SHANGHAI, Jan 4 (Reuters) - China Mobile Ltd will start trading in Shanghai on Wednesday after raising 48.7 billion yuan ($7.7 billion) in China"s biggest public share offering in a decade. China Mobile"s Shanghai debut will be closely watched as an increasing number of companies including BeiGene Ltd have fallen below their offering prices on debut in China. The world"s largest mobile network operator by total subscribers, China Mobile sold 845.7 million shares at 57.58 yuan ($9.06) each in Shanghai, the company said in an exchange filing on Tuesday announcing the debut date. The company"s Hong Kong-listed shares (0941.HK) ended at HK$47.1 ($6.04) on Monday, representing a 33% discount to its Shanghai offering price. The size of China Mobile"s share sale would be expanded to 56 billion yuan if an over-allotment option is fully exercised, making the public offering China"s fifth-biggest on record, according to Refinitiv data. China Mobile"s smaller state-owned rivals, China Telecom and China Unicom (0762.HK), are already listed in China. The three were delisted from the New York stock exchange after a Trump-era decision to restrict investment in Chinese technology firms, amid continuing tensions between Washington and Beijing. read more China Mobile said proceeds from the offering would be used to develop projects including premium 5G networks, infrastructure for cloud resources and intelligent ecosystems. ($1 = 6.3521 yuan) ($1 = 7.7981 Hong Kong dollars)