While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Nokia Corporation (NOK -0.27%) rallied 3% this morning after Jefferies upgraded the communications equipment giant from hold to buy.

So what: Along with the upgrade, analyst Lee Simpson raised his price target to 7.41 euros (from 5.34 euros), representing about 35% worth of upside to yesterday's close. So while momentum traders might be turned off by Nokia's price sluggishness in recent months, Simpson's call could reflect a sense on Wall Street that its intellectual property is just too cheap to pass up.

Now what: According to Jefferies, Nokia's risk/reward trade-off is rather attractive at this point. "Although the rerate in Technologies sales is further out (2014+) and HERE appears to need a new round of investment, we think the story on Nokia is a very promising one (future IPR potential, focused infrastructure play) with the math on IPR royalties offering an intriguing value upside," said Simpson. "Our expectation is that the firm, now shorn of its handset business, can charge an average royalty rate of 1.4-1.5% for essential patents alone." With Nokia shares now up about 120% over their 52-week lows and trading at a forward P/E of 20, however, I'd hold out for a wider margin of safety before betting on it.