JP2816429B2 - Direct spreading wave monitoring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA (Code Division Multicast) using a direct spreading system which is one of frequency spreading systems for a multiplex radio communication system, a satellite communication system and the like.
ple Access) A method for monitoring direct spread waves in a communication system, particularly for terminals grouped according to characteristics such as organization and priority, so that the number of transmitting terminals for each group can be recognized. Regarding the transmission method of the direct spread wave and the recognition method of the transmission wave, without receiving instructions from a control station that manages the entire communication system,
Each terminal can grasp the communication status of the entire communication system and determine the start or end timing of transmission. For this reason, the present invention, in a CDMA communication system using the direct spreading method, each terminal grasps the communication status by itself without providing a control station that receives an instruction regarding the timing of start or end of transmission, It can be used for a communication status monitoring method of each terminal in an autonomous decentralized communication system that can determine the start or end of transmission.

[0002]

2. Description of the Related Art In a CDMA communication system using the direct spreading method, all receiving terminals become noise except for the intended transmission wave, and the greater the number, the smaller the signal-to-noise ratio of each receiving terminal. Eventually, it becomes impossible to decode the transmission signal, so that it does not function as a communication system. Therefore, the maximum number of terminals that can be transmitted is determined in consideration of the code length of the spreading code used for the direct spreading method and the ambient noise intensity, and the number of transmission terminals must be suppressed to the maximum number of terminals or less. In addition, when a plurality of organizations use one communication system for effective use of frequency, or when each terminal is assigned a priority and is ranked, the communication system as a whole It is natural to keep the number of terminals below the maximum number, but it is necessary to suspend the transmission of the terminal that is trying to transmit a certain organization or a certain priority rank, or to terminate the transmission of some terminals that are transmitting midway. is required.

[0003] As a conventional method of suppressing the number of transmitting terminals to a certain number or less in the entire communication system or suspending transmission, a terminal to be transmitted first inquires a control station managing the entire communication system, Transmission starts with permission from the control station, and when the transmission ends, the transmitting terminal reports the transmission end to the control station. Also, in the conventional method of terminating transmission, the control station informs the transmitting terminal to be terminated halfway using a channel different from the receiving channel, and the transmitting terminal issues an instruction from the control station. The transmission is terminated according to the following. Therefore, the control station can grasp each organization and each priority rank at that time, that is, the number of transmission terminals for each group. Here, in order for the control station to permit, suspend, or terminate transmission halfway, the control station only needs to know the number of transmission terminals for each group. For example, suspending transmission from a certain group means that the predetermined maximum number of transmitting terminals of the group has been reached, and terminating transmission of a certain group of transmitting terminals means that This means that the number of transmitting terminals of the group (for example, having a higher priority) has increased.

[0004]

As described above, the conventional C
In the DMA communication system, a control station for managing the entire system is required, and if the control station is disabled, the entire communication system is paralyzed. Requests and reports from each terminal are sent to the control station at the start and end of transmission, and the control station must respond to and process the request without delay, and it is necessary to provide a control station with a relatively large processing capacity. Also, when starting transmission, the control station must be inquired and permission must be obtained, so the waiting time from the request time to the transmission start time must be considered. Furthermore, since the control station communicates with each terminal only at the start and end of transmission, if a transmission error occurs in the communication, it will cause a great obstacle to management of the control station.

According to the present invention, in view of the above, each terminal grasps the communication status by itself, without providing a control station for receiving an instruction regarding the timing of transmission start or end, and starts or terminates transmission. It is an object of the present invention to provide a method for monitoring a direct spread wave in an autonomous decentralized communication system that can determine the spread spectrum.

[0006] Other objects and novel features of the present invention will be clarified in embodiments described later.

[0007]

In order to achieve the above object, a direct spreading wave monitoring method according to the present invention is directed to a CDMA communication system using the direct spreading method, wherein each terminal controls a whole communication system. so as not to provide a kind of station, tissue, provided with a means for transmitting the group code indicating characteristics of a terminal, such as priority and specific code assigned to each terminal individually synthesized to as the spreading code , Sending terminal
Situation to understand themselves from the transmission wave of the entire communication system of the transmitting terminal of
As can be determined the timing of the start or end of transmission Te, Bei means capable of recognizing the number of transmission terminals of each group
For example, it means capable of recognizing the number of transmission terminals of each of said groups
Is the difference between the signal received the transmission wave and the group code.
It has a receiving circuit for taking a correlation .

[0008] The transmitting means may be configured to spread specific bits of transmission information with the unique code and the remaining bits with the group code to form the spread code.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a direct spreading wave monitoring system according to the present invention.

FIG. 1 shows a process until transmission information is transmitted in the embodiment of the present invention, and FIG. 2 shows an example of a transmission signal.

Here, before starting the description of FIGS. 1 and 2, an application example of the present invention shown in FIG. 3 will be described. In FIG. 3, transmitting terminals 1, 2, 3, receiving terminals 4,
5 and 6 show that a certain terminal 7 monitors the transmission status (however, each terminal has both a transmission function and a reception function). Assuming that there are three groups A, B, and C, and that transmitting terminals 1 and 2 transmit using spreading codes belonging to group A and transmitting terminal 3 transmits using spreading codes belonging to group B, terminal 7 transmits The number of transmission waves belonging to the C group can be recognized as 2, 1 and 0, respectively. Here, the terminal 7 is represented as a terminal that is neither transmitting nor receiving, but in the scheme of the present invention,
All terminals belonging to the communication system can monitor the transmission wave, regardless of the transmitting terminal or the receiving terminal.

Next, a method of transmitting information to be transmitted by combining a group code and a unique code will be described.
In a CDMA communication system using the direct spreading method, each transmitting terminal must use a spreading code of a sequence having a small correlation coefficient with each other. For example, a so-called GOLD code is widely used. A set of codes such as the GOLD code is GS, and each element of the set of codes GS is S ₁ , S ₂ , S
_3, ... (each of these elements S _1, S _2, S _3, ... it is 1 or -1
).
The cross-correlation coefficient between any two elements is small. It has been found that a GOLD code can form a set of codes having the above-mentioned properties with a length of 2 ⁿ -1 ^where n is an integer.

The set of codes having a small cross-correlation coefficient is redefined as GS, and the elements of the set of codes GS are designated as unique codes S ₁ , S ₂ , S ₃ , S ₄ , S ₅ ,. Assignment and some of the remaining elements of the set of codes GS are group codes S _A , S _B ,. In a conventional CDMA communication system using the direct spreading method, there is no group code, and only a unique code is assigned to each terminal. In the present invention, in addition to the unique code S _i (where i is a positive integer) assigned to each terminal itself, a group code S _j assigned according to the terminal's characteristics such as the organization to which the terminal belongs and the priority order. (Where j: A, B, C,...) Are both used as spreading codes. In this case, the transmission information is multiplied by the unique code and the group code, respectively, and is usually 0 and 1 as shown in FIG.
Is converted to -1 and 1, and then this multiplication is performed. On the time axis, one bit of transmission information corresponds to the entire sequence of the unique code or group code (the entire signal sequence composed of 1 or -1). That is, for one piece of transmission information, S _i or S _j , −
Will be converted into a signal sequence corresponding to the inversion of S _i or S _j for 1 transmission information.

[0014] In an embodiment of the present invention is a distributed transmission information to the odd bits and even bits bit distributing unit 10 of FIG. 1, multiplies the odd bits of the transmission information at the multiplier 11 and the specific code S _i With the multiplier 12
Multiplies the even-numbered bits of the transmission information by the group code _Sj . Thereby, as shown in FIG. 2, the odd bits of the transmission information are spread with the unique code, and the even bits are spread with the group code at the same timing (that the unique code and the group code sequence match on the time axis). These are arithmetically added by the adder 13 in FIG. 1 and transmitted. Therefore, any one of -2, 0, and 2 is used as a transmission signal by the modulator 15.
And modulates the carrier of the transmission frequency source 14 to be transmitted.

Next, a method for recognizing the number of transmission terminals for each group when a plurality of the transmission signals are transmitted,
Then, a method of decoding a transmission signal into transmission information as a receiving terminal will be described. Since the transmission signal from one transmission terminal is a combination of the group code and the unique code, it can be considered as a transmission signal from two terminals each using both codes as spreading codes. Therefore, considering only the group code, one terminal transmits one group code. Here, the signal arriving at the terminal being monitored contains the unique code of each transmitting terminal, and the timing does not match as shown in FIG. 5 (that the beginning and end of each spreading code do not match). A) some transmitted signals spread by the group code. FIG. 5 shows, by way of example, that two devices belonging to group A and one device belonging to group B have arrived. Here, each transmitting terminal independently transmits a signal, and since each terminal has a different frequency for each terminal even if the terminals have the same nominal frequency oscillation source, even if they transmit using the same group code. , The two will never overlap for a long time.

Therefore, a receiving circuit including two orthogonal detection circuits 20, an integrating circuit 21, a correlation circuit 22, and a sum-of-squares circuit 23 of the correlation output as shown in FIG. The correlation value is calculated every moment using the code (S _j : S _A , S _B ,...). Then, when a certain element sequence in the received signal sequence coincides with the monitoring sequence S _j , FIG.
A correlation pulse such as Therefore, as shown in FIG. 5, during one cycle of the sequence, when the monitoring sequence is S _A , the correlation peak is two, and when the monitoring sequence is S _B , the correlation peak is one.
Thus, the number of transmission terminals matches each group number. Here, even if the number of terminals is large, the number of groups is suppressed to a small number, so that even if all the group codes _Sj are monitored one by one, it can be completed in a relatively short time (at most about several seconds). This does not hinder the grasp of the communication status.

Since the output is lost if the phase of the received signal and the demodulation source used for detection are orthogonal, the output is lost. Without the need for detection output.

Next, a method for decoding transmission information from the transmission signal will be described. As described above, the transmission signal from one terminal is the same as the transmission signal from two terminals each using the group code and the unique code as spreading codes. Therefore, first, the receiving side can decode the odd-numbered bits of the transmission information as a frequency spread wave transmitted using the unique code as a spread code. Further, at this time, since the transmission timing of the unique code and the group code match as shown in FIG. 2, it is possible to decode a frequency spread wave based on the group code at the same timing as the unique code. , The even bits of the transmission information can be extracted.

As for the transmission start timing, the communication status is monitored, and the transmission can be started if the number of transmission terminals of the own group has a margin or when it becomes such. On the other hand, as a method of finding the timing of transmission end, if one terminal of a certain group must be terminated from the communication status, each terminal of the group generates its own random number by itself, and a time corresponding to the number is generated. An autonomous termination method, such as disconnecting the line after the elapse, is assumed. Therefore, the terminal that has generated the smallest random number is terminated, and the other terminals in the group have one transmitting terminal.
The transmission can be continued as it is. In this way, each terminal can make its own decision not only at the start of transmission but also at the end.

In FIG. 1, the odd bits of the transmission information are spread by the unique code and the even bits are spread by the group code to form the spread code. On the contrary, the odd bits are converted to the group code and the even bits are converted to the spread code. It may be spread with the unique code.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0022]

As described above, the direct spreading wave monitoring system according to the present invention is a CDMA communication system using the direct spreading system, in which the group code indicating the characteristics of the terminal such as the organization and the priority order and each terminal. Means for combining and transmitting individually assigned unique codes as spreading codes, and means for recognizing the number of transmitting terminals for each group from the transmitted waves. To be able to recognize the total number of sending terminals for (the total number of terminals for each group)
Even without a control station, there is a control station that can determine the start and end timing of transmission by itself according to the transmission rules predetermined based on the organization, priority, etc. Not only does this not only increase the reliability of the communication system, but also has the effect that the use of a group code for recognizing the group does not lead to a reduction in transmission efficiency. Terrestrial wireless communication and satellite communication using the direct spreading method Etc. will bring great effects.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a process until transmission information is transmitted in an embodiment of a direct spreading wave monitoring system according to the present invention.

FIG. 2 is a timing chart showing a method of allocating odd and even bits of transmission information to unique and group codes in the embodiment.

FIG. 3 is a schematic diagram showing an application example of the present invention.

FIG. 4 is a timing chart of multiplication of transmission information with a unique code and a group code, which are spread codes, from signal conversion of transmission information.

FIG. 5 is a timing chart showing a process of recognizing the number of transmitting terminals in each group from a plurality of group codes received.

FIG. 6 is a block diagram of a receiver for recognizing the number of transmitting terminals of each group in the embodiment.

[Explanation of symbols]

 1, 2, 3 Transmission terminal 4, 5, 6 Receiving terminal 7 Arbitrary terminal of communication system 10 Bit distribution unit 11, 12 Multiplier 13 Adder 14 Transmission frequency source 15 Modulator 20 Detection circuit 21 Integration circuit 22 Correlation circuit 23 Sum of squares circuit

Claims (2)

(57) [Claims] 1. A CDMA (Code Division M) using a direct spreading method which is one of the frequency spreading methods.
In the multiple access communication system, each end
At the end, there is provided means for combining and transmitting, as a spread code, a group code indicating characteristics of the terminal such as organization and priority and a unique code assigned to each terminal , and a transmitting terminal.
Grasp the status of transmitting terminals in the entire communication system from the last transmitted wave
And so can determine the start or end timing of transmission, Bei means capable of recognizing the number of transmission terminals of each group
For example, it means capable of recognizing the number of transmission terminals of each of said group prior to
The correlation between the received signal and the group code
A direct spreading wave monitoring method characterized by having a receiving circuit . 2. The direct spreading wave monitoring method according to claim 1, wherein said transmitting means spreads specific bits of transmission information with the unique code and the remaining bits with the group code to form the spreading code.