公开(公告)号：GB2314487A

公开(公告)日：1997-12-24

申请号：GB9712244

申请日：1997-06-13

Applicant: IBM

Inventor： GFELLER FRITZ RUDOLF ,  HORTENSIUS PETER DIRK ,  KAM PATRICK K ,  KERMANI PARVIZ ,  MCKAY DANNY M ,  NAGHSHINEH MAHMOUD ,  OLSEN CLAUS MICHAEL ,  REZVANI BABAK

IPC: H04L1/00 ,  H04L1/08 ,  H04L12/413

Abstract: A method of wireless communications in a network having a plurality of terminals comprises transmitting media access coordination information at a first repetition rate and other information at a second repetition rate lower than said first repetition rate. A Media Access and contention resolution scheme for using multirate wireless,/infrared communication is described. In such an environment, each physical layer frame is broken into two portions: (1) the robust header portion which contains all svmbols important to the MAC protocol and media coordination and is sent with a repetition rate Rmax where Rmax is selected in such a way that all stations within the interference environment can decode the reservation symbols with a desired probability; and (2) data symbols which are sent with a repetition rate R where R can be less than Rmax. Here R depends on the channel conditions at any destination with respect to the source station transmitting such data symbols.

公开(公告)号：CA2241937A1

公开(公告)日：1997-07-17

申请号：CA2241937

申请日：1996-01-03

Applicant: IBM

Inventor： GFELLER FRITZ RUDOLF ,  DE LANGE MARTIN ,  HIRT WALTER

IPC: H04B10/114 ,  H04L1/00 ,  H04L7/04 ,  H04L12/28 ,  H04B10/04 ,  H04B10/06 ,  H04B10/10

Abstract: Disclosed is an optical communication system enabling communication between several co-existing transmitting and receiving stations. In order to allow communication between the co-existing stations, a robust physical layer header (RPLH; 50) is employed which can be understood by all participating stations. This robust header (50) at least comprises a preamble (52) consisting of frames forming a periodic sequence of pulses, the number of slots per frame and the frame content being known to all participating stations. The preamble (52) serves for relative synchronization and carrier detection of the receiving stations. The robust header (50) further comprises a unique synchronization word (53) used for absolute synchronization of the receiving stations. This synchronization word (53) is followed by a control field (59) of fixed length and known structure. By means of this control field (59) the receiving stations are informed which modulation method will be used for the transmission of data. Under certain circumstances it is also useful to provide other control information in said control field (59) for communication link and network control. Furthermore, information may be exchanged to allow negotiation and/or adaptation of the data rate used for transmission. This allows to optimize the throughput depending on the conditions (quality) on the channel.

公开(公告)号：DE3787427D1

公开(公告)日：1993-10-21

申请号：DE3787427

申请日：1987-07-14

Applicant: IBM

Inventor： FRANKE HILMAR ,  GFELLER FRITZ RUDOLF

IPC: G02B6/00 ,  G01J1/02 ,  G01J1/58 ,  G02B6/42 ,  H04B10/04 ,  H04B10/06 ,  H04B10/10 ,  H04B10/14 ,  H04B10/158 ,  H04B10/26 ,  H04B10/43 ,  G01J5/28 ,  H04B10/00

Abstract: A fluorescent activated light detector for detection of time modulated IR signals of preselected wavelength includes an IR light collecting member (12) made of a solid transparent core material (13) with a fluorescent light absorbing dye (15) molecularly dispersed throughout the core. Photodiodes (14) are operatively associated with the collecting member for detecting fluorescent light emitted by the collecting member upon exposure to incident IR radiation of the preselected wavelength. The light collecting member has a surface area A1 much greater than an active area A2 of the photosensing means. Use of this fluorescent activated light detector allows for increasing the effective transmission distance of infrared free space communication links without requiring an increase in transmitter radiated power.