Capacity increases and call dropping probability decreases in a 3G cell with embedded WLAN(s) (i.e., mixed cell). Two factors reduce the 3G traffic. One, users initiate new calls through WLANs and two, ongoing sessions are handed over from 3G to WLAN. As a result, call blocking probability in 3G system decreases and overall system capacity increases with increasing WLAN coverage. It is observed that call dropping rate in an entire mixed cell decreases as long as the call blocking probability in WLAN remains less than that in the 3G system. But new call arrival rate in WLAN also increases with increasing call intercepting (CI) probability of WLAN (i.e., probability with which WLAN shares a call in a mixed cell). Thus call blocking probability in WLAN increases. At higher values of CI probability, the blocking probability of WLAN becomes more than that in the 3G system duo to rise in new calls. At this juncture, call dropping rate increases with increasing CI probability. We propose an efficient take-back call admission control (TB-CAC) scheme in which a mobile station always prefers to access WLAN and the blocked calls of WLAN are immediately taken back by 3G systems. Proposed TB-CAC scheme shows considerable improvement of call dropping rate under increasing CI probability of WLAN.
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|Journal||Data powered by TypesetCommunications in Computer and Information Science Global Trends in Computing and Communication Systems|
|Publisher||Data powered by TypesetSpringer Berlin Heidelberg|