HK1094497B - Access point for providing assistance data to wireless transmit/receive unit - Google Patents

Description

Access point for providing support data to a wireless transmit/receive unit

Technical Field

The present invention relates to wireless communication systems, and more particularly, to delivering support data to a wireless transmit/receive unit (WTRU).

Background

Referring to fig. 1, a conventional wireless communication system 100 is shown. The system 100 includes at least one wireless transmit/receive unit (WTRU)102, an access point 104, and at least one system controller 106 for controlling, and otherwise managing, communications in the system 100. Whereas, typically, in a Wireless Local Area Network (WLAN) type system, the network may be deployed as shown in fig. 2.

In fig. 2, the wireless network 200 includes a system controller 206, multiple access points 214, 216, and multiple WRTUs 212, 218, with the multiple WTRUs 212, 218 clustered together at the access points 214, 216, respectively. These groups are conventionally referred to as Basic Service Sets (BSSs) 220, 222. A plurality of BSSs 220, 222 are typically connected via a Distribution System (DS)224, wherein the BSSs are conventionally referred to as an Extended Service Set (ESS). Further, the access points 214, 216 are preferably connected to the system controller 206 via a network 219.

In general, support data is provided to (or accessible at) WTRUs associated with a particular access point. Typically, the support data can include any type of data regarding any type of information associated with any access points in the vicinity of the particular access point (i.e., access points whose respective coverage areas are adjacent to the coverage area of the particular access point). Providing support data may facilitate roaming/handover (handover) of a WTRU by providing the necessary information regarding finding/identifying neighboring access points.

For example, the support data may include information about neighboring access points, such as operating frequencies, access modes (e.g., 802.11 Frequency Hopping Spread Spectrum (FHSS)/Direct Sequence Spread Spectrum (DSSS), 802.11a, 802.11b high speed direct sequence spread spectrum (HR/DSSS), etc.), timing, system architecture information about neighboring Basic Service Sets (BSSs) (e.g., Ready To Send (RTS)/Clear To Send (CTS), Point Coordination Function (Point Coordination Function, PCF), wired equivalent Privacy (wired equivalent Privacy, WEP), etc.).

Currently, the support data is transmitted using point-to-point (i.e., unicast) signaling. In 802.xx type systems, for example, the support data is provided in the form of an Information Element (IE) containing neighbor information that is incorporated into existing Probe Response (Probe Response) frames that are typically sent by an access point in reply to a Probe Request (Probe Request) management frame sent by a WTRU when the WTRU attempts to discover neighboring BSSs. However, this configuration is inefficient because the transmission of the support data using point-to-point signaling results in a large amount of network traffic, thereby also greatly increasing the likelihood of significant delays associated not only with the transmission/reception of the support data, but also with general transmission/reception.

Therefore, there is a need for a method and system for providing support data to a WTRU that does not have the above limitations.

Disclosure of Invention

It is an object of the present invention to provide a method and system for providing support data to a wireless transmit/receive unit (WTRU), the support data including information about neighboring access points of the access point, and the support data being transmitted using multicast and/or broadcast type signaling and facilitating roaming and handover of the WTRU from one access point to another.

Drawings

FIG. 1: a block diagram of a conventional wireless communication system is shown;

FIG. 2: a block diagram of a conventional wireless communication system having multiple access points and multiple WTRUs is shown;

FIG. 3: a block diagram of a wireless communication system in accordance with the present invention is shown;

FIG. 4: a graph showing neighbor information transmitted by an access point when the access point transmits a predetermined multiple of its beacon's time period;

FIG. 5: a diagram showing neighbor information transmitted with beacons in the form of extended beacons when the access point transmits a predetermined multiple of its regular beacon time period;

Detailed Description

Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone (without the other features and elements of the preferred embodiments) or in various combinations with or without other features and elements of the present invention.

A wireless transmit/receive unit (WTRU) herein includes, but is not limited to, a user equipment, a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. As used herein, an access point includes, but is not limited to, a base station, a node B, a location controller (sitecontroller), an access point, or any type of interfacing device in a wireless environment. In this context, the term handover refers to an access point change when a WTRU is actively receiving/sending data, and the term roaming refers to an access point change when a WTRU is not actively receiving/sending data. The present invention is equally applicable to both scenarios (security), and these noun handovers and roamings may be used interchangeably herein, where both nouns generally refer to the situation where a WTRU that is affiliated with, or working with, a first access point becomes affiliated with a second access point, and the affiliation with the first access point eventually terminates.

Generally, in the present invention, an access point obtains support data by OAM, inter-access point signaling, scanning, commanding WTRUs to scan, or a combination thereof, and transmits this information as a single message to multiple WTRUs. Once obtained, an access point may also share neighbor information with other access points so that those access points may also transmit the information to the WTRU.

Referring now to fig. 3, therein is shown a wireless communication system 300. And the system 300 includes at least one Extended Service Set (ESS). However, for purposes of describing the present invention, two ESS's 336, 338 are shown in FIG. 3. The first ESS 366 is constructed in accordance with the present invention and includes a system controller 302, a plurality of access points 304, 306, 308, and a plurality of WTRUs 310, 312, 314. Of course, the first ESS 336 may be configured with a single access point and in this case, it is considered a BSS, as appropriate. The total coverage area of the first ESS 336 is depicted by thick black lines and includes coverage areas 324, 326, 328. Furthermore, the second ESS 338 also includes a system controller 316, a plurality of access points 318, 320, 322, and a plurality of WTRUs (not shown). The total coverage area of the second ESS 338 includes coverage areas 330, 332, 334.

In the present invention, each of the access points 304, 306, 308 of the first ESS 336 includes a processor 340, 342, 344 for obtaining and providing support data to its respective WTRU. The supporting data facilitates handover and roaming of the WTRU. It should be noted herein that the first ESS 336 is shown only in accordance with the inventive arrangements simply to simplify the description of the present invention. Thus, of course, any number of aps, whether they are affiliated with an ESS or BSS, may be configured in accordance with the present invention.

The support data (i.e., neighbor list or neighbor information) is preferably obtained by operation and maintenance (OAM), inter-access point proprietary signaling (i.e., inter-access point signaling), active/passive scanning for channels other than the channel used by the access point being scanned, and/or measurement reports from the WTRU.

For example, in fig. 3, when the ap 304 is searching for information about aps 306 and 308 within the same ESS 336 of the ap 304, it may preferably use inter-ap signaling, and/or OAM, which may be a preferred option because, for example, the aps 304, 306, 308 share a common system controller 302 so that neighbor information about the aps 304, 306, 308 may be provided to the ap 304 via OAM at the controller 302. Inter-ap signaling may be preferred because, for example, a distribution network, such as that shown in fig. 2, is typically provided between the aps 304, 306, 308 comprising the ESS 306, while direct connections between the aps 304, 306, 308 are shown for simplicity. The distribution network provides a direct wired connection through which the inter-access point signaling can be efficiently performed. And when Inter-Access Point signaling is used, an Inter-Access Point Protocol (IAPP) may be used.

As mentioned previously, the access point 304 has other options for obtaining neighbor information from neighboring access points 306, 308. For example, the access point 304 may instruct the WTRU 310 to scan for channels other than those used by the access point 304 to obtain neighbor information for any detected channel and report the information. Alternatively, the ap 304 may also scan other channels by itself. This scanning may be done independently of, or in conjunction with, any scanning done by the WTRU 310 while the access point 304 is scanning. In this embodiment, a quality metric (quality metric), e.g., received power, may be used for selection between measurements obtained by the access point 304 relative to measurements obtained by the WTRU 310 for the same channel.

Where the access point 304 obtains information about a neighboring access point 318 that occurs outside the ESS 336 of the access point 304, it may obtain the information, preferably via scanning. As previously discussed, the access point 304 may perform the scanning itself (either actively or passively) or command the WTRU 310 to perform the scanning (either actively or passively) and report back. Of course, the access point 304 is not limited to using scanning to obtain neighbor information about the access point 318. The access point 304 may also obtain information about the access point 318 using OAM and inter-access point signaling.

As noted above, the processor 340 of the access point 304 is preferably configured to obtain this neighbor information. Of course, more than one processor may be used if desired. Information obtained by processor 340 may be stored in memory 350 when needed. Further, the processor 340 of the access point 304 is also configured to provide neighbor information as explained below.

It is noted that the above methods may be used in combination, if appropriate. For example, when an access point 304 is initially online and it does not have a neighbor information defined by OAM, it may scan its surroundings and/or instruct some of its WTRUs 310 to scan the same. Once the access point 304 has the results of this scan, it can use this information to inform other access points 306, 308 within its ESS 336 of the discovery. This minimizes the amount of scanning performed by the aps 306, 308 (which may cause some small amount of traffic fragmentation). This configuration is particularly helpful when the ap 304 seeks neighbor information from an ap 318 outside of the ESS 324, since the ap 304 information will not include aps 318, 320, 322 outside of the ESS 324. It should also be noted that in a preferred embodiment, the ap 304 should periodically scan (or request one of its WTRUs to scan) after the neighbor information is started and found to search for a change in the neighbor information.

The neighbor information obtained by the access point 304 is preferably periodically broadcast, or multicast, to WTRUs 310 operating within the coverage area 336 of the access point 304. Referring now to fig. 4, using WLAN as an example, all access points and WTRUs operating in a particular BSS transmit and receive using a single channel (i.e., frequency), as shown in fig. 4, the access points periodically transmit a beacon 402 on their respective channels, and the time period during which the beacon 402 transmits is typically referred to as a beacon frame (beacon frame). The beacon 402 is transmitted approximately every 100ms although it is possible, an access point typically does not need to transmit the neighbor information it obtains to its wtrus at every beacon, therefore, in a preferred embodiment, the access point is configured to transmit its neighbor information at a predetermined multiple of the time period during which the access point transmits its beacon 402, and the multiple is set as desired, and is preferably a function of the mobility level of WTRUs affiliated with their respective access points.

For example, in fig. 4, the neighbor information 406 is shown as being transmitted by the access point at a particular multiple of the beacon interval. The particular ap transmitting the neighbor information 406 shares the channel with the WTRUs to which it belongs. Thus, in a beacon interval during which neighbor information is transmitted, once the access point has completed its transmission of its beacon 402, it waits a fixed amount of time until it can again gain access to the channel, which is typically referred to as a Contention phase 404 because the access point contends with its respective WTRU for access to the channel. Once the access point gains access to the channel, it transmits the neighbor information 406 with information about neighboring access points provided therein, as explained above, to WTRUs affiliated with the access point.

The adjacency information 406 is transmitted as multicast information(s) to a predetermined group(s) of WTRUs affiliated with the access point transmitting the adjacency information 406. In yet another embodiment, the neighbor information 406 may be broadcast to all WTRUs affiliated with the transmitting access point. It is noted that the WTRUs that provide neighbor information 406 to them in parallel with the success of the aps may also use peer-to-peer probe requests and/or channel scanning. The WTRUs may perform such techniques as a backup and/or supplement to receive information from the ap.

Preferably, the neighbor information is transmitted using a management type frame (i.e., during a time period in which system management information is transmitted). In one embodiment, the management type frame used is preferably the same as that used in the prior art when the WTRU obtains neighbor information using point-to-point signaling. Further, the correlation procedure performed after a WTRU receives the neighbor information 406 is the same as a point-to-point message except for the WTRU's acknowledgement.

Referring now to FIG. 5, another embodiment of the present invention is shown. In this embodiment, the exemplary beacon signal is configured with an extra bit. Wherein the extra bit indicates the presence/absence of neighbor information. The beacons 502 that transmit in a regular beacon are shown with empty signaling bits 506, and the beacons 502 are transmitted by an access point according to a predetermined schedule, as normal, in a regular beacon frame. The period over which the neighbor information is sent is a predetermined multiple of the time period during which the beacons 502 are transmitted as previously discussed. Further, when it is time for the neighbor information to be transmitted by an access point to its respective WTRU, the neighbor information 508 is added to the beacon 502 and transmitted with it in an extended beacon frame 504. In this scenario, the signaling bit 506 of the beacon 502 can reliably reflect the fact that the bit is set to indicate that neighbor information 508 is present within the extended beacon frame 504. In a preferred embodiment, the neighbor information 508 is added to the beacon 502 as an Information Element (IE). As previously discussed, the neighbor information 508 includes information that assists the WTRU in efficient handover from an access point to a neighboring access point.

It is important to note that the present invention can be implemented in any type of wireless communication system, for example, a Wireless Local Area Network (WLAN), a Wireless Personal Area Network (WPAN), a Wireless Metropolitan Area Network (WMAN), or any type of wireless communication system/network, and further, although the features and elements of the present invention are described in the preferred embodiment in particular combinations, each feature or element can be used alone or in various combinations with or without other features and elements of the present invention.

Although the present invention has been described with reference to the present specific embodiments, it will be appreciated by those skilled in the art that the above embodiments are merely illustrative of the present invention, and various equivalent changes and substitutions may be made without departing from the spirit of the invention, and therefore, it is intended that all changes and modifications to the above embodiments within the spirit and scope of the present invention be covered by the appended claims.

Claims (16)

1. An access point configured to provide support data to a wireless transmit/receive unit, the access point comprising:

means for obtaining neighbor information regarding neighboring access points from at least one neighboring access point whose respective coverage area is adjacent to the coverage area of the access point and generating support data, wherein the support data includes neighbor information for facilitating handover of a wireless transmit/receive unit from the access point to a neighboring access point from which the support data has been obtained; and

means for the access point to broadcast a beacon to a plurality of wireless transmit/receive units operating within a coverage area of the access point, wherein the beacon comprises an indicator for indicating that the beacon contains support data, wherein the support data comprises channel information and information about at least one access mode associated with the neighboring access point.

2. The access point of claim 1, wherein the at least one access mode comprises an IEEE802.11 access mode.

3. The access point of claim 1, wherein obtaining neighbor information related to neighboring access points comprises:

neighbor information is received from at least one wireless transmit/receive unit associated with the access point.

4. The access point of claim 1, wherein obtaining neighbor information related to neighboring access points comprises:

requesting neighbor information data from the neighboring access point; and

neighbor information data is received from the neighboring access point.

5. The access point of claim 1, wherein obtaining neighbor information related to neighboring access points comprises:

neighbor information is received from the neighboring access point.

6. The access point of claim 1, wherein the neighbor information is obtained by scanning for channels outside of a channel utilized by the access point.

7. The access point of claim 6, wherein the scanning is passive scanning.

8. The access point of claim 6, wherein the scanning is an active scanning.

9. The access point of claim 1, wherein the neighbor information is obtained by obtaining measurements of wireless transmit/receive units operating with a coverage area of the access point.

10. The access point of claim 1, wherein the support data includes operating frequencies of neighboring wireless transmit/receive units and access points that obtain the neighbor information.

11. The access point of claim 1, wherein the support data comprises an access mode used by a neighboring access point that obtained the neighbor information.

12. The access point of claim 1, wherein the support data comprises timing information of a neighboring access point that obtained the neighbor information.

13. The access point of claim 1, wherein the support data comprises configuration information of a neighboring access point that obtained the neighbor information.

14. The access point of claim 1, wherein the support data is transmitted at a predetermined multiple of a time period while the AP transmits a beacon.

15. The access point of claim 14, wherein the support data is transmitted separately from the beacon.

16. The access point of claim 1, wherein the support data is transmitted as a multicast message.