beacon and selectively listen for subsequent beacons at repeated intervals corresponding to the time period. The absolute time may be calculated from a reference time known by the STA106 and the AP 104.

In another aspect, the additional information may include: indicating the relative time of the time offset from the transmission of the synchronization beacon by the AP104 to the transmission of the next beacon. For example, the STA106 may have received the absolute time for synchronization in the first beacon. The STA106 may then receive a subsequent beacon including a sequence number and a time offset indicating a time offset between when the subsequent beacon is scheduled to be transmitted and when the subsequent beacon is actually transmitted due to, for example, contention. As described above, the STA106 may also have information about the time period between transmissions of beacons. Based on multiplying the sequence number by the time period, the STA106 may determine when subsequent beacons are scheduled to transmit. Further, by adding the time offset to the scheduled time, the STA106 may determine when the subsequent beacon is actually transmitted. The STA106 may then synchronize its time with the time of the actual transmission of the subsequent beacon. Thus, the STA106 may sleep until the AP104 transmits the next beacon at a time period after the synchronized time, and then the STA106 wakes up and receives the next beacon.

The time offset may be the same between successive beacon messages, which generally allows the STA106 to know the transmission schedule of the beacon. Further, as described above, the STA106 may have information related to the order in which beacon messages are transmitted, including when to transmit synchronization beacons. As described above, based on this information, the STA106 may determine when different beacon messages with different information are to be transmitted by the AP104 and only listen for related beacon messages based on their offset from the synchronization beacon. For example, the synchronization beacon may be the third of 5 beacon messages that are transmitted in sequence by the AP 104. Thus, the STA106 may determine from the third beacon in sequence that the sequence is to be transmitted by the AP104 upon receiving the synchronization beacon.

In another aspect, the additional information may include: an index indicating the relative position of the synchronization beacon in the transmission of the sequence of beacon messages. Thus, the STA106 may determine from the index position indicated in the synchronization beacon that the sequence is to be transmitted from the AP 104. Further, the STA106 may assume that the next beacon will be transmitted at a fixed time interval upon receipt of the synchronization beacon, as described above.

In an aspect, the information discussed above for the synchronization beacon may be transmitted in the location of a SERVICE (SERVICE) field in the physical layer (PHY) preamble of the packet. In some aspects, the synchronization beacon may be transmitted in a PHY layer preamble of a packet consisting of only a PHY header.

Fig. 5C illustrates an example of a PHY preamble 500C including a synchronization beacon that may be used in the wireless communication system of fig. 1. In certain aspects, the PHY preamble 500c includes a high-throughput short training field (HT-STF)592 followed by a high-throughput long training field (HT-LTF1)594 followed by a signal SIG-a (which is also referred to as SIG) 596. Other embodiments need not be limited to high throughput as mentioned in the previous sentence. As discussed herein, the information of the synchronization beacon may be transmitted in the SIG-a field 596.

In another aspect, the information discussed above for the synchronization beacon may be transmitted in the MAC data field of the packet. In another aspect, the information discussed above for the synchronization beacon may be transmitted at the location of a Signal (SIG) field in the physical layer preamble of the packet.

For example, the normal SIG field of the physical layer preamble may include the following information:

for a sync beacon, in an aspect, the SIG field of the physical layer preamble may be modified to include the following information:

SIG-A field	Number of bits	Note
			MCS	4	MCS for SU case, reserved for MU
Number of SS	2	Number of spatial streams for SU and reserved for MU
			Beacon/NDP	1	Indicating whether the frame is a synchronization beacon or a Neighbor Discovery Protocol (NDP)
Length of	12	Is set to be all zero
			Relative position	3	Indexing of synchronization beacons relative to corresponding primary beacons
SSID hashing	8	Hash value of SSID/BSSID
			Offset of	10	With the expected beaconTime offset (in time slots)
Retention	2
			CRC	4
Tail part	6
			Total number of	52

In some aspects, the length field may be set to all zeros to indicate to the STA106 that the SIG field is for a synchronization beacon. Based on the length fields all being zero, the STA106 may determine that subsequent fields in the SIG field no longer serve the same function as the normal SIG field. In turn, these subsequent fields perform new functions. For example, a subsequent relative position field may indicate the sequential position of the synchronization beacon relative to the first beacon in the beacon sequence. Further, the subsequent offset field may indicate: the offset time of the synchronization beacon is transmitted relative to the time at which it is expected to be transmitted in one slot (assuming the AP104 is off schedule). The STA106 may use this information as discussed above to synchronize timing with the AP 104.

Fig. 6 shows a flow diagram depicting an example process by which the wireless device of fig. 2 obtains a data frame (e.g., a shortened beacon message). First, a wireless device, such as the STA106, may be in a sleep state and then awaken to an awake state at a random or predetermined time. The process then begins at 601. At 602, now awake, the STA106 receives a first shortened frame (e.g., a shortened beacon message) from the AP 104. The STA106 may wait a predetermined period of time in anticipation of receiving such a first shortened frame from the AP 104. If no frames arrive, the STA106 may return to the sleep state until a subsequent attempt may be made.

At 603, the STA106 may then obtain content information and/or timing information for a plurality of subsequent frames from the first shortened frame. The processor 204 running the software may play this role.

Using the content information and/or timing information as discussed above, the STA106 may then identify which of the plurality of subsequent shortened frames (e.g., shortened beacon messages) are of interest to the STA106 and/or the transmission times of the shortened frames of interest at 604. At 605, the STA106 may then synchronize the wake-up period of the transceiver 214 to coincide with the transmission time of the shortened frames of interest. In some aspects, the period between shortened frame transmissions by the AP104 is known a priori to the STA 106. The STA106 may thus synchronize reception by introducing an offset from the time the first shortened frame was received. This offset allows the wake-up time of the transceiver 214 of the STA106 to coincide with the transmission time of the shortened frame of interest. In some aspects, the timing information may alternatively comprise an absolute indication of a time offset until the beacon message. At 606, the STA106 receives the shortened frame of interest. At 607, the process may end.

Fig. 7 shows a flow diagram depicting another exemplary process by which the wireless device of fig. 2 generates and transmits data frames. Here, a wireless device such as AP104 may begin the process at 701. At 702, the AP104 can determine a plurality of transmission time intervals for a first beacon message type and a second beacon message type. In some aspects, the first beacon message type comprises a synchronization beacon message type and the second beacon message type comprises a normal beacon message type, the normal beacon message type comprising information such as an IE.

At 703, the AP104 may insert timing information and/or content information related to other beacon messages into at least one beacon message of the first beacon message type. This may include: a sequence number or similar identifier is inserted into the synchronization signal message. The STA106 waking from the sleep state may decode the beacon message and resynchronize with the remaining beacon messages sent by the AP104, as discussed herein.

At 704, the AP104 may transmit the plurality of beacon messages according to the determined transmission time interval using, for example, the transceiver 214. At 705, the process ends.

Fig. 8 is a functional block diagram of another exemplary wireless device 800 that may be used in the wireless communication system 100 of fig. 1. The device 800 includes a receiving module 802 for receiving a beacon message from a device, such as the AP 104. The receiving module 802 may be configured to: one or more of the functions discussed above with reference to blocks 602 and 606 of fig. 6 are performed. The receiving module 802 may correspond to the receiver 212. Further, the device 800 includes an identifying module 804 for identifying a transmission time of a beacon message through a frame, such as a synchronization beacon. The identification module 804 may be configured to: one or more of the functions discussed above with reference to blocks 604 and 605 of fig. 6 are performed. The identifying module 804 may correspond to one or more of the processor 204 and the DSP 220. Further, the device 800 also includes a decoding module 806 for decoding the beacon message as discussed above. The decode module 806 may correspond to one or more of the processor 204 and the DSP 220.

As used herein, the term "determining" encompasses a wide variety of actions. For example, "determining" can include calculating, computing, processing, deriving, studying, querying (e.g., a look-up table, database, or other data structure), ascertaining, and the like. Further, "determining" may also include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Further, "determining" may also include resolving, selecting, establishing, and the like. Further, in certain aspects, "channel width" as used herein may encompass bandwidth, or it may also be referred to as bandwidth.

As used herein, a phrase referring to "at least one of a list of items" refers to any combination of those items, including a singular member. For example, "at least one of a, b, or c" is intended to cover: a. b, c, a-b, a-c, b-c and a-b-c.

The various operations of the methods described above may be performed by any suitable means (e.g., various hardware and/or software components, circuits, and/or modules) that is capable of performing the operations. In general, any operations shown in the figures may be performed by respective functional units capable of performing the operations.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a field programmable gate array signal (FPGA) or other Programmable Logic Device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

In one or more aspects, the functions described herein may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Further, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects, computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media). Further, in some aspects, computer readable media may include transitory computer readable media (e.g., signals). Combinations of the above should also be included within the scope of computer-readable media.

The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the invention. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the invention.

The functions described herein may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored as one or more instructions on a computer-readable medium. A storage media may be any available media that can be accessed by a computer. By way of example and not limitationSuch computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray discOptical disks, in which a magnetic disk usually reproduces data magnetically, and an optical disk reproduces data optically with a laser.

Accordingly, certain aspects of the present invention may comprise a computer program product for performing the operations illustrated herein. For example, such a computer program product may include a computer-readable medium having stored (and/or encoded) instructions thereon, which may be executed by one or more processors to perform the operations described herein. For certain aspects, a computer program product may include packaging materials.

The software or instructions may also be transmitted over a transmission medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of transmission medium.

Further, it should be appreciated that modules and/or other suitable means for performing the methods and techniques described herein can be downloaded and/or obtained by a user terminal and/or base station as needed. For example, such a device may be coupled to a server to facilitate the transfer of modules that perform the methods described herein. Alternatively, the various methods described herein can be provided via a storage unit (e.g., RAM, ROM, a physical storage medium such as a Compact Disc (CD) or floppy disk, etc.), such that the various methods are available when the storage unit is coupled to or provided to the device by the user terminal and/or base station. In addition, any other suitable technique for providing the methods and techniques described herein to a device may also be used.

It should be understood that the invention is not limited to the precise arrangements and components shown above. Various modifications, changes, and variations may be made in the arrangement, operation, and details of the methods and apparatus described above without departing from the scope of the invention.

While the foregoing is directed to aspects of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims (100)

1. A method of transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the method comprising:

transmitting a repeating finite sequence of beacon messages from the access point to the access terminal, the sequence comprising a first beacon message comprising a relative location identifier indicating a timing of a subsequent beacon message in the finite sequence and identifying content included in the subsequent beacon message, wherein the subsequent beacon message comprises information not included in the first beacon message;

transmitting a time offset, an absolute time, and a sequence number from the access point to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number; and

decoding, at the access terminal, the first beacon message and a proper subset of a sequence of beacon messages based on the relative location identifier, wherein the access terminal is in a low power state during transmission of a second subset of a sequence of beacon messages, and the second subset of beacon messages includes beacon messages that are not in the proper subset and does not include the first beacon message;

decoding, by the access terminal, a second beacon message that provides the absolute time; and

decoding, by the access terminal, a third beacon message subsequent to the second beacon message, wherein the third beacon message includes the sequence number and the time offset relative to the first beacon message, and the time offset indicates a time difference between a time at which the third beacon message is scheduled to be transmitted by the access point and a time at which the third beacon message is actually transmitted.

2. The method of claim 1, wherein the first beacon message comprises: including information for the network bandwidth of the base station subsystem.

3. The method of claim 1, wherein the first beacon message comprises: indicating that a second beacon message in the sequence has information comprising capabilities of the access point.

4. The method of claim 3, wherein the capability comprises a number of antennas of the access point.

5. The method of claim 1, wherein the first beacon message includes a full beacon following field indicating whether the access point transmits a full beacon message immediately following the first beacon message in order.

6. The method of claim 1, wherein the second beacon message comprises a physical layer preamble having a length field consisting of all zeros.

7. The method of claim 1, wherein the repeating sequence of beacon messages has a short beacon interval and a beacon interval, the beacon interval being an integer multiple of the short beacon interval.

8. The method of claim 1, wherein the base station subsystem has a Basic Service Set Identification (BSSID) and the first beacon message has information comprising a compressed BSSID value.

9. The method according to claim 8, wherein the compressed BSSID value is a cyclic redundancy check, CRC, of the BSSID.

10. The method of claim 1, wherein the first beacon message has a four byte timestamp consisting of the four least significant bytes of an access point timestamp.

11. The method of claim 1, wherein the first beacon message includes a one byte change sequence field, and further comprising: increasing, by the access point, a value of the change sequence field to indicate a change in network information.

12. The method of claim 1, wherein the first beacon message comprises a frame control field comprising a three-bit bandwidth, BW, field.

13. A method of communicating in a base station subsystem comprising an access point and an access terminal, wherein the base station subsystem is identified by a basic service set identification, BSSID, the method comprising:

transmitting beacon messages from the access point to the access terminal, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type;

transmitting a time offset, an absolute time, and a sequence number from the access point to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted; and

transmitting a beacon message of the short beacon message type at a first time interval; and

transmitting a full beacon message of the full beacon message type at a second time interval, the second time interval being equal to an integer multiple of the first time interval,

wherein each beacon message of the short beacon message type includes a compressed BSSID field having a value indicating a cyclic redundancy check of the BSSID.

14. The method of claim 13, wherein the access point provides a timestamp and each beacon message of the short beacon message type includes a four byte timestamp consisting of the four least significant bytes of the access point timestamp.

15. The method of claim 13, wherein each beacon message of the short beacon message type includes a one-byte change sequence field having a value, and the method further comprises:

incrementing a value of the change sequence field in the beacon message of the short beacon message type to indicate a change in information about the base station subsystem.

16. The method of claim 13, wherein each beacon message of the short beacon message type includes a full beacon following field indicating whether an immediately subsequent beacon message is of the full beacon message type.

17. The method of claim 16, wherein the access point provides a timestamp, and when a next beacon message of the full beacon message type is scheduled for transmission, the time of the next beacon message indicated in the full beacon follow field is the upper three bytes of the four least significant bytes of the value of the timestamp.

18. The method of claim 13, wherein each beacon message of the short beacon message type comprises a frame control field comprising a three-bit bandwidth, BW, field.

19. A method of transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the method comprising:

decoding, by the access terminal, a first beacon message that provides absolute time;

decoding, by the access terminal, a second beacon message subsequent to the first beacon message, wherein the second beacon message includes a sequence number relative to the first beacon message and a time offset indicating a time difference between a time at which the second beacon message is scheduled to be transmitted by the access point and a time at which the second beacon message is actually transmitted; and

transitioning the access terminal from a low power state to a high power state at a time determined as a function of the time offset, the absolute time, and the sequence number.

20. A method of communicating a set of information elements in a base station subsystem comprising an access point and an access terminal, the method comprising:

transmitting beacon messages from the access point to the access terminal, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type, and each beacon message of the full beacon message type includes the set of information elements;

transmitting a plurality of beacon messages of the short beacon message type, wherein each of the plurality of beacon messages includes a proper subset of the set of information elements, and the plurality of beacon messages includes the set of information elements; and

transmitting a time offset, an absolute time, and a sequence number to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

21. The method of claim 20, wherein the set of information elements includes network information about the base station subsystem.

22. A method of communicating in a base station subsystem comprising an access point and an access terminal, the method comprising:

transmitting beacon messages from the access point to the access terminal, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type;

transmitting a first beacon message including content information specifying information included in a beacon message of the short beacon message type transmitted after the first beacon message; and

transmitting a time offset, an absolute time, and a sequence number to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

23. The method of claim 22, further comprising:

transmitting a plurality of beacon messages of the short beacon message type after the first beacon message, wherein each of the plurality of beacon messages includes information according to the content information; and

changing a power state of the access terminal to the low power state for a portion of the plurality of beacon messages of the short beacon message type based on the content information.

24. The method of claim 22, wherein the first beacon message is of the short beacon message type.

25. A method of communicating in a base station subsystem comprising an access point and an access terminal, the method comprising:

transmitting beacon messages from the access point to the access terminal, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type;

transmitting a plurality of beacon messages of the short beacon message type, wherein each of the plurality of beacon messages comprises a physical layer preamble comprising a signal, SIG, field, the SIG field comprising a length field; and

decoding the plurality of beacon messages into a synchronization beacon message at the access terminal, provided that: the length field of the beacon message is set to all zeros,

wherein each beacon message decoded as a synchronization beacon message includes a subsequent relative position field indicating a sequence position of the synchronization beacon relative to a first beacon message in a sequence of beacon messages and a subsequent offset field indicating an offset time at which the synchronization beacon is transmitted relative to a time at which the synchronization beacon is expected to be transmitted.

26. A system for transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the system comprising:

the access point, comprising: a transmitter configured to transmit a repeating finite sequence of beacon messages, wherein the sequence comprises a first beacon message comprising a timing indicative of a subsequent beacon message in the finite sequence and a relative location identifier configured to identify content included in the subsequent beacon message, and the subsequent beacon message comprises information not included in the first beacon message; and

the access terminal, comprising:

a decoding module configured to:

decoding a proper subset of the first beacon message and beacon message sequence based on the relative location identifier;

decoding a second beacon message that provides an absolute time; and

decoding a third beacon message subsequent to the second beacon message, wherein the third beacon message includes a sequence number and a time offset relative to the first beacon message, and the time offset indicates a time difference between a time at which the third beacon message is scheduled to be transmitted by the access point and a time at which the third beacon message is actually transmitted; and

a processor configured to change a state of the access terminal to a low power state when the transmitter of the access point transmits a second subset of a sequence of beacon messages, wherein,

a second subset of the beacon messages includes beacon messages not in the proper subset and does not include the first beacon message, and is configured to transition the access terminal from the low-power state to a high-power state at a time determined according to the time offset, the absolute time, and the sequence number.

27. The system of claim 26, wherein the first beacon message comprises: including information for the network bandwidth of the base station subsystem.

28. The system of claim 26, wherein the first beacon message comprises: indicating that a second beacon message in the sequence has information comprising capabilities of the access point.

29. The system of claim 28, wherein the capability comprises a number of antennas of the access point.

30. The system of claim 26, wherein the first beacon message includes a full beacon following field that indicates whether the access point transmitted a full beacon message immediately following the first beacon message.

31. The system of claim 26, wherein the second beacon message comprises a physical layer preamble having a length field consisting of all zeros.

32. The system of claim 26, wherein the repeating sequence of beacon messages has a short beacon interval and a beacon interval, the beacon interval being an integer multiple of the short beacon interval.

33. The system of claim 26, comprising:

a base station subsystem comprising the access point and having a Basic Service Set Identification (BSSID), wherein the first beacon message comprises information including a compressed BSSID value.

34. The system of claim 33, wherein the compressed BSSID value is a cyclic redundancy check, CRC, of the BSSID.

35. The system of claim 26, wherein the first beacon message has a four byte timestamp consisting of the four least significant bytes of an access point timestamp.

36. The system of claim 26, wherein the first beacon message includes a one byte change sequence field, and the access point is configured to increment a value of the change sequence field to indicate a change in network information.

37. The system of claim 26, wherein the first beacon message comprises a frame control field comprising a three-bit bandwidth, BW, field.

38. An access point identified by a basic service set identification, BSSID, the access point comprising:

a transmitter configured to transmit a beacon message, wherein:

each beacon message is an instance of a full beacon message type or an instance of a short beacon message type;

the transmitter is configured to:

transmitting a beacon message of the short beacon message type at a first time interval;

transmitting a full beacon message of the full beacon message type at a second time interval, the second time interval being equal to an integer multiple of the first time interval;

transmitting a time offset, an absolute time, and a sequence number to an access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted; and

each beacon message of the short beacon message type includes a compressed BSSID field,

the compressed BSSID field has a value indicating a cyclic redundancy check of the BSSID.

39. The access point of claim 38, wherein the access point is configured to provide a timestamp, and each beacon message of the short beacon message type includes a four byte timestamp consisting of the four least significant bytes of the access point timestamp.

40. The access point of claim 38, wherein each beacon message of the short beacon message type includes a one-byte change sequence field having a value, and the access point is configured to increment the value of the change sequence field in the beacon message of the short beacon message type to indicate a change in information about a base station subsystem.

41. The access point of claim 38, wherein each beacon message of the short beacon message type includes a full beacon following field indicating whether an immediately subsequent beacon message is of the full beacon message type.

42. The access point of claim 41, wherein the access point is configured to provide a timestamp, and when a next beacon message of the full beacon message type is scheduled for transmission, the time of the next beacon message indicated in the full beacon follow field is the upper three bytes of the four least significant bytes of the value of the timestamp.

43. The access point of claim 38, wherein each beacon message of the short beacon message type comprises a frame control field comprising a three-bit bandwidth, BW, field.

44. An access terminal configured to receive beacon messages in a base station subsystem, the access terminal comprising:

a decoding module configured to:

decoding a first beacon message that provides an absolute time;

decoding a second beacon message subsequent to the first beacon message, wherein the second beacon message includes a sequence number and a time offset relative to the first beacon message, and the time offset indicates a time difference between a time at which the second beacon message is scheduled to be transmitted and a time at which the second beacon message is actually transmitted; and

transitioning the access terminal from a low power state to a high power state at a time determined from the time offset, the absolute time, and the sequence number.

45. An access point configured to communicate a set of information elements in a base station subsystem, the access point comprising:

a transmitter configured to:

transmitting beacon messages, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type, and each beacon message of the full beacon message type includes the set of information elements;

transmitting a plurality of beacon messages of the short beacon message type, wherein each of the plurality of beacon messages includes a proper subset of the set of information elements, and the plurality of beacon messages includes the set of information elements; and

transmitting a time offset, an absolute time, and a sequence number to an access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

46. The access point of claim 45, wherein the set of information elements includes network information about the base station subsystem.

47. A system comprising an access point, the access point comprising:

a transmitter configured to:

transmitting beacon messages, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type; transmitting a first beacon message including content information,

the content information specifies information included in a beacon message of the short beacon message type transmitted after the first beacon message; and

transmitting a time offset, an absolute time, and a sequence number to an access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

48. The system of claim 47, wherein:

the transmitter is further configured to transmit a plurality of beacon messages of the short beacon message type after the first beacon message;

each of the plurality of beacon messages including information according to the content information;

the system also includes an access terminal including a processor configured to change a power state of the access terminal to the low power state for a portion of the plurality of beacon messages of the short beacon message type based on the content information.

49. The system of claim 47, wherein the first beacon message is of the short beacon message type.

50. An access terminal configured to receive beacon messages for a base station subsystem, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type, the access terminal comprising:

a receiver configured to receive a plurality of beacon messages of the short beacon message type, wherein each of the plurality of beacon messages comprises a physical layer preamble comprising a signal, SIG, field, the SIG field comprising a length field; and

a decoding module configured to decode the plurality of beacon messages, wherein a beacon message of the plurality of beacon messages is decoded as a synchronization beacon message if: the length field of the beacon message is set to all zeros,

wherein each beacon message decoded as a synchronization beacon message includes a subsequent relative position field indicating a sequence position of the synchronization beacon relative to a first beacon message in a sequence of beacon messages and a subsequent offset field indicating an offset time at which the synchronization beacon is transmitted relative to a time at which the synchronization beacon is expected to be transmitted.

51. A system for transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the system comprising:

the access point comprising means for transmitting configured to:

transmitting a repeating finite sequence of beacon messages, wherein the sequence comprises a first beacon message comprising a relative position identifier indicating a timing of a subsequent beacon message in the finite sequence,

identifying content included in the subsequent beacon message, wherein the subsequent beacon message includes information not included in the first beacon message, an

Transmitting a time offset, an absolute time, and a sequence number to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number,

wherein the access terminal comprises:

a module for decoding configured to

Decoding a proper subset of the first beacon message and the sequence of beacon messages based on the relative location identifier;

decoding a second beacon message that provides the absolute time; and

decoding a third beacon message subsequent to the second beacon message, wherein the third beacon message includes the sequence number and the time offset relative to the first beacon message, and the time offset indicates a time difference between a time at which the third beacon message is scheduled to be transmitted by the access point and a time at which the third beacon message is actually transmitted; and

means for processing configured to change a state of the access terminal to a low power state when the means for transmitting of the access point transmits a second subset of a sequence of beacon messages, wherein the second subset of beacon messages includes beacon messages that are not in the proper subset and does not include the first beacon message.

52. The system of claim 51, wherein the first beacon message comprises: including information for the network bandwidth of the base station subsystem.

53. The system of claim 51, wherein the first beacon message comprises: indicating that a second beacon message in the sequence has information comprising capabilities of the access point.

54. The system of claim 53, wherein the capability comprises a number of antennas of the access point.

55. The system of claim 51, wherein the first beacon message comprises a full beacon following field indicating whether the access point transmits a full beacon message immediately following the first beacon message in order.

56. The system of claim 51, wherein the second beacon message comprises a physical layer preamble having a length field consisting of all zeros.

57. The system of claim 51, wherein the repeating sequence of beacon messages has a short beacon interval and a beacon interval, and the beacon interval is an integer multiple of the short beacon interval.

58. The system of claim 51, further comprising:

a base station subsystem comprising the access point and having a Basic Service Set Identification (BSSID), wherein the first beacon message comprises information including a compressed BSSID value.

59. The system of claim 58, wherein the compressed BSSID value is a Cyclic Redundancy Check (CRC) of the BSSID.

60. The system of claim 51, wherein the first beacon message comprises a four byte timestamp consisting of the four least significant bytes of an access point timestamp.

61. The system of claim 51, wherein the first beacon message includes a one byte change sequence field, and the access point is configured to increment a value of the change sequence field to indicate a change in network information.

62. The system of claim 51, wherein the first beacon message comprises a frame control field comprising a three-bit bandwidth BW field.

63. An access point identified by a basic service set identification, BSSID, the access point comprising:

means for transmitting beacon messages, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type, and the means for transmitting is configured to transmit beacon messages of the short beacon message type at first time intervals;

means for transmitting a full beacon message of the full beacon message type at a second time interval, the second time interval being equal to an integer multiple of the first time interval;

wherein each beacon message of the short beacon message type includes a compressed BSSID field having a value indicating a cyclic redundancy check of the BSSID; and

means for transmitting a time offset, an absolute time, and a sequence number to an access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

64. The access point of claim 63, wherein the access point is configured to provide a timestamp, and each beacon message of the short beacon message type includes a four byte timestamp consisting of the four least significant bytes of the access point timestamp.

65. The access point of claim 63, wherein each beacon message of the short beacon message type includes a one-byte change sequence field having a value, and the access point is configured to increment the value of the change sequence field in beacon messages of the short beacon message type to indicate a change in information about a base station subsystem.

66. The access point of claim 63, wherein each beacon message of the short beacon message type includes a full beacon following field indicating whether an immediately subsequent beacon message is of the full beacon message type.

67. The access point of claim 66, wherein the access point is configured to provide a timestamp, and when a next beacon message of the full beacon message type is scheduled for transmission, the time of the next beacon message indicated in the full beacon follow field is the upper three bytes of the four least significant bytes of the value of the timestamp.

68. The access point of claim 63, wherein each beacon message of the short beacon message type comprises a frame control field comprising a three-bit bandwidth BW field.

69. An access terminal for receiving beacon messages in a base station subsystem, the access terminal comprising:

a module for decoding configured to:

a first beacon message providing an absolute time is decoded,

decoding a second beacon message subsequent to the first beacon message, wherein the second beacon message includes a sequence number and a time offset relative to the first beacon message, and the time offset indicates a time difference between a time at which the second beacon message is scheduled to be transmitted and a time at which the second beacon message is actually transmitted; and

means for transitioning the access terminal from a low power state to a high power state at a time determined as a function of the time offset, the absolute time, and the sequence number.

70. An access point for communicating a set of information elements in a base station subsystem, the access point comprising:

means for transmitting beacon messages, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type, and each beacon message of the full beacon message type includes the set of information elements;

means for transmitting a plurality of beacon messages of the short beacon message type, wherein each of the plurality of beacon messages includes a proper subset of the set of information elements, and the plurality of beacon messages includes the set of information elements; and

means for transmitting a time offset, an absolute time, and a sequence number to an access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

71. The access point of claim 70, wherein the set of information elements includes network information about the base station subsystem.

72. A system comprising an access point, the access point comprising:

means for transmitting beacon messages, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type;

means for transmitting a first beacon message including content information specifying information included in a beacon message of the short beacon message type transmitted after the first beacon message; and

means for transmitting a time offset, an absolute time, and a sequence number to an access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

73. In accordance with the system of claim 72,

wherein the means for transmitting a beacon message is configured to transmit a plurality of beacon messages of the short beacon message type after the first beacon message, wherein each of the plurality of beacon messages includes information according to the content information; and

the system also includes an access terminal, the access terminal including: means for changing a power state of the access terminal to the low power state for a portion of the plurality of beacon messages of the short beacon message type based on the content information.

74. The system of claim 72, wherein the first beacon message is of the short beacon message type.

75. An access terminal configured to receive beacon messages for a base station subsystem, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type, the access terminal comprising:

means for receiving a plurality of beacon messages of the short beacon message type, wherein each of the plurality of beacon messages comprises a physical layer preamble containing a signal, SIG, field, the SIG field comprising a length field; and

means for decoding the plurality of beacon messages, wherein a beacon message of the plurality of beacon messages is decoded as a synchronization beacon message if: the length field of the beacon message is set to all zeros,

wherein each beacon message decoded as a synchronization beacon message includes a subsequent relative position field indicating a sequence position of the synchronization beacon relative to a first beacon message in a sequence of beacon messages and a subsequent offset field indicating an offset time at which the synchronization beacon is transmitted relative to a time at which the synchronization beacon is expected to be transmitted.

76. An article of manufacture comprising a computer-readable storage medium having instructions stored thereon which, when executed by at least one processor, perform a method for transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the method comprising:

transmitting a repeating finite sequence of beacon messages from the access point to the access terminal, the sequence comprising a first beacon message comprising a relative location identifier indicating a timing of a subsequent beacon message in the finite sequence and identifying content included in the subsequent beacon message, wherein the subsequent beacon message comprises information not included in the first beacon message;

transmitting a time offset, an absolute time, and a sequence number from the access point to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number; and

decoding, at the access terminal, the first beacon message and a proper subset of a sequence of beacon messages based on the relative location identifier, wherein the access terminal is in a low power state during transmission of a second subset of a sequence of beacon messages, and the second subset of beacon messages includes beacon messages that are not in the proper subset and does not include the first beacon message;

decoding, by the access terminal, a second beacon message that provides the absolute time; and

decoding, by the access terminal, a third beacon message subsequent to the second beacon message, wherein the third beacon message includes the sequence number and the time offset relative to the first beacon message, and the time offset indicates a time difference between a time at which the third beacon message is scheduled to be transmitted by the access point and a time at which the third beacon message is actually transmitted.

77. The article of manufacture of claim 76, wherein the first beacon message comprises: including information for the network bandwidth of the base station subsystem.

78. The article of manufacture of claim 76, wherein the first beacon message comprises: indicating that a second beacon message in the sequence has information comprising capabilities of the access point.

79. The article of claim 78, wherein the capability comprises a number of antennas of the access point.

80. The article of manufacture of claim 76, the first beacon message comprising a full beacon following field indicating whether the access point sent a full beacon message immediately following the first beacon message in order.

81. The article of manufacture of claim 76, wherein the second beacon message comprises a physical layer preamble having a length field consisting of all zeros.

82. The article of claim 76, wherein the repeating sequence of beacon messages has a short beacon interval and a beacon interval, the beacon interval being an integer multiple of the short beacon interval.

83. The article of manufacture of claim 76, wherein the base station subsystem has a Basic Service Set Identification (BSSID) and the first beacon message has information comprising a compressed BSSID value.

84. The article of manufacture of claim 83, wherein the compressed BSSID value is a Cyclic Redundancy Check (CRC) of the BSSID.

85. The article of manufacture of claim 76, wherein the first beacon message has a four byte timestamp consisting of the four least significant bytes of the access point timestamp.

86. The article of manufacture of claim 76, wherein the first beacon message comprises a one-byte change sequence field, and the method further comprises: increasing, by the access point, a value of the change sequence field to indicate a change in network information.

87. The article of manufacture of claim 76, wherein the first beacon message comprises a frame control field comprising a three-bit bandwidth BW field.

88. An article of manufacture comprising a computer-readable storage medium having instructions stored thereon that when executed by at least one processor perform a method for transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the base station subsystem identified by a basic service set identification, BSSID, the method comprising:

transmitting beacon messages from the access point to the access terminal, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type;

transmitting a time offset, an absolute time, and a sequence number from the access point to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted; and

transmitting a beacon message of the short beacon message type at a first time interval; and

transmitting a full beacon message of the full beacon message type at a second time interval, the second time interval being equal to an integer multiple of the first time interval,

wherein each beacon message of the short beacon message type includes a compressed BSSID field having a value indicating a cyclic redundancy check of the BSSID.

89. The article of manufacture of claim 88, wherein the access point provides a timestamp and each beacon message of the short beacon message type includes a four byte timestamp consisting of the four least significant bytes of the access point timestamp.

90. The article of manufacture of claim 88, wherein each beacon message of the short beacon message type includes a one-byte change sequence field having a value, and the method further comprises:

incrementing a value of the change sequence field in the beacon message of the short beacon message type to indicate a change in information about the base station subsystem.

91. The article of manufacture of claim 88, wherein each beacon message of the short beacon message type includes a full beacon following field indicating whether an immediately subsequent beacon message is of the full beacon message type.

92. The article of manufacture of claim 91, wherein the access point provides a timestamp and the time of the next beacon message indicated in the full beacon follow field is the upper three bytes of the four least significant bytes of the value of the timestamp when the next beacon message of the full beacon message type is scheduled for transmission.

93. The article of manufacture of claim 88, wherein each beacon message of the short beacon message type comprises a frame control field comprising a three-bit bandwidth, BW, field.

94. An article of manufacture comprising a computer-readable storage medium having instructions stored thereon which, when executed by at least one processor, perform a method for transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the method comprising:

decoding, by the access terminal, a first beacon message that provides absolute time;

decoding, by the access terminal, a second beacon message subsequent to the first beacon message, wherein the second beacon message includes a sequence number relative to the first beacon message and a time offset indicating a time difference between a time at which the second beacon message is scheduled to be transmitted by the access point and a time at which the second beacon message is actually transmitted; and

transitioning the access terminal from a low power state to a high power state at a time determined as a function of the time offset, the absolute time, and the sequence number.

95. An article of manufacture comprising a computer-readable storage medium having instructions stored thereon which, when executed by at least one processor, perform a method for communicating a set of information elements in a base station subsystem comprising an access point and an access terminal, the method comprising:

transmitting beacon messages from the access point to the access terminal, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type, and each beacon message of the full beacon message type includes the set of information elements;

transmitting a plurality of beacon messages of the short beacon message type, wherein each of the plurality of beacon messages includes a proper subset of the set of information elements, and the plurality of beacon messages includes the set of information elements; and

transmitting a time offset, an absolute time, and a sequence number to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

96. The article of manufacture of claim 95, wherein the set of information elements comprises complete network information for the base station subsystem.

97. An article of manufacture comprising a computer-readable storage medium having instructions stored thereon which, when executed by at least one processor, perform a method for transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the method comprising:

transmitting beacon messages from the access point to the access terminal, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type;

transmitting a first beacon message including content information specifying information included in a beacon message of the short beacon message type transmitted after the first beacon message; and

transmitting a time offset, an absolute time, and a sequence number to the access terminal to enable the access terminal to transition from a low-power state to a high-power state at a time determined from the time offset, the absolute time, and the sequence number, wherein the time offset indicates a time difference between a time a beacon message is scheduled to be transmitted by the access point and a time the beacon message is actually transmitted.

98. The article of manufacture of claim 97, the method further comprising:

transmitting a plurality of beacon messages of the short beacon message type after the first beacon message, wherein each of the plurality of beacon messages includes information according to the content information; and

changing a power state of the access terminal to the low power state for a portion of the plurality of beacon messages of the short beacon message type based on the content information.

99. The article of manufacture of claim 97, wherein the first beacon message is of the short beacon message type.

100. An article of manufacture comprising a computer-readable storage medium having instructions stored thereon which, when executed by at least one processor, perform a method for transmitting beacon messages in a base station subsystem comprising an access point and an access terminal, the method comprising:

transmitting beacon messages from the access point to the access terminal, wherein each beacon message is an instance of a full beacon message type or an instance of a short beacon message type;

transmitting a plurality of beacon messages of the short beacon message type, wherein each of the plurality of beacon messages comprises a physical layer preamble comprising a signal, SIG, field, the SIG field comprising a length field; and

decoding the plurality of beacon messages into a synchronization beacon message at the access terminal assuming the following: the length field of the beacon message is set to all zeros,

wherein each beacon message decoded as a synchronization beacon message includes a subsequent relative position field indicating a sequence position of the synchronization beacon relative to a first beacon message in a sequence of beacon messages and a subsequent offset field indicating an offset time at which the synchronization beacon is transmitted relative to a time at which the synchronization beacon is expected to be transmitted.