Shares in CAI Wireless Systems Inc rose over 30% yesterday on excitement over its wireless Internet access plans, soarding $17.50 at one point, 35% up on the day and almost double its value since it announced last Thursday that it would begin offering high-speed wireless Internet access by the end of the year. CAI wants to launch its Internet service, which it is trialling in Washington, DC, in the Northeast this fall and is using Hybrid modems. Bell Atlantic, which, along with Nynex Corp owns 45% of CAI, plans to deliver video services through the wireless system the first quarter of 1997.