You can adjust the camera frame rate and, if needed resolution to meet the bandwidth you have. For example, a 3MP cam at 30FPs takes ~10Mbps, but 15FPS takes half that. Personally I have some of my cams set to 20FPS. Worst case you cut back the resolution to something like 1080P.

Not to throw a curve-ball, but many of the 4MP cams do H.264+ codec as well as H.264. While H.264 is good, the newer h.264+ reduces bandwidth by about 50%. (the future protocol is H.265 but in the meantime h.264+ codec is the in-between codec). Cams that can do h.264+ can also do h.264 for compatibility. http://overseas.hikvision.com/en/Press-Release-details_79_i1022.html

https://www.securitymagazine.com/ext/resources/whitepapers/Hikvision-H264-Encoding-Technology.pdf

If you have an extra $150, a pair of Ubiquiti Nanostation NSM5 will give you up a 150 Mbps wireless link. (these can also go 5 miles!). https://www.amazon.com/Ubiquiti-Nanostation-NSM5-802-11a-Hi-power/dp/B00HXT8KJ4