U.S. patent number 3,644,680 [Application Number 04/859,285] was granted by the patent office on 1972-02-22 for time-assignment speech-interpolation control system.
This patent grant is currently assigned to Fujitsu Limited. Invention is credited to Kitsutaro Amano, Masao Hashimoto, Hisao Kanzaki, Chuichi Ota, Yasuhiko Sakamoto, Nobuyuki Yasoshima.
United States Patent |
3,644,680 |
Amano , et al. |
February 22, 1972 |
TIME-ASSIGNMENT SPEECH-INTERPOLATION CONTROL SYSTEM
Abstract
A TASI system for satellite use is disclosed in which voice
signals from the individual trunks are stored prior to being
transmitted and in which TASI control data are transmitted in a
frame preceding the frame in which associated speech data are
transmitted.
Inventors: |
Amano; Kitsutaro (Yokohama-shi,
JA), Ota; Chuichi (Tokyo, JA), Hashimoto;
Masao (Kanagawa-ken, JA), Kanzaki; Hisao (Tokyo,
JA), Sakamoto; Yasuhiko (Kawasaki-shi, JA),
Yasoshima; Nobuyuki (Tokyo, JA) |
Assignee: |
Fujitsu Limited (Kawasaki,
JA)
|
Family
ID: |
13407687 |
Appl.
No.: |
04/859,285 |
Filed: |
September 19, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Sep 25, 1968 [JA] |
|
|
43/69607 |
|
Current U.S.
Class: |
370/435; 370/428;
455/516; 455/13.2 |
Current CPC
Class: |
H04J
3/172 (20130101); H04J 3/24 (20130101) |
Current International
Class: |
H04J
3/17 (20060101); H04J 3/24 (20060101); H04j
005/00 () |
Field of
Search: |
;179/15AS |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Proceedings IEEE, Vol. III, No. 4, pp. 675-684, "Time Assignment
Speech Interpolation in Time-Compression Multiplier Transmission,"
Author: Flood et al..
|
Primary Examiner: Claffy; Kathleen H.
Assistant Examiner: Stewart; David L.
Claims
We claim:
1. A time-assignment speech-interpolation control system having a
transmitter comprising
discriminating means for determining the voice condition of each
trunk of a voice communication system by determining if said voice
condition transmitted via each trunk exceeds a specific level and
allotting a time-assignment speech-interpolation system channel to
each trunk which exceeds the specific level, said discriminating
means comprising level-comparing means for determining whether the
transmission data supplied from the trunks exceeds the specific
level;
input means connected to said discriminating means for supplying
thereto information from the trunks of a voice communication system
having a plurality of trunks;
a channel condition memory coupled to said discriminating means for
recording time-assignment speech-interpolation informations
indicating the corresponding relationship between trunks and
time-assignment speech-interpolation channels determined by said
discriminating means, said channel condition memory comprising a
first memory unit for storing the result of the determination of
the level-comparing means of the discriminating means by comparison
with data from corresponding trunks and a second memory unit for
storing data indicating whether time assignment speech
interpolation information may be allotted, said discriminating
means further comprising time-assignment speech-interpolation
allotting means for allocating time-assignment speech-interpolation
information in accordance with the data stored in the first memory
unit;
a voice information memory coupled to said discriminating means and
said input means for storing voice informations supplied from the
trunks to which time-assignment speech-interpolation channels are
allotted from said voice informations in the order of the
time-assignment speech-interpolation channels in accordance with
the time-assignment speech-interpolation informations stored in
said channel condition memory; and
time-assignment speech-interpolation information-adding circuit
means connected to said discriminating means for adding
time-assignment speech-interpolation informations stored in the
second memory unit of said channel condition memory to voice
informations stored in said voice information memory and
transmitting the informations, said channel condition memory
including a memory for storing the time-assignment
speech-interpolation informations controlling the voice
informations being transmitted, a memory for storing the
time-assignment speech-interpolation informations transmitted by
being added to the voice informations and a memory for storing the
time-assignment speech-interpolation informations.
2. A time-assignment speech-interpolation control system as claimed
in claim 1, further comprising means for dividing the
time-assignment speech-interpolation informations into a plurality
of frames and transmitting the divided informations.
3. A time-assignment speech-interpolation control system as claimed
in claim 1, wherein the second memory unit of said channel
condition memory stores one bit corresponding to the trunks.
4. A time-assignment speech-interpolation control system as claimed
in claim 1, further comprising means for converting the
time-assignment speech-interpolation informations to an information
train of binary signals indicating if the time-assignment
speech-interpolation channels are allotted to bit positions
corresponding to the trunks and transmitting said binary
signals.
5. A time-assignment speech-interpolation control system as claimed
in claim 1, further comprising a receiver having a separating and
compiling circuit for deriving time-assignment speech-interpolation
informations from a received burst, input means connected to said
separating and compiling circuit for supplying a received burst to
said separating and compiling circuit, a voice information memory
coupled to said input means for storing voice informations directed
to said receiver, and a channel condition memory coupled to said
separating and compiling circuit and to said voice information
memory for storing time-assignment speech-interpolation
informations provided by said separating and compiling circuit to
read out the voice informations stored in said voice information
memory corresponding to the trunks, said channel condition memory
including a pair of memories each of which is alternately utilized
as a memory for storing the time-assignment speech-interpolation
informations for controlling the voice informations being read out
and a memory for storing the time-assignment speech-interpolation
informations being transmitted to said receiver.
6. A time-assignment speech-interpolation control system as claimed
in claim 5, wherein each of the pair of memories of said channel
condition memory has addresses corresponding to the trunks and one
bit which indicates whether time-assignment speech-interpolation
information is allocated to a corresponding trunk and is stored in
each of said addresses.
7. A time-assignment speech-interpolation control system as claimed
in claim 1, wherein the second memory unit of the channel condition
memory comprises three memory units corresponding to the respective
trunks for storing information of corresponding trunks with the
data indicating whether time-assignment speech-interpolation
information may be allotted, one of the memory units storing the
information of the trunk in which voice information is transmitted,
another of the memory units storing the information of the trunk in
which the voice signal is added in transmission and the third of
the memory units storing the information of the trunk corresponding
to the allotting of time-assignment speech-interpolation
information, the three memories being utilized in cycles.
Description
DESCRIPTION OF THE INVENTION
The present invention relates to a time-assignment
speech-interpolation control system. More particularly, our
invention relates to a control system in a communication system
utilizing a time-division multiplexing multiple-access system part
or all of which utilizes a time-assignment speech-interpolation
control system.
A time-assignment speech-interpolation system is hereinafter
referred to as a TASI system. A TASI system is a control system,
which, due to the fact that in a multiplex communication system
talk or voice signals are often broken or interrupted, enables
other voice signals to be transmitted during the idle time created
by the breaking or interruption of the voice signals and utilizes
the channels in accordance with the principle of time division to
reduce the number of channels utilized. The high cost of channels
of communication systems, such as satellite communication systems
and submarine cable communication systems, may be effectively
reduced by the utilization or application of the TASI control
system. For this reason, efficiency of utilization of channels has
heretofore been increased due to the utilization of the TASI system
when voice is transmitted via expensive long-distance telephone
channels. In the prior art, frequency-division multiplex channels
are main channels to which the TASI system may be applied and
pulse-amplitude modulation systems are chiefly applied to the part
wherein there is switching operation of the TASI control system. In
accordance with the development of the pulse-code modulation
system, however, such PCM system has become active and PCM
international channels are utilized and it is possible to now
utilize TASI control on the PCM level.
In the TASI system, switching is essentially required at high
speed, since channels are switched in accordance with the condition
of the voice signals of a call which is in duration. For this
reason, switching is at electronic speeds without regard to
channels whose efficiency of utilization must be increased. When
the channels are an analog system, it is generally required to
provide a modulating and demodulating device for the switching
operation. In the case of PCM channels, however, a modulating and
demodulating device is not required, so that a PCM system is more
economical than an analog system. When the signals are coded,
however, there is generally a tendency for the required magnitude
or capacity of the memory or storage to become enormous, and in a
PCM TASI system the magnitude of the memory is an extremely
important element affecting the cost of the system.
The principal object of our invention is to provide a new and
improved time-assignment speech-interpolation control system.
An object of the invention is to provide a TASI control system
which utilizes a minimum memory capacity.
In the application of a TASI system, it is necessary to transmit
informations representing the corresponding relationship between a
channel device or trunk and the TASI channel or informations
representing the modification of the corresponding relationship,
that is, the TASI informations, besides the voice informations.
There is, however, a considerable magnitude of TASI informations.
Therefore, if the TASI informations and the voice informations are
transmitted within a constant period of time, the voice
informations are limited and it is impossible to transmit a large
magnitude of voice informations.
An object of the invention is to provide a TASI control system
which permits the transmission of a large magnitude of voice
informations.
An object of the invention is to provide a TASI control system
which transmits a large magnitude of voice informations and which
comprises an extremely inexpensive structure.
An object of our invention is to provide a TASI system which
functions with efficiency, effectiveness and reliability.
In accordance with the invention, a time-assignment
speech-interpolation control system has a transmitter comprising a
discriminator for determining the voice condition of each trunk of
a voice communication system by determining if the voice condition
transmitted via each trunk exceeds a specific level and allotting a
time-assignment speech-interpolation system channel to such trunk.
An input connected to the discriminator supplies thereto the trunks
of a voice communication system having a plurality of trunks. A
channel condition memory coupled to the discriminator records
time-assignement speech-interpolation informations indicating the
corresponding relationship between trunks and time-assignment
speech-interpolation channels determined by the discriminator. A
voice information memory coupled to the discriminator and the input
stores voice informations from the trunks to which time-assignment
speech-interpolation channels are allotted from the voice
informations in the order of the time-assignment
speech-interpolation channels in accordance with the
time-assignment speech-interpolation informations stored in the
channel condition memory. A time-assignment speech-interpolation
information-adding circuit connected to the discriminator adds
time-assignment speech-interpolation informations stored in the
channel condition memory to voice informations stored in the voice
information memory and transmits the informations. The channel
condition memory includes a memory for storing the time-assignment
speech-interpolation informations controlling the voice
informations being transmitted, a memory for storing the
time-assignment speech-interpolation informations transmitted by
being added to the voice informations and a memory for storing the
time-assignment speech-interpolation informations in rewriting
condition.
The time-assignment speech-interpolation control system further
comprises means for dividing the time-assignment
speech-interpolation informations into a plurality of frames and
transmitting the divided informations. Each of the memories of the
channel condition memory stores addresses corresponding to the
trunks and each of the addresses comprises one bit.
The time-assignment speech-interpolation control system further
comprises means for converting the time-assignment
speech-interpolation informations to an information train of binary
signals indicating if the time-assignment speech-interpolation
channels are allotted to bit positions corresponding to the trunks
and transmitting the binary signals.
The time-assignment speech-interpolation control system further
comprises a receiver having a separating and compiling circuit for
deriving time-assignment speech-interpolation informations from a
received burst. An input connected to the separating and compiling
circuit supplies a received burst to the separating and compiling
circuit. A voice information memory coupled to the input stores
voice informations directed to the receiver. A channel condition
memory coupled to the separating and compiling circuit and to the
voice information memory stores time-assignment
speech-interpolation informations provided by the separating and
compiling circuit to read out the voice informations stored in the
voice information memory corresponding to the trunks. The channel
condition memory includes a pair of memories each of which is
alternately utilized as a memory for storing the time-assignment
speech-interpolation informations for controlling the voice
informations being read out and a memory for storing the
time-assignment speech-interpolation informations being transmitted
to the receiver.
Each of the pair of memories of the channel condition memory has
addresses corresponding to the trunks and each of the addresses
comprises one bit.
In order that our invention may be readily carried into effect, it
will now be described with reference to the accompanying drawings,
wherein:
FIG. 1 is a block diagram illustrating a satellite communication
system;
FIG. 2 illustrates a burst train of a satellite communication
system;
FIG. 3 illustrates a burst of the burst train of FIG. 2;
FIG. 4 is a block diagram of an embodiment of the time-assignment
speech-interpolation control system of our invention;
FIG. 5 is a block diagram of another embodiment of the
time-assignment speech-interpolation control system of the
invention;
FIGS. 6a, 6b, 6c, 6d and 6e illustrate the time relations of
various informations;
FIG. 7 is a block diagram of an embodiment of the transmitter of
FIG. 4;
FIG. 8 is a block diagram of an embodiment of the discriminator of
FIG. 4;
FIG. 9 illustrates the operation of the channel condition memory of
the transmitter;
FIG. 10 is a block diagram of an embodiment of the receiver of FIG.
4; and
FIG. 11 illustrates the operation of the channel condition memory
of the receiver.
Although the TASI system of our invention is described with
reference to a satellite communication system, the invention may be
applied to any suitable communication system such as, for example,
a submarine cable communication system, or the like.
In the figures, the same components are identified by the same
reference numerals.
FIG. 1 illustrates a satellite communication system comprising a
communication satellite S in space and N ground stations A, B, . .
. N. Bursts B1, B2, . . . BN are radiated from the ground stations
A, B, . . . N, respectively, at corresponding regulated times. The
bursts are relayed by the communication satellite S and are
received by each ground station.
FIG. 2 illustrates a burst train which comprises a burst B1
radiated from the ground station A at time t1 and a burst BN
radiated from the ground station N at time tN, so that the bursts
are not mutually overlapping on the satellite. Furthermore, the
bursts are repeatedly radiated at a sampling period T of the time
division system. The repetition is referred to as a frame.
Each burst, as shown in FIG. 3, comprises voice information CH and
control information P. Part of the control information comprises
the TASI information TS. The TASI information TS is transmitted as
part of the control information P.
The TASI information transmission system may be divided into a
system in which the TASI information is provided as an information
train indicating whether or not the trunks are allotted to the
channels and a system in which the TASI information indicates only
the content of change of the corresponding relation between the
trunks and the channels. The first-mentioned system is known as a
condition or state signal system and the last-mentioned system is
known as a change signal system. The condition signal system may be
divided into a system in which the condition of allotment of the
trunks to the channels is transmitted in one frame and a system
wherein said condition is divided into a plurality of parts which
are transmitted in a plurality of frames.
Each of the two systems into which the condition signal system may
be divided may be further divided into a system wherein the same
condition signal is transmitted only once and a system wherein the
same condition signal is transmitted a number of times. The
last-mentioned system may be further divided into a system wherein
the signal is transmitted by adding a parity check code or
error-correcting code thereto, the correct information being
discriminated and regenerated from this at the receiver and
utilized as an effective TASI signal and a system wherein the same
information is transmitted an odd number of times and the receiver,
in accordance with the logic of decision by majority, obtains
effective TASI information with the greatest number of
informations.
The system in which the same condition signal is transmitted only
once includes a system wherein an additional code or
error-correcting code is added to the condition signal. The change
signal system may also be divided into a system wherein the
information concerning the change of corresponding relation between
the trunks and the channel is transmitted in a frame and a system
wherein said information is divided into a plurality of parts which
are transmitted in a plurality of frames, and each of these systems
may be divided into a system wherein the change signal is
transmitted once and a system wherein said signal is transmitted a
number of times.
Our invention may adopt the aforedescribed various signals in the
TASI information-transmitting system. However, an embodiment of the
invention is hereinafter described in which the condition signal
type is adopted as the signal type, TASI information is divided
into a plurality of frames and an error-correcting code is added in
the transmission.
FIG. 4 illustrates an embodiment of the TASI system of the
invention. In FIG. 4, in order to maintain the clarity of
illustration, communication between two ground stations A and B is
illustrated. That is, voice informations from ground station A are
all directed to ground station B. In FIG. 4, a plurality of
subscribers 15a, 15b, . . . 15i are provided at the station A and a
plurality of subscribers 25a, 25b, . . . 25j are provided at the
station B. A plurality of trunks 17-1, 17-2, . . . 17-m are
provided at the station A and a plurality of trunks 27-1, 27-2, . .
. 27-m are provided at the station B. There are thus m trunks at
each station. There is mutual correspondence between the trunks
17-1 and 27-1, 17-2 and 27-2, . . . and 17-m and 27-m. There is no
connection between or possible for connecting the trunks 17-1 and
27-2 or 17-2 and 27-m.
The subscribers 15a, 15b, . . . 15i, 25a, 25b, . . . 25j and the
corresponding trunks 17-1, 17-2, . . . 17-m, and 27-1, 27-2, . . .
27-m are connected via exchange equipment 16 in accordance with
arbitrary switching combinations. A PCM modulator 18 provides PCM
modulation and time-multiplexes the voice informations from the
trunks. The PCM modulator 18 may comprise any suitable known
circuit. A voice information memory 10 is connected to the output
of the PCM modulator 18 and functions to rearrange information
having addresses of a number equal to the number of TASI channels,
that is, n addresses. The voice information memory 10 comprises
core memories, magnetic thin film memories, IC memories, or the
like, and the operation of said voice information memory is
described hereinafter. A channel condition memory 8 is connected to
the voice information memory 10. The channel condition memory 8
comprises three sets of channel condition memories each having a
number of addresses equal to the number of trunks 17-1, 17-2, . . .
17-m, that is, m addresses. The channel condition memory 8 stores
information as to whether or not the TASI channel is allotted to
each trunk. The channel condition memory 8 may comprise any
suitable core memories, magnetic thin film memories, IC memories,
or the like. The operation of the channel condition memory 8 is
hereinafter described.
At station B, a voice information memory 53 functions to rearrange
information and has addresses equal in number to the TASI channels,
that is, n addresses. The voice information memory 53 comprises any
suitable core memories, magnetic thin film memories, IC memories,
or the like. The operation of the voice memory 53 is hereinafter
described. A channel condition memory 58 is connected to the voice
information memory 53 and comprises two channel condition memories
having addresses equal in number to the trunks 27-1, 27-2, . . .
27-m, that is, m addresses. The channel condition memory 58 records
whether or not the TASI channel is allotted to each trunk. The
channel condition memory 58 may comprise any suitable core
memories, magnetic thin film memories, IC memories, or the like.
The operation of the channel condition memory 58 is hereinafter
described. A PCM demodulator 60 is connected to the output of the
voice information memory 53. The PCM demodulator 60 functions to
demodulate and space divide the PCM time-multiplex signals and may
constitute any suitable known circuitry. The PCM demodulator 60 is
coupled to the subscribers 25a, 25b, . . . 25j via the plurality of
corresponding trunks 27-1, 27-2, . . . 27-m and the exchange
equipment 16.
In the embodiment of FIG. 4, voice informations are transmitted
from m trunks 17-1, 17-2, . . . 17-m at the station A to the
corresponding m trunks 27-1, 27-2, . . . 27-m at the station B. The
transmission is achieved via n TASI channels, m being greater than
n. Where there is communication between more than two stations A,
B, . . . N, our invention may be carried into effect by the
embodiment of FIG. 5.
In the embodiment of FIG. 5, there is mutual correspondence between
the trunk 17-1 of the station A and the trunk 27-1 of the station
B, the trunk 17-2 of the station A and the trunk 27-2 of the
station B, and the trunk 17-m of the station A and the trunk 97-1
of the station N. Furthermore, there is mutual correspondence
between the trunk 97-m of the station N and a trunk of another
station, not shown in the drawing.
Of n TASI channels allotted to the station A, p channels are
directed to the station B and q channels are directed to the
station N. Similarly, part of the TASI channels allotted to each of
the station B and the station N is directed to the station A and
the other part is directed to either the station N or the station
B. By dividing the trunks of each station and the TASI channels
allotted thereto into a plurality of parts and directing them to
the other stations, as hereinbefore described, it becomes possible
to utilize a system similar to that described with relation to FIG.
4, as hereinafter disclosed in greater detail.
In order to describe the system of FIG. 4 in detail, the
information train or burst transmitted from the PCM modulator 18
and the information train or burst B1 transmitted to the station B
are described with reference to FIGS. 6a, 6b, 6c, 6d and 6e. FIG.
6a shows a PCM signal train of trunks 17-1, 17-2, . . . 17-m
sampled and coded in synchronism with the frame-timing signals by
the PCM modulator 18. FIG. 6a shows that the informations of the
trunks 17-1, 17-2, . . . 17-m are in the trunks TRK1, TRK2, . . .
TRKm, respectively. FIG. 6b illustrates whether each of the trunks
of FIG. 6a is in speech condition S or pose condition P. TASI
channels are allotted only to the trunks which are in the speech
condition.
TASI channels allotted to the trunks which are in the speech
condition are transmitted as a series in the order of said trunks.
Therefore, the information train of FIG. 6a from the PCM modulator
18 is, as shown in FIG. 6c, based upon FIG. 6b, and is transmitted
to the station B. In FIG. 6c, TS is a part of the TASI control
signal. A TASI control signal comprises a plurality of parts TS of
the burst B1 of a plurality of frames, referred to as the signal
frames SF, as shown in FIG. 6d. Thus, the TASI channels are
preferentially allotted to the trunks in the speech condition and
the information concerning such allotment is transmitted to the
other station by the TASI control signal, which control signal is
constituted by the parts TS of the burst B1 of a plurality of
frames.
The transmitter and receiver for transmitting and receiving the
aforedescribed information are described with reference to FIGS. 7
and 10. FIG. 7 includes the voice information memory 10 and the
channel condition memory 8 of the station A of FIG. 4, and circuits
related thereto. In FIG. 7, PCM signals 1 are provided by the PCM
modulator 18 (not shown in FIG. 7). PCM signals 2 are transmitted
to the station B via the communication satellite S. Timing control
signals 3 comprise, for example, the frame timing representing the
start and end of a sampling period.
The signals 1 are PCM signals which are compressed by the TASI
control signal forming parts 4, 5, 6, 7 and 8. Regardless of
whether the trunks 17-1, 17-2, . . . 17-m are in the talking, voice
or speech condition or in the nontalking or pose condition, PCM
signals coded in correspondence with the signal levels are included
in the signals 1. The signals 2 are PCM signals which have been
compressed by the TASI control signal forming parts, and PCM
signals corresponding to trunks which are in the speech condition
are, as shown in FIG. 6c, transmitted in series in their order of
arrival.
In FIG. 7, a buffer register 4 stores the PCM modulated signals of
one trunk once. The information stored in the buffer register 4 is
scanned or searched each time by a level discriminator 5 connected
to said buffer register. The level discriminator 5 determines
whether the signal from the trunk exceeds the designated level and
determines whether the trunk is in the speech condition or pose
condition. The TASI channel is allotted in accordance with such
determination and the information is transmitted to other circuits
requiring same.
In order that the discriminator 5 completely determine the
condition of the trunks, it is necessary that the trunks be
supervised over several frames, so that a considerably long period
of time is required. If the discriminator 5 is occupied by a single
trunk during this period of time, the communication will be
obstructed so that, in the invention, the channel condition memory
8 is provided. The condition of each trunk is written or read into
the channel condition memory 8 in each frame and the written
information is read out in the next frame and the new information
so provided in the frame is added. It thus becomes possible to
determine the condition of all the trunks.
Speech informations of the trunks 17-1, 17-2, . . . 17-m are all
transmitted from the PCM modulator 18 within one time division
period, that is, one frame period. Therefore, voice informations
are stored in and read out of the buffer register 4 the same number
of times as the number of all the trunks within one frame period. A
writing buffer register 7 writes from the discriminator 5 into the
channel condition memory 8. A reading buffer register 7 reads from
the channel condition memory 8 to the discriminator 5.
The voice information memory 10 rearranges information in which
only the voice informations of the trunks to which the TASI
channels have been allotted are stored via a buffer register 9. The
writing of information into the voice information memory 10 is
controlled by a gate control circuit 12. The information is read
out to a buffer register 11 under the control of the gate control
circuit 12. An error correcting code is added to the information by
a TASI control signal adding circuit 13. After the transmission of
the TASI control signals, informations stored in the voice
information memory 10 are transmitted in succession via the buffer
register 11.
The writing into and readout of voice information memory 10 of FIG.
7 is described in detail with reference to FIGS. 6a to 6e. Voice
informations of all the trunks 17-1, 17-2, . . . 17-m are
transmitted from the PCM modulator 18 to the buffer register 9 of
FIG. 7 in the pattern shown in FIG. 6a regardless of whether each
trunk is in the speech condition or the pose condition. As
hereinafter described, however, information as to whether or not
the TASI channel is allotted to each trunk is stored in the channel
condition memory 8 of FIG. 7, and the gate control circuit 12
provides a suitable control based upon the information from the
channel condition memory 8. Thus, only the voice informations of
the trunks to which TASI channels have been allotted from the voice
informations stored once in the buffer register 9 may be written in
succession in the addresses 1- n of the voice information memory 10
in the order of their arrival (FIG. 7).
There is mutual correspondence between the addresses of the voice
information memory 10 and the TASI channels. The address 1
corresponds to the TASI channel 1, which is CH1, and the address n
corresponds to the TASI channel n, which is CHn. Voice informations
are read out from the voice information memory 10 in the following
manner. If voice informations are read out in succession from the
address 1 of the voice information memory 10, the readout
information train is that shown in FIG. 6c, and only the voice
informations of trunks to which TASI channels have been allotted
are transmitted to the station B. At this time, TASI informations
are added by the TASI information-adding circuit 13 in the form of
the information train of FIG. 6e and are transmitted. That is, the
TASI informations are transmitted as an information train of binary
signals "1" and "0" indicating whether or not the TASI channels are
allotted to the bit positions corresponding to the trunks, as shown
in FIG. 6e.
The capacity of the voice information memory 10 may thus be
reduced, in accordance with our invention, by storing only the
voice informations of trunks to which TASI channels have been
allotted and by not storing voice informations of trunks to which
TASI channels have not been allotted.
In FIG. 7, the gate control circuit 12 controls the writing into
the voice information memory 10 under the control of the TASI
information-forming part and controls a series of reading
operations via the timing control signals 3. The TASI
information-forming part comprises the buffer register 4 in which
PCM signals are stored once, the level discriminator 5, the channel
condition memory 8, the writing buffer register 7 and the reading
buffer register 6. The circuits 4, 5, 6, 7 and 8 all function
synchronously with the timing control signals 3.
The discriminator 5 determines whether or not PCM signals of one
voice information stored in the buffer register 4 exceed the
designated level. If the designated level is exceeded, there is a
possibility that the trunk is in the speech condition, whereas if
said designated level is not exceeded, there is a possibility that
the trunk is in the pose condition. Only the possibility may be
determined, since it is difficult, due to noise and the like, to
instantaneously determine whether or not the speech condition or
the pose condition is present. The counting of the duration time of
the speech level or condition is therefore indicated in the
positive direction and the counting of the duration time of the
pose level or condition is indicated in the negative direction. The
counting of the two directions is performed for each trunk.
Counting is performed once in each frame for a trunk. Since the
discriminator 5 is required to perform such counting for a
plurality of trunks in a frame, the counting result is immediately
recorded in a D part of the address (FIG. 7) corresponding
exclusively to the trunk in the channel condition memory 8. If it
is determined that a PCM signal corresponding to a specific trunk
in a specific frame is in the speech level or condition, +2n is
added to the D part of the corresponding address. If it is
determined that the PCM signal is in the pose level or condition, 1
is subtracted from the D part of the corresponding address. In this
instance n may be a suitable positive integral value corresponding
to the degree of necessity for reducing the delay of time for
determining the speech condition.
If the result provided by providing addition of subtraction, as
hereinbefore described, exceeds a specific value, it is concluded
that the trunk is in the speech condition. If the result is less
than a specific value, it is concluded that the trunk is in the
pose condition. A TASI channel is allotted to the trunk which is in
the speech condition. Whether or not a TASI channel is allotted is
indicated in A, B and C parts of the address (FIG. 7), each of
which comprises one bit of the address corresponding to the trunk
within the channel condition memory 8. Whether or not a TASI
channel is allotted is determined by the binary indication "1" or
"0". If it is determined that the trunk for which there is a "0"
indication, which indicates that there is an indication in the
parts A, B and C that there is no allotment, and if the total
number of trunks to which TASI channels are allotted is less than
the total number n of TASI channels, said A, B and C parts
corresponding to the trunk are immediately changed to "1" to
indicate that there is an allotment.
If the total number of trunks arrives at the total number n of TASI
channels, only the fact that the trunk requires the allotment of a
TASI channel is recorded. Another trunk to which a TASI channel has
been allotted, but which is in the pose condition, is scanned or
searched, and the indication is changed to "0" to indicate that
there is no allotment. The trunk requiring the allotment is changed
to "1" indicating that there is an allotment. The total number of
trunks to which TASI channels are allotted is thus always
maintained under the total number n of TASI channels by modifying
the allotment of TASI channels corresponding to the voice
condition.
In FIG. 8, the level discriminator 5 is shown in greater detail.
The level discriminator 5 comprises a level-comparing circuit 5a, a
counting circuit 5b, a frame-controlling circuit 5c, a
TASI-allotting circuit 5d and a time control circuit 5e. The
information stored in the buffer register 4 is read out to the
level-comparing circuit 5a, which determines whether or not such
information is above a specific level. The condition of a trunk is
stored in the address position in the channel condition memory 8
exclusively corresponding to the trunk. The information of the D
part of the address position corresponding to the trunk stored in
the buffer register 4 is therefore read out via the buffer register
6. The counting circuit 5b provides the required addition in
accordance with the result of the previous determination by the
level comparing circuit 5a.
If, for example, the result is under a specific level, -1 is added
to the information of the D part of the address. If the result is
above a specific level, +2n is added to the information of the D
part of the address. The result of the addition is again stored in
the original position in the channel condition memory 8. If the
result of the addition is positive, "1" is written in the D part of
the address, and if said result is negative, "0" is written in said
D part. This is repeated for all the trunks within one frame period
and the timing of the process is determined by the control provided
by the time control circuit 5e via the time signals 3. A negative
addition result is immediately stored in the original position in
the channel condition memory 8 via the writing buffer register 7. A
positive addition result is transferred to the TASI-allotting
circuit 5d.
The TASI-allotting circuit 5d comprises an allotting register in
which the number of allotted channels is recorded and the contents
of the A, B and C part of the address indicating whether or not the
channel is allotted corresponding to the trunk are read out
together with the D part of the address and are transferred to said
TASI-allotting circuit without passing through the counting circuit
5b. The channel is thus allotted to the trunk in accordance with
the contents of the A, B and C part of the address, the result of
the addition and the contents of the allotting register of the TASI
allotting circuit 5d. That is, if there is an indication that a
channel is allotted to the trunk which is being processed, the
result of the addition is returned to the channel condition memory
8 via the writing buffer register 7 without modification. Even if
it is not indicated that a channel is allotted, the result of the
addition is similarly entered to the channel condition memory 8 via
the writing buffer register 7 without modification, if the contents
of the allotting register of the TASI-allotting circuit 5d equal
the total number of TASI channels.
If there is no indication of channel allotment, and the contents of
the allotting register of the TASI-allotting circuit 5d are less
than the total number n of the TASI channels, a channel is allotted
to the trunk. That is, an indication of channel allotment is
written in and is entered to the channel condition memory 8 via the
writing buffer register 7. This processing is performed in each
frame period, and when the result of the addition is positive, that
is, the D part of the address is all "1," a request for speech is
represented. When there is no indication of channel allotment, an
allotment is awaited. The A, B and C parts of the address perform
three types of operations, as hereinafter described. The
TASI-allotting circuit 5d switches between the operations performed
by the A, B and C parts of the address and the operation of copying
the indicated information. The frame-controlling circuit 5c is
controlled by the time control circuit 5e, which is initiated in
operation by the time signals 3. The frame-controlling circuit 5c
controls the timing of the burst to be transmitted by the station
of the equipment, and informations of the A, B and C parts of the
address are transferred from the TASI-allotting circuit 5d to the
gate control circuit 12 and the TASI information adding circuit 13
at the control times, and the necessary control is thus
provided.
The operation of the A, B and C parts of the address in indicating
the condition of allotment of the TASI channels is as follows. In
order to transmit voice informations continuously when TASI
informations are transmitted by dividing them into a plurality of
frames, it is necessary to transmit the TASI informations earlier
than the voice informations controlled by said TASI informations by
one signal frame, as hereinafter described, since all the TASI
informations are received by the receiver after the reception of
one signal frame. It thus becomes possible to control the
transmitted voice informations by TASI informations transmitted one
signal frame earlier. In other words, a TASI information
transmitted with a voice information is a TASI information delayed
by one signal frame.
It is therefore necessary to provide a memory for recording the
TASI information being transmitted together with the voice
information, that is, the TASI information in the transmission
condition. It is also necessary to provide a memory for recording
the TASI information already transmitted and controlling the
transmission of the voice information being transmitted, that is,
the TASI information in the operating condition. Furthermore, three
types of memories are necessary, because in the memory for storing
the TASI information in the transmission condition, the contents
cannot be rewritten until all the TASI informations are transmitted
to the other station, and in the memory for recording the TASI
information in the operating condition, the voice informations
transmitted to the receiver are controlled in accordance with the
information recorded in said memory, so that the contents of the
memory cannot be rewritten until the new TASI informations are all
transmitted to the receiver, that is, until the end of the
transmission of one signal frame.
For the foregoing reason, it is necessary to provide the third
memory for determining the present condition of each trunk, that
is, for determining whether each trunk is in the speech condition
or the pose condition and recording such information for the
succeeding control such as, for example, a memory for recording the
TASI information in the rewriting condition. Therefore, in
accordance with our invention, the memory for indicating the
condition of allotment of the TASI channels is divided into the
three bit positions A, B and C, shown in FIG. 8 and said three bit
positions or parts are mutually utilized for periodically
exchanging the functions. The TASI informations comprise, for
example, 25 sampling periods or 25 frames, and in each period, each
of the parts A, B and C is utilized in the same manner, that is,
the mutual exchange of functions. The period is referred to as one
signal frame. This is illustrated in FIG. 9.
In FIG. 9, D-ST is the memory of the channel condition memory 8 for
storing TASI information in the rewriting condition. SGT-ST is the
memory of the channel condition memory 8 for storing the TASI
information in the operating condition. In a specific signal frame,
for example, in a signal frame which is in time position 1, the
condition of allotment of TASI channels is changed in accordance
with the rewriting process hereinbefore described in the memory A
which is utilized as the memory D-ST of the channel condition
memory 8. In the same signal frame, the memory C, which was in the
memory D-ST in the preceding signal frame, is utilized as the
memory SGT-ST. In the same signal frame, the memory B, which was
utilized in the memory SGT-ST in the preceding signal frame, is
utilized as the memory SP-ST.
When a specific memory A, B or C is switched from SP-ST to D-ST,
the contents of the memory indicate the condition of allotment
determined two signal frames before, and only the part in which the
allotment is changed is rewritten. The contents are therefore
obviously unsuitable as indicative of the initial condition of
D-ST. For this reason, the first frame of D-ST includes the
operation of copying the contents of a memory in which rewriting
has just been completed and which is switched to SGT-ST as the
initial condition. By completing this operation, it becomes
possible to provide continuity to the right of priority of the
channel to which the TASI channel has once been allotted.
When the memory in D-ST is rewritten, the threshold value utilized
for the change from the pose condition to the speech condition is
higher than the threshold value utilized for the change from the
speech condition to the pose condition, out of threshold values
relating to the counting value of the D part of the address. By
providing different threshold values to the aforedescribed increase
and decrease, it is possible to avoid frequent changes of the
indication of condition around the threshold value.
FIG. 10 shows a receiver. The receiver of FIG. 10 includes the
voice information memory 53, the channel condition memory 58 and
the related components of the station B of the communication system
of our invention, as shown in FIG. 4. In FIG. 10, signals 50 are
voice informations and TASI informations received from another
station of the system. The TASI informations are coded to increase
their reliability. When the TASI informations are decoded, whether
or not a TASI channel is allotted to an arbitrary trunk is
indicated in the bit position corresponding to such trunk. If a
TASI channel is allotted, the number of such TASI channels may be
derived from the fact that the TASI channel is arranged in
accordance with the order of the trunk to which said TASI channel
is allotted.
Signals 51 indicate that the PCM signals of the received TASI
channels rearranged in the order of the trunks 27-1, 27-2, . . .
27-m of the station B corresponding to the trunks 17-1, 17-2, . . .
17-m, respectively, are applied and that when there is no talking
or voice transmission, PCM signals are applied at the PCM
demodulator 60 to the trunk of the station B corresponding to the
trunk of the station A to which no TASI channel is allotted.
Signals 59 are the synchronizing signals from the PCM transmission
line and function as the timing or time control signals to provide
the timing for receiving the TASI informations and voice
informations of the TASI channels and the timing for applying the
rearranged received PCM signals to the PCM demodulator
synchronously with the PCM transmitter.
In FIG. 10, the voice information memory 53 stores or records the
voice informations in one frame and has addresses equal in number
to the TASI channels. Writing into the voice information memory 53
is via a writing buffer memory 52 and readout from said voice
information memory is via a reading buffer memory 54. A separating
and compiling circuit 55 includes a decoding circuit for extracting
TASI informations for the burst received at the station and
determining from the error-correcting code whether or not there is
error in the received TASI information. The decoding circuit of the
separating and compiling circuit 55 also extracts TASI informations
from which the error-correcting code has been removed. A
discriminator 57 is connected to the output of the separating and
compiling circuit 55 and is coupled to the voice information memory
53 via a gate control circuit 56. The discriminator 57 includes a
counter for counting in each frame the number of frames
constituting one signal frame. The counter of the discriminator 57
supervises to ensure that the synchronizing signal of the TASI
control signal is always received at a specific constant value of
said counter and fits the signal to the received synchronizing
signals when the synchronism is shifted. The discriminator 57
writes the TASI informations provided by the separating and
compiling circuit 55 into a channel condition memory 58, and also
exchanges the functions of memories E and F of said channel
condition memory 58.
When the voice informations and TASI informations are received via
the signals 50, the voice informations, excluding the TASI
informations, are written in succession into the voice information
memory 53 via the writing buffer memory 52 commencing with the
foremost channel, that is, the head of the voice informations. The
TASI informations are separated and compiled by the separating and
compiling circuit 55 and the available TASI informations are
determined by the discriminator 57. Thus, TASI informations are
provided at the output of the separating and compiling circuit 55.
The bits corresponding to the trunks indicate whether or not the
TASI channels are allotted to the channels, and the discriminator
57 records such indications in the channel condition memory 58 in
unchanged order.
When TASI informations are transmitted by dividing them, if the
receiver controls the reception of such TASI informations, such
reception is controlled on the basis of incomplete TASI
informations and there is confusion in the communication system.
The transmitter must therefore transmit all of the TASI
informations utilized for the control of reception before such TASI
informations are utilized to control the reception. For this reason
the TASI informations transmitted by being provided ahead of the
voice informations are for the control of the voice informations of
the next-transmitted signal frame. When the transmission of the
TASI control signals is completed, the next-succeeding control
signals are immediately transmitted.
Therefore, in order to control reception continuously at the
receiver, it is necessary, in accordance with our invention to
provide two memories. One memory is for storing or recording TASI
informations utilized for the control of the received voice
informations, that is, TASI informations in operating condition,
and a memory for storing or recording TASI informations utilized
for controlling the next-succeeding signal frame, that is, TASI
informations in the receiving condition. The memories E and F are
thus provided in the channel condition memory 58. Each of the
memories E and F comprises one bit corresponding to each trunk, as
shown in FIG. 11. The memories E and F, as shown in FIG. 11 perform
the two functions of SGR-ST, which is the memory for storing the
TASI informations in the receiving condition, and SP-ST, which is
memory for storing the TASI informations in the operating
condition, alternating under the control of the discriminator 57
(FIG. 10). The switching between the functions of the memories E
and F of the channel condition memory 58 is in complete synchronism
with the switching of the transmitter memories.
Thus, the memory E is utilized as SGR-ST in a specific signal
frame. The memory E in a signal frame in the time position I (FIG.
11) becomes SP-ST in the next signal frame. Therefore, while TASI
informations are written in the memory in SGR-ST, the C memory of
the channel condition memory controls the readout of the voice
information memory 53 in SP-ST. Whether or not a TASI channel is
allotted to a trunk is indicated in one bit in the address
exclusively corresponding to such trunk. Only as to the trunk to
which a TASI channel is allotted, +1 is added to the contents of
the address, whereby the contents of the voice information memory
53 are successively read out and transmitted to the PCM decoder 60
(not shown in FIG. 10) via the reading buffer memory 54.
There is no readout from the voice information memory 53 to the
trunk for which there is no indication of readout. Instead, a PCM
signal pattern during nonconnection is transmitted from a circuit
component not shown in FIG. 10. As hereinbefore described, and in
accordance with our invention, the functions of the memories A, B,
C, E and F (FIGS. 8 and 10) are periodically exchanged, and in the
memory which stores the TASI informations, one bit is provided for
each trunk. The TASI control may therefore be realized with simple
memories and with economy.
Each of the blocks of each of FIGS. 4, 5, 7, 8 and 10 comprises any
suitable circuit arrangement for providing the operation ascribed
thereto.
While the invention has been described by means of specific
examples and in specific embodiments, we do not wish to be limited
thereto, for obvious modifications will occur to those skilled in
the art without departing from the spirit and scope of the
invention.
* * * * *