A method and apparatus for allocating subcarriers in an orthogonal frequency division multiple access (OFDMA) system is described. In one embodiment, the method comprises allocating at least one diversity cluster of subcarriers to a first subscriber and allocating at least one coherence cluster to a second subscriber.

Ofdma with adaptive subcarrier-cluster configuration and selective loading

A method and apparatus are provided for performing acquisition, synchronization and cell selection within an MIMO-OFDM communication system. A coarse synchronization is performed to determine a searching window. A fine synchronization is then performed by measuring correlations between subsets of signal samples, whose first signal sample lies within the searching window, and known values. The correlations are performed in the frequency domain of the received signal. In a multiple-output OFDM system, each antenna of the OFDM transmitter has a unique known value. The known value is transmitted as pairs of consecutive pilot symbols, each pair of pilot symbols being transmitted at the same subset of sub-carrier frequencies within the OFDM frame.

System access and synchronization methods for mimo ofdm communications systems and physical layer packet and preamble design

Multi-carrier communications with adaptive cluster configuration and switching

A method and apparatus for antenna switching, grouping, and channel assignments in wireless communication systems. The invention allows multiuser diversity to be exploited with simple antenna operations, therefore increasing the capacity and performance of wireless communications systems. Channel characteristics indicative of signal reception quality for downlink or bi-directional traffic for each channel/antenna resource combination are measured or estimated at a subscriber. Corresponding channel characteristic information is returned to the base station. Channel characteristics information may also be measured or estimated for uplink or bi-directional signals received at each of multiple receive antenna resources. The base station employs channel allocation logic to assign uplink, downlink and/or bi-directional channels for multiple subscribers based on channel characteristics measured and/or estimated for the uplink, downlink and/or bi-directional channels.

Method and system for switching antenna and channel assignments in broadband wireless networks

Apparatus in a receiver, for processing transmitted entitlement control information, includes a packet transport processor for selecting signal packets having payloads containing a conditional access payload header and a remaining payload of entitlement data. Respective payload headers include groups of bytes which are coded in a manner to allow or disallow the respective receiver from processing the entitlement data. A conditional access filter preprogrammed with a subscriber specific conditional access codeword examines respective byte groupings of the conditional access header for a match with the subscriber specific conditional access codeword. Only if a match occurs is the processor permitted to process the entitlement data. The entitlement data is thereafter utilized to generate decryption keys for descrambling portions of the transmitted signal.

Conditional access filter as for a packet video signal inverse transport system

Received OFDM signals are transformed from a time domain into a frequency domain by Fourier transformation (12) to generate a vector sequence of each carrier wave in the frequency domain. Necessary dispersion pilot signals and termination pilot signals are extracted (13) from the vector sequence and divided (15) by a modulation complex vector to estimate transmission line characteristics relative to the dispersion/termination pilot signals, and the transmission line characteristics are interpolated (16) to estimate transmission line characteristics relative to the information transmission carrier wave of a synchronous detection segment. The vector sequence is delayed (17) by one symbol. The interpolation output is selected (18) in the case of the synchronous detection segment, and the delay output is selected (18) in the case of a differential detection segment. The vector sequence is divided (19) by the selected output, and the result is subjected to synchronous detection or differential detection and demodulated (20) to generate digital information. Thus, high quality demodulation and demodulation suitable for mobile reception are realized.

Orthogonal frequency-division multiplex transmission system, and its transmitter and receiver

A frequency interleaving circuit frequency-interleaves main signals generated according to sound data by parameters set according to frequencies of transmission channels. A sub-signal generating circuit generates sub-signals for transmission control including pilot signals. Mapping circuits modulate the sub-signals by using pseudo-random sequences generated based on initial values of random codes set according to frequencies of transmission channels. The frequency-interleaved main signals and the sub-signals modulated by the mapping circuits are OFDM-modulated. Then, they are converted to the frequencies of the transmission channels. An increase of a dynamic range of transmission signals can be suppressed by controlling the initial values of random codes set.

Digital broadcasting apparatus

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

PROBLEM TO BE SOLVED: To provide a receiver for ground digital broadcast that reduces a time for frame synchronization establishment that is a main cause to a delay time when a channel is switched. SOLUTION: In the ground digital broadcast transmission method and its receiver adopting the OFDM system, in order to set up frame synchronization in a short time even at broadcast channel switching, initialization of energy diffusion is executed at a place other than a head of an OFDM transmission frame. A transmission symbol of a TMCC(Transmission and Multiplexing Configuration Control) carrier is shifted by a predetermined symbol number for each TMCC carrier and transmitted, and a frame synchronizing signal is transmitted by using an AC(Auxiliary Channel) carrier so as to reduce the time from channel switching until signal decoding.

Makoto Sasaki

Papers

Orthogonal frequency-division multiplex transmission system, and its transmitter and receiver

Digital broadcasting apparatus

Digital signal transmission method

Orthogonal frequency division multiplex modulation signal transmission system

Digital transmission method and receiver