Pulse or digital communications – Spread spectrum
Patent
1997-11-24
2000-10-24
Chin, Stephen
Pulse or digital communications
Spread spectrum
375133, 375147, 375149, 375136, H04B 1500
Patent
active
061378240
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for estimating signal quality, the method being used in a spread spectrum radio system having several transmitters and receivers, and in which each transmitted signal is pseudonoise-coded by a separate spreading code into a wideband form and the signal being converted into modulation symbols having a vector form, said modulation symbols being submatrices of a substantially orthogonal known transform matrix, said submatrices being chosen on the basis of a combination of bits to be transmitted, the signal being multiplied by a spreading code in the receiver in which a correlation is formed between the received modulation symbols and the known transform matrix, the correlation forming correlation vectors which comprise correlation values and by means of which the signal is detected.
The invention further relates to a method for estimating the quality of noise, the method being used in a spread spectrum radio system having several transmitters and receivers, and in which each transmitted signal is pseudonoise-coded by a separate spreading code into a wideband signal and the signal being converted into modulation symbols having a vector form, said modulation symbols being submatrices of a substantially orthogonal known transform matrix, said submatrices being chosen on the basis of a combination of bits to be transmitted, the signal being multiplied by a spreading code in the receiver in which a correlation is formed between the received modulation symbols and the known transform matrix, the correlation forming correlation vectors which comprise correlation values and by means of which the signal is detected.
The invention additionally relates to a receiver of a spread spectrum radio system, the system comprising several transmitters and receivers, each transmitted signal in the system being pseudonoise-coded by a separate spreading code into a wideband signal and the signal being converted into modulation symbols having a vector form, said modulation symbols being submatrices of a substantially orthogonal known transform matrix, said submatrices being chosen on the basis of a combination of bits to be transmitted, the signal being multiplied by a spreading code in the receiver which comprises a correlator for forming a correlation between the received modulation symbols and the known transform matrix, the correlation forming correlation vectors which comprise correlation values and by means of which the signal is detected.
BACKGROUND OF THE INVENTION
In a spread spectrum radio system, and particularly in a CDMA technique, the narrowband data signal of the user is modulated by a spreading code of much wider bandwidth to a relatively wide band. In the known experimental systems, the bandwidths used include, for example, 1.25 MHz, 10 MHz and 50 MHz. The spreading code usually consists of a long pseudo-random sequence of bits. The bit rate of the spreading code is much higher than that of the data signal, and to make a distinction between data bits and symbols, the bits of the spreading code are referred to as chips. Each data symbol of a user is multiplied by all the spreading code chips. Consequently, the narrowband data signal spreads to the frequency band used by the spreading code. The signal of each user has a separate spreading code. Several users transmit their signals simultaneously by using the same frequency band, and the signals from the users can be identified from one another in the receivers on the basis of the pseudo-random spreading code.
Regardless of the efficient interference and fading protection based on spread spectrum technology, the connection quality, affected by the signal and noise quality, between a base station and a mobile station in the radio system constantly varies. The variation results from disturbance present on the radio path and the attenuation of radio waves as a function of distance and time in the channel fading out. The connection quality can be measured for example by monitoring the strength level recei
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Chin Stephen
Liu Shuwang
Nokia Telecommunications Oy
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