User guide

45 Mbps Backhaul User Guide
Issue 3, December 2004 Page 55 of 113
6.3.5 Spectrum Management (Non UK)
Spectrum Management Selection (previously referred to by the acronym DFS) is the 45 Mbps Backhaul
wireless feature that monitors the available wireless spectrum and directs both ends of the wireless link to
operate on a channel with the minimum level of co and adjacent levels interference.
6.3.5.1 Wireless Channels
The 45 Mbps Backhaul wireless operates using a set of predefined overlapping channels. There are 19
predefined channels starting at 5734 MHz and ending at 5842 MHz. Each channel occupies 11 MHz of wireless
spectrum and is offset in center frequency from its neighboring channel by 6 MHz.
It is important to note that adjacent channels on the Spectrum management display have a 5 MHz overlap to the
adjacent channel.
The default channelization can be modified by varying lower center frequency attribute in the installation
wizard see section 6.3.3.3.1 ‘Lower Center Frequency’.
6.3.5.2 Spectrum Management Measurements
The 45 Mbps Backhaul wireless units perform four Spectrum Management measurements per TDD cycle, per
channel. The measurements are subdivided into two signal peak measurements and two mean signal
measurements. The peak measurements represent the peak received signal power with a resolution down to 100
nS. The mean measurement represents the mean received signal power for the 40 µS measurement period.
The Spectrum Management algorithm collects measurements equally from all channels. This process is called
the Channel Availability Check (hereafter referred to by the acronym CAC). The CAC uses a round-robin
channel select process to collect an equal amount of measurements from each channel. It is important to note
that the CAC measurement process is not altered by channel barring process. Measurements are still collected
for all channels irrespective of the number of barred channels.
6.3.5.3 Measurement Analysis
Spectrum Management uses statistical analysis to process the received peak and mean measurement. The
statistical analysis is based on a fixed measurement quantization period. Spectrum Management collects data for
the specified quantization period and only at the end of the period is the statistical analysis performed. The
analysis produces four key metrics for each channel:
• Peak of Peaks
• Peak of Means
• 99.9% Percentile of the Means
• Mean of Means
Peak of Peaks is the largest peak interference measurement encountered during the quantization period. This
metric is useful for detecting large short duration spikes in the interference environment.
Peak of Means is the largest mean interference measurement encountered during the quantization period. The
peak of means is similar to the peak of peaks and is useful for detecting slightly longer duration spikes in the
interference environment.
99.9% Percentile of the Means is the value of mean interference measurement for which 99.9% of all mean
measurements fall below during the quantization period. The 99.9% percentile metric is useful for detecting
short duration repetitive interference that by its very nature has a minimal effect of the mean of means.