Abstract: Provided is a multimode optical transmission system for reducing a deterioration of a noise characteristic and a distortion characteristic caused by an interference between modes. In an optical transmitter 11, a signal output section outputs a predetermined signal based on an inputted electrical signal. A control section 130 controls the signal output section so as to adjust a frequency component of the signal outputted by the signal output section based on group delay information of modes which propagate in a multimode optical transmission line 310. An electric-optic conversion section 110 converts, into an optical signal, the signal outputted by the signal output section, and transmits the optical signal via the multimode optical transmission line 310.

Abstract: A wireless access system is provided which prevents the occurrence of a hidden terminal problem and minimizes the reduction in throughput. In the wireless access system, an access point (12) divides terminals into groups such that terminals in one group cannot recognize radio waves sent from terminals in another group, and performs communication with the terminals on a per-group basis. By this, the wireless access system avoids the occurrence of the hidden terminal problem. RTS/CTS packets used to avoid the occurrence of the hidden terminal problem are exchanged between the access point (12) and terminals (131 to 133, 141 to 142) on a per-group basis, whereby overhead is reduced and the reduction in throughput is minimized.

Abstract: A SW (70) receives an Ethernet® signal from an outside of areas E and F. The SW (70) selects and outputs the obtained Ethernet® signal to any one of APs (91a to 91e) in accordance with a network structure managed by the SW (70). The AP (91a to 91e) converts the Ethernet® signal to an electrical signal type wireless LAN signal, which is in turn output to a main station (10). The main station (10) frequency-multiplexes the signal output from each of the APs (91a to 91e), and converts the signal to an optical signal, which is in turn output to sub-stations (20a and 20b) The sub-station (20a and 20b) transmits the signal transmitted from the main station (10) to a terminal in the form of a wireless radio wave. Thereby, when a plurality of communication areas are present, the accommodation capacity of an AP can be effectively utilized in each communication area.

Abstract: The present invention is directed to a wireless communication system capable of keeping a level of a wireless signal received by a relay apparatus (20) within a predetermined dynamic range. In a control apparatus (10), a transmitting section (102) converts a downstream electric signal into a downstream optical signal and transmits the downstream optical signal to the relay apparatus (20) via an optical transmission path (40). The relay apparatus (20) converts the received downstream optical signal into a downstream electric signal and transmits the downstream electric signal as a wireless signal to a wireless communication terminal (30) from a transmitting/receiving antenna section (204). In the relay apparatus (20), a level adjustment section (207) adjusts the level of the wireless signal transmitted by the relay apparatus (20) such that the receiving level of the wireless signal received by the relay apparatus is kept within a predetermined range.

Abstract: A wireless access system and method are provided by which the wireless communications area covered by a single access point is increased while maintaining the maintainability of the access point, minimizing an increase in system cost, and avoiding the hidden terminal problem. An access point (12) and terminals (16a to 16c) are connected via a master station (13), an optical multiplexing/demultiplexing section (14), and slave stations (15a to 15c). A downstream signal to the terminals (16a to 16c) from the access point (12) is transmitted such that the master station (13) outputs the downstream signal to each of the slave stations (15a to 15c) in a distributed manner through the optical multiplexing/demultiplexing section (14).

Abstract: A light emitting section 12 outputs an optical signal having an intensity corresponding to a transmission timing signal 81, the optical signal modulated based on a radio transmission signal 82. A received photocurrent detection section 22 detects an intensity of an optical signal received by a light receiving section 21. In accordance with the detected intensity, a high frequency amplification section 23 amplifies the output signal of the light receiving section 21, and a transmission timing signal reconstruction section 24 reconstructs the transmission timing signal. The use of the light emitting section 12 outputting no optical signal in a non-transmission state and the use of the high frequency amplification section 23 outputting no signal in the non-transmission state allow noise caused in an antenna side base station 20 in the non-transmission state to be reduced.