KR101057056B1 - Signal transmission control method in a system for assigning orthogonal codes according to code hopping - Google Patents

Abstract

The present invention relates to a method of allocating orthogonal codes using code hopping, wherein when two orthogonal codes allocated to a specific transmission symbol overlap each other, grouping the two or more mobile stations on the basis of a symbol to be transmitted; For each group, the step of selecting a mobile station having the minimum symbol transmission power, comparing the symbol transmission power corresponding to the selected mobile station with each other, and selecting a symbol to be transmitted according to the comparison result. As a control method, when a code collision occurs in an orthogonal code hopping multiplexing system, an optional transmission scheme in consideration of the transmission power and transmission data rate of each mobile station is provided, thereby improving signal transmission efficiency.

Walsh Code, Code Hopping, Selective Transmission

Description

Method for Controlling Transmitting Signals in A Systme Allocating Orthogonal Codes Based on Code Hopping}

1 is a diagram illustrating an embodiment of a code hopping pattern that varies with a specific symbol period.

2 is a diagram illustrating an embodiment of a method of transmission symbol selection and transmission power determination in accordance with the present invention.

3 is a diagram illustrating an embodiment of a transmission chain of a modulation and spreading unit according to the present invention;

The present invention relates to a signal transmission control method in a system for allocating an orthogonal code, and more particularly, to control a symbol and a transmission power to be transmitted when a code collision occurs in an orthogonal code assignment according to code hopping. It relates to a signal transmission control method.

In the forward link of a conventional code division multiple access (CDMA) mobile communication system, each mobile station is distinguished by a unique orthogonal code assigned to each mobile station. The orthogonal code is a Walsh code. (Walsh Code) is used. According to the prior art, the method of assigning the Walsh code is as follows.

If a new mobile station appears requesting the establishment of a call, or if an existing mobile station additionally requests the connection of a service, Walsh code assignment for that mobile station is required. Accordingly, the base station randomly selects among the Walsh codes not assigned to the mobile stations to which the current call is set, and assigns the new mobile station.

In a state in which a call is established between a base station and a mobile station, since the base station distinguishes each mobile station using a Walsh code individually assigned to each mobile station, the Walsh code assigned to the specific mobile station to which the current call is set is overlapped with another mobile station in the same cell. Can not. However, when the call with the mobile station is released or the service is stopped, the Walsh code assigned to the mobile station becomes available for assignment to another mobile station.

As described above, the Walsh code assigned to the mobile station in the call setup state cannot be assigned to another mobile station redundantly, and therefore, if the mobile stations exceeding the number of Walsh codes available at the base station request the call setup, the Walsh code Insufficient cases may occur.

The number of Walsh codes available at the base station is determined by the length of the Walsh code itself. For example, in the case of allocating Walsh codes of length 64 for call setup, the total number of Walsh codes available is 64. Therefore, in such a case, the number of mobile stations that can set up a call in one cell is limited to a maximum of 64.                         

As described above, the conventional Walsh code allocation method has a problem in that the maximum number of mobile stations that one base station can accommodate is limited depending on the length of the Walsh code.

The present invention has been proposed to solve the above problems, and in the system for transmitting by using the orthogonal code and the system to allocate according to the code hopping when using the orthogonal code, the number of mobile stations (terminals) is increased. If a code collision occurs according to the present invention, the purpose of performing efficient signal transmission by performing transmission power control and symbol selection.

In order to achieve the above object, the present invention provides a signal transmission control method for two or more mobile stations in which an orthogonal code assigned to a specific transmission symbol is overlapped with each other in a system for allocating an orthogonal code using code hopping. Grouping the two or more mobile stations on a symbol basis, selecting a mobile station having the minimum symbol transmission power for each group, comparing the symbol transmission power corresponding to the selected mobile station with each other, and And selecting the symbols to be transmitted according to the comparison result.

In a mobile communication system in which an orthogonal code is variably assigned to each mobile station in a cell at a specific time period, when there is an orthogonal code assigned to two or more mobile stations at the same time, the method for controlling signal transmission includes: Calculating a transmission power for the transmission symbol, determining whether all of the symbols to be transmitted to the two or more mobile stations match, and if the at least one symbol is different, determining the calculated transmission power. And selecting a symbol to transmit.

In addition, the present invention is a signal transmission control apparatus provided in a mobile communication base station for transmitting a signal to a mobile station using an orthogonal code, hopping pattern generator for generating an orthogonal code hopping pattern corresponding to each mobile station at a reference time period And comparing the generated hopping patterns to determine whether orthogonal codes corresponding to two or more mobile stations overlap each other, and based on the determination result and the transmission power calculation values for the two or more mobile stations, It comprises a comparison control unit for controlling the power.

The above-mentioned objects, features and advantages will become more apparent from the following detailed description in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In order to overcome the limitation of the mobile station that can be accommodated by one base station due to the limitation of the number of orthogonal codes, the orthogonal code symbol may be hopped by a predetermined time unit between the base station and the mobile station. That is, a method of allocating an orthogonal code to each mobile station according to a specific hopping pattern with N times the transmission symbol interval. Using this method, mobile stations can be accommodated by the number of hopping patterns.                     

As described above, in a multiplexing system using orthogonal code hopping, if the required number of hopping patterns (number of mobile stations to which the call is connected) is smaller than the length of orthogonal code N, not only the hopping pattern generation method but also as in the conventional CDMA system. The method of assigning a specific unique orthogonal code also prevents the same orthogonal code from being assigned to the same mobile station (collision phenomenon of orthogonal code).

However, as the number of mobile stations to establish a call with the base station increases, when the number of required hopping patterns becomes larger than the length N of the orthogonal code, even if an orthogonal code is assigned according to the code hopping method, collision of the orthogonal code is completely prevented. There is no number.

FIG. 1 is a diagram illustrating an embodiment of a code hopping pattern that varies with a specific symbol period. As shown in Fig. 1, when a call is set up between one base station and M mobile stations, orthogonal codes can be assigned to each mobile station by using a code hopping pattern that varies with the period of the symbol interval Ts on the time axis. In addition, according to Figure 1, it can be seen that when the orthogonal code is assigned through code hopping in the above manner, a code collision may occur.

In order to control the transmission signal when the above code collision occurs, the following method can be used. Since the base station knows the code hopping patterns currently assigned to all mobile stations, it is possible to compare the codes of the transmitted symbols and the orthogonal codes selected by the code hopping patterns for all mobile stations. Therefore, when there is a mobile station using the same orthogonal code in the same symbol period, it is possible to compare transmission symbols transmitted to the mobile station in which the collision occurred. As a result of the comparison, when all the transmission symbols are the same, the transmission is performed as it is, and when the transmission symbols are different from each other, it is possible to cope with the code collision phenomenon by not transmitting a signal to all the mobile stations where mutual collision occurs.

According to the method, a code hopping technique can be used to accommodate more mobile stations than the number of orthogonal codes limited by the code length. However, when a code collision occurs due to a code hopping pattern between mobile stations and transmission symbols transmitted to each mobile station are different, puncturing is completely performed on transmission symbols for all mobile stations in which collision occurs. Efficiency may be lowered. Therefore, when allocating orthogonal codes according to code hopping, a method of selectively transmitting symbols based on the transmission power and the data rate is efficient.

Hereinafter, a method of minimizing inefficiency due to a code collision phenomenon will be described in detail by allocating an orthogonal code by applying a code hopping scheme, by selectively transmitting a symbol in consideration of a transmission power and a data rate.

The following describes a first embodiment according to the present invention.

를 i번째 이동국에 대해 전력 제어 알고리즘에 의해 설정된 전송 전력이라고 할 때, 수학식 1 의 값들을 계산한다. First, assume that a code collision has occurred between K mobile stations. In this case, K mobile stations are grouped according to transmission symbols. That is, grouping is performed on the mobile stations that want to transmit the symbol "0" and the mobile stations that want to transmit the symbol "1", respectively. And,

Is calculated by the power control algorithm for the i < th > mobile station, the values of Equation 1 are calculated.

및

에 대하여, 다음과 같이 결정된 전송 전력 레벨로 신호를 전송한다. As shown in Equation 1, among the mobile stations in each group, a mobile station requiring a minimum transmit power and a maximum transmit power is selected. And selected according to Equation 1

And

For, transmit a signal at the transmit power level determined as follows.

인 경우에는, 수학식 2 에 따라 결정된 전송 전력 레벨에 따라, 심볼 "1" 을 전송하되, 해당 직교 코드를 사용하여 전송한다.In other words,

In the case of, the symbol “1” is transmitted according to the transmission power level determined according to Equation 2, but is transmitted using the orthogonal code.

인 경우에는, 수학식 3 에 따라 결정된 전송 전력 레벨에 따라, 심볼 "0" 을 전송하되, 해당 직교 코드를 사용하여 전송한다. Meanwhile,

In the case of, the symbol "0" is transmitted according to the transmission power level determined according to Equation 3, but is transmitted using the orthogonal code.

However, α is a value which is set in advance according to the system situation and is smaller than 1.

If none of the above two, the symbol associated with the orthogonal code is not transmitted.

Hereinafter, the above-described transmission symbol selection and transmission power determination method will be described in detail with reference to FIG. 2.

As shown in Fig. 2, it is assumed that a code collision occurs between four mobile stations when an orthogonal code is allocated according to a code hopping scheme. At this time, using the assigned orthogonal code, the first mobile station and the fourth mobile station attempt to transmit a symbol of "1", and the second mobile station and the third mobile station attempt to transmit a symbol of "0".

In this case, first, mobile stations (second and third mobile stations) intending to transmit a symbol of "0" and mobile stations (first and fourth mobile stations) intended to transmit a symbol of "1" are respectively grouped. Then, the mobile station capable of transmitting at the minimum transmit power is selected in the group to which the symbol "0" is to be transmitted. In the example shown in Fig. 2, it becomes a third mobile station. On the other hand, a mobile station that can transmit at the minimum transmit power is selected even within a group to which a symbol of "1" is to be transmitted. In the example shown in Fig. 2, it becomes a fourth mobile station.

Then, the transmission power required for the fourth mobile station is compared with a value obtained by multiplying the transmission power required for the third mobile station by a constant α (hereinafter, 'transmission power correction value'). As a result of the comparison, when the transmission power correction value is larger than the transmission power required for the fourth mobile station, it is decided to transmit a symbol of "1". Then, the transmission power correction value is compared with the transmission power of the mobile station (first mobile station in this embodiment) that needs the maximum transmission power in the group to which the symbol "1" is to be transmitted, and according to the result, The symbol "1" is transmitted using a low transmit power value.                     

The transmission symbol selection criterion is to transmit a transmission symbol of a mobile station requiring a lower transmission power in the event of a code collision. When the transmission symbol is selected by applying the above criterion, a mobile station requiring a low transmission power can transmit the symbol as in the case where there is no code collision. On the other hand, a mobile station that needs to transmit another symbol can minimize the effects of transmission of the opposite symbol.

In other words, a mobile station that requires high transmit power is accompanied by such a heavy fading that it is not significantly affected by opposite symbols transmitted at low transmit power. Furthermore, the greater the difference in transmit power required between mobile stations requiring the transmission of opposite symbols, the smaller the impact on each other.

In the first embodiment, it is assumed that the transmission data rate is the same for all mobile stations in one cell. In the following second embodiment, a symbol transmission method will be described taking into account that the transmission data rate for each mobile station is different, that is, the coding gain obtained by each mobile station is different.

를 i 번째 이동국에 설정된 전송 전력이라고 할 때,

에 대하여 전송 데이터 레이트를 고려하여 가중치가 부여된

를 사용한다. 즉,

를 이용한다. 여기서,

는 데이터 레이트 및 코딩 레이 트에 의해 결정되는 함수이다.

를 이용하여 수학식 4 의 값들을 계산한다. First, as in the first embodiment, it is assumed that a code collision has occurred between K mobile stations. In this case, K mobile stations are grouped according to transmission symbols. That is, grouping is performed on the mobile stations that want to transmit the symbol "0" and the mobile stations that want to transmit the symbol "1", respectively. And,

Is the transmit power set in the i < th > mobile station,

Weighted for the transmission data rate

Use In other words,

Use here,

Is a function determined by the data rate and coding rate.

Calculate the values of Equation 4 using.

및

에 대하여, 다음과 같이 결정된 전송 전력 레벨로 신호를 전송한다. As shown in Equation 4, a mobile station requiring a minimum transmit power and a maximum transmit power from among mobile stations in each group is selected. And selected according to Equation 1

And

For, transmit a signal at the transmit power level determined as follows.

인 경우에는, 수학식 5 에 따라 결정된 전송 전력 레벨에 따라, 심볼 "1" 을 전송하되, 해당 직교 코드를 사용하여 전송한다.In other words,

In the case of, the symbol "1" is transmitted according to the transmission power level determined according to Equation 5, but is transmitted using the orthogonal code.

인 경우에는, 수학식 6 에 따라 결정된 전송 전력 레벨에 따라, 심볼 "0" 을 전송하되, 해당 직교 코드를 사용하여 전송한다. Meanwhile,

In the case of, the symbol "0" is transmitted according to the transmission power level determined according to Equation 6, but is transmitted using the orthogonal code.

However, α is a value which is set in advance according to the system situation and is smaller than 1.                     

If none of the above two, the symbol associated with the orthogonal code is not transmitted.

)이 낮아지도록 함으로써, 해당 전송 심볼이 전송될 가능성을 더 높여주게 된다. In the second embodiment, the basic concept of the transmission symbol selection rule is to give a large weight to a mobile station that does not obtain a large coding gain due to a high transmission data rate.

By lowering), the probability of transmission of the corresponding transmission symbol is increased.

3 is a diagram illustrating an embodiment of a transmission chain of a modulation and spreading unit according to the present invention. More specifically, in an orthogonal code hopping multiplexing system using a QPSK data modulation scheme, a transmission chain of a modulation and spreading unit for transmitting a signal to a specific mobile station is shown.

Data to be transmitted to each mobile station is input to a demultiplexer 31 through channel coding and channel interleaving.

The hopping pattern generator 32 generates a hopping pattern corresponding to each mobile station, and the orthogonal code generator 33 generates a code while changing the orthogonal code according to the generated hopping pattern.

The comparison controller 34 controls the code collision phenomenon between the mobile stations. That is, the first amplifier 35 is first amplified by the transmission power set by the power control algorithm, the transmission power value is input to the comparison controller 34. The comparison control section 34 then determines the transmission power of the symbol transmitted to the actual mobile station in accordance with the method described in the first and second embodiments. Then, the second amplifier 36 performs secondary amplification to transmit the transmission symbol according to the determined power.

In FIG. 3, two amplifiers are used to determine the transmission power of a symbol. However, when the comparison controller 34 receives the transmission power to be set by the power control algorithm as another level, only one amplifier is used. It is also possible to implement the transmission stage provided.

The comparison controller collects information on orthogonal codes, transmission symbols, and transmission symbols of all transmission channels to control symbol selection and symbol transmission power according to the methods described in the first and second embodiments when a code collision occurs. .

The orthogonal code generated in the orthogonal code generator is multiplied by the output of the signal coordinate mapping unit 37 to generate a spread signal, and is input to the second amplifier 36. Then, the amplified signals are summed together, scrambling by the PN code unique to the base station through the PN code generating unit 38, and are transmitted to the transmission frequency band and then transmitted through the antenna.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

According to the present invention, when a code collision occurs in an orthogonal code hopping multiplexing system, by providing a selective transmission scheme considering transmission power and transmission data rate of each mobile station, signal transmission efficiency can be improved.

Claims (17)

In a system for assigning orthogonal codes using code hopping, a signal transmission control method for mobile stations in which orthogonal codes overlap each other, Grouping the mobile stations into at least two groups based on symbols to transmit; Selecting a mobile station having a minimum transmit power of the symbol for each group; Comparing the transmit powers of symbols for the selected mobile stations for each group; And Selecting a symbol having a small transmission power as a symbol to be transmitted according to the comparison result Comprising a signal transmission control method. The method of claim 1, Comparing the mutual step, And comparing a transmission power of the symbol for the first group of each group with a value obtained by multiplying a transmission constant of the symbol for the second group of each group by a specific constant. The method of claim 2, Selecting the symbol to be transmitted, According to the comparison result, the symbol corresponding to the smaller value of the multiplication of the transmission power of the symbol for the first group and a specific constant for the transmission power of the symbol for the second group is selected. Signal transmission control method. The method of claim 2, The specific constant is a signal transmission control method, characterized in that less than one. delete The method of claim 1, The orthogonal code is a Walsh code (Walsh Code) characterized in that the transmission control method. delete delete delete delete delete delete delete A signal transmission control apparatus provided in a mobile communication base station for transmitting a signal to a mobile station using an orthogonal code, A hopping pattern generator for generating an orthogonal code hopping pattern corresponding to each mobile station at a reference time interval; And Comparing the generated hopping patterns, it is determined whether orthogonal codes corresponding to two or more mobile stations overlap each other, and based on the determination result and the transmission power calculation values for the two or more mobile stations, a symbol to be transmitted and a transmission power Control unit for controlling the Signal transmission control device comprising a. The method of claim 14, The transmission power calculation value is a signal transmission control device, characterized in that the value calculated by the transmission power control algorithm. The method of claim 14, A first amplifying unit amplifying a signal using the calculated transmission power value; And Under the control of the comparison control unit, further comprising a second amplifier for amplifying the signal output from the first amplifier, And the comparison control unit detects the transmission power calculated value through the output of the first amplifier. delete

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