Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-03-05
2001-09-18
Hunter, Daniel (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C370S335000
Reexamination Certificate
active
06292663
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a communication method, a transmitter and a receiver, and more particularly, is applicable to radio communication system such as a portable telephone system or the like.
2. Description of the Related Art
In this kind of radio communication system, an area for providing communication service is divided into cells having a desired size and a base station is set as a fixed radio station in the cell. The portable telephone device as a mobile radio station is installed in the cell so that the portable telephone device as a fixed radio station is constituted to be engaged in communication with the base station in the cell in which the portable telephone device is present. At that time, in this kind of radio communication system, the interference problem of an electronic wave is avoided by using a channel of frequency which is different between cells (this is simply referred to as a channel).
By the way, when a different channel is used between adjacent cells in this manner, the problem of interference can be avoided, but at the same time, there arises a disadvantage in that the usage efficiency of the frequency is reduced. As a consequence, in recent years, the interference problem is avoided by changing the channel which is used in each cell at random for each predetermined timing, and the usage efficiency of the frequency is improved.
By the way, in such radio communication system, the channel is only changed at random so that it is not necessarily possible to avoid that the channel becomes the same between adjacent cells. Thus, it is feared that the timing becomes the same. In the case where the same channel is used, there might arise an interference problem in the same manner as the prior art.
For example, as shown in
FIG. 1
, in the cell
1
A, when the portable telephone device
2
A uses the predetermined channel to be engaged in communication with the base station
3
A, and the same channel as the cell
1
A is used in the adjacent cell
1
B so that the portable telephone device
2
B is engaged in communication with the base station
3
B, it sometimes happens that the sending signal CB which is sent by the portable telephone device
2
B reaches the base station
3
A. In this case, the sending signal CB which reaches the base station
3
A becomes an interference wave (so-called hindrance wave) with respect to the sending signal CA which is sent to the base station
3
A. In this manner, even when an interference wave I is generated to the sending signal CA in this manner, the signal level of the sending signal CA is larger than the interference wave I, and no considerable problem is generated in normal cases. However, in the case where because, for example, the portable telephone device
2
A is distant from the base station
3
A and the signal level of the sending signal CA becomes smaller than the interference wave I, the base station
3
A receives the interference wave I by mistake instead of the sending signal CA from the portable telephone device
2
A. As a consequence, the signal series transmitted by the portable telephone device
2
B is restored, and the communication content of the other person is leaked with the result that a situation which is not preferable as a radio communication system might arise. For reference, in such a situation, even when the received data is not obtained as the radio communication system, it is desirable that the interference wave I is not demodulated.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of this invention is to provide a communication method which is capable of avoiding restoring the signal series which is sent in other communication by mistake when the same channel is used in the other communication, and is to provide a transmitter and receiver which use the communication method.
The foregoing object and other objects of the invention have been achieved by the provision of a communication method. In the communication method, the orthogonal conversion is performed by multiplying an orthogonal matrix which is different for each communication with the signal series which is sent, and the signal series to which the orthogonal conversion is performed is sent by using the predetermined channel. On the receiving side, the signal series before the orthogonal conversion is restored by multiplying the inverse matrix of the orthogonal matrix which is used on the sending side of the communication partner with the received signal series.
With the above arrangement, the signal series is multiplied with the orthogonal matrix which is different for each communication and transmitted, and at a receiving side, the received signal series is multiplied with an inverse matrix of the orthogonal matrix used at a transmitting side of the communication partner, so that the signal series before orthogonal conversion is restored. Therefore, even when another communication is performed and received by using the same channel, since the orthogonal matrix used for the orthogonal conversion differs from one communication to another, inverse orthogonal conversion cannot be attained for one communication if an inverse matrix for another communication is multiplied, thereby the signal series sent in another communication is not restored.
REFERENCES:
patent: 3715508 (1973-02-01), Blasbalg
patent: 3833767 (1974-09-01), Wolf
patent: 4688210 (1987-08-01), Eizenhofer
patent: 5793759 (1998-08-01), Rakib
patent: 5960029 (1999-09-01), Kim
patent: 5966376 (1999-10-01), Rakib
patent: 5978413 (1999-11-01), Bender
patent: 5983113 (1999-10-01), Asanuma
Sakoda Kazuyuki
Suzuki Mitsuhiro
Corsaro Nick
Hunter Daniel
Maioli Jay H.
Sony Corporation
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