WO2019239467A1

WO2019239467A1 - Terminal device, base station, wireless communication system and wireless communication method

Info

Publication number: WO2019239467A1
Application number: PCT/JP2018/022272
Authority: WO
Inventors: 木下　裕介; 啓二郎武; 亮松永; 佐和橋　衛
Original assignee: 三菱電機株式会社
Priority date: 2018-06-11
Filing date: 2018-06-11
Publication date: 2019-12-19

Abstract

This terminal device (10) is characterized by comprising a transmission unit (100) which includes: a division unit (12) which divides a preamble sequence into a plurality of sub-blocks; and a mapping unit (13) which respectively allocates the plurality of sub-blocks to a plurality of resource blocks in different frequency bands, wherein the sub-blocks are transmitted to a base station (20) by using the allocated resource blocks.

Description

Terminal device, base station, radio communication system, and radio communication method

The present invention relates to a terminal device, a base station, a wireless communication system, and a wireless communication method.

In recent years, so-called IoT (Internet of Things), all things such as consumer devices, industrial control devices such as factories, sensors, meters, automobiles, etc. are connected to the Internet with communication functions. It has become to. The wireless standard used in IoT requires a reduction in power consumption of the terminal device.

The number of information bits transmitted by an IoT device is often smaller than that of a general information terminal such as a smartphone. For this reason, in order to reduce the power consumption of the terminal device, it is effective to narrow the transmission bandwidth. The narrower the transmission bandwidth, the lower the baseband modulation and demodulation processing clock frequency, and the power consumption of the terminal device can be reduced. Further, since the transmission power per 1 Hz can be increased as the transmission bandwidth is narrowed, the coverage area can be expanded.

Also, Non-Patent Document 1 discloses a random access procedure that is executed to establish a connection between a base station and a terminal device in wireless communication. When the random access procedure is performed between the terminal device and the base station, if the transmission bandwidth is narrow, the frequency diversity effect cannot be obtained like a wideband signal. For this reason, the received power level of the entire transmission band decreases due to frequency flat fading. For this reason, in downlink transmission from the base station to the terminal device, a decrease in the reception power level is suppressed by increasing the transmission power.

However, when the above conventional technique is applied to the IoT environment, there is a restriction on the maximum transmission power in uplink transmission from the terminal device to the base station. For this reason, there is a problem that the transmission power cannot be increased, the reception power level is lowered, and the detection probability of the preamble sequence transmitted from the terminal apparatus to the base station is lowered.

The present invention has been made in view of the above, and an object of the present invention is to obtain a terminal device, a base station, a radio communication system, and a radio communication method that can improve the detection probability of a preamble sequence transmitted in uplink. To do.

In order to solve the above-described problems and achieve the object, a terminal apparatus according to the present invention includes a dividing unit that divides a preamble sequence into a plurality of sub-blocks, and a plurality of sub-blocks each having a plurality of different frequency bands. A mapping unit that is allocated to each of the resource blocks, and a transmission unit that transmits the sub-block to the base station using the allocated resource block.

The terminal device according to the present invention has an effect of improving the detection probability of a preamble sequence transmitted in uplink.

The figure which shows the structure of the radio | wireless communications system concerning Embodiment 1 of this invention. The sequence diagram which shows the random access procedure performed between the terminal device shown in FIG. 1, and a base station The figure which shows the structure of the sub-frame transmitted to the base station from the terminal device shown in FIG. Explanatory drawing about frequency hopping performed by the terminal device shown in FIG. The figure which shows the structure of the transmission part shown in FIG. Explanatory drawing of the 1st example of the transmission block production | generation method which the transmission block production | generation part shown in FIG. 5 performs. Explanatory drawing of the 2nd example of the transmission block production | generation method which the transmission block production | generation part shown in FIG. 5 performs. The figure which shows the structure of the receiving part shown in FIG. The figure which shows the structure of the sub-frame used in Embodiment 2 of this invention. The figure which shows the structure of the transmission block production | generation part concerning Embodiment 2 of this invention. The figure which shows the structure of the receiving part concerning Embodiment 2 of this invention. Explanatory drawing of the resource block which the base station concerning Embodiment 2 of this invention allocates to a terminal device. The figure which shows the 1st example of the processing flow of random access which shortened processing delay The figure which shows the 2nd example of the processing flow of the random access which shortened the processing delay.

Hereinafter, a terminal device, a base station, and a wireless communication system according to an embodiment of the present invention will be described in detail based on the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration of a wireless communication system 1 according to the first embodiment of the present invention. The wireless communication system 1 includes a plurality of terminal devices 10 and a base station 20. The terminal device 10 is an IoT device having a communication function. Specifically, the terminal device 10 is a consumer device, an industrial control device, a sensor, a meter, an automobile, or the like. The base station 20 is a device that can communicate with a plurality of terminal devices 10. The terminal device 10 includes a transmission unit 100 and a reception unit 110. The base station 20 includes a transmission unit 210 and a reception unit 200. Information can be transmitted bi-directionally between the terminal device 10 and the base station 20.

The wireless communication system 1 is an IoT system including an IoT device. As a service using the IoT system, a home security service using a terminal device 10 that detects the state of a house such as a fire alarm, or information transmitted from an AED (Automated External Defibrillator) connected to the Internet is used. AED monitoring service that monitors the state of the vehicle, weather observation service, the state of the vehicle and the parking lot, the smart parking service that efficiently guides each vehicle to the parking lot, the imaging machine etc. Examples include a pet monitoring service for monitoring and a line temperature monitoring service for monitoring the temperature measured by a thermometer installed on the line.

Wireless communication between the terminal device 10 and the base station 20 is performed according to a wireless specification specialized for IoT transmission. Conditions required for IoT transmission include long life and low power consumption, low cost, and wide coverage of the terminal device 10. In particular, in the terminal device 10 such as a sensor, it is required to replace the battery every several years, and thus low power consumption is required. The wireless specification specialized for IoT transmission is called LPWAN (Low Power Wide Area Network). Examples of LPWANs that use frequency bands that do not require a radio license include SIGFOX, a wireless specification created by SIGFOX, and LoRaWAN supported by the non-profit organization LoRa Alliance. Examples of LPWAN using a frequency band that requires a radio wave license include 3GPP category M1 (eMTC: Machine Type Communications), NB (Narrow Band) -IoT, and the like.

IoT transmission is characterized in that the number of information bits is small and the information bit rate is low compared to communication performed by a general information terminal such as a smartphone. For this reason, in order to reduce the power consumption of the terminal device 10, it is effective to narrow the transmission bandwidth. The narrower the signal band, the lower the baseband modulation and demodulation processing clock frequency, and the power consumption of the terminal device 10 can be reduced. Further, since the transmission power density and the reception power density per 1 Hz can be increased as the signal band is narrowed, the reachable range of radio waves, that is, the coverage area can be expanded.

Therefore, in the wireless specification specialized for the IoT transmission exemplified above, bands such as 100 Hz, 125 kHz, and 250 kHz are used. In this case, although the power consumption of the terminal device 10 can be reduced, since frequency flat fading is received, a decoding error occurs when the reception level is lowered. That is, the frequency diversity effect can be obtained with a wideband signal, whereas the reception level in the frequency domain is not averaged with a narrowband signal, and the frequency diversity effect cannot be obtained. Furthermore, in the case of a single antenna configuration in order to reduce the power consumption of the terminal device 10 that is an IoT terminal, the space diversity effect is not obtained. A decoding error occurs.

FIG. 2 is a sequence diagram showing a random access procedure executed between the terminal apparatus 10 and the base station 20 shown in FIG. A random access procedure is performed to establish a connection. The transmission unit 100 of the terminal device 10 transmits a signal including a preamble sequence to the base station 20 using a physical random access channel (step S101). There are two types of random access procedures: a first mode that allows collisions and a second mode that avoids collisions. In the first mode, the base station 20 assigns a plurality of preamble sequences to each terminal group composed of the plurality of terminal devices 10, and the terminal device 10 uses the assigned preamble sequences. A preamble sequence is selected, and a signal including the selected preamble sequence is transmitted to the base station 20. In this case, a plurality of terminal devices 10 may use the same preamble sequence, and a collision may occur. In the second mode, the base station 20 assigns a different preamble sequence for each terminal device 10, and the terminal device 10 transmits a signal including the assigned preamble sequence to the base station 20. In this case, since the preamble sequence transmitted by the terminal device 10 is unique to the terminal device 10, no collision occurs. The second mode is used at the time of handover where a short control delay is required.

Of the 64 preamble sequences, (64−N _cf ) sequences excluding N _cf sequences used in the second mode are used in the first mode. The preamble sequence assigned to the first mode is further divided into two groups according to the request message size in step S103 described later. Further, power ramping is applied to the physical random access channel. The terminal device 10 determines transmission power when transmitting the preamble sequence, and transmits a signal including the preamble sequence with the determined transmission power.

When receiving the signal including the preamble sequence, the receiving unit 200 of the base station 20 returns a random access response to the terminal device 10 through the physical downlink shared channel (step S102). The random access response multiplexes the Random Access Radio Network Temporary Identifier (RA-RNTI) indicating the frequency resource when the preamble sequence is detected. When a plurality of terminal apparatuses 10 transmit the same preamble sequence with the same time and frequency resource, a collision occurs and the plurality of terminal apparatuses 10 receive a random access response. The random access response includes the detected preamble sequence ID (RA-RNTI), time alignment information, information indicating the resource used by the terminal device 10 to transmit a message in the subsequent step S103, an identifier of the terminal device 10, for example, Includes Cell Radio Network Temporary Identifier (C-RNTI).

When the receiving unit 110 of the terminal device 10 receives the random access response, the transmitting unit 100 of the terminal device 10 transmits a Layer2 (L2) / Layer3 (L3) message to the base station 20 (step S103). The terminal device 10 transmits the L2 / L3 message using the resource notified by the random access response. The L2 / L3 message transmitted here is a connection request signal, a scheduling request signal, or the like.

When the receiving unit 200 of the base station 20 receives the L2 / L3 message, the transmitting unit 210 of the base station 20 transmits connection setup information including cell setting information for establishing a connection (step S104). The terminal device 10 whose connection setup information includes its own terminal device identifier completes the random access process and establishes a connection. If the connection setup information including its own terminal device identifier cannot be received, the terminal device 10 determines that the random access channel detection has failed and repeats the random access procedure from step S101 again.

In the above random access procedure, in downlink transmission from the base station 20 to the terminal device 10, the transmission power from the base station 20 can be increased to make it less susceptible to frequency flat fading. However, in uplink transmission from the terminal device 10 to the base station 20, since the transmission power of the terminal device 10 is severely limited, the transmission power cannot be increased and is affected by frequency flat fading. The probability of detection of the preamble sequence to be reduced is reduced. For this reason, in this Embodiment, the detection probability of a preamble sequence is improved using frequency hopping in uplink transmission.

FIG. 3 is a diagram illustrating a configuration of the subframe 5 transmitted from the terminal device 10 illustrated in FIG. 1 to the base station 20. The subframe 5 is composed of a plurality of subblocks 5-1 and 5-2 including a preamble sequence, and a CP (Cyclic Prefix) added to each of the plurality of subblocks 5-1 and 5-2. . The CP added to the subblock 5-1 is a copy of the end part of the preamble sequence # 1. The CP added to the sub-block 5-2 is a copy of the end part of the preamble sequence # 2. In the present embodiment, frequency hopping is performed in which a plurality of sub-blocks 5-1 and 5-2 included in sub-frame 5 are mapped to resource blocks in different frequency bands and transmitted.

FIG. 4 is an explanatory diagram of frequency hopping performed by the terminal device 10 shown in FIG. In the present embodiment, a set of resource blocks composed of a plurality of resource blocks having different frequency bands are defined in advance as system information or cell specific information. The resource block is a resource having a frequency bandwidth allocated to one terminal apparatus 10 and a subframe length in the time domain. In the example of FIG. 4, the resource block RB1 and the resource block RB2 constitute a set of resource blocks.

When the bandwidth used by the wireless communication system 1 is a system bandwidth W _BS and the number of resource blocks N _RB , the bandwidth per resource block is W _BS / N _RB . When frequency hopping is performed on two resource blocks, the frequency hopping interval is Δf _FH = W _BS / 2. That is, the frequency interval between a set of resource blocks that perform frequency hopping is Δf _FH = W _BS / 2.

FIG. 5 is a diagram illustrating a configuration of the transmission unit 100 illustrated in FIG. The transmission unit 100 includes a transmission block generation unit 11, a division unit 12, a mapping unit 13, an IFFT (Inverse Fast Fourier Transform) unit 14, and a CP insertion unit 15.

The transmission block generation unit 11 generates a transmission block including a preamble sequence predetermined in the wireless communication system 1. As the preamble sequence, a Zadoff-chu sequence subjected to cyclic shift can be used. The Zadoff-chu sequence belongs to the Constant Amptitude Zero Auto-Correlation (CAZAC) sequence, and the code sequence has a constant amplitude and a phase different from each other. The Zadoff-chu sequence is a sequence in which the correlation power at the time of zero time shift is large and the accident correlation at the time shift is small. The sequence length N Zadoff-chu sequence a _n (i) is expressed by the following equation (1). Here, i is an integer of 0 or more and N−1, and N is a prime number.

In Equation (1), n is a root index having a prime relationship with N. Different Zadoff-chu sequences can be generated by using different values of n. Furthermore, a plurality of different sequences can be generated by cyclically shifting the Zadoff-chu sequence. A plurality of Zadoff-chu sequences generated by using cyclic shift has a feature that cross-correlation can be reduced mutually. Assuming that the cyclic shift length is Δ _CS , N _CS = N / Δ _CS sequences can be generated for the same route index sequence. Cyclic shift length delta _CS is a value larger than the maximum value of the propagation delay time gold propagation distance difference to the base station 20 of each terminal apparatus 10. Against Zadoff-chu sequence _{a n (i), Zadoff-} chu sequence generated by cyclic shift is represented by the following equation (2).

In the following explanation, when a character with a tilde is indicated, (tilde) may be written after the character. Similarly, when a character with a hat is shown, (hat) may be written after the character.

In Equation (2), k represents an index of a cyclic shift sequence generated from a Zadoff-chu sequence having the same root index (k = 0, 1,..., K−1). K has a relationship of K ≦ N _CS . If the number of root indexes of a Zadoff-chu sequence having a sequence length N is N _RI , N _ZC = N _RI × N _CS orthogonal sequences are generated.

The dividing unit 12 divides the transmission block generated by the transmission block generation unit 11 into a plurality of sub blocks. In the present embodiment, the dividing unit 12 divides the transmission block into two blocks, the first half and the second half.

The mapping unit 13 maps each of the plurality of sub blocks generated by the dividing unit 12 to each of the plurality of resource blocks allocated by the base station 20. Here, the plurality of resource blocks determined in advance by the base station 20 have different frequency bands. For this reason, each of the plurality of sub-blocks is mapped to resource blocks in different frequency bands. In LTE (Long Term Evolution), the bandwidth of the resource block is 12 subcarriers, that is, 180 kHz, but the bandwidth W _BS / N _RB of the resource block should be optimized according to the requirements of the wireless communication system 1. Is desirable. The frequency hopping interval is defined in advance as system information or cell specific information. The mapping unit 13 inputs the frequency domain signal after mapping to the IFFT unit 14.

The IFFT unit 14 converts an input frequency domain signal into a time domain signal. The IFFT unit 14 inputs the converted time-domain signal to the CP insertion unit 15. The CP insertion unit 15 adds a CP to the head of each of the plurality of sub-blocks included in the input time domain signal.

Two methods for generating a transmission block by the transmission block generation unit 11 will be described below. FIG. 6 is an explanatory diagram of a first example of a transmission block generation method performed by the transmission block generation unit 11 illustrated in FIG. In the first example illustrated in FIG. 6, the transmission block generation unit 11 can generate a first sequence that is a Zadoff-chu sequence having a sequence length _Npa , and can use the generated first sequence as a transmission block. . The first sequence is divided into two sub-blocks of the first half and the second half by the dividing unit 12, and becomes preamble sequences # 1 and # 2, respectively. The mapping unit 13 maps each of the preamble sequences # 1 and # 2 to resource blocks in different frequency bands. In this case, the number of orthogonal sequences is N _ZC .

FIG. 7 is an explanatory diagram of a second example of a transmission block generation method performed by the transmission block generation unit 11 illustrated in FIG. In the second example illustrated in FIG. 7, the transmission block generation unit 11 generates and generates a second sequence and a third sequence that are two types of Zadoff-chu sequences having a sequence length N _pa / 2. A transmission block composed of the sequence and the third sequence can be generated. The second sequence generated by the transmission block generation unit 11 is a preamble sequence # 1, and the third sequence is a preamble sequence # 2. In this case, the number of orthogonal sequences per terminal apparatus 10 is N _ZC / 2.

In addition, the timing which transmits a random access channel is notified to the terminal device 10 from the base station 20 using the control information of the broadcast channel of a downlink. The transmission unit 210 of the base station 20 can use the resource from the number of resource blocks K _RB = W _BS / N _RB , the number of preamble sequences K _ps = N _ZC or N _ZC / 2, using the control information. Resources such as blocks and preamble sequences can be notified to the terminal device 10. The terminal device 10 selects a resource to be used from among resource block and preamble sequence candidates notified by the base station 20. As a preamble sequence selection method, there are a method of random selection, a method of selection based on an identifier of the terminal device 10, and the like. When multiple terminal devices 10 select the same resource block and the same preamble sequence, a collision occurs. Moreover, the transmission part 100 has a function which determines the transmission power at the time of transmitting a preamble series. The transmission unit 100 can determine transmission power by open-loop transmission power control.

Also, the base station 20 can notify the transmission power of the base station 20 using the control information of the downlink broadcast channel. The receiving unit 110 has a function of measuring the received power. When the transmission power is notified from the base station 20, the base station 20 and the terminal device 10 are based on the notified transmission power and the measured received power. It is possible to calculate an average propagation loss due to distance attenuation and shadowing. The terminal device 10 can determine the transmission power so that the calculated propagation loss can be compensated to satisfy the required received signal to noise ratio.

FIG. 8 is a diagram illustrating a configuration of the receiving unit 200 illustrated in FIG. The receiving unit 200 includes a CP removing unit 21, an FFT (Fast Fourier Transform) unit 22, an extracting unit 23, a cyclic shift Zadoff-chu sequence generating unit 24, a correlation signal generating unit 25, and a correlation value calculating unit 26. A series detection unit 27.

Note that the preamble sequence candidates transmitted by the terminal device 10 and the resource block candidates used for frequency hopping are already known. However, a round-trip propagation delay time delay corresponding to the distance between the terminal device 10 and the base station 20 occurs. Assume that the number of resource blocks notified to the terminal apparatus 10 is K (tilde) _RB , and the number of preamble sequences is K (tilde) _ps . The terminal apparatus 10 selects a resource block to be used when transmitting a preamble sequence from among K (tilde) _RB resource blocks, and selects a preamble sequence to be transmitted from among K (tilde) _ps preamble sequences. select.

The CP removal unit 21 removes the CP added to the received preamble sequence. The CP removing unit 21 inputs the signal from which the CP has been removed to the FFT unit 22. The FFT unit 22 performs FFT processing on the signal after removing the CP, and converts the time domain signal into a frequency domain signal. The FFT unit 22 inputs the converted signal to the extraction unit 23. The extraction unit 23 removes a carrier frequency component from the input frequency domain signal and extracts a complex baseband signal. The extraction unit 23 inputs the extracted baseband signal to the correlation signal generation unit 25.

Let h be the index of the terminal apparatus 10 that transmits the preamble sequence using the same resource block (0 ≦ h ≦ (H−1)). H is the number of terminal apparatuses 10 that transmit a preamble sequence using the same resource block. A collision occurs when the terminal apparatus 10 using the same resource block uses the same preamble sequence. The preamble sequence can be represented by d _h (j), where d _h (j) is a subset of a (tilde) _{n, k} (i) (0 ≦ j ≦ (N−1)). For simplicity of explanation, assuming a one-pass channel, the discrete value display of the received signal is expressed by the following equation (3).

In Equation (3), j is a sample index of the sequence, ξ _h (j) is a channel response including distance attenuation, shadowing, and fading variation of the terminal device 10 at the index h, and τ _h is an index h. The delay time from the terminal device 10 to the base station 20, w _h (j) indicates an average zero noise component.

The cyclic shift Zadoff-chu sequence generation unit 24 generates the same Zadoff-chu sequence as the preamble sequence candidate used by the terminal device 10. The cyclic shift Zadoff-chu sequence generation unit 24 inputs the generated sequence to the correlation signal generation unit 25.

The correlation signal generation unit 25 multiplies the baseband signal input from the extraction unit 23 by the sequence input from the Zadoff-chu sequence generation unit 24 to generate a correlation signal for each sub-block. The correlation signal generation unit 25 inputs the generated correlation signal and baseband signal to the correlation value calculation unit 26.

The correlation value calculation unit 26 adds a plurality of correlation signals input from the correlation signal generation unit 25 to calculate a correlation value between blocks. Correlation value calculation unit 26 inputs the calculated correlation value and baseband signal to sequence detection unit 27.

The sequence detection unit 27 determines the reception timing of the preamble sequence based on the timing at which the input correlation value is maximized, and detects the preamble sequence from the baseband signal. The sequence detection unit 27 outputs the detected preamble sequence and the reception timing.

When the terminal device 10 uses the frequency hopping of the present embodiment, the first half block and the second half block are transmitted in resource blocks having a low frequency correlation. The correlation value between them is obtained by averaging the power. The reception timing μ (hat) _h of the terminal device 10 is expressed by the following formula (4).

Further, when the terminal device 10 does not use frequency hopping, the preamble sequence is transmitted using the same resource block, and thus the correlation detection of the entire subframe is performed by in-phase addition. In this case, the reception timing μ (hat) _h of the terminal device 10 is expressed by the following formula (5).

As described above, according to Embodiment 1 of the present invention, terminal apparatus 10 divides a preamble sequence into a plurality of subblocks, and uses resource blocks of different frequency bands for each of the plurality of subblocks. To the base station 20. Therefore, the frequency diversity effect can be obtained, and the detection probability of the preamble sequence transmitted in the uplink can be improved.

Embodiment 2. FIG.
FIG. 9 is a diagram showing a configuration of subframe 6 used in Embodiment 2 of the present invention. Subframe 6 includes preamble sequences # 1 and # 2, control information, and CP. Each of the first half 6-1 and the second half 6-2 of the subframe 6 is mapped to resource blocks in different frequency bands. The CP is added to the preamble sequences # 1 and # 2 and each of the control information.

FIG. 10 is a diagram illustrating a configuration of the transmission block generation unit 11 according to the second embodiment of the present invention. The transmission block generation unit 11 includes a cyclic shift Zadoff-chu sequence generation unit 101, a channel encoding unit 102, a modulation mapping unit 103, and a multiplexing unit 104. In the second embodiment, since the configuration other than the transmission block generation unit 11 is the same as that of the first embodiment, detailed description thereof is omitted.

The cyclic shift Zadoff-chu sequence generation unit 101 can generate a preamble sequence using the two methods described in the first embodiment. The channel coding unit 102 channel codes the control bits. Channel coding section 102 inputs the control bits after channel coding to modulation mapping section 103. The channel coding unit 102 can perform channel coding using a Reed-Muller code, a Polar code, a convolutional code, and the like. The modulation mapping unit 103 interleaves the input control bits, and then generates a symbol in which the control bits are mapped. Modulation mapping section 103 inputs the generated symbol to multiplexing section 104. Multiplexing section 104 multiplexes the preamble sequence and the control information. Specifically, the multiplexing unit 104 multiplexes the input symbols on each of the first half 6-1 and the second half 6-2.

FIG. 13 is a diagram illustrating a first example of a random access procedure in which a transmission delay is shortened. The base station 20 determines in advance the time, frequency resource, and preamble sequence candidate for the terminal apparatus 10 to transmit the random access channel, and the time, frequency, and preamble sequence candidate are transmitted by the downlink broadcast channel. Notify users in The random access channel of this embodiment is composed of a preamble signature and a message part. A Zadoff-Chu sequence using a cyclic shift is used as the preamble sequence. The message part is composed of small-size control information with a small number of bits. The message part includes a UE ID (User Equipment IDentifier) which is a user ID.

As the structure of the message part, (1) a method of directly multiplexing symbols mapped with control bits, (2) a method of multiplying symbols by a scramble sequence, and (3) multiplexing symbols by spreading them with spreading codes. Method. The aforementioned scrambled sequence or spread sequence of information symbols is associated with the preamble sequence, and when the preamble sequence is detected, the subsequent scramble sequence of the information symbol part is restored (descrambled) or spread. Symbols can be despread. As shown in the flow of FIG. 13, a plurality of users transmit random access channels using the same time and frequency resources. In this case, when a plurality of users transmit random access channels using different preamble sequences, that is, Zadoff-Chu sequences with different cyclic shifts, the preamble sequences are almost orthogonal, so that a plurality of random access channels are detected. There is a high probability. However, when a plurality of users transmit random access channels using the same preamble sequence, there is a high probability that both will not be detected or only one user's random access channel will be detected. When the preamble sequence and the control bits of the message part can be correctly decoded, the base station 20 returns an Ack (Acknowledgement) / Nack (Non-acknowledgement) signal together with the UE ID to the terminal device 10 in the downlink. In order to determine whether or not the control bits of the message part have been correctly decoded, the control bits are subjected to cyclic redundancy check coding (CRC).

FIG. 11 is a diagram showing a configuration of the receiving unit 200A according to the second embodiment of the present invention. The receiving unit 200A includes a CP removing unit 21, an FFT unit 22, an extracting unit 23, a cyclic shift Zadoff-chu sequence generating unit 24, a correlation signal generating unit 25, a correlation value calculating unit 26, and a sequence detecting unit 27. And a demodulator 28 and an error correction decoder 29.

Hereinafter, the differences from the first embodiment will be mainly described. In addition to the process of extracting the control symbol, the extracting unit 23 descrambles the scramble sequence when the control symbol is multiplied by the scramble sequence, and the despread process when the control symbol is spread. including. The extraction unit 23 inputs the extracted baseband signal to the demodulation unit 28 in addition to the correlation signal generation unit 25. The correlation signal generation unit 25 inputs the generated correlation signal to the demodulation unit 28 in addition to the correlation value calculation unit 26.

The demodulator 28 synchronously detects control symbols using the input correlation signal as a reference signal, and demodulates control information from the baseband signal. The demodulator 28 inputs the demodulated control information to the error correction decoder 29. The error correction decoding unit 29 performs error correction decoding on the soft decision bits after synchronous detection, that is, the log likelihood ratio or the hard decision bits, and reproduces the control bits.

FIG. 14 is a diagram showing a sequence of a random access procedure with a reduced transmission delay. The base station 20 determines in advance the time, frequency resource, and preamble sequence candidate for the terminal apparatus 10 to transmit the random access channel, and the time, frequency, and preamble sequence candidate are transmitted by the downlink broadcast channel. Notify users in In this case, when a plurality of users transmit random access channels using different preamble sequences, that is, Zadoff-Chu sequences with different cyclic shifts, the preamble sequences are almost orthogonal, so that a plurality of random access channels are detected. There is a high probability. However, when a plurality of users transmit random access channels using the same preamble sequence, there is a high probability that both will not be detected or only one user's random access channel will be detected.

When receiving the signal including the preamble sequence, the receiving unit 200 of the base station 20 returns a random access response to the terminal device 10 through the physical downlink shared channel. The random access response multiplexes RA-RNTI indicating the frequency resource at the time when the preamble sequence is detected. When a plurality of terminal devices 10 transmit the same preamble sequence with the same frequency resource for the same time, a collision occurs and the plurality of terminal devices 10 receive a random access response. Similarly to the LTE random access response, the base station 20 notifies the terminal device 10 of the time and frequency resource allocation information for transmitting the subsequent uplink data channel. The base station 20 also notifies the identifier of the terminal device 10, for example, C-RNTI.

The terminal device 10 transmits the user information together with its own ID, that is, the UE ID, on the uplink shared channel using the time and frequency resources allocated from the base station 20. Here, the user information may include Layer1 / Layer2 control information or higher layer control information. The difference from the LTE RACH procedure shown in FIG. 2 is that RA-RNTI and temporary CRNTI may be received by multiple users. Therefore, in the next step, multiple users simultaneously receive user information on the uplink shared channel. May be transmitted. By allowing collision of uplink data channels, it is possible to reduce processing delay.

If the user information of the data channel can be correctly decoded, the base station 20 returns an Ack / Nack signal together with the UE ID to the terminal device 10 in the downlink. Here, in order to determine whether the user information has been correctly decoded, the control bits are subjected to cyclic information check coding. As described above, even when a plurality of users transmit data channels with the same frequency resource at the same time at the same time, by receiving and decoding the Ack / Nack signal fed back from the base station 20, at the time of retransmission, There is no data channel collision. That is, only the UE ID terminal device 10 to which the base station 20 has transmitted the Nack signal retransmits the data channel.

FIG. 12 is an explanatory diagram of resource blocks assigned to the terminal device 10 by the base station 20 according to the second embodiment of the present invention. As described above, by applying frequency hopping to the narrowband random access channel, a frequency diversity effect can be obtained, and the probability that the reception level of the entire random access channel is lowered can be greatly reduced. For this reason, the detection probability of the preamble sequence transmitted by uplink can be improved.

However, as shown in the above equation (4), the terminal device 10 divides into resource blocks in different frequency bands with low frequency correlation and transmits the preamble sequence and control information. The correlation value between the blocks in the second half 6-2 cannot be added in phase, and power is added. The power addition is less effective in suppressing noise components and interference components than in-phase addition. For this reason, when the received signal-to-noise ratio is less than or equal to the threshold value, the terminal apparatus 10 does not perform frequency hopping in order to enhance the noise component and interference component suppression effect.

The received signal-to-noise ratio is obtained based on the transmission power of the base station 20 notified through the downlink broadcast channel and the reception power measured by the terminal device 10. Specifically, the receiving unit 110 of the terminal device 10 is based on the transmission power of the base station 20 and the measured received power, and averages due to distance attenuation and shadowing between the base station 20 and the terminal device 10. To calculate the correct propagation loss. The receiving unit 110 can estimate the uplink received signal-to-noise ratio from the calculated propagation loss. When the estimated received signal-to-noise ratio is lower than the threshold, the transmission unit 100 transmits the preamble sequence without performing frequency hopping.

As described above, the terminal apparatus 10 may perform frequency hopping or may not perform frequency hopping depending on the estimated received signal-to-noise ratio. Therefore, each of the plurality of resource blocks to be allocated to the terminal device 10 is classified in advance into a first resource block used when frequency hopping is performed and a second resource block used when frequency hopping is not performed. ing. In the example of FIG. 12, resource blocks RB1 and RBn are first resource blocks, and resource block RBn-1 is a second resource block. The first resource block and the second resource block may be determined as system information in advance, or may be notified from the base station 20 to the terminal device 10 through a downlink broadcast channel.

When the base station 20 notifies the resource block type, the transmission unit 210 of the base station 20 determines whether the resource block used for the terminal apparatus 10 to transmit the preamble sequence is the first resource block or the second resource block. It is possible to notify the terminal device 10 of control information including information indicating whether or not.

As described above, according to Embodiment 2 of the present invention, as in Embodiment 1, terminal apparatus 10 divides a preamble sequence into a plurality of subblocks, and each of the plurality of subblocks is different. It is transmitted to the base station 20 using the resource block of the frequency band. Therefore, the frequency diversity effect can be obtained, and the detection probability of the preamble sequence transmitted in the uplink can be improved.

Also, according to the second embodiment, the control information is divided into a plurality of subblocks together with the preamble sequence, and each of the plurality of subblocks is transmitted to the base station 20 using resource blocks of different frequency bands. For this reason, the detection probability of control information is also improved by the frequency diversity effect, and the transmission delay is shortened.

Also, according to the second embodiment, frequency hopping is not performed when the received signal-to-noise ratio is less than or equal to the threshold value. For this reason, it becomes possible to improve the suppression effect of a noise component and an interference component.

The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1 wireless communication system, 5, 6 subframe, 5-1, 5-2 subblock, 6-1 first half, 6-2 second half, 10 terminal device, 11 transmission block generation unit, 12 division unit, 13 mapping unit , 14 IFFT unit, 15 CP insertion unit, 20 base station, 21 CP removal unit, 22 FFT unit, 23 extraction unit, 24, 101 cyclic shift Zadoff-chu sequence generation unit, 25 correlation signal generation unit, 26 correlation value calculation unit 27 sequence detection unit, 28 demodulation unit, 29 error correction decoding unit, 100, 210 transmission unit, 102 channel coding unit, 103 modulation mapping unit, 104 multiplexing unit, 110, 200 reception unit.

Claims

A dividing unit for dividing the preamble sequence into a plurality of sub-blocks;
A mapping unit that allocates each of the plurality of sub-blocks to each of a plurality of resource blocks in different frequency bands;
Have
A terminal apparatus comprising: a transmission unit that transmits the sub-block to the base station using the allocated resource block.
The transmission unit generates a transmission block by adding control information to the preamble sequence allocated from the base station,
Further comprising
The terminal device according to claim 1, wherein the division unit divides the transmission block generated by the transmission block generation unit into a plurality of subblocks.
The terminal apparatus according to claim 1 or 2, wherein the preamble sequence is a sequence generated by cyclically shifting a Zadoff-chu sequence.
A receiver for measuring the received power,
Further comprising
The transmission unit determines transmission power so that a propagation loss calculated based on the transmission power of the base station and the reception power measured by the reception unit satisfies a required reception signal noise ratio. The terminal device according to any one of claims 1 to 3.
The receiving unit calculates a propagation loss between the base station and the terminal device based on the transmission power of the base station notified from the base station and the measured received power, and the calculated Based on the propagation loss, estimate the received signal to noise ratio at the base station,
The terminal apparatus according to claim 4, wherein the division unit does not divide the preamble sequence into the plurality of sub-blocks when the estimated received signal-to-noise ratio is lower than a predetermined threshold.
A base station that receives a signal transmitted by the terminal device according to any one of claims 1 to 5,
An extraction unit that removes a carrier frequency component of the received signal and extracts a baseband signal;
A correlation signal generation unit that generates a correlation signal for each sub-block by multiplying the baseband signal by the preamble sequence;
A correlation value calculation unit for adding a plurality of correlation signals to detect a correlation value of a block;
A sequence detection unit that determines reception timing of the preamble sequence based on the timing at which the correlation value of the block is maximized, and detects the preamble sequence;
A base station comprising: a receiving unit having:
A base station that receives a signal transmitted by the terminal device according to claim 2,
An extraction unit that removes a carrier frequency component of the received signal and extracts a baseband signal;
A correlation signal generation unit that generates a correlation signal for each sub-block by multiplying the baseband signal by the preamble sequence;
A correlation value calculation unit for adding a plurality of correlation signals to detect a correlation value of a block;
A sequence detection unit that determines reception timing of the preamble sequence based on the timing at which the correlation value of the block is maximized, and detects the preamble sequence;
A demodulator that demodulates the control information using the correlation signal of the detected preamble sequence as a reference signal;
A base station comprising: a receiving unit having:
The preamble sequence is a sequence unique to each terminal device,
The base station according to claim 6 or 7, wherein the terminal device is identified based on the preamble sequence and a set of the resource blocks used for transmitting the preamble sequence.
The preamble sequence is a sequence unique to each terminal group composed of a plurality of the terminal devices,
The base station according to claim 6 or 7, wherein the terminal group is identified based on the preamble sequence and a set of the resource blocks used for transmitting the preamble sequence.
A transmission unit for notifying the terminal device of control information indicating the preamble sequence and a set of the resource blocks used by the terminal device to transmit the preamble sequence;
The base station according to claim 6, further comprising:
Each of the plurality of resource blocks to be allocated to the terminal device is a first resource block used when performing frequency hopping to allocate each of the plurality of sub-blocks to each of the plurality of resource blocks in different frequency bands, The base station according to claim 10, wherein the base station is classified into a second resource block used when the frequency hopping is not performed.
The transmission unit includes the control information including information indicating whether a resource block used by the terminal device to transmit the preamble sequence is the first resource block or the second resource block. The base station according to claim 11, wherein the base station is notified to the apparatus.
The terminal device according to any one of claims 1 to 5,
A base station according to any one of claims 6 to 12,
A wireless communication system comprising:
A wireless communication method performed between a base station and a terminal device,
The terminal device divides a preamble sequence into a plurality of sub-blocks;
The terminal device assigning each of the plurality of sub-blocks to each of a plurality of resource blocks in different frequency bands;
The terminal device transmits the sub-block to the base station using the allocated resource block;
A wireless communication method comprising: