FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] TERMINAL AND COMMUNICATION METHOD THEREOF; PANASONIC CORPORATION, A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 1006, OAZA KADOMA, KADOMA-SHI, OSAKA 571-8501, JAPAN THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. DESCRIPTION Technical Field [0001] The present invention relates to a terminal and a communication method thereof. Background Art [0002] When there is a data signal on an uplink of 3GPP LTE (3rd Generation Partnership Project Long Term Evolution), the data signal and control information are time-multiplexed and transmitted using PUSCH (Physical Uplink Shared CHnnel) to maintain low CM (Cubic Metric). This control information includes a response signal (acknowledgment/negative acknowledgment (ACK/NACK)) and channel quality (Channel Quality Indicator, hereinafter, referred to as "CQI"). [0003] Different assignment methods are employed for these ACK/NACK and CQI (e.g., see Non-Patent Literatures 1 and 2). To be more specific, some data signals (4 symbols) mapped to resources adjacent to pilot signals (Reference Signal, RS) are punctured and ACK/NACK signals are thereby arranged in some of the resources. On the other hand, CQI is arranged over an entire subframe (2 slots). At this time, since data signals are arranged in resources other than resources in which CQI is arranged, the data signals are never punctured by CQI (see FIG.l). This is because whether or not ACK/NACK is assigned is determined according to the presence or absence of downlink data signals. That is, since it is more difficult to predict the occurrence of ACK/NACK than predict the occurrence of CQI, puncturing that allows resources to be assigned even when ACK/NACK occurs suddenly is used when mapping ACK/NACK. On the other hand, in the case of CQI, since transmission timing (subframe) is determined beforehand by report information, it is possible to determine resources of data signals and CQI. Since ACK/NACK is important information, ACK/NACK is assigned to symbols close to pilot signals whose channel estimation accuracy is high. This makes it possible to reduce ACK/NACK errors. [0004] Here, MCS (Modulation and Coding Rate Scheme) corresponding to uplink data signals is determined by the base station based on uplink channel quality. Furthermore, MCS of uplink control information is determined by adding an offset to MCS of data signals. To be more specific, since control information is information more important than data signals, MCS of a lower transmission rate than that of MCS of data signals is set for MCS of control information. This allows control information to be transmitted with high quality. [0005] Furthermore, standardization of 3GPP LTE-Advanced which realizes faster communication than 3GPP LTE has been started. The 3GPP LTE-Advanced system (hereinafter may also be referred to as "LTE-A system") follows the 3GPP LTE system (hereinafter may also be referred to as "LTE system"). 3GPP LTE-Advanced is expected to introduce base stations and terminals communicable at a wide band frequency of 40 MHz or higher to realize a downlink transmission rate of a maximum of 1 Gbps. [0006] Studies are being carried out on the support of SU (Single User)-MIMO communication on LTE-Advanced uplinks. In SU-MIMO communication, a data signal is generated with a plurality of codewords (CWs) and CWs are transmitted in different layers. For example, CW#0 is transmitted in layer #0 and CW#l is transmitted in layer #1. Here, "codeword" can be interpreted as a unit of retransmitting a data signal. On the other hand, "layer" is synonymous to "stream." [0007] Furthermore, studies are being carried out on "Layer Shifting" that changes a layer of each CW for every slot (or symbol) to average channel quality of each CW in LTE-Advanced (see FIG.2). For example, in slot #0, CW#0 is transmitted in layer #0 and CW#1 is transmitted in layer #1. On the other hand, in slot #1, CW#0 is transmitted in layer #1 and CW#l is transmitted in layer #0. Thus, effects of space diversity are obtained in CW#0 and CW#1. [0008] LTE-Advanced downlinks support carrier aggregation that uses a plurality of downlink unit bands (CC: Component Carrier) for data transmission. When this carrier aggregation scheme is used, A/N is generated for a downlink data signal of each CC. Therefore, A/N needs to be transmitted for a plurality of CCs on uplinks. Citation List Non-Patent Literature [0009] NPL 1 TS36.212 v8.7.0, "3GPP TSG RAN; Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding NPL 2 TS36.213 v8.8.0, "3GPP TSG RAN; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Layer Procedure Summary of Invention Technical Problem [0010] However, non-MIMO transmission is assumed to be a precondition for uplinks of the systems disclosed in Non-Patent Literatures 1 and 2 above. In this non-MIMO transmission, only one layer is used in each terminal. That is, data signals and control information (ACK/NACK, CQI) are transmitted in one layer as described above, [0011] In contrast to this, studies are being carried out on MIMO transmission that transmits data signals in a plurality of layers on an LTE-Advanced uplink. In this case, it is assumed as a first method that data signals are transmitted in a plurality of layers and ACK/NACK and CQI are transmitted in one of the plurality of layers. In this case, for example, all of data signals, ACK/NACK and CQI are assigned to layer #0 and only data signals are assigned to layer #1. Furthermore, it is assumed as a second method that all of data signals, ACK/NACK and CQI are transmitted in a plurality of layers. For example, all of data signals, ACK/NACK and CQI are assigned to layers #0 and #1. [0012] That is, it is assumed in LTE-Advanced that all of data signals, ACK/NACK and CQI are assigned to common layers. [0013] Furthermore, LTE-Advanced supports carrier aggregation as described above. In this case, ACK/NACK is generated for downlink data on a downlink of each CC. In this case, ACK/NACK needs to be transmitted to a plurality of CCs on an uplink. Furthermore, studies are also being carried out in LTE-Advanced on an asymmetric carrier aggregation scheme in which ACK/NACK for downlink data transmitted with N (N>2) downlink CCs is transmitted with less than N uplink CCs. Therefore, when asymmetric carrier aggregation is adopted and the number of ACKs/NACKs transmitted on an uplink increases, the probability that ACK/NACK may intrude into a CQI region assigned to CQI (that is, probability that ACK/NACK may be unavoidably mapped to the CQI region) increases in both the first method and the second method and CQI is punctured by ACK/NACK (see FIG.3). As a result, there is a problem that CQI-related reception errors are more likely to occur. [0014] It is an object of the present invention to provide a terminal and a communication method thereof capable of preventing degradation of the error characteristic of control information even in a case of employing an asymmetric carrier aggregation scheme and employing a MIMO transmission method on an uplink. Solution to Problem [0015] An aspect of a terminal according to the present invention includes a reception section that receives downlink data using N (N is a natural number equal to or greater than 2) downlink component carriers, an error detection section that detects an error of the downlink data, a transmission signal forming section that forms a transmission signal by arranging the error detection result and downlink quality information in a plurality of layers based on a arrangement rule, and a transmission section that transmits the transmission signal using uplink component carriers corresponding to the N downlink component carriers, wherein according to the arrangement rule, the error detection result is preferentially arranged in a layer different from a layer in which the channel quality information is arranged. [0016] An aspect of a communication method according to the present invention includes the steps of: receiving downlink data using N (N is a natural number equal to or greater than 2) downlink component carriers, detecting errors of the downlink data, forming a transmission signal by arranging the error detection result and downlink quality information in a plurality of layers based on a arrangement rule, and transmitting the transmission signal using uplink component carriers corresponding to the N downlink component carriers, wherein according to the arrangement rule, the error detection result is preferentially arranged in a layer different from a layer in which the channel quality information is arranged. Advantageous Effects of Invention [0017] According to the present invention, it is possible to provide a terminal and a communication method thereof capable of preventing degradation of the error characteristic of control information even in a case of employing an asymmetric carrier aggregation scheme and employing a MIMO transmission method on an uplink. Brief Description of Drawings [0018] FIG.l is a diagram illustrating a conventional method of arranging ACK/NACK and CQI; FIG.2 is a diagram illustrating layer shifting; FIG.3 is a diagram illustrating a problem to be solved; FIG.4 is a block diagram illustrating a configuration of a base station according to Embodiment 1 of the present invention; FIG.5 is a block diagram illustrating a configuration of a terminal according to Embi odiment 1 of the present invent FIG.6 is a diagram illustrating arrangement rule 1 FIG.7 is a diagram illustrating arrangement rule 2 FIG.8 is a diagram illustrating arrangement rule 3 FIG.9 is a diagram illustrating arrangement rule 4 FIG.10 is a diagram illustratin; g arrangement rul e FIG.11 is a diagram illustrating arrangement rule 6; FIG.12 is a diagram illustrating arrangement rule 8 according to Embodiment 2 of the present invention; and FIG.13 is a diagram illustrating arrangement rule 10 according to Embodiment 2 of the present invention. Description of Embodiments [0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Identical components among embodiments will be assigned the same reference numerals and overlapping explanations thereof will be omitted. [0020] [Embodiment 1] [Overview of communication system] A communication system including base station 100 and terminal 200, which will be described later, performs communication using M (M>1) uplink component carriers and N (N>2, N FIG.6 is a diagram illustrating arrangement rule 1. According to arrangement rule 1, ACK/NACK signals are arranged in a layer different from a layer in which CQI is arranged. This prevents CQI from being punctured by ACK/NACK, and can thereby reduce a CQI-related error rate. [0083] Furthermore, according to arrangement rule 1, ACK/NACK signals may be preferentially arranged in a layer different from the layer in which CQI is arranged. [0084] To be more specific, according to arrangement rule 1, when the number of downlink component carriers N used for downlink communication is less than a predetermined threshold (that is, when the number of ACK/NACK signals is a small number), ACK/NACK signals are only arranged in a layer different from the layer in which CQI is arranged, whereas when N is equal to or greater than the threshold, ACK/NACK signals may also be arranged in a layer different from the layer in which CQI is arranged or in the same layer as the layer in which CQI is arranged. ACK/NACK signals are arranged in this way for the following reasons. That is, the amount of ACK/NACK or CQI transmitted increases as the number of downlink component carriers N used for downlink communication increases. For this reason, ACK/NACK or CQI may exceed the maximum amount of ACK/NACK or CQI transmitted in one layer and some ACK/NACK or CQI may not be able to be transmitted in the one layer. Therefore, when the number of downlink component carriers is large, ACK/NACK and CQI may also be assigned to the same layer and some ACK/NACK or CQI that could not be transmitted in the above-described one layer can be transmitted. When the amount of ACK/NACK or CQI increases, this method is suitable for an environment in which resources capable of arranging ACK/NACK in a layer different from the layer of CQI become deficient. [0085] Here, the layer in which ACK/NACK and CQI are arranged may be predetermined between base station 100 and terminal 200 or may be included in control information or setting information from base station 100 to terminal 200, and reported. [O086] Furthermore, as another method of arrangement rule 1, when the number of downlink component carriers N used for downlink communication is equal to or greater than a predetermined threshold, ACK/NACK signals are arranged in a layer different from the layer in which CQI is arranged. When the number of downlink component carriers N used for downlink communication is less than the predetermined threshold, ACK/NACK signals may be arranged in the same layer as the layer in which CQI is arranged. ACK/NACK signals are arranged in this way for the following reason. That is, the amount of ACK/NACK or CQI transmitted increases as the number of downlink component carriers increases. In such a situation, in order to prevent CQIs from being punctured by ACK/NACK arranged in the same layer, ACK/NACK signals and CQI are arranged in different layers. On the other hand, when the number of downlink component carriers is small, it is possible to reduce the error rate of ACK/NACK or CQI by arranging ACK/NACK or CQI in a plurality of layers to gain transmission power. Even when the amount of ACK/NACK and CQI increases, this method is suitable for an environment in which there are enough resources capable of arranging ACK/NACK in a layer different from that of CQI. [0087] When the number of downlink component carriers N is less than the predetermined threshold, both ACK/NACK and CQI may be assigned to one layer as in the case of the prior art or another assignment method may be used. [0088] FIG.7 is a diagram illustrating arrangement rule 2. Arrangement rule 2 basically shares a commonality with arrangement rule 1 in that ACK/NACK signals are arranged in a layer different from a layer in which CQI is arranged. According to arrangement rule 2, the layers in which ACK/NACK. and CQI are arranged vary from one slot to another irrespective of the presence or absence of layer shifting. That is, according to arrangement rule 2, the layers in which ACK/NACK and CQI are arranged vary for every slot. In other words, layer shifting is performed with respect to ACK/NACK and CQI. [0089] To be move specific, when layer shifting is performed, the layer in which an arbitrary codeword is arranged is changed for every slot. Therefore, when layer shifting is present, arrangement rule 2 is realized by assigning ACK/NACK and CQI to certain codewords (see FIG.7A). On the other hand, when layer shifting is absent, arrangement rule 2 is realized by changing codewords to be assigned to ACK/NACK and CQI for every slot (see FIG.7B). [0090] Thus, a space diversity effect can be obtained with respect to ACK/NACK and CQI by performing layer shifting with respect to ACK/NACK and CQI. [0091] FIG.8 is a diagram illustrating arrangement rule 3. Arrangement rule 3 basically shares a commonality with arrangement rule 1 in that ACK/NACK signals are arranged in a layer different from a layer in which CQI is arranged. According to arrangement rule 3, ACK/NACK and CQI are assigned to certain codewords between slots irrespective of the presence or absence of layer shifting. [0092] To be more specific, when layer shifting is performed, the layer in which an arbitrary codeword is arranged is changed for every slot. Therefore, when layer shifting is present, layer-shifting of ACK/NACK and CQ1 is realized by assigning ACK/NACK and CQI to certain codewords (see FIG.8A). On the other hand, when layer shifting is absent, ACK/NACK and CQI are also arranged in a certain layer by assigning ACK/NACK and CQI to certain codewords. [0093] Thus, control information applied for every codeword can also be used for ACK/NACK and CQI by assigning ACK/NACK and CQI to certain codewords between slots irrespective of the presence or absence of layer shifting. For example, MCS to be applied to ACK/NACK and CQI can be obtained by adding an offset to MCS applied to data signals in the same way as LTE. [0094] FIG.9 is a diagram illustrating arrangement rule 4. Arrangement rule 4 basically shares a commonality with arrangement rule 1 in that ACK/NACK signals are arranged in a layer different from a layer in which CQI is arranged. According to arrangement rule 4, when only CQI is arranged, the number of layers in which CQI is arranged is greater than that when both ACK/NACK and CQI are arranged. That is, the number of layers assigned to ACK/NACK and CQI is changed depending on whether or not both ACK/NACK and CQI are present. [0095] To be more specific, when both ACK/NACK and CQI are present in each slot, one layer is assigned to ACK/NACK and CQI respectively in each slot (see FIG.9A). On the other hand, when only one of ACK/NACK and CQI is present in each slot, one of ACK/NACK and CQI is assigned to a plurality of layers in each slot (FIG.9B). In FIG.9, the layer to which ACK/NACK and CQI are assigned is fixed between the first slot and second slot, but the layer to which ACK/NACK and CQI are assigned may be switched round between the first slot and the second slot. [0096] By so doing, when only one of ACK/NACK and CQI is present, it is possible to obtain a time diversity effect with respect to ACK/NACK or CQI. [0097] FIG.10 is a diagram illustrating arrangement rule 5. Arrangement rule 5 defines layers from the standpoint of codewords and is applicable to aforementioned arrangement rules 1 to 4. [0098] According to arrangement rule 5, ACK/NACK is preferentially arranged in a layer corresponding to a codeword having the largest data size. CQI is arranged in a layer in which no ACK/NACK is arranged. [0099] In FIG.10, layer #0 is associated with CW#0 of a small data size and layer #1 and layer #2 are associated with CW#1 of a large data size. ACK/NACK is assigned to layer #1 or layer #2 corresponding to CW#1 of a large data size and CQI is assigned to the other layers. [0100] The reason that arrangement rule 5 is used is as follows. That is, ACK/NACK is assigned by puncturing data signals. Therefore, when this puncturing is performed, the probability that errors may occur in data signals increases. On the other hand, since rate matching is applied to CQI, when CQI is assigned, the probability that errors may occur in data signals is lower than in the case where ACK/NACK is assigned. [0101] Furthermore, there is normally a difference in data size among a plurality of codewords and when the same number of punctured signals is assumed, the probability that errors may occur in data signals due to puncturing increases in codewords having a smaller data size. [0102] As described above, it is preferable to assign CQI to a layer corresponding to a codeword having a small data size and assign ACK/NACK to a layer corresponding to a codeword having a large data size. [0103] Furthermore, arrangement rule 5 is preferably applied to a terminal requiring the following condition. That is, arrangement rule 5 is suitable for a terminal for which a delay time is less acceptable and errors are preferred to be minimized in data signals having high QoS (Quality of Service). [0104] In FIG.l 0, CQI is assigned to i plurality of layers, but the present invention is not limited to this and CQI may also be assigned to only one layer. [0105] By so doing, data signals are punctured in a codeword having a large data size, and influences of puncturing are thereby reduced, and it is thereby possible to reduce errors in data signals. Therefore, it is possible to reduce retransmission of data signals and thereby satisfy high QoS (Quality of Service) requirements of a terminal whose delay time is hardly acceptable. [0106] FIG. 11 is a diagram illustrating arrangement rule 6. Arrangement rule 6 defines a layer from the standpoint of codewords and is applicable to above-described arrangement rules 1 to 4. [0107] According to arrangement rule 6, ACK/NACK is preferentially arranged in a layer corresponding to a codeword having the smallest data size. CQI is arranged in a layer in which ACK/NACK is not arranged. [0108] In FIG.ll, layer #0 is associated with CW#0 of a small data size and layer #1 and layer #2 are associated with CW#1 of a large data size, ACK/NACK is assigned to layer ,#0 associated with CW#0 of a small data size and CQI is assigned to the other layers. [0109] Arrangement rule 6 is used for the following reason. That is, ACK/NACK is assigned by puncturing data signals. Therefore, when this puncturing is performed, the probability that errors may occur in data signals increases. On the other hand, since rate matching is applied to CQI, the probability that errors may occur in data signals is lower in the case where CQI is assigned than in the case where ACK/NACK is assigned. [0110] Furthermore, there is normally a difference in data size among a plurality of codewords. Since data signal errors are more likely to occur due to the puncturing, when the retransmission frequency of an arbitrary codeword increases, the smaller the data size of the arbitrary codeword, the smaller the amount of retransmission data becomes. [0111] As described above, it is preferable to assign ACK/NACK to a layer corresponding to a codeword having a small data size and assign CQI to a layer corresponding to a codeword having a large data size. [0112] Arrangement rule 6 is preferably applied to a terminal requiring the following condition. That is, when arrangement rule 6 is applied, a retransmission count increases compared to the case with arrangement rule 5, whereas the amount of retransmission data in each retransmission decreases. For this reason, arrangement rule 6 is suitable for a terminal for which the amount of retransmission data is preferred to be reduced. [0113] When, for example, there are data signals having a small amount of data and having an acceptable retransmission delay, a codeword having a small data size is punctured using ACK/NACK so as to prevent retransmission of a codeword having a large data size. In this case, even when the probability that errors may occur in data signals due to the puncturing increases, retransmission is acceptable and it is therefore preferable to reduce the data size upon retransmission. Alternatively when there are data signals having a small amount of data and having strong error resistance, a codeword having a small data size is punctured using ACK/NACK so as to prevent retransmission of a codeword having a large data size. In this case, even when data signals are punctured, the probability that errors may occur in data signals is low, and it is therefore preferable to reduce the data size upon retransmission. [0114] By so doing, data signals are punctured with a codeword having a small data size, and therefore data errors are more likely to occur in a codeword having a small data size. For this reason, the amount of data to be retransmitted can be reduced, Therefore, in an environment in which the probability that errors may occur in data signals can be minimized even when data signals are punctured (e.g., when both data sizes are relatively large), the total amount of retransmission data can be reduced. [0115] According to arrangement rule 6, data signals may not be assigned to a codeword to which ACK/NACK is assigned. That is, only ACK/NACK is transmitted with a codeword to which ACK/NACK is assigned. For example, in FIG.ll, only ACK/NACK is transmitted in layer #0. This makes it possible to prevent retransmission with a codeword to which ACK/NACK is assigned. Furthermore, since ACK/NACK is assigned to a codeword having a small data size even in this case, throughput is unlikely to degrade even if no data signal is arranged in the codeword. [0116] Furthermore, according to arrangement rule 6, MCS applicable to a codeword to which ACK/NACK is assigned may be set to be lower than usual. This makes the error resistance of data signals stronger, and can reduce the error rate. For example, in FIG.ll, MCS of a data signal is set to a low level in layer #0. This makes error resistance of data signals stronger, and can thereby suppress retransmission of the data signals. [0117] Furthermore, arrangement rules 5 and 6 may be combined as follows. That is, a preferred application environment differs between arrangement rule 5 and arrangement rule 6. For this reason, arrangement rule 5 or arrangement rule 6 can be selected according to the environment. Higher layer signaling is used for this switching. In this way, it is possihle to perform control according to an application environment and reduce extra retransmission of data signals. [0118] ACK/NACK is information more important than CQI. Thus, it is preferahle to reduce the error rate of ACK/NACK and ACK/NACK may be arranged in a layer (or codeword) having higher MCS. This makes it possible to reduce the error rate of ACK/NACK. That is, when information of higher importance is arranged in a layer (or codeword), the information is arranged in a layer (or codeword) having higher MCS. [0119] Base station 100 performs reception processing on ACK/NACK, CQI and uplink data according to a rule corresponding to the arrangement rule adopted in terminal 200. [0120] As described above, according to the present embodiment, transmission signal forming section 212 in terminal 200 arranges ACK/NACK and CQI in a plurality of layers based on the arrangement rule and thereby forms a transmission signal. According to the arrangement rule, an error detection result is preferentially arranged in a layer different from a layer in which the channel quality information is arranged. [0121] In this way, the puncturing of CQI using ACK/NACK can be minimized, with the result that the error characteristic of control information can be prevented from being degraded. [0122] [Embodiment 2] Embodiment 1 arranges an ACK/NACK signal in a layer different from a layer in which CQI is arranged and thereby prevents the error rate of CQI from being degraded. By contrast, Embodiment 2 maps one ACK/NACK signal to the same time and same frequency of a plurality of layers (that is, using transmission diversity). This makes it possible to increase the transmission rate of the ACK/NACK signal and reduce resources in which the ACK/NACK signal is arranged in each layer. As a result, it is possible to reduce the probability that CQI may be punctured by the ACK/NACK signal and thereby prevent the error rate of CQI from being degraded. [0123] Since a base station and a terminal according to Embodiment 2 have basic configurations in common with Embodiment 1, the configurations will be described using FIGs.4 and 5. [0124] In the case of a MIMO transmission mode, transmission signal forming section 212 of terminal 200 according to Embodiment 2 forms a transmission signal by arranging an ACK/NACK signal (that is, error detection result of downlink data) and downlink quality information (CQI) in a plurality of layers based on a "arrangement rule." [0125] FIG.12 is a diagram illustrating arrangement rule 8. According to arrangement rule 8, one ACK/NACK signal is mapped to the same time and frequency of a plurality of layers. Furthermore, according to arrangement rule 8, CQI is mapped to some of the plurality of layers. [0126] As shown in FIG.12, when, for example, the same ACK/NACK signal is arranged in the same time and frequency of layer #0 and layer #1, no interference between ACK/NACK signals occurs. Furthermore, the receiving side of the ACK/NACK signal receives in combination ACK/NACK signals transmitted in layer #0 and layer #1. Therefore, in this case, it is possible to secure equal received quality of ACK/NACK signals even when transmitting ACK/NACK signals at a high transmission rate compared to a case where there is interference between signals. [0127] However, since the same ACK/NACK is arranged in a plurality of layers in this case, transmission resources of the ACK/NACK signals in all layers as a whole may increase. However, it is possible to reduce transmission resources of ACK/NACK signals in each layer and thereby reduce the probability that CQI may be punctured by the ACK/NACK signals. This makes it possible to reduce degradation of the error rate of CQI. [0128] Furthermore, since a diversity effect is obtained by arranging the same ACK/NACK signal at the same time and the same frequency in a plurality of layers, ACK/NACK transmission can be realized with higher reliability. [0129] Furthermore, an ACK/NACK signal requires high quality (e.g., error rate 0.1%), whereas CQI only requires relatively low quality (e.g., error rate 1%). Therefore, as shown in FIG.12, ACK/NACK signals are transmitted from two layers, whereas CQI is transmitted in one layer, with the result of satisfying required qualities of both the ACK/NACK signals and CQI. [0130] As in the case of arrangement rule 9 which will be described later, CQI as well as ACK/NACK signals can also be arranged in a plurality of layers. However,, since CQI has more bits than the ACK/NACK signal, resources used for CQI transmission may drastically increase. Thus, CQI is preferably arranged in one layer (or codeword). [0131] At this time, CQI is preferably arranged in a layer of high received quality (that is, high MCS). This is because if CQI is arranged in a layer of high received quality (that is, high MCS), resources for mapping CQI can be reduced and it is possible to reduce the possibility that CQI may be punctured by an ACK/NACK signal. CQI may also be arranged in one or more layers belonging to CW of high received quality (that is, high MCS). [0132] Furthermore, at this time, CQI may also be arranged in CW (codeword) of a large data size. This can reduce the possibility of CQI of reaching a region where an ACK/NACK signal is located. CQI may also be arranged in one or more layers belonging to CW of greater data size. [0133] According to arrangement rule 8, the same ACK/NACK signal is mapped to a plurality of the same times and same frequencies of a plurality of layers to prepare a condition for allowing an ACK/NACK signal to be transmitted at a high transmission rate. However, it is also possible to transmit an ACK/NACK signal at a high transmission rate according to arrangement rule 9. That is, according to arrangement rule 9, an ACK/NACK signal is transmitted in one layer, and neither data nor ACK/NACK signal is transmitted in other layers. This reduces interference between signals with ACK/NACK signals, and can thereby transmit the ACK/NACK signals at a high transmission rate. That is, according to arrangement rule 9, ACK/NACK signals match time/frequency resources to be mapped in an arbitrary layer, whereas no transmission signal is mapped to time/frequency resources in any layer other than the arbitrary layer. [0134] According to arrangement rule 8, ACK/NACK signals are arranged in a plurality of layers (or codewords), whereas CQI is arranged in one layer (or codeword). By contrast, arrangement rule 10 is similar to arrangement rule 8 regarding ACK/NACK signals, whereas CQI is arranged in a plurality of layers (see FIG.13). That is, regarding CQI, different CQIs are arranged in a plurality of layers to thereby perform spatial multiplexing. By so doing, it is possible to reduce, in each layer, both resources in which ACK/NACK signals are arranged and resources in which CQI is arranged, and thereby reduce the possibility that CQI may be punctured by ACK/NACK. Furthermore, required qualities of both ACK/NACK signals and CQI are also satisfied. [0135] [Other embodiments] (1) The above embodiments have described arrangement control of ACK/NACK and CQI for every slot, but the present invention is not limited to this, and arrangement control may also be performed for every symbol. Furthermore, it may be possible to use only one of the presence of layer shifting and the absence of layer shifting. [0136] (2) The MIMO transmission mode in the above embodiments may be transmission modes 3 and 4 defined in LTE, that is, a transmission mode in which transmission of two CWs is supported, and the non-MIMO transmission mode may be any other transmission mode, that is, a transmission mode in which only one CW is transmitted. [0137] Furthermore, the codeword in the above embodiments may be rearranged by a transport block (TB), [0138] (3) The above embodiments have described ACK/NACK and CQI as control information, but the present invention is not limited to this, and the present invention is applicable to any information (control information) requiring higher received quality than that of data signals. For example, CQI or ACK/NACK may be rearranged by PMI (precoding-related information) or RI (rank-related information). [0139] (4) The "layer" in the above embodiments refers to a virtual channel in the space. For example, in MIMO transmission, a data signal generated in each CW is transmitted through different virtual channels (different layers) in the space at same time and same frequency. The "layer" may also be called "stream." [0140] (5) The above embodiments have described the case where the present invention is applied to an antenna, but the present invention is likewise applicable to an antenna port. [0141] The antenna port refers to a theoretical antenna including a single or a plurality of physical antenna(s). That is, the antenna port is not limited to a single physical antenna, but may refer to an array antenna made up of a plurality of antennas. [0142] For example, 3 GPP LTE does not define the number of physical antennas that constitute an antenna port, but 3 GPP LTE defines the antenna port as a minimum unit that allows the base station to transmit different reference signals. [0143] In addition, the antenna port may also be defined as a minimum unit for multiplying a precoding vector by a weight. [0144] (6) The above embodiments have been described on the assumption of asymmetric carrier aggregation. However, in the case where control information such as ACK/NACK or CQI is multiplexed with data in MIMO transmission using a plurality of layers, the present invention is not limited to asymmetric carrier aggregation. Furthermore, N is assumed to be a natural number equal to or greater than 2, but arrangement rules from arrangement rule 2 onward are not limited to this, and N may also be 1. [0145] (7) Regarding arrangement rule 1, Embodiment 1 has shown an example where an ACK/NACK signal is arranged in a layer different from a layer in which CQI is arranged, but CQI may also be arranged in a layer different from a layer in which an ACK/NACK signal is arranged. [0146], (8) The above embodiments have described an example where an ACK/NACK signal or CQI is arranged in a layer, but the present invention is not limited to this, and an ACK/NACK signal or CQI may also be arranged in a codeword. For example, in the case where data is transmitted in a total of four layers, codeword 1 is transmitted using layers 1 and 2, codeword 2 is transmitted using layers 3 and 4, Embodiment 1 may be adapted so that an ACK/NACK signal is arranged in codeword 1 (that is, layers 1 and 2) and CQI is arranged in codeword 2 (that is, layers 3 and 4). Furthermore, Embodiment 2 may also be adapted so that an ACK/NACK signal is arranged in codewords 1 and 2 (that is, layers 1 to 4) and CQI is arranged in codeword 2 (that is, layers 3 and 4). [0147] (9) In Embodiment 2, according to arrangement examples 8 and 10, the same ACK/NACK signal is arranged in the same time and frequency in a plurality of layers. Furthermore, the ACK/NACK signal may be subjected to scrambling which differs from one layer to another. This makes it possible to prevent an unintended beam from being formed because of a phase relationship in each layer. [0148] The component carrier may be defined by a physical cell number and a carrier frequency number or may be called "cell." [0149] (10) Also, although cases have been described with the above embodiment as examples where the present invention is configured by hardware, the present invention can also he implemented by software. [0150] Each function block employed in the description of each of the aforementioned embodiments may typically be implemented as an LSI constituted by an integrated circuit. These may be individual chips or partially or totally contained on a single chip. "LSI" is adopted here but this may also be referred to as "IC," "system LSI," "super LSI," or "ultra LSI" depending on differing extents of integration. [0151] Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. After LSI manufacture, utilization of a programmable FPGA (Field Programmable Gate Array) or a reconfigurable processor where connections and settings of circuit cells within an LSI can be reconfigured is also possible. [0152] Further, if integrated circuit technology comes out to rearrange LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Application of biotechnology is also possible. [0153] The disclosure of Japanese Patent Application No.2010-027959, filed on February 10, 2010 and Japanese Patent Application No.2010-1 05326, filed on April 30, 2010, including the specification, drawings and abstract is incorporated herein by reference in its entirety, Industrial Applicability [0154] The terminal and the communication method thereof of the present invention is useful in preventing the error characteristic of control information from being degraded even when employing an asymmetric carrier aggregation scheme and further employing a MIMO transmission method on an uplink. Reference Signs List [0155] 100 base station 101 setting section 1 02 control section 104 PDCCH generation section 105, 107, 108 coding/modulation section 106 assignment section 109 multiplexing section 110, 215 IFFT section 111, 216 CP adding section 112, 217 RF transmission section 113, 201 antenna 114, 202 RF reception section 115, 203 CP removing section 116, 204 FFT section 117 extraction section 118 IDFT section 119 data reception section 120 control information reception section 200 terminal 205 demultiplexing section 206 setting information reception section 207 PDCCH reception section 208 PDSCH reception section 209, 210, 211 modulation section 212 transmission signal forming section 213 DFT section 214 mapping section 221 data/CQI assignment section 222 puncturing section »Ve Claim : CLAIMS Claim 1 A terminal comprising: a receiver configured to receive downlink data using N (N is a natural number equal to or greater than 2) downlink component carriers; an error detector configured to detect errors of the downlink data; a transmission signal forming section configured to form a transmission signal by arranging the error detection result and downlink quality information in a plurality of layers based on a arrangement rule; and a transmitter configured to transmit the transmission signal using an uplink component carrier corresponding to the N downlink component carriers, wherein: according to the arrangement rule, the error detection result is preferentially arranged in a layer different from a layer in which the channel quality information is arranged. Claim 2 The terminal according to claim 1, wherein according to the arrangement rule, the error detection result is arranged in only the layer different from the layer in which the channel quality information is arranged when N is less than a threshold, and the error detection result is arranged in the layer different from the layer in which the channel quality information is arranged or in the same layer as the layer in which the channel quality information is arranged when N is equal to or greater than the threshold. Claim 3 The terminal according to claim 1, wherein according to the arrangement rule, the layer in which the error detection result and the channel quality information are arranged differs for every symbol or every slot. Claim 4 The terminal according to claim 1, wherein according to the arrangement rule, when only the downlink quality information is arranged in the plurality of layers, the number of layers in which the downlink quality information is arranged is greater than that when both the error detection result and the downlink quality information are arranged. Claim 5 The terminal according to claim 1, wherein according to the arrangement rule, codewords in which the error detection result and the downlink quality information are arranged match between neighboring symbols or between neighboring slots. Claim 6 The terminal according to claim 1, wherein according to the arrangement rule, the error detection result is preferentially arranged in a layer corresponding to a codeword having the largest data size. Claim 7 The terminal according to claim 1, wherein according to the arrangement rule, the error detection result is preferentially arranged in a layer corresponding to a codeword having the smallest data size. Claim 8 The terminal according to claim 7, wherein according to the arrangement rule, a data signal is arranged in a layer other than a layer in which the error detection result is arranged. Claim 9 A communication method comprising: receiving downlink data using N (N is a natural number equal to or greater than 2) downlink component carriers; detecting errors of the downlink data; forming a transmission signal by arranging the error detection result and downlink quality information in a plurality of layers based on a arrangement rule; and transmitting the transmission signal using an uplink component carrier corresponding to the N downlink component carriers, wherein: according to the arrangement rule, the error detection result is preferentially arranged in a layer different from a layer in which the channel quality information is arranged.