User's Manual

Vectron User manual
© Höft & Wessel AG
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Subject to amendment, errors excepted HW8660UserMan.doc 1.0 02.02.2001 Lin
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Each basestation has assigned a fixed generic hopping pattern. Co-located basestations may use the
same generic hopping pattern or different generic hopping patterns without restriction.
Endpoints support the whole set of generic hopping patterns. When an endpoint establishes a connection
to a basestation it detects, during the synchronization procedure, the generic hopping pattern to be used.
10.5.4 Hopping channels
Hopping channels are derived by shifting a generic frequency hopping pattern along the time axis. For
each generic hopping pattern f(i)[n] a set of L=12 hopping channels h(i,l)[n] is generated through the fol-
lowing equation: h(i,l)[n] = f(i)[n-8l]
10.5.5 Bearer position
The position of a bearer in the combined time / frequency multiplex is marked as b(i,l,k), where
i denotes the generic frequency hopping pattern
l denotes the hopping channel
k denotes the time slot
10.6 Medium Access Procedures
10.6.1 Synchronization
Two transceivers are synchronized, if their bit clock, frame clock, multiframe and superframe clocks are in
phase alignment and they use the same generic hopping pattern.
In a basic network the basestation is the synchronization master and the endpoints are synchronization
slaves, i.e. the endpoints synchronize their clocks to the basestation.
Even when no connection is active, any basestation sends a dummy bearer. On that bearer all informa-
tion is contained which is needed by an endpoint in order to establish synchronization to the basestation.
The dummy bearer is sent using the generic hopping pattern f(i)[n] on an arbitrary bearer b(i,l,k). Before
setting up the dummy bearer, the basestation performs RSSI (Received Signal Strength Indication) scan
on all available bearer positions and selects the quietest bearer position.
During dummy bearer operation the basestation observes adjacent timeslots in order to detect sliding
collisions. In this situation it will move the dummy bearer to another bearer position.
Information contained in the dummy bearer contains the identification of the generic hopping pattern used
by the base station.
An endpoint obtains synchronization by continuously scanning a single frequency channel. In the course
of its hopping pattern the dummy bearer of the basestation will hit this channel every 480ms. In this event,
the receiver obtains bit synchronization from the synchronization word and it retrieves the generic hop-
ping pattern f(i)[n] from the information contained in the dummy bearer.
Although at this stage of synchronization the actual hopping channel and time slot are still unknown to the
endpoint, it is already able to set the correct frequency channel for the next transmission burst of the
dummy bearer. By monitoring the dummy bearer over a several frames, the endpoint retrieves all re-
quired information to establish and maintain synchronization of frame, multiframe and superframe clocks,
including the values of l and k for the dummy bearer.
An endpoint will not transmit any radio signal before it is synchronized to a base station.