Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via frequency channels
Reexamination Certificate
1998-04-09
2001-06-05
Ton, Dang (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via frequency channels
C370S465000, C370S476000, C370S477000, C370S478000, C370S479000, C370S498000, C370S342000
Reexamination Certificate
active
06243397
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a parallel combinatory code-division multiple access (PC-CDMA) system that transmits and receives data by applying a predetermined pseudo number (PN) code corresponding to a plurality of bits, and more particularly relates to a multi-carrier PC-CDMA system that enhances its efficiency by mixing the PN codes corresponding to the plurality of bits with respective orthogonal frequencies.
2. Discussion of Related Art
Recently, according as various communication equipments have applied wireless and digital increasingly, communication systems have applied a code-division multiple access (CDMA) gradually, instead of a time-division multiple access (TDMA) or a frequency-division multiple access (FDMA), and more detailedly a direct sequence CDMA (DC-CDMA) and a parallel combinatory CDMA (PC-CDMA) system, etc. have been commonly used. Especially, the PC-CDMA system, which can minimize its complexity and at the same time transmit a great deal of information at high speed, is being watched with keen interest as a mobile communications system such as cellular system.
FIG. 1
a
and
1
b
are block diagrams explaining an outline of the PC-CDMA system that transmits and receives, for example, 128-bit data,
FIG. 1
a
shows a transmitting part and
FIG. 1
b
a receiving part. In
FIG. 1
a
, reference numeral
11
denotes a serial-to-parallel converter converting a series of serial data into that of parallel data, reference numerals
12
1
to
12
32
denote mappers receiving predetermined bits (for example, 4-bit) of data from the serial-to-parallel converter
11
and outputting PN codes corresponding to the bit values and reference numeral
13
denotes a multiplexer mixing the PN codes from the mappers
12
1
to
12
32
to output. The PN codes outputted from the multiplexer
13
are digital-modulated by means of phase shift keying (PSK) or quadrature PSK (QPSK) and then transmitted through a radio communications network.
In
FIG. 1
b
, reference numerals
21
1
to
21
31
denote correlators for outputting level signals corresponding to the PN codes of data received and demodulated from the transmitting part.
FIG. 2
illustrates a configuration of the correlators
21
1
to
21
31
of
FIG. 1
b
, comprising a plurality of multiplicators
211
1
to
211
16
mixing received data with respective intrinsic PN codes [PN(1), PN(2), . . . , PN (15) and PN(16)] and a plurality of integrators
212
1
to
212
16
integrating signals outputted from the multiplicators
211
1
to
211
16
.
In
FIG. 1
b
, reference numerals
22
1
to
22
32
denote data detectors detecting PN codes, transmitted from the transmitting parts of
FIG. 1
a
, based on the level signals inputted from the correlators
21
1
to
21
31
. Reference numeral
23
denotes a parallel-to-serial convertor converting parallel data from the data detectors
22
1
to
22
32
into serial data.
The mappers
12
1
to
12
32
of the transmitting part output PN codes corresponding to 4-bit data values inputted, the PN codes from the mappers
12
1
to
12
32
are mixed by multiplexer
13
and digital-modulated to be transmitted. Here, as the mappers
12
1
to
12
32
output respective intrinsic PN codes corresponding to the 4-bit data values inputted, all data outputted from the mappers
12
1
to
12
32
have orthogonal feature.
In the receiving part, each of the correlators
21
1
to
21
32
mixes received and demodulated data with all the PN codes [PN(1), PN(2), . . . , PN(511) and PN(512)] which are to be transmitted from the transmitting part and then integrates respective data to output, and each data detector
22
1
to
22
32
detects the PN codes of received data, based on 512-signal level outputted from the correlators
21
1
to
21
32
, and restores 128-bit data (respectively 4-bit) to output. Accordingly, in the above configuration, data can be transmitted and received at high speed as 128-bit data are transmitted and received at the same time.
However, the above described PC-CDMA system has the following problems. When transmitting 128-bit data, 512-PN code (16×32) are needed as shown in
FIG. 1
as 16-PN code (2
4
) are needed when transmitting 4-bit data in a conventional PC-CDMA system. At least 256-PN code are needed and even plus (+) PN codes and minus (−) PN codes are applied to decrease the number of PN code. Accordingly, a PN code generator becomes complicated to generate a large number of PN codes, which prevents diminishing the size of cellular system. The above described PC-CDMA system deteriorates data restoration at the receiving part due to the large number of PN codes. That is, when denoting a signal energy transmitted as an Eb and a noise as a No, the data restoration in a CDMA system is expressed as Eb/No in general, here, all the other PN codes except relevant PN codes act as noise signals. Therefore, in a cellular system using the above described PC-CDMA system, when a great deal of users try to make phone calls simultaneously, PN codes transmitted and received from and to the other cellular phones act as noise signals, which increase the whole noise level, thus all the users cannot make phone calls.
Furthermore, in a PC-CDMA system as described above, considering the receiving part needs correlators
21
1
to
21
32
and data detectors
22
1
to
22
32
as much as the number of the mappers
12
1
to
12
32
needed at the transmitting part, it is an obstacle to minimize a portable communications terminal where the PC-CDMA system is applied.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a multi-carrier PC-CDMA system that substantially obviates one or more of the limitations and disadvantages of the related art.
It is an object of the present invention to provide a multi-carrier PC-CDMA system which decreases the number of PN codes needed.
It is a further object of the present invention to provide a multi-carrier PC-CDMA system which transmits and receives data at higher speed than a conventional PC-CDMA system.
Another object of the present invention is to provide a multi-carrier PC-CDMA system which decreases the number of correlators
21
and data detectors
22
needed at a receiving part.
A multi-carrier PC-CDMA system according to a first aspect of the present invention, including a plurality of mappers for converting a plurality of data bits into PN codes corresponding to the data values to spread transmitting data with predetermined PN codes and detecting PN codes from received data to restore the original data, comprises a mixing means for mixing respective PN codes outputted from the plurality of the mappers with frequency signals having orthogonal feature at a transmitting part, and a plurality of mixing means for mixing received signals with frequency signals, which are the same with the ones mixed by the mappers of the transmitting part, at a receiving part, through which PN codes are detected from signals outputted, each mapper generating intrinsic PN codes independently to output.
According to a second aspect of the invention, a multi-carrier PC-CDMA system comprises a transmitting apparatus for mixing a plurality of data bits with PN codes corresponding to the data values and mixing the PN codes again with frequency signals having an orthogonal feature, and a receiving apparatus for mixing the received signals with frequency signals having the orthogonal feature again to detect PN codes and restore the original data, the receiving apparatus is comprised of a plurality of storing means for storing PN code data obtained by mixing the above frequency signals, a multiplexer reading the PN code data in turn to output, a correlator outputting level signals corresponding to the PN codes from the multiplexer and a data detector detecting transmitting data based on the level signals outputted from the correlator.
According to a third aspect of the invention, a multi-carrier carrier PC-CDMA system comprises a transmitting apparatus for mixing a plurality of data bits
Lilling & Lilling P.C.
Mercury Corporation
Ton Anthony
Ton Dang
LandOfFree
Multi-carrier PC-CDMA system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-carrier PC-CDMA system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-carrier PC-CDMA system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2491079