Abstract: A CATV system (1) operating as a two-way multiple access communication system in which a plurality of user stations (US1 to US5) communicate with a central station (CS) which can provide video programs. The system (1) can be an interactive TV system in which the user stations (US1 to US5) can order a specific program, or can respond to multiple choice questions in a program, or the like. For exchanging session accompanying information between the central station (CS) and the user stations (US1 to US5) a common control channel is provided. For true interactivity in high capacity and high user density systems, session accompanying control information is exchanged between the central station (CS) and the user stations (US1 to US5) via dedicated control channels (DSCS, USCS). Such a system (1) satisfies the needs of all kinds of multi-media systems, interactivity being an important feature in such systems.

Abstract: Known in a digital communication system (1) are phase recovery methods for QPSK modulated signals. It is proposed to extend such methods to multi-resolution QAM signals, which can be represented by rotationally invariant signal constellations. To this end, with each received symbol (r.sub.i), a phase reference (.phi..sub.i) for a high priority-bit (HP-bits) constellation is determined, and with respect to this phase reference (.phi..sub.i), a sub-constellation (CLx) for low-priority bits (LP-bits) is constructed, the sub-constellation (CLx) being rotationally invariant. The sub-configuration (CLx) is translated to an origin (O) of the signal constellation, and then the low priority-bits (LP-bits) are determined by determining a minimum squared Euclidean distance (Ed) of the rotated and translated received symbol (b.sub.i ') with respect to the rotated and translated sub-constellation. For a 2R(2,2)-QAM signal constellation a simple detection method is thus provided.

Abstract: In a diversity transmission system the problem arises that almost no improvement can be obtained when the signals to be received show frequency selective fading within the band width of the signal to be transmitted. To solve this problem the signal to be received is separated by filter banks into a number of sub-band signals. Corresponding sub-band signals of different filter banks are combined by the combiners into combined sub-band signals. These combined sub-band signals are combined to a broad band signal by a final combiner.

Abstract: Improved transmitter network with a single transmitter frequency.A transmitter network comprising a plurality of transmitters having a like transmitter frequency may cause disturbance to occur in an adjacent similar transmitter network. This disturbance is not of an echo signal type, so that cancellation thereof is difficult. For eliminating this disturbance as much as possible, a transmitter network is used wherein a main transmitter is associated with auxiliary transmitters having an aerial height which becomes smaller for auxiliary transmitters located more closely to the boundary of the desired coverage area of the system.