To transmit data in a manner to mitigate the deleterious effects of delay spread, the expected coverage areas for multiple transmissions to be sent in multiple time slots are initially determined. Cyclic prefix lengths for these transmissions are selected based on the expected coverage areas. The cyclic prefix length for each transmission may be selected from among a set of allowed cyclic prefix lengths based on the expected coverage area for that transmission, the pilot staggering used for the transmission, and so on. For example, a shorter cyclic prefix length may be selected for each local transmission, and a longer cyclic prefix length may be selected for each wide-area transmission. The selected cyclic prefix lengths may be signaled to the terminals. The transmissions are processed (e.g., OFDM modulated) based on the selected cyclic prefix lengths. The cyclic prefix lengths may be selected periodically, e.g., in each super-frame.

Wireless communication system with configurable cyclic prefix length

An orthogonal frequency division multiplexing signal transmitted from the transmitting end to the receiving end intermittently includes a particular symbol S0 having a predetermined particular pattern in addition to a symbol Sm including data to be transmitted. At the receiving end, the variation in the receiving level and/or the variation in the frequency band of a received signal are detected and corrected on the basis of the received particular symbol S0. Since the particular symbol S0 has a particular pattern, the variation in the level and/or the variation in the frequency are strongly correlated with the variation in the receiving level and/or the variation in the frequency band of the received signal. Consequently, the variation in the receiving level and/or the variation in the frequency band of the received signal can be accurately detected from the particular symbol S0 and consequently high-precision correction can be made.

Method of transmitting orthogonal frequency division multiplexing signal and receiver thereof

An underwater apparatus for transmitting and receiving high rate data and voice communication including a transmitter, a receiver, and a Doppler frequency shift compensator. The transmitter includes a data source comprising digital data to be transmitted by the apparatus through the water, a serial-to-parallel data processor for splitting the serial digital data into n parallel data channels, a n-channel modulator for receiving the n parallel data channels and for modulating those channels with n pairs of ultrasonic carriers to produce a modulated signal. The transmitter also includes a hydrophone for receiving and transmitting the modulated signal. The receiver includes a hydrophone for receiving a modulated signal. The receiver also includes RF circuitry for amplifying and shaping the received modulated signal, a serial-to-parallel data processor for splitting the amplified and shaped data into n parallel channels, a n-channel demodulator for demodulating the shaped signal and for outputting n channels of digital data, and a parallel-to-serial data processor for receiving n parallel channels of data from the demodulator and for combining those channels into serial data. The Doppler compensator measures the frequency of at least one of two unmodulated signals transmitted as part of the modulated signal and compares the measured frequency with a predetermined frequency. Operation of the demodulator is adjusted to compensate for any deviation between the measured and predetermined frequency.

Method and apparatus for carrying out high data rate and voice underwater communication

Techniques for transmitting data in a wireless communication system are described. Physical channels to be sent in a super-frame are identified and allocated time slots in the super-frame. The coding and modulation for each physical channel are selected based on its capacity. The data for each physical channel is selectively encoded based on an outer code rate, e.g., for a Reed-Solomon code, and further encoded based on an inner code rate, e.g., for a Turbo code. The encoded data for each physical channel is mapped to modulation symbols based on a selected modulation scheme. The modulation symbols for each physical channel are further processed (e.g., OFDM modulated) and multiplexed onto the time slots allocated to the physical channel. Data to be sent using another radio technology (e.g., W-CDMA) is also processed and multiplexed onto time slots allocated for this radio technology.

Coding and modulation for broadcast and multicast services in a wireless communication system

A transmitting apparatus includes a first OFDM modulator that generates a first OFDM modulation signal by modulating a first information signal using a first modulation scheme, the first OFDM modulation signal having a plurality of subcarriers. A second OFDM modulator generates a second OFDM modulation signal by modulating a second information signal using the first modulation scheme, the second OFDM modulation signal having a plurality of subcarriers, and that generates a third OFDM modulation signal by changing a second position in an in-phase quadrature-phase plane in which a signal point of the second OFDM modulation signal is positioned, to a third position, the third position being different from a first position in the in-phase quadrature-phase plane in which a signal point of the first OFDM modulation signal is positioned. A multiplexer generates a multiplexed signal to be transmitted in a common frequency band, by multiplexing the first OFDM modulation signal and the third modulation signal. A transmitter transmits the multiplexed signal.

Transmission device, reception device and radio communication method

PURPOSE: To reduce the reception error by multiplexing a signal transmitted by the SS transmission method and an OFDM digital signal in a broad band including a channel for the transmission of the digital signal. CONSTITUTION: Information with high importance is sent by using the SS(spread spectrum) transmission method and other information is sent by using the OFDM (orthogonal frequency division multiplex) transmission method through a channel of the same frequency band. That is, the transmission information is classified by an information classification circuit 8 depending on the importance of information and the important information is sent by using the SS transmission methods 2, 5 and the other information is sent by using the OFDM transmission methods 3, 7. For example, as to video information coded by the MPEG II, the information classification circuit 8 classifies the information into G.O.P header information with high importance and other information. Then the G.O.P header information with high importance is sent by the SS transmission methods 2, 5 and the other information is sent by using the OFDM transmission methods 3, 7. An adder 4 multiplexes signals modulated by modulators 2, 3 on a same channel. COPYRIGHT: (C)1995,JPO

Digital signal transmission method

PURPOSE:To send each OFDM modulation signal at a maximum bit rate per a transmission frequency band by allocating a transmission band in a form that an adjacent spectrum is in contact with spectrums of each OFDM modulation signal and locking a symbol clock phase. CONSTITUTION:At first frequency intervals DELTAf1, DELTAf2 of a carrier of 1st and 2nd OFDM modulation signals are set equal. An interval fbfa between a maximum carrier frequency fa of a 1st signal and a minimum carrier frequency fb of a 2nd signal is selected to be an integral multiple of DELTAf=DELTAf1=DELTAf2. A symbol clock phase of a 1st OFDM modulation signal and that of a 2nd OFDM modulation signal are locked to each other thereby making ideally symbol switching position of the both coincident with each other. Then the setting above is made to set a value N of NDELTAf=fb-fa to be an integer being one or over, then a DFT window applied discrete Fourier transformation to the 1st and 2nd OFDM modulation signals, then the relation of the 1st and 2nd OFDM modulation signals is set to be a relation as shown in figure. Thus, no interference disturbance is caused between them.

Orthogonal frequency division multiplex modulation signal transmission system

PURPOSE: To reduce crosstalk disturbance onto other services and to prevent disturbance from being concentrated on a specific layer even when a large effect is caused only to a specific frequency band in transmission bands due to multi-path disturbance by adopting the specific hierarchical modulation system so as to keep a power spectrum density of an OFDM signal flat in the transmission band. CONSTITUTION: The power to each carrier for each transmission symbol of a multi-carrier signal and the assignment of the modulation system are changed when hierarchical modulation is implemented by changing the power of each carrier and the modulation system for each carrier or each carrier block in the orthogonal frequency division multiplex modulation OFDM system. That is, the system is provided with a mapping memory circuit 3 and the content of correspondence between complex data and each carrier is set to the circuit 3 as a mapping pattern to be registered therein so as to set freely the power of each carrier and the modulation system. A data conversion assignment circuit 4 converts transmission data into complex data based on the mapping pattern of the circuit 3. COPYRIGHT: (C)1995,JPO

Hierarchical modulation system and transmitter-receiver

PROBLEM TO BE SOLVED: To prevent the strength of digital data to be transmitted by each carrier modulating system from being dispersed by equalizing the transmission characteristics of respective carrier modulating systems when the plural carrier modulating systems to be used for orthogonal frequency division multiplexing(OFDM) modulation exist. SOLUTION: On the side of transmission equipment 2a, power is distributed to respective carriers so that the power of a carrier modulated by a 16 QAM modulating system and the power of a carrier modulated by a 32 QAM modulating system can be respectively increased just for about 7 dB and about 10 dB in comparison with the power of a carrier modulated by a QPSK modulating system, an OFDM signal is generated and this signal is sent onto a transmission line 3 and reproduced on the side of reception equipment 4. COPYRIGHT: (C)1999,JPO

Ofdm transmission method, transmission equipment and reception equipment

PROBLEM TO BE SOLVED: To improve responsiveness in a program selecting operation by means of a user by storing an N-page of program information every program so as to instantaneously display the contents of the selected program when the user selects the program. SOLUTION: A control part 7 judges whether or not the number of a last page in the area of a memory 6 corresponding to the program number of the generated program exceeds the N-page, and the memory 6 is controlled so as to stored generated program information in the area corresponding to the program number when it is equal to or below the N-page. In the other hand, when it exceeds the N-pages, it is judged whether the page number of the generated program exceeds the N-page. When it is judged that the page number is equal to or below N-page, after the memory 6 is controlled so as to erase information on the max. page number which is stored in the area corresponding to the program number of the generated program, generated program information is stored in the area corresponding to the program number. When the page number is equal to or below N-page, generated program information is judged to be unnecessary, so that it is not stored in the memory 6 and the succeeding program is received.

Yamada Tsukasa

Papers

Digital signal transmission method

Orthogonal frequency division multiplex modulation signal transmission system

Hierarchical modulation system and transmitter-receiver

Ofdm transmission method, transmission equipment and reception equipment

Fm multiplex broadcasting receiver