WO2011026262A1

WO2011026262A1 - Method for capturing control logic channel used in china mobile multimedia broadcasting system

Info

Publication number: WO2011026262A1
Application number: PCT/CN2009/001499
Authority: WO
Inventors: 程鑫豪
Original assignee: 卓胜微电子（上海）有限公司
Priority date: 2009-09-03
Filing date: 2009-12-18
Publication date: 2011-03-10
Also published as: CN102006254B; CN102006254A

Abstract

A method for capturing Control Logic Channel (CLCH) used in China Mobile Multimedia Broadcasting (CMMB) system is disclosed in the present invention. The method comprises the following steps of: detecting a complex pseudorandom sequence scrambled on Orthogonal Frequency Division Multiplexing (OFDM) symbols of a current time slot in a variety of complex pseudorandom sequences by using a complex pseudorandom sequence carried in a discrete pilot frequency position firstly; after accurately identifying the complex pseudorandom sequence used by the current time slot, re-descrambling transmission indication information by using the complex pseudorandom sequence; after performing corresponding processes of soft demodulation and repetitive decoding according to the modulation code characteristic of the transmission indication information, detecting the transmission indication information; and then starting a corresponding time slot logic number accumulator by means of the time slot logic number comprised in the detected transmission indication information, until the number 0 time slot is captured. Applying the method of the present invention, the number 0 time slot corresponding to the Control Logic Channel can be captured reliably, control information of the broadcast system can be resumed accurately and the method can be realized easily.

Description

Method for capturing control logic channel applied to China Mobile Multimedia Broadcasting System

Technical field

The present invention relates to the field of digital communications, and in particular to a method for capturing a control logical channel applied to a China Mobile Multimedia Broadcasting System.

Background technique '

Mobile multimedia broadcasting is a communication system that provides broadcast television services to users by using wireless digital communication technology. It has the characteristics of mobile reception, wide coverage, and efficient power saving. It can meet the receiving users' receiving audio and video programs and information services anytime and anywhere. demand. Defined in our country

The CMMB (China Mobile Multimedia Broadcasting) standard defines a series of signal frame structures, channel coding techniques, modulation techniques, etc. related to the physical layer transmission of mobile multimedia broadcast channels. At the same time, the physical layer of the mobile multimedia broadcast channel is defined to provide a transmission channel configurable transmission channel to the upper layer service in the form of a physical layer logical channel (PLCH).

According to the definition of the CMMB standard, the physical layer signal is composed of broadcast channel frames with a frame length of 1 second. At the same time, each broadcast channel frame is evenly divided into 40 equal-length time slots, each time slot has a duration of 25 milliseconds, respectively. The number is 0~39. The information of these logical numbers is transmitted in the transmission indication information of each slot. The indication information is transmitted in the CMMB protocol definition by a total of 16 bits, where bit 0 to bit 5 are used to indicate the current slot number, bit 6 is the byte interleaver synchronization indicator, bit 7 is the configuration change indication, and the remaining bits 8 to 15 are given. Reserved.

As shown in FIG. 1, the time slot 0 is specifically allocated to carry the broadcast system control information, and the broadcast system control information carried by the broadcast system specifically includes the modulation mode and channel coding of other service logical channels. The physical layer parameter, such as the code mode, the data interleaving mode, and the like, so its corresponding physical layer logical channel is also called a control logical channel (CLCH). The other 39 time slots are used to carry broadcast service data, which can be allocated to different physical layer logical channels to support different upper layer services, and different physical layer logical channels can be allocated a different number of time slots, so these The physical layer logical channel used to carry broadcast service data is also referred to as a service logical channel. Such a physical layer definition ensures that the physical layer can support a flexible multi-service hybrid combination form, which satisfies the requirements of different services to match different propagation rates and different propagation qualities.

As shown in Figure 2, the signal format of each time slot is fixed, both by TxID (transmitter identification) signal, synchronization signal and standard OFDM (Orthogonal Frequency Division Multiplexing) symbol. The composition, wherein the slot logical number used to identify the slot is defined in the transmission indication signal in the OFDM symbol. The protocol defines a fixed mapping relationship between the transmission indicator signals to the contiguous pilot subcarriers, and specifies that all frequency domain subcarrier signals are scrambled with a complex pseudo-random sequence. There are eight options for such a pseudo-random random sequence. Except for the special definition to use the No. 0 time slot carrying the broadcast system control information to be fixed by the 0-bit pseudo-random random sequence, the other time slots used for carrying the service may be different. The complex pseudo-random sequence is scrambled, and the information of which complex pseudo-random sequence is used in different logical information is defined in the broadcast system control information carried in slot 0.

Therefore, before correctly receiving the multimedia service broadcasted by the China Mobile Multimedia Broadcasting System, the receiving terminal must not only complete the timing synchronization, carrier frequency synchronization and sampling frequency synchronization required by the general OFDM system, but must also correctly capture the time slot 0. Synchronization of gap logic sorting. Only after the time slot 0 is captured can the physical layer parameter information of other service logical channels be correctly recovered from the broadcast system control information carried by the time slot 0, thereby selecting a suitable multimedia industry. Receive it.

As shown in FIG. 2, the receiver can implement timing synchronization of physical time slots according to the synchronization signal of the CMMB physical layer signal in each time slot, and correctly distinguish the start position of each time slot and the start position of the synchronization signal in the time slot. And the starting position of each OFDM symbol, but the logical number corresponding to each physical time slot cannot be obtained, and the control logical channel used to propagate the broadcast system control information shown in FIG. 1 cannot be correctly captured.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for acquiring a control control logical channel of a China Mobile Multimedia Broadcasting System, which can ensure that a receiver can be reliably received under different channel conditions and scrambled for any complex pseudo-random sequence. The time slot 0 (ie, the control logical channel) is captured, and the broadcast system control information carried in the control logical channel is obtained therefrom, which is easy to implement and reliable in performance.

To solve the above technical problem, the method for capturing a control logical channel applied by the China Mobile Multimedia Broadcasting System described in the present invention includes the following steps:

1. For the received signal after timing synchronization, the receiver separates the synchronization signal on the current receiving time slot, and uses the known frequency domain binary pseudo-random sequence information in the synchronization signal to obtain the effective signal bandwidth of the current time slot propagation channel. Frequency domain channel response estimation; performing fast FFT transform on N OFDM symbols after the synchronization signal to implement OFDM demodulation, obtaining a corresponding frequency domain signal, and then performing subcarrier mapping of discrete pilot and continual pilot according to CMMB protocol a OFDM mapping operation of the frequency domain signals corresponding to the N OFDM symbols, to obtain received data of corresponding discrete pilot subcarrier positions and received data of corresponding contiguous pilot subcarrier positions in each OFDM symbol; According to the discrete pilot and continuous pilot subcarrier mapping rules defined by the CMMB protocol, the OFDM demapping is performed on the frequency domain channel response estimation obtained in step one by using the zero order holding technique on the N OFDM symbols after the synchronization signal. Operation (the demapping operation here is the same as the OFDM demapping operation performed on the frequency domain signals corresponding to the N OFDM symbols in step 2), and obtaining channel estimation values and corresponding continuous guides of corresponding discrete pilot subcarrier positions on each OFDM symbol. Channel estimate of the frequency subcarrier position;

3. Multiplying the received data at the discrete pilot subcarrier position by the conjugate value of the channel estimate at the corresponding subcarrier position, and multiplying the received data at the contiguous pilot subcarrier position by the channel at the corresponding subcarrier position Estimating the conjugate value of the value, obtaining the discrete pilot data and the continuous pilot data after the channel coherent processing;

4. The discrete pilot data after the channel coherent processing is cross-correlated with the 8 pseudo-random sequences corresponding to the scattered pilot positions locally known by the receiver to obtain 8 cross-correlation values;

Performing the maximum value detection among the eight cross-correlation values, and judging the complex pseudo-sequence corresponding to the largest cross-correlation value according to the one-to-one correspondence between the eight cross-correlation values and the eight complex pseudo-random sequences , the sequence is a complex pseudo-random sequence used in the current time slot;

6. Based on the complex pseudo-random sequence obtained in the step 5, multiplying the continuous pilot data after the channel coherent processing in step 3 by the conjugate value of the complex pseudo-random sequence corresponding to the continuous pilot position, and obtaining the complex descrambling process Continuous continual pilot data;

7. Perform soft demodulation processing on the continuous pilot data after the complex descrambling process to obtain soft demodulation data of the continuous pilot;

VIII. For continuous pilot data carrying the same transmission indication information, in frequency dimension and time The maximum ratio combining of the soft demodulation data of the continuous pilots in the two dimension directions is obtained, and 16 soft demodulation data are obtained after the combination, respectively, corresponding to 16 bits of the transmission indication information;

IX. Performing a binary bit hard decision on the combined soft demodulated data, thereby detecting 16-bit transmission indication information;

10. Converting the first 6 bits of binary data in the detected transmission indication information into a decimal number to obtain a time slot logical number corresponding to the current time slot;

XI. Set the logical number of the time slot detected at the current time to the initial value, start a time slot logical number accumulator, with a period of 25ms as the period, every other time slot, the corresponding time slot logical number plus 1. The maximum number of the accumulator is 39, and then return to slot 0. According to the accumulator information, the time slot 0 is captured, that is, the control logical channel.

In the fourth step, the locally known pseudo-random sequence may be a complex pseudo-random sequence or a pseudo-random random sequence. When the pseudo-random random sequence is used, the cross-correlation operation is performed directly on the scattered pilot data after the channel coherent processing and the locally known complex pseudo-random sequence. When the real pseudo-random sequence is used, the real pilot and the imaginary part of the discrete pilot data after the channel coherent processing are multiplied to obtain real discrete pilot data, and the real discrete pilot data is locally Known pseudo-random random sequences perform cross-correlation operations.

In the step 6 described above, the complex descrambling process may be performed only for the contiguous pilot carrying the slot logical number information in the transmission indication information.

In the seventh step and the eighth step, the processing sequence of the two may be reversed, and the continuous pilot data after the complex descrambling processing is first combined in the frequency dimension and the time dimension, and then merged. The data is subjected to soft demodulation processing to obtain combined soft demodulation data.

The method for capturing a control logical channel by the CMMB receiver of the present invention is based on the detected complex The pseudo-random sequence performs complex descrambling on the continuous pilot data carrying the transmission indication information, and recovers the original transmission indication information. Since the transmission indication information is BPSK modulation and has undergone repeated coding processing, BPSK soft demodulation processing and repeated decoding combining processing may be performed on the data after the complex descrambling, and the subcarrier data carrying the same transmission indication information is maximized. Ratio combining can effectively utilize the performance gains brought by frequency diversity and time diversity. The original transmission indication information is binary bit mapped, so that the original transmission indication information bits can be recovered by performing a bit hard decision on the combined data. In the 16-bit transmission indication information, the first 6 bits are used to indicate the logical slot number signal corresponding to the current physical time slot, and the logical number of the time slot can be correctly resolved, that is, the synchronization of the time slot in the logical sequence can be completed, and reused. The known slot timing information can accurately capture the slot data of the first logical 0 number that arrives after the current slot according to the currently detected slot logical number, thereby completing the capture of the entire slot 0. . By processing and parsing the broadcast system control information in the control logical channel corresponding to the time slot 0, the physical layer parameter configuration of other service logical channels can be correctly acquired. It can ensure that the receiver can reliably capture the time slot 0 (ie, control logical channel) for the received signal scrambled by any pseudo-random sequence under different channel conditions, and obtain the broadcast system control information carried in the control logical channel. , easy to implement, reliable performance.

DRAWINGS

The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

1 is a schematic diagram of a physical channel frame structure of a CMMB physical layer signal;

2 is a schematic diagram of a physical layer slot structure of a CMMB physical layer signal;

FIG. 3 is a schematic diagram of functional modules for implementing control logic channel capture according to the present invention.

detailed description As shown in FIG. 2, for the received signal after timing synchronization, the receiver can correctly distinguish the start position of each slot, the start position of the synchronization signal in the slot, and the start position of each OFDM symbol. Therefore, at the beginning of each slot signal, based on the known frequency domain binary pseudo-random sequence information in the synchronization signal, the channel estimation value H( ) of the current slot propagation channel on each effective frequency domain subcarrier can be obtained first. 0 ≤ ≤ 3075.

After the frequency domain subcarrier channel estimation value is obtained, as shown in FIG. 3, for N OFDM symbols after the synchronization signal, cyclic prefix removal, fast Fourier transform (FFT) time-frequency transform, and the like are performed to obtain a frequency domain OFDM W. _{_{^ R n {k 2 \ 0≤n≤Nl}} , 0≤k 2 ≤ 4095, 1≤ N≤ 53.

It is also known that the frequency domain OFDM symbol R„ is composed of discrete pilot subcarriers, contiguous pilot subcarriers, valid data subcarriers, and virtual subcarriers. Therefore, the subcarrier mapping of discrete pilots and continual pilots according to the CMMB protocol is defined. A rule is to perform a demapping operation on a frequency domain OFDM symbol in units of subcarriers, to obtain received data O, 0 ≤ t ₃ ≤ 383 corresponding to discrete pilot subcarrier positions in each OFDM symbol, and receive the corresponding contiguous pilot subcarrier position The data ε Ο, 0 ≤ ≤ 81. These data are scrambled by a complex pseudo-random sequence and suffer from the fading of the propagation channel.

After obtaining the received data at the discrete pilot subcarrier position after the demapping and the received data at the contiguous pilot subcarrier position, it is also necessary to obtain their respective corresponding frequency domain channel estimation values, and thus are defined according to the C awake protocol. The subcarrier mapping rule is based on the channel estimation value HO, 0 ≤ <3075 of the first obtained effective frequency domain subcarrier, and performs N demapping operations in units of subcarriers in N OFDM symbol periods, and obtains N corresponding The channel estimation value of the received data at the discrete pilot subcarrier position of the OFDM symbol, ^, 0 ≤ ≤ 383 and the channel estimation value of the received data at the contiguous pilot subcarrier position H „, O, 0 ≤) t ₄ ≤ 81. With continued reference to FIG. 3, channel coherent processing is performed on the received data at the position of the scattered pilot subcarrier obtained after the demapping and the received data at the position of the contiguous pilot subcarrier, that is, the position of the scattered pilot subcarrier obtained after the demapping is performed. Multiplying the received data by the conjugate value of the channel estimation value at the corresponding subcarrier position to obtain the discrete pilot data after the channel coherent processing; multiplying the received data at the contiguous pilot subcarrier position obtained after the demapping by the corresponding sub The conjugate value of the channel estimate at the carrier position is obtained by channel coherently processed continual pilot data to eliminate the adverse effects caused by the propagation channel, and then the discrete pilot data after the channel coherent processing is locally known 8 An ideal pseudo-random sequence is subjected to cross-correlation processing to obtain 8 cross-correlation values. When the locally known pseudo-random sequence adopts a complex pseudo-random sequence, the cross-correlation operation can be directly performed on the discrete pilot data after the channel coherent processing and the locally known complex pseudo-random sequence, but from the perspective of reducing the complexity of the cross-correlation operation In the specific implementation, before the cross-correlation processing, the discrete pilot data after the channel coherent processing can be multiplied by the real part and the imaginary part to obtain new real discrete pilot data, and then the local Knowing the ideal real pseudo-random sequence for cross-correlation operation can effectively reduce the complexity of the cross-correlation operation in the implementation process.

After the cross-correlation operation is completed, the obtained maximum value of the cross-correlation values is detected, and the maximum cross-correlation value is determined according to the one-to-one correspondence between the eight cross-correlation values and the eight complex pseudo-sequences. Corresponding complex pseudo-random sequence, the sequence is the complex pseudo-random sequence used in the current time slot; the more discrete pilot data after the channel coherent processing used in the cross-correlation operation, the more obvious the correlation gain, the reliability of detection The higher the complexity, but the corresponding computational complexity increases. Specifically, in the implementation application, the number of OFDM symbols used can be flexibly selected in combination with specific applications.

The complex pilot data after the channel coherent processing carrying the transmission indication information is subjected to complex descrambling processing based on the detected pseudo-random random sequence used in the current time slot. Upcoming channel The contiguous pilot data processed by the phase is multiplied by the conjugate value of the complex pseudo-random sequence used in the current time slot to obtain the continuous pilot data after the complex descrambling process.

Because according to the definition of the CMMB protocol, these transmission indication information is BPSK modulation and the 16-bit transmission indication information is subjected to repeated coding processing (in the frequency dimension, each bit corresponds to transmission on 4 different consecutive subcarriers, in time dimension The upper 16 bits are repeatedly transmitted on each OFDM symbol), so BPSK soft demodulation processing and repeated decoding combining processing can be performed on the continuous pilot data after the complex descrambling processing. The multiplex continuous pilot data after the complex descrambling process may be subjected to soft demodulation processing, and then the maximum ratio in the two dimensional directions of the frequency dimension and the time dimension is performed for the soft demodulated data of the continuous pilot carrying the same transmission indication information. Combining and combining to obtain soft demodulation data corresponding to 16-bit transmission indication information; or merging the continuous pilot data after complex descrambling processing in the frequency dimension and the time dimension, and then combining The data is subjected to soft demodulation processing to obtain combined soft demodulated data. The principle of the repetitive coding and combining process is to perform maximum ratio combining on the continuous pilot data after complex descrambling at different locations based on the same transmission indication information, effectively utilizing the performance gain brought by frequency diversity and time diversity. After the combination, the soft demodulated data corresponding to the 16-bit transmission indication information can be obtained. Then, by performing a binary bit hard decision on the combined soft demodulated data, the original transmission indication information can be recovered. In the 16-bit transmission indication information, the first 6 bits are used to indicate the logical slot number corresponding to the current physical time slot. Therefore, converting the 6 binary bits into decimal can correctly resolve the logical number of the current time slot, that is, the synchronization of the time slots in the logical ordering is completed. Then, using the known slot timing information, the corresponding timer is started, and 1 is added to the slot logical number every time slot is passed, and the loop is counted between the logical numbers 0 to 39 defined by the protocol until the current slot. After the arrival of the first time slot numbered 0, the entire time slot 0 is completed. Capture work. By processing and parsing the broadcast system control information in the control logical channel corresponding to the time slot 0, the physical layer parameter configuration of other service logical channels can be correctly acquired.

Claims

Rights request

A method for capturing a control logical channel in a China Mobile Multimedia Broadcasting System, characterized in that it comprises the following steps:

1. For the received signal after timing synchronization, the receiver separates the synchronization signal on the current receiving gap, and uses the known frequency domain binary pseudo-random sequence information in the synchronization signal to obtain the effective signal bandwidth of the current time slot propagation channel. Frequency domain channel response estimation; performing fast FFT transform on N OFDM symbols after the synchronization signal to implement OFDM demodulation, obtaining a corresponding frequency domain signal, and then performing subcarrier mapping of discrete pilot and continual pilot according to CMMB protocol a OFDM mapping operation is performed on the frequency domain signals corresponding to the N OFDM symbols, and the received data of the corresponding discrete pilot subcarrier positions and the received data of the corresponding contiguous pilot subcarrier positions in each OFDM symbol are obtained;

According to the discrete pilot and continuous pilot subcarrier mapping rules defined by the CMMB protocol, the OFDM demapping is performed on the frequency domain channel response estimation obtained in step one by using the zero order holding technique on the N OFDM symbols after the synchronization signal. Operation, obtaining channel estimation values corresponding to discrete pilot subcarrier positions on each OFDM symbol and channel estimation values corresponding to consecutive pilot subcarrier positions;

Multiplying the received data at the discrete pilot subcarrier position by the conjugate value of the channel estimate at the corresponding subcarrier position, and multiplying the received data at the contiguous pilot subcarrier position by the channel at the corresponding subcarrier position Estimating the conjugate value of the value, obtaining discrete pilot data and continuous pilot data after channel coherence processing;

4. The discrete pilot data after the channel coherent processing is mutually correlated with the 8 pseudo-random sequences corresponding to the scattered pilot positions locally known by the receiver, and 8 cross-correlation values are obtained; V. Perform maximum value detection among 8 cross-correlation values, and judge the corresponding maximum cross-correlation value according to the one-to-one correspondence between the 8 cross-correlation values and the .8 complex pseudo-random sequences. a pseudo-random sequence, which is a complex pseudo-random sequence used in the current time slot;

For the continuous pilot data carrying the same transmission indication information, the soft demodulation data of the continuous pilots are combined in maximum dimension in the two dimensions of the frequency dimension and the time dimension, and 16 soft demodulation data are obtained after the combination, respectively One-to-one corresponding to 16 bits of transmission indication information;

XI. Set the logical number of the time slot detected at the current time to the initial value, start a time slot logical number accumulator, with a period of 25ms as the period, every other time slot, the corresponding time slot logical number plus 1. The maximum number of the accumulator is 39, and then return to slot 0. According to the accumulator information, the time slot 0 is captured, that is, the logical channel is controlled.

2. The method for capturing a control logical channel of a China Mobile Multimedia Broadcasting System according to claim 1, wherein in the step 4, the locally known pseudo-random sequence is a complex pseudo-random sequence or a pseudo-pseudo-random sequence. Random sequence, when using a pseudo-random random sequence, directly to the channel The discrete pilot data after the coherent processing and the locally known complex pseudo-random sequence are cross-correlated. When the real pseudo-random sequence is used, the discrete pilot data after the channel coherent processing is multiplied by the real part and the imaginary part. The real discrete pilot data is obtained, and the real discrete pilot data is cross-correlated with the locally known real pseudo-random sequence.

The method for applying a control control logical channel to a China Mobile Multimedia Broadcasting System according to claim 1, wherein in the step (8), only the continuation of the logical number information of the time slot in the bearer transmission indication information is used. The pilot performs complex descrambling processing.

4. The method for capturing a control logical channel applied to a China Mobile Multimedia Broadcasting System according to claim 1, wherein in the step 7 and the eighth step, the processing sequence of the two is reversed, and the complex solution is first solved. The continuous pilot data after the scrambling process is subjected to maximum ratio combining in the frequency dimension and the time dimension, and then the combined data is soft demodulated to obtain the combined soft demodulated data.