When looking at a streaming WiFi audio system, there are several potential bandwidth bottlenecks.
- The Ethernet Switch
- The Venue Server
- The Wi-Fi Access Points
- IP Address space
In our last technical blog, here, we looked at the Wi-Fi access points. Access points must be added to reach the total number of clients (smart phones and tablets) that will be listening at one time.
Doing some quick calculations on data rates and bandwidth, assume 150 kbps for the communication to each phone and a 50% load capacity on the Ethernet, then 100 baseT (100 MHz) Ethernet can support about 300 phones and Gigabit Ethernet can support about 3000 phones, assuming no other significant traffic. It would presumably be best to use a cut-through switch for minimum latency, but as a practical matter, no one does this because of the cost.
ExXothermic has designed a range of systems that can handle different number of clients depending on the processor and network interface, starting with 150 client phones for the most basic offering.
Finally, one does need to get enough IP address space in the network so that each phone can grab one from DHCP. The usual netmask of 255.255.255.0, for instance, only provides for about 250 addresses. And don’t forget about the impact of DHCP lease times (we recommend 120 minutes). An IP address for a phone that has left the building cannot be reused until it is released.
The proper system deployment considers all of these potential bottlenecks.