User Guide

AB-Access Config & User Guide 5.5 Axxcelera Broadband Wireless
July 27, 2004 Company Confidential Page 22 of 129
sector, simply change the channel of the AP and wait for the SUs to scan and lock on again (i.e. after
3 minutes plus the duration of a scan). If some SUs fail to regain contact with the AP due to an issue
on the new RF channel then simply change the AP back to the original channel and the SUs will
regain contact after a short period (i.e. after 3 minutes plus the duration of a scan).
4.11 PTP Power Control
This feature makes point-to-point links more robust, by increasing the signal power received
at the AP. The AP then has a higher tolerance to noise and interference. When enabled on both
units, both the AP and SU transmit at full power, and both the AP and SU adjust their receiver gain
according to the signal power received. This means that the AP receiver has a similar RSSI to the
SU, rather than a level of -74dBm as with standard power control. For example, if the backhaul SU
has an RSSI of -65dBm then the backhaul AP will also have an RSSI of approximately -65dBm,
9dBm higher than with the normal power control scheme.
A unit's power control mode (i.e. standard or PTP) is determined by the new "ptp" parameter
in the system.conf file (see section 3.1 for details). This parameter can be viewed and changed with
the new CLI command "hmm system ptp enable/disable" or via the system.conf file.
Both ends of a point-to-point link must be operating in the same power control mode for the
link to work. Point-to-multipoint sectors cannot use the new PTP power control mode. If enabled on
a point-to-multipoint sector it will sever communication between the AP and the majority of SUs.
When an AP is operating in the new PTP power control mode the "hmm modem rssi"
command becomes meaningful at the AP, and the "hmm modem txpower" command shows extra
information.
The new PTP power control mode should be used with care, ensuring that the boosted
upstream signal will not affect other units, i.e. with units co-located with the point-to-point AP or
SU.