DESCRIPTION
TRANSMITTER, TRANSMISSION METHOD, AND NON-TRANSITORY
COMPUTER-READABLE MEDIUM STORING PROGRAM
5 Technical Field
[0001]
The present invention relates to a transmitter, a transmission
method, and a non-transitory computer-readable medium storing a
program, and more particularly, to a technique for performing delay
10 compensation in accordance with switching of a modulation system.
Background Art
[0 0 02]
Various methods have been proposed for synchronizing the clock
15 frequency and time of a plurality of devices by using a burst signal
having no synchronization information, such as a packet. There are
standard specifications such as IETF Network Time Protocol (NTP),
IEEE 1588-2002 Precision Time Protocol (PTP) version. 1, ITU-TG.
82821Y. 1362 Synchronous Ethernet@, and Pseudo Wire Emulation
20 Edge to Edge (PWE3).
[0003 ]
When high-precision synchronization of the clock frequency and
time is required, the communication standards, such as TDD LTE,
which require a frequency precision in units of ppb and a time
25 precision in units of ps, €ffiploy a method such as IEEE 1588-2008 PTP
version. 2, or a method of synchronizing with Global Navigation
Satellite Systems (GNSS) in each device.
[0004]
In IEEE 1588 PTP, a master device transmits a timing packet to
30 a slave device and the slave device performs processing for
reproducing the frequency and time of the slave device based on a time
stamp value included in the packet. At this time, the propagation
delay itself of the timing packet and a fluctuation in the delay affect
l0
2
the synchronization accuracy.
[000s]
In view of this, IEEE recommends a method of compensating for
a delay in a slave device by adding a propagation delay due to a
physical transmission rate between devices and a buffer retention
period within devices to a specific field of a timing packet.
[0006]
In a similar technique, Patent Literature I discloses a system in
which a master station device and a slave station device perform time
synchronization by using Gigabit Ethernet-Passive Optical Network
(GE-PON), which is an asynchronous multiplex transmission system.
In the system, the master station device periodically notifies the slave
station device of synchronization signals, and also notifies the slave
station device of a propagation delay time based on a physical
transmission distance to the slave station device. This enables time
synchronization with high precision even when a plurality of slave
station devices are arranged at different distances.
[0 00 7]
As a solution to the problem of a fluctuation in the propagation
delay, IEEE 1588 also proposes a method in which a transmission
device located on the transmission side adds, to a specific field of a
timing packet, a link delay that is determined by factors including a
retention period of packets in a transmission device, such as a buffer
in a layer 2 switch, on a transmission path, a transmission rate of a
physical line, such as l0/100/l000BASE, which constitutes the
transmission path, and a packet length. This makes it possible to
compensate for a fluctuation in the delay caused due to buffering or
line redundancy switching.
Citation List
Patent Literature
[0008]
[Patent Literature 1] Japanese Unexamined Patent Application
Publication No. 2010-206327
15
20
25
30
aJ
Summary of Invention
Technical Problem
[0ooe]
5 The above-mentioned method of compensating for a fluctuation
in the propagation delay as specified in IEEE 1588 assumes a route
change due to, for example, switching of a redundant line.
Specifically, the method employs a system in which a propagation
delay is measured in advance for each delivery port of a transmission
l0 device, and when the delivery port is changed, the propagation delay to
be used is changed. Thus, in this method, the period for updating the
propagation delay is long.
[0010]
For example, Fig.7 shows a configuration of a transmitter 70
l5 that calculates a propagation delay in accordance with the
recommendation of IEEE 1588 PTP.
[001 I ]
In the transmitter 70, a packet switch unit 2l receives timing
packets from a user network 10, and outputs a packet addressed to the
20 transmitter 70 to a timing processing unit 22 and outputs a packet
addressed to a device other than the transmitter 70 to a radio framer
unit 25. The packet switch unit 21 measures a retention period in an
internal buffer, and adds the retention period to a specific field of the
timing packet.
2s [0012]
The transmitter 70 measures a propagation delay in a
propagation path from the packet switch unit 2l to each delivery
destination, for example, a receiver 30, by using a control packet in
accordance with the recommendation of the IEEE 1588 PTP.
30 Generally, according to the recommendation of IEEE 1588 PTP, a
propagation delay in a propagation path is obtained as a static value on
the premise that the transmission capacity and propagation distance of
the propagation path are constant, and even a long-period measurement
period is satisfactorilY used.
l0
4
[0013 ]
On the other hand, an adaptive modulation system is widely
employed in the field of radio transmission. The adaptive modulation
system is a communication system in which a modulation system
having a high resistance to a fluctuation of a radio transmission path
and having a small transmission capacity is used when the quality of
the radio transmission path has deteriorated, and the ihodulation
system is automatically switched to a modulation system having a low
resistance to a fluctuation of the radio transmission path and having a
large transmission capacity when the quality of the radio transmission
path has improved. Appropriate switching of the modulation systems
in this manner allows the adaptive modulation system to satisfy both
the quality and the transmission capacity of the radio transmission
path.
[00 r 4]
In a radio transmission device employing the adaptive
modulation system, the modulation system of the radio transmission
path, i.e., the transmission capacity, DoY be dynamically changed in
units of radio frame, due to weather conditions and the like. In this
case, the propagation delay may also be changed in units of radio
frame according to the change of the transmission capacity. For this
reason, in the measurement of a delay for a long period of time by
using the control packet described above, the actual fluctuation in the
propagation delay cannot be sufficiently followed.
[001s]
Further, a radio transmission using the adaptive modulation
system requires processing, such as radio framing, analog
modulation/demodulation, and frequency conversion, unlike a
transmission via a wire. Accordingly, a delay component specific to
each modulation system is present. On the other hand, in the technique
of measuring a transmission delay as specified in the recommendation
of IEEE 1588, a total propagation delay between endpoint nodes is
merely measured, and components such as a specific delay within each
transmission device and a distance between radio sections are not
15
20
25
30
10
5
taken into consideration. Thus, in this technique, it is difficult to
calcul ate a delay time based on a delay component specific to each
modulation system.
[0016]
The present invention has been made to solve the abovementioned
problems, and an object of the present invention is to
provide a transmitter, a transmission method, and a non-transitory
computer-readable medium storing a program, which are capable of
performing delay compensation in accordance with switching of a
modulation system.
Solution to Problem
[0017]
A transmitter according to an exemplary aspect of the present
invention includes: input means for receiving an input of a timing
packet from a master device; delay compensation means for obtaining a
packet length of the timing packet and a modulation system used for
radio transmission, calculating a device-specific delay value and a
first propagation delay value based on the modulation system and the
packet length, and calculating a delay compensation value based on the
device-specific delay value and the first propagation delay value; filter
means for adding the delay compensation value to a specific field of
the timing packet; and output means for wirelessly transmitting the
timing packet to a receiver.
[0018]
A transmission method according to an exemplary aspect of the
present invention includes: a calculation step of calculating a devicespecific
delay value and a first propagation delay value based on a
packet length of a timing packet and a modulation system used for
radio transmission, and calculating a delay compensation value based
on the device-specific delay value and the first propagation delay
value; an addition step of adding the delay compensation value to a
specific field of the timing packet; and an output step of wirelessly
transmitting the timing packet to a receiver.
15
20
25
30
6
[001e]
A non-transitory computer-readable medium storing a program
according to an exemplary aspect of the present invention stores a
program that causes a computer to execute: a calculation step of
5 calculating a device-specific delay value and a first propagation delay
value based on a packet length of a timing packet and a modulation
system used for radio transmission, and calculating a delay
compensation value based on the device-specific delay value and the
first propagation delay value; an addition step of adding the delay
l0 compensation value to a specific field of the timing packet; and an
output step of wirelessly transmitting the timing packet to a receiver.
Advantageous Effects of Invention
I o 020]
15 According to the present invention, it is possible to provide a
transmitter, a transmission method, and a non-transitory computerreadable
medium for storing a program, which are capable of
performing delay compensation in accordance with switching of a
modulation system.
20
Brief Description of Drawings
[0021]
Fig. I is a block diagram of a transmitter according to a first
exemplary embodiment;
25 Fig- 2 is a block diagram of the transmitter according to the first
exemplary embodiment;
Fig. 3 is a flowchart showing processing of the transmitter
according to the first exemplary embodiment;
Fig. 4 is a block diagram of a transmitter according to a second
3 0 exemplary embodiment;
Fig. 5 is a flowchart showing processing of the transmitter
according to the second exemplary embodiment;
Fig. 6 is a block diagram of a transmitter according to a third
exemplary embodiment; and
7
Fig.7 is a block diagram of a transmitter of related art.
Description of Embodiments
[00221
5 Hereinafter, specific embodiments of the present invention will
be described in detail with reference to the drawings-
[0023 ]

Referring first to Fig. l, a configuration of a transmitter
l0 according to a first exemplary embodiment of the present invention
will be described.
100241
A transmitter 90 is a device that wirelessly transmits received
data packets as radio frames to a receiver which is an opposite radio
t5 station (not shown). Typically, the transmitter 90 is connected to a
user network A (not shown), and receives the input of data packets
from the user network A. The transmitter 90 wirelessly transmits the
data packets to a receiver 30. The receiver 30 is connected to a user
network B (not shown), and outputs the received data packets to the
20 user network B. Assume that in this exemplary embodiment, the
receiver 30 has a configuration similar to that of a transmitter 20.
[002s]
The transmitter 90 according to this exemplary embodiment
includes at least input means 91, delay compensation means 93, filter
25 means 94, and output means 95.
100261
The input means 91 is connected to an external device or a
network (the user network A in this exemplary embodiment), and
receives an input of a LAN input signal from the user network A. The
30 LAN input signal includes a timing packet output from a master device
in IEEE 1588 PTP which is present in the user network A.
100271
The delay compensation means 93 receives, from a
predetermined source, an input of a packet length of the timing packet
8
and a radio modulation system used for radio transmission. The abovementioned
source may be, for example, another processing means for
analyzing packets or acquiring a radio modulation system in the
transmitter 90, or input means for inputting these pieces of information
5 from the outside of the transmitter 90. The delay compensation means
93 calculates a device-specific delay value and a propagation delay
value by a predetermined method to be described later, by using these
pieces of information as parameters, and calculates a delay
compensation value based on these values.
I 0 [0028]
The filter means 94 adds the delay compensation value, which is
calculated by the delay compensation means 93, to a specific field of
the timing packet.
l0o2el
15 The output means 95 performs modulation into a frame,
frequency conversion, and the like on the timing packet to which the
delay compensation value is added, and outputs the timing packet to
the receiver as a radio output signal.
[003 o]
20 Referring to Fig. 2, the configuration of the transmitter 20,
which is a more detailed implementation example of the transmitter 90
of the first exemplary embodiment, will be described.
[003 r ]
The transmitter 20 includes a packet switch unit 2l serving as
25 the input means 91, a delay compensation unit 23 serving as the delay
compensation means 93, a filter unit 24 serving as the filter means 94,
and a radio framer unit 25 and a radio modulation unit 26, each of
which serves as the output means 95.
[00 3 2]
30 The transmitter 2O may also include a radio demodulation unit
27, which receives a radio signal from the receiver 30 serving as an
opposite radio station, and a radio deframer unit 28.
[003 3]
In addition, the transmitter 20 may include a timing processing
10
9
vnit 22 that processes a timing packet addressed to the transmitter 20,
when the timing packet addressed to the transmitter 20 is included in
the timing packet received from the user network A 10.
[0034]
Next, processing in the transmitter 20 will be described.
[003 5]
(1) The packet switch unit 21 receives an input of a LAN input
signal l0l from the user network A 10. The LAN input signal l0l
includes a timing packet output by the master device in IEEE 1588 PTP
which is present in the user network A 10. The packet switch unit 21
transfers the LAN input signal l0l to the filter anit 24.
[003 6]
When the LAN input signal l0l includes both a timing packet
for the transmitter 20 and a timing packet for a device other than the
transmitter 20, the packet switch unit 2l may allocate the timing
packet for the transmitter 20 to the timing processing unit 22 as a
terminal timing packet signa[ 212, and may allocate the LAN input
signal 101 including the timing packet for a device other than the
transmitter 20 to the filter ull-it 24.
[003 7]
In this case, the timing processing unit 22 can reproduce a clock
frequency and a time based on a time stamp value within the allocated
timing packet for the transmitter 20. Further, the timing processing
unit 22 may generate a timing packet to be delivered to the abovementioned
master device, and may output the generated timing packet
as a generated timing packet signal 221 to the packet switch unit 21 .
Furthermore, the timing processing unit 22 may output, to an external
device 60, the reproduced clock, timing pulse, time data, or the like as
a timing signal 222 based on IEEE 1588 PTP.
[0038]
In IEEE 1588 PTP, a propagation delay due to buffer retention
or a transmission rate of a physical line is added to a specific field of
a timing packet, and a slave station adds a time stamp value within the
timing packet to a compensation value for the specific field, thereby
l5
20
25
30
l0
l0
making it possible to obtain a time stamp of a master station to which
the propagation delay is added. Also in this exemplary embodiment,
the same function can be obtained by providing the timing processing
unit 22.
[003 e]
(2) The filter unit 24 receives a LAN input signal 2l I from the
packet switch unit 2l and transfers the LAN input signal to the radio
framer unit 25.
[0040]
(3) The radio framer unit 25 outputs, to the delay compensation
unit 23, the timing packet included in the LAN input signal 2ll, as a
transmission radio frame pulse signal 251. Further, the radio framer
unit 25 receives an opposite reception state signal 283 from the radio
deframer unit 28 to be described later. The radio framer unit 25
determines the modulation system, with which a maximum transmission
capacity can be realized without causing any error, based on the
received power of the receiver 30 and an error detection result for each
radio frame, which are included in the opposite reception state signal
283, and notifies the delay compensation unit 23 of the modulation
system as a radio modulation system notification signal 252.
[0041]
Operations of the radio demodulation unit 27 and the radio
deframer unit 28 will now be described.
100421
The radio demodulation unit 27 receives a radio input signal 300
from the receiver 30, and outputs, to the radio framer unit 25, the
received power as a radio received power signal 271.
[0043 ]
The radio deframer unit 28 performs frequency conversion and
demodulation on the radio input signal 300, thereby obtaining a radio
frame. The radio deframer unit 28 outputs, to the packet switch unit
21, a main signal packet separated from the radio frame, as a separated
LAN signal 281. On the other hand, upon detecting an error from the
radio frame, the radio deframer unit 28 outputs a radio error detection
l5
20
25
30
il
signal 282 to the radio framer unit 25. Further, the radio deframer
unit 28 separates radio receiving power, which is detected by the
receiver 30 and is multiplexed on the radio frame, from the radio
frame, and outputs the power to the radio framer unit 25 as the
5 opposite reception state signal 283.
[0044]
(a) The delay compensation unit 23 receives, from the radio
framer unit 25, the transmission radio frame pulse signal 251 and the
radio modulation system notification signal 252. The delay
l0 compensation unit 23 calculates an in-device fixed delay based on the
radio modulation system indicated by the radio modulation system
notification signal 252. The delay compensation unit 23 also
calculates a propagation delay based on the packet length of the timing
packet received as the transmission radio frame pulse signal 251, the
l5 above-mentioned radio modulation system, and a transmission distance.
[004s]
The in-device fixed delay and the propagation delay can be
calculated in the following manner. For example, in the case of
calculating the in-device fixed delay, a table or the like for associating
20 the radio modulation system with the in-device fixed delay may be
stored in a given storage means in advance, and the delay
compensation unit 23 may be configured to specify the in-device fixed
delay corresponding to the radio modulation system by referring to the
table. Alternatively, a predetermined formula, function, or the like
25 using a parameter representing the radio modulation system as a
variable or an argument may be defined in advance, and the delay
compensation unit 23 may be configured to obtain the in-device fixed
delay by giving the parameter representing the radio modulation
system to the above-mentioned formula, function, or the like as a
30 variable or an argument. Note that a similar configuration can be used
for calculation of the propagation delay.
[0046]
The delay compensation unit 23 calculates the delay
compensation value based on the in-device fixed delay and propagation
t2
delay calculated as described above. Typically, the delay
compensation value can be calculated by adding up the in-device fixed
delay and the propagation delay. The delay compensation unit 23
outputs this delay compensation value to the filter unit 24 as a delay
5 compensation signal 231.
100471
(5) The filter lunit 24 receives the delay compensation signal
231, which is received from the delay compensation unit 23, and
obtains the delay compensation value. The filter unit 24 adds this
10 delay compensation value to a specific field of the timing packet, and
outputs it to the radio framer unit 25.
[004 8 ]
(6) The radio framer unit 25 notifies the radio modulation unit
26 of the modulation system determined as described above, and
15 outputs the timing packet as a radio frame. At this time, the radio
framer unit 25 may receive the radio received power signal 271 from
the radio demodulation unit 27 to be described later and the radio error
detection signal 282 from the radio deframer unit 28, and may perform
processing for multiplexing bits for error detection on the radio frame.
20 [004e]
(7) The radio modulation unit 26 performs analog modulation in
the radio modulation system determined by the radio framer unit 25
and frequency conversion into a radio frequency on the radio frame
generated by the radio framer unit 25, and outputs it to the receiver 30
25 as a radio output signal 261.
[00 s 0]
Each step of the operation of the delay compensation unit 23 in
the above item (a) will now be described with reference to Fig.3.
[00s 1]
30 (S l) The transmitter 20 is activated to start processing.
[00s2]
(S3) The delay compensation unit 23 obtains the modulation
system of the radio frame from the radio framer unit 25, and calculates
the in-device fixed delay which is preliminarily set for each
13
modulation system.
[00s3]
(S4) The delay compensation unit 23 obtains the timing packet
from the radio framer unit 25. The delay compensation unit 23
5 calculates the propagation delay based on the packet length of this
timing packet and the above-mentioned modulation system, i.e., the
transmission capacity.
[0 0 s4]
(S5) The delay compensation unit 23 calculates the delay
10 compensation value based on the above-mentioned in-device fixed
delay and propagation delay, and outputs the delay compensation value
to the filter trnit 24 as the delay compensation signal 231.
[0055]
In this exemplary embodiment, based on the packet length of the
15 timing packet received from the input means 91 and the radio
modulation system, the delay compensation means 93 calculates the
delay compensation value, the filter means 94 adds the delay
compensation value to the timing packet, and the output means 95
delivers the timing packet, thereby making it possible to perform delay
20 compensation depending on the radio modulation system and the packet
length of the timing packet. Further, the above-mentioned
configuration enables real-time compensation of a fluctuation in the
propagation delay due to dynamic switching of radio bands by an
adaptive modulation system.
2s [00s6]

Referring to Fig. 4, the configuration of the transmitter 2O
according to a second exemplary embodiment of the present invention
will be described.
30 [00s7]
The transmitter 20 according to the second exemplary
embodiment has a feature that the delay compensation unit 23 is
configured to be able to receive an input from a control terminal 50.
The other components are similar to those of the first exemplary
t4
embodiment described above.
[00s8]
The control terminal 50 is typically a computer operable by an
operator. Information input from the control terminal 50 is output to
5 the delay compensation unit 23. In this exemplary embodiment, a
transmission distance to the receiver 30 is supplied as input
information to the delay compensation unit 23.
[00 s e]
Although this exemplary embodiment is described assuming that
l0 the control terminal 50 is provided outside of the transmitter 20, the
configuration is not limited to this. For example, in place of the
control terminal 50, a predetermined storage area may be provided
inside or outside of the transmitter 20 to store the above-mentioned
transmission distance in the storage area, and the delay compensation
l5 unit 23 may obtain the transmission distance by referring to the
storage atea. The transmission distance may be input from the control
terminal 50 only during installation work for the transmitter 20, for
example, and subsequently, the above-mentioned transmission distance
may be stored in the storage area and the delay compensation unit 23
20 may refer to the storage area.
[0060]
Next, processing of the transmitter 20 according to this
exemplary embodiment will be described. Note that this exemplary
embodiment is characterized by the processing set forth in the item
25 (4), and the processings set forth in the items (l) to (3) and (5) to (7)
are similar to those of the first exemplary embodiment described
above.
[0061]
(1) The packet switch unit 2l receives the input of the LAN
30 input signal 101 from the user network A 10, and transfers the signal
to the filter unit 24.
100621
(2) The filter unit 24 transfers the LAN input signal 211 to the
radio framer unit 25.
10
t5
[0063 ]
(3) The radio framer lul;-it 25 outputs, to the delay compensation
unit 23, the timing packet included in the LAN input signal 2ll and
the radio modulation system.
[0 0 64]
(a) The delay compensation unit 23 receives the transmission
radio frame pulse signal 251, the radio modulation system notification
signal 252, and a device control signal 501 from the control terminal
50. The delay compensation unit 23 calculates the in-device fixed
delay based on the radio modulation system indicated by the radio
modulation system notification signal 252. The delay compensation
unit 23 calculates the propagation delay based on the packet length of
the timing packet received as the transmission radio frame pulse signal
251, the above-mentioned radio modulation system, and the
transmission distance.
[006s]
The propagation delay can be calculated in the following
manner. In the case of calculating the propagation delay, a table or
the like for associating the packet length, radio modulation system,
and transmission distance with the radio modulation system may be
stored in a given storage means in advance, and the delay
compensation unit 23 may be configured to specify the propagation
delay corresponding to the packet length, radio modulation system, and
transmission distance, by referring to the table. Alternatively, u
predetermined formula, function, or the like using a parameter
representing the packet length, radio modulation system, and
transmission distance as a variable or an argument may be defined in
advance, and the delay compensation unit 23 may be configured to
obtain the propagation delay by giving the parameter representing the
packet length, radio modulation system, and transmission distance to
the above-mentioned formula, function, or the like as a variable or an
argument. Note that a similar configuration can be used for
calculation of the in-device fixed delay.
[0066]
15
20
25
30
5
t6
The delay compensation unit 23 calculates the delay
compensation value based on the in-device fixed delay and propagation
delay calculated as described above. Typically, the delay
compensation value can be calculated by adding up the'in-device fixed
5 delay and the propagation delay. The delay compensation unit 23
outputs the delay compensation value to the filter unit 24 as the delay
compensation signal 231.
[0067]
(5) The filter unit 24 adds the delay compensation value to a
l0 specific field of the timing packet, and outputs it to the radio framer
unit 25.
[006 8 ]
(6) The radio framer unit 25 notifies the radio modulation unit
26 of the modulation system determined as described above, and
15 outputs the timing packet as a radio frame.
[006e]
(7) The radio modulation unit 26 modulates the radio frame by
the above-mentioned radio modulation system, and outputs the radio
frame to the receiver 30.
20 [0070]
Each step of the operation of the delay compensation unit 23 in
the above item (a) will now be described with reference to Fig.5.
Note that this exemplary embodiment is characterized by the
processings in (Sl) and (S2), and the processings in (S3) to (S5) are
25 similar to those of the first exemplary embodiment described above.
[0071]
(Sl) In an initial state after activation of the transmitter 20, the
delay compensation unit 23 obtains the transmission distance between
radio transmission devices from the control terminal 50.
30 [0072]
(S2) The delay compensation unit 23 calculates the propagation
delay in a radio transmission section based on the obtained
transmission distance.
[00 73 ]
17
(S3) The delay compensation unit 23 obtains the modulation
system of the radio frame from the radio framer unit 25, and calculates
the in-device fixed delay which is preliminarily set for each
modulation system.
5 (S4) The delay compensation unit 23 obtains the timing packet
from the radio framer unit 25. The delay compensation unit 23
calculates the propagation delay based on the packet length of the
timing packet and the above-mentioned modulation systeD, i.e., the
transmission capacity.
r 0 [00741
(S5) The delay compensation unit 23 calculates the delay
compensation value based on the above-mentioned in-device fixed
delay and propagation delay, and outputs delay compensation value to
the filter unit 24 as the delay compensation signal 231.
1s [007s]
In this exemplary embodiment, based on the packet length of the
timing packet received from the input means 91, the radio modulation
system, and the transmission distance, the delay compensation means
93 calculates the delay compensation value, the filter means 94 adds
20 the delay compensation value to the timing packet, and the output
means 95 delivers the timing packet, thereby making it possible to
perform delay compensation depending on the radio modulation system,
the packet length of the timing packet, and the transmission distance.
Further, the above-mentioned configuration enables real-time
25 compensation of a fluctuation in the propagation delay due to dynamic
switching of radio bands by an adaptive modulation system.
1007 61

Referring to Fig. 6, the configuration of the transmitter 20
30 according to a third exemplary embodiment of the present invention
will be described.
lo07 7l
The transmitter 2O according to the third exemplary embodiment
is characterized by including a radio delay measurement unit 29. The
l0
18
other components are similar to those of the first or second exemplary
embodiment described above.
[0078]
The radio delay measurement unit 29 receives the input of the
transmission radio frame pulse signal 251 from the radio framer unit
25 and a reception radio frame pulse signal 284 from the radio
deframer unit 28. The radio delay measurement unit 29 detects a
propagation delay in a radio transmission section based on a phase
difference between the transmission frame pulse 251 and the reception
frame pulse 284, and notifies the delay compensation lunit 23 of the
propagation delay.
[0 0 7e]
As described above, the radio framer unit 25 of this exemplary
embodiment outputs the reception radio frame pulse signal 284 not
only to the delay compensation unit 23, but also to the radio delay
measurement unit 29.
[0080]
The detection of a propagation delay in a radio transmission
section wilt be described. Generally, during the operation state of the
transmitter 20 and the receiver 30, transmission and reception radio
frame pulses are unrelated. However, assuming that only for a limited
period of time after power-on of the these devices, the transmitter 20
transmits the radio frame pulse in a specific modulation system and the
receiver 30, which is an opposite radio station, sends back the received
radio frame pulse by return, the transmitter 20 compares the phases of
the transmission and reception radio frame pulses, thereby making it
possible to detect the propagation delay in the radio section.
[0081]
Sending back the radio frame pulse by return can be achieved by
inputting the reception radio frame pulse signal 284, which is output
from the radio deframer unit 28, to the radio framer unit 25. Since the
receiver 30 of this exemplary embodiment has a configuration similar
to that of the transmitter 20, the receiver 30 can send back the radio
frame pulse by return in a manner similar to that of the transmitter 20.
15
20
25
30
5
19
[0082]
The configuration described above allows the transmitter 20 of
this exemplary embodiment to automatically measure a propagation
delay in a radio transmission section. Accordingly, the configuration
5 for setting a radio transmission distance as described in the second
exemplary embodiment can be eliminated from the control terminal 50.
The propagation delay detected by the radio delay measurement unit 29
may be held by the radio delay measurement unit 29 and the
notification thereof may be given to the delay compensation unit 23, as
10 needed, or may be stored in a predetermined storage area that is
provided inside or outside of the transmitter 20 so that the delay
compensation unit 23 can refer to the storage area to obtain the
propagation delay.
[0083]
l5 In this exemplary embodiment, based on the packet length of the
timing packet received from the input means 91, the radio modulation
system, and the propagation delay detected by the radio delay
measurement unit 29, the delay compensation means 93 calculates the
delay compensation value, the filter means 94 adds the delay
20 compensation value to the timing packet, and the output means 95
delivers the timing packet, thereby making it possible to perform delay
compensation depending on the radio modulation system, the packet
length of the timing packet, and the transmission distance. Further,
the above-mentioned configuration enables real-time compensation of a
25 fluctuation in the propagation delay due to dynamic switching of radio
bands by an adaptive modulation system.
[0084]

Note that the present invention is not limited to exemplary
30 embodiments described above, and can be modified in various manners
without departing from the gist of the present invention.
[008s]
Although the present invention is described as a hardware
configuration in the above exemplary embodiments, the present
10
20
invention is not limited to this, and any processing can be implemented
by causing a CPU (Central Processing Unit) to execute a computer
program. In this case, the computer program can be stored and
provided to a computer using any type of non-transitory computer
readable media. Non-transitory computer readable media include any
type of tangible storage media. Examples of non-transitory computer
readable media include magnetic storage media (such as floppy disks,
magnetic tapes, hard disk drives, etc.), optical magnetic storage media
(e.g. magneto-optical disks), CD-ROM (Read Only Memory), CD-R,
CD-R/W, and semiconductor memories (such as mask ROM, PROM
(Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM
(Random Access Memory), etc.). The program may be provided to a
computer using any type of transitory computer readable media.
Examples of transitory computer readable media include electric
signals, optical signals, and electromagnetic waves. Transitory
computer readable media can provide the program to a computer via a
wired communication line, such as electric wires and optical fibers, or
a wireless communication line.
[00 8 6]
This application is based upon and claims the benefit of priority
from Japanese patent application No. 20ll-245306, filed on November
9,201 l, the disclosure of which is incorporated herein in its entirety
by reference.
Industrial Applicability
[0087]
The present invention relates to a transmitter, a transmission
method, and a non-transitory computer-readable medium storing a
program, and more particularly, to a technique for compensating for a
delay in accordance with switching of a modulation system.
Reference Signs List
[0088]
IO USER NETWORK A
15
20
25
30
2t
20 TRANSMITTER
2I PACKET SWITCH UNIT
22 TIMING PROCESSING UNIT
23 DELAY COMPENSATION UNIT
5 24 FILTER UNIT
25 RADIO FRAMER UNIT
26 RADIO MODULATION UNIT
27 RADIO DEMODULATION UNIT
28 RADIO DEFRAMER UNIT
1O 29 RADIO DELAY MEASUREMENT UNIT
3 O RECEIVER
50 CONTROL TERMINAL
60 EXTERNAL DEVICE
7 O TRANSMITTER
15 90 TRANSMITTER
9I INPUT MEANS
93 DELAY COMPENSATION MEANS
94 FILTER MEANS
95 OUTPUT MEANS
20
l0
22
C LAIMS
1. A transmitter comprising:
input means for receiving an input of a timing packet from a
master device;
delay compensation means for obtaining a packet length of the
timing packet and a modulation system used for radio transmission,
calculating a device-specific delay value and a first propagation delay
value based on the modulation system and the packet length, and
calculating a delay compensation value based on the device-specific
delay value and the first propagation delay value;
filter means for adding the delay compensation value to a
specific field of the timing packet; and
output means for wirelessly transmitting the timing packet to a
re c ei ver.
2. The transmitter according to Claim l, wherein the delay
compensation means further obtains a transmission distance to the
receiver, calculates a second propagation delay value based on the
transmission distance, and calculates the delay compensation value
based on the device-specific delay value, the first propagation delay
value, and the second propagation delay value.
3. The transmitter according to Claim 1, further comprising
radio delay measurement means for detecting a phase difference
between a transmission frame pulse wirelessly transmitted to the
receiver by the transmitter and a reception frame pulse wirelessly
transmitted by the receiver and received by the transmitter, and
calculating a third propagation delay value based on the phase
difference,
wherein the delay compensation means calculates the delay
compensation value based on the device-specific delay value and the
third propagation delay value.
l5
20
25
30
23
4. The transmitter according to any one of Claims I to 3,
further comprising radio framer means for determining a modulation
system in the radio transmission based on a result of the radio
transmission between the transmitter and the receiver, and notifying
5 the delay compensation means of the modulation system.
5. The transmitter according to Claim 4, further comprising
radio deframer means for receiving a reception state signal of the radio
transmission from the receiver,
l0 wherein the radio framer means determines a modulation system
in the radio transmission based on the reception state signal.
6. A transmission method comprising:
a calculation step of calculating a device-specific delay value
I 5 and a first propagation delay value based on a packet length of a
timing packet and a modulation system used for radio transmission,
and calculating a delay compensation value based on the devicespecific
delay value and the first propagation delay value;
an addition step of adding the delay compensation value to a
20 specific field of the timing packet; and
an output step of wirelessly transmitting the timing packet to a
receiver.
7. The transmission method according to Claim 6, wherein the
25 calculation step further includes: calculating a second propagation
delay value based on a transmission distance to the receiver; and
calculating the delay compensation value based on the device-specific
delay value, the first propagation delay value, and the second
propagation delay value.
30
8. The transmission method according to Claim 6, wherein the
calculation step further includes: calculating a third propagation delay
value based on a phase difference between a transmission frame pulse
wirelessly transmitted to the receiver by the transmitter and a
24
reception frame pulse wirelessly transmitted by the receiver and
received by the transmitter; and calculating the delay compensation
value based on the device-specific delay value and the third
propagation delay value.
5
9. A non-transitory computer-readable medium storing a
program for causing a computer to execute:
a calculation step of calculating a device-specific delay value
and a first propagation delay value based on a packet length of a
10 timing'packet and a modulation system used for radio transmission,
and calculating a delay compensation value based on the devicespecific
delay value and the first propagation delay value;
an addition step of adding the delay compensation value to a
specific field of the timing packet; and
l5 an output step of wirelessly transmitting the timing packet to a
receiver.