USRE41531, titled “Communications Systems For Radio Frequency Identification”, is one of key patents that is used to sue retail companies (Macy’s, Gap, J.C. Penney etc.) by Round Rock Research LLC. Round Rock Research LLC is founded by John Desmarais, a famous patent attorney for his won in a $1.52 billion verdict for Alcatel-Lucent against Microsoft in 2007.Ref. RFID Patent Lawsuit Early Warning: http://techipm-innovationfrontline.blogspot.com/2010/06/rfid-patent-lawsuit-early-warning.html
USRE41531 relates to collision avoidance technology, which is essential in operating passive UHF RFID system (standardized as ISO 18000-6C & EPC Global Gen 2):
BACKGROUND OF THE INVENTION: When the interrogator sends a message to a transponder device requesting a reply, there is a possibility that multiple transponder devices will attempt to respond simultaneously, causing a collision, and thus causing an erroneous message to be received by the interrogator. For example, if the interrogator sends out a command requesting that all devices within a communications range identity themselves, and gets a large number of simultaneously replies, the interrogator may not be able to interpret any of these replies. Thus, arbitration schemes are employed to permit communications free of collision.
SUMMARY OF THE INVENTION: One aspect of the invention provides a method of establishing wireless communications between an interrogator and individual ones of multiple wireless identification devices. The method comprises utilizing a tree search method to establish communications without collision between the interrogator and individual ones of the multiple wireless identification devices. A search tree is defined for the tree search method. The tree has multiple levels respectively representing subgroups of the multiple wireless identification devices. The method further comprising starting the tree search at a selectable level of the search tree. In one aspect of the invention, the method further comprises determining the maximum possible number of wireless identification devices that could communicate with the interrogator, and selecting a level of the search tree based on the determined maximum possible number of wireless identification devices that could communicate with the interrogator. In another aspect of the invention, the method further comprises starting the tree search at a level determined by taking the base two logarithm of the determined maximum possible number, wherein the level of the tree containing all subgroups is considered level zero, and lower levels are numbered consecutively.
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The court granted plaintiffs' motion for summary judgment of noninfringement where defendant failed to served infringement contentions. We are also providing Patent Litigation at the most prestigious law firms in the country.
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