E&M Voice Interface + Radio over IP / IP over Radio Issue

Unanswered Question
Oct 23rd, 2010

Hi all, I've got a bit of an issue with a Radio over IP solution that I'm currently enginering in.

I've spent the past 2 days straight trying to work out what the issue is but have gotten to the point where I've burn't just about all bridges.

The situation is mentioned below:

The implementation is a "Twistpair WAVE solution" over "Cisco Architecture".

I've configured Wave with two channels, and all clients on the network can transmit/Receive between themselves. This means the Wave configuration is fine.

The Cisco router i'm using has a DSP module with 4 x E&M voice interfaces on the back. I'm using 2 of these voice interfaces for two seperate radio channels i.e... 1 x VHF and 1 x VHF/UHF radio.

The VHF radio is hooked up to the 1st E&M port using a Wave cable (AN/PRC-148) to RJ-45 adapter.

When transmitting off another 148, The 148 thats attached to the router keys, uses the DSP module to convert the analogue signal to digital, and all clients on the network receive the radio voice.

The issue lies with transmitting from the a client on the IP network, to the radio net on the outside. I cannot get it working the opposite way.

The Router configuration is below....

ip multicast-routing

voice-card 0

no dspfarm

voice service voip

h323

no call service stop

session transport tcp calls-per-connection 1

voice class permanent 1

signal timing oos timeout disabled

signal keepalive disabled

signal sequence oos no-action

interface Vif1

ip address 192.168.13.1 255.255.255.0

ip pim dense-mode

interface FastEthernet0/0

ip address x.x.x.x x.x.x.x

ip pim sparse-mode-dense

voice-port 0/0/0

voice-class permanent 1

auto-cut-through

operation 4-wire

type 2

signal lmr

lmr e-lead voice

lmr duplex half

no comfort-noise

timeouts call-disconnect 3

timing hookflash-in 30

connection trunk 1000

description VHF-CH

music-threshold -10

voice-port 0/0/1

voice-class permanent 1

auto-cut-through

operation 4-wire

type 2

signal lmr

lmr e-lead voice

lmr duplex half

no comfort-noise

timeouts call-disconnect 3

timing hookflash-in 30

connection trunk 1001

description VHF-UHF-CH

music-threshold -10

dial-peer voice 100 voip

description VHF-CH

destination-pattern 1000

session protocol multicast

session target ipv4:230.139.32.1:30002

codec g711ulaw

vad aggressive

dial-peer voice 101 voip

description VHF-UHF-CH

destination-pattern 1001

session protocol multicast

session target ipv4:230.139.32.1:30002

codec g711ulaw

vad aggressive

gateway

timer receive-rtp 1200

The VHF-CH and VHF-UHF-CH trunks appear when I transmit from radio to radio then into the IP network, but when I go to transmit from the IP network back out the radio channels in wave, the Radio does not key, so the audio isn't transferred.

Any ideas would be greatly appreciated. If it works one way, then the link is definately good.

Kindest Regards,

Andrew Hardy

I have this problem too.
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SysEngrNZ Tue, 11/02/2010 - 00:23

I found the solution to the problem, with a bit of an electrifying experience in the process.

Touching the chassis that the router was mounted in, I got an electric shock. Frame was 97VAC to ground.(Can anyone say Random??...)

Removed the router and the problem dissapeared. Tested the power cable, the ground on the cable was non-existant due to suspected damage.

This problem in effect mean't that when the IP voice was transferring back to the router, where the Digital to Analogue conversion occurs, the E-Lead in effect wasn't providing enough voltage down the line to key the radio.

If I didn't get the shock, the problem would have still been there and potentially could have caused a lot more damage to both the equipment in the rack, and to technicians such as my self.

Thought i'd post this fix, as you never know when a similar issue could arise.

Andrew.

jamie39801 Wed, 11/24/2010 - 14:14

Hi Andrew

I'm very interested in what your doing and am looking into trying somthing similar myself. Would you be able to email me at jamie398@googlemail.com to dicuss further. Thanks Jamie

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Posted October 23, 2010 at 11:14 AM
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