Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Patent
1997-11-14
2000-12-05
Olms, Douglas W.
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
370329, H04B 7216
Patent
active
06157628&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a retransmission control method and to a mobiles communication system employing the method, for use in the case where data communications are carried out between a base station and a plurality of mobile stations and the mobile communication employs CDMA (Code Division Multiple Access).
BACKGROUND ART
In mobile communications, in the case of data communication in which retransmission control is carried out, it has been the conventional practice to adopt full duplex communication for a circuit switching mode which employs equal capacity channels which operate in opposite directions. FIG. 7 is a block diagram showing a structural example of a conventional mobile data communication system. This figure will now be used to explain the method by which terminal 11 of mobile station 10 transmits data to terminal 61 which is connected to a public telephone network. However, since terminal 11 and terminal 61 may be connected using a well-known procedure such as one determined according to RCR STD-27C, the digital automobile telephone system standard in Japan, for example, the following explanation will address a data transmission method where a fill duplex line is already established between terminal 11 and terminal 16.
First, terminal 11 of mobile station 10 supplies data (user data) to be transmitted to data communication unit 12. Data communication unit 12 forms a data frame which is used with radio transmission by adding an error detecting code and an error correction code to the user data which is supplied from terminal 11. Data communication unit 12 supplies a signal of the data frame to transmission and transmitter-receiver 13, and simultaneously records the user data for the retransmission. Transmission and transmitter-receiver 13 modulates the signal supplied from data communication unit 12, and transmits the modulated signal to base station 40. Transmission and transmitter-receiver 41 of base station 40 receives the modulated signal, demodulates the received signal, and then supplies the demodulated signal to control station of base station 50. Switching apparatus 51 of control station 50 relays a signal which is supplied from transmission and transmitter-receiver 41 to data communication unit 52.
Data communication unit 52 demodulates the user data, the error correction code and the error detecting code in the relayed signal (signal of aforementioned data frame). When data communication unit 52 is able to determine that there is no error in the user data, data communication unit 52 transforms the demodulated user data to a signal format for the public telephone network, and outputs the transformed data to terminal 61 through the public telephone network. On the other hand, when data communication unit 52 determines that the user data has an error, data communication unit 52 carries out retransmission between itself and data communication 12 of mobile station 10. In this way, then, retransmission control is carried out between data communication unit 12 of mobile station 10 and data communication unit 52 of control station 50.
Next, an explanation will be made of a conventional retransmission control method, FIG. 8 is a conceptual diagram showing the frame constitution of data (signal) which is transmitted and received between data communication unit 12 and data communication unit 52. An explanation will now be made of the operation of data communication unit 12 with reference to FIG. 8.
Data communication unit 12 first adds a forward control signal and a backward control signal to the user data upon receiving the user data from terminal 11. The forward control signal is a signal used in retransmission control which is carried out when data communication unit 52 of control station 50 does not correctly receive transmitted data from data communication unit 12. In general, the forward control signal consists of a frame number for the transmitted data and a retransmission signal recognition bit. The backward control signal is a signal for reporting to data c
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Esmailadeh R et al. "Quasi-Synchronous Time Division Duplex CDMA", IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. E78-A, No. 9, Sep. 1, 1995, pp. 1201-1205, XP000544198.
Uebayashi Shinji
Zhao Hui
NTT Mobile Communications Network Inc.
Olms Douglas W.
Pizarro Ricardo M.
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