| 摘要 |
A dual-band wireless subscriber unit (SU) ( 112 ) having an enterprise address of E 1 and a cellular address of C 1 , corresponding method ( 200 ), software program ( 310-320 ), and WLAN ( 104 ) determines ( 202 ) that the SU is about to leave a wireless local area network (WLAN) ( 104 ). In response, when the SU is involved in a call on E 1 , the SU sends ( 212, 208 ) to the WLAN a SIP message, for example a Refer message with a "Refer To" field of C 1 if an ongoing call or a SIP Redirect message with a contact address of C 1 if a new call is attempting to begin on E 1 . In response to receiving either message, the WLAN seamlessly transfers ( 210, 214 ) the call to C 1.
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