{HEAD ~ A cross layer optimization} is presented between {TAIL ~ the MAC} and Network layers to enhance the performance of VoIP services in advanced wireless networks 
is presented between
{ HEAD ~ A cross layer optimization } is presented between { TAIL ~ the MAC } and Network layers to enhance the performance of VoIP services in advanced wireless networks
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH