Techniques to more efficiently transmit pilot and signaling on the uplink in an OFDM system. With subband multiplexing, M usable subbands in the system are partitioned into Q disjoint groups of subbands. Each subband group may be assigned to a different terminal for uplink pilot transmission. Multiple terminals may transmit simultaneously on their assigned subbands. The transmit power for the pilot may be scaled higher to attain the same total pilot energy even though S instead of M subbands are used for pilot transmission by each terminal. Pilot transmissions from the terminals are received, and a channel estimate is derived for each terminal based on the pilot received on the assigned subbands. The channel estimate comprises a response for additional subbands not included in the assigned group. Subband multiplexing may also be used for uplink signaling transmission.

Uplink pilot and signaling transmission in wireless communication systems

A method and apparatus are provided for providing an acknowledgement (ACK) message combined with one or more communication message of a data packet that is transmitted using a single channel. The method comprising acts of associating the ACK with a channel ID of a recipient; building the ACK information data pattern, wherein the length of the ACK message is based on number of ACK messages to be transmitted; and combining the ACK information data pattern with one or more communication message by applying an encoding scheme over the combined message.

A method and apparatus of using a single channel to provide acknowledgement and assignment messages

Method and apparatus for OFDM synchronization and channel estimation. In a temporal embodiment, received embedded system pilot symbols are inverse Fourier transformed at expected index locations and correlated with computed complex conjugates of inverse Fourier transforms of pilot symbols for providing a correlation function for the channel impulse response. In a frequency domain embodiment, embedded system pilot symbols are augmented with pilot-spaced inferred guard band symbols, multiplied by scaled complex conjugates of computed pilot systems, and inverse Fourier transformed into the channel impulse response. Time and frequency are synchronized in feedback loops from information in the channel impulse response. The channel impulse response is filtered, interpolated, and then Fourier transformed for determining channel estimates for equalization.

Method and Apparatus for Multicarrier Channel Estimation and Synchronization Using Pilot Sequences

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

A closed form formula is derived for the bit error rate (BER) of orthogonal-frequency-division-multiplexing (OFDM) with M-ary differential-phase-shift-keying (MDPSK) systems in frequency-selective Rayleigh and Rician fading channels with diversity reception. New BER curves are obtained as a function of the rms delay spread of the diffused component for three different types of delay profiles: (1) one-sided exponential, (2) uniform and (3) double spike profiles. Both slow and fast fading conditions are considered. It is shown that the existence of a strong line-of-sight (LOS) component and the use of reception diversity can effectively improve transmission performance.

BER performance of OFDM-MDPSK system in frequency-selective Rician fading with diversity reception

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

PROBLEM TO BE SOLVED: To provide a retransmitter capable of reducing bandwidth when a digital broadcast signal is retransmitted. SOLUTION: An apparatus 10 which receives digital broadcast signals comprised of a plurality of segments from a plurality of broadcasting stations and transmits an ISDB-T signal on the basis of the received signals, is provided with a plurality of receiving parts 200 for receiving digital broadcast signals by channels; a carrier selection circuit 203 for selecting at least one of segments in the received digital broadcast signals, by channels, on the basis of a preset segment number; a segment delay control circuit 301 for carrying out synchronization of selected signals; a carrier symbol composition circuit 303 for converting phases of carriers constituting a synchronized segment by channels and connecting a plurality of phase-converted carriers; and a transmission conversion circuit 305 for transmitting a connected signal from a predetermined channel that is different from the channel. COPYRIGHT: (C)2006,JPO&NCIPI

Digital broadcast signal retransmitter

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

PROBLEM TO BE SOLVED: To provide an OFDM signal demodulating device which can perform an effective soft decision decoding operation by making every carrier obtained by an FFT circuit equalize the amplitude and phase of the complex data based on a reference symbol obtained by a reference symbol estimating circuit and using the said reference symbol as the reliability information on the soft decision decoding operation. SOLUTION: An OFDM receiving signal 10 undergoes FFT via an FFT circuit 11 and the complex data on every carrier are obtained. A pilot symbol extracting circuit 12 extracts the complex data equivalent to the position of a pilot symbol included in a frame constitution from the complex data obtained by the circuit 11. A demodulated data equalizing circuit 14 corrects the transmission line characteristic of the complex data on every carrier obtained by the circuit 11 based on a reference symbol that is obtained by a reference symbol estimating circuit 13. Thus, the corrected complex data are obtained and then demapped by a demapping circuit 15 to obtain the soft decision data.

Ofdm signal demodulating device

PROBLEM TO BE SOLVED: To suppress equivalent errors resulting from transmission line distortion and thermal noise, which occur during equalization of a receiving wave, in spite of the number of receiving antennas SOLUTION: A receiving section 10 converts a receiving signal into a base band digital signal, performs quadrature detection and discrete Fourier- transform, and outputs carrier data of an OFDM wave A local signal for this frequency conversion is fed by a synchronous circuit section 40 In a repeating process section 20, an equalization circuit 201 equalizes input carrier data, a discrimination circuit 202 discriminates the values of incoming data, and a pilot insertion circuit 203 newly inserts a previously prepared correct pilot into the carrier data A transmission section 30 performs inverse discrete Fourier-transform and quadrature modulation on the carrier data that the correct pilot is newly inserted into, converts the data into an OFDM signal of a desired frequency, and then sends the signal

Shunji Nakahara

Papers

Digital signal transmission method

Digital broadcast signal retransmitter

Orthogonal frequency division multiplex modulation signal transmission system

Ofdm signal demodulating device

Ofdm digital signal repeater