1. A synchronization apparatus comprising: frequency synchronization means for performing frequency synchronization based on a synchronization signal transmitted from a synchronization signal source through a network, and outputting a frequency synchronization signal; phase synchronization means for performing phase synchronization based on a synchronization signal transmitted from the synchronization signal source through a network, and outputting a phase synchronization signal; and phase synchronization control means for generating an offset value by using a phase difference between the frequency synchronization signal and the phase synchronization signal, and correcting a phase of the frequency synchronization signal by using the offset value.

2. The synchronization apparatus according to Claim 1, wherein the phase synchronization means receives a synchronization signal transmitted from the synchronization signal source through a packet network.

3. The synchronization apparatus according to Claim 1 or 2, wherein the frequency synchronization means receives a synchronization signal transmitted from the synchronization signal source through a signal transmitted by using a physical layer.

4. The synchronization apparatus according to any one of Claims 1 to 3. wherein the frequency synchronization signal is a frequency synchronization pulse signal having a pulse waveform, and the phase synchronization signal is a phase synchronization pulse signal having a pulse waveform, and the phase synchrpnidation control means comprises: phase comparison means for calculating phase differences between the frequency synchronization pulse signal and the phase synchronization pulse signal in a predetermined period; and offset value calculation means for correcting a phase of the frequency synchronization signal by using an offset value, the offset value being generated by statistically processing a plurality of phase differences.

5. The synchronization apparatus according to Claim 4, wherein the offset value calculation means does not generate the offset value when the phase difference calculated by the phase comparison means is greater than a predefined value.

6. The synchronization apparatus according to Claim 4, wherein the offset value calculation means does not generate the offset value when a second phase difference between the frequency synchronization pulse signal and the phase synchronization pulse signal in a second predetermined period is greater than a first phase difference between the frequency synchronization pulse signal and the phase synchronization pulse signal in a first predetermined period by a predefined value, the second predetermined period being different from the first predetermined period.

7. The synchronization apparatus according to Claim 4, wherein the offset value calculation means does not generate the offset value when a second phase difference between the frequency synchronization pulse signal and the phase synchronization pulse signal in a second predetermined period is smaller than a first phase difference between the frequency synchronization pulse signal and the phase synchronization pulse signal in a first predetermined period by a predefined value, the second predetermined period being different from the first predetermined period. a synchronization signal source; a synchronization signal transmitting apparatus that converts a synchronization signal transmitted from the synchronization signal source into a signal in a physical layer and transmits the converted signal as a first synchronization signal, and transmits the synchronization signal as a second synchronization signal through a packet network; and a synchronization apparatus that generates a frequency synchronization signal by performing frequency synchronization based on the first synchronization signal, generates a phase synchronization signal by performing phase synchronization based on the second synchronization signal, and corrects a phase of the frequency synchronization signal by using an offset value, the offset value being generated by using a phase difference between the frequency synchronization signal and the phase synchronization signal.

9. The synchronization system according to Claim 8, wherein the synchronization signal transmitting apparatus transmits the first and second synchronization signals to the synchronization apparatus through the same transmission path.

10. The synchronization system according to Claim 8, wherein the synchronization signal transmitting apparatus transmits the first and second synchronization signals to the synchronization apparatus through different transmission paths. 11 . The synchronization system according to Claim 8, further comprising a first synchronization signal transmitting apparatus that receives a synchronization signal transmitted from the synchronization signal source, and a second synchronization signal transmitting apparatus that receives a synchronization signal transmitted from the synchronization signal source, wherein the first synchronization signal transmitting apparatus transmits the first sy nchroni zatjon. signal_to jt h_e synchronization apparatus, and the second synchronization signal transmitting apparatus transmits the second synchronization signal to the synchronization apparatus

12. A radio communication comprising: first synchronization signal receiving means for receiving a p l u r a l i t y of synchronization signals from a synchronization signal source through a network, the p l u r a l i t y of synchronization signals being used for frequency synchronization; second synchronization signal receiving means for receiving a p l u r a l i t y of synchronization signals from the synchronization signal source through a network, the plurality of synchronization signals being used for phase synchronization; frequency synchronization means for performing frequency synchronization based on a synchronization signal selected in the first synchronization signal receiving means, and outputting a frequency synchronization signal; phase synchronization means for performing phase synchronization based on a synchronization signal selected in the second synchronization signal receiving means, and outputting a phase synchronization signal; and phase synchronization control means for generati ng. an offset value by using a phase difference between the frequency synchronization signal and the phase synchronization signal, and c o r r e c t i n g a phase of the frequency synchronization signal by using the offset value.

13. A synchronization method comprising: performing frequency synchronization based on a synchronization signal transmitted from a synchronization signal source through a network, and outputting a frequency synchronization signal; performing phase synchronization based on a synchronization signal transmitted fron^ the syji^chronj zati on signal source through a network, and outputting a phase synchronization signal; and generating an offset value by using a phase difference between the frequency synchronization signal and the phase synchronization signal, and correcting a phase of the frequency synchronization signal by using the offset value.

DESCRIPTION
SYNCHRONIZATION APPARATUS, SYNCHRONIZATION SYSTEM,
RADIO COMMUNICATION APPARATUS AND
SYNCHRONIZATION METHOD
Technical Field
[0001]
The present invention relates to a synchronization apparatus, a
synchronization system, a radio communication apparatus, and a
10 synchronization method. In p a r t i c u l a r , the present invention relates to
a synchronization apparatus, a synchronization system, a radio
communication apparatus, and a synchronization method for performing
synchronization by using a synchronization signal transmitted from a
synchronization signal source.
15
Background Art
[0002]
Techniques in which a signal broadcasted from a GNSS (Global
Navigation Satellite System) s a t e l l i t e ( i . e . , a signal for
synchronization) is received by a GNSS receiver, and a timing signal
synchronized with the UTC (Universal Time, Coordinated) is output
have been proposed in the past (see, for example, Patent Literature 1).
[0003]
Further, in some cases, in order to enable a synchronization
apparatus located in a place where it cannot directly receive the signal
for synchronization from the GNSS s a t e l l i t e to use the synchronization
signal, the GNSS receiver, which has received the synchronization
signal from the GNSS s a t e l l i t e , transmits the synchronization signal to
the synchronization apparatus through a network.
3 0 Citation List
Patent Literature
[0004]
Patent Literature 1: Japanese Unexamined Patent Application
20
25
3
Publication No. 2010-273148
Summary of Invention
Technical Problem
5 [0005]
However, when the GNSS receiver transmits the synchronization
signal to the synchronization apparatus through an asynchronous
network such as a packet network, fluctuations occur in
synchronization signals received by the GNSS receiver due to
10 congestion, a transmission delay, or the like in the network. Therefore,
there is a problem that phase and time synchronization c h a r a c t e r i s t i cs
comparable to those of the GNSS c a n n o t b e obtained in a
synchronization apparatus that receives a synchronization signal from
the GNSS receiver through a network.
15 [0006]
In order to the above-described problem, an object of the present
invention is to provide a synchronization apparatus, a synchronization
system, a radio communication apparatus, and a synchronization
method capable of reducing the effect of the fluctuations in
20 synchronization signals that are caused when the synchronization
signals are received through a network.
Solution to Problem
[0007] ,
25 A synchronization apparatus according to a first aspect in
accordance with the present invention includes: a frequency
synchronization unit that performs frequency synchronization based on
a synchronization signal transmitted from a synchronization signal
source through a network, and outputs a frequency synchronization
30 signal; a p h a s e ' s y n c h r o n i z a t i o n unit that performs phase
synchronization based on a synchronization signal transmitted from the
synchronization signal source through a network, and outputs a phase
synchronization signal; and a phase synchronization control unit that
generates an offset value by using a phase difference between the
TP Q DELHX.. 2 6 - 0 :&- 2.B 1 S 1-6 ~ 2 Sr •
4
frequency synchronization signal and the phase synchronization signal,
and corrects a phase of the frequency synchronization signal by using
the offset value.
[0008]
5 A synchronization system according to a second aspect in
accordance with the present invention includes: a synchronization
signal source; a synchronization signal transmitting apparatus that
converts a synchronization signal transmitted from the synchronization
signal source into u signal in a physical layer and transmits the
10 converted signal as a first synchronization signal, and transmits the
synchronization signal as a second synchronization signal through a
packet network; and a synchronization apparatus that generates a
frequency synchronization signal by performing frequency
synchronization based on the first synchro'nization signal, generates a
15 phase synchronization signal by performing phase synchronization
based on the second synchronization signal, and corrects a phase of the
frequency synchronization signal by using an offset value, the offset
value being generated by using a phase difference between the
frequency synchronization signal and the phase synchronization signal.
20 [0009]
A radio communication apparatus according to a third aspect in
accordance with the present invention includes: a first synchronization
signal receiving unit that receives a p l u r a l i t y of synchronization
signals from a synchronization signal source through a network, the
2 5 plurality of synchronization signals being used for frequency
synchronization; a second synchronization signal receiving unit that
receives a plurality of synchronization signals from the
synchronization signal source through a network, the plurality of
synchronization signals being used for phase synchronization; a
30 frequency synchronization unit that performs frequency
synchronization based on a synchronization signal selected in the first
synchronization signal receiving unit, and outputs a frequency
synchronization signal; a phase synchronization unit that performs
phase synchronization based on a synchronization signal selected in
5
the second synchronization signal receiving unit, and outputs a phase
synchronization signal; and a phase synchronization control unit that
generates an offset value by using a phase difference between the
frequency synchronization signal and the phase synchronization signal,
5 and corrects a phase of the frequency synchronization signal by using
the offset value.
[0010]
A synchronization method according to a fourth aspect in
accordance with the present invention includes: performing frequency
10 synchronization based on a synchronization signal transmitted from a
synchronization signal source through a network, and outputting a
frequency synchronization signal; performing phase synchronization
based on a synchronization signal transmitted from the synchronization
signal source through a network, and outputting a phase
15 synchronization signal; and generating an offset value by using a phase
difference between the frequency synchronization signal and the phase
synchronization signal, and correcting a phase of the frequency
synchronization signal by using the offset value.
20 Advantageous Effects of Invention
[0011]
According to the present invention, it is possible to provide a
synchronization apparatus, a synchronization system, a radio
communication apparatus, and a synchronization method capable of
25 reducing the effect of the fluctuations in synchronization signals that
are caused when the synchronization signals are received through a
network.
cription of Drawings
. 1 is a configuration diagram of a synchronization system
to a first exemplary embodiment;
. 2 is a configuration diagram of a synchronization system
to a second exemplary embodiment;
> R - Q S - - 2: BI S 1 6- - 2 8-
Brief Des
30 [0012]
Fig
according
Fig
according
f p Q : EJE-.L 14 X
Fig. 3 is a configuration diagram of a synchronization apparatus
according to the second exemplary embodiment;
Fig. 4A is a diagram for. explaining a phase deviation of a pulse
signal according to the second exemplary embodiment;
5 Fig. 4B is a diagram for explaining a phase deviation of a pulse
signal according to the second exemplary embodiment;
Fig. 4C is a diagram for explaining a phase deviation of a pulse
signal according to the second exemplary embodiment;
Fig. 5 is a diagram showing a flow of processes for applying an
10 offset value according to the second exemplary embodiment;
Fig. 6 is a configuration diagram of a synchronization apparatus
according to a third exemplary embodiment;
Fig. 7 is a configuration diagram of a synchronization apparatus
according to the third exemplary embodiment;
15 Fig. 8 is a diagram showing a process flow for applying an
offset value according to the third exemplary embodiment;
Fig. 9A is a diagram for explaining a phase deviation of a pulse
signal according to a third exemplary embodiment;
Fig. 9B is a diagram for explaining a phase deviation of a pulse
20 signal according to the third exemplary embodiment; and
Fig. 10 is a configuration diagram of a radio communication
apparatus according to a fourth exemplary embodiment.
D e s c r i p t i o n of Embodiments
25 [0013]
(First exemplary embodiment)
Exemplary embodiments according to the present invention are
explained hereinafter with reference to the drawings. A configuration
example of a synchronization system and a synchronization apparatus
30 according to a first exemplary embodiment in accordance with the
present invention is explained with reference to Fig. 1 . A
synchronization system shown in Fig. 1 includes a synchronization
signal source 10 and a synchronization apparatus 20. The
synchronization signal source 10 communicates with the
•E*ev rtEL.H-1; 2 S - € * & - 2 . - Q - ! 5- 1& - 2S7
synchronization apparatus 20 through a network 30.
[0014]
The synchronization signal source 10 may be, for example, an
apparatus that generates a synchronization signal synchronized with
5 the UTC. Alternatively, the synchronization signal source 10 may be
an apparatus that generates a synchronization signal synchronized with
the Japan standard time, the TAI (the international atomic time), the
GPS (Global Positioning System) time, or the like, which is used in
synchronization with the UTC.
10 [0015]
The network 30 may be, for example, a packet network through
which packets are transmitted using the Ethernet (registered
trademark) or an optical transmission network in which an SDH
(Synchronous Digital Hierarchy) is used in its physical layer. Further,
15 Fig. 1 shows a configuration in which only the network 30 is used
between the synchronization signal source 10 and the synchronization
apparatus 20. However, for example, different networks may be used
for communication between the synchronization signal source 10 and a
frequency synchronization unit 21 of the synchronization apparatus 20
20 and for communication between the synchronization signal source 10
and a phase synchronization unit 23 of the synchronization apparatus
20.
[0016] -
The synchronization apparatus 20 may be a single (or separate)
25 apparatus that performs synchronization control, or may be an
apparatus that carries out a plurality of functions. For example, the
synchronization apparatus 20 may be formed as a part of a radio
communication apparatus. A configuration example of the
synchronization apparatus 20 is explained hereinafter.
30 [0017]
The synchronization apparatus 20 includes a frequency
synchronization unit 21, a phase synchronization control unit 22, and a
phase synchronization unit 23. The frequency synchronization unit 21
performs frequency synchronization based on a synchronization signal
p& DE4-KI: 2-6-OS-2.*** 1S-2.S
transmitted from the synchronization signal source 10 through the
network 30. That is, the frequency synchronization unit 21 generates a
frequency synchronization signal synchronized with the frequency of
the synchronization signal transmitted from the synchronization signal
5 source 10. The frequency synchronization unit 21 outputs the
generated frequency synchronization signal to a c i r c u i t ( s ) or the like
c o n s t i t u t i n g an external apparatus different from the synchronization
apparatus 20, and to the phase synchronization control unit 22.
[0018]
10 The phase synchronization unit 23 performs phase
synchronization based on a synchronization signal transmitted from the
synchronization signal source 10 through the network 30. That is, the
phase synchronization unit 23 generates a phase synchronization signal
synchronized with the phase of the synchronization signal transmitted
15 from the synchronization signal source 10. The phase synchronization
unit 23 outputs the generated phase synchronization signal to the phase
synchronization control unit 22.
[0019]
The phase synchronization control unit 22 obtains a phase
2 0 difference between the frequency synchronization signal output from
the frequency synchronization unit 21 and the phase synchronization
signal output from the phase synchronization unit 23. Further, the
phase synchronization control unit 22 calculates an offset value that is
applied to the frequency synchronization signal output from the
25 frequency synchronization unit 21 by using the obtained phase
difference. The frequency synchronization unit 21 outputs the
calculated offset value to the frequency synchronization unit 21 and
corrects the phase of the frequency synchronization signal.
[0020]
30 As explained above, by using the synchronization apparatus 20
according to the first exemplary embodiment of the present invention,
it is possible to generate an offset value by using the phase difference
between the frequency synchronization signal and the phase
synchronization signal and correct the phase of the frequency
- p.. Q. . | \ P- L. 14. X 2 & •"" fc&- 2.Q. i. R - 2,: ter
synchronization signal by using the generated offset value, rather than
generating a synchronization signal by using only the frequency
synchronization signal obtained in the phase synchronization unit 23.
As a result, the synchronization apparatus 20 can generate a highly
5 accurate synchronization signal.
[0021J
(Second exemplary embodiment)
Next, a configuration example of a synchronization system
according to a second exemplary embodiment of the present invention
10 is explained with reference to Fig. 2. A synchronization system shown
in Fig. 2 includes a GNSS s a t e l l i t e 11, a GNSS receiver 12, a
synchronization signal t r a n s m i t t i n g apparatus 13, and a
synchronization apparatus 20. Further, the synchronization signal
transmitting apparatus 13 is connected with the synchronization
15 apparatus 20 through a network 30. Note that the following
explanations are given while assigning symbols similar to those in Fig.
1 to apparatuses similar to those in the configuration shown Fig. 1.
[0022]
The GNSS s a t e l l i t e 11 transmits a GNSS broadcast signal
20 synchronized with the UTC. Note that the term "GNSS" is a general
term for navigation s a t e l l i t e system including GPS, GLONASS, Galileo.
Compass, quasi-zenith s a t e l l i t e systems (QZSS), and so on. The GNSS
receiver 12 receives the GNSS broadcast signal transmitted from the
GNSS s a t e l l i t e 11, reproduces a synchronization signal based on the
25 received GNSS broadcast signal, and transmits the reproduced
synchronization signal to the synchronization signal transmitting
apparatus 13.
[0023]
The synchronization signal transmitting apparatus 13 transmits
30 the synchronization signal to the synchronization apparatus 20 through
the network 30. The synchronization signal is, for example, a clock
signal generated by using the GNSS broadcast signal. Note that the
synchronization signal transmitting apparatus 13 transmits the
synchronization signal by using a method specified in, for example,
T P-R DEL.B.X 2:8- - OS-- 2;©-I 5 IS ' 2 S •
10
IEEE 1 5 8 8 (hereinafter called "IEEE1588 transmission") and a
Synchronous Ethernet (registered trademark) (hereinafter expressed as
"SyncE") method. The IEEE1588 transmission and the SyncE
transmission are performed through the Ethernet (registered trademark).
5 Further, the IEEE1588 may also be referred to as "PTP (Precision Time
P r o t o c o l ) " .
[0024]
As explained above with reference to Fig. 1, the synchronization
apparatus 20 generates a frequency synchronization signal
10 synchronized with the frequency of the synchronization signal
t r a n s m i t t e d from the synchronization signal transmitting apparatus 13
and a phase synchronization signal synchronized with the phase of the
synchronization signal transmitted from the synchronization signal
t r a n s m i t t i n g apparatus 13.
15 [0025]
Next, a detailed configuration example of the synchronization
apparatus 20 according to the second exemplary embodiment of the
present invention is explained with reference to Fig. 3. The
synchronization apparatus 20 shown in Fig. 3 includes a physical layer
20 data receiving unit 24, a pulse generation unit 25, a timing offset unit
26, a packet data receiving unit 27, a phase comparison unit 28, and an
offset value calculation unit 29. Note that the physical layer data
receiving unit 24 and the pulse generation unit 25 correspond to the
frequency synchronization unit 21 in Fig. 1. Further, the packet data
25 receiving unit 27 corresponds to the phase synchronization unit 23.
Further, the timing offset unit 26, the phase comparison unit 28, and
the offset value calculation unit 29 correspond to the phase
synchronization control unit 22.
[0026]
30 The physical layer data receiving unit 24 receives a
synchronization signal transmitted from the synchronization signal
t r a n s m i t t i n g apparatus 13 through a physical layer of a SyncE
transmission path. The physical layer data receiving unit 24 is formed
by, for example, using a phase synchronization circuit (or PLL: Phase-
T'P'D [ l E L B I 2 8- - BB ~ 2 ©• 15 I- B - 2B
11
Locked Loop). The physical layer data receiving unit 24 synchronizes
the frequency of a signal generated by using an oscillator with the
frequency of the synchronization signal transmitted from the
synchronization signal transmitting apparatus 13 by using the PLL
5 circuit. The physical layer data receiving unit 24 outputs the signal,
whose frequency has been synchronized with that of the
synchronization signal transmitted from the synchronization signal
t r a n s m i t t i n g apparatus 13, as an output clock. The physical layer data
receiving unit 24 outputs the output clock to the pulse generation unit
10 25, a c i r c u i t ( s ) located outside the synchronization apparatus 20, and
so on.
[0027]
The pulse generation unit 25 generates an output timing pulse
based on the output clock output from.the physical layer data receiving
15 unit 24. For example, the pulse generation unit 25 extracts the clock
timing of the output clock and thereby generates a pulse signal as an
output timing pulse. Note that the clock timing is, for example, the
r i s i ng timing or the falling timing of the output clock. The pulse
generation unit 25 outputs the generated output timing pulse to the
20 timing offset unit 26. Further, the timing offset unit 26 outputs the
output timing pulse to the phase comparison unit 28.
[0028]
Note that the physical layer data receiving unit 24 receives a
synchronization signal that is transmitted through a physical layer.
25 Therefore, even w h e n a number of packet data, which correspond to a
layer higher than the physical layer, are transmitted and hence
congestion occurs in the network 30, the congestion does not directly
affect the transmission of the synchronization signal transmitted
through the physical layer. Therefore, no fluctuation occurs in
30 synchronization signals received by the physical layer data receiving
unit 24. That is. when the pulse generation unit 25 generates output
timing pulses by using the output clock output from the physical layer
data receiving unit 24, the pulse intervals of the generated output
timing pulses are the same as t h e j ) u l s e intervals of the synchronization
TP-£* DEL.«X 2i - BB - 2 .BI S 16- - 2Br
12
signal reproduced by the GNSS receiver 12 based on the GNSS
broadcast signal. However, the synchronization signal transmitted
through the physical layer includes no phase information. Therefore,
as shown in Fig. 4A, a phase deviations occurs between the
5 synchronization source phase and the reproduced phase by the SyncE.
The synchronization source phase means the synchronization signal
output by the synchronization signal transmitting apparatus 13, and the
reproduced phase by the SyncE means the output timing pulse. Note
that the synchronization signal is shown in the form in which the
10 synchronization signal is converted into a pulse signal. Further, Fig.
4A also shows that the pulse interval of the reproduced phase by the
SyncE is equal to the pulse interval in the pulse signal generated based
on the synchronization signal of the synchronization source ( i . e . , the
pulse signal generated based on the synchronization signal reproduced
15 by the GNSS receiver 12 based on the GNSS broadcast signal).
[0029]
The packet data receiving unit 27 receives a synchronization
signal transmitted through the IEEE1588 transmission. The packet
data receiving unit 27 receives a synchronization signal that is
20 transmitted as packet data. For example, when the synchronization
signal transmitting apparatus 13 serves as a PTP (Precision Time
Protocol) server, the packet data receiving unit 27 may serve as a PTP
client. The packet data receiving unit 27 generates timing pulses,
which are a pulse signal, based on the received synchronization signal.
25 As for the method for generating timing pulses based on the
synchronization signal received through the IEEE1588 transmission, a
commonly used method may be used. Further, the method is not
limited to any particular methods. The packet data receiving unit 27
outputs the generated timing pulses to the phase comparison unit 28.
30 [0030]
The synchronization signal .transmitted through the 1EEE1588
transmission includes phase information. Therefore, fundamentally,
the phase of the timing pulses coincides with the phase of the
synchronization signal ^output b^ th^ejsynchronization signal
P © O-E L H1. 2.S- - OS- - 2.Q-1 fe I %>• - 2 B13
t r a n s m i t t i n g apparatus 13. However, fluctuations occur in
synchronization signals transmitted through the IEEE1588 transmission
because of the state of the network between the synchronization signal
t r a n s m i t t i n g apparatus 13 and the packet data receiving unit 27 such as
5 a congested state, network switching, a band change, an AMR
(Adaptive Modulation Radio) in radio transmission, and so on.
Therefore, as shown in Fig. 4B, a deviation occurs between the phase
of the pulse signal generated based on the synchronization signal of
the synchronization source ( i . e . , the pulse signal generated based on
10 the synchronization signal reproduced by the GNSS receiver 12 based
on the GNSS broadcast signal) and that of the timing pulses. The
reproduced phase by the IEEE1588 in Fig. 4B represents the clock
timings of the timing pulses. Note that in the reproduced phase by the
1EEE1588, the vertical dotted-line arrows indicate clock timings when
15 the reproduced phase coincides with the phase of the pulse signal
generated based on the synchronization signal of the synchronization
source. The solid-line arrows indicate actually generated timing
pulses. When the actually generated timing pulse coincides with the
clock timing of the pulse signal generated based on the
20 synchronization signal of the synchronization source, only the solidline
arrow is drawn. This also holds true in the following explanations.
[0031]
The phase comparison unit 28 compares the output timing pulses
output from the timing offset unit 26 with the timing pulses output
25 from the packet data receiving unit 27. Specifically, the phase
comparison unit 28 calculates phase differences between the output
timing pulses and the timing pulses as shown by the horizontal arrows
in Fig. 4B. The phase difference between the output timing pulse and
the t i m ing pulse is calculated at each clock timing such as each rising
30 timing. As a result, the phase comparison unit 28 has information
about a plurality of phase differences.
[0032]
The offset value calculation unit 29 s t a t i s t i c a l l y processes the
information about a plurality of phase differences and thereby
*£*• O-ELH'X. 2.B--- 06-™ 2.0-1 S-- I B - - 2.-S14
calculates an offset value to be applied to the output timing pulses.
The offset value is a value that is uniformly applied to a p l u r a l i t y of
clock timings. Further, the offset value is used to conform the phase
of the output timing pulses with the pulse signal generated based on
5 the signal of the synchronization source (e.g., the synchronization
signal generated based on the GNSS broadcast signal transmitted from
the GNSS s a t e l l i t e ) . For example, the offset value calculation unit 29
may use the average value of a plurality of phase differences as the
offset value. Alternatively, the offset value calculation unit 29 may
10 use the median among a p l u r a l i t y of phase differences as the offset
value. Alternatively, the offset value calculation unit 29 may use the
minimum value among a p l u r a l i t y of phase differences as the offset
value. Note that when the offset value calculation unit 29 determines
what kind of value is used as the offset value, the offset value
15 calculation unit 29 may obtain a distribution of phase differences and
determine that the average value, the median, or other values is used as
the offset value according to the obtained d i s t r i b u t i o n state of the
phase differences. The offset value calculation unit 29 outputs the
calculated offset value to the timing offset unit 26.
20 [0033]
As shown in Fig. 4C, the timing offset unit 26 applies the offset
value to the output timing pulses and thereby controls the phase of the
output timing pulses so that it conforms to the phase of the pulse
signal generated based on the synchronization signal of the
25 synchronization source. The timing offset unit 26 outputs the output
timing pulses, whose phase has been controlled, to other circuits or the
like that require synchronous processing.
[0034]
Next, a flow of processes for applying an offset value according
30 to the second exemplary embodiment of the present invention is
explained with reference to Fig. 5. Firstly, the physical layer data
receiving unit 24 receives a synchronization signal transmitted from
the synchronization signal transmitting apparatus 13 through a physical
layer of a SyncE transmission p_a t h ^ Further, the physical layer.data
- p f t P E L 14. X. 2 8- ~ Q-S*'™ 2 81 S 1.6- - 2.8-
15
receiving unit 24 synchronizes the frequency of a signal generated by
using an oscillator with the frequency of the received synchronization
signal and thereby outputs an output clock ( S l l ) .
[0035]
5 Next, the pulse generation unit 25 generates output timing
pulses by using the output clock output from the physical layer data
receiving unit 24 (S12).
[0036]
Next, the packet data receiving unit 27 receives a
10 synchronization, signal transmitted through the IEEE1588 transmission
(S13). The packet data receiving unit 27 generates timing pulses based
on the received synchronization signal.
[0037]
Next, the phase comparison unit 28 measures phase differences
15 between the output timing pulses output from the pulse generation unit
25 and the timing pulses output from the packet data receiving unit 27
(S14). For example, the phase comparison unit 28 measures phase
differences between the output timing pulses and the timing pulses
output from the packet data receiving unit 27 in a. predetermined period,
20 and thereby generates information about a plurality of phase
differences.
[0038]
The phase comparison unit 28 determines whether or not there is
a phase difference that is greater than a pre-defined threshold in the
25 generated information about the plurality of phase differences (SI 5).
When it is determined that there is a phase difference greater than the
pre-defined threshold among the plurality of measured phase
differences by the-phase comparison unit 28 (S15, Yes), the process in
the step S13 is repeated. When the phase difference is larger, it can be
30 presumed that fluctuations in the timing pulses are large. In such
cases, it is very difficult to correct and conform the phase of the
output timing pulses to the phase of the pulse signal generated based
on the synchronization signal of the phase source based on the timing
pulses having large fluctuations. Therefore, it is controlled so that the
> 0 DEL H X 26- - Gi-S- - 2 Q I S 16- - 2.6-
16
process in t h e . s t e p S13, in which packet data are acquired, is repeated.
[0039]
When it is determined that there is no phase difference greater
than the pre-defined threshold among the plurality of measured phase
5 differences by the phase comparison unit 28 (S15, No), the offset value
c a l c u l a t i o n unit 29 s t a t i s t i c a l l y processes the information about the
p l u r a l i t y of phase differences and thereby calculates an offset value to
be applied.to the output timing pulses (S16). Next, the timing offset
unit 26 applies the offset value calculated by the offset value
10 calculation unit 29 to the output timing pulses (S17).
[0040]
As explained above, by using the synchronization apparatus 20
according to the second exemplary embodiment of the present
invention, it is possible to generate output timing pulses by using the
15 synchronization signal transmitted through the physical layer of the
SyncE transmission path or the like and the synchronization signal
transmitted through the IEEE1588 transmission or the like.
[0041]
Note that the synchronization signal transmitted through the
20 physical layer of the SyncE transmission path or the like is transmitted
without being affected by the congestion of packet data and the like in
the network. Therefore, when synchronization signals are received in
the synchronization apparatus 20, no fluctuation occurs in the arrival
intervals of the synchronization signals. Accordingly, the frequency
25 of the output clock that is generated in synchronization with the
frequency of the synchronization signal coincides with the frequency
of the synchronization signal. As a result, the pulse intervals of the
output timing pulses generated by using the output clock are constant
i n t e r v a l s .
30 [0042]
Since synchronization signals transmitted through the 1EEE1588
transmission are affected by congestion of packet data and the like,
fluctuations occur in their arrival intervals in the synchronization
apparatus 20. However, it is possible to calculate an offset value for
TPFt Q-'E-LHiX 2-€r~ €£S " 2 01 S I B - - 2©-
17
reducing the effect of the synchronization signal fluctuations and
thereby correcting the phase of the output timing pulses by
s t a t i s t i c a l l y processing phase differences between the output timing
pulses, whose pulse intervals are constant, and the timing pulses, in
5 which fluctuations occur. As described above, by using the offset
value for reducing the effect of the synchronization signal fluctuations,
the phase of the output timing pulse.s can be conformed to the phase of
the pulse signal determined based on the synchronization signal of the
synchronization source. In this way, the synchronization apparatus 20
10 according to the second exemplary embodiment can generate highly
accurate output timing pulses.
[0043]
(Third exemplary embodiment)
Next, a configuration example of a synchronization system
15 according to a third exemplary embodiment of the present invention is
explained with reference to Fig. 6. A synchronization system shown in
Fig. 6 includes a GNSS s a t e l l i t e 11, a GNSS receiver 14, a packet data
transmission apparatus 15, a GNSS receiver 16 and a synchronization
apparatus 20. The GNSS s a t e l l i t e 1 1 and the phase synchronization
20 control unit 22 are similar to those shown in Fig. 2, and therefore their
detailed explanations are omitted.
[0044]
The GNSS receiver 14 receives a GNSS broadcast signal
transmitted from the GNSS s a t e l l i t e 11, reproduces a synchronization
25 signal based on the received GNSS broadcast signal, and transmits the
reproduced synchronization signal to the packet data transmission
apparatus 15.
[0045]
The packet data transmission apparatus 15 transmits the
30 synchronization signal to the synchronization apparatus 20 through a
packet network 31. The synchronization signal is, for example, a clock
signal generated by using the synchronization signal transmitted from
the GNSS receiver 14. The packet network 31 is a network through
which communication specified in th„e IEEE1588 can be performed.
18
[0046]
The GNSS receiver 16 receives the GNSS broadcast signal
transmitted from the GNSS s a t e l l i t e 11, reproduces a synchronization
signal based on the received GNSS broadcast signal, and transmits the
5 reproduced synchronization signal to an SDH apparatus 17. The SDH
apparatus 17 is an apparatus capable of performing data transmission
by using an SDH in a physical layer. The SDH apparatus 17 transmits
the synchronization signal to the synchronization apparatus 20 through
a network in which an SDH is specified in its physical layer
10 (hereinafter, referred to as "SDH network 32").
[0047]
Similarly to Fig. 2, the synchronization apparatus 20 generates
output timing pulses by using a frequency synchronization signal
(output clock) synchronized with the frequency of a synchronization
15 signal transmitted from the SDH apparatus 17 and a phase
synchronization signal (timing pulse) synchronized with the phase of a
synchronization signal transmitted from the packet data transmission
apparatus 15. Note that the packet data transmission apparatus 15 and
the SDH apparatus 17 need to transmit respective synchronization
20 signals that are generated by using a broadcast signal transmitted from
the same synchronization source apparatus, i.e., from the same GNSS
s a t e l l i t e 11, to the synchronization apparatus 20.
[0048]
Next, an operation in a case where the GNSS receiver 16 cannot
25 receive the GNSS broadcast signal is explained with reference to Fig. 7
[0049]
Fig. 7 shows a case where the GNSS receiver 16 cannot receive
the GNSS broadcast signal from the GNSS s a t e l l i t e 11. In such cases,
the GNSS receiver 16 outputs a clock signal that is generated by'using
30 an oscillator disposed in the GNSS receiver 16 itself to the SDH
apparatus 17. The state where the GNSS receiver 16 generates a clock
signal by using an oscillator disposed in the GNSS receiver 16 itself,
instead of generating a synchronization signal based on the GNSS
broadcast signal transmitted from the GNSS s a t e l l i t e 11, and operates
P D DELH1. 2 & - D8- - 2 D ! 5 1-. S - 2 6-
19
based on the generated clock signal as described above is called a
"free-running" state.
[0050]
The packet data transmission apparatus 15 transmits the
5 synchronization signal transmitted from the GNSS s a t e l l i t e 11 to the
synchronization apparatus 20, and the SDH apparatus 17 transmits the
synchronization signal generated based on the clock signal generated
in the GNSS receiver 16 to the synchronization apparatus 20. In this
case, since the generation sources of the two synchronization signals
10 received by the synchronization apparatus 20 are different from each
other, the frequencies of the two synchronization signals are different
from each other. In such cases, the synchronization apparatus 20 may
refrain from performing the synchronous processing until the GNSS
receiver 16 can receive the GNSS broadcast signal transmitted from the
15 GNSS s a t e l l i t e 1 1.
[0051]
Next, a flow of processes in a case where the synchronization
apparatus 20 receives a synchronization signal generated based on a
clock internally generated by the GNSS receiver 16 is explained with
20 reference to Fig. 8.
[0052]
Steps S21 to S24 in Fig. 8 are similar to the steps S l l to S14 in
Fig. 5, and therefore their detailed explanations are omitted. The
phase comparison unit 28 determines whether or not a plurality of
2 5 phase differences measured in the step S24 tend to increase or decrease
over time (S25).
[0053]
Here, phase differences that are obtained when the frequencies
of synchronization signals transmitted from the packet data
30 transmission apparatus 15 and the SDH apparatus 17 are different form
each other are explained with reference to Figs. 9A and 9B. Fig. 9A
shows a state of output timing pulses generated in the step S22 shown
in Fig. 8. The output timing pulses are shown as reproduced phases by
the SyncE. In this exajripfe, it jjs .ajssjimed that the frequency of the
p'Ci rfcfcLHi 2LS-~ 0-6" ~ Zy-'-i S I f e '• it
20
synchronization signal transmitted form the SDH apparatus 17 is lower
than the frequency of the synchronization source phase, i.e., the pulse
signal generated based on the GNSS broadcast signal. Therefore, the
pulse width of the output timing pulses becomes longer than the pulse
5 width of the pulse signal generated based on the GNSS broadcast
signal. The vertical dotted-line arrows in Fig. 9A represent output
timing pulses when the frequency of the synchronization source phase
is equal to that of the synchronization signal transmitted from the SDH
apparatus 17. Fig. 9A shows a state where the pulse widths for the
10 second and third output timing pulses gradually become longer
compared to the case where the frequencies of the synchronization .
signals transmitted from the packet data transmission apparatus 15 and
the SDH apparatus 17 are equal to each other.
[0054]
15 Similarly to Fig. 4B, Fig. 9B shows a state where a deviation
occurs between the phase of the pulse signal generated based on the
synchronization signal of the synchronization source ( i . e . , the pulse
signal generated based on the synchronization signal output from the
GNSS receiver 12) and that of the output timing pulses. Note that
20 when the pulse width of the output timing pulses gradually becomes
longer, the phase difference between the output timing pulses and the
timing pulses has an increasing tendency, i.e., gradually increases.
Note that while the phases of the timing pulses reproduced by the
IEEE1588 may be somewhat advanced or delayed due to the
25 fluctuations in the arrival times, the phase difference between the
output timing pulses and the timing pulses has an increase tendency.
[0055]
In Figs. 9A and 9B, a case where the frequency of the
synchronization signal transmitted form the SDH apparatus 17 is lower
30 than that of the synchronization signal output from the packet data
transmission apparatus 15 is shown. In contrast to this, when the
frequency of the synchronization signal transmitted form the SDH
apparatus 17 is higher than that of the synchronization signal output
from the packet data transmission gLpjDaratus 15. the phase difference
^Ci D-ELHI 2.S-- Q-6-- 2.©L-S I S ' - 2 .b
21
between the output timing pulses and the timing pulses has a
decreasing tendency.
[0056]
Referring to Fig. 8 again, in the step S25, when it is determined
5 that the plurality of measured phase differences tend to increase or
decrease over time by the phase comparison unit 28 (S25., Yes), the
process in the step S23 is repeated. It can be presumed that, when it is
determined that the plurality of measured phase differences tend to
increase or decrease over time by the phase comparison unit 28, the
10 synchronization signal output from the SDH apparatus 17 is not
generated based on the GNSS broadcast signal but is generated based
on a signal output from the oscillator disposed in the GNSS receiver 16
connected to the SDH apparatus 17. Therefore, in such cases, the
process in the step S23 is repeated until the synchronization signal
15 generated based on the GNSS broadcast signal is transmitted from the
SDH apparatus 1 7.
[0057]
In the step S25, when it is determined that the plurality of
measured phase differences tend to neither increase nor decrease over
20 time by the phase comparison unit 28 (S25, No), the processes in the
steps S26 and S27 are performed. The steps S26 and S27 are similar to
the steps S16 and S17 in Fig. 5, and therefore their detailed
explanations are omitted.
[0058]
25 As explained above, by using the synchronization system shown
in Fig. 6, the synchronization apparatus 20 can receive synchronization
signals used for performing frequency synchronization and phase
synchronization through different networks, i.e., the packet network 31
and the SDH network 32. As a result, even when there is an apparatus
30 that can perform only the IEEE1588 transmission or an apparatus that
can perform only the SDH transmission, the synchronization apparatus
20 can receive a synchronization signal'from each of these apparatuses.
[0059]
Further, in Fig. 6, a_configuratjon in which the packet data
I'PO- DELHI 2;8r~ 0-t" 2.0-'! 5 1 8- - 2.S22
transmission apparatus 15 receives a synchronization signal from the
GNSS receiver 14 and the SDH apparatus 17 receives a synchronization
signal from the GNSS receiver 16 is explained. However, the packet
data transmission apparatus 15 and the SDH apparatus 17 may be
5 connected to the common GNSS receiver.
[0060]
Further, the synchronization apparatus 20 can determine whether
or not a transmitted synchronization signal has been generated based
on the GNSS broadcast signal by determining whether or not the phase
10 difference between synchronization signals transmitted from the packet
data transmission apparatus 15 and the SDH apparatus 17 has an
increasing tendency or a decreasing tendency. In this way, the
synchronization apparatus 20 does not perform the offset value
c a l c u l a t i o n when, the synchronization signal generated based on the
15 GNSS broadcast signal is not transmitted, and does perform the offset
value calculation when the synchronization signal generated based on
the GNSS broadcast signal is transmitted. Therefore, the
synchronization apparatus 20 can calculate a highly accurate offset
value.
20 [0061]
(Fourth exemplary embodiment)
Next, a configuration example of a radio communication •.
apparatus 100 according to a fourth exemplary embodiment is
explained with reference to Fig. 10. The radio communication
25 apparatus 100 is an apparatus including a synchronization apparatus 20.
The radio communication apparatus 100 includes in addition to the
synchronization apparatus 20, a ToD/lPPS termination unit 101, a PTP
termination unit 102, a time/phase signal input selector 103, a
frequency signal conversion unit 104, a radio termination unit 105, a
30 SyncE termination unit 106, an ACR termination unit 107, an STM-1
termination unit 108, an E l / T l termination unit 109, a 2.048-MHz
termination unit 110, a frequency signal input selector 111, a
d i s t r i b u t i o n unit 121, a ToD/lPPS output unit 122, a PTP output unit
123, a frequency signal cojivejsjon^ujiit 124, a distribution unit 125, a
X'p ©? DE-L li-X. '£. S-" fcfS " 2 0-1 S 1 S- - i. b23
radio output unit 126, a SyncE output unit 127, an ACR output unit 128,
an STM-1 output unit 129, an E l / T l output unit 130, and a 2.048-MHz
output unit 13 1.
[0062]
5 The ToD/lPPS termination unit 101 receives a time/phase signal
including a signal relating to a time specified in NMEA-0183, IRIG
Std.200-04, or the like, and a signal that indicates a phase by using
1PPS (Pulse Per Second). The PTP termination unit 102 receives a
time/phase signal used in a packet network standardized in ITU-T
10 G.8265.1, IEEE1588-2008, or the like.
[0063]
The time/phase signal input selector 103 receives the time/phase
signals from the ToD/lPPS termination unit 101 and the PTP
termination unit 102, and outputs a selected one of these time/phase
15 signals to the synchronization apparatus 20.
[0064]
The frequency signal conversion unit 104 receives the
time/phase signals from the ToD/lPPS termination unit 101 and the
PTP termination unit 102, and outputs a frequency signal indicating
20 frequency information of the time/phase signals to the frequency signal
input selector 111.
[0065]
The radio termination unit 105 receives a radio signal through
an antenna or the like, and outputs a frequency signal indicating
25 frequency information of the received radio signal tO'the frequency
signal input selector 111. The SyncE termination unit 106 and the
ACR (Adaptive Clock Recovery) termination unit 107 receive a signal
standardized in ITU-T G.8261 or the like, and output a frequency
signal indicating frequency information of the received signal to the
30 frequency signal input selector 111.
[0066]
The STM-1 termination unit 108, the E l / T l termination unit 109,
and the 2.048-MHz termination unit 110 receive a signal standardized
in ITU-T G.703 or the like^ and^outjnit a frequency signal indicating
24
frequency information of the received signal to the frequency signal
input selector 111.
[0067]
The frequency signal input selector 1 1 1 outputs one frequency
5 signal selected from among the received frequency signals to the
synchronization apparatus 20. The synchronization apparatus 20
applies an offset value to the time/phase signal by using the received
time/phase signal and the frequency signal as explained above with
reference to Fig. 3. The synchronization apparatus 20 outputs the
10 time/phase signal, to which the offset value has been applied, to the
d i s t r i b u t i o n unit 121. Note that the time/phase signal output from the
synchronization apparatus 20 corresponds to the output timing pulses
explained above with reference to Fig. 3. Further, the frequency signal
and the time/phase signal output to the synchronization apparatus 20
15 correspond to the respective synchronization signals.
[0068]
The distribution unit 121 distributes and outputs the time/phase
signal received from the synchronization apparatus 20 to the ToD/lPPS
output unit 122 and the PTP output unit 123. The ToD/lPPS output
20 unit 122 and the PTP output unit 123 outputs the received time/phase
signal to other apparatuses and the like. Further, the distribution unit
121 outputs the time/phase signal received from the synchronization
apparatus 20 to the frequency signal conversion unit 124.
[0069]
25 The frequency signal conversion unit 124 converts the
time/phase signal received from the distribution unit 121 into a
frequency signal indicating frequency information. The frequency
signal conversion unit 124 outputs the frequency signal to the
d i s t r i b u t i o n unit 125.
30 [0070]
The distribution unit 125 outputs the frequency signal received
from the frequency signal conversion unit 124 to at least one of the
radio output unit 126, the SyncE output unit 127, the ACR output unit
25
2.048-MHz output unit 131.
[0071]
The radio output unit 126, the SyncE output unit 127, the ACR
output unit 128, the STM-1 output unit 129, the E l / T l output unit 130,
5 and the 2.048-MHz output unit 131 output the received frequency
signal to other apparatuses and the like.
[0072]
As explained above, by using the radio communication apparatus
100 according to the fourth exemplary embodiment of the present
10 invention, it is possible to output a signal that is selected from among
a p l u r a l i t y of signals standardized by various methods to the
synchronization apparatus 20. Therefore, the synchronization
apparatus 20 can generate a highly accurate time/phase signal (output
timing pulses) or a frequency synchronization signal by using a
15 plurality of signals standardized by different methods. Consequently,
the radio communication apparatus 100 can operate in various networks
using different methods, thus enabling flexible network designing.
[0073]
Note that the invention is not limited to the above-described
20 exemplary embodiments and various changes may be made therein
without departing from the spirit and scope of the present invention.
[0074]
Although the present invention is explained above with reference
to exemplary embodiments, the present invention is not limited to the
25 above-described exemplary embodiments. Various modifications that
can be understood by those skilled in the art can be made to the
configuration and details of the present invention within the scope of
the invention.
[0075]
30 This application is based upon and claims the benefit of priority
from Japanese patent applications No. 2012-260716, filed on November
29, 2012. the disclosure of which is incorporated herein in its entirety
by reference.
u- iEL&4X ' sz* - OS ~ 2 0--J. S- 3i.'S-' - 2'.S
26
Reference Signs List
[0076]
10 SYNCHRONIZATION SIGNAL SOURCE
1 1 GNSS SATELLITE
5 12 GNSS RECEIVER
13 SYNCHRONIZATION SIGNAL TRANSMITTING APPARATUS
14 GNSS RECEIVER
15 PACKET DATA TRANSMISSION APPARATUS
16 GNSS RECEIVER
10 17 SDH APPARATUS
20 SYNCHRONIZATION APPARATUS
21 FREQUENCY SYNCHRONIZATION UNIT
22 PHASE SYNCHRONIZATION CONTROL UNIT
23 PHASE SYNCHRONIZATION UNIT
15 24 PHYSICAL LAYER DATA RECEIVING UNIT
25 PULSE GENERATION UNIT
26 TIMING OFFSET UNIT
27 PACKET DATA RECEIVING UNIT
28 PHASE COMPARISON UNIT
20 29 OFFSET VALUE CALCULATION UNIT
30 NETWORK
31 PACKET NETWORK
32 SDH NETWORK
100 RADIO COMMUNICATION APPARATUS
25 101 ToD/lPPS TERMINATION UNIT
102 PTP TERMINATION UNIT
103 TIME/PHASE SIGNAL INPUT SELECTOR
104 FREQUENCY SIGNAL CONVERSION UNIT
• 105 RADIO TERMINATION UNIT
30 106 SyncE TERMINATION UNIT
107 ACR TERMINATION UNIT
108 STM-1 TERMINATION UNIT
109 El/Tl TERMINATION UNIT
110 2.048-MHz TERMINATION UNIT
p Ft. O-E L.H'X £B- ~ S^fci-"" 2 kk 2. S I. S - £, B- •
27
111 FREQUENCY SIGNAL INPUT SELECTOR
121 DISTRIBUTION UNIT
122 ToD/lPPS OUTPUT UNIT
123 PTP OUTPUT UNIT
124 FREQUENCY SIGNAL CONVERSION UNIT
125 DISTRIBUTION UNIT
126 RADIO OUTPUT UNIT
127 SyncE OUTPUT UNIT
128 ACR OUTPUT UNIT
129 STM-1 OUTPUT UNIT
130 El/Tl OUTPUT UNIT
131 2.048-MHz OUTPUT UNIT

WE CLAIM:
1. A synchronization apparatus comprising:
frequency synchronization means for performing frequency
synchronization based on a synchronization signal transmitted from a
synchronization signal source through a network, and outputting a
frequency synchronization signal;
phase synchronization means for performing phase
synchronization based on a synchronization signal transmitted from the
synchronization signal source through a network, and outputting a
phase synchronization signal; and
phase synchronization control means for generating an offset
value by using a phase difference between the frequency
synchronization signal and the phase synchronization signal, and
correcting a phase of the frequency synchronization signal by using the
offset value.
2. The synchronization apparatus according to Claim 1, wherein
the phase synchronization means receives a synchronization signal
transmitted from the synchronization signal source through a packet
network.
3. The synchronization apparatus according to Claim 1 or 2,
wherein the frequency synchronization means receives a
synchronization signal transmitted from the synchronization signal
source through a signal transmitted by using a physical layer.
4. The synchronization apparatus according to any one of Claims
1 to 3. wherein
the frequency synchronization signal is a frequency
synchronization pulse signal having a pulse waveform, and the phase
synchronization signal is a phase synchronization pulse signal having a
pulse waveform, and
the phase synchrpnidation control means comprises:
phase comparison means for calculating phase differences
between the frequency synchronization pulse signal and the phase
synchronization pulse signal in a predetermined period; and
offset value calculation means for correcting a phase of the
frequency synchronization signal by using an offset value, the offset
value being generated by statistically processing a plurality of phase
differences.
5. The synchronization apparatus according to Claim 4, wherein
the offset value calculation means does not generate the offset value
when the phase difference calculated by the phase comparison means is
greater than a predefined value.
6. The synchronization apparatus according to Claim 4, wherein
the offset value calculation means does not generate the offset value
when a second phase difference between the frequency synchronization
pulse signal and the phase synchronization pulse signal in a second
predetermined period is greater than a first phase difference between
the frequency synchronization pulse signal and the phase
synchronization pulse signal in a first predetermined period by a predefined
value, the second predetermined period being different from
the first predetermined period.
7. The synchronization apparatus according to Claim 4, wherein
the offset value calculation means does not generate the offset value
when a second phase difference between the frequency synchronization
pulse signal and the phase synchronization pulse signal in a second
predetermined period is smaller than a first phase difference between
the frequency synchronization pulse signal and the phase
synchronization pulse signal in a first predetermined period by a predefined
value, the second predetermined period being different from
the first predetermined period.
a synchronization signal source;
a synchronization signal transmitting apparatus that converts a
synchronization signal transmitted from the synchronization signal
source into a signal in a physical layer and transmits the converted
signal as a first synchronization signal, and transmits the
synchronization signal as a second synchronization signal through a
packet network; and
a synchronization apparatus that generates a frequency
synchronization signal by performing frequency synchronization based
on the first synchronization signal, generates a phase synchronization
signal by performing phase synchronization based on the second
synchronization signal, and corrects a phase of the frequency
synchronization signal by using an offset value, the offset value being
generated by using a phase difference between the frequency
synchronization signal and the phase synchronization signal.
9. The synchronization system according to Claim 8, wherein the
synchronization signal transmitting apparatus transmits the first and
second synchronization signals to the synchronization apparatus
through the same transmission path.
10. The synchronization system according to Claim 8, wherein
the synchronization signal transmitting apparatus transmits the first
and second synchronization signals to the synchronization apparatus
through different transmission paths.
11 . The synchronization system according to Claim 8, further
comprising a first synchronization signal transmitting apparatus that
receives a synchronization signal transmitted from the synchronization
signal source, and a second synchronization signal transmitting
apparatus that receives a synchronization signal transmitted from the
synchronization signal source, wherein
the first synchronization signal transmitting apparatus transmits
the first sy nchroni zatjon. signal_to jt h_e synchronization apparatus, and
the second synchronization signal transmitting apparatus
transmits the second synchronization signal to the synchronization
apparatus
12. A radio communication comprising:
first synchronization signal receiving means for receiving a
p l u r a l i t y of synchronization signals from a synchronization signal
source through a network, the p l u r a l i t y of synchronization signals
being used for frequency synchronization;
second synchronization signal receiving means for receiving a
p l u r a l i t y of synchronization signals from the synchronization signal
source through a network, the plurality of synchronization signals
being used for phase synchronization;
frequency synchronization means for performing frequency
synchronization based on a synchronization signal selected in the first
synchronization signal receiving means, and outputting a frequency
synchronization signal;
phase synchronization means for performing phase
synchronization based on a synchronization signal selected in the
second synchronization signal receiving means, and outputting a phase
synchronization signal; and
phase synchronization control means for generati ng. an offset
value by using a phase difference between the frequency
synchronization signal and the phase synchronization signal, and
c o r r e c t i n g a phase of the frequency synchronization signal by using the
offset value.
13. A synchronization method comprising:
performing frequency synchronization based on a
synchronization signal transmitted from a synchronization signal
source through a network, and outputting a frequency synchronization
signal;
performing phase synchronization based on a synchronization
signal transmitted fron^ the syji^chronj zati on signal source through a
network, and outputting a phase synchronization signal; and
generating an offset value by using a phase difference between
the frequency synchronization signal and the phase synchronization
signal, and correcting a phase of the frequency synchronization signal
by using the offset value.