The project is being undertaken by the City in partnership with Wi-Fi firm The Cloud which will install and manage the network.
Expected to go live in the next few months, with virtually all the City covered within six months, the Wi-Fi network will be installed in existing street furniture including lamp posts and street signs.
The network will allow City workers and visitors with Wi-Fi enabled devices to access the internet on streets and in open spaces.
Supported applications include high speed internet access, email, music, video and other entertainment services, and voice over Wi-Fi services.
The network is also designed to support secure access and private data networks for the emergency services and other public services customers in the City.
Michael Snyder, chairman of the City of London's Policy Committee, said: " City workers and visitors will be able to use wireless broadband to work more efficiently and to stay in touch with their office via handheld devices while on the move.
"The City is a fast moving and dynamic environment and we are responding to the increasing time pressures faced by City workers by providing the technology for them to stay up to date wherever they are in the City."
George Polk, chief executive at The Cloud, added: "Corporate users are increasingly turning to Wi-Fi for a range of services, including converged voice services.
"We have strong demand from existing customers for coverage in high density and high profile locations like the City of London, and we expect this trend to continue."
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