LTE was designed for data only. Everything is IP packets.
So how do you make voice calls?
The Old Way: Fall Back to 3G
When LTE first launched, phones had to drop to 3G to make calls.
This is called CSFB (Circuit-Switched Fallback).
Problems:
- Takes 5-7 seconds to switch networks
- You lose LTE data during the call
- What happens when carriers shut down 3G?
CSFB was always a temporary fix.
The Solution: VoLTE
VoLTE = Voice over LTE = Send voice as data packets.
Instead of falling back to 3G, just treat voice like any other data.
Your voice becomes IP packets, sent over LTE, just like a web page or video.
No fallback. No switching. Just data.
Why VoLTE is Better
| CSFB (Old) | VoLTE | |
|---|---|---|
| Call setup | 5-7 seconds | Under 1 second |
| Voice quality | Narrowband | HD Voice |
| Data during call | No | Yes |
| Future-proof | Dies with 3G | Long-term |
QoS: Priority for Voice
Voice packets can’t wait behind someone’s Netflix stream.
LTE creates a dedicated bearer (a priority lane) for voice:
- Guaranteed bandwidth
- Low latency
- No waiting
Voice gets VIP treatment.
Think of it like a fast lane on a highway.
HD Voice
Old calls: Narrowband (300 - 3,400 Hz) - sounds muffled
VoLTE: Wideband (50 - 7,000 Hz) - clear and rich
More frequencies = better sound quality.
Like upgrading from AM radio to FM.
Summary
| Concept | Key Point |
|---|---|
| CSFB | Fall back to 3G for calls (old way) |
| VoLTE | Voice as IP packets over LTE |
| QoS | Priority lane for voice packets |
| HD Voice | Better audio with wideband codec |
VoLTE = voice is just data, with VIP treatment.