I presume you're actually talking about throughput? Zigbee (802.15.4) is not designed for high throughput. It is designed for low power, small connected devices use. Use something else, like WiFi for PC transfers.
You can't speed up the flow of water in a tap more than fully open. Zigbee protocol can't be 'sped up'. (Again, I assume you're
actually talking about throughput).
I don't use Xbee, so I don't have a circuit for it unfortunately. However there are lots of resources on it, even youtube videos when
I googled it.