FIBRE broadband will be rolled out to around 98% of West Sussex homes and businesses within three years.
A new fibre network will transform broadband speeds across the county and its rural areas, said West Sussex County Council.
The deal follows a multi-million partnership project between West Sussex County Council and BT , whose Openreach engineers will build the new fibre infrastructure..
The Better Connected West Sussex Broadband project builds on BT's on-going commercial fibre deployment across the count
It will provide broadband infrastructure to over 44,000 premises with superfast speeds of at least 24Mbps by the start of Spring 2016.
On completion of the rollout, the aim is for all premises within West Sussex to receive a minimum of 2Mbps but with a vast majority achieving speeds well in excess of this.
According to Ofcom, the county's average downstream speed is currently 11.7Mbps while 9.7% of premises receive less than 2Mbps.
BT is contributing £7.6m towards the overall cost of deployment in "non-commercial" areas while West Sussex County Council is contributing £6.26m.
Some £6.26m coming from the Government's Broadband Delivery UK (BDUK) funds.
Council leader Louise Goldsmith said the arrangement would significantly increase the county's opportunity to grow its economy, and help residents to enjoy the benefits of being online.
"West Sussex County Council is very aware of the problems that slow speeds or in some cases, no broadband at all can cause local businesses and people working and running businesses from home.
"This was a key rationale behind the Council's decision to invest more than £6 million to provide more access to better, faster broadband across the county.
"We are now looking to BT, having won the contract, to deliver services to those areas which we know are without."
Fibre to the Cabinet will be the main technology deployed.
This can deliver wholesale downstream speeds of over 24Mbps (and in some cases up to 80Mbps), and upstream speeds of up to 20Mbps.
Fibre to the Premises technology – delivering ultra-fast wholesale speeds of up to 330Mbps – will also be deployed in certain areas.
It will also be available on demand throughout the whole of the fibre footprint should local businesses want the ultra-fast speeds it offers.
Bill Murphy, BT managing director for Next Generation Access, said: "The county is mainly rural and over half of it lies in Areas of Outstanding Natural Beauty.
"There is a need to balance new development and infrastructure needed by communities to reduce congestion and support a vibrant local economy while maintaining the character of the county.
"This is where fibre broadband can play a key role, for example, by revitalising small towns, villages and hamlets by making it possible to start and run a connected business from these locations."
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