Media Access Control (Mac) - GE MDS SD Series Technical Manual

• Terminal Server capability to enable IP addressing of serial interface ports on individual ra-
dios
• Store and Forward capability
• Frequency Re-use that offers approximately 20 dB of additional co-channel isolation when
operating networks on the same frequency.
• Supports use of MDS™ PulseNET Network Management Software
• Supports a wide variety of modem speeds and bandwidths for regulatory compliance in vir-
tually all regions of the world
• Ethernet & serial interfaces — ideal for migration to IP networks
• Dual serial functionality (RS-232 and RS-485)
• Modbus TCP to RTU Conversion in both Terminal Server and IP Payload features elimi-
nates the need for extra equipment.
• Over-the-air reprogramming of remote units — no unnecessary trips to radio sites
• Licensed 5-watt design, maximizes communications range with low interference risk from
other users
• Configurable via software as a Remote or an AP unit
• Low power "sleep mode" — ideal for battery-powered solar sites
• Virtual Radio Channels (VRC) support multiple polling applications on one radio
NOTE Some features may not be available on all units, depending on the options purchased and
regulatory constraints for the region in which the radio will operate.

Media Access Control (MAC)

An important feature of the transceiver is Media Access Control (MAC). The radio's MAC is
specifically designed for use with narrow bandwidth, half duplex radio networks such as those
commonly used in licensed telemetry systems. When the MAC is enabled, it provides efficient
support of multiple data traffic models including multiple hosts, synchronous and asynchronous
polls, and report-by-exception (push traffic). MAC ensures that every transceiver in the network
has an equal probability of gaining access to the radio channel when it has data to send.
Coordination of Channel Access
The main objective of the MAC is to coordinate channel access for all radios in the network,
preventing data "collisions" that can occur with simultaneous transmissions from radios on the
same RF channel. With MAC operation, a single radio is configured as an Access Point (AP) and
other units are designated as Remotes. The AP serves as the controller of the RF network. Re-
motes request permission from the AP to use the RF channel before sending payload data, thus
avoiding collisions of data, and creating a highly reliable wireless network. The MAC is respon-
sible for allocating which unit gets access to the broadcast medium (the RF channel), when, and
for how long.
Data Validation
Additionally, the MAC validates all messages and purges corrupted data from the system. Suc-
cessful delivery of data is ensured through the use of retries and acknowledgements. Minimal
overhead is used to accomplish these tasks, which translates to increased bandwidth efficiency of
the radio channel with minimal latency, ensuring that messages are delivered in a timely manner.
4 SD Series Technical Manual MDS 05-4846A01, Rev. I