NTP, which holds valuable wireless patents, is basing a major part of the new litigation on the precedents developed in the RIM case.

For instance, in a lawsuit filed Sept. 7 against Verizon Wireless in U.S. District Court for the Eastern District of Virginia, NTP stated: "RIM extensively litigated the validity and enforceability of the five patents at issue, as well as the issue of RIM's infringement. The issues of infringement and validity were tried in a 13-day jury trial in November 2002. The jury returned a verdict finding that RIM willfully infringed all of the claims of the patents that were asserted at trial."

NTP is citing a total of eight patents in the litigation against the Big Four wireless service providers.

In the new cases, NTP noted that it also has filed patent infringement action against Palm, which hasn't been resolved. The validity of that patent is in dispute. NTP has appealed a preliminary decision by the U.S. Patent and Trademark Office, which ruled against NTP, according to media reports.

Much of NTP's new litigation against wireless service providers involves intellectual property for wireless e-mail services on mobile devices.

The mobile phone industry has been roiled in recent months by intellectual property litigation. In addition to the NTP-RIM case, Qualcomm has squared off against Broadcom and Nokia in high-visibility cases. Verizon Communications and Vonage Holdings also have been involved in patent litigation.