[Hidden-tech] Satellite internet services

Matthew Crocker matthew at crocker.com
Mon Aug 8 16:16:18 EDT 2005

> I should think for most of us workers that latencey isn't much of an
> issue, unless we developed games for a living. There is an internal
> latency built into internet. It all works with fiber or wire, both of
> which operate around 60% the speed of light. Distance takes time.

Normal internet latency is on the order of milliseconds.  Satellite  
latency is on the order of seconds.   Satellite latency will kill any  
interactive session.  SSH, VPN, VoIP. It is fine for web browsing.   
Downloading large files is also affected because the TCP windows size  
needs to be HUGE to make up for the ACK latency.

> I have found that Verizon DSL has a true speed of about 40 to 50  
> Kbuad at
> best. Often worse.

Our DSL subscriber regularly get full bandwidth out of their DSL  
service.  1.5mbps DSL = 185 kBps, 3.0 mbps = 375 kBps

DSL uses ATM in the core so you do get hit with a cell tax. Your IP  
packet becomes IP over PPP over Ethernet over ATM over DSL.  All told  
you'll get a 10% hit on efficiency. A 768k DSL line is actually 856K  
delivered,  768K is usable so it already has the ATM cell tax  
factored in.

> WiFi range
> The range of WiFi is limited by several things, some of which the  
> user has
> control. Range is determined by:
> Power output of units, 1 watt is allowed, but often 0.1 to 0.2  
> watts are used
> Antennas, A gain antenna is allowed under the FCC rules
> Bandwidth, Contrary to advertisements, less bandwidth = more range,  
> Multipath, Signals arriving from bounces don't help, but hurt  
> reception.
>     Gain antennas provide directionallity, which can reduce multipath.
> Manufacturer of equip, Some stuff is good, some not so.
> Receiver sensitivity, Lower is better ALWAYS!

We run 900Mhz radios in Springfield with 5 mile range, 120 deg  
antennas on our end and 3-5 degree yagi on customer end.  1mbps  
throughput.  The system is pretty reliable but took 6 months to work  
out the kinks.  We can burn it through buildings,  there is a lot of  
900Mhz noise in Springfield.

Matthew S. Crocker
Vice President
Crocker Communications, Inc.
Internet Division
PO BOX 710
Greenfield, MA 01302-0710


More information about the Hidden-discuss mailing list