Alcatel N.v.

Willem J Verbiest

Gert Van Der Plas

Bart F Voeten

Frank Octaaf Van Der Putten

Denis J Mestdagh

Christiaan H Sierens

Frank C Defoort

Jan L De Groote

Christophe D Vermeulen

Ingrid Zulma Van De Voorde

Werner J Stessens

Peter F Joos

Vincent Pirson

Marc M Duponcheel

A method is provided of determining access in a communication network having a main station (CS) and user stations (US1-USM) with distinct N-bit binary addresses, and having an access protocol including transmitting from the main station (CS) an invitation-to-send signal, and upon receipt thereof by the user stations (US1-USM), starting an access group which includes all user stations (US1-USM) wanting access to the main station (CS).

Method used in a communication network for determining access of user

A video on demand network (VODN), transmits video signals (VS) to user stations (US11, . . . , US2N) pursuant to the receipt of control signals (CS) issued by these user stations. In order to optimize the retrieval costs, this video on demand network maintains a large video library in a central video server (CS) and stores locally popular video signals in a plurality of local distributed video servers (DS1/2) from which the latter video signals are transmitted to the user stations. The video signals provided by the local distributed servers are updated from the central server based upon the changing popularity of the video signals. The present invention proposes in particular to store the video signals in the local distributed servers in random access read/write memories (HDA), e.g., electronic RAMs, magnetic or optical disks, and/or the like, from which the video signals can flexibly be supplied on-line to the user stations and to store the video signals in the central server in sequential access memories, e.g. Digital Audio Tapes (DAT) and CD-ROMs (CDR), providing cheap mass storage.

Video on demand network, including a central video server and

The system includes two transmitters (T1, T2) and two receivers (R1, R2). One transmitter (T1) may include a wavelength tunable laser, sending an FSK optical signal (OS1) which has a constant intensity. In a first receiver (R1) this FSK optical signal (OS1) is transformed into an IM signal (OS1') by an optical pass band filter. This IM signal (OS1') is then detected by a first direct detection receiver (DM). In a second direct detection receiver (R2) the FSK optical signal (OS1) is not detected, since it has constant intensity. A second transmitter (T2) includes a Fabry Perot laser or a LED with a broad linewidth, sending an IM optical signal (OS2). This IM optical signal (OS2) is detected by the second direct detection receiver (R2). It is not detected by the first direct detection receiver (DM), because it is strongly attenuated when passing through the narrow bandpass optical filter (TM) before being applied to the first direct detection receiver. This system is especially advantageous in bidirectional optical transmission systems, due to its inherent insensitivity to reflections.

Optical transmission system

The time slot management system is included in a digital time division multiple access system includes a main station MS and a plurality of substations U1/16 connected to each other via a tree network. The substations U1/16 send to the main station MS upstream information packets in time slots assigned to each of the former stations by the main station. Part of the time slots are reserved for management information and used by the substation to inform the main station about the bandwidth needed for the further transfer of the upstream information, According to this information the time slot management system allocates the time slots and informs the substations thereof. In this way a flexible and dynamic time slot allocation is provided.

Time slot management system

Encoder arrangement including the cascade connection of a data source (VSS), an encoder circuit (ENC) and a buffer circuit (BUFC) which is part of a preventive policing circuit (PPC) adapted to reduce the data output rate of said buffer circuit when said output rate does not satisfy a predetermined probability distribution function (CCCP/CR) of said output rate. The PPC at the end of each measurement interval measures this data output rate, determines the interval (BRI) to which the measured data output rate belongs and generates an alarm signal (AL). Via a gating arrangement (AG, GC) the alarm signal controls the connection of a clock signal (CLO/3) with a reduced output rate to the read-out input (RO) of the buffer circuit (BUFC) when for the measured interval the cell rate has to be decreased.

Encoder arrangement having preventive policing circuit (PPC) with

The measurement equipment (SMC) is used in a telecommunication switching system to check if the cell rate of each of a plurality of individual cell streams multiplexed in a same link remains within the limits on the basis of which its multiplexing was allowed. To this end the equipment checks at the end of each measurement interval (MTI) and for a plurality of cell rates [(M-S)/A, (M-S/2)/A, . . .] if the expected probabilities to exceed these cell rates are exceeded or not. In the positive the cell rate is limited by dropping cells. Thus an expected complementary (with respect to 1) cumulative probability distribution function of the cell rate is approximated by a staircase-shaped function.

Statistical measurement equipment and telecommunication system using same

An image signal (V1) is transform coded in a Discrete cosine Transform Coder (DCT) and the output coefficients thus provided are encoded in a zonal encoder (QZ). The output of QZ is inversely coded (IQZ) and substracted from the coefficients of the DCT. The resulting error is encoded in an entropy encoder. Both the zonal coder and the entropy encoder have quality inputs (TZQ, TEQ) controlling the compression factor, and have their outputs combined in a single compressed data stream (TXD3).

Image processing system

Conditional multiplexer wherein an input bitstream having a variable bitrate is allowed as part of a multiplexed output bitstream of input bitstreams or not depending on the result of an operation performed by processing means (TPR1) and which consists in calculating an estimated output bandwidth (B2) of said output bitstream from the mean values (mi) and variances (vi) of the probability distribution functions of the bitrates of said input bitstreams and in the subsequent comparison of said estimated output bandwidth (B2) with the maximum allowable output bandwidth (B). Further processing means (RPR1) continuously measure the mean and variance parameters and continuously verify if the sources of the bitstreams operate within the assigned bandwidths.

Conditional multiplexer

Information signals (Y1, C1; Y2, C2: Y3, C3) relating to the same video image but each defining the image with a different accuracy are transmitted asynchronously and on a time division basis as packet sets (Y1, C1; Y21, C21; Y32, C32). In a receiving station (SS2) the information signals are derived from the received packet sets and by means of selection circuit (SEC1/3) two or more of these signals are supplied to a combination device (VTE) and are combined therein to form an image.

Information transmission system

The image processing system includes a fast packet switching network (PSNW) to which send an receive stations (SR, RC) are connected. Each image (AA) to be transmitted is subdivided into blocks by a grid (GR) which is displaceable with respect to the image and the groups of image signals corresponding to these blocks are encoded and transmitted to the network together with a signal (DX, DY), indicating the grid position, as a bitstream having a variable bitrate. The grid position is changed for each image transmission and in the receiver station use is made of a phaselocked loop (PLL) to derive a clock signal from reference signals of this bitstream.

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Sint Gillis Waas, Belgium

Willem J Verbiest