1. Field of the Invention
The present invention relates to a transmission/reception apparatus and a transmission/reception method for enabling coexistence of systems. More particularly, the present invention relates to a technique of enabling coexistence of two communication systems which use the same communication medium and have different communication schemes, a transmission/reception apparatus included in each of the communication systems, and a method which is executed by the transmission/reception apparatus.
2. Description of the Background Art
Power line communication technology is a communication means for connection of a Personal Computer (PC) in a home to a network apparatus, such as a broadband router or the like, so as to access from the PC to the Internet. In the power line communication, since an existing power line is used as a communication medium, it is not necessary to perform a new wiring work, and high-speed communication can be achieved only by inserting a power supply plug into a power supply outlet available throughout a home. Therefore, research and development, and demonstration experiments of the power line communication technology have been vigorously conducted all over the world, and in Europe and the USA, a number of power line communication projects have already been commercialized.
An example of the power line communication is HomePlug Ver. 1.0, which is a specification created by the HomePlug Powerline Alliance (USA). The specification is intended to be used mainly in applications, such as the Internet, mailing, and file transfer which are performed by a PC. HomePlug employs a CSMA/CA technique for a medium access control of which power line communication modem accesses a power line, and provides best-effort communication which does not guarantee a band to be used.
In Europe (Spain, etc.), an access power line communication modem has been used which employs, as an access line to the Internet, a power line for supplying a power to a home.
Thus, by using the access power line communication modem, access to the Internet can be provided without withdrawing a cable or the like into a home. In addition, since the access power line communication modem 2702 is installed at any arbitrary outlet in a home, the degree of freedom of installing is higher than that of ADSL, FTTH, and the like.
Assuming that Ethernet packets are transmitted onto a power line, when an IP packet arrives from an Ethernet 2811, the communication control section 2809 is informed of the arrival via the Ethernet I/F section 2810. The communication control section 2809 determines a state of a communication channel, and outputs frame data to the digital modulation section 2808 with appropriate timing. The digital modulation section 2808 performs error correction addition, encoding, framing, and the like to modulate the frame data into a transmission data sequence. The D/A conversion section 2807 converts the transmission data sequence from a digital signal to an analog signal. The PA 2806 amplifies the analog signal. The LPF 2805 cuts off signals other than communication band components from the amplified analog signal, and inputs only the communication band components onto a power line. Next, in the case of reception from a power line, the BPF 2802 extracts a signal in a communication band. The AGC 2803 amplifies the extracted signal. The AID conversion section 2804 converts the amplified analog signal into digital data. The digital modulation section 2808 performs frame synchronization detection, equalization, decoding, error correction, and the like with respect to the digital data to demodulate the digital data and informs the communication control section 2809 of the resultant data as received data. Thereafter, the received data is transmitted as an Ethernet packet from the Ethernet I/F section 2810 to the Ethernet 2811.
On the other hand, there is IEEE802.11a, which is a representative standard for wireless LAN. In 802.11a, a band used therein is divided into a plurality of channels for IP communication. IEEE802.11h is added to IEEE802.11a so as to meet requirements in Europe when a 5-GHz band is used. See, for example, IEEE Std., 802.11h-2003: “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications, Amendment 5: Spectrum and Transmit Power Management Extensions in the 5 GHz band in Europe”. One of the functions specified in 802.11h is a Dynamic Frequency Selection (DFS) function of detecting a band which is used by a radar, such as a meteorological radar or the like, and automatically shifting to a channel which avoids the band to avoid interference. An exemplary DFS operation will be hereinafter described.
The AP 2901 transmits a command to stop communication using a beacon frame in predetermined time intervals to the STAs 2902 and 2903, to temporarily stop communication on a network. The AP 2901 performs scanning to determine whether or not radar wave is present in a channel currently used and other channels during the communication stop period. Also, the AP 2901 transmits an observation command frame to the STAs 2902 and 2903 to cause the STAs 2902 and 2903 to similarly perform scanning to determine whether or not radar wave is present in the channel currently used and other channels. After scanning for radar wave, the STAs 2902 and 2903 transmit an observation result reporting frame to the AP 2901. Thereafter, the AP 2901 determines a channel on which radar wave is present, based on the scan result by itself and the san result by the STAs 2902 and 2903. If radar wave is present on the currently used channel, the AP 2901 transmits a used channel shift command frame to the STAs 2902 and 2903, so that the channel is shifted to one in which radar wave is not present, avoiding interference between the communication wave of 802.11a and the radar wave.
Thus, various power line communication techniques have been developed, however, there is no unified standard for power line communication. However, all power lines in a home are connected to a distribution switchboard, and are also connected to an outdoor power line. Therefore, when power line communication modems of different schemes are used in the same home or in a home and near outside the home, the modems mutually receive communication signals. The power line communication modem of each scheme cannot demodulate signals of other schemes transmitted onto a communication channel by the power line communication modems of other schemes, i.e., for the power line communication modem of each scheme, signals of other schemes are merely noise. Therefore, when two different schemes coincidently perform communication, the schemes mutually interfere with communication, so that communication fails in both the schemes, communication speed is significantly reduced, or the like.
As a method for avoiding such a problem, it is considered that a unified standard for power line communication is newly established. However, the establishment of a new standard requires huge time and cost, and therefore, cannot be immediately realized. Alternatively, it is considered that a band or a communication time is uniquely assigned to each communication system, thereby avoiding interference. In the above-described 802.11a, since meteorological radars are the only significant noise source in the 5-GHz band used therein, it is possible to achieve DFS as in 802.11h only by providing to all terminals a simple carrier sense mechanism even for radio waves of different modulation schemes. However, in a short wave band used by a power line communication modem, attenuated modem signals of different modulation schemes and noise of electronic appliances have substantially the same signal level, so that it is not possible to determine the presence or absence of power line communication using a carrier sense mechanism, and therefore, a DFS mechanism as in 802.11h cannot be easily constructed.
Therefore, an object of the present invention is to provide a transmission/reception apparatus and method for easily enabling coexistence of two communication systems which use the same communication medium and have different communication schemes.
The present invention is directed to a first communication system connected to a second communication system having a different communication scheme, via the same communication medium, using frequency division multiplexing or time division multiplexing, and a transmission/reception apparatus for a master station and a transmission/reception apparatus for a slave station belonging to the first communication system. To achieve the object, the transmission/reception apparatus for a master station comprises a detection section, a determination section, and an informing section, and the transmission/reception apparatus for a slave station comprises a reception section and a setting section.
In the transmission/reception apparatus for a master station, the detection section detects a frequency band or a time region used by the second communication system, or the presence or absence of the second communication system. The determination section determines a frequency band or a time region to be used in the first communication system, based on the frequency band or the time region or the presence or absence of the second communication system detected by the detection section. The informing section informs the transmission/reception apparatus for a slave station belonging to the first communication system of the frequency band or the time region determined by the determination section.
In this case, preferably, the informing section informs of the frequency band or the time region determined by the determination section using a control signal which is regularly transmitted in the first communication system and in which the frequency band is included, or using a frequency band or a time region minimally required for coexistence with the second communication system.
In the transmission/reception apparatus for a slave station, the reception section receives information about a frequency band or a time region to be used in the first communication system from the transmission/reception apparatus for a master station belonging to the first communication system. The setting section sets a frequency band or a time region to be used for data communication in accordance with the information about the frequency band or the time region received by the reception section.
Typically, the first and second communication systems are each a power line communication system, and the communication medium is a power line. In this case, for example, the first communication system is a power line communication system for in-home communication, and the second communication system is a power line communication system for access communication. Alternatively, the first and second communication systems are each a wireless communication system, and the communication medium is radio wave.
The processes performed by the parts of the above-described transmission/reception apparatuses may be considered as a transmission/reception method providing a series of processes. This method is provided in the form of a program for causing a computer to execute the series of processes. The program may be recorded on a computer-readable recording medium, which is introduced into a computer. The whole or a part of the functional blocks of the above-described transmission/reception apparatuses may be implemented as an integrated circuit (LSI)
According to the present invention, a master station belonging to a first communication system detects the presence or absence of a second communication system or a frequency band or a time region used by the second communication system, and informs a slave station belonging to the first communication system so that the slave station uses a frequency band or a time region which prevents the communication systems from interfering with each other. Thereby, it is possible to cause the two communication systems which utilize the same communication medium and have different communication schemes to coexist in an easy and inexpensive manner.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments will be described, assuming that a communication medium is a power line, though the communication medium may be a wireless, or a wired medium other than power lines.
In a first embodiment, an example will be described in which two communication systems are caused to coexist using a Frequency Division Multiplexing (FDM) technique.
The in-home communication system 110 is a power line communication system which utilizes a power line 113 provided in a home, and is composed of an in-home-system master station 111 which controls coexistence of the in-home communication system 110 and the access communication system 120, and an in-home-system slave station 112 other than the in-home-system master station 111. The in-home-system master station 111 is a transmission/reception apparatus which has a function of receiving a coexistence signal which is issued by a station belonging to the access communication system 120, and transferring the coexistence signal to the in-home-system slave station 112. In general, only one in-home-system master station 111 is provided in a home, and may be fixedly specified or may be dynamically determined or changed during operation. The in-home-system slave station 112 is a transmission/reception apparatus which is operated in a control of the in-home-system master station 111, and one or more in-home-system slave stations 112 are provided in one in-home communication system 110.
The access communication system 120 is a power line communication system which utilizes the in-home power line 113, a low voltage power distribution line 124 provided from the home to a pole transformer 126 provided on a utility pole 123, and an intermediate voltage power distribution line 125 from the pole transformer 126 to an electric power substation (not shown). Of transmission/reception apparatuses belonging to the access communication system 120, there are an access-system master station 121, and an access-system in-home apparatus (hereinafter referred to as an access-system slave station) 122 provided in the home, which are located within a range which causes interference with the in-home communication system 110. The access-system master station 121 may be provided as a transmission/reception apparatus separated from the pole transformer 126 as illustrated in
Note that, for example, the access-system slave station 122 can also be provided on the low voltage power distribution line 124 outside the home, and a communication function of the in-home communication system 110 can be assigned to the access-system slave station 122. Although not illustrated in
In the first embodiment, the in-home communication system 110 and the access communication system 120 are assumed to have a function capable of using a frequency band of 2 MHz to 28 MHz.
In the first embodiment, the in-home communication system 110 uses the coexistence signal subchannel 211 to detect a frequency band which is used by the access communication system 120, and the in-home communication system 110 and the access communication system 120 share and utilize the data communication subchannel 212, thereby achieving coexistence using frequency division multiplexing. Hereinafter, system coexistence by frequency division multiplexing will be specifically described. Note that a band used by the coexistence signal subchannel 211 is defined as a coexistence signal band 201, and a band used by the data communication subchannel 212 is defined as a data communication band 202.
Initially, transmission/reception of a coexistence signal which is performed by the in-home communication system 110 and the access communication system 120, will be described.
Next, a detailed configuration and process operation of each station in the in-home communication system 110 and the access communication system 120 will be described.
A frame receiving section 402 receives a transmitted frame via a data transmission/reception I/F section 404, and subjects the frame into a required process to generate received data. A frame transmitting section 401 frames data to be transmitted in the access communication system 120, and transfers the data to the data transmission/reception I/F section 404, thereby performing data transmission. In this case, a communication control section 403 which controls data transmission/reception while referencing information from the frame receiving section 402, controls timing of data transmission of the frame transmitting section 401.
A coexistence signal generating section 411 receives information about a subchannel (frequency band) used by the access communication system 120 from the communication control section 403, and based on this, generates a coexistence signal (the signals 331 and 332 in
A frame receiving section 502 receives a transmitted frame via a data transmission/reception I/F section 504, and subjects the frame into a required process to generate received data. A frame transmitting section 501 frames data to be transmitted in the in-home communication system 110, and transfers the data to the data transmission/reception I/F section 504, thereby performing data transmission. In this case, a communication control section 503 which controls data transmission/reception while referencing information from the frame receiving section 502, controls timing of data transmission of the frame transmitting section 501.
A coexistence signal receiving section 516 checks whether or not a coexistence signal has been received via a coexistence signal reception I/F section 514 (step S802). When a coexistence signal has been received, the coexistence signal receiving section 516 analyzes the coexistence signal to obtain information about a subchannel used by the access communication system 120, and informs the coexistence control section 515 of the information. Based on this information, the coexistence control section 515 determines a subchannel which should be used by the in-home communication system 110 (step S803), and informs the communication control section 503 of the subchannel. The communication control section 503 instructs the informed subchannel to the data transmission/reception I/F section 504. The data transmission/reception I/F section 504 performs frame transmission/reception using the instructed subchannel. Also, the communication control section 503 generates a frame including information about a frequency band to be used in the in-home communication system 110 (the information 341 and 342 in
Note that information about a subchannel (frequency band) to be used may be informed of using a dedicated frame. Alternatively, in a communication system in which a master station regularly transmits a special control frame, the information about a subchannel to be used may be stored in the special control frame. For example, the dedicated frame is a frame for an access control function of CSMA/CA or the like, and the special control frame is a frame for polling or beaconing.
A frame receiving section 602 receives a transmitted frame via a data transmission/reception I/F section 604, and subjects the data to a required process to generate received data. A frame transmitting section 601 frames data to be transmitted in the in-home communication system 110, and transfers the data to the data transmission/reception I/F section 604, thereby performing data transmission. In this case, a communication control section 603 which controls data transmission/reception while referencing information from the frame receiving section 602, controls timing of data transmission of the frame transmitting section 601. Also, the frame receiving section 602 checks whether or not a frame including information about a subchannel to be used in the in-home communication system 110 (the information 341 and 342 in
Next, a frame for informing of information about a frequency band to be used, which is transmitted from the in-home-system master station 111 to the in-home-system slave station 112, will be described.
The frame of
The payload 1002 is a field for storing data transferred from an upper layer protocol, or protocol control information. In this frame, band-to-be-used information 1021 which is information about a frequency band to be used is stored in the payload 1002. The band-to-be-used information 1021 is generally considered to be specified by a subchannel number illustrated in
The CRC 1003 is a Cyclic Redundancy Code (CRC) for detecting an error in the payload 1002 occurring in a reception station. By using this error detection code, a transmission channel error can be detected up to a predetermined amount. By adding an error correction code (Reed-Solomon code, etc.) in addition to the error detection code, it is possible to provide a capability to correct a transmission channel error up to a predetermined amount.
On the other hand, as illustrated in
In a second embodiment, another example will be described in which two communication systems are caused to coexist using a frequency division multiplexing technique similar to that of the first embodiment.
The communication system A1210 is a power line communication system which utilizes a power line 1213 provided in a home, and is composed of a master station A1211 which controls coexistence with the communication system B1220, and a slave station A1212 other than the master station A1211. The master station A1211 is a transmission/reception apparatus which has a function of receiving a coexistence signal which is issued by a master station belonging to the communication system B1220, and transferring the coexistence signal to the slave station A1212. The communication system B1220 is also a power line communication system which utilizes the power line 1213, and is composed of a master station B1221 which controls coexistence with the communication system A1210, and a slave station B1222 other than the master station B1221. The master station B1221 is a transmission/reception apparatus which has a function of receiving a coexistence signal which is issued by a master station belonging to the communication system A1210, and transferring the coexistence signal to the slave station B1222. In general, only one master station is present in each communication system, and may be either fixedly specified or dynamically determined or changed during operation. A slave station is a transmission/reception apparatus which is operated in a control of a master station. One or more slave stations are present in each communication system.
In the second embodiment, any one of the communication system A1210 and the communication system B1220 detects a frequency band used by the other communication system using the coexistence signal subchannel 211, and the two communication systems share and utilize the data communication subchannel 212, thereby achieving coexistence using frequency division multiplexing (see
A frame receiving section 1302 receives a transmitted frame via a data transmission/reception I/F section 1304, and subjects the frame to a required process to generate received data. A frame transmitting section 1301 frames data to be transmitted in the communication system to which the master station A1211 or the master station B1221 belong, and transfers the data to the data transmission/reception I/F section 1304, thereby performing data transmission. In this case, a communication control section 1303 which controls data transmission/reception while referencing information from the frame receiving section 1302, controls timing of data transmission of the frame transmitting section 1301.
When a coexistence signal is transmitted, a coexistence signal generating section 1311 receives information about a subchannel used by the communication system to which the master station A1211 or the master station B1221 belong, from the communication control section 1303, and based on this, generates a coexistence signal including information about a subchannel to be used by the other communication system, and transfers the coexistence signal to a coexistence signal transmitting section 1313. A zero-crossing point detecting section 1312 detects a zero-crossing point of an alternating current flowing through a power distribution line, and informs a coexistence control section 1315 of the detection result (step S1502). The coexistence control section 1315 instructs timing of transmission of the coexistence signal to the coexistence signal transmitting section 1313 in accordance with the information from the zero-crossing point detecting section 1312. The coexistence signal transmitting section 1313 transmits the coexistence signal via a coexistence signal transmission/reception I/F section 1314 in accordance with the timing instructed by the coexistence control section 1315 (step S1503).
When a coexistence signal is received, a coexistence signal receiving section 1316 checks whether or not the coexistence signal has been received via the coexistence signal transmission/reception I/F section 1314 (step S1504). When the coexistence signal has been received, the coexistence signal receiving section 1316 analyzes the coexistence signal to obtain information about a subchannel used by the other communication system, and informs the coexistence control section 1315 of the information. Based on the information, the coexistence control section 1315 determines a subchannel which should be used by the communication system to which the master station A1211 or the master station B1221 belong (step S1505), and informs the communication control section 1303 of the subchannel. The communication control section 1303 instructs the informed subchannel to the data transmission/reception I/F section 1304. The data transmission/reception I/F section 1304 performs frame transmission/reception using the instructed subchannel. Also, the communication control section 1303 generates a frame including information about a frequency band to be used by the communication system to which the master station A1211 or the master station B1221 belong, and transfers the frame to the frame transmitting section 1301. The frame transmitting section 1301 transmits a frame including information about the subchannel via the data transmission/reception I/F section 1304 to a slave station of the communication system to which the master station A1211 or the master station B1221 belong (step S1506). Thereafter, the processes of steps S1502 to S1506 are repeatedly performed. Note that the frame including the information about the frequency band to be used in the communication system to which the master station A1211 or the master station B1221 belong, may be transmitted using a subchannel which is already used before reception of a coexistence signal from the other communication system, instead of using a new subchannel instructed by the data transmission/reception I/F section 1304 as described above.
A frame receiving section 1402 receives a transmitted frame via a data transmission/reception I/F section 1404, and subjects the data to a required process to generate received data. A frame transmitting section 1401 frames data to be transmitted in the communication system to which the slave station A1212 or the slave station B1222 belong, and transfers the data to the data transmission/reception I/F section 1404, thereby performing data transmission. In this case, a communication control section 1403 which controls data transmission/reception while referencing information from the frame receiving section 1402, controls timing of data transmission of the frame transmitting section 1401. Also, the frame receiving section 1402 checks whether or not a frame including information about a frequency band to be used in the communication system to which the slave station A1212 or the slave station B1222 belong has been received (step S1602). When the frame has been received, the frame receiving section 1402 transfers the information to the communication control section 1403. The communication control section 1403 instructs the information to the data transmission/reception I/F section 1404. Based on the instructed information, the data transmission/reception I/F section 1404 sets a subchannel to be used for frame transmission/reception (step S1603). Thereafter, the processes of steps S1602 and S1603 are repeatedly performed.
In a third embodiment, an example will be described in which two communication systems are caused to coexist using a Time Division Multiplexing (TDM) technique. A communication system employing a transmission/reception apparatus according to the third embodiment of the present invention has a rough configuration in which two communication systems, i.e., an in-home communication system 110 and an access communication system 120, are provided as in the first embodiment of
An example of use of the frequency in this case is illustrated in
In the coexistence signal transmitting station (see
In the in-home-system master station 111 (see
In the in-home-system slave station 112 (see
In a fourth embodiment, an example will be described in which two communication systems are caused to coexist using a frequency division multiplexing technique different from those of the first and second embodiments. A communication system employing a transmission/reception apparatus according to the fourth embodiment of the present invention has a rough configuration in which two communication systems, i.e., an in-home communication system 110 and an access communication system 120, are provided as in the first embodiment of
In the fourth embodiment, the in-home communication system 110 and the access communication system 120 are assumed to have a function capable of using a frequency band of 4 MHz to 28 MHz.
Next, a detailed configuration and process operation of each station of the in-home communication system 110 and the access communication system 120 will be described.
A frame receiving section 2002 receives a transmitted frame via a data transmission/reception I/F section 2004, and subjects the frame to a required process to generate received data. A frame transmitting section 2001 frames data to be transmitted in the access communication system 120, and transfers the data to the data transmission/reception I/F section 2004, thereby performing data transmission. In this case, a communication control section 2003 which controls data transmission/reception while referencing information from the frame receiving section 2002, controls timing of data transmission of the frame transmitting section 2001.
A frame receiving section 2102 receives a transmitted frame via a data transmission/reception I/F section 2104, and subjects the frame to a required process to generate received data. A frame transmitting section 2101 frames data to be transmitted in the in-home communication system 110, and transfers the data to the data transmission/reception I/F section 2104, thereby performing data transmission. In this case, a communication control section 2103 which controls data transmission/reception while referencing information from the frame receiving section 2102, controls timing of data transmission of the frame transmitting section 2101.
An access-system signal detection section 2111 checks whether or not a communication signal of the access-system master station 121 or the access-system slave station 122 has been detected (step S2302). When the communication signal of the access-system master station 121 and the access-system slave station 122 has been detected, the access-system signal detection section 2111 informs the communication control section 2103 of the detection result. The communication control section 2103 determines that a subchannel used for communication is limited to #2 (step S2303), and instructs the subchannel #2 to the data transmission/reception I/F section 2104. The data transmission/reception I/F section 2104 uses the instructed subchannel to perform frame transmission/reception. Also, the communication control section 2103 creates a frame for informing the in-home-system slave station 112 of the limitation on use of the subchannel, and transfers the frame to the frame transmitting section 2101. The frame transmitting section 2101 transmits a frame including information about the subchannel via the data transmission/reception I/F section 2104 to the in-home-system slave station 112 (step S2304). Thereafter, the processes of steps S2302 to S2304 are repeatedly performed. Note that the frame including the information about the subchannel is transmitted from the in-home-system master station 111 to the in-home-system slave station 112 using both the subchannel #1 and the subchannel #2, instead of using only the subchannel #2 as described above.
Note that, if a mechanical switch or the like is used so that the user can explicitly set the presence or absence of the access communication system 120, the configuration of the in-home-system master station 111 to the access-system signal detection section 2111 can be removed.
A frame receiving section 2202 receives a transmitted frame via a data transmission/reception I/F section 2204, and subjects the frame to a required process to generate received data. A frame transmitting section 2201 frames data to be transmitted in the in-home communication system 110, and transfers the data to the data transmission/reception I/F section 2204, thereby performing data transmission. In this case, a communication control section 2203 which controls data transmission/reception while referencing information from the frame receiving section 2202, controls timing of data transmission of the frame transmitting section 2201. Also, the frame receiving section 2202 checks whether or not a frame including information about a frequency band to be used in the in-home communication system 110 has been received. When the frame has been received, the frame receiving section 2202 transfers the information to the communication control section 2203. The communication control section 2203 instructs the information to the data transmission/reception I/F section 2204. Based on the instructed information, the data transmission/reception I/F section 2204 limits and determines a frequency band which should be used for frame transmission/reception, only to the in-home-system-specific subchannel #2.
Note that the configuration of a frame for informing of information about a frequency band to be used, which is transmitted from the in-home-system master station 111 to the in-home-system slave station 112, may be basically similar to that of
As described above, according to the transmission/reception apparatus and the transmission/reception method according to the first to fourth embodiments of the present invention, a master station of an in-home communication system detects the presence of another communication system, or a frequency band or a time region used by another communication system, and informs a slave station of the in-home communication system of the frequency band or the time region so that a frequency band or a time region which avoids communication interference between the two communication systems can be used. Thereby, it is possible to cause two communication systems which utilize the same communication medium and have different communication schemes, to coexist in an easy and inexpensive manner.
Note that the method for coexistence of communication systems by time division multiplexing which is described in the third embodiment can be applied to coexistence of in-home communication systems described in the second embodiment. Also, the method described in the fourth embodiment in which transmission/reception of a coexistence signal is not explicitly performed, can be applied to any of the first to third embodiments.
The first to fourth embodiments have been described, assuming that, in the in-home communication systems 110, 1210 and 1220, only the in-home-system master stations 111, 1211 and 1221 can detect a coexistence signal or a communication signal which is transmitted from the other communication system. However, a portion or all of the in-home-system slave stations 112, 1212 and 1222 in the in-home communication systems 110, 1210 and 1220 may have a function capable of detecting a coexistence signal or a communication signal.
In this case, preferably, the in-home-system slave stations 112, 1212 and 1222 which detect a coexistence signal or a communication signal, inform the in-home-system master stations 111, 1211 and 1221 of information about a used frequency or a used time, and after a frequency band or a time which should be used is determined in the in-home-system master stations 111, 1211 and 1221, the in-home-system slave stations 112, 1212 and 1222 are informed again of the contents of the determination (see
Also, the first to fourth embodiments have been described, assuming that information transmitted from the in-home-system master stations 111, 1211 and 1221 to the in-home-system slave stations 112, 1212 and 1222 is a frequency band or a time to be used in the in-home communication systems 110, 1210 and 1220. However, the transmitted information may be a frequency band or a time used in the other communication system which are detected using a coexistence signal.
Also, the first to fourth embodiments have been described, assuming that a communication system is a power line communication system. However, the communication systems 110 and 120, and the communication systems 1210 and 1220 may be both wireless communication systems. In this case, if each station in a wireless communication system is connected to a commercialized AC mains, it is possible to achieve synchronization with a zero-crossing point of the commercialized AC mains as a reference, as is similar to the case of power line communication systems. In this case, the zero-crossing point detecting section (reference numeral 412 in
Note that the above-described embodiments may be each implemented by causing a CPU to interpret and execute predetermined program data capable of executing the above-described procedure, the program being stored in a storage apparatus (a ROM, a RAM, a hard disk, etc.). In this case, the program data may be stored into the storage apparatus via a recording medium, or may be executed directly from the recording medium. The recording medium refers to a semiconductor memory, such as a ROM, a RAM, a flash memory or the like; a magnetic disk memory, such as a flexible disk, a hard disk or the like; an optical disc, such as a CD-ROM, a DVD, a BD or the like; a memory card; or the like. The recording medium is a concept including a communication medium, such as a telephone line, a transfer line, or the like.
Functional blocks of each embodiment, such as the frame transmitting section, the frame receiving section, the communication control section, the coexistence signal transmitting section, the coexistence signal receiving section, the coexistence control section, the coexistence signal generating section, and the like, may be typically implemented as an integrated circuit (LSI: LSI is be called IC, system LSI, super LSI or ultra LSI, depending on the packaging density). Each functional block may be separately mounted on one chip, or a part or the whole of the functional blocks may be mounted on one chip. Also, a portion involved in communication and a portion involved in transmission/reception of a coexistence signal in one communication system may be mounted on separate LSI chips.
The integrated circuit is not limited to LSI. The integrated circuit may be achieved by a dedicated circuit or a general-purpose processor. Further, an Field Programmable Gate Array (FPGA) which can be programmed after LSI production or a reconfigurable processor in which connection or settings of circuit cells in LSI can be reconfigured, may be used.
Furthermore, if an integrated circuit technology which replaces LSI is developed by an advance in the semiconductor technology or the advent of other technologies derived therefrom, the functional blocks may be packaged using such a technology. A biotechnology may be applicable.
The in-home communication apparatus of the present invention may be in the form of an adaptor which converts a signal interface, such as Ethernet interface, IEEE1394 interface, USB interface, or the like, into interface for power line communication, and thereby, can be connected to multimedia apparatuses, such as a personal computer, a DVD recorder, a digital television, a home system server, and the like, which have various kinds of interface. Thereby, a network system which transmits digital data, such as multimedia data or the like, via a power line as a medium with high speed, can be constructed. As a result, a power line which is already provided in homes, offices and the like can be directly used as a network line without newly introducing a network cable, such as a conventional wired LAN. Therefore, the present invention is considerably useful in terms of cost and ease of installation.
The functions of the present invention may be incorporated into the above-described multimedia apparatuses in the future. Thereby, data transfer can be achieved between the multimedia apparatuses via a power source cable thereof. In this case, an adaptor, an Ethernet cable, an IEEE1394 cable, a USB cable, and the like are not required, thereby simplifying wiring. Also, the high-speed power line transmission system of the present invention can be connected via a rooter to the Internet, or via a hub to a wireless LAN or a conventional wired cable LAN, thereby extending a LAN system in which the high-speed power line transmission system of the present invention is used without any problem. Communication data transferred via a power line by power line transmission may be intercepted by an apparatus directly connected to the power line, but is free from an eavesdrop problem with wireless LAN. Therefore, the power line transmission scheme is effective for data protection in terms of security. Further, data transferred on a power line may be protected by IPSec of an IP protocol, encryption of the contents themselves, other DRM schemes, or the like.
As compared to conventional power line communication, high-quality AV content transmission on a power line can be achieved by using a copyright protection function employing the above-described encryption of contents or efficient communication media (an effect of the present invention), and further implementing a QoS function.
While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention.
Number | Date | Country | Kind |
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2005-196366 | Jul 2005 | JP | national |