Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Reexamination Certificate
1998-04-30
2001-12-11
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
C370S351000, C370S345000, C370S474000
Reexamination Certificate
active
06330233
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CDMA radio transmitting apparatus and a CDMA radio receiving apparatus used for digital radio communications, etc.
2. Description of the Related Art
One of the line connection systems in digital radio communications is the multiple access system in which a plurality of stations can perform communications with the same frequency band simultaneously. A type of the multiple access system that allows improvement of frequency utilization is the CDMA system.
CDMA (Code Division Multiple Access) means code division multiple accesses and refers to a technology that achieves multiple accesses through spread spectrum combinations in which an information signal spectrum is spread in a band sufficiently wide compared to the original information band width. It is also sometimes called spread spectrum multiple access (SSMA). The system in which a spread code is directly multiplied by an information signal is called “direct sequence system.”
FIG.1
shows an outline of configuration example of a conventional CDMA transmitting apparatus. With the CDMA transmitting apparatus shown in the figure, variable data
1201
is assembled by frame assembly circuit
1202
in frame units, and then time-multiplexed with fixed data
1204
by slot assembly circuit
1203
. At this time, slot timing, symbol timing and data rate information
1205
, etc. are input to slot assembly circuit
1203
to control the time-multiplexing timing.
FIG.2
shows the configuration of the slot assembly circuit. Transmit data
1301
which is variable data and fixed data
1204
are time-multiplexed and output by switch
1303
which is controlled by timing control circuit
1302
. In slot assembly circuit
1203
, a slot-assembled signal is primary-modulated by modulator
1206
, CDMA-modulated by spread circuit
1207
, and then amplified by RF section
1208
and transmitted from antenna
1209
.
The data format of radio signals used for the CDMA transmitting apparatus above is explained below.
FIG.3
shows an example of radio signal format. A transmit signal includes slots as its basic units, with K slots making up one frame and N frames making up one super frame.
FIG.4
shows an example of transmit signal format in one slot. One slot includes a fixed data section with the quantity of data constant with time and a variable data section with the quantity of data variable with time.
The fixed data includes a pilot symbol which is a known signal for coherent detection on the receiving side, control signal such as power control signal, or rate information of the variable data section transmitting the quantity of data, etc. The variable data is coding data with the quantity of data variable with time such as voice information and image information.
The slot shown in FIG.
4
(
a
) indicates a slot configuration when the data rate is high such as voice period; FIG.
4
(
b
), when there is no data such as silent period; and FIGS.
4
(
c
) and (
d
), when there is little data such as when the data rate is low.
FIG. 5
shows the power of the conventional CDMA transmitting apparatus for each frame. For example, if the data rate of transmit data is high, it transmits variable data
1602
with the same power as that of fixed data
1601
as shown in FIG.
4
(
a
). If there is no data as shown in FIG.
5
(
b
), fixed data
1603
is transmitted in the same way as in FIG.
5
(
a
), while variable data
1604
is set to power 0. Furthermore, when the data rate is low as shown in FIG.
5
(
c
), fixed data
1605
is transmitted in the same way as in FIG.
5
(
a
), whereas variable data
1606
is transmitted with small power instead of transmitting the same signal repeatedly. This allows the quality of variable data
1606
to be kept equivalent to the quality of fixed data
1605
. At the same time, transmitting variable data
1606
with low power can reduce interference with other users in that portion of data. Furthermore, when the data rate is low as shown in FIG.
5
(
d
), fixed data
1607
is transmitted in the same way as in FIG.
5
(
a
), and variable data
1608
is also transmitted with the same power, but can also be cut midway if there is little data. This allows the quality of variable data
1608
to be kept equivalent to the quality of fixed data
1607
.
When the data rate is high, this results in a power pattern as shown in FIG.
5
(
a
); when there is no data, a power pattern as shown in FIG.
5
(
b
); and when the data rate is low, power patterns as shown in FIGS.
5
(
c
) or (
d
).
On the other hand, in the CDMA receiving apparatus on the receiving side, as shown in
FIG. 6
, the signal received by an antenna
1701
is down-converted by RF circuit
1702
and then despread by despread circuit
1703
, demodulated by demodulator
1704
and separated by slot disassembly circuit
1705
into the fixed data section and variable data section. Frame disassembly circuit
1707
output the variable data as receive data. In slot disassembly circuit
1705
as shown in
FIG. 7
, demodulator output
1801
resulting from time-multiplexing of the variable data and fixed data is separated into fixed data
1805
and variable data
1806
by switch
1804
controlled by timing control circuit
1802
using slot timing, symbol timing and data rate information, etc.
1803
.
However, as shown in
FIGS. 5
(
b
) and (
c
), with the conventional transmitting apparatus above, when there is no data or the data rate is low, turning transmit energy ON/OFF will generate a pulse signal with a power pattern of specific cycles, producing line spectrums with large power in specific frequency components, which will get mixed in hearing aids causing unnecessary sound with a specific frequency, a so-called hearing aid problem, or may affect peripheral appliances.
FIG. 8
shows an example of frequency spectrum when transmit power is turned ON/OFF in a cycle of 1.6 kHz. In this case, line spectrums generating unnecessary sound are observed in the audible range such as 1.6 kHz and 3.2 kHz.
SUMMARY OF THE INVENTION
Taking into account the above circumstances, the objective of the present invention is to provide a CDMA radio transmitting apparatus and CDMA radio receiving apparatus capable of suppressing unnecessary frequency components generated when storing multi-rate data, eliminating hearing aid problems and preventing influences on peripheral appliances in CDMA transmissions.
When time-multiplexing variable data with the quantity of data variable with time and fixed data with the quantity of data constant with time, the present invention randomizes the transmit timing of fixed data in the case that there is no variable data at least.
According to the present invention, in the case that the data rate of variable data is low or there is no variable data, the power ON/OFF timing of fixed data is randomized, which randomizes the power ON/OFF timing, and thus the present invention restrains pulses from generating in each slot, suppressing generation of line spectrums with large power in specific frequency components.
Furthermore, the present invention provides a CDMA radio transmitting apparatus that allows the transmit timing of fixed data to be randomized by controlling placement of fixed data in transmit data.
The present invention also provides a CDMA radio receiving apparatus that determines placement patterns of fixed data according to the frame number and slot number, stores only a number of slots that are housed in a super frames with a plurality of frames forming one unit and selects placement patterns based on the frame number and slot number to which the fixed data belongs.
The present invention allows mobile radio communication systems to control placement patterns of fixed data using the slot number and frame number which are kept synchronized between the transmitting side and receiving side, facilitating disassembly of slots on the receiving side. Furthermore, since placement patterns are stored in quantity corresponding to the number of slots housed in a super frame, different place
Miya Kazuyuki
Uesugi Mitsuru
Greenblum & Bernstein P.L.C.
Kizou Hassan
Matsushita Electric - Industrial Co., Ltd.
Qureshi Afsar M.
LandOfFree
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