We Found Prior Art for a 4G Telecom patent using Link Adaptation Concept from 90s.
In the first season of the series The Terror, two ships carrying 129 men venture into the unmapped icy waters of the Arctic. Their aim is to find the fabled, shortcut sea route to Asia called The Northwest Passage. When they are deep into the sea, however, the weather turns unfavorable on them. The ocean starts freezing. Sir John Franklin, the captain, has to make a difficult choice. He can either turn back or wait 8 months for the next summer stuck on the frozen sea.
Grand sea expeditions have little in common with patent invalidation searches, but they do require the same mindset as would be required to find unknown sea routes. Without a map, firstly, you need to strongly believe that a prior-art does exist and that you can find it, and secondly, you must be good at finding subtle clues and acting on them.
When prior art search gets tough, you may end up spending weeks after weeks, pursuing lead after lead, and still, nothing might turn up. It is in those moments that you are faced with a similar “should I give up or should I keep going” kind of choice that Sir Franklin faced while searching for the elusive passage.
A while ago, I worked with my team on a similar search – It was an invalidation search for a telecom patent that applied to a 4G mobile phone and described a special way of encoding the signal strength data. This type of encoding used fewer bits, hence saved bandwidth.
Every technology domain has one source that is a gold mine of prior art. For telecom, it is 3GPP. 3GPP is the organization that made the 3G and 4G standards. It is also the one that is now defining 5G. We love 3GPP because it makes all its documents freely available and is our first choice while working on telecom patents. In this case, however, we didn’t have much luck there because this patent was filed in the early 2000s. 3GPP was young back then and didn’t have much literature.
So we turned our search towards patents. We searched far and wide, but to no avail. We searched in research papers and Ph.D. thesis and sort of boiled the ocean but found no killer prior-art. We searched in books, in libraries, in product manuals, and all other places we knew about, yet the kind of reference we were looking for did not appear. I think this was the point where most researchers would shrug and say, “Well, this patent seems legit. There is no prior-art!”
I had a taste of it early on when I joined GreyB in 2014. Whenever I used to tell my mentors that I couldn’t find prior art, it seems it doesn’t exist, I would be told something on the lines of:
“That does not mean that the prior-art does not exist. It means it exists in a place where you haven’t looked. How about search in databases X, Y, Z…? Have you used keywords like A, B, C…?”
Honestly, this annoyed me. So much that instead of seeking my mentor’s advice I’d often just keep searching in some more X, Y, Z databases with some more A, B, C keywords. It didn’t always work, but a couple of times I found perfect prior art even after having given up all hope. That was surprising.
Slowly it dawned on me that when it comes to prior art search, the absence of evidence is not evidence of absence. The first requisite is that you must believe that it exists. This belief keeps the intensity of the search from going down.
Coming back to the case, despite many failures, we didn’t give up. Instead, we decided to find and scan every document discussing signal strength encoding in every wireless protocol conceived before the cut-off date.
It was a hard job because –
- (a) standard drafts from the ’90s are not readily available, and
- (b) the standard terminologies differed a lot (e.g., in 4G only, signal strength can be: channel quality, channel state, channel characteristics, CQI, CSI, RI, PMI, etc.).
TBH, We were at our wits’ end.
Fortunately, we found a very popular term that researchers used in the ‘90s to refer to this concept: link adaptation. Using this term, we found a lot of documents on the topic relatively quickly and then started studying them.
While WiFi, WiMax, HiperLAN, GSM, EVDO, and ITU standards didn’t give us much, the EDGE standard (aka 2.5G) caught our attention. One draft had a section that seemed related to our concept. Though some details were missing it referred to two other EDGE specifications like a jigsaw puzzle. When those documents were put together and their information combined, they seemed to describe the same encoding that we were looking for.
This standard used obscure and unintuitive terms like RXLEV, I_LEVEL, C_VALUE to describe this encoding which made it super hard to discover. But with grit and intelligence, we got through the unfavorable weather – unlike the damned expedition – and found our path ahead.
Here at GreyB, we are not afraid to experiment with the unknown and often climb insurmountable heights and dive the deepest metaphorical oceans in the search of prior-art. Have I told you that we hate giving up? Because we do. Love our thought process and think we can help you find just the right prior art? Because we really can. To get started, send us an email here with your requirements and we will get back to you within no time.
To success, yours and ours!
Authored by: Mahesh Maan, Search Team.
Related Read: Heard a ton about using unconventional approaches for invalidation, but never saw them at work? Finally, you can. I give you not one or two, but four unconventional approaches that we used to invalidate patents. Click on the post below to read.