The rancorous world of wireless is heating up yet again, with two subsidiaries of Motorola suing Aruba Networks, alleging the wireless LAN company infringed four patents.

Symbol Technologies and Wireless Valley Communications charge that Aruba is knowingly using their patented WLAN switch technologies and techniques for designing and managing WLANs. On Monday, they filed suit in the US District Court for the District of Delaware. The companies want a jury trial and are seeking a permanent injunction against Aruba as well as unspecified monetary damages, tripled because of willful infringement.

The airwaves have become a dangerous place to do business, with a series of suits between Qualcomm and two of its mobile rivals, Nokia and Broadcom, following on the heels of NTP's litigation against Research In Motion Ltd. and other companies. An Australian research body won an injunction against Buffalo Technology (USA) for WLAN patent infringement, and the development of the hotly anticipated IEEE 802.11n WLAN specification has also sparked fierce battles, though not in court. As in other fast-growing markets, litigants may see future riches at stake.

Aruba makes a variety of WLAN equipment and technology for putting the gear together in large networks for enterprises and other customers. The company, based in California, is incorporated in Delaware, according to the suit. Aruba has not yet seen the suit and has no comment, spokesman Michael Tennefoss said.

All of Aruba's WLAN switch, site planning and radio-frequency management and monitoring products infringe the patents, and they have since the company began selling its first products, said Aaron Bernstein, vice president and deputy general counsel at Symbol. The companies don't want to license the technology to Aruba, but to stop the company from using it, he said.

Motorola isn't suing Aruba because the patents were issued to Symbol and Wireless Valley, which are separate legal entities wholly owned by Motorola. Wireless Valley was acquired in 2005 and Symbol earlier this year. They didn't sue Aruba until now because the WLAN switch patents weren't awarded to Symbol until early this year, Bernstein said.