Abstract: A system for measuring quality-of-service (QoS) provided to each connection included in a stream of packets and allowing a bottleneck to be identified is disclosed. When a packet enters a network at a node or passes through a via-point node, its destination node in the network is determined based on its source and final destination addressee. Feature data identifying the inflow or passing packet is forwarded to the egress at the destination node. At the egress, it is determined whether an outflow packet captured at the egress is identical to the inflow or passing packet by feature data comparison. When they match. QoS for that packet provided by the network can be computed by detecting a difference between inflow time stamp and outflow time stamp thereof.

Abstract: Interference between adjacent sections is prevented in an optical wireless communication system, in which a center device is capable of concurrently communicating through lines with a plurality of parent devices each disposed in one of the sections into which a communication area of the system is divided and each of the parent devices communicates with a plurality of child devices disposed in the same section where said parent device is disposed. The sections is grouped into some groups of sections which do not adjoin each other. Optical wireless communications are done only within one group of sections in each communication period. Some techniques for improving the effect of communication are disclosed.

Abstract: An optical radio communication system comprising a first light transmitting system and a second light transmitting system. Each of said first and second light transmitting system comprising a transmitting means and a receiving means. Said transmitting means comprising a light emitting element positioned in a region including and surrounding a focal point of a first parabolic reflector for emitting light beams, said first parabolic reflector having an inner reflective surface for reflecting said light beams emitted from said light emitting element, and a means for driving said light emitting element with a signal to be transmitted.

Abstract: An optical radio system includes a host device, an end device, and a repeater. The host device and the end device communicate with each other via the repeater by use of optical radio. The repeater includes a section for receiving a first light signal from one of the host device and the end device, a section for converting the received first light signal into a first electric signal, a section for frequency-converting the first electric signal into a second electric signal, and a section for generating a second light signal in response to the second electric signal and transmitting the generated second light signal. The repeater also includes a section for demodulating one of the first electric signal and the second electric signal into a baseband signal, a section for detecting a quality of the baseband signal, and a section for enabling transmission of the second light signal only when the detected quality of the baseband signal is equal to or greater than a predetermined quality.

Abstract: A repeater for packet data optical communication between terminal devices includes a first section and a second section. The first section includes a first device for receiving a first optical signal transmitted from a terminal device and for converting the first optical signal into a first electric signal, a second device for frequency-converting the first electric signal to a second electric signal, and a third device for converting the second electric signal into a second optical signal and for transmitting the second optical signal. The second section includes a fourth device for receiving a third optical signal and for converting the third optical signal into a third electric signal, a fifth device for frequency-converting the third electric signal to a fourth electric signal, and a sixth device for converting the fourth electric signal into a fourth optical signal and for transmitting the fourth optical signal to a terminal device.