WO2014068456A1

WO2014068456A1 - Channel switching scheme for wireless networks

Info

Publication number: WO2014068456A1
Application number: PCT/IB2013/059624
Authority: WO
Inventors: Timo Koskela; Sami-Jukka Hakola; Samuli Turtinen; Anna Pantelidou
Original assignee: Renesas Mobile Corporation
Priority date: 2012-10-30
Filing date: 2013-10-24
Publication date: 2014-05-08
Also published as: GB201219503D0; GB2507494B; GB2507494A

Abstract

A method of operating an access point in a wireless network comprises determining to switch from a first communication channel to a second communication channel, generating a message frame comprising a channel switch announcement element having a channel list identifying a plurality of second communication channels, and wirelessly transmitting the message frame.

Description

Channel Switching Scheme for Wireless Networks

Cross Reference to Related Application

This application claims the benefit under 35 U.S.C. § 119(a) and 37 CFR § 1.55 to UK patent application no. 1219503.8, filed on October 30, 2012, the entire content of which is incorporated herein by reference.

Technical Field

The present disclosure relates the field of wireless communications, and more particularly to a channel switching scheme for wireless networks.

Background

As shown in FIG. 1, when operating in an infrastructure mode, wireless local area networks (WLANs) 10 typically include one or more wireless access points (AP) 12 and one or more client stations (ST A) 14. The access point provides the client stations connectivity to the wired networks or distribution system (DS). A basic service set or BSS is a wireless network that includes a single wireless access point supporting one or more wireless stations.

Over the past decade, the Institute for Electrical and Electronics Engineers (IEEE) has developed 802.1 1a, 802.11b, 802.1 lg, and 802.11η Standards to achieve improved single-user peak data throughput. For example, the IEEE 802.11b Standard specifies a single-user peak throughput of 11 megabits per second (Mbps), the IEEE 802.1 la and 802.1 lg Standards specify a single-user peak throughput of 54 Mbps, the IEEE 802.1 In Standard specifies a single-user peak throughput of 600 Mbps, and the IEEE 802.1 lac Standard specifies a single-user peak throughput in the gigabits per second (Gbps) range.

Work is currently underway on a number of new wireless standards, one of which is the IEEE 802.11 ah Standard that will specify wireless network operation in sub-1 GHz (SIG) frequencies. Lower frequency communication channels are generally characterized by better propagation qualities and extended propagation ranges. There are a few frequency bands in the sub 1-GHz range that remain unlicensed, with different specific unlicensed frequencies in different geographical regions. The IEEE 802.11 ah Standard will specify wireless operation in available unlicensed sub-1 GHz frequency bands.

The medium-access-control (MAC) layer and physical (PHY) layer characteristics for WLANs are specified in the IEEE 802.11(h) standard. The standard provides a mechanism for the announcement of a channel switch performed at the MAC layer. Specifically, the MAC layer provides Channel Switch Announcement and Extended Channel Switch Announcement Elements that are used by an AP in a basic service set (BSS) network or a STA in an infrastructure basic service set (IBSS) network to announce when it is changing to a new channel and the new channel number. The Channel Switch Announcement Element includes a "channel switch count" field which is set equal to the number of Target Beacon Transmission Time (TBTT) which must expire before the network is switched to the new channel. The present disclosure proposes a number of improvements on the channel switch process. In addition the Extended Channel Switch Announcement Element includes a "new operating class" which indicates a set of values for radio operation in a regulatory domain (e.g. operating channels may differ in USA and Europe).

Summary

A first exemplary embodiment provides a method of operating an access point in a wireless network, the method comprising determining to switch from a first communication channel to a second communication channel, generating a message frame comprising a channel switch announcement element having a channel list identifying a plurality of second communication channels, and wirelessly transmitting the message frame.

A second exemplary embodiment provides a wireless network communication device comprising a host processor, a network interface coupled to the host processor and comprising a transceiver operable to generate and transmit a message frame including a channel switch announcement information element to a plurality of client stations, the a channel switch announcement information element including: an element ID field, a length field, and a channel list identifying a plurality of communication channels.

A third exemplary embodiment provides a method of operating a client station in a wireless network, the method comprising receiving a message frame comprising a channel switch announcement element having a channel list identifying a plurality of communication channels, and switching to operate on one of the plurality of communication channels.

A fourth exemplary embodiment provides a method of operating an access point in a wireless network, the method comprising determining to switch from a first communication channel to a second communication channel, generating a message frame comprising a channel switch announcement element having a channel field identifying the second communication channel and a validity timer field identifying a length of time that the second communication channel is valid, and wirelessly transmitting the message frame.

Brief Description of the Drawings

The present disclosure makes reference to a number of drawing figures listed below:

FIG. 1 is a simplified block diagram of an exemplary wireless network;

FIG. 2 is a more detailed block diagram of an exemplary wireless network;

FIG. 3 is a diagram illustrating IEEE 802.11 ah frequency channel allocation in the United States of America;

FIG. 4 is a diagram illustrating a general information element format in 802.11 specification;

FIG. 5 is a diagram illustrating an existing Channel Switch Announcement Information Element specified in the 802.11 Standard;

FIG. 6 is a diagram illustrating an existing Extended Channel Switch Announcement Information Element specified in the 802.11 Standard;

FIG. 7 is a diagram of a new Channel Switch Announcement Information Element according to the teachings of the present disclosure; FIG. 8 is a diagram of a new Channel Switch Announcement Information Element specifying M channels according to the teachings of the present disclosure;

FIG. 9 is a diagram of a new Reserve Channel List Information Element specifying M channels according to the teachings of the present disclosure;

FIG. 10 is a diagram of another embodiment of a new Reserve Channel List

Information Element specifying a validity timer field according to the teachings of the present disclosure;

FIG. 1 1 is a diagram of yet a third embodiment of a new Reserve Channel List Information Element specifying M channels according to the teachings of the present disclosure;

FIG. 12 is a diagram of a new Channel Switch Announcement Information Element specifying a validity timer according to the teachings of the present disclosure;

FIG. 13 is a diagram of a validity timer field in the new Channel Switch Announcement Information Element shown in FIG. 12 according to the teachings of the present disclosure; and

FIG. 14 is a diagram of a new Channel List Validity Timer Information Element according to the teachings of the present disclosure.

Detailed Description

FIG. 2 is a more detailed block diagram of an exemplary wireless network or wireless local area network (WLAN) 20. An access point (AP) 22 includes a host processor 24 coupled to a network interface 26. The network interface 26 includes a Medium Access Control (MAC) processing unit 28 and a Physical (PHY) layer processing unit 30, both of which are operable to execute a plurality of computer program instructions according to the communication protocols. The PHY processing unit 30 includes a plurality of transceivers 32, which are coupled to a plurality of antennas 34.

The wireless network 20 further includes a plurality of client stations (STA) 36 that communicate with the access point 22. The client station 36 also includes a host processor 38 coupled to a network interface 40. The network interface 40 includes a Medium Access Control (MAC) processing unit 42 and a Physical (PHY) layer processing unit 44, both of which are operable to execute a plurality of computer program instructions according to the communication protocols. The PHY processing unit 44 includes a plurality of transceivers 46, which are coupled to a plurality of antennas 48.

The wireless network device such as the access point 22 of a wireless local area network 20 transmits data streams to one or more client stations via a wireless medium. The access point and client stations are configured to operate according to communication protocols such as IEEE 802.11 and IEEE 802.11 ah, for example. The IEEE 802.11 ah communication protocol defines data communication operations in a sub-1 GHz frequency range, and is typically used for applications requiring long range wireless communication with relatively low data rates or applications using battery- powered client devices requiring long operating time without battery replacements or re-charging. In some embodiments, the access point is also configured to operate with client stations according to one or more other communication protocols which define operation in generally higher frequency ranges and are typically used for communication in closer ranges and with generally higher data rates.

Because of the long range capabilities of the access point under IEEE 802.1 lah, the access point may serve a large number of client stations. When the stations are equipped with power amplifiers, reasonable data rates may be achieved at long ranges. However, as the trend is to further reduce the energy consumption of the client devices, the elimination of the power amplifiers provides a viable and desirable solution. Without the use of power amplifiers, the resultant data rates that can be achieved by the stations are drastically reduced. Given the lower data transmission rates in the long range wireless network that mandate long operating time of battery-powered client devices, greater efficiency in the message formats becomes necessary to maintain data throughput, reduce transmission time of control messages, and improve energy efficiency in communication.

The IEEE 802.1 lah client stations may operate on very strict energy budgets and typically remain dormant or in low power operating mode for long periods of time. These client stations typically transmit and receive data very infrequently. However, even with limited data transmissions, there may still be a contention problem due to the large number of associated stations operating in random access mode. Accordingly, the AP may utilize various techniques to restrict the contention to the channel to avoid collisions. One exemplary technique is to group multiple client stations and assign certain parameters to each group to regulate access to the channel. Such grouping of assignment information may be transmitted to the client stations by using broadcast beacons.

FIG. 3 is a diagram illustrating IEEE 802.11 ah frequency channel allocation in the United States, which has a 26 MHz spectrum availability. According to the IEEE 802.1 lah Standard, the frequency channels are defined to be 26 1-MHz channels, 13 2- MHz channels, six 4-MHz channels, three 8-MHz channels, and one 16-MHz channel. Introduced in the IEEE 802.1 lh Standard is the channel switch mechanism in which the AP may select and switch to a new operating channel. Heretofore, a channel switch announcement mechanism has been provided to notify the client stations to follow the AP to the new channel. However, current discussions have not considered the option of specifying multiple backup or reserve channels. Also the current message indicates that the AP switches to a new channel at any time after the indication in the channel switch message. With Reserve Channel/ Back Up Channel list the AP indicates options that if the current channel cannot be used as an operating channel AP will most likely be in one of the channels indicated in the list.

FIG. 4 is a diagram illustrating a general information element format 50 in

802.11 specification. The general information element 50 includes an 1 -octet Element ID field 51, a 1 -octet Length field 52, and a variable-length Information field 53. The Element ID field 51 is used to contain information that specifies the type of information element, and the Length field 52 is used to contain a value that indicates the number of octets of the Information field(s) 53 that would occur after the Length field 52.

FIG. 5 is a diagram illustrating an existing Channel Switch Announcement Information Element 60 specified in the 802.1 lh Standard. The Channel Switch Announcement Element 60 is used by an AP in a BSS, a station in an IBSS, or a mesh station in an MBSS to advertise when it is changing to a new channel and the channel number of the new channel. The Channel Switch Announcement Information Element 60 includes an Element ID field 61, a Length field 62, a Channel Switch Mode field 63, a New Channel Number field 64, and a Channel Switch Count field 65, each being 1- octet long. A Channel Switch Announcement Element is identified by an Element ID set to "37" and the Length field 62 is set to "3". The Channel Switch Mode field 63 indicates any restriction on transmission until a channel switch. An AP in a BSS or a station in an IBSS sets the Channel Switch Mode field 63 to either "0" or "1" on transmission. The New Channel Number field 64 is set to the number of the new channel. For non-mesh stations, the Channel Switch Count field 65 is either set to the number of TBTTs until the station sending the Channel Switch Announcement element switches to the new channel or is set to "0". A value of "1" indicates that the switch occurs immediately before the next TBTT. A value of "0" indicates that the switch occurs at any time after the frame containing the element is transmitted. The Channel Switch Announcement element 60 may be included in Channel Switch Announcement frames, and may also be included in Beacon frames, and Probe Response frames.

FIG. 6 is a diagram illustrating an existing Extended Channel Switch Announcement Information Element specified in the 802.11 Standard. The Extended Channel Switch Announcement Information Element 70 includes an Element ID field 71, a Length field 72, a Channel Switch Mode field 73, a New Operating Class field 74, a New Channel Number field 75, and a Channel Switch Count field 76. The Extended Channel Switch Announcement element is used by an AP in an infrastructure BSS, a STA in an IBSS, or a mesh STA in an MBSS to advertise when the BSS is changing to a new channel or a new channel in a new operating class. The announcement includes both the operating class and the channel number of the new channel. The element is present only when an extended channel switch is pending. The Channel Switch Mode field indicates any restrictions on transmission until a channel switch. An AP in an infrastructure BSS or a STA in an IBSS sets the Channel Switch Mode field to either "0" or "1" on transmission. The Channel Switch Mode field is reserved in an MBSS. The New Operating Class field is set to the number of the operating class after the channel switch. The New Channel Number field is set to the number of the channel after the channel switch. The channel number is a channel from the STA's new operating class. For non-mesh ST As, the Channel Switch Count field indicates either the number of target beacon transmission times (TBTTs) until the STA sending the Extended Channel Switch Announcement element switches to the new channel or a value of "0". A value of 1 indicates that the switch occurs immediately before the next TBTT. A value of "0" indicates that the switch occurs anytime after the frame containing the element is transmitted. For mesh STAs, the Channel Switch Count field is encoded as an octet with bits 6 to 0 set to the time, in units of 2TU when the MSB (bit 7) is "0", or in units of 100TU when the MSB (bit 7) is "1", until the mesh STA sending the Channel Switch Announcement element switches to the new channel. A value of "0" for bits 6 to 0 indicates that the switch occurs at any time after the frame containing the element is transmitted. For example, a 200 TU channel switch time is encoded as X'82' and a 10TU channel switch time is encoded as ΧΌ5'.

FIG. 7 is a diagram of a new Channel Switch Announcement Information Element 80 for announcing a reserve channel list according to the teachings of the present disclosure. The new Channel Switch Announcement Information Element 80 retains the same Element ID field 81, Length field 82, and Channel Switch Mode field 83, however the Channel Switch Mode field 83 is set to a value other than "0" or "1" to indicate that the Information Element contains a reserve channel list of M channels rather than the New Channel Number and Channel Switch Count fields. The new Channel Switch Announcement Information Element 80 includes a 2-octet Channel List field 84. A number of exemplary configurations for the Channel List field 84 are contemplated; for example, this field may include a Control field 85 (1-bit), and three Channel fields 86-88 (5-bits each) that are used to identify three preferred channels of the AP. Such Control field 85 may be used to indicate control information, e.g., priority information. For example, if the Control field 85 is set to "1" then the listed channels are in priority order. Alternatively, the Channel List field 84 may include four Channel fields 90-93 (4-bits each) that identify four preferred channels of the AP. Yet a third exemplary configuration may be used to specify four Channel Group Fields 94-97 (4- bits each). The channel index mapping and/or channel group assignment may be fixed, arranged prior to signaling, or made dynamically via management frame exchanges between the AP and the client stations. Full or short beacon broadcast messages may also be used to specify such mapping information. FIG. 8 is a diagram of another embodiment of a new Channel Switch Announcement Information Element 100 specifying M channels according to the teachings of the present disclosure. The new Channel Switch Announcement Information Element 100 retains the same Element ID field 101, Length field 102, and Channel Switch Mode field 103. The new Channel Switch Announcement Information Element 100 further includes a variable-length channel list containing M one-octet Channel fields 104-106, where each octet specifies a single channel number. Accordingly, the Length field 102 contains the value "1 + M" (octets) to indicate the number of octets of information that occurs after the Length field 102. Therefore, to enhance connectivity the AP may maintain the reserve channel list to identify its preferred channels to which it would deploy in the event that the current channel cannot support the required operation. By using the reserve channel list, the client station has prior knowledge which channel the AP may switch to and continue operations.

Additionally or alternatively (and throughout this invention) the Information Element can be an "extended channel switch" element where also the "new operating class" element is reinterpreted and used to indicate reserve channels. E.g. channel switch mode indicates a new interpretation for the field in "extended channel switch" element so that it may include 3 reserve channels (if the length field is kept fixed at 3 octets. Alternatively the "channel switch count" field can be used as a timer field as described below.

FIG. 9 is a diagram of a new Reserve Channel List Information Element 110 specifying M channels according to the teachings of the present disclosure. The new Reserve Channel List Information Element 110 includes an Element ID field 111, a Length field 112, a Control field 113, and a variable-length channel list of M Channels 114-116. The reserve channel list identifies those channels that the AP is most likely to switch to. It may be seen that the Control field 113 replaces the Channel Switch Mode field 103 to provide control information that may include, for example, whether the channels identified in the Channel fields 114-116 are listed by priority. The AP is operable to transmit an updated Reserve Channel List Information Element 110 to the stations to maintain connectivity when a change to a new channel occurs. FIG. 10 is a diagram of another embodiment of a new Reserve Channel List Information Element 120 specifying an additional control element according to the teachings of the present disclosure. The new Reserve Channel List Information Element 120 includes an Element ID field 121, a Length field 122, a Control field 123, an Additional Control Element field 124, and a reserve channel list of M Channels 125- 127. The Additional Control Element field 124 may be used to provide more control data related to the reserve channel list. The additional control data may include, for example, the length of time that the channel list will remain valid. Due to the addition of the Additional Control Element field 124, the Length field 122 would hold a value of "2 + M" (octets). The value for 'M' may also be zero "0".

FIG. 1 1 is a diagram of yet a third embodiment of a new Reserve Channel List Information Element 130 further specifying a validity timer according to the teachings of the present disclosure. The new Reserve Channel List Information Element 130 includes an Element ID field 131, a Length field 132, a Control field 133, a Validity Timer Element field 134, and a reserve channel list of M Channels 135-137. Due to the addition of the Validity Timer Element field 134 instead of the Additional Control Element field 124 (FIG. 10), the Length field 132 would hold a value of "2 + M" (octets). The Validity Timer Element field 134 is used to specify the length of time the reserve channel list will remain valid. The value in the Validity Timer field 134 may be expressed in a number of exemplary ways, such as the number of full or short beacon intervals, or as the number of symbols, seconds, microseconds, etc. The AP may use a default timer setting in the event that no specific validity timer value has been provided for the reserve channel list. Upon the expiration of time indicated by the Validity Timer Element, a station may check for further AP announcements of a new or updated channel list. In response to an absence of an updated channel list, the station may reset the validity timer of the current channel list, or request a channel list update from the AP. The station may also determine whether the AP has set a new value for the validity timer for the current channel list. Alternatively, the AP may convey the timer information by broadcasting a beacon or short beacon message, or otherwise transmit a new Validity Timer Information Element shown in FIG. 14 and described below. Upon waking, if a station listening for the AP in the current channel cannot hear the AP, it refers to the channels in reserve channel list to locate the AP. Once the AP decides to change to a channel in the reserve channel list and the validity timer has expired, it triggers a reconfiguration of the list. The value for 'M' in the FIGs. 8-11 may also be zero "0" to indicate that there are no channels signaling in this information element. The non-existing channel fields are implicitly indicated by the length field. In this case the STA receiving the message may only decode the control information in the message or alternatively depending on the message format a timer value, etc.

FIG. 12 is a diagram of a new Channel Switch Announcement Information Element 140 specifying a validity timer according to the teachings of the present disclosure. The new Channel Switch Announcement Information Element 140 retains the same Element ID field 141, Length field 142, and Channel Switch Mode field 143, and Reserve Channel field 144, but instead of the channel switch count, specifies a Validity Timer field 145. FIG. 13 is a diagram of a Validity Timer field 145. The Timer field 145 includes a Timer subfield 148 and a Control field 149. The 4-bit length of the Timer subfield 148 and the Control subfield 149 are exemplary lengths. In one alternative the "channels switch mode" value other than "1" or "0" indicates that the new channel number contains the "second channel" number that the AP will deploy in case it cannot operate on the current channel, and the "channel switch count" will be interpreted as a timer how long the current "secondary" channel is valid. The value can be expressed in beacon intervals, time units (e.g microseconds), or in symbols. In one example the "timer" field is divided between timer and control part. Control part may indicate additional info such as channels adjacent (or channels which are N channels away) to the indicated reserve channel are also considered as reserve channels.

FIG. 14 is a diagram of a new Channel List Validity Timer Information Element 150 according to the teachings of the present disclosure. The Channel List Validity Timer Information Element 150 includes an Element ID field 151, a Length field 152, a Validity Timer field 153, and optional Additional Information field(s) 154. The Additional Information field 154 may include, for example, additional configuration information such as multiple timer values for multiple channels. The Additional Information fields 154 are implicitly indicated by the Length field 152, e.g., a 1-byte length would indicate that no Additional Information field 154 is present. The Validity Timer field 153 further includes a 2-bit Control field 156 and a 6-bit Validity Timer field 157. The Control field 156 may be used to specify the time unit used for the validity timer, such as the scaling of the bit values. Alternatively, the Control field 156 may indicate whether the current timer value is the time left before the current timer expires, or a validity timer reset with the new value in the Validity Timer field 157. Alternatively, validity timer reset can be signaled by the AP by setting the Length field value to "0" to indicate that the previous timer value is to be used again as the new timer value.

Accordingly, the AP may provide the validity timer information to the client stations either in the Reserve Channel List Information Element or in the Validity Timer Information Element. The AP may transmit the Validity Timer information periodically at an interval shorter than the validity timer interval, so that the same validity timer information is repeated and can be received by sleeping stations upon wakening. If the AP switches to a new channel, the AP may opt to extend the duration that the current Reserve Channel List is valid before transmitting the new channel list to ensure connectivity with stations that may have missed the Channel Switch Announcement. The timer extension may be signaled by transmitting or broadcasting the Channel List Validity Timer Information Element.

Although described herein in the context of 802.11 Standards (802.11a, 802.11b, 802.11G, 802.11η, 802.1 lac, 802.11 ah, 802.1 laf) and its future amendments, the solutions are also applicable to situations where the AP moves between frequency bands (e.g. from 2.4GHz to 5GHz) or operating classes, and to other communication protocols as well. In one example, the AP may be a so-called multimode AP and may have reserve channels in multiple frequency bands. The above mentioned signaling can be modified so that the channel numbers point to different frequency bands (e.g. a control element indicates that the channel may be in 5 GHz or 2.4GHz band or TVWS (Television White Spaces)) or the channel numbering can be arranged so that one channel in frequency band has a unique identifier. Alternatively, the AP may signal new mappings of the channels to new indices if needed. Alternatively, the reserve channel may point to different bandwidths (20/40/80/160 MHz) or combinations of bandwidths such as 8Mhz+8MHz mode (802.1 laf TVWS) or 80+80MHz mode (802.1 lac). The information elements or signaling described herein can be made, e.g., during association phase (association request/association response). A STA may request a reserve channel list (RCL) from the AP in the association request (the association request may include an "information element" or the request is indicated in the Frame Control field or MAC header/PHY header). The AP may or may not respond with the reserve channel list element in the association response. Further updates can be made by additional management frame exchanges between STA and AP.

Alternatively or additionally, the AP may transmit the RCL element in the beacon upon detecting the RCL request from the STA. Alternatively or additionally, the AP may push the RCL element (without request) in the "association response" and STA may choose whether to utilize it.

The features of the present invention which are believed to be novel are set forth below with particularity in the appended claims. However, modifications, variations, and changes to the exemplary embodiments described above will be apparent to those skilled in the art, and the system and method described herein thus encompass such modifications, variations, and changes and are not limited to the specific embodiments described herein.

GLOSSARY

AP Access Points

BSS Basic Service Set

DS Distribution System

IBSS Infrastructure Basic Service Set

MAC Medium Access Control

RCL Reserve Channel List

STA Station

S1G Sub-1 GHz

TBTT Target Beacon Transmission Time

TVWS Television White Spaces

WLAN Wireless Local Area Network

Claims

1. A method of operating an access point in a wireless network, the method comprising:

determining to switch from a first communication channel to a second communication channel;

generating a message frame comprising a channel switch announcement element having a channel list identifying a plurality of second communication channels; and

wirelessly transmitting the message frame.

2. The method of claim 1 , wherein the message frame comprises control information.

3. The method of claim 2, wherein the control information specifies a priority ordering of the plurality of second communication channels.

4. The method of claim 2 or claim 3, wherein the control information comprises validity timer information that specifies a length of time that the channel list is valid.

5. The method of any preceding claim, wherein the channel list identifies a plurality of channel groups.

6. The method of any preceding claim, wherein the channel list is of a fixed length.

7. The method of any of claims 1 to 5, wherein the channel list is of a variable length.

8. The method of any preceding claim, wherein the message frame comprises a validity timer field that specifies a length of time that the channel list is valid.

9. The method of any preceding claim, further comprising:

generating a second message frame comprising a validity timer element specifying a length of time that a current channel list is valid; and

wirelessly transmitting the second message frame.

10. A wireless network communication device comprising:

a host processor;

a network interface coupled to the host processor and comprising a transceiver operable to generate and transmit a message frame including a channel switch announcement information element to a plurality of client stations, the channel switch announcement information element including:

an element ID field;

a length field; and

a channel list identifying a plurality of communication channels.

11. The wireless network communication device of claim 10, wherein the transceiver is operable to generate and transmit a message frame including a channel switch announcement information element comprising a channel list identifying a plurality of channel groups.

12. The wireless network communication device of claim 10 or claim 11, wherein the transceiver is operable to generate and transmit a message frame including a channel switch announcement information element comprising a control field.

13. The wireless network communication device of any of claims 10 to 12, wherein the transceiver is operable to generate and transmit a message frame including a channel switch announcement information element comprising a control field specifying a priority ordering of the plurality of communication channels.

14. The wireless network communication device of any of claims 10 to 13, wherein the transceiver is operable to generate and transmit a message frame including a channel switch announcement information element comprising a control field including validity timer information that specifies a length of time that the channel list is valid.

15. The wireless network communication device of any of claims 10 to 14, wherein the transceiver is operable to generate and transmit a message frame including a channel switch announcement information element comprising a validity timer field that specifies a length of time that the channel list is valid.

16. The wireless network communication device of any of claims 10 to 14, wherein the transceiver is further operable to generate and transmit a message frame having a validity timer element including:

an element ID field;

a length field; and

a validity timer field that specifies a length of time that the channel list is valid.

17. A method of operating a client station in a wireless network comprising: receiving a message frame comprising a channel switch announcement element having a channel list identifying a plurality of communication channels; and

switching to operate on one of the plurality of communication channels.

18. The method of claim 17, wherein receiving a message frame comprises receiving the message frame comprising control information.

19. The method of claim 17 or claim 18, wherein receiving a message frame comprises receiving the message frame having control information that specifies a priority ordering of the plurality of communication channels, and switching to a highest priority communication channel in the channel list.

20. The method of any of claims 17 to 19, wherein receiving a message frame comprises receiving the message frame having control information that includes validity timer information that specifies a length of time that the channel list is valid.

21. The method of any of claims 17 to 20, wherein receiving a message frame comprises receiving the message frame having a channel list that identifies a plurality of channel groups.

22. The method of any of claims 17 to 21, wherein receiving a message frame comprises receiving the message frame having a validity timer field that specifies a length of time that the channel list is valid.

23. The method of any of claims 17 to 22, further comprising receiving a second message frame comprising a validity timer element specifying a length of time that a current channel list is valid.

24. A method of operating an access point in a wireless network, the method comprising:

generating a message frame comprising a channel switch announcement element having a channel field identifying the second communication channel and a validity timer field identifying a length of time that the second communication channel is valid; and

wirelessly transmitting the message frame.

25. The method of claim 24, wherein generating a message frame comprises generating a validity timer field having a control field and a timer field.