Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2000-01-07
2003-03-25
Le, Thanh Cong (Department: 2684)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000, C455S436000, C455S437000, C455S442000
Reexamination Certificate
active
06539233
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a personal digital cellular telecommunication system (PDC) using a code division multiple access (CDMA) system and, in particular, to a call control method for use in mobile communication to fix a radio zone upon call origination at a mobile terminal irrespective of a communication traffic and to a system therefor.
In a conventional mobile/hand-held cellular telecommunication system, a plurality of service areas (PDC/cell, PHS [personal handyphone system]/microcell) are continuously formed to enable connection of a communication line upon continuous movement of a mobile terminal. In each radio service area (may be referred to as a radio zone), a single radio base station (cell base station) accommodated in a mobile communication control station via a wired or a wireless line or channel (WILL system) is arranged. The mobile terminal moves between the radio zones from one to another. In a CDMA system for example, the radio base station notifies information such as an identifier assigned to the station and an available radio channel by continuously transmitting the information via a radio channel called a pilot channel.
Moving in the radio zone of each radio base station, the mobile terminal at first receives the pilot channel and also receives and collects the information of peripheral radio base stations. Upon call origination, the mobile terminal originates a call to a particular radio base station having a strongest reception field strength (RSSI (Reception Signal Strength Indicator)) among the information of the radio base stations collected as mentioned above, and starts communication therewith. Each radio base station can use a plurality of radio channels and determines a radio channel to be used with reference to a radio wave propagation state between the station and the mobile terminal to communicate therewith.
If the radio wave propagation state of a current radio channel being used is deteriorated during communication, i.e., upon occurrence of decrease in reception field strength (RSSI) or deterioration in quality data (QI (Quality Indicator)) representative of presence/absence of word errors, the current radio channel is switched into another radio channel. Specifically, a mobile assisted handover procedure is executed to switch the current radio channel being involved in communication into another radio channel so that no line interruption occurs. Proposal is also made of a method (diversity handover) in which a same signal is transmitted from a plurality of radio base stations to a mobile terminal and the mobile terminal selects a particular reception signal among a plurality of reception signals (see Masuhito AKEBI et al “Handover Control Schemes Using Micro-Diversity Techniques for Microcellular Communications Systems”, Technical Report of IEICE, RCS 93-86, 1994).
In a CDMA mobile communication system, diversity handover may be called soft handover. In the CDMA, mobile communication system of an IS-95 standard, transmission is carried out under closed/open loop control for fixing transmission power of the pilot channel. In addition, a particular mobile terminal controls connection of a radio base station upon soft handover by the use of a peripheral zone set including the information of the pilot channels of the peripheral radio zones and an active set of a combination of the radio base stations simultaneously connected to the mobile terminal.
As conventional mobile communication systems of the type, “CDMA Radio Transmission System and Transmission Power Control Device and Transmission Power Controlling Measuring Device Used in the System” is disclosed in Japanese Unexamined Patent Publication (JP-A) No. H10-56421 and “Mobile Communication System” is disclosed in Japanese Patent No. 2739850.
If the control is carried out to fix the transmission power of the pilot channel in the conventional systems described above, variation in communication/control traffic in and out of each radio zone causes the fluctuation in reception quality of the pilot channel at the mobile terminal. This results in variation in area of the radio zone. In other words, it is required to provide a control method for fixing the area of the radio zone upon call origination at the mobile terminal irrespective of the communication/control traffic.
If the mobile terminal transmits an access request (or a connection request) to a particular radio base station for multiple access on the basis of the above-mentioned peripheral radio zone set, the particular radio base station as a requested station determines allowance/rejection of the multiple access request, taking into account the communication traffic at the station and the communication quality, and notifies the result of determination to the mobile terminal. However, production of such control signal also constitutes a factor of deterioration of the communication quality. In the above-mentioned call control method, a mobile terminal during soft handover and a mobile terminal originating a new call are similarly dealt with. This increase a call loss ratio.
Systems disclosed as conventional systems in the above-mentioned publications have similar problems.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a call control method in mobile communication and a system therefor, which are capable of starting stable communication.
It is another object of this invention to provide a call control method in mobile communication and a system therefor, which are capable of fixing a call origination allowable area irrespective of a downlink communication traffic.
It is still another object of this invention to provide a call control method in mobile communication and a system therefor, in which a mobile terminal can produce a multiple access request in correspondence to a propagation loss.
It is yet another object of this invention to provide a call control method in mobile communication and a system therefor, in which a radio base station can control whether or not the station acts as a multiple access destination depending upon the communication traffic of the station without carrying out useless call control.
It is a further object of this invention to provide a call control method in mobile communication and a system therefor, which is capable of assuring, in case where a call setup request is produced by a mobile terminal when a communication traffic at a radio base station exceeds a threshold level, a communication capacity for a requested call to decrease a call loss ratio by suppressing the possibility that the radio base station acts as a multiple access destination.
According to this invention, there is provided a call control method in mobile communication in which communication is carried out through a radio channel between a mobile terminal and each of a plurality of radio base stations accommodated in a mobile communication control station and each radio base station at first carries out notification of information through a pilot channel to the mobile terminal moving into a radio zone thereof, wherein:
each of the radio base stations carries out:
a step of storing pilot channel transmission power level information into the pilot channel to be transmitted; and
a step of carrying out transmission by the pilot channel;
the mobile terminal carrying out:
a step of receiving the pilot channel from each of the radio base stations;
a step of calculating a difference between a reception field strength of the pilot channel of each of the radio base stations and the transmission power level information received;
a step of detecting from the difference a particular radio base station of a minimum propagation loss; and
a step of originating a call to the particular radio base station of a minimum propagation loss thus detected.
According to this invention, there is provided a call control method in mobile communication in which communication is carried out through a radio channel between a mobile terminal and each of a plurality of radio base stations accommodated in a mobi
Cong Le Thanh
NEC Corporation
Tran Tuan
LandOfFree
Call control method in mobile communication and system therefor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Call control method in mobile communication and system therefor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Call control method in mobile communication and system therefor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3024463