Femtocell synchronization is disclosed, in which a femtocell transmits a request over an out-of-band (OOB) link to a proximate mobile device for synchronization assistance. In response to the request, the mobile device transmits an access probe to a serving macro base station. The femtocell detects the access probe and uses aiding information to decode the access probe to determine the timing and/or frequency information. The femtocell uses this timing and/or frequency information for its synchronization.