Space Diversity Solution Description – using LPN Radios

SGT-LPN Space Diversity Solution Description

Terminology: SD = Space Diversity, IDU = Indoor Unit, ODU = Outdoor Unit

Sometimes a non-protected 1+0 microwave radio link will not perform well over long distances, or over a body of water such as the sea or a lake.  Strong signal reflections from the water surface can cause fading at the receiver(s).  In this case, the 1+1 SD topology can be used instead to guarantee better “link availability”.

1+1 SD entails the use of two ODUs per side.  Each ODU is connected to an antenna.  So, there are two antennas per side of a 1+1 SD link.  On one side, one radio transmits and on the receive side, both ODUs are receiving – the best-performing received data stream is chosen by the IDU.

The use of SD for a microwave radio link allows the IDUs on each side of a radio link to coordinate between each other and to then choose the best-performing microwave link receive path across a “water body” e.g. a lake or the sea.  This process is seamless from the radio user’s perspective (no bit errors are encountered while the IDUs automatically choose the best-performing receiver for signal reception).

The SGT-LPN Space Diversity solution works as follows:

On each side of a SGT-LPN link, there is only one IDU. Each IDU on a side connects to 2 ODUs.  Each IDU uses 2 modem cards, one for each ODU.  An IDU connects to an ODU via a modem card and IF cable (e.g. RG213/RG8).  For 1+1 SD, each ODU connects to its own antenna.

In the IDU photo below:

• on the right are 2 “modem cards”, each with a TNC connector that allows connection to an ODU through an IF cable.  So, when there are two “modem cards” slotted into an IDU, 2 ODUs can be connected to one IDU.

• on the left are 4 “service card” slot interfaces.  For an Ethernet bridge solution where no E1s are needed, only one SCLAN (SC=Service Card) is fitted to allow transfer of 64Mbps/64Mbps Ethernet (if a 28MHz channel is used).

IDU fitted with 2 modem card and 4 x 8E1 "Service Cards"
IDU fitted with 2 modem card and 4 x 8E1 “Service Cards”

Below, you can see ODU photographs – the ODU has a waveguide interface that allows direct connection to the antenna.

LPN Outdoor Unit
LPN Outdoor Unit


Microwave Radio attached to an antenna
Microwave Radio attached to an antenna


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