On the Impact of Soft Handoff in Cellular Systems.pdf

On the Impact of Soft Hand-off in Cellular Systems Nidhi Hegdeand Khosrow Sohraby Computer Science Telecommunications University of Missouri-Kansas City 5100 Rockhill Rd. Kansas City, MO 64110 {nhegde,sohraby}@cstp.umkc.edu ABSTRACT Mobile communication systems use different types of cells We present a model for soft hand-off in wireless cellular net- which are linked either two-dimensionally or three-dimen- works. In such networks, due to overlapping cells, hand-offs sionally (within buildings) and may have a hierarchical struc- are not instantaneous and multiple channels may be occu- ture (overlay cells). The smaller the cell size, the greater pied by a single mobile for a non-zero freeze time period. the available capacity per unit area. In the pico-cellular and micro-cellular range, this facilitates higher quality tele- We provide a mathematical model of wireless cellular net- phony or even support for video-telephony. A smaller cell works with soft hand-offs. We examine different perfor- size also implies more frequent crossing of cell boundaries mance measures and show that freeze time may have a ma- by the mobile terminals. In the pico-cellular environment, jor im