CA1281111C - Wireless network for wideband indoor communications - Google Patents
Wireless network for wideband indoor communicationsInfo
- Publication number
- CA1281111C CA1281111C CA000559613A CA559613A CA1281111C CA 1281111 C CA1281111 C CA 1281111C CA 000559613 A CA000559613 A CA 000559613A CA 559613 A CA559613 A CA 559613A CA 1281111 C CA1281111 C CA 1281111C
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- CA
- Canada
- Prior art keywords
- information
- packet
- transmitter
- central node
- transmitters
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/04—Scheduled or contention-free access
- H04W74/06—Scheduled or contention-free access using polling
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
Abstract
WIRELESS NETWORK FOR WIDEBAND
INDOOR COMMUNICATIONS
Abstract The present invention relates to a wideband communication network using wireless radio transmissions either on a stand-alone basis or to supplement a hard-wired network. The exemplary network comprises (a) a plurality of transceivers associated with separate users of the network; (b) optionally at least one concentrator associated with certain separate subgroups of wireless and possibly hard-wired transceivers for providing duplex operation; and (c) a central node (i) capable of providing both duplex communications directly via a radio channel using radio links with certain subgroups of the transceivers and via a hard-wired connection with each optional concentrator, and (ii) for polling the needs of all transceivers and directing all packets of information from active transceivers through the central node and to the destined transceivers during each frame period. The network also preferably includes diversity and resource sharing techniques to provide added protection against channel impairments on an as-needed basis.
INDOOR COMMUNICATIONS
Abstract The present invention relates to a wideband communication network using wireless radio transmissions either on a stand-alone basis or to supplement a hard-wired network. The exemplary network comprises (a) a plurality of transceivers associated with separate users of the network; (b) optionally at least one concentrator associated with certain separate subgroups of wireless and possibly hard-wired transceivers for providing duplex operation; and (c) a central node (i) capable of providing both duplex communications directly via a radio channel using radio links with certain subgroups of the transceivers and via a hard-wired connection with each optional concentrator, and (ii) for polling the needs of all transceivers and directing all packets of information from active transceivers through the central node and to the destined transceivers during each frame period. The network also preferably includes diversity and resource sharing techniques to provide added protection against channel impairments on an as-needed basis.
Description
WIRELESS NETWORK FOR WIDEBAND
INDOOR COMMUNICATIONS
Technic~ ield The present invention relates to a wideband communication network S using radio either on a stand-alone basis or to supplement a hard-wired network where complete portability of off~lce design is de~ired.
Descri~Lon ~ ~h~ prio~ ~
Local Area Networks (LANs) have included many different architectures such as the bus, loop, ring, star, tree, etc. One such L.~N is disclosed in the 10 article "A New Local Area Network Architecture Using A Centralized Bus" by A. Acampora et al. in IE~E~ Comrr uniç~tions Magazirle, Vol. 22, No. 8, August - 1984, at pages 12-21. There, a centralized bus is used with all user devices being hard-wired to a central node as shown in FIGs; 1-3 of the article.
Indoor wireless communications networks have also been developed over 15 the years. In the article "Cordless Telephone System" by M. Komura et al., published in the l~an~ TelecommunicatiQn~ R~view, Vol. 15, No. 4, 1973, at pages 257-261, a cordless radio telephone system is disclosed which permits telephones to communicate via radio to a localized antenna which is directly connected to a ba~e station. Another technique for wireless indoor 20 communication is disclosed by F. C~feller in the I~M Tecllni~Ll l>isclosure 1~1~, Vol. 24, No. 8, January 1982, at pages 4043-4046 wherein an infrared microbroadcasting network for in-house data communication is disclosed.
There, a host controller is directly connected to a plurality of spaced-apart transponders for transmitting 2-way communications via infrared signals with 25 the various stations forming the in-house system.
More recently, an office information network was disclosed in lobecom '85, Vol. 1, December 2-5, 1985, New Orleans, Louisiana, at pages 15.2.1-15.2.6 wherein a slotted-ring access protocol and a dynamic bandwidth allocation scheme offering preferential service to high-priority traffic is provided. There, a 30 dual optical fiber ring, transmitting in opposite directions, propagates the communication signals to various nodes along the fibers. Connections between the network nodes and local facilities or servers are copper pairs or, where appropriate, wireless drops.
~.2~
Indoor radio communication is not without problems, however.
Buildings in qeneral, and office buildings in particular, present a harsh environment ~or high-speed radio transmission because o~
numerous reflections from stationary objects such as walls, furniture, and movable objects such as people. The link between a given pair of transmitters and receivers is thereby corrupted by severe multipath distortion arising from the random superimposi~ion of all reflected rays, and by shadow fading caused by the ahsence o~ line-of-sight paths. At low data rates, the effects of multipath can be characterized by Raleigh fading, while at higher rates the channel additionally exhibits dispersion over the communication band. Shadow fading is spectrally flat and characterized by a log-normal distribution.
It is to be understood that all ef~ects vary dynamically with time as the environment slowly changes. Raleigh fading produces a wide variation in the level of signals arriving at a particular receiver from different transmitters, thereby precluding the use of standard techniques for multiple access of the radio channel.
Dispersion within the channel produces serious intersymbol interferenca, thereby limiting the maximum data rate of the channel and causing a fraction of users to experience an unacceptably high bit error rate, and a link experiencing such condition is said to have suffered an outrage and is temporarily unavailable.
Therefore, the problem in the prior art is to provide a technique or network which will permit as high a data rate as possible while encountering changing conditions.
Summary of the Invention In accordance with one aspect of the invention there is provided a wideband packet communication network comprising: a plurality of transmitters (10-19), each transmitter being associated with a separate user or group of users of the network for transmitting packets of information between an active user or group of users and the network via either one of a hard-wired or wireless connection during a frame period; and a central node (30) for communicating with each o~ the pluralit~ o~ transmitters via the hard-wired or wireless connection, the central node comprising, processor means (35) for (a) determining packet transmission requirements associated with each transmitter communicatiny with the central node via a wireless connection during a first subperiod of each frame period, (b) causing each wireless transmitter determined to have a packet transmission requirement, to transmit its packets of information during a separate second subperiod of time of each frame period, (c) detecting during the ~irst and/or second subperiods o~ each frame period, transmission impairments associated with each wireless transmitter, and (d) causing packets of information transmitted from each transmitter determined to have a transmission impairment to be transmitted at a transmission rate sufficient to lessen the determined transmission impairment, and means (32-34) for (a) receiving pacXets of information from the plurality of transmitters of the network, and (b) retransmitting the packets to receivers associated with the destined users of the packets of information via an appropriate hard-wired or wireless connection.
It is also an aspect of the present invention to provide a wideband indoor communications network as described above where (1) diversity antennas can be used at the concentrators and central ~o node, and one or more antennas can be used at each transceiver, and (2) access to the radio channel used by all wireless transceivers is performed by a modified polling scheme which permits resource sharing to provide added protection against channel impairments on an as-needed basis.
In accordance with another aspect o~ the invention there is provided a method of transmitting information between a plurality of transmitters and a central node, including a processor means, via either one of a hard-wired or wireless connection during a frame period in a wideband packet communication network, each transmitter being associated with a separate user or group of users of the network, the method comprising the steps of: ~a) the processor means in the central node determining ths packet transmission requirements of each transmitter communicating with the central node during a first subperiod of time of each frame period; (b) causing a wireless transmitter determined in step (a) to have packet transmission requirements, to transmit its packets of in~ormation during a separate second subperiod of time of each . .
~2~
frame period; (c) the processor means detecting, during the ~irst and/or second subperiods of time of each frame period, kransmission impairments associated with each wireless transmitter; and (d) the processor means causing packets of information transmitted from each transmitter determined to have a transmission impairment in step (c~ to be transmitted at a transmission rate sufficient to lessen the determined transmission impairment.
Other and further aspects o~ the present invention will become apparent during the course of the following description and by reference to the accompanying drawings.
Brief Description of the_Drawings FIG. 1 is a block diagram of an exemplary arrangement of a wideband communication network in accordance with the present invention including various hard-wired and wireless user connections; and FIG. 2 is a diagram of a media access technique using polling that can be employed in the network of FIG. 1.
Detailed Description FIG. 1 illustrates an exemplary system topology which is Zo functionally that of a star Local Area Network (LAN) comprising a central node 30, remote concentrators 20 and 21, and a plurality of user devices 10-19. Each user device 10-19 is associated with a separate user o~ the network and can communicate with central node 30(1) via a hard-wired connection 26, as shown for the - ~ -indirect connections between user devices 1~13 and concentrators 20 and 21; or (2) via a wireless link as shown for (a) the channel comprising links 27 between a subgroup of user devices 18-19 and central node 30, or (b) the indirect channel comprising links 28 between a subgroup of users 14-15 and a subgroup of users 5 16-17 and concentrators 20 and 21, respectively. It is to be understood that user devices 1~1~ can each be coupled to a separate user terminal (not sllowll) such as, for example, a data device, printer, personal computer, host computer, telephone, etc.
Each of remote concentrators 20 and 21 is positioned between the 10 associated subgroup of user terminals 10-17 and central node 30 and is shown as including (a) user interface modules (UIM) 22 and 23 which are each coupled to a separate portion of the associated subgroup of user devices 10-17, (b) a clockmodule 24, and (c) a trunk module 25. It is to be understood that each of exemplary concentrators 20 and 21 includes only two UIMs, for purposes of 15 simplicity and that additional UIMs could be disposed in parallel with UIMs 2~-23 shown, and connected to other portions of the associated user devices (notshown) via either separate hard~wired or wireless connections.
Each UIM 22 or 23 functions to translate the protocol of the signal received from the associated user devices to a standard protocol of the network 20 as used by central node 30. The translated signal is then transmitted, at theappropriate time, to trunk module 25 on a time division multiplex (TDM) basis via a concentrator bus 29a for transmission to central node 30, and vice versa for the other direction of two-way communications using concentrator bus 29b.
Where a user device already transmits and receives signals using the standard 25 network protocol, an associated UIM need only transmit the received signal atthe appropriate time based on the received clock signals from clock module 24.
The trunk module 25 in each of remote concentrators 20 and 21 functions to transmit each of the signals associated with that concentrator between each of the UIMs 22 and 23 and central node 30 at the appropriate times. The clock 30 modules 24 provide the timing signals for each of the UIMs 22 and 23, and trunk module 2S to achieve coordinated operation within the associated remote concentrator 20 or 21. Central node 30 is shown as including a clock module 3:L
for providing the clock signals used in central node 30; network interface units(NIU) 32-34 which are each coupled either to a separate one of remote concentrators 20 or 21 or to a separate subgroup of one or more user devices; a call processor 35; and buses 3~ and 37.
To describe the operation of the present network, the network components associated only with hard-wired user devices, e.g., user devices 1~
S 13, UIMs 22 and NIUs 32 and 3~ will first be considered. Each hard-wired user device 10-13 is shown connected to the network via terminal interface wires 26 and a UIM 22. Continuous (voice) or bursty ~data) traf~lc arriving at UIM 2Z in concentrator 20 from user devices 10-11, or at UIM 22 in concentrator 21 flom user devices 12-13, are formed into fixed length packets for time-multiplexed 10 high speed transmission to central node 30 via trunk module 25. Each such packet is provided therein with a logical channel number which allows central node 30 to re-route the packet to the appropriate concentrator 20 or 21 where the indicated destination user's device is connected. Central node 30 includes acontention bus 36, 37 operating at the speed of each high speed link, to 15 accomplish this re-routing. All traffic, including that traffic arising at a particular concentrator 20 or 21 and destined for that same concentrator1 is routed through central node 30.
The receiving concentrator demultiplexes all arriving packets from central node 30 for distribution via bus 29b to the appropriate UIM and 20 transmission to the destined user device. Logical channel numbers are preferably assigned for the entire network at the beginning of a predetermined time period of communications by call processor 35 in central node 30.
Additional device configurations and operational details are described in the article "A New Local Area Network Architecture Using A Centralized Bus"~ by 25 Acampora et al. in EE~ ComTnunications agazine, Vol. 22, No. 8, August 1984, at pages 12-21.
Radio links may be introduced, as shown in FIG. 1, via either a wireless link between a UIM 23 in either one of concentrators 20 or 21 as shown for link 28, or a wireless link directly to a NIU 33 in central node 30 as shown for link30 27. For link 27, the high-speed links from trunk modules 25 in concentrators 20 and 21 to central node 30 have been augmented by the inclusion of an NIU 33 in central node 30 which becomes a radio base station providing a high-speed channel to collect traffic from a subgroup of radio user devices 18-19 located throughout the building. It is to be understood that the term channel .
. . '.
128~
hereinafter implies full duplex operation, with separate bands used to transmit to and receive from NIU 33. This radio channel operates at a rate less than Gr equal to that of the central node's contention buses 36 and 37 and each of the high-speed links between trunk modules 25 and NIUs 32 and 34. With an 5 appropriate access protocol, the radio channel may be shared among all radio users 1~-1Q and appear, to central node 30, as a virtual concentrator. Fixed length packets arriving over links 27 contend for the nodal bus 3B along with packets arriving via high-speed buses at NIUs 32 and 3~1 from trunk modules 25.
The packets arriving from the wired links 26 may be rerouted by central node 10 30 to a radio link 27, and vice-versa, according to a destination address included in each packet.
A wireless link 28 establishes a communication path from each user of a subgroup of users, 14-15 or 16-17, to an associated UIM 23 in one of remote concentrators 20 or 21. Although multiple paths are established within a 15 subgroup of users associated with a UIM 23 or NIU 33, these links time-share a single radio channel. More particularly, at any moment, only one radio user of asubgroup of users may access the radio channel. It should be noted that there is no need to provide an aggregate data rate over all radio linlcs 27 or 28 in excess of the transmission speed of central node 30 since all packets must be 20 routed through central node 30. Therefore, it is pointless to reuse the radiochannel among user subgroups, as this increased capacity could not be ~lsed.
Thus, by sharing a single channel, operating at the speed of central node 30, among all radio users, each user can potentially access the full system bandwidth, and interference among clusters caused by simultaneous use of the 25 channel by users in different clusters is avoided. ~rom the perspective of central node 30, a radio link 28 established from each concentrator 2û or 21 to each of its subgroups of radio users appears as another wired port (UIM ~2) on the concentrator.
Regarding the radio or wireless links only, each of the UIMs 23 or NIU 33 30 are preferably equipped with multiple antennas for diversity to protect against multipath fading, and each user device 14-lQ is preferably equipped with only a single antenna, although multiple antennas could be used. The combination of limited diversity at the concentrators 20 and 21, and central node 30, along with resource sharing can be used to provide arbitrarily high availability. No direct ~;~81~
communication is permitted among users, since all users may communicate only with concentrators 20 or 21 or central node 30. It should be understood that common media access techniques, such as Carrier Sense Multiple Access (CSM~), are inappropriate in the radio environment because free space path 5 loss and multipath fading result in too large a variation of signal strength to insure that all channel usage can be detected. To keep the wireless user devices14-1~ inexpensive, sophisticated timing requirements should be avoided.
Finally, because of problems with delay spread, it is clesired that the thro~ghput of the system not be signircantly reduced by a media access technique, and 10 separate receive and transmit channels must be provided to allow full duplex operation .
For the present network shown in FIG. 1~ an exemplary modirled polling technique is used, with central node 30 controlling the transmit token. Polling is performed by call processor 35 in central node 30; with the radio UIMs 23, located at concentrators 20 and 21, and NIU 33, located at central node 30, being slaved to processor 35 such that, at any point in time, only one UIM 23 orNIU 33 is allowed to transmit the token to its community of UDs. It should be understood that all of radio IlDs 14-19 time share a single radio channel without frequency reuse.
The present exemplary polling technique for use with the radio channel associated with the wireless UDs 14-19 is shown in FIG. 2. There, time is divided into a sequence of fixed length intervals called frames, as shown at thetop of FIG. 2. At the start of each frame a polling interval 40 appears, followed by multiple intervals for transmission of continuous (voice) trafflc packets 41,25 and bursty (data) traffic packets 42. The length of the continuous trafflc intervals 41 depends on the amount of continuous trafrlc. This continuous traffic is transmitted periodically, at least once per frame period, with the tirne interval between continuous traffic intervals used for bursty traffic.
Transmission of one rlxed length packet per continuous trafrlc interval 30 constitutes some standard grade service, e.g., 64 kbps. Continuous trafrlc UDs may request multiples of this basic rate by accessing multiple time slots per continuous traffic interval. The polling sequence is shown at the bottom two lines of FIG. 2 for transmissions from and to central node 30.
The following steps forming the exemplary overall transmission sequence for the radio channel are:
1. Via the UIMs 23 located at concentrators 20 and 21, and NIU 33, call processor 35 at central node 30 sequentially polls each UD associated with the 5 radio channel using sub-packets P1-PN.
2. When polled, UDs 1~ ) seque~tially respond, after being polled, using the associated one of packets R1-RN as to whether the UD has continuous or ~ursty traffic, and, if bursty traffic, the number of blocks of data.
INDOOR COMMUNICATIONS
Technic~ ield The present invention relates to a wideband communication network S using radio either on a stand-alone basis or to supplement a hard-wired network where complete portability of off~lce design is de~ired.
Descri~Lon ~ ~h~ prio~ ~
Local Area Networks (LANs) have included many different architectures such as the bus, loop, ring, star, tree, etc. One such L.~N is disclosed in the 10 article "A New Local Area Network Architecture Using A Centralized Bus" by A. Acampora et al. in IE~E~ Comrr uniç~tions Magazirle, Vol. 22, No. 8, August - 1984, at pages 12-21. There, a centralized bus is used with all user devices being hard-wired to a central node as shown in FIGs; 1-3 of the article.
Indoor wireless communications networks have also been developed over 15 the years. In the article "Cordless Telephone System" by M. Komura et al., published in the l~an~ TelecommunicatiQn~ R~view, Vol. 15, No. 4, 1973, at pages 257-261, a cordless radio telephone system is disclosed which permits telephones to communicate via radio to a localized antenna which is directly connected to a ba~e station. Another technique for wireless indoor 20 communication is disclosed by F. C~feller in the I~M Tecllni~Ll l>isclosure 1~1~, Vol. 24, No. 8, January 1982, at pages 4043-4046 wherein an infrared microbroadcasting network for in-house data communication is disclosed.
There, a host controller is directly connected to a plurality of spaced-apart transponders for transmitting 2-way communications via infrared signals with 25 the various stations forming the in-house system.
More recently, an office information network was disclosed in lobecom '85, Vol. 1, December 2-5, 1985, New Orleans, Louisiana, at pages 15.2.1-15.2.6 wherein a slotted-ring access protocol and a dynamic bandwidth allocation scheme offering preferential service to high-priority traffic is provided. There, a 30 dual optical fiber ring, transmitting in opposite directions, propagates the communication signals to various nodes along the fibers. Connections between the network nodes and local facilities or servers are copper pairs or, where appropriate, wireless drops.
~.2~
Indoor radio communication is not without problems, however.
Buildings in qeneral, and office buildings in particular, present a harsh environment ~or high-speed radio transmission because o~
numerous reflections from stationary objects such as walls, furniture, and movable objects such as people. The link between a given pair of transmitters and receivers is thereby corrupted by severe multipath distortion arising from the random superimposi~ion of all reflected rays, and by shadow fading caused by the ahsence o~ line-of-sight paths. At low data rates, the effects of multipath can be characterized by Raleigh fading, while at higher rates the channel additionally exhibits dispersion over the communication band. Shadow fading is spectrally flat and characterized by a log-normal distribution.
It is to be understood that all ef~ects vary dynamically with time as the environment slowly changes. Raleigh fading produces a wide variation in the level of signals arriving at a particular receiver from different transmitters, thereby precluding the use of standard techniques for multiple access of the radio channel.
Dispersion within the channel produces serious intersymbol interferenca, thereby limiting the maximum data rate of the channel and causing a fraction of users to experience an unacceptably high bit error rate, and a link experiencing such condition is said to have suffered an outrage and is temporarily unavailable.
Therefore, the problem in the prior art is to provide a technique or network which will permit as high a data rate as possible while encountering changing conditions.
Summary of the Invention In accordance with one aspect of the invention there is provided a wideband packet communication network comprising: a plurality of transmitters (10-19), each transmitter being associated with a separate user or group of users of the network for transmitting packets of information between an active user or group of users and the network via either one of a hard-wired or wireless connection during a frame period; and a central node (30) for communicating with each o~ the pluralit~ o~ transmitters via the hard-wired or wireless connection, the central node comprising, processor means (35) for (a) determining packet transmission requirements associated with each transmitter communicatiny with the central node via a wireless connection during a first subperiod of each frame period, (b) causing each wireless transmitter determined to have a packet transmission requirement, to transmit its packets of information during a separate second subperiod of time of each frame period, (c) detecting during the ~irst and/or second subperiods o~ each frame period, transmission impairments associated with each wireless transmitter, and (d) causing packets of information transmitted from each transmitter determined to have a transmission impairment to be transmitted at a transmission rate sufficient to lessen the determined transmission impairment, and means (32-34) for (a) receiving pacXets of information from the plurality of transmitters of the network, and (b) retransmitting the packets to receivers associated with the destined users of the packets of information via an appropriate hard-wired or wireless connection.
It is also an aspect of the present invention to provide a wideband indoor communications network as described above where (1) diversity antennas can be used at the concentrators and central ~o node, and one or more antennas can be used at each transceiver, and (2) access to the radio channel used by all wireless transceivers is performed by a modified polling scheme which permits resource sharing to provide added protection against channel impairments on an as-needed basis.
In accordance with another aspect o~ the invention there is provided a method of transmitting information between a plurality of transmitters and a central node, including a processor means, via either one of a hard-wired or wireless connection during a frame period in a wideband packet communication network, each transmitter being associated with a separate user or group of users of the network, the method comprising the steps of: ~a) the processor means in the central node determining ths packet transmission requirements of each transmitter communicating with the central node during a first subperiod of time of each frame period; (b) causing a wireless transmitter determined in step (a) to have packet transmission requirements, to transmit its packets of in~ormation during a separate second subperiod of time of each . .
~2~
frame period; (c) the processor means detecting, during the ~irst and/or second subperiods of time of each frame period, kransmission impairments associated with each wireless transmitter; and (d) the processor means causing packets of information transmitted from each transmitter determined to have a transmission impairment in step (c~ to be transmitted at a transmission rate sufficient to lessen the determined transmission impairment.
Other and further aspects o~ the present invention will become apparent during the course of the following description and by reference to the accompanying drawings.
Brief Description of the_Drawings FIG. 1 is a block diagram of an exemplary arrangement of a wideband communication network in accordance with the present invention including various hard-wired and wireless user connections; and FIG. 2 is a diagram of a media access technique using polling that can be employed in the network of FIG. 1.
Detailed Description FIG. 1 illustrates an exemplary system topology which is Zo functionally that of a star Local Area Network (LAN) comprising a central node 30, remote concentrators 20 and 21, and a plurality of user devices 10-19. Each user device 10-19 is associated with a separate user o~ the network and can communicate with central node 30(1) via a hard-wired connection 26, as shown for the - ~ -indirect connections between user devices 1~13 and concentrators 20 and 21; or (2) via a wireless link as shown for (a) the channel comprising links 27 between a subgroup of user devices 18-19 and central node 30, or (b) the indirect channel comprising links 28 between a subgroup of users 14-15 and a subgroup of users 5 16-17 and concentrators 20 and 21, respectively. It is to be understood that user devices 1~1~ can each be coupled to a separate user terminal (not sllowll) such as, for example, a data device, printer, personal computer, host computer, telephone, etc.
Each of remote concentrators 20 and 21 is positioned between the 10 associated subgroup of user terminals 10-17 and central node 30 and is shown as including (a) user interface modules (UIM) 22 and 23 which are each coupled to a separate portion of the associated subgroup of user devices 10-17, (b) a clockmodule 24, and (c) a trunk module 25. It is to be understood that each of exemplary concentrators 20 and 21 includes only two UIMs, for purposes of 15 simplicity and that additional UIMs could be disposed in parallel with UIMs 2~-23 shown, and connected to other portions of the associated user devices (notshown) via either separate hard~wired or wireless connections.
Each UIM 22 or 23 functions to translate the protocol of the signal received from the associated user devices to a standard protocol of the network 20 as used by central node 30. The translated signal is then transmitted, at theappropriate time, to trunk module 25 on a time division multiplex (TDM) basis via a concentrator bus 29a for transmission to central node 30, and vice versa for the other direction of two-way communications using concentrator bus 29b.
Where a user device already transmits and receives signals using the standard 25 network protocol, an associated UIM need only transmit the received signal atthe appropriate time based on the received clock signals from clock module 24.
The trunk module 25 in each of remote concentrators 20 and 21 functions to transmit each of the signals associated with that concentrator between each of the UIMs 22 and 23 and central node 30 at the appropriate times. The clock 30 modules 24 provide the timing signals for each of the UIMs 22 and 23, and trunk module 2S to achieve coordinated operation within the associated remote concentrator 20 or 21. Central node 30 is shown as including a clock module 3:L
for providing the clock signals used in central node 30; network interface units(NIU) 32-34 which are each coupled either to a separate one of remote concentrators 20 or 21 or to a separate subgroup of one or more user devices; a call processor 35; and buses 3~ and 37.
To describe the operation of the present network, the network components associated only with hard-wired user devices, e.g., user devices 1~
S 13, UIMs 22 and NIUs 32 and 3~ will first be considered. Each hard-wired user device 10-13 is shown connected to the network via terminal interface wires 26 and a UIM 22. Continuous (voice) or bursty ~data) traf~lc arriving at UIM 2Z in concentrator 20 from user devices 10-11, or at UIM 22 in concentrator 21 flom user devices 12-13, are formed into fixed length packets for time-multiplexed 10 high speed transmission to central node 30 via trunk module 25. Each such packet is provided therein with a logical channel number which allows central node 30 to re-route the packet to the appropriate concentrator 20 or 21 where the indicated destination user's device is connected. Central node 30 includes acontention bus 36, 37 operating at the speed of each high speed link, to 15 accomplish this re-routing. All traffic, including that traffic arising at a particular concentrator 20 or 21 and destined for that same concentrator1 is routed through central node 30.
The receiving concentrator demultiplexes all arriving packets from central node 30 for distribution via bus 29b to the appropriate UIM and 20 transmission to the destined user device. Logical channel numbers are preferably assigned for the entire network at the beginning of a predetermined time period of communications by call processor 35 in central node 30.
Additional device configurations and operational details are described in the article "A New Local Area Network Architecture Using A Centralized Bus"~ by 25 Acampora et al. in EE~ ComTnunications agazine, Vol. 22, No. 8, August 1984, at pages 12-21.
Radio links may be introduced, as shown in FIG. 1, via either a wireless link between a UIM 23 in either one of concentrators 20 or 21 as shown for link 28, or a wireless link directly to a NIU 33 in central node 30 as shown for link30 27. For link 27, the high-speed links from trunk modules 25 in concentrators 20 and 21 to central node 30 have been augmented by the inclusion of an NIU 33 in central node 30 which becomes a radio base station providing a high-speed channel to collect traffic from a subgroup of radio user devices 18-19 located throughout the building. It is to be understood that the term channel .
. . '.
128~
hereinafter implies full duplex operation, with separate bands used to transmit to and receive from NIU 33. This radio channel operates at a rate less than Gr equal to that of the central node's contention buses 36 and 37 and each of the high-speed links between trunk modules 25 and NIUs 32 and 34. With an 5 appropriate access protocol, the radio channel may be shared among all radio users 1~-1Q and appear, to central node 30, as a virtual concentrator. Fixed length packets arriving over links 27 contend for the nodal bus 3B along with packets arriving via high-speed buses at NIUs 32 and 3~1 from trunk modules 25.
The packets arriving from the wired links 26 may be rerouted by central node 10 30 to a radio link 27, and vice-versa, according to a destination address included in each packet.
A wireless link 28 establishes a communication path from each user of a subgroup of users, 14-15 or 16-17, to an associated UIM 23 in one of remote concentrators 20 or 21. Although multiple paths are established within a 15 subgroup of users associated with a UIM 23 or NIU 33, these links time-share a single radio channel. More particularly, at any moment, only one radio user of asubgroup of users may access the radio channel. It should be noted that there is no need to provide an aggregate data rate over all radio linlcs 27 or 28 in excess of the transmission speed of central node 30 since all packets must be 20 routed through central node 30. Therefore, it is pointless to reuse the radiochannel among user subgroups, as this increased capacity could not be ~lsed.
Thus, by sharing a single channel, operating at the speed of central node 30, among all radio users, each user can potentially access the full system bandwidth, and interference among clusters caused by simultaneous use of the 25 channel by users in different clusters is avoided. ~rom the perspective of central node 30, a radio link 28 established from each concentrator 2û or 21 to each of its subgroups of radio users appears as another wired port (UIM ~2) on the concentrator.
Regarding the radio or wireless links only, each of the UIMs 23 or NIU 33 30 are preferably equipped with multiple antennas for diversity to protect against multipath fading, and each user device 14-lQ is preferably equipped with only a single antenna, although multiple antennas could be used. The combination of limited diversity at the concentrators 20 and 21, and central node 30, along with resource sharing can be used to provide arbitrarily high availability. No direct ~;~81~
communication is permitted among users, since all users may communicate only with concentrators 20 or 21 or central node 30. It should be understood that common media access techniques, such as Carrier Sense Multiple Access (CSM~), are inappropriate in the radio environment because free space path 5 loss and multipath fading result in too large a variation of signal strength to insure that all channel usage can be detected. To keep the wireless user devices14-1~ inexpensive, sophisticated timing requirements should be avoided.
Finally, because of problems with delay spread, it is clesired that the thro~ghput of the system not be signircantly reduced by a media access technique, and 10 separate receive and transmit channels must be provided to allow full duplex operation .
For the present network shown in FIG. 1~ an exemplary modirled polling technique is used, with central node 30 controlling the transmit token. Polling is performed by call processor 35 in central node 30; with the radio UIMs 23, located at concentrators 20 and 21, and NIU 33, located at central node 30, being slaved to processor 35 such that, at any point in time, only one UIM 23 orNIU 33 is allowed to transmit the token to its community of UDs. It should be understood that all of radio IlDs 14-19 time share a single radio channel without frequency reuse.
The present exemplary polling technique for use with the radio channel associated with the wireless UDs 14-19 is shown in FIG. 2. There, time is divided into a sequence of fixed length intervals called frames, as shown at thetop of FIG. 2. At the start of each frame a polling interval 40 appears, followed by multiple intervals for transmission of continuous (voice) trafflc packets 41,25 and bursty (data) traffic packets 42. The length of the continuous trafflc intervals 41 depends on the amount of continuous trafrlc. This continuous traffic is transmitted periodically, at least once per frame period, with the tirne interval between continuous traffic intervals used for bursty traffic.
Transmission of one rlxed length packet per continuous trafrlc interval 30 constitutes some standard grade service, e.g., 64 kbps. Continuous trafrlc UDs may request multiples of this basic rate by accessing multiple time slots per continuous traffic interval. The polling sequence is shown at the bottom two lines of FIG. 2 for transmissions from and to central node 30.
The following steps forming the exemplary overall transmission sequence for the radio channel are:
1. Via the UIMs 23 located at concentrators 20 and 21, and NIU 33, call processor 35 at central node 30 sequentially polls each UD associated with the 5 radio channel using sub-packets P1-PN.
2. When polled, UDs 1~ ) seque~tially respond, after being polled, using the associated one of packets R1-RN as to whether the UD has continuous or ~ursty traffic, and, if bursty traffic, the number of blocks of data.
3. Processor 35 then sequentially sends a signal, i.e., transmit token, TSl-TSJ,10 to each continuous trafi~lc user to send one fixed length packet, designated Vl to VJ, including a preset number of data symbols in each packet.
4. Processor 35 then sequentially sends a signal, designated TSK-TSL, i.e., a transmit token, to each bursty traffic user to send their first data block designated packets DK-~L, then the second data block, etc.
15 5. During steps 3 and 4, while the UDs are transmitting to concentrators 20 and 21 in blocks Vl_VJ and DK-DL, processor 35, through the UIMs 23 at the concentrators, is transmitting voice and data to the UDs 14-17 in associated blocks 44.
6. When it is time again for continuous traffic to be transmitted, then step 3 is 20 reiterated.
7. When it is time again for polling, i.e., the beginning of another frame, thenstep 1 is reiterated.
The above described polling technique meets necessary requirements since (a) the system handles continuous traffic, i.e., periodic data or voice, with 25 priority, (b) the system has the same maximum data rate for each user, i.e., a fair distribution of resources, which depends on the system loading, (c) there is no timing requirements at the remote UDs 14-19, (d) the throughput on the channel is not significantly reduced by this technique because the polling has alow duty cycle, mainly due to the short propagation delays between the 30 concentrators 20, 21 and the remote UI~s 14-19, and (e) the system has duplex operation.
What must also be considered is that in a multipath environment, paths of different lengths cause delay spread at a receiver. The delay spread, i.e., the dispersion or frequency selective fading in the cha~nel, produces intersymbol ~;28~
interference which limits the maximum data rate in a gi~en building and depends primarily on the rms delay spread and not the delay spread function. Thus, wit'nin the coverage area, there is some probability that the received signal 5 bit error ra-te (BER) Eor each UD is more than the required value, hereinafter called the outage probability. IE one UD 14-19 does not worlc in one location, the user can mo~e the UD or its antenna. ~lowever, ~he delay sprea~ may vary slowly with time as people and objects move within the 10 building. Therefore, it is desirable to keep the outage probability due to delay spread as low as possible so that the wireless system is almost as reliable as any wired portion of the system.
In addition to the technique described above, resource 15 sharing can be used to increase the maximum data rate and/or decrease the outage probability. With resource sharing, users normally transmit at some high rate Rl.
When channel conditions between concentrators 20 or 21, or central node 30, and a particulax UD no longer permits 20 operation at this high rate, the rate is lowered to some value such as R2 such that the BER objective is maintained. Such techniques are well known in the satellite system art as disclosed, for example, in the articles by A.S. Acampora in BSTJ, Vol. 58, ~o. 3, 25 November 1979, at pages 2097-2111; and IEEE Journal On Selected Areas In Communications, Vol. SAC-l/ Jan. 1983, at pages 133-142 where a pool of spare time slots are used, and each packet is transmitted with or without coding, to reduce the outage probability. Although it 30 takes longer to complete transmission at this lower rate, the number of users simultaneously slowed down is usually a small fraction of the total population/ and the overall throughput remains high. More particularly, during non-fade conditions, convolutional codes with a large ' r~
1~8~
-9a-channel signaling alphabet are employed to permit a high rate of in:Eormation transfer as described hereinbefore for the 7 step transmission sequence, and when the Eade depth exceeds the built in fade margin, the signaling alphabet is reduced and enough time slo-ts are borrowed from a resource sharing reserved time slot pool to mainta.in the data rate at the fade site. From the prior art, it is known that a small pool of spare time slots can protect a large community of users. In the present technique, the 10 use of coding during fade events is not considered because the channel is dispersive.
..
,~ .
~2~
Implementation of resource sharing with two transmission rates requires modification of the 7-step media access technlque described hereinbefore. With resource sharing, transmission would normally be at the higher rate Rl during non-transmission impairment periods. If errors are detected at the higher rate S via standard error detection techniques, a receiver in UDs 1'1-19, IJIMs 23, or NIU 33 can request call processor 35 to schedule a retransmission o~ the last block Or data at the lower rate R2. Call processor 35 would then cause the transmitter to retranslrlit the last block of information during a subsequent corresponding continuous 41 or bursty 42 traffic period at the lower data using,10 for example, a longer block Vj, Dj, or 44, or two or more equal length blocks. A
transmitter for accomplishing such technique of resource sharing is described, for example, in U. S. patent 4,309,764 issued to A. Acampora on January 5, 1982, and the previously cited article to A. Acampora in ~S~J, Vol. 58, No. 9, November 1979, at pages 2097-2111. Periodically the transmitter can retry 15 transmission at the higher rate. The frequency of retries depends on the dynamics of the delay spread in the channel. Requests for lower rate transmission and retries at the higher rate need only occur infrequently since the channel normally varies very slowly with time.
15 5. During steps 3 and 4, while the UDs are transmitting to concentrators 20 and 21 in blocks Vl_VJ and DK-DL, processor 35, through the UIMs 23 at the concentrators, is transmitting voice and data to the UDs 14-17 in associated blocks 44.
6. When it is time again for continuous traffic to be transmitted, then step 3 is 20 reiterated.
7. When it is time again for polling, i.e., the beginning of another frame, thenstep 1 is reiterated.
The above described polling technique meets necessary requirements since (a) the system handles continuous traffic, i.e., periodic data or voice, with 25 priority, (b) the system has the same maximum data rate for each user, i.e., a fair distribution of resources, which depends on the system loading, (c) there is no timing requirements at the remote UDs 14-19, (d) the throughput on the channel is not significantly reduced by this technique because the polling has alow duty cycle, mainly due to the short propagation delays between the 30 concentrators 20, 21 and the remote UI~s 14-19, and (e) the system has duplex operation.
What must also be considered is that in a multipath environment, paths of different lengths cause delay spread at a receiver. The delay spread, i.e., the dispersion or frequency selective fading in the cha~nel, produces intersymbol ~;28~
interference which limits the maximum data rate in a gi~en building and depends primarily on the rms delay spread and not the delay spread function. Thus, wit'nin the coverage area, there is some probability that the received signal 5 bit error ra-te (BER) Eor each UD is more than the required value, hereinafter called the outage probability. IE one UD 14-19 does not worlc in one location, the user can mo~e the UD or its antenna. ~lowever, ~he delay sprea~ may vary slowly with time as people and objects move within the 10 building. Therefore, it is desirable to keep the outage probability due to delay spread as low as possible so that the wireless system is almost as reliable as any wired portion of the system.
In addition to the technique described above, resource 15 sharing can be used to increase the maximum data rate and/or decrease the outage probability. With resource sharing, users normally transmit at some high rate Rl.
When channel conditions between concentrators 20 or 21, or central node 30, and a particulax UD no longer permits 20 operation at this high rate, the rate is lowered to some value such as R2 such that the BER objective is maintained. Such techniques are well known in the satellite system art as disclosed, for example, in the articles by A.S. Acampora in BSTJ, Vol. 58, ~o. 3, 25 November 1979, at pages 2097-2111; and IEEE Journal On Selected Areas In Communications, Vol. SAC-l/ Jan. 1983, at pages 133-142 where a pool of spare time slots are used, and each packet is transmitted with or without coding, to reduce the outage probability. Although it 30 takes longer to complete transmission at this lower rate, the number of users simultaneously slowed down is usually a small fraction of the total population/ and the overall throughput remains high. More particularly, during non-fade conditions, convolutional codes with a large ' r~
1~8~
-9a-channel signaling alphabet are employed to permit a high rate of in:Eormation transfer as described hereinbefore for the 7 step transmission sequence, and when the Eade depth exceeds the built in fade margin, the signaling alphabet is reduced and enough time slo-ts are borrowed from a resource sharing reserved time slot pool to mainta.in the data rate at the fade site. From the prior art, it is known that a small pool of spare time slots can protect a large community of users. In the present technique, the 10 use of coding during fade events is not considered because the channel is dispersive.
..
,~ .
~2~
Implementation of resource sharing with two transmission rates requires modification of the 7-step media access technlque described hereinbefore. With resource sharing, transmission would normally be at the higher rate Rl during non-transmission impairment periods. If errors are detected at the higher rate S via standard error detection techniques, a receiver in UDs 1'1-19, IJIMs 23, or NIU 33 can request call processor 35 to schedule a retransmission o~ the last block Or data at the lower rate R2. Call processor 35 would then cause the transmitter to retranslrlit the last block of information during a subsequent corresponding continuous 41 or bursty 42 traffic period at the lower data using,10 for example, a longer block Vj, Dj, or 44, or two or more equal length blocks. A
transmitter for accomplishing such technique of resource sharing is described, for example, in U. S. patent 4,309,764 issued to A. Acampora on January 5, 1982, and the previously cited article to A. Acampora in ~S~J, Vol. 58, No. 9, November 1979, at pages 2097-2111. Periodically the transmitter can retry 15 transmission at the higher rate. The frequency of retries depends on the dynamics of the delay spread in the channel. Requests for lower rate transmission and retries at the higher rate need only occur infrequently since the channel normally varies very slowly with time.
Claims (3)
1. A wideband packet communication network comprising:
a plurality of transmitters (10-19), each transmitter being associated with a separate user or group of users of the network for transmitting packets of information between an active user or group of users and the network via either one of a hard-wired or wireless connection during a frame period; and a central node (30) for communicating with each of the plurality of transmitters via the hard-wired or wireless connection, the central node comprising, processor means (35) for (a) determining packet transmission requirements associated with each transmitter communicating with the central node via a wireless connection during a first subperiod of each frame period, (b) causing each wireless transmitter determined to have a packet transmission requirement, to transmit its packets of information during a separate second subperiod of time of each frame period, (c) detecting during the first and/or second subperiods of each frame period, transmission impairments associated with each wireless transmitter, and (d) causing packets of information transmitted from each transmitter determined to have a transmission impairment to be transmitted at a transmission rate sufficient to lessen the determined transmission impairment, and means (32-34) for (a) receiving packets of information from the plurality of transmitters of the network, and (b) retransmitting the packets to receivers associated with the destined users of the packets of information via an appropriate hard-wired or wireless connection.
a plurality of transmitters (10-19), each transmitter being associated with a separate user or group of users of the network for transmitting packets of information between an active user or group of users and the network via either one of a hard-wired or wireless connection during a frame period; and a central node (30) for communicating with each of the plurality of transmitters via the hard-wired or wireless connection, the central node comprising, processor means (35) for (a) determining packet transmission requirements associated with each transmitter communicating with the central node via a wireless connection during a first subperiod of each frame period, (b) causing each wireless transmitter determined to have a packet transmission requirement, to transmit its packets of information during a separate second subperiod of time of each frame period, (c) detecting during the first and/or second subperiods of each frame period, transmission impairments associated with each wireless transmitter, and (d) causing packets of information transmitted from each transmitter determined to have a transmission impairment to be transmitted at a transmission rate sufficient to lessen the determined transmission impairment, and means (32-34) for (a) receiving packets of information from the plurality of transmitters of the network, and (b) retransmitting the packets to receivers associated with the destined users of the packets of information via an appropriate hard-wired or wireless connection.
2. A wideband packet communication network according to claim 1 wherein the receiving and retransmitting means comprises:
a high-speed bus for propagating packets of information from the plurality of transmitters on a time division multiplexed basis; and a plurality of network interface units (NIUs), each NIU being associated with a separate subgroup of one or more of the plurality of transmitters, and connected to She transmitters of the separate subgroup via a wireless communication link or separate hard-wired connections for receiving the packets of information from the associated subgroup of transmitters and transmitting each packet over the high-speed bus during a free time slot period to the NIU associated with a user destined to receive the packet of information. 3. A wideband packet communication network according to claim 2 wherein the network further comprises:
at least one concentrator, each concentrator being disposed between a separate subgroup of the plurality of transmitters and a predetermined one of the plurality of NIUs, each concentrator comprising;
a plurality of user interface modules (UIM), each UIM providing duplex communications with a separate portion of the subgroup of transmitters associated with that concentrator, where at least one of the subgroup portions communicates with its UIM via a separate wireless link, a trunk module for providing duplex communications between the UIMs of the concentrator and the predetermined associated one of the plurality of NIUs in the central node on a time division multiplexed basis, and a bus for propagating packets of information between the plurality of UIMs of the concentrator and the trunk module on a time division multiplexed basis.
4. A wideband packet communication network according to claim 1, 2 or
a high-speed bus for propagating packets of information from the plurality of transmitters on a time division multiplexed basis; and a plurality of network interface units (NIUs), each NIU being associated with a separate subgroup of one or more of the plurality of transmitters, and connected to She transmitters of the separate subgroup via a wireless communication link or separate hard-wired connections for receiving the packets of information from the associated subgroup of transmitters and transmitting each packet over the high-speed bus during a free time slot period to the NIU associated with a user destined to receive the packet of information. 3. A wideband packet communication network according to claim 2 wherein the network further comprises:
at least one concentrator, each concentrator being disposed between a separate subgroup of the plurality of transmitters and a predetermined one of the plurality of NIUs, each concentrator comprising;
a plurality of user interface modules (UIM), each UIM providing duplex communications with a separate portion of the subgroup of transmitters associated with that concentrator, where at least one of the subgroup portions communicates with its UIM via a separate wireless link, a trunk module for providing duplex communications between the UIMs of the concentrator and the predetermined associated one of the plurality of NIUs in the central node on a time division multiplexed basis, and a bus for propagating packets of information between the plurality of UIMs of the concentrator and the trunk module on a time division multiplexed basis.
4. A wideband packet communication network according to claim 1, 2 or
3 wherein the processor means comprises:
means responsive to the beginning of a frame period for (a) sequentially sending first control signals (Pi) to each of the plurality of transmitters and sequentially receiving second control signals (Ri) from the transmitters indicative of whether or not a transmitter has a packet of information to be transmitted during the frame period, and (b) in response to each received second control signal indicating that a transmitter is active and has a packet information to be sent, sequentially transmitting third control signals (TSi) tothe active transmitters for causing the packet of information to be sent by the transmitter for routing by the central node to a destined user of the packet of information.
5. A wideband packet communication network according to claim 4 wherein the receiving and retransmitting means in the central node comprises means for detecting that a packet of information was received from a transmitter with a bit error rate that is less than a predetermined value, and for generating a separate transmission impairment control signal to the determining and causing means; and the determining and causing means is responsive to a transmission impairment control signal from the receiving and retransmitting means for transmitting a subsequent second control signal to the transmitter detected as having a transmission impairment for causing the transmitter to retransmit the packet of information at a slower data rate using a predetermined resource sharing technique.
6. A wideband packet communication network according to claim S
wherein the receiving and retransmitting means includes diversity antennas associated with wireless connections.
7. A wideband packet communication network according to claim 1, 2 or 3 wherein the receiving and retransmitting means includes diversity antennas associated with the wireless connections.
8. A method of transmitting information between a plurality of transmitters and a central node, including a processor means, via either one of a hard-wired or wireless connection during a frame period in a wideband packet communication network, each transmitter being associated with a separate user or group of users of the network, the method comprising the steps of:
(a) the processor means in the central node determining the packet transmission requirements of each transmitter communicating with the central node during a first subperiod of time of each frame period;
(b) causing a wireless transmitter determined in step (a) to have packet transmission requirements, to transmit its packets of information during a separate second subperiod of time of each frame period;
(c) the processor means detecting, during the first and/or second subperiods of time of each frame period, transmission impairments associated with each wireless transmitter; and (d) the processor means causing packets of information transmitted from each transmitter determined to have a transmission impairment in step (c) to be transmitted at a transmission rate sufficient to lessen the determined transmission impairment.
9. A method according to claim 8 wherein the method comprises the further steps of:
in performing step (a) performing the substeps of (a1) the processor means sequentially transmitting first control signals (Pi) to each of the plurality of transmitters, and (a2) sequentially receiving second control signals (R1) from the plurality of transmitters indicative of whether or not a transmitter has a packet of information to be transmitted during the frame period; and (b1) in response to each received second control signal in step (a2) indicating that a transmitter is active and has a packet of information to be sent, sequentially transmitting third control signals (TSi) to the active transmitters for causing the packet of information to be sent by the transmitter for routing by the central node to a destined user of the packet of information.
10. A method according to claim 8 or 9 wherein in performing step (c) performing the substeps of (c1) detecting at the central node that a packet of information was received from a transmitter with a bit error rate that is less than a predetermined value; and (c2) transmitting a subsequent second control signal to the transmitter detected as having a transmission impairment in response to the detection of a bit error rate more than a predetermined value in step (c1);
(c3) a transmitter having a transmission impairment being responsive to a subsequent second control signal transmitted in step (c2) for retransmitting the packet of information at a slower transmission rate using a predetermined resource sharing technique such that the packet of information is received at the central node with a bit error rate below the predetermined value.
means responsive to the beginning of a frame period for (a) sequentially sending first control signals (Pi) to each of the plurality of transmitters and sequentially receiving second control signals (Ri) from the transmitters indicative of whether or not a transmitter has a packet of information to be transmitted during the frame period, and (b) in response to each received second control signal indicating that a transmitter is active and has a packet information to be sent, sequentially transmitting third control signals (TSi) tothe active transmitters for causing the packet of information to be sent by the transmitter for routing by the central node to a destined user of the packet of information.
5. A wideband packet communication network according to claim 4 wherein the receiving and retransmitting means in the central node comprises means for detecting that a packet of information was received from a transmitter with a bit error rate that is less than a predetermined value, and for generating a separate transmission impairment control signal to the determining and causing means; and the determining and causing means is responsive to a transmission impairment control signal from the receiving and retransmitting means for transmitting a subsequent second control signal to the transmitter detected as having a transmission impairment for causing the transmitter to retransmit the packet of information at a slower data rate using a predetermined resource sharing technique.
6. A wideband packet communication network according to claim S
wherein the receiving and retransmitting means includes diversity antennas associated with wireless connections.
7. A wideband packet communication network according to claim 1, 2 or 3 wherein the receiving and retransmitting means includes diversity antennas associated with the wireless connections.
8. A method of transmitting information between a plurality of transmitters and a central node, including a processor means, via either one of a hard-wired or wireless connection during a frame period in a wideband packet communication network, each transmitter being associated with a separate user or group of users of the network, the method comprising the steps of:
(a) the processor means in the central node determining the packet transmission requirements of each transmitter communicating with the central node during a first subperiod of time of each frame period;
(b) causing a wireless transmitter determined in step (a) to have packet transmission requirements, to transmit its packets of information during a separate second subperiod of time of each frame period;
(c) the processor means detecting, during the first and/or second subperiods of time of each frame period, transmission impairments associated with each wireless transmitter; and (d) the processor means causing packets of information transmitted from each transmitter determined to have a transmission impairment in step (c) to be transmitted at a transmission rate sufficient to lessen the determined transmission impairment.
9. A method according to claim 8 wherein the method comprises the further steps of:
in performing step (a) performing the substeps of (a1) the processor means sequentially transmitting first control signals (Pi) to each of the plurality of transmitters, and (a2) sequentially receiving second control signals (R1) from the plurality of transmitters indicative of whether or not a transmitter has a packet of information to be transmitted during the frame period; and (b1) in response to each received second control signal in step (a2) indicating that a transmitter is active and has a packet of information to be sent, sequentially transmitting third control signals (TSi) to the active transmitters for causing the packet of information to be sent by the transmitter for routing by the central node to a destined user of the packet of information.
10. A method according to claim 8 or 9 wherein in performing step (c) performing the substeps of (c1) detecting at the central node that a packet of information was received from a transmitter with a bit error rate that is less than a predetermined value; and (c2) transmitting a subsequent second control signal to the transmitter detected as having a transmission impairment in response to the detection of a bit error rate more than a predetermined value in step (c1);
(c3) a transmitter having a transmission impairment being responsive to a subsequent second control signal transmitted in step (c2) for retransmitting the packet of information at a slower transmission rate using a predetermined resource sharing technique such that the packet of information is received at the central node with a bit error rate below the predetermined value.
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| US022,255 | 1987-03-05 | ||
| US07/022,255 US4789983A (en) | 1987-03-05 | 1987-03-05 | Wireless network for wideband indoor communications |
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| CA1281111C true CA1281111C (en) | 1991-03-05 |
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| CA000559613A Expired - Lifetime CA1281111C (en) | 1987-03-05 | 1988-02-23 | Wireless network for wideband indoor communications |
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-
1987
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- 1988-02-23 CA CA000559613A patent/CA1281111C/en not_active Expired - Lifetime
- 1988-02-26 EP EP88301691A patent/EP0281334B1/en not_active Expired - Lifetime
- 1988-02-26 DE DE3852772T patent/DE3852772T2/en not_active Expired - Lifetime
- 1988-02-26 SG SG1995903563A patent/SG30544G/en unknown
- 1988-03-04 CN CN88101150A patent/CN1009891B/en not_active Expired
- 1988-03-04 JP JP63051435A patent/JPS63233631A/en active Pending
- 1988-03-05 KR KR1019880002283A patent/KR910002016B1/en not_active IP Right Cessation
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| JPS63233631A (en) | 1988-09-29 |
| EP0281334B1 (en) | 1995-01-18 |
| EP0281334A3 (en) | 1990-11-22 |
| DE3852772T2 (en) | 1995-08-31 |
| EP0281334A2 (en) | 1988-09-07 |
| US4789983A (en) | 1988-12-06 |
| KR880012049A (en) | 1988-10-31 |
| CN88101150A (en) | 1988-11-23 |
| SG30544G (en) | 1995-09-01 |
| CN1009891B (en) | 1990-10-03 |
| DE3852772D1 (en) | 1995-03-02 |
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