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WIFI-VoIP-PSTN and back

Started by Fiasco, December 28, 2013, 12:39:00 PM

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Fiasco

Hi

Great and informative forum - I feel dangerously educated and would value the opinions of the obitalk grey beards on my plans....

I live in an old house with thick stone walls that limit the effectiveness of radio, wifi and DECT etc comms.  I've managed to provide 802.11n wifi throughout the place using range extenders giving ADSL connectivity and internet radio - next is to tackle the phone system.

It's a simple residential set up, a single PSTN line into the property carrying both ADSL and telecoms.  I have a mass market phone base station with cordless DECT handsets that deliver limited range which means calls are often missed or fail as the handset drops it's signal.  I don't want to install DECT extenders as it seems a dying technology, so can I create an architecture that uses VOIP technology across my Wifi LAN to provide house wide call pick-up of calls arriving on the PSTN line?  Specifically:

- install an OBi110 to bridge between the external PSTN line and the internal VOIP network
- use VOIP handsets to connect to the WIfi network, ultimately connecting to the OBi110
- use Asterix (maybe?) to manage the routing of handset calls to/from the OBi?
- keep my existing handset for use in the event of power failure.

Intuitively this feels similar to setting up a small, single line, office solution with all the inherent limitations I can live with at home, each handset having an extension number of its own.

Note - I'm not interested in moving to a full VOIP solution to replace my existing PSTN service, the few calls I make are done using the free minutes on my mobile contract and I need to continue paying for my landline and Broadband, but I do need to be able to reliably answer incoming calls on my existing number.

IT I can do, but telecoms is a world and vocabulary all it's own and getting it wrong could be an expensive mistake so stop me if I'm being stupid!

Thank you.

ianobi

The simple answer is yes it can be done using just one OBi110. It's worth saying at this point that the OBi was not designed to be used this way, so there may be limitations that I have not yet seen.

I created something similar in my house connecting softphones, two OBi110s, cell phone used as a wifi handset etc. See:

http://www.obitalk.com/forum/index.php?topic=4944.msg31966#msg31966

Ignore the digit maps for now, they are way more complex than you need. Do notice the caveats:

All devices (extensions) must be set to call without registration. (Not all voip phones can do this).
All devices (except OBiAPP/OBiONs) must be in the same router subnet.
All devices must be on static subnet addresses.

A further limitation may be that an incoming call can only be forked to a maximum of four different phones/devices.

You could plug the dect base unit into the OBi110 and use them where they work - the base unit only counts as one device, then go for voip phones etc for further away places.

I have a similar problem in my old three storey house. I find the dect phones work fine vertically - the base unit is on the ground floor. Floors and ceilings are wood and plaster so no problem. It's only horizontally that's a problem!

There are other solutions - asterix etc, but as you need the OBi110 anyhow, then you may as well squeeze the last drop of functionality out of it. I like saving money   :)

Fiasco

Great thank you for the help - I'll give it a go when the holiday distractions have subsided.

I've seen the same limitations with DECT signals; vertically through wood and plaster fine, horizontally through rubble and flint farmhouse walls it's quickly attenuated.  No one seems interested in solving the problem using the now ubiquitous wifi - guess the money's in business solutions not the residential market.

One last question.  The Asterix attraction was because I've a raspberry-pi looking for a project and there's a Asterix based PBX distro available.  If I went that route would the (cheaper!) Cisco SPA3102 be a viable alternative, though having read the forums and the inherent difficulties it seems a big ask for a telecoms newbie?

drgeoff

FWIW I haven't noticed that Wi-Fi is better than DECT at going through walls.  Indeed I reckon that my European DECT phones hold up better than 2.4 GHz Wi-Fi.  Perhaps the fact that the transmit power of US DECT systems is only 40% of the level of the European DECT systems is significant.

ianobi

Fiasco,

The Raspberry Pi / Asterix / ATA project is one I have considered for 2014, but I'm putting it off for now due to time being limited - I think it will need quite a big commitment. There are people on this forum who have experience of Asterix who may wish to comment.

Cisco v OBi - there are pros and cons. Where I live in the UK an OBi110 used to cost just £35 - that's cheap for what you get. However they seem unavailable at Amazon.co.uk just now. Both will do the basic PSTN to VOIP conversion that you need. I don't think that the Cisco will fork calls simultaneously to more than one device. The OBi110 does a lot more (which you may not want). However, that lot more allowed me to use it as a PSTN to VOIP bridge, VOIP to VOIP bridge, PBX etc. Also you get free access to the OBiTALK network allowing you to join OBi devices up around the world so bridging services in one country with those in another. This is just for future reference in your case!

In your case I would be tempted to buy an OBi110 and set up some tests using free softphones on Laptops and PCs to be the extensions. They cost nothing and would more or less simulate a VOIP phone experience and use pretty much the same OBi110 configuration.

Interestingly, the founders of Obihai also founded the companies that invented and developed ATAs. Those companies were bought by Cisco to obtain their ATA capabilities. The ATA world is a small one!

Fiasco

Thanks again for the help.

Sofhone and an Obi it is then - I'm also in the UK so finding one could be a challenge with only ebay imports  looking available.


ianobi

I would wait a while to see if Amazon.co.uk restock. They are Obihai's main supplier throughout Europe and the OBi110 is popular outside of North America as many use it with a PSTN line.

sdb-

Before spending too much time and/or money on VoIP using your WiFi distribution, please check the latency and jitter at various points in your house.

WiFi adds a lot of latency, and it sounds like you might have created multiple WiFi links between the nether reaches of your home and the incoming DSL connection.

I'd check with ping at first, and if that works I would try a softphone or two, or at least Skype.  (Could use a Localphone SIP account for testing with a softphone.)

Personally I'd be inclined to add DECT repeater(s), but if your existing WiFi solution works well with VoIP and you are OK with the use model as well as setting up and configuring for multiple IP phones then go for it.

Fiasco

Hmm, latency is a good point.

I've hard wired a Gb/s network infrastructure through the house with commercial grade switches; the wifi coverage is provided through a central wireless router and 2 further wireless access points hanging off the wired network at opposite ends of the house.  This gives a good quality and stable 2.5Mhz connection throughout the house with 5Mhz available at the centre.

I can stream HD quality content to a wireless TV without problem so I'm confident about the raw speeds and available bandwidth.  But latency is a good point - a ping between wireless devices at opposite ends of the house records  gives an average rtt of 90ms - what does good (or bad) look like in terms of VOIP?


sdb-

90ms is OK.  But that is within your house?  How much does it add when you ping 8.8.8.8 (google public DNS)?

The other factor is jitter - the difference in timing packet to packet.  If the jitter is high you will either hear problems or the equipment will use a larger jitter buffer which adds a delay to your conversation. Ever talk between continents via cable vs satellite? The satellite delay of ca. 1-2s would be like a really bad jitter.

On my wired network in house I typically have sub-1ms latency.  My internet connection adds about at least 20-30ms.  Right now to 8.8.8.8 I am at 40-45ms.  Even my in-house 802.11n is typically less than 5ms. And except for wireless, jitter is minimal in-house.

My obihai is a wired connection:
--- obi202.internal ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9001ms
rtt min/avg/max/mdev = 0.477/0.545/0.718/0.079 ms


My roku is via 802.11n (the router is 3x3ac):
--- roku.internal ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9014ms
rtt min/avg/max/mdev = 1.383/1.987/3.205/0.634 ms

The jitter is higher than the average latency on the wired connection...

An 802.11g client:
--- myth1.internal ping statistics ---
10 packets transmitted, 9 received, 10% packet loss, time 9015ms
rtt min/avg/max/mdev = 0.943/4.302/26.425/7.912 ms


I think my roku wifi connection would be great for VoIP. The 802.11g 'myth1' would be likely be OK, but if it really loses 10% of packets you will probably hear it.  Both of those generally have no problem streaming video.

sdb-

Quote from: Fiasco on January 03, 2014, 04:02:36 PMI've hard wired a Gb/s network infrastructure through the house with commercial grade switches; the wifi coverage is provided through a central wireless router and 2 further wireless access points hanging off the wired network at opposite ends of the house.

Oh, that architecture should be good.  From your first description I was concerned you were using wireless distribution (WDS) with the multiple access points connecting to each other via WiFi. 

drgeoff

Quote from: Fiasco on January 01, 2014, 02:56:54 PM
I'm also in the UK so finding one could be a challenge with only ebay imports  looking available.
Amazon UK is showing OBi110s back in stock at £35 including free SuperSaver delivery.

Fiasco

Thanks for the tip off.  Mine was waiting for me on Saturday and I think I have the basic configuration working:

- lights are green
- ObiTalk shows the device registered
- incoming PSTN calls are routed to Phone
- Phone calls routed to Line
- emergency numbers in rules changed to 999 | 112
- calls made over ObiOne are routed out through the line

Realise this is out of the box behaviour but its reassuring nonetheless!  Can I infer from this that my in\out router ports are correctly set?

I'm using a fixed IP address for the Obi - but as a fixed assignment from my router rather than a hardwired static address into the OBI, as I prefer to have IP assignments managed in one place.

Stability of router and internet connection is a concern with router restarts needed every 30mins yesterday but its improved this evening and run for 7 hrs without a problem.

Next step is to start introducing a soft-phone into the configuration, I've got X-lite installed on an old netbook, but that's going to take some reading to understand the authentication and port conventions.


ianobi

Some people have found this useful:

Change the Ethernet port on the OBi from 10 mb/s half-duplex to 100 mb/s full duplex:

1. Dial *** 0

2. Enter option 27 and press #

3. Press 1 to set a new value

4. Enter a value of 1 and press #

5. Press 1 to confirm/save

6. Hang up

7. Wait for the OBi to reboot

Of course, that's undocumented   :)


If your happy with using an X-lite softphone, then fine. Many here have found it difficult to use in OBi configurations. For testing purposes, I would recommend PhonerLite - it's free, easy to use and has a good debugging facility.


When I get time later today I'll post some UK settings to make your OBi more British!

ianobi

#14
These settings should speed up outbound and incoming calls and generally make your OBi more compatible with British phone systems:

Physical Interfaces > LINE Port > LINE Port > DigitMap:
([2-9]xxxxxxS0|0[1-9]xxxxxxxxxS0|xx.S4)
Assumes that local numbers are seven digits. May need adjusting to your local format.

Physical Interfaces > LINE Port > LINE Port > RingDelay: 0
Physical Interfaces > LINE Port > LINE Port > RingProfile: B
Physical Interfaces > LINE Port > LINE Port > DialDigitOnTime: 80
Physical Interfaces > LINE Port > LINE Port > DialDigitOffTime: 80
Physical Interfaces > LINE Port > PSTN Disconnect Detection > DetectFarEndLongSilence: uncheck
Physical Interfaces > LINE Port > Port Settings > ACImpedance: 370+(620||310nF)
Physical Interfaces > LINE Port > Port Settings > CallerIDDetectMethod: FSK(V.23)

Physical Interfaces > PHONE Port > Ringer > RingFrequency: 25
Physical Interfaces > PHONE Port > Port Settings > Impedance: 320+(1050||230nF)
Physical Interfaces > PHONE Port > Port Settings > CallerIDMethod: FSK(V.23)
Physical Interfaces > PHONE Port > Port Settings > CallerIDTrigger: Before First Ring

Let's hope that it still works after that many changes   :)

Fiasco


It still works - thank you !   :)

ianobi

Missed an obvious one - matching the OBi to the PSTN line:

Physical Interfaces > LINE Port > Port Settings > ACImpedance: 370+(620||310nF)

I have added it to the original post in case anyone copies it.