Nec Corporation

Filip Zalio

Vasic Dobrica

Duong Pham

Dobrica Vasic

Holly He

Mikhail Shnaider

A device for performing channel estimation in an OFDM system includes a non-volatile memory, a G matrix selector and a channel estimate generator. The non-volatile memory stores a set of G matrices indexed by signal to noise ratio, the G matrices being precalculated for a plurality of signal to noise ratios using a fixed Doppler frequency and a fixed delay spread. The G matrix selector uses a quantised signal to noise ratio to select a G matrix from the set of G matrices stored in the non-volatile memory. The channel estimate generator multiplies the selected G matrix by LS estimates for the reference signal to obtain a channel estimation.

Channel estimation for OFDM systems

The invention is suitable for use in an OFDM system, such as the 3GPP-LTE mobile phone system. A method of estimating Doppler spread in a mobile communications device includes: (a) selecting a channel estimate from each of a sequence of time slots at each of a series of selected sub-carrier frequencies; (b) performing a Digital Fourier Transform (DFT) on the selected channel estimates at each selected sub-carrier frequency to thereby compute DFT components at different frequency bins; (c) summing the DFT components at all selected sub-carrier frequencies for each different frequency bin; (d) detecting the frequency bin at which the summed DFT components first falls below a predetermined threshold; and (e) converting the detected frequency bin into a Doppler spread estimate.

Device and method for estimating doppler spread in a mobile communications terminal

In a method of identifying a time reference in signal received from a transmitter, a replica of a synchronization sequence is generated on the basis of at least one known transmission parameter and is compared to a sequence derived from the signal received from the transmitter to identify a reference point in the signal received from the transmitter.

Time reference identification method

A method of scheduling cell search activity in a mobile communication user terminal () during transmission gap sequencing in burst mode, the method comprising the steps of:

Method of scheduling cell search operations

A method of cancelling interference induced by a coherent interference source in a spread spectrum receiver comprising the steps of: quantifying () first interference values induced by the coherent interference source (SCH) in symbols on a first spread spectrum physical channel (P-CCPCH; CPICH); calculating () second interference values induced by the coherent interference source in symbols on a second spread spectrum channel (DPCH) from the first interference values; and applying () a correction value, derived from the second interference values, to the symbols on the second spread spectrum channel.

Interference cancellation in a spread spectrum receiver

A method of cell search in a wireless communication systems having a plurality of base stations and a mobile station, each of the plurality of base stations serving a separate cell within a service area and transmitting a common primary synchronization code (PSC) in a primary synchronization channel within a slot of a radio frame, the method including the steps of: (a) scanning () through radio channels in scanning increments corresponding to a standard channel raster; (b) estimating () the PSC signal-to-noise ratio of each radio channel; (c) if a PSC signal-to-noise ratio is above a first predetermined threshold level (), completing a cell search procedure including slot synchronization, frame synchronization and scrambling code detection steps for that radio channel; (d) if the cell search procedure is successfully completed () for the radio channel in step (c), increasing the scanning increments to the broadcast frequency separation between cells; (e) when all radio channels are scanned in step (d), sorting () the scanned radio channels in descending order by PSC signal-to-noise ratio; and (f) performing () the cell search procedure on each sorted radio channel in descending order.

Cell search process for wireless communication system

A method of performing a continuous cell search for new cells in a wireless communication systems having a plurality of base stations and a mobile station, the method including the steps of: (a) using (1) a primary synchronization code to acquire slot synchronization for identified cells; (b) using (2) a secondary synchronization code to find frame synchronization and identify a code group of the identified cells; (c) determining (3) a primary scrambling code used by the identified cells; and (d) rejecting (4) cells corresponding to previously identified primary scrambling codes from post-processing, wherein the method further includes the steps of: (e) correlating slot timings identified in step (a) with frame timings corresponding to primary scrambling codes identified in previous runs of steps (b) and (c); and (f) rejecting slot timings identified in step (a) from further processing in steps (b) and (c) when correlation is detected.

A clock generation circuit for a dual system radio frequency station is provided. The station includes a digital synthesis circuit clocked by a first clock signal for a first RF system that is adapted to generate a base signal output of a predetermined frequency. A second clock signal is derived from the sum of the frequency of the base signal and the frequency of the first clock signal.

Method and circuit for deriving a second clock signal from a first clock signal

An automatic gain control circuit () for a direct sequence spread spectrum receiver. A discrimination unit () generates a discrimination signal error from received in-phase and quadrature base band signals, whilst multiplication unit () multiplies the discrimination signal error by a first loop gain constant during signal acquisition and a second different loop gain constant during signal tracking. A recursive integrator () then acquires an integrated AGC value from the multiplied discrimination signal error. By using two different values of loop gain, the circuit is able to alternate between a 'fast mode' during signal acquisition, and a 'slow track' mode during signal tracking.

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Victoria, Australia

Filip Zalio