HK1159350B - Method for performing ack/nack feedback for downlink data transmission in radio communication system - Google Patents

Abstract

According to the present invention, a method for performing ACK(positive acknowledge)/NACK(negative acknowledge) feedback for downlink data transmission in radio communication system is provided. The method comprises at a mobile terminal the following steps: receiving downlink data; calculating, for each of component carriers (CCs), a number of ACKs for ACK/NACK information of respective downlink data subframes that the CC has; and feeding back the number of ACKs for the ACK/NACK information of the downlink data subframes of the respective CCs.

Description

Method for executing ACK/NACK feedback aiming at downlink data transmission of wireless communication system

Technical Field

The present invention relates to a wireless communication system, and more particularly, to a method of performing Acknowledgement (ACK)/Negative Acknowledgement (NACK) feedback for downlink data transmission of a wireless communication system, which can support hybrid automatic repeat request (HARQ) -based data transmission in the wireless communication system.

Background

The Long Term Evolution (LTE) system of the 3GPP standardization organization supports two duplexing modes, Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD). Fig. 1 is a frame structure of the LTETDD system. Each radio frame is 10ms in length and is equally divided into two half-frames of 5ms in length. Each field contains 8 time slots with the length of 0.5ms and 3 special fields, namely a downlink pilot time slot (DwPTS), a Guard Period (GP) and an uplink pilot time slot (UpPTS), and the sum of the lengths of the 3 special fields is 1 ms. Each subframe consists of two consecutive slots, i.e., the k-th subframe includes slot 2k and slot 2k + 1. The lte tdd supports 7 uplink and downlink configurations as shown in table 1. Here, D represents a downlink subframe, U represents an uplink subframe, and S represents the above-described special subframe including 3 special fields.

Table 1: uplink and downlink configuration of LTETDD

The LTE system is based on hybrid automatic repeat request (HARQ) for data transmission. The data receiving side transmits Acknowledgement (ACK) or Negative Acknowledgement (NACK) feedback information according to whether the data is correctly received. The scheduling of dynamic downlink data transmission is done through a Physical Downlink Control Channel (PDCCH). Each PDCCH may contain 1, 2, 4, or 8 Control Channel Elements (CCEs), and each CCE maps an acknowledgement/negative acknowledgement (ACK/NACK) channel. In this way, a PDCCH including a plurality of CCEs actually maps a plurality of ACK/NACK channels at the same time, and in the LTE system, the ACK/NACK channel actually used to transmit ACK/NACK information is implicitly determined by the smallest-indexed CCE among the CCEs constituting the PDCCH. Besides semi-persistent scheduling (SPS), PDCCH does not need to be sent for initial transmission of downlink data, and an ACK/NACK channel for feeding back ACK/NACK information is configured semi-statically; the retransmission of the downlink data is realized by PDCCH scheduling, and as with dynamic scheduling, an ACK/NACK channel for feeding back ACK/NACK information is determined by the PDCCH. The ACK/NACK feedback signal for HARQ transmission of downlink data is transmitted on an ACK/NACK channel of a Physical Uplink Control Channel (PUCCH).

In the LTE system, there are various feedback methods of ACK/NACK information. The first feedback method is to transmit ACK/NACK feedback information of only one downlink subframe in one uplink subframe. It is suitable for the uplink and downlink configuration of FDD and a part of TDD. When data is not transmitted by adopting MIMO, generating 1-bit ACK/NACK information; when data is transmitted using MIMO, 2-bit ACK/NACK information is generated. The second feedback method is to bind ACK/NACK feedback information of a plurality of downlink subframes to 1 or 2 bits, thereby transmitting the ACK/NACK information in the same manner as the first feedback method. It is only used for TDD systems. The bundling operation is performed on a codeword (codeword), that is, ACK/NACK information of a codeword having the same index for each downlink subframe that transmits data is bundled as one ACK/NACK information. The third feedback method is to transmit ACK/NACK feedback information of a plurality of downlink subframes within one uplink subframe, generate one ACK/NACK information for data transmission of each downlink subframe, and transmit a plurality of bits of ACK/NACK information based on QPSK modulation and an ACK/NACK channel selected for use among the plurality of ACK/NACK channels. In the LTE system, this number of bits is 2, 3, and 4. It is only used for TDD systems.

In LTE, downlink data transmission is dynamically scheduled through the PDCCH, and the UE may not correctly receive the PDCCH transmitted by the base station. Thus, in LTETDD, when ACK/NACK information for data transmission in multiple downlink subframes needs to be sent in one uplink subframe, a mechanism is needed so that a UE can detect whether it has lost a PDCCH in one or multiple downlink subframes. To achieve this, in LTETDD, a PDCCH includes a field, which includes 2 bits and is called a Downlink Assignment Indication (DAI). The DAI indicates how many downlink subframes the base station transmits the PDCCH in all up to the current downlink subframe in N (N is greater than or equal to 1) downlink subframes corresponding to one uplink subframe. The change sequence is 1, 2, 3 and 4. For example, the UE receives two PDCCHs and their DAIs are 1 and 3, respectively, the UE may determine that it misses one PDCCH with a DAI of 2. In addition, the DAI cannot detect the case where the last several PDCCHs are missed, e.g., the UE cannot confirm whether the base station transmits a PDCCH with a DAI equal to 4 in the above example. For the second method for feeding back ACK/NACK, the UE is specified to feed back ACK/NACK information on an ACK/NACK channel determined by the last subframe of the PDCCH received by the UE. By adopting the method, the base station can know whether the PDCCH of the last subframe or a plurality of subframes is lost by the UE according to the ACK/NACK channel actually occupied by the UE.

Since the DAI cannot detect the case where the last several PDCCHs are lost, in lte tdd, when it is necessary to simultaneously transmit ACK/NACK and a Scheduling Request (SR), or simultaneously transmit ACK/NACK and a Channel Quality Indication (CQI), another method is adopted to indicate ACK/NACK information. That is, the number of ACKs in the ACK/NACK information of each downlink data received by the UE is fed back, and if the number of downlink subframes is M, the number of indication ACKs in this method is 0, 1, … M; this number equal to 0 is also used to indicate the case where the UE detects at least one downlink data loss. By adopting the method, the base station can judge whether the UE correctly receives all the downlink data according to the number of the downlink data actually sent by the base station and the number of the ACK reported by the UE, thereby sending new data or retransmitting the new data.

In order to support higher transmission rate, in an enhanced long term evolution (LTE-a) system, a plurality of Component Carriers (CCs) are combined to obtain a larger working bandwidth, and downlink and uplink of a communication system, i.e., carrier combining (carrieraggrange), are formed. For example, to support a bandwidth of 100MHz, it can be obtained by combining 5 CCs of 20 MHz.

For LTE-a, there is a method for feeding back ACK/NACK by UE, which is based on multi-code transmission, assuming that the UE receives downlink data on N CCs at the same time, and each downlink data corresponds to an ACK/NACK channel, the UE sends ACK/NACK information on the N ACK/NACK channels at the same time, and sends ACK/NACK feedback information of the downlink data on the ACK/NACK channel corresponding to one downlink data. The method is a simple extension of an LTE processing method, but has the disadvantages that a plurality of ACK/NACK channels are occupied in parallel, the single carrier property of an uplink signal is damaged, so that the Cubic Metric (CM) of the uplink signal is higher, and the larger the number of the ACK/NACK channels transmitted in parallel is, the larger the CM value of the uplink signal and the downlink signal is; meanwhile, the transmitting power of the UE is dispersed to a plurality of ACK/NACK channels, which limits the coverage of uplink signals.

The invention provides a corresponding processing method for realizing compromise between feedback ACK/NACK information quantity and signal coverage or CM value.

Disclosure of Invention

An object of the present invention is to provide a method of performing Acknowledgement (ACK)/Negative Acknowledgement (NACK) feedback for downlink data transmission of a wireless communication system, capable of supporting hybrid automatic repeat request (HARQ) -based data transmission in the wireless communication system.

In order to achieve the above object, according to the present invention, there is provided a method of performing acknowledgement ACK/negative acknowledgement NACK feedback for downlink data transmission of a wireless communication system, the method comprising, at a mobile terminal, the steps of: receiving downlink data; calculating the ACK number of ACK/NACK information of each downlink data subframe of each CC aiming at each CC; and feeding back the ACK number of the ACK/NACK information of the downlink data subframe of each CC.

Drawings

The above objects, advantages and features of the present invention will become apparent by reference to the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, in which:

fig. 1 is a schematic diagram showing a frame structure of LTETDD; and

fig. 2 is a flowchart of a method of performing ACK/NACK feedback based on ACK/NACK channel selection according to an embodiment of the present invention.

Fig. 3 is a flowchart of a method of performing ACK/NACK feedback for downlink data transmission of a wireless communication system according to the present invention.

Fig. 4 is a flowchart of a method of performing ACK/NACK feedback based on joint coding according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

For the method of transmitting ACK/NACK information based on multi-code transmission, the more ACK/NACK channels are used simultaneously, the larger the CM value thereof is, and the smaller the maximum transmission power that can be used by each ACK/NACK channel is, so there is a tradeoff that the UE is allowed to transmit ACK/NACK information on two ACK/NACK channels at most. One benefit of this is that when the UE is configured with 2 power amplifiers and 2 antennas, the UE can actually use different antennas to transmit ACK/NACK information on different ACK/NACK channels, i.e., the transmitted signal on each antenna satisfies the single-carrier property, so that the CM value does not increase.

For each downlink CC, it is assumed that data of M downlink subframes is transmitted within one uplink subframe. For a subframe in a CC, generating 1-bit ACK/NACK information when data is not transmitted by adopting MIMO; when data is transmitted using MIMO, 2-bit ACK/NACK information is generated. And assuming that the UE detects downlink data on N CCs at the same time, the ACK/NACK information to be fed back by the UE is at most 2MN bits. When the values of M and N are both large, feeding back ACK/NACK information of 2MN bits completely requires occupying resources of multiple ACK/NACK channels, which is not favorable for reducing the CM value and uplink coverage of the uplink signal. Therefore, a certain processing is required for the 2MN bits to reduce the uplink overhead. The method of bundling data of each subframe of a CC is adopted, for example, ACK/NACK information of CW (code word) with the same index in each subframe is bundled to obtain 1 or 2 bits, but since the DAI cannot find the case of losing data of the last several subframes, it is not enough to transmit only the 2 bundled bits in order to enable the base station to recognize that the UE is bundling ACK/NACK information of those subframes, which inevitably increases the overhead of uplink feedback.

Referring to fig. 3, fig. 3 is a basic flow chart of the present invention. As shown in fig. 3, the process may include the following steps:

step 301, respectively calculating the number of ACKs in the ACK/NACK information of the downlink data for each CC.

When SPS data does not exist within one CC, the number of ACKs may be the number of consecutive ACKs in ACK/NACK information of each downlink data calculated in an increasing order of DAI from downlink data scheduled by PDCCH whose DAI is equal to 1. One calculation method is that for a CC, ACK/NACK information in each subframe obtains 1 ACK/NACK information through spatial binding, and then the number of continuous ACKs of the ACK/NACK information of each downlink data is calculated according to the ascending sequence of DAI from the downlink data scheduled by the PDCCH with the DAI equal to 1. For example, the UE receives data of 4 subframes and its ACK/NACK information is ACK, NACK, ACK, respectively, and the number of consecutive ACKs is equal to 2. The base station receives the information of the number of the continuous ACKs, and can know that the UE correctly receives downlink data of a plurality of continuous subframes from the subframe where the PDCCH with the DAI equal to 1 is located, so that only the downlink data which is not correctly received is retransmitted. Another calculation method is that no spatial bundling is performed on the ACK/NACK information of each subframe, and the number of consecutive ACKs of the ACK/NACK information of each CW is calculated in an ascending order of the DAI from the downlink subframe where the PDCCH with the DAI equal to 1 is located, where the number of consecutive ACKs may be counted for each subframe in an order of CW0 first and CW1 second. For example, assuming that the UE receives data of three subframes, the first subframe transmits two CWs using MIMO and the feedback information is ACK, the second subframe transmits only one CW and the feedback information is ACK, the third subframe transmits two subframes using MIMO and the feedback information is ACK, NACK, and then the number of consecutive ACKs is 4. The base station receives the information of the number of continuous ACKs, and can know how many continuous CW downlink data are correctly received by the UE from the subframe where the PDCCH with the DAI equal to 1 is located, so that only the downlink data which are not correctly received are retransmitted. For the case of no SPS, when the UE finds that downlink data scheduled by PDCCH with DAI equal to 1 is lost, the number of consecutive ACKs is 0.

When SPS data exists in one CC, when the number of continuous ACKs is calculated, the ACK/NACK information of each subframe is sequenced firstly, the ACK/NACK information of the SPS subframes is put in front, then the ACK/NACK information of downlink data scheduled by each PDCCH is sequenced in the ascending order of the DAI from the PDCCH with the DAI equal to 1, and then the number of the continuous ACKs is calculated. Similar to the absence of SPS data, 1 piece of ACK/NACK information may be obtained by spatially bundling ACK/NACK information in each subframe of one CC, and then the number of consecutive ACKs of ACK/NACK information of each downlink data is sequentially calculated; alternatively, spatial bundling is not performed for ACK/NACK information of each subframe, but the number of consecutive ACKs of ACK/NACK information of the respective CWs is sequentially calculated. For the case of SPS, when the UE finds that downlink data scheduled by PDCCH with DAI equal to 1 is lost, if the SPS data is correctly received, the number of consecutive ACKs is 1, otherwise the number of consecutive ACKs is 0.

In addition, the number of ACKs may be calculated directly, without depending on the value of DAI, in the ACK/NACK information of the downlink data on one CC. One calculation method is that for one CC, the ACK/NACK information in each subframe is spatially bound to obtain 1 ACK/NACK information, and then the number of ACKs of the ACK/NACK information of each downlink data is calculated. For example, the UE receives data of 4 subframes and its ACK/NACK information is ACK, NACK, ACK, respectively, and the number of ACKs is equal to 3. The base station receives the information of the number of the ACKs, if the number of the ACKs is equal to the number of the subframes which are actually sent by the base station, the base station knows that the UE correctly receives all the sent downlink data, otherwise, the base station needs to retransmit all the downlink data. Another calculation method is to calculate the number of ACKs of ACK/NACK information for each CW without performing spatial bundling for ACK/NACK information of each subframe. For example, assuming that the UE receives data of three subframes, the first subframe transmits two CWs using MIMO and the feedback information is ACK, the second subframe transmits only one CW and the feedback information is NACK, the third subframe transmits two subframes using MIMO and the feedback information is ACK and NACK, the number of ACKs is 3. The base station receives the information of the number of ACKs, if the number of ACKs is equal to the number of CWs in the subframe in which the base station actually transmits data, the base station knows that the UE correctly receives all transmitted downlink data, otherwise, the base station needs to retransmit all downlink data.

After the number of ACKs is calculated according to the above method, in order to further control the overhead of feedback, the number of consecutive ACKs may be further mapped many-to-one. Assuming that the downlink subframe M corresponding to the same uplink subframe is equal to 4, the number of consecutive ACKs may be 0, 1, 2, 3, 4, and these 5 values may be mapped into 4 states, and thus may be represented by two bits. For example, ACK numbers 2 and 3 are mapped to the same state, and ACK numbers 0, 1, and 4 are mapped to the other 3 states, respectively, and thus can be represented by 2 bits. However, with this many-to-one mapping method, the base station cannot distinguish whether the number of ACK fed back is 2 or 3, and one possible way is that the base station processes the number of consecutive ACKs received by the UE as 2. Alternatively, the base station maps the ACK numbers 3 and 4 to the same state, and the ACK numbers 0, 1, and 2 are mapped to the other 3 states, respectively, and thus can be represented by 2 bits; with this many-to-one mapping method, the base station cannot distinguish whether the number of ACKs fed back is 3 or 4, and one possible way is that the base station processes the number of consecutive ACKs received by the UE as 3. Alternatively, the base station maps the ACK numbers 1 and 4 to the same state, and the ACK numbers 0, 2, and 3 are mapped to the other 3 states, respectively, and thus can be represented by 2 bits; by adopting the many-to-one mapping method, the base station cannot distinguish whether the number of the fed back ACKs is 1 or 4, and one possible way is to process the data according to the number of the continuous ACKs as 4 when the base station actually sends data of 4 subframes; and when the number of the actual transmission subframes of the base station is less than 4, the base station processes the continuous ACK number as 1.

The above-described repeated mapping of the number of consecutive ACKs may be performed only when needed. For example, according to the number and position of the subframes of each downlink data received by the UE, the UE may analyze the maximum value of the number of consecutive ACKs that may occur, so as to determine whether to select the many-to-one mapping method. For example, when the UE determines that the maximum value of the number of possible consecutive ACKs is greater than 4, many-to-one mapping is performed, ACK numbers 2 and 3 are mapped to the same state, and ACK numbers 0, 1, and 4 are respectively mapped to the other 3 states, and thus may be represented by 2 bits. When the UE determines that the maximum value of the number of possible consecutive ACKs is 4 or less, the many-to-one mapping is not performed, but the number of consecutive ACKs is directly expressed by two bits. For some many-to-one mapping methods, such as the method in which ACK numbers 3 and 4 are mapped to the same state, and ACK numbers 0, 1, and 2 are mapped to the other 3 states, respectively, when the number of possible consecutive ACKs is less than or equal to 4, this method can naturally degenerate to the method without one-to-one mapping.

And step 302, feeding back the number of ACK in the ACK/NACK information of the downlink data of each CC. Here, the method for feeding back the ACK number of each CC may determine and transmit an ACK/NACK channel and a QAM symbol used when feeding back ACK/NACK information according to the ACK number of each CC, or jointly encode and transmit the ACK number of each CC, or transmit the ACK number of each CC by using another method.

Referring to fig. 2, fig. 2 is a basic flowchart of a method of transmitting the number of ACKs for each CC by selecting ACK/NACK channels and QAM symbols in accordance with the present invention. As shown in fig. 2, the process may include the following steps:

step 201, calculating the number of ACKs in the ACK/NACK information of the downlink data for each CC. Here, step 201 is the same as step 301 in fig. 3.

Step 202, determining an ACK/NACK channel and a QAM symbol used when feeding back ACK/NACK information according to the number of ACKs of each CC. Here, it is defined that one ACK/NACK channel and one QAM constellation point constitute one resource state.

Here, one ACK/NACK channel and QAM symbols to be transmitted may be selected according to the number of consecutive ACKs of each CC. In addition, assuming that the UE can simultaneously transmit information on K ACK/NACK channels, for example, K is equal to 2, it may be that K ACK/NACK channels are selected according to the number of consecutive ACKs of the respective CCs and QAM symbols transmitted on each of the selected ACK/NACK channels. For the case of selecting K channels, to reduce complexity, the information of the number of consecutive ACKs of each CC may be first divided into K groups, and then an ACK/NACK channel and a QAM symbol to be transmitted are respectively selected for each group of information.

For each CC, the number of consecutive ACKs equal to k means that the UE knows at least exactly the index of the k ACK/NACK channels. Specifically, when there is no SPS traffic, the number of consecutive ACKs equal to k means that the UE has received at least PDCCH from DAI equal to 1, 2, …, k, so that the UE knows at least k ACK/NACK channels exactly, i.e. the k ACK/NACK channels correspond to subframes of PDCCH with DAI equal to 1, 2, …, k, respectively; when there is SPS service, the number of consecutive ACKs equal to k means that the UE receives at least PDCCH with DAI equal to 1, 2, …, k-s in addition to SPS data, s is greater than or equal to 1, so that the UE knows at least k ACK/NACK channels exactly, i.e. s ACK/NACK channels are ACK/NACK channels semi-statically allocated for SPS service, and the other k-s ACK/NACK channels correspond to subframes of PDCCH with DAI equal to 1, 2, …, k-s, respectively. When determining which ACK/NACK channels can be used for transmitting ACK/NACK information, it may be that any one of the k ACK/NACK channels can be used to feed back ACK/NACK information; alternatively, a subset of the k ACK/NACK channels may be restricted for feeding back ACK/NACK information, e.g., two of the k ACK/NACK channels may be used for ACK/NACK transmission, considering that the number of consecutive ACKs is represented as 2 bits. When there is no SPS traffic, a PDCCH with DAI equal to 1 and an ACK/NACK channel mapped by a PDCCH with DAI equal to 2 may be used for ACK/NACK transmission. If there is SPS service, a semi-statically allocated ACK/NACK channel for SPS data and a PDCCH mapped ACK/NACK channel with DAI equal to 1 are selected for ACK/NACK transmission.

And step 203, feeding back the number of ACK in the ACK/NACK information of the downlink data of each CC by using the selected QAM symbols on the selected ACK/NACK channel.

Several preferred embodiments of the invention are described below.

Suppose that the UE receives data of N CCs simultaneously, each CC has M subframes, and the UE finally feeds back ACK/NACK information on one ACK/NACK channel.

Step 201, for a CC, obtaining 1 ACK/NACK information by spatially bundling the ACK/NACK information in each subframe, and calculating the number of consecutive ACKs.

Step 202, selecting an ACK/NACK channel and QAM symbols to be transmitted according to the number of consecutive ACKs of each CC. It is assumed here that when the number of consecutive ACKs on one CC is equal to k, any one of the corresponding k ACK/NACK channels can be used to feed back ACK/NACK information.

The following describes a case where the UE needs to feed back ACK/NACK information for two CCs and M is equal to 4 on each CC. At this time, the number of consecutive ACKs on each CC may be 0, 1, 2, 3, 4. An example of mapping ACK/NACK feedback information to resource status is shown in Table 1, n_PUCCH ⁽¹⁾Represents an index of the selected ACK/NACK channel, which is equal to a value of the DAI of the PDCCH corresponding thereto. The constellation point of QPSK is two bits b₀b₁To indicate. Here, states 1-24 traverse all possible combinations of the number of consecutive ACKs on both CCs except for feedback information where the number of consecutive ACKs is 0; states 24-32 are further developed for feedback information with the number of consecutive ACKs of both CCs being 0, which mainly realizes that no uplink signal (i.e. DTX) is sent only when no downlink data is received by the UE. As shown in table 1, the number of available resource states is exactly equal to the number of states that need to be indicated. Here, "CC # y, AN # x" indicates that the selected ACK/NACK channel is a PDCCH-mapped ACK/NACK channel with DAI equal to x on CC # y. "0 (Datax)" indicates that the DAI in the PDCCH corresponding to the first downlink data received by the UE is equal to x, or that the UE does not receive data of the PDCCH of which the DAI is equal to 1, 2, …, x-1; and the feedback information of the data scheduled by the PDCCH with the DAI equal to x is NACK; the QPSK constellation point is represented by two bits b0, b 1. Table 1 is merely an example, and the present invention is not limited to the specific form of using other ACK/NACK channel selection and constellation point allocation.

Table 1: mapping table with M being 4

Table 2 is a table assuming that the UE needs to feed back ACK/NACK information for two CCs and M is equal to 3 on each CC. It is further assumed that one of the 3 subframes of CC #0 transmits SPS service, that is, the SPS subframe transmits downlink data but does not have PDCCH, and accordingly, only dynamic downlink data of M-1-2 subframes can be transmitted in CC #0 at most, that is, the value range of DAI in PDCCH is 1 and 2. For CC #1, the value range of DAI in PDCCH is 1, 2, 3 because there is no SPS service. For CC #0, taking the ACK/NACK information of the SPS subframe as the first ACK/NACK information, then sequencing the ACK/NACK information of the downlink data scheduled by each PDCCH in the ascending order of DAI from the DAI equal to 1, and calculating the number of continuous ACKs. At this time, the number of consecutive ACKs on each CC may be 0, 1, 2, 3. An example of mapping ACK/NACK feedback information to resource states is shown in table 2, where states 1-15 traverse all possible combinations of consecutive ACK numbers for two CCs; states 16-21 are the further development of the feedback information with the number of consecutive ACKs of both CCs being 0, which is mainly used for not sending any uplink signal (i.e. DTX) only when no downlink data is received by the UE. Here, "CC #0, AN # 1" indicates that the selected ACK/NACK channel is a semi-statically allocated ACK/NACK channel for SPS data on CC #0, and "CC #0, AN # x" (x is greater than 1) indicates that the selected ACK/NACK channel is a PDCCH mapped ACK/NACK channel with DAI equal to x-1 on CC # 0. "CC #1, AN # x" indicates that the selected ACK/NACK channel is the ACK/NACK channel of the PDCCH mapping with DAI equal to x on CC # 1. For CC #0, "0 (Data 1)" indicates that the UE received Data of SPS but its feedback information is NACK; in the case where the SPS service is configured to CC #0, "0 (Datax)" (x is greater than 1) is a state that does not occur. For CC #1, "0 (Datax)" indicates that the DAI in the PDCCH corresponding to the first downlink data received by the UE is equal to x, or that the UE does not receive data of the PDCCH with the DAI equal to 1, 2, …, x-1; and the feedback information of the data scheduled by the PDCCH with the DAI equal to x is NACK; the QPSK constellation point is represented by two bits b0, b 1. Table 2 is merely an example, and the present invention is not limited to the specific form of the other ACK/NACK channel selection and constellation point allocation.

Table 2: mapping table of M-3 for existence SPS

Note that since the UE received at least SPS traffic data on CC #0, there are no other states to indicate that distinguish DTX, i.e., states 17 and 18 are redundant. Table 2 the purpose of the reservation states 17 and 18 is to illustrate that the same table can be applied to situations other than no SPS, in which case "CC # y, AN # x" indicates that the selected ACK/NACK channel is the one mapped by the PDCCH on CC # y with a DAI equal to x. "0 (Datax)" indicates that the DAI in the PDCCH corresponding to the first downlink data received by the UE is equal to x, or that the UE does not receive data of the PDCCH of which the DAI is equal to 1, 2, …, x-1; and the feedback information of the data scheduled by the PDCCH with DAI equal to x is NACK. The analysis here applies equally to table 1, i.e. table 1 may also be used in the case where SPS services are involved.

Assuming that the UE receives data of N CCs simultaneously, when N is large, the amount of ACK/NACK information to be fed back is large, and it is not enough to indicate such much feedback information with only one ACK/NACK channel. Two ACK/NACK channels may be occupied to feed back ACK/NACK information at this time.

Step 201, for a CC, obtaining 1 ACK/NACK information by spatially bundling the ACK/NACK information in each subframe, and calculating the number of consecutive ACKs.

In step 202, two ACK/NACK channels and QAM symbols to be transmitted are selected according to the number of consecutive ACKs of each CC. It is assumed here that when the number of consecutive ACKs on one CC is equal to k, any one of the corresponding k ACK/NACK channels can be used to feed back ACK/NACK information.

Here, when defining the mapping relationship between the number of consecutive ACKs of each CC and the resource status, two ACK/NACK channels and their corresponding QAM symbols may be directly selected from the candidate ACK/NACK channels on the N CCs. This method is advantageous to avoid repeated mapping of ACK/NACK information of each CC to resource status, but is very complex.

In order to reduce the complexity of mapping the resource state by the ACK number information of each CC, the information of the continuous ACK number of N CCs may be divided into two groups, and then an ACK/NACK channel is selected for each group of feedback information to indicate. Here, when N is an even number, it may be equally divided into 2 groups, i.e., each group contains information of the number of consecutive ACKs of N/2 CCs; when N is an odd number, continuous ACK number information of ceil (N/2) and floor (N/2) CCs can be contained in the two groups respectively; or each group is made to contain the continuous ACK number information of floor (N/2) CCs, respectively, and the continuous ACK number information of the other CC is divided into two parts to be transmitted in the two groups, respectively. Where ceil is the ceiling function and floor is the floor function. Here, a first method for dividing the continuous ACK information of one CC into two parts is to divide M subframes into two sets, each set including ceil (M/2) or floor (M/2) subframes, on the assumption that one CC includes M subframes, so that the two sets of feedback information respectively include the number of continuous ACKs in one set. A second method for dividing the continuous ACK information of a CC into two parts is to represent the continuous ACK number information of the CC as 2 bits, and each group of feedback information includes one bit. Here, when M is equal to 4, there are 5 possible values of the number of consecutive ACKs, i.e. 0, 1, 2, 3, 4, and 4 states can be obtained by using a many-to-one mapping method so as to be represented by two bits.

Assuming that the UE receives data of N equal to 4 CCs at the same time, the feedback information of the 4 CCs may be equally divided into 2 groups, for example, the first group includes the number of consecutive ACKs of CC #0 and CC # 1; accordingly, the second group includes the number of consecutive ACKs for CC #2 and CC # 3. Thus, assuming that M is equal to 4, mapping of ACK/NACK information to resource status can be done on each set of feedback information using the method shown in table 1; assuming that M is equal to 3, the mapping of ACK/NACK information to resource status can be done on each set of feedback information using the method shown in table 2.

Suppose the UE receives data for N equal to 5 CCs simultaneously and M is equal to 2 on each CC, i.e. the possible number of consecutive ACKs on each CC is 0, 1, 2. It can be represented by 2 bits, for example, using the mapping method of table 3. The mapping method of table 3, when there is no SPS service, may be such that bit b_iCorresponding to an ACK/NACK channel mapped by a PDCCH with DAI equal to i + 1; when the SPS service is present, it may be that bit b0 corresponds to an ACK/NACK channel of the SPS service, and bit b1 corresponds to an ACK/NACK channel with DAI equal to 1. Thus, when bit b_iWhen 1, i is 0, 1, it is guaranteed that there is one ACK/NACK channel and bit b_iCorresponding; when bit b_iAt 0, the AND bit b may not be present_iCorresponding ACK/NACK channel. At this time, the feedback information of 5 CCs is divided into 2 groups, for example, if two bits of feedback information of CC #4 are transmitted in two groups, the first group includes the number of consecutive ACKs of CC #0 and CC #1 and bit b0 of CC # 4; accordingly, the second group includes the number of consecutive ACKs of CC #2 and CC #3 and bit b1 of CC # 4. Next, a mapping relationship of each ACK/NACK information in each set of feedback information to a resource state needs to be defined. Since the two groups are similar in structure and thus can be handled in the same way, only the mapping method example of the first group is described below.

Table 3: method for mapping 2 bits

Number of consecutive ACKs	b0	b1
			0	0	0
1	1	0
			2	0	1
3	1	1

As shown in table 4, the number of consecutive ACKs of the first two CCs is 3, and the number of bits b0 of CC #4 is 2, that is, the number of states is 3x3x2 ═ 18; in order to distinguish the DTX state, the feedback information of all 0's is further divided into 5 states, i.e., the total number of states required is 18+ 5-1-22. However, since only 2+2+ 1-5 ACK/NACK channels are available for selection, they can provide a total number of states of 5x 4-20, which is smaller than the required number of states, which can be solved by many-to-one mapping. In table 4, states 2 and 5 map to the same resource state (CC #1, AN #1), and states 15 and 16 map to the same resource state (CC #0, AN # 2). Table 4 is only an example, and the present invention is not limited to the specific form of using other ACK/NACK channel selection and constellation point allocation.

Table 4: mapping table for 5 CCs

If the requirement for DTX is relaxed, e.g., in the absence of SPS traffic, the case where the UE loses data for PDCCH scheduling with DAI equal to 1 is treated as DTX. At this point, the number of available resource states is exactly equal to the number of states that need to be indicated, as shown in Table 5. Also, table 5 is only an example, and the present invention is not limited to the specific form of using other ACK/NACK channel selection and constellation point allocation.

Table 5: mapping table for 5 CCs

For the case where the CC number N is equal to 5, the mapping tables of M ═ 3 and M ═ 4 can be obtained by a method similar to that of M ═ 2 described above. Also, since the number of available resource states is limited, the mapping relationship between the ACK/NACK information and the resource states when M is 3 and M is 4 has to be obtained by a many-to-one mapping method.

In addition, assume that the UE receives data on 3 CCs simultaneously, and M is 3. The feedback information of 3 CCs is divided into two groups, and it is assumed that the feedback information of CC #2 is transmitted in two subframes, respectively. Thus, the first group may contain the number of consecutive ACKs within the first two subframes of CC #0 and CC #2, and correspondingly, the second group contains the number of consecutive ACKs within the last subframe of CC #1 and CC # 2. Here, since the feedback information on CC #2 is transmitted in two groups, the number of consecutive ACKs is calculated for the subframes belonging to the first group by the above-mentioned method; for the subframes belonging to the second group, when no data loss is found in the subframes belonging to the first group according to the DAI, counting the number of continuous ACKs of the dynamic data if no SPS service exists; counting the number of continuous ACKs of the SPS data and the dynamic data if the SPS service exists; when data loss is found in the subframe belonging to the first group according to the DAI, only the number of consecutive ACKs of SPS data is counted. For the sub-frames of CC #2 belonging to the first group, obtaining corresponding alternative ACK/NACK channels according to the PDCCH corresponding to the continuous ACK; similarly, for the sub-frame belonging to CC #2 in the second group, the corresponding candidate ACK/NACK channel is also obtained from the PDCCH corresponding to the continuous ACK.

Next, a mapping relationship of each ACK/NACK information in each set of feedback information to a resource state needs to be defined. For example, for the first set of feedback information, the possible values of the number of consecutive ACKs on CC #0 are 0, 1, 2, 3; and the number of consecutive ACKs of a subframe on CC #2 belonging to the first group may take the values 0, 1, 2. An example of a mapping for this case is shown in table 6. For the second set of feedback information, the possible values of the number of consecutive ACKs on CC #1 are 0, 1, 2, 3; and the number of consecutive ACKs of a subframe on CC #2 belonging to the second group may take the value 0, 1. An example of a mapping for this case is shown in table 7. In table 7, "CC #2, AN # 1" is AN alternative ACK/NACK channel of a subframe of CC #2 belonging to the second group, which is either AN ACK/NACK channel of SPS traffic or a value of DAI in PDCCH corresponding thereto depends on the number of consecutive ACKs of a subframe of CC #2 in the first group. Tables 6 and 7 are merely examples, and the present invention is not limited to the specific form of the other ACK/NACK channel selection and constellation point allocation.

Table 6: mapping table of first group of feedback information when N is 3

Table 7: mapping table of second group of feedback information when N is 3

In fact, the possible feedback information of the two sets of ACK/NACK information when N is 3 is N equal to 2 and M is 3 on each CC is a subset of all possible feedback information, so tables 6 and 7 may not be designed separately but directly from table 2, when the corresponding rows in table 2 are used according to the actually existing feedback information. This property can be applied to many different combinations of N and M, simplifying the design.

Referring to fig. 4, fig. 4 is a basic flowchart of a method of transmitting the number of ACKs for each CC through joint coding according to the present invention. As shown in fig. 4, the process may include the following steps:

step 401, respectively calculating the number of ACKs in the ACK/NACK information of the downlink data for each CC. Here, step 401 is the same as step 301 in fig. 3.

Step 402, jointly encoding the number of ACKs for each CC.

Here, the number of ACKs per CC may be respectively expressed as N (e.g., N is equal to 2) bits, so that the total number of bits of the ACK number of N CCs is B ═ N · N; then, if the number of channel bits of the physical channel resource is G, the B bits are channel coded to obtain G coded bits. Or, the number of ACKs of each CC may be jointly represented as M bits, for example, if the number of ACKs of each CC is k, and the number of CCs is N, the total possible values of the number of ACKs of the N CCs is k^NAccordingly, this k is expressed^NThe number of bits of each value is B-log₂(k^N)＝N·log₂(k) (ii) a Then, if the number of channel bits of the physical channel resource is G, the B bits are channel coded to obtain G coded bits.

It is noted that the physical channel resource for transmitting the number of ACKs of each CC may include only one physical channel, or may be composed of a plurality of physical channels. The physical channel resources may be configured semi-statically by a higher layer or dynamically indicated by a physical control channel. For example, each physical channel herein may multiplex the structure of PUCCH format 2 channel (i.e., CQI channel) defined in the LTE system. The channel coding may also be a multiplexing method of coding the CQI information in the LTE system, or may use another method, such as a convolutional code.

Step 403, the number of ACKs of each CC after joint coding is sent on physical channel resources.

Two preferred embodiments of the invention are described below. Here, the number of ACKs fed back on each CC may be the number of consecutive ACKs of downlink data received by the UE on one CC as described above, or the total number of ACKs of downlink data received by the UE on one CC.

First, an example in which the information of the number of consecutive ACKs for each CC is transmitted on one PUCCH format 2 channel is described. Suppose the UE needs to feed back ACK/NACK information for 5 CCs and M equals 4 on each CC. In this case, the number of consecutive ACKs on each CC may be 0, 1, 2, 3, 4, for a total of 5 values. Thus, the total number of possible consecutive ACKs for 5 CCs is 5⁵3125, it needs to be represented by 12 bits. And the method for channel coding the CQI in the LTE system can support transmission of 13 bits at most, so the 12 bits can be coded by directly multiplexing the channel coding method in LTE, and then the coded bits are transmitted on a channel corresponding to PUCCH format 2. Suppose the UE needs to feed back ACK/NACK information for 5 CCs and M equals 2 on each CC. At this time, the number of consecutive ACKs on each CC may be 0, 1, 2, for a total of 3 values. Thus, the total number of possible consecutive ACKs for 5 CCs is 5³It needs to be represented by 7 bits 125. The 7 bits can still directly multiplex the channel coding method in LTE to code the 12 bits, and then the coded bits are transmitted on a channel corresponding to PUCCH format 2.

Next, an example in which the information of the number of consecutive ACKs for each CC is transmitted on two PUCCH format 2 channels is described. Suppose the UE needs to feed back ACK/NACK information for 5 CCs and M equals 4 on each CC. In this case, the number of consecutive ACKs on each CC may be 0, 1, 2, 3, 4, for a total of 5 values. Thus, the total number of possible consecutive ACKs for 5 CCs is 5⁵3125, it needs to be represented by 12 bits. Next, the 12-bit information may be encoded by multiplexing the channel coding method for CQI in LTE, and then the same coding ratio may be transmitted on two PUCCH format 2 channelsParticularly, the method is used for preparing the high-performance liquid crystal display. Or, if the total number of physical channel bits of the two PUCCH format 2 channels is G, performing channel coding on the 12 bits to obtain G physical bits, and then mapping the G physical bits to the two PUCCH format 2 channels for transmission. The channel coding may be a convolutional code or other coding method.

Although the present invention has been described in conjunction with the preferred embodiments thereof, it will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention. Accordingly, the present invention should not be limited by the above-described embodiments, but should be defined by the appended claims and their equivalents.

Claims (12)

1. A method of performing acknowledgement, ACK, or negative acknowledgement, NACK, feedback for a downlink data transmission of a wireless communication system, the method comprising, at a mobile terminal, the steps of:

receiving downlink data;

for each CC, calculating the number of continuous ACKs of the CC by sequencing the ACK/NACK information of each downlink data subframe of the CC;

feeding back the continuous ACK number of the ACK/NACK information of the downlink data subframe of each CC;

the step of calculating the number of continuous ACKs of the CC by sequencing the ACK/NACK information of each downlink data subframe of the CC comprises the following steps:

when no SPS data subframe exists in the CC, starting from a downlink data subframe scheduled by a PDCCH (physical downlink control channel) with a downlink allocation indication DAI equal to 1, and calculating the continuous ACK number of ACK/NACK information of each downlink data subframe of the CC according to the ascending order of the DAI; or

When a semi-persistent scheduling SPS data subframe exists in the CC, firstly sorting the ACK/NACK information of each subframe, putting the ACK/NACK information of the SPS data subframe in front, then sorting the ACK/NACK information of the downlink data subframe scheduled by each PDCCH according to the ascending order of the DAI from the PDCCH which indicates that the DAI is equal to 1, and further calculating the continuous ACK number of the ACK/NACK information of each downlink data subframe which the CC has.

2. The method of claim 1, wherein the step of calculating the number of consecutive ACKs for the CC comprises:

and then, starting from the downlink data subframe scheduled by the PDCCH with the downlink allocation indication DAI equal to 1, calculating the continuous ACK number of the ACK/NACK information of each downlink data subframe according to the ascending sequence of the DAI.

3. The method of claim 1, wherein the step of calculating the number of consecutive ACKs for the CC comprises:

continuous ACK data of ACK/NACK information of the respective codewords CW is calculated in an increasing order of DAI from a downlink data subframe scheduled by a PDCCH indicating that DAI is equal to 1 without performing spatial bundling on the ACK/NACK information of each downlink data subframe.

4. The method of claim 1, further comprising the step of: performing a many-to-one mapping on the calculated number of consecutive ACKs.

5. The method of claim 1, wherein the step of feeding back the number of consecutive ACKs of ACK/NACK information for downlink data subframes of each CC comprises:

selecting an ACK/NACK channel and a corresponding channel modulation symbol required for feeding back the continuous ACK number of each CC from a plurality of ACK/NACK channels determined according to the continuous ACK number of each CC; and

feeding back the number of consecutive ACKs of the respective CCs using the channel modulation symbols on the selected ACK/NACK channel.

6. The method of claim 5, wherein a number of the plurality of ACK/NACK channels is equal to the number of consecutive ACKs.

7. The method of claim 6, wherein the selected ACK/NACK channel is any one selected from the plurality of ACK/NACK channels.

8. The method of claim 6, wherein the selected ACK/NACK channel is any one selected from a subset of the plurality of ACK/NACK channels.

9. The method of claim 1, wherein the step of feeding back the number of consecutive ACKs of ACK/NACK information for downlink data subframes of each CC comprises:

jointly encoding and then transmitting the number of consecutive ACKs of each CC.

10. The method of claim 9, wherein the number of consecutive ACKs per CC is represented as N bits, the number of CCs is N, the total number of bits of N CCs is B ═ N · N, or the number of consecutive ACKs per CC is k, and then the total number of possible values of the number of consecutive ACKs per CC is k^NPhase of changeShall mean that k^NThe number of bits of each value is B-log₂(k^N)＝N·log₂(k)。

11. The method of claim 9, wherein the step of feeding back the number of consecutive ACKs of ACK/NACK information for downlink data subframes of each CC comprises:

only one physical channel is utilized to feed back the number of consecutive ACKs for each CC.

12. The method of claim 9, wherein the step of feeding back the number of consecutive ACKs of ACK/NACK information for downlink data subframes of each CC comprises:

the number of consecutive ACKs for each CC is fed back using physical channel resources including a plurality of physical channels.