User's Manual

Spectral Management

SkyExtenders and SkyConnectors require no pre-configuration and automatically search or “hunt” among all supported frequencies

and, in the case of the SkyExtender, all antennas. When a SkyExtender or SkyConnector is powered up, it checks non-volatile

memory for a Preferred Frequency. This is the frequency that should be favored in any search, and is set after a successful

connection to the network or by operator configuration. In addition to the Preferred Frequency, there is also a Frequency Hunt List.

This list, defined by the operator, specifies the frequencies that should be searched if the Preferred Frequency is unavailable. The

Frequency Hunt List is not stored in non-volatile memory and, therefore, is not preserved through a power reset.

If there is a Preferred Frequency defined, the SkyExtender or SkyConnector will first attempt to listen for Hello messages on that

frequency. A Hello message is transmitted on each of the eight antenna approximately once per second. These messages provide

system timing information, as well as timing for the associated Hello Response message. A SkyConnector will listen for 2 seconds

on its single antenna. A SkyExtender will listen for 2 seconds on each of its eight antennas for a total of 16 seconds at that

frequency. If no Hello messages are heard, the node will then check the Frequency Hunt List. If a list is defined, it will start at the

lowest frequency in that list, testing each in turn while alternating with the Preferred Frequency. For instance, if an operator defines

a Preferred Frequency of 5765 MHz and a Frequency Hunt List of 5775, 5800 and 5825 MHz, then the sequence becomes 5765,

5775, 5765, 5800, 5765, 5825 MHz. This search of the Frequency Hunt List is attempted a total of two times. The SkyConnector

listens for 2 seconds at each frequency, while the SkyExtender listens for 16 seconds.

After checking the Preferred Frequency and any frequencies defined in the Frequency Hunt List, the node searches the complete

frequency band indicated by the product model number. In the US, this is the UNII band frequencies of 5745-5835 MHz. The

search starts with the non-overlapping channels (5745, 5765, 5785, 5805, 5825 MHz). If there is a defined Preferred Frequency,

the node continues to alternate between listening on each of these channels and that stored frequency. This search of the non-

overlapping channels is attempted a total of two times.

If the non-overlapping channel frequency hunt fails, then the node will scan all frequencies with an increment of 5 MHz. In the US

this means 5745, 5750, 5755, etc. up to 5835 MHz. During this search the node continues to alternate with the Preferred

Frequency. If, after two attempts this hunt also fails, then the Preferred Frequency is deleted and the node will continue hunt the

full frequency range with a 5 MHz increment.

If a node hears a Hello message at any frequency, the search will be stopped for a time equal to four complete listening periods.

This translates into 64 seconds for SkyExtenders and 8 seconds for SkyConnectors. This allows the node time to gather enough

Hello messages to start the link optimization process. If a connection is made (see Link Management), this unit will change to the

discovery phase and its frequency hunt will be halted.

The discovery phase lasts 45 seconds and allows a node time to complete link establishment, authorization and configuration, and

possibly to receive Hello messages from other nodes (that may offer lower cost routes). The following may also occur during the

discovery phase:

• If, at the completion of the discovery phase timer no link has been establish and no link establishment is in progress, then the

node will resume frequency hunting.

• If, at the completion of the discovery phase timer a link establishment is in progress, then the node will restart the discovery

timer with a 90 second duration.

• If, at the completion of the discovery phase timer a link has been successfully established and the node authenticated, then a

final 45 second discovery timer is started and the node is marked as being connection-ready.

• If, at the completion of the discovery phase timer a node is marked as being connection-ready, then the best route is selected

(see Mesh Routing) and the node is placed online.