|Publication number||US20060029023 A1|
|Application number||US 11/246,577|
|Publication date||Feb 9, 2006|
|Filing date||Oct 7, 2005|
|Priority date||Jul 7, 2000|
|Also published as||CN1572086A, EP1282961A2, US6985465, US20020060995, WO2002023819A2, WO2002023819A3|
|Publication number||11246577, 246577, US 2006/0029023 A1, US 2006/029023 A1, US 20060029023 A1, US 20060029023A1, US 2006029023 A1, US 2006029023A1, US-A1-20060029023, US-A1-2006029023, US2006/0029023A1, US2006/029023A1, US20060029023 A1, US20060029023A1, US2006029023 A1, US2006029023A1|
|Inventors||Gerard Cervello, Sunghyun Choi, Stefan Mangold, Amjad Soomro|
|Original Assignee||Cervello Gerard G, Sunghyun Choi, Stefan Mangold, Soomro Amjad A|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (31), Classifications (17)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of U.S. Provisional Applications Ser. No. 60/217,145 filed July 7, 2000 and Ser. No. 60/233,179 filed on Sep. 15, 2000, the teachings of which are incorporated herein by reference.
1. Field of the invention
The present invention relates to a dynamic channel selection (DCS) method in an IEEE 802.11 wireless local area network (WLAN) in which a plurality of wireless channels are used by a plurality of wireless stations in communication with an access point (AP), wherein each channel is selected dynamically according to channel determination made by the access point (AP).
2. Description of the Invention
Basically, there are two variants of wireless local area networks (WLAN): infrastructure-based and ad hoc-type. In the former network, communication typically takes place only between the wireless nodes, called stations (STAi), and the access point (AP), not directly between the wireless nodes as in the latter network. Thus, the wireless nodes can exchange data via the AP. The stations and the AP, which are within the same radio coverage, are known as a basic service set (BSS).
When two adjacent basic service sets (BSSs) are located close to each other and operate at the same channel, which are referred to as overlapping BSSs, it is difficult to support the required quality-of-service (Qos) due to the possible contentions between the overlapping BSSs. It is not always possible to avoid contentions by planning channel allocations to BSSs carefully before the WLAN deployment, especially in the home/office environment where other WLAN devices are operating independently in the vicinity, e.g., in the neighboring houses or offices. Currently, IEEE 802.11 does not provide a mechanism to address this type of contention.
Accordingly, there is a need for a dynamic channel selection (DCS) scheme enabling the access point (AP) to select a channel for all stations (STAs) associated with its basic service set (BSS), without requiring any changes in the physical layer (PHY) specification of IEEE 802.11 WLAN.
The present invention is directed to a dynamic channel selection method in an IEEE 802.11 wireless local area network (WLAN), wherein each channel is selected dynamically according to the criteria determined by the access point (AP).
Accordingly, the method of dynamically selecting a communication channel between an access point (AP) and a plurality of stations (STAs) located within the coverage area of a basic service set (BSS) is initially performed by determining whether a new channel to be used by the plurality of wireless stations is needed, then by requesting a channel signal quality measure to a subset of stations by the AP. To achieve this process, a set of channels available for use by the stations is determined to find out whether a signal from an adjacent BSS is received or if there are other interfering devices. The received signal strength indication (RSSI) and a packet error rate (PER) of all the channels that are measured by the stations are reported to the AP. Also, an interference level is measured. The interference level is based on the absence of a signal reception from the BSS for a predetermined time period that is caused by another communication system and is measured and reported. Thereafter, a new channel based on the decision criteria of the AP is selected using the measure of RSSI, PER, and the interference level information.
The foregoing and other features and advantages of the invention will be apparent from the following, more detailed description of preferred embodiments as illustrated in the accompanying drawings in which reference characters refer to the same parts throughout the various views.
In the following description, for purposes of explanation rather than limitation, specific details are set forth such as the particular architecture, interfaces, techniques, etc., in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details.
The IEEE 802.11 standard specifies the medium access control (MAC) and the physical (PHY) characteristics for wireless local area networks. The IEEE 802.11 standard is defined in International Standard ISO/IEC 8802-111, “Information Technology—Telecommunications and information exchange area networks”, 1999 Edition, which is hereby incorporated by reference in its entirety. The available number of non-overlapping or orthogonal channels for IEEE 802.11 WLAN systems depends on the underlying PHY layer. For example, the 802.11 Direct-Sequence Spread-Spectrum (DSSS) and 802.11b Complementary Code Keying (CCK) PHYs have three non-overlapping channels at 2.4 GHz. The 802.11a PHY has up to 12 channels at 5 GHz. The key principle of the present invention is to provide a dynamic channel selection (DCS) scheme enabling an access point (AP) to select a channel for all stations (STAs) associated with its basic service set (BSS), without requiring any changes in the physical layer (PHY) specification of IEEE 802.11 WLAN.
The AP and each STA within the WLAN of
Referring now to
Initiating Channel Measurement (step 100 of
Requesting Channel Measurement (stet 110 of
A management frame is transmitted by the AP to request a channel quality measurement to a set of stations (STAs) associated with its BSS. It should be noted that if the channel selection process has been initiated due to the start of a new BSS, the AP does not have to make such a request. The transmission of a request for channel quality measurement to the stations (STAs) can be unicast, multicast, or broadcast.
Processing Channel Measurement (step 120 of
The measurement of a channel quality is performed by both the AP and non-AP STA. Referring to
After detecting the presence of other BSSs (at step 610), a further analysis of the channel condition (at step 620) is performed to obtain a channel to run a BSS. In particular, it is determined how busy the channel is and how close the stations (STAs) of other BSSs are to the STA, which was requested to measure the channel condition. In the embodiment, the measurements of the strength of the received signal to determine the channel condition. The 802.11 PHYs define a parameter called received signal strength indicator (RSSI), which ranges from 0 through the RSSI maximum. This parameter is measured by the PHY layer and indicates the energy level observed at the antenna that is used to receive the current PLCP Protocol Data Unit (PPDU). The RSSI is measured during the reception of the PLCP preamble. In addition, the RSSI information could also be used to indicate how close the STA that was requested to measure the channel condition is from the STAs of other BSSs. Furthermore, a packet error rate (PER) could be used in combination with the RSSI measurement to determine the status of the channel condition according to the present invention. The PER can be measured from the frame reception statistics which define the number of frames received; the number of frames received in error (e.g., FCS errors); and, the ratio of the busy period over the total measurement period. The packet error rate (PER) is calculated by dividing the number of frames received in error by the total number of frames received.
Referring back to
Reporting Channel Measurement (step 130 of
After the completion of a channel quality measurement, the STA that was requested to measure the channel(s) reports back to the AP. The report will include all three parts of the measurements described in the previous paragraphs. Those include (1) the parameters of SCAN.confirm; (2) the measured values of RSSI and PER for the channels; and, (3) the measurement of noise/interference by the non-802.11 device. This report may be transmitted upon being polled by the AP during a contention-free period (CFP) or during the contention period (CP).
Selecting a New Channel (step 140 of
Upon receiving the channel quality report from the STAs, it is determined, by the AP, whether to switch the current channel or not. In order to determine whether to make a switch, the AP compares the status of other channels with that of the current channel in order to select a new channel, based on the criteria implemented in the AP. It should be noted that the decision to switch out of the current channel is implementation-dependent. Thus, various modifications readily apparent to those skilled in the art can be used.
Transmitting Channel Switch Announcement (step 150 of
Once the AP determines a new channel, the AP transmits the new channel information to every STA within the BSS.
Switching to the New Channel (step 160 of
Finally, the movement into a new channel is performed by changing the carrier frequency (or frequencies in case of a 802.11a OFDM PHY). In the embodiment, the switching is preferably to occur during a target beacon transmission time (TBTT).
As is apparent from the foregoing, the present invention has an advantage in that a dynamic channel selection (DCS) mechanism can be obtained with some minor modification in the current 802.11 specifications, without requiring any change in the underlying PHY specifications of IEEE 802.11 WLAN standard.
Having thus described a preferred embodiment of a dynamic channel selection (DCS) method for determining a channel for use within a WLAN system, it should be apparent to those skilled in the art that certain advantages of the system have been achieved. The foregoing is to be constructed as only being an illustrative embodiment of this invention. Persons skilled in the art can easily conceive of alternative arrangements providing a functionality similar to this embodiment without any deviation from the fundamental principles or the scope of this invention.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7782828||Aug 22, 2006||Aug 24, 2010||Computer Associates Think, Inc.||Method and system for managing channels in a wireless network|
|US7796988||Jul 22, 2008||Sep 14, 2010||Interdigital Technology Corporation||Escape mechanism for a wireless local area network|
|US7864768 *||Oct 13, 2006||Jan 4, 2011||Intel Corporation||Device, system and method of multicast/broadcast communication|
|US7869380||Oct 26, 2007||Jan 11, 2011||Lg Electronics Inc.||Method of channel assessment and channel searching in a wireless network|
|US7912002||May 7, 2007||Mar 22, 2011||Hitachi, Ltd.||System and method of QOS-based channel selection for WLAN access points or stations|
|US7990883 *||May 3, 2004||Aug 2, 2011||Sony Corporation||Communication system, communication method, communication apparatus, communication control method, and computer program|
|US8081615 *||May 22, 2009||Dec 20, 2011||Mediatek Inc.||Method and apparatus to allow coexistence between wireless devices|
|US8351390||Feb 10, 2011||Jan 8, 2013||Hitachi, Ltd.||System and method of QOS-based channel selection for WLAN access points or stations|
|US8451808||Dec 27, 2006||May 28, 2013||Intel Corporation||Techniques for 40 megahertz (MHz) channel switching|
|US8462749 *||Jul 9, 2010||Jun 11, 2013||Intel Corporation||Techniques for 40 megahertz (MHz) channel switching|
|US8514807 *||Feb 1, 2007||Aug 20, 2013||Lg Electronics Inc.||Method of transmitting messages in communication networks|
|US8537877 *||Apr 1, 2009||Sep 17, 2013||Intel Mobile Communications GmbH||Channel qualification for an adaptive frequency hopping method by means of bit or packet error rate measurement and simultaneous field strength measurement|
|US8565183 *||Dec 28, 2012||Oct 22, 2013||Marvell World Trade Ltd.||Method and apparatus for preventing interference between collocated transceivers|
|US8570984||Nov 30, 2010||Oct 29, 2013||Lg Electronics Inc.||Method of channel assessment and channel searching in a wireless network|
|US8626074||May 21, 2008||Jan 7, 2014||Canon Kabushiki Kaisha||Method for controlling a control station for determining a bandwidth for data communication|
|US8630255 *||Sep 17, 2007||Jan 14, 2014||Marvell International Ltd.||Wireless adapter with auxiliary radio channel for advanced channel scanning|
|US8780819 *||Jan 12, 2010||Jul 15, 2014||Samsung Electronics, Co., Ltd||Method and system for controlling wireless communication channel|
|US8811364||Sep 14, 2012||Aug 19, 2014||Canon Kabushiki Kaisha||Method for controlling a control station, a method for controlling terminal station, a control station, a terminal station, and a computer readable storage medium|
|US8855079||Oct 22, 2013||Oct 7, 2014||Marvell World Trade Ltd.||Method and apparatus for, based on communication of a first physical layer device, permitting transmission of data to a second physical layer device collocated with the first physical layer device|
|US8918102||Jul 29, 2011||Dec 23, 2014||At&T Intellectual Property I, L.P.||Method and system for selecting from a set of candidate frequency bands associated with a wireless access point|
|US9001773||Sep 24, 2013||Apr 7, 2015||Lg Electronics Inc.||Method of channel assessment and channel searching in a wireless network|
|US20040264425 *||May 3, 2004||Dec 30, 2004||Sony Corporation||Communication system, communication method, communication apparatus, communication control method, and computer program|
|US20050153667 *||Sep 16, 2004||Jul 14, 2005||Interdigital Technology Corporation||Escape mechanism for a wireless local area network|
|US20050220131 *||Mar 31, 2004||Oct 6, 2005||Boris Ginzburg||Method and apparatus to multicast transmission|
|US20080002659 *||Jun 20, 2007||Jan 3, 2008||Thomson Licensing||Method of communication adapted to the transmission of data packets|
|US20090185601 *||Jul 23, 2009||Britta Felbecker||Channel qualification for an adaptive frequency hopping method by means of bit or packet error rate measurement and simultaneous field strength measurement|
|US20100177639 *||Jan 12, 2010||Jul 15, 2010||Samsung Electronics Co., Ltd.||Method and system for controlling wireless communication channel|
|US20130114548 *||Dec 28, 2012||May 9, 2013||Marvell International Ltd.||Coexistence and collocation of remote network and local network radios|
|CN101193025B||Nov 24, 2006||May 19, 2010||鸿富锦精密工业（深圳）有限公司;鸿海精密工业股份有限公司||Access point and its channel switching method|
|EP2057786A2 *||Oct 26, 2007||May 13, 2009||LG Electronics Inc.||Method of channel assessment and channel searching in a wireless network|
|WO2008051049A2||Oct 26, 2007||May 2, 2008||Lg Electronics Inc||Methods of channel assessment and channel searching in a wireless network|
|U.S. Classification||370/333, 370/338|
|International Classification||H04L12/28, H04W72/02, H04L12/56, H04W28/04, H04W92/10, H04W48/08, H04W84/12, H04W24/00|
|Cooperative Classification||H04W72/08, H04W92/10, H04W84/12, H04W72/02, H04W24/10, H04W48/08|