HK1175615B - Control channel information transmission system - Google Patents

Description

Control channel information transmission system

This application is a divisional application of an invention patent application having a parent application number of 200580051722.9 (international application number: PCT/JP2005/018117, application date: 9/30/2005, title of the invention: control channel information transmission method and base station and terminal using the same).

Technical Field

The present invention relates to a control channel information transmission method and a base station and a terminal using the same, and more particularly, to a control channel information transmission method for packet communication using a control channel to adaptively control communication parameters, and a base station and a terminal using the same.

Background

In the third generation mobile communication system, adaptive radio links such as adaptive modulation/demodulation, HARQ (hybrid automatic repeat request), and scheduling are used to increase the transmission efficiency of data packets.

Such an adaptive radio link is controlled using an individual or common control channel, and each user terminal is informed of link parameters used in a data channel transmitted substantially simultaneously with the control channel.

For example, in case of an Adaptive Modulation and Coding (AMC) scheme, the control channel transmits a modulation scheme and a coding rate of a data channel. In the case of HARQ, the control channel transmits information such as the packet number of a packet to be transmitted on the data channel and the number of retransmissions. In the case of scheduling, the control channel transmits information such as a user ID.

According to HSDPA (high speed downlink packet access) standardized by 3GPP (third generation partnership protocol) of the third generation mobile communication system, as described in non-patent document 1, control information transmission as shown in table 1 is performed by using a common control channel called HS-SCCH (shared control channel for HS-DSCH).

TABLE 1

Further, according to the HSDPA described above, when the AMC scheme is applied in fig. 1 showing the relationship between the radio environment and the transmission speed, high-speed data transmission is performed with an increased coding rate by setting the modulation scheme to 16QAM (quadrature amplitude modulation) under a good propagation state (exceeding the threshold level TH) in the varying radio environment i.

On the other hand, in a bad propagation state (below the threshold level TH), data transmission is performed at a low speed with a reduced coding rate by setting the modulation scheme to QPSK (quadrature phase shift keying).

Thus, by changing the user transmission speed using the AMC scheme, the quality is kept constant. That is, as shown in fig. 1 above, according to HSDPA, the modulation scheme and coding rate of HS-DSCH, user data, may be made variable according to the propagation state i. In addition, HS-SCCH, which is control information related to the above-mentioned user data, is also transmitted together with the user data (HS-DSCH).

At this time, however, with respect to HS-SCCH, i.e., control information, as shown in fig. 2 showing the relationship between the radio environment and the amount of information, the coding rate of error correction coding for the control information iv is constant, and thus the amount of information to be transmitted remains constant regardless of whether the radio environment i is good or bad.

In the above-described case, when the radio environment i is in a good state, the quality becomes excessive for the control information transmitted.

In addition, in the next-generation mobile communication system, in order to realize high-speed data transmission, multicarrier transmission and MIMO (multiple input multiple output) transmission using a plurality of antennas are employed. In this case, the transmission characteristics can be further improved by using radio parameter adaptive control on a subcarrier-by-subcarrier basis and on a transmission antenna-by-transmission antenna basis.

When the above-described MIMO is used, control of whether MIMO is applied is performed according to whether the propagation state i is good or bad, as shown in fig. 3. That is, in fig. 3 showing the relationship between whether MIMO is applied and the transmission speed, the transmission speed becomes high when MIMO is applied, and becomes low when the other way around.

Further, the applicant of the present invention has previously proposed the following inventions: one control channel format is selected from a plurality of control channel formats each having a different amount of information according to a predetermined state (whether MIMO is applied) in a transmission system employing MIMO, and the control channel is transmitted using the selected control channel format (international application WO/2006/070466 publication: hereinafter, referred to simply as a previous application).

The above-mentioned prior application addresses the hypothetical case where: the number of control channel information bits is different according to whether MIMO is applied or not. As a prerequisite, when MIMO is applied to user data (period III), the number of information bits IV increases as shown in fig. 4, and when MIMO is not applied to user data, the number of information bits decreases as shown in fig. 5.

Thus, as shown in fig. 6 showing the relationship between MIMO application and the amount of control channel information, in period III of the propagation environment i to which MIMO is applied, there is a problem as follows: the number of variable parameters increases and the number of information bits required for the control channel increases. Further, when the number of simultaneously multiplexed users in a single frame increases, there is a problem in that control channel information also increases in proportion to the number of users.

[ non-patent document 1]

3GPPTS25.212V5.9.0（2004-06）

Disclosure of Invention

Problems to be solved by the invention

Accordingly, the present invention has been made keeping in mind the above problems in packet-type data transmission to which an AMC (adaptive modulation and coding) scheme is applied by making the coding rate of error correction coding of HS-SCCH, i.e., control channel information, variable.

Means for solving the problems

As a first aspect of the present invention to solve the above problems, a control channel information transmission method includes the steps of: performing error correction coding on the control channel information based on an adaptive modulation and coding scheme; modulating and transmitting the error-correction-coded control channel information by using a predetermined modulation scheme; the coding rate in error correction coding is different depending on the propagation state.

Further, as a second aspect of the present invention to solve the above problems, a control channel information transmitting method includes the steps of: performing error correction coding on the control channel information based on an adaptive modulation and coding scheme using a constant coding rate; modulating and transmitting the error-correction-coded control channel information by using a predetermined modulation scheme; before modulation, the error-correction-coded signal is subjected to code extraction or code repetition depending on the propagation state.

Further, as a third aspect of the present invention to solve the above problems, a control channel information transmission system based on an adaptive modulation and coding scheme includes: an error correction encoding unit that performs error correction encoding on the control channel information on the base station side; and a modulation unit that modulates the encoded output of the error correction encoding unit in accordance with a predetermined modulation scheme. Further, the following are set: the coding rate in the error correction coding unit is made different according to the propagation state.

Further, in the above-described aspect, the coding rate of the control channel when multiple-input multiple-output is applied is set to be larger than the coding rate when multiple-input multiple-output is not applied, so that the number of transmission code bits is constant regardless of whether multiple-input multiple-output is applied or not.

In the above-described aspect, on the reception side, the respective error correction decoding units corresponding to the coding rates different depending on the propagation state perform error correction decoding of the commonly received signal, and further, the likelihood of the error correction decoded signal is determined, and the error correction decoded signal determined to be valid is output based on the likelihood determination result.

The features of the present invention will become apparent from the embodiments of the present invention described with reference to the accompanying drawings.

Drawings

Fig. 1 is a diagram showing a relationship between a radio environment and a transmission speed in AMC control of HS-DSCH as a related art HSDPA.

Fig. 2 is a diagram showing a relationship between a radio environment and an information amount in HS-SCCH as the HSDPA of the related art.

Fig. 3 is a diagram showing a relationship between a radio environment and a transmission speed in the HS-DSCH to which MIMO is applied in the previous application.

Fig. 4 is a diagram illustrating an embodiment of a control channel format when MIMO is applied.

Fig. 5 is a diagram illustrating an embodiment of a control channel format when MIMO is not applied.

Fig. 6 is a diagram showing a relationship between a radio environment and an information amount in HS-SCCH when MIMO is applied.

Fig. 7 shows a block diagram of a transmission system including a base station 1 and a user terminal 2 to which the present invention is applied.

Fig. 8 is a diagram showing the configuration of the control channel generating section 12 corresponding to the invention of the previous application.

Fig. 9 is a diagram showing a first exemplary structure of the control channel generating section 12 according to the present invention.

Fig. 10 is a diagram illustrating a relationship between the application of MIMO and the amount of control channel information when the present invention is applied.

Fig. 11 is a diagram illustrating another exemplary structure of the control channel generating section 12 according to the present invention.

Fig. 12 is a diagram illustrating an exemplary structure of a control channel demodulation section in a user terminal according to the present invention.

Fig. 13A and 13B are graphs showing comparison of the effect of the present invention and the case of using the invention of the previous application.

Detailed Description

Hereinafter, embodiments of the present invention are described with reference to the drawings.

Fig. 7 shows a block diagram of a transmission system including a base station 1 and a user terminal 2 to which the present invention is applied. Specifically, the present invention is characterized by the configuration of the embodiment of the control channel generation unit 12.

The features of the present invention are described using the embodiments of the previous application in which MIMO is applied in relation to downlink control channel transmission from the base station 1 to the user terminal 2. However, the application of the present invention is not limited to the transmission system structure shown in fig. 7.

The format selection/specification section 10 in the base station 1 selects a control channel format based on information including the number of multiplexed users, the transmission/reception function of the user terminal, downlink QoS, and downlink CQI (channel quality indicator).

Here, examples of the control channel format to be selected are shown in fig. 4 (table 2) and fig. 5 (table 3) previously.

The control format a shown in fig. 4 includes a modulation scheme (antenna 1) -a modulation scheme (antenna 4), a coding rate, a spreading factor, and a code set as adaptive control parameters. For example, in the modulation scheme (antenna 1) -modulation scheme (antenna 4), four (4) modulation scheme types (QPSK, 8PSK, 16QAM, 64 QAM) are set as variable ranges. In the above-described control channel format a shown in table 2, the type and variable range of the adaptive parameter are wide, and for example, in MIMO transmission, the modulation scheme may be changed from antenna to antenna.

Meanwhile, the control format B shown in fig. 5 includes a modulation scheme (common to antennas), a coding rate, a spreading factor, and a code set as adaptive control parameters. For example, in the modulation scheme (common), two modulation scheme types (QPSK, 16 QAM) are provided as the variable range. In the above-described control channel format B shown in table 3, the type and variable range of adaptive control parameters are limited compared to the control channel format a, and the number of bits is approximately 1/2 of the control channel format a.

Referring back to fig. 7, information indicating the designation of the control channel format selected in the format selection/designation section 10 is notified from the signaling generation section 11 to the user terminal 2 as signaling information via the selector 15 and the transmitter 16. Then, the format specification information is notified to the control channel generation unit 12 and the data channel generation unit 13.

The control channel generating section 12 is a characteristic part of the present invention, and has different structures and functions corresponding to the embodiments described later, but as an infrastructure, the structure includes an error correction coding unit and a modulation unit.

The control channel and the data channel generated in the control channel generation section 12 and the data channel generation section 13 are multiplexed in the multiplexing section 14 based on the format designation information, and thereafter, the control channel and the data channel are transmitted to the user terminal 2 via downlink by the transmitter 16.

The signaling demodulation section 22 in the user terminal 2 demodulates the signaling information (format specification information) notified from the base station 1 by the receiver 20, and notifies the control channel demodulation section 23 of the downlink control channel format. The control channel demodulation unit 23 demodulates the control channel based on the downlink control channel format notified from the signaling demodulation unit 22. The control channel demodulation section 23 notifies the data channel demodulation section 21 of the downlink adaptive control parameters demodulated from the control channel.

The data channel demodulation section 21 demodulates the data channel using the adaptive control parameter notified from the control channel demodulation section 23.

The propagation path measuring section 24 in the user terminal 2 measures a downlink CQI for selecting a downlink control channel format. The downlink CQI is transmitted to the base station 1 through an uplink control channel from the user terminal 2 to the base station 1 together with the uplink QoS and the transmission/reception function of the user terminal 2.

Next, uplink control channel transmission from the user terminal 2 to the base station 1 will be described.

Similarly to the downlink control format, the uplink control channel format is selected in the format selection/specification section 10 of the base station 1. In order to select the uplink control channel format, an information set including the number of multiplexed users, the transmission/reception function of the user terminal, uplink QoS, uplink CQI (channel quality indicator), and the like is used.

The selected uplink control format is notified from the signaling generation section 11 to the user terminal 2 as signaling information via the selector 15 and the transmitter 16. The signaling demodulation section 22 demodulates the signaling information notified from the base station 1, specifies the designation (multiplexing method) of the control channel and the data channel on the uplink, and notifies the format designation information to the control channel generation section 25 and the data channel generation section 27.

In the base station 1, the uplink control channel format selected by the format selection/specification section 10 is notified to the control channel demodulation section 18 for uplink.

The control channel demodulation section 18 demodulates the control channel based on the uplink control channel format notified from the format selection/specification section 10. The control channel demodulation section 18 notifies the data channel demodulation section 19 of the demodulated uplink adaptive control parameters.

The data channel demodulation section 19 performs demodulation processing on the data channel using the adaptive control parameter notified from the control channel demodulation section 18. The uplink CQI for selecting the uplink control channel format is measured by the propagation path measuring section 17 in the base station 1.

The format selection/specification unit 10 is also notified of the measured uplink CQI from the propagation path measurement unit 17. Also, the uplink QoS, the downlink CQI, and the transmission/reception function of the user terminal 2, which are transmitted to the base station 1 through the uplink control channel from the user terminal 2 to the base station 1, are transmitted to the format selection/specification section 10.

Next, in fig. 7, an exemplary structure of the control channel generating section 12 constituting a feature of the present invention will be described. Here, in the previous application, a case of applying MIMO has been assumed, in which the number of control channel information bits is different according to whether MIMO is applied or not, as shown in fig. 4 and 5.

That is, from among a plurality of control channel formats, one control channel format is selected and used such that the number of control channel information sets is large when MIMO is applied to user data (refer to fig. 4), and the number of control channel information sets is small when MIMO is not applied to user data (fig. 5).

In the above case, the structure of the control channel generating section 12 is as shown in fig. 8.

An error correction coding unit 120 and a modulation unit 121 are provided. Error correction coding is performed in error correction coding section 120, and in response thereto, error correction decoding is performed in control channel demodulation section 23 on the user terminal 2 side.

Now, let the coding rate R be R =0.241, where R is the ratio of the number of bits of code information to be transmitted to the number of transmission code bits it obtains by error correction coding. When MIMO is not applied in fig. 8, the number of bits of code information in a frame to be transmitted is 68, and the number of transmission code bits becomes 282= (68 × 1/0.241) bits.

Meanwhile, when MIMO is applied, if the number of bits of code information in a frame to be transmitted is 141, the number of transmission code bits becomes 585= (141 × 1/0.241) bits.

Thus, since the coding rate is fixed, there is a problem in that: the number of transmission code bits becomes large when MIMO is applied, as shown in fig. 6.

The object of the present invention is thus to solve the above problems.

Fig. 9 is a diagram showing a first exemplary structure of the control channel generating section 12 according to the present invention. Similar to the structure shown in fig. 8, the control channel generating section 12 includes an error correction coding unit 120 and a modulation unit 121.

A feature different from the structure shown in fig. 8 is that the coding rate in the error correction coding unit 120 is variable.

The case of a large coding rate is weak against propagation path errors, and the case of a small coding rate is strong against propagation path errors. Meanwhile, MIMO is applied when there are few propagation errors, and MIMO is not applied when propagation errors frequently occur.

Therefore, according to the present invention, when MIMO is applied to user data, the coding rate of an error correction coding unit that generates a control channel increases. In contrast, when MIMO is not applied to user data, the coding rate of the error correction coding unit that generates the control channel decreases.

As one embodiment, when MIMO is applied to user data, the coding rate of the error correction coding unit 120 in the control channel generating section 12 is set to 0.5.

Thus, the transmission code number is 282 (= 141 ÷ 0.5), and when MIMO is not applied to user data, as in the exemplary case shown in fig. 8, the coding rate in the error correction coding unit 120 is set to 0.24, and thus 282 (= 141 ÷ 0.5) bits are transmitted.

Thereby, the number of transmission code bits is the same regardless of whether MIMO is applied, and a constant control information quality can be obtained without wasting radio resources.

Fig. 10 is a diagram illustrating a relationship between the application of MIMO and the amount of control channel information when the present invention is applied. Compared with fig. 6, even if MIMO is applied, the number of transmission code bits of error correction coding can be made constant. Therefore, waste of resources can be prevented.

Fig. 11 is a diagram illustrating another exemplary structure of the control channel generating section 12 according to the present invention. In the present embodiment, there is a feature that: a unit 122 selectively applying a puncturing (puncturing) function or a repetition function is provided between the error correction encoding unit 120 and the modulation unit 121.

That is, according to the present embodiment, the coding rate of the error correction coding unit 120 is made constant regardless of whether MIMO is applied. Meanwhile, the settings are as follows: the coding rate is changed in an equivalent manner by providing a unit 122 having a puncturing function or a repetition function at the output of the error correction coding unit 120.

This makes the coding rate variable at the input of modulation section 121, which has the same meaning as the configuration of control channel generation section 12 shown in fig. 9.

Now, in the case where the puncturing function is provided, by the puncturing function, when MIMO is applied, unit 122 performs extraction processing of output data of error correction coding unit 120 at certain time intervals. When MIMO is not applied, the output data of the error correction coding unit 120 is made to pass through without change. Thus, the bit count is the same when the output of error correction coding section 120 is input to modulation section 121 regardless of whether MIMO is applied or not.

Further, when the repetition function is provided, by the repetition function, when MIMO is not applied, the unit 122 repeatedly outputs the same bits of the output data of the error correction coding unit 120. Also in this case, the number of transmission bits when MIMO is not applied may be made substantially equal to the number of transmission bits when MIMO is applied.

Fig. 12 shows another embodiment of the present invention. In the transmission system shown in fig. 7, as a function of the signaling generation section 11 in the base station 1, it is notified whether or not the format in the MIMO and control channel generation section 12 is applied. The embodiment shown in fig. 12 makes the above-described function of the signaling generation section 11 unnecessary.

That is, the user terminal 2, i.e., the receiving side, receives using two control channel formats corresponding to the case where MIMO is applied and MIMO is not applied. Any format that appears to be correct is then detected from the received data. Thus, the base station 1, i.e., the transmitting side, can notify the receiving side whether MIMO is applied or not without using the information bit resource to notify whether MIMO is applied or not.

In the control channel demodulation section 23 shown in fig. 12, two error correction decoding units 231a, 231b are provided on the output side of the demodulator 230 for demodulating a signal transmitted from the base station 1 side without performing signaling demodulation, and correspond to the two control channel formats, respectively.

The first error correction decoding unit 231a can obtain a correct output when error correction decoding is performed on the frame signal of which the number of bits is 68 when MIMO is not applied. For this reason, the error correction decoding unit 231a performs error correction decoding based on the assumed coding rate = 0.24.

Meanwhile, the second error correction decoding unit 231b can obtain a correct output when error correction decoding is performed on the frame signal of which the bit number is 141 when MIMO is applied. For this reason, error correction decoding is performed based on the assumed coding rate = 0.5.

The reliability determination and selection unit 232 determines which decoding result appears correct from the outputs of the first error correction decoding unit 231a and the second error correction decoding unit 231b, and selects the output of either side of the error correction decoding units 231a, 231b based on the above results.

Thereby, it is possible to save information bit resources for informing whether MIMO is applied.

Fig. 13A and 13B are graphs showing comparison of the effect of the present invention and the case of using the invention of the previous application.

Fig. 13A shows the transmission power ratio from a base station using HSDPA. The remaining power not shown in fig. 13A corresponds to the power assigned to the traffic channel.

Figure 13B shows the available power in the traffic channel obtained from figure 13A based on the number of channels in the HS-SCCH. As described earlier, according to the invention in the previous application, the encoding rate of the HS-SCCH is constant even if the information amount is large. The available power of the traffic channel becomes different according to whether MIMO is applied or not (refer to III in fig. 13B). In contrast, according to the present invention, the above power is constant (refer to IV in fig. 13B).

For example, in the case where the traffic channel is two channels (indicated by arrows in fig. 13B), the effect of the present invention is 1.5 times greater in power angle than the invention in the previous application.

Industrial applicability

As has been described with reference to the drawings, in the present invention, by making the coding rate of error correction coding variable according to the control channel mode, the transmission quality can be kept constant regardless of whether the propagation state is good or bad, and furthermore, the excessive quality of transmission of control information bits can be prevented even if MIMO is applied.

Claims (3)

1. A control channel information transmission system for transmitting control channel information for adaptive coding and modulation, the control channel information transmission system comprising:

on the side of the base station,

an error correction encoding unit configured to error correction encode the control channel information; and

a modulation unit configured to modulate the encoded output of the error correction encoding unit according to a predetermined modulation scheme,

wherein the error correction encoding unit is configured to set a coding rate of the control channel information before modulation when the multiple input multiple output is applied to be greater than a coding rate when the multiple input multiple output is not applied, so that a number of bits of the error correction encoded control channel information transmitted becomes constant regardless of the application of the multiple input multiple output.

2. The control channel information transfer system of claim 1, further comprising:

at the location of the receiving station,

a unit configured to receive and demodulate the control channel information transmitted from the transmission station according to the predetermined modulation scheme, the unit error-correction-decoding the demodulated control channel information corresponding to each coding rate according to whether multiple-input multiple-output is applied.

3. The control channel information transfer system of claim 1, further comprising:

at the location of the receiving station,

a plurality of error correction decoding units respectively configured to error-correction decode the commonly received signal corresponding to a coding rate distinguished according to whether or not the multiple input multiple output is applied; and

a unit configured to determine a likelihood of the error-correction decoded signal, and based on a likelihood determination result, output the error-correction decoded signal determined to be valid.