US 5,103,459 A · System and method for generating signal waveforms in a CDMA cellular telephone system

Abstract

A system and method for communicating information signals using spread spectrum communication techniques. PN sequences are constructed that provide orthogonality between the users so that mutual interference will be reduced, allowing higher capacity and better link performance. With orthogonal PN codes, the cross-correlation is zero over a predetermined time interval, resulting in no interference between the orthogonal codes, provided only that the code time frames are time aligned with each other. In an exemplary embodiment, signals are communicated between a cell-site and mobile units using direct sequence spread spectrum communication signals. In the cell-to-mobile link, pilot, sync, paging and voice channels are defined. Information communicated on the cell-to-mobile link channels are, in general, encoded, interleaved, bi-phase shift key (BPSK) modulated with orthogonal covering of each BPSK symbol along with quadrature phase shift key (QPSK) spreading of the covered symbols. In the mobile-to-cell link, access and voice channels are defined. Information communicated on the mobile-to-cell link channels are, in general, encoded, interleaved, orthogonal signalling along with QPSK spreading.

Claims49

Dependent claims

A system for modulating an information signal in a spread spectrum communication system, comprising:

means for generating an orthogonal function signal representative of an orthogonal function selected from a plurality of orthogonal functions;
means for generating a pseudorandom noise (PN) signal of a predetermined PN code;
means for combining said orthogonal function signal, said PN signal and an information signal, and for providing a resultant first modulation signal.

A code division multiple access (CDMA) transmission system for spread spectrum modulation and transmission of a plurality of input digital user information signals each intended for a respective recipient user, said transmission system comprising:

spreading means for generating first and second spectrum spreading signals;
pilot channel means for, generating a pilot channel orthogonal function signal representative of a first orthogonal function selected from a set of orthogonal functions, combining said first and second spectrum spreading signals with said pilot channel orthogonal function signal, and providing as an output first and second pilot channel output signals;
a plurality of user channel means each for, receiving a respective one of a plurality of user information signals, generating a user channel orthogonal function signal representative of a selected one of said orthogonal functions of said set of orthogonal functions wherein each user channel orthogonal function signal is of a different orthogonal function with respect to each other user channel orthogonal function signal and said pilot channel orthogonal function signal, combining said received user information signal with said generated user channel orthogonal function signal so as to provide a resultant user channel orthogonalized information signal, combining each resultant user channel orthogonalized information signal with said first and second spectrum spreading signals, and providing as an output from each respective user channel means corresponding first and second user channel output signals;
transmission means for, receiving and converting said first and second pilot channel output signals to analog form, receiving and converting each user channel means first and second user channel output signals to analog form, combining said analog first pilot channel output signal and each analog first user channel output signal to provide a first combined signal, combining said analog second pilot channel output signal and each analog second user channel output signal to provide a second combined signal, combining said first combined signal with a first carrier signal so as to provide a first modulated carrier signal, combining said second combined signal with a second carrier signal so as to provide a second modulated carrier signal, combining said first and second modulated carrier signals as a composite modulated carrier signal, and transmitting said composite modulated carrier signal.

1 more element

In a code division multiple access (CDMA) cellular telephone system, a cell-site transmission system for spread spectrum modulation and transmission of a plurality of input digital user information signals each containing user information intended for a respective recipient user, said transmissin system comprising:

a spectrum spreading signal generator comprising:
(a) an In-Phase channel pseudorandom noise (PN) generator having an output;
and
(b) an Quadrature-Phase channel PN generator having an output;
a pilot channel signal generator comprising:
(a) a pilot channel Walsh function generator having an output;
(b) pilot channel first and second exclusive-OR gates each having a pair of inputs and an output, one input of each of said pilot channel first and second exclusive-OR gates coupled to said pilot channel Walsh function generator output, another input of said pilot channel first exclusive-OR gate input coupled to said In-Phase channel PN generator output, and another input of said pilot channel second exclusive-OR gate input coupled to said Quadrature-Phase channel PN generator output;
(c) pilot channel first and second finite impulse response (FIR) filters each having an input and an output, said pilot channel first FIR filter input coupled to said pilot channel first exclusive-OR gate output and said pilot channel second FIR filter input coupled to said pilot channel second exclusive-OR gate output;
and
(d) pilot channel first and second gain control elements each having a pair of inputs and an output, one input of each of said pilot channel first and second gain control elements receiving a respective one of a plurality of gain control signals, another input of said pilot channel gain first control element coupled to said pilot channel first FIR filter output, and another input of said pilot channel second gain control element coupled to said pilot channel second FIR filter output;
a plurality of user channel signal generators each comprising:
(a) a user channel Walsh function generator having an input and an output, each user channel Walsh function generator input receiving a function select signal;
(b) a user channel first exclusive-OR gate having a pair of inputs and an output, one input of said user channel first exclusive-OR gate for receiving a respective input digital user information signal and another input of said user channel first exclusive-OR gate coupled to said user channel Walsh function generator output;
(c) user channel second and third exclusive-OR gates each having a pair of inputs and an output, one input of each of said user channel second and third exclusive-OR gates coupled to said user channel first exclusive-OR gate output, another input of said user channel second exclusive-OR gate input coupled to said In-Phase channel PN generator output, and another input of said user channel third exclusive OR gate input coupled to said Quadrature-Phase channel PN generator output;
(d) user channel first and second FIR filters each having an input and an output, said user channel first FIR filter input coupled to said user channel second exclusive-OR gate output and said user channel second FIR filter input coupled to said user channel third exclusive-OR gate output;
and
(e) user channel first and second gain control elements each having a pair of inputs and an output, one input of each of said user channel first and second gain control elements receiving a respective one of said plurality of gain control signals, another input of said user channel first gain control element coupled to said user channel first FIR filter output, and another input of said user channel second gain control element coupled to said user channel second FIR filter output;
and
a transmit power amplifier comprising:
(a) first and second sets of digital to analog (D/A) converters, each D/A converter having an input and an output, each D/A converter of said first set having an input coupled to an output of a respective one of said pilot channel first gain control element and said user channel first gain control elements, and each D/A converter of said second set having an input coupled to an output of a respective one of said pilot channel second gain control element and said user channel second gain control elements;
(b) first summer and second summers each having a plurality of inputs and an output, each one of said first summer inputs coupled to an output of a respective D/A converter of said first set of D/A converters and said second summer inputs coupled to an output of a respective D/A converter of said second set of D/A converters;
(c) first and second mixers each having a pair of inputs and an output, one input of said first mixer coupled to said first summer output, another input of said first mixer receiving a first local oscillator signal, one input of said second mixer coupled to said second summer output, and another input of said second mixer receiving a second local oscillator signal;
(d) a third summer having a pair of inputs and an output, one input of said third summer coupled to said first mixer output and another input of said third summer coupled to said second mixer output;
(e) a third mixer having a pair of inputs and an output, one input of said third mixer coupled to said third summer output and another input of said third mixer for receiving an RF carrier signal;
(f) a bandpass filter having an input and an output, said bandpass filter input coupled to said third mixer output;
and
(g) a variable gain RF amplifier having a pair of inputs and an output, one input of said RF amplifier coupled to said bandpass filter output, another input of said RF amplifier for receiving an RF power gain control signal and said RF amplifier output for coupling to an antenna system.

24 more elements

In a code division multiple access (CDMA) communication system, a method for spread spectrum modulation and transmission of a plurality of input digital user information signals each intended for a respective recipient user, said method comprising the steps of:

generating first and second spectrum spreading signals;
generating a pilot channel orthogonal function signal representative of a first orthogonal function selected from a set of orthogonal functions;
combining said first and second spectrum spreading signals with said pilot channel orthogonal function signal so as to form first and second pilot channel output signals;
receiving in parallel a plurality of user information signals each intended for a different recipient user;
generating for each received user information signal a respective user channel orthogonal function signal representative of a selected one of said orthogonal functions of said set of orthogonal functions wherein each user channel means orthogonal function signal is of a different orthogonal function with respect to each other user channel orthogonal function signal and said pilot channel orthogonal function signal;
combining each user information signal with a respective user channel orthogonal function signal so as to form a respective resultant user channel orthogonalized information signal;
combining each user channel orthogonalized information signal with said first and second spectrum spreading signals so as to form respective pairs of first and second user channel output signals;
converting said first and second pilot channel output signals to analog form;
converting each each pair of first and second user channel output signals to analog form;
combining said analog first pilot channel output signal and each analog first user channel output signal so as to form a first combined signal;
combining said analog second pilot channel output signal and each analog second user channel output signal so as to form a second combined signal;
generating first and second carrier signals;
combining said first combined signal with said first carrier signal so as to form a first modulated carrier signal;
combining said second combined signal with said second carrier signal, so as to form a second modulated carrier signal;
combining said first and second modulated carrier signals so as to form a composite modulated carrier signal;
and
transmitting said composite modulated carrier signal.

14 more elements

Dependencies are inferred from the claim text.

System and method for generating signal waveforms in a CDMA cellular telephone system

Life of this patent

System and method for generating signal waveforms in a CDMA cellular telephone system

Life of this patent

Abstract

Claims49