Multiplex communications – Generalized orthogonal or special mathematical techniques
Reexamination Certificate
1998-03-17
2003-07-08
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Generalized orthogonal or special mathematical techniques
C370S347000, C375S341000
Reexamination Certificate
active
06590860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a receiving device and a signal receiving method, and more particularly, is applicable to a wireless communication system such as a portable telephone system.
2. Description of the Related Art
In this kind of wireless communication system, an area for offering the communication service is divided into cells with the desired size and a base station is provided in each cell as the fixed wireless station respectively, and portable telephone equipment as the mobile wireless station is arranged to wireless-communicate with the base station in the cell in which the portable telephone equipment itself exists. Although various types of communication systems have been proposed, one of typical devices is a time division multiple access system called the TDMA system.
This TDMA system is a system to divide the predetermined frequency channel into frames of the fixed time width F
0
, F
1
, . . . , as shown in
FIGS. 1A and 1B
and further divides the frame into time slots of the fixed time width TS
0
to TS
3
respectively, and users transmit the transmission signal when the time slot TS
0
is allocated to his own station using a common frequency channel, and this system has made possible the realization of multiple communications (i.e., multiplex communications), users share a common frequency and frequency can be utilized efficiently. Thereinafter the time slot TS
0
allocated to transmission is referred to as transmission slot TX, and the data block to be transmitted by one transmission slot TX is referred to as slot.
At this point, the transmitting device and receiving device of the wireless communication system for transmitting and receiving the digital signal using this TDMA system will be described referring to
FIGS. 2A
,
2
B,
3
A and
3
B. In this connection, the transmitting device and the receiving device shown in
FIGS. 2A
,
2
B,
3
A and
3
B are loaded on the portable telephone equipment and the base station of the portable telephone system, and are used for the communication from the portable telephone equipment to the base station or the base station to the portable telephone equipment.
As shown in
FIG. 2A
, the transmitting device
1
is roughly comprised of a convolutional coding circuit
2
, an interleave buffer
3
, a slotting processing circuit
4
, a differential quadrature phase shift keying (DQPSK) modulation circuit
5
, a transmission circuit
6
and an antenna
7
, and first, inputs the transmission data S
1
to be transmitted to the convolutional coding circuit
2
.
The convolutional coding circuit
2
is comprised of a register and exclusive OR circuit of the fixed number of stages, and it applies convolutional coding to the input transmission data S
1
and outputs the resultant transmission symbol S
2
to the interleave buffer
3
. The interleave buffer
3
sequentially stores the transmission symbol S
2
in the memory area in order, and when the transmission symbol S
2
is stored in said whole memory area (i.e., the desired volumes of transmission symbol S
2
is stored), it permutes the transmission symbols S
2
in random order (hereinafter this permutation is referred to as interleave) and outputs the resultant transmission symbol S
3
to the slotting processing circuit
4
. In this connection, the interleave buffer
3
has the memory capacity for multiple slots so that the transmission symbols can be spread out over a large number of transmission slots TX.
The slotting processing circuit
4
divides said transmission symbol S
3
into slots in order to allocate the transmission symbol S
3
to the transmission slots TX and sequentially outputs the transmission symbols S
4
slotted to the DQPSK modulation circuit
5
per slot. The DQPSK modulation unit
5
, by applying the DQPSK modulation processing to the transmission symbol S
4
to be supplied per slot, forms a transmission signal S
5
of which the symbol information is shown by the phase value and outputs this to the transmission circuit
6
.
The transmission circuit
6
, after applying the filtering processing to the transmission signal S
5
to be supplied per slot, converts said transmission signal S
5
to the analog signal, and forms the transmission signal with the fixed frequency channel by applying the frequency conversion onto the analog transmission signal, and after amplifying this to the fixed power, transmits this via an antenna
7
. Thus, the transmission signal S
6
divided into slots is transmitted from the transmitting device
1
synchronizing with the timing of transmission slots TX. In this connection, for reference purposes, a brief diagrammatic sketch of the signal processing to be conducted in each circuit of the transmitting device
1
described above is shown in FIG.
2
B.
On the other hand, as shown in
FIG. 3A
, the receiving device
10
is roughly comprised of an antenna
11
, a receiver circuit
12
, a DQPSK demodulation circuit
13
, a slot connecting processing circuit
14
, a deinterleave buffer
15
and a Viterbi decoding circuit
16
, and receives the transmission signal S
6
transmitted from the transmitting device
1
by the antenna
11
and inputs this to the receiving circuit
12
as the received signal S
11
. The receiver circuit
12
, after amplifying the input signal received S
11
, takes out a baseband signal by applying frequency conversion to said received signal S
11
and after applying the filtering processing to this baseband signal S
11
, takes out received signal S
12
which is DQPSK modulated by converting the baseband signal to the digital signal, and outputs this to the DQPSK demodulation circuit
13
.
The DQPSK demodulation circuit
13
takes out symbol information by applying the DQPSK demodulation processing to the received signal S
12
and outputs this to the slot connecting processing circuit
14
as a received symbol S
13
. In this connection, the value of this received symbol S
13
is not binary signal such as “0” or “1” but it is a multi-level signal since noise element has been added on the transmission route. The slot connecting processing circuit
14
is a circuit to connect the received symbol S
13
to be obtained fragmentally on a slot-by-slot basis to become continuous signal, and when the received symbol S
13
is stored for the memory capacity of the deinterleave buffer
15
of the later stage, connects said received symbol S
13
and outputs the connected received symbol S
14
to the deinterleave buffer
15
.
The deinterleave buffer
15
has a memory capacity for multiple slots, and after successively storing the received symbol S
14
to be fed to the internal memory area, returns the received symbol S
14
to the former order by permuting said received symbol S
14
with the procedure contrary to the procedure conducted in the interleave buffer
3
of the transmitting device
1
and outputs the resulting received symbol S
15
to the Viterbi decoding circuit
16
(hereinafter the procedure returning to the former order is referred to as deinterleave). The Viterbi decoding circuit
16
is comprised of a soft-decision Viterbi decoding circuit and by estimating the most likelihood condition the data can take from among all changing conditions (i.e., the maximum likelihood sequence estimation) considering the trellis of convolutional code based on the received symbol S
15
, the received data S
16
showing the data transmitted is restored and output. In this connection,
FIG. 3B
is a brief diagram showing the signal processing to be conducted in each circuit of the receiving device
10
explained above.
However, in the receiving device
10
, the received data S
16
is restored conducting the maximum likelihood sequence estimation by the Viterbi-decoding circuit
16
. However, in order to restore the received data S
16
with higher accuracy it is desirous to further improve the efficiency of the maximum likelihood sequence estimation.
This point will be described more specifically in the following paragraphs. The received symbol S
13
to be supplied from the DQPSK de
Sakoda Kazuyuki
Suzuki Mitsuhiro
Hsu Alpus H.
Nguyen Toan
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