Analog sensor data interference

Hello.
I’m designing wireless sensor data network using Xbee in API mode.
http://byungjun.pe.kr/xe/?document_srl=21079
MCU gets analog reading of Accelerometer then Xbee sends out to the host.
Analog sensor data gets extremely jittery(almost 1V) as soon as I power Xbee.
and It gets more jittery when I turn on other wireless sensor module.
could you help me solving this problem?

Thank you in advance,

jun