CA2148381A1 - 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 (52) selectively in communication with a plurality of base transceiver units which communicate with one or two host computers (42) 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.

Description

WO 94/1077~ 2 1 ~ ~ 3 8 1 P~/US93/10~28 ~ITLE. RAD:I:O F~EQ~ ~CY CO~NICAq!:EC)~
N13!1!110~ !; IIA~I~G ;~DAP!lrIVB
C~ICA~IO~I PA~!I~

..
BP~CR~;ROIJND C)F T~B INV~TION
The present invenkion in a pref erred implementation relates to improv~ments in radio data communication networks whereill a number of mobile transceiver units are to transmit data to ~.
a n~er of base stzltions under a wide range of l0 opera~ing conditions . To compensate f or the wide range of operating con~îtion~;, adaptability has been pro~rided using an exch2a~ge of parame~ers that def ine the nature of th~ network ::ommunication . ::
- The in~entiQn is preferably to be appli~able as an 15 upgrade of an exis~ing data capture ~;ystem wherein a number of :hand-held transGei~rer units of an earli~r design are ~ alr~ady in the field representing a substantial economic: investmerlt in comparison to lthe cost of base ~tations, 2 0 accessories and components . I:n installations spread over an extensive area, a larg~ number of rnobil~ portable transcei~fer units may be employed to gather data in various places and multiple base tations ~ay be r~quired. ~ In a variety of su~h 25 ins~allations ~;uch ~ as warehouse facilitiPs, di~trlbuti~n centers, ~ and retail establishments, it m y be ~advantageou6 to utilize not only ;multiple basè capable of communic::ation with a single `host, but with mul~iple~ hosts as well.

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-- ~
SUBSTITUTE SHEET (RULE 26) Wl~ 94/1077~ 2 1 4 8 3 ~ 1 PCr/US93/1052~ .

B~aRY O:F ~H~ INvBN~rIoN
~ he present invention provides an improved data c:o~nunication system which maintain~ RF
communication links between one or more host computers and one or ~ore base tran~cei~rer units, each of which may b~ communicative with many mobile portable transceiver units being moved about a warehous~ complex for ~he collection of data. Specific:ally, ~he inven~ion provides a data communic:ation sy~;tem for collecting and communicating da~a in the form o~ RF signals which has a plurality of RF transceivers tha~ store and modify at least one variable operating parameter.
From the stored parameter ( s ), each of transceivers sontrol t~e operation of tran~;mission and receptiorl. The transceivers also e~raluate the ef f ect of the stored parameter based by analyz ing eac:h transmi~;sion r~ceived, and determine whether to make changes in the stored parameter. If changes are needed? the transceivers, modify and store the modif ied operatirlg parameter and begin operation based thereon .
:rh~ operating parameters in~volve: l) the size o~ data segments to be transmi~ted; 2 ) the length or frequency of the spreading coàe used for direct-~equencl~ spread spectrum commurlication; 3 ) the hopping rate, coding, and interleaving f or frequerlcy-hopping spread spectrum communication;
and 4 ) the type of RF source encoding us~d .

3 û , In addition ~ the RF transcei~ers us d in' t~e data communication n~twork s: f the present invention use system-de~ault ~ralues to reset the operating parame~ers if a serie~ of f ailed c:ommunication exchanges occurs, so that communication can be re-established.
It i~ therefore an object of the invention to provide an adaptive radio communication system which permits the intercormection of one or two SUBSTITUTE SHEET (RULE 26~

wo g4/l0774 2 1 ~ ~ ~ 8 1 PCT~S~3/105~8 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.
}t is a ~urther object of the invention to provide an adapti~e RF data communication system which optimizes communication based on a set of operating parameters.
It is a further ob~ect of the in~ention to ~O provide an adaptiYe RF data co~munication system which maintains communication based on a ~et of operating parameters ~or~optimazing communication, wherein the operating parameters involve: l) the siz~ of data ~agments to~be transmitted; 2) the length or frequency of the spreading code used for dire~t-sequence fipread pectrum communication; 3~
the hopping rate, ooding, and interleaYing ~or - frequency-happing 6pread 6pect~um communication;
and 4) the type of RF source encoding to be ~lsed.
, 20 It is a ~urther object of the invention to ~i provide a radio communication Bystem network . ~ contro}ler which via a communication exchange --: optimizes a set of operating parameters, yet returns the paramet~rs to t~eir ~previous or system-de~ault ~alues upon failQd com~unicat~ion.
These and other objects of the invention will . . be apparent from examination of the detailed description which f~llows.

'D~CRIPTION OF~5~ DRA~IN~ FI~R~8 ! ~ i : 30 Fi~ure 1 is a block diagram of the prior art data communication system.
Figure 2 is a perspectiYe ~iew of the inven~ion.~ ~
Figure 3 is a s~hematic representation of an ~ : : 35 exempIary radio communication ystem utilizing ~he : : invention. ~:

:~ ~ SUBSTITUTE SHEET(RULE 26) :

4 ~ s~ P~T/US93/1O~Z8 2 1~'83`81 4 Figure ~ is a diagrammatic illustration of the control circuitry elements of the invention.
Figure 5 i5 a rear elevation view of the invention.
Figure 6 is a diagrammatic illustration of the application spe~ific integrated circuit of the ;;
invention. ,`.
Figure 7 is a block diagram showing an I ex~mplary implementation of intelligent network and router transceiver units such as the network tra~sceiver uni~s of Fisure 3.
Figure 8 is a diagram of an RF ~y~tem utilizing a network controller according to Figures 2-~, with nne of its network ports confi~ured for commun~cation with a second host, and another of its ports coupled with a multiplicity of RF transceivers via an adapter u~it~
Figure 9 is a diagram illu~trating the use of two network controllers according to Figures 2-6, configured for dual ho~t computers each, and having their relatively high data rate extended distance network port~ coupled with a multiplicity o~ intelligent network and router transceiver :~
units implemented according to Figure 7.
~i~ure 10 is a diagram similar to Figure 9 but ~howing the paxi of coupled network ~:
controllers interfaced to a common relatively high --.
data rate sy~tem having multiple hosts le q.) a ~ 30 ~ocal ~area network o~ ~he E~hernet type or ; equivalent ~g~ fi~r optic type.
Figure ll is a diagram similar to Figure 10 but indicating the netwQrk controllers being c~upled to re~pectlve diff~rent high data rate multiple host sys~ems (e.q., token ring type local :.
area networ~s or other indi~idual networks e.g~, fiber optic loop networks of thP collision-sense multiple-access type)~- -- SllBSTITlJTE SHEET (RULE 2S) ~V094/1~774 21~ PCr/U~93/11)528 Figure 12 is a viaw similar to Figure 9 but intended to diagrammatically ir.dicate a distribution of network and router transcei~ers and oth~r elements c~f an on-line RF da~a colll3ction system over an extensive area o~ a f acility ~ of one o~ the type~; previc~usly mentioned O
Figure 13 show~; an intelligent control ler and radio base unit which unifi~s controller and radio rompon~nts such as sho~n in Figure 7 illtO a single housing of the size represented in Figures 2 and 5.
Figure 14 shows a diagrammatic illustration of the signal proce~;sing for two of four paiis of communication ports of~ the multiple bas~ adapter of the RF da~a collection system illustrated in Figure 8.
Figure 15 is a diagram of parts of an RF data collection sys1:em utilizing a network c:ontroller according to Figures 2-6 ~ and a multiple bas~
adapter according to Figure 14, with eight ba~;e transceiver units coupled to the multiple base adapter ~

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D~TA~ED lD~ RIP~IO~ OF q!:E~E~I~V~NTION
Figur~ 1 shows an existing ~adio frequency data tranqmission system 10 wherein a ~se sta~ion t~ansceiver means îl has a number of mobile transceiYer units suoh as 12A, 12B , . . ., 12N in radio c~immunication therewith.
By~ way of example, the base station may be compri~ed of a radio base unit 14 ~;uch as the ~: ~model RB3021 of Norand Corpoxation, ~Cedar Rapids, Iowa, whic:h forms part of ~ a produet family know~
: as the RT3210 system. In this c:ase, the r~dio base 14: may recei~e data from ~he respective mobile;RF te:rminals, e.g. of ~ type RT3210, and transmit the received data ~ via a network SUBSTlTUTE SHEET (RULE 26) : : ~: : :

W~ 94/10774 2, 1 48 ~3 8~ 1 P~r/V~93/1~5~8 .t ~
. 6 coIItroller and a communications link 16 ( e . g .
utilizing an RS-232 format) to a host computer 17.
The data capture terminals 12A , 12B , . . ., 12N
may each be provided with a keyboard such as 18, a di E;play as at 19, and a bar code scanning capability~
Figure 2 provides a perspectiv~ view of the inventi~n 4 0 in the pref erred embodiment case 2 0 .
Front pan21 2 2 is provided with display 2 4 and selec:t key ~, up key ~8 and down key 30. Power indicator 32 comprises a low power green light emittirlg diode which is energized wh2n power is supplied to the invention lO. Error condition indicator 34 is a yellow LED which is software controlled to be ener~ized i~ the invention 10 is in error coTI~ition.
Figure 3 discloses a diagrammati ::
illustratioll of a radio com~unication system in : accordance with the pre~ent invention. Invention 2 0 networ}c controller 4 0 is coupled to host computer 4 2 ~uch that data may b~ interchanged batween the . device~; ov~r host communications link 44, which . may be either in ~ an RS232C forma~ or selectively in an RS422 fo~at. The host communication link 44 couples to c:ontroll~r 40 a~ host port 46~
First co~munication port 48 of controll~r 40 provides ~ means fox coupling of ne~work S0 to contxoller 40. Network 50 cc:mprises a mlmber of ba~ RF ~ransceiver units 52A, 52B and 53B, ~ach 3 0 c~f which may be selsctively employed irl the radio frequency communi~ation of data ~rom mo}: ile trarlsceiver uni~s. It is to be understood that base transceivar lmits 52 are dei,igned and equipped to be operable in the exchange of data with; network c:ontrGller 40 over network link 56 such that ~ach base transceiver unit 52A, 52B, or 53C may independerltly ~ixchange data with networX
conl:roller 40 through first communication port ~8.

W094/l0774 2 1 ~ 8 3 ~ 1 PCT/y~93/l0528 When first communication port 48 is int~nded for operation with a network such as network 50 of base transceiver units s2A, 52~ and 53C, for example, network controller 40 is se1ective1y operatod to pr~vide an RS485 inkerface at first communication port;4~.: First c~mmunication port 48 ~ay be a1ternat~1y se1ected to opera~e as an RS232C interface, as an RS422 interface, as a proprietary NORAND~ Radio Qne N~de Network int~rface or as a high speed V.35 interface. The se1ection of interface to be provided at first communication port 48 is front panel~ controlled, that is, the user may oper~te front panel keys 28, 30 and 26 (See Fiyure ~2~to direct the proper int~rface to be provi~ed at fir~t communication :: port 48.
: Base transceiver units 52A, 52B, a~d 52C are coup1ed to network link 56:by serial m~ans, rather .
~: : than para1lel~ means, `and .ea~h may;be caused to transmit or to recei~e:independentl-~ from the ~.
others:while~àdditionally~being communicative~with ~ - ~
. ~ ~ network controlIer 40::~in :a random1y chosen `:
~ fashion.
: ~ : : It;is ~urther~to be~understood that~in~erface ~ -25~ translati~n is~provided with~in~;controller 40 fiuCh ~ that:data~communicated at first~co~munication por~
;~ : 48~may~be~ directed to:~host~42~;at port~46 via~
proper:1y chosen~interfac~ means~:as~is~r~quired~by ~ : : .' : the host 4~2~with which communication is intended.
~1 ~`:Like first communication~port :`~8, ~second'` .
co unication~por~57;~may~be:;internally~6witched~
among~inter~ace~ choices~:~of ~h~se~ypes:. RS232C~, .35~ Rs4~g5~an~propri~e~ary NORAND~ Badio~
One~ Node~ Nètwork~interfaae.~ In the :i11ustrated~
35~ ;arrang~men~ ;of~:Fi~gure~ 3~ o~ ~example, ~second~
communication~:port~57~ is ~coupled over thi~d 1ink 53 to previously~lnstalled base transceiver 54, S~ which heretofore~had~been used:in a prior art~

WO 94/~0774 ~ ; 2;1 4`8 3 8 1 P~rtU~S93/105~8 system as is illustrated in Figure l. Because of :Limitations of base trarlsceiver 54, it must communicate Yia RS232C interface format and therefor~3, second communication port 57 mus~ be 5 se1 ~cted to operate in RS232C interface mode .
However, when second communication port 57 is desired to communicate with a network ~ria RS485 interface, front pan~l keys 26, 28 and 30 may be manipuiat~d by the user tct pro~ride the RS4 8 5 lû int2rface availability at sec:ond communication poxt 570 IJikewise, second coI~ununicativn port 57 may be selected to operate as an RS4 2 2 interf ace, as a V.25 interface, or as the propriet ry NO~AND~ :
Radio One Node Network interf ace .
Diagno~tic port ~ 55 provid~s a f ourth cc~mmunicatioIl pathway f or network ::ontroller 4 0, providing an async:hronous port operable at 3 o0 to 19, 200 baud as an RS232C interface . When d~sirable, diagnostic port 55 may be couplsd by diagnostic lin)c 58 to diagnostic device 60 for purposes of error diagnosis of corltroller 40 by diagnostic device 60, or for reprogramming of memory devices within controller 40 when desired.
It is co~templated that diagnos1:ic device ~0 comprises a 16 or 32 bit microproce~sor commonly known as a personal computer or "PC". ~he mode of coupling between diagnostic: device 60 and network controller 4 0 may be direc~ or through remote means by use of a modem~ :
i j ~ R~ferring now to Figure 4, a~ cer~tral proc:e~ing unit 70 is pro~rided wilth at least four data communication ports, illustrated at num~rals 71t 72, 73, and 74. First data cs:mmuilic:a ion port 71 may be selectively coupled to RS232 interIa ::e membar 76 or~VO35 interface msmber 780 The choice of whether :E~S232 interface member 76 or V. 35 interf~cQ member 78 is chosen i~ dependent upon the opera~ing characteristics presented by the .
T} ''T~ T (~ r;~

WO94~10774 '21 ~ 83 PCTtlVS93/10~28 9 ..
host computer, such a~ host ~omputer 4Z of Figure 3, with which network controller 40 will communicate, The choice of whether first ~;
commUnication port 71 is coupled ~o interface member 76 or ~o interface member 78 depends on the front panel s~lection made by the user by keys 26, 28~ and 30 shown in Figure 2. :
Second communication port 72 may be selectively coupled to RS232 membPr 80 or to RS485 I 10 interPace memb~r 8~ or to RS422 interface member j . 84 or to NOR~ND~ Radio One Node N~twork .;
I proprietary interface member 86. By use of front panel keys 2~, 28, and 30 o~ Figure 2, the user may select ~econ~ communica~ion port 72 'to be .
1~5 coupled to any one of~interface me~b~rs 80, 82, 84/ and 86.
: Third communication~ port 73 is ide~tical to ~ ~ second~ communica~ion port 72 in functionality, : : ~ being ~electively couplable to RS232 interface ~ 20 member 8~, to RS485 in~erface member ~0, to~RS422 .`
: ~ inter~ace member ~2::or to:NORAND~ Radio One Node ~ -; ~ Network proprietary interface member ~4. -~
: : ,~ In~the~pre~erred~embodiment of the inventiOn :~ ~ 40, central proces irlg unit ~70 of ~Figure ~ 4 :Z5 ~comprises; d~ Motorolan'~ ~68302 ~ integrated chip : cooperative with I an: application ~ æpècific integrated ~circuit. ~entral prace~sin~ ~unit 7 0 employs novel features allowing-the bidirectiona~ ~ :
~ ~ use of ~~a data co~municative ~line~of the ~o~orola~:~ ~ 3 0 '68302 c:hip and a singlei clock: signal line to `~
~ ~ ~ eliminate~the need ~or coder-decoder~members to be : ~ associated w~ th~ ~ the ~ N~torola~ : 683 Q2 : chip:~; while:
::~ ~ : allowing the~use oiE only c: ne pair of signal wir:~s to be::;coup~led to~:the RS4~8S ~interfaces 82 and 90~ of 3 5 ~ Fi~ure ~4 Fourth ~ communication port 74 of ~: central : ;~
processing unit is coupled to a~ynchronou~: RS23 SUBSTI~UrE SI~E~T (RULE 263 ~ :

~ir ~ ~r .\~

W094/10774 ~ 1~ 8 3 8 1 PCT/US93/105~8 , 10 inter~ace member 97 to be avallable for interconnection of a diagnostic device therewith.
Also coupled to central processing unit 70 are display member 24 and keyboard member 31 with which keys 26, 28, and 30 of front panel 22 (Figure 2) are interactiv~
Memory alements including EPRO~ element 96, DRAM u~it 98, FLASH memory unit 100 and EEPROM
element ~02 are intercoupled with each other and with central processing unit 7a.
Power supply member 104 is selecti~ely attachable to invention network controller ~0. In order to avQid the necessity of different models . of network controller 40 depending on the local electr~cal power ~ utility's operating characteristics, power ~upply 104 is provided in optional model~ depending on the country in which .i it is to be used, power supply 104 being eapable of providing ~atisfactory output power to network controller 40 regardless of the ~oltage or frequency of thP input source provided to power ; I s~pply 104. ~:
The application speci~ic integrated circui. :~
tASIC) us~d in the inventio~ n~twork controller 40 is disclo~ed in Fi ~re 6 and is identified by ~he num~ral: 12C. ~SIC 120 comprise~ a central . processor unit interface 122 member which is coupled to the central processor unit bus by CPU
bus link 124 which extends from ASIC 120, Also ' 30 coupled to t~e CPU bus link 124 is dynamic ~andom acc~ss memory (~RAMj timing element 126, which provides network controller 40 with timin~ signals for the DRAM member 98 illustrated in Fiqure 4 when m~mory refresh of the DRAM ~8 is indicated.
DRAM timing elemen~ 126 is also coupled exteriorly to khe ASIC 120 to DRAM member 98 by DR~M link 127.
:

., , ~ t~f~ t ~

W~4/10774 2 1 ~ 8 3 8;~ PCT/US93/1~528 ._.~) .
11 .
Central proc~ssing unit interface 122 is coupled to a~ynchronous signal processing ~lement 128 by signal path 130. ~s~nchronous signal prvce~sing element 128 co~prisas a ~aud rate ~.
generator cooperative with a univer~al as~nchronous receiver-transmitter.
Also coupled to central processing unit .-inter~ace 122 i~ network clock and control member :~
132 w~ich compris~s a~programmable net~ork clock gen~rator which can be selectively programmed to generat~ an op~ional clock speed:for~a network to be coupled through RS485 interfaces ~2 and 90 seen :~
in Figure 4. Network clock~and contxol member 132 ; also provides detection ~eans for detections of failure conditions ~n a~ linked network! and provides control signals to system components in respo~se thereto, including interrupt signal~ to programmable interrupt coordinator circuitry included in~ ~entral prooess$ng interface 122.
Network clocX and controller member 132 provides data encoding by the F~O standard, then the : : encoded data may ~e opera~ed upon by RS485 ; interfa~es 82 and 84 and transmitted and received :
by single twisted pair means o multiple serially networked: bass tra~sceiver units exemplified ~y ~:: 1 : ;base ;~ transceiver unit ~52A, 52B, and 52C~
~ :illustrated in~Figure 3. ~ ~ è
:~ . ~ : Keyboard con~roller element 134 is coupled to central:processing uni~ interface and provides a:
3 0 ~ink exterior to ASI~ 120 to~eyboard 31 (See Figure~3~
FLASH m2mory/EEPRO~ logio control member 136 :
is coupled~to cen~ral processing uni~ in~erface : 122 and ~comprises~dontrol functions for FLASH
35 ~ memory elem~nt lO0 and EEPROM memory element 102 of Figur~ 3.~
, :
7 g~ T' 5 ~

W094/10774 2 1 ~ 8 3 8 1 PCT/US93/10528 Central processing unit interface 1~2 is also coupled by line 13~ to latches exterior to ASIC
120.
It is to be understood that the base :l 5 transcei~er units 52A, 52B, and 5~C illustrated in Figure 3 are communicative with mobile transceiver units by ~lectromagnetic radio mea~s. The mobile transceiver units may be associated with bar code scanning devic~ such as the: NORAND~ 20/20 High Performance Bar ode Reader whereby the scanning device~ ~can an object having a bar codP
associated therewith and collect information stored in the bar code, which information is then . transmitted through the mobile tran~ceiver units . 15 to base transceiver uni~s such as base transc~iver units 52A, 52B, and 52C or base tran~ceiver unit 54 of Figure 3. Th~ bar code data received by - said base transc2iver units i6 then transmitted in the example of Figure 3~ o~er network 5~ by base transceiver units 52A, 52B, or 52C, or over link 53 by base transceiver unit 54, to network . contro~ler 40 which performs the routing and :`, delivery: of the data ~to the ~tationary data : processor, or processors, such as shown for example, by host ~2 of Figure 3~ ;

~: De~L~hrouah 11 Figure 7 ~hows : a block diagram of ~.
particularly pr~ferred intelligent base transceiver unit known as ~he ~B4000. It will be observ~d that the oomponents ~orrespond with components o~ the:n~twork controll~r of Fiyure 4, :
and~similar reference numerals (preceded by 7-) :: have: been~ applied in Fi~re 7 . Thus, the :; significanc~ of components 7-70 through 7~73, 7-:
: ~ : : :: .

- :
5 3BSTITUTE S~IEET (R~LF ~) W094/10774 21 ~8~8f pCT/US93/10528 76, 7-82, 7-9~, 7-98, 7-100 and 7-104 will be apparent from the preceding de~cription with respect to Figure 4 and 6, for example. I/O bus 700 may be c~upl~d with a spread spectrum S transmission (S5T) or ultra high frequency (UHF) transceiver 701 which may correspond with any of the transcei~ers of units 52~, 52B, 52C or 54 previously referred to. The network controller 70 ~ould have a similar RF transcei~er coupled with its data port 72 or 73 and controlled via input/output bus 400, e g. for direc~ RF ~oupling with router transceiver6 such as 901, 901, Figure . 9^ ....
Referring to Figure 8, a network controller 40 is shown with:port 71 configured ~or interfac~
: wlth a ho6t port typ~ SNA ~. 35 5~K/64K bits per ,'r,:' . second. Port 72 is shown as con~igured for . communic~tion with a personal compu~er of the P5/2 type operating asynchronously at 38.~R bits per ; 20 second, Port 74 is co~p~ed with a mod~m 8-~0 : providing for r~mote diagnostics and reprogramming of the network controller 40.
Port 73 of network controller 40 is shown as being connected with: an adapter component 801 .~` 25 kno~ as Norand Corporation MBA30000 In the : operating mode i~dicated in ~igure 8, the adapter 801 serves to couple ontroller 40 5equentlally with four radio base tran~ceiver units uch as indieated at 811 through 814. Compone.~t 811 is a :
SUBSTITIJT~ SitEET (RUL~ 26) ' I W09~10774 ; 2 1 4 ~ ~ 8 1 P~T/yS93/10528 I commercially a~ailable radio base known as the RB3021 of Norand Corporation. Base station 811 may co~municate with a multiplicity of hand-held RF data te~minals such as indicated at 821. Base 814 is indicated as being coupled with the adaptor 80~ via RF broadband modems 831 and ~3~ Base units 813 ahd 814 may communicate with mobile transaeiver units such as those indicated at 833 .and 834.
Figure 9 ~hows two network controllers 40A
and 4OB each with i~s host ports configured as with the controller 40 of ~Figure 8. In this : ~ example~ the second ports 72 of the controllers . 40A and 40B are confi~ured for communic~tion a relativ~ly high data rate rel~tively along a distance netvork channel 56 which may have the j characteri~tics o~ the serial channel 56 of Figure .. 3, for example, an RS485 channel operating at 384 kilobits ~er second (334K bps). Network base : ~ ; 20 transceivers 52A, 52B:and 52C may correspond with the~correspo~ndingly n ~ ered transiceiver~units of Figure 3, for example, and`the network may have , ~ a~ditional network~transceivers such ag 52D.
Furthermore, the network~transceivers may have~RF
coupling with router~transceiver uni~s such as indicated at 901, 902 and:903. Router transceiver ; unit 302 is:illustrated as a RB4000 intelligent transceiver such as represented in Figure 7 ~nd SUBSTITUT~ SHEET (R~LE 26) ~ .
~ ; ~

21 ~S381 :
WO9~/1077~ P~TJUS93J10528 .

~:
having its input/output bus 700 coupled with a peripheral~ ;:
Figure 10 is entirely similar to Figure 9, for example, except that ports 72 of the controllers 40A and 40B are coupled with separat serYal type high data rate network channels, and .~.
ports 73 of theirespectiveinetwork controllers are `~
coupled to a very high ipeed network e.~. in the several megabi~s per second range such ~s an Ethernet local area nekwork 1000. Suitable interfaces are indicat~d at 1001 and 1002.
Figure 11 i& entirely~similar to Figure 9 ~^
except :tha~ the ports 73 of the network ~`
. controllers ~ 40A and 40B ~are eoupled with respective local ar~a ring:type networks which may .-be separate fro~each other and each have two or . more ho&ts such as ~repre~ented in Fi~re 9 associated with the~respective ring networks &uch as token rings llOOA and 1100B. Suitable interface means are~indicated~at 1101 and 1102.

Descr~E~ion of Fi~re 12 Flgure~12 shows, for example, two network : controllers 40A~and 40B, each with two host ; computer units such as 42 lA. Host 42-2A i shown with~a printer or~ other perîpheral P1 ~hich may .' generate bar code&:, for exampley for replacement ~ of damaged bar codes or the liki. Another printer ;~ P2 i& &hown a& ociated with base 52C, again for SUBSTITUTE SHEET (R~LE 26~ -example, for producing bar code labels where those are needed in the vicinity of a ba~e stationO In a large warehouso, relatively large distances may be involved for a worker to return to a printer such as Pl ~o o~tain a new bar ~ode label. Thus, it may~e very advan~ageous to provide a printer P2 at the base stati~n 52C which may be relatively close to a processing location which requires printed labels, e ~. a:processing location in the ~icinity of hand~held terminal 12-2 in Figure 12.
A base S2F may have a peripheral P3 assoc;iated therewith such as a l~rge screen display, a printer or the like which may supplemen~ the .
: capabilities of a hand-held terminal, for example printing out new bar code labels at a convenient :~
location, or providing:a full scxeen display, rather ~han the more limited screen display area of the hand-held terminal ~12-2r -: If, for example, a base radio 52D which might ~ b located at the ~eiling level of a warehouse ; became inoperative at a time when qualified repair p2rsonnel~were not i~ ediately available, with the pres~nt~system it would be feasible to provlde a : substitute base radio or base radiost f~r exa~ple,; 25 as indicated at 5~Dl l~cated at ta~le level or the .: . : ~ ~
like.
: : With~: the present system, the base radio : stations ~ do not necessarily forward data co~munications received from a ~iven terminal to ~:; :
~: - SUBSTITUTE SHEET (RULE 26) WO~/l0774 2 1 ~ ~ 3 8 1 PcT/us93~los28 a particular host. For example, hand-held terminal 12-2 may request a path to printer P~, and such a path may be created via base ~tations 52Dl and 52C. Station 52C upon receipt o~ the me~sage form terminal 1~ 2 would not transmit the message to a hos~ but would, for example, produce the desired bar code label by means of printer P2.
Furthar, terminal 12-2 may have provi~ion for digitizing a voice message which might, for example, be addressed to terminal 12-1. The sy~tem as illustrated would be operable to automatica11y establish a suitabl~ path for example, ~ia stations 52D1, 52C, 52B, 52E and 1~-1 for the transmis~ion of this voice message in digita} form. 5uccessive ~egments of such a voice message would be ~tored~ ~or example, by the terminal 12-l, and when the complete message was assAmbled, the ~gmen~s would be synthesized into ~ continuouæ voice mes~age for the user of termin~ 1 ~ by m2ans of a speaker 1201 also useful ~or send~ng tone signals indicating valid bar code read, etc.
In accordance with the~present in~ention, a hardware system such a~ illustrated in Figure 12 may be physically laid out and ~hen upon ~uitable command to one of the network controllers ~uch as 42~2B, the entixe system would be progressively automatically sel~-confi ~ red for efficient operation. For example, controller 4OB could - SUBSTITllTE SHEET (RULE 26) W~94/1~774 ~1 4 8 3 8 1 PCT/US93/10528 successively try its communications options with it~ output ports such as 71-73, determining for example, that host processors were coupled with ports 71 and 72, one operating on a 38.4 kilobit per second asynchronous basis and the other pr~senting a SNA port for the V.35 protocol at 64 kilobits per:se~ondO For example, on host, 42-lB
might be a main ~rame computer, while the other host 42-2B migh~ be a PS/2 type computer system.
The controller 40B having thus automatically configured itself ~o as to:be compatible with the devices connected to ports 71 and 72~ could proceed to transmit via~port 73 a su1table in~uiry message to the network cha~nel 56. Althouyh a ~polli~g protocol is preferred, each of the base stations could operatej for example, on a carrier-~ ~ ~ sense multiple-access !CSMA) basis or using a busy : tone protocol to respond to the in~uiry message from the controller ~OB, until each of the ; 20 successive bases on the network had responded and identi~ied~itself. Each base, for example, would have a respective unigue address identification which it could transmit in response to the inquiry :
~:~ message :50 as to es~ablish its presence on~ the :~
network.
The controller~40B could then tran~mit auto configure commands to the successiYe bases in turn, instructing the bases to det~rmine what :~
: peripherals and router bases such as 52D1, 52E and SUBSTITUTE SHEET (RULE 26) WO 94/~0774 . 21 ~ ~ 3 8 I PCr/U93/10528 19 ~:
52F were within the range o~ such base~ and to report back to the controller. For example, bases such as 52C and 52F could determine the nature of peripherals P2 and P3 associated therewith so as 5 to be able to re~:pond to an inquiry f orm a terminal such as 12-2 ts:~ advise the terminal that a b~ar ccde printer, for example, was within direct RF range.
In the case of a breakdown of a component of 10 the system such a~ 52D, it would merely be necessary to place a router device such as 52Dl at a convenient location and acti~rate ~he unit, wh~reupon the unit could send out its own bxoadcast inquiry which, for example, could be 15 answered by the base ~;tations 52C and 52F, station 52C in turn, advising a relevant host or hosts of the ac:tivation of a substitute router station.
Thus, lthe sys~em is corlveni~ntly re-self-configured without the nece~sity for a technician 20 familiar with the particular configuration procedure. As another example, where the base stations are operating utilizing spread spec:trum transmission, the introduction of barriers ( s~ach as a ~ new stack of inventory goods) to suc:h 25 transmis~io3l between a given base such as 52A and various terminals, could result in the base 52A
contac:ting roulter 52E, for example~ with a requ~st to become active with respect to the blocked terminals. ~:

r~ T t~in;i ' , ~;~~3,~

WO94/1077~ 2 1 4 8 3 8 1 pi~T/ys93/lo528 Description of Fi~ure 13 Figure 13 shows an intelligent integrated controller and radio base unit 1300 which is integrated into a single housing or case 1301 corresponding to the case or housing 20 of Figure 2. the housing 1301 may be pr~vided with an external antenna as diagrammatically indicated at 1302 with suitable RF: coupling to the radio circuitry indioated at 1303. Components 13-70 through 13-74, 13-76, }3-78, 13-96, 13-97, 13-98, 13-100, and 13-1~2 may oorrespond withi the : correspondingly numbered components described with ; reference to Figure 4.
::
SUPPLEMENTARY DISCUSSION
In accordance with the present disclosure, a network contro1ler, ~ or : integrated network contro1ler and radio~ unit`is;coupled to one or more host computers via`~ standard interface such as commonly encountered in practice (e.q. ~S232, . .
; 20 V. 35, Ethernet, ~oken ring, FDDI,:and so on). In this way, no specialized intérface or adapter is re'quired for the host.
` Since the preferred network cantri~ller can connect to two hosts,: if one h~st i~ detected to have failed, or in the event of a system crash, loss of commùnication link, or the like, the : network contrQller can automatically switch to the : : . ~
second~host. ~ The second host may be a truly~

SUBSTITUTE SHEET (RULE 26) :
..

W094/10774 21~33 Pcr/us93/

redundant syste~r or may bP a simpler computer of the PC type (a so~called personal computer) that can 8imply store transactions until the main host is restored~ As ~nother example, a single host may ha~e a second port coupled to a second port of the controller especially if a CnmmunicatiQn link failure may be a problem. For examp}e, two ports of the network controller may be coupled ~y separate modems with separate phone lines, leading to separate ports of a sing~e 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 th~ IBM3090.
The disclosed network controller can al50 connect one radio network to two hosts using RS232 or V.35 ports vr to many host~ using a local area network uch as Ethernet, token ring, or FDDI. A
number of the disclosed network controllers (for example, up to thirty-two) can be connected kogether 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.
For example where Qn~ port of the disclosed : network controller is coupled via its ~S232 interface to a mainframe computer such as the IBM3090, another of its ports may be coupled via : an FDDI network with a super computer ~ ~ the u-r~ r~

WO94/10774 2 1 ~;8 3 8 1 PCT/US93/1052~

Cray X-MP. Then mobile and/or portable terminals can access eithe~ the main frame or the super computçr J or in general, ~ny of the hosts that are connected to the networX controller.
As indicated in Figure 9, four hosts can be on one network. Referring to Figures 10 and 11, a multiplicity of hosts may be coupled with each local area network so as to be in co~munication with one or more of the disclosed network controllers. Furthe~more, a single disclosed network contr~ller can control two radio networks such as the one indicated at 50 in Figure 3.
Where each network such as 50 is limited to thirty-two devices, the number of devices is : 15 doubled with the use of two radio networks. Two : such radio networks may also be utilized for the ~ sake o~ r~dundancy, with a provision for automatic switch-over from one radio network to the second if a~pro~lem develops on thP first. ~wo radio , .
~0 networks may also facilitate the use of different ~: radio technologies in-one ins~allation.
~.
The various multi-drop local area networks referrèd to herein, for example at 7-82 in Figure ~; 7 and as ~represented at 56, 56~, 56B, Figures 9 through 12, and at:13~ in Figure 13 may comprise HDL~ based local area networks operating at up to :~
2.S megabits ~ per secon~ and using biphase space ancoding (F~O3 for clock recovery from data.
.
-:::: : :
SUF~`~3Ti~r- S~ T ~ULE ~v) W~94/10774 ~ PCT/US93/10528 The component~ 86 and 94, Figure 4, and component 13~ igure 13, provides a low-cos~
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 ~he radio to the controller. The third twisted pair is also RS422 and is used to communicate from thP controller to the radio transceiver to effect mode selection.
An aspect of the invention resides in the provision of a network controller having port means selectively configurable for couplin~ in first mode with network RF transcei~er units at a relatively high data rate such as l00 kilobits per second or higher, and for coupling in a second mode with network transceiver units at a -., relatively low :data rat~ such as ab~ut twenty kilobits per second. Preferably a single port -:
means such as 2, 3, or 5, 6, Figure 5, can be so~tware configured to inter ace selectively in the first mode or in the second mode. It is preisently ~less expensive to ` use mult~ple ., : connectors per port rathe~ than a single 37~pin :~
.
connector~for exampIe.
Where: :a network controller such as 40 operates two bigh data rate netw~rks, for examp~e, one network of RF base transceivers could operate with the RTC protocoI, and the second network SllBS~ITlJTE SHEET ~RULE 26) W094/~0774 Z~ 81 PCT/US93/105 8 co~ld operate according to a different protocol.
It will be apparent that many modifications and variati~ns may be effected without departing from the scope of t~e teachings and concept of the present disclosure.

De~criptiQn of_Fiqures 14 and 15 : ~ Figure 14 is a block diagram of the circuitry for one pair of ~ommunication:ports 1401 and 1403 o~ adapter ~01:(fig.:8) for use in coupling to base transceiver u~its. Three additional pairs of communication parts for c~upling to six additional base transceiver~ un~its are provided in the mbodim~nt of adapter 801 a~ :exemplified by the Norand Corporation MBA3000 Multiple Base Adapter.
: : : ~
: 15 It is to be understood that ~he:circuit components ~ coupled to each additional pair o~ communication . ~ ~
ports of~adapter 801 is ~identical to that shown .`
for first port pair lA/:lA,;that is ports 1401 and 1403 of Figure;14.: The adapter 801 provides means ~Por connecting the controller 40 (Fig. 8)` at its:~
port 73 to a multiplicity of radio base uni~s : illus~rated in Fig.~8~as, for~example, 811, 812,`
813,~ 814,~ including;in selected pairsO~ In the preferred~embodiment:o~adapter ~01, up to eight :
radi~ ba6e~ unit6 may~be coupled ~hrou~h use of ; adapter ~801~ to~a;n2twork controller 40, to be : controlled ~by controller 40 in seIected pair~
the~eof. The contraller 40 may control the radio SUBSTlTUTE SHFET (RULE`~) W094/l0774 ~ ~ PCr/US93/10528 base units such as 811, 812, 813, 81~, (Fig. 8) in simulcast mode, that is, with all base radios interrogating mobile transceiver units such as 821, 833, and 834 of Fig. 3 simultaneously, or with the base units being employed in pairs to interrogate the mobile transceiver units.
¦ Referring again to Figure 14, the network controller 40 pro~ides transmit data and baud rate select sig~als to adapter 801. Within adapter 801, the controller outputs are converted to TTL
levels by TTL converter 14~2 and they are then provi~ed to buffer 1404 which provides the signals to paired RS232 transceivers 1406 and 1408, and to paired RS422 transceivers 1410 and 1412 which deliver the conver~ed ~ignals to ports 1401 and 1403 respe~tively. By this means, the ..
controll~r'~ DUtpUt signals are provided to a pair of output ports 1401 and 1403 in both RS232 and RS422 in~erface at the same time. An additional three output-port-pairs are provided which may be denominated 2A/2B, 3A/3B and 4A/4B, which ports are controlled and operated identically to ports lAllB identified in Fig. 14 as ports 1401 and 1402. The ~5232 transceivers 1406 and 1408 and , ~ 25 RS422 transceivers l410 and 1412 and ports 1401 I and 1403 are illustrati~e of all circuitry coupledi to port pairs of adapter 801.

Similarly, signals provided to adapter 801 by b~se radios coupled to the output port pairs, W094/10774 ~ 8 3 8 1 PCT/~S93/lQ~2g ports 1401 and 1403 of Fig. 14, are first cs:~nverted to TTL levels by the RS232 transceivers 1406 and 1408 or by the RS422 transceivers 1410 and 1412, depending upon which interface is presented by a pair of base radlos at port 1401 ;~
and 1403. The signals provided to adapter 80~ are then forwarded by the transceivers 1406 and 1408 or 1410 and l412 at TT~ levels to controller 40t A selection unit 1414 provides a push-to-talk selec~ion signal to the RS232 t~ansceivers 1406 and 1408 and to the RS422 transceivers 141q and . . .i .
1412 to provide PTT select-ion signals at ports 1401 and 1403 in both R523~ and RS422 format. It is to be und~erstood that similar selection units 1S ~ are ~associaCod with remaining port~ pairs 2Aj2B, 3A/3B~ 4~/4B so that the ports may be independently~operated.
The àdapter~ 801~of Fig.8 is exemplified by the NBA3000~ mu~ltiple~ base adapter ~ unit 20~ manufactured~by~the NORAND~Corporation of~Cedar Rapids,~;Iowa. ~Because of the operation of the MBA3000 multiple base adapter by dual method~ in ; eith~r R5232 or RS422 signal énvironments, the MBA3000~ may~be incorporated~into 6ystems having 25 ~ exi~ting~in~tà~lled base radios whlch present only an~R5232~interface or~it may~be incorporated into systems~having base~radios some~of which operate at RS~22~and some at RS232.

5~^3TlT'JTE9'~ R'JLE7~

W094/l077~ 2~33 PCT/US93/105~8 Fig. 15 illustrates a preferred arrangement of controller 40 and adapter 801 when used in an environment with multiple base radios in multiple warehouse environments~ Controller 40 is coupled to adapter 801 which is coupled to paired bases 1511, 1512; 1513, 1514; 1515, 1516; and 1517, 1518, which are located in warehouses 1501, 1502, 1503 and 1504~ By geographical separation in warehouse l501, for example, base radios 1511 and 1513 provide subskantial coverage of warehouse 1501 such tha~ a mobile transceiver beiny iused ~ithin warehouse 1501 would be communicate~ with b~ either base radio 1511 or 1513, By the u5e of adapter 801, controller 40 may cause interrogation simultaneously by base radios 1511, 1512, 1513, 1514, 1515, 1516, 1517, 1718, or it may cause .
sequential interrogation by radio pairs lSll/1512, 1513/15l4, 1515/1516, or 1517/1518 in successionO
When a mobil~ transceiver re~pon~s by RF
communication means with a base radio, e.q. base radio 1511, the response is transmitted by base radio 1511 through coupling lS21 to adapter ~01 whlch automatically converts the incoming response to RS232 interface as necessary, to make it 2S suita~le for reception by controller 40.
Through a system as exemplified in Fig.15, : data collection from a number of roving mobile transceivers may be initiated by a ne~work controller 40 through a ~our warehouse , T~ ~H~ J~

WO94/10774 ~ 4 8 3 ~ 1 P~T/VS93/10528 environm~nt. When base transceiver units 1511 and 1512 have been unsuccessful in establishing communication with the desired mobile transceiver ¦ unit, controller 40 will then cause bases 1513 and ¦ 5 1514 to attempk communication and if bases 1513 and 1514 are unsuccessful, controller 40 will proceed ~hrough the other base radio pairs, namely 1515/1516 and 1517/1518, as needed, to es~ablish communi~ation with the desired mobile transceiver `:
.lO unit. ~ ~
The adapter 801 is:provided to operate in ~ : either slmulcast or sequential moda. In ~he ! : ~ normal or simulcast mod~, adapter 801 allows the use of one to cight bases,~where the bases are configured as four pairs of two ba~es. In this mode the~adapter 801 simulcasts to a ingle ba~e : : pair at a time and the four sets:of base pairs are selected~ using¦ a dynamio time-dlvision multip~lexing method. The user:::can configure the 20~ : adapter 801:to use any :o~ the eight base ports, usin~g simulcasting or time-division multiplexing to~best advantage.
Thère are two sets of base transceiver units, referred~ to as set~A (identifled as lA, 2A, 3A, 25~ ~and~4A):and ;set B (:identified as lB, 2B, 3B, and 4B~. With~in~a~set, the base transceiver units are ` selected~byltime-division multiplexing. ~
It can be se~en in Fig. l5,~ that there are four pairs~ of base~transceiver units de~ir.ed-as :: : :. : : : .

3 U ~-- S~ iL ~;) W094/10774 ~ ~ ~ PCT/~593/10528 pairs lA/lB, 2A/2B, 3A/3B, 4A/4B. Each base transceiver unit of a base pair is simulcasted to at the same time.
The hardw~re of the adapter 801 allows the ~election of the base pairs ~pair 1~/lB through 4A/4B) using control lines from the controller 40.

Adapter 801 transmits to both base transceiver units of a base pair at the same time and receives independently from each base simultaneously.
10The use of adapter 80~ allows an extension of the number of ~ase transceiver units that oan be used in a~facility to allow for adequate coveraye, i~ is important to understand how the base transceiver units operate when simulcasting is ¦ 15used, and when time-division multiplexing is ~lsed.
: The adapker 801 distributes signals :transmitted by controller 40 to base transceiver pairs at the same time,~so if there is an overlap in the coverage for the two base transceiver u~its, there may be some interference. The a~ount : of interference depends on the relative signal strengths; if the strength is similar in one spot the chance o~f interference is larger that if the signal~ strengths are di~ferent. This type of interference could be avoided in some con~iguration~ by splitting coverage areas of ~: ~ pairs of base transceiver units. Another ~ethod of covering:the overlap area is to place another : : base (not one of the base pairs) to cover the SuByl~U7~E S~EFT (RULE 26~

WO94/10774'~ 8 381 PCT/US93/10528~

overlap area. The radi~ signals from ~he mobile :
transceiver unit may be picked up fully or : partially by either or both base transceiver units of a given pair. However the adapter 801 first 5tries to receive from one base transceiver unit, ~or example base 1511, and if unsuccessful, it then~switches to~try to receive from a second base transceivex unit, for exàmple base transceiver . unit 1513. If the~information is successfully 10received from the~first base transceiver unit, the infarmation from the second base transceiver unit is ignored. Thus the~controller assures data does ~ ~ ~ not get s nt to the~ ho~t data processor in : ~: duplicate.
15 ~:The ~ user may:couple~from one to eight base .~ ; ;transceiver:~units to the adapter 8~01:and can then : ` ~
:~ ~ ~ configure those base transceiver;units as required ;~ to meet the installation's needs.~ Any~combination ; : : of ports of the adap~er~801 can be used. Thus the ~ :20 user~ can take advantage of ~the ability ~to :~ ~ :simulcast~r sequentially ~via time-division ~:
: ~ ~
multiplexing) access~:the base transceiver units 15ll, 1512, ~1513,~ 1514, 1515, 1516~ 1517, and : :~ : : :: : : :

2~5 Multipath adlnq and::D
In a~ referred~embodiment, the data (or ~ messages~ to~be sent;~through~the RF communication ; ~ : link is~se~mented into a plurality of DATA packets ;~ SUBSTITU~E SHEET (RULE 26) `

WO94/10774 ~d,g~ PCT/U593/105~8 and is then transmi~ted. Upon receipt, the DATA
packets are reassembled for use or storage. Data se~mentation on ~he 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 comp~etely avoidPd, sending the data in small segments resuIts in an overall , decrea~e in data loss in ~he network, i.e., only the small segments which collide have to be re-sent.
Similarly, choosing smaller data packets for transmission also reduces the amount of data loss by reducing the inherent effects of perturba~ions and fluctuations found in R~ 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 ~ .
signal~ that hav~ reached that receiver by takin~
all available paths~from the transmitter. The ~; receiYed signal is therefore often ref:erred 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 ~-;~ 25 the:signals making up the composite signal are of :

:~ amplitudes that add "out of p~ase", the desired .
~`~- data signal decreases in amplitude. If the signal amplitudes are approximately equal, an effective W094/10774 2 ~ 4~3 ~ 1 PCT/US93/10528 null (no detectable signal at the receiver) ;.
results. This condition is termed ~Ifading~.
Normally changes in the propagation en~ironment occur relatively slowly, i.e., over periods of time ranging from several tenths ~l/lO's) of seconds to several seconds. However, in a mobile RF environment, receivers (or the corresponding transmitter~) 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 bQtwe~n 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 o the recei~er. .
Over small distances, the signal components that determine the composi~e signal are well correlated, i.e., there is a small probability that a significant change in the signal power e~velope Will occur over the distance. If a transmission of a data packet can be initiated and completed before ~he relative movement between the receiver and transmltter exceeds the "small distance", data loss to fading is unlikely to OGCUr~. The maximum "small distance" wherein a SUBSTITUTE SM~ET (RULE 26) :

W094/10774 ~ ~1 PCT/~S93/1052 high degree of correlation exists is referred to hereafter as the "correlation distance".
' As expressed in wavelength~ of the carrier fre~uency, the corxelation distance is one half (l/2) of the wavelength, while a more conservative value is one quarter tl/4) of the wavelength.
Taking this correlation distance into consideration~ the ~ize of the data pa~ket for segmentation purposes can be calculated. For example, at 915 ~H~ (a prefe~red RF transmission frequency) j a quarter wavelength is about 8.2 centimeters . A mobile radio moving at ten ( 10) miles per hour, or 447 centimeters per sec:ond, . travels the quarter wavelength in about 18.3 milliseconds. In such an en~ironment, as long as the se~ment packet siz~e remains well under 18.3 . milliseconds, significant signal fluctuations . ~ during the duration of a packet transmission is :~ : unlikely.~ In such an preferred embodiment, fi~e 20(5) millisecond data packet ~egments are cho~en : which ~ provid~s~ a quasi-statlc multipath communicat on environment~
~ l ` The faster the relative moYement between a : ~ transmitter and a~receiver the greater the effect : : 25of fading, and, therefore, the smaller the data ~ : ~ : :
: ~ segment should be. Similarly, if the relatiYe . :movement is slower, the data segment can be larger.
:

SUBSTITUTE SHEET (RUL~ 26) ` ' W~94~10774 2 1 4 8 3 8 1 PCT/US93/10528 _ :

34 :~
Slower fading effec~s which might be experienced between stationary transceivers in an office huilding due to thP mov~ment of p20ple, mail cart~, and the like. In a typical applîcation of the present invention, the RF
transc~iver 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 ~ s~anner. In such an example, the bar code data ¦ lO could be transmitted to the base station as the RF
transceiver ~nd a ~canner device were being jointly transported by a vehicle (e.g. a forklift truck~ to another site~ or the RF transceiver and a ~canner, e.g. as a unitary band-held device, could be carri~d by th~ operator to another site as the bar code ~ata was being transmitted to the base station. In such situations, fading is more pronounced~
I~ fading does not pose a problem on a given network, the overhead associated with segmentation, handwshaking and reconstruction may not be justi~iable. Howe~er, where fading exists, such~overhead may be required.
In many commun}cation environments, the : ~5 degree of fading effects varies dramatically both from t~me to time and from installation to insta~lation. In the preferred embodiment, : transmitters and receivers communicate using an optimal data se~ment size parameter by adapting :

3 (Pll~L~

W094/l0774 ~3~1 PCT/US93/lG528 the size to conform to the communication envi~onment of the network at any given time. For example~ if a receiver detects repeated faulty i transmissions, the data se~ment size parameter might be incrementally reduced (under the assumption that fa~ing 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 degre~ of fading in the network.
One example of a receiver making such a measurement of fading can be found in the aba~doned patent application of Ronald L. Mahany, - U.S. Serial No. 07~485,313, filed February 26, j 15 1990. Specifically, in that reference, a receiv~d , signal strength indicator (RSSI)~circuit is found :! in the receiver. ~The RSSI circuit samples the signal strength of a transmission. If the signal . ~trength samples are evaluated in sequence and the trend analyzed~ the degree of fading can be measured. If thè signal strength samples decrease in value, it is likely that fading is present' in the network. However, just beJause fading e~ists do~s not ~equire segmentation. Only if fading causes the signal strength to drop balow the level of the receiYer ' s sensiti~ity i5 segmentation required.
A fixed~ threshold value that is located a .
~ safe margain above the receiver's sensitivity is .
~ ~ t ~ t; ~ 2~ ~

wo g4/l0774 2 1 4 8 3 g 1 PCT/US93/1~52~

used to determine whether to change the data segment size. ~f a trend in signal strength shows values falling below the threshold, ~he data segment size is decreased. I~ the threshold S level is never reached, the segment size might be increased. In addition, the trend associated with a gr~up of signal strength samples can be used to predict the optimal data packet size -- th~
intersection of the signal strength samples with the threshold defines a s gment length that, with a safe margain, can be used effectively used;with the current degree of fading.
After receiving a data segment, the receiver sends to the transmitter indications regarding: l) whether the data segment was received without fault; and 2~ what the new optimal se~ment size ~hould be. The transmitter responds ~y ad~usting . the data segment .size and then sending the.next segment. As can be appreciated, the data segments are adapted based on the prPvious transmi~sion.
Instead of adjusting on the basis of the reception of a sin~le data segment (the previous ~ransmission), other techni~ues for adju~tmen~ are contemplated. For example, the transmitter may al~o utilize a threshold window (or weighted averaging), inside of which the segment siz~ will : not be changed. ~nly if the reque~tPd change by the receiver falls outside of the ~hreshold window - will the segment size change. Similarly, the iS ~ E S!A~ T i~ 2~) -094/]0774 21 ~ 8 3 81 PCT/US93/10528 receiver might also utilize such a window -- only requesti~g a change when the newly forecasted, ` optimal segment size falls outside of the window.

Direct-Seauence Spread S~ectrum Parameters.
As described above, the network controller :~
prQvide~ 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. Tt is the subject~of~standards issued by the Federal Communications Commission (FCC) ~hat provide usable spectrum at low power le~els for ~5 communication in:limited areas~such as warehouses, . office buildings, and the like. The use of !
spread-spectrum techni~ues minimizes interference with others using the same channels in the : spectrum.
: :
A tran mitter 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 ~requency I .
is achieved by increasing; the chip clock rate (wherein each chip constitutes an element of the spreading-code). Using the same spreading codel the rece:iver d codes the received signal while :
ignoring minor faults which occurred in `
~ ~ t~Sw~ L~ ~6) WO94/10774 PCT~U$93/105~8 transmi~sion, 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 improv~d communication, increasing the frequency or length of the spreading-code requires additional overhead which may not ~e justifiable unless necessary.

Frequency~Hoppinq Spread S~ectrum Parameters.~
Frequency-hopping is the switching of tr~nsmlssion frequencies according to a ~equence that is fixed or pseudo-random and that is available to both the transmltter and receiver.
lS Adaptation to the communication environment via an exchange in frequenzy-hoppi~g 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 selectlvity of the fadiny envelope (i.e., when fading is significant only over a portion of the spectrum of hopping fre~uencies3, the greaterlthe benefit of sUch adaptation.
Particular~y, a parameter indicating the hopping rate can be varied to minimize the probability that the channel characteristics will detrimentally ~hange during th2 course of a communication exchange. To vary the hopping rate ~ ' ~s ~r~ L ~ ~P-r (~ &~

W094/10774 2l ~838l PCT/US~3/10528 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 ~rame might consist of: 1) a base station transmitting a polling packet to a roaming terminal; 2) the roaming terminal transmitting data in respvnse; 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.
For optimization, the hop ~rame length is adjusted to be as long as possible, while remaining shorter than the coherence time of thP
channel by some safety maryin. Although such :~ adjustment: does ~ot 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 pa ket ::
transmission is suacessfully received, the ~` probability of successful receipt of the data (or message) and ack~owledge is high.
: : .
~:~ 2S ~Another parameter for changing frequency-: hopping performance is that of coding. Codin~ ~n the channel ~or error correction purposes can ~e selectively used whenever the probability of data or message 10s5 due to fading is high. In :~ .
: ~ :

WO94/1~7742 ~ ~ g ~ 8 1 pCT/~93/10528 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 a1low some portion of the data to be lost and reconstructed at the expense ~f a 30-50%
reduction in throughput~ ~he operating parameter ~or coding indicates whether coding sh~uld be used and, if so, the type of coding to be used.
lOAn operating parameter indicating whether interleaving should be used also helps to opt1mize the cummunication channel. Interleaving involves breaking down the data into segm~nts 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 hoppiny frame.
The recei~ing tr~nsceiver compares each segment received with the redundantly r~ceived se~ment to Yerify that the transmission was successful. If .
errors are detected, further transmissions muist be made until verification is achieved. Once :achieved, the transceiver reconstructs the data from the segments.

WO9~t~0774 1 ~ 381 PCT/US93/10528 Other methods of interlea~ing 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).
As can be appreciated, interleaving provides for a redundancy cbeck 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.
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, selectin~ interleaving and coding, ~;; : : through their r~spective parameters, might result in a more complex communication sc~eme which : combines segmentation and error correctiQn in some : 20 alternate fashion. ~

$ource _Encodinq Parameters I For _N~rrowband A~lications~
In the ~United~ States, :data communication equipment;operating in~ the~ ultra-high frequency (U~F)~ ~ra~ge~ under~ conditi~ns of frequency modulation: (FM? is~ subject ~to the following limitations.

~ .

WC~ 9~/10774 ~ PCr/US93/10528 21 ~838~
42 :
( 1 ) The occupied }: and width is sixteen kilohertz ~axi~um with fi~e kilohertz maximum f re~uency deviation .
(2~ The c:hannel spacing is 25 kilohertz~
Tlhis requires the use of highly s~lected filtering in the receiYer to reduce the potential for interference from nearby radio equipment operating on ad j acent channels .
(3) The maximum ou~put power is generally in the range of tPn to three hundred watts. For localize~ operation in a f ixed location, however, transmitter power output may be ~limited to two watts maximum, and limitations may be placed on -~
antenDa height as well. These restrictions are inkended to limit system range so as to allow ef~icient re-use of frequencies.
For non-return to zero (Nl~Z) data modulation, the highest modulating ~requency is equal to one ~: : half the data rate in baud. Maximum- deviation of ~20 five kilohertz may be utilized ~for a highest m~dulation~ fre~uency which is less than three kilohertz, but lo~er deviations are general ly required for hlgher modulation frequencies. Thus, at a data ~ :rate of : ten thousand~ baud, and an occupied bandwidth~ o~ sixteen kilohertz, the peak FM deviation which can be utilized for NRZ data ~: ~ ; may be~three kilohertz or less, ConElderations of cost versus performance tradeo~fs are the major reason for the selection ~ : .

~ ~Z ~ nr~

~3 .~. ~.. .~v.

W094/10774 21~381 ~ PCT/U593/105~8 of the fre~uency modulation approach used in the system. The approach utilizes shaped non-return to-zero (NRZ3 data for bandwidth efficiency and non-coherent demodu~ation using a 5 limiter-discriminator detector for reasonable performance at weak RF signal levels. Howaver, the channel bandwidth ~oonstralnts limit the maximum data "high" data ra~e that can be utilized for transmitting NRZ coded datas S~ignificant improvements in system throughput potential can be realized within the allotted ~ bandwidth~ by extending~the concept of~adaptively selecting data rate to inolude switching between sourc2 encoding ; methods. ~e~pr~eferred~approach is to continue to 15~ ~ use NRZ ooding f~or~the lower~system~data rate and substitute~partia;l~response (PR~encoding for~the higher; rate.~ The throughput~improvements of a NRZ/PR s;oheme~over~an~NRZ~/NRZ~ mplementation are~
obtained~;~at the expense~of~additional complexity in~thè~ aseband prooessing oircuitry.~
Partial ~rèsponse~encoding methods ~are line coding~techniques which allow a potential doubling~
of the~data~rate over NRZ enooding uzing the~same baséband bandwid~th. ~Examples~of PR encoding 25~ mèthods~include'duobina,ry and;modified~duobinary~
encoding.~ Bandwldth~ efficiency;~is improve~d~ by' co'~verting~ binary~ ata into~ three level/ ~r pseudo-ternary ~signals~. Beoause`~the receiver decision circuitry~must distinguish;betweèn three JE;~:~ll'uTE~SH,r~ RLLI: ~36) ~ -W~94/10774 ,f.~l ~ &3 81 PCT/US93/10$~8 44 `
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 feliminated ~ffy appropriate selection of the baud rate switching threshold.
Since PR encoding offers a doubling of the da~a ra~e of NRZ encoded da~a in the same ~andwidth, one possible~implementation of a NRZ/PR
baud rate switchiny system would be a 4800l9600 bit/sec system in which the low-pass filter bandwidth is not switched. This migh!t be desirable for example if complex low-pass filters constructed of discrete components had to be used.
Use of a:single filter`could reduff~e circuit costs l~ and printed:circuit board area requirements. This approach might also be desirable if thfe channel ~:
bandwidth were reduced below what is currently ~.

: available. ~ ~

:~: The~ preferred ~ implementation with the -;
.:
bandwidth:available is to use P~ e~coding to increase the high data rate wel1~beyond the 9600 bit/sec implementation previousl:y described. An approach using 4800 bit/sec NRZ encoded data for : ~ the low rate thereby~providing high reliability and backward compati~ility with existing products/
~: : and~16R bit/sec~PR èncoded transmission for the high ~rate:~may be utilized. The PR encoding .
~ . ~ technique is a hybrid ~orm similar to duobinary : and se~eral of its variants which has been de~ised ff~s ~ ff~f-- ~ f~f~ ffr`) WO94/10774 21~8~81 PcT/US93/10528 to aid decoding, minimize the increase in hardware complexity, and provide similar performance characteristics to that ~f the previously described 4800/9600 bit/sec implementation. While PR encoding could potentially provide a high data rate of up to:20R bit/sec in the available channel bandwldth, 16X bit/sec is preferab}e because of the practical constraints imposed by oscillator temperature stabil ity ~ and: the distortion cha~acteristi~s of IF bandpass filters.

: Exchan~inq Parameters All of the above re~erenced~parameters must be maintained in local ~memory at both :the :~ ~ transmitter and the~receiver so ~that successful communication can occur. To change the~
communication envircnment~ by changing an Qperating ~` parameter~ requires both;synchronizati~n be~ween ~.
the transceivers and a method:for recovering in case synchroni~zation fails.
2;0 ~ ~ In~:a preferred~emb~diment,~ if a transceiver~
: receiving a:transmission thereinafter referred to as thè~"destination")~determines that an operating parameter needs to be changed,~it must~transmit~a~
regues~t ~or change to~the~:t~ansceiver sending the 25 ~ transmission:~(berei~nafter~ the "source").: If~
` received, the ~ource~may~send an first acknowledge to the destination: based on the current operating paraoeter. Therean r, the sou-c- modif1es its Tr ~r, J~

W~94J1~774 PCT/US93/1052 2`1`~'8381 46 currently stored operating parameter, stores the modification, and awaits a transmission from the de~tination ba~ed on the newly stored operating i parame~er. The source may also send a "n~
acknowledge" message, rejecting the requested modification.
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 messa~e from the source. If the desti~ation does not receive the first acknowledge, the des~ination sends the request againO If after several attempts the first acknowledge is not received, the destination modifies the currentIy stored parameter, stores the modification as the new operating parameter, I and, based on the new parameter, transmits a ,~ 20 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 ~cknowledge. After the ~; secon'd acknowledge is received, communication between the source and destination based on the : newly stored operating parameter begins.
:; ' `
S~ fP~ L~ c~

Pcr/uss3/los2s ~O94tl~77~ 381 If the destination does not receive either the first or the second acknowledge mPssage~ from the source after repeated requests, the destination ~eplaces the current operating 5parameter with a factory preset system-default (which is also loaded upon power-up). Therea~ter, using : the system-default, the destination transmits repeated requests for a~knowledge until receiving a response from the~source. The system- ;
10default parameters preferably define the most robust configuration for communication.
If a~ter a time-out period the second request for acknowledge bas~d on the newly stored operating parameters is not received, the source :: 15restores the previously ~ modified operating parameters and listens~ for a request fGr ~ acknowledge. If after a further time-out period r' j~ a request ~or: acknowledge is not received, the ``: ~ source replaces the current operating parameter ; : 20with the factory prese~ system-default (which is : ~ ~ the same as ~hat stored in:the destination, and which is also loaded upon power-up~. Thereafter, using the ~common sy~tem-default, ~the sourcè
: ~ listens~ for an acknowledge~ request ~rom the 25~ destination.~ Once~received, communication i5 re-established O
; Other~ synch~ronization~ and recovery methods are~also ~contemplated. For example, instead of :acknowledge requests originating solely from the WO94/1~774 . ;`` PCr/US93/10528 2 14 8 3 ~ 1 !

destination, the ~ource might also participate in such requests. Similarly, although polling is the preferred protocol for carrying out the communication exchan~es described above, carrier sense mu1tiple-access (CSMA~ or busy tone protocol~ mi~ht also be used.
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. ~owever, the scope of the present invention is intended to cover all variations and æubstitutions which are and which may become apparent from the illustrative - embodiment of the present invention that is 15 provided above, and the scope of the invention should be extended to the claimed invention and its equivalents. It is to be understvod that many :
variations ~nd modifications may be effected .
without departing from ~he scope~of ~he present ; disclosure. ~: ~
:
:

~: ~ . . ;
.

:

, S'` G~ E I (R~LE 2~)

Claims (9)

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 indicative of the size of data segments to be communicated;
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 size of the data segment should be made; and means within said first terminal that is responsive to said determination means for changing the operating parameter.

2. A spread spectrum 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 indicative of the length of the spreading code for spread spectrum communication;
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 length of the spreading code should be made; and means within said first terminal that is responsive to said determination means for changing the operating parameter.

3. A spread spectrum data communication system for collecting and communicating data using a spreading code, 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 indicative of the chip clock rate of the spreading code for spread spectrum communication;
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 chip clock rate should be made; and means within said first terminal that is responsive to said determination means for changing the operating parameter.

4. A spread spectrum 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 frequency hopping parameters 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 frequency hopping parameters should be made; and means within said first terminal that is responsive to said determination means for changing the frequency hopping parameters.

5. A spread spectrum 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 a source encoding 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 type of source encoding should be made; and means within said first terminal that is responsive to said determination means for changing the source encoding parameter.

6. 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 indicative of a data segment size to be communicated;
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.

7. A frequency hopping 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 a frequency hopping 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.

8. A frequency hopping 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 indicative of whether coding is to be used, and, if so, the type of coding;
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.

9. 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 indicative of whether interleaving is to be used, and, if so, the type of interleaving;
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.