KR100792993B1 - Method for discriminating information signals in a mobile communication system - Google Patents

Abstract

The present invention relates to a method for transmitting information in a mobile communication system.

The present invention provides a mobile communication system in which a plurality of user terminals receive control information provided from one base station through a shared channel and classify the control information signal for the user terminal using a code specified for the user terminal. The code specified for the user terminal is characterized in that it changes over time.

The present invention also provides a method for generating new code information by changing an initial state of a scrambling code with a mobile station and / or time; And transmitting the information to the corresponding mobile station by using the generated code information.

Therefore, according to the present invention, when distinguishing UEs using a user-specific scrambling code, the correlation value of the codes is high according to the UEs, so that each user (UE) cannot be distinguished, thereby preventing continuous classification errors. have.

Description

{Method for discriminating information signals in a mobile communication system}             

1 is a structural diagram showing a general PN sequence generator (scrambling code generator)

2 is a diagram illustrating the configuration of a convolutional code input signal in a common shared channel;

3 is a diagram showing the structure of a transmitter (HS) of the HS-SCCH of the HSDPA system

4 shows a structure of a downlink shared control channel for transmitting downlink control information

5 is a flowchart illustrating a method of generating and using a long PN code having randomness

The present invention relates to a method for transmitting information in a mobile communication system, in particular

When transmitting a short frame such as control information in a mobile communication system, when multiple users share the same physical channel and transmit information, a method for determining which user signal is received by the receiver It is about.

More specifically, in the present invention, when a short frame is converted into a convolutional code and transmitted, and each user identification information is used as a user-specific masking method, an initial generation of a long PN code having a random characteristic is generated. The present invention relates to a method of generating new code information by using random code strings different in state information according to user information and / or time, and allocating the generated code information to each user mobile station (UE) to transmit control information. .

That is, in order for the USMC allocated to each UE to change over time, code information is generated using different random code strings over time and control information is transmitted.

In the above, the meaning that the long PN code has a random characteristic means that the generation characteristic of the generated code bits does not have any pattern.

In other words, among the binary bit strings generated by the shift register (SR) of the code generator, there is no correlation between each bit, and when two portions of a random bit string are separated, a correlation between the two portions gives a value. It is the random code of the literature definition that it has or is unpredictable.

However, since the actual random code does not occur artificially in real life, a code having similar properties to the above random characteristics is designed using several SRs and named as a random PN code. Scrambling code currently used in 3GPP.

The scrambling code is a base station identification code or a user (UE) identification code.

The scrambling code in the downlink is a long PN code having randomness composed of 24 shift registers, and the scrambling code in the uplink is a long PN code having randomness composed of 18 shift registers.

Hereinafter, the prior art will be described.

First, methods related to transmitting and receiving information will be described.

1. convolutional code

In general, in a wireless communication channel, a receiver transmits a channel encoding result previously performed by a transmitter in order to have error correction capability.

Channel coding schemes widely used in current commercial systems are convolutional codes. The convolutional codes generate coded bits as a combination of registers while passing an input value to be encoded to a shift register.

The receiving end receives the transmission of the encoded bits and passes the Viterbi decoder to obtain the original transmission information before encoding.

2. Viterbi decoder

The Viterbi decoder decodes the original transmission bit by using the coded bit string encoded and transmitted by the convolutional encoder.

Viterbi decoder compares the path metric (PM) of codewords (codewords) generated in each state using the transition value of each state on Trellis, and provides a survival path for the optimal codeword. Determine.

This method is repeatedly performed every time a transition occurs on the Trellis. Finally, after finding all the survival paths for each state using all the coded bits, the survival path corresponding to the zero state is selected from the survival paths. Decode the transmission bits of.

Such a Viterbi decoder is widely used in commercial systems, and is known as an optimal decoding method for convolutional codes by exhibiting the properties of a maximum likelihood (ML) decoder.

3. path metric

In the Viterbi decoder, the survival paths finally obtained in each final state form one codeword. The difference between this codeword and the received coded bits is the path metric for the survival path.

4. Tail bits

In the convolutional code encoder, input information to be coded first is inputted to the input of the transition register SR, and then a zero bit string is additionally inserted so that the value of the final transition register goes to zero state.

The sequence of zero bits is called tail bits, and the role of tail bits later determines which final state is selected from the remaining survival paths of each state in the Viterbi decoder.

5. Scheduler

When a packet sender provides a packet transmission service to a plurality of receivers in a wireless channel, services for a plurality of receivers may be scheduled over time in order to increase the packet service processing capability of the entire system.

For example, when there is only one target transmitted in a unit time, it is a method of providing a service to one of the receivers having the best wireless channel environment at that time. By doing so, it is possible to increase the packet processing capacity of the entire system. Factors affecting such scheduling can be set in various ways and can be arbitrarily set by the service provider who makes or services the system.

To do this, the state information of the packet transmission channel for each packet receiving side is required.

6. Control information passed before packet transmission

The transmitting end of the wireless packet transmission system transmits, to the receiving end, control information such as a use modulation scheme, user identification information, and a packet number of the packet before transmission of the packet.

The receiving end must decode the control information without error before the arrival of the transport packet to receive the forwarded packet.

The previously transmitted control information is transmitted with channel coding and error detection information (cyclic redundancy code) so as to be suitable for the wireless channel, and the receiving end demodulates and decodes the received information to check whether there is an error in the received information. Figure out.

7. Short frame transmitted on shared physical channel (SCCH)

In a general wireless communication system, a short information such as control information is widely used to set a common physical channel so that it can be shared among multiple users.

In this case, the transmission signal receiving end needs to know whether the information transmitted through the common channel is information corresponding to itself. Therefore, information for identifying the user should be transmitted together.

For example, in the case of 1x-EV / DV control information transmission, which is a type of 3rd generation wireless communication US standard, when transmitting information on a common physical channel, a user ID is inserted after a transmission signal so that a receiver checks the user ID after decoding. It is designed to determine whether the information is transmitted to itself.

1 is a structural diagram showing a general PN sequence generator (scrambling code generator).

의 다항식을 갖는 경우이고, PN 시퀀스의 레지스터는 쉬프트(shift) 레지스터이다.In the PN sequence generator shown in FIG. 1, X is

In the case of having a polynomial of, the register of the PN sequence is a shift register.

(1)

(One)

(2)

(2)

The initial value of the PN sequence register is given as in Equation (1), and then the PN sequence x (n) is generated while the register values are shifted by Equation (2).

If the period of the PN sequence register is 38400 chips, the sequence value exists from x (0) to x (38399).

In the case of the PN sequence generator shown in FIG. 1, for example, a method of generating a sequence is as follows.

First, the shift registers of the PN sequence generator are 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 in the left-to-right direction by Equation (1) above. , 0,0,1 bits are stored.

Since '1' at address 0 of the register is shifted to the right, the first sequence value is x (0) = 1, and at address 0, '0' of address 1 is shifted to the right and output of x (1) = 0. This comes out.

PN sequences x (0) to x (17) are output as they are, and x (18) to x (38399) can be represented by the operation of equation (2). Same as

After the bit information of register 0 is output during the initial shift, the bits from address 17 to address 1 of the register are shifted to the right by one space.

That is, it operates in such a way that '0' originally located at 1 is shifted to 0, and '0' originally located at 2 is shifted to empty 1, and 17 is the most significant bit (MSB). '0' at the address is shifted to 16.

The 17th register is then emptied. Here, '0' of 0 is the least significant bit (LSB) and '0' of 7 is Exclusive OR (hereinafter referred to as 'EXOR'). The result is '0' inserted into address 17 of the register.

The value inserted into the 17th address is the x (18) value, which is the 19th value of the PN sequence.

In the same way, the PN sequence generator can be driven to find all values up to x (38399).

When the terminal accesses the base station, it is necessary to generate the forward PN sequence used by the base station to interpret the scrambling code transmitted by the base station. Since the period of the PN sequence is very long, the amount of computation is too large to generate the forward PN sequence from the initial sequence value. In many cases, you need to create sequences with delays as needed.

In order to generate such a PN sequence with a desired delay, there is a conventional method of covering a mask.

In FIG. 1, if the normal PN sequence without delay is x (n), the PN sequence which is delayed by 131072 (for example) by x (n) using a mask specific to registers is x (n + 131072). .

In the case of the delay, the mask used (EXOR operation with the mask written in registers 4, 6, and 15) is a mask corresponding to the delay 131072. To generate another delay, a mask of another type is used. do.

의 다항식을 갖는 경우이고, PN 시퀀스의 레지스터는 쉬프트(shift) 레지스터이다. In addition, in the PN sequence generator shown in FIG.

In the case of having a polynomial of, the register of the PN sequence is a shift register.

The above operation in the Y generator proceeds in the same manner as the above operation of the X generator.

Therefore, as shown in the figure, the masked codes MXI and MYI are EXOR (exclusively compatible), and the scrambling code I and the masked codes MXQ and MYQ are EXOR (exclusively compatible) to generate the scrambling code Q.

2 is a diagram illustrating a configuration of a convolutional code input signal in a common shared channel.

As shown in the figure, a signal is transmitted through a common common physical channel, and a receiving end shows a configuration of a signal that is used in determining a transmission receiving side ID without any other information.

The UE ID is a unique identification bit string assigned to the user, and has a wrong value for each user. The receiver determines the user's transmitted or generated signal with the UE ID after demodulation of the received signal.

For example, if one transmitter transmits a physical shared channel for multiple receivers, all receivers decode the signal of FIG. 2 and compare the values of their IDs with the decoded UE IDs to match the two values. If you do, judge the information to be delivered to you and use the information.

However, when a signal is transmitted with the signal configuration as shown in FIG. 2, the transmission power loss due to the UE ID and tail bits is increased in a situation where information to be transmitted is short.                         

8. Transmission of control information in High Speed Downlink Packet Access (HSDPA) system

3GPP, which is developing a European CDMA system that is considered as a third generation communication, is developing High Speed Downlink Packet Access (HSDPA) system as a next generation service.

As described above, the control information transmitted on the downlink of the HSDPA system is designed to transmit information on a plurality of common physical channels called High-Speed Shared Control Channel (HS-SCCH).

However, as mentioned above, in order to reduce power loss due to tail bits due to UE ID and convolutional code, instead of UE ID as shown in FIG. 3, user-specific masking code is used to perform masking on coded bits. It takes the role of id.

3 is a diagram illustrating a transmitter structure of the HS-SCCH of the HSDPA system, and information and tail bits are encrypted in a convolutional encoder and output N bits.

N-bits are output by masking coded bits using a user-specific masking code instead of a UE ID indicating a transmitting end.

The information is output by multiplying the N bits output from the convolutional encoder and the N bits output from the user-specific masking and modulated / output by a modulator.                         

9.User-specific masking code: USMC

The USMC outputs a unique binary sequence according to the input user ID, and may be considered a PN code for distinguishing a UE in a general CDMA system.

However, the PN code has a property that the entire code length is multiplied by one bit, but masking using the USMC has a property that one USMC chip is multiplied and masked by one coded bit.

Therefore, as shown in FIG. 3, if the output bit string of the convolutional code is N bits and the UE ID is 10 bits, the code rate of the USMC is (N, 10).

Therefore, by uniquely masking the coded bit for each UE, when the receiver receives the Viterbi decoder, the path-metric shows a low value only for its own signal, and the path metric size for other users' signals. Since R is relatively large, the receiver determines whether a signal is transmitted as the path metric.

This method is less reliable than the method of directly inserting the UE ID into the transmission information and can be used when it is difficult to directly insert the UE ID. The present method is similar to the blind rate detection of the 3GPP W-CDMA system. This is used.

In the current HSDPA system, it is proposed to make and use the (32, 10) TFCI code applied to the (16,5) Transport Format Combination Indicator (TFCI) code designed by USMC in the current W-CDMA system.

The control information transmission in the HSDPA system through the HS-SCCH described above will be described.

4 is a structure of a downlink shared control channel for transmitting downlink control information.

Referring to FIG. 4, multiple users may be simultaneously supported, and control information for this uses a shared control channel allocated to each user. The number of Shared Control Channels for one UE in Node B, which is one base station, is M.

When the HI (HS-DSCH Indicator) is transmitted on the downlink DPCH, the UE first receives the HI, reads whether the data is transmitted and the number of the HS-SCCH, and then receives the corresponding HS-SCCH.

At this time, the UE identity is decoded to determine whether the control information is its own. If it is its own, the UE decodes the data transmitted to the HS-DSCH through control information.

On the other hand, if HI (HS-DSCH Indicator) is not transmitted on the downlink DPCH, the UE receives the HS-SCCH (s) every TTI (2ms). At this time, the UE reads the UE identity every TTI (2ms) to determine whether the control information is its own, and if it is its own, the UE decodes the data transmitted to the HS-DSCH through the control information.

4, in the current HSDPA system, as shown in FIG. 4, one UE receives a plurality of HS-SCCH channels to determine which channel is transmitting its information. A masking method using USMC is proposed.                         

That is, when M path metric result values are decoded from M channels, it is assumed that information is transmitted to the HS-SCCH channel having the smallest path metric among them.

However, using the conventional method of masking the coded bits sequence using the conventional USMC as described above, if a high correlation (correlation) occurs between the M USMCs transmitted at the same time any HS-SCCH at the receiving end There is a situation in which it is difficult to know whether the information is transmitted to the channel.

This phenomenon is unavoidable because the coded bit sequence is random because USMC is masking the coded bit sequence unlike the PN code.

Therefore, when the indicated state occurs, the M-name takes the wrong HS-SCCH channel and receives the control information. Therefore, the transmission of the M-name requires the packet transmitter to retransmit the HS-SCCH and HS-DSCH.

However, since HSDPA or a wireless packet transmission system under consideration is designed to schedule such a packet retransmission request as the highest priority, scheduling may be performed to retransmit at the same time if M retransmissions occur for the reasons described above. In many cases, the problems mentioned are more likely to recur.

Therefore, UEs having a high correlation of USMC have a problem of continuously receiving service by reducing the above problems.

Therefore, in the present invention, in order to eliminate the problem of the correlation characteristics of each other fixed according to the UE as described above, and the possibility that the problem recurs over time when these UEs are scheduled at the same time, they are assigned to each UE. It is proposed to make the USMC change randomly with time.

In addition, if you use a code such as (32,10) TFCI code, which is a limited number of codes, the number of available codes is limited. Therefore, the number of acceptable users decreases proportionally when the code assigned to the same UE changes over time. Since the long PN code having randomness is used by the USMC, the long PN code, which is the scrambling code information, is generated differently according to a mobile station and / or time, and thus, a different random code string is used.

The present invention relates to a method for generating and transmitting code information in a mobile communication system, wherein a plurality of user terminals (UEs) mobile stations receive control information provided from one base station Node B through a shared channel and receive user information. A mobile communication system for classifying a control information signal for a user terminal by using a code specified for the terminal, characterized in that the code specified for the user terminal changes over time.

In this case, the control information signal for the user terminal may be classified by masking the code specific to the user terminal.

In particular, the present invention is a mobile communication system that transmits information through a common control channel and distinguishes user signals using a USMC, so that the USMC assigned to each UE is changed over time, Code information is generated using a random code string.

The present invention also provides a method for generating new code information by changing an initial state of a scrambling code with a mobile station and / or time; Allocating an initial state usable for each UE by dividing the generated scrambling code period by the number of divisions of the UE; And transmitting the information to the corresponding mobile station by using the generated code information.

In the present invention, the process of allocating / assigning the initial state of the scrambling code to each mobile station; Generating new code information by changing an initial state allocated to each mobile station over time; And transmitting the information to the corresponding mobile station by using the generated code information.

The present invention relates to a method for generating and transmitting code information in a mobile communication system. The present invention relates to a mobile communication system that transmits information through a common control channel and distinguishes a user signal using a USMC. In order to change according to the, it is characterized in that the code information is generated by using a random code sequence different over time.

The present invention also provides a method for generating new code information by changing an initial state of a scrambling code with a mobile station and / or time; Allocating an initial state usable for each UE by dividing the generated scrambling code period by the number of divisions of the UE; And transmitting the information to the corresponding mobile station by using the generated code information.

In the present invention, the process of allocating / assigning the initial state of the scrambling code to each mobile station; Generating new code information by changing an initial state allocated to each mobile station over time; And transmitting the information to the corresponding mobile station by using the generated code information.

Other objects and features of the present invention will become apparent from the detailed description of the embodiments with reference to the accompanying drawings.

Hereinafter, a method of generating and transmitting information in a mobile communication system according to the present invention will be described with reference to the accompanying drawings.

As described above, a long PN code generation having randomness to be used in the present invention can be generated without designing a new code by using a scrambling code generator of a conventional CDMA system.

That is, the initial generation state information of the conventional long PN code generator having randomness may be generated by using a predetermined number of bits while changing the UE ID and time.

In general, what happens in Long PN code is a binary bit string.

That is, like a convolutional encoder, several shift registers are connected and have a loop that returns from the last shift register (SR) to the first SR.

The loop that returns to the first SR is entered first by regression from the middle SR and XOR operation.

As the generated bits are outputted in the last SR for each unit time, binary bits are continuously output as time passes.

For example, if the SR consists of four, the repetition period is 2 ⁴ = 16 bits, and 16 bits constitute one code.

Therefore, since the downlink scrambling code is composed of 24 SRs, after 2 ²⁴ bits are generated, a binary bit is generated by repeating from the first bit again.

Each bit within the ²⁴ bits has randomness.

In the above description, the period of the random code should be infinite, but in fact, 2 ²⁴ or 2 ¹⁸ is expressed as having randomness since a repetitively long number of bits passes.

The configuration of the regression loop determines the characteristics of the output binary bit string, and the binary bit string has a periodic characteristic which is repeated later.

Considering the SR structure, if the final state of the convolutional code is 0, the state of the initial occurrence state is the bit combination contained in the SR when the first bit signal is extracted. Say.

For example, assuming that the initial generation state is 7 and the SR is composed of four, it means that the SR values at the beginning of bit heat generation are set to (0,1,1,1).

This initial occurrence state indicates at what point the actual bit stream begins.

That is, if the initial occurrence state is 1 and SR = 3, assuming that the generation code is [1,1,1,0,0,0,1,1] (since the period is 8 bit strings), When the initial generation state is 4, it becomes [0,1,1,1,1,1,0,0]. (Three bits shifted)

As another example, if the scrambling code uses 24 SRs, the period is 2 ^{24, which} is very long.

Thus, the initial occurrence state is also 2 ²⁴ .

For example, if the number of bits to be obtained after the generation of the code is 40, 40 bits are generated and the 40 bits are used.

If we get the initial state to 1 and get 9 bits, and the initial state to 2, we get [1,1,0.0,0,0,0,1,1] and [1,1,1,0, 0,0,0,0,1], but it is called a shift version, but the two may be different codes.

In the HSDPA system, suppose the two UEs were the above two bits when a 9-bit code was used to allocate a UE ID for service.

If the correlation between the two codes is large, you may not know what information is being multiplied.

In other words, if the code is initially assigned to have a large correlation between two users, the two users must continue to suffer bad performance until the service is terminated.

However, when the code continues to change over time (in the present invention, the initial occurrence state continues to change), the correlation may be low at some time, and may be high at some time, but eventually changes over time, so that the bad case is maintained at an early stage. You can prevent bad situations.

5 is a flowchart illustrating a method of generating and using a long PN code having randomness.

A new code is generated by changing the initial state of the long PN code, which is a scrambling code, according to the UE ID and / or time. (Step 500).

The period of the scrambling code is divided by the number of divisions of the UE to allocate an initial state available for each UE. (Step 510).

The initial state information allocated to each UE is distributed over time. (Step 520).

Control information is transmitted to the corresponding UE using code information corresponding to an initial state value assigned to each UE over time. (Step 530).

In the above, in order to generate a different code for each user and / or each time, the initial state value of the random code generator may be differently provided for each user or / and code generation time.

In addition, each piece of time information is used by the packet sender and the receiver in common with each other, and only a part of a specific subset of the codesets generated by the above method can be selected to use only codes belonging to the subset.                     

It is proposed to apply a random long PN code generated by the above method to the HSDPA system.

The conventional W-CDMA system has its own scrambling code having a period of 2 ²⁴ .

Thus, the discernible initial state is 2 ²⁴ , and the bit stream coming from each initial state is random.

Therefore, the currently considered UE ID is configured to accommodate 1024 people with 10 bits, so that each UE can be allocated 2 ¹⁴ state information.

Therefore have a different initial state of each UE are in accordance with the time for each user identification, which therefore must not overlap is the initial state of the other UE, when to change in accordance with the initial state of the 2 ¹⁴ possible to the time information to solve the above conventional problems There is a number.

There may be a variety of time information that is a reference for code design (design), but the base station and the UE should be known in common, for example, SFN (System Frame Network).

As described above, in the present invention, in a mobile communication system that transmits information through a common control channel and classifies a user signal using a user-specific masking code (USMC), the scrambling code information is changed according to the mobile station and / or time. And generating information and transmitting the information to the mobile station using the generated code information.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments.

Therefore, the above description is not limited to the scope of the present invention by the limitation of the claims.

Therefore, according to the present invention, when distinguishing UEs using a user-specific scrambling code, the correlation value of the codes is high according to the UEs, so that each user (UE) cannot be distinguished, thereby preventing continuous classification errors. have.

Claims (11)

A mobile communication system in which a plurality of user terminals receive control information provided from one base station through a shared channel and classify control information signals for the user terminal by using a code specified for the user terminal. And a code specified for the user terminal changes over time. The method of claim 1, wherein the control information signal for the user terminal is masked and classified by a code specified for the user terminal. 3. The method of claim 2, wherein the code specified for the user terminal is assigned by taking a part of a random code string longer than twice as long as the code. A mobile communication system in which a plurality of user terminals receive control information provided from one base station through a shared channel and classify control information signals for the user terminal using a code specified for the user terminal. Generating new code information by changing an initial state of the scrambling code with a mobile station and / or time; And transmitting the information to the corresponding mobile station by using the generated code information. A mobile communication system in which a plurality of user terminals receive control information provided from one base station through a shared channel and classify control information signals for the user terminal using a code specified for the user terminal. Allocating / allocating the initial state of the scrambling code to each mobile station; Generating new code information by changing an initial state allocated to each mobile station over time; And transmitting the information to the corresponding mobile station by using the generated code information. 6. The information signal classification method according to claim 4 or 5, wherein newly generated code information is allocated to the mobile station by time distribution. 6. The information signal classification method according to claim 4 or 5, wherein the code state value of the scrambling code generator can be given differently for each mobile station and / or time. The information signal classification method according to claim 4 or 5, wherein the scrambling code is a Long PN code or a Short PN code having randomness. 8. The information signal classification method according to claim 7, wherein each time information uses time information which is common to both the information transmitting side and the receiving side. The method of claim 4, further comprising: dividing the generated scrambling code period by the number of divisions of the UE and allocating an initial state usable for each UE. 6. The method according to claim 4 or 5, wherein time information which is known to the packet transmitting side and the receiving side in common with each time information is used, and only a certain subset of the code sets generated by the above method is selected and assigned to the subset. Information signal classification method, characterized in that it can use only the code belonging.

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