Be applied to the method for China Mobile multimedia broadcasting system acquisition control logic channel
Technical field
The present invention relates to digital communicating field, particularly relate to a kind of method that is applied to China Mobile multimedia broadcasting system acquisition control logic channel.
Background technology
Mobile Multimedia Broadcasting is a kind of communication system of utilizing the radio digital communication technology that broadcast television service is provided to the user, characteristics with removable reception, wide coverage, efficient power saving can satisfy the demand that the user receives audio/video program and information service whenever and wherever possible that receives.CMMB (China Mobile Multimedia Broadcasting in China's definition, the China Mobile multimedia broadcasting television system) in the standard, a series of signal frame structure relevant, channel coding technology, modulation technique etc. have been defined with the mobile multimedia broadcasting channel physical layer transmission.Stipulated that simultaneously the mobile multimedia broadcasting channel physical layer provides transmission rate configurable transmission channel with the form of physical layer logic channel (PLCH) to upper-layer service.
According to the definition of CMMB standard, physical layer signal is that 1 second broadcast channel frame is formed by frame length; Simultaneously each broadcast channel frame is divided equally into 40 isometric time slots again, each time slot duration is 25 milliseconds, and logical number is 0~39 respectively.The information of these logical numbers is included in and transmits in the transmission indication information of each time slot.Transmission indication information totally 16 bits in the CMMB protocol definition, wherein bit 0 is used to indicate current time slots number to bit 5, and bit 6 is the byte interleaver device sync id, and bit 7 is that configuration change is indicated, and all the other bits 8 are kept to bit 15.
As shown in Figure 1, No. 0 the time slot specific assigned is used for carrying the broadcast system control information, the broadcast system control information of its carrying has specifically comprised the modulation system, channel coding method, data interlacing pattern of other service logical channels or the like physical layer parameter, so its corresponding physical layer logic channel is called control logic channel (CLCH) again.Other 39 time slots then are used for carrying broadcast service data, can distribute to different physical layer logic channels and be used for supporting different upper-layer service, and different physical layer logic channels can distribute the different timeslot number of number, so these physical layer logic channels that are used for carrying broadcast service data are called service logical channels again.The definition of such physical layer has guaranteed that physical layer can support the form of multi-service hybrid combining flexibly, satisfies the demand of different propagation rate of different business coupling and different propagation quality.
As shown in Figure 2, the signal format of each time slot is changeless, all by OFDM (the Orthogonal Frequency DivisionMultiplexing of TxID (sender unit identification) signal, synchronizing signal and standard, being OFDM) symbol forms, and the time slot logical number that wherein is used for identifying time slot is to define in the transmission index signal in the OFDM symbol.Defined the fixedly mapping relations of transmission index signal in the agreement, stipulated simultaneously all to use multiple pseudo random sequence to carry out scrambling all subcarrier in frequency domain signals to the continuous pilot subcarrier.Multiple pseudo random sequence like this has 8 kinds of options, removing special definition to adopt outside No. 0 multiple pseudo random sequence scrambling with No. 0 time slot of carrying broadcast system control information is fixing, other time slots that are used for bearer service can adopt different multiple pseudo random sequences to carry out scrambling, adopt the information of which multiple pseudo random sequence to define in the broadcast system control information of No. 0 time slot carrying specific to different logical messages.
Therefore before the multimedia service of correct reception China Mobile multimedia broadcasting system broadcasts, receiving terminal not only to finish the required timing of general ofdm system synchronously, carrier frequency synchronization and sample frequency synchronously outside, also must correctly catch No. 0 time slot, realize the synchronous of time slot logic ordering.Only finish after No. 0 time slot catches, could correctly from the broadcast system control information of No. 0 time slot carrying, recover the physical layer parameter information of other service logical channels, thereby select suitable multimedia service to receive.
As shown in Figure 2, receiver can realize that the timing of physical slot by time is synchronous according to the synchronizing signal of CMMB physical layer signal in each time slot, correctly distinguish out the starting position of synchronizing signal in the starting position, time slot of each time slot and the starting position of each OFDM symbol, but can't obtain the logical number of each physical slot by time correspondence, also just can't correctly catch the control logic channel that being used for shown in Fig. 1 propagated the broadcast system control information.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of method that is applied to China Mobile multimedia broadcasting system acquisition control logic channel, can guarantee that receiver is under different channel conditions, can both catch No. 0 time slot (being the control logic channel) reliably at the received signal of any multiple pseudo random sequence scrambling, therefrom obtain the broadcast system control information of carrying in the control logic channel, be easy to realize, dependable performance.
For solving the problems of the technologies described above, the method that is applied to China Mobile multimedia broadcasting system acquisition control logic channel described in the invention may further comprise the steps:
One. to the received signal after the timing synchronously, receiver is on current receiving slot, isolate synchronizing signal, utilize frequency domain binary pseudo-random sequence information known in the synchronizing signal, obtain the domain channel response of current time slots propagation channel on effective signal bandwidth and estimate; N OFDM symbol after the synchronizing signal carried out fast fourier transform realize the OFDM demodulation, obtain corresponding frequency-region signal, then according to the scattered pilot of CMMB protocol definition and the subcarrier mapping ruler of continuous pilot, respectively the frequency-region signal of this N OFDM symbol correspondence is OFDM and separates map operation, obtain the reception data of corresponding scattered pilot sub-carrier positions in each OFDM symbol and the reception data of corresponding continuous pilot sub-carrier positions;
Two. according to the scattered pilot and the continuous pilot subcarrier mapping ruler of CMMB protocol definition, on N after synchronizing signal the OFDM symbol, adopt zeroth order to keep technology, the domain channel response that step 1 is obtained is estimated to carry out OFDM and is separated map operation (to separate map operation with the OFDM that carries out at the frequency-region signal of N OFDM symbol correspondence in the step 2 identical for the map operation of separating here), obtains the channel estimation value of corresponding scattered pilot sub-carrier positions on each OFDM symbol and the channel estimation value of corresponding continuous pilot sub-carrier positions;
Three. the reception data on the scattered pilot sub-carrier positions be multiply by the conjugate of the channel estimation value on the corresponding sub-carrier positions, and the reception data on the continuous pilot sub-carrier positions be multiply by the conjugate of the channel estimation value on the corresponding sub-carrier positions, scattered pilot data and continuous pilot data after obtaining that channel is relevant and handling;
Four. to the relevant scattered pilot data afterwards of handling of channel, carry out cross-correlation operation with local known 8 pseudo random sequences of receiver respectively, obtain 8 cross correlation values corresponding to the scattered pilot position;
Five. in 8 cross correlation values, carry out maximum and detect, and according to concerning one to one between these 8 cross correlation values and 8 multiple pseudo random sequences, rule out the multiple pseudo random sequence of maximum cross correlation value correspondence, this sequence is the multiple pseudo random sequence that adopts on the current time slots;
Six. based on the multiple pseudo random sequence that obtains of judgement in the step 5, the continuous pilot data that channel in the step 3 is relevant after handling be multiply by conjugate corresponding to the multiple pseudo random sequence of continuous pilot position, obtain the continuous pilot data after the multiple scramble process;
Seven. the continuous pilot data after the multiple scramble process are carried out soft demodulation process, obtain the soft demodulating data of continuous pilot;
Eight. for the continuous pilot data of carrying identical traffic indication information, soft demodulating data to continuous pilot on frequency dimension and two dimension directions of time dimension carries out the high specific merging, obtain 16 soft demodulating datas after the merging, respectively one by one corresponding to 16 bits that transmit indication information;
Nine. the soft demodulating data after being combined carries out the binary bits hard decision, thereby detects the transmission indication information of 16 bits;
Ten. the preceding 6 bit-binary data in the detected transmission indication information are converted to decimal number, obtain current time slots time slot corresponding logical number;
11. it is initial value that the setting current time detects the time slot logical number that obtains, start a time slot logical number accumulator, time slot length with 25ms is the cycle, long every a time slot, the time slot corresponding logical number adds 1, and the maximum of accumulator is numbered 39, return time slot afterwards No. 0, according to accumulator information, capture time slot No. 0, i.e. the control logic channel.
In described step 4, local known pseudo random sequence can be that multiple pseudo random sequence also can be real pseudo random sequence.When adopting again pseudo random sequence, directly scattered pilot data after the relevant processing of channel and local known multiple pseudo random sequence are carried out cross-correlation operation.And when adopting real pseudo random sequence, need earlier the scattered pilot data that channel is relevant after handling are carried out obtaining real scattered pilot data after real part and imaginary part multiply each other, more described real scattered pilot data are carried out cross-correlation operation with local known real pseudo random sequence.
In described step 6, can only carry out multiple scramble process at the continuous pilot of the time slot logical number information in the carrying transmission indication information.
In described step 7 and step 8, can change both processing sequences, earlier the continuous pilot data after the multiple scramble process are carried out high specific on frequency dimension and time dimension and merge, the data after being combined are again carried out soft demodulation process, the soft demodulating data after obtaining merging.
The method of CMMB receiver acquisition control logic channel of the present invention based on the multiple pseudo random sequence that detection obtains, is carried out multiple scramble process to the continuous pilot data that carry the transmission indication information, recovers original transmission indication information.Because these transmission indication informations are BPSK modulation and have passed through the repeated encoding processing, so can carry out soft demodulation process of BPSK and repeat decoding merging processing to the data after the multiple descrambling, carry and carry out high specific between the subcarrier data of identical transmission indication information and merge, can effectively utilize the performance gain that frequency diversity and time diversity are brought.Original transmission indication information is the binary bits mapping, and the data after therefore being combined are carried out the bit hard decision and promptly can be recovered original transmission indication information bit.In this 16 bit transfer indication information, preceding 6 bits are used to indicate the logic time-gap number signal of current physical slot by time correspondence, the correct logical number that parses time slot promptly can finish time slot in the logic ordering synchronously, utilize known slot timing information again, the time slot logical number that obtains according to current detection, can be captured in the time slot data of first logical zero numbering that arrives after the current time slots exactly, thereby finish the work of catching of whole No. 0 time slot.By the broadcast system control information in the control logic channel of handling and resolve No. 0 time slot correspondence, promptly can correctly obtain the physical layer parameter configuration of other service logical channels.Can guarantee that receiver is under different channel conditions, can both catch No. 0 time slot (being the control logic channel) reliably at the received signal of any multiple pseudo random sequence scrambling, therefrom obtain the broadcast system control information of carrying in the control logic channel, be easy to realize, dependable performance.
Description of drawings
The present invention is described in further detail below in conjunction with the drawings and specific embodiments.
Fig. 1 is the physical channel frame structure schematic diagram of CMMB physical layer signal;
Fig. 2 is the physical layer time slot structural representation of CMMB physical layer signal;
Fig. 3 realizes the high-level schematic functional block diagram of control logic channel acquisition for the present invention.
Embodiment
As shown in Figure 2, at the received signal after regularly synchronously, receiver can correctly be distinguished out the starting position of synchronizing signal in the starting position, time slot of each time slot and the starting position of each OFDM symbol.Therefore in the zero hour of each time slot signal,, can obtain the channel estimation value H (k of current time slots propagation channel on each effective subcarrier in frequency domain earlier based on frequency domain binary pseudo-random sequence information known in the synchronizing signal
1), 0≤k
1≤ 3075.
After obtaining the subcarrier in frequency domain channel estimation value, as shown in Figure 3, N OFDM symbol for after the synchronizing signal carries out operations such as Cyclic Prefix removes, fast Fourier transform (FFT) time-frequency conversion, obtains frequency-domain OFDM symbol R
n(k
2), 0≤n≤N-1,0≤k
2≤ 4095,1≤N≤53.
Known frequency-domain OFDM symbol R of while
n(k
2) form by scattered pilot subcarrier, continuous pilot subcarrier, valid data subcarrier and virtual subnet carrier wave.Therefore according to the scattered pilot of CMMB protocol definition and the subcarrier mapping ruler of continuous pilot, to frequency-domain OFDM symbol R
n(k
2) be that unit separates map operation with the subcarrier, obtain the reception data R of corresponding scattered pilot sub-carrier positions in each OFDM symbol
N, s(k
3), 0≤k
3≤ 383, the reception data R of corresponding continuous pilot sub-carrier positions
N, c(k
4), 0≤k
4≤ 81.These data all are the multiple pseudo random sequence scramblings of process, and have suffered the influence of fading of propagation channel.
After the reception data and the reception data on the continuous pilot sub-carrier positions on the scattered pilot sub-carrier positions after obtaining separating mapping, each self-corresponding frequency domain channel estimated value that also needs to obtain them, therefore according to the subcarrier mapping ruler of CMMB protocol definition, based on the channel estimation value H (k of the effective subcarrier in frequency domain that obtains at first
1), 0≤k
1≤ 3075, in N OFDM symbol period, be that unit carries out separating for N time map operation with the subcarrier, obtain channel estimation value H corresponding to the reception data on the scattered pilot sub-carrier positions of N OFDM symbol
N, s(k), 0≤k
3≤ 383 and the continuous pilot sub-carrier positions on the channel estimation value H of reception data
N, c(k
4), 0≤k
4≤ 81.
Continuation is with reference to figure 3, the reception data and the reception data on the continuous pilot sub-carrier positions of separating on the scattered pilot sub-carrier positions that obtains after the mapping are carried out the relevant processing of channel, be about to separate the conjugate that reception data on the scattered pilot sub-carrier positions that obtains after the mapping multiply by the channel estimation value on the corresponding sub-carrier positions, the scattered pilot data after obtaining that channel is relevant and handling; The conjugate that the reception data of shining upon on the continuous pilot sub-carrier positions that obtains afterwards multiply by the channel estimating on the corresponding sub-carrier positions will be separated, continuous pilot data after obtaining that channel is relevant and handling, to eliminate the adverse effect that propagation channel brings, and then the scattered pilot data that channel is relevant after handling are carried out cross correlation process with local 8 kinds of known desirable pseudo random sequences, obtain 8 cross correlation values.When local known pseudo random sequence adopts again pseudo random sequence, can directly carry out cross-correlation operation to the relevant known multiple pseudo random sequence of scattered pilot data afterwards and this locality of handling of channel, but from reducing the complexity angle of computing cross-correlation, in concrete enforcement, can be before cross correlation process, the scattered pilot data that channel is relevant after handling are carried out real part and imaginary part multiplication mutually earlier, obtain the scattered pilot data of new reality, and then carry out computing cross-correlation with the pseudo random sequence of local known desirable reality, can reduce the complexity of computing cross-correlation in the implementation procedure effectively.
After finishing computing cross-correlation, 8 cross correlation values that obtain are carried out maximum to be detected, and according to concerning one to one between these 8 cross correlation values and 8 multiple pseudo random sequences, rule out the multiple pseudo random sequence of maximum cross correlation value correspondence, this sequence is the multiple pseudo random sequence that adopts on the current time slots; Scattered pilot data after the relevant processing of the channel that adopts in computing cross-correlation are many more, related gain is obvious more, and the reliability of detection is just high more, but corresponding computational complexity just rises, specifically in realize using, can select the OFDM symbol numbers that adopted in conjunction with concrete applying flexible.
The multiple pseudo random sequence that adopts in the current time slots that obtains based on detection is carried out multiple scramble process to the continuous pilot data through channel is relevant after handling that carry the transmission indication information.Continuous pilot data after being about to that channel is relevant and handling multiply by the conjugate of the multiple pseudo random sequence that adopts on the current time slots, obtain the continuous pilot data after the multiple scramble process.
Because definition according to the CMMB agreement, the transmission indication information that these transmission indication informations are BPSK modulation and 16 bits has passed through the repeated encoding processing and (has transmitted on 4 different continuous subcarriers in each bit correspondence on the frequency dimension, on each OFDM symbol, all repeat transmission at 16 bits on the time dimension), so can carry out soft demodulation process of BPSK and repeat decoding merging processing to the continuous pilot data after the multiple scramble process.Can carry out soft demodulation process to the continuous pilot data after the multiple scramble process earlier, then for the soft demodulating data of the continuous pilot of carrying identical traffic indication information, on frequency dimension and two dimension directions of time dimension, carry out high specific and merge, obtain one by one soft demodulating data after the merging corresponding to 16 bit transfer indication informations; Also can carry out high specific to the continuous pilot data after the multiple scramble process on frequency dimension and time dimension earlier and merge, the data after being combined are again carried out soft demodulation process, the soft demodulating data after obtaining merging.The principle that the repeated encoding merging is handled is based on identical transmission indication information the continuous pilot data after the multiple descrambling of diverse location is carried out the high specific merging, has effectively utilized the performance gain that frequency diversity and time diversity are brought.Promptly can obtain the soft demodulating data of 16 bit transfer indication information correspondences after having merged.Soft demodulating data after then being combined again carries out the binary bits hard decision promptly can recover original transmission indication information.In this 16 bit transfer indication information, preceding 6 bits are used to indicate the logic time-gap number of current physical slot by time correspondence.Therefore these 6 binary bits are converted to the logical number that the decimal system promptly can correctly parse current time slots, promptly finished time slot in the logic ordering synchronously.Utilize known slot timing information again, start corresponding timer, whenever, promptly on the time slot logical number, add 1 through a time slot, between the logical number 0~39 of protocol definition, carry out cycle count, first is numbered the arrival of 0 time slot after current time slots, thereby finishes the work of catching of whole No. 0 time slot.By the broadcast system control information in the control logic channel of handling and resolve No. 0 time slot correspondence, promptly can correctly obtain the physical layer parameter configuration of other service logical channels.