As we undertake challenging technical research and prior-art search projects related to 5G and telecom SEPs, we often come across certain scenarios that leave an indelible impression. One such scenario was when we were assigned to work on an invalidation case related to 5G technology and the client’s aim was to find the closest prior art for a certain patent.

The technology of the patent in question was related to numerology. When conducting prior-art searches, before jumping on the searching part, it is very crucial to understand the true essence behind the patent and to know the key inventors, assignees, important classifications and keywords related to the patent. In the absence of efficient execution of the above step, a prior-art search can be a very daunting task.

Our first step was to dig deep into the technology to understand the concept behind the patent. In 5G, numerology is defined as Subcarrier Spacing. Although the concept of numerology or sub-carrier spacing was present in 4G, however, there was only one type of subcarrier spacing or numerology in 4G, whereas, in 5G, multiple types of numerology or subcarrier spacings are available.

After understanding the subject patent, we analyzed the prosecution history of the target patent and focused on the following novel elements of the independent claim:

1. A numerology design in which a slot comprising the first numerology (e.g., A) and second numerology (e.g., B) such that a symbol length of each symbol of the first numerology (e.g., X) is equal to a sum of symbol lengths of two or more corresponding symbols (e.g., Y and Z) of the second numerology.

2. A symbol of the first numerology or second numerology has a symbol length different from a symbol length of other symbols of the same numerology.

We then started with the search by performing our first search strategy - spider search (i.e., forward and backward citation search), however, nothing fruitful could be identified. Thereafter, we checked the 3GPP domain by exploring meetings related to numerology (3GPP meeting search plays a prominent role in projects related to patents on wireless communication, there are a lot of chances to get a promising art during meeting search and hence, it should be one of the top strategies). Here, we came across a few 3GPP meeting drafts/documents which could be considered as a possible lead. However, in this case, the potential reference (R1-164692) which we came across, was published 5 days after the priority date of the subject patent (i.e., the cut-off date of the search).

The lead we got from the 3GPP meeting search opened up one more possibility of locating prior-art in the 3GPP email discussions (i.e., 3GPP Email List Server) just prior to the cut-off date. However, nothing relevant turned up in our examination.

Moving on to our next step, we started exploring patents by using all search strategies such as keywords, CPC, IPC, US & F-term (native Japanese classes) classification search, inventor- and assignee-based search. The motive was to identify a prior-art document published before the cut-off date. However, even the patent search did not relent in a useful result.

Time was ticking away and gradually we were approaching our target date of submission to our Client. We still were left with some patent references having only a priority date before the cut-off date - however, they were filed/published later.

We scrutinized them one by one in-depth to identify the novel aspect and finally, we came across a patent (US20160352551A1) that disclosed the same concept disclosed by the subject patent and also depicted in the identified meeting document (R1-164692).

The identified reference had four priority documents wherein, the two priority documents were filed before the priority date of the subject patent. However, the relevant text was missing in these two priority documents. We carefully analyzed every word of these two priority documents to locate the novel element of the target patent.

Finally, we come across a table given below in which different subcarriers were disclosed:
Now, let’s see how the given table had disclosed the two novel elements of the subject patent:

1. The symbol length of the first numerology is equal to the sum of the symbol length of two symbols of the second numerology:
The “type 1 OFDM symbols" or "type 2 OFDM symbols" in table 1 provide the symbol duration corresponding to each sub-carrier spacing. For example, the symbol duration of "type 1 OFDM symbol" for the first sub-carrier spacing (i.e., 3.75 kHz) is 287.50 which is equal to the sum of the symbol duration of two symbols of "type 1 OFDM symbol" for the second sub-carrier spacing (i.e.,7.5 KHz) wherein, the symbol duration of type 1 OFDM symbol for second sub-carrier spacing is 143.75.



2. A symbol of the first numerology or second numerology has a symbol length different from a symbol length of other symbols of the same numerology:
In table 1 the notation 7(1,6) corresponding to "# per symbol TTI" indicates that each subcarrier-spacing or numerology comprises 7 OFDM symbols wherein the "6 OFDM symbols" are of " type 2 " and "1 OFDM symbol" is of "type 1". Further, the first column of Table 1, it is given that the value of "type 1 OFDM symbol(us) (1)+ (3)" (287.50) is different as compared to symbol length of "type 2 OFDM symbol (us) (2) + (3)" (285.42) for first numerology (i.e. 3.75 kHz). It indicates that the symbol length of "type 1 OFDM symbol" is different from "type 2 OFDM symbol" wherein there is only one "type 1 OFDM symbol" and the other six symbols are “type 2 OFDM symbol".

Voila! Finally, we got what we are looking for!! Our client was thrilled and the feedback we received was brilliant.

Conclusion

For us, prior-art searching is an art that requires continuous innovation of processes and skills. Based on our experience related to this case, we have observed that it is important to thoroughly analyze each and every facet of a reference. We shouldn’t simply skip a priority document just because the corresponding patent doesn’t contain the relevant text and figures that we are looking for. Rather, it is important to analyze such priority documents carefully, there may be chances that we locate prior-art among the text, tables or figures given in a priority document.

Note : Our experts at Expertlancing employ proven and innovative processes to locate killer prior-art for all kinds of prior-art searches. Please reach out to us for more information.