Communication system including allocating free signalling channels to individual substations having data to transmit A communication system includes a main station (MS) and a plurality of substations (SX/SZ) which include each a transceiver and are all connected in parallel to first (UL) and second (DL) unidirectional links on which recurrent first and second cells of fixed length are transmitted in opposite direction. Each of these cells contains a plurality of signalling channels smaller than the number of substations. When a substation has to transmit data it starts an allocation procedure wherein the substation cooperates with the main station and by which a channel is allocated to it. Afterwards prior to transmitting the data the substation transmits a request signal in the allocated channel and starts transmission after having received from the main station a grant signal in the homologous signalling channel of a second cell. De-allocation of a channel occurs as soon as the latter is no longer needed. Medium access control (MAC) protocol for single bus multimedia fair access local area network A method provides for data transmission utilizing medium access control protocol with a fair cell-access scheme in a local area network having a unidirectional looped bus and a plurality of network stations coupled to the bus for asynchronous cell transmissions from one network station to other network stations. A head-of-bus is used to generate continuously time slots to the bus. Each of the time slots includes a busy bit, a reserved bit, and a slot reservation bit. The medium access control protocol makes use of the busy bit, the reserved bit, and the slot reservation bit so as to provide fair bandwidth sharing by all of the network stations connected to the bus. Communications system and method for bi-directional communications between an upstream control facility and downstream user terminals Cordless telephones generate cell relay packets. Packets from each cordless telephone are polled by an upstream polling unit avoiding multi-unit interference. Cell packets are transmitted via a cable TV system. Radiated frequencies of the cordless telephones are shifted in frequency as they enter or leave the TV feeder cable to allow frequency reuse. The upstream polling unit appends header information on the cell packets and converts them into standard SONET ATM protocol packets. The cell relay packets are switched by a cell relay type switch to create a cost-effective, alternative telephone system. Wide area fiber and TV cable fast packet cell network 53 byte length ATM compliant cells are transmitted over a digital optical fiber path to interconnect with a coaxial feeder cable TV system to support two-way digital services at a plurality of sites connected to the TV cable system. At the point of interconnection between the fiber optic path and the cable TV feeder subsystem, digital signals are converted to a UHF rf carrier frequency above the cutoff pass-band of the analog signal feeder amplifier carrying TV broadcast signals. This rf carrier conveys a high data rate digitally modulated signal limited to sections of feeder cable between the cable TV broadcast channel amplifiers. In-house access to this UHF carrier signal is via the normal TV cable tap and drop cable to a SIU, located near the subscriber's TV set. The feeder cable and the passive taps used in cable TV practice have a higher cutoff frequency than the feeder amplifiers themselves. This allows passage of an UHF signal over the feeder cable. Low pass filters at the feeder amplifiers prevent this UHF signal from being shorted out by the in-cable amplifiers. Each SIU so connected sends and receives the UHF carrier signal, which conveys the ATM type cells. Each cell's payload contains the local address of the source and destination of that cell. Each SIU decodes each cell's address and accepts only those cells that are for itself. The SIUs speak to and receive signals from an FTU located at the TV cable headend or at a fiber connection node. The common channel conveying the ATM cells alternatively sends and receives cells in a ping-pong fashion.