US20010050943A1 - Radio frequency communication network having adaptive communication parameters - Google Patents

Abstract

Improved apparatus for a radio communication network having a multiplicity of mobile transceiver units selectively in communication with a plurality of base transceiver units which communicate with one or two host computers for storage and manipulation of data collected by bar code scanners or other collection means associated with the mobile transceiver units. The radio network is adaptive in that in order to compensate for the wide range of operating conditions a set of variable network parameters are exchanged between transceivers in the network. These parameters define optimized communication on the network under current network conditions. Examples of such parameters include: the length and frequency of the spreading code in direct-sequence spread spectrum communications; the hop frame length, coding, and interleaving in frequency-hopping spread spectrum communications; the method of source encoding used; and the data packet size in a network using data segmentation. The invention is preferably to be applicable as an upgrade of an existing data capture system wherein a large number of hand-held transceiver units operate over an extensive area to gather data in various places, requiring the use of multiple base stations. In a variety of such installations such as warehouse facilities, distribution centers, and retail establishments, it may be advantageous to utilize not only multiple bases capable of communication with a single host, but with multiple hosts as well.

Description

AUTHORIZATION PURSUANT TO 37 C.P.R. 1.71(d) AND (e)
• A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserve all copyright rights whatsoever.[0001]
INCORPORATION BY REFERENCE
• The following patent applications are incorporated in their entirety by reference:[0002]
• 1. abandoned application of Charles D. Gollnick, et al., U.S. Ser. No. 07/857,603 filed Mar. 30, 1992 (Attorney Docket Nos. DN37834XA; 92 P 327);[0003]
• 2. pending U.S. patent application of Meier, et al., Ser. No. ______, filed Oct. 30, 1992 (Attorney Docket Nos. DN37882YA; 92 P 758);[0004]
• 3. abandoned application of Ronald L. Mahany, U.S. Ser. No. 07/485,313 filed Feb. 26, 1990 (Attorney Docket Nos. DN36500Y; 91P349);[0005]
• 4. pending application of Steven E. Koenck, et al., U.S. Ser. No. 07/305,302 filed Jan. 31, 1989 (Attorney Docket Nos. DN36649; 91 P 422);[0006]
• 5. application of Ronald L. Mahany, et al., U.S. Ser. No. 07/389,727 filed Aug. 4, 1989 (Attorney Docket Nos. DN36500X; 91P258), now issued as U.S. Pat. No. 5,070,536 on Dec. 3, 1991;[0007]
• 6. application of Marvin L. Sojka, U.S. Ser. No. 07/292,810 filed Jan. 3, 1989 (Attorney Docket Nos. DN36625X; 91P420), now issued as U.S. Pat. No. 4,924,462 on May 8, 1990; and[0008]
• 7. European Published Patent Application EPO 353759 published Feb. 7, 1990.[0009]
BACKGROUND OF THE INVENTION
• The present invention in a preferred implementation relates to improvements in radio data communication networks wherein a number of mobile transceiver units are to transmit data to a number of base stations under a wide range of operating conditions. To compensate for the wide range of operating conditions, adaptability has been provided using an exchange of parameters that define the nature of the network communication. The invention is preferably to be applicable as an upgrade of an existing data capture system wherein a number of hand-held transceiver units of an earlier design are already in the field representing a substantial economic investment in comparison to the cost of base stations, accessories and components. In installations spread over an extensive area, a large number of mobile portable transceiver units may be employed to gather data in various places and multiple base stations may be required. In a variety of such installations such as warehouse facilities, distribution centers, and retail establishments, it may be advantageous to utilize not only multiple bases capable of communication with a single host, but with multiple hosts as well.[0010]
• An early RF data collection system is shown in Marvin L. Sojka, U.S. Pat. No. 4,924,462 assigned to the assignee of the present application. This patent illustrates (in the sixth figure) a NORAND® RC2250 Network Controller which supports one base transceiver for communication with multiple mobile portable transceivers. The exemplary prior art device is capable of communicating with a host computer through an RS232C interface at up to 19,200 baud in asynchronous mode. In order for an optional RS422 interface to be substituted for an RS232C interface, the unit must be opened and substitute circuitry components installed within it.[0011]
SUMMARY OF THE INVENTION
• The present invention provides an improved data communication system which maintains RF communication links between one or more host computers and one or more base transceiver units, each of which may be communicative with many mobile portable transceiver units being moved about a warehouse complex for the collection of data. Specifically, the invention provides a data communication system for collecting and communicating data in the form of RF signals which has a plurality of RF transceivers that store and modify at least one variable operating parameter. From the stored parameter(s), each of transceivers control the operation of transmission and reception. The transceivers also evaluate the effect of the stored parameter based by analyzing each transmission received, and determine whether to make changes in the stored parameter. If changes are needed, the transceivers, modify and store the modified operating parameter and begin operation based thereon.[0012]
• The operating parameters involve: 1) the size of data segments to be transmitted; 2) the length or frequency of the spreading code used for direct-sequence spread spectrum communication; 3) the hopping rate, coding, and interleaving for frequency-hopping spread spectrum communication; and 4) the type of RF source encoding used.[0013]
• In addition, the RF transceivers used in the data communication network of the present invention use system-default values to reset the operating parameters if a series of failed communication exchanges occurs, so that communication can be re-established.[0014]
• It is therefore an object of the invention to provide an adaptive radio communication system which permits the interconnection of one or two host computer devices to a multiplicity of base transceiver units which may include both prior art existing installed units and new generation units capable of spread spectrum radio transmission.[0015]
• It is a further object of the invention to provide an adaptive RF data communication system which optimizes communication based on a set of operating parameters.[0016]
• It is a further object of the invention to provide an adaptive RF data communication system which maintains communication based on a set of operating parameters for optimizing communication, wherein the operating parameters involve: 1) the size of data segments to be transmitted; 2) the length or frequency of the spreading code used for direct-sequence spread spectrum communication; 3) the hopping rate, coding, and interleaving for frequency-hopping spread spectrum communication; and 4) the type of RF source encoding to be used.[0017]
• It is a further object of the invention to provide a radio communication system network controller which via a communication exchange optimizes a set of operating parameters, yet returns the parameters to their previous or system-default values upon failed communication.[0018]
• These and other objects of the invention will be apparent from examination of the detailed description which follows.[0019]
DESCRIPTION OF THE DRAWING FIGURES
• FIG. 1 is a block diagram of the prior art data communication system.[0020]
• FIG. 2 is a perspective view of the invention.[0021]
• FIG. 3 is a schematic representation of an exemplary radio communication system utilizing the invention.[0022]
• FIG. 4 is a diagrammatic illustration of the control circuitry elements of the invention.[0023]
• FIG. 5 is a rear elevation view of the invention.[0024]
• FIG. 6 is a diagrammatic illustration of the application specific integrated circuit of the invention.[0025]
• FIG. 7 is a block diagram showing an exemplary implementation of intelligent network and router transceiver units such as the network transceiver units of FIG. 3.[0026]
• FIG. 8 is a diagram of an RF system utilizing a network controller according to FIGS.[0027]2-6, with one of its network ports configured for communication with a second host, and another of its ports coupled with a multiplicity of RF transceivers via an adapter unit.
• FIG. 9 is a diagram illustrating the use of two network controllers according to FIGS.[0028]2-6, configured for dual host computers each, and having their relatively high data rate extended distance network ports coupled with a multiplicity of intelligent network and router transceiver units implemented according to FIG. 7.
• FIG. 10 is a diagram similar to FIG. 9 but showing the pari of coupled network controllers interfaced to a common relatively high data rate system having multiple hosts (e.g.) a local area network of the Ethernet type or equivalent e.g. fiber optic type.[0029]
• FIG. 11 is a diagram similar to FIG. 10 but indicating the network controllers being coupled to respective different high data rate multiple host systems (e.g., token ring type local area networks or other individual networks e.g., fiber optic loop networks of the collision-sense multiple-access type).[0030]
• FIG. 12 is a view similar to FIG. 9 but intended to diagrammatically indicate a distribution of network and router transceivers and other elements of an on-line RF data collection system over an extensive area of a facility e.g. of one of the types previously mentioned.[0031]
• FIG. 13 shows an intelligent controller and radio base unit which unifies controller and radio components such as shown in FIG. 7 into a single housing of the size represented in FIGS. 2 and 5.[0032]
• FIG. 14 shows a diagrammatic illustration of the signal processing for two of four paiis of communication ports of the multiple base adapter of the RF data collection system illustrated in FIG. 8.[0033]
• FIG. 15 is a diagram of parts of an RF data collection system utilizing a network controller according to FIGS.[0034]2-6 and a multiple base adapter according to FIG. 14, with eight base transceiver units coupled to the multiple base adapter.
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1 shows an existing radio frequency[0035]data transmission system10 wherein a base station transceiver means11 has a number of mobile transceiver units such as12A,12B, . . . ,12N in radio communication therewith.
• By way of example, the base station may be comprised of a[0036]radio base unit14 such as the model RB3021 of Norand Corporation, Cedar Rapids, Iowa, which forms part of a product family known as the RT3210 system. In this case, theradio base14 may receive data from the respective mobile RF terminals, e.g. of type RT3210, and transmit the received data via a network controller and a communications link16 (e.g. utilizing an RS-232 format) to ahost computer17.
• The[0037]data capture terminals12A,12B, . . . ,12N may each be provided with a keyboard such as18, a display as at19, and a bar code scanning capability, e.g., via an instant bar code reader such as shown in U.S. Pat. No. 4,766,300 issued Aug. 23, 1988, and known commercially as the 20/20 High Performance Bar Code Reader of Norand Corporation.
• FIG. 2 provides a perspective view of the[0038]invention40 in thepreferred embodiment case20.Front panel22 is provided withdisplay24 and select key26, upkey28 and downkey30.Power indicator32 comprises a low power green light emitting diode which is energized when power is supplied to theinvention10.Error condition indicator34 is a yellow LED which is software controlled to be energized if theinvention10 is in error condition.
• FIG. 3 discloses a diagrammatic illustration of a radio communication system in accordance with the present invention.[0039]Invention network controller40 is coupled tohost computer42 such that data may be interchanged between the devices over host communications link44, which may be either in an RS232C format or selectively in an RS422 format. The host communication link44 couples tocontroller40 athost port46.
• [0040]First communication port48 ofcontroller40 provides means for coupling ofnetwork50 tocontroller40.Network50 comprises a number of baseRF transceiver units52A,52B and53B, each of which may be selectively employed in the radio frequency communication of data from mobile transceiver units. It is to be understood that base transceiver units52 are designed and equipped to be operable in the exchange of data withnetwork controller40 overnetwork link56 such that eachbase transceiver unit52A,52B, or53C may independently exchange data withnetwork controller40 throughfirst communication port48. Whenfirst communication port48 is intended for operation with a network such asnetwork50 ofbase transceiver units52A,52B and53C, for example,network controller40 is selectively operated to provide an RS485 interface atfirst communication port48.First communication port48 may be alternately selected to operate as an RS232C interface, as an RS422 interface, as a proprietary NORAND® Radio One Node Network interface or as a high speed V.35 interface. The selection of interface to be provided atfirst communication port48 is front panel controlled, that is, the user may operatefront panel keys28,30 and26 (See FIG. 2) to direct the proper interface to be provided atfirst communication port48.
• [0041]Base transceiver units52A,52B, and52C are coupled tonetwork link56 by serial means, rather than parallel means, and each may be caused to transmit or to receive independently from the others while additionally being communicative withnetwork controller40 in a randomly chosen fashion.
• It is further to be understood that interface translation is provided within[0042]controller40 such that data communicated atfirst communication port48 may be directed to host42 atport46 via properly chosen interface means as is required by thehost42 with which communication is intended.
• Like[0043]first communication port48,second communication port57 may be internally switched among interface choices of these types: RS232C, RS422, V.35, RS485 and proprietary NORAND® Radio One Node Network interface. In the illustrated arrangement of FIG. 3, for example,second communication port57 is coupled overthird link53 to previously installedbase transceiver54, which heretofore had been used in a prior art system as is illustrated in FIG. 1. Because of limitations ofbase transceiver54, it must communicate via RS232C interface format and therefore,second communication port57 must be selected to operate in RS232C interface mode. However, whensecond communication port57 is desired to communicate with a network via RS485 interface,front panel keys26,28 and30 may be manipulated by the user to provide the RS485 interface availability atsecond communication port57. Likewise,second communication port57 may be selected to operate as an RS422 interface, as a V.25 interface, or as the proprietary NORAND® Radio One Node Network interface.
• [0044]Diagnostic port55 provides a fourth communication pathway fornetwork controller40, providing an asynchronous port operable at 300 to 19,200 baud as an RS232C interface. When desirable,diagnostic port55 may be coupled bydiagnostic link58 todiagnostic device60 for purposes of error diagnosis ofcontroller40 bydiagnostic device60, or for reprogramming of memory devices withincontroller40 when desired. It is contemplated thatdiagnostic device60 comprises a 16 or 32 bit microprocessor commonly known as a personal computer or “PC”. The mode of coupling betweendiagnostic device60 andnetwork controller40 may be direct or through remote means by use of a modem.
• Referring now to FIG. 4, a[0045]central processing unit70 is provided with at least four data communication ports, illustrated atnumerals71,72,73, and74. Firstdata communication port71 may be selectively coupled toRS232 interface member76 or V.35interface member78. The choice of whetherRS232 interface member76 or V.35interface member78 is chosen is dependent upon the operating characteristics presented by the host computer, such ashost computer42 of FIG. 3, with whichnetwork controller40 will communicate. The choice of whetherfirst communication port71 is coupled tointerface member76 or to interfacemember78 depends on the front panel selection made by the user bykeys26,28, and30 shown in FIG. 2.
• [0046]Second communication port72 may be selectively coupled toRS232 member80 or toRS485 interface member82 or toRS422 interface member84 or to NORAND® Radio One Node Networkproprietary interface member86. By use offront panel keys26,28, and30 of FIG. 2, the user may selectsecond communication port72 to be coupled to any one ofinterface members80,82,84, and86.
• [0047]Third communication port73 is identical tosecond communication port72 in functionality, being selectively couplable toRS232 interface member88, toRS485 interface member90, toRS422 interface member92 or to NORAND® Radio One Node Networkproprietary interface member94.
• In the preferred embodiment of the[0048]invention40,central processing unit70 of FIG. 4 comprises a Motorola™ 68302 integrated chip cooperative with an application specific integrated circuit.Central processing unit70 employs novel features allowing the bidirectional use of a data communicative line of the Motorola™ 68302 chip and a single clock signal line to eliminate the need for coder-decoder members to be associated with the Motorola™ 68302 chip while allowing the use of only one pair of signal wires to be coupled to the RS485 interfaces82 and90 of FIG. 4.
• [0049]Fourth communication port74 of central processing unit is coupled to asynchronousRS232 interface member97 to be available for interconnection of a diagnostic device therewith.
• Also coupled to[0050]central processing unit70 aredisplay member24 andkeyboard member31 with whichkeys26,28, and30 of front panel22 (FIG. 2) are interactive.
• Memory elements including[0051]EPROM element96,DRAM unit98,FLASH memory unit100 andEEPROM element102 are intercoupled with each other and withcentral processing unit70.
• [0052]Power supply member104 is selectively attachable toinvention network controller40. In order to avoid the necessity of different models ofnetwork controller40 depending on the local electrical power utility's operating characteristics,power supply104 is provided in optional models depending on the country in which it is to be used,power supply104 being capable of providing satisfactory output power to networkcontroller40 regardless of the voltage or frequency of the input source provided topower supply104.
• The application specific integrated circuit (ASIC) used in the[0053]invention network controller40 is disclosed in FIG. 6 and is identified by the numeral120.ASIC120 comprises a centralprocessor unit interface122 member which is coupled to the central processor unit bus byCPU bus link124 which extends fromASIC120. Also coupled to theCPU bus link124 is dynamic random access memory (DRAM)timing element126, which providesnetwork controller40 with timing signals for theDRAM member98 illustrated in FIG. 4 when memory refresh of theDRAM98 is indicated.DRAM timing element126 is also coupled exteriorly to theASIC120 toDRAM member98 byDRAM link127.
• Central[0054]processing unit interface122 is coupled to asynchronoussignal processing element128 bysignal path130. Asynchronoussignal processing element128 comprises a baud rate generator cooperative with a universal asynchronous receiver-transmitter.
• Also coupled to central[0055]processing unit interface122 is network clock andcontrol member132 which comprises a programmable network clock generator which can be selectively programmed to generate an optional clock speed for a network to be coupled through RS485 interfaces82 and90 seen in FIG. 4. Network clock andcontrol member132 also provides detection means for detections of failure conditions on a linked network and provides control signals to system components in response thereto, including interrupt signals to programmable interrupt coordinator circuitry included incentral processing interface122. Network clock andcontroller member132 provides data encoding by the FMO standard, then the encoded data may be operated upon byRS485 interfaces82 and84 and transmitted and received by single twisted pair means to multiple serially networked base transceiver units exemplified bybase transceiver unit52A,52B, and52C illustrated in FIG. 3.
• [0056]Keyboard controller element134 is coupled to central processing unit interface and provides a link exterior toASIC120 to keyboard31 (See FIG. 3).
• FLASH memory/EEPROM[0057]logic control member136 is coupled to centralprocessing unit interface122 and comprises control functions forFLASH memory element100 andEEPROM memory element102 of FIG. 3.
• Central[0058]processing unit interface122 is also coupled byline138 to latches exterior toASIC120.
• It is to be understood that the[0059]base transceiver units52A,52B, and52C illustrated in FIG. 3 are communicative with mobile transceiver units by electromagnetic radio means. The mobile transceiver units may be associated with bar code scanning devices such as theNORAND® 20/20 High Performance Bar Code Reader whereby the scanning devices scan an object having a bar code associated therewith and collect information stored in the bar code, which information is then transmitted through the mobile transceiver units to base transceiver units such asbase transceiver units52A,52B, and52C orbase transceiver unit54 of FIG. 3. The bar code data received by said base transceiver units is then transmitted in the example of FIG. 3, overnetwork50 bybase transceiver units52A,52B, or52C, or overlink53 bybase transceiver unit54, to networkcontroller40 which performs the routing and delivery of the data to the stationary data processor, or processors, such as shown for example, byhost42 of FIG. 3.
• Description of FIGS. 7 through 11[0060]
• FIG. 7 shows a block diagram of a particularly preferred intelligent base transceiver unit known as the RB4000. It will be observed that the components correspond with components of the network controller of FIG. 4, and similar reference numerals (preceded by[0061]7-) have been applied in FIG. 7. Thus, the significance of components7-70 through7-73,7-76,7-82,7-96,7-98,7-100 and7-104 will be apparent from the preceding description with respect to FIG. 4 and6, for example. I/O bus700 may be coupled with a spread spectrum transmission (SST) or ultra high frequency (UHF)transceiver701 which may correspond with any of the transceivers ofunits52A,52B,52C or54 previously referred to. Thenetwork controller70 could have a similar RF transceiver coupled with itsdata port72 or73 and controlled via input/output bus400, e.g. for direct RF coupling with router transceivers such as901,901, FIG. 9.
• Referring to FIG. 8, a[0062]network controller40 is shown withport71 configured for interface with a host port type SNA V. 35 56K/64K bits per second.Port72 is shown as configured for communication with a personal computer of the PS/2 type operating asynchronously at 38.4K bits per second.Port74 is coupled with a modem8-60 providing for remote diagnostics and reprogramming of thenetwork controller40.
• [0063]Port73 ofnetwork controller40 is shown as being connected with anadapter component801 known as the MBA3000. A specification for the MBA3000 if found in Appendix A following this detailed description. In the operating mode indicated in FIG. 8, theadapter801 serves to couplecontroller40 sequentially with four radio base transceiver units such as indicated at811 through814. Component811 is a commercially available radio base known as the RB3021 which utilizes features of Sojka U.S. Pat. No. 4,924,462 and of Mahany U.S. Pat. No. 4,910,794 both assigned to the present assignee, and the disclosures of which are hereby incorporated herein by reference in their entirety. Base station811 may communicate with a multiplicity of hand-held RF data terminals such as indicated at821. Details concerningbase transceiver units812 and813,814 are found in the attached Appendices B and C, respectively.Base814 is indicated as being coupled with theadaptor801 viaRF broadband modems831 and832.Base units813 and814 may communicate with a variety of mobile transceiver units such as those indicated at833 and834 which are particularly described in Appendices D and E.
• FIG. 9 shows two[0064]network controllers40A and40B each with its host ports configured as with thecontroller40 of FIG. 8. In this example, thesecond ports72 of thecontrollers40A and40B are configured for communication a relatively high data rate relatively along adistance network channel56 which may have the characteristics of theserial channel56 of FIG. 3, for example, an RS485 channel operating at 384 kilobits per second (384K bps).Network base transceivers52A,52B and52C may correspond with the correspondingly numbered transceiver units of FIG. 3, for example, and the network may have additional network transceivers such as52D. Furthermore, the network transceivers may have RF coupling with router transceiver units such as indicated at901,902 and903.Router transceiver unit902 is illustrated as a RB4000 intelligent transceiver such as represented in FIG. 7 and having its input/output bus700 coupled with a peripheral.
• FIG. 10 is entirely similar to FIG. 9, for example, except that[0065]ports72 of thecontrollers40A and40B are coupled with separate serial type high data rate network channels, andports73 of the respective network controllers are coupled to a very high speed network e.g. in the several megabits per second range such as an Ethernetlocal area network1000. Suitable interfaces are indicated at1001 and1002.
• FIG. 11 is entirely similar to FIG. 9 except that the[0066]ports73 of thenetwork controllers40A and40B are coupled with respective local area ring type networks which may be separate from each other and each have two or more hosts such as represented in FIG. 9 associated with the respective ring networks such astoken rings1100A and1100B. Suitable interface means are indicated at1101 and1102.
• Description of FIG. 12[0067]
• FIG. 12 shows, for example, two[0068]network controllers40A and40B, each with two host computer units such as42-1A. Host42-2A is shown with a printer or other peripheral P1 which may generate bar codes, for example, for replacement of damaged bar codes or the like. Another printer P2 is shown associated withbase52C, again for example, for producing bar code labels where those are needed in the vicinity of a base station. In a large warehouse, relatively large distances may be involved for a worker to return to a printer such as P1 to obtain a new bar code label. Thus, it may be very advantageous to provide a printer P2 at thebase station52C which may be relatively close to a processing location which requires printed labels, e.g. a processing location in the vicinity of hand-held terminal12-2 in FIG. 12. Abase52F may have a peripheral P3 associated therewith such as a large screen display, a printer or the like which may supplement the capabilities of a hand-held terminal, for example printing out new bar code labels at a convenient location, or providing a full screen display, rather than the more limited screen display area of the hand-held terminal12-2.
• If, for example, a base radio[0069]52D which might be located at the ceiling level of a warehouse became inoperative at a time when qualified repair personnel were not immediately available, with the present system it would be feasible to provide a substitute base radio or base radios, for example, as indicated at52D1 located at table level or the like.
• With the present system, the base radio stations do not necessarily forward data communications received from a given terminal to a particular host. For example, hand-held terminal[0070]12-2 may request a path to printer P2, and such a path may be created via base stations52D1 and52C.Station52C upon receipt of the message form terminal12-2 would not transmit the message to a host but would, for example, produce the desired bar code label by means of printer P2. Further, terminal12-2 may have provision for digitizing a voice message which might, for example, be addressed to terminal12-1. The system as illustrated would be operable to automatically establish a suitable path for example, via stations52D1,52C,52B,52E and12-1 for the transmission of this voice message in digital form. Successive segments of such a voice message would be stored, for example, by the terminal12-1, and when the complete message was assembled, the segments would be synthesized into a continuous voice message for the user of terminal12-1 e.g. by means of aspeaker1201 also useful for sending tone signals indicating valid bar code read, etc.
• In accordance with the present invention, a hardware system such as illustrated in FIG. 12 may be physically laid out and then upon suitable command to one of the network controllers such as[0071]42-2B, the entire system would be progressively automatically self-configured for efficient operation. For example,controller40B could successively try its communications options with its output ports such as71-73, determining for example, that host processors were coupled withports71 and72, one operating on a 38.4 kilobit per second asynchronous basis and the other presenting a SNA port for the V.35 protocol at 64 kilobits per second. For example, on host,42-1B might be a main frame computer, while the other host42-2B might be a PS/2 type computer system. Thecontroller40B having thus automatically configured itself so as to be compatible with the devices connected toports71 and72, could proceed to transmit via port73 a suitable inquiry message to thenetwork channel56. Although a polling protocol is preferred, each of the base stations could operate, for example, on a carrier-sense multiple-access (CSMA) basis or using a busy tone protocol to respond to the inquiry message from thecontroller40B, until each of the successive bases on the network had responded and identified itself. Each base, for example, would have a respective unique address identification which it could transmit in response to the inquiry message so as to establish its presence on the network.
• The[0072]controller40B could then transmit auto configure commands to the successive bases in turn, instructing the bases to determine what peripherals and router bases such as52D1,52E and52F were within the range of such base, and to report back to the controller. For example, bases such as52C and52F could determine the nature of peripherals P2 and P3 associated therewith so as to be able to respond to an inquiry form a terminal such as12-2 to advise the terminal that a bar code printer, for example, was within direct RF range.
• In the case of a breakdown of a component of the system such as[0073]52D, it would merely be necessary to place a router device such as52D1 at a convenient location and activate the unit, whereupon the unit could send out its own broadcast inquiry which, for example, could be answered by thebase stations52C and52F,station52C in turn, advising a relevant host or hosts of the activation of a substitute router station. Thus, the system is conveniently re-self-configured without the necessity for a technician familiar with the particular configuration procedure. As another example, where the base stations are operating utilizing spread spectrum transmission, the introduction of barriers (such as a new stack of inventory goods) to such transmission between a given base such as52A and various terminals, could result in thebase52A contacting router52E, for example, with a request to become active with respect to the blocked terminals.
• A more detailed example of auto-configuration of the network can be found in pending U.S. patent application of Meier, et al., Ser. No. ______ (Attorney Docket Nos. DN37882YA; 92 P 758) filed Oct. 30, 1992, which is incorporated herein by reference.[0074]
• Description of FIG. 13[0075]
• FIG. 13 shows an intelligent integrated controller and[0076]radio base unit1300 which is integrated into a single housing orcase1301 corresponding to the case orhousing20 of FIG. 2. thehousing1301 may be provided with an external antenna as diagrammatically indicated at1302 with suitable RF coupling to the radio circuitry indicated at1303. Components13-70 through13-74,13-76,13-78,13-96,13-97,13-98,13-100, and13102 may correspond with the correspondingly numbered components described with reference to FIG. 4.
• Supplementary Discussion[0077]
• In accordance with the present disclosure, a network controller, or integrated network controller and radio unit is coupled to one or more host computers via a standard interface such as commonly encountered in practice (e.g. RS232, V. 35, Ethernet, token ring, FDDI, and so on). In this way, no specialized interface or adapter is required for the host.[0078]
• Since the preferred network controller can connect to two hosts, if one host is detected to have failed, or in the event of a system crash, loss of communication link, or the like, the network controller can automatically switch to the second host. The second host may be a truly redundant system, or may be a simpler computer of the PC type (a so-called personal computer) that can simply store transactions until the main host is restored. As another example, a single host may have a second port coupled to a second port of the controller especially if a communication link failure may be a problem. For example, two ports of the network controller may be coupled by separate modems with separate phone lines, leading to separate ports of a single mainframe computer, for example an IBM3090. In a fully redundant system, two ports of a network controller may be connected respectively to two mainframe computers such as the IBM3090.[0079]
• The disclosed network controller can also connect one radio network to two hosts using RS232or V.35 ports or to many hosts using a local area network such as Ethernet, token ring, or FDDI. A number of the disclosed network controllers (for example, up to thirty-two) can be connected together to interface many hosts to a single radio network. The hand-held portable terminals in such a network can then talk to any of the hosts they choose.[0080]
• For example where one port of the disclosed network controller is coupled via its RS232 interface to a mainframe computer such as the IBM3090, another of its ports may be coupled via an FDDI network with a super computer e.g. the Cray X-MP. Then mobile and/or portable terminals can access either the main frame or the super computer, or in general, any of the hosts that are connected to the network controller.[0081]
• As indicated in FIG. 9, four hosts can be on one network. Referring to FIGS. 10 and 11, a multiplicity of hosts may be coupled with each local area network so as to be in communication with one or more of the disclosed network controllers. Furthermore, a single disclosed network controller can control two radio networks such as the one indicated at[0082]50 in FIG. 3. Where each network such as50 is limited to thirty-two devices, the number of devices is doubled with the use of two radio networks. Two such radio networks may also be utilized for the sake of redundancy, with a provision for automatic switch-over from one radio network to the second if a problem develops on the first. Two radio networks may also facilitate the use of different radio technologies in one installation.
• The various multi-drop local area networks referred to herein, for example at[0083]7-82 in FIG. 7 and as represented at56,56A,56B, FIGS. 9 through 12, and at13-82 in FIG. 13 may comprise HDLC based local area networks operating at up to 2.5 megabits per second and using biphase space encoding (FMO) for clock recovery from data.
• The[0084]components86 and94, FIG. 4, and component13-11, FIG. 13, provides a low-cost base radio interface using three pairs of twisted conductors. One pair provides a bidirectional RS485 data line. Another pair is used for the clock and has an RS422 electrical configuration, and is one directional from the radio to the controller. The third twisted pair is also RS422 and is used to communicate from the controller to the radio transceiver to effect mode selection.
• Since it is advantageous to operate the network and router RF transceiver units so as to be compatible with existing mobile data collection terminals such as shown in Appendix D[0085]1 et seq., a preferred mode of operation is based on the RTC protocol as disclosed in the aforementioned incorporated Mahany and Sojka patents and the following applications:
• (1) U.S. Ser. No. 07/389,727 filed Aug. 4, 1989 (Attorney Docket Nos. 36500X; 91 P 258), now issued as U.S. Pat. No. 5,070,536 on Dec. 3, 1991.[0086]
• (2) European Published Patent Application EPO 353759 published Feb. 7, 1990.[0087]
• (3) U.S. Ser. No. 07/485,313 filed Feb. 26, 1990 (Attorney Docket Nos. 36500Y; 91 P 349).[0088]
• The disclosures of applications (1), (2) and (3) are hereby incorporated herein by reference in their entirety.[0089]
• An aspect of the invention resides in the provision of a network controller having port means selectively configurable for coupling in first mode with network RF transceiver units at a relatively high data rate such as[0090]100 kilobits per second or higher, and for coupling in a second mode with network transceiver units at a relatively low data rate such as about twenty kilobits per second. Preferably a single port means such as 2, 3, or 5, 6, FIG. 5, can be software configured to interface selectively in the first mode or in the second mode. It is presently less expensive to use multiple connectors per port rather than a single 37-pin connector for example.
• Where a network controller such as[0091]40 operates two high data rate networks, for example, one network of RF base transceivers could operate with the RTC protocol, and the second network could operate according to a different protocol such as that disclosed in pending application Ser. No. 07/660,618 filed on or about Feb. 25, 1991 (Attorney Docket No. 37734), in its entirety. It will be apparent that many modifications and variations may be effected without departing from the scope of the teachings and concept of the present disclosure.
• Description of FIGS. 14 and 15[0092]
• FIG. 14 is a block diagram of the circuitry for one pair of[0093]communication ports1401 and1403 of adapter801 (FIG. 8) for use in coupling to base transceiver units. Three additional pairs of communication parts for coupling to six additional base transceiver units are provided in the preferred embodiment ofadapter801 as exemplified by the MBA3000 Multiple Base Adapter further described in Appendix A. It is to be understood that the circuit components coupled to each additional pair of communication ports ofadapter801 is identical to that shown for first port pair1A/1A, that isports1401 and1403 of FIG. 14. Theadapter801 provides means for connecting the controller40 (FIG. 8) at itsport73 to a multiplicity of radio base units illustrated in FIG. 8 as, for example,811,812,813,814, including in selected pairs. In the preferred embodiment ofadapter801, up to eight radio base units may be coupled through use ofadapter801 to anetwork controller40, to be controlled bycontroller40 in selected pairs thereof. Thecontroller40 may control the radio base units such as811,812,813,814, (FIG. 8) in simulcast mode, that is, with all base radios interrogating mobile transceiver units such as821,833, and834 of FIG. 8 simultaneously, or with the base units being employed in pairs to interrogate the mobile transceiver units.
• Referring again to FIG. 14, the[0094]network controller40 provides transmit data and baud rate select signals toadapter801. Withinadapter801, the controller outputs are converted to TTL levels byTTL converter1402 and they are then provided to buffer1404 which provides the signals to pairedRS232 transceivers1406 and1408, and to pairedRS422 transceivers1410 and1412 which deliver the converted signals toports1401 and1403 respectively. By this means, the controller's output signals are provided to a pair ofoutput ports1401 and1403 in both RS232 and RS422 interface at the same time. An additional three output-port-pairs are provided which may be denominated2A/2B,3A/3B and4A/4B, which ports are controlled and operated identically to ports1A/1B identified in FIG. 14 asports1401 and1402. TheRS232 transceivers1406 and1408 andRS422 transceivers1410 and1412 andports1401 and1403 are illustrative of all circuitry coupled to port pairs ofadapter801.
• Similarly, signals provided to[0095]adapter801 by base radios coupled to the output port pairs,e.g. ports1401 and1403 of FIG. 14, are first converted to TTL levels by theRS232 transceivers1406 and1408 or by theRS422 transceivers1410 and1412, depending upon which interface is presented by a pair of base radios atport1401 and1403. The signals provided toadapter801 are then forwarded by thetransceivers1406 and1408 or1410 and1412 at TTL levels tocontroller40. Aselection unit1414 provides a push-to-talk selection signal to theRS232 transceivers1406 and1408 and to theRS422 transceivers1410 and1412 to provide PTT selection signals atports1401 and1403 in both RS232 and RS422 format. It is to be understood that similar selection units are associated with remaining port pairs2A/2B,3A/3B.4A/4B so that the ports may be independently operated.
• The[0096]adapter801 of FIG. 8 is exemplified by the MBA3000 multiple base adapter unit manufactured by the NORAND Corporation of Cedar Rapids, Iowa as shown in Appendix A. Because of the operation of the MBA3000 multiple base adapter by dual methods in either RS232 or RS422 signal environments, the MBA3000 may be incorporated into systems having existing installed base radios which present only an RS232 interface or it may be incorporated into systems having base radios some of which operate at RS422 and some at RS232.
• FIG. 15 illustrates a preferred arrangement of[0097]controller40 andadapter801 when used in an environment with multiple base radios in multiple warehouse environments.Controller40 is coupled toadapter801 which is coupled to pairedbases1511,1512;1513,1514;1515,1516; and1517,1518; which are located inwarehouses1501,1502,1503 and1504. By geographical separation inwarehouse1501, for example,base radios1511 and1513 provide substantial coverage ofwarehouse1501 such that a mobile transceiver being used withinwarehouse1501 would be communicated with by eitherbase radio1511 or1513. By the use ofadapter801,controller40 may cause interrogation simultaneously bybase radios1511,1512,1513,1514,1515,1516,1517,1718, or it may cause sequential interrogation byradio pairs1511/1512,1513/1514,1515/1516, or1517/1518 in succession. When a mobile transceiver responds by RF communication means with a base radio,e.g. base radio1511, the response is transmitted bybase radio1511 through coupling1521 toadapter801 which automatically converts the incoming response to RS232 interface as necessary, to make it suitable for reception bycontroller40.
• Through a system as exemplified in FIG. 15, data collection from a number of roving mobile transceivers may be initiated by a[0098]network controller40 through a four-warehouse environment. Whenbase transceiver units1511 and1512 have been unsuccessful in establishing communication with the desired mobile transceiver unit,controller40 will then causebases1513 and1514 to attempt communication and ifbases1513 and1514 are unsuccessful,controller40 will proceed through the other base radio pairs, namely1515/1516 and1517/1518, as needed, to establish communication with the desired mobile transceiver unit. Details regardingbase transceiver units1511,1512,1513, and1514 are found in Appendix B. Details regardingbase transceiver units1515,1516,1517, and1518 are found in Appendix D.
• The[0099]adapter801 is provided to operate in either simulcast or sequential mode. In the normal or simulcast mode,adapter801 allows the use of one to eight bases, where the bases are configured as four pairs of two bases. In this mode theadapter801 simulcasts to a single base pair at a time and the four sets of base pairs are selected using a dynamic time-division multiplexing method. The user can configure theadapter801 to use any of the eight base ports, using simulcasting or time-division multiplexing to best advantage.
• There are two sets of base transceiver units, referred to as set A (identified as[0100]1A,2A,3A, and4A) and set B (identified as1B,2B,3B, and4B). Within a set, the base transceiver units are selected by time-division multiplexing.
• It can be seen in FIG. 15, that there are four pairs of base transceiver units defined as pairs[0101]1A/1B,2A/2B,3A/3B,4A/4B. Each base transceiver unit of a base pair is simulcasted to at the same time.
• The hardware of the[0102]adapter801 allows the selection of the base pairs (pair1A/1B through4A/4B) using control lines from thecontroller40.Adapter801 transmits to both base transceiver units of a base pair at the same time and receives independently from each base simultaneously.
• The use of[0103]adapter801 allows an extension of the number of base transceiver units that can be used in a facility to allow for adequate coverage, it is important to understand how the base transceiver units operate when simulcasting is used, and when time-division multiplexing is used.
• The[0104]adapter801 distributes signals transmitted bycontroller40 to base transceiver pairs at the same time, so if there is an overlap in the coverage for the two base transceiver units, there may be some interference. The amount of interference depends on the relative signal strengths; if the strength is similar in one spot the chance of interference is larger that if the signal strengths are different. This type of interference could be avoided in some configurations by splitting coverage areas of pairs of base transceiver units. Another method of covering the overlap area is to place another base (not one of the base pairs) to cover the overlap area. The radio signals from the mobile transceiver unit may be picked up fully or partially by either or both base transceiver units of a given pair. However theadapter801 first tries to receive from one base transceiver unit, forexample base1511, and if unsuccessful, it then switches to try to receive from a second base transceiver unit, for examplebase transceiver unit1513. If the information is successfully received from the first base transceiver unit, the information from the second base transceiver unit is ignored. Thus the controller assures data does not get sent to the host data processor in duplicate.
• The user may couple from one to eight base transceiver units to the[0105]adapter801 and can then configure those base transceiver units as required to meet the installation's needs. Any combination of ports of theadapter801 can be used. Thus the user can take advantage of the ability to simulcast or sequentially (via time-division multiplexing) access thebase transceiver units1511,1512,1513,1514,1515,1516,1517, and1518.
• The following Appendix E provides an exemplary computer program listing for preferred control instruction for the system disclosed herein.[0106]
• Multipath Fading and Data Packet Size Parameters.[0107]
• In a preferred embodiment, the data (or messages) to be sent through the RF communication link is segmented into a plurality of DATA packets and is then transmitted. Upon receipt, the DATA packets are reassembled for use or storage. Data segmentation on the RF link provides better communication channel efficiency by reducing the amount of data loss in the network. For example, because collisions between transmissions on an RF link cannot be completely avoided, sending the data in small segments results in an overall decrease in data loss in the network, i.e., only the small segments which collide have to be re-sent.[0108]
• Similarly, choosing smaller data packets for transmission also reduces the amount of data loss by reducing the inherent effects of perturbations and fluctuations found in RF communication links. In particular, RF signals are inherently subject to what is termed “multi-path fading”. A signal received by a receiver is a composite of all signals that have reached that receiver by taking all available paths from the transmitter. The received signal is therefore often referred to as a “composite signal” which has a power envelope equal to the vector sum of the individual components of the multi-path signals received. If the signals making up the composite signal are of amplitudes that add “out of phase”, the desired data signal decreases in amplitude. If the signal amplitudes are approximately equal, an effective null (no detectable signal at the receiver) results. This condition is termed “fading”.[0109]
• An data communication system using segmentation can be found in a pending application of Steven E. Koenck, et al., U.S. Ser. No. 07/305,302 filed Jan. 31, 1989 (Attorney Docket Nos. DN36649; 91 P 422), which is incorporated herein by reference in its entirety. Specific reference is made to Appendix A thereof.[0110]
• Normally changes in the propagation environment occur relatively slowly, i.e., over periods of time ranging from several tenths (1/10's) of seconds to several seconds. However, in a mobile RF environment, receivers (or the corresponding transmitters) often travel over some distance in the course of receiving a message. Because the signal energy at each receiver is determined by the paths that the signal components take to reach that receiver, the relative motion between the receiver and the transmitter causes the receiver to experience rapid fluctuations in signal energy. Such rapid fluctuations can result in the loss of data if the amplitude of the received signal falls below the sensitivity of the receiver.[0111]
• Over small distances, the signal components that determine the composite signal are well correlated, i.e., there is a small probability that a significant change in the signal power envelope will occur over the distance. If a transmission of a data packet can be initiated and completed before the relative movement between the receiver and transmitter exceeds the “small distance”, data loss to fading is unlikely to occur. The maximum “small distance” wherein a high degree of correlation exists is referred to hereafter as the “correlation distance”.[0112]
• As expressed in wavelengths of the carrier frequency, the correlation distance is one half ({fraction (1/2)}) of the wavelength, while a more conservative value is one quarter ({fraction (1/4)}) of the wavelength. Taking this correlation distance into consideration, the size of the data packet for segmentation purposes can be calculated. For example, at 915 MHz (a preferred RF transmission frequency), a quarter wavelength is about 8.2 centimeters. A mobile radio moving at ten (10) miles per hour, or 447 centimeters per second, travels the quarter wavelength in about 18.3 milliseconds. In such an environment, as long as the segment packet size remains well under 18.3 milliseconds, significant signal fluctuations during the duration of a packet transmission is unlikely. In such an preferred embodiment, five (5) millisecond data packet segments are chosen which provides a quasi-static multipath communication environment.[0113]
• The faster the relative movement between a transmitter and a receiver the greater the effect of fading, and, therefore, the smaller the data segment should be. Similarly, if the relative movement is slower, the data segment can be larger.[0114]
• Slower fading effects which might be experienced between stationary transceivers in an office building due to the movement of people, mail carts, and the like. In a typical application of the present invention, the RF transceiver of a mobile unit may be secured with a bar-code scanner such as a deflected laser beam bar-code scanner or an instant CCD bar-code scanner. In such an example, the bar code data could be transmitted to the base station as the RF transceiver and a scanner device were being jointly transported by a vehicle (e.g. a forklift truck) to another site, or the RF transceiver and a scanner, e.g. as a unitary hand-held device, could be carried by the operator to another site as the bar code data was being transmitted to the base station. In such situations, fading is more pronounced.[0115]
• If fading does not pose a problem on a given network, the overhead associated with segmentation, hand-shaking and reconstruction may not be justifiable. However, where fading exists, such overhead may be required.[0116]
• In many communication environments, the degree of fading effects varies dramatically both from time to time and from installation to installation. In the preferred embodiment, transmitters and receivers communicate using an optimal data segment size parameter by adapting the size to conform to the communication environment of the network at any given time. For example, if a receiver detects repeated faulty transmissions, the data segment size parameter might be incrementally reduced (under the assumption that fading caused the faults) until the data throughput reaches an optimal level. Similarly, the size of the data segment can be reduced based on a measured indication of the degree of fading in the network.[0117]
• One example of a receiver making such a measurement of fading can be found in the abandoned patent application of Ronald L. Mahany, U.S. Ser. No. 07/485,313, filed Feb. 26, 1990, which is incorporated herein by reference. Specifically, in that reference, a received signal strength indicator (RSSI) circuit is found in the receiver. The RSSI circuit samples the signal strength of a transmission. If the signal strength samples are evaluated in sequence and the trend analyzed, the degree of fading can be measured. If the signal strength samples decrease in value, it is likely that fading is present in the network. However, just because fading exists does not require segmentation. Only if fading causes the signal strength to drop below the level of the receiver's sensitivity is segmentation required.[0118]
• A fixed threshold value that is located a safe margain above the receiver's sensitivity is used to determine whether to change the data segment size. If a trend in signal strength shows values falling below the threshold, the data segment size is decreased. If the threshold level is never reached, the segment size might be increased. In addition, the trend associated with a group of signal strength samples can be used to predict the optimal data packet size—the intersection of the signal strength samples with the threshold defines a segment length that, with a safe margain, can be used effectively used with the current degree of fading.[0119]
• After receiving a data segment, the receiver sends to the transmitter indications regarding: 1) whether the data segment was received without fault; and 2) what the new optimal segment size should be. The transmitter responds by adjusting the data segment size and then sending the next segment. As can be appreciated, the data segments are adapted based on the previous transmission. Instead of adjusting on the basis of the reception of a single data segment (the previous transmission), other techniques for adjustment are contemplated. For example, the transmitter may also utilize a threshold window (or weighted averaging), inside of which the segment size will not be changed. Only if the requested change by the receiver falls outside of the threshold window will the segment size change. Similarly, the receiver might also utilize such a window—only requesting a change when the newly forecasted, optimal segment size falls outside of the window.[0120]
• Direct-sequence Spread Spectrum Parameters.[0121]
• As described above, the network controller provides an interface to both the older generation UHF radio transceivers and newer generation spread spectrum transceivers. A spread spectrum broadcasting system uses a sequential pseudo-noise signal to spread a signal that is in a relatively narrow band over a wider range of frequencies. It is the subject of standards issued by the Federal Communications Commission (FCC) that provide usable spectrum at low power levels for communication in limited areas such as warehouses, office buildings, and the like. The use of spread-spectrum techniques minimizes interference with others using the same channels in the spectrum.[0122]
• A transmitter using direct-sequence spread spectrum transmission uses a spreading-code of a higher frequency than that of the data rate to encode the data to be sent. This higher frequency is achieved by increasing the chip clock rate (wherein each chip constitutes an element of the spreading-code). Using the same spreading code, the receiver decodes the received signal while ignoring minor faults which occurred in transmission, providing noise immunity and multipath signal rejection. The frequency and length of the spreading-code can be varied to offer more or less multipath signal rejection or noise immunity. Although it may result in improved communication, increasing the frequency or length of the spreading-code requires additional overhead which may not be justifiable unless necessary.[0123]
• Frequency-hopping Spread Spectrum Parameters.[0124]
• Frequency-hopping is the switching of transmission frequencies according to a sequence that is fixed or pseudo-random and that is available to both the transmitter and receiver. Adaptation to the communication environment via an exchange in frequency-hopping operating parameters is possible, for example, via selective control of the hopping rate or through the use of coding or interleaving. The greater the degree of frequency selectivity of the fading envelope (i.e., when fading is significant only over a portion of the spectrum of hopping frequencies), the greater the benefit of such adaptation.[0125]
• Particularly, a parameter indicating the hopping rate can be varied to minimize the probability that the channel characteristics will detrimentally change during the course of a communication exchange. To vary the hopping rate is to vary the length of a hopping frame. Although multiple data (or message) exchanges per hopping frame is contemplated, the preferred hopping frame consists of a single exchange of data. For example, in a polling environment, the hopping frame might consist of: 1) a base station transmitting a polling packet to a roaming terminal; 2) the roaming terminal transmitting data in response; and 3) the base station responding in turn by transmitting an acknowledge packet. Each hopping frame exchange occurs at a different pseudo-randomly chosen frequency.[0126]
• For optimization, the hop frame length is adjusted to be as long as possible, while remaining shorter than the coherence time of the channel by some safety margin. Although such adjustment does not eliminate the effects of fading, it increases the probability that the characteristics of the channel will remain consistent during each hopping frame. Thus, in the preferred embodiment, if the polling packet transmission is successfully received, the probability of successful receipt of the data (or message) and acknowledge is high.[0127]
• Another parameter for changing frequency-hopping performance is that of coding. Coding on the channel for error correction purposes can be selectively used whenever the probability of data or message loss due to fading is high. In particular, coding methods which provide burst error correction, e.g., Reed-Solomon coding, can be applied if the hop length is likely to exceed the coherence time of the channel. Such coding methods allow some portion of the data to be lost and reconstructed at the expense of a 30-50% reduction in throughput. The operating parameter for coding indicates whether coding should be used and, if so, the type of coding to be used.[0128]
• An operating parameter indicating whether interleaving should be used also helps to optimize the communication channel. Interleaving involves breaking down the data into segments which are redundantly transmitted in different hopping frames. For example, in a three segment exchange, the first and second segments are sequentially combined and sent during a first hopping frame. In a subsequent hopping frame, the second and third segments are combined and sent. Finally, the third and first segments are sequentially combined and transmitted in a third hopping frame. The receiving transceiver compares each segment received with the redundantly received segment to verify that the transmission was successful. If errors are detected, further transmissions must be made until verification is achieved. Once achieved, the transceiver reconstructs the data from the segments.[0129]
• Other methods of interleaving are also contemplated. For example, a simpler form of interleaving would be to sequentially send the data twice without segmentation on two different frequencies (i.e., on two successive hops).[0130]
• As can be appreciated, interleaving provides for a redundancy check but at the expense of data or message throughput. The interleaving parameter determines whether interleaving is to be used and, if so, the specific method of interleaving.[0131]
• In addition, any combination of the above frequency-hopping parameters might interact to define an overall operating configuration, different from what might be expected from the sum of the individual operating parameters. For example, selecting interleaving and coding, through their respective parameters, might result in a more complex communication scheme which combines segmentation and error correction in some alternate fashion.[0132]
• Source Encoding Parameters (For Narrowband Applications).[0133]
• In the United States, data communication equipment operating in the ultra-high frequency (UHF) range under conditions of frequency modulation (FM) is subject to the following limitations.[0134]
• (1) The occupied band width is sixteen kilohertz maximum with five kilohertz maximum frequency deviation.[0135]
• (2) The channel spacing is 25 kilohertz. This requires the use of highly selected filtering in the receiver to reduce the potential for interference from nearby radio equipment operating on adjacent channels.[0136]
• (3) The maximum output power is generally in the range of ten to three hundred watts. For localized operation in a fixed location, however, transmitter power output may be limited to two watts maximum, and limitations may be placed on antenna height as well. These restrictions are intended to limit system range so as to allow efficient re-use of frequencies.[0137]
• For non-return to zero (NRZ) data modulation, the highest modulating frequency is equal to one half the data rate in baud. Maximum deviation of five kilohertz may be utilized for a highest modulation frequency which is less than three kilohertz, but lower deviations are generally required for higher modulation frequencies. Thus, at a data rate of ten thousand baud, and an occupied bandwidth of sixteen kilohertz, the peak FM deviation which can be utilized for NRZ data may be three kilohertz or less.[0138]
• Considerations of cost versus performance tradeoffs are the major reason for the selection of the frequency modulation approach used in the system. The approach utilizes shaped non-return-to-zero (NRZ) data for bandwidth efficiency and non-coherent demodulation using a limiter-discriminator detector for reasonable performance at weak RF signal levels. However, the channel bandwidth constraints limit the maximum data “high” data rate that can be utilized for transmitting NRZ coded data. Significant improvements in system throughput potential can be realized within the allotted bandwidth by extending the concept of adaptively selecting data rate to include switching between source encoding methods. The preferred approach is to continue to use NRZ coding for the lower system data rate and substitute partial response (PR) encoding for the higher rate. The throughput improvements of a NRZ/PR scheme over an NRZ/NRZ implementation are obtained at the expense of additional complexity in the baseband processing circuitry. An example of a transceiver using such an approach can be found in the previously incorporated patent application of Ronald L. Mahany, U.S. Ser. No. 07/485,313, filed Feb. 26, 1990.[0139]
• Partial response encoding methods are line coding techniques which allow a potential doubling of the data rate over NRZ encoding using the same baseband bandwidth. Examples of PR encoding methods include duobinary and modified duobinary encoding. Bandwidth efficiency is improved by converting binary data into three level, or pseudo-ternary signals. Because the receiver decision circuitry must distinguish between three instead of two levels, there is a signal to noise (range) penalty for using PR encoding. In an adaptive baud rate switching system, the effects of this degradation are eliminated by appropriate selection of the baud rate switching threshold.[0140]
• Since PR encoding offers a doubling of the data rate of NRZ encoded data in the same bandwidth, one possible implementation of a NRZ/PR baud rate switching system would be a 4800/9600 bit/sec system in which the low-pass filter bandwidth is not switched. This might be desirable for example if complex low-pass filters constructed of discrete components had to be used. Use of a single filter could reduce circuit costs and printed circuit board area requirements. This approach might also be desirable if the channel bandwidth were reduced below what is currently available.[0141]
• The preferred implementation with the bandwidth available is to use PR encoding to increase the high data rate well beyond the 9600 bit/sec implementation previously described. An approach using 4800 bit/sec NRZ encoded data for the low rate thereby providing high reliability and backward compatibility with existing products, and 16K bit/sec PR encoded transmission for the high rate may be utilized. The PR encoding technique is a hybrid form similar to duobinary and several of its variants which has been devised to aid decoding, minimize the increase in hardware complexity, and provide similar performance characteristics to that of the previously described 4800/9600 bit/sec implementation. While PR encoding could potentially provide a high data rate of up to 20K bit/sec in the available channel bandwidth, 16K bit/sec is preferable because of the practical constraints imposed by oscillator temperature stability and the distortion characteristics of IF bandpass filters.[0142]
• Exchanging Parameters.[0143]
• All of the above referenced parameters must be maintained in local memory at both the transmitter and the receiver so that successful communication can occur. To change the communication environment by changing an operating parameter requires both synchronization between the transceivers and a method for recovering in case synchronization fails.[0144]
• In a preferred embodiment, if a transceiver receiving a transmission (hereinafter referred to as the “destination”) determines that an operating parameter needs to be changed, it must transmit a request for change to the transceiver sending the transmission (hereinafter the “source”). If received, the source may send an first acknowledge to the destination based on the current operating parameter. Thereafter, the source modifies its currently stored operating parameter, stores the modification, and awaits a transmission from the destination based on the newly stored operating parameter. The source may also send a “no acknowledge” message, rejecting the requested modification.[0145]
• If the first acknowledge message is received, the destination modifies its currently stored operating parameter, stores the modification, sends a verification message based on the newly stored operating parameter, and awaits a second acknowledge message from the source. If the destination does not receive the first acknowledge, the destination sends the request again. If after several attempts the first acknowledge is not received, the destination modifies the currently stored parameter, stores the modification as the new operating parameter, and, based on the new parameter, transmits a request for acknowledge. If the source has already made the operating parameter modification (i.e., the destination did not properly receive the first acknowledge message), the destination receives the request based on the new parameters and responds with a second acknowledge. After the second acknowledge is received, communication between the source and destination based on the newly stored operating parameter begins.[0146]
• If the destination does not receive either the first or the second acknowledge messages from the source after repeated requests, the destination replaces the current operating parameter with a factory preset system-default (which is also loaded upon power-up). Thereafter, using the system-default, the destination transmits repeated requests for acknowledge until receiving a response from the source. The system-default parameters preferably define the most robust configuration for communication.[0147]
• If after a time-out period the second request for acknowledge based on the newly stored operating parameters is not received, the source restores the previously modified operating parameters and listens for; a request for acknowledge. If after a further time-out period a request for acknowledge is not received, the source replaces the current operating parameter with the factory preset system-default (which is the same as that stored in the destination, and which is also loaded upon power-up). Thereafter, using the common system-default, the source listens for an acknowledge request from the destination. Once received, communication is re-established.[0148]
• Other synchronization and recovery methods are also contemplated. For example, instead of acknowledge requests originating solely from the destination, the source might also participate in such requests. Similarly, although polling is the preferred protocol for carrying out the communication exchanges described above, carrier-sense multiple-access (CSMA) or busy tone protocols might also be used.[0149]
• In addition, Appendix F provides a list of the program modules which are found in Appendix G. These modules comprise another exemplary computer program listing of the source code (“C” programming language) used by the network controllers and intelligent base transceivers of the present invention. Note that the term “AMX” found in Appendices F and G refers to the operating system software used. “AMX” is a multitasking operating system from KADAK Products, Ltd., Vancouver, B.C., Canada.[0150]
• As is evident from the description that is provided above, the implementation of the present invention can vary greatly depending upon the desired goal of the user. However, the scope of the present invention is intended to cover all variations and substitutions which are and which may become apparent from the illustrative embodiment of the present invention that is provided above, and the scope of the invention should be extended to the claimed invention and its equivalents. It is to be understood that many variations and modifications may be effected without departing from the scope of the present disclosure.[0151]

Claims (47)

What is claimed is:

1. A data communication system for collecting and communicating data using RF data signal transmission, comprising:

a first terminal having transmission and reception capability from which communication is desired;

a second terminal having transmission and reception capability to which communication from said first terminal is desired;

said first and second terminals being responsive to an operating parameter for determining and maintaining the operation of transmission and reception;

means within said second terminal that is responsive to transmissions received from said first terminal for evaluating the current data communication system;

means responsive to said evaluation means for determining whether a change in the operating parameter should be made; and

means within said first terminal that is responsive to said determination means for changing the operating parameter.

2. The data communication system of

claim 1

wherein said determination means bases its inquiry on the percentage of RF signals which have been successfully received.

3. The data communication system of

claim 1

wherein said evaluation means bases its evaluation on the signal strength of the received RF signal.

4. The data communication system of

claim 1

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means basing its determination on the signal produced by said measuring circuit.

5. The data communication system of

claim 4

wherein said evaluation means utilizes a threshold for making its evaluation.

6. The data communication system of

claim 4

wherein said determination means utilizes a threshold window for making its determination.

7. The data communication system of

claim 1

wherein said operating parameter indicates the size of data segments to be transmitted.

8. The data communication system of

claim 7

wherein said determination means bases its determination on the percentage of RF signals that have been successfully received.

9. The data communication system of

claim 7

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means bases its determination on the signal produced by said measuring circuit.

10. The data communication system of

claim 1

having spread spectrum communication capability wherein said operating parameter indicates the length of the spreading code for spread spectrum communication.

11. The data communication system of

claim 10

wherein said evaluation means bases its evaluation on the percentage of RF signals that have been successfully received.

12. The data communication system of

claim 10

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means bases its determination on the signal produced by said measuring circuit.

13. The data communication system of

claim 1

having spread spectrum communication capability wherein said operating parameter indicates the chip clock rate of the spreading code for direct-sequence spread spectrum communication.

14. The data communication system of

claim 14

wherein said determination means bases its determination on the percentage of RF signals that have been successfully received.

15. The data communication system of

claim 14

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means bases its determination on the signal produced by said measuring circuit.

16. The data communication system of

claim 1

having frequency-hopping spread spectrum communication capability wherein said operating parameter defines characteristics of frequency-hopping transmissions.

17. The data communication system of

claim 16

wherein said evaluation means bases its evaluation on the percentage of RF signals that have been successfully received.

18. The data communication system of

claim 16

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means bases its determination on the signal produced by said measuring circuit.

19. The data communication system of

claim 1

having frequency-hopping spread spectrum communication capability wherein said operating parameter indicates the hopping rate.

20. The data communication system of

claim 19

wherein said evaluation means bases its evaluation on the percentage of RF signals that have been successfully received.

21. The data communication system of

claim 19

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means bases its determination on the signal produced by said measuring circuit.

22. The data communication system of

claim 1

having frequency-hopping spread spectrum communication capability wherein said operating parameter indicates whether coding is to be used, and, if so, the type of coding.

23. The data communication system of

claim 22

wherein said evaluation means bases its evaluation on the percentage of RF signals that have been successfully received.

24. The data communication system of

claim 22

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means bases its determination on the signal produced by said measuring circuit.

25. The data communication system of

claim 1

having frequency-hopping spread spectrum communication capability wherein said operating parameter indicates whether interleaving is to be used, and, if so, the type of interleaving.

26. The data communication system of

claim 22

wherein said evaluation means bases its evaluation on the percentage of RF signals that have been successfully received.

27. The data communication system of

claim 22

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means bases its determination on the signal produced by said measuring circuit.

28. The data communication system of

claim 1

having RF source encoding wherein said operating parameter indicates the type of source encoding to be used in maintaining RF communication.

29. The data communication system of

claim 28

wherein said evaluation means bases its evaluation on the percentage of RF signals that have been successfully received.

30. The data communication system of

claim 28

wherein said evaluation means comprises a measuring circuit that produces a signal indicative of the signal strength of received RF signals, and said determination means bases its determination on the signal produced by said measuring circuit.

31. A data communication system for collecting and communicating data in the form of RF signals comprising:

a plurality of RF transceivers that store and modify a variable operating parameter;

each of said transceivers controlling the operation of transmission and reception based on the stored of parameter;

means within said transceivers for evaluating the stored parameter based on each transmission received;

means responsive to said evaluation means for determining whether the operating parameter should be modified; and

said plurality of RF transceivers responding to said determination means by storing modified operating parameters.

32. The data communication system of

claim 31

wherein said operating parameter indicates the size of data segments to be transmitted.

33. The data communication system of

claim 31

having spread spectrum communication capability wherein said operating parameter indicates the length of the spreading code for spread spectrum communication.

34. The data communication system of

claim 31

having spread spectrum communication capability wherein said operating parameter indicates the chip clock rate of the spreading code for direct-sequence spread spectrum communication.

35. The data communication system of

claim 31

having frequency-hopping spread spectrum communication capability wherein said operating parameter defines characteristics of frequency-hopping transmissions.

36. The data communication system of

claim 31

having frequency-hopping spread spectrum communication capability wherein said operating parameter indicates the hopping rate.

37. The data communication system of

claim 31

having frequency-hopping spread spectrum communication capability wherein said operating parameter indicates whether coding is to be used, and, if so, the type of coding.

38. The data communication system of

claim 31

having frequency-hopping spread spectrum communication capability wherein said operating parameter indicates whether interleaving is to be used, and, if so, the type of interleaving.

39. The data communication system of

claim 31

having RF source encoding wherein said operating parameter indicates the type of source encoding to be used in maintaining RF communication.

40. The data communication system of

claim 31

further comprising:

means within said transceivers being responsive to a series of failed communication exchanges for replacing said stored operating parameter with a system default value.

41. A data communication system for collecting and communicating data using RF data signal transmission, comprising:

a first terminal having transmission and reception capability from which communication is desired;

a second terminal having transmission and reception capability to which communication from said first terminal is desired;

said first and second terminals being responsive to an operating parameter for determining and maintaining the operation of transmission and reception;

means within said second terminal being responsive to transmissions received from said first terminal for evaluating the performance of the transmission;

means within said second terminal for determining whether a change in the operating parameter is needed, and, if so, for transmitting a request for change signal to said first terminal;

said first terminal responding to a received request for change signal by transmitting an acknowledge signal then modifying and storing the operating parameter; and

means at said second terminal responsive to the acknowledge signal for modifying and storing the operating parameter.

42. The data communication system of

claim 41

further comprising:

means at said terminals being responsive to a series of failed communication exchanges for replacing said stored operating parameter with a system default value.

43. The data communication system of

claim 42

wherein said operating parameter indicates the size of data segments to be transmitted.

44. The data communication system of

claim 42

having spread spectrum communication capability wherein said operating parameter indicates the length of the spreading code for spread spectrum communication.

45. The data communication system of

claim 42

having spread spectrum communication capability wherein said operating parameter indicates the chip clock rate of the spreading code for direct-sequence spread spectrum communication.

46. The data communication system of

claim 42

having RF source encoding wherein said operating parameter indicates the type of source encoding to be used in maintaining RF communication.

47. The data communication system of

claim 42

having frequency-hopping spread spectrum communication capability wherein said operating parameter defines characteristics of frequency-hopping transmissions.

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