Which Header is Compressed in VoLTE Call?
In VoLTE (Voice over LTE) calls, one key feature that enhances the efficiency of communication is header compression. This technique is crucial for reducing the overhead and ensuring that the call remains efficient, even in terms of data usage. Let’s break down how it works and which headers are compressed during a VoLTE call.
As we learned in previous articles, LTE networks are designed to handle both data and voice services. However, the challenge with voice calls over an IP-based network (such as LTE) is that there are several protocol headers that could increase the overhead of each voice packet, thus reducing overall network efficiency. To overcome this, header compression is employed.
In VoLTE, the main headers that are compressed are part of the signaling used for the establishment, maintenance, and termination of the call. These headers belong to different protocols used in the call setup process, which includes:
- RTP (Real-Time Protocol) Header: This header is used to manage the voice stream once the call is active. Compressing the RTP header helps reduce the size of each voice packet transmitted over the network, improving bandwidth utilization.
- RTCP (Real-Time Control Protocol) Header: This header works alongside RTP to monitor call quality. Like the RTP header, the RTCP header is also compressed to minimize overhead and improve call quality.
- IP/UDP Headers: In VoLTE, both the IP and UDP headers are compressed. These headers help route and deliver the data packets between the devices involved in the call. By compressing these headers, VoLTE ensures that only essential information is transmitted, improving the efficiency of the communication.
- Signaling Protocol Headers (SIP): SIP (Session Initiation Protocol) is used for initiating and managing the call. Compressing SIP headers is crucial to maintaining low latency and efficient signaling during the call setup process.
To achieve this compression, VoLTE uses a standard known as RoHC (Robust Header Compression). RoHC is a compression scheme designed specifically for real-time applications like VoLTE, ensuring that only the necessary parts of the headers are sent, while still allowing the receiver to reconstruct the original information when necessary.
By applying header compression to these protocols, VoLTE ensures that voice calls consume less bandwidth and experience lower latency. This ultimately leads to a better user experience, especially in congested network environments. The key advantage of this compression is that it reduces the amount of data needed to maintain the call, which allows more efficient use of available resources.
So, when you make a VoLTE call, the system uses header compression on RTP, RTCP, SIP, and IP/UDP headers to make the communication as efficient as possible, ensuring high-quality voice service with minimal network impact. This optimization is one of the factors that help VoLTE deliver superior voice quality over LTE compared to traditional 2G or 3G voice calls.