Mobile-phone network operator Vodafone was weighing on the mobile telecommunications sector on Tuesday after the stock was hit by a downgrade from Berstein.The US broker cut its rating for Vodafone from 'market perform' to 'underperform' and reduced its target price from 170p to 135p, citing concerns about the company's troubles in Europe."Vodafone's European operations are in structural decline - in the oversupplied and commoditised business of European wireless Vodafone is neither the lowest-cost provider nor a differentiated operator," Berstein analyst Robin Bienenstock said.He said that the firm's European assets, which make up two fifths of group operating profit, could shrink by 23% in the next three years.Shares were down 2.29% at 162.98p before the end of trade on Tuesday, close to a three-week low.Top performing sectors so far todayAerospace and Defence 4,331.04 +2.34%Chemicals 9,212.80 +1.91%Life Insurance 5,478.38 +1.82%Software & Computer Services 1,051.83 +1.81%Insurance (non-life) 1,777.65 +1.66%Bottom performing sectors so far todayMobile Telecommunications 3,830.38 -1.94%BC