Ocu-Sync is a really good version of Lightbridge, very true. The integrity of the signal is strong and consistent, meaning the degradation of the signal is gradual with distance. Ocu-Sync also has something very unique, which other Lightbridge implementation don't. This is the ability to have multiple wireless receivers receive the video signal from the craft. No other DJI Lightbridge implementation can do that. DJI makes (but doesn't sell) a product called RoboMaster. It's a wall powered stand-alone Ocu-Sync receiver that can be linked to the craft that will decode the video stream from the craft and send the 720 resolution video out an HDMI port to a TV, as a second video display, separate from the iPad which is connected to the RC. This receiver can be a mile away from the RC, because it's a wireless connection DIRECT to the craft. This is the same principle as using DJI googles as a second display, linked directly to the craft. The video signal does NOT go through the controller, like Inspire for the second controller view. I hope, and expect Ocu-Sync will be implemented in a P5 design, hopefully coming out this year. DJI would be fools not to use Ocu-Sync in a P5, for compatibility with their DJI goggles. Then maybe they'll start selling RoboMaster, demonstrated at CES2016 with Mavic in the DJI flight cage.
Trivia to know: WiFi implementations (P3SE, Spark, Mavic Air, Yuneec and GoPro craft) that use TCP/IP protocol in their communications cannot connect to multiple clients from the craft like Ocu-Sync. WiFi is point to point only, without a router to help.
The P4 craft does not exhibit this same stable signal behavior as Ocu-Sync. The P4 controller (GL300C) has a control signal that's very fragile as you mention, signals can come and go spontaneously. This can be mitigated by using a GL658A Inspire controller with the P4, as I have been doing for the last 20 months.
The
P4P is a yet another implementation of Lightbridge, adding 5.8Ghz to the options when flying. It's been established that 5.8Ghz AUTO is the best connection for the
P4P with range of 4 to 5 mile in urban areas! I believe this works so well because there is less usage of 5.8Ghz WiFi in homes and businesses, and even then, if it is used, 5.8Ghz doesn't go through walls as easy as 2.4Ghz, keeping the flight area more clear of 5.8Ghz WiFi interference. My
P4P flies 3 to 4mi away from home point all the time, it's a beast for range IMO. I never fly 2.4Ghz unless someone near me is flying 5.8Ghz, so I'll yield that band to the other pilot as long as I'm not flying too far away. Flying on different bands is good practice if there's only two flying near each other, which helps mitigate interference. I use a stock GL300F with my
P4P and it exhibits good signal integrity, a stable signal
almost as good a Ocu-Sync. I'll use a windsurfer when I plan to fly more than 2 miles away. The
P4P is an incredible craft IMO, I'm pretty happy with it's capabilities, especially the new found freedoms of 1.3.509 craft firmware. It's my go to craft for most flights. Although my Mavic has great range and flight time, it gets neglected, mostly because of the lesser camera.