Wireless access point (AP) automatic channel selection
View Patent ↗An automatic channel selection (ACS) process enables an access point to determine a best channel available, i.e., the channel with a least amount of interference, for it operation. When ACS is enabled, the access point scans frequencies for all neighboring access points and their signal strengths. Based on this data, the access point then determines which frequency is least likely to be interfered with by these other access points. The access point switches itself to this frequency and begins operation. During normal operation, the access point may periodically rescan the air space and reevaluate its current operating channel. Preferably, every neighboring access point has its own channel, and the co-channel interference levels should be low enough so that there is a maximum coverage and high throughput for the network. If these characteristics cannot be achieved, the access point may then adjust its power automatically to reduce the interference level in the network. This automatic power adjustment (APA) feature preferably operates across a set of access points, each of which has the function. In this manner, the transmitting power of the neighboring access points in the wireless network is “cooperatively” adjusted to minimize the channel interference and maximize the coverage and throughput for the network. A method of determining optimal access point locations for access points that perform the ACS and APA functions is also described.
1. A method, operative within a wireless network access point, for selecting a radio channel, the wireless network access point operating in proximity to a set of other access points within a given area, comprising:
upon a given occurence, scanning a set of available radio channels;
for each available radio channel, calculating a cost function that represents a cumulative signal strength generated by relative radio frequency activity levels at a given frequency due to the other access points and other RF sources operating within the given area, the cost function being independent of transmission medium activity; and
switching the wireless network access point to a radio channel having a given value of the cost function.
2. The method as described in claim 1 wherein the given occurrence is boot-up of the wireless network access point.
3. The method as described in claim 1 wherein the given occurrence is a given timeout following a last iteration of the cost function calculation.
4. The method as described in claim 1 wherein the available radio Channels are associated with a given regulatory domain and the cost function is a sum of unwanted radio frequency signals that leak into the available radio channel from the radio channels in which the one or more other access points are operating.
5. The method as described in claim 1 wherein radio frequency activity level from the one or more other access points on a given radio channel is proportional to the wireless network access point's transmitting power on the given radio channel.
6. The method as described in claim 1 wherein a radio frequency activity level of a wireless network access point is determined by transmitting power and is represented as a given signal strength function P(k) attenuated by a given transmit mask function S(f).
7. The method as described in claim 1 wherein the given value of the cost function is a minimum cost.
8. The method as described in claim 1 further including the step of adjusting a transmit power of the wireless network access point after switching the wireless network access point to a radio channel having a given value of the cost function.
9. The method as described in claim 8 further including the step of re-adjusting the transmit power of the wireless network access point to a higher transmit power.
10. The method as described in claim 8 further including the step of readjusting the transmit power of the wireless network access point to a lower transmit power.
11. A method, operative within a wireless network access point, for selecting a radio channel, the wireless network access point operating in proximity to a set of other access points within a given area, comprising:
upon a given occurrence, scanning a set of available radio channels;
for each available radio channel, calculating a cost function that measures a relative amount of unwanted radio frequency signal at a given frequency due to the other access points operating within the given area; and
switching the wireless network access point to a radio channel having a given value of the cost function;
wherein the available radio channels are associated with a given regulatory domain and the cost function is a sum of unwanted radio frequency signals that leak into the available radio channel from the radio channels in which the one or more other access points are operating;
wherein an amount of radio frequency signal leakage from the one or more other access points on a given radio channel is proportional to the wireless network access point's transmitting power on the given radio channel;
wherein the wireless network access point's transmitting power is a given signal strength function P(k) attenuated by a given transmit mask function S(f);
wherein the cost function is;
C
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f
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13
P
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S
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2417
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2472
where:
P(k)=Cumulative signal strength of all access points at channel k
S(f)=Spectrum of transmitted signal.
12. A method, operative within a wireless network access point operating at a current channel, for selecting a new radio channel, the wireless network access point operating nearby a set of one or more other access points, comprising:
scanning a set of available radio channels;
for each available radio channel, calculating a cost function that represents a cumulative signal strength generated by relative radio frequency activity levels at a given frequency due to the set of one or more other access points and other RF sources operating nearby the wireless network access point, the cost function being independent of transmission medium activity;
defining the new radio channel as the radio channel that has a minimum value of the cost function; and
if a difference between interference in the current channel and interference in the new radio channel exceeds a given interference threshold, switching the wireless network access point to the new radio channel.
13. In a wireless access point operating in proximity to a set of other access points within a given area, the wireless access point having a processor, the improvement comprising:
code executable by the processor to scan a set of available radio channels;
code executable by the processor to calculate a cost function, for each available radio channel, that represents a cumulative signal strength generated by relative radio frequency activity levels at a given frequency due to the other access points and other RF sources operating within the given area, the cost function being independent of transmission medium activity; and
code executable by the processor to switch the wireless network access point to a radio channel having a minimum value of the cost function.