Golden Bridge Technology, Inc.

Nec America, Inc.

Gang Yang

Don Li

Jiang Shen

Ning Zhang

A power of a square matrix is determined in a time approximately proportional to the upper integer of the base-2 logarithm of the order of the matrix. A preferred embodiment uses two types of look-up tables and two multipliers for a matrix of 15&#xd7;15, and is applied to a pseudorandom noise (PN) sequence phase correlation or state jumping circuit. An exact state of a PN code can be determined or calculated from applying an appropriate offset value into a control circuit. The control circuit can produce a PN sequence state from the offset value and typically does so within one system clock period regardless of the amount of the offset. Once the exact state is determined, it is loaded into a state generator or linear sequence shift register (LSSR) for generating a subsequent stream of bits or symbols of the PN code. The PN generator system may include state computing logic, a maximum length PN generator, a zero insertion circuit and a zero insertion skipping circuit.

Apparatus and method for immediate non-sequential state transition in a PN code generator

A multi-channel spread-spectrum system separates a data stream, for example from a convolutional encoder and an interleaver, into sub-channel data-sequence signals. For each sub-channel data-sequence signal, m bits are translated to one code of a unique set of orthogonal chip-sequence signals. The other k bits of the same sub-channel data-sequence signal are translated to a distinct phasor. Each phasor is used to modulate the respective chip-sequence signal. A complex-signal combiner combines the real and imaginary components of all the phase-modulated chip-sequence signals into in-phase (I) and quadrature (Q) spread-spectrum multi-channel signals, which are spread by a cell-site specific signature-sequence. The receiver decorrelates the received spread-spectrum signal, preferably with a bank of matched filter (MF) joint-detectors, to recover the bits from all the spread-spectrum sub-channel signals for remultiplexing into the transmitted data stream. The multi-channel spread-spectrum system supports constant data rate throughout the cell by maintaining a large processing gain, at the demultiplexed sub-channel data sequence level, thus a code-reuse-one type spread-spectrum system can be deployed with the aid of power control.

Multi-channel spread spectrum system

A novel power-controlled random-access method allows a mobile station to gain fast access to the base station. At the mobile station, a composite power control command is devised after an initial access attempt. The determination of the composite command uses an open-loop power-control symbol and a closed-loop power-control symbol, to decide the action of the mobile station upon transmission of its next random-access signal. In the preferred embodiment, the composite power control command can specify different levels of increase or decrease in transmission power, and the composite power control command can specify a back-off by the mobile station. This composite power-control mechanism can help resolve collision between mobile stations accessing the same random access sub-channel and therefore maintain a low-delay in the random-access process and a high-utilization on the access-channel resource.

Power-controlled random access

In a burst-mode, high-speed spread-spectrum communications system, faster convergence of a receiver's automatic gain control (AGC) circuit reduces the time required to bring a received signal within the operating range of an operation amplifier and other radio-frequency and digital sections of the receiving system. A gain control circuit includes a coarse-gain feedback loop and a fine-gain feedback loop to improve convergence speed and at the same time maintain the stability of the AGC circuit. The coarse-gain feedback loop quickly brings the received signal, using a large gain signal, to the desired operating range. The fine-gain feedback loop uses a smaller gain signal to gradually smooth the received signal to avoid saturation on the A/D converters.

Method and apparatus of a fast two-loop automatic gain control circuit

A programmable matched filter bank comprises a sliding integrator and compensation calculation circuits. The integrator receives a chip stream of samples derived from a received spread-spectrum signal and integrates a number of the most recent samples, to form a common integration value. Each of the compensation calculation circuits receives the same most recent samples and receives a respective one of the possible reference spreading code sequences. In operation, each compensation calculation circuit derives a compensation value, and an associated circuit modifies the common integration value by the respective compensation value. The result is a value of correlation between the predetermined number of most recent samples, for each respective reference code sequence. The inventive approach reduces the number of bit adders and inverters in the implementation of a matched-filter, a programmable matched filter and a programmable matched filter bank for spread spectrum receivers.

Programmable matched filter bank

A spread-spectrum communication system utilizes spreading code sequences, which can be expressed as a matrix. The matrix of code sequences has or can be transformed to have a certain orthogonal relationship. In accord with the invention, a matched filter bank in a spread-spectrum receiver processes input signals that purport to contain the code matrix using two halves of an input stream matrix and only two of four possible quadrants of the code matrix as the reference inputs. Such processing produces two quadrants of a correlation signal matrix. It is then possible to determine the other two quadrants of the full correlation signal matrix from the known relationship with the two quadrants derived from the matching operations. The processing of only two of the quadrants of the signal matrix substantially reduces the number of computations and the amount of processor hardware needed to implement a matched filter bank to recognize the codes embedded in a received spread-spectrum signal.

Digital matched filter bank for othogonal signal set

A demodulator system for a receiver in a multiple user-code spread-spectrum system, such as in a CDMA base station, utilizes a Quasi-Newtonian optimization routine to identify received codes and recover user data based on detected correlations between the received spread-spectrum signal and a set of the possible codes available to users of the system. The preferred optimization routine is a Davis-Fletcher-Powell (DFP) routine.

Method and apparatus of joint detection of a CDMA receiver

Multi-path effects are common in mobile communications. When coupled with spread-spectrum signals utilizing spreading code sequences, detection of more than one multi-path signal becomes a necessity in order to output a clean signal with little loss. In accord with the invention, a spread-spectrum sliding matched-filter searcher system comprises a partial matched-filter that receives the input spread-spectrum signal. The searcher matches samples of the input signal with a tap length m of the reference code and produces a first correlation value. The first correlation value is compared to a first threshold. When it equals or exceeds the first threshold, the first correlation value is integrated to produce a second correlation value. This second value is compared with a second threshold, which if met signifies the detection of the multi-path signal. The process is repeated until all significant multi-path signals are detected. This design of the present invention is flexible in nature because the searcher can be programmed to act like a matched-filter, a correlator, or a combination of both while significantly improving the search time and reducing the amount of hardware and complexity characteristic of a matched-filter.

Sliding matched filter with flexible hardware complexity

A multi-channel spread-spectrum system separates a data stream, for example from a convolutional encoder and an interleaver, into sub-channel data-sequence signals. For each sub-channel data-sequence signal, m bits are translated to one code of a unique set of orthogonal chip-sequence signals. The other k bits of the same sub-channel data-sequence signal are translated to a distinct phasor. Each phasor is used to modulate the respective chip-sequence signal. A complex-signal combiner combines the real and imaginary components of all the phase-modulated chip-sequence signals into in-phase (I) and quadrature (Q) spread-spectrum multi-channel signals, which are spread by a cell-site specific signature-sequence. The receiver decorrelates the received spread-spectrum signal, preferably with a bank of matched filter (MF) joint-detectors, to recover the bits from all the spread-spectrum sub-channel signals for remultiplexing into the transmitted data stream. The multi-channel spread-spectrum system supports constant data rate throughout the cell by maintaining a large processing gain, at the demultiplexed sub-channel data sequency level, thus a code-reuse-one type spread-spectrum system can be deployed with the aid of power control.

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Eatontown, NJ, United States of America

Gang Yang