JP2009273171A - Base station, user device and method used in mobile communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the probability that an uplink control channel is transmitted with desired quality in a mobile communication system that employs a single carrier scheme for uplink transmission. <P>SOLUTION: A base station used in a mobile communication system, with a single carrier method adopted for an uplink comprises a scheduler for allocating not less than one resource block of the uplink to each of user devices, and a means for notifying the user device of scheduling information indicative of the planning contents of resource allocation, according to an uplink-channel state of each of the user devices. An uplink control channel of a user device is mapped so that the uplink control channel draws a predetermined hopping pattern in a transmission frame, including a plurality of resource blocks, in accordance with scheduling information. The uplink control channel is mapped with the same hopping pattern, whether the uplink control channel is associated with a user data channel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to the technical field of mobile communication, and more particularly to a base station and method in a mobile communication system.

  In this type of technical field, research and development on next-generation communication systems are rapidly progressing. In a currently assumed communication system, a single carrier scheme is used for the uplink from the viewpoint of widening the coverage while suppressing a peak-to-average power ratio (PAPR).

  The radio resources for both the uplink and the downlink are appropriately allocated according to the channel state of each user in the form of a channel shared by a plurality of users (shared channel). The process for determining the allocation content is called scheduling. In order to appropriately perform uplink scheduling, each user apparatus transmits a pilot channel to the base station, and the base station evaluates the uplink channel state based on the reception quality. In addition, in order to perform downlink scheduling, the base station transmits a pilot channel to the user apparatus, and the user apparatus reports information (CQI: Channel Quality Indicator) indicating the reception quality of the pilot channel to the base station. Based on the CQI reported from each user apparatus, the base station evaluates the downlink channel state. For example, Non-Patent Document 1 describes a technique in which frequency scheduling is performed so that resources (time and frequency) used for a control channel of a certain user apparatus follow a predetermined hopping pattern.

3GPP, R1-060320, "L1 / L2 Control Channel Structure for E-UTRA Uplink", 2006.2.13

  The uplink control channel includes control information (essential control information or first control information) that must be transmitted along with the uplink data channel, and control information (second control information) that is transmitted regardless of the presence or absence of the uplink data channel. ) The first control information includes information essential for data channel demodulation, such as a data channel modulation scheme and a channel coding rate. The second control information includes information such as CQI information, downlink data channel acknowledgment information (ACK / NACK), and resource allocation request. In the above Non-Patent Document 1, the uplink control channel including the second control information of a certain user apparatus is transmitted in various times and frequencies according to a predetermined hopping pattern in principle. However, when the user apparatus transmits an uplink data channel, the uplink control channel including the first control information is transmitted in the same resource block as the data channel. In this case, the control channel including the first control information does not follow a predetermined hopping pattern and is simply transmitted along with the transmission of the data channel.

  By the way, the control channel including the first and second control information is difficult to expect retransmission if it cannot be demodulated satisfactorily, and is different in character from a data channel that can be expected to be retransmitted. The need for high quality and reliable transmission is greater for the control channel than for the data channel.

  Even if it is determined that a certain resource block is good for the user apparatus at the time of scheduling of the uplink data channel and is allocated, the communication situation may be different when it is actually transmitted from the user apparatus. That is, even if the uplink control channel is transmitted in the same resource block as the uplink data channel, the uplink control channel cannot always be transmitted as expected.

  An object of the present invention is to improve the certainty that an uplink control channel is transmitted with a required quality in a mobile communication system employing a single carrier scheme for uplink.

  In the present invention, a base station used in a mobile communication system employing a single carrier scheme for uplink is used. A base station that allocates one or more uplink resource blocks to individual user apparatuses according to an uplink channel state for each user apparatus, and means for notifying the user apparatus of scheduling information indicating a plan content of resource allocation; Have An uplink control channel of a certain user apparatus is mapped so as to draw a predetermined hopping pattern in a transmission frame including a plurality of resource blocks according to the scheduling information. The uplink control channel is mapped with the same hopping pattern whether or not it accompanies the user data channel.

  According to the present invention, in a mobile communication system employing a single carrier scheme for uplink, it is possible to improve the certainty that an uplink control channel is transmitted with required quality.

It is a figure which shows the user apparatus and base station which are used in one Example of this invention. It is a figure which shows the utilization example of the band used with a mobile communication system. It is a figure which shows the utilization example of the band used with a mobile communication system. FIG. 3 is a diagram illustrating a control channel and a data channel of a certain user equipment transmitted according to an embodiment of the present invention. It is a graph which shows the correlation of resource block size, a scheduling effect, signaling overhead, and resource utilization efficiency. It is a figure which shows the utilization example of the band used with a mobile communication system. It is a figure which shows the utilization example of the band used with a mobile communication system. FIG. 2 is a block diagram illustrating a transmission unit of a base station according to an embodiment of the present invention. FIG. 3 shows a block diagram of a user equipment according to an embodiment of the present invention. The block diagram regarding the transmission part of the user apparatus by one Example of this invention is shown. It is a figure which shows the utilization example of the band used with a mobile communication system. It is a figure which shows the utilization example of the band used with a mobile communication system. It is a figure which shows the example of a transmission frame. It is a figure which shows the example of a frame structure of an uplink.

  In the embodiment described below, various channels are transmitted in the uplink. These channels are roughly divided into (A) an uplink shared data channel, (B) a shared control channel, and (C) a pilot channel.

(A) [Uplink Shared Data Channel]
The uplink shared data channel (or uplink data channel) includes traffic data and / or layer 3 control messages. The control message may include information related to handover, information necessary for retransmission control, and the like. One or more resource blocks (which may be called frequency chunks) are allocated to the uplink shared data channel according to both time and frequency scheduling. In this case, resource allocation is planned at the base station (scheduling) so that users associated with better channels (channels) can transmit packets preferentially in the time domain or both time and frequency domains. )

(B) [Uplink Shared Control Channel]
The uplink shared control channel (or uplink control channel) transmits a physical control message and a layer 2 control message (FFS). For this reason, the uplink control channel is also called an L1 / L2 control channel. The base station allocates resource blocks to each user apparatus and performs scheduling so as to avoid contention for the shared control channel. For the uplink shared control channel, the base station performs scheduling depending on the number of users. In order to keep the packet error rate low, it is desirable to perform highly accurate transmission power control. Also, it is desirable to improve the quality of received packets by transmitting the uplink shared control channel over a wide frequency range and obtaining the frequency diversity effect.

  Specifically, the uplink shared control channel includes (1) control information related to a scheduled uplink shared data channel, (2) control information related to a scheduled downlink shared data channel, and (3) an uplink shared data channel. And (4) one or more pieces of control information for scheduling the downlink shared data channel.

  (1) Control information related to a scheduled uplink shared data channel is transmitted along with the uplink shared data channel only when the uplink shared data channel is transmitted. This control information, also referred to as associated control channel or essential control information, relates to information necessary for demodulating the shared data channel (modulation scheme, channel coding rate, etc.), transmission block size, and retransmission control. It may include information etc. and may be expressed with an information amount of about 14 bits, for example. For example, the retransmission control information may include information indicating whether a packet transmitted on the uplink shared data channel is a retransmission packet or a new packet, information indicating a method of using the retransmission packet, and the like. For example, in the first usage method, the data of the retransmission packet is the same as the data of the previously transmitted packet (for example, the first transmission data). However, in the second usage method, the data of the retransmission packet is the data of the previously transmitted packet. And may be different. In the latter case, packet combining can be performed together with redundant information for error correction coding.

  (2) The control information associated with the scheduled downlink shared data channel is transmitted to the base station only when the downlink shared data channel is transmitted from the base station and received by the mobile station. This control information indicates whether or not the packet has been properly received on the downlink (ACK / NACK), and can be expressed by 1 bit in the simplest case.

  (3) The control information for changing the scheduling content of the uplink shared data channel is transmitted to notify the base station of the buffer size and / or transmission power of the mobile station. This control information may be transmitted regularly or irregularly. For example, it may be transmitted from the mobile station when the buffer size and / or transmission power changes. The base station may change the scheduling content according to such a change in the situation of the mobile station. The buffer size and transmission power status may be expressed by an information amount of about 10 bits, for example.

  (4) Control information for scheduling a downlink shared data channel is transmitted to notify downlink channel quality information (CQI: channel quality indicator) to the base station. The CQI may be a received SIR measured by a mobile station, for example. This information may be sent regularly or irregularly. For example, it may be reported to the base station when the channel quality changes. This control information may be expressed by an information amount of about 5 bits, for example.

(C) [Pilot channel]
The pilot channel can be transmitted from the mobile station by time division multiplexing (TDM), frequency division multiplexing (FDM), code division multiplexing (CDM), or a combination thereof. However, it is desirable to use the TDM method from the viewpoint of reducing the peak-to-average power ratio (PAPR). By making the pilot channel and the data channel orthogonal by the TDM method, the pilot channel can be accurately separated on the receiving side, which can contribute to improvement of channel estimation accuracy.

  Hereinafter, the present invention will be described in several embodiments, but the division of each embodiment is not essential to the present invention, and two or more embodiments may be used as necessary.

  FIG. 1 shows a schematic block diagram of a user equipment (UE) and a base station (NodeB) according to an embodiment of the present invention. In FIG. 1, a pilot channel generation unit 231, a shared control channel generation unit 233, a shared data channel generation unit 234, a multiplexing unit 235, a discrete Fourier transform unit (DFT) 236, a mapping unit 237, and a fast inverse Fourier transform unit 238 are depicted. ing.

  The pilot channel generation unit 231 generates a pilot channel used in the uplink.

  The shared control channel generation unit 233 generates a shared control channel that may include various control information. As described above, the shared control channel includes (1) essential control information, (2) information indicating whether the downlink channel is received correctly—acknowledgment (ACK) and negative acknowledgment (NACK) —, and (3) scheduling contents. And (4) channel state information (CQI) indicating reception quality of the downlink pilot channel, and the like.

  The shared data channel generation unit 234 generates a shared data channel transmitted on the uplink. The shared data channel and the shared control channel are data-modulated with the designated modulation scheme and channel-coded with the designated coding scheme.

  The multiplexing unit 235 multiplexes and outputs one or more of various channels according to the scheduling information notified from the base station (the scheduling information is also notified to the elements 231, 233 and 234 that create each channel). . In the uplink, various channel mappings are possible. Therefore, it is not essential that all the illustrated channels are multiplexed, and one or more channels are multiplexed as necessary. In general, in the illustrated example, the multiplexing unit 235 performs time division multiplexing, and the mapping unit 237 performs allocation to frequency components.

  A discrete Fourier transform unit (DFT) 236 performs a Fourier transform on the signal (the multiplexed signal in the illustrated example) input thereto. At this stage of signal processing, the signal is a discrete digital value, so a discrete Fourier transform is performed. Thereby, a series of signal sequences arranged in time order are expressed in the frequency domain.

  The mapping unit 237 maps each signal component after Fourier transform to a predetermined subcarrier on the frequency domain. Thereby, for example, a local type FDM (localized FDM) or a distributed type FDM (distributed FDM) is performed. The former divides the band into the number of users along the frequency axis. In the latter method, the phase of each user's signal is adjusted so that a large number of frequency components arranged in a comb shape at equal intervals are included and different users have different frequency components. Note that such signal processing may be performed by, for example, a variable spreading factor chip repetition factor CDMA (VSCRF-CDMA: Variable Spreading Chip Repetition Factor-CDMA) method, or in the frequency domain after Fourier transform as illustrated. Any other technique such as inverse Fourier transform after processing may be used. In any case, even a single carrier system can be handled as a signal having a large number of frequency spectra.

  The fast inverse Fourier transform unit 238 performs fast inverse Fourier transform on the mapped signal components and outputs a signal sequence arranged in a series of time sequences.

  FIG. 1 also shows an outline of a base station according to an embodiment of the present invention. The base station in FIG. 1 includes a discrete Fourier transform unit (DFT) 241, a mapping unit 242, a fast inverse Fourier transform unit 243, a multiplexing unit 244, a CQI measurement unit 246, and a scheduler 247.

  A discrete Fourier transform unit (DFT) 241 performs a Fourier transform on a signal (received signal in the illustrated example) input thereto. Thereby, a series of signal sequences arranged in time order are expressed in the frequency domain.

  The mapping unit 242 extracts a predetermined subcarrier component from the signal after Fourier transform. As a result, for example, signals multiplexed by a local type FDM or a distributed type FDM are separated.

  The fast inverse Fourier transform unit 242 performs fast inverse Fourier transform on the separated signal components and outputs a signal sequence arranged in a series of time sequences.

  The separation unit 244 separates and outputs one or more of various channels. In the illustrated example, the signal mapped to the frequency component is restored to the signal before mapping by the demapping unit 242, and the time-multiplexed signal is separated by the separation unit 244.

  The CQI measurement unit 246 measures the reception signal quality (reception SIR and / or CQI) of the uplink pilot channel and estimates the channel state based on the measurement.

  The scheduler 247 determines uplink resource allocation contents (performs scheduling) based on the channel state regarding each user apparatus. A user apparatus in a better channel state can receive resource allocation with priority. The base station also performs downlink scheduling and the like, but the description is omitted. The scheduling information indicating the resource allocation content is notified to the user apparatus.

  One or more channels generated by the generation unit of each channel of the user apparatus are time-multiplexed (switched appropriately) by the multiplexing unit 235, input to the DFT 236, and converted into a frequency domain signal. The converted signal is appropriately mapped to frequency components by the mapping unit 237, input to the IFFT 238, and converted into a time-series signal. Thereafter, it is wirelessly transmitted through a processing element such as a wireless unit (not shown). This signal is received at the base station. The received signal is input to the DFT 241 and converted into a frequency domain signal. The converted signal is a signal mapped to the frequency component, but is separated into a signal before mapping by the demapping unit 242. The separated signal is converted into a time-series signal by IFFT 243, and the time-multiplexed signal series is appropriately separated by separation section 244, and further demodulated by a processing element (not shown). The uplink channel state is measured based on the received pilot channel, uplink scheduling is performed, and scheduling information indicating the resource allocation content is notified to the user apparatus.

  FIG. 2 shows a frequency band used in a certain mobile system. A frequency band given to the system (also referred to as an entire frequency band or a system band) includes a plurality of system frequency blocks, and a user apparatus performs communication using one or more resource blocks included in the system frequency block. Can do. In the illustrated example, the system band is 10 MHz, the system frequency block is 5 MHz, and two system frequency blocks are included in the system band. For simplicity of illustration, the system frequency block 2 is not drawn. The resource block is 1.25 MHz, and one system frequency block includes four resource blocks. Which of the two system frequency blocks can be used by the user apparatus is determined by the base station according to the bandwidth in which the user apparatus can communicate and the number of users communicating in the system. The bandwidth of the system frequency block is designed as a band in which all user apparatuses that can communicate in the system can communicate. In other words, the bandwidth of the system frequency block is determined as the maximum transmission bandwidth for the assumed lowest grade user equipment. Accordingly, only one of the system frequency blocks can be assigned to a user apparatus that can communicate only in the 5 MHz band, but the user apparatus capable of communicating in the 10 MHz band has a band so that both system frequency blocks can be used. May be assigned. The user apparatus transmits an uplink pilot channel using one or more resource blocks included in the allocated system frequency block. Based on the reception level of the uplink pilot channel, the base station determines (schedules) what one or more resource blocks the user apparatus uses for transmission of the shared data channel. The contents of scheduling (scheduling information) are reported to the terminal through the downlink shared control channel or another channel. The user apparatus transmits the uplink shared data channel using the allocated resource block.

  FIG. 3 shows an example in which a resource block in which a certain user apparatus transmits a shared control channel changes with time. In the figure, the uplink shared control channel of the user apparatus is transmitted in the shaded resource block portion. The resource block that can be used by this user apparatus follows a certain frequency hopping pattern indicated by the arrow pointing to the lower right, and the contents of the hopping pattern may be known before the start of communication between the base station and the user apparatus, or necessary. Accordingly, the user equipment may be notified from the base station. Since frequency hopping is performed, not only a specific resource block but also various resource blocks are used, so that the average signal quality of the uplink shared control channel can be maintained. The illustrated frequency hopping pattern is merely an example, and various patterns may be employed. Further, not only one type but also a plurality of types of frequency hopping pattern candidates may be prepared, and the patterns may be changed as appropriate.

  In the illustrated example, this user apparatus transmits control information other than the essential control information except for the third third subframe (which may be referred to as a unit transmission time interval (TTI)) in time order. In the third subframe, the uplink shared data channel is transmitted using the rightmost resource block, and the shared control channel is also transmitted using this resource block. A resource block different from the frequency hopping pattern is used in the third subframe, but information regarding such a change is reported from the base station through a shared control channel. Depending on whether or not a resource block is allocated to the uplink data channel, it may be determined in advance whether the uplink control channel is transmitted in a dedicated resource block or transmitted together with the uplink data channel.

  By the way, as described above, it is difficult to expect retransmission of the control channel of the essential control information and the other control information (first and second control information) if it cannot be demodulated well, It differs from the data channel that can be expected to be retransmitted. The need for high quality and reliable transmission is greater for the control channel than for the data channel.

  Even if it is determined that a certain resource block is good for the user apparatus at the time of scheduling of the uplink data channel and is allocated, the communication situation may be different if it is actually transmitted from the user apparatus thereafter. Absent. That is, even if the uplink control channel is transmitted in the same resource block as the uplink data channel, the uplink control channel cannot always be transmitted as expected.

  FIG. 4 illustrates a control channel and a data channel transmitted according to an embodiment of the present invention. The point that the uplink control channel of a certain user apparatus is transmitted according to a predetermined hopping pattern is the same as that shown in FIG. The point that the data channel is allocated to the fourth resource block in the third subframe is the same as the example shown in FIG. However, it differs from the example of FIG. 4 in that the control channel is transmitted in the third resource block according to the hopping pattern in the third subframe. This control channel includes essential control information associated with the uplink data channel transmitted in the fourth resource block, and other control information as necessary. In this embodiment, the uplink control channel is always transmitted according to a predetermined hopping pattern regardless of the presence or absence of the uplink data channel. In the first place, the hopping pattern transmits the control channel at various frequencies and times so as to disperse the interference received by the own channel and the interference on other channels, and ensure that the control channel is transmitted with the required quality. It has been decided. By maintaining the hopping pattern as in the present embodiment, it is possible to ensure the effect expected by hopping (the effect of dispersing the interference received by the own channel and the interference on other channels). As shown in the third subframe of FIG. 4, if the transmission periods of the control channel and the data channel are different, the carrier frequency is changed from the frequency of the third resource block to the frequency of the fourth resource block in the third subframe. By switching, the user apparatus can appropriately transmit them on a single carrier.

  In the existing mobile communication system, the size of the resource block is fixed to one. In the basic research of the present invention, the inventors of the present invention paid attention to the interrelationships of resource block size, scheduling effect, signaling overhead, and resource utilization efficiency.

  FIG. 5 is a chart showing the mutual relationship. As shown in the first line of the chart, if the resource block size is small, the resource blocks can be precisely allocated according to the quality of the channel state, and the effect of improving the throughput of the entire system can be greatly expected. Conversely, if the resource block size is large, it becomes difficult to precisely allocate resource blocks, and the degree of improvement in throughput of the entire system becomes small. In general, the channel fluctuation fluctuates more in the frequency direction than in the time direction, but the same tendency occurs in any direction regarding the relationship between the size of the resource block and the throughput.

  As shown in the second row of the chart, when the resource block size is small, there are a large number of resource blocks, so that the amount of scheduling information indicating which resource block is used by which user increases. End up. That is, there is a concern that signaling overhead increases. On the other hand, when the resource block size is large, the number of resource blocks is small, so that the signaling overhead is small.

  As shown in the third row of the chart, when data transmission with a small data size (for example, control channel data transmission) is performed, if the resource block size is large, resources may be wasted. This is because one resource block is used by one user. In this respect, if the resource block size is reasonably small, such waste can be reduced.

  For example, as shown in FIG. 6, it is assumed that a control channel of a certain user apparatus is transmitted in a shaded resource block. Since the information amount of the control channel is generally small, there is a concern that resources are wasted in individual resource blocks. Furthermore, the resources allocated to the data channel are also reduced. However, as shown in FIG. 7, it is not a good idea to reduce the number of resource blocks or the allocation frequency allocated to the uplink control channel of a certain user apparatus. If the resource block allocation frequency is reduced, the uplink control channel is prevented from being transmitted promptly, the transmission timing of control information that requires immediacy such as acknowledgment information (ACK / NACK) is delayed, and data transmission efficiency There is a concern that it will decrease.

  As described above, it is difficult to determine a preferable resource block size from all viewpoints such as an effect of improving the throughput of the entire system, a small amount of signaling overhead, and resource utilization efficiency. The second embodiment of the present invention also addresses such problems. Specifically, by preparing resource blocks of different sizes and using them appropriately, it is possible to improve the transmission efficiency of data of large and small sizes and effectively use resources while reducing the signaling overhead.

  FIG. 8 is a block diagram illustrating a transmission unit of a base station according to an embodiment of the present invention. In FIG. 8, a transmission buffer 31, an OFDM transmission unit 32, a scheduler 33, a pattern determination unit 34, and a memory 35 are depicted.

  The transmission buffer 31 accumulates downlink transmission data and outputs it according to scheduling information.

  The OFDM transmitter 32 creates a transmission signal for wirelessly transmitting downlink transmission data according to the scheduling information. More specifically, the transmission data is encoded at the designated channel coding rate, for example, modulated by the designated data modulation scheme, modulated by the OFDM scheme by fast inverse Fourier transform, and given guard interval. And transmitted from the antenna. The downlink transmission data includes at least a downlink control channel and a downlink data channel. The downlink control channel includes not only a control channel associated with the downlink data channel but also information related to the uplink, and particularly includes uplink scheduling information.

  The scheduler 33 performs time scheduling and frequency scheduling on the uplink and downlink based on the downlink received signal quality (CQI) reported from the user apparatus, the uplink received signal quality measured by the base station, and the notified resource block size. To output scheduling information. The scheduler 33 determines scheduling information so as to allocate resource blocks to users in better channel states based on the CQI of the upper and lower links. The scheduling information includes information indicating a combination (MCS number) of a modulation scheme and a channel coding rate in addition to information indicating which resource block is allocated to which user. In determining the scheduling information, not only the CQI but also the amount of untransmitted data accumulated in the transmission buffer and an index for achieving some fairness may be considered.

  The pattern determination unit 34 adjusts the size of the resource block based on the data size and / or CQI of the transmission data. In this embodiment, resource blocks of two sizes, large and small, are prepared, and either or both resource blocks are assigned to each user apparatus.

  The memory 35 stores the arrangement pattern of resource blocks. An arrangement pattern of resource blocks and usage examples thereof will be described later.

  FIG. 9 is a block diagram illustrating a receiving unit of a user apparatus according to an embodiment of the present invention. In FIG. 9, an OFDM receiving unit 41, a resource identifying unit 42, an arrangement pattern determining unit 43, a memory 44, a CQI measuring unit 45, and a transmitting unit 46 are depicted.

  The OFDM receiver 41 derives a control data channel and a traffic data channel from the received signal. More specifically, the OFDM receiver 41 demodulates the OFDM scheme by removing the guard interval from the received signal, performs fast Fourier transform on the received signal, and performs data demodulation and channel decoding according to the scheduling information notified from the base station. To derive a control data channel and / or a traffic data channel.

  The resource identification unit 42 outputs mapping information specifying the position of the resource block on the time axis and the frequency axis based on the scheduling information and the resource block arrangement pattern.

  The arrangement pattern determination unit 43 extracts an arrangement pattern corresponding to the pattern number notified from the base station from the memory 44 and notifies the resource identification unit 42 of the contents.

  The memory 44 stores an arrangement pattern of resource blocks together with a pattern number.

  The CQI measurement unit 45 measures the CQI of the received signal. The measured downlink CQI is reported to the base station at a predetermined frequency.

  The transmission unit 46 creates an uplink channel transmission signal that is wirelessly transmitted from the antenna.

  FIG. 10 shows a detailed functional block diagram of the transmission unit 46. FIG. 10 shows a transmission signal sequence output unit 131, a discrete Fourier transform unit (DFT) 132, a data mapping unit 133, an inverse Fourier transform unit 134, and a transmission frame timing adjustment unit 135.

  Transmission signal sequence output section 131 generates or outputs a transmission signal sequence. The transmission signal sequence may include any channel transmitted on the uplink. Particularly in this embodiment, the transmission signal sequence output unit 131 outputs an uplink control channel and an uplink data channel. The control channel includes a control channel (essential control channel or first control channel) that must accompany the uplink data channel and a control channel (second control channel) that is transmitted regardless of the presence or absence of the uplink data channel. . The CQI and ACK / NACK shown belong to the second control channel.

  A discrete Fourier transform unit (DFT) 132 performs a Fourier transform on the transmission signal and converts a time domain signal into a frequency domain signal.

  The data mapping unit 133 performs mapping so that the transmission signal has a desired component in the frequency domain according to the instruction parameter. The instruction parameter includes a transmission bandwidth, a transmission band (frequency), a repetition factor, and the like. The data mapping unit 133 maps the transmission signal component on the frequency axis so that the transmission signals of user apparatuses having different bandwidths are orthogonal to each other by the distributed FDM method.

  The inverse Fourier transform unit 134 performs fast inverse Fourier transform on a signal having a desired frequency component, and converts it into a time domain signal.

  The transmission frame timing adjustment unit 135 adjusts the transmission timing of the transmission signal and outputs the transmission signal. In particular, when time division multiplexing (TDM) is performed, the adjustment unit 135 performs signal transmission in accordance with the transmission slot of the own station.

  The operation will be described with reference to FIGS. The downlink transmission data is stored in the transmission buffer 31 and input to the OFDM transmission unit according to the downlink scheduling information, and the transmission signal for radio transmission is subjected to processing such as channel coding, data modulation, mapping to a resource block, and fast inverse Fourier transform. To be transmitted. Scheduling information on scheduling related to the uplink is reported to the user apparatus through the downlink control channel. For both the upper and lower links, the scheduling information specifies a channel coding scheme, a data modulation scheme, a resource block, and the like. In this case, in this embodiment, resource blocks having different sizes are used as necessary.

  The user apparatus restores the received signal and creates a transmission signal based on the arrangement pattern used in the base station. The resource block arrangement pattern to be used is determined by the pattern determination unit 34 of the base station in FIG. 8, and the determination content is notified to the scheduler 33. This information (specifically, the pattern number) and scheduling information are notified to the user apparatus through an appropriate control channel. The user apparatus extracts the pattern number and scheduling information by restoring the received control channel. The pattern number is given to the arrangement pattern determination unit 43 in FIG. Based on the notified pattern number, the arrangement pattern determination unit 43 notifies the resource identification unit 42 of information regarding the arrangement pattern specified by the number. The resource identification unit 42 identifies a resource block including data addressed to the own station according to the identified downlink arrangement pattern and downlink scheduling information, and notifies the OFDM reception unit 41 of the resource block. Further, the resource identification unit 42 identifies a resource block used in the uplink according to the identified uplink arrangement pattern and uplink scheduling information, and notifies the transmission unit 46 of the resource block. The OFDM receiver 41 extracts and restores the data channel addressed to itself according to this information. The transmission unit 46 creates a transmission signal based on the uplink scheduling information and the uplink mapping information.

  FIG. 11 shows an example of an uplink arrangement pattern. In the illustrated example, resource blocks having two types of data sizes, large and small, are prepared. The larger resource block has a bandwidth of 1.25 MHz and a duration of 0.5 ms. The smaller resource block has a bandwidth of 375 kHz and a duration of 0.5 ms. The number of resource blocks having different sizes and the numerical value relating to the size are merely examples, and any appropriate number may be used. Five resource blocks are arranged in the frequency axis direction, small resource blocks are arranged on the left and right, and the arrangement pattern in each subframe is the same. However, the arrangement pattern of resource blocks having different sizes can be set in various ways, and only needs to be known at both the transmission and reception ends. In the example shown in the figure, the control channel (first control channel) associated with the uplink data channel and the second control as necessary in a part of the large resource block (second, third and fourth resource blocks). The uplink scheduling is performed so that the channel is transmitted, and the control channel (second control channel) is transmitted with a small resource block (first or fifth resource block) regardless of the presence or absence of the uplink data channel. Done. The time ratio of the control channel and data channel in a large resource block is not necessarily the same for all user devices, and may be changed as appropriate depending on the amount of control information required for each user device. . Furthermore, the second control channel of a certain user equipment is transmitted using two small resource blocks. In the illustrated example, the second control channel of user apparatus A is transmitted using the fifth and first resource blocks in the second and third subframes, respectively. Similarly, the second control channel of user equipment B is transmitted using the fifth and first resource blocks in the third and fourth subframes, respectively. As described above, since the second control channel is transmitted while hopping in the frequency axis and time axis directions, a frequency diversity effect can be obtained and the reliability of the second control channel being appropriately demodulated at the base station can be increased. it can. In the illustrated example, as a typical use example, the first control channel is transmitted in a large resource block and the second control channel is transmitted in a small resource block. Such proper use of resource blocks is essential for the present invention. Instead, the resource block may be used for any control channel.

  In FIG. 11, a small resource block is depicted as if all the resource blocks are monopolized by the user apparatus A as “Control A”, but such usage is not essential to the present invention. A resource block may be shared by a plurality of user apparatuses. For example, the fifth resource block of the second subframe may be shared by user apparatuses A and C. Typically, such a plurality of user apparatuses may share one resource block in a frequency multiplexing manner.

FIG. 12 shows another arrangement pattern example of the uplink. Similar to the case of FIG. 11, resource blocks of two types of data sizes, large and small, are prepared. In the present embodiment, for smaller resource blocks (first and fifth resource blocks), the subframe period T _RB is further divided into two sub-periods. In the illustrated example, the second control channel of user equipment A is transmitted using the fifth and first resource blocks in the first and second subdivision periods (first half and second half of the subframe) of the third subframe, respectively. The The second control channel of user equipment B is transmitted using the first and fifth resource blocks of the first and second subdivision periods of the third subframe, respectively. As described above, since the second control channel is transmitted while hopping in the frequency axis and time axis directions, the frequency diversity effect is obtained, and the certainty that the second control channel is appropriately demodulated at the base station is increased. it can. Further, the transmission of the control channel of the user apparatus A is completed within a period of one subframe, and the transmission of the control channel of the user apparatus B is also completed within a period of one subframe. Therefore, this embodiment is preferable from the viewpoint of shortening the transmission delay of the uplink control channel.

  Also in FIG. 12, a resource block may be shared by a plurality of user apparatuses. For example, the fifth resource block in the first sub-period of the third subframe may be shared by the user apparatuses A and C. Typically, such a plurality of user apparatuses may share one resource block in a frequency multiplexing manner.

  It is theoretically conceivable that the number of sub-periods included in one subframe is more than two. The frame used in FIG. 12 typically has a configuration as shown in FIG. Each of the first and second subdivision periods includes a pilot channel. Therefore, data transmitted in any sub-period (control channel) can be appropriately subjected to channel compensation or the like using a pilot channel included therein. However, if this frame is divided into three sub-periods, a sub-period that does not include the pilot channel is generated, and it is difficult to appropriately perform channel compensation or the like for the channel transmitted during that period. Therefore, it is desirable that the number of sub-periods per subframe be suppressed to the number of pilot channel insertions at most.

  As described above, the uplink control channel includes control information associated with the uplink data channel and control information transmitted regardless of the presence or absence of the uplink data channel. The latter includes a small data size and a strong demand for immediacy and high reliability, and a relatively weak demand for such demand. A typical example of the former is downlink data channel acknowledgment information (ACK / NACK). The latter includes CQI reported to the base station at a predetermined frequency. The delivery confirmation information is important information that plays a central role in retransmission control. Depending on whether the packet is ACK or NACK, the retransmission of the packet is performed or not performed, so the content of the delivery confirmation information greatly affects the data throughput and the delay time. Therefore, it is desirable that transmission is performed with high reliability. On the other hand, in principle, the delivery confirmation information has a small data size that is sufficient for one bit, but this makes it difficult to expect a high correction capability by error correction coding. For this reason, even if the delivery confirmation information is transmitted in the same manner as other control information having a relatively large data size, it is not necessarily expected to obtain the same high reliability.

  From this point of view, in the fourth embodiment of the present invention, as shown in FIG. 14, in the uplink transmission frame, the control channel including the acknowledgment information (ACK / NACK) is code-multiplexed with other channels, and the transmission is performed. Control channels other than the confirmation information are multiplexed by frequency multiplexing and / or time multiplexing. Acknowledgment information (ACK / NACK) having a small amount of information is spread and transmitted with a large spreading factor, so that the spreading gain is large. This is advantageous from the viewpoint of transmitting the delivery confirmation information to the base station with high reliability. Also, advantageously, for other channels (eg, data channels) that are code-multiplexed, a signal spread with such a large spreading factor contributes only as a small noise. Few.

  The resource block on which the code confirmation of the delivery confirmation information is not necessarily fixed, and may be code multiplexed with various resource blocks. The resource block on which code multiplexing is performed may change every moment according to some hopping pattern.

  Such a method is not limited to ACK / NACK, but has a small data size (for example, it can be appropriately set to be less than a few bits or less than 10 bits) and information that requires immediacy and high reliability. When other information is transmitted, the former can be code-multiplexed with another channel, and the latter can be frequency-multiplexed and / or time-multiplexed for transmission.

  With respect to the example shown in FIG. 3, from the viewpoint of suppressing quality degradation of the uplink control channel as much as possible, in the embodiment shown in FIG. 4, the uplink control channel including the second control information of a certain user apparatus is associated with the uplink data channel. Even if it was not, it was transmitted with the same hopping pattern. However, the problem associated with the example shown in FIG. 3 can also be addressed by prohibiting allocation of resource blocks for data channel transmission under certain conditions.

  For example, in FIG. 12, when a certain user apparatus does not have an uplink data channel (or when resources are not allocated), the uplink control channel of the user apparatus (second control information—particularly, ACK / NACK, CQI) is transmitted in resource blocks (first and fifth resource blocks) having a small data size, and when one or more of the second to fourth resource blocks are allocated to the uplink data channel of the user apparatus, the resource Assume that the uplink control channel is transmitted in blocks.

  In order to describe the method in this embodiment, for example, instead of transmitting the uplink control channel (second control channel) of a certain user apparatus in the fifth and first resource blocks of the third subframe of FIG. Consider transmitting the control channel in a second resource block of 3 subframes (in a wider band and in a shorter period). When the uplink control channel is transmitted in the fifth and first resource blocks of the third subframe, transmission can be instantaneously performed with high power corresponding to the narrow band, and hopping is performed in the first and fifth resource blocks. Therefore, the frequency diversity effect can be expected. Therefore, it is possible to expect a certain level of reception quality at the base station. However, when the control channel is transmitted over a short period of time in the second resource block in a wide band, the instantaneous power per band is reduced by the amount of the wide band, the frequency diversity effect is diminished, and the channel state is reduced. If not good enough, control channel quality degradation may be a concern. In particular, this is due to the fact that the user equipment moving at high speed and the user equipment located at the cell edge are permitted to transmit the uplink data channel (assigned the second to fifth resource blocks). There is concern about quality degradation of the control channel. As described above, since the control channel cannot be retransmitted, high quality is required from the first time. In particular, the acknowledgment information (ACK / NACK) for the downlink data channel is an important parameter that is directly related to the data throughput, and therefore needs to be transmitted accurately and promptly to the base station.

  From such a viewpoint, in the fifth embodiment of the present invention, a new criterion is added to the uplink scheduling at the base station. As in the prior art, the base station evaluates the uplink channel state based on the quality of the reception quality (CQI) of the pilot channel transmitted from the user apparatus. In addition, in this embodiment, the mobility of the user apparatus and the distance from the base station are calculated. Mobility can be derived by measuring the Doppler frequency. A large Doppler frequency indicates that the user apparatus is moving at high speed. The distance from the base station of the user apparatus can be estimated from a path loss or the like that is greatly affected by the distance fluctuation. A large path loss means that the user apparatus is far away from the base station. For example, the scheduler of the base station selects user apparatuses that are candidates for resource allocation based on the quality of the uplink channel state (CQI). Among the selected user devices, user devices with relatively small mobility and / or distance are prioritized over those with large numbers. For example, even if two user apparatuses report the same good channel state (CQI), resources for data channels are preferentially allocated to user apparatuses moving at a lower speed. Further, even if two user apparatuses report the same good channel state (CQI), resources for data channels are preferentially allocated to user apparatuses located closer to the base station. In other words, the allocation of data channel resources to a user apparatus that is moving at a high speed or a user apparatus at the cell edge where the channel state is not so good is prohibited. As a result, it is possible to avoid quality degradation of the control channel due to permission of transmission of the uplink data channel (assignment of the second to fifth resource blocks).

  Hereinafter, the means taught by the present invention will be listed as an example.

(Section 1)
A base station used in a mobile communication system employing a single carrier scheme for uplink,
A scheduler that assigns one or more uplink resource blocks to individual user devices according to the uplink channel state for each user device;
Means for notifying user equipment of scheduling information indicating the plan contents of resource allocation;
And an uplink control channel of a user apparatus is mapped so as to draw a predetermined hopping pattern in a transmission frame including a plurality of resource blocks according to the scheduling information,
The base station, wherein the uplink control channel is mapped with the same hopping pattern whether or not accompanied by a user data channel.

(Section 2)
The base station according to claim 1, wherein an uplink control channel and an uplink user data channel included in the same resource block are transmitted in different periods in the transmission frame.

(Section 3)
The base station according to claim 1, wherein the hopping pattern is determined so that an uplink control channel of a certain user apparatus is transmitted in an adjacent resource block when a subframe changes with time.

(Section 4)
The base station according to claim 1, wherein one or more resource blocks having different data sizes are allocated to each user apparatus.

(Section 5)
The base station according to claim 4, wherein an uplink control channel of the same user apparatus is allocated to a plurality of resource blocks having a small data size belonging to at least two different time subframes and at least two different bands.

(Section 6)
5. Each of a plurality of resource blocks having a small data size belonging to the same time subframe is subdivided into two or more sub-periods, and a different uplink control channel of a user apparatus is allocated to each sub-period. Base station.

(Section 7)
A channel including control information smaller than a predetermined amount of information is code-multiplexed, and a channel including control information larger than a predetermined amount of information is multiplexed with other channels in both time multiplexing and frequency multiplexing. The base station according to claim 1, wherein the scheduling information is determined.

(Section 8)
A method used in a base station of a mobile communication system adopting a single carrier scheme for uplink,
A scheduling step of assigning one or more uplink resource blocks to individual user devices according to the uplink channel state for each user device;
A step of notifying user equipment of scheduling information indicating a plan content of resource allocation;
And an uplink control channel of a user apparatus is mapped so as to draw a predetermined hopping pattern in a transmission frame including a plurality of resource blocks according to the scheduling information,
The uplink control channel is mapped with the same hopping pattern whether or not accompanied by a user data channel.

(Section 9)
A user apparatus used in a mobile communication system adopting a single carrier scheme for uplink,
Means for receiving a downlink control channel;
Means for extracting, from the downlink control channel, scheduling information indicating the allocation content of one or more uplink resource blocks allocated according to the uplink channel state of the user apparatus;
Means for transmitting at least an uplink control channel according to the scheduling information;
The uplink control channel is mapped so as to draw a predetermined hopping pattern in a transmission frame including a plurality of resource blocks according to the scheduling information,
The user apparatus, wherein the uplink control channel is mapped with the same hopping pattern regardless of whether it is accompanied by a user data channel.

(Section 10)
The user apparatus according to claim 9, wherein an uplink control channel and an uplink user data channel included in the same resource block are transmitted in different periods in the transmission frame.

(Section 11)
The user apparatus according to claim 9, wherein the hopping pattern is determined so that the uplink control channel is transmitted in an adjacent resource block when a subframe changes with time.

(Section 12)
The user device according to claim 9, wherein one or more resource blocks having different data sizes are allocated to each user device.

(Section 13)
The user apparatus according to claim 12, wherein uplink control channels of the same user apparatus are allocated to a plurality of resource blocks having a small data size belonging to at least two time subframes and at least two bands.

(Section 14)
Each of a plurality of resource blocks having a small data size belonging to the same time subframe is subdivided into two or more sub-periods, and the uplink control channel of the user apparatus is separated at a frequency of a certain resource block in a sub-period. 13. The user apparatus according to claim 12, wherein resources are allocated so that transmission is performed at a frequency of another resource block in the sub-period.

(Section 15)
A channel including control information smaller than a predetermined amount of information is code-multiplexed, and a channel including control information larger than a predetermined amount of information is multiplexed with other channels, either time-multiplexed and / or frequency-multiplexed. The user equipment according to claim 12, wherein the uplink control channel is transmitted.

(Section 16)
A method used in a user apparatus of a mobile communication system adopting a single carrier scheme for uplink,
Receiving a downlink control channel;
Extracting, from the downlink control channel, scheduling information indicating allocation contents of one or more uplink resource blocks allocated according to the uplink channel state of the user apparatus;
Transmitting at least an uplink control channel according to the scheduling information;
The uplink control channel is mapped so as to draw a predetermined hopping pattern in a transmission frame including a plurality of resource blocks according to the scheduling information,
The uplink control channel is mapped with the same hopping pattern whether or not accompanied by a user data channel.

(Section 17)
A base station used in a mobile communication system employing a single carrier scheme for uplink,
According to the uplink channel state for each user apparatus, a scheduler that allocates one or more resource blocks with different uplink data sizes to individual user apparatuses,
Means for notifying user equipment of scheduling information indicating the plan contents of resource allocation;
The uplink control channel of a certain user apparatus is transmitted in the resource block when the resource block is allocated to the uplink data channel of the user apparatus, and the resource block is allocated to the uplink data channel of the user apparatus. If not, scheduling information is created so that the uplink control channel is transmitted in a dedicated resource block,
The dedicated resource block is a plurality of resource blocks having a small data size belonging to at least two different periods and at least two different bands,
If the mobility of the user equipment is greater than a predetermined value or if the distance from the base station of the user equipment is greater than a predetermined value and the uplink channel state for the user equipment is worse than a predetermined level, A base station characterized in that a resource block is prohibited from being allocated to an uplink data channel.

(Section 18)
A method used in a base station of a mobile communication system adopting a single carrier scheme for uplink,
A scheduling step of assigning one or more uplink resource blocks to individual user devices according to the uplink channel state for each user device;
A step of notifying user equipment of scheduling information indicating a plan content of resource allocation;
The uplink control channel of a certain user apparatus is transmitted in the resource block when the resource block is allocated to the uplink data channel of the user apparatus, and is allocated to the uplink data channel of the user apparatus. If not, scheduling information is created so that the uplink control channel is transmitted in a dedicated resource block,
The dedicated resource block is a plurality of resource blocks having a small data size belonging to at least two different periods and at least two different bands,
If the mobility of the user equipment is greater than a predetermined value or if the distance from the base station of the user equipment is greater than a predetermined value and the uplink channel state for the user equipment is worse than a predetermined level, A method characterized by allocating resource blocks to an uplink data channel is prohibited.

DESCRIPTION OF SYMBOLS 21 Transmission bandwidth determination part 22 Transmission band determination part 23 Transmission band management part 24 Code allocation part 25 Code management part 31 Transmission buffer 32 OFDM transmission part 33 Scheduler 34 Pattern determination part 35 Memory 41 OFDM reception part 42 Resource identification part 43 Arrangement pattern Determination unit 44 Memory 45 CQI measurement unit 46 Transmission unit 131 Transmission signal sequence output unit 132 Discrete Fourier transform unit 133 Data mapping unit 134 Inverse Fourier transform unit 135 Transmission frame timing adjustment unit 231 Pilot channel generation unit 233 Shared control channel generation unit 234 Sharing Data channel generation unit 235 Multiplexing unit 236, 241 Discrete Fourier transform unit 237, 242 Mapping unit 238, 243 Fast inverse Fourier transform unit 244 Separation unit 246 CQI measurement unit 247 Scheduler

Claims (1)

A base station used in a mobile communication system employing a single carrier scheme for uplink,
A scheduler that assigns one or more uplink resource blocks to individual user devices according to the uplink channel state for each user device;
Means for notifying user equipment of scheduling information indicating the plan contents of resource allocation;
And an uplink control channel of a user apparatus is mapped so as to draw a predetermined hopping pattern in a transmission frame including a plurality of resource blocks according to the scheduling information,
The base station, wherein the uplink control channel is mapped with the same hopping pattern whether or not accompanied by a user data channel.

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