Partially Overlapped Channels Not Considered Harmful Article by Mishra, Shrivastava, Banerjee, Arbaugh Presentation by Chen Li

The Big Idea Current networks utilize non-overlapping channels (1, 6, and 11) Partially overlapping channels can also be used if interference minimal

Channel Capacity C is data capacity B is bandwidth SNR is signal to noise ratio Real Usage Channel AChannel B Power Channel CChannel D Waste of spectrum

Channel Capacity As trans power goes up, SNR goes up 11 Channels defined by  44 MHz bandwidth, center frequency 5 MHz apart (1, 6, 11 non-overlapping) Think home router setup Using only 1,6,11 leads to capacity waste  As seen from previous figure

Model for Partial Overlap Power is attenuated at 0dB at Fc, increasingly attenuated as one moves from Fc

Model for Partial Overlap Interference Factor Tau = Ft - Fr, frequency separation between the two signals Power received by i divided by power transmitted from j PiPjPiPj I-factor(i,j) =

Estimating I-Factor at a receiver on channel Normalized I-factor Receiver Channel I(theory) I(measured) On same channel, would definitely cause collision, but would require 1/I-F transmitters simultaneously to cause collision if not the same channel

Partial Overlap Effects Spatial Effect  Separation necessary decreases dramatically as channel separation increases

Partial Overlap Effects Bit Rate Effect  To match the effect of same channel interference on a channel separated by 2 channels, one would need to have 14 simultaneous transmissions

Benefit of Using Non-overlapping Channels Higher density of trans/receive possible

Benefits Proves channels outside of the non- overlapping channels can be used for communication by controlling interference This translates to both spatial and frequency usage improvement

Use Random Compaction for client AP (channel) assignment. Client performs the scan operation Random Compaction builds a channel maximum interference vector for each channel based on APs that would interfere on that channel Modified to sum on own channel plus all POV Channels POV(x,x ch,y,y ch ) = 1 if nodes x and y on their channels interfere with each other Implementation in WLANs

Results of WLAN Deployment Higher throughput and fewer collisions

Implementation on Mesh Network Mesh network flow managed by calculating edge costs By changing the equation to account for POV interference, the integration of POV channels is accomplished While it adds to the possible number of conflicts, by adding more channels for connection, contention can be reduced up to a theoretical factor of 3 (average gain of 1.6)

The Overall Methodology Wireless Communication Technology Such as , Estimate I-Factor Theory/Empirical I-Factor Model Algorithm for Channel Assignment with overlapped channels Estimated once per wireless technology Repeated for each wireless network

Final Thoughts Thinks outside the established system of using non-overlapping channels Potential to open up new frequency space without the need of new frequency space POV will be difficult to calculate Does not account for mobility Usefulness mainly only in very dense networks with numerous APs

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