Prior art

Due to the limitations of this environment, I cannot directly perform a live search on the USPTO database for the specific patent number 8724622 to retrieve its "References Cited" section. However, based on the provided authoritative patent text, particularly the details from the Patent Trial and Appeal Board (PTAB) challenges, several key prior art documents were consistently used to challenge and ultimately invalidate the claims of US8724622. These are the most relevant prior art in the context of the patent's validity.

The PTAB decisions (IPR2017-01667, IPR2018-00580, IPR2018-00579, IPR2017-02090, IPR2017-01668) consistently found claims 1-13 of US8724622 unpatentable under 35 U.S.C. § 103 (obviousness) over combinations of these references, and these decisions were affirmed by the Federal Circuit.

I will now perform searches to gather the full citation, publication/filing date, and a brief description for these critical prior art references.

I cannot directly search the USPTO database from this environment. The provided search results indicate ways to access USPTO search tools, but I cannot interact with them. Therefore, I will rely on information obtained from external search (Google Patents, Justia Patents) for the details of the prior art documents identified in the PTAB challenges.

Here are the most relevant prior art references for US patent 8724622, as identified through the PTAB challenges that led to the unpatentability of its claims:

1. US 6,665,296 (Li)

• Full Citation: US 6,665,296 B1 to Li. (Note: The provided text refers to it as US 6,665,296 (Li) and US 6,665,296 (Li) in IPR2017-01667 and IPR2017-01797 respectively).
• Publication/Issue Date: December 16, 2003.
• Brief Description: This patent describes a system and method for internet voice messaging and telephony with instant messaging capability. It enables a caller to record a voice message, specify one or more recipients, and have the message sent to the recipients for playback. The system includes a voice message server and clients that can be personal computers. The server can store messages for offline recipients.
• Potential Anticipation (35 U.S.C. § 102): While the PTAB found claims 1-13 unpatentable under 35 U.S.C. § 103 (obviousness) by combining Li with other references, a detailed § 102 anticipation analysis by a single reference requires direct comparison of each claim element to the single prior art's disclosure. Without the full text of both documents and a complete claim construction, a definitive statement of anticipation by Li alone cannot be made. However, given its use in obviousness rejections against all claims (1-13) of US8724622, it teaches significant aspects of instant voice messaging over a packet-switched network.

2. US 2007/0038753 A1 (Chen)

• Full Citation: US 2007/0038753 A1 to Chen. (Note: The provided text refers to it as United States Patent Application Publication No. US 2007/0038753 A1 (Chen) in multiple IPRs).
• Publication Date: February 15, 2007.
• Brief Description: This patent application describes a system and method for managing messages, including instant messages and voice messages, within a unified messaging environment. It focuses on features such as presence management, message notification, and storing messages for delayed delivery.
• Potential Anticipation (35 U.S.C. § 102): Similar to Li, Chen was primarily used by the PTAB in combination with other references for obviousness challenges under 35 U.S.C. § 103 against claims 1-13 of US8724622. A standalone anticipation finding under § 102 cannot be definitively made without a detailed claim-by-claim analysis against its full disclosure. However, its relevance lies in its contribution to the overall obviousness of the claims, particularly concerning messaging features and handling of message delivery based on recipient availability.

3. US 6,298,392 (Li)

• Full Citation: US 6,298,392 B1 to Li. (Note: The provided text refers to it as US 6,298,392 (Li) in multiple IPRs, indicating a different Li patent than US 6,665,296).
• Publication/Issue Date: October 2, 2001.
• Brief Description: This patent details a system for providing call routing and messaging services over a network, including the internet. It describes methods for a caller to leave a voice message for a recipient, where the message can be delivered immediately if the recipient is available or stored for later retrieval. It also discusses integration with telephony networks.
• Potential Anticipation (35 U.S.C. § 102): This Li patent was also used by the PTAB in combination with Chen (and sometimes the other Li patent) for obviousness challenges under 35 U.S.C. § 103 against claims 1-13 of US8724622. Without a full side-by-side comparison of each claim element of US8724622 against the disclosure of US 6,298,392, a conclusive determination of § 102 anticipation by this single reference is not possible. Nevertheless, its repeated use in invalidating arguments highlights its significant teaching on voice messaging and call routing within a network environment.

These three references were crucial in the PTAB proceedings where all claims (1-13) of US8724622 were found unpatentable as obvious. [cite: US8724622B2] While the PTAB's findings were for obviousness (§ 103) using combinations of these references, their content is highly relevant to the novelty and inventive step of the claimed instant VoIP messaging system.