Cell configuration and resource management in urban microcellular systems

Abstract

In this dissertation, various types of urban microcell configurations are investigated, and effective radio resource management schemes are proposed. In the first part of this dissertation, low-tier user mobility is characterized in typical urban microcells i.e., cross-shaped cells and cigar-shaped cells, and then the two types of microcells are evaluated and compared. It is shown that a more suitable cell shape with respect to handoff traffic and its signaling load is determined by a user mobility feature characterized by a probability of straight movement at an intersection. On the other hand, blocking probability mainly depends on the cell size, not the shape. In the second part of this dissertation, an urban fiber-optic microcellular system is considered in which a cigar-shaped cell consists of several microzones with their own antenna sites connected to a central station through optical fibers. To increase the efficiency of radio resources and reduce unnecessary handoffs between microzones, a movable safety zone scheme is proposed. A safety zone is a virtually guarded area that does not permit co-channel interference. Outside the safety zone, co-channels can be reused. The safety zone can move under the condition that its user does not encounter co-channel interference, as the user moves to an adjacent microzone. The proposed system can handle a traffic capacity of approximately 12 erlangs for 7 traffic channels with a call blocking probability of 1%. In the last part of this dissertation, a four-sector cross-shaped urban microcellular system with intelligent switched-beam antennas is proposed. Each sector covers a street block with a base station located at an intersection, and an intelligent beam-switching scheme is used to locate mobile users in the most suitable beam coverage. In this system, a channel can be reused simultaneously in multiple neighboring cells as long as co-channels do not encounter each other along the line of sight. The system als...