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 with the mobile multimedia broadcasting channel physical layer transmission, channel coding technology, modulation technique etc. have been defined.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 forms by frame length; Simultaneously each broadcast channel frame is divided equally into again 40 isometric time slots, 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 etc. physical layer parameter, so the physical layer logic channel of its correspondence is called again control logic channel (CLCH).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 again service logical channels.The definition of such physical layer has guaranteed that physical layer can support flexibly multi-service hybrid combining form, satisfies the demand of the 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 to the continuous pilot subcarrier in the agreement, stipulated simultaneously all to use multiple pseudo random sequence to carry out scrambling to all subcarrier in frequency domain signals.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 Synchronization of general ofdm system, 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 be realized according to the synchronizing signal of CMMB physical layer signal in each time slot the Timing Synchronization of physical slot by time, correctly distinguish 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 logical number corresponding to each physical slot by time, 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 reliably No. 0 time slot (being the control logic channel) for the reception 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 reception signal after the Timing Synchronization, 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 this N the frequency-region signal that the OFDM symbol is corresponding is OFDM and separates map operation, obtain the receive data of corresponding scattered pilot sub-carrier positions in each OFDM symbol and the receive data of corresponding continuous pilot sub-carrier positions;
Two. according to 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 obtains is estimated to carry out OFDM solution map operation (it is identical that the solution map operation is here separated map operation with the OFDM that carries out for N frequency-region signal corresponding to OFDM symbol in the step 2), obtain 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 receive 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 receive 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 processing;
Four. to the relevant scattered pilot data afterwards of processing of channel, carry out cross-correlation operation with local known 8 pseudo random sequences corresponding to the scattered pilot position of receiver respectively, obtain 8 cross correlation values;
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 maximum multiple pseudo random sequence corresponding to cross correlation value, 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 processing 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 front 6 bit-binary data in the detected transmission indication information are converted to decimal number, obtain time slot logical number corresponding to current time slots;
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, take the time slot length of 25ms as the cycle, long every a time slot, corresponding time slot logical number adds 1, and the maximum of accumulator is numbered 39, return afterwards time slot 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 multiple pseudo random sequence, directly the 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 first the scattered pilot data that channel is relevant after processing 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 for 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, first the continuous pilot data after the multiple scramble process are carried out the high specific merging in frequency dimension and time dimension, 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 the 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 namely can be recovered original transmission indication information bit.In this 16 bit transfer indication information, front 6 bits are used to indicate logic time-gap number signal corresponding to current physical slot by time, the correct logical number that parses time slot namely can finish time slot in the logic ordering synchronously, recycle known slot timing information, the time slot logical number that obtains according to current detection, can be captured in exactly the time slot data of first logical zero numbering that arrives after the current time slots, thereby finish the work of catching of whole No. 0 time slot.By processing and resolve the broadcast system control information in control logic channel corresponding to No. 0 time slot, the physical layer parameter configuration that namely can correctly obtain other service logical channels.Can guarantee that receiver is under different channel conditions, can both catch reliably No. 0 time slot (being the control logic channel) for the reception 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 is the high-level schematic functional block diagram that the present invention realizes the control logic channel acquisition.
Embodiment
As shown in Figure 2, for the reception signal after the Timing Synchronization, receiver can correctly distinguish 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, based on frequency domain binary pseudo-random sequence information known in the synchronizing signal, can obtain first the channel estimation value H (k of current time slots propagation channel on each effective subcarrier in frequency domain
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 the 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) formed 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) separate map operation take subcarrier as unit, obtain the receive data R of corresponding scattered pilot sub-carrier positions in each OFDM symbol
N, s(k
3), 0≤k
3≤ 383, the receive data R of corresponding continuous pilot sub-carrier positions
N, c(k
4), 0≤k
4≤ 81.These data are all through multiple pseudo random sequence scrambling, and have suffered the influence of fading of propagation channel.
After the receive data and the receive data on the continuous pilot sub-carrier positions on the scattered pilot sub-carrier positions after obtaining separating mapping, each self-corresponding channel estimation in frequency domain 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, carry out N time take subcarrier as unit and separate map operation, obtain the channel estimation value H corresponding to the receive data on the scattered pilot sub-carrier positions of N OFDM symbol
N, s(k
3), 0≤k
3≤ 383 and the continuous pilot sub-carrier positions on the channel estimation value H of receive data
N, c(k
4), 0≤k
4≤ 81.
Continuation is with reference to figure 3, receive data and the receive data on the continuous pilot sub-carrier positions of separating on the scattered pilot sub-carrier positions that obtains after the mapping carried out the relevant processing of channel, be about to separate the conjugate that receive 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 processing; Receive data on the continuous pilot sub-carrier positions that obtains after the solution mapping be multiply by the conjugate of the channel estimating on the corresponding sub-carrier positions, continuous pilot data after obtaining that channel is relevant and processing, the adverse effect of bringing to eliminate propagation channel, and then the scattered pilot data that channel is relevant after processing 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 multiple 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 processing of channel, but from reducing the complexity angle of computing cross-correlation, in implementation, can be before cross correlation process, the scattered pilot data that channel is relevant after processing are carried out first mutually multiplication of real part and imaginary part, 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 effectively reduce the complexity of computing cross-correlation in the implementation procedure.
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 maximum multiple pseudo random sequence corresponding to cross correlation value, 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 more, related gain is more obvious, and the reliability of detection is just higher, but corresponding computational complexity just rises, specifically in realize using, can select the OFDM symbol numbers that adopts 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 processing that carry the transmission indication information.Continuous pilot data after being about to that channel is relevant and processing 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 the 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 (each bit correspondence is transmitted at 4 different continuous subcarriers on frequency dimension, on each OFDM symbol, repeat transmission at 16 bits on the time dimension), so can carry out the 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 first, then for the soft demodulating data of the continuous pilot of carrying identical traffic indication information, carry out high specific in frequency dimension and two dimension directions of time dimension and merge, obtain one by one the soft demodulating data corresponding to 16 bit transfer indication informations after the merging; Also can carry out the high specific merging to the continuous pilot data after the multiple scramble process in frequency dimension and time dimension first, 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 processed 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.Namely can obtain soft demodulating data corresponding to 16 bit transfer indication informations after having merged.Soft demodulating data after then being combined again carries out the binary bits hard decision namely can recover original transmission indication information.In this 16 bit transfer indication information, front 6 bits are used to indicate logic time-gap number corresponding to current physical slot by time.Therefore these 6 binary bits are converted to the logical number that the decimal system namely can correctly parse current time slots, namely finished time slot in the logic ordering synchronously.Recycle known slot timing information, start corresponding timer, whenever, namely add 1 in the time slot logical number through a time slot, between the logical number 0~39 of protocol definition, carry out cycle count, until first is numbered the arrival of 0 time slot after the current time slots, thereby finish the work of catching of whole No. 0 time slot.By processing and resolve the broadcast system control information in control logic channel corresponding to No. 0 time slot, the physical layer parameter configuration that namely can correctly obtain other service logical channels.