[aprssig] Digital two-way Radio communication in emergency situations

andrewemt andrewemt at hotmail.com
Sat Sep 6 16:13:57 EDT 2014

Maybe the US overturned the patent,  but did other countries overturn theirs? I thought AIS was originally a Swedish invention.

-------- Original message --------
From: Heikki Hannikainen <hessu at hes.iki.fi>
Date:09/05/2014  23:48  (GMT-05:00)
To: TAPR APRS Mailing List <aprssig at tapr.org>
Subject: Re: [aprssig] Digital two-way Radio communication in emergency situations

On Fri, 5 Sep 2014, andrewemt wrote:

> team, but runs into trouble as soon as an uncoordinated outsider comes on frequency. The marine
> AIS system has a solution,  but it's patent-encumbered.

By the way:

The United States Patent and Trademark Office (USPTO) canceled all claims
in the original patent on March 30, 2010.

USPTO ex-parte reexamination certificate (7428th), issued on March 30, 2010

(Source: wikipedia, but I think I saw/read the USPTO documents back in
2010, it was news then)

> Also, the fixed equal-size timeslot
> scheme only works with stations sending about the same amount and size of traffic (in your
> case, only trackers transmit, not mixed station types).

AIS supports a few different sizes, the shorter position packets are sent
often, and every now and then the station reserves a larger slot for
sending it's full name and/or other information.

   - Hessu
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