GB2507344A

GB2507344A - Transmitting information concerning an operational parameter of a wireless device mode

Info

Publication number: GB2507344A
Application number: GB1219399.1A
Authority: GB
Inventors: Anna Pantelidou; Timo Kalevi Koskela; Juho Pirskanen
Original assignee: Broadcom Corp
Current assignee: Broadcom International Ltd; Broadcom Corp
Priority date: 2012-10-29
Filing date: 2012-10-29
Publication date: 2014-04-30
Anticipated expiration: 2032-10-29
Also published as: WO2014068467A3; GB201219399D0; GB2507344B; WO2014068467A2

Abstract

A wireless device switching (or desiring to switch) from a first mode of operation to a second mode, e.g. power saving modes, transmits information relating to at least one operational parameter of the second mode, e.g. the battery level of the device. In one embodiment the device transmits the information as part of a message containing data if the device has data to send, otherwise a separate message is transmitted. In another embodiment, the information is transmitted in a header of a message containing data (figure 5), e.g. in a Frame Control field of the header, or as part of the data payload of a message. Other examples of the information include whether the device decodes a Traffic Indication Map (TIM), listen interval parameters and group information. The device may operate in accordance with the IEEE 802.11ah standard.

Description

METHOD, APPARATUS AND

COMPUTER PROGRAM FOR A WIRELESS DEVICE

Technical Field

The present invention relates to a method, apparatus and computer program for a wireless device.

Background

Thc following abbreviations which may bc found in the specification and/or the drawing figures arc defined as follows: AID association identifier A? access point BSS basic service set TBSS independent basic service set IEEE Institute of Electrical and Electronics Engineers MAC medium access control PS-Poll power save poll STA station TIM traffic indication map WNM wireless network management Wireless networks are often arranged such that each of a plurality of wireless devices has a wireless connection to a central node. The central node is often termed an access point or A? and often provides access or a gateway to another network, including for example the Internet (possibly via other devices or apparatus). For example, in the IEEE 802.11 family of standards, an A? is associated with one or nre wireless devices known as stations or STAs. In this terminology, a single access point or AP and its associated stations or STAs are termed a basic service set or BSS.

Another known arrangement under IEEE 802.11 is a so-called IBSS (Independent Basic Service Set) which is a wireless network consisting of at least two STAs which can communicate directly with each other as an ad hoc wireless network. In addition, 802.1 Is specifics mesh networking where STAs may communicate with each other or with APs. While the network configuration may be according to the IEEE 802.11 family of standards, other network configurations may support the method, apparatus and computer program product of embodiments of the present invention, including S those configured in accordance with Wideband Code Division Multiple Access (W-CDMATM), CDMA2000, Global System for Mobile Communications (GSMTM), General Packet Radio Service (GPRSIM), Long Term Evolution (LTE), Wireless Local Access Network (WLANTM) Worldwide Interoperability for Microwave Access (WiMAXTM) protocols, and/or the like.

As a particular example, IEEE 801.llah is an amendment on operation at frequencies below I GHz. It has several proposed use cases, one of which includes metering-to-pole and sensors, where the STAs may be located up to 1 km from the AP and thus may need to operate at very low rates. Under this particular use ease, the sensors used for the smart metering or the like are typically low data rate sensors and are often battery powered or powered by a small solar panel or the like, and therefore energy efficiency is very important for the sensors or STAs. Furthermore, under this use case the network may comprise a large number of STAs, which may be 6000 or more. When a large number of STAs are associated with a single AP, hidden terminal problems become more pronounced. Furthermore, the number of Association Identifiers (AIDs) that the AP can assign at any given moment is limited and much smaller than 6000, which is the potential number of associated STAs. Grouping of the STAs may ameliorate both of the problems above. Furthermore, under this use case of 802.1 lah, as will be discussed in more detail below, it has been proposed that a STA will operate in one of two basic power-saying modes, depending particularly on the amount of uplink and downlink traffic that the STA is expected to require. In addition, there are various other operational parameters that the STAs use while being in either of those two basic power-saving modes. In use, a STA may want to switch between the two basic power-saving modes, andlor adjust the operational parameters, for example because its data transmission and/or reception requirements change or because of more stringent power requirements (perhaps because the level of battery charge is running low for example).

Summary

S According to a first aspect of the present invention, there is provided a method of operating a wireless device that is in wireless communication with a second wireless device, the method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a said second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data if the wireless device has data to transmit, else the wireless device transmits the information relating to the at least one operational parameter in a separate message if the wireless device does not have data to transmit.

In a specific example, this allows an AP to make optimal management decisions for the STAs in the BSS, as the AP leams at least some of the operational parameters and/or the power-saving mode being used by the individual STAs. In other specific examples, such as in an ad hoc network or mesh networking or the like, it allows better coordination between the STAs.

In an embodiment, in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data, the information relating to the at least one operational parameter is transmitted in a header of the message.

In an embodiment, information relating to at least one of size and type of the message header is transmitted as part of a Frame Contr& field of the message header.

In an embodiment, the information relating to at least one of size and type of the message header is transmitted using a Protocol Version subfield of the Frame Control

S field.

In an embodiment, the information relating to the at least one operational parameter is transmitted in a Frame Control field of the message header. In an cmbodimcnt, an indication that the Frame Control field contains information relating to the at least one operational parameter is included in at least one of a Type subfield

and a Subtype subfield of the Frame Control field.

In an embodiment, in the case that the wireless device transmits the information rdating to the at least one operational parameter as part of a message that contains data, the information relating to the at least one operational parameter is transmitted as part of the data payload of the message.

According to a second aspect of the present invention, there is provided a method of operating a wireless device that is in wireless communication with a second wireless device, the method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a said second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data or as part of a data payload of a message that contains data.

In a specific example, again this allows an AP to make optimal management decisions for the STAs in the BSS, as the AP leans at least some of the operational parameters and/or the power-saving mode being used by the individual STAs. In other specific exampcs, such as in an ad hoc network or mesh networking or the like, again this allows better coordination between the STAs.

S In an embodiment, in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data, information relating to at least one of size and type of the message header is transmitted as part of a Frame Control field of the message header. In an embodiment, the information relating to at least one of size and type of thc message hcader is transmitted using a Protocol Version subfield ofthc

Frame Control field.

In an embodiment, in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data, the information relating to the at least one operational parameter is transmitted in a Frame Control field of the message header.

In an embodiment, an indication that the Frame Control field contains information relating to the at least one operational parameter is included in at least one of a Type subfield and a Subtype subfield of the Frame Control field.

In either of the aspects above, the at least one operational parameter may be at least one of: (i) an indication whether or not the wireless device decodes a traffic indication map frame; (ii) an indication of the degree of the need for energy saving by the wireless device; (iii) listen interval parameters being used by the wireless device; (iv) group information for a group of wireless devices to which the wireless device currently belongs.

In an embodiment of either aspect, said second wireless device is an access point.

In a specific example, again this allows an AP to make optimal management S decisions for the STAs in the BSS, as the AP leams at least some of the operational parameters and/or the power-saving mode being used by the individual STAs. In other specific examples, such as in an ad hoc network or mesh networking or the like, again this allows better coordination between the STAs.

According to a third aspect of the present invention, there is provided apparatus for a wireless device, the apparatus comprising a processing system constructed and arrange to cause the wireless device to carry out a method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data if the wireless device has data to transmit, else the wireless device transmits the information relating to the at least one operational parameter in a separate message if the wireless device does not have data to transmit.

According to a fourth aspect of the present invention, there is provided apparatus for a wireless device, the apparatus comprising a processing system constructed and arrange to cause the wireless device to carty out a method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a second wireless device information relating to at least one operational parameter that relates to the second S mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data or as part of a data payload of a message that contains data.

According to a fifth aspect of the present invention, there is provided a computer program comprising a set of instructions for causing a wireless communications device to carry out a method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a said second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data if the wireless device has data to transmit, else the wireless device transmits the information relating to the at least one operational parameter in a separate message if the wireless device does not have data to transmit.

According to a sixth aspect of the present invention, there is provided a computer program of operating a wireless device that is in wireless communication with a second wireless device, the method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation;

S

thc wirciess dcvicc transmitting for rcccipt by a said second wireless device information relating to at least one operational parameter that r&ates to thc second mode of operation; wherein the wireless device transmits the information relating to the at least S one operational parameter as part of a message header of a message that contains data or as part of a data payload of a message that contains data.

Further features and advantages of the inycntion will become apparent from the following description of prefcrrcd embodiments of the invention, givcn by way of cxamplc only, which is madc with reference to the accompanying drawings.

Brief Description of the Drawinus

Figure 1 shows schematically an acccss point and plural wircless dcvices; Figure 2 shows schematically the structure of a MAC (medium access control) header; Figure 3 shows schematically the structure of a Frame Control field; Figure 4 shows schematically the structure of a Short ACK; Figure 5 shows schematically the structure of an example of a header according to an embodiment of the present invention; Figure 6 shows schematically an example of the sub-elements of the Listen

Interval Parameters field; and

Figure 7 shows schematically an example of the sub-elements of the Group

Parameters field.

Detailed Description

"Wireless devices" include in general any device capable of connecting wirelessly to a network, and includes in particular mobile devices including mobile or cell phones (including so-called "smart phones"), personal digital assistants, pagers, S tablet and laptop computers, content-consumption or generation devices (for music and/or video for example), data cards, USB dongles, etc., as well as fixed or more static devices, such as personal computers, game consoles and other generally static entertainment devices, various other domestic and non-domestic machines and devices, etc. Thc term "user equipment" or UE is often used to refer to wireless devices in general, and particularly mobile wireless devices. In some applications, the term STA is used to refer to a wireless device.

Much of the present specific description of specific examples of embodiments of the present invention rdates to devices operating in accordance with the IEEE 801.11 family of standards, and the proposed 802.llah standard in particular.

1-lowever, the principles of the present invention may be applied to other devices operating in accordance with other wireless technologies or standards. In the particular context of IEEE 802.11, the wireless devices are often called stations or STAs.

Figure 1 shows schematically an access point or AP 1 and plural wireless devices or STAs 2 serviced by the AP 1. Only four STAs 2 are shown in the Figure, but in practice there may be just one STA 2 up to hundreds or thousands or more STAs 2 serviced by the AP 1. Each STA 2 has the necessary radio module 3, processor(s) and memory/memories 4, antenna 5, etc. to enable wireless communication with the AP 1, which likewise has the necessary radio module 6, processor(s) and memory/memories 7, antenna 8, etc. to enable wireless communication with the STAs 2. One or more, or indeed all, of the STAs 2 may be machine-type communication devices, including for example so-called smart meters or other sensors that relay readings and other information wirelessly to the AP 1.

The STAs 2 typically operate in one of two modes, synchronous and asynchronous.

In synchronous mode, the STA 2 wakes up periodically to listen for beacons S or TIM (Traffic Indication Map) frames being transmitted by the AP 1. A beacon frame is a type of management frame that enables STAs 2 to establish and maintain communications in an orderly fashion. A TIM frame is sent periodically by the AP 1 within a beacon to identify which STAs 2 using a powcr saving mode have data framcs waiting for them in the buffer of the AP 1. The TIM identifies a STA 2 by an association ID which the AP 1 assigned during the association process for that STA 2.

If a STA 2 hears that data is waiting for it, then the STA 2 will awake more fully and send a PS-Poll (Power Save Poll) packet to the AP I to request the transmission of this waiting data.

In asynchronous mode, the STA 2 does not need to listen for beacons or TIM frames and may sleep for long periods of time. The STA 2 can asynchronously wake up and send a PS-Poll to the AP 1 asking whether there is downlink data for it. As is known per se, when and how often this occurs depends on the STA 2 and its current operational requirements and, in many cases, its power-saving requirements. For example, it may depend on how often the STA 2 expects that the AP I has traffic for it. It may also depend on the energy efficiency requirements of the STA 2 and its remaining battery power. If for example the STA 2 has very little battery power left, it may decide to sleep more and wake up to request for downlink traffic from the AP 1 less often. In the synchronous mode, the wake up for downlink traffic is more regular and the STAs 2 are not on such a strict energy budget so they can decide to wake up every beacon say, as opposed to deciding to sleep more and asynchronously wake up to request this traffic.

As noted above, it has been proposed for 802.llah in particular that a STA 2 will operate in one of two basic power-saving modes, or minor variations of those basic power-saving modes, depending particularly on the amount of uplink and downlink traffic that the STA 2 is expected to require as well as its energy efficiency requirements. These power-saving modes in essence correspond to the synchronous and asynchronous modes discussed above.

S The first power-saving mode involves STAs 2 that regularly have downlink traffic and thus operate in the synchronous mode discussed above to listen to the TIM in the beacon frames. Those STAs 2 can sleep, wake up at so-called Listen Intervals to listen to the TIMs and, if paged in the TIM to indicate that downlink data is available, send a PS-Poll message to request data from the AP 1.

The second power-saving mode is intended primarily for very low duty cycle STAs 2 that typically have only uplink traffic to transmit to the AP 1. Due to mostly their lack of downlink traffic, there is no need for such STAs 2 to read the Traffic Indication Map (TIM) or the beacon frames regularly or frequently, and therefore they operate asynchronously. Occasionally, such STAs 2 wake and send PS-Poll messages to the AP I to request downlink data in case there is any. The AP I either responds with an ACK or a DATA frame, or sends no response. If neither an ACK or a DATA frame is received by the STA 2, the STA 2 will attempt transmission of the PS-Poll again at a later time. Alternatively, if an ACK is received, then it becomes the responsibility of the AP Ito deliver a downlink frame to the STA 2 at some point.

One extension of this asynchronous power-saving mode (see for example ll-12-0127-01-OOah "Low Power Medium Access" available in the IEEE8O2.11 document server) requires the AP I always to respond with either DATA or with an ACK. If it responds with an ACK, the AP 1 also indicates if it has a data packet available for the STA 2, in which case the STA 2 should stay awake waiting for the data, or the AP 1 indicates that it does not have a data packet available for the STA 2, in which case the STA 2 can go back to sleep until the next beacon. Ifan ACK is sent indicating that there is no downlink data and if the STA 2 does not have uplink traffic, then the STA 2 can sleep for the rest of the time. Another extension to this was agreed in ll-12-0409-06-OOah "Supporting Low Power Operation" available in the IEEE8O2.11 document server. There, in the presence of data to be sent to the STA 2, the AP I indicates with a timer to the STA 2 when this data will be available. This allows the STA 2 additional sleeping capability since it can sleep until the timer expires and the data is available.

S

However, it has been appreciated that over time, it is possible that a STA 2 changes its power-saving mode. For example, if the level of battery charge of the STA 2 is severely drained, the STA 2 may decide to switch from the first power-saving modc to the second power-saving mode. As another example, the STA 2 may switch to the first power-saving mode if its uplink and downlink traffic increases.

Also, a STA 2 may want to switch to different Listen Intervals to save energy. For example, when the battery power is severely depleted, the STA 2 may wish to use a longer Listen Interval which allows it to sleep for longer periods of time.

In addition, reference is made to our British patent application no. 1119210.1 tiled on 7th November 2011 and our US patent application no. 13/293,396 tiled on 10th November 2011, the entire content of each of which is hereby incorporated by reference. In those patent applications, it is disclosed that, in an example, the STAs associated with an AP may form groups. Those groups may be overlapping or not in the sense that any particular STA may be a member of any two groups or not. The AP assigns a group number to each group. At any given time the AP may allow a single group or multiple groups to be active. Active here means that at least one STA within an active group has a non-zero probability to attempt contention and subsequent transmission of its data packet. The AP has to communicate to the STAs grouping related parameters, which may include for examplc the number of groups in the network, the STAs associated with each group, the groups that can be active at any given time and the corresponding duration that they can be active. However, it may be that the grouping parameters need to be updated or amended from time to time.

Grouping parameters may need to change when for example the composition of the various groups changes and/or the requirements of a specific STA change. Also, this can be the case for example if the performance of a STA under an assigned group is not satisfactory, e.g. due to interference. Then the STA may send a message to the AP to suggest new group parameters.

In addition to the above, the individual STAs 2 may also change other S operational parameters in view of changing requirements or conditions for the STAs 2, particularly relating to transmission or reception requirements or battery charge conditions for the STA 2.

Examplcs of embodiments of the present invention provide for efficient relaying of information from the STAs 2 to the AP 1, or from one STA 2 to another in the case of for example an ad hoc or mesh network where for example STAs can be relays of each other's traffic, about changes in or the current values of at least one of the operational parameters being used by the individual STAs 2. Such operational parameters include one or more of the power-saving mode being used by the STA 2 and values of particular operating parameters used in the power-saving mode, as well as other specific operational parameters. This allows the AP to make optimal management decisions for the STAs 2 in a BSS, and allows better coordination of transmissions and the like in the ease of ad hoe or mesh networks or the like.

The following description of a specific example is principally in the context of one or more STAs sending messages to some control node, such as an AP. However, the same principles apply when for example a STA is sending messages to another STA, in a peer to peer or ad hoc network manner.

In one example, this is achieved by including information relating to the mode of operation in a message header that the STAs 2 use for sending messages to the AP 1. In this regard, reference is now made to Figure 2 which shows schematically the known structure for the so-called MAC (medium access control) header used and proposed to be used in some wireless transmissions, including 802.11 wireless transmissions and 802.11 ah wireless transmissions in particular. The MAC header is followed by the frame body which contains the data that is being transmitted and typically that is followed by some transmission error checking or error control arrangement, such as cyclic redundancy check or FCS. In Figure 2, the size in bytes or octets of each field of the MAC header is indicated.

S In the MAC header shown schematically in Figure 2, as is well known per se, there are fields for frame control, durationilD (which is used to indicate the remaining duration needed to receive the next frame transmission), addresses of various types as known per sc (for cxamplc for the transmitter, receiver, BSS, etc.), sequence control, quality of scrvicc control and high throughput control.

The Frame Control field is shown in more detail in Figure 3, with the size of each subfield of the Frame Control field in bits being indicated. The Protocol Version subfield provides the current version of the 802.11 protocol being used. Type and Subtype determine the ifinction of the frame. To DS and From DS indicate whether the frame is going to or exiting from the "distributed system" (DS), and is only used in data type frames of STAs 2 associated with an AP 1. More Fragments indicates whether more fragments of the frame, either data or management type, are to follow.

Retry indicates whether or not the frame is being retransmitted. Power Management indicates whether the sending STA 2 is in active mode or power-save mode. More Data indicates to a STA 2 in power-save mode that the AP I has more frames to send.

It is also used for APs I to indicate that additional broadcast!multicast frames arc to follow. Protected Frame indicates whether encryption has been used for the data.

Order indicates that all received data frames must be processed in order.

A short form has been proposed particularly for smart sensor/machine-type communications to reduce the amount of data traffic and prolong battery life, particularly in the context of IEEE 802.1 lah networks. For example the short beacon format (sec II-II-1503-02-OOah "Short Beacon" available in the IEEE8O2.II document server) was agreed to save the transmission time of Beacons, as those frames are sent frequently. The short Beacon frame is created from the long Beacon frame, by removing fields that are not necessary. Also, a different approach is taken for other frames that are made short by removing the MAC header and appending only its necessary field, e.g. the frame's type and subtype, information about the transmitter and receiver of the frame, etc., in an updated signal (SIC) field. Using this principle, short frame formats were agreed for the NDP Probe Request frame (see for S example 1 1-12-0830-0O-00ah "ndp Probing"), the Beamforming Report Poll frame (see for example ll-12-0842-02-OOah "Short Beamforming Report Poll Frame"), the Short Probe Response frame (see for example 11-12-0869-00-OOah "Active Scanning For I lab"), the ACK (see for example I l-12-0324-02-OOah "Short Ack"), the Block ACK (scc for cxamplc 1 1-12-0859-0O-00ah "Short BA"), thc CTS (sec for example 1l-12-0643-00-OOah "Short CTS"), and the NDP PS-Poll (scc for example 11-12-0848-00-OOah "ndp Type ps Poll Frame), all available in the IEEE8O2.11 document server. An example of a Short ACK as discussed in 11-12-0324-02-OOah "Short Ack" is shown schematically in Figure 4, where a short ACK frame only contains an STF field, an LTF field and special SIC with all the necessary information for acknowledging a frame. For the short ACK design and under the observation that the modulation and coding scheme (MCS) in the SIC is not used in an ACK frame, it was agreed to use the reserved MCS bits to indicate that it is a Short ACK. Also, it was proposed to include an ACK ID field in the special SIG of the Short ACK.

However, since the ACK ID field cannot fit the whole receiver address (RA) it was agreed to usc a partial address or AID and usc the remaining bits to indicate an ACK ID. Also a More Data bit was proposed to be addcd in thc special SIG as in this way, a short ACK can be used also as a response to a PS-Poll message to indicate the presence of downlink data.

In onc example of an cmbodiment of thc present invention, a message hcadcr is used for transmission by a STA 2 to the AP I (or more generally any other STA 2) that includes information regarding the mode of operation being used by the STA 2.

This header, an example of which is shown schematically in Figure 5, may include one or more of the following "operation mode information" elements or parameters: (1) An indication whether the STA 2 decodes the TIM or the STA 2 does not decode the TIM. In essence, this indicates whether the STA 2 is operating in synchronous mode or asynchronous mode respectively, as discussed in more detail above. This information can be indicated for example by 1 bit, where for example a S zero (0) could indicate asynchronous mode while a one (1) could indicate synchronous mode operation. Alternatively, more bits can be used to indicate the energy operation mode. For instance, 2 bits can be used giving two additional values to indicatc the various enhancements and variations, some of which are mentioned earlier, of thc asynchronous and asynchronous modcs.

(2) An indication of the degree of the need for energy saving. This indication may indicate relatively simplistically whether for example the battery charge is almost full or almost empty. Alternatively or additionally, this indication may bc a quantiscd value, relating more directly to the actual level of battery charge. As an example, 2 bits can be reserved for that with a value 11 indicating for instance a battery that is almost fill and 00 a battery that is almost empty. Values 10 and 01 may indicate battery levels that lie in between those extremes.

(3) LI (Listen Interval) parameters. These may include for example the actual value of the Listen Interval and the units of the Listen Interval currently being used by the STA 2. If the units of Listen Interval and that of the BSS max idle period and WNM-Sleep interval are unified, then the common unit is preferably indicated.

(WNM-Sleep (where "WNM" is wireless network management) enables a STA 2 to signal to an AP I that it will be sleeping for a specified length of time.) Curently, 2 octets arc used to determine the listen interval. Furthermore, 2 bits (or 1 byte) can be used to indicate the units that would map the number of intervals to time according to different sealing options. For instance, the tuple "00" can mean that the units are in seconds, "01" that they arc multiplied by 10 seconds, "10" that they are multiplied by seconds, and "1 1" that they are multiplied by 1000 seconds. Naturally, if the units of the BSS max idle period and WNM-Sleep are larger, then the units of the LI should be increased accordingly. As another example, the 2 octets used for the Listen Intcrval can be split into two (2) parts, one to indicate the scaling and onc to indicate to the AP how often a STA in power save mode wakes up to hsten to Beacon management frames, as shown schematically by way of example in Figure 6. In the figure, the number of bits used for the different fields is controlled by the parameter x.

S For example, if x =1 two bits are used for the scaling and fourteen are used for the number of beacon intervals.

(4) If grouping is enabled, group information for the group to which the STA cunently belongs. This group information may be or include for example the group number and the above mentioned grouping parameters. Alternatively or additionally, this group information may be or include the Sector ID on which the STA 2 hears transmissions by the AP 1. An example of the sub-elements of the Group Parameters field is shown schematically in Figure 7. In this field a STA 2 may indicate to the AP I (or more generafly any other STA 2) its current group number (or the Sector ID) and an indicator of the interference that it receives on that group or sector. Optionally the STA may indicate or suggest a new group number or Sector ID that it would like to join.

It should be noted that the fields of this message header may be in combination with the fields of a conventional MAC header, and that the order of the fields, within the header itself and/or when in combination with a conventional MAC header, is not important. The addition of information regarding the mode of operation being used by the STA 2 to the MAC header will in one example increase the size of the message header by a certain number of bytes or octets.

In a variant of this example, the size and type of the message header that is used by the STA 2 can be indicated within the Frame Control field of the message header. (The conventional Frame Control field is discussed above with reference to Figure 3.) For example, currently the Protocol Version subfield of the Frame Control field has two bits. This enables a maximum of four different types of header to be indicated using the Protocol Version bits. As just one example, this may be used as follows, it being understood that other variations and allocations for the bits may be used: 00: short header without operational mode information 01: short header with operational mode information 10: long header without operational mode information 11: long header with operational mode information In another example of an embodiment of the present invention, instead of increasing thc size of thc conventional message hcadcr to include information regarding the mode of operation being used by the STA 2 as discussed above, that information may be relayed using subfields of the Frame Control field. For instance, one or both of the Type and Subtype subfields of the Frame Control field may be used to indicate that the frame that is being transmitted includes operational mode information. As an example, the bits B3 B2 = 01 which correspond to a "Control" type of frame have subtype bits B7 B6 B5 B4 = 0000-0110 as reserved. Also, the bits B3 B2 = 11 correspond to a reserved type for which all bits B7 B6 B5 B4 = 0000- 1111 of the subtype are reserved. The type of header as well as the operational mode indication can be indicated through these fields. Furthermore, the rest of the bits B8 to B15 may be used to indicate one or more of the operational mode parameters discussed more filly above under items (1) to (4).

In another example of an embodiment of the present invention, rather than using the message header, or the Frame Control field of the message header, to relay the operation mode information, the operation mode information can be piggybacked with the data payload that the STA 2 sends to the AP 1. Again, this operation mode information may be one or more of the operational mode parameters discussed more fully above under items (1) to (4). An advantage of this example is that no new packet is sent, though typically the packet size, and in particular the size of the data payload of the packet, increases according to the operation mode information that is being transmitted.

In a variant of the examples discussed above, as long as it has data to send, the STA 2 always piggybacks the operation mode information to the packet that contains the data, which may be as part of the header or the Frame Control field of the header or part of the data payload in the examples above. This data may be "user" data, S including for example sensor readings and the like, or control data. The operation mode information may be piggybacked on other messages, such as RTS (request to send) for example. Otherwise, if no data is to be sent, the STA 2 may send a separate packet containing the operation mode information. This can be a new message, which may for example be termed "Mode Operation Indication" or the like, that contains all the operation mode information relevant to for example the power-saving mode and grouping mode of the STA 2.

Whichever way the STA 2 relays the operation mode information to the AP 1, in an example the STA 2 may send along with the operation mode information a mode switching pattern, indicating that the STA 2 will be switching among different modes according to that pattern. The new pattern can be selected by the STA in a deterministic manner from a set of available patterns. For example, as time progresses and the STA's battery power is depleted, the next pattern can be deterministically obtained by the STA based on the remaining battery power. The STA 2 only needs to indicate when the next pattern will be selected. As an alternative, a new pattern can be selected at random, and the STA 2 indicates to the AP 1 which is the new pattern and when it will select/activate it.

In any of the examples above, where a STA 2 provides an indication of the degree of the need for energy saving by the STA 2, as mentioned this may for example be related to the level of charge of a battery that powers the STA 2. In a particular example, two bits may be reserved for this, giving a maximum of 4 possible battery level states. (It will be appreciated that further states maybe indicated, though this will require a larger number of bits.) As just one specific example for this, the indication may be as follows: 11: Battery almost full 10: Battery almost empty 01: Battery above average 00: Battery almost empty S When an AP 1 receives a request from a STA 2 to change operation mode, the AP 1 may respond with an ACK that can have an indication to "accept" or "reject" the mode change. The ACK can be for example a "normal" 802.11 ACK or a "short" ACK.

In the case that the ACK from the AP 1 has an indication to "accept" or "reject" the mode change, this can be achieved using a bit in the ACK message. As a particular example, this may be interpreted as follows: 1: Accept operation mode 0: Reject operation mode If no such bit is set in the ACK, then the STA 2 receiving the ACK may simply assume that no frirther indication about acceptance or rejection of the mode change request has been sent by the AP 1.

To indicate this bit, an extra field can be added to the conventional ACK, though this inevitably increases the overhead of sending an ACK. As an alternative therefore, this accept/reject indication bit from the AP I can be indicated through the Type and Subtype subfields of the Frame Control field. As a particular example, in the reserved bits of the Type and Subtype subfields of the Frame Control field, four combinations can bc used to indicate that it is a message of type: (i) Normal ACK/ Accept operation mode configuration (ii) Normal ACK! Reject operation mode configuration (iii) Short ACK! Accept operation mode configuration (iv) Short ACKI Reject operation mode configuration With regard to (i) and (ii), for normal ACKs there are already bits reserved in the Type and Subtype subfields to indicate the norma' ACK. An extra bit field can be used to indicate the Accept/Reject of the operation mode configuration requested by the STA 2. Alternatively, as just one particular example to illustrate this, when the S Type/Subtype bits B3 B2 = 11, the values 0000-1111 of the Subtype bits B7 B6 B5 B4 are reserved and can be used to indicate the two new types of messages "Normal ACK with Accept operation mode Configuration" and "Normal ACK with Reject operation mode configuration". Additionally the Type/Subtype bits B3 B2 = 01 can be uscd and the reserved values B7 B6 B5 B4 = 0000-0110. The normal ACK without any indication can still be a valid response if thc AP I responds with the Type bits set to B3 B2 =01 and Subtype bits set to B7 B6 B5 B4 = 1101.

With regard to (iii) and (iv), for short ACKs, to indicate a short ACK message with the Accept'Reject configuration, in an example the Type/Subtype bits of the Frame Control field can be used. As a specific example to illustrate this, when the Type bits B3 B2 = 11, the values 0000-1111 of the Subtype bits B7 B6 B5 B4 are reserved and can be used to indicate a Short ACK with Accept/Reject operation mode configuration, similarly to above for the normal ACKs. As an alternative, the reserved values of the protocol version bits can be used to indicate that a new message type is present. Currently version 00 is used and all other values are free for use for this purpose. Alternatively also the Type/Subtype bits B3 B2 = 01 can be used and the reserved values B? B6 B5 B4 = 0000-0110.

With further reference to (iii) and (iv), for short ACKs, a Short ACK without any indication may also be a valid response. In this case, again the reserved values of the Type/Subtype fields can be used to indicate the Short ACK. Alternatively, again the reserved values of the protocol version bits can be used.

Furthermore, fewer than four combinations for the ACK may be sufficient in some cases, for example in the case that not both Short and Normal ACKs need to be supported, or in the case that the AP 1 has for example always to accept the response.

Examples of embodiments of the present invention provide an efficient way of communicating the operation mode or operational parameters of the STAs 2 to the AP 1 and/or to other STAs 2. In certain examples, the overhead associated with having to S send extra message transmissions is avoided when possible, such as when the information about the operation mode information is sent along with data that the STA 2 already had to send.

It may be noted that embodiments of the present invention may be used when for example a STA 2 sends a request to change the operational parameters and/or mode of operation to the AP 1 and the AP I either accepts or rejects the change, i.e. the AP I effectively controls the operational parameters and mode of operation of the STA 2. Embodiments of the present invention may also be used when a STA 2 effectively autonomously changes its operational parameters and/or mode of operation, and simply wishes to inform an AP, and/or other STAs 2, of the change(s).

Although at least some aspects of the embodiments described herein with reference to the drawings comprise computer processes performed in processing systems or processors, the invention also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice.

The program may be in the form of non-transitory source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other non-transitory form suitable for use in the implementation of processes according to the invention. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a solid-state drive (SSD) or other semiconductor-based RAM; a ROM, for example a CD ROM or a semiconductor ROM; a magnetic recording medium, for example a floppy disk or hard disk; optical memory devices in general; etc. It will be understood that the processor or processing system or circuitry referred to herein may in practice be provided by a single chip or integrated circuit or plural chips or intcgratcd circuits, optionally providcd as a chipsct, an application-specific integrated circuit (ASIC), field-programmable gatc array (FPGA), digital signal processor (DSP), etc. The chip or chips may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or S processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry, which are configurable so as to operate in accordance with the exemplary embodiments. In this regard, the exemplary embodiments may be iimplcmcntcd at Icast in part by eomputcr softwarc storcd in (non-transitory) mcmory and cxccutablc by thc processor, or by hardwarc, or by a combination of tangibly stored software and hardware (and tangibly stored firmwarc).

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to anyone embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

CLAIMS1. A method of operating a wireless device that is in wireless communication with a second wireless device, the method comprising: S the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a said second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data if the wireless device has data to transmit, else the wireless device transmits the information relating to the at least one operational parameter in a separate message if the wireless device does not have data to transmit.
2. A method according to claim 1, wherein in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data, the information relating to the at least one operational parameter is transmitted in a header of the message.
3. A method according to claim 2, wherein information relating to at least one of size and type of the message header is transmitted as part of a Frame Control field of the message header.
4. A method according to claim 3, wherein the information relating to at least one of size and type of the message header is transmitted using a Protocol Versionsubfield of the Frame Control field.
5. A method according to claim 2, wherein the information relating to the at least one operational parameter is transmitted in a Frame Control field of the message header.
6. A method according to claim 5, wherein an indication that the Frame Control field contains information relating to the at least one operational parameter is included in at least one of a Type subfield and a Subtype subfield of the Frame Control field.
7. A method according to claim 1, whercin in the case that the wireless device transmits the information relating to the at least onc operational parameter as part of a message that contains data, the information relating to the at least one operational parameter is transmitted as part of the data payload of the message.
8. A method of operating a wireless device that is in wireless communication with a second wireless device, the method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a said second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data or as part of a data payload of a message that contains data.
9. A method according to claim 8, wherein in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data, information relating to at least one of size and type of the message header is transmitted as part of a Frame Control field of the message header.
10. A method according to claim 9, wherein the information relating to at least one of size and type of the message header is transmitted using a Protocol Versionsubfield of the Frame Control field.
11. A method according to claim 8, wherein in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data, the information relating to the at least one operational parameter is transmitted in a Frame Control field of the message header.
12. A method according to claim 11, wherein an indication that the Frame Control field contains information relating to the at least one operational parameter is included in at least one of a Type subfield and a Subtype subfield of the Frame Control field.
13. A method according to any of claims I to 12, wherein the at least one operational parameter is at least one of: (i) an indication whether or not the wireless device decodes a traffic indication map frame; (ii) an indication of the degree of the need for energy saving by the wireless device; (iii) listen interval parameters being used by the wireless device; (iv) group information for a group of wireless devices to which the wireless device currently belongs.
14. A method according to any of claims 1 to 13, wherein said second wireless device is an access point.
15. Apparatus for a wireless device, the apparatus comprising a processing system constructed and arrange to cause the wireless device to carry out a method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a second wireless device information relating to at least one operational parameter that relates to the second S mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data if the wireless device has data to transmit, else the wireless device transmits the information relating to the at least one operational parameter in a separate message if the wireless device does not have data to transmit.
16. Apparatus according to claim 15, arranged such that in the ease that the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data, the information relating to the at least one operational parameter is transmitted in a header of the message.
17. Apparatus according to claim 16, arranged such that information relating to at least one of size and type of the message header is transmitted as part of a FrameControl field of the message header.
18. Apparatus according to claim 17, arranged such that the information relating to at least one of size and type of the message header is transmitted using a ProtocolVersion subfield of the Frame Control field.
19. Apparatus according to claim 16, arranged such that the information relating to the at least one operational parameter is transmitted in a Frame Control field of the message header.
20. Apparatus according to claim 19, arranged such that an indication that the Frame Control field contains information relating to the at least one operational parameter is included in at least one of a Type subfield and a Subtype subfield of theFrame Control field.
21. Apparatus according to claim 15, arranged such that in the case that the S wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data, the information relating to the at least one operational parameter is transmitted as part of the data payload of the message.
22. Apparatus for a wireless device, the apparatus comprising a processing system constructed and arrange to cause the wireless device to carry out a method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data or as part of a data payload of a message that contains data.
23. Apparatus according to claim 22, arranged such that in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data, information relating to at least one of size and type of the message header is transmitted as part ofa Frame Control field of the message header.
24. A method according to claim 23, arranged such that the information relating to at least one of size and type of the message header is transmitted using a ProtocolVersion subfield of the Frame Control field.
25. Apparatus according to claim 22, arrangcd such that in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data, the information S relating to the at least one operational parameter is transmitted in a Frame Controlfield of the message header.
26. Apparatus according to claim 25, arranged such that an indication that the Frame Control ficld contains information relating to the at least one operational paramctcr is includcd in at icast one of a Type sublicid and a Subtype subfield of theFrame Control field.
27. Apparatus according to any of claims 15 to 26, whcrcin thc at lcast one operational parameter is at Icast one of: (i) an indication whether or not the wireless device decodes a traffic illdication map frame; (ii) an indication of the degree of the need for energy saving by the wireless device; (iii) listen illterval parameters being used by the wireless device; (iv) group information for a group of wireless devices to which the wireless dcvicc currently bclongs.
28. A computer program comprising a set of instructions for causing a wireless communications device to carry out a method comprising: the wireless device operating according to a first mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting for receipt by a said second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data if the wireless device has data to transmit, else the wireless device transmits the information relating to the at least one operational parameter in a separate message if the wireless device S does not have data to transmit.
29. A computer program according to claim 28, wherein in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data, the information relating to the at least onc operational parameter is transmitted in a header of the message.
30. A computer program according to claim 29, wherein infomiation relating to at least one of size and type of the message header is transmitted as part of a FrameControl field of the message header.
31. A computer program according to claim 30, wherein the information relating to at least one of size and type of the message header is transmitted using a ProtocolVersion subfield of the Frame Control field.
32. A computer program according to claim 29, wherein the information relating to the at least one operational parameter is transmitted in a Frame Control field of the message header.
33. A computer program according to claim 32, wherein an indication that the Frame Control field contains information relating to the at least one operational parameter is included in at least one of a Type subfield and a Subtype subfield of theFrame Control field.
34. A computer program according to claim 28, wherein in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message that contains data, the information relating to the at least one operational parameter is transmitted as part of the data payload of the message.
35. A computer program of operating a wireless device that is in wireless communication with a second wireless device, the method comprising: the wireless device operating according to a fimt mode of operation; the wireless device switching or desiring to operate according to a second mode of operation; the wireless device transmitting %r receipt by a said second wireless device information relating to at least one operational parameter that relates to the second mode of operation; wherein the wireless device transmits the infbrmation relating to the at least one operational parameter as part of a message header of a message that contains data or as part of a data payload of a message that contains data.
36. A computer program according to claim 35, wherein in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data, infbmiation relating to at least one of size and type of the message header is transmitted as part ofa Frame Control field of the message header.
37. A computer program according to claim 36, wherein the information relating to at least one of size and type of the message header is transmitted using a ProtocolVersion subfield of the Frame Control field.
38. A computer program according to claim 35, wherein in the case that the wireless device transmits the information relating to the at least one operational parameter as part of a message header of a message that contains data, the information relating to the at least one operational parameter is transmitted in a Frame Controlfield of the message header.
39. A eomputcr program according to claim 38, wherein an indication that the Frame Control field contains information re'ating to the at least one operational parameter is included in at least one of a Type subfield and a Subtype subfield of theFrame Control field.S
40. A computer program according to any of claims 28 to 39, wherein the at least one operational parameter is at least one of: (1) an indication whether or not the wireless device decodes a traffic indication map frame; (ii) an indication of the degree of the need for energy saving by the wireless device; (iii) listen interval parameters being used by the wireless device; (iv) group information for a group of wireless devices to which the wireless device currently belongs.
41. A method of operating a wireless communications device, substantially in accordance with any of the examples as described herein with reference to and illustrated by the accompanying drawings.
42. Apparatus for a wireless device, the apparatus comprising a processing system constructed and arrange to cause the wireless device to operate substantially in accordance with any of the examples as described herein with reference to and illustrated by the accompanying drawings.