KR20090068900A - Method for control channel mapping in mobile communication system - Google Patents

Abstract

A control channel mapping method of a terminal in a mobile communication system is provided to use other control channels efficiently and to improve the efficiency of an ACK channel. A terminal generates an encoded bit through channel encoding of information bit such as downlink channel information or acknowledgement signal, etc(S710). A terminal generates symbols by modulating encoded bits(S720). A terminal generates a spreading code as to length(S730), and maps the generated spreading signal to the correspondent region of each tile(S740).

Description

Control channel mapping method of terminal in mobile communication system {Method for control channel mapping in mobile communication system}

The present invention relates to a control channel, and more particularly, to a control channel mapping method capable of improving efficiency of a limited uplink control channel of a terminal and enabling multiplexing in an uncomplicated manner.

Various approaches have been proposed to efficiently use limited resources to support wireless broadband systems. Mobile WiMAX system based on Orthogonal Frequency Division Multiple Access (OFDMA) can obtain multi-user frequency diversity through frequency selective schedule in frequency selective fading environment in wideband channel. Subcarriers may be allocated in various forms according to a permutation scheme for a subcarrier. Thus, such a system can increase the capacity of a wireless channel with a multi-user diversity effect. In addition, the multi-antenna improves the efficiency of the spatial domain in the uplink and downlink. In the time domain, fast scheduling and link adaptation are used through a MAP signal containing uplink scheduling information. That is, in order to maximize downlink capacity, a downlink channel quality indicator (CQI) transmission scheme and a hybrid automatic repeat request (HARQ) for packet data transmission are applied.

As such, a control signal between the base station and the terminal is required in order to quickly react to a change in channel state in time, space, and frequency. In particular, in order to use adaptive resources for downlink, the UE needs to allocate resources for information transmission purpose for the downlink channel through the CQI channel. The terminal must also allocate resources for transmission of HARQ-related information for packet data transmission.

1 illustrates an example of a downlink frame structure of a mobile WiMAX system.

As shown in FIG. 1, a UE supporting downlink information transmits 4 to 6 bits of CQI for downlink through a CQI channel (CQICH) to a base station in a time-frequency resource in an uplink subframe structure. . As described above, a method of transmitting a control signal considering a plurality of users to a limited CQI channel structure using a spreading code in a time and frequency domain or classifying users through an orthogonal code may be applied.

For example, in the mobile WiMAX, the uplink control signal is transmitted using 4 to 6 bits of CQI information in a Partial Usage Sub-Carrier (PUSC) including three OFDM symbols on a time axis and 24 subcarrier regions on a frequency axis. . In other words, one tile may have a tile form of 3X4 (PUSC) or 3X3 (Optional PUSC), which is composed of three OFDM symbols on the time axis and four subcarriers on the frequency axis. In addition, six tiles are represented by one subchannel. Here, the uplink CQI channel is modulated with a QPSK symbol. If the index of the k-th modulation symbol in the m-th tile of the n-th uplink CQI channel is M _{n , 8m + k} (0≤k≤7), the possible modulation types are M _{n , 8m} , M _n as shown in Table 1. _{, 8m + 1} , M _{n , 8m + 2} , ..., M _{n , 8m + 7} .

Here, P0, P1, P2, and P3 are as shown in Equation 1 below.

Meanwhile, the ACK channel uses half the channel in the CQI channel structure.

However, conventional control signal transmission methods such as CQI and ACK have a limitation in capacity increase even if additional resources are allocated on the frequency axis or extended on the time axis in order to cope with an increase in the number of users. In order to send a large number of subchannels, it is not efficient, and there is a problem that waste of control signal resources increases.

Accordingly, an aspect of the present invention is to provide a method for mapping a control channel of a terminal capable of increasing capacity and improving efficiency of channel use in a control signal resource allocated to the terminal. have.

In order to achieve the above technical problem, in the control channel mapping method of a terminal according to an embodiment of the present invention, the terminal generates an encoded bit by channel encoding information bits of downlink channel information, and modulates the encoded bit. Generating symbols, generating a spreading code having a length set in the terminal, generating a spreading signal by applying the spreading code to the symbols within each tile of a CQI channel, and generating the spreading signal using the corresponding spreading signal in the corresponding region of each tile. Mapping to.

Advantageously, in order to provide a new control channel structure, each tile may comprise a structure in which pilot subcarriers are arranged consecutively on a time axis. In this case, each tile may have a tile form of a partial usage sub-carrier (PUSC), and three pilot subcarriers consecutive on a time axis may be arranged in two rows on a frequency axis.

Preferably, each tile may have a structure in which the number of pilot subcarriers and the number of data subcarriers are equally arranged.

Preferably, in order to provide a new control channel structure, each tile may include a structure in which pilot subcarriers are arranged consecutively on a frequency axis. In this case, each tile may have a shape of a PUSC tile, in which four pilot subcarriers consecutive on the frequency axis are arranged in one column on the frequency axis. In addition, each tile may have a structure to reduce degradation for frequency selective fading by applying permutation to obtain frequency frequency diversity.

Preferably, in the process of generating the encoded bits, the information bits may be encoded according to any one of 1/2, 1/4, 1/6, and 1/8. In this case, in the process of mapping the spread signal to the corresponding region of each tile, the process may include mapping a number of QPSK symbols determined according to the coding rate to each tile.

In addition, in order to achieve the above technical problem, the control channel mapping method of the terminal according to another embodiment of the present invention to generate the encoded bit by channel-encoding the information bits of the confirmation signal in the terminal, by modulating the encoded bit Generating symbols, generating a spreading code having a length set in the terminal, generating a spreading signal by applying the spreading code to the symbols in each tile of an ACK channel, and generating the spreading signal by using the corresponding spreading signal in the corresponding region of each tile. Mapping to.

Preferably, the ACK channel may be composed of three tiles.

Preferably, in the process of generating the encoded bits, the information bits may be encoded according to an encoding rate of 1/4 or less.

Advantageously, in order to provide a new control channel structure, each tile may comprise a structure in which pilot subcarriers are arranged consecutively on a time axis. In this case, each tile may have a tile shape of a PUSC, and three pilot subcarriers consecutive on the time axis may be arranged in two rows on the frequency axis.

Preferably, each tile may have a structure in which the number of pilot subcarriers and the number of data subcarriers are equally arranged.

Advantageously, in order to provide a new control channel structure, each tile may comprise a structure in which pilot subcarriers are arranged continuously on the frequency axis. In this case, each tile may have a shape of a PUSC tile, in which four pilot subcarriers consecutive on the frequency axis are arranged in one column on the frequency axis.

According to embodiments of the present invention, it is possible to improve the efficiency of a limited uplink control channel, for example, the CQI channel and the ACK channel of the terminal, to efficiently utilize other control channels, and control only by user-divided orthogonal code The channel may be reused, and the terminal may adaptively transmit CQI and ACK according to channel environment and mobility.

Hereinafter, with reference to the drawings will be described a preferred embodiment of the present invention. However, embodiments of the present invention illustrated below may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

Embodiments of the present invention propose a method of increasing capacity by effectively utilizing an allocated time and frequency resource region for transmitting uplink CQI information and ACK / NACK information.

2 illustrates a structure of a CQI channel having a tile form of 4 × 3 (PUSC).

3 illustrates a structure of a CQI channel having a tile form of 3X3 (Optional PUSC). In FIG. 2 and FIG. 3, the number of data subcarriers is the same as 48, but the number of pilot subcarriers is different.

The CQI channel structure defined in WiMax is composed of 48 sequences as shown in FIGS. 2 and 3 and transmits them as QPSK symbols. In the conventional CQI channel structure, a CQI channel structure is generated using various encoding and modulation schemes in which the CQI information is transmitted based on a conventional sequence to be allocated to a plurality of users. The transmission capacity for uplink can be increased by spreading the generated CQI information through orthogonal coding to enable multi-use.

In particular, embodiments of the present invention maximize the number of users that can be multiplexed by modifying the pilot number and position on the time and frequency axes from the conventional CQI channel structure. In the future, the IEEE 802.16m WiMAX may change the structure of the uplink control channel from the conventional PUSC type to various forms. That is, since the channel structure will be changed due to the consideration of mobility and the increase of users, the sequence-based uplink control channel structure needs to be modified into various structures.

Considering the conventional CQI channel structure, a channel structure can be generated by giving QPSK modulation and coding rate to various subcarriers corresponding to 48 subcarriers. Specifically, if the bit rate is set to 1/2, 1/4, 1/8, etc. when transmitting 6-bit CQI, the coded bits are 12 bits, 24 bits, and 48 bits, respectively. 12 and 24 symbols can be transmitted. Coding uses a convolutional code, a Reed-Muller code, a Reed-Solomon code, and the like. Each QPSK modulated symbol is spread through 48 orthogonal codes and mapped to 48 subcarriers. At this time, if the spread length of the orthogonal code in time and frequency is w, it can be represented by w ₀ , w ₁ , ..., w _{N -1} for N pieces, and multiple uses of N pieces are possible. In this case, when the spreading code is assigned to one or more tiles, since the channel between the tiles is different in nature due to the nature of the PUSC resource structure, the orthogonality of the spreading code may be damaged. Therefore, it is desirable to diffuse in one tile.

4 illustrates a region in which a symbol is spread through an orthogonal code in a conventional CQI channel structure when the coding rate is 1/2. When six bits of CQI information are encoded at a coding rate of 1/2, and subjected to QPSK modulation to spread with a spread code length of 8, eight users may be multiplexed.

FIG. 5 illustrates a region in which a symbol is spread through an orthogonal code in a conventional CQI channel structure when the coding rate is 1/4. Four users can be multiplexed by encoding 6-bit CQI information at a coding rate of 1/4 and spreading the spread code length by performing QPSK modulation.

FIG. 6 illustrates a region in which a symbol is spread through an orthogonal code in a conventional CQI channel structure when the coding rate is 1/8. Two users can be multiplexed by encoding 6-bit CQI information with a coding rate of 1/8 and spreading the spread code length by performing QPSK modulation.

In FIG. 4 to FIG. 6, the structure applied to one tile is equally applied to six tiles, and a dotted line indicates an area diffused through N orthogonal codes.

In summary, for one subchannel having 48 subcarriers, multiple uses satisfying the condition of (number of QPSK symbols) x length of spreading code used in one tile) = 48 are possible. In this case, multiple users may be multiplexed by the number of spreading codes, or the CQI transmission capacity of one terminal may be increased.

The mapping process as described above may be arranged as shown in FIG. 7. 7 is a flowchart illustrating a control channel mapping method of a terminal according to an embodiment of the present invention.

First, the terminal generates an encoded bit by channel encoding information bits such as downlink channel information or an acknowledgment signal (S710). In this case, the terminal uses a channel encoder suitable for a preset coding rate.

Next, symbols are generated by modulating the encoded bit (S720). The symbols are mapped to each tile constituting the control channel. In this case, the modulation scheme may be PSK, QAM, differential modulation, or the like.

Next, a spreading code having a length set in the terminal is generated (S730). In this case, examples of the generated spreading code include a Walsh-Hadamard sequence, a DFT-spreading code, and a Zadoff-Chu sequence.

Finally, a spreading signal is generated by applying the spreading code to symbols in each tile of the control channel, and the generated spreading signal is mapped to a corresponding region of each tile (S740).

CQI transmission is performed by mapping to six tiles through the above process. The decoding process can be interpreted inversely. In addition, in the above process, it is also possible to configure the CQI transmission scheme by selecting one or more steps.

Hereinafter, various transport channel structures in the time and frequency domains are derived by adjusting the number and position of pilots from the conventional CQI channel structure.

FIG. 8 illustrates a region in which a symbol is spread through an orthogonal code in a CQI channel structure in which pilot subcarriers are continuously arranged on a time axis when a coding rate is 1/2. In this case, if the coded bit is 12 bits and 6 QPSK symbols are spread with the spread code length 6, a total of 6 users can be multiplexed.

FIG. 9 illustrates a region in which a symbol is spread through an orthogonal code in a CQI channel structure in which pilot subcarriers are continuously disposed on a time axis when a coding rate is 1/4. In this case, if the coded bit is 24 bits, and 12 QPSK symbols are spread with a spread code length of 3, a total of 3 users can be multiplexed.

10 illustrates a region in which a symbol is spread through an orthogonal code in a CQI channel structure in which pilot subcarriers are continuously disposed on a time axis when a coding rate is 1/6. In this case, if the coded bit is 36 bits and 18 QPSK symbols are spread with the spread code length 2, a total of 2 users can be multiplexed.

FIG. 11 illustrates a region in which a symbol is spread through an orthogonal code in a CQI channel structure in which a pilot subcarrier is continuously disposed on a frequency axis when a coding rate is 1/2, according to an embodiment of the present invention. In this case, if the coded bit becomes 12 bits and 6 QPSK symbols are spread with a spread code length of 8, a total of 8 users can be multiplexed.

FIG. 12 illustrates a region in which a symbol is spread through an orthogonal code in a CQI channel structure in which pilot subcarriers are continuously disposed on a frequency axis when a coding rate is 1/4, according to an embodiment of the present invention. In this case, if the coded bit is 24 bits, and 12 QPSK symbols are spread with a spread code length of 4, a total of 4 users can be multiplexed.

FIG. 13 illustrates a region in which a symbol is spread through an orthogonal code in a CQI channel structure in which pilot subcarriers are continuously disposed on a frequency axis when a coding rate is 1/8, according to an embodiment of the present invention. In this case, if the coded bit becomes 48 bits and spreads 24 QPSK symbols with spreading code length 2, a total of 2 users can be multiplexed.

In summary, the 6-bit CQI transmission scheme can be shown in Table 2.

Each structure proposed above is a form for efficiently coping with channel changes with time and frequency. In addition, a structure may be considered that transmits each structure in a continuous tile to maintain orthogonality of the encoded signal distributed over six tiles. In the conventional PUSC transmission type, each tile is distributed to give frequency diversity to independently take a sequence within the tile to maintain orthogonality within each tile. However, when multiple users or mobility are considered in the future of IEEE 802.16m, tiles need to be continuously formed.

According to an embodiment of the present invention, multiple use is possible through spreading codes in a time and frequency domain within one tile, and CQI transmission adaptive to multiplexing is possible by having various types of CQI channel structures.

Currently, the CQI transmission method in IEEE 802.16e maps a vector index composed of orthogonal spreading codes to one tile, and maps the 6-bit CQI information to six tiles with one of 64 codewords. Is designed to be detected in a coherent or non-coherent manner. Embodiments of the present invention extend this to reduce the complexity of detection by transmitting a real modulation symbol, for example, a QPSK symbol to each tile, and move away from the conventional codeword-based detection scheme to improve symbol capacity or terminal performance. Can be improved.

Hereinafter, a detailed transmission structure for the ACK channel will be described.

Basically, in the case of the ACK channel, ACK / NACK 1 bit is transmitted using resources corresponding to 1/2 compared to the CQI channel of the PUSC 1 subchannel. In the CQI transmission channel structure proposed in FIGS. 4 to 6 and 8 to 13, one ACK channel capable of multiplexing a plurality of users through an orthogonal code is applied by applying a ratio 1/2 to an encoding and modulation scheme. Can be.

In addition, another ACK transport channel structure may be considered. That is, as the ACK transmission channel structure, a sequence-based transmission scheme based on the code rate 1/4 is proposed in the structure proposed in FIGS. 8 to 13.

In this regard, in FIG. 9, a spreading code may be assigned from one tile to a time domain and two pilot symbols and a data symbol 2 may be allocated to four frequency domains. In other words, in three tiles, it means that six sequences can be transmitted as data.

In FIG. 12, two data symbols and one pilot symbol are allocated to three OFDM symbols by applying a spreading code to the frequency domain.

14 through 16 illustrate a multi-user ACK channel transmission structure for sequence lengths 6 (= S ₀ , S ₁ ,..., S ₅ ) and 9 (= S ₀ , S ₁ , ..., S ₈ ). Indicates.

FIG. 14 illustrates a region in which a symbol is spread through an orthogonal code in an ACK channel structure in which pilot subcarriers are continuously disposed on a time axis according to another embodiment of the present invention. In FIG. 14, a redundancy sequence of three lengths and a length 3 spreading code are possible.

FIG. 15 illustrates a region in which a symbol is spread through an orthogonal code in an ACK channel structure in which pilot subcarriers are continuously disposed on a time axis according to another embodiment of the present invention. In FIG. 15, two sequences can be used in a spread code having a length of 2 through a sequence of length 9.

FIG. 16 illustrates a region in which a symbol is spread through an orthogonal code in an ACK channel structure in which pilot subcarriers are continuously disposed on a frequency axis according to another embodiment of the present invention. In FIG. 16, four redundant uses are possible with a sequence of length 6 and a spreading code of length 4.

Table 3 shows an example of a length 6 sequence and a length 9 sequence according to a 1 bit-ACK / NACK transport channel structure.

As shown in Table 3, when only two sequences allocated by four for conventional 1-bit transmission are selected and used, transmission can be simply performed. Table 4 shows an example of a length 6 sequence and a length 9 sequence according to a 2 bit-ACK / NACK transport channel structure.

In Table 4, a sequence of length 6 and a sequence of length 9 are allocated four by one. That is, in the ACK transmission channel structure based on the conventional 1-bit transmission can be configured as shown in Table 4 for 2-bit transmission.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. And, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The present invention relates to a control channel mapping method that can improve efficiency of a limited uplink control channel of a terminal and can be multiplexed in an uncomplicated method. The present invention relates to a related apparatus such as a terminal, a base station, and the like in an OFDMA-based mobile communication system. Applicable to the algorithm.

1 illustrates an example of a downlink frame structure of a mobile WiMAX system.

2 illustrates a structure of a CQI channel having a tile form of 4 × 3 (PUSC).

3 illustrates a structure of a CQI channel having a tile form of 3X3 (Optional PUSC).

4 to 6 illustrate a region in which a symbol is spread through an orthogonal code in a conventional CQI channel structure according to various coding rates.

7 is a flowchart illustrating a control channel mapping method of a terminal according to an embodiment of the present invention.

8 to 10 illustrate regions in which symbols are spread through an orthogonal code in a CQI channel structure in which pilot subcarriers are continuously disposed on a time axis according to various embodiments of the present invention, according to various coding rates.

11 to 13 illustrate regions in which a symbol is spread through an orthogonal code in a CQI channel structure in which pilot subcarriers are continuously disposed on a frequency axis according to various embodiments of the present invention, according to various coding rates.

14 to 16 illustrate regions in which a symbol is spread through an orthogonal code in the proposed ACK channel structure according to various embodiments of the present disclosure according to various user numbers.

Claims (16)

Generating encoded bits by channel encoding information bits of downlink channel information at a terminal; Generating symbols by modulating the encoded bit; Generating a spreading code having a length set in the terminal; And Generating a spreading signal by applying the spreading code to the symbols in each tile of a CQI channel, and mapping the generated spreading signal to a corresponding region of each tile Control channel mapping method of the terminal. The method of claim 1, Each tile is And a structure in which pilot subcarriers are arranged consecutively on a time axis. The method of claim 2, Each tile is A control channel mapping method of a terminal having a tile form of a partial usage sub-carrier (PUSC) and having three pilot subcarriers consecutive on a time axis arranged in two rows on a frequency axis. The method of claim 1, Each tile is The control channel mapping method of a terminal, characterized in that the number of pilot subcarriers and the number of data subcarriers are the same arrangement. The method of claim 1, Each tile is And a structure in which pilot subcarriers are arranged consecutively on a frequency axis. The method of claim 5, wherein Each tile is A control channel mapping method of a terminal having a tile form of a partial usage sub-carrier (PUSC) and having four pilot subcarriers consecutive on the frequency axis arranged in one column on the frequency axis. The method of claim 1, Generating the encoded bits, And encoding information bits according to a coding rate of any one of 1/2, 1/4, 1/6, and 1/8. The method of claim 7, wherein The step of mapping the spread signal to the corresponding area of each tile, And mapping the number of QPSK symbols determined according to the coding rate to each tile. Generating encoded bits by channel encoding information bits of the confirmation signal at the terminal; Generating symbols by modulating the encoded bit; Generating a spreading code having a length set in the terminal; And Generating a spreading signal by applying the spreading code to the symbols in each tile of an ACK channel and mapping the generated spreading signal to a corresponding region of each tile Control channel mapping method of the terminal. The method of claim 9, The ACK channel is, Control channel mapping method of the terminal, characterized in that consisting of three tiles. The method of claim 9, Generating the encoded bits, And encoding information bits according to a coding rate of 1/4 or less. The method of claim 9, Each tile is And a structure in which pilot subcarriers are arranged consecutively on a time axis. The method of claim 12, Each tile is A control channel mapping method of a terminal having a tile form of a partial usage sub-carrier (PUSC) and having three pilot subcarriers consecutive on a time axis arranged in two rows on a frequency axis. The method of claim 9, Each tile is The control channel mapping method of a terminal, characterized in that the number of pilot subcarriers and the number of data subcarriers are the same arrangement. The method of claim 9, Each tile is And a structure in which pilot subcarriers are arranged consecutively on a frequency axis. The method of claim 15, Each tile is A control channel mapping method of a terminal having a tile form of a partial usage sub-carrier (PUSC) and having four pilot subcarriers consecutive on the frequency axis arranged in one column on the frequency axis.

Images