Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Reexamination Certificate
2000-02-25
2004-11-02
Duong, Frank (Department: 2731)
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
C370S335000
Reexamination Certificate
active
06813261
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of mobile communication for transmitting and receiving data between a base station and a plurality of mobile terminals after having determined schedules for transmitting data, and to an apparatus therefor. Particularly, the invention relates to a method of mobile communication wherein, in transmitting a plurality of data packets from mobile terminals to the base station, the base station is informed that the data packets to be transmitted are present in the mobile terminals, and wherein the schedules for transmitting and receiving the data packets are determined and then the data packets are transmitted and received.
BACKGROUND OF THE INVENTION
In the prior art, a reservation-type mobile communication system has been proposed to transmit and receive data by radio communication between a base station and a plurality of mobile terminals after having reserved data channels for transmission and reception.
SUMMARY OF THE INVENTION
The present inventors have developed a system for overcoming the problems associated with the conventional system as discussed below. The above-mentioned conventional mobile communication system of the reservation type has been provided with a plurality of channels such as a preservation channel for transmitting and receiving a reservation packet, a response channel for transmitting and receiving a response packet for the reservation packet, and data channels for transmitting and receiving data, and wherein mobile terminals which wish to transmit the data use the reservation channel to transmit the reservation packet to the base station in order to let the base station know the presence of data that are to be transmitted.
The base station that has received the reservation packet from the mobile terminal assigns a data channel and a time slot which is a transmission timing that will be used by the mobile terminal, and transmits the assigned data channel and the time slot to the mobile terminal by using the response channel.
The mobile terminal that has received a response from the base station transmits data to the base station by using the assigned data channel and the time slot. The mobile terminal of the conventional transmission system of the reservation type transmits the data by using the data channel and the time slot assigned by the base station, and avoids the collision of data on the data channel even when the data are transmitted from a plurality of mobile terminals.
In the above-mentioned conventional mobile communication system of the reservation type, however, a plurality of reservation packets collide in the base station when the reservation packets are transmitted from a plurality of mobile terminals to the base station, and the contents of the reservation packets cannot be correctly read out in the base station. Therefore, the mobile terminals must transmit reservation packets again. In order to transmit the reservation package again as described above, waiting times are set in a random fashion so that the reservation packages will not collide again. When the reservation packets collide, the transmission efficiency of data greatly decreases.
Furthermore, in the above-mentioned conventional mobile communication system of the reservation type, data for making a reservation are transmitted and received in addition to the data that are to be transmitted. Therefore, a ratio of the data that are desired to be transmitted decreases in the whole data that are transmitted and received between the base station and the mobile terminals. When the consecutive data are to be transmitted being divided into a plurality of data packages in the above-mentioned conventional mobile communication system of the reservation type, in particular, a reservation packet is transmitted for the transmission of each data packet, and the packets occupy a large ratio in the whole data transmitted and received between the base station and the mobile terminal.
A mobile communication system of the reservation type applying a code division multiple access (CDMA) has been disclosed in an article to R. Esmailzadeh, N. Doi, H. Masui, Y. Ohgoshi and T. Yano, entitled “Spread Spectrum Slot Reservation Multiple Access”, IEEE VTC, April 1996, Vol. 3, pp. 1715-1719. The outline of this system involves forming a plurality of reservation channels, response channels and data channels by using pseudo noise (PN) as a plurality of different dispersion codes, requesting the transmission of data through the plurality of reservation channels, and transmitting and receiving data by using a data channel designated by the response channel. According to the conventional mobile communication system of the reservation type using the above-mentioned CDMA, the contents of the reservation packets can be correctly read out by the base station even when a plurality of mobile terminals are transmitting reservation packets to the base station. A plurality of reservation packets received by the base station are partially overlap each other on the time axis, provided the timings deviate by more than a chip which is a minimum unit for constituting a PN signal among the reservation packets.
However, in the conventional mobile communication system of the reservation type using the above-mentioned CDMA, when the deviation of timing is not larger than a chip among the reservation packets that are partly overlapping one another, the contents of the reservation packets are not correctly read by the base station. Therefore, the mobile terminals must transmit the reservation packets again. Also, the data for making a reservation are transmitted and received in addition to the data that are to be transmitted. Therefore, the ratio of the data that are desired to be transmitted becomes low with respect to the entire amount of data transmitted and received between the base station and the mobile terminals.
The present inventors have studied the above-mentioned prior art and have found the following problems. First, in the above-mentioned conventional mobile communication system of the reservation type, it is not possible to read the contents of the reservation packets when the reservation packets simultaneously arrive at the base station from a plurality of mobile terminals. When the plurality of reservation packets collide, it becomes necessary to transmit the reservation packets again.
Second, reservation packets are transmitted for determining schedules for transmitting data. For this purpose, therefore, an output is necessary for transmitting the reservation packets in addition to an output for transmitting the data, and the communication capacity of data decreases by an amount corresponding to the electric power of transmitting the reservation packets.
An object of the present invention is to provide technology capable of efficiently transmitting and receiving data between the base station and a plurality of mobile terminals.
Another object of the present invention is to provide technology capable of detecting the individual alert signals even when a plurality of alert signals are transmitted from a plurality of mobile terminals to the base station.
Yet another object of the present invention is to provide technology capable of maintaining, at a low level, the value of the alert signals transmitted from the mobile terminals.
The following are representative examples of methods and apparatuses which realize the above-mentioned and other objects of the present invention.
(1) A method of mobile communication includes determining schedules for transmitting and receiving data, and transmitting and receiving data between a base station and a plurality of mobile terminals according to the schedules. Particular orthogonal codes are transmitted from mobile stations to the base station as alert signals indicating the presence of data to be transmitted. The base station checks whether particular orthogonal codes are contained in the alert signals transmitted from the mobile terminals to the base station. When the particular orthogonal codes are detected in the
Doi Nobukazu
Esmailzadeh Riaz
Yano Takashi
Duong Frank
Mattingly Stanger & Malur, P.C.
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