In spite of a number of headwinds facing Vodafone, JPMorgan Cazenove has retained an 'overweight' stance on the stock, saying it still expects a return to revenue growth at the telecoms group in the second half of 2015.The shares have underperformed the wider FTSE and telecoms sector by 5% and 15% respectively so far this year due to concerns about euro weakness and uncertainties relating to the Indian spectrum auction.JPMorgan said Vodafone is "meaningfully exposed" to the euro given that 52% of group earnings are euro-denominated. The single currency has weakened 10% against the pound year-to-date, though the negative impact is mitigated by the fact that 68% of group gross debt is euro-denominated.Meanwhile, prices are rising in the Indian spectrum auction, while revenue growth could be dampened in the country by recent mobile termination rate cuts, lower roaming rate caps and tax hikes."Whilst these overhangs may persist short term, April should see attention refocus onto the full-year results and Vodafone's improving European outlook," said JPMorgan analyst Akhil Dattani."Crucially we anticipate ongoing sequential improvements in organic revenue growth, with this largely predicated on Southern Europe, and believe this should enable Vodafone to return to growth in H2, supporting a material multiple re-rating."JPMorgan kept a 265p target price for the stock, which was up 1.2% at 221.46p by 11:02.