U.S. patent application number 12/781747 was filed with the patent office on 2010-09-09 for power line communication apparatus and data relay method.
This patent application is currently assigned to PANASONIC CORPORATION. Invention is credited to Eiji Kobayashi, Tomiya MIYAZAKI.
Application Number | 20100226391 12/781747 |
Document ID | / |
Family ID | 37985333 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100226391 |
Kind Code |
A1 |
MIYAZAKI; Tomiya ; et
al. |
September 9, 2010 |
POWER LINE COMMUNICATION APPARATUS AND DATA RELAY METHOD
Abstract
The PLC 20 adaptor corresponding to a power line communication
apparatus has four PLC bridges 30A to 30D, each of which is
correspondingly connected to Ethernet communication connectors 26A
to 26D, operation mode setting switches 27A to 27D, display units
28A to 28D. Each PLC bridge 30A to 30D includes a PLC modem unit
301, a bridge unit 302, an Ethernet IF unit 303, and a
communication control unit 304. The communication control unit 304
obtains data type information on the basis of setting conditions of
switches 27A to 27D corresponding to each communication port. Since
the time slot required for the communication link corresponding to
the communication port of the PLC network can be obtained on the
basis of the data type information, the reservation request can be
transmitted to the control terminal.
Inventors: |
MIYAZAKI; Tomiya; (Fukuoka,
JP) ; Kobayashi; Eiji; (Fukuoka, JP) |
Correspondence
Address: |
Dickinson Wright PLLC;James E. Ledbetter, Esq.
International Square, 1875 Eye Street, N.W., Suite 1200
Washington
DC
20006
US
|
Assignee: |
PANASONIC CORPORATION
Osaka
JP
|
Family ID: |
37985333 |
Appl. No.: |
12/781747 |
Filed: |
May 17, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11582979 |
Oct 19, 2006 |
7729375 |
|
|
12781747 |
|
|
|
|
Current U.S.
Class: |
370/468 ;
340/815.4; 370/465 |
Current CPC
Class: |
H04B 3/58 20130101; H04B
2203/545 20130101; H04B 3/542 20130101; H04L 12/403 20130101; H04B
2203/5445 20130101 |
Class at
Publication: |
370/468 ;
370/465; 340/815.4 |
International
Class: |
H04L 5/22 20060101
H04L005/22; H04L 5/00 20060101 H04L005/00; G08B 5/00 20060101
G08B005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2005 |
JP |
2005-305968 |
Claims
1. A power line communication apparatus for communicating data,
comprising: a first communication unit for performing communication
via a power line; a second communication unit for performing
communication via another communication line other than the power
line; a manipulation unit for setting a operation mode of the power
line communication apparatus, wherein the operation mode is
corresponding to a format of the data; a relay unit for relaying
the data on the basis of the operation mode.
2. The power line communication apparatus according to claim 1,
further comprising: a time slot setting unit for setting a time
slot on the basis of the operation mode; wherein the relay unit for
relaying the data within the time slot set by the time slot setting
unit between the first communication unit and the second
communication unit.
3. The power line communication apparatus according to claim 2,
wherein the time slot setting unit sets the time slot on the basis
of a packet format of the data.
4. The power line communication apparatus according to claim 2,
wherein the time slot setting unit issues a time slot reservation
request for requesting a time slot required to transmit the data to
other power line communication apparatuses connected to the power
line, and sets the time slot required to transmit the data when a
time slot reservation response is received from other power line
communication apparatuses.
5. The power line communication apparatus according to claim 1,
wherein a quality of service (QoS) required on a network including
the second communication unit is guaranteed by setting a priority
on the communication line in the second communication unit.
6. The power line communication apparatus according to claim 2,
wherein at least a part of the data are transmitted via the power
line on the basis of a time division multiple access (TDMA) method,
and wherein the time slot setting unit sets the time slot required
to transmit the data on the basis of a time period of the time slot
for transmitting the data.
7. The power line communication apparatus according to claim 1,
further comprising a display unit for displaying operation
conditions including at least one of a communication condition and
a setting condition of the data transmission via the communication
line.
8. The power line communication apparatus according to claim 1,
further comprising: a power input unit connected to the first
communication unit to input power from the power line; a
communication connector connected to a communication medium for
transmitting data by connecting the second communication unit and
an electronic device; and a power socket connectable to a power
cord of the electric device for allowing power input from the power
input unit to be supplied to the electronic device, wherein the
power input unit is connected to the first communication unit.
9. A method of relaying data in a power line communication
apparatus for transmitting data using a power line as a
communication line, the method comprising steps of: performing,
with the power line communication apparatus, a first communication
via the power line; performing a second communication via at least
one of communication lines other than the power line; setting a
operation mode of the power line communication apparatus, wherein
the operation mode is corresponding to a format of the data.
relaying the data on the basis of the operation mode.
10. The method according to claim 9, further comprising: setting a
time slot on the basis of the operation mode; wherein the step of
relaying the data within the time slot set by the time slot setting
unit between the first communication unit and the second
communication unit.
11. The method according to claim 10, wherein, in the step of
setting the time slot, the time slot is set on the basis of a
packet format of the data.
12. The method according to claim 10, wherein, in the step of
setting the time slot, a time slot reservation request for
requesting a time slot required to transmit the data is issued to
other power line communication apparatuses connected to the power
line, and wherein the time slot required to transmit the data is
set when a time slot reservation response is received from other
power line communication apparatuses.
13. The method according to claim 9, wherein a quality of service
(QoS) required on a network including the second communication unit
is obtained by setting a priority of the communication line in the
second communication unit.
14. The method according to claim 10, wherein at least a part of
the data are transmitted via the power line on the basis of a time
division multiple access (TDMA) method, and wherein, in the step of
setting the time slot, the time slot required to transmit the data
is set on the basis of a time period of a time slot for
transmitting the data.
15. The method according to claim 9, further comprising a step of
displaying an operation condition including at least one of a
setting condition and a communication condition of data
transmission via the communication line.
16. A power line communication apparatus for communicating data,
comprising: a first communication unit for performing communication
via a power line; a second communication unit for performing
communication via another communication line other than the power
line; a setting unit for setting a operation mode of the power line
communication apparatus, wherein the operation mode is
corresponding to a format of the data; a relay unit for relaying
the data on the basis of the operation mode.
Description
[0001] This is a divisional application of application Ser. No.
11/582,979 filed Oct. 19, 2006, which is based on Japanese
Application No. 2005-305968 filed Oct. 20, 2005, the entire
contents of each of which are incorporated by reference herein.
BACKGROUND
[0002] The present invention relates to a power line communication
apparatus and a data relay method, in which an electronic device
having a communication function can be connected to a transmission
path using a power line as well as a communication interface such
as an Ethernet (Registered Trademark), and data can be transmitted
between the electronic device and the transmission path.
[0003] For example, a system capable of easily implementing
communication operations in a house by communicatably connecting a
plurality of devices including an information device such as a
personal computer and a variety of electric devices such as a
television set, a recorder device, a video reproducing device, and
an Internet protocol (IP) telephone with one another on a
predetermined communication network has been proposed. When a wired
data communication is implemented in a house, typically, a cable
used as a transmission path or a wire line including connectors
should be provided in necessary areas. Therefore, various
construction processes are necessary when a communication system is
established.
[0004] In a house, a commercial electric power voltage, such as AC
120V (60 Hz) or 100V (50/60 Hz) is used in most of the cases.
Therefore, a power line for supplying this commercial electric
power is already provided in every region in a house. This power
line can be used as a transmission path for data communication by
connecting a communication device to an electric socket of a
commercial electric power to obtain a transmission path without
installing a separate wire line for data communication.
[0005] Such a power line communication (PLC) technology for using
the power line in communication is disclosed in Japanese Patent
Application Publication No. 2000-165304. In the present, some
manufacturers are studying or developing this PLC technology for a
predetermined frequency band (such as 1.7 MHz to 80 MHz in U.S. and
2 MHz to 30 MHz in Japan). Specifically, it has been conceived that
multi-carrier signals are generated using a plurality of
sub-carriers as in an orthogonal frequency division multiplexing
(OFDM) method and transmitted through a power line.
[0006] In addition, the electric devices having a communication
function based on an Internet protocol typically use an Ethernet
(Registered Trademark) interface as a standard communication
interface. Therefore, when a communication network is constructed
by using a power line as a transmission path in a house, it is
necessary to provide a bridge unit for relaying data transmission
between a power line and an Ethernet (Registered Trademark)
communication interface. In this case, in order for the bridge unit
to perform communication through the power line, the bridge unit
should have an internal modem unit (i.e., a PLC bridge) for power
line communication. Otherwise, the bridge unit should have an
external modem unit (i.e., a PLC modem unit) for power line
communication.
[0007] However, a power line wiring in an indoor environment is
abnormally complicated, and a wiring condition is significantly
different from each building. Therefore, performance of the power
line as a transmission path is significantly different in every
place in the indoor environment. Furthermore, since types of
electric devices connected to this power line are also different,
various noises and variations in impedance may possibly occur. For
this reason, when communication is performed via the power line, a
desired communication rate may not be obtained, or a communication
quality may be degraded due to the reduced signal-to-noise (S/N)
ratio in comparison with a dedicated wired transmission path.
[0008] Accordingly, in the power line communication, a transmission
path is predicted in a predetermined timing before or during the
communication on a transmission path between a transmit terminal
and a receive terminal, transmission path conditions (i.e.,
transmission path characteristics) such as the S/N ratio are
measured in order to set transmission parameters such that a
maximum transmission rate (i.e., a bit rate) can be obtained with
an allowable range. In this case, as a transmission parameter,
modulation factors (i.e., a data duplication rate) of each carrier
in a multi-carrier signal are determined. When the condition of the
transmission path is satisfactory, a data transmission amount
within a unit time interval is increased (i.e., a bit rate is
increased) by increasing the modulation factor. On the contrary,
when the condition of the transmission path is not satisfactory,
the data transmission amount within a unit time interval is reduced
(i.e., the bit rate is reduced) by decreasing the modulation
factor. As a result, it is possible to reduce an error rate during
communication under a predetermined value.
[0009] Meanwhile, when various electric devices are connected with
one another on a network in a house to transmit streaming data such
as video or audio data, it is necessary to guarantee a quality of
service (QoS) in order to prevent loss of data.
[0010] However, according to a conventional power line
communication apparatus, there was no means for guaranteeing the
QoS, and it was impossible to obtain a time slot by combining the
power line communication with other communication interfaces such
as Ethernet (Registered Trademark). Therefore, it was impossible to
guarantee a satisfactory QoS when electric devices are connected to
transmit the streaming data. As a result, errors such as loss of
data may occur.
[0011] As described above, in a conventional power line
communication apparatus, there was no means for guaranteeing the
QoS, and it was impossible to obtain the time slot by combining the
power line communication with other communication interfaces such
as Ethernet (Registered Trademark). Therefore, it was impossible to
guarantee a satisfactory QoS when the connected electric devices
transmit streaming data. In addition, it was impossible to allocate
the time slot to each communication line for connecting a
predetermined electric device or control the priority.
SUMMARY
[0012] The present invention has been made to conceive the
aforementioned problems, and provide a power line communication
apparatus and a data relay method, by which an appropriate QoS can
be guaranteed depending on connected electric devices, transmitted
data, and the like, when a power line is used as a communication
transmission path.
[0013] According to an aspect of the present invention, there is
provided a data relay apparatus for relaying data, comprising: a
first communication unit for performing communication via a power
line; a second communication unit for performing communication via
another communication line other than the power line; a time slot
setting unit for setting a time slot on the basis of a format of
the data; and a relay unit for relaying the data within the time
slot set by the time slot setting unit between the first
communication unit and the second communication unit.
[0014] According to the above construction, it is possible to
obtain a time slot required for a communication link corresponding
to the communication line on the power line communication (PLC)
network using the first communication unit on the basis of the
format of the data transmitted to a communication line other than
the power line connected to the second communication unit. For
example, a time slot reservation request may be issued to another
power line communication apparatus functioning as a control
terminal to obtain the time slot. As a result, it is possible to
transmit data via the first and second communication units while a
predetermined QoS is guaranteed by obtaining the time slot required
for the data transmitted through the communication line connected
to the second communication unit on the PLC network. Therefore, it
is possible to guarantee an appropriate QoS depending on the
electric devices connected to the communication line or the types
of the data to be transmitted, when the power line is used as a
communication transmission path, for example, even when the data
requiring a satisfactory QoS, such as streaming data including
video or audio, are transmitted.
[0015] In addition, according to another aspect of the present
invention, there is provided a method of relaying data in a power
line communication apparatus for transmitting data using a power
line as a communication line, the method comprising steps of:
performing first communication via the power line; performing
second communication via at least one of communication lines other
than the power line; setting a time slot on the basis of a format
of the data; and relaying the data within the time slot set on the
basis of the format of the data between the first communication and
the second communication.
[0016] According to the above method, it is possible to allow the
communication link of the communication line on a power line
communication network used for the first communication to obtain a
necessary time slot according to the format of the data transmitted
through the communication line used for the second communication.
For example, it is possible to obtain the time slot by issuing a
time slot reservation request to another power line communication
apparatus functioning as a control terminal.
[0017] According to the above method, it is possible to obtain the
necessary time slot on the power line communication network for the
data transmitted through the communication line used in the second
communication, and guarantee a desired QoS while the data is
transmitted via the first and second communication units.
Therefore, it is possible to guarantee an appropriate QoS depending
on the electric devices connected to the communication line or the
type of the data to be transmitted when the power line is used as a
communication transmission path, for example, even when a QoS
should be guaranteed in transmission of the streaming data such as
video or audio data.
[0018] It is possible to provide a power line communication
apparatus and a data relay method, by which an appropriate QoS can
be guaranteed depending on the connected electric devices and the
type of data to be transmitted, when the power line is used as a
communication transmission path.
[0019] There is provided a power line communication apparatus and a
data relay method, by which an appropriate quality of service (QoS)
can be guaranteed depending on the connected electric devices and
the type of data to be transmitted, when the power line is used as
a communication transmission path.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic diagram illustrating an example of a
communication system including a power line communication apparatus
according to an embodiment.
[0021] FIG. 2 is a diagram illustrating external appearance of a
power line communication apparatus according to an embodiment.
[0022] FIG. 3 is a block diagram illustrating an internal
functional construction of a power line communication apparatus
according to the first embodiment.
[0023] FIG. 4 is a block diagram illustrating a schematic
construction of a PLC network according to an embodiment.
[0024] FIG. 5 is a timing chart illustrating an operation example
for allocating a time slot on a PLC network according to an
embodiment
[0025] FIG. 6 is a schematic diagram illustrating a data
duplication rate on a PLC network according to an embodiment.
[0026] FIG. 7 is a sequence diagram illustrating an operation
sequence in a time slot allocation process on a PLC network
according an embodiment.
[0027] FIG. 8 is a diagram illustrating a setting input window for
setting time slot reservation.
[0028] FIG. 9 is a block diagram illustrating an internal
functional diagram of a power line communication apparatus
according to the second embodiment.
[0029] FIG. 10 is a diagram illustrating a first connection example
of a PLC adaptor according to an embodiment.
[0030] FIG. 11 is a diagram illustrating a second connection
example of a PLC adaptor according to an embodiment.
[0031] FIG. 12 is a diagram illustrating a third connection example
of a PLC adaptor according to an embodiment.
[0032] FIG. 13 is a block diagram schematically illustrating a
hardware construction of a power line communication apparatus
according to an embodiment.
[0033] FIG. 14 is a block diagram illustrating a hardware
construction of a power line communication apparatus of FIG. 13 in
detail.
[0034] FIG. 15 is a block diagram illustrating an internal
functional construction of a power line communication apparatus
according a modification of the first embodiment.
[0035] FIG. 16 is a block diagram illustrating an internal
functional construction of a power line communication apparatus
according to a modification of the second embodiment.
[0036] FIG. 17 is a block diagram illustrating a second example of
a hardware construction of a power line communication apparatus
according to an embodiment.
DETAILED DESCRIPTION
[0037] In the present embodiment, a power line communication (PLC)
network is constructed by using a power line equipped in a house as
a transmission path to provide streaming data such as video or
audio data.
[0038] Herein, a "time slot" of the present embodiment includes a
temporal channel which has a successive time interval and is
capable of transmitting data between communication devices.
Although, in the following descriptions, a time slot used in a Time
Division Multiple Access (TDMA) method is exemplified, the time
slot used in other methods such as a Carrier Sense Multiple Access
with Collision Avoidance (CDMA/CA) or a Carrier Sense Multiple
Access with Collision Detection (CSMA/CD) method may be adopted in
the present invention.
[0039] As shown in FIG. 1, a power line 11 for supplying a
commercial electric power is equipped in an inner space of a house
10, and AC sockets 41A to 41F connected to the power line 11 is
provided in each room. A plurality of devices are connected to the
AC sockets 41A to 41F, and in the drawing, PLC adaptors 20A to 20F
are connected to the AC sockets 41A to 41F as an example of
communication devices having a power line communication function.
Specifically, a hard disk drive (HDD) recorder 42 which records and
reproduces video data is connected to the PLC adaptor 20A, an
Internet protocol (IP) telephone 44 which performs a voice over
Internet protocol (VoIP) telephone communication is connected to
the PLC adaptor 20B, an IP camera 46 which captures an image and
transmits the captured image on an IP network is connected to the
PLC adaptor 20C. In addition, a television set 43 such as a high
definition plasma television set is connected to the PLC adaptor
20D, another IP telephone 45 is connected to the PLC adaptor 20E,
and a personal computer (PC) 47 is connected to the PLC adaptor
20F.
[0040] Furthermore, communication interfaces such as an Ethernet
(Registered Trademark) and a universal serial bus (USB) having a
physical layer different from that of the power line communication
are inserted between the PLC adaptor 20A and the HDD recorder 42,
between the PLC adaptor 20B and the IP telephone 44, between the
PLC adaptor 20C and the IP camera 46, between the PLC adaptor 20D
and the television set 43, between the PLC adaptor 20E and the IP
telephone 45, and between the PLC adaptor 20F and the PC 47. As a
result, a PLC network 15 having a local power line communication
function capable of transmit data by using the power line 11 as a
common transmission path is constructed.
[0041] In the construction illustrated in FIG. 1, when high
definition video information that can be reproduced in the HDD
recorder 42 is distributed and displayed on the television set 43,
streaming data of the video are transmitted via a path including
the PLC adaptor 20A--the AC socket 41A--the power line 11--the AC
socket 41D--the PLC adaptor 20D. In addition, when audio
communication is established between the IP telephone 44 and the IP
telephone 45 using VoIP interface, streaming data of a telephone
call voice are transmitted via a path including the PLC adaptor
20B--the AC socket 41B the power line 11--the AC socket 41E--the
PLC adaptor 20E. When an image of an object captured by the IP
camera 46 is monitored using the PC 47, the data on the captured
image are transmitted via a path including the PLC adaptor 20C--the
AC socket 41C--the power line 11--the AC socket 41F--the PLC
adaptor 20F. When the data on the image captured by the IP camera
46 has a high definition and a high frame rate, they may be
transmitted as the streaming data similarly to the above case.
Otherwise, when they have a low definition, they can be transmitted
as typical IP packet data.
[0042] The PLC adaptor 20 illustrated in FIG. 2 is a table top type
as a detailed example of an assembly of the PLC adaptors 20A to 20F
illustrated in FIG. 1. The PLC adaptor 20 according to the present
invention also has a Ethernet (Registered Trademark) communication
interface having a physical layer different from that of the power
line communication so as to have a network communication function
based on Ethernet (Registered Trademark) as well as a power line
communication function for allowing the power line to be used as a
transmission path.
[0043] The PLC adaptor 20 includes four AC sockets 25A to 25D for
connecting AC power cords of electric devices, four communication
connectors 26A to 26D such as an RJ45 connector for connecting
communication cables from the electric devices, four switches 27A
to 27D corresponding to a manipulation unit for performing a
setting manipulation for each communication line, four display
units 28A to 28D for displaying operation conditions such as a
setting condition or a communication condition of each
communication line, and an AC electric cord 29 corresponding to an
example of a power input unit.
[0044] The AC electric cord 29 is connected to an AC socket 41
provided in the house in order to obtain a transmission path for
power line communication as well as an AC power voltage (e.g.,
100V) required to operate the electric devices, so that a
commercial power voltage is received. AC electric cords of various
electric devices such as a television set, a HDD recorder, an IP
telephone, an IP camera, and a personal computer are connected to
the AC sockets 25A and 25D provided in the PLC adaptor 20. In
addition, the communication connectors 26A to 26D function as
Ethernet (Registered Trademark) communication ports, and
communication cables (such as a LAN cable) are connected to the
communication connectors 26A to 26D so as to be connected to the
communication ports of the electric devices. The LAN cable is an
example of a transmission medium other than the power line. A
coaxial cable or a typical telephone cable may be used as the
transmission medium.
[0045] The switches 27A to 27D may include a slide switch, a DIP
switch, or a dial switch. The switches function as a manipulation
unit. The switches 27A to 27D receive a switching manipulation
input for setting the communication lines (e.g., the Ethernet)
corresponding to the communication connectors 26A to 26D. In this
case, in order to guarantee the QoS of the communication link of
each communication line, a user performs switching operations of
the switches 27A to 27D by manually manipulating them.
[0046] The display units 28A to 28D are constructed of light
emitting diodes (LEDs) or liquid crystal display panels in order to
display operating conditions such as a setting condition or a
communication condition of each communication line (e.g., Ethernet)
corresponding to each communication connector 26A to 26D. For
example, various information on the data transmission such as a
transmission band set for each communication line and an actual
data transmission speed on each communication line is displayed on
the display units 28A to 28D depending on a type of the electric
device connected to each communication connector 26A to 26D or a
type of the data (contents) transmitted through each communication
line. Conditions of the display units 28A to 28D may be indicated
by a color of the LED, the number of turned-on LEDs, flickering by
turning on/off the LED, or indicator images such as alphabetic or
numerical characters displayed on the liquid crystal display
panel.
[0047] FIG. 3 is a block diagram illustrating an internal
functional construction of the PLC adaptor 20 illustrated in FIG.
2. The PLC adaptor 20 includes four independent PLC bridges 30A to
30D connected to the communication connectors 26A to 26D, the
switches 27A to 27D, and the display units 28A to 28D,
respectively. Each PLC bridge 30A to 30D includes a PLC modem unit
301, a bridge unit 302, an Ethernet interface (IF) unit 303, and a
communication control unit 304.
[0048] The PLC modem unit 301 is provided as an example of the
first communication unit, and has a modem function needed to
perform the power line communication on the PLC network.
Specifically, the PLC modem unit 301 transmits and receives a
multi-carrier signal generated from a plurality of sub-carriers on
the basis of an OFDM (orthogonal frequency division multiplexing)
method to/from a counterpart terminal. The Ethernet IF unit 303 is
provided as an example of the second communication unit, and has a
communication interface function needed to perform communication on
an Ethernet (Registered Trademark) network. The bridge unit 302 is
provided as an example of the relay unit, and has a protocol
conversion function or a packet transformation function for the
transmitted data. Also, the bridge unit 302 relays the data (i.e.,
at the communication interface) between the PLC network and the
Ethernet network. The communication control unit 304 performs
various control operations required in the communication. The
communication control unit 304 has functions of a data type
information obtaining unit and a time slot setting unit. Its
control operations include a control operation for obtaining the
time slot on the basis of the selection states of the switches 27A
to 27D as described below.
[0049] On the PLC network 15 of the communication system
illustrated in FIG. 1, a master device and slave devices are set
among a plurality terminals of the power line communication
devices, so that a communication control on a network is performed
under the control of the master device. In the case of where a
plurality of terminals constitutes a network, a master is defined
as a terminal that controls communications of the other terminals,
while a slave is defied as a terminal that communications of which
is controlled by the master. In the construction illustrated in
FIG. 1, one of the PLC adaptors 20A to 20F is selected as a master
device, and other communication devices are selected as slave
devices. The master device has a QoS control function for
controlling the QoS of the PLC network in the communication control
unit as one of the functions of the PLC device on a network. The
master device transmits a beacon for obtaining a communication
timing including the control information to the PLC network 15 with
a predetermined period, and performs time slot reservation for
allocating the time slot to the communication link established
between particular communication devices within one period between
the beacons, so that the QoS of the PLC network 15 is controlled.
It is necessary to guarantee a predetermined QoS depending on the
data transmission speed required for the data in order not to
generate loss of data at the receiver side during the transmission
of the streaming data, such as transmission of high definition
video data (i.e., high definition (HD) video streaming) from the
HDD recorder 42 to the television set 43, or transmission of audio
data through the VoIP communication between the IP telephones 44
and 45, as shown in FIG. 1.
[0050] A time slot required to guarantee the QoS is allocated on
the basis of the type of the data (contents) to be transmitted (on
the basis of the transmission speed of the data). For example, the
HD video contents transmission requires a maximum speed of 24 Mbps,
the video signal transmission of a general television requires a
maximum speed of 6 Mbps, phone call signal transmission of IP
communication using the VoIP communication requires 128 Kbps
(64K.times.2), transmission of audio contents such as a music
requires 5.20 Mbps (384+706 K.times.7). The time slot may have a
different time interval depending on the type of the data to be
transmitted as described above.
[0051] Although a Carrier Sense Multiple Access with Collision
Avoidance (CDMA/CA) control is implemented when each terminal
transmits data on the Ethernet (Registered Trademark) network,
there is a possibility of collision of signals simultaneously
transmitted from a plurality of terminals, and thus, it is not
ensured that the time slot required for the data transmission can
be always obtained. However, as in the first embodiment, in which
the communication connectors 26A to 26D of Ethernet (Registered
Trademark) communication ports are connected to the electric
devices in a one-to-one manner, a dedicated time slot can be
obtained in the transmission path using the Ethernet (Registered
Trademark) communication interface.
[0052] In the construction of the present embodiment, when the data
such as streaming data in which the QoS should be guaranteed is
transmitted, it is very important to guarantee the QoS on the PLC
network. Now, an operation for guaranteeing the time slot will be
described.
[0053] FIG. 4 is a block diagram illustrating a schematic
construction of the PLC network. A plurality of PLC adaptors 21,
22, 22, . . . are connected to the power line 11, and a PLC device
functioning as a master device 21 and a PLC device functioning as a
slave device 22 are set. The master device 21 and the slave device
22 constitute a single PLC logic network 16. In the PLC logic
network 16 (tied up in a dotted line), the master device 21 has a
function of the transmission speed control unit. Although not shown
in the drawing, a plurality of PLC logic network may be constructed
by using a plurality of PLC devices connected in a common power
line.
[0054] A relay unit 31 corresponding to the PLC bridge 30A to 30D
is connected to the master device 21 and the slave device 22.
Electric devices 48 such as a television set, a video recorder, a
telephone, and a personal computer are connected via the relay unit
31. In addition, in the PLC adaptor 20 illustrated in FIG. 3
according to the present embodiment, the relay unit 31 is
internally provided. In this case, data are transmitted from the
master device 21 to the slave device 22 or from the slave device 22
to the master device 21 using the power line communication. On the
contrary, data are transmitted from the master device 21 and the
slave device 22 via the relay unit 31 to the electric device 48
using the Ethernet (Registered Trademark) communication
interface.
[0055] The slave device 21 is a control terminal having a function
of a QoS controller, and at least one slave device 21 is provided
in the PLC logic network 16. The slave device 21 has control
functions such as (1) management of information on terminals
provided on a network, (2) receiving and scheduling a time slot
reservation, and (3) transmitting the beacon with a predetermined
period and notifying the schedule to each terminal. On the other
hand, the slave device 22 communicates on the basis of the schedule
described in the beacon transmitted on the network. As described
above, the communication is established between the master device
21 and the slave device 22 on the PLC network, while the
communication control is performed in a concentrated manner using
the master device 21.
[0056] FIG. 5 is a timing chart illustrating an operation example
of allocating a time slot on a PLC network according to the present
embodiment.
[0057] On the PLC network, as shown in FIG. 5, the beacon B is
transmitted from the master device 21 at a regular interval with a
predetermined period (for example, 50 msec). Within one period of
the beacon B (hereinafter, referred to as a beacon period), data
are transmitted/received between the communication devices on the
basis of the scheduling of the slave device 21. In this case,
allocation of the required time slot is set by the slave device 21
corresponding to the QoS controller for the communication link for
transmitting the data required to guarantee the QoS, such as
streaming data, among communication links established between
communication devices, so that the time interval of the time slot
used in the communication link is determined.
[0058] The beacon period is divided into a contention-free period
(CFP) allocated to a former half based on an intelligent TDMA
method and a contention period (CP) allocated to a latter half
based on a CSMA/CA method. In other words, the contention-free
period (CFP) and the contention period (CP) are mixed in each
beacon period. In the contention-free period (CFP), the time slot
is set on the basis of the intelligent TDMA method, in which the
time interval is changed for each communication line, and the data
are transmitted within each time slot. In a communication link for
transmitting streaming data such as video or audio data that
requires the time slot, a time slot having a predetermined time
interval is allocated within the contention-free period (CFP)
depending on the transmission speed of the corresponding data to
guarantee the QoS. In the contention period (CP), data are
transmitted on the basis of a CSMA/CA method at a predetermined
timing in response to a communication request generated from each
communication device. The data packet that does not require
real-time transmission or successive transmission, such as
transmission of PC data or control information, has a contention
period (CP) and is intermittently transmitted. According to this
data transmission construction, it is possible to simultaneously
transmit the data, such as streaming data that should be
successively transmitted while the QoS is guaranteed, and the data,
such as PC data, that can be intermittently transmitted.
[0059] In the example shown in FIG. 5, within the contention-free
period, each time slot is allocated to each of three communication
links #1, #2, and #3. For example, the communication link #1
corresponds to the link for transmitting video data between the HDD
recorder 42 and the television set 43 in the communication system
illustrated in FIG. 1, and the communication link #2 corresponds to
the link for transmitting voice data between the IP telephones 44
and 45. In this case, a transmission band is widened as the time
interval of the time slot increases.
[0060] The master device 21 transmits information on the schedule
of the time slots allocated to each communication link by inserting
them in the beacon B during the CFP. As a result, various
communication devices (including the master device 21 and the slave
device 22) on the PLC network can identify an available time slot
in the communication link established for a particular terminal by
referring to the timing and information included in the beacon and
perform data communication using the time slot allocated to their
terminals.
[0061] The actually available size of the transmission range is
changed depending on a maximum bit rate determined by a modulation
method actually used by each communication link as well as the time
interval of the time slot. FIG. 6 is a schematic diagram
illustrating a detailed example of a data duplication rate on a PLC
network according to the present embodiment.
[0062] Since the transmission paths between each of the
communication devices of the PLC adaptors 20A to 20E have different
conditions on the PLC network 15, different transmission parameters
(such as a modulation pattern that shows a modulation method) are
set for each transmission path. Referring to FIG. 6, as an example
of the transmission parameters, a modulation factor (corresponding
to the data duplication rate) of each sub-carrier frequency of a
multi-carrier signal on a frequency axis are represented for each
transmission path. A communication capability within a unit time
(i.e., a maximum bit rate) is determined depending on the
transmission parameters.
[0063] In such a PLC network 15, transmission path estimation is
performed in every predetermined timing before the communication
starts or during the communication for each transmission path
between communication units to measure the condition (such as a S/N
ratio) of the transmission path, and the transmission parameters
are set such that a maximum transmission speed (i.e., a bit rate)
can be obtained within an allowable range. For example, a
modulation method having a high modulation factor such as 256QAM
and 16QAM is adopted in an allowable environment having little
noise and a high S/N ratio in the transmission path. On the
contrary, a modulation method having a low modulation factor such
as 4QAM and 2PAM is adopted in an bad environment having much noise
and a low S/N ratio. In addition, sub-carriers actually used in the
communication and sub-carriers that are not actually used are
determined from a plurality of sub-carriers on the basis of the
conditions of the detected noises. Accordingly, different
transmission parameters are set for each transmission path
established between the communication devices.
[0064] The master device having the aforementioned QoS controller
function controls allocation of the time interval of the time slot
to a particular communication link established between the
communication devices in such a way that a transmission band
capable of providing a highest bit rate within a maximum bit rate
range established for each transmission path of each communication
device as described above can be obtained.
[0065] FIG. 7 is a sequence diagram illustrating an operation means
of processing allocation of time slots on the PLC network according
the present embodiment. Now, the time slot allocation process will
be described by using three communication devices including a QoS
controller 24 corresponding to the master device 21, a transmit
terminal 20T corresponding to the transmission means of the data
receive side among the slave devices 22, a receive terminal 20R
corresponding to the communication device of the data receive side.
At least a transmit terminal 20T is the PLC adaptor 20 having the
construction illustrated in FIGS. 2 and 3 among the communication
devices.
[0066] In the PLC adaptor 20 of the transmit terminal 20T, an
operation mode for guaranteeing the QoS is set for each of the
communication connectors 26D to 26D of each communication port
provided for connecting the electric devices depending on the
selection states of the switches 27A to 27D. More specifically, the
switches 27A to 27D output the input signal to the PLC-LSI 131,
which will described later, when a user manipulates the switches in
the operation mode. The PLC-LSI 131 that has received the input
signal sets the operation mode. In other words, the operation mode
may be set on the basis of the type of the input signal (such as a
voltage). The following five modes are set as operation modes, and
they can be manually selected by the switches 27A to 27D.
[0067] Mode A (for video A): is set to obtain a time slot
appropriate for a bit rate of high definition video contents such
as a high vision video.
[0068] Mode B (for video B): is set to obtain a time slot
appropriate for a bit rate of normal video contents such as a
television program. Since the definition is significantly different
between normal video contents such as a television program and high
definition video contents such as a high-vision video, and the bit
rate is significantly different, it is preferable to use two modes
for video contents.
[0069] Mode C (for VoIP): is set to obtain a time slot appropriate
for a bit rate of the VoIP contents such as an IP telephone.
[0070] Mode D (for typical transmission): is set to transmit the
data of normal contents that do not care about a transmission delay
time. The selected time slot is not modified.
[0071] Mode E (for automatic transmission): is set to automatically
obtain the time slot required to guarantee the QoS by automatically
identifying the type of the contents to be transmitted.
[0072] When communication is established by connecting the electric
device to the communication connector of the PLC adaptor 20, the
communication control unit 304 of the PLC bridge 30A reads a
selection state of the switch 27A to identify the operation mode.
When an electric device such as a HDD recorder capable of providing
video contents such as a television program is connected to the
communication network 26A, a user previously manipulates the switch
27A such that the mode B or E can be selected.
[0073] When an application program of the transmit terminal 20T
starts to transmit the streaming data, a request to transmit the
streaming data is issued from an upper layer application APP to a
lower layer media access control MAC. (S11). In this example, it is
assumed that streaming data is transmitted with a maximum
transmission speed of 20 Mbps. In the streaming data such as video
or audio data, a real-time property or successive connectivity is
important. Also, a time slot capable of providing a transmission
speed required to transmit the data in the transmission path should
be obtained in order not to generate loss of data during the
transmission. Therefore, the transmit terminal 20T issues a time
slot reservation request for obtaining the required time slot
depending on the type of the streaming data to be transmitted in
the lower layer MAC (S12).
[0074] In this case, the communication control unit 304 of the PLC
adaptor 20 identifies the operation mode on the basis of the
selection state of the switch 27A of its port as a function of the
data type info illation obtaining unit and issues the time slot
reservation request so as to obtain the time slot corresponding to
the operation mode as a function of the time slot setting unit. For
example, when the mode B is selected by the switch 27A, a time slot
reservation request for obtaining the time slot appropriate for a
bit rate of the video contents is issued. This time slot
reservation request is notified to the lower layer MAC of the QoS
controller 24.
[0075] When the mode E is selected by the switch 27A of the PLC
adaptor 20, the type of the transmission data is automatically
identified by the communication control unit 304 as a function of
the data type information obtaining unit, and the time slot
reservation request for reserving the time slot required to
guarantee the QoS is issued as a function of the time slot setting
unit. In the data transmission using the Internet protocol (IP), a
UDP short packet is used for the VoIP data, and a UDP long packet
is used for the video data. For this purpose, whether or not the
data relates to the VoIP or the video (i.e., the type of the data)
may be identified by referring to the header of the transmitted
data packet. The communication control unit 304 automatically
determines the size of the time slot that should be obtained on the
basis of the result of the identification and issues the time slot
reservation request for obtaining the necessary time slots.
[0076] When the time slot reservation request is received from the
transmit terminal 20T, the QoS controller 24 performs a scheduling
for allocating the time interval of the time slot to the
corresponding communication link depending on the size of the
requested time slot (S13). In this case, as shown in FIG. 5, a time
slot is allocated to each communication link. Although the
requested time slot may not be always obtained, whether or not the
time slot is successfully obtained can be notified to the transmit
terminal 20T by using the time slot reservation response (S14).
[0077] In other words, when the QoS controller 24 obtains the time
slot, it is necessary to recognize a maximum bit rate for each
transmission path as described above. For this reason, transmission
path estimation is previously performed for the transmission path
established by communicating between the transmit terminal 20T and
the receive terminal 20R, and the information on a maximum bit rate
determined on the basis of the result of the transmission path
estimation is transmitted from the receive terminal 20R to the QoS
controller 24.
[0078] Subsequently, when the transmit terminal 20T receives the
time slot reservation response in the lower layer MAC, whether or
not the time slot is obtained is notified from the lower layer MAC
to the upper layer APP to obtain the time slot (S15). When the time
slot is successfully obtained, the streaming data starts to be
transmitted from the transmit terminal 20T to the receive terminal
20R (S16). As a result of the aforementioned process, it is
possible to previously allocate the time slots required for each of
the communication link and each communication line corresponding to
the communication link.
[0079] In the aforementioned operation example, although the time
slot reservation request is transmitted from the transmit terminal
20T to the QoS terminal 24 to obtain the time slot, the time slot
may be obtained by reading the setting of the operation mode from
the receive terminal 20R, obtaining the data type information, and
issuing the time slot reservation request from the receive terminal
20R.
[0080] In other words, parameters for guaranteeing the QoS may be
previously set by the master device 21 in detail. FIG. 8 is a
diagram illustrating an example of a setting input window for
setting the time slot reservation. A user inputs the setting of the
required time slot, the type of the data transmitted between
communication devices on the PLC network 15, or the like, in order
to set the time slot reservation using a PLC adaptor functioning as
a master device having a QoS control function. In this case, the
input window illustrated in FIG. 8 is displayed on a display
monitor of a personal computer connected to the PLC adaptor or a
television set, and a value or a selection instruction is input
using a manipulation means such as a key.
[0081] On the setting input window for setting the time slot
reservation, some input items such as a QoS parameter 81 relating
to modification deviations of a transmission speed or a delay time
of the transmitted data and terminal information 82 relating to
where the data is to be transmitted from and to, and the like, are
set. The QoS parameter 81 may be manually set by directly inputting
values such as a time interval of the time slot, or previously
established values may be input by selecting the type of the data,
such as high definition video data and the VoIP data. As described
above, the time slot allocation is performed by the QoS controller
on the basis of the setting information obtained by setting
information on the communication devices corresponding to a source
and a destination for transmitting and receiving the data and
information on the type of the data.
[0082] In the construction of the communication system illustrated
in FIG. 1, one of the PLC adaptors 20A to 20F is set as a master
device operated as a control terminal having a QoS control
function, and other PLC adaptors are set as slave devices operated
as the transmit terminal or the receive terminal having a switch
for setting the operation mode. Accordingly, the allocation and
control of the time slot are performed for each communication line
corresponding to the communication link established between
particular communication devices by using the QoS controller of the
master device on the basis of the setting of the slave device. As a
result, it is possible to allocate and obtain an appropriate time
slot depending on the type of the data transmitted from each
communication line by performing setting of the switches 27A to 27D
for each Ethernet communication port corresponding to the
communication connectors 26a to 26d to which electric devices are
connected in the PLC adaptor 20 of the slave device as shown in
FIG. 2.
[0083] According to the first embodiment, it is possible to perform
data communication by interconnecting the PLC network and the
Ethernet network having the Ethernet communication interface with
each other and obtaining the required time slot between the
networks.
[0084] FIG. 9 is a block diagram illustrating internal functional
components of a power line communication apparatus according to the
second embodiment. In FIG. 9, like reference numerals denote like
elements, similarly to those of the first embodiment illustrated in
FIG. 3, in which only constructions and operations different from
those of the first embodiment will be described.
[0085] The PLC adaptor 50 according to the second embodiment
includes a single PLC bridge 51 and a four-port Ethernet interface
(IF) unit 52. External appearance of the PLC adaptor 50 is similar
to that shown in FIG. 2, in which four AC sockets 25A to 25D, four
communication connectors 26A to 26D, four switches 27A to 27D, four
display units 28A to 28D, and an AC electric cord 29 are
included.
[0086] Similarly to the first embodiment, the PLC bridge 51
according to the second embodiment includes a PLC modem unit 301, a
bridge unit 302, and a communication control unit 304. Switch units
27A to 27D are connected to the communication control unit 304 of
the PLC bridge 51. In addition, communication connectors 26A to 26D
and display units 28A to 28D are correspondingly connected to each
port of a four-port Ethernet IF unit 52. This four-port Ethernet IF
unit 52 is a communication interface having four independent
Ethernet communication ports, and functions as a conventional
switching hub or a hub.
[0087] In the aforementioned construction according to the second
embodiment, it is necessary to set priorities of communication
ports in a particular communication line on an Ethernet network in
order to guarantee the QoS, in addition to the allocation of the
time slot on the PLC network described in the first embodiment.
Since the CSMA/CA control is performed when each communication
device transmits data on the Ethernet network, collision may occur
between the signals simultaneously transmitted from a plurality of
communication devices, so that a delay time may increase.
Therefore, the required QoS may not be guaranteed when the
streaming data is transmitted.
[0088] Therefore, according to the second embodiment, priorities of
data packets are controlled when the data packets are transmitted
from the PLC modem unit 301 of the PLC bridge 51 of the PLC adaptor
50 to the communication connectors 26A to 26D via the bridge unit
302 and the four-port Ethernet IF unit 52.
[0089] First of all, the communication control unit 304 of the PLC
bridge 51 identifies an operation mode of the communication port
corresponding to each communication connector 26A to 26D on the
basis of the selected condition of the switches 27 to 27D of a
corresponding device, and issues a time slot reservation request so
as to obtain the time slot depending on the operation mode in the
communication link of each communication port. For example, when
the switch 27A is set to the mode C (for VoIP), and the switch 27B
is set to the mode B (for video B), the time slot reservation
request is transmitted to the master device so as to obtain the
time slot required for both the VoIP contents and the normal video
contents in order to prevent loss of data from both the VoIP and
normal video contents. Operations of the time slot allocation
process on the PLC network are similar to those of the first
embodiment. The communication unit of the master device allocates
the time slot required to transmit the data on both the contents on
the PLC network in response to the time slot reservation request
when the time slot reservation request is received from the
communication unit of the slave device.
[0090] In addition, the communication control unit 304 determines
whether or not the Ethernet communication ports corresponding to
the communication connectors 26A to 26D are connected to the
communication line of the communication link to which the time slot
is allocated on the basis of the selection state of the switches
27A to 27D. As a result, the priorities of the communication ports
are set by writing information on the priorities to a header
portion of the data packet transmitted from the PLC modem unit 303
when the data are transmitted between the communication ports to
which the time slot is allocated. Finally, the data are transmitted
from the PLC modem unit 301 to the corresponding Ethernet
communication ports in the order of a higher priority.
[0091] In other words, when the data are transmitted between the
corresponding communication ports by detecting the communication
ports used by the communication link to which the time slot is
allocated without reading the selection states of the switches 27A
to 27D, information on priorities is written to the header portion
of the data packet transmitted from the PLC modem unit 301 to
control the priorities of the communication ports.
[0092] The data packet transmitted from the PLC modem unit 301 is
transmitted to the four-port Ethernet IF unit 52 via the bridge
unit 302. On the Ethernet network, the data packet is transmitted
to a destination node (e.g., the communication connector 26A to 26D
of the corresponding communication port) on the basis of the
priority of the transmitted data packet while the required QoS is
guaranteed. When the four-port Ethernet IF unit 52 has a function
of the switching hub, the data may be transmitted by switching to
each communication port. Therefore, it is possible to certainly
guarantee the QoS of a particular communication line on the
Ethernet network by using a function of the switching hub.
[0093] When different types of electric devices are connected to
the communication connectors 26A to 26D of the PLC adaptor 50, a
variety of types of data packets are mixedly transmitted from the
PLC bridge 51 to the communication connectors 26A to 26D via the
four-port Ethernet IF unit 51 at any time. Therefore, a possibility
of signal collision may increase due to an increased amount of
traffics, and a transmission delay time of the data packet may also
increase. However, when the data packets of the streaming data are
transmitted by controlling the priority as described above using
the PLC bridge 51, they are processed with a higher priority in
comparison with other data packets. Therefore, it is possible to
control the increased transmission delay time and guarantee the
QoS.
[0094] As described above, according to the second embodiment,
similarly to the first embodiment, it is possible to connect the
PLC network and the Ethernet communication network with each other
and perform data communication while the time slot is obtained
between these networks.
[0095] FIG. 10 is a diagram illustrating a first connection example
of the PLC adaptor according to the present embodiment. In FIG. 10,
the PLC adaptor 60 corresponds to the PLC adaptors 20 and 50 of the
first and second embodiments. In the first connection example, four
electric devices capable of performing IP communication, including
a television set 71A, a HDD recorder 71B, an IP camera 71C, and a
set top box (STB) 71D, are connected to a single PLC adaptor. Each
AC socket 25 of the PLC adaptor 60 is connected to each AC electric
cord 75 of each electric device 71A to 71D. In addition, a
communication cable 76 for connecting the communication ports of
the electric devices 71A to 71D is connected to each communication
connector 26 of the PLC adaptor 60. In addition, the AC electric
cord 29 of the PLC adaptor 60 is connected to the AC socket 41.
According to this construction, it is possible to transmit the data
such as video data between a plurality of electric devices on the
PLC network and the Ethernet network.
[0096] FIG. 11 is a diagram illustrating a second connection
example of a PLC adaptor according to the second embodiment. In the
second connection example, the Ethernet communication network is
connected to a four-port PLC adaptor 60A and a one-port PLC adaptor
60B. Four electric devices capable of performing IP communication,
including a television set 72A, an IP camera 72B, a personal
computer 72C, and a printer 72D, are connected to the PLC adaptor
60A using an AC electric cord 75 and a communication cable 76. In
addition, a digital video server 73 as an electric device capable
of performing IP communication is connected to another PLC adaptor
60B using the AC cord 75 and the communication cable 76. In
addition, the PLC adaptors 60A and 60B are connected using AC
sockets 41A and 41B and a power line 11. According to this
construction, the data such as video data are transmitted on the
PLC network and the Ethernet network. For example, as shown in the
drawing, video contents may be transmitted between the digital
video server 73 and the television set 72A provided in different
rooms in a house 10 to allow a user to watch the video. In
addition, the image captured by the IP camera 27B may be displayed
on the personal computer 72C, and the data on the personal computer
72C may be printed out on the printer 72D.
[0097] FIG. 12 is a diagram illustrating a second connection
example of the PLC adaptor according to the present embodiment. In
the third connection example, the Ethernet communication network is
connected to two one-port PLC adaptors 60C and 60D. A television
set 72A as an electric device capable of performing IP
communication is connected to the PLC adaptor 60C using the AC cord
75 and the communication cable 76. In addition, a digital video
server 73 as an electric device capable of performing IP
communication is connected to another PLC adaptor 60D using the AC
cord 75 and the communication cable 76. In addition, the PLC
adaptors 60C and 60D are connected to the AC sockets 41C and 41D
using a power line 11. According to this construction, similarly to
the second connection example, video contents may be transmitted
between the digital video server 73 and the television set 72A
provided in different rooms in a house 10 on the PLC network and
the Ethernet network to allow a user to watch the video.
[0098] FIG. 13 is a block diagram schematically illustrating a
hardware construction of a power line communication apparatus
according to the present embodiment. FIG. 14 is a block diagram
illustrating a hardware construction of the power line
communication apparatus of FIG. 13 in detail.
[0099] FIGS. 13 and 14 illustrate a first example of a detailed
construction of the PLC adaptor (in this example, denoted as a
reference numeral 290) which functions as a power line
communication apparatus according to the aforementioned
embodiments. The PLC adaptor 20 includes an adaptor main body 100,
an AC electric cord 29, a display unit 28 constructed of LEDs or a
liquid crystal display device, a manipulation unit 27 such as a
switch, and a communication connector 26 used for Ethernet
communication.
[0100] The AC electric cord 29 is connected to the power line using
the AC socket provided in a house in order to supply a commercial
power voltage (for example, AC 100 V) and connect the transmission
path. The display unit 28 is constructed of LEDs or a liquid
crystal display device and used to display operation conditions of
the communication ports corresponding to each communication
connector of the PLC adaptor 20 and notify a user of them. The
manipulation unit 27 is constructed of manipulation input switches
and used to input various manipulations such as switching of
operation modes of each communication port of the PLC adaptor 20.
Various electric devices such as a HDD recorder, a set top box
(STB), a television set, an IP telephone, an IP camera, and a
personal computer are connected to the communication network 26 to
allow the data to be transmitted to other devices.
[0101] The adaptor main body 110 internally includes a power supply
board 110 and a main board 120. The power supply board 100 receives
a commercial power voltage through the AC electric cord 29 and
generates a DC power voltage to output it to the main board 120 and
other elements in the device. In addition, the power supply board
110 and the main board 120 are electrically connected with each
other in order to supply a DC current and a variety of signals. In
addition, the display unit 28 and the manipulation unit 27 are
connected to the main board 120 using the communication connector
26.
[0102] The power supply board 110 and the main board 120 are
internally constructed as shown in FIG. 14. The power supply board
110 includes an AC/DC power supply unit 111, a synchronization
pulse generator unit 112, and an AC coupler 113.
[0103] The AC/DC power supply unit 111 generates a DC power voltage
(for example, DC 10.5 V) required for circuit operations from the
commercial power voltage (for example, AC 100 V) supplied from the
AC electric cord 101. The AC/DC power supply unit 111 internally
includes a circuit for stabilizing the power voltage, such as a
line filter, an input rectification and smoothing unit, a DC/DC
converter unit, and an output rectification and smoothing unit. The
synchronization pulse generator unit 112 outputs a timing signal
synchronized with the AC waveform of the power as a synchronization
pulse. Specifically, the synchronization pulse generator unit 112
periodically outputs the pulse in every timing having a zero DC
voltage. The AC coupler 113 includes a combined transformer and the
like, and is provided between the AC electric cord 101 and the main
board 120 in order to cut off a DC power or an AC power having a
relatively low frequency and transmit only communication
signals.
[0104] The main board 120 includes a control unit 121, a PLC front
end 122, an Ethernet physical layer control unit (Ether PHY IC)
123, a user interface 124 including a display unit and a
manipulation unit, and DC/DC converter units 125 and 126.
[0105] The control unit 121 includes a PLC integrated circuit (PLC
LSI) 131, a RAM (SDRAM) 132, a ROM (F-ROM) 133, and a clock signal
generator unit (TCXO: Temperature Compensated. Xtal Oscillator)
134. The PLC integrated circuit 131 includes a digital processing
circuit such a microprocessor, a MAC (Media Access Control Layer)
block 131A, and a physical layer (PHY) block 131B. The RAM 132 is a
readable and writable memory, and the ROM 133 is a read-only
memory. They transmit and receive data from/to the PLC integrated
circuit 131. The ROM 133 previously stores a program or data
required for the PLC integrated circuit 131. The PLC integrated
circuit 131 sequentially executes necessary programs in
synchronization with the clock signal generated by the clock signal
generator unit 134 in order to perform a processing for
transmitting the data or a modern function in the power line
communication.
[0106] The PLC front end 122 is provided between the control unit
121 and the AC coupler 113, and includes a D/A converter unit 141,
a transmit filter 142, a transmit driver IC 143, a receive
attenuator 144, a receive filter 145, and an A/D converter unit
146. The D/A converter unit 141 and the A/D converter unit 146 are
included in an analog front end (AFE) IC shown in a dotted
line.
[0107] According to the above construction, the PLC integrated
circuit 131 inputs the data packets to be transmitted from the
electric device connected to the PLC adaptor 20 using the Ethernet
communication connector 26 and the Ethernet physical layer control
unit 123, modulates the transmission data, and generates a PLC
multi-carrier signal using the OFDM or the like for the digital
transmission signal. The PLC multi-carrier signal output as a
transmission signal from the PLC integrated circuit 131 is
converted into a digital signal using the DID converter unit 141 in
the PLC front end 122, a predetermined band of signals are filtered
by the transmit filter 142, and the filtered signal is amplified by
the transmit driver 143. As a result, the PLC multi-carrier signal
is transmitted to the power line 11 corresponding to the
transmission path via the AC coupler 113 of the power supply board
110.
[0108] On the other hand, the signal transmitted from another PLC
adaptor 20 corresponding to a communication counterpart to the
power line 11 as a multi-carrier signal is input to the PLC front
end 122 using the AC electric cord 29 of the PLC adaptor 20 of its
terminal and the AC coupler 113 of the power supply board 110. An
amplitude of the PLC multi-carrier signal input to the PLC front
end 122 is adjusted by the receive attenuator 144, and a
predetermined band of signals are passed through the signal filter
145 and converted into digital signals in the A/D converter unit
146, so as to be input to the PLC integrated circuit 131 as digital
receive signals.
[0109] The PLC integrated circuit 131 demodulates the PLC
multi-carrier signal that has received to obtain receive data. The
obtained receive data is output from the PLC integrated circuit 131
to the electric device connected to the PLC adaptor 20 via the
Ethernet physical layer control unit 123 and the communication
connector 26.
[0110] In addition, the PLC integrated circuit 131 has a
communication control function in the PLC adaptor operated as a
master device. In other words, the PLC integrated circuit 131 has a
function of managing information on the communication devices
connected to the PLC network as a QoS controller function, a
function of allocating the time slot to the communication link of
each communication port, a function of scheduling the allocated
time slot, and a function of outputting a beacon signal including
the scheduling information, and performs various processes for
these functions. In addition, in the PLC adaptor operated as a
slave device, the PLC integrated circuit 131 has a function of
requesting to obtain the time slot required for the master device
on the basis of the setting of the operation mode set by the
manipulation unit 27 for each communication port or results of
automatic determination for the type of the transmitted data, and a
function of controlling the communication timing of its terminal on
the basis of the scheduling set by the master device. In other
words, the PLC integrated circuit 131 requests the required time
slot to the master device on the basis of the type of the data
transmitted from each communication port to obtain the time slot,
detects the beacon signal from the receive signals, and determines
the timing of the time slot used in its terminal on the basis of
the scheduling information included in the beacon signal.
[0111] Now, a power line communication apparatus including a
wireless communication unit having a wireless LAN function will be
described as a modification of the aforementioned power line
communication apparatus. Although, in the PLC adaptor according to
the present embodiment described above, the data transmission to
the electric device is performed by using an Ethernet (Registered
Trademark) communication interface, a wireless LAN communication
interface may be used. In order to implement such a PLC adaptor, a
wireless communication unit may be added to the PLC bridges 30A to
39D illustrated in FIG. 3 or the PLC bridge 51 illustrated in FIG.
9.
[0112] FIG. 15 is a block diagram illustrating a internal
functional construction of a power line communication apparatus
according a modification of the first embodiment of the present
invention. In the PLC adaptor 20W according to the medication of
the second embodiment, the PLC adaptor 30A illustrated in FIG. 3 is
substituted with a PLC bridge 30 fin having a wireless
communication unit, and other portions are similar to those of the
first embodiment. The PLC bridge 30W includes a wireless
communication unit and an antenna 306 in addition to the PLC modem
unit 301, the bridge unit 302, the Ethernet IF unit 303, and the
communication control unit 304.
[0113] FIG. 16 is a block diagram illustrating an internal
functional construction of a power line communication apparatus
according to a modification of the second embodiment of the present
invention. In the PLC adaptor 50W of this modification, the PLC
bridge 51 illustrated in FIG. 9 is substituted with a PLC bridge
51W having a wireless communication unit, and other portions are
similar to those of the second embodiment. The PLC bridge 51
includes a wireless communication unit 305 and an antenna 306 in
addition to the PLC modem unit 301, the bridge unit 302, and the
communication control unit 304.
[0114] In FIGS. 15 and 16, the wireless communication unit 304
provides a wireless communication function according to IEEE
802.11a, b, and g. According to the aforementioned modifications, a
wireless LAN network is added to the Ethernet (Registered
Trademark) network and the PLC network and connected with one
another via the Ethernet communication interface and the wireless
LAN communication interface. As a result, it is possible to perform
data communication while the required transmission band is obtained
between these networks.
[0115] FIG. 17 is a block diagram illustrating a second example of
a hardware construction of a power line communication apparatus
according to the present embodiment. This second example
corresponds to FIGS. 15 and 16, and shows a hardware construction
of the PLC adaptor 70 having a wireless communication function.
Similarly to the aforementioned PLC adaptor 20, the PLC adaptor 70
includes a power supply board 110, a main board 120, an AC socket
25, an AC electric cord 29, and a communication connector 26. In
addition, fundamental functions or operations are similar to those
of the aforementioned PLC adaptor 20.
[0116] The main board 120 internally includes a main integrated
circuit 201, an analog front end integrated circuit (APE IC) 202, a
filter 25, a driver integrated circuit 215, a filter 261, a coupler
206, an amplifier (AMP IC) 208, a filter 221, an AD converter
integrated circuit (ADC IC) 222, a memory 210, an Ethernet physical
layer integrated circuit (Ethernet PHY IC) 212, a wireless unit
250, and an antenna 251.
[0117] The main integrated circuit 201 includes a central
processing unit (CPU) 201a, a power line communication media access
control (PLC/MAC) block 201b, and a power line communication
physical layer (PLC/PHY) block 201c. The AFE integrated circuit 202
includes a D/A converter (DAC) 253, amplifiers 254 and 262, and an
A/D converter (ADC) 262. The coupler 206 includes a coil
transformer 206a and a condenser 206b.
[0118] The wireless unit 250 includes a transceiver unit, a
modulation/demodulation unit, a signal processing unit, and the
like to provide a wireless communication function according to IEEE
802.11 a, b, and g. The antenna 251 may be internally installed in
the main body or may be externally installed in a protruded
shape.
[0119] In the PLC adaptor 70 of the second example, the PLC
network, the Ethernet (Registered Trademark) network, and the
wireless LAN network are connected with one another via the
Ethernet communication interface and the wireless LAN communication
interface. As a result, it is possible to perform data
communication while the time slot required between these networks
is obtained.
[0120] In the PLC adaptor according to the present embodiment, the
following notification functions can be provided as an example of a
function of notifying a user of operation conditions. According to
the present embodiment, although it is possible to obtain the time
slot required to transmit the streaming data or the like on the PLC
network, the time slot may not be obtained when actual conditions
of the transmission path is changed, or the traffic amount
increases. Therefore, the PLC adaptor is preferably constructed to
measure the actual condition (such as a transmission speed) of the
transmission path, for example, in a test mode operation
automatically executed before the communication is initiated and
notify a user of the result of the measurement.
[0121] The result of the measurement may be notified to a user by
turning on/off an LED light, displaying characters or symbols on a
liquid crystal display, alarming using a voice or a buzzer, or
transmitting data to a terminal (such as a mobile phone) remotely
distributed on a network.
[0122] For example, if three LEDs are provided in a display unit,
the following four conditions can be notified as the measurement
result by controlling a combination of the ON/OFF states of the
LEDs.
[0123] (1) Excellent Condition (a high transmission speed (over 40
Mbps)): turning on three LEDs for ten seconds;
[0124] (2) Normal Condition (an intermediate transmission speed (20
to 40 Mbps)): turning on two LEDs for ten seconds;
[0125] (3) Bad Condition (a low transmission speed (5 to 20 Mbps):
turning on a single LED for ten seconds; and
[0126] (4) Significantly Bad Condition (a significantly low
transmission speed (under 5 Mbps)): flickering a single LED for ten
seconds.
[0127] In addition, as a modification of this notification
function, an actual operation condition for the operation mode set
by a user may be notified. In other words, whether or not the
communication condition can actually provide a satisfactory QoS for
the operation mode selected by manipulating the switch 27 may be
identified on the basis of the measurement result of the test mode
as described above, and the result may be notified to a user.
Furthermore, when it is impossible to guarantee a desired QoS from
the condition of the transmission path or the allocation of the
time slot, the allocation of the time slot may stop due to errors,
and a fact that the QoS can not be guaranteed may be displayed. As
a result, a user can easily identify whether or not the desired
data can be appropriately transmitted on the basis of the condition
notification.
[0128] In addition, the setting of the operation mode using the
switch 27 is not limited to the switching among five modes
described above. Instead, the setting of the operation mode may be
simplified, and various types of settings may be applied depending
on use conditions. For example, the operation mode may be switched
over between the VoIP and the video modes. In addition, the
operation mode may be switched over between manual and automatic
modes, and the QoS control may be switched on and off.
[0129] Although the PLC adaptor has a construction different from
that of the electric device in the aforementioned embodiment, the
PLC adaptor and the electric device may be integrated into a single
body. In other words, the PLC adaptor may be internally provided in
electric devices having an application device of an upper layer,
such as a telephone, a facsimile, a video phone, and a personal
computer.
[0130] According to the aforementioned embodiments, when a
communication system is constructed using a PLC network, an
Ethernet network, and a wireless LAN network in a house, various
data including the streaming data such as video or audio data can
be transmitted and reproduced without loss of data in a receiver
side while a required time slot is obtained. In this case, since
the required time slot can be allocated and obtained depending on a
setting condition of an operation mode or the type of the data
actually transmitted, it is possible to effectively use a limited
amount of the time slots and transmit and reproduce the data in a
high quality.
[0131] Although a data relay apparatus for promoting effective use
of the time slot by modifying the time interval of the time slot
has been described in the aforementioned embodiments, one or more
time slots may be additionally allocated to the streaming data
having a single time slot of a predetermined time interval between
the beacons when the condition of the transmission path is
allowable.
[0132] When the condition of the transmission path is not
allowable, the number of allocated time slots may be reduced for
the streaming data having two or more allocated time slots of a
predetermined time interval between the beacons.
[0133] Furthermore, it is possible to promote effective use of the
time slots on an entire network by setting the number and the time
interval of the time slots.
[0134] The present invention can be usefully applied to a power
line communication apparatus and a data relay method, in which an
appropriate quality of service can be provided depending on the
type of the connected electric devices and the type of the
transmitted data when a power line is used as a communication
transmission path, and an electric device having a communication
function is connected to an Ethernet network via an Ethernet
(Registered Trademark) communication interface and connected to a
power line also functioning as a transmission path in order to
perform data transmission between these electric devices and the
transmission path.
[0135] This application is based upon and claims the benefit of
priority of Japanese Patent Application No. 2005-305968 filed on
Oct. 20, 2005, the contents of which are incorporated herein by
reference in its entirety.
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