Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-03-10
2001-03-27
Vu, Huy D. (Department: 2739)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C455S063300, C370S431000
Reexamination Certificate
active
06208629
ABSTRACT:
THE BACKGROUND OF THE INVENTION
1. The Field of the Invention
This invention relates to the field of wireless local area networks (LANs). In particular, the invention relates to assigning spectrum to access points in a wireless LAN.
2. A Description of the Related Art
Computer networks supply data and services to the computers and devices connected to the network. Traditionally, the connection to the network has been through a wired medium such as coaxial cable, fiber optics, twisted pair, etc. However, there are a number of applications that benefit from a completely, or partially, mobile computer (or other device). Such computers connect to the network using wireless communications. Wireless communications rely on data transfers using radio transmitters and receivers.
A wireless LAN includes access points and wireless network nodes. The access points connect wireless network nodes to the wired part of the LAN or to some other wireless part of the LAN. An access point communicates, using wireless communications, with the wireless network nodes in that access point's communications area. Thus, an access point maintains a number of simultaneous wireless communications links with a number of wireless network nodes. The access points and the wireless network nodes include transceivers (transmitters and receivers) to establish and maintain the wireless communications links. The transceivers transmit and receive signals in the electromagnetic spectrum, for example, in the infrared spectrum, at 902 MHz or at 2.4 GHz.
The access points typically support multiple channels. This allows two or more access points, communicating on different channels, to have overlapping coverage areas. Different channels can be supported by access points in different ways. For example, Proxim, Inc. supplies a wireless LAN product line called RangeLAN2™. The RangeLAN2 uses frequency hopping spread spectrum communications. A RangeLAN2 transmitter hops from frequency to frequency while transmitting to a receiver. Different channels are supported by different, orthogonal, hopping sequences. Another technique is called direct sequence spread spectrum (DSSS) communications. DSSS breaks the electromagnetic spectrum into a number of sub-bands. Each sub-band corresponds to a different channel.
One of the problems with DSSS communications, or any communications technique where a channel corresponds to a specific part of spectrum, is that access points with overlapping coverage areas need to be assigned to different channels. If access points with overlapping coverage areas are not assigned to different channels, then the transmissions will interfere with each other. This leads to a need to assign different channels to the access points that have overlapping coverage areas.
To adjust for changes in the wireless communications environment, new access points may be added or access points may need to be moved. This may change the overlapping areas of the access points, possibly causing some access points to interfere with other access points. Thus, what is needed is a method and apparatus for displaying the amount of interference between access points and for generating a new set of channel assignments for the access points that will reduce, or eliminate, the interference of the access points.
A SUMMARY OF THE INVENTION
A method and apparatus for maintaining non-interfering frequency assignments of wireless-based computer networking products is described.
One embodiment of the invention includes assigning channels to a set of access points coupled to a network. The network includes a set of wireless network nodes. Each access point communicates, using one of the channels, to a subset of the wireless network nodes. Each channel corresponds to a different frequency range in the electromagnetic spectrum. The embodiment includes the following steps. At least a first access point of the set of access points transmits a plurality of messages. A measure of interference between access points communicating on a first channel is determined from the plurality of messages. A second set of channel assignments, that results in a lower amount of interference between access points communicating on the first channel, is determined. The second set of channel assignments is assigned to the set of access points. Thus, non-interfering frequency assignments for the access points can be determined.
In one embodiment, each access points transmits a message requesting all the access points that detect the message to reply. Each access point measures the strengths of the reply messages to determine the radio proximity of that access point's neighbors. The reply messages indicate to what degree other access points are directly interfering with a given access point's wireless communications, by communicating on the same channel as that access point. The reply messages also indicate which neighbors are transmitting on channels that are near the channel being used by an access point. The reply messages also indicate which neighbors can be detected by an access point but are assigned to channels that neither directly or nearly interfere. In one embodiment, the radio proximity information is tabulated by a network manager. The table indicates to what degree each access point is directly conflicting with any neighboring access points, given that access point's present channel assignment. The table also indicates near conflicts (neighbors communicating on near channels) and other signals detected for each access point.
In one embodiment, the radio proximity information is processed to reduce or eliminate direct conflicts and near conflicts; thereby, significantly improving the wireless communications of the network. In one embodiment, an iterative process is used to find better channel assignments by comparing any possible new channel assignments with the previous best (lowest amount of direct and/or near conflict) channel assignments.
In one embodiment, the new channel assignments are then displayed to the user with the radio proximities shown graphically. The user can then change any of these new assignments before the new assignments are transmitted to the access points.
Although many details have been included in the description and the figures, the invention is defined by the scope of the claims. Only limitations found in those claims apply to the invention.
REFERENCES:
patent: 5285494 (1994-02-01), Sprecher et al.
patent: 5734646 (1998-03-01), I et al.
patent: 5870385 (1999-02-01), Ahmadi et al.
patent: 5933420 (1999-08-01), Jaszewski et al.
patent: 6128498 (2000-10-01), Benveniste
Chambers Richard C.
Fisher David A.
Jaszewski Gary M.
3Com Corporation
Vu Huy D.
Weitz David J.
Wilson Sonsini Goodrich & Rosati
LandOfFree
Method and apparatus for assigning spectrum of a local area... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for assigning spectrum of a local area..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for assigning spectrum of a local area... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2486300