ExpertLancing Blog Case Studies How analysis of post-dated documents helped in a validity search
Case Studies

How analysis of post-dated documents helped in a validity search

For any prior-art search, finding a Tier-I/Category X reference is the best thing to happen to a researcher and a client. It is always expected that a prior-art search will churn out a novelty-destroying reference and simply put the case to rest. However, this may not always be the case.
There may be searches where you may not even locate a combinational or peripheral prior art, let alone a “killer novelty-destroying” reference. In such scenarios, it is very important to provide a strategic solution to the client instead of simply concluding that ‘we did not find any result for you’. We faced a similar situation where we had no strong prior-art to showcase, continue reading to know more –

The Foundation:

One of our clients was interested in buying a patent portfolio. He contacted us for performing Due Diligence on the patent portfolio. Due diligence generally entails checking the validity of the patent – could the patent withstand invalidity assertions? Everything was going according to the plan till we picked up a certain patent (say patent P) for validity analysis.

Subject Patent:

This patent P was related to the mapping of a PHICH to a OFDM symbol. PHICH refers to Physical Hybrid Automatic Repeat Request Indicator Channel and OFDM refers to Orthogonal Frequency Division Multiplexing. The main element, or the search focus, was an equation that seemed to be used for determining indexes of the resource element groups for transmitting PHICH. Well, looking at the equation, we immediately realized that it’s going to be a tough case to crack. Just to add, the patent P already had an opposition that was rejected and the patent was intact.

Strategy & Client Interaction:

Nevertheless, we started working on the case. Our researcher did a thorough research of the patent P and confirmed the cut-off date; say date CD1, for the search by analyzing the priority document. As a practice, we also analyzed the file history of the patent P. Soon, we realized that even the examiner could not present a substantial document against the patent P to reject it or even try out a combination. Well, we already knew that this wasn’t going to be a simple case and we need to act accordingly.

So, we decided to strategize and brainstorm rather than directly starting with the search. We involved our specialized subject matter experts in the discussion to get their opinion on the case.

A set of initial strategies were formulated and, at the same time, a discussion call was set up with the client to make him aware of the search complexities.

This time, we decided to start with a specific assignee search. A list of potential assignees was fetched based on our observation of the domain and frankly speaking, the subject patent’s assignee turned out to be the most active entity in the domain.

Although, our assignee search did reveal related references, however, they were not valid as potential prior art under the subject patent’s jurisdiction law. Multiple filings from the same assignee and that too with the same inventor, and yet not being able to cover the full claimed equation, were mostly encountered. There was just an idea of the claimed concept without any explicit disclosure. It seemed that the patent universe only had the filings from our subject patent’s assignee, sitting at the top and dominating the domain.

Although, we could not locate presentable prior art in our initial strategy, it provided us with a clear picture of the search. We worked upon other strategies and were able to shortlist relevant classes and modify the set of keywords that were being used initially. We still had hope, as we were yet to explore other strategies. We decided to start with classes and also performed a dedicated inventor-based search. Again, we did not get any relevant references to our search. We sent a quick update to the client to make him aware about the search progress. As expected, after knowing the status of the search, the client was as tensed as we.

Specialized Non-Patent Search:

As a matter of fact, we were yet to explore the Non-Patent Literature, specifically, standard documents. We had seen our analysts’ turning tables with their standard searching skills. Thus, our last hope was on standard documents. When we say standard documents, we mean documents, such as, standard drafts, meeting DOCs, emails, etc.

Wasting no time, we switched to standard searching. We already had some idea of the concept being highlighted in 3GPP specifications. Thus, we started looking for the relevant standard without any date restriction.

Well, here we got the relevant standard (say, TS 36.211 v8.2.1) that was available after the subject patent’s cut-off date CD1. We then tried to trace back the standard and realized that the previous version, say TS 36.211 v8.2.0, had no indications of the required equation. It was clear that there must have been some amendment available as a CR (Change Request) that was introduced to the concept in a later version.

Committed to identifying the relevant CR, we started scanning the available meeting documents before the cut-off date of our subject patent. It was confusing to see that there was no CR describing the required concept before the cut-off date. So, we decided to try our hands on the post-dated meeting documents, and here, we came across the relevant CRs (obviously all published after the cut-off date CD1). These CRs had multiple assignees (including our subject patent assignee) mentioned as the contributors. We highlighted this fact to our client. The client now wanted us to explore all the contributors with respect to patents. Just to mention, we had already explored most of these initially, and we knew there were very few chances of locating something from these assignees. However, we decided to give it a shot, but, again, the effort did not result in any references.

The client wanted us to be absolutely sure about the validity of the patent. It was very critical as there seemed to be a lot at stake. It wasn’t clear whose contribution exactly introduced the relevant text (equation) in the standard as there were multiple contributors.

Our idea:

We knew that the only way to help our client was to showcase him as the individual who, where and when introduced the contribution for the first time. An idea struck us – if we could establish a clear relation between the subject patent inventor and the proposed text, we could solve the problem. This would mean that the subject patent was valid and it was indeed the work of the subject patent’s inventor only. 

Final Shot:

Deciding to give it one more shot, we started searching the email archives for the claimed concept. At this time, we were only coming across documents that were marginally related to the subject patent’s concepts. We narrowed down our search to documents from the subject patent’s inventor as well as removed the cut-off date filter. Eureka!

We identified the starting contribution (available just two days after the cut-off date). It was available as an attachment in the email from the subject patent’s inventor. This was part of the email-trail related to a discussion for approving the contributions without actually presenting the documents in the meetings themselves. The proposal was introduced in one of the emails of the trail, agreed upon and then included as an updated draft in the email-trail itself.


We got crystal clear evidence that it was our subject patent’s inventor who was the first to introduce the concept in the standard specifications. Promptly we highlighted this to our client. After learning about our finding, the client gained clarity about the validity of the subject patent. He was now more than sure that it will be nigh impossible to render this patent invalid. The client was thoroughly impressed with our idea of presenting the same inventor’s email to establish a clear pointer on the validity of the subject patent.

At Expertlancing, we leave no stone unturned to meet our client’s objectives – please feel free to reach out to us for more information.

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