314results about How to "Improve frequency band utilization" patented technology

Embodiments are provided for guard band utilization for synchronous and asynchronous communications in wireless networks. A user equipment (UE) or a network component transmits symbols on data bands assigned for primary communications. The data bands are separated by a guard band having smaller bandwidth than the data bands. The UE or network component further modulates symbols for secondary communications with a spectrally contained wave form, which has a smaller bandwidth than the guard band. The spectrally contained wave form is achieved with orthogonal frequency-division multiplexing (OFDM) modulation or with joint OFDM and Offset Quadrature Amplitude Modulation (OQAM) modulation. The modulated symbols for the secondary communications are transmitted within the guard band.

The invention discloses an information transmission method for reducing the peak to average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal. In the method, after being coded and interleaved, data stream is modulated by a new distorted constellation diagram so as to acquire a frequency domain signal; for the frequency domain signal, a phase rotation sequence is selected to reduce the PAPR of a time domain signal which is subjected to inverse fast Fourier transform (IFFT); at a receiver end, the received signal is subjected to fast Fourier transform (FFT) and channel estimation so as to acquire the frequency domain signal; for the frequency domain signal, recovering is performed by different phase rotation sequences so as to acquire candidate signals; amongthe candidate signals, only the signal which is recovered by the right phase rotation sequence has a minimal mean square error when the signals are subjected to hard decision together with the constellation diagram; and the candidate signal which has the minimal mean square error is selected as the original signal, and the corresponding phase rotation sequence is the recovered side band information. The method can effectively reduce the peak to average power ratio of the OFDM signal, does not need to send the side band information simultaneously, improves the frequency band utilization ratio of systems, and can be applied to various communication systems using OFDM technology.

A method for receiving-transmitting ground mobile multimedia broadcast based on free charge DAB includes configuring parameter according multimedia service to carry out source and channel coding and embedding coded service data in master service channel MSC as well as carrying out channel coding to form T-MMB transmission frame being sent out at sending end, synchronizing and decoding received signal and picking up configured parameter as well as carrying out decoding on source and channel at receiving end.

The invention discloses a synchronization method for orthogonal frequency division multiplexing system, including: the launcher firstly constructs the originated / synchronous sequence that is sent out with OFDM data symbols together. Based on the correlation of CP effective length in OFDM symbols form the receiving end, the correlation result conducts a time domain processing to the correlation sequence energy to get the best synchronization points set after one synchronization. Based on the originated sequence and CP, the departure estimation and departure compensation of fractional part DF several times are processed. During a range of synchronization points set output at once, the long pre-symbol received after the compensation is made time-domain correlation with the symbol to find the second time synchronization point. Then after time-domain of the short pre-symbol and the received pre-sequence is made frequency departure compensation, time-domain-related operations is conduct to get the DF departure estimation of integer times, and departure compensation is conduct.

The method changes symmetric parameter of waveform alpha directly by using binary information code-element so as to reach minimum difference between waveforms of modulated signal and sine signal, its information transmission rate is equal to carrier frequency. Waveform g(t, iota) is modulated by logic '0', and waveform g(t, T-iota) is modulated by logic '1'. Here, T is cycle of signal waveform, also is symbol width and code-element width of information, and f=1/T is frequency of signal waveform, or equal to transmission rate of code-element in numerical value. Since information transmission rate is euqal to carrier frequency, and transmission signal is very close to sine wave, thus, energy of frequency spectrum is concentrated highly so as to use very narrow bandwidth. The invented method possesses features of very high utilization rate of frequency band, and applicable to high-speed digital transmission in ultra narrow bandwidth.

The invention relates to method for measuring synthetic aperture sonar movement error and underwater sound channel error. The invention employs an irradiation matrix which is arranged along platform trace and different phase center to irradiate plural orthogonal signal with same frequency at the same time.

A information modulating and demodulating method used on digital communication includes realizing modulation by utilizing binary information code element to directly vary abrupt phase of sine carrier wave, utilizing lock phase ring to realize demodulation, making modulated signal g0(t) corresponding to number zero be sine wave of N carrier wave period and making g1(t) corresponding to number one be in sine wave of N carrier wave period with frequency of fc, applying phase jump off angle theta and parameter tau as modulation index for varying signal bandwidth and transmission code rate as well as demodulation property.

A method for modulating and demodulating information of equivalent amplitude high frequency band usage utilizes binary information symbols to directly change the waveform of a sine carrier wave to minimize the waveform difference between the modulated signal corresponding to logic 'D' go (t) and g1(t) corresponding to logic '1' and the sine signals and only one parameter is used to control the waveform difference and signal bandwidth. Since in the process of zero-cross detection to the information demodulation, only one sample judgment is needed at the middle of the received signal waveform (t=T/2) to finish the demodulation and hard limitation is applied to suppress interference of pulse noise.

The invention discloses a method for reducing a peak-to-average power ratio of multiple input multiple output (MIMO) - orthogonal frequency division multiplexing (OFDM) signal for space-frequency coding. On a transmitter end, data is coded, interlaced, modulated and alamounti space-frequency coded to obtain a group of frequency-domain sequence, the group of frequency-domain sequence is grouped, so multiple groups of candidate time-domain signals are obtained by selecting appropriate parameters, and a group of time-domain signals with the minimum peak-to-average power ratio (PAPR) is selected to be transmitted. On the end of a receiver, after the operation of a received signal such as fast fourier transformation (FFT), estimation of a channel, space-frequency coding and the like, a frequency-domain signal which is superimposed by the channel noise is obtained, and the hard decision is performed on the frequency-domain signal to obtain a nose-free frequency-domain signal. The signal is restored according to all possible combination ways to obtain candidate data, and only the data which is restored by adopting a correct restoring way conforms to the original modulation constellation.The method can effectively reduce the peak-to-average power ratio of the MIMO-OFDM signal, is free from transmitting the side information, improves the frequency band utilization rate of the system, and can be applied to different communication systems based on the space-frequency coding-based MIMO-OFDM technology.

The invention discloses an extended binary phase shift keying modulation and demodulation method for frequency spectrum compression, which is an information modulation method used for digital communication. The method uses a binary information code element to directly change a continuous phase of a sinusoidal carrier to realize modulation, and uses a type of special simple-zero multi-pole narrowband digital filters with quite close resonance frequencies to realize demodulation so that a modulated signal f0(t) corresponding to the number '0' is sine wave of N carrier cycles, while a f1(t) corresponding to the number '1' is in the sine wave of N carrier cycles with an angular frequency of omega, and the phases and carrier frequencies of front K cycles synchronize and change continuously according to the sine rule. The method directly controls the continuous changed magnitude of the phases of the sinusoidal carrier and the time duty ratio thereof by using data bits, namely the method can change the signal bandwidth, transmission code rate and transmission performance respectively or simultaneously, and can realize high-speed data transmission of extremely narrow bandwidth.

The invention discloses an estimation method for a signal interference noise ratio in an orthogonal frequency division multiplexing (OFDM) system. Through obtaining a period self-correlation function of a received signal on a receiving end of the OFDM system, the energy distribution rule of a transmission signal, a radio frequency interference signal and the period self-correlation function of Gauss white noise is analyzed, the signal power can be effectively separated from the noise-added interference power by selecting an appropriate delay variable and a circulating frequency, and then according to the definition of the signal interference noise ratio, a signal interference noise ratio value during a signal transmission process is effectively estimated. By the adoption of the estimation method, the calculation complexity is low, the estimation precision is high, aiming to the situation that current frequency spectrum resource is gradually deficient, the utilization rate of a frequency band can be well increased, and under the environment of more serious radio frequency interference, performance of the communication system can be effectively improved.

The invention relates to a 1553B digital communication device. In order to expand the communication capacity, expand the data-transfer capacity and enhance the communication properties such as property in resisting interference and the like in a 1553B bus, the invention provides the technical scheme: a receiving method for bandwidth expansion of a 1553B communication bus. The following method sub-modules: an analog front end (AFE), a frame detecting module, a symbol synchronizing module, an inverse FFT (fast Fourier transformation) module, a block floating point module, a channel balancing module, a frequency offset synchronizing module, a QAM (quadrature amplitude modulation) de-mapping module of a dynamic threshold and a base-band processing module are provided in the receiving method, wherein the AFE is used for performing signal amplification and AD (analog-to-digital) conversion, sampling an analog signal into a digital signal and transmitting; the frame detecting module is used for detecting the access situation of a frame; the IFFT module is used for processing a base-band signal. The method provided by the invention is mainly used for 1553B digital communication.

The invention discloses a polarization multiplexing band interpolation based OFDMA-PON (orthogonal frequency division multiple access-passive optical network) system which is characterized in that: two paths of OFDM (orthogonal frequency division multiplexing) signals are respectively produced at an optical line terminal, and sub-bands of the two paths of OFDM signals are mutually interleaved; and through respectively carrying out optical modulation and polarization control on the OFDM signals, two paths of optical OFDM signals in the x and y polarization directions are respectively obtained, and then combined into one path so as to form optical OFDM signals without protection bands, in such a way, the bandwidth of the system is fully used. An optical distribution network divides the received optical OFDM signals into optical OFDM signals in the x and y polarization directions, then an optical beam splitter divides the OFDM signals into multiple paths, and an optical filter extracts the optical OFDM signals divided by the optical beam splitter, selects required different sub-band optical OFDM signals or different numbers of sub-band optical OFDM signals, and sends the selected signals to respective optical network units, thereby achieving the variable-speed access of the optical network units.

The invention discloses an MIMO radar detection method based on double optical frequency combs and difference frequency multiplexing. According to the method, an existing MIMO radar detection technology based on microwave photon orthogonal difference frequency multiplexing is improved, and M paths of modulated optical signals of a transmitting end are generated through the following method: firstly, an optical carrier is divided into an upper path and a lower path; The local oscillator signal is used for carrying out modulation processing on the uplink optical carrier wave to generate a firstoptical frequency comb signal, and the intermediate frequency signal and the intermediate frequency linear frequency modulation signal are used for carrying out modulation processing on the next optical carrier wave to generate a second optical frequency comb signal; After the first optical frequency comb signal and the second optical frequency comb signal are coupled into one path, the first optical frequency comb signal and the second optical frequency comb signal are divided into M paths of modulated optical signals respectively consisting of a single intermediate frequency linear frequencymodulation spectrum line and a single local oscillator signal spectrum line through beam shaping filtering. The invention also discloses an MIMO radar detection device based on the double optical frequency combs and the difference frequency multiplexing. According to the invention, the structure of the transmitter can be greatly simplified, the implementation cost of the system is reduced, and the coherence between signals can be effectively ensured.

The invention provides a water sound frequency hopping communication method for linear modulation signal modulation and demodulation, and relates to a water sound frequency hopping communication. The water sound frequency hopping communication method comprises the following steps: carrying out source encoding on original information so as to obtain compressed digital signals; carrying out channel coding; using data obtained by the channel coding as a linear modulation signal control code; controlling to generate a linear modulation signal according to a frequency hopping sequence as a carrier for modulation, so as to obtain modulation signals; carrying out D/A (Digital/Analogue) conversion and power amplification on the modulation signals; converting the modulated signals into sound waves to spread in an ocean underwater acoustic channel through a transmission energy converter; receiving and converting acoustic signals spreading in the ocean underwater acoustic channel into electric signals through the receiving energy converter; obtaining stimulation signals through front amplification and band-pass filtering; carrying out A/D (Analogue/Digital) conversion on the received stimulation signals; after detecting that the digital signals after the A/D conversion are synchronous, carrying out linear modulation signal demodulation center frequency and demodulation frequency to obtain demodulation data; and carrying out channel decoding on the demodulation data; and carrying out source decoding on the digital signals to obtain information.

The invention provides a multiple-input-multiple-output OFDM shallow sea underwater acoustic communication pattern selection PAR restraining method. By the aid of the manner of multiplying scrambling patterns by sent data, the occurrence probability of an OFDM symbol peak is reduced; and pilot frequency carrying scrambling information of different distribution patterns is used and combined with the sparsity characteristic of a shallow sea underwater acoustic channel, the scrambling patterns are distinguished independently at a receiving end, the pattern selection PAR restrain for sideband-free information is realized, and the efficiency and the reliability of a communication system are effectively improved at the same time. According to an endless information transmission pattern selection PAR restraining algorithm, on the premise that the restrain performance of the PAPR (peak to average power ratio) is not lost, the distribution patterns are calculated accurately, and the reliable underwater acoustic communication for the endless information is realized.

The invention discloses a transmitting method of an HSDPA high-order modulating upstream signal of a TD-SCDMA system, overcomes the problem that existing systems can not indicate a high-order modulating way, and adopts the technical proposal that the method comprises the following steps: 1. a terminal receives a message from a downstream control channel and indicates transmission resource distribution situations of next high-speed downstream sharing channel; 2. the terminal implements channel measurement; 3. the terminal selects proper transmission block size and high-order modulating way according to the resource distribution situations of the high-speed downstream sharing channel and the channel measuring result, and generates channel quality indication; 4. the channel quality indication and acknowledgment information of a hybrid automatic retransmission request are encoded and multiplexed by adopting multiple Hadamard sequences or orthogonal code sequences, and then reported to a base station through a corresponding upstream control channel; and 5. high layers of the base station select proper transmission block size and high-order modulating way according to the channel quality indication report of the terminal and send the proper transmission block size and high-order modulating way to the terminal through the downstream control channel. The transmitting method of the HSDPA high-order modulating upstream signal of the TD-SCDMA system is applied to the field of mobile communication.