Mobile phone users on 4G plans will soon enjoy clearer phone calls and faster call connection times - though the number of supporting handsets could be limited, initially.
On Monday, SingTel announced it will roll out its 4G ClearVoice service from May 31, allowing users to make calls over SingTel's 4G network.
At the same time, StarHub announced it would launch its 4G call service "in the coming weeks", while M1 is planning a launch in the second half of the year.
SingTel said the service will be free for its existing 4G customers and assured them that 4G calls will use a mobile plan's existing talk time and not eat into data bundles.
However only the Galaxy Note 3 handset will support 4G calls initially, with other popular 4G phones - such as Android, iOS and Windows Phone handsets - expected to get a software update for the service in the coming months.
Currently, calls made by 4G customers are still on 3G networks. But when they are moved to 4G networks, the call quality is said to be much clearer because a lot of background noise is eliminated. Call connection times on 4G calls are also faster at one to two seconds, instead of six to seven seconds for 3G.
But if a call is made to someone without support for 4G calls - such as a 3G user or, for now, a subscriber from another telco - the call quality and connection time drops back to 3G.
As revenue from voice calls and text messages dips, experts said 4G calls could be a way for telcos to encourage subscribers to make voice calls instead of using chat apps that send messages online.
Mr Michael Stephens, from United States-based telecoms equipment-maker Coriant, said: "It could be a way for operators to justify a premium for voice services based on improved voice quality."