The use of infrared radiation (IR) communications for the transmission of audio, video, data and control signals is rapidly growing. Applications using infrared transmission include remote controls for television, cable set top boxes, videocassette recorders (VCRs), digital versatile disk (DVD) players, compact disk changers and the like, remote keyboards, wireless LAN networks, video-conferencing equipment, computer peripherals, medical equipment, and personnel and equipment locating monitors.
In IR communications, commands and keystrokes are conveyed serially in IR packets via an IR transmission channel. The transmitted packet(s) include modulated data pulses preceded by a leader. The leader is much wider than a data pulse. The leader marks the beginning of the packet, and initiates a gain adjustment by an automatic gain control (AGC) circuit in the corresponding IR Receiver, for optimum data detection and subsequent decoding.
Before the rapid growth in functionality of IR remote control devices, a remote control had relatively few keys, and performance of the IR channel was not an issue. The user performed simple operations, such as: switch channel, adjust audio volume, toggle mute switch, and the like. These manual key operations were relatively slow. During a key press, a remote control device typically entered an autorepeat mode and emitted several copies of the same IR packet in a row, usually separated by an autorepeat interval. The repetition of IR Packets raised the IR channel reliability. Excess auto-repeated packets were discarded by the receiving device.
The appearance of more complex audio-video systems and interactive television (ITV)—in which the user utilizes an IR wireless keyboard—caused rapid saturation of the IR control channel. To meet performance requirements, typed keystrokes are now buffered in the transmitting device and are transmitted as a series of distinct IR Packets. Complex remote controls and keyboard with a multitude of keys, and pointing devices (e.g.: mouse) encode some keystrokes as a single IR packet and encode other keystrokes as a combination of several distinct IR Packets.
Such complex systems have been observed to suffer the problem of data loss in the same lighting conditions where simpler devices or functions still function as before. The proliferation of fluorescent lamps as a cost effective source of ambient light further degrades the reliability of the IR communication channel.
Loss of data in the IR communication channel causes the user to repeat operations (commands, keystrokes), or choose to sit in a less desirable position much closer to the IR receiver. Errors during keyboard typing often cause marker (cursor) repositioning and necessitate retyping of lost letters on the screen. This considerably slows down typing in comparison to a (wired) computer keyboard input, drastically diminishing customer satisfaction. Some important operations are rendered difficult or impossible, e.g.: secure password entry.
An apparatus and method for increasing reliability without taxing performance of IR channel is desired.