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M3SR Series 4100
From an IP layer point of view, the radios act as routers between the wired networks and the
air network (e.g. SECOM-H).
The IPoA protocol is available with these waveforms:
SECOM-V
SECOM-H
OFDM (Orthogonal Frequency Di-
vision Multiplex)
ALE-3G / xDL (Low Data Rate Link
Protocol (LDL), High Data Rate
Link Protocol (HDL))
A radio-enhanced network provides complete IP transparency, meaning that any OSI layer
4 (and higher) protocol can be transported over IP. Of course, timing and error constraints
imposed by the radio channel cannot be hidden from the higher OSI layers like TCP (Trans-
mission Control Protocol) and under some circumstances can severely degrade end-to-end
performance.
A radio channel will always provide lower data rates (down to 2.4 kbit/s), will have a higher
delay or higher delay variations and will be more erroneous compared to a wired network.
Therefore it is recommended to use UDP (User Datagram Protocol) as transport protocol.
Please refer to "Recommendations for the Transport Layer" on p. 5.36 for recommendations
about the usage and/or configuration of upper layer protocols (OSI layers 4 to 7).
Since UDP is a connection-less protocol (no acknowledgments, no flow control), it is up to
an upper layer protocol / application to provide a secured connection and to provide any sort
of flow control. Without flow control, data rates exceeding the air network capacity may lead
quickly to data loss. The radio offers only a limited amount of memory to queue incoming da-
ta, and there is no mechanism to inform an application when data is being dropped, no matter
what reasons caused the packet loss.
For each network (Ethernet, air, Point-to-Point Protocol (PPP)) the radio provides an IP in-
terface specifying the respective network settings (IP address, netmask, Figure 5.7).
5.34
R&S M3TR
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Operating Manual 6175.4760.02 – 01
IP over Air (IPoA)
R&S M3SR Series 4100
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