Pulse or digital communications – Systems using alternating or pulsating current – Angle modulation
Reexamination Certificate
1998-10-23
2002-09-24
Pham, Chi (Department: 2631)
Pulse or digital communications
Systems using alternating or pulsating current
Angle modulation
C375S260000, C375S317000
Reexamination Certificate
active
06456669
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to data communication methods, transmitters, and cellular radio communication systems, and more particularly, is suitable for use in a radio communication system such as a portable telephone system.
2. Description of the Related Art
In this kind of radio communication system, an area providing communication services is segmented into cells with a predetermined size. Base stations as stationary radio stations are deployed within the cells, respectively.
A portable telephone as a mobile radio station can communicate with the base station within the cell where the portable telephone exists. Thus, a so-called cellular system is constructed. For the cellular system, various systems have been proposed as the communication system between a portable telephone and a base station. As the representative one, there is a time division multiple access (TDMA) system.
In this TDMA system, as shown in
FIGS. 1A and 1B
, a predetermined frequency channel is segmented temporally into frames (F
0
, F
1
, . . . ) each having a predetermined time interval. Each frame is further divided into time slots TS
0
to TS
3
, each time slot has a predetermined time interval. At the timing of time slot TS
0
allocated to a user, the user uses the time slot to transmit a transmission signal. This system realizes a plurality of communications (so-called multiplex communication) by the same frequency channel and therefore utilizes frequency efficiently. Note that in the following description, time slot TS
0
allocated for transmission is called transmission slot TX, while a block of data (i.e., data unit) that is sent with one transmission slot TX is called a slot.
Here, the transmitter and receiver of a radio communication system to transmit and receive data by taking an advantage of this TDMA system will be described with
FIGS. 2 and 3
. Incidentally, the transmitter and receiver shown in
FIGS. 2 and 3
are mounted, for example, in the portable telephone and base station of a portable telephone system, respectively. The transmitter and the receiver are used in the communication from a portable telephone to a base station (so-called uplink communication) and the communication from a base station to a portable telephone (so-called downlink communication).
As shown in
FIG. 2
, the transmitter
1
is roughly constituted by a convolution coding circuit
2
, an interleave buffer
3
, a segmenting circuit
4
, a modulation circuit
5
, a pilot symbol adding circuit
6
, a transmitting circuit
7
, and an antenna
8
. A data bit series S
1
(transmission data) is first input to the convolution coding circuit
2
.
The convolution coding circuit
2
consists of a predetermined stage-number of shift registers and exclusive OR circuits. The convolution coding circuit
2
performs convolution coding on the input data bit series S
1
and then outputs the resulting coded bit series S
2
to the interleave buffer
3
. The interleave buffer
3
stores the coded bit series S
2
in its internal storage region in order. If the coded bit series S
2
is stored in the entire storage region (i.e., if the coded bit series S
2
is accumulated by a desired amount), then the order of the coded bit series S
2
will be randomly rearranged (rearranging this order will hereinafter be referred to as interleaving). The resulting coded bit series S
3
is output to the segmenting circuit
4
. Incidentally, the interleave buffer
3
has a storage capacity equivalent to a plurality of slots so that the coded bit series S
3
is dispersed to a plurality of transmission slots TX.
The segmenting circuit
4
segments the coded bit series S
3
at intervals of a predetermined number of bits in order to allocate the coded bit series S
3
to transmission slots TX. The resulting coded bit group S
4
is output to the modulation circuit
5
in order. The modulation circuit
5
performs a predetermined modulation process (e.g., a modulation process in a synchronous detection system such as QPSK modulation) on the supplied coded bit group S
4
and then outputs the resulting data symbol group S
5
to the pilot symbol adding circuit
6
.
As shown in
FIG. 4
, the pilot symbol adding circuit
6
adds pilot symbols P as a header at the head of each symbol group (i.e., the head of data symbol I) of the data symbol group S
5
segmented according to the transmission slots TX, and then outputs the resulting transmission group S
6
to the transmitting circuit
7
. Incidentally, the pilot symbols P added here are a known symbol pattern that has previously been known at the receiver side, and at the receiver side these pilot symbols P are employed to estimate the characteristics of the transmission path (e.g., fading, etc.).
The transmitting circuit
7
performs a filtering process on the transmission symbol group S
6
added with these pilot symbols P in sequence and then performs a digital-to-analog conversion process on the transmission symbol group S
6
to generate a transmission signal. And the transmitting circuit
7
performs a frequency transformation on the transmission signal, thereby generating a transmission signal S
7
having a predetermined frequency channel. After this signal has been amplified to a predetermined electric power, it is transmitted through the antenna
8
. In this manner, the transmission signal S
7
is transmitted from the transmitter
1
in synchronization with the timing of the transmission slots TX.
On the other hand, as shown in
FIG. 3
, the receiver
10
is roughly constituted by an antenna
11
, a receiving circuit
12
, a transmission path estimating circuit
13
, a demodulation circuit
14
, a slot coupling circuit
15
, a deinterleave buffer
16
, and a Viterbi decoding circuit
17
. The transmission signal S
7
transmitted from the transmitter
1
is received by the antenna
11
, and this is input to the receiving circuit
12
as a received signal S
11
.
The receiving circuit
12
amplifies the input received signal S
11
and then performs a frequency transformation on the received signal S
11
, thereby taking out a base band signal. The receiving circuit
12
performs a filtering process on the base band signal and then performs an analog-to-digital. conversion process on the base band signal, thereby taking out a received symbol group S
12
corresponding to the transmission symbol group S
6
. The received symbol group S
12
is output to the transmission path estimating circuit
13
.
The transmission path estimating circuit
13
is one which investigates the characteristic of the transmission path and also performs an equivalent process according to the result of investigation. The transmission path estimating circuit
13
estimates the characteristic of the transmission path by making a reference to the pilot symbols P included in the received symbol group S
12
, and computes the inverted characteristic of the transmission path, based on the result of estimation. And the transmission path estimating circuit
13
convolution-multiples a numerical value, which indicates the inverted characteristic of the transmission path, and each data symbol portion of the received symbol group S
12
, by using an equalizing circuit consisting of an equalizer. With this multiplication, the influence of fading caused on the transmission path is removed. With this process, the transmission path estimating circuit
13
restores the transmitted data symbol group
85
and outputs this to the modulation circuit
14
as a received data symbol group S
13
.
The modulation circuit
14
performs a predetermined modulation process on the received data symbol group S
13
, thereby restoring the coded bit group S
14
corresponding to the coded bit group S
4
on the transmitter side. The coded bit group S
14
is output to the slot coupling circuit
15
. Incidentally, each bit in the coded bit group S
14
is not a binary signal such as a logic 0 or a logic 1 but has become a multi-level signal because of a noise component added on the transmission path.
The slot coupling circuit
15
Al-Beshrawi Tony
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pham Chi
Sony Corporation
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