Among the major mobile carriers in Malaysia, Digi is the first mover in Voice over LTE (VoLTE) service, enabling voice calls, video calls and SMS to be handled through 4G LTE network since a few years ago, in 2016. UMobile had also followed suit in 2017.
Without VoLTE, only data is handled by 4G LTE. When the phone is calling out or receiving an incoming call while it is in 4G LTE network, it will need to temporary fall back to 3G network to handle the call, and revert back to 4G LTE network after the call hang up. The switching from 4G to 3G will take some times (can be as slow as a few seconds). You can experiment and feel the latency time by putting 2 phones together and make a call from one to another, then calculating how long you need to wait to pick up the call.
Celcom and Maxis are among the last to offer VoLTE service to their subscribers. Celcom has made available VoLTE service to selected iPhone models only in March 2020.
Now, Maxis finally also rolls out VoLTE to both Maxis postpaid and Hotlink postpaid subscribers who use selected iPhone and Android phones that support VoLTE function. Currently supported brands include iPhone, Huawei, Samsung, Xiaomi, Oppo, ZTE, and Vivo.
VoLTE enables much faster call connection, since both of the connecting phones no longer need to fall back to 3G network to establish the call.
The voice quality will also improved by making good use of LTE higher bandwidth. If the caller and recipient phones are both using VoLTE, the call can be established with High Definition (HD) voice quality.
When you are on VoLTE call, switching between voice and voice call is possible. Your Internet activities and data transfer also won't be affected during the call, unlike the previous GSM call that will pause your Internet activities during a call.
Note that your phone needs to be within the coverage of 4G LTE network in order to enjoy the benefit of using VoLTE. If the phone is connected with 3G network, its call will still be using the traditional GSM method.