Radio-over IP

If you look at the two-way radio systems public safety agencies, utilities, and other intense users use, it’s not at all uncommon to see circuits between a radio console at a dispatch center and remote tower site.  These could be landline circuits like E&M, voice-grade leased lines, or even T1s.  If the radio system operator is concerned about the wireline infrastructure availability, they might use a microwave radio as a backup path or replacement for wireline service where it’s unreliable, not available, or simply too expensive.

As this blog’s reader, you know T1s, E&M lines, and the like can be connected to a voice gateway.  The gateway will sample, digitize, encode and packetize that audio for transmission across an IP network.  Why would you do this?  It’s actually pretty simple.  Leased line circuits run from point A to point B.  If you wake up one morning and decide to move your dispatch center from B to C, you’ll have to work with the telco to reconfigure the leased line.  Microwave links might take even longer than landlines to reconfigure because of frequency coordination, path analysis, moving dishes around, replacing feedlines, and so on.

But, if you used an IP network, the dispatch consoles could be anywhere on the network as long as they have connectivity to the tower site.  Radio-over-IP, or RoIP, gives the customer new flexibility.  Not only can we move consoles around, but we can even replace them with PC-based applications emulating that functionality.  Perhaps this could all be accessed across a QoS-enabled VPN.  Due to concern over pandemic flu, some agencies are looking at telecommuting dispatchers as one part of operations plan continuity.

There are many vendors in the RoIP space.  Some are old school.  They’re building the same consoles, except with an Ethernet interface instead of a telco interface. Cisco is also present in the space with the IPICS product.  The Cisco solution goes beyond circuit replacement to focus on Unified Communications instead.

Sounds like a great marketing or sales pitch, but what does it mean in practice?  With IPICS I can use a service on my IP phone to access the radio channel.  Any authorized user can use an IP phone to communicate with radio-equipped field personnel.  There’s also the ability to cross-connect the telephony and radio systems to allow radio users to place and receive phone calls.  On the data side, newer digital radios support messaging which IPICS can bridge into SMS, SMTP, and IM.  In other words, while RoIP is about carrying audio across the IP network, Unified Communications is about accessibility.

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