Abstract: A handover reestablishment method capable of effectively re-accessing the serving base station when the mobile terminal fails ranging while moving to the target cell and performs ranging through the handover process, or when the direction of the mobile terminal is changed and thus, the mobile terminal enters into the serving area, is provided. The method includes receiving a handover request message from the mobile terminal; waiting without canceling a connection to the mobile terminal when receiving the handover request message; and performing a reconnection with the mobile terminal when receiving a handover reconnection message from the mobile terminal.

Abstract: A channel scanning apparatus in a portable Internet system establishes a radio link with each of neighboring access points without disconnecting a wireless link with a serving access point and collects radio channel state information of each of the respective neighboring access points. That is, apart from a RF signal processing unit that processes a radio signal from the serving access point, the channel scanning apparatus includes a dedicated scanning processing unit for processing a radio signal of a neighboring access point and measuring radio channel state information of the neighboring access point from the radio signals received by the dedicated scanning processing unit, and collects radio channel state information of the respective neighboring access points. In such a way, communication with the serving access point is not disconnected, and therefore the access terminal and the serving access point do not need to buffer traffic data.

Abstract: An apparatus and method for estimating a cell coverage includes: a terrain data processor for dividing an area for calculation of the coverage into pixels of a size; a traffic calculator for estimating a traffic volume by the pixels; a forward coverage estimator for calculating path loss information according to the pixel-based traffic volume and a traffic carrying capacity of the base station and determining a forward link capacity and a forward coverage; and a backward coverage estimator for calculating a same-cell interference and an adjacent-cell interference using the path loss information between the base stations and determining a backward link capacity and a backward coverage, thus determining a cell coverage approximating the actual coverage by including a same-cell interference and an adjacent-cell interference.