Adaptive channel reservation scheme for soft handoff in DS-CDMAcellular systems

摘要

Soft handoff techniques in direct-sequence code-divisionnmultiple-access (DS-CDMA) systems provide mobile calls with seamlessnconnections between adjacent cells. Channel reservation schemes are usednto give high priority to more important soft handoff attempts over newncall attempts. However, since the number of soft handoff attempts variesnaccording to environmental conditions, fixed reservation schemes fornhandoff attempts can be inefficient. An adaptive channel reservationnscheme is herein proposed to control the size of reservation capacitynaccording to varying the number of soft handoff attempts. The proposednscheme also includes a balancing procedure between soft handoff failurenand new call blocking to maximize the system capacity. To evaluate thenperformance of the proposed scheme, a Markovian model is developed thatnconsiders the interference-limited capacity effect of DS-CDMA systems.nThe analytical result shows that the proposed scheme yields anconsiderable enhancement in terms of new call blocking and soft handoffnfailure probabilities when compared with the conventional fixed channelnreservation scheme