System for and its method of controlling handover, mobile terminal, and apparatus for controlling handover

Abstract

A system for controlling handover is disclosed that includes a mobile terminal that enables communications with multiple wireless systems having wireless access stations, and a handover-controlling apparatus that executes control of handover for the mobile terminal, which travels among multiple types of wireless systems. The mobile terminal includes a destination wireless system determining unit that receives downlink signals from the corresponding wireless access stations so as to determine which wireless system accommodates a destination wireless access station based on reception quality of downlink signals. The mobile terminal also includes a destination wireless system reporting unit that sends information indicating the determined wireless system to the handover-controlling apparatus. The handover-controlling apparatus includes a handover-controlling unit that controls handover operations for the mobile terminal based on the information indicating the determined wireless system, which is sent from the destination wireless system reporting unit.

What is claimed is:  
     
         1 . A system for controlling handover, comprising: 
 a mobile terminal which enables communication with a plurality of wireless systems having wireless access stations; and    a handover-controlling apparatus which executes control of handover for said mobile terminal which travels among a plurality of types of the wireless systems,    wherein said mobile terminal comprises:    a destination wireless system determining unit which receives downlink signals from two or more of the wireless access stations so as to determine which of the corresponding wireless systems accommodates a destination wireless access station based on reception quality of the downlink signals; and    a destination wireless system reporting unit which sends information indicating said determined wireless system to said handover-controlling apparatus, and    said handover-controlling apparatus comprises a handover-controlling unit which controls handover operations for said mobile terminal based on the information indicating the determined wireless system which is sent from said destination wireless system reporting unit.    
     
     
         2 . The system for controlling handover as claimed in  claim 1 , 
 wherein said handover-controlling apparatus is connected to the two or more wireless access stations via a plurality of connecting access routers; and    said handover-controlling unit comprises:    a database which manages corresponding relationships between said wireless access stations and said access routers;    a router compatibility determination unit which makes a determination by referring to said database, at the time the information indicating the wireless system which accommodates said destination wireless access station is reported, as to whether the access router which is connected to the destination wireless access station differs from the access router which is connected to the currently connecting wireless access station;    a handover method determining unit which determines a handover method based on the wireless system which accommodates the destination wireless access station in the case that said determination is affirmative; and    a handover processing executing unit which executes handover processing based on said determined handover method.    
     
     
         3 . The system for controlling handover as claimed in  claim 1 , 
 wherein said mobile terminal further comprises:    a travelling speed projecting unit which projects the travelling speed of the mobile terminal based on received power characteristics of the downlink signals from the two or more wireless access stations; and    a travelling speed reporting unit which sends the information indicating said projected travelling speed of the mobile terminal to said handover-controlling apparatus.    
     
     
         4 . An apparatus for controlling handover which executes control of handover for a mobile terminal that travels among a plurality of types of wireless systems, comprising a handover-controlling unit which controls handover operations for said mobile terminal based on information indicating a wireless system which is sent from said mobile terminal.  
     
     
         5 . The apparatus for controlling handover as claimed in  claim 4 , which is connected to corresponding wireless access stations within said wireless systems via connecting access routers, 
 wherein said handover-controlling unit comprises:    a database which manages corresponding relationships between said wireless access stations and said access routers;    a router compatibility determination unit which makes a determination by referring to said database, at the time that information indicating the wireless system which accommodates a destination wireless access station is reported, as to whether the access router which is connected to the destination wireless access station differs from the access router which is connected to the currently connecting wireless access station;    a handover method determining unit which determines a handover method based on the wireless system which accommodates the destination wireless access station in the case that said determination is affirmative; and    a handover processing executing unit which executes the handover processing based on said determined handover method.    
     
     
         6 . The apparatus for controlling handover as claimed in  claim 5 , 
 wherein said handover method determining unit determines one of a hard-handover method, a soft-handover method, and an IP-packet-buffering method as the handover method based on the wireless system which accommodates the destination wireless access station.    
     
     
         7 . The apparatus for controlling handover as claimed in  claim 5 , 
 wherein said handover method determining unit comprises:    a high-speed handover method selecting unit which determines based on travelling speed information of the mobile terminal which is reported by a travelling speed information reporting unit, whether the handover of said mobile terminal is executed by a high-speed handover method; and    a high-speed handover method selection reporting unit which reports said determination result to said handover processing executing unit, and    said handover processing executing unit comprises a high-speed handover method executing unit which executes the high-speed handover method in response to said reported determination result.    
     
     
         8 . A mobile terminal which enables communication with a plurality of wireless systems having wireless access stations and handover to a plurality of types of the wireless systems, comprising: 
 a destination wireless system determining unit which receives downlink signals from two or more of the wireless access stations so as to determine which of the corresponding wireless systems accommodates a destination wireless access station based on reception quality of the received downlink signals; and    a destination wireless system reporting unit which sends to an apparatus for controlling handover at the network side the information indicating said determined wireless system.    
     
     
         9 . The mobile terminal as claimed in  claim 8 , comprising: 
 a travelling speed projecting unit which projects a travelling speed of the mobile terminal based on received power characteristics of the downlink signals from the two or more wireless access stations; and    a travelling speed information reporting unit which sends information indicating said projected travelling speed of said mobile terminal to the apparatus for controlling handover which executes control of handover for said mobile terminal travelling among the types of wireless systems.    
     
     
         10 . The mobile terminal as claimed in  claim 8 , 
 wherein the wireless system which is determined at said destination wireless system determining unit is one of a homogeneous system and a heterogeneous system.    
     
     
         11 . A method of controlling handover in a system for controlling handover which comprises a mobile terminal that enables communication with a plurality of wireless systems having wireless access stations and an apparatus for controlling handover that executes control of the handover for said mobile terminal that travels among a plurality of types of the wireless systems, 
 said method comprising the steps of:    receiving, at said mobile terminal, downlink signals from two or more wireless access stations so as to determine which of the corresponding wireless systems accommodates a destination wireless access station based on reception quality of received downlink signals; and    sending, from said mobile terminal, information indicating said determined wireless system to said apparatus for controlling handover, and    controlling, by said apparatus, handover operations for said mobile terminal based on the information indicating said reported wireless system.