User's Manual

PMP 400/430 and PTP 200/230 Series Motorola PMP Solutions User Guide Supplement
Issue 6.0 May 2011 Page 41 of 77
4 Configuring
Most PMP 400/430 Series and PTP 200/230 Series configuration items are identical or very
similar to configuration items in standard FSK Canopy modules. This section discusses those that
are new or changed and also remarks on some that remain unchanged.
4.1 LINK OPERATION – 1X/2X/3X
PMP 400/430 and PTP 200/230 Series products offer three levels or speeds of operation – 1X,
2X, and 3X. If received power is less due to distance between the AP/BHM and the SM/BHS or
due to obstructions, or interference affects the RF environment, the Canopy system will
automatically and dynamically adjust links to the best operation level. Distance, rates and other
information associated with the operation levels are shown in
Table 8 on page 32.
The system chooses its operation rate dynamically, based on Canopy’s internal ARQ (Automatic
Repeat reQuest) error control method. With ARQ, every data slot of every frame sent over the air
(except downlink broadcast) is expected to be acknowledged by the receiver, and if
acknowledgement is not received, the data is resent. The sending unit monitors these resends,
and adjusts the operation rate accordingly. A normal system may have links that move from 3X to
2X (or 1X) and back as the RF environment changes. Furthermore, the links operate
independently; normal operation can have a downlink running at 3X while the uplink RF
environment only supports 2X.
The default is for both AP/BHM and SM/BHS to be enabled for 3X operation. An operator may
“lock down” a link to 1X/2X operation or to only 1X operation using the Dynamic Rate Adapt
parameter on the SM’s/BHS’s Configuration => General page as shown in
Figure 24. This
parameter locks down the uplink or downlink operation. An operator may lock down an entire
sector to 2X and 1X operation, or to only 1 X operation, using the Dynamic Rate Adapt parameter
on the AP’s Configuration => General page. This parameter locks down uplink or downlink of all
links in the sector, and overrides any SM 1X/2X/3X settings. For example, if an individual link is
set for 3X operation at the SM and the sector is set for 1X operation at the AP, all links in the
sector will be locked down to 1X operation.
Figure 24: Dynamic Rate Adapt on AP "Configuration => General" page
In most cases an operator is well-served to leave the setting at 1X/2X/3X and let the system
automatically and dynamically choose the best rate for each link. Cases when it may be useful to
lock down a link to 1X or 2X include:
If you are having trouble aiming a link or getting it to register, locking the link down to 2X
or 1X may help in some cases.
If the link is suspected to be oscillating between operation rates to the detriment of
throughput, locking the link down may increase throughput. Usually, even if the link is
moving rapidly between operation rates, overall link throughput and sector capacity are
highest if the link is left at 3X and the link can choose its own rate dynamically.
General link troubleshooting
Optimal sector utilization involves having as many links as possible running at 3X. This provides
as much capacity as possible for the sector. As an example, you want to limit throughput to an
individual subscriber to 1X rates. This does not mean you should set that link to 1X operation.