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MCU-30 User Manual
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7 TDMA
Time division multiple access (TDMA) is a channel access method for shared
medium networks. It allows several MCUs to share the same frequency channel by
dividing the signal into different time slots. The MCUs transmit and receive on the
same frequency in a synchronized manner. Every MCU transmits in its own
dedicated time slots. On the other time slots it receives the transmission sent by the
other units’ which are members of the same network (which are also transmitting on
their own dedicated slots).
medium networks. It allows several MCUs to share the same frequency channel by
dividing the signal into different time slots. The MCUs transmit and receive on the
same frequency in a synchronized manner. Every MCU transmits in its own
dedicated time slots. On the other time slots it receives the transmission sent by the
other units’ which are members of the same network (which are also transmitting on
their own dedicated slots).
TDMA require synchronization system. The system is synchronized internally,
externally or via GPS (synchronization varies between topologies and method used).
externally or via GPS (synchronization varies between topologies and method used).
The MCU uses TDMA regardless of the application type, Mobile PTP, Mobile MESH
or Collaborative MESH.
or Collaborative MESH.
8 Mobile PTP (Point-to-Point)
A Mobile PTP network is a radio link between 2 MCUs. The configuration (frequency
and profile) of both units must be the same with only one difference, one MCU is
configured as a VC (Virtual Concentrator) while the other unit is configured as a
Node.
and profile) of both units must be the same with only one difference, one MCU is
configured as a VC (Virtual Concentrator) while the other unit is configured as a
Node.
The VC works with its internal clock and synchronizes the Node. After power-up the
VC starts transmitting regardless of link status. The node however, does not transmit
and stays in RX mode, it tries to acquire synchronization by finding a preamble
(synchronization pattern). As soon as the node recognizes the pattern, it starts to
transmit according to its allocated time slot.
VC starts transmitting regardless of link status. The node however, does not transmit
and stays in RX mode, it tries to acquire synchronization by finding a preamble
(synchronization pattern). As soon as the node recognizes the pattern, it starts to
transmit according to its allocated time slot.
The transmission bandwidth ratio is pre-defined as part of the profile configuration. It
can be symmetric when full duplex communications is required (50% to each unit) or
asymmetric up to 10% to one unit (VC or node) and 90% to the other unit.
can be symmetric when full duplex communications is required (50% to each unit) or
asymmetric up to 10% to one unit (VC or node) and 90% to the other unit.
Figure 7: shows the transmit frames of VC and Node from Power Up