Structure of a coherent dual channel QPSK transceiver using pilot symbols in a code division multiple access system

• US 6,219,374 B1
• Filed: 07/14/1998
• Issued: 04/17/2001
• Est. Priority Date: 11/25/1997
• Status: Expired due to Term

• Current Assignee: Pil Woo Park
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kang, Sugbong, Kim, Seong Rag, Lee, Jeong Goo
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Tran, Khai
• Application Number:
  US09/115,072
• Time in Patent Office: 1,008 Days
• Field of Search: 375/130, 375/135, 375/136, 375/139, 375/219, 375/316, 375/320, 375/329, 375/295, 370/208, 370/209, 370/342, 370/335, 370/515
• US Class Current: 375/130
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04L 25/0202 Channel estimation
• CPC Class Codes: H04L 27/206 using a pair of orthogonal carriers, e.g. quadrature carriers
• CPC Class Codes: H04L 27/227 using coherent demodulation

Abstract

The present invention proposes a structure of a coherent dual-channel QPSK transceiver using pilot symbols in a code division multiple access system, which can reduce the variation width of the entire transmission signal by putting pilot symbols into data bit streams, can remove a crosstalk by separating input information bits into two channels and then allocating different quadrature codes to respective channels, and can also improve the error performance of the entire system by preventing changes in phases of the transmission carrier and reducing the degree of the envelope variation of the entire signals.

Claims

1. A coherent dual-channel Quadrature Phase Shift Keying (QPSK) transceiver device using pilot symbols in a code division multiple access system, comprising:

a serial-to-parallel converter for dividing a communication signal which comprises data bits into an in-phase channel signal and a quadrature channel signal;

a first pilot symbol adder for periodically inserting pilot symbols into said in-phase channel signal;

a second pilot symbol adder for periodically inserting said pilot symbols into said quadrature channel signals;

first and second mixers for spreading said in-phase channel signals and said quadrature channel signals into which said pilot symbols are periodically inserted using different Walsh codes;

third and fourth mixers for spreading said in-phase channel signals and said quadrature channel signals which have been spread by said different Walsh codes using different PN codes;

first and second pulse-shaping filters for pulse-shaping outputs of said third and fourth mixers, respectively;

fifth and sixth mixers for frequency-modulating said pulse-shaped in-phase channel signals and quadrature channel signals into carriers cos(2π

f₀t+θ

_k) and sin(2π

f₀t+θ

k), respectively; and

a high-power amplifier for amplifying outputs of said fifth and sixth mixers and transmitting resulting transmit signals to an antenna.

2. A coherent dual-channel Quadrature Phase Shift Keying (QPSK) receiver device using pilot symbols in a code division multiple access system, comprising:

first and second mixers for frequency-modulating signals received through in-phase channel and quadrature channel from a transceiver using carrier wave cos(2π

f₀t) for said in-phase channel and carrier wave sin(2π

f₀) for said quadrature channel;

first and second matched filters for filtering said frequency-demodulated in-phase channel signals and quadrature channel signals;

a sampler for sampling by a positive number of a chip period said in-phase and quadrature channel signals which passed through said first and second matched filters;

third and fourth mixers for despreading said sampled signals using PN codes of a k-th user and producing despreaded in-phase channel signals and despreaded quadrature channel signals, respectively;

a fifth mixer for combining said despreaded in-phase channel signal with cosine-terms for producing channel estimation values of a first amplitude and phase;

a sixth mixer for combining said despreaded quadrature channel signal with sine-terms for producing channel estimation values of a second amplitude and phase;

a first summer for summing the output of said fifth mixer with the output of said sixth mixer to correct said in-phase channel signal;

a seventh mixer for combining said in-phase channel signal after said despreading with sine-terms for producing said channel estimation values of said first amplitude and phase;

an eighth mixer for combining said quadrature channel signals after said despreading with cosine-terms for producing said channel estimation values of said second amplitude and phase;

a second summer for summing the output of said seventh mixer with the output of said eighth mixer to correct said quadrature channel signal;

ninth and tenth mixers for despreading the outputs of said first and second summers, respectively, using different Walsh codes;

first and second adders for adding signal values using the outputs of said ninth and tenth mixers as inputs during 2N chip periods, said first adder outputting an in-phase channel determination signal and an in-phase channel pilot determination signal and said second adder outputting a quadrature channel determination signal and a quadrature channel pilot determination signal; and

first and second channel estimators for generating cosine-terms of channel estimation values and sine-terms of channel estimation values, respectively, which are used in demodulation channel estimation values, using said in-phase channels and quadrature channel pilot determination signals as inputs, respectively.