KR100878802B1 - Method for Receiving of Walsh code allocation Information - Google Patents

Abstract

The present invention relates to wireless communication, and more particularly, to a method for receiving Walsh code assignment information in a terminal of a mobile communication system using a code division method and a time division method. To this end, the base station receives a bit sequence including Walsh code assignment information for the terminal from the base station, and the Walsh code assignment information for at least one terminal stored in the terminal is a set of mapped bit sequences. Bit sequence is obtained by obtaining Walsh code assignment information for the terminal from the mapped Walsh code assignment information.

PDCCH, MAC Identifier, Walsh Code

Description

Method for Receiving of Walsh code allocation Information}

1 is a diagram showing an example of data transmission by a TDM scheme.

2 is a diagram showing an example of data transmission by the CDM / TDM scheme.

3 is a diagram illustrating possible Walsh codes when the maximum CDM terminal is 2;

The present invention relates to wireless communication, and more particularly, to a method for receiving Walsh allocation information in a CDM / TDM for efficiently transmitting high-speed data through a wireless channel.

Since the wireless communication environment is a channel that changes according to the location and mobility of the terminal, there is a need for a method that can adapt to a changing channel.

As a method of enabling high-speed data transmission while efficiently using a wireless channel in a wireless channel environment that changes over time, a method of accommodating and adapting a channel to change a modulation scheme and a channel coding are changed. There is a way to.                         

In order to reduce the error rate by adding an extra amount of information data using channel coding, an increase in the amount of data transmitted on an actual wireless channel is essential.

Since the wireless communication environment is a channel that changes according to the location and mobility of the terminal, it is possible to increase the transmission speed by sending a lot of actual information data by using a high code rate coding, which reduces the amount of redundancy when the communication environment is good. In addition, when the wireless communication environment is bad, it is necessary to use a low code rate coding that gives a lot of redundancy so that it is resistant to errors, and thus, the transmission rate should be low.

On the other hand, in the modulation method, when a wireless communication environment is good, high-speed data transmission such as quadrature amplitude modulator (QAM) or phase shift keying (PSK), which transmits several information bits in one transmission symbol, is performed. When this possible transmission method is used, if the wireless communication environment is bad, a transmission method such as BPSK (Binary Phase Shift Keying), which is strong against interference noise but has a slow transmission speed, is selected.

The above modulation scheme should send information about the channel environment from the receiver for estimating the channel environment in order to adapt the environment of the channel to change the modulation method and the coding method.

In addition, a system requiring efficient high-speed data transmission uses a time division multiplexing (TDM) scheme for scheduling a terminal to transmit data in every transmission unit interval in consideration of channel environment information and amount of data to be sent.

Before describing the data transmission of the TDM scheme, the parameters discussed below will be described.

Walsh code is a generic name for codes that are orthogonal to each other used when transmitting physical channels.
W (k, n) means the k th Walsh code of the Walsh matrix of length n. This means the k th row of the Hadamard matrix, where n = 2 ^m (0 ≦ k ≦ n−1).
The following is an example of a Walsh code of length 8. At this point, there are eight Walsh codes.
W (0,8) = 1, 1, 1, 1, 1, 1, 1, 1
W (1,8) = 1, -1, 1, -1, 1, -1, 1, -1
W (2,8) = 1, 1, -1, -1, 1, 1, -1, -1
W (3,8) = 1, -1, -1, 1, 1, -1, -1, 1
W (4,8) = 1, 1, 1, 1, -1, -1, -1, -1
W (5,8) = 1, -1, 1, -1, -1, 1, -1, 1
W (6,8) = 1, 1, -1, -1, -1, -1, 1, 1
W (7,8) = 1, -1, -1, 1, -1, 1, 1, -1
It can be seen that the generated Walsh codes are orthogonal to each other.

The Walsh Code Space is a collection of Walsh codes currently available when the base station transmits packet data. The components change over time. As shown in the Walsh code generation example above, the number of orthogonal Walsh codes is limited so that Walsh codes assigned to one terminal cannot be used by other terminals. Therefore, if a terminal is assigned a Walsh code by the base station when accessing the base station and then disconnects, the corresponding Walsh code may be assigned to another terminal.
The base station and the terminal must share information about the current Walsh code length and the total number of Walsh codes. The base station informs the specific terminal of allocation information about Walsh codes to be assigned to a specific terminal among available Walsh codes, which is called Walsh code assignment information.

Packet Data CHannel (PDCH) (i) means the i-th PDCH when more than two PDCHs are available. In this case, each PDCH uses Walsh codes in Walsh code space separately. That is, each PDCH must be masked with a different Walsh code so that the PDCH can be distinguished from each other due to orthogonality.

PDCCH (i) is a generic name of a physical channel that contains control information transmitted by a base station to terminals in order to successfully receive PDCH (i) when more than one PDCH may exist.

Figure 1 shows an example of data transmission by the TDM method.

In FIG. 1, the transmission unit time length may be fixed or variable.

However, if only one terminal is transmitted in every transmission unit interval as in TDM, data is good, but if the amount of data to be transmitted is small, Walsh space remains, resulting in an inefficient system.

Accordingly, in the TDM packet data transmission system, CDM / TDM (Code) is used to transmit data to other terminals by using Walsh which has been spared even after assigning Walsh to one terminal in each transmission unit interval for efficient use of resources. Division Multiplexing / Time Division Multiplexing) has been introduced.

2 shows an example of transmission by the CDM / TDM method.

As shown in FIG. 2, several CDM terminals may exist in one transmission unit section.

When the CDM / TDM method is used, when the number of CDM terminals is 3 or more, it is known that the performance of the entire system is not greatly improved. Therefore, the maximum number of CDM terminals is limited to two in the 1 × EVDV system.

Fields of the PDCCH (or SPDCCH: also called Secondary PDCCH) proposed in 1 × EVDV to implement CDM / TDM are shown in Table 1 below.

Field Length (bits) MAC Identifier (Inner CRC) 8 ARQ channel identifier 2 Subpacket identifier 2 Encoder packet size 3 Last Walsh Code Index 5 Sequence bits One Sum 21

In Table 1, the MAC identifier is a terminal identifier, and values except for (00000000) _{2 indicate} to which terminal information of the PDCCH being transmitted is transmitted.

The ARQ channel identifier and the sub packet identifier are binary information bits that inform the terminal whether to retransmit information on the PDCH corresponding to the PDCCH. The encoder packet size tells the number of bits of data information transmitted on the PDCH.

The Last Walsh Code Index is a binary information bit indicating information on a Walsh code used by a corresponding PDCH (i) among codes on a Walsh code space. The last Walsh code index indicates information on a Walsh code assigned to each terminal. It tells you (ie Walsh code assignment information).

In addition, in order to indicate whether an error occurs when the information bits shown in Table 1 are transmitted through a physical channel, error detection coder bits such as a CRC code are added during transmission, or whether an error occurs in the MAC identifier. It adds a function to distinguish between them. Like the latter, since the MAC identifier is used to distinguish the occurrence of an error in the transmission, it is also called the inner CRC (Internal CRC).

For example, if there are two terminals to be CDM, the base station sends PDCCH1 to terminal 1 and PDCCH2 to terminal 2 to inform the PDCH information.

Terminal 1 receives the Last Walsh Code Index WCI1 of the PDCCH1, and reads the Walsh code assigned to it from the Walsh code list according to the WCI1.

The terminal 2 reads the last Walsh code index WCI1 of the PDCCH1 and the last Walsh code index WCI2 of the PDCCH2 to obtain Walsh code information allocated to the terminal from the Walsh code list.

Table 2 shows an example of the Walsh code list.

Last Walsh Code Index 32-ary Walsh Code Last Walsh Code Index 32-ary Walsh Code One 31 15 30 2 15 16 14 3 23 17 22 4 7 18 6 5 27 19 26 6 11 20 10 7 19 21 18 8 3 22 2 9 29 23 28 10 13 24 12 11 21 25 20 12 5 26 4 13 25 27 24 14 9 28 8

For example, if the last Walsh code index (WCI1) reads from the PDCCH1 by the terminal 1 is 5, and the last Walsh code index (WCI2) reads from the PDCCH2 by the terminal 2 is 8, the terminal 1 displays the Walsh code index of Table 2 above. Walsh codes from 1 to WCI1, that is, 1 to 5 (31, 15, 23, 7, 27) are assigned, and terminal 2 is assigned to WCI1 + 1 to WCI2, that is, 6 to 8 (11, 19, 3). ) Walsh code is assigned.

As described above, in the related art, the PDCCH field transmitted in parallel with the PDCH transmits a last Walsh code index including Walsh code assignment information.

However, if the change in the channel environment decreases, the change of Walsh code allocation information allocated to each terminal also decreases. Therefore, the last Walsh code index bits included in the PDCCH each time the PDCH is transmitted, the number of bits is increased without any role. .

As a result, there is a problem that the decoding capability of the PDCCH field is degraded and the performance of the system is degraded.

Accordingly, the present invention has been made in view of the above-mentioned problems of the prior art, and is to provide a Walsh code information transmission method in CDM / TDM that is suitable for improving the performance of the system.

In an aspect of the present invention for achieving the above object, a method for receiving Walsh code assignment information in a terminal of a mobile communication system using a code division scheme and a time division scheme are disclosed. To this end, receiving a bit sequence including Walsh code assignment information for the terminal from the base station and the reception in a mapping table that is a set of bit sequences mapped Walsh code assignment information for at least one terminal stored in the terminal And obtaining the Walsh code assignment information for the terminal from the Walsh code assignment information to which the bit sequence is mapped.
Advantageously, said bit sequence is received via a Packet Data Control Channel (PDCCH).
Advantageously, the base station further assigns a Walsh code for said terminal in accordance with Walsh code assignment information for said terminal.
Preferably, when mapping Walsh code assignment information for two terminals to the bit sequence, the value of Walsh code assignment information allocated to one terminal is greater than the value of Walsh code assignment information assigned to another terminal. To be equal.
Preferably, when the terminal identifier included in the packet data control channel does not perform an identification function, the bit sequence is broadcast using the remaining bits except for the terminal identifier in the packet data control channel.
Preferably, the terminal identifier uses a MAC identifier.
Preferably, the mapping table is shared between the terminal and the base station.

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Hereinafter, the configuration and operation according to an embodiment of the present invention will be described with reference to the accompanying drawings.

The present invention proposes a method for receiving Walsh code assignment information in a terminal for improving performance of a system in a CDM / TDM packet data transmission system.

Table 3 below shows fields of the PDCCH used in the present invention.

Field Length (bits) MAC Identifier (Inner CRC) 8 ARQ channel identifier 2 Subpacket identifier 2 Encoder packet size 3 Sequence bits One Sum 16

In the PDCCH used in the present invention, as shown in Table 3, the last Walsh code index has been deleted compared to the prior art, thereby reducing 5 bits. Other types of information bits other than the information bits shown in Table 3 may be added, which is irrelevant to what the present invention intends to achieve.

In Table 3, the ARQ channel identifier and the sub packet identifier are binary information bits that inform the terminal whether to retransmit information on the PDCH corresponding to the PDCCH.

In detail, the ARQ channel identifier is for identifying each encoder packet when a plurality of encoder packets are transmitted in parallel to one terminal, and the sub packet identifier is a number of sub packets in one encoder packet. Information about whether a symbol encoded from one information stream is repeated and divided into predetermined subpackets.

The encoder packet size is a binary information bit that tells the number of data information bits to be transmitted on the PDCH.

The MAC identifier is a terminal identifier and indicates to which terminal the information of the PDCCH being transmitted is transmitted in values except for (00000000) ₂ .

As shown in the field structure of the PDCCH of Table 3, the PDCCH of the present invention has no bit structure for transmitting Walsh code assignment information. Therefore, in the present invention, Walsh code assignment information is not transmitted when the PDCH and the PDCCH are transmitted.

In the present invention, the Walsh code assignment information for at least one terminal is mapped to a bit sequence consisting of predetermined bits prior to service, and the mapping table is configured by repeating the mapping corresponding to the number of bit sequences. And save it to the terminal.

In this case, the number of bits of the bit sequence is 8 bits, that is, the number of bits of Walsh code allocation information to be transmitted to the terminal of the terminal, that is, the number of bits except the MAC identifier in the PDCCH.

The Walsh information is broadcasted to all terminals when the MAC identifier of the PDCCH has a specific bit value.

For example, when the MAC identifier is a bit that does not have a terminal identification function, such as (00000000) ₂ , the Walsh code allocation information is broadcast by broadcasting information on Walsh code assignment in the remaining 8 bits except the MAC identifier of the PDCCH. Update

At this time, when the change in the channel environment is large and the change in the Walsh code assignment information allocated to each terminal is large, the number of times of broadcasting the Walsh code assignment information is increased, and the change in the channel is small so that the change in the Walsh code assignment information allocated to each terminal is small. In this case, the number of times of Walsh code assignment information is reduced.

That is, since the use of bits for the transmission of Walsh code allocation information can be reduced when the channel change is small, the present invention can be particularly useful when the channel environment changes little.

In the present invention, the maximum number of CDM terminals is not limited, but in general, when the number of CDM terminals is three or more in the CDM / TDM scheme, it is known that the performance of the entire system is not significantly improved compared to the complexity of the algorithm. Currently, two CDM maximum terminals are considered preferable. In fact, in the 1 × EVDV system, the maximum number of CDM terminals is limited to two.

Hereinafter, the present invention will be described in more detail by taking an example when the maximum CDM terminal is two.

In an embodiment of the present invention, Walsh code allocation information should be informed to two terminals served using 8 bits other than 8 bits of MAC identifier of the PDCCH.

Since the maximum number of Walsh codes that can be allocated to the terminal is 28, if the number of Walsh codes assigned to the terminal 1 is WSC1 and the number of Walsh codes assigned to the terminal 2 is WSC2, WSC1 + WSC2≤28. A total of 10 bits are required, 5 bits per terminal.

Therefore, since 10 bits cannot be represented by 8 bits except the MAC identifier, the present embodiment proposes that WSC1 > WSC2. That is, Walsh is allocated to terminal 1 more than terminal 2.

In this case, as shown in Table 4 and FIG. 3, the total number of possible Walsh code assignments is limited to 224, which enables expression in an 8-bit bit sequence.

Bit sequence WSC1 WSC2 00000000 One 0 00000001 One One 00000010 2 0 00000011 2 One 00000100 2 2 00000101 3 0 … … … 11011111 27 One 11100000 28 0

The bit sequence corresponds to a bit stream that Walsh code assignment information may have, and is equal to the number of bits except for the MAC identifier of PDCCH, which is a transmission channel of Walsh code assignment information. That is 8 bits.

Subsequently, the Walsh code assignment information is broadcast in 8 bits except the MAC identifier.

At this time, each of the terminals (terminals 1 and 2) and the base station is previously stored in the mapping table of Table 4, the terminal 1, 2 has its own Walsh code number WSC1, according to the bit value contained in 8 bits except the MAC identifier Recognize each WSC2

Subsequently, from Table 2, the terminal 1 can know the WSC1 Walsh codes from 1 to WSC1, and the terminal 2 finds that the WSC2 Walsh codes from WSC1 + 1 to WSC1 + WSC2 are the Walsh codes assigned thereto.

By using the present invention as described above, since the Walsh code allocation information does not need to be transmitted for each PDCCH sent during PDCH transmission, the number of bits of the PDCCH can be reduced and the PDCCH decoding capability can be improved. There is an effect to be improved.

In particular, the present invention is more effective in an environment in which the change in the channel environment is small and the change in the Walsh code assignment information allocated to each terminal is small, that is, the frequency in which the Walsh code assignment information is updated is low.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the examples, but should be defined by the claims.

Claims (7)

A method for receiving Walsh code assignment information in a terminal of a mobile communication system using a code division method and a time division method, Receiving a bit sequence comprising Walsh code assignment information for the terminal from a base station; and Obtaining Walsh code assignment information for the terminal from the received Walsh code assignment information to which the bit sequence is mapped in a mapping table that is a set of bit sequences mapped with the Walsh code assignment information for at least one terminal stored in the terminal; Walsh code information receiving method comprising a. The method of claim 1, wherein the bit sequence is received through a Packet Data Control Channel (PDCCH). 2. The method of claim 1, further comprising the step of assigning a Walsh code for the terminal by the base station according to Walsh code assignment information for the terminal. 2. The method of claim 1, wherein when mapping Walsh code assignment information for two terminals to the bit sequence, the value of Walsh code assignment information allocated to one terminal is greater than the value of Walsh code assignment information assigned to another terminal. Walsh code information receiving method characterized in that to be greater than or equal to. The method of claim 2, wherein the bit sequence is to be broadcast using the remaining bits except the terminal identifier in the packet data control channel when the terminal identifier included in the packet data control channel does not perform an identification function. How to receive Walsh code information. 6. The method of claim 5, wherein the terminal identifier uses a MAC identifier. The method of claim 1, And the mapping table is shared between the terminal and the base station.

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