A multiple-access MIMO WLAN system that employs MIMO, OFDM, and TDD. The system (1) uses a channel structure with a number of configurable transport channels, (2) supports multiple rates and transmission modes, which are configurable based on channel conditions and user terminal capabilities, (3) employs a pilot structure with several types of pilot (e.g., beacon, MIMO, steered reference, and carrier pilots) for different functions, (4) implements rate, timing, and power control loops for proper system operation, and (5) employs random access for system access by the user terminals, fast acknowledgment, and quick resource assignments. Calibration may be performed to account for differences in the frequency responses of transmit/receive chains at the access point and user terminals. The spatial processing may then be simplified by taking advantage of the reciprocal nature of the downlink and uplink and the calibration.

MIMO WLAN system

A MIMO system supports multiple spatial multiplexing modes for improved performance and greater flexibility. These modes may include (1) a single-user steered mode that transmits multiple data streams on orthogonal spatial channels to a single receiver, (2) a single-user non-steered mode that transmits multiple data streams from multiple antennas to a single receiver without spatial processing at a transmitter, (3) a multi-user steered mode that transmits multiple data streams simultaneously to multiple receivers with spatial processing at a transmitter, and (4) a multi-user non-steered mode that transmits multiple data streams from multiple antennas (co-located or non co-located) without spatial processing at the transmitter(s) to receiver(s) having multiple antennas. For each set of user terminal(s) selected for data transmission on the downlink and/or uplink, a spatial multiplexing mode is selected for the user terminal set from among the multiple spatial multiplexing modes supported by the system.

MIMO system with multiple spatial multiplexing modes

Pilots suitable for use in MIMO systems and capable of supporting various functions are described. The various types of pilot include - a beacon pilot, a MIMO pilot, a steered reference or steered pilot, and a carrier pilot. The beacon pilot is transmitted from all transmit antennas and may be used for timing and frequency acquisition. The MIMO pilot is transmitted from all transmit antennas but is covered with different orthogonal codes assigned to the transmit antennas. The MIMO pilot may be used for channel estimation. The steered reference is transmitted on specific eigenmodes of a MIMO channel and is user terminal specific. The steered reference may be used for channel estimation. The carrier pilot may be transmitted on designated subbands/antennas and may be used for phase tracking of a carrier signal. Various pilot transmission schemes may be devised based on different combinations of these various types of pilot.

Pilots for mimo communication systems

A method and apparatus for pilot-symbol aided channel estimation in a wireless digital communication system which transmits packets of N OFDM data blocks, each data block comprising a set of K orthogonal carrier frequencies. At the transmitter, pilot symbols are inserted into each data packet at known positions so as to occupy predetermined positions in the time-frequency space. At the receiver, the received signal is subject to a two-dimensional inverse Fourier transform, two-dimensional filtering and a two-dimensional Fourier transform to recover the pilot symbols so as to estimate the channel response.

Pilot-aided channel estimation for OFDM in wireless systems

System traffic may be arranged into different categories (e.g., control data, user data, and pilot data). For each category, one or more OFDM symbols of the proper sizes may be selected for use based on the expected payload size for the traffic in that category. For example, control data may be transmitted using OFDM symbols of a first size, user data may be transmitted using OFDM symbols of the first size and a second size, and pilot data may be transmitted using OFDM symbols of a third size or the first size. In one exemplary design, a small OFDM symbol is utilized for pilot and for transport channels used to send control data, and a large OFDM symbol and the small OFDM symbol are utilized for transport channels used to send user data.

Ofdm communication system with multiple ofdm symbol sizes

A digital signal modulation analysis device is to shorten the time for modulation analysis, and at the same time to structure a measurement device that is small in scale and inexpensive. A digital signal modulation analysis device includes a frequency converter which converts a signal from a device under test to a first intermediate frequency signal, a sampling part which converts the first intermediate frequency signal to a second intermediate-frequency signal whose frequency is lower than that of the first intermediate frequency to store the second intermediate frequency signal in a memory, a Hilbert converter which converts an incoming signal into orthogonal component signals through a quadrant-modulate detection process, an initial synchronization part which determines a carrier center frequency, a symbol-demodulation/parameter-estimation part which determines optimal parameters to minimize a modulation error and demodulates all symbol data to determine reference data for the all symbol data, and a modulation-precision calculation component which calculates modulation-precision data and modulation-error data for each symbol.

Digital signal modulation analysis device

An apparatus and method for measuring power of carrier channel in question and power leaked from an adjacent channel (leakage power) of a transmitter, and calculating a ratio between the leakage power and the carrier power in the time domain using a digital signal processing technique. The power measurement apparatus includes a frequency mixer which receives a signal from a transmission channel in consideration, an A/D converter for converting an output of the frequency mixer to a digital signal, a Hilbert converter for converting the digital signal into a complex signal, a low pass filter for removing low frequency components from the output signal of the Hilbert converter, a bandpass filter for separating the output of the low pass filter into the carrier power and the leakage power, and a power processing unit for computing the ratio between the leakage power and the carrier power.

Leakage power measurement apparatus and method

The analyser (1) comprises a multiple sine wave signal generator (10) operating with a sample signal generator (11), D-A converters (12,13), deep pass filters (14,15) and a quadrature modulator (16) to produce a signal consisting of a synthesis of several sine waves of different frequencies within a chosen band. This signal is applied to the DUT i.e. component or equipment under test (3). The measuring signal then transmitted from the DUT to the analyser is changed to a digital value through an A-D converter (35), and fed into a signal processor (30) where it is conducted through a quadrature analysis section (36) and fast Fourier transformation (43) to the phase/amplitude comparator (44) for evaluation. The system ensures high accuracy of measurement in a very short time span.

Electrical mains supply analyser for components or equipment

A digital signal modulation analyser has a frequency changer which converts the output signal of the equipment under test to a first intermediate frequency signal using a mixer stage (102). A second mixer stage (202) forms the input module of a signal scanner (250) in which, after further frequency reduction and low-pass filtering (210), the resultant is digitally converted (220) and stored (240) as 252 word symbol data formats.This data is further resolved into its quadrature vector components by a Hilbert converter (310) and demodulation of individual symbols undertaken (740, 400, 900) using self-identified optimum values of the several variable parameters to minimise modulation error.

Compact digital signal modulation analyser for digital multiple channel access

PURPOSE:To analyze a modulation signal in a short time and to provide a measurement device with a small size at a low cost. CONSTITUTION:This analyzer is provided with a frequency conversion section 190 converting a DUT signal into an intermediate frequency signal, a sampling section 250 converting the intermediate frequency signal into a further lower intermediate frequency signal, A/D-converting the signal and storing the converted signal into a memory, a Hilbert conversion section 310 applying orthogonal detection to the signal to convert it into I and Q components, an initial synchronization section 740 obtaining a carrier center frequency OMEGAf0 and a slot synchronization address dly0, a total symbol demodulation/parameter estimate section 400 that obtains an optimum parameter (gain constant, initial phase, carrier frequency, burst droop factor) minimizing a modulation error e, demodulates demodulation data (amplitude A[n] and phase angle theta(n)) of all symbols and specifies ideal data (amplitude Ar(n) and phase angle thetar(n)) of all symbols and a modulation accuracy arithmetic section 900 obtaining the modulation accuracy data epsilon and modulation error data for each symbol.

Masao Nagano

Papers

Digital signal modulation analysis device

Leakage power measurement apparatus and method

Electrical mains supply analyser for components or equipment

Compact digital signal modulation analyser for digital multiple channel access

Digital modulation analyzer