Flexible binary phase shift keying/quadrature phase shift...

Details Flexible binary phase shift keying/quadrature phase shift... Flexible binary phase shift keying/quadrature phase shift...

1999-09-15

2002-06-11

Chin, Stephen (Department: 2734)

Pulse or digital communications

Spread spectrum

Direct sequence

C375S295000

Reexamination Certificate

active

06404802

ABSTRACT:

CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 arising from an application entitled, A FLEXIBLE BINARY PHASE SHIFT KEYING/QUADRATURE PHASE SHIFT KEYING MODULATOR OF WIDEBAND CDMA SYSTEM, earlier filed in the Korean Industrial Property Office on Sep. 22, 1998, and there duly assigned Serial No. 1998-39294.
FIELD OF THE INVENTION
The present invention relates to a flexible modulator for binary phase shift keying/quadrature phase shift keying for a wide-band code division multiple access system. More specifically, the present invention relates to a flexible modulator for use in a binary phase shift keying (BPSK) method and a quadrature phase shift keying (QPSK) method for a wide-band code division multiple access system.
DESCRIPTION OF THE RELATED ART
In a code division multiple access system, each signal of each subscriber has a common frequency transmitted by a frequency after multiplying by their own code, and spreading in a spectrum. In the case of a received signal, such a received signal is identified by reverse spreading and multiplying by their own codes, which is identical to the case of transmitting.
In the code division multiple access system, it is possible to increase the efficiency of frequency allocation by using a spreading spectrum and executing coding by multi-keying by their code.
Generally, the frequency spreading process decreases noise and an interference of the signal, but increases the required bandwidth. However, in the code division multiple access system, it is possible to accommodate a plurality of subscribers to one frequency by using a code, therefore an increase of the bandwidth due to spreading does not pose a significant drawback.
In the code division multiple access system, a channel which is used for transmission from a base station to a radio terminal is called a forward link, and a reverse channel is from the radio terminal to the base station is called a reverse link.
Typically, in the code division multiple access system, an interval between channels (channel spacing) is 5 Mhz. The bit error for transmission can be decreased by using a convolutional encoder, and an essential orthogonal code is allocated to each channel for identifying the forward link.
In the code division multiple access system, when direct sequence spreading is used, a chip rate is 4.096 Mega chip per second (Mcps), and each channel is modulated by a QPSK process after executing a BPSK process. But, the channel spacing is extended with a lager spreading rates.
A reverse channel comprises an access channel and a reverse traffic channel, and each channel has a reverse pilot channel. A mobile terminal transmits a reverse pilot channel synchronized with a pilot signal received from a base station. The reverse traffic channel also comprises a reverse information channel and a reverse signaling channel. These channels own jointly a CDMA frequency allocated by using a direct sequence—code division multiple access (DS-CDMA) technology. Each access channel and its reverse traffic channel is identified by an essential long code sequence of the subscriber.
FIGS. 1
a
and
1
b
illustrate a structure of a conventional access channel of a wideband CDMA system. A reverse link sequence
101
(
110
) and a Hadamard code
102
(
111
) have a same pseudo-noise chip rate (Rc). As shown in
FIG. 1
b
, a modulation symbol rate input to reverse link sequence
110
is 64 ksps, 128 ksps, and 256 ksps for a system having a bandwidth of 3.5/5 MHz, 7/10/10.5 MHz, and 14/15 Mhz, respectively. A code rate (r) of a convolutional encoder
107
is 1/2, and a constraint length (k) is 7 or 9.
An access channel comprises a reverse pilot channel and a reverse access channel. The reverse pilot channel is used for determining the phase references of the reverse channel, an acquired channel, and a track channel in a base station.
FIGS. 1
a
and
1
b
show the reverse pilot signal s(t)
105
(
114
) comprises a non-modulated long code sequence.
FIG. 1
a
shows a pilot channel composed of zeros is converted by a reverse link sequence
101
, and then divided into an in-phase signal (I) and a quadrature signal (Q). Each divided signal (I and Q) is spread out by using a Hadamard code H
0
and H
1
102
, respectively, and passed by a baseband filter
103
, and multiplied by cos(2pf
c
t) and sin(2pf
c
t)
104
, respectively. Finally, after summing together the two multiplied I and Q signals
105
together, the composite signal s(t)
105
is output for transmitting.
FIG. 1
b
illustrates the structure of a reverse access channel. An information bit of the reverse access channel is 154 bits per frame (or 152 bits per frame) while the constraint length k is 9.
The information bit of the access channel generated with 7.7 (or 7.6) kbps is added by 6 (or 8) bits for encoding at adder
106
, and is then output to a convolutional encoder
107
at a speed of 8 kbps.
The convolutional encoder
107
constantly maintains a symbol rate of 16 kilo symbols per second (ksps) by iterating input bits as the occasion demands for error correction.
A block interleaver
108
writes a code symbol received from the convolutional encoder with a unit of columns, and reads with a unit of rows.
A symbol repeater
109
iterates each block interleaved symbol as required for an access channel having a fixed data rate, and the iterated signal is constantly maintained with a speed of a modulation symbol rate.
The iterated signal is converted by a reverse link sequence
110
, and then is divided into an in-phase signal (I) and a quadrature signal (Q).
Each divided signal (I and Q) is spread out by using a Hadamard code H
0
and H
1
respectively
111
, passed by a baseband filter
112
, multiplied by one of cos(2pf
c
t) and sin(2pf
c
t)
113
, respectively. Finally the two multiplied I and Q signals are summed together and output as a composite signal s(t)
114
for transmission.
FIGS. 2
a
and
2
b
illustrate a reverse traffic channel structure with a single signal mode in a conventional wideband code division multiple access system. The reverse traffic channel operates at four kinds of variable data rates, and a reverse information channel operates at 16, 32 and 64 kbps. A signaling channel operates at 2 and 4 kbps.
FIG. 2
a
illustrates the structure of a reverse pilot power control signaling (PPCS) channel. The pilot information (all zeros), power control information, redundant information bit, and a signaling channel information are all modulated.
The pilot channel bit, which is composed of zeros, is directly transferred to multiplexer
201
. The power control information bit, which has 10 bits per frame, is transferred to the multiplexer
201
via a quadruple symbol repeater
202
.
The signaling channel information bit having 74 bits (or 72) bits per frame is added with a predetermined number of bits (e.g. 6 or 8 bits) for encoding, then is encoded convolutionally by encoder
204
; the information output from encoder
204
is block interleaved
205
, iterated by a symbol repeater
206
, and subsequently transferred to multiplexer
201
.
The multiplexer
201
generates a spread symbol with 16 ksps after a time division multiplexing bits of a pilot channel with 4 ksps, a power control information channel with 2 ksps, and a redundant information channel with 2 ksps, and a signaling channel information channel with 8 ksps.
The generated spread symbol is transferred to a symbol post-repeater
207
. The iterated signal by the symbol post-repeater
207
is converted by a reverse link sequence
208
and then divided into an in-phase signal (I) and a quadrature signal (Q).
Each divided signal (I and Q) is spread out by using a Hadamard code H
0
and H
1
respectively
209
, passed by a baseband filter
210
, and multiplied by one of cos(2pf
c
t) and sin(2pf
c
t)
211
, respectively. Finally, the multiplied I and Q signals are summed together and the composite signal is output as signal s(t) for transmission.
FIG. 2
b
illustrates the structure of a reverse inform

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