Afar AR24027, Руководство оператора

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AR24027 Operator’s Manual
2-3
When the remote radios transmit they include a bandwidth request parameter, informing the hub of
how much inbound traffic they have queued up. The hub allocates slots to the remotes based on this
information. On a given cycle, each remote may be allocated zero, one, or several contiguous slots to
transmit. If the aggregate requested bandwidth exceeds the network throughput the hub divides the
available bandwidth fairly among the active remotes.
Once in a while the hub allocates a single slot to remotes that have remained idle to check if they now
have inbound traffic. This check only takes a single inbound slot and this slot is allocated
dynamically depending on current traffic load, available slots, and traffic history.
2.2.3 Automatic Remote Association
When a new remote radio is first powered up, it listens for transmissions from a hub radio. Since the
hub radio starts the cycle with a broadcast packet (containing the inbound slot allocation), the remote
radio receives these packets and synchronizes its TDD cycle to that of the hub.
Once in a while the hub radio allocates the first inbound slot for an invitation to new remote nodes to
join the network. When the new remote detects this invitation, it transmits, on the first slot of the
inbound phase, an
attach request packet . The hub authenticates the remote, and replies, during the
outbound phase, with an accept or reject packet. Once the remote receives the accept packet the
association is complete and the units start passing data packets.
If multiple remotes transmit the attach request packet at the same time, there may be a collision
preventing the hub from receiving either packet. When the remotes do not get an accept or reject
packet in response to their attach request, they realize that there was a collision. The remotes will then
perform a backoff collision avoidance algorithm that spreads their next attach request transmissions
allowing all remotes to quickly join in.
You can specify the maximum number of remotes that a hub may acquire (use the node command).
Once the hub acquires this maximum numbers of remotes it stops allocating the first slot to attach
request packets, therefore increasing the inbound throughput slightly.
2.3 PULSAR Network - Overcoming Interference
2.3.1 Radio co-location
As a network grows it often becomes necessary to deploy multiple radios at the same site. The
reasons to co-locate radios include the following:
1. In a Point-to-Multipoint network you want to achieve 360 degree coverage around a central site,
but would like to use sector antennas rather than one omni. Sector antennas have higher gain than
the omni and provide shielding from interfering signals originating at different sectors. In this
situation you might deploy a central site with six hub radios for example, each one feeding a
sector antenna covering 60 degree sectors.
2. The number of remote radios serviced by a single hub has grown to a point where the shared
bandwidth is no longer adequate. You may then add a second hub radio operating on a different
channel and split the remotes between two or more hubs.
3. You want to deploy a repeater site with two “back to back” radios.