Scramble code revision method during communication

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a method of scrambling the communication content by a scramble code and changing the scramble code during communication in wireless communication in which communication is performed by a digital communication method.

【0002】

[Conventional technology]

Figure 3A shows the configuration of a general mobile communication system. The mobile station 104 moving in the zone (service area) 103 covered by the base station 102 communicates with the base station 102 via a wireless channel. The base station 102 is connected through a communication line 106 that transmits communication with the exchange station 105 and a control line 107 that transmits control signals, and processes such as establishment of synchronization with mobile station 104 / generation of wireless frames / encryption. It is carried out. Before moving to the communication channel between the mobile station 104 and the base station 102, the base station 102 sends a random number to the mobile station 104, and the base station 102 and the mobile station 104 store the original code of the mobile station and the above. An encryption operation is performed using random numbers to generate a scramble code used for communication, and the same scramble code is used simultaneously for the base station 102 and the mobile station 104.

【0003】

In this way, conventionally, when switching a channel from a control channel to a communication channel, a scramble code used for communication is generated and used at the same time.

【0004】

[Problems to be Solved by the Invention]

It is not preferable from the viewpoint of safety that the same scramble code is continuously used during communication. From this point, it is preferable to change the scramble code during communication. Conventionally, a new scramble code is used when switching to a communication channel. Therefore, as shown in Fig. 3B, the base station is forcibly switched to another communication channel even during communication, and the scramble code is used during communication. It is possible to change it. However, if there is no empty communication channel, the scramble code cannot be changed by channel switching. Also, if channel switching fails due to factors such as interference, the scramble code cannot be changed.

【0005】

An object of the present invention is to provide a scramble code changing method during communication which enables a scramble code change during communication regardless of a line usage situation and a channel interference situation in a radio station.

【0006】

[Means for solving problems]

According to the present invention, a random number and / or a specified original code is transmitted from one radio station to the other radio station during communication, and the other radio station that receives the random number and / or the specified original code receives the random number and / or the specified original code. A scramble code is generated using the specified original code, or using the original code held with the random number or the holding random number and the specified original code, and then the scramble code generation end signal is sent to the above. Send to one radio station. One radio station that has received the scramble code generation end signal interrupts communication and transmits a synchronization establishment signal to the other radio station. As a result, the other radio stations are out of synchronization, and after resynchronizing again, communication is performed using the scramble code generated earlier.

【0007】

[Action]

That is, the present invention changes the scramble code between two radio stations at the same time by resynchronizing the channel during communication. Therefore, the scramble code can be changed during communication regardless of the presence or absence of an empty communication channel, and even if interference occurs, the scramble code can be changed by repeating the same procedure again.

【0008】

[Example]

FIG. 1A shows a configuration example of a base station used when the present invention is applied to mobile communication. The modulation circuit 301 performs radio signal transmission processing, and the demodulation circuit 302 performs radio signal reception processing. The clock signal from the transmission clock generator 303 is supplied to the framing circuit 304 and used to frame the communication signal and the control signal, and the framed signal is supplied to the modulation circuit 301. For the demodulation output from the demodulation circuit 302, a communication signal and a control signal are extracted from the signal framed by the deframing circuit 305. The control circuit 306 controls random number generation, scramble code generation, random number designation to mobile stations, etc., and can read or write different mobile station original codes for the same mobile station stored in memories 307 and 308. it can. This example is when each mobile station has two mobile station original codes. The synchronization establishment signal processing unit 309 performs transmission / reception processing of the synchronization establishment signal in response to a command from the control circuit 306.

【0009】

FIG. 1B shows a configuration example of a mobile station corresponding to the base station. The mobile station also has a modulation circuit 401, a demodulation circuit 402, a transmission clock generator 403, a framing circuit 404, a deframing circuit 405, a control circuit 406, a memory 407, 408, and a synchronization establishment signal processing unit 409, which have the same name as the base station. Each has the same function as the part of. The control circuit 406 also generates a scramble code when a random number and a mobile station original code are specified from the base station, and also controls to notify the base station of the end of the generation. The original code of each mobile station in the memories 407 and 408 is the same as each key in the memories 307 and 308 of the base station. Scramble of the communication content is performed by the framing circuit 304,404, and descramble is performed by the deframing circuit 305,405.

【0010】

The procedure when the scramble code change during communication is applied to mobile communication according to the present invention will be described with reference to FIG. It is assumed that the mobile station and the base station generate a scramble code by using the mobile station original code of the memory 307 (407) at the start of communication, and scramble the communication signal and the control signal by using the scramble code.

【0011】

The base station that decides to change the scramble code generates a random number (505) and notifies the mobile station of a random number / original code designation signal 501 indicating that another mobile station original code 308 (408) is used. In addition, the scramble code generation process is performed using the random number and the original code (509). Upon receiving this notification, the mobile station generates a scramble code using the specified random number and the mobile station original code of the memory 408 (506), and then sends a scramble code generation end signal 502 to the base station.

【0012】

The base station that has received this scramble code generation end signal starts transmitting the synchronization establishment signal 503 instead of the communication signal. Since the communication signal from the base station was cut off at the mobile station, out-of-synchronization was detected (507), and the synchronization establishment mode was set from this, and the synchronization establishment signal 504 sent from the base station was received in this state. The resynchronization process (508) is performed.

【0013】

When this resynchronization process is completed and synchronization with the base station is established again, the communication content is scrambled and communication is performed using the scramble code generated in the scramble code generation process 506. The base station also uses the scramble code generated by the scramble code generation process (509). In this way, the scramble code is changed during communication.

【0014】

After transmitting the random number / original code designation signal 501 at the base station, the signal 501 is not received at the mobile station due to factors such as interference / weak electric field, or the scramble code generation end signal 502 has elapsed at the base station for a predetermined time. If the signal is not received, the base station transmits the random number / original code designation signal 501 again and repeats the scramble code change process from the beginning.

【0015】

Since the random number / original code designation signal 501 and the scramble code generation end signal 502 generally have many information elements, it takes time to send and receive signals when the signals are retransmitted, and in the meantime, out of synchronization occurs due to interference / weak electric field, etc. In this case, even though the mobile station does not transmit the synchronization establishment signal 503 at the base station, there is a risk of malfunction by treating it as having transmitted it.

【0016】

To avoid such danger, for example, the base station transmits a resynchronization warning signal to the mobile station after receiving the scramble code generation end signal 502, and the mobile station loses synchronization until the resynchronization warning signal is received. However, you should not change the scramble code. In the above, the base station and mobile station hold only one mobile station original code, and when the scramble code is changed, only the random number is changed and transmitted from the base station, and the random number and one common mobile station original code are used. You may create a new scramble code with. Further, a plurality of mobile station original codes may be retained, and when the scramble code is changed, the mobile station original code may be specified and a scramble code may be created from the specified original code and the random number first received from the base station. Although the present invention has been applied to mobile communication in the above description, it can also be applied to fixed communication.

【0017】

[Effect of the invention]

As described above, according to the present invention, since the scramble code is changed by reestablishing synchronization, the scramble code is changed during communication even if there is no empty communication channel or there is interference. be able to.

[Simple explanation of drawings]

[Figure 1]

A is a block diagram showing a configuration example of a base station used when the present invention is applied to mobile communication, and B is a block diagram showing a configuration example of a mobile station corresponding to the base station of A.

[Figure 2]

The figure which shows the processing procedure of the Example of this invention.

[Fig. 3]

A is a block diagram showing a general configuration of a mobile communication system, and B is a diagram showing a procedure of a conventional scramble code changing method.