EP0602228A1 - Systeme de communication infrarouge a debit binaire eleve permettant de maitriser le brouillage dans la propagation par trajets simples - Google Patents

Systeme de communication infrarouge a debit binaire eleve permettant de maitriser le brouillage dans la propagation par trajets simples

Info

Publication number
EP0602228A1
EP0602228A1 EP93915434A EP93915434A EP0602228A1 EP 0602228 A1 EP0602228 A1 EP 0602228A1 EP 93915434 A EP93915434 A EP 93915434A EP 93915434 A EP93915434 A EP 93915434A EP 0602228 A1 EP0602228 A1 EP 0602228A1
Authority
EP
European Patent Office
Prior art keywords
terminal
data
signals
device arrays
communication
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93915434A
Other languages
German (de)
English (en)
Other versions
EP0602228A4 (fr
Inventor
Bruce C. Eastmond
Alameh Rachid
Thomas A. Freeburg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Motorola Solutions Inc
Original Assignee
Motorola Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Motorola Inc filed Critical Motorola Inc
Publication of EP0602228A1 publication Critical patent/EP0602228A1/fr
Publication of EP0602228A4 publication Critical patent/EP0602228A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/1149—Arrangements for indoor wireless networking of information

Definitions

  • This invention relates generally to a high data rate infrared radiation (IR) communication system, and more particularly, to a method and apparatus for overcoming reception errors caused by multipath interference in such an IR communication system.
  • IR infrared radiation
  • Multipath interference results in such systems when two or more signals are received offset in time. This often occurs in an environment having signal deflecting structures. Each signal deflection delays the arrival of the transmitted signal. These deflections can generate signals having differential path delays exceeding a substantial fraction of the data symbol duration, e.g., where the differential path delay is more than half of the data symbol width, thereby causing overlapping signals that impair or destroy signal intelligibility at the receiver.
  • IR infrared radiation
  • channel equalization typically employ some form of equalization scheme such as, for example, linear equalization, decision feedback equalization (DFE) , or maximum-likelihood sequence estimation (MLSE) equalization on the received data in order to correct for the intersymbol interference (ISI) caused by channel-induced distortions such as multipath and Rayleigh fading.
  • equalization is a very complex and expensive solution to multipath interference, which in many application is impracticable.
  • point-to-point, multipoint or otherwise aimed communication links include either fiber optic cables, direct free-space aimed or reflectively aimed transmission, and therefore typically fail to provide uniform service throughout an area of geographic coverage (cell) .
  • the present invention is a method and apparatus for use within a wireless infrared (IR) communications system for selecting a communication path between a CM and at least one UM employing infrared transceivers.
  • IR infrared
  • the UM comprises a plurality of IR device arrays for receiving IR signals in relatively narrow IR field of view sectors, and selection means, coupled to said plurality of IR device arrays, for selecting a communication path between the CM and one of said plurality of IR device arrays, based at least partly on received signal integrity, so as to overcome reception errors caused by multipath interference.
  • FIG. 1 illustrates a wireless packet communication system suited for incorporating the present invention
  • FIG. 2 is a block diagram of a packet device in accordance with the present invention and suited for use in the system shown in FIG. 1;
  • FIG. 3 is a partial block diagram of the IR transceiver as shown in FIG 2;
  • FIG. 4 illustrates a flow chart diagram of the steps performed in accordance with the present invention to determine the best UM to CM communication path in order to overcome reception errors caused by multipath interference.
  • FIG. 1 illustrates a wireless packet communication system 100 in which a control module 12 utilizes infrared radiation (IR) to communicate with user modules 14 that are each coupled to one or more user devices 16 consisting of a terminal, personal computer, telephone, or other information input/output device.
  • the control module 12 is also coupled by a data channel 18 to a data network.
  • the control module (CM) 12 controls communications within the illustrated network and passes information from the data network via channel 18 to user devices 16 via the associated user module (UM) 14 utilizing IR.
  • the control module also controls local communications by receiving information from one user module and relaying the information to a different user module.
  • the wireless information is conveyed in the form of packets.
  • the data network to which control module 10 is connected may consist of an Ethernet network.
  • the CM and UMs communicate with each other using any one of six directional IR arrays A1-A6 oriented to cover a 360° field of view (FOV) in the horizontal plane.
  • IR arrays A1-A6 oriented to cover a 360° field of view (FOV) in the horizontal plane.
  • FOV field of view
  • a different IR array will likely provide the best communications path.
  • a direct communications path may not always be available because of obstacles or may change due to the movement of people.
  • different IR arrays will be utilized between a UM and a CM based upon the signalling environment and changes therein.
  • FIG. 2 illustrates a block diagram of an embodiment of a structure common to both the CM and UM.
  • An IR transceiver 22 modulates digital data onto a current signal to transmit the desired data and its receiver convert received IR signals into corresponding digital data.
  • Any one of the IR arrays A1-A6 can be selected by the array selector 20, to transmit and/or receive IR signals.
  • Each IR array A1-A6 may comprise IR emitters and detectors, preferably arranged to provide uniform coverage in a horizontal plane with appropriate vertical field of view (FOV) widths to provide latitude for the reception of signals from virtually any location relative to the CM or UM. It will be apparent to those skilled in the art that array selector 20 may be physically housed within transceiver 22 if desired.
  • FOV vertical field of view
  • a Microprocessor 24 operates under the control of an operating system contained in read only memory 26 and utilizes random access memory 28.
  • the microprocessor 24 controls in bound and out bound data carried by path 32, the array selector 20 and the IR transceiver 22.
  • An interface 30 may consist of the line drivers, input/output buffers and registers as is conventional in microprocessor systems.
  • the path 32 corresponds to communication channel 18 when the embodiment is utilized as a CM and corresponds to the connection to a terminal 16 when the embodiment is utilized as a UM.
  • the array selector 20 in conjunction with the microprocessor 24 is capable of selecting any one of the six IR arrays A1-A6 for transmission and reception of IR signals.
  • electronic switching is preferably utilized. It will be apparent to those skilled in the art that conventional mechanical switching is a viable alternative. The microprocessor operation relating to array selection is explained below.
  • communications between the CM and UMs is accomplished using a time division multiple access system in which packets of data are transmitted via IR signals.
  • the CM send packets containing an address and other related overhead information along with data destined for a user module which will recognize this information by means of its unique address.
  • the user modules transmit messages to a CM's addressed for the CM itself or another UM.
  • Part of the information transmitted by each CM is the periodic transmission of reference packets which are received by the UMs.
  • the bit error rate or other merit factor associated with the reception of the reference packets is utilized in the array selection process which will be described below.
  • FIG. 3 is a partial block diagram of the IR transceiver 22 as shown in FIG. 2.
  • This device has a transmitter block 300 and a receiver block 320.
  • each IR device array A1-A6 has an associated transmit block 300 and receive block 320. Since they are all identical, only the transmit and receive blocks for the array Al is illustrated.
  • the transmitter block 300 receives a binary input signal 302 representing packetized data communicated from the interface 30 via array selector 20 of FIG. 2.
  • This information is routed to an encoder 304 which encodes the information prior to intensity-modulation by modulator 306.
  • the encoder 304 performs Manchester bi-phase encoding of the input data.
  • Manchester encoding is performed in order to efficiently utilize the available modulation bandwidth thereby increasing the data bit rate supportable by the reception of diffuse IR signals. While Manchester bi ⁇ phase encoding is suggested, it will be appreciated by those skilled in the art that other forms of encoding may also be employed.
  • the encoded data is then routed to the intensity modulator 306 which transforms the encoded data into coded pulses. These pulses are coupled to a driver 308 in order to increase the current driving capability of the modulated signal.
  • the output from the driver 308 is applied to one or more light emitting diodes (LEDs) 310. Each LED receives the modulated signal having increased drive and emits in response thereto, an infrared radiation signal 312, representative of the packetized input signal 302.
  • Each LED 310 may have an individual driver circuit 308.
  • each array A1-A6 comprises a 60°FOV sector utilizing 24 LEDs to provide the IR coverage. While not shown, the infrared signals 312 will reflect off reflecting surfaces with some amount of dispersion such that the reflected IR signals 312' will radiate in all directions for possible reception by devices within the geographic area covered by the array Al.
  • each array A1-A6 comprises a 60°FOV utilizing 6 photodiodes to provide the desired IR coverage.
  • an apparatus for obtainibg increased gain may be imposed between the received IR radiation signals 312 and 312' and the photodiodes 322.
  • This apparatus may consist of appropriate lenses or reflectors which will maintain a uniform value of gain over the desird field of view.
  • a photodiode 322 is a photon-to- current converter.
  • a detected IR signal 312' is converted to electrical signal 323 representative of the encoded and intensity modulated packetized data generated by the transmitter block 300.
  • each photodiode 322 is coupled to a transimpedance amplifier circuit 324.
  • the transimpedance amplifier circuit 324 performs a current-to-voltage transformation of the electrical signal 323 to provide voltage signal 325.
  • the voltage signals 325 are capacitively coupled to a summing network 326 which sums the voltage signals 325 in order to provide a signal of sufficient gain to realize a desired receiver 320 sensitivity.
  • the coupling capacitors are employed to prevent overloading of the summing network 326 by the receipt of high intensity ambient optical signals such as sunlight.
  • the summing network 326 is a summing amplifier like those known in the art.
  • a bandpass filter 327 Prior to data detection, a bandpass filter 327 is employed to filter the summation signal and reject any low frequency optical noise from sources such as fluorescent lights and to bandlimit resistive noise from previous amplifier stages so as to maximize the overall receiver noise figure. Thereafter, a comparator 328 is employed to detect the presence of Manchester encoded data in the bandpass filter 327 output. Finally, decoder circuit 329 is employed to decode the Manchester data in order to recover a replica 302* of the packetized input signal 302 which in turn is routed to the array selector 20 of FIG. 2. A detected bit error rate associated with the reception of said information at each of the arrays A1-A6 is utilized in the array selection process which will be described below.
  • a preferred embodiment employs multiple sectors provided by the multiple arrays A1-A6 at a receiving UM or CM to overcome multipath interference.
  • the device receiving the multipath signal evaluates the signal at each of the multiple sectors and selects to use the data that is receive via the path which has the least amount of signal degradation caused by multipath interference. This selected path is then used for subsequent transmission of data between the devices in a duplex operation.
  • all six sectors created at each CM and UM are employed to overcome the multipath problem.
  • Such an implementation provides 36 transmission paths from which to choose to overcome the multipath problem. Essentially, the 36 paths result from providing six sectors from which a signal is transmitted and six sectors from which a signal is received. Although any number of sectors may be chosen at either device, the six sectors that are shown provide more than an adequate number of options for overcoming multipath in the typical in-building office environment.
  • the Microprocessor 24 operating under the control of an operating system contained in read only memory 26 has overall control of a CM 12 or UM 14. In accordance, it is the microprocessor 24 that analyzes the received data 302' determines the quality of the transmission paths between the CM and UMs and stores the path information in a table in RAM memory 28. Before the structure of the table is discussed, some background of the system communication process is needed.
  • a special TDMA data transmission referred to as a "sounding pulse” is transmitted via each each of the six sector arrays in sequence.
  • the six "sounding pulse" transmissions are received are received on one sector array (A1-A6) .
  • the UM1 After receiving this TDMA transmission, repeated six times, at the one sector array, e.g., array Al, the UM1 receives the next TDMA transmissions, repeated six times, on the next array, e.g., array A2. This process continues throughout system operation.
  • the table stored in RAM memory 28 is used to prioritize the transmission paths. For example, after receiving and analyzing data on sector array Al, the microprocessor 24 of UM1 identifies that the data was transmitted from CM array sector A5. A quality measurement is made for the communication made therebetween a stored for path 5-A1. A similar measurement and record is made- after each TDMA transmission is received. After each quality measurement is made for the corresponding communication path (CM array sector to UM array sector) , the measurement is compared to measurements made for other communication paths between the CM and the UM. Based upon such comparisons, each measurement is ranked.
  • the table may include the following CM/UM path data entries:
  • the highest quality is 50, the lowest is a 1; and the highest rank is a 1, the lowest rank is 36.
  • each packet that is transmitted from an array sector includes a packet header, data, and validation information.
  • the header preferably includes identification information including the source device and the transmitting sector array, using this information, the receiving device, in this case UMl, can readily determine the sector array which was used to transmit the packet in order to provide an appropriate entry in the RAM memory table.
  • the quality measurements made for the table are used to establish the ranked order of preference. The better the quality, the higher the rank.
  • signal quality may be measured by determining how many transmitted symbols exceed a predetermined receiver demodulation window or may be based upon other known signal quality type measurements such as bit error rate (BER) . Such measuring and ranking continues so long as information is received by the UM.
  • BER bit error rate
  • the UM After each UM completes a path selection table for each of the CMs with which it can communicate, the UM makes a determination of the best CM sector array. This determination is transmitted from the UM to each respective CM thereby informing the CM which of its sector arrays to use when communicating with the UM.
  • the UM sector array to be utilized for each CM is selected at the UM based upon the path selection table. Since the table at the UM is based upon IR signals received from a CM, it will be apparent to those skilled in the art that this system relies upon the principal of reciprocity in making the CM IR sector array selection, i.e.
  • the best IR sector array for transmitting from the CM to the UM is also the best IR sector array for receiving IR signals from the UM.
  • This method according to the present invention allows additional UMs to be installed subsequent to initial system configuration with automatic reconfiguration and selection of the best IR sector array choices.
  • FIG. 4 is a flow chart diagram of an exemplary method in accordance with the present invention for determining the best UM to CM communication path in order to overcome multipath in a high bit rate IR communication system.
  • the flow chart begins at block 410 where a test is performed to determine if a replica signal 302' frame corresponding to a "sounding pulse" has been detected. If the "sounding pulse" replica signal 302' frame has not been detected, monitoring continues. If the "sounding pulse” replica signal frame has been detected, flow proceeds to to block 420 where the signal quality of the received signal is measured. At block 430 a quality value is assigned to the communication path which provided the received information.
  • the assigned value (from block 430) is compared to the quality values recorded for the other communication paths in the table. Thereafter, each communication path is is ranked to indicate the appropriateness of that path with respect to the other 35 communication paths. At block 440 the ranking and the quality is stored in the communication path memory table.
  • a test is performed to determine if six such replica signal frames have been analyzed, measured and ranked. If the sixth replica signal corresponding to the "sounding pulse" frame has not been received, flow proceeds to block 470 where the appropriate UM activity is scheduled for operation. Upon receipt of the sixth replica signal corresponding to the "sounding pulse” frame, flow proceeds to block 455 where a test is performed to determine whether a change in the selected communication path is required. It should be noted that a path change at block 455 should not occur each time a different communication path reaches the highest quality ranking. Thus, in order to avoid service disruption due to instantaneous changes in the best communication path, a communications path is preferably changed only after it maintains the highest ranking for a predetermined period of time. Selection of the appropriate time period is best done on a system by system basis.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computing Systems (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention concerne un système de communication (100) infrarouge (IR) sans fil qui transmet des informations en paquets (302) entre un module de commande (12) et une pluralité de modules utilisateurs (14) par l'intermédiaire d'émetteurs-récepteurs infrarouges (300/320), et présentant un itinéraire de communication sélectionnable. Dans ce système, au moins les modules utilisateurs (14) comprennent une pluralité de groupements de dispositifs IR (A1-A6) destinés à recevoir les signaux infrarouges (312/312') dans un champ IR relativement étroit de secteurs d'observation, et un sélecteur (20) couplé à ladite pluralité de groupements de dispositifs IR (A1-A6) et destiné à sélectionner un itinéraire de communication entre le module de commande (12) et un desdits groupements de dispositifs IR (A1-A6), partiellement en fonction de l'intégrité du signal reçu (302'), de façon à maîtriser les erreurs de réception dues au brouillage dans la propagation par trajets simples.
EP19930915434 1992-07-01 1993-06-21 Systeme de communication infrarouge a debit binaire eleve permettant de maitriser le brouillage dans la propagation par trajets simples. Withdrawn EP0602228A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US90664892A 1992-07-01 1992-07-01
PCT/US1993/005907 WO1994001942A1 (fr) 1992-07-01 1993-06-21 Systeme de communication infrarouge a debit binaire eleve permettant de maitriser le brouillage dans la propagation par trajets simples
US904468 1997-08-01

Publications (2)

Publication Number Publication Date
EP0602228A1 true EP0602228A1 (fr) 1994-06-22
EP0602228A4 EP0602228A4 (fr) 1994-11-17

Family

ID=25422763

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19930915434 Withdrawn EP0602228A4 (fr) 1992-07-01 1993-06-21 Systeme de communication infrarouge a debit binaire eleve permettant de maitriser le brouillage dans la propagation par trajets simples.

Country Status (3)

Country Link
EP (1) EP0602228A4 (fr)
BR (1) BR9306647A (fr)
WO (1) WO1994001942A1 (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9401643D0 (en) * 1994-01-28 1994-03-23 Lee Communications Ltd Data transmission system
JP2959666B2 (ja) * 1994-11-15 1999-10-06 インターナショナル・ビジネス・マシーンズ・コーポレイション 無線通信装置
JPH08242205A (ja) * 1995-03-06 1996-09-17 Nec Corp 赤外線通信機能付携帯型電子機器
JPH10505698A (ja) * 1995-07-05 1998-06-02 フィリップス エレクトロニクス ネムローゼ フェンノートシャップ 複数の装置から成る動的なグループ間での通信システム
GB9615036D0 (en) * 1996-07-17 1996-09-04 Northern Telecom Ltd Optical interference measurement method and system
US5999258A (en) * 1997-06-26 1999-12-07 Nortel Networks Corporation Optical interference measurement method and system
DE19755646A1 (de) * 1997-12-15 1999-06-17 Pagenkemper Sarah Yvette Kabellose Infrarot-Datenübertragungsanlage

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4531238A (en) * 1981-12-03 1985-07-23 Xerox Corporation Statistical contention control for star configured communication networks
US4727600A (en) * 1985-02-15 1988-02-23 Emik Avakian Infrared data communication system
US4864651A (en) * 1985-10-22 1989-09-05 Canon Kabushiki Kaisha Light communication apparatus with tracking ability
US4792998A (en) * 1986-05-23 1988-12-20 Siemens Aktiengesellschaft Receiver for optical digital signals having different amplitudes
US4809362A (en) * 1987-03-13 1989-02-28 Center For Innovative Technology Fiber-optic star tree network
US5060303A (en) * 1988-09-06 1991-10-22 Wilmoth Thomas E Optical data link system, and methods of constructing and utilizing same
JPH0362637A (ja) * 1989-07-31 1991-03-18 Fujitsu Ten Ltd 赤外線通信方式

Also Published As

Publication number Publication date
EP0602228A4 (fr) 1994-11-17
BR9306647A (pt) 1998-12-08
WO1994001942A1 (fr) 1994-01-20

Similar Documents

Publication Publication Date Title
US5371623A (en) High bit rate infrared communication system for overcoming multipath
Djahani et al. Analysis of infrared wireless links employing multibeam transmitters and imaging diversity receivers
Kahn et al. Imaging diversity receivers for high-speed infrared wireless communication
US4977618A (en) Infrared data communications
US4975926A (en) Wireless indoor data communication system
EP1062752B1 (fr) Appareil et procede permettant d'ameliorer la capacite de connexion dans les systemes de communication a fibres optiques sans fil
Tanaka et al. Wireless optical transmissions with white colored LED for wireless home links
EP0748542B1 (fr) Procede et appareil de communications optiques sans cable
Haas et al. Space-time codes for wireless optical communications
JPH09508249A (ja) 適応データ速度及び／又は適応光パワーレベルを有するワイヤレス光通信システム
Yang et al. Full-duplex relay VLC in LED lighting triangular system topology
EP0602228A1 (fr) Systeme de communication infrarouge a debit binaire eleve permettant de maitriser le brouillage dans la propagation par trajets simples
Audeh et al. Performance evaluation of L-pulse-position modulation on non-directed indoor infrared channels
Bhowal et al. Transmit laser selection for two hop decode and forward FSO communication with pointing errors
Glushko et al. Gigabit optical wireless communication system for personal area networking
US6252690B1 (en) Satellite onboard data transmission system
WO1991009477A1 (fr) Systeme de reseau local avec espace libre
FR2770706A1 (fr) Repeteur radio
US5650868A (en) Data transfer system
WO2009095428A1 (fr) Système mimo optique
Matsuo et al. Rate-adaptive indoor infrared wireless communication systems using punctured convolutional codes and adaptive PPM
Akella et al. Multi-element array antennas for free-space optical communication
Khozeimeh et al. Dynamic spot diffusing configuration for indoor optical wireless access
JPH0797763B2 (ja) 空間伝搬光通信における中継方法
Kouhini Integrated optical wireless communication and positioning by using distributed multiple-input multiple-output topology

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19940331

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE ES GB

A4 Supplementary search report drawn up and despatched
AK Designated contracting states

Kind code of ref document: A4

Designated state(s): DE ES GB

17Q First examination report despatched

Effective date: 19970908

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19981215

P01 Opt-out of the competence of the unified patent court (upc) registered

Effective date: 20230522