[ILUG] Help needed with VOIP & Digital Phone

[Michael Watterson]

Kevin Brennan wrote:
>
>
>>
> Since I'm not a specialist on the air interface for 3G I will refer to 
> the Harri Holma and Antti Toskala book
Ah. but I'm a real communications engineer.  Weaned on  Shannon  & 
Nyquist.  Studied , tested and  analysed  GSM/ GPRS/EDGE/EDGE2,   W-CDMA 
based FOMA and 3G/HSDPA/HSUPA/HSPA+, Mobile WiMax, Flash-OFDM, 
IPWireless, DVB-h+ DVB-RCT, and LTE for mobile data and VOIP.  Also  
WiDox, Full DOCSIS over Wireless, VSAT, Fixed WiMax, Proprietary Fixed 
Wireless,  Nomadic  S-CDMA  (Ripwave) and  WiFi  Municipal Mesh for Data 
and VOIP.

I've even looked at the issues of IPTV and VOD on these and on DSL and 
Cable.

> (http://books.google.ie/books?id=-xAlDHXpzxYC&pg=PA458&lpg=PA458&dq=Harri+Holma+and+Antti+Toskala++voip+hsdpa&source=bl&ots=xSZprhlMyT&sig=MuqC33OxTOZYjyHzhLvqP_O4-Fg&hl=en&ei=yS6xSZzgOtSujAf0m_3TBQ&sa=X&oi=book_result&resnum=5&ct=result) 
>
> "the maximum number of simultaneous users per sector per 5Mhz 
> carrier"...."with HSPA release 7" ...is estimated to be "120 users" 
> etc..etc..
> .. then more on reasons why a flat architecture is of benefit...
>
At which point you'd be lucky to get dialup speed. The **total** cell 
throughput then with  14.4 or 21 or 42MBps peak speed mast will then be 
1Mbps to 2Mbps shared among the 120 users.

You can't beat mathematics and physics. Mobile systems operate near the 
shannon limit. Thus you have 1/4 speed (shared) everytime you double the 
distance.

Mobile Phone companies  make all  their  money  from  SMS and  voice.  
Data  makes them no money. LTE will cost to them at least 100 Euro a 
Gigabyte, inc getting ROI in a sensible time frame.

Mobile Data is for occasional use On The Go / Mobile phones / Gadgets. 
It's not viable for VOIP nor as a replacement for Fixed Wireless, DSL, 
fibre or Cable.

You do realise that DSL is only limited by backhaul, and eircoms 
existing 3Mbps DSL has x10 to x20 average performance of 14.4Mbps I-HSPA 
or HSPA+

I get 5Mbps+ at peak  time and  28ms  ping to  Heanet  on Fixed  
Wireless and rarely ever better  than   700kbps  @ 150ms  latency on  
O2  at home, and  frequently lower speed and 500ms in some places in 
Dublin on HSDPA.

Nokia's own research concludes that VOIP is on average a poor experience 
on HSDPA.  SIP (and Skype clients in a new model)  in Nokia phones are 
really  for  WiFi  in Home /Office.  3's  Skype  phone  uses iSkoot a  
Java  client that  uses  GPRS,  EDGE  or  3G to  set up a  call  and  
then  ordinary  3G  voice (not VOIP) to  3's basement  Skype  Client  to 
convert  to  VOIP. That's actually the best model for Mobile Skype, but 
of course not at all actually VOIP on 3's Network.


3G modems are not Broadband replacements, or even Fixed Wireless 
Replacement. MOBILE Data will never be reliable as VOIP / Broadband 
platform.

It's not very Linux friendly either.


 



-- 
Mike