[cisco-voip] LMR

Tue Jan 10 16:16:39 EST 2006

I'm sorry a head of time for the long e-mail reply.

We've got a lot of customers who use Digital LMR radios with Cisco
routers. A lot of our customers use WAVE with Cisco routers which is
mentioned in the SRND Case Study linked below because it greatly extends
the capability of the solution and makes it easier to manage. But you
don't need WAVE for really small radio deployments or no radio mixing
(i.e. Radio interoperability). 

I don't want to go into WAVE since it's not exactly what you asked for
other than to explain how we fit with Cisco's LMR feature set using E&M
ports. WAVE specializes in communications interoperability and we use
Multicast IP and VoIP standards to do this. WAVE is simply a software
solution provide the inter-connectivity glue. We extend voice
communications to and from any audio source, including IP Phones, PDAs,
PCs, intercoms, phone and LMR systems. We put these audio sources onto
the network into logical items called "channels" or virtual talk groups.
Channels are primarily Multicast or unicast Audio Streams that can be
mixed with other Channels but it also be mixed with H.323 unicast calls
from voice gateways such as Cisco's routers using E&M. In larger
deployments, you can even use ISDN PRI with Cisco's LMR feature set. 

We've seen a lot of Motorola trunking systems integrated with Cisco
routers. Basically it's works out as one talk group per E&M connection.
In larger or denser systems you can use an ISDN PRI card in a Cisco
router with a channel back such as an ADTRANS instead of an E&M port. 

A Cisco router is an audio gateway using H.323 unicast or Multicast
audio streaming to bring audio source such as a LMR system onto the
network.

Here are the considerations when connecting a LMR with a Cisco router:

-- An LMR system is simply another audio source / target on a Channel
(read Multicast Audio stream here)

-- Audio from the radio is passed onto the network as if it was sourced
from any other analog device

-- Audio from the network is passed back in the same way

-- An E&M port on a Cisco router is typically used as the gateway to the
radio

-- One big gotcha applies - how to "key" the radio

There are three main ways to get radios on the network. The main thing
is we need to "tell" the radio to transmit the audio sent to the radio
from the router

The three ways to key a radio are:
-- VOX
-- E&M signaling
-- Tones

VOX Keying

Relies on voice energy from the E&M port to key the radio

Advantages
-- Simple concept & router configuration
-- Supported on older IOS loads and lower-end hardware (e.g. 1751)

Disadvantages
-- Unreliable depending on the radio system
-- Generally results in clipping ("shoot / don't shoot" scenario)
-- Not supported by all radio systems

E&M Keying
-- Relies on a newer IOS feature-set
-- 12.2.8T or greater & IP Advanced Services or better

Advantages
-- Simple concept & router configuration
-- Functionality resides at the network edge in a high-availability
device

Disadvantages
-- May Require an IOS upgrade which may require additional RAM and Flash
-- May require router hardware upgrade (currently supported on 2600XM, 
-- 2800, 3700, 3800 series routers)
-- Not supported by all radio systems

Tone Keying

Special tones need to be embedded in the audio stream sent to the radio

Tones need to be generated by WAVE PC Clients and/or Media Servers but
Cisco now supports limited tone generation within their routers and with
their new product IPICS

Advantages
-- Simple router configuration
-- Supported on older IOS loads and lower-end hardware (e.g. 1751)
-- Fine-grained control over radio operation (channel select, repeater 
-- select, power level, etc.)

Disadvantages
-- Keying removed from network edge
-- Potential "unkeying" if packets are dropped over a bad network
-- Limited number of codecs can be used for tone embedding
-- Not supported by all radio systems

The Basic router configuration is like this:

Voice Port:
-- Typically E&M
-- LMR on E&M has two signaling options:
	Audio pass-through
	"E&M signaling" (Requires the correct IOS)

Dialpeer:
-- IP Multicast
-- H.323 call

Voice Port Audio Pass-through:
(No signaling performed by router)

Tradeoffs:

Advantages
-- Simple configuration
-- Operates on practically all router hardware and recent IOS loads

Disadvantages
-- None

Audio Pass-Through Voice Port Example:
voice-port 1/0/0
 voice-class permanent 1
 auto-cut-through
 operation 4-wire
 type 3
 no comfort-noise
 timeouts call-disconnect 3
 timing hookflash-in 30
 connection trunk 1112
 description VHF Radio
 music-threshold -10

Voice Port "E&M Signaling":
(Signaling performed by router based on RTP packets)

Tradeoffs:

Advantages
-- Simple configuration for PTT
-- LMR signaling pushed to the network edge
-- Can use any codec supported by Cisco router
-- Can be used in conjunction with tones on supported radio systems
-- (e.g. repeater select, channel change, etc.)

Disadvantages
-- Designed only for PTT-type operations
-- Requires 2600XM, 2800, 3700 or 3800 series routers
-- Requires IOS upgrade - possibly hardware too - $$$

E&M Signaling Voice Port Example:
voice-port 1/0/0
 voice-class permanent 1
 auto-cut-through
 operation 4-wire
 type 3
 no comfort-noise
 timeouts call-disconnect 3
 timing hookflash-in 30
 connection trunk 1112
 description VHF Radio
 signal lmr
 lmr e-lead voice
 lmr m-lead audio-gate-in

Dialpeer IP Multicast:
(Uses the Cisco Hootie configuration)

Tradeoffs:
-- Advantages
-- Very simple to configure on router
-- Direct mapping to WAVE Channel configuration
-- No delay between router transmission & endpoint receipt
-- Very scalable from router to network

Disadvantages
-- IP multicast required on the router
-- Requires IOS with Cisco Hootie support
-- Router can only mix 3 simultaneous sources - same codec too (WAVE can

-- be used to get around this)
-- No DTMF digits relayed from LMR to WAVE system (This limitation may
be 
-- fixed)
-- Not very scalable from network to router (due to the mixing
limitations 
-- of the router, WAVE can fix this too)

Direct to IP Multicast to a WAVE Channel or Another Router example:
dial-peer voice 100 voip
 description VHF Radio
 destination-pattern 1112
 session protocol multicast
 session target ipv4:234.1.11.1:21890
 codec g711ulaw

Dialpeer H.323 Call:

Funnels communications through an H.323 call

Tradeoffs:

Advantages
-- Failover implemented through hunting configured on router
-- If made via CallManager, CM can be used for hunting
-- Can function over the PSTN
-- DTMF digits from radio system are relayed
-- No multicast required on the router
-- No codec / scalability issues - all unicast
-- Supported on non-Hootie IOS loads and hardware

Disadvantages

Significantly more complicated to setup - requires more router
configuration
Increased audio delay (~20ms)

H.323 Call to WAVE Media Server or another router example:
dial-peer voice 100 voip
 description VHF Radio
 destination-pattern 1112
 session target ipv4:192.168.35.201
 dtmf-relay h245-alphanumeric
 codec g711ulaw
 no vad

Another thing you asked is who uses Cisco gateways with LMR. I don't
know all of them, but a lot them that I've worked with have been public
safety and Department of Defense agencies, NATO member militaries, and
different critical infrastructural and financial customers. The LMR
stuff is deployed a lot in Iraq and Afghanistan to support the U.S.
Army. I worked a lot with them in troubleshooting different situations
for them. You got to love a 13 hour time difference when you are
troubleshooting an issue over the phone. 

I've included a link below from Networkedradio.com. They make cables
specifically for Cisco E&M ports to LMR radios. It takes a lot of the
layer one guesswork out of the picture. Also, if you don't see a cable
on their website they'll make custom cables including ones that will
meet Military specifications. One piece of advice I offer is when you
order cables from them, get a couple of backup cables. I had a couple of
cases where I got bad cables but, overall, they are very reliable. 

I've also included a link I use a lot for the E&M pin outs for Cisco E&M
ports. I use this a lot when I make cables.

I hope this helps.

Pre-made Cable from Networked Radio
http://www.networkedradio.com/

E&M Pinouts
http://www.cisco.com/en/US/products/hw/gatecont/ps2250/products_tech_not
e09186a008009452e.shtml

Scott Crosby 
Consulting Systems Engineer 
Twisted Pair Solutions, Inc. 
Email: scott.crosby at twistpair.com 
Web: http://www.twistpair.com 
Tel:   +1 (206) 812-2361
Cell:  +1 (206) 321-2474 
Fax:  +1 (425) 812-0737 

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Fretz, EA Eric
@ IS
Sent: Tuesday, January 10, 2006 10:39 AM
To: 'cisco-voip at puck.nether.net'
Subject: RE: [cisco-voip] LMR

We don't use Land Mobile Radios in our setup, but we do use LMR
signaling
with other devices.  I am assuming you will be use the 1 or 2 port E&M
VWICs
on a NM-HDV2 netmodule.  Pins 2(E) and 7(M) are your signal pins and
4(TIP)
and 5(RING) are your audio pins.  I could not find a way to effectively
simulate COR or PTT with our transmit equipment, so I wound up using VAD
to
do VOX detection to signal that there was audio to send to the radio
from
the router.   So far, that has worked pretty well.

Cheers,
Eric

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Sean Watkins
Sent: Tuesday, January 10, 2006 12:17 PM
To: 'cisco-voip at puck.nether.net'
Subject: [cisco-voip] LMR

Hi,
We have a number of Motorola trunking radios; and were looking at
connecting
them to our CME router. Reading through Ciscos Docs on LMR (Land Mobile
Radio)

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123newft
/123
t/123t_7/lmrip/lmrsrnd/index.htm

Its pretty simple to setup. Wondering if anyone on list 

1) Has done this
2) What the results were. 

I'm looking for pinouts for the radios, and if anyone is interested in
the
results I'd be more than happy to pass them along.

Sean

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