摘要:
In apparatus for receiving digital data signals in a digital communication system, especially an Integrated Services Digital Network, timing recovery problems associated with erratic zero crossing when multiple terminals transmit to a common receiver are mitigated by detecting the rate of change of the digital data signal between two predetermined positions (C1, C2) and controlling sampling of the digital data signal in dependence upon the difference between such rate of change and a reference. The rate of change conveniently corresponds to the trailing ''corner'' of a framing pulse (F), i.e. the point at which the signal commences the transition from one polarity to the other. The ''corner'' is much more stable, i.e. less susceptible to variation due to multiple terminal effects, than the zero-crossing which follows it, since the zero crossing may vary relative to the ''corner''. The transition may be determined by sampling the digital data signal at two discrete positions and determining when the two resulting samples differ in amplitude by a predetermined amount. One of the two pulses (C1, C2), namely the one with the larger amplitude (1), may then be used for data recovery.
摘要:
A small telephone system provides telecommunications services for personal wireless telephone sets over an area which is divided into service cells. Each of the cells is defined by reception characteristics of a plurality of radio base stations within the cell. During a call progress, if the wireless telephone set is mobile, a radio link with the set is handed off from one cell to another as the wireless telephone set moves along. The telephone system includes a service controller and a port being wireline connected between each radio base station and the service controller. The service controller selects radio base stations for setting up radio links with wireless sets of a calling or called persons, and responds to received signal strengths for handing a radio link from radio base station to radio base station, to maintain the quality of the radio link with an active mobile wireless telephone set.
摘要:
In a wavelength division optical transmission system incorporating optical amplifiers, an identifying pilot tone is modulated on to each multiplexed wavelength. Each system amplifier determines from the pilot tones the total number of wavelengths being transmitted and thereby provides a corresponding adjustment of the amplifier gain. This prevents overamplification when one or more wavelengths is missing from the multiplexed signal e.g. as the result of a transmitter fault.
摘要:
A method of performing handover of a call associated with a mobile station (P2) in one cell (3) but moving towards another cell (2), which includes making a first attempt, using for example a MUX1 SNIFF procedure, on the channel allocated to the mobile station for that call, and if that attempt fails allocating the mobile station a different channel in the one cell (3) and making a second attempt. This different channel allocation (intracell handover) is performed even if there are no better signal characteristics achieved as a result. This procedure makes it more likely to be possible to achieve handover when a second mobile station (P1) associated with an adjacent cell (1) and operating on the same channel as the first mobile station (P2) is also within range of the basestation (5) of the other cell (2).
摘要:
Un récepteur pour les données codées en code Manchester comporte une boucle de retour d'auto-étalonnage qui génère une impulsion d'horloge pour récupérer les signaux d'horloge et de données. La boucle de retour d'auto-étalonnage comprend une première ligne à retard numérique (12) échantillonnée par plusieurs bascules de type D (52) en fonction du signal d'horloge récupéré (RCLK) de manière à fournir un mot de contrôle CNT(O:N) indiquant le nombre d'éléments à retard numériques (50) nécessaires pour évaluer par approximations la moitié de la période d'horloge récupérée. Une seconde ligne à retard numérique (14), mise en correspondance par connexion (58) avec la première, fournit les trois-huitièmes d'un retard de période d'horloge. Le signal d'horloge retardé (DCLK) est dérivé de la suite de bits par échantillonnage en fonction des impulsions d'horloge (TPLS). Le signal de données décodées (RDATA) est dérivé de la suite de bits par multiplexage de l'entrée d'échantillonnage en fonction de l'impulsion d'horloge et du signal de données décodées.
摘要:
An improved method of assigning frequencies in an N=9 frequency plan so as to eliminate adjacent channels. The frequency plan disclosed reduces the effects of adjacent channel and co-channel interference and further enhances channel capacity.