I 1111111111111111 11111 111111111111111 1111111111 1111111111 111111111111111111
`
`US005907540A
`
`
`United States Patent
`[19J
`Hayashi
`
`5,907,540
`[11] Patent Number:
`
`May 25, 1999
`[45]Date of Patent:
`
`[54]RADIO DATA COMMUNICATION
`FOREIGN PATENT DOCUMENTS
`APPARATUS HAVING A RELAY FUNCTION
`
`3-250820 11/1991 Japan .
`AND RADIO DATA COMMUNICATION
`METHOD AND SYSTEM USING THE SAME
`
`OTHER PUBLICATIONS
`
`
`
`
`
`
`
`Hitachi, [73]Assignee: Ltd., Tokyo, Japan
`
`[21]Appl. No.: 08/530,709
`
`[22]Filed:Sep. 19, 1995
`
`
`
`"Nikkel Communications", Mar. 7, 1994, vol. 3, No. 7, pp.
`Kenji Hayashi, Hadano, Japan[75] Inventor:
`100-105.
`"An Ethernet Address Resolution Protocol -or-Convert­
`
`
`
`
`
`
`ing Network Protocol Addresses to 48. Bit Ethernet Address
`
`
`
`for Transmission on Ethernet Hardware", David C. Plum­
`
`mer, Nov. 1982, RFC826.TXT, pp. 1-9.
`"Information Technology-Telecommunications and Infor­
`
`
`
`
`mation Exchange Between Systems-Local Area Net­
`
`
`works-Media Access Control (MAC) Bidges", Draft
`
`
`
`Amendment ISO/IEC DIS 10038/DAM 2, 1992, pp. 1-42.
`
`Sep. 21, 1994 [JP] Japan .................................... 6-226246
`
`
`
`
`
`[30] Foreign Application Priority Data
`
`
`
`. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`H04B 7/15; H04J 3/26
`Primary Examiner-Hassan Kizou
`
`[51]Int. Cl.6
`
`
`Attorney, Agent, or Firm-Fay, Sharpe, Beall, Fagan,
`
`
`
`.......................... 370/315; 370/349; 370/351;
`[52]U.S. Cl.
`
`Minnich & McKee
`
`370/393; 455/11.1
`
`[58]Field of Search ..................................... 370/315, 328,
`
`[57]
`ABSTRACT
`
`
`370/338, 349, 351, 312, 393, 492, 501;
`
`455/7, 11.1, 13.1
`In a radio data communication network where a plurality of
`
`
`
`
`
`
`
`
`radio data communication apparatuses mutually communi­
`
`
`
`cate information through frames carried by radio waves, a
`
`
`communication method using radio data communication
`
`
`
`
`apparatuses having a relay function is provided. When two
`
`
`
`4,081,612 3/1978 Hafner .................................... 370/393
`
`
`
`
`radio data communication apparatuses cannot directly com­
`
`
`4,999,833 3/1991 Lee .......................................... 370/312
`
`
`
`municate with each other due to the limit of the radio wave
`
`
`5,007,052 4/1991 Flammer ................................. 370/389
`
`
`
`
`
`range, another radio data communication apparatus serves as
`
`
`
`5,115,433 5/1992 Baran et al. ............................ 370/400
`
`
`
`a relay station to relay frames between the two apparatuses,
`
`
`
`5,200,955 4/1993 Mcfarlane et al. .................... 370/315
`
`
`thus extending a communicable range.
`
`
`
`
`5,265,150 11/1993 Helmkamp et al. ...................... 379/58
`
`
`
`5,287,356 2/1994 Parkhideh ............................... 370/445
`
`24 Claims, 14 Drawing Sheets
`
`
`
`5,570,354 10/1996 Simon ..................................... 370/315
`
`,_
`... --•·····,
`
`ZONE B
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`ZONE A
`
`ZONE C
`
`. ZONED
`
`, ,. , ,
`
`,:
`/. , :
`
`ZONE E
`
`-···
`
`Page 1 of 26
`
`

`

`U.S. Patent
`US. Patent
`
`May 25, 1999
`May 25,1999
`
`Sheet 1 of 14
`Sheet 1 0f 14
`
`5,907,540
`5,907,540
`
`FIG.
`
`
`
`IIII
`II
`fI
`
`II
`
`Page 2 of 26
`
`Page 2 of 26
`
`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 2 of 14
`
`5,907,540
`
`
`
`F. G. 2
`
`w
`
`- - - - - - - -
`
`l
`
`
`
`
`
`PUBLIC RADIO
`COMMUNICATION
`NETWORK
`
`LOCAL RADIO
`COMMUNICATION
`NETWORK
`
`Page 3 of 26
`
`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 3 of 14
`
`5,907,540
`
`
`
`1 103
`
`1105
`
`t MEMORY ton
`
`11 O2
`
`1104
`
`Page 4 of 26
`
`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 4 of 14
`
`5,907,540
`
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`Page 5 of 26
`
`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet S of 14
`
`5,907,540
`
`F.G. 5
`
`
`
`COMMAND DIRECT RADIO
`COMMUNICATIONS
`DESTINATION ADDRESS (-X
`IDENTIFICATION FLAG (-DATA
`REMITTENT ADDRESS (-Y
`DENTIFICATION INFORMATION
`<-N
`
`TRANSMIT
`DATA FRAME
`
`503
`
`TIME OUT FOR
`RESPONSE
`
`
`
`
`
`504
`
`NO
`PROCESS
`RESPONSE FRAME
`
`5O1
`
`5O2
`
`S
`
`COMMAND TRANSMISSION OF
`SEARCH FRAME
`C-X
`SEARCH ADDRESS
`IDENTIFICATION FLAG (-REQ
`REMITTENT ADDRESS e-Y
`DESTINATION ADDRESS - 3
`IDENTIFICATION INFORMATION
`(-N
`EMPTYRSAS
`
`505
`
`BROADCAST
`SEARCH FRAME
`
`506
`
`507
`
`TIME OUT FOR
`RESPONSE?
`
`509
`
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`YES
`
`
`
`
`
`TIME OUT FOR
`RESPONSE
`
`512
`
`
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`
`
`
`
`
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`
`
`
`TRANSMIT THROUGH PUBLIC
`NO
`RADIO COMMUNICATION NETWORK
`513 COMMAND REMITTENT
`SPECIFYING RELAY
`DESTINATION ADDRESS eX
`IDENTIFICATION FLAG (-DATA
`515 REMITTENT ADDRESS -Y
`DENTIFICATION INFORMATION
`<-N
`RSAS (-ROUTE INFORMATION
`
`GENERATE
`ERROR
`MESSAGE
`
`
`
`RESPONSE
`RECEPTION
`PROCESSING
`
`OEND D
`
`51O
`
`TRANSMIT
`DATA FRAME
`
`END
`
`Page 6 of 26
`
`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 6 of 14
`
`5,907,540
`
`F.G. 6
`
`622
`NO
`
`DIRECTED TO
`OWN ADDRESS
`
`623
`
`
`
`DATA RECEPTION
`PROCESSING
`
`TRANSMT RECEPTION
`RESPONSE SIGNAL
`
`OVERWRITE DESTINATION
`ADDRESSEY ADDDRESS NEXT
`TO OWN ADDRESS IN RSAF
`
`627
`
`TRANSMT
`DATA FRAME
`
`END
`
`
`
`
`
`
`
`DELETE FRAME
`
`613 624
`
`RECEIVE FRAME
`
`SEARCH FRAME
`DATAFRAME
`
`REQ? / RSP?
`REO
`
`
`
`
`
`UNRECEIVED DENTIFICATION
`INFORMATION
`YES
`
`SEARCHADDRESS
`OWN ADDRESS
`NO
`
`6O1
`6O2
`
`603
`
`604
`
`605
`YES
`
`
`
`EFICATION
`DESTINATION
`ADDRESS (-C
`RSAS -RECEIVEDRSAS
`
`END
`610 C END D
`
`615
`NO
`
`619
`
`DIRECTED TO
`OWN ADDRESS
`
`TRANSMIT RSP FRAME
`
`611
`
`END
`
`6061, REGISTER DENTIFICATION
`INFORMATION
`
`
`
`616
`
`OVERWRITE DESTINATION
`ADDRESS BY ADDRESS
`IMMEDIATELY PREVIOUS TO
`OWN ADDRESS IN RSAF
`
`SEARCH FRAME
`
`RESET TIMER
`
`END
`
`607 rRESEROWN ADDRESSAT
`END OF RSAF
`
`617
`
`TRANSMT
`SEARCH FRAME
`
`62O
`
`608
`
`BROADCAST
`SEARCH FRAME
`
`END
`C END D
`
`Page 7 of 26
`
`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 7 of 14
`
`5,907,540
`
`
`
`
`
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`Page 8 of 26
`
`

`

`US. Patent
`
`May 25, 1999
`
`Sheet 8 0f 14
`
`5,907,540
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`Page 9 of 26
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`Page 9 of 26
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`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 9 of 14
`
`5,907,540
`
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`Page 10 of 26
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`

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`U.S. Patent
`
`May 25, 1999
`
`Sheet 10 of 14
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`5,907,540
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`Page 11 of 26
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`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 11 of 14
`
`5,907,540
`
`F.G. 12
`
`
`
`802 - IDENTIFICATION FLAG-CONF
`REMITTENT ADDRESS (-Y
`DESTINATION ADDRESS - 3 (BROADCAST)
`DENTIFICATION INFORMATION<-N
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`Page 12 of 26
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`

`

`US. Patent
`
`May 25, 1999
`
`Sheet 12 0f 14
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`5,907,540
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`Page 13 of 26
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`

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`U.S. Patent
`
`May 25, 1999
`
`Sheet 13 of 14
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`5,907,540
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`Page 14 of 26
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`

`

`U.S. Patent
`
`May 25, 1999
`
`Sheet 14 of 14
`
`5,907,540
`
`F.G. 15
`
`DESTINATION ADDRESS - 3 (BROADCAST)
`1002 -- IDENTIFICATION FLAG-RD
`REMITTENT ADDRESS (-Y
`IDENTIFICATION INFORMATION<-N
`FINAL TARGET ADDRESS (-X
`
`1 OO3
`
`BROADCAST RELAY SPECIFIED FRAME
`
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`RECEIVE RELAY SPECIFIED FRAME
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`Page 15 of 26
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`

`

`5,907,540
`
`1O
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`15
`
`1
`RADIO DATA COMMUNICATION
`APPARATUS HAVING ARELAY FUNCTION
`AND RADIO DATA COMMUNICATION
`METHOD AND SYSTEM USING THE SAME
`BACKGROUND OF THE INVENTION
`The present invention relates to a radio data communica
`tion apparatus, and a radio data communication method and
`System using the Same, and more particularly, to radio data
`communication techniques which enable two radio data
`communication apparatuses, located at a distance too long to
`enable direct communication between them, to communi
`cate with each other through at least one radio data com
`munication apparatus which performs a relay function and
`exists between the two radio data communication appara
`tuSeS.
`Conventionally, as disclosed in JP-A-3-250820 entitled
`“Local Area Network and Communication Network’, radio
`communication ranges have been extended by additionally
`installed wired LAN (Local Area Network) for connecting
`base stations each other. However, the installation of wired
`LAN implies a problem that it needs additional expense and
`the System design requires extra labor and time. Generally,
`the installation of wired LAN requires a System design,
`construction, connectivity tests, and So on. In addition, once
`the network System is configured, it cannot be flexibly
`changed. Further, the cabling may often Spoil good appear
`ances. Thus, the construction of a wired LAN is not Some
`times desirable in hired stores, offices with walls made of
`expensive materials (marble or the like), windows for Serv
`ing customers, which must maintain good appearances, Sales
`floors, and So on.
`An example of the prior art for direct communications
`between radio terminals without intervention of a base
`station has been proposed in Mar. 7, 1994 issue of a
`magazine called "Nikkei Communications'. In the Scheme
`proposed in this example, however, communications avail
`able to each radio terminal is limited to a range in which
`radio waves Sent from a transmitter directly reach a desti
`nation Stations.
`If radio waves from a transmitter do not directly reach a
`destination Stations, a relay Station is generally utilized for
`communications therebetween. The relay Station may be
`Searched through the following two techniques.
`A first technique is ARP (Address Resolution Protocol)
`which is used for address resolution for a protocol called
`TCP/IP. This technique, however, is intended to search for a
`physical address of a destination Station but not for an
`address Sequence of relay Stations. Neither one performs
`chain extension of broadcast in consideration of a radio
`wave range (Zone) which is particular in the radio data
`communication network. For reference, ARP is described in
`RFC826 “An Ethernet Address Resolution Protocol” pub
`lished from Internet Society.
`A second technique is source routing in IEEE802.5 in
`which, however, a relaying System is limited to a particular
`bridge. Further, every Station does not perform a chain
`extension of broadcasts in consideration of a radio wave
`reachable range (Zone) which is particular in the radio data
`communication network. In the Source routing, an alterna
`tive route must be previously prepared for a failure of the
`bridge. Otherwise, a bypass route cannot be ensured for the
`communications in case a failure occurs.
`In the prior art as described above, an extension of radio
`communication area requires the installation of wired LAN
`65
`which is Sometimes Severely restricted in terms of location,
`time and cost.
`
`2
`Also, as the route of communication is fixed, the prior art
`for the communication System has other problems that its
`resistance to failures for the cable and extra communication
`devices is lower and controlling distribution of traffic loads
`is difficult.
`
`SUMMARY OF THE INVENTION
`It is an object of the present invention to provide radio
`data communication techniques which are capable of con
`Veniently extending a radio communicable area in a short
`working time without relying on a restricted wired LAN as
`a relay Station.
`It is another object of the present invention to provide
`radio data communication techniques which achieve a high
`resistance to failure and easy distribution of loads.
`In the present invention, each radio data communication
`apparatus is provided with a relay function. Thus, when two
`radio data communication apparatuses, located too far that
`radio waves do not directly reach from one to the other, are
`to communicate with each other, the radio data communi
`cations are relayed with intervention of one or more other
`radio data communication apparatuses, to which each of the
`two radio data communication apparatuses can access
`directly or indirectly with other relay Stations. In this way, a
`communicable range is extended.
`Also, if a radio data communication apparatus
`(hereinafter called the “communication apparatus) func
`tioning as a relay is Searched without Success, a wide area
`radio communication network, for example, a public radio
`communication network Such as the digital cellular, PHS
`(Personal Handy Phone System, Japanese specific digital
`relation System), or the like, is used as an alternative
`communication route for accomplishing the communica
`tions with a destination communication apparatus. In this
`case, however, a device and Software for connecting the
`wide area radio communication network with the radio LAN
`is additionally required.
`Thus, the above-mentioned objects are achieved by merg
`ing radio wave ranges (this range is called the "Zone') of
`other communication apparatuses.
`In a first embodiment, when a Sending end communica
`tion apparatus is to communicate with a destination com
`munication apparatus, the Sending end communication appa
`ratus first makes an attempt to see whether a direct
`communication is possible. A data frame used in this com
`munication may be one according to the present invention,
`later described, or another one. In either case, a data frame
`for direct communications should be distinguishable from a
`data frame for communications using relay communication
`apparatuses in order to reduce traffic.
`Afterward, when the Sending end communication appa
`ratus knows, for example, by detecting a State in which no
`response has been returned thereto even after a predeter
`mined time period, that the direct communication is
`impossible, the Sending end communication apparatus
`Searches for relay communication apparatuses through
`which a user data frame should pass before it reaches the
`destination communication apparatus, Stores into the user
`data frame information on the addresses of the Searched
`relay communication apparatuses and the order in which the
`user data frame passes through the relay communication
`apparatuses, and transmits this user data frame. Each relay
`communication apparatus transmits the user data frame to
`the destination apparatuses in accordance with the addresses
`of the relay communication apparatuses and the Specified
`passing order thereof, recorded in the user data frame.
`
`Page 16 of 26
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`

`

`3
`As a method of Searching for a Station for relaying a
`frame, the Sending end communication apparatus broadcasts
`a Search frame to other communication apparatuses within
`its Zone. Each communication apparatus, when receiving the
`Search frame, examines whether the communication appa
`ratus itself is being Searched. If So, the communication
`apparatus returns information on the relay communication
`apparatus to the Sending end. If not, the communication
`apparatus records its address in the Search frame next to the
`last recorded relay apparatus address, and broadcasts the
`Search frame only once within its Zone. Each communica
`tion apparatus repeats this processing in a chain manner to
`Search for relay communication apparatuses over the entire
`communicable range of the radio data communication SyS
`tem. The broadcasting of the Search frame from each com
`15
`munication apparatus is desirably limited to only once in
`order to prevent the Search frame from infinitely circulating
`from one communication apparatus to another to increase
`traffic. Further, for broadcasting the Search frame, Some
`techniques are necessary So as to enable all communication
`apparatuses within the Zone to receive the Search frame in
`one broadcasting operation. For example, the Search frame
`may be broadcast while any other communication apparatus
`is not communicating in each Zone.
`The above method is used when a necessary communi
`cation cannot be directly achieved from a Sending end to a
`destination. Alternatively, as a Second embodiment, topol
`ogy information (information on the configuration of relay
`communication apparatuses which are passed through by a
`data frame before it reaches a destination communication
`apparatus) within a communicable range, required for the
`relay communications, may be previously exchanged among
`asSociated communication apparatuses, Such that a transmit
`ted frame is sent by way of Specified relay communication
`apparatuses, based on the topology information, to the
`destination. Also, for this method, the Sequentially chained
`broadcasting may be used to distribute the topology infor
`mation to associated communication apparatuses within the
`Zone periodically or when a change in the configuration is
`detected.
`In this way, Since route information indicating relay
`communication apparatuses to a destination can be acquired
`without intervention of dedicated relay apparatuses, base
`Station, or the like, the communicable range can be eco
`nomically and conveniently extended.
`Further, as a third embodiment in addition to the above
`two methods, it is also possible to transmit data without
`previously examining the possibility of data arrival to the
`destination or the addresses of relaying communication
`apparatuses. This is a method which Simultaneously
`executes data transmission and route Search. More
`Specifically, a Sending end communication apparatus broad
`casts a user data frame to respective communication appa
`ratuses located in its Zone. Each of the communication
`apparatuses which have received the user data frame broad
`casts the received frame only once within its own Zone when
`the communication apparatus itself is not the destination of
`the frame. By repeating this in-Zone broadcasting in a chain
`manner, the user data frame from the Sending end commu
`nication apparatus can be distributed to all communication
`apparatuses over the entire communicable range.
`When this third method is used, the user data frame must
`be provided with information on a destination communica
`tion apparatus (address) in addition to a broadcast address.
`Each communication apparatus receiving the frame
`determines, from the information on a destination commu
`nication apparatus, whether the frame is destined to the
`
`65
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`5,907,540
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`4
`communication apparatus itself. If So, the communication
`apparatus receives the user data contained in the frame as a
`destination apparatus. Otherwise, the communication appa
`ratus broadcasts the user data frame in order to forward it to
`the destination communication apparatus.
`In this way, Since data can be forwarded to the destination
`communication apparatus by broadcasting a user data frame
`once per Zone, the communicable range can be extended in
`a reduced communication time as compared with the above
`mentioned two prior art methods.
`Thus, according to the present invention, Since the com
`municable range can be extended without additionally
`installing wired LAN, the system is free from spoiled
`appearance and additional cost due to the construction of
`wired LAN, and a variety of restrictions imposed to the
`wired LAN. Also, the communicable range can be freely
`modified in a short time period by moving the locations of
`relay communication apparatuses.
`Also, by radio communication with a destination com
`munication apparatus through a wide area radio communi
`cation network, the communicable range can be extended
`without wired connection to each communication apparatus,
`although the public network fee is charged, as compared
`with the conventional radio LAN system which is only
`limited to communications within an area in which radio
`waves are directly received.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a diagram conceptually illustrating an exemplary
`configuration of a radio data communication System accord
`ing to an embodiment of the present invention;
`FIG. 2 is a diagram conceptually illustrating an exemplary
`configuration when Two radio data Systems communicate
`each other through a wide area radio data communication
`network in the radio data communication System according
`to the embodiment of the present invention;
`FIG. 3 is a block diagram illustrating an exemplary
`configuration of a radio data communication apparatus
`according to an embodiment of the present invention;
`FIG. 4 is a block diagram illustrating an exemplary
`configuration of a radio data communication apparatus
`according to another embodiment of the present invention;
`FIG. 5 is a flow chart representing a communication
`operation procedure for a Sending end communication appa
`ratus according to the present invention;
`FIG. 6 is a flow chart representing a communication
`operation procedure for a receiving communication appara
`tus according to the present invention;
`FIGS. 7-10 are diagrams conceptually illustrating the
`Structures of data frames and Search frames, respectively, for
`use in the radio data communications according to the
`present invention;
`FIGS. 11 and 13 are diagrams conceptually illustrating
`frame Structures for use in another embodiment of the
`present invention; and
`FIG. 12 is a flow chart representing a communication
`procedure executed utilizing the frame illustrated in FIG. 11;
`FIG. 14 is a diagram conceptually illustrating a frame
`Structure for use in a communication System according to a
`further embodiment of the present invention; and
`FIG. 15 is a flow chart representing a communication
`procedure executed utilizing the frame illustrated in FIG. 14.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`Embodiments of the present invention will hereinafter be
`described in detail with reference to the accompanying
`drawings.
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`FIG. 1 conceptually illustrates examples of possible com
`munication routes among a plurality of radio data commu
`nication apparatuses composing a radio data communication
`System according to an embodiment of the present invention
`for explaining the concept of the System. Denoted by A-E
`are radio data communication apparatuses in this embodi
`ment. It should be particularly noted that these communi
`cation apparatuses are each provided not only with a
`transmission/reception function but also with a relay
`function, and may serve as a fixed Station or as a mobile
`Station as the case may be.
`Referring to FIG. 1, a range in which radio waves from
`each radio data communication apparatus can reach without
`degradation is called a Zone, and Zones for the respective
`communication apparatuses A-E are designated Zone
`A-Zone E, respectively. Here, a procedure of radio data
`communications will be described, when performed from
`the communication apparatus A as a Sending end to the
`communication apparatus E as a destination, on the assump
`tion that the respective radio data communication appara
`tuses are in an available State for communication. It should
`be noted however that the description to be made below will
`be limited to an outline of the procedure, assuming that the
`communication A is already aware of information on routes
`to the communication apparatus E. Details of a route infor
`mation acquiring method and a data communication method
`will be described later.
`First, the communication apparatuS A transmits a frame to
`the communication apparatus C located in the Zone A. The
`communication apparatus C, when knowing from informa
`tion in the frame that the frame is addressed to the commu
`nication apparatus E, transmits the frame to the communi
`cation apparatus D which serves as a next relay Station
`required for the frame to reach the communication apparatus
`E. The communication apparatus D, when knowing in a
`Similar manner that the received frame is addressed to the
`communication apparatus E, directly transmits the frame to
`the communication apparatus E. In this way, any commu
`nication apparatus can communicate with a station located in
`a wider area beyond its own Zone. The Zone is not always
`limited to a circular shape and may take a rather complicated
`shape in an electroStatically shielded place Such as a room in
`a building. In this case, the radio data communication
`method according to the present invention enables commu
`nications between rooms by installing a Station or commu
`45
`nication apparatus near the entrance of each room.
`In the prior art, the radio data communication System as
`described above is generally designed to be effective only
`within a local radio communication network of a specific
`building or the like, So that communications cannot be made
`with a Station located outside of the local radio communi
`cation network.
`FIG. 2 illustrates as an example how a communication
`apparatus outside of a local radio communication network
`NL communicates with a destination communication appa
`ratus through a wide area radio communication network. If
`a communication apparatus F were located within the local
`radio communication network, it would function as a radio
`LAN terminal in the network NL to perform the radio data
`communications according to the present invention.
`However, Since the communication apparatus F is located
`outside of the local radio communication network NL, radio
`waves transmitted therefrom will not reach the radio com
`munication network in the area. In this event, the commu
`nication apparatus F connects to the local radio communi
`cation network NL (Radio LAN) through a public radio
`communication network NP for communications with a
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`destination communication apparatus. A communication
`method used in the local radio communication network NL
`has been described above. The Switching from a search for
`a destination communication apparatus within the local
`radio communication network NL to a communication
`through the public radio communication network NP may be
`automatically carried out when the destination communica
`tion apparatus cannot be found or when no response is
`returned from any communication apparatus located within
`the local radio communication network NL. There is of
`course a case where the local radio communication network
`NL need not be accessed, always by way of the public radio
`communication network NP, in order to avoid charges on the
`public radio communication network. Therefore, the com
`munication apparatus should be provided with a means to
`disable the automatic Switching by a mode Selection or the
`like.
`Next, a method of tracing a route to a destination com
`munication apparatus and a method of relaying and trans
`ferring data, according to the present invention, will be
`described, by way of examples, in connection with the
`following three embodiments.
`The first one is a Sending end Specifying relay, where the
`addresses of a relay communication apparatuses are
`Searched as required by a method called a "relay Station
`Search method’, and the address of the relay communication
`apparatuses obtained as a result of the Search is used to relay
`data.
`The Second one is a Sending end Specifying relay, where
`route information for each destination communication appa
`ratus (the addresses of a passed-through relay communica
`tion apparatuses) is previously distributed to all communi
`cation apparatuses located within a communicable range
`(this is called a “network topology (NT) search method), and
`data is transmitted based on the route information.
`The third one is a relay-specified method which searches
`for a destination communication apparatus together with
`transmitted data without previously examining information
`on a route to the destination communication apparatus.
`FIG. 3 is a block diagram illustrating an exemplary
`configuration of a radio data communication apparatus for
`use in the radio data communication System according to
`this embodiment. The illustrated radio data communication
`apparatus constitutes each of the plurality of communication
`apparatuses A-E. AS an example, the apparatus is composed
`of a transmitter 1103 for transmitting frames; a receiver 1102
`for receiving frames, an antenna 1101 for transmitting
`frames therethrough as radio waves; a processor 1104 for
`performing a Sequence of processing mentioned above on
`frames to be transmitted or on received frames, and a
`memory 1105 for storing frames, route information, frame
`identification information, processing programs, and So on.
`The processor 1104 may be implemented by a central
`processing unit Such as that used in an ordinary information
`processing System which may execute necessary control
`procedures in the form of programs, or a specifically pro
`grammed logic device or the like.
`FIG. 4 is a block diagram illustrating an exemplary
`configuration of a radio data communication apparatus
`according to another embodiment.
`In FIG. 4, the configuration illustrated in FIG. 3 is added
`to a general-purpose information processing unit 300 as a
`radio communication adaptor 2000 so as to function as the
`radio data communication apparatus. More specifically, the
`radio communication adaptor 2000 is composed of a trans
`mitter 2103 for transmitting frames; a receiver 2102 for
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`receiving frames, an antenna 2101 for transmitting there
`through frames as radio waves, a processor 2104 for per
`forming a Sequence of processing mentioned above on
`frames to be transmitted or received frames, and a memory
`2105 for storing frames, route information, frame identifi
`cation information, processing programs, and So on.
`The processor 2104 may be implemented by a general
`purpose microprocessor or the like, or by a dedicated logic
`LSI or the like having specific functions programmed
`therein.
`The information processing unit 300 has its components
`connected to a system bus 307. Specifically, connected to the
`system bus 307 are a central processing unit 301 comprising
`a general-purpose microprocessor or the like, a main Storage
`unit 302 comprising Semiconductor memories or the like for
`Storing operating programs and data for the central proceSS
`ing unit 301; a Secondary Storage unit 303 comprising a hard
`disk drive or the like; a keyboard 304 for the operator to
`input data, commands, and So on; a display unit 305 for
`displaying information; a printer 306 for printing informa
`tion; and so on. The system bus 307 is also connected to the
`radio communication adaptor 2000.
`Thus, a plurality of information processing units 300 as
`described above are provided to function as the communi
`cation apparatuses in the radio data communication network
`according to this embodiment, thereby constituting an infor
`mation network which has the plurality of information
`processing units 300 mutually connected through the radio
`data communication network and can extend its radio com
`munication area.
`Next, the processing for Searching for the address of a
`relay communication apparatus will be described with ref
`erence to FIGS. 5 and 6. This processing is performed by use
`of the relay Station Search method prior to data transmission.
`The processing is executed by the processors 1104, 2104
`(FIGS. 3, 4) in the respective communication apparatuses.
`The operations of these processors are represented by FIGS.
`5 and 6, respectively. In the following description, the
`address of a Sending end communication apparatus and a
`destination communication apparatus are designated “Y”
`and “X”, respectively.
`Referring first to FIG. 5, the sending end communication
`apparatus first attempts direct radio communications within
`its Zone on the assumption that a destination communication
`apparatus, to which the data is transmitted, is located within
`its Zone. In the trial communications, a data frame 9 as
`shown in FIG. 7 is used. In the data frame 9, “Y” is
`registered as a S