BLE pheripheral not detected when ios app on background

i am develop a ble based iOS application on iOS 8.0. i have a peripheral device, that advertise data . am just open my application , the scanning started on viewdidload. then it detect the peripheral and listed in a table view. it is working fine. but when am switch off the peripheral device, after am start the iOS app, scanning started on didload, and am pressed center key, then app going to background. after am just switch on peripheral device. but it could not detect the device.

(current situation, am switch off and on the bluetooth of an iOS device manually. then background app detected the peripheral and got notification message.)

what is the actual problem with my app? and if any solutions?