The bandwidth required varies with the codec used. You may check your PBX configuration or hardware provider on which codec you are using for connecting to Hoiio SIP server. The values below are estimated per concurrent voice call.

  • G.729: 24Kbps upstream; 24 Kbps downstream
  • GSM: 29 Kbps upstream; 29  Kbps downstream
  • G.711: 80 Kbps upstream; 80 Kbps downstream

The values above are for 1 concurrent voice call. Multiply the values above for each concurrent call you are expecting to estimate your bandwidth required. For example, G.711 codec for 10 concurrent calls, bandwidth required = (80 x 10) = 800 Kbps upstream and downstream.

If bandwidth is insufficient, voice quality will degrade. If you are expecting poor voice quality, please check through the following possible reasons:

Find out your connection quality to Hoiio SIP Server.

Monster eats up internet bandwidth, leaving none for the IP-Phones.

Are you sharing the internet?

This is the most common reason for poor voice quality with SIP. If the internet used by the PBX or IP-phones is shared with other computers or machines, the quality drops significantly when these machines are active. Even though you may have very high internet connection speed, a single machine downloading or uploading data on the internet could use up all the bandwidth. This is because most routers distribute bandwidth in a free-for-all manner.

To detect whether your network is experiencing this problem, try turning off all other machines while you make test calls to see if there're improvements to the voice quality.

The best way to resolve this problem is to set QoS on you router. Allocate and reserve bandwidth to you PBX or IP-Phones. Please refer to your router manual about setting QoS. Alternatively, you might need to purchase dedicated internet access for your PBX or IP-Phones, separate from your usual computer networks.

Is your internet connection asymmetric?

You will need equally high bandwidth upstream and downstream for good SIP connections. Your internet connection with your internet provide could be asymmetric. Meaning, your internet connection could be rated, for example 2 Mbps, but you could be getting 2 Mbps downstream and only 128 kbps upstream. Asymmetric internet connection is common in ADSL connections. Please check with your internet provider.

Are you located outside Singapore?

Hoiio SIP servers are located in Singapore. Most internet providers offer overseas connection speed much lower than your rated internet connection speed. For example, a 2 Mbps connection may only connects with 200 Kbps outside your country. Please check with your internet provider. You may also perform a speed test to a Singapore server from

Is your internet speed just enough?

Actual internet connection speed is usually lower than the rated connection speed offered by the internet providers. You should estimate your actual connect speed about 10% lower than the rated speed.