Globalstar Product Management – Technical Support

WiFi Interference with Globalstar (TB-06-04)

leave a comment »

Product Management Technical Bulletin No. 06-04
Last updated: 30-November-2006

WiFi Interference with Globalstar
 
This technical bulletin applies to all Globalstar phones.

There are two types of radio interference that can disrupt Globalstar communications,

  1. Interference outside of the Globalstar radio frequency bands
  2. Interference within the Globalstar radio frequency bands

Because several versions of 802.11 WiFi (802.11b, 802.11g) use radio frequencies directly adjacent to the “receive” band of Globalstar phones, and because of the wide proliferation of 802.11 devices, many people have wondered whether 802.11 can interfere with Globalstar. 

Out-of-Band Interference:
The Globalstar phone is designed to ignore all signals outside of the assigned, licensed, Globalstar receive band. 

In-Band Interference:
When radio waves at different frequencies mix with one another, they generate harmonics which are outside of either of the original bands.  In this case, a combination of 802.11 out-of-band emissions can and do generate harmonics within the Globalstar receive band.  Calculations show that certain combinations of 802.11 channels (e.g., channels 6 and 11) will produce a harmonic frequency within the Globalstar band.  So, the important question is whether the resultant harmonic is strong enough to disrupt Globalstar communications.  The answer is that consumer devices (routers, WiFi cards in laptops, etc.) which are operating properly will not interfere with Globalstar unless the routers are 4 meters apart from one another and the Globalstar user is right in between them.  This is unlikely and, if it does happen, it is very likely that the person will simply move to another location.

However, there are an increasing number of city-wide 802.11 networks that are being deployed with high-power transmitters.  Although it is possible that these transmitters, in combination with other transmitters, could generate harmonics strong enough to interfere with Globalstar communications, we have not documented a case where this has happened. 

Nevertheless, if a customer is having difficulty making or receiving calls in a certain locale, it would be advisable to determine the 802.11 signals present in that area and to document the strengths of those signals.  This can be done with a PC laptop and freeware such as NetStumbler, or a commercial protocol analyzer could be used. 

Once you have gathered such data, please call Customer Care so that they can help diagnose your particular situation and troubleshoot the connectivity problems, whether due to 802.11 issues, physical blockage, or even installation issues.

Advertisements

Written by Joseph Crowley

September 15, 2008 at 9:57 pm

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: