Abstract:
Embodiments of the invention include methods, articles, and apparatuses to provide information related to channels transmitted and received according to a wireless communications protocol. One embodiment of the invention provides a method comprising generating channel offset information corresponding to an extension channel within a channel of a wireless communications protocol, and transmitting the channel offset information as part of channel information to be transmitted to one or more remote devices communicating according to the wireless communications protocol. Other embodiments are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/775,135 filed on Feb. 18, 2006. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments of the invention relate to wireless communications. More particularly, embodiments of the invention relate to wireless local area network (WLAN) communications utilizing 40 MHz channel switching including, for example, IEEE 802.11n based communications. 
       BACKGROUND 
       [0003]    Current Institute of Electrical and Electronics Engineers (IEEE) 802.11b/g wireless local area network (WLAN) standards offer the convenience of wireless connections with adequate performance for many tasks. The IEEE 802.11b standard corresponds to IEEE Std. 802.11b-1999 entitled “Local and Metropolitan Area Networks, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Higher-Speed Physical Layer Extension in the 2.4 GHz Band,” approved Sep. 16, 1999 as well as related documents. The IEEE 802.11g standard corresponds to IEEE Std. 802.11g-2003 entitled “Local and Metropolitan Area Networks, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, Amendment 4: Further Higher Rate Extension in the 2.4 GHz Band,” approved Jun. 27, 2003, as well as related documents. Related documents may include, for example, the IEEE 802.11a standard. 
         [0004]    However, for some operations under current WLAN standards, such as streaming high quality multimedia content, throughput provided by these standards may not be adequate. In response to demand, IEEE approved the creation of the IEEE 802.11 Task Group N (TGn) to define modifications to the Physical Layer and Medium Access Control Layer (PHY/MAC) to deliver 100 megabit-per-second (Mbps) or greater throughput. The result is an upcoming specification referred to as ‘IEEE 802.11n’ that is an addition to the 802.11 family of standards that is intended to increase wireless network speed and reliability. 
         [0005]    IEEE 802.11n communications are based on multiple input, multiple output (MIMO) technology that uses multiple antennae at both the transmitter and receiver sides of a communication link. The 802.11n standard may use orthogonal frequency-division multiplexing (OFDM) to increase speed, as well as techniques to transmit multiple redundant copies of data to increase reliability. With prior art standards, a 20 MHz channel bandwidth was utilized. However, MIMO approaches using only 20-MHz channel require higher implementation costs to meet the IEEE TGn requirement of 100 Mbps throughput. Meeting the IEEE TGn requirement with only 20-MHz channels would require at least three antenna analog front ends at both the transmitted and receiver. At the same time, a 20-MHz approach will struggle to provide a robust experience with applications that demand higher throughput in real user environments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements. 
           [0007]      FIG. 1  illustrates a block diagram of one embodiment of a wireless local area network; 
           [0008]      FIG. 2  illustrates one embodiment of a New Extension Channel Offset element; 
           [0009]      FIG. 3  is a conceptual illustration of one embodiment of a channel switch request primitive; 
           [0010]      FIG. 4  is a conceptual illustration of one embodiment of a channel switch indication primitive; and 
           [0011]      FIG. 5  is a conceptual illustration of one embodiment of a channel switch response primitive. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    In the following description, numerous specific details are set forth. However, embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. 
         [0013]    Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
         [0014]    Embodiments of the invention provide for 40 MHz channel switching in wireless local area network (WLAN) communications, such as in IEEE 802.11n based communications. In one embodiment, a 40 MHz channel may include both control and extension channels (each 20 MHz). To implement 40 MHz channel switching, described herein are an Extension Channel information element and a format for a Channel Switch Announcement frame. 
         [0015]    It should be understood that embodiments of the present invention may be used in a variety of applications. Although the present invention is not limited in this respect, the circuits disclosed herein may be used in many apparatuses such as in the transmitters and receivers of a radio system. Radio systems intended to be included within the scope of the present invention include, by way of example only, wireless local area networks (WLAN) devices and wireless wide area network (WWAN) devices including wireless network interface devices and network interface cards (NICs), base stations, access points (APs), gateways, bridges, hubs, cellular radiotelephone communication systems, satellite communication systems, two-way radio communication systems, one-way pagers, two-way pagers, personal communication systems (PCS), personal computers (PCs), personal digital assistants (PDAs), and the like, although the scope of the invention is not limited in this respect. 
         [0016]    Types of wireless communication systems intended to be within the scope of the present invention include, although not limited to, Wireless Local Area Network (WLAN), Wireless Wide Area Network (WWAN), Code Division Multiple Access (CDMA) cellular radiotelephone communication systems, Global System for Mobile Communications (GSM) cellular radiotelephone systems, North American Digital Cellular (NADC) cellular radiotelephone systems, Time Division Multiple Access (TDMA) systems, Extended-TDMA (E-TDMA) cellular radiotelephone systems, third generation (3G) systems like Wide-band CDMA (WCDMA), CDMA-2000, and the like, although the scope of the invention is not limited in this respect. 
         [0017]      FIG. 1  illustrates a block diagram of one embodiment of a WLAN. In the wireless local area network (WLAN) system  100  shown in  FIG. 1 , a first device  110  may include a wireless transceiver  112  to couple to an antenna  118  and to a baseband processor  116 . Baseband processor  116  in one embodiment may include a single processor, or alternatively may include a baseband processor and an applications processor, although the scope of the invention is not limited in this respect. Baseband processor  116  may couple to a memory  114  which may include volatile memory such as DRAM, non-volatile memory such as flash memory, or alternatively may include other types of storage such as a hard disk drive, although the scope of the invention is not limited in this respect. Some portion or all of memory  114  may be included on the same integrated circuit as baseband processor  116 , or alternatively some portion or all of memory  114  may be disposed on an integrated circuit or other medium, for example a hard disk drive, that is external to the integrated circuit of baseband processor  116 , although the scope of the invention is not limited in this respect. Likewise, a second device  120  may include a transceiver  122 , memory  124 , baseband processor  126 , and antenna  128 . Access point  140  may include a transceiver  142 , memory  144 , baseband processor  146  and antenna  136 . 
         [0018]    First device  110  and second device  120  may communicate with access point  140  via wireless communication links  132  and  134 , respectively. Access point  140  may include at least one antenna  136 . Alternatively, access point  140 , and optionally first device  110  and second device  120 , may include two or more antennas to provide a diversity antenna arrangement, to provide spatial division multiple access (SDMA), or to provide a multiple input, multiple output (MIMO) system, or the like, although the scope of the invention is not limited in this respect. Access point  140  may couple with network  138  so that first device  110  and second device  120  may communicate with network  138 , including devices coupled to network  138 , by communicating with access point  140  via wireless communication links  132  and  134 . Network  138  may include a public network such as a telephone network or the Internet, or alternatively network  138  may include a private network such as an intranet, or a combination of a public and a private network, although the scope of the invention is not limited in this respect. 
         [0019]    Communication between user first device  110  and second device  120  and access point  140  may be implemented in accordance with one or more wireless standards including, for example, one or more wireless cellular standards, one or more wireless networking standards, one or more radio frequency identification (RFID) standards, and/or others. In at least one implementation, for example, the communication is implemented in accordance with the Bluetooth short-range wireless protocol (Specification of the Bluetooth System, Version 1.2, Bluetooth SIG, Inc., November 2003, and related specifications and protocols). Other possible wireless networking standards include, for example: IEEE 802.11 (ANSI/IEEE Std 802.11-1999 Edition and related standards like 802.11n), HIPERLAN 1, 2 and related standards developed by the European Telecommunications Standards Institute (ETSI) Broadband Radio Access Networks (BRAN), HomeRF (HomeRF Specification, Revision 2.01, The HomeRF Technical Committee, July, 2002 and related specifications), Ultrawideband, and/or others. 
         [0020]    In accordance with one embodiment of the invention, access point  140  may be a multimode access point (MAP) in that access point  140  may allow first device  110  and second device  120  to communicate with access point  140  even though first device  110  and second device  120  may not be capable of communicating with one another, for example where first device  110  is arranged to communicate using a first wireless standard, such as the IEEE 802.11b/g standards, and where second device  120  is arranged to communicate using a second wireless standard, such as a higher throughput wireless communication standard directed toward, for example, operation at or near the 5 GHz frequency of the IEEE 802.11a standard, although the scope of the invention is not limited in this respect. 
         [0021]    In one embodiment, WLAN system  100  includes multiple devices capable of communicating with first device  110  and access point  140 . WLAN system  100  may include multiple other devices capable of communicating with second device  120  and access point  140 . The multiple devices capable of communicating with first device  110  may all communicate using a first wireless standard, such as the IEEE 802.11b/g standards. The multiple other devices capable of communicating with second device  120  may all communicate using a second wireless standard such as a higher throughput wireless communication standard directed toward, for example, operation at or near the 5 GHz frequency of the IEEE 802.11a standard, although the scope of the invention is not limited in this respect. 
         [0022]    In accordance with one embodiment, access to the medium is controlled by a media access control (MAC) sublayer of the Data Link Layer as described in a wireless standard. In particular, MAC operations control which devices, AP  140 , first device  110  and/or second device  120 , can initiate communications over the medium. 
         [0023]    In one embodiment, first device  110 , second device  120 , and access point  140  may be arranged to communicate over an identical or similar frequency band, for example near 5 GHz, wherein the transceivers  112 ,  122 , and  142  of first device  110 , second device  120 , and access point  140 , respectively, are arranged to operate on a compatible physical layer, although the scope of the invention is not limited in this respect. 
         [0024]    In one embodiment, first device  110  may be a legacy device, operating according to an older wireless standard and second device may be a newly developed device, operating according to a newly developed or newer standard. According to the newer standard, second device  120  may be required to receive and process communications according to the older, legacy standard. In such embodiments, first device  110  may not be able to receive and honor communications according to the newer standard, for example, a new format wireless medium reservation made by access point  140 , or may not receive or process medium reservation packets sent by second device  120 , although the scope of the invention is not limited in this respect. Additionally, second device  120  may be able to receive and honor communications according to the older standard, for example, an old format wireless medium reservation made by access point  140 , and may receive or process medium reservation packets sent by first device  110 , although the scope of the invention is not limited in this respect. 
         [0025]    Because first device  110  cannot process communications from second device  120 , protection mechanisms may be used to prevent first device  110  and second device  120  from initiating communications that may collide with communications of the other device. In one embodiment, access point  140  may allow both first device  110  and second device  120  to operate with access point  140  and with their peers without requiring a modification to the protocol under which the devices operate, although the scope of the invention is not limited in this respect. 
         [0026]    To implement 40 MHz channel switching, for example in the WLAN system  100  described with respect to  FIG. 1 , an Extension Channel information element and a Channel Switch Announcement frame may be utilized. In one embodiment, the Extension Channel information element may include offset information corresponding to an extension channel. The Channel Switch Announcement frame may include the Extension Channel information element. A base station, such as AP  140  of  FIG. 1 , that receives the Channel Switch Announcement may determine control and extension channels in a 40 MHz channel. 
         [0027]    In general, a wireless communication may be classified as Independent Basic Service Set (IBSS) or the Basic Service Set (BSS). The IBSS is those wireless networks in which an AP may help identify the remote clients. The BSS is those wireless networks of an ad hoc nature in which no APs are provided. A 40/20 MHz capable BSS/iBSS device is one that may support a 20-MHz extension channel and a 20-MHz control channel in a single 40-MHz channel. 
         [0028]    In one embodiment, a New Extension Channel Offset element may be utilized by an AP in a BSS or a mobile station (STA) in an IBSS together with a Channel Switch Announcement element when changing to a new (e.g., 40 MHz) channel. One embodiment of a New Extension Channel Offset element is illustrated in  FIG. 2 . In one embodiment, each field  210 ,  220 ,  230  illustrated in  FIG. 2  is an octet; however, any field size may be supported. 
         [0029]    In one embodiment, the New Extension Channel offset field  230  may indicate the position of the extension channel relative to the control channel. For example, a value of “1” may indicate that the extension channel is above the control channel, a value of “2” may indicate that the extension channel is below the control channel, and a value of “0” may indicate that no extension channel is present. Alternate indications may also be used. In one embodiment, the New Extension Channel Offset element  200  may be included in a Channel Switch Announcement frame and also may be included in Beacon frames and Probe Response frames. 
         [0030]    Layers within a wireless communication architecture communicate with each other via service primitives having, but not limited to, the following forms: 
         [0031]    (1) Request A layer uses this type of primitive to request that another layer perform a specific service of scheduling a channel switch and announce this switch to peer entities in the BSS; 
         [0032]    (2) Indication A layer uses this type of primitive to indicate to another layer that a significant event has occurred. This primitive indicates that a channel switch announcement has been received from a peer entity; and 
         [0033]    (3) Response A layer uses this type of primitive to complete a procedure initiated by an indication primitive. This primitive is used to schedule an accepted channel switch. 
         [0034]    Particularly, in embodiments of the present invention, such primitives may be utilized when implementing 40 MHz channel switching. 
         [0035]      FIG. 3  is a conceptual illustration of one embodiment of a channel switch request primitive  300 . In one embodiment, the channel switch request  300  is a primitive used for requesting a 40 MHz channel switch. Channel switch request primitive  300  may include mode  310 , channel number  320 , new extension channel offset  330 , and channel switch count fields  340 . 
         [0036]    The channel switch request primitive  300  is generated by a system management entity (SME) to schedule a channel switch and announce this switch to peer entities in the IBBS/BBS. Mode  310  is defined in a Channel Switch Announcement element. Channel Number  320  is the new channel number being switched to. New Extension Channel Offset  330  is the same as New Extension Channel Offset element  230  of  FIG. 2 . This parameter provides the position of the extension channel in relation to the control element. In one embodiment, a 40/20 MHz capable BSS/IBSS device may insert the New Extension Channel Offset parameter  330  into channel switch request  300 . Channel Switch Count  340  identifies the number of Target Beacon Transmission Time (TBTTs) until the channel switch event as described by the Channel Switch Announcement element. 
         [0037]      FIG. 4  is a conceptual illustration of one embodiment of a channel switch indication primitive  400 . In one embodiment, the channel switch indication primitive  400  is a primitive used for indicating that a 40 MHz channel switch announcement has been received from a peer entity. Channel switch indication primitive  400  may include peer MAC address  410 , mode  420 , channel number  430 , new extension channel offset  430 , and channel switch count field  450 . 
         [0038]    Peer MAC address  410  identifies the address of a peer MAC from which a channel switch frame is received. Mode  420  identifies the mode as defined in the Channel Switch Announcement element. Channel number  430  indicates the new channel number. New Extension Channel Offset  440  is the same as New Extension Channel Offset element  230  of  FIG. 2 . This parameter provides the position of the extension channel in relation to the control element. In one embodiment, a 40/20 MHz capable BSS/IBSS device may insert the New Extension Channel Offset parameter  440  into channel switch request  400 . Channel Switch Count  450  identifies the number of TBTTs until the channel switch event as described by the Channel Switch Announcement element. 
         [0039]      FIG. 5  is a conceptual illustration of one embodiment of a channel switch response primitive  500 . In one embodiment, the channel switch response primitive  500  is a primitive used for completing a 40 MHz channel switch procedure initiated by an indication primitive, such as indication primitive  400  described with respect to  FIG. 4 . Channel switch response primitive  500  may include mode  510 , channel number  520 , new extension channel offset  530 , and channel switch count field  540 . 
         [0040]    Mode  510  identifies the mode as defined in the Channel Switch Announcement element. Channel number  520  indicates the new channel number. New Extension Channel Offset  530  is the same as New Extension Channel Offset element  200  of  FIG. 2 . This parameter provides the position of the extension channel in relation to the control element. In one embodiment, a 40/20 MHz capable BSS/IBSS device may insert the New Extension Channel Offset parameter  530  into channel switch request  500 . Channel Switch Count  540  identifies the number of TBTIs until the channel switch event as described by the Channel Switch Announcement element. 
         [0041]    While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.