RoHC for VoLTE and Cell Coverage

4G LTE
,
1

Hello mates,

When i have a look of Robust Header Compression feature. The main purpose of RoHC is to compress the headers of primarily radio bearers carrying VoIP calls in order to increase capacity and it seems coverage ?

When i read about this feature it is said one of the benefit is " increases the cell coverage when segmentation occurs during H-ARQ retransmissions.

Here is my question :

I understand RoHC increase the capacity but why the cell coverage exactly ?
Why by reducing the size of a VoIP packet this will increase cell coverage ?

Thanks in advance for your feedback.

Regards,

2

Great question! The key to understanding why Robust Header Compression (RoHC) improves cell coverage lies in its impact on HARQ retransmissions and signal-to-noise ratio (SNR).

1. Understanding the impact of packet size on retransmissions

  • In wireless networks, HARQ (Hybrid Automatic Repeat reQuest) is used to handle errors in transmission.
  • If a packet is too large, it may need to be segmented before transmission.
  • When a segment of a packet gets lost due to poor radio conditions, the entire packet might need to be retransmitted.

2. How RoHC helps with segmentation and retransmissions

  • RoHC reduces the size of VoIP packets by compressing the header, meaning each packet is smaller.
  • Smaller packets are less likely to require segmentation.
  • If segmentation does not occur, the retransmission process via HARQ is more efficient, reducing the delay and the chances of packet loss.

3. Impact on Cell Coverage

  • In weak signal conditions (e.g., at the cell edge), a larger packet is more susceptible to errors.
  • Since RoHC reduces the packet size, it lowers the probability of errors and improves the success rate of transmissions.
  • This means fewer retransmissions, which in turn improves the effective link budget.
  • A better link budget means users can maintain a connection at a lower signal strength, effectively expanding the coverage area of the cell.

Summary

By reducing the packet size, RoHC minimizes segmentation and retransmissions, leading to a more robust link and improved cell-edge performance. This extends usable cell coverage because users at the edge can maintain VoIP calls with fewer errors and retransmissions.