Load balancing inter-frequency handover scheme in IEEE 802.16e system

Abstract

In IEEE 802.16e system, a BS has multiple Frequency Assignment(FA). So the handover among FA is possible for load balancing theoretically when a certain FA is too crowded to accommodate additional bandwidth requests. However, it substantially had to implement with frequecy because BS cannot indicate the target FA through the handover request message explicitly in the current standard. We propose a novel handover algorithm, inter-FA handover, which possibly handover among FA for load balancing. It also reduces handover latency and satisfies HO user``s QoS. There has been several handover approaches on handover for load balancing. First handover algorithm is by using inter-frequency handover (IFHO). It handover users among different frequencies when there are multiple frequencies. Second scheme is by controlling base station``s (BS) pilot power. It is also called as ``cell breathing`` or ``adaptive cell sizing scheme``. It can solve congestion problem by reducing pilot power and forcing a cell edge user to handover to a neighbor BS. Third one is by controlling handover parameter. Last one is HO among different systems, inter-system HO. However these HO scheme are not proper to use in packet-based OFDMA system like IEEE 802.16e. The load measure also needs to be defined. We explain handover procedure and inter-sector HO scheme in IEEE 802.16e. We modify the present handover procedure and message format to verify a propose algorithm. When Data Service Addition (DSA) or Data Service Change (DSC) request failed due to resource shortage, MS can notice other FA``s load from modified Mobile Neighbor Advertisement (MOB_NBR_ADV) message. If other FAs are available, MS send Mobile Handover Request (MOB_MSHO_REQ) message to a serving BS. After a receiving handover response message from the serving BS, the MS can handover to other FA with considering channel condition. We provide load measure by packet drop rate. Proposed algorithm shows significantly improvement in...