Australian operators Vodafone Hutchison Australia (VHA) and Optus are set to expand their network joint venture, to provide improved 3G and 4G coverage for consumers in the country.

Subject to approval from the Australian Competition and Consumer Commission, the alliance will “accelerate the delivery of improved 3G and new 4G services to customers by 12–18 months by using existing mobile sites.”

According to a VHA statement, the deal will see it accessing around 400 existing Optus sites, with the two companies also building 500 new, shared sites, over the next four years.

It also includes provision for Optus to be VHA’s national roaming partner for a period of five years from 2013.

Areas which will see improved coverage include Sydney, Melbourne, Brisbane, Adelaide, Perth, Gold Coast and Canberra.

VHA has suffered from the impact of a poor network performance in recent years, leading it to invest heavily to improve its infrastructure. In a statement, Bill Morrow, its chief executive, said the company has invested “more than AU$1 billion” in its network, including the implementation of an 850MHz 3G layer.

Vodafone announced the end of a network sharing agreement with Telstra, Australia’s biggest operator, in 2010.

Earlier this week, Optus announced plans to cut around 750 jobs, as part of a move to a “more streamlined and centralised structure.”