摘要:
A receiver for the third-generation (“3G”) CDMA wireless system is disclosed. The receiver is adapted to mitigate the correlated interference by adaptive antenna process which will maximize the signal-to-interference-plus-noise ratio. After the mitigation of correlated interference from first step space process, the second step is to counter fading with MRC which is optimum after the mitigation of correlated interference. After these first two steps of interference mitigation by adaptive antennas and fading compensation through MRC, the decision signal for the first stage of MPIC will have the strongest desired part and least interference compared to any MPIC available. As can be appreciated, the first stage BER of the present receiver will be the lowest. Then, this low BER will result in a more accurate MAI regeneration, which will further cause a lower BER for the next stage and any subsequent stages. Therefore, the BER of the receiver of the present invention is more likely to converge to the BER of a single user, i.e. MAI-free, faster than those in the conventional systems. In other words, for a given BER requirement, the receiver of the present invention will take the least number of iterations to achieve.
摘要:
This invention relates to a receiver of an ultra wide band signal and the associated method. The receiver comprises: means (7) of outputting two orthogonal signals by projection of the received signal (R(t)) onto two periodic orthogonal functions with frequency approximately equal to the central frequency of the received signal, sampling means (7) of two orthogonal signals to output a discrete data stream (X(k), Y(k)) with two components, estimating means (8) for calculating a reference signal starting from the discrete data stream with two dimensions, and comparison means (9) for comparing all or some of the data contained in the discrete data stream with all or part of the data forming the reference signal. The invention is applicable to high-speed transmissions and positioning of transmitters/receivers.
摘要:
In a chip radio communication system, a novel technique for increasing the number of transmitters, or users, that can be simultaneously accommodated in the communication system and the data capacity of the system without increasing frequency bandwidth. A system may include plural transmitters, receivers, and a central station for establishing chirp radio communications. Each receiver may discriminate between chirp radio transmitter type based on the differing chirp signal characteristics.
摘要:
Systems and methods for despreading received spread spectrum signals are described. Despreading can be performed using both channel estimates and impairment correlation estimates. Techniques for selecting delays of interest are also described, along with a despreading mechanism which saves power by operating only on delays of interest.
摘要:
A method of channel estimation in a Code Division Multiple Access (CDMA) transmission system that incorporates Pilot Symbol Assisted Modulation (PSAM) using an iterative coherent detection method to estimate the phase and frequency of the received pilot symbols. Arctangent calculations are used to estimate phase and frequency. An iterative least squares linearization identifies and corrects values of the arctangent associated with an incorrect 2π alias, which arise due to the multiple-valued nature of the arctangent function. An alternative non-iterative least squares linearization also corrects the arctangent values, based on a calculation involving stored values of the pilot symbols.
摘要:
The present invention is a system and method for increasing user capacity on a slotted random access channel in a spread spectrum communications system by using a multi-part access probe. First and second parts of the access probe are modulated using a short PN code sequence, and the entire access probe is modulated using a long PN code sequence. Information to be transmitted by the access probe is modulated on the second part of the access probe, and the access probe is transmitted so that the first part of the probe falls within the boundaries of an access channel slot. In one embodiment, time slots in access channels used for access signal reception are made the length of the first part. In a further embodiment, time slots in a plurality of adjacent access channels used for access signal reception may be longer than said first part but are offset in time from each other by the length or period of the first part.
摘要:
A spread spectrum transmitter and receiver are provided wherein data can be accurately decoded by removing the effect of mutual interference of the quadrature component and in-phase component even when there is carrier frequency error. In a method of spread spectrum communication using a QPSK modulation system, there are provided: a demodulating circuit that receives and demodulates a signal transmitted with a prescribed time difference Td applied between the IQ components; correlators that find the mutual correlation of the IQ components and spreading code; a sampling circuit that samples their output signals; a phase calculator that calculates the phase from the ratio of the IQ components of these output signals; a differential decoding circuit that performs differential decoding on this output signal; an automatic frequency control circuit that corrects the frequency error of this output signal; a decoding circuit; and a clock recovery circuit.
摘要:
A spread-spectrum signal receiving method and apparatus in which a correlation operation is performed for obtaining a correlation between a base-band component of a received spread-spectrum signal and a spread code, so as to demodulate the received signal. In the method, a correlation operation between the spread code and the base-band component, and a correlation operation at a timing equal to a timing difference between the spread code and the base-band component in the former correlation operation step, the timing difference being 1/2 of a spread-code interval, are performed. Then, based on results obtained in these correlation operations, a correlation operation result at the timing point where a timing difference between the spread code and the base-band component is less than 1/2 of the spread-code interval, is estimated.
摘要:
The present invention provides a spread spectrum radio transmission digital mobile communication device having RAKE receiving functions and capable of decreasing influence of a delay wave having a delay time smaller than chip time width of a diffusion signal. The device includes an inverse diffusion circuit for taking correlation of a received signal and the diffusion signal to perform inverse diffusion, a synthesizing circuit for synthesizing paths by giving the delay time to match paths to the inversely diffused signals, whereby a plurality of receiving branches are provided, variable gain amplifiers for adjusting amplification factor of signals received at each of the receiving branches, an adder for adding the signals outputted from each of the variable gain amplifiers and for inputting to the inverse diffusion, and a gain controller for controlling amplification factor of the variable gain amplifiers to decrease influence of the delay wave having a delay time smaller than chip time width of the diffusion signal in the signals inputted to the inverse diffusion circuit. By adding an arrangement of an adaptive antenna to control directivity of a receiving antenna to a spread spectrum radio transmission digital mobile communication device having RAKE receiving functions, it is possible to decrease influence of a co-channel interference wave and influence of a delay wave having a delay time smaller than chip time width in a diffusion signal which are not achievable by RAKE receiving functions.
摘要:
A frequency hopping-communications system, assigned a system bandwidth B, with the system bandwidth B divided into N sets of frequencies, with each set of the N sets of frequencies not having the same frequencies as other sets of the N sets of frequencies, for communicating base-message data to a plurality of remote units. The frequency-hopping-communications system includes a plurality of base stations for communicating base-message data to the plurality of remote units. Each of the base stations has a coverage area divided into a plurality of concentric regions with each concentric region assigned one of the N sets of frequencies. For communicating with a selected-remote unit located within a particular-concentric region, each base station has a frequency-hopping device for frequency hopping the base-message data over a set of frequencies assigned to the particular-concentric region, thereby generating a frequency-hopped signal, a controller, responsive to the selected-remote unit being located in the particular-concentric region, for controlling the set of frequencies use by said frequency-hopping device, and a base antenna coupled to the power amplifier for radiating the frequency-hopped signal. Each of the remote units has a receiver for recovering the base-message data from the frequency-hopped signal.