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).