Method and apparatus for cordless infrared communication
First Claim
1. An infrared digital and analog communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate with a plurality of portable infrared devices located within a building through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots a respective pair of which is, when needed to establish communication, designated to transmit and receive signals between a portable infrared device and a base unit, comprising:
- a base unit operatively located between the signal processing unit and the portable devices for enabling communication therebetween;
a plurality of spaced apart stationary infrared receiver and transmitter (RT) modules operatively interposed between the base unit and said portable devices for transmitting and receiving infrared signals at a desired carrier frequency;
a plurality of cables connecting the base unit to the RT modules, each of said cables carrying transmission signals in said transmission slots from the base unit to the RT modules and carrying received signals in said receiving slots from the RT modules to the base unit;
with the transmission of signals through the cables between the base unit and RT modules being so controlled that signals from the base unit arrive at substantially the same time at RT modules which are near each other and with phase differences between infrared carrier signals received by a portable device from nearby RT modules not exceeding a preselected amount; and
a receiving signal selector, operative for each designated receiving slot, to select a received signal from one of several RT modules responding to a portable device transmission for transfer to said signal processing unit, whereby the system'"'"'s IR connection to a portable infrared device can be effectively, automatically and instantly handed off from an RT module experiencing an unacceptable infrared input signal to an RT module having an acceptable infrared input signal.
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0 Petitions
Accused Products
Abstract
An infrared (IR) communication system is described in which a base unit for a cell can communicate with a plurality of infrared portable devices through distributed infrared receiver/transmitter (RT) modules over a plurality of channels using IR carrier signals. A call processor, referred to as a radio exchange unit, and controlling communication of a cell, communicates with the base unit to place or receive calls with the IR portable devices. The communication occurs in standard communication frames divided into transmission and receiving segments with each segment further divided into slots and with the slots containing digital data, with each communication channel formed by a slot. Each transmission segment to an RT module is immediately followed by a responsive receiving segment. As an IR portable device moves from the vicinity of one RT module to another, the base unit automatically and seamlessly and in a robust manner hands over control to the nearer RT module by monitoring signal strength signals from various RT modules coupled to the base unit. When an IR portable device moves from one cell to another, the call processor hands over control to another base unit using standard protocols. Since an IR portable device may receive IR communication signals from several RT modules, care is taken to avoid signal interference by effectively controlling signal propagation lengths between the base unit and RT modules so that signals arriving from nearby RT modules at a common IR portable device do not have a phase difference more than a predetermined amount. The path lengths can be controlled by selecting cable lengths or by insertion of delays between the base unit and the RT modules to assure that IR signals arrive at portable devices with a minimum amount of interference.
51 Citations
31 Claims
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1. An infrared digital and analog communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate with a plurality of portable infrared devices located within a building through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots a respective pair of which is, when needed to establish communication, designated to transmit and receive signals between a portable infrared device and a base unit, comprising:
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a base unit operatively located between the signal processing unit and the portable devices for enabling communication therebetween; a plurality of spaced apart stationary infrared receiver and transmitter (RT) modules operatively interposed between the base unit and said portable devices for transmitting and receiving infrared signals at a desired carrier frequency; a plurality of cables connecting the base unit to the RT modules, each of said cables carrying transmission signals in said transmission slots from the base unit to the RT modules and carrying received signals in said receiving slots from the RT modules to the base unit; with the transmission of signals through the cables between the base unit and RT modules being so controlled that signals from the base unit arrive at substantially the same time at RT modules which are near each other and with phase differences between infrared carrier signals received by a portable device from nearby RT modules not exceeding a preselected amount; and a receiving signal selector, operative for each designated receiving slot, to select a received signal from one of several RT modules responding to a portable device transmission for transfer to said signal processing unit, whereby the system'"'"'s IR connection to a portable infrared device can be effectively, automatically and instantly handed off from an RT module experiencing an unacceptable infrared input signal to an RT module having an acceptable infrared input signal. - View Dependent Claims (2, 4, 5, 6, 7)
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3. An infrared digital and analog communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate with a plurality of portable infrared devices located within a building through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots, a respective pair of which is, when needed to establish communication, designated to transmit and receive signals between a portable infrared device and a base unit, comprising:
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a base unit operatively located between the signal processing unit and the portable devices for enabling communication therebetween; a plurality of spaced apart stationary infrared receiver and transmitter (RT) modules, interposed between the base unit and said portable devices, for transmitting and receiving infrared signals at a desired carrier frequency; a plurality of cables connecting the base unit to the RT modules, each of said cables carrying transmission signals in said transmission slots from the base unit to the RT modules and carrying, to said base unit received signals from RT modules responding to infrared signals from infrared portable devices and incident on the responding RT modules;
wherein said cables connected to nearby RT modules have electrical lengths which do not differ more than an equivalent electrical delay of about a quarter wavelength of the highest infrared carrier frequency employed between the nearby RT modules and portable devices so that signals from the base unit arrive at substantially the same time at RT modules which are near each other and phase differences between infrared carrier signals received by a portable device from different nearby RT modules are sufficiently low so as to reduce signal interference at the portable devices; anda receiving signal selector, operative for each designated receiving slot, to select a received signal from one of several RT modules responding to a portable device transmission for transfer to said signal processing unit.
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8. An infrared digital and analog communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate with a plurality of portable infrared devices located within a building through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots, comprising:
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a base unit operatively coupled to the signal processing unit for sending transmission and receiving signals in respective transmission and receiving slots to and from portable infrared devices; a plurality of spaced apart stationary infrared receiver and transmitter (RT) modules interposed between the base unit and portable devices, said RT modules including means for sending signals received from the base unit within transmission slots at infrared carrier frequencies to portable infrared devices and means for sending signals received from portable devices within receiving slots to the base unit; a plurality of cables connecting the base unit to the RT modules, each of said cables carrying transmission signals in said transmission slots from the base unit to the RT modules and carrying receiving signals in said receiving slots from the RT modules to the base unit;
the lengths of cables connecting at least nearby RT modules being selected so that transmission signals from the base unit arrive at said nearby RT modules at a time selected to limit phase differences between infrared carrier frequency signals received by a portable device from said nearby RT modules below a preselected amount. - View Dependent Claims (9, 10, 11, 12)
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13. A base unit for use in a communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate with a plurality of portable infrared devices located within a building through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots, with a plurality of distributed infrared transmitter and receiver (RT) modules coupled to the base unit and interposed to enable the base unit to communicate with portable infrared devices, comprising:
a signal selection network responsive to signals in receiving slots and originating from infrared portable devices for selecting, during respective receiving slots, at least an adequate infrared signal received by RT modules from infrared portable devices and related to a common receiving slot, whereby the system'"'"'s IR connection to a portable infrared device can be effectively, automatically and instantly handed off from an RT module experiencing an unacceptable infrared input signal to an RT module having an acceptable infrared input signal. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A method for communicating with a plurality of infrared portable devices via a communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots, comprising the steps of:
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generating transmission signals destined for the infrared portable devices via spatially distributed stationary RT modules during transmission slots for retransmission at carrier frequencies and delaying selected transmission signals so that the transmission signals arrive at RT modules essentially at the same time with phase differences that are less than about a quarter wavelength of the highest infrared carrier frequency employed; sending the transmission signals over an infrared carrier to said infrared portable devices; and passing selected received signals representative of infrared signals from infrared portable devices to a base unit and delaying selected received signals so as to enable them to be processed at said base unit at essentially the same time. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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26. An infrared digital and analog communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate with a plurality of portable infrared devices located within a building through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots, a respective pair of which is, when needed to establish communication, designated to transmit and receive signals between a portable infrared device and a base unit, comprising:
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a base unit operatively located between the signal processing unit and the portable devices for enabling communication therebetween; a plurality of spaced apart stationary infrared receiver and transmitter (RT) modules, interposed between the base unit and said portable devices, for transmitting and receiving infrared signals at a desired carrier frequency to and from said portable devices; said RT modules each including a signal processor, which produces a characteristic signal representative that the intensity or the signal-to-noise ratio of IR carrier signals from portable devices incident on the respective RT module for each receiving slot exceeds a minimum threshold level; a receiving signal selector in the base unit, responsive to said characteristic signals from RT modules, to select a received signal from one of several RT modules which respond to an infrared portable device transmission for transfer of the selected received signal to said signal processing unit, whereby the system'"'"'s IR connection to a portable infrared device can be effectively, automatically and instantly handed off from an RT module experiencing an unacceptable infrared input signal to an RT module having an acceptable infrared input signal. - View Dependent Claims (27, 28, 29)
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30. An infrared digital and analog communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate with a plurality of portable infrared devices located within a building through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots, a respective pair of which is, when needed to establish communication, designated to transmit and receive signals between a portable infrared device and a base unit, comprising:
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a base unit operatively located between the signal processing unit and the portable devices for enabling communication therebetween; a plurality of spaced apart stationary infrared receiver and transmitter (RT) modules, interposed between the base unit and said portable devices, for transmitting and receiving infrared signals at a desired carrier frequency to and from said portable devices; said RT modules each including a signal processor, which produces a characteristic signal representative of the signal strength or signal-to-noise ratio of IR carrier signals from portable devices incident on the respective RT module for each receiving slot prior to reception of received signals related to the receiving slot; a receiving signal selector in the base unit, responsive to said characteristic signals from RT modules, to select, prior to their arrival at the base unit, a received signal from one of several RT modules which respond to an infrared portable device transmission for transfer of the selected received signal to said signal processing unit, whereby the system'"'"'s IR connection to a portable infrared device can be effectively, automatically and instantly handed off from an RT module experiencing an unacceptable infrared input signal to an RT module having an acceptable infrared input signal.
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31. An infrared digital and analog communication system using a time division multiple access communication protocol for enabling a central control unit connected to telephone lines to communicate with a plurality of portable infrared devices located within a building through a signal processing unit which produces a repetitive frame signal having time spaced transmission and receiving segments each of which includes a plurality of time spaced respective transmission and receiving slots, a respective pair of which is, when needed to establish communication, designated to transmit and receive signals between a portable infrared device and a base unit, comprising:
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a base unit operatively located between the signal processing unit and the portable devices for enabling communication therebetween; a plurality of spaced apart stationary infrared receiver and transmitter (RT) modules, interposed between the base unit and said portable devices, for transmitting and receiving infrared signals at a desired carrier frequency to and from said portable devices; said RT modules each including a signal strength or signal-to-noise ratio signal processor, which produces digital amplitude signals representative of the signal strength or signal-to-noise ratio of IR carrier signals from portable devices incident on the respective RT module for each receiving slot prior to reception of received signals related to the receiving slot; means for coupling the digital amplitude signals to the base unit; a receiving signal selector in the base unit, responsive to said digital amplitude signals from RT modules, to select, for respective receiving slots, the best received signal from one of several RT modules which respond to an infrared portable device transmission for transfer of the selected received signal to said signal processing unit, whereby the system'"'"'s IR connection to a portable infrared device can be effectively, automatically and instantly handed off from an RT module experiencing an unacceptable infrared input signal to an RT module having an acceptable infrared input signal.
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Specification