Location management congestion problem in wireless networks

We propose and study the location management congestion problem arising in the group mobility scenarios. In the hot-spot locations, e.g., supermarket, bus interchange, or public transportation systems, a large number of travelers move into the same area concurrently and trigger the location update (LU) procedure simultaneously to register their new locations. However, due to the limited bandwidth in a base station, only a small part of the LU requests has the opportunity to capture a radio channel and succeeds in refreshing the new information to the corresponding database in the wireless networks. The remaining mobile terminals (MTs) are unable to obtain a radio channel, and consequently, the LU requests are rejected. A significant consequence of a failed LU is the out-of-date location identity in the network databases and, thereafter, the incapability in establishing the valid route for the potential call connection request, which will seriously degrade the network quality-of-service (QoS). We develop a queueing model to characterize the congestion issue and propose a buffer scheme to eliminate this problem. The consequence of the LU failure on the MT's call activity is also investigated. The comparison demonstrates the high efficiency of the proposed approach in decreasing the LU failure as well as the resulting call blocking probability. The analytical model has been validated by the discrete event simulation.