Data communication method and mobile communication system

• US 7,885,235 B2
• Filed: 09/26/2006
• Issued: 02/08/2011
• Est. Priority Date: 09/26/2006
• Status: Active Grant

• Current Assignee: TCL Communication Technology Holdings Ltd. (TCL Technology Group Corp.)
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Maeda, Miho, Tani, Shigenori, Fukui, Noriyuki, Okubo, Akira, Fujie, Ryoichi, Iwane, Yasushi, Takano, Michiaki, Ozaki, Keisuke, Mochizuki, Mitsuru, Mishuku, Tetsuya
• Primary Examiner(s): Ly; Anh-Vu
• Application Number:
  US12/278,357
• Publication Number:
  US 20090175183A1
• Time in Patent Office: 1,596 Days
• Field of Search: None
• US Class Current: 370/331
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/04 Arrangements for maintaining operational condition
• CPC Class Codes: H04W 36/0007 for multicast or broadcast services, e.g. MBMS multicast or broadcast application services H04W4/06; resource management for broadcast services H04W72/30; connection management for selective distribution or broadcast H04W76/40
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 72/30 Resource management for broadcast services
• CPC Class Codes: H04W 88/02 Terminal devices
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

Since OFDM (Orthogonal Frequency Division Multiplexing), which is a downlink access scheme used for an LTE (Long Term Evolution) communication system, is weak at interference, it is preferable that the number of base stations for transmitting the same E-MBMS (Evolved Multimedia Broadcast Multicast Service) data be not excessive.

Thus, the mobile terminal performs: processing of obtaining measurement quality values by measuring reception quality of each base station; processing of deciding on whether the measurement quality value of a serving base station exceeds a certain receiving level; processing of adding measurement quality values of other base stations to the measurement quality value of the serving base station until the sum exceeds the certain receiving level; and processing of notifying the serving base station of the serving base station and other base stations as candidates for an active set for E-MBMS. This makes it possible to select as the active set for E-MBMS an appropriate number of base stations that make it compatible to maintain good reception quality and to prevent interference.

Claims

1. A data communication method executed in a communication system including a plurality of base stations for carrying out broadcast data transmission for providing point-to-multipoint broadcast communication service using an OFDM (Orthogonal Frequency Division Multiplexing) scheme as a downlink access scheme, and a mobile terminal for receiving and combining the broadcast data transmitted from the plurality of base stations, said data communication method comprising:

receiving, by a serving base station, a service entry request from said mobile terminal;

selecting, by the serving base station, one or more base stations from said plurality of base stations as an active set of base stations for transmitting the broadcast data to said mobile terminal, said serving base station included in the active set of base stations to transmit the broadcast data to the mobile terminal; and

scheduling by the serving base station, a transmission and reception schedule of said mobile terminal.

2. The data communication method according to claim 1, further including candidate base station selecting processing executed by said mobile terminal, said candidate base station selecting processing comprising:

determining measurement quality values by measuring reception qualities of said one or more base stations from which said mobile terminal receives the broadcast data;

determining whether the measurement quality value of said serving base station is higher than a threshold notified by said serving base station;

determining a sum measurement quality value by adding measurement quality values of other base stations to the measurement quality value of said serving base station until the sum measurement quality value satisfies a reception quality defined by the threshold; and

notifying, when the sum measurement quality value satisfies the reception quality defined by the threshold, said serving base station of the one or more base stations, whose signals are combined with a signal received from said serving base station, as candidate base stations.

3. The data communication method according to claim 2, wherein

said mobile terminal is notified of a first threshold and a second threshold, said first threshold defining an upper limit reception quality of a combined received signal obtained by combining signals received from one or more base stations by said mobile terminal, and said second threshold defining a lowest limit reception quality of the combined received signal, and

the candidate base station selecting processing is executed when reception quality of the combined received signal is higher than the first threshold, or when the reception quality of the combined received signal does not satisfy the reception quality the second threshold requires.

4. The data communication method according to claim 2, wherein the candidate base station selecting processing is executed at least at a handover that changes the serving base station for arranging a schedule of said mobile terminal.

5. The data communication method according to claim 1, wherein

said mobile terminal is notified of a first threshold and a second threshold, said first threshold defining an upper limit reception quality of a combined received signal obtained by combining signals received from one or more base stations by said mobile terminal, and said second threshold defining a lowest limit reception quality of the combined received signal, and

said mobile terminal performs notification processing in which when the reception quality of the combined received signal is higher than the first threshold, said mobile terminal notifies said serving base station that the reception quality is too high, and when the reception quality of the combined received signal does not satisfy reception quality the second threshold requires, said mobile terminal notifies said serving base station that the reception quality is insufficient.

6. The data communication method according to claim 1 or 5, wherein said one or more base stations for transmitting the broadcast data to said mobile terminal are determined in advance concerning said serving base station, and said selecting processing selects one or more corresponding base stations in accordance with said serving base station.

7. A mobile communication system comprising:

a plurality of base stations for carrying out broadcast data transmission for providing point-to-multipoint broadcast communication service using an OFDM (Orthogonal Frequency Division Multiplexing) scheme as a downlink access scheme;

a mobile terminal for receiving and combining the broadcast data transmitted from the plurality of base stations,

said mobile terminal configured to;

determine measurement quality values by measuring reception qualities of one or more base stations selected by a serving base station from said plurality of base stations from which said mobile terminal receives the broadcast data,

determine whether a measurement quality value of said serving base station is higher than a threshold notified by said serving base station,

determine a sum measurement quality value by adding measurement quality values of other base stations to the measurement quality value of said serving base station until the sum measurement quality value satisfies reception quality defined by the threshold, and

notify, when the sum measurement quality value satisfies the reception quality defined by the threshold, said serving base station of the one or more base stations, whose signals are combined with a signal received from said serving base station, as candidate base stations; and

said serving base station configured to select from said candidate base stations notified by said mobile terminal one or more base stations for transmitting the broadcast data to said mobile terminal.

8. A data communication method executed in a communication system including a plurality of base stations for carrying out broadcast data transmission for providing point-to-multipoint broadcast communication service using an OFDM (Orthogonal Frequency Division Multiplexing) scheme as a downlink access scheme, and a mobile terminal for receiving and combining the broadcast data transmitted from the plurality of base stations, said data communication method including:

selecting processing of selecting one or more base stations for transmitting the broadcast data to said mobile terminal, and of creating a set of said base stations for transmitting the broadcast data, said selecting processing being executed by a serving base station that arranges a transmission and reception schedule of said mobile terminal;

receiving processing of receiving the broadcast data transmitted from said one or more base stations selected by the selecting processing; and

candidate base station selecting processing executed by said mobile terminal, said candidate base station selecting processing including;

processing of obtaining measurement quality values by measuring reception qualities of said one or more base stations from which said mobile terminal receives the broadcast data;

processing of making a decision on whether the measurement quality value of said serving base station is higher than a threshold notified by said serving base station;

processing of obtaining a sum measurement quality value by adding measurement quality values of other base stations to the measurement quality value of said serving base station until the sum measurement quality value satisfies a reception quality defined by the threshold; and

processing of notifying, when the sum measurement quality value satisfies the reception quality defined by the threshold, said serving base station of the one or more base stations, whose signals are combined with a signal received from said serving base station, as candidate base stations.

9. The data communication method according to claim 8, wherein

said mobile terminal is notified of a first threshold and a second threshold, said first threshold defining an upper limit reception quality of a combined received signal obtained by combining signals received from one or more base stations by said mobile terminal, and said second threshold defining a lowest limit reception quality of the combined received signal, and

the candidate base station selecting processing is executed when reception quality of the combined received signal is higher than the first threshold, or when the reception quality of the combined received signal does not satisfy the reception quality the second threshold requires.

10. The data communication method according to claim 8, wherein the candidate base station selecting processing is executed at least at a handover that changes the serving base station for arranging a schedule of said mobile terminal.

11. A data communication method executed in a communication system including a plurality of base stations for carrying out broadcast data transmission for providing point-to-multipoint broadcast communication service using an OFDM (Orthogonal Frequency Division Multiplexing) scheme as a downlink access scheme, and a mobile terminal for receiving and combining the broadcast data transmitted from the plurality of base stations, said data communication method comprising:

selecting processing of selecting one or more base stations for transmitting the broadcast data to said mobile terminal, and of creating a set of said base stations for transmitting the broadcast data, said selecting processing being executed by a serving base station that arranges a transmission and reception schedule of said mobile terminal; and

receiving processing of receiving the broadcast data transmitted from said one or more base stations selected by the selecting processing, wherein

said mobile terminal is notified of a first threshold and a second threshold, said first threshold defining an upper limit reception quality of a combined received signal obtained by combining signals received from one or more base stations by said mobile terminal, and said second threshold defining a lowest limit reception quality of the combined received signal, and

said mobile terminal performs notification processing in which when the reception quality of the combined received signal is higher than the first threshold, said mobile terminal notifies said serving base station that the reception quality is too high, and when the reception quality of the combined received signal does not satisfy reception quality the second threshold requires, said mobile terminal notifies said serving base station that the reception quality is insufficient.

12. The data communication method according to claim 11, wherein said one or more base stations for transmitting the broadcast data to said mobile terminal are determined in advance concerning said serving base station, and said selecting processing selects one or more corresponding base stations in accordance with said serving base station.