Method and apparatus for supporting HARQ

Abstract

A method of supporting Hybrid Automatic Repeat Request (HARQ) includes receiving an initial uplink grant on a downlink channel, transmitting uplink data on an uplink channel using the initial uplink grant, receiving a request for retransmission of the uplink data, determining at least one transmission parameter of a channel quality indicator (cqi) from the initial uplink grant, multiplexing retransmission data of the uplink data with the cqi, and transmitting the multiplexed data on the uplink channel. Amount of resources for transmission of the cqi is determined based on the at least one transmission parameter.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a
b_k=p_k−A for k=A,A+1, . . . ,A+L−1   [Equation 1]

The CRC-attached bits b₀, b₁, . . . , b_B−1 are segmented in a code block unit, and the CRC, parity bits are re-attached in the code block unit (step 210). c_r0, c_r1, . . . c_r(Kr−1) denote a bit sequence output after the code block segmentation. Herein, if a total number of code blocks is C, r denotes a code block number, and Kr denotes the number of bits for the code block number r.

Channel coding is performed on a bit sequence for a given code block (step 220). d⁽ⁱ⁾₀, d⁽ⁱ⁾₁, . . . , d⁽ⁱ⁾_D−1 denote encoded bits. D denotes the number of encoded bits for each output stream, and i denotes an index of a bit stream output from an encoder.

Rate snatching is performed on the encoded bits (step 230), Then, code block concatenation is performed on the rate-matched bits (step 240). As a result, a data bit sequence f₀, f₁, . . . , f_G−1 is generated. Herein, G denotes a total number of encoded bits used to transmit bits other than bits that is used in control information transmission when the control information is multiplexed on a PUSCH.

The control information can be multiplexed together with data. The data and the control information can use different coding rates by allocating a different number of coded symbols for transmission thereof. Hereinafter, a CQI is considered as the control information.

Channel coding is performed on CQI values o₀, o₁, . . . , o_O−1 (where O is the number of CQI bits) to generate a control information bit sequence q₀, q₁, q_Q−1 (step 260). The CQI can use independent channel coding different from that used for the data. For example, when a block code (32, O) is used as channel coding for the CQI, a basis sequence M_i,n is as shown in Table 1 below.

TABLE 1
i	Mi, 0	Mi, 1	Mi, 2	Mi, 3	Mi, 4	Mi, 5	Mi, 6	Mi, 7	Mi, 8	Mi, 9	Mi, 10
0	1	1	0	0	0	0	0	0	0	0	1
1	1	1	1	0	0	0	0	0	0	1	1
2	1	0	0	1	0	0	1	0	1	1	1
3	1	0	1	1	0	0	0	0	1	0	1
4	1	1	1	1	0	0	0	1	0	0	1
5	1	1	0	0	1	0	1	1	1	0	1
6	1	0	1	0	1	0	1	0	1	1	1
7	1	0	0	1	1	0	0	1	1	0	1
8	1	1	0	1	1	0	0	1	0	1	1
9	1	0	1	1	1	0	1	0	0	1	1
10	1	0	1	0	0	1	1	1	0	1	1
11	1	1	1	0	0	1	1	0	1	0	1
12	1	0	0	1	0	1	0	1	1	1	1
13	1	1	0	1	0	1	0	1	0	1	1
14	1	0	0	0	1	1	0	1	0	0	1
15	1	1	0	0	1	1	1	1	0	1	1
16	1	1	1	0	1	1	1	0	0	1	0
17	1	0	0	1	1	1	0	0	1	0	0
18	1	1	0	1	1	1	1	1	0	0	0
19	1	0	0	0	0	1	1	0	0	0	0
20	1	0	1	0	0	0	1	0	0	0	1
21	1	1	0	1	0	0	0	0	0	1	1
22	1	0	0	0	1	0	0	1	1	0	1
23	1	1	1	0	1	0	0	0	1	1	1
24	1	1	1	1	1	0	1	1	1	1	0
25	1	1	0	0	0	1	1	1	0	0	1
26	1	0	1	1	0	1	0	0	1	1	0
27	1	1	1	1	0	1	0	1	1	1	0
28	1	0	1	0	1	1	1	0	1	0	0
29	1	0	1	1	1	1	1	1	1	0	0
30	1	1	1	1	1	1	1	1	1	1	1
31	1	0	0	0	0	0	0	0	0	0	0

b₀, b₁, b₃₁ denote an intermediate sequence for CQI channel coding and can be generated by Equation 2 below.

$\begin{array}{cc}{b}_1=\sum _{n=0}^{O-1}\left(o_n·M_{1,n}\right)\mathrm{mod}2,\mathrm{where}i=0,1,2,\dots ,31& \left[\mathrm{Equation}2\right]\end{array}$

The control information bit sequence q₀, q₁, . . . , q_Q−1 is generated by cyclically repeating the intermediate sequence b₀, b₁, . . . , b₃₁ according to Equation 3 below.
g₁=b_{(i mod 31)}, where i=0,1, . . . , Q−1   [Equation 3]

A data bit sequence f₀, f₁, . . . , f_G−1 is generated as described above and is multiplexed together with the control information bit sequence q₀, q₁, . . . , q_Q−1 into a multiplexed sequence g₀, g₁, . . . , g_H−1 (step 270). In a process of multiplexing, the control information bit sequence q₀, q₁, . . . , q_Q−1 can be arranged first and thereafter the data bit sequence f₀, f₁, . . . , f_G−1 can be arranged. That is, if H=G+Q, [g₀, g₁, . . . , g_H−1] may be configured such as [q₀, q₁, . . . , q_Q−1, f₀, f₁, . . . , f_G−1].

The multiplexed sequence g₀, g₁, . . . , g_H−1 is mapped to a modulation sequence h₀, h₁, h_H′−1 (step 280). Herein, h_i denotes a modulation symbol on constellation, and H′=H/Q_m′, Q_m denotes the number of bits for each modulation symbol of a modulation scheme. For example, when quadrature phase shift keying (QPSK) is used as the modulation scheme, Q_m=2.

Each modulation symbol of the modulation sequence h₀, h₁, h_H′−1 is mapped to a resource element for the PUSCH (step 290). The resource element is a unit of allocation on a subframe defined with one SC-FDMA symbol (or OFDMA symbol) and one subcarrier. The modulation symbols are mapped in a time-first manner. FIG. 8 shows resource mapping on a PUSCH. One slot includes 7 SC-FDMA symbols. In each slot, a 4^th SC-FDMA symbol is used to transmit a reference signal. Therefore, up to 12 SC-FDMA symbols can be used for the PUSCH in one subframe. A modulation sequence h₀, h₁, h_H′−1 is first mapped in a 1^st subcarrier region in an SC-FDMA symbol direction, and is then mapped in a 2^nd subcarrier region also in the SC-FDMA symbol direction. A front portion of the modulation sequence h₀, h₁, . . . , h_H′−1 corresponds to a CQI. Thus, the CQI is first mapped to resource elements in a front subcarrier region.

As described above, to transmit the CQI on the PUSCH, an amount of resources required to transmit the CQI needs to be determined first. The amount of resources is determined based on a transmission parameter (e.g., MCS, etc.) used in CQI transmission. The transmission parameter for the CQI denotes a parameter used for CQI transmission, and includes various parameters for determining the MCS and/or the amount of resources. If the amount of resources is expressed by the number Q′ of modulation symbols for the CQI, Q′ can be determined by Equation 4 below.

$\begin{array}{cc}{Q}^{\prime }=\left[\frac{\left(O+L\right)·M_{\mathrm{sc}}·N_{\mathrm{symb}}}{{10}^{\frac{-\Delta }{10}}·\sum _{r=0}^{C-1}{K}_r}\right]& \left[\mathrm{Equation}4\right]\end{array}$

In Equation 4, O denotes the number of CQI bits, L denotes the number of CRC bits, Δ denotes a parameter, C denotes a total number of code blocks, K_r denotes the number of bits for a code block number r, M_sc denotes the number of subcarriers used in PUSCH transmission, and N_symb denotes the number of SC-FDMA symbols used in PUSCH transmission. Transmission parameters for determining the aforementioned Q′ may be at least one of C, K_r, M_sc, and N_symb.

Now, a method of multiplexing retransmission data and a CQI and transmitting the multiplexed result through a PUSCH in a process of performing HARQ will be described.

When the HARQ is performed, the CQI may he transmitted by being multiplexed with initial data or retransmission data. This may occur when a CQI transmission period coincides with a retransmission period in periodic CQI reporting or when a response for a CQI transmission request coincides with the retransmission period in non-periodic CQI reporting.

When the CQI is multiplexed with the retransmission data, there is an issue as to how transmission parameters (e.g., MCS, etc.) for the CQI are determined. The issue is related to how to determine the transmission parameters used for the CQI multiplexed with the retransmission data. This is because, when the transmission parameters for CQI transmission have to be additionally reported by the BS to the UE even at retransmission, the reporting of the transmission parameters may act as a signaling overhead.

If the CQI is transmitted when the data is retransmitted, a CQI transmission parameter can, be determined according to the transmission parameters used in initial data transmission. For example, an MCS used in initial data transmission is used for CQI transmission when the data is retransmitted.

FIG. 9 is a flow diagram showing an HARQ method according to an embodiment of the present invention.

Referring to FIG. 9, in step S510, a BS transmits an initial uplink grant on a PDCCH. The initial uplink grant includes radio resource allocation information for initial uplink data in the HARQ method. In step S520, a UE transmits uplink data on a PUSCH indicated by the initial uplink grant.

In step S530, upon detecting a decoding error of the uplink data, the BS transmits a NACK signal as a retransmission request. The NACK signal may be transmitted on a PHICH.

In step S560, if a transmission subframe of retransmission data coincides with a transmission subframe of a CQI, the UE determines a transmission parameter of the CQI from the initial uplink grant. The transmission parameter is a parameter for determining an amount of radio resources required to transmit the CQI, and may be related to an MCS of the CQI. For example, when the amount of radio resources of the CQI is determined by Equation 4, at least one of transmission parameters C, K_r, M_sc, and N_symb can be obtained from the initial uplink grant.

In step S570, the UE multiplexes the CQI and the retransmission data of the uplink data by using the transmission parameter. In step S580, the UE transmits the multiplexed data on the PUSCH.

In HARQ retransmission, when the retransmission data is transmitted together with the CQI, the MCS of the CQI is determined according to the initial uplink grant, so that a signaling overhead can be reduced without additional signaling for the transmission parameter of the CQI to be multiplexed.

FIG. 10 is a flow diagram showing an HARQ method according to another embodiment of the present invention.

Referring to FIG. 10, in step S610, a BS transmits an initial uplink grant on a PDCCH. In step S620, a UE transmits uplink data on a PUSCH indicated by the initial uplink grant. In step S630, upon detecting a decoding error of the uplink data, the BS transmits a NACK signal as a retransmission request.

In step S640, the BS transmits a retransmission grant on the PDCCH. The retransmission grant includes radio resource allocation information for retransmission data regarding the uplink data.

In step s650, if a transmission subframe of retransmission data coincides with a transmission subframe of a CQI, the UE determines a transmission parameter of the CQI from the initial uplink grant. In step S670, the UE multiplexes the CQI and the retransmission of the uplink data by using the transmission parameter. In this case, the retransmission data is multiplexed using a transmission parameter obtained from the retransmission grant, and the CQI is multiplexed using a transmission parameter obtained from the initial grant. In step S680, the UE transmits the multiplexed data on the PUSCH.

FIG. 11 is a flow diagram showing an HARQ method according to another embodiment of the present invention.

Referring to FIG. 11, in step S700, a BS configures a periodic CQI. A UE periodically transmits the CQI according to a period determined by the BS. In step S710, the BS transmits an initial uplink grant on a PDCCH. The initial uplink grant includes radio resource allocation information for initial uplink data in the HARQ method. In step S720, the UE transmits uplink data on a PUSCH indicated by the initial uplink grant.

In step S730, the UE transmits the CQI at a CQI transmission period. In this case, if an available PUCCH resource exists, the CQI can be transmitted on a PUCCH. In step S740, upon detecting a decoding error of the uplink data, the BS transmits a NACK signal as a retransmission request.

In step S760, if a transmission subframe of retransmission data coincides with a transmission subframe of a CQI, the UE determines a transmission parameter of the CQI from the initial uplink grant.

In step S770, the UE multiplexes the CQI and the retransmission data of the uplink data by using the transmission parameter. In step S780, the UE transmits the multiplexed data on the PUSCH.

FIG. 12 is a flow diagram showing an HARQ method according to another embodiment of the present invention.

Referring to FIG. 12, in step S810, a BS transmits an initial uplink grant on a PDCCH. In step S820, a UE transmits uplink data on a PUSCH indicated by the initial uplink grant. In step S830, upon detecting a decoding error of the uplink data, the BS transmits a NACK signal as a retransmission request.

In step s840, the BS transmits a retransmission grant and a CQI request on the PDCCH. The CQI request is a signal optionally used by the BS to request the UE to transmit the CQI. Although the CQI request is transmitted on the PDCCH together with the retransmission grant the CQI request can be transmitted to the UE through an additional message.

In step S860, the UE determines a transmission parameter of the CQI from the initial uplink grant according to the CQI request of the BS. In step S870, the U multiplexes the CQI and the retransmission of the uplink data by using the transmission parameter. In this case, the retransmission data is multiplexed using a transmission parameter obtained from the retransmission grant, and the CQI is multiplexed using a transmission parameter obtained from the initial grant. In step S880, the UE transmits the multiplexed data on the PUSCH.

Although CQI multiplexing first retransmission has been proposed m the aforementioned embodiments, the CQI transmission parameter can be obtained from the initial uplink grant even if the CQI is transmitted by being multiplexed at n-th retransmission (where n>1).

By using the transmission parameter used in initial data transmission as the CQI transmission, parameter, additional signaling for the CQI transmission parameter is not necessary.

While performing the HARQ, to multiplex and transmit the retransmission data and the CQI on the PUSCH, a CQI transmission parameter can be obtained not only from the initial uplink grant but also from other grants. For example, the transmission parameter used for the retransmission data multiplexed together with the CQI can be set to the CQI transmission parameter. This is a case where the same MCS used for the retransmission data is used to transmit the CQI at retransmission. For another example, the transmission parameter used in previous transmission can be used as the CQI transmission parameter. This is a case where, when second retransmission data and the CQI are multiplexed at second retransmission, the transmission parameter used for the first retransmission data is set to the transmission parameter.

As described above, a non-periodic CQI is transmitted at the request of the BS. In general, the CQI request can be transmitted on the PDCCH. In this case, a transmission indicator for the CQI transmission parameter can be transmitted along with the CQI request. The CQI may be transmitted using an allocated resource (or transmission parameter) according to the transmission indicator, or the CQI may be transmitted using a previously allocated resource (or transmission parameter).

FIG. 13 is a block diagram showing an apparatus for wireless communication according to an embodiment of the present invention. An apparatus 50 for wireless communication may be a part of a UE. The apparatus 50 for wireless communication includes a processor 51, a memory 52, a radio frequency (RF) unit 53, a display unit 54, and a user interface unit 55. The RF unit 53 is coupled to the processor 51 and transmits and/or receives radio signals. The memory 52 is coupled to the processor 51 and stores an operating system, applications, and general files. The display unit 54 displays a variety of information of the UE and may use a well-known element such as a liquid crystal display (LCD), an organic light emitting diode (OLED), etc. The user interface unit 55 can be configured with a combination of well-known user interfaces such as a keypad, a touch screen, etc. The processor 51 supports HARQ and AMC. The processor 51 can configure a PUCCH or a PUSCH and can perform multiplexing of data and a CQI. The aforementioned embodiments of the HARQ method can be implemented by the processor 51.

The present invention can be implemented with hardware, software, or combination thereof. In hardware implementation, the present invention can be implemented with one of an application specific integrated circuit (ASIC), a digital signal processor (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microprocessor, other electronic units, and combination thereof, which are designed to perform the aforementioned functions. In software implementation, the present invention can be implemented with a module for performing the aforementioned functions. Software is storable in a memory unit and executed by the processor. Various means widely known to those skilled in the art can be used as the memory unit or the processor.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.

Claims

1. A method for supporting retransmission in a wireless communication system, the method performed by a user equipment (UE) and comprising:

receiving a channel quality indicator (cqi) request from a base station;

multiplexing retransmission data of an initial uplink data with a cqi channel quality indicator (cqi); and

transmitting the multiplexed data on a physical uplink shared channel (PUSCH) to a base station,

wherein a radio resource for the cqi is determined based on a transmission parameter including information on an allocated resource used for transmission of the initial uplink data.

2. The method of claim 1, wherein the cqi is an aperiodic cqi.

3. The method of claim 1, further comprising:

receiving an initial uplink grant on a physical downlink control channel (PDCCH),

wherein the initial uplink grant is used for the initial uplink data.

4. The method of claim 1, further comprising:

receiving a cqi request from the base station,

wherein the cqi request is used to trigger transmission of the cqi from the UE.

5. The method of claim 1, further comprising:

receiving a retransmission uplink grant on a PDCCH,

wherein the multiplexed data is transmitted based on a radio resource which is determined based on the retransmission uplink grant.

6. A user equipment (UE) supporting retransmission in a wireless communication system, the UE comprising:

a radio frequency unit transmitting and receiving a radio signal; and

a processor coupled to the radio frequency unit and configured for:

receiving a channel quality indicator (cqi) request from a base station;

multiplexing retransmission data of an initial uplink data with a cqi channel quality indicator (cqi); and

transmitting the multiplexed data on a physical uplink shared channel (PUSCH) to a base station,

wherein a radio resource for the cqi is determined based on a transmission parameter including information on an allocated resource used for transmission of the initial uplink data.

7. The UE of claim 6, wherein the cqi is an aperiodic cqi.

8. The UE of claim 6, wherein the processor is further configured for:

receiving an initial uplink grant on a physical downlink control channel (PDCCH),

wherein the initial uplink grant is used for the initial uplink data.

9. The UE of claim 6, wherein the processor is further configured for:

receiving a cqi request from the base station,

wherein the cqi request is used to trigger transmission of the cqi from the UE.

10. The UE of claim 6, wherein the processor is further configured for:

receiving a retransmission uplink grant on a PDCCH,

wherein the multiplexed data is transmitted based on a radio resource which is determined based on the retransmission uplink grant.

11. A method for supporting retransmission in a wireless communication system, the method performed by a base station (BS) and comprising:

transmitting a channel quality indicator (cqi) request to a user equipment (UE); and

receiving multiplexed data on a physical uplink shared channel (PUSCH) from the UE,

wherein the multiplexed data includes retransmission data of an initial uplink data with a cqi,

wherein a radio resource for the cqi is determined based on a transmission parameter including information on an allocated resource used for transmission of the initial uplink data.

12. The method of claim 11, wherein the cqi is an aperiodic cqi.

13. The method of claim 11, further comprising:

transmitting an initial uplink grant on a physical downlink control channel (PDCCH),

wherein the initial uplink grant is used for the initial uplink data.

14. The method of claim 11, wherein the cqi request is used to trigger transmission of the cqi from the UE.

15. The method of claim 11, further comprising:

transmitting a retransmission uplink grant on a PDCCH,

wherein the multiplexed data is transmitted based on a radio resource which is determined based on the retransmission uplink grant.

16. A base station (BS) supporting retransmission in a wireless communication system, the BS comprising:

a radio frequency unit transmitting and receiving a radio signal; and

a processor coupled to the radio frequency unit and configured for:

transmitting a channel quality indicator (cqi) request to a user equipment (UE); and

receiving multiplexed data on a physical uplink shared channel (PUSCH) from the UE,

wherein the multiplexed data includes retransmission data of an initial uplink data with a cqi,

wherein a radio resource for the cqi is determined based on a transmission parameter including information on an allocated resource used for transmission of the initial uplink data.

17. The BS of claim 16, wherein the cqi is an aperiodic cqi.

18. The BS of claim 16, wherein the processor is further configured for:

transmitting an initial uplink grant on a physical downlink control channel (PDCCH),

wherein the initial uplink grant is used for the initial uplink data.

19. The BS of claim 16, wherein the cqi request is used to trigger transmission of the cqi from the UE.

20. The BS of claim 16, wherein the processor is further configured for:

transmitting a retransmission uplink grant on a PDCCH,

wherein the multiplexed data is transmitted based on a radio resource which is determined based on the retransmission uplink grant.

21. A method for supporting retransmission in a wireless communication system, the method performed by a user equipment (UE) and comprising:

performing an initial transmission of uplink data to a base station, based on at least one initial transmission parameter related to a first allocated resource for the initial transmission of the uplink data;

receiving a channel quality indicator (cqi) request from the base station; and

performing a retransmission of the uplink data which is multiplexed with a cqi,

wherein performing the retransmission of the uplink data which is multiplexed with the cqi comprises:

multiplexing the uplink data with the cqi, based on receiving the cqi request; and

transmitting the uplink data multiplexed with the cqi on a physical uplink shared channel (PUSCH) to the base station,

wherein the uplink data is multiplexed based on at least one retransmission parameter related to a second allocated resource for the retransmission of the uplink data, and

wherein the cqi is multiplexed based on the at least one initial transmission parameter related to the first allocated resource for the initial transmission of the uplink data.

22. The method of claim 21, wherein the cqi is an aperiodic cqi.

23. The method of claim 21, further comprising:

receiving, on a physical downlink control channel (PDCCH), an initial uplink grant for the initial transmission of the uplink data,

wherein the at least one initial transmission parameter is determined based on the initial uplink grant.

24. The method of claim 21, wherein the cqi request is used to trigger transmission of the cqi from the UE.

25. The method of claim 21, further comprising:

receiving, on a PDCCH, a retransmission uplink grant for the retransmission of the uplink data,

wherein the at least one retransmission parameter is determined based on the retransmission uplink grant.

26. The method of claim 21, wherein the at least one initial transmission parameter comprises at least one of (i) a parameter related to a size of a resource region, (ii) a parameter related to a modulation order, or (iii) a parameter related to a coding scheme for the initial transmission of the uplink data.

27. The method of claim 21, wherein the at least one retransmission parameter comprises at least one of (i) a parameter related to a size of a resource region, (ii) a parameter related to a modulation order, or (iii) a parameter related to a coding scheme for the retransmission of the uplink data.

28. The method of claim 21, wherein the at least one initial transmission parameter comprises first resource allocation information for the initial transmission of the uplink data, and

wherein the at least one retransmission parameter comprises second resource allocation information for the retransmission of the uplink data.