Using Forced Handover as Load Balancing Technique in IEEE 802.16e/WiMAX Networks to Ensure QoS Guarantees

Wireless networks perform handover to enable MS (Mobile Stations) to move from one BS (Base Station) to other BS during a session and without hiccups. Handovers are performed for many reasons such as, MS movement, varying radio conditions and capacity offloading to achieve negotiated service quality. Network congestion is generally observed at popular business places (like downtowns) and during busy hours, when load on network increases sporadically. We propose forced handover, as a load balancing technique to handle such congestion in IEEE 802.16e networks. Existing approaches like adding more channels, forming sectors, increasing channel duration and using relay stations etc. to overcome congestion are not cost effective solutions, in situations when there is episodic increase in network load; moreover such techniques are always encumbered by the modifications that involve both licensing and cost. Our strategy to cater situations of periodic congestion is to enforce BS initiated handover of MSs at cell boundaries, observing acceptable SNR (Signal to Noise Ratio) from one of the neighboring BSs with enough capacity and thereby freeing resources for MSs that cannot be switched from one cell to another (observing high SNR for being near to BS). The proposed mechanism is tested using OPNET environment using Wireless Modeler. Performance analysis validates the proposed strategy and its effectiveness to overcome such sporadic congestion is confirmed through observable improvement in traffic statistics.