Abstract: In a communications system a transmitter is arranged to transmit asynchronous transfer mode (ATM) cells in which synchronous transfer mode (STM) channels are assembled. In order to minimise the bandwidth required at lease some of the ATM cells include one or more switch command(s) (12) that indicate a change in the activation state of one or more STM channels (11-0 to 11-n). The switch commands (12) and STM channels (11) fill the ATM cell from opposite ends of the cell. Activate switch commands comprise two bytes, a high byte including a pointer (18) pointing to the start of a block of STM channels (11) and a low byte that includes a pointer (19) that points to the channel within a block of STM channels (11) to which the switch command applies.

Abstract: A wireless communications system in which an access point (AP) transmits a downlink signal for reception by one or more subscriber unit(s) (SU) and the subscriber unit (SU) transmits an uplink signal for reception by the access point (AP). The downlink signal from the access point (AP) carries syncronisation bursts (2) at predetermined times and data contained in frames interleaved between the synchronisation bursts. Each synchronisation burst comprises an offset pointer (4) to the start of the subsequent downlink frame.

Abstract: A fixed wireless access communications system comprises an access point and a plurality of subscriber units. Each subscriber unit (502) contends for access to a communications channel to the access point by transmitting a contention word to the access point during a contention time slot. The contention word is predistorted to compensate for the channel impulse response of the transmission channel so that the access point can decode the contention words without using equalisation. A control unit (512), which may comprise a microprocessor, loads the predistorted contention word (a) into a memory (520) and causes the stored predistorted contention word (a) to be applied to a transmitter (508) during a contention time slot when the subscriber unit (502) wishes to request a transmission channel to transmit data to the access point.

Abstract: A dynamic channel allocation method and system for use in a wireless network operates by monitoring at least the allocated channel allocated to a particular network node to generate one or more channel metrics relating to radio conditions on the channel. The metrics generated are Received signal power, signal to noise ratio of transmissions on the network and long-term mean square of the equaliser error used in each terminal. The generated metrics are communicated back to the cell access point or the network control server over a signalling channel, and a new frequency is allocated to the cell if it is determined from the metrics that the presently allocated channel is suffering interference. The signalling channel is preferably an ATM VPI/VCI pair, such that signalling messages are transmitted as ATM cells which can be communicated across the wireless channel using the sane signalling frame as is used for payload cells.

Abstract: A communications system operator provides to each user of a multi-user communications system a committed information rate (CIR). When a user requests bandwidth for transmission, a system controller queues the user in a high-priority subclass A. The system controller allocates bandwidth to the user at the head of the queue as requested but if the user's bandwidth, measured as an average over a sampling time, exceeds its CIR, it is moved into a low-priority subclass B. The user can then only obtain further bandwidth after other users in the high-priority subclass have been allocated bandwidth up to their CIRs. If a user in the low-priority subclass only receives allocation of a small amount of bandwidth, so that its average inforamtion rate falls below its CIR, it is moved back in to the queue in the high-priority subclass.

Abstract: A packet switched communications network comprises a controller (11) and a plurality of controlled units (12, 13, 14) arranged in a ring. Each of the controlled units comprises a switch (31) at its input, each switch including control means (44) that are responsive to control instructions transmitted by the controller (11). Depending on the instructions the switch (33) will either be configured to pass control instructions and data into or out of the controlled unit (12, 13, 14), or to forward the control instructions and data to a further controlled unit (12, 13, 14) that is connected to the controller (11) or back to the controller (11). In order for units in the ring, that are not registered with the controller (11), to acquire an address, the controller (11) transmits periodically broadcast packets, which contain a unique registration address to be used by an unregistered unit. Once registered, the unit can receive control instructions from the controller (11) as well as data.

Abstract: A dynamic channel allocation method and system for use in a wireless network operates by monitoring at least the allocated channel allocated to a particular network node to generate one or more channel metrics relating to radio conditions on the channel. The metrics generated are Received signal power, signal to noise ratio of transmissions on the network and long-term mean square of the equaliser error used in each terminal. The generated metrics are communicated back to the cell access point or the network control server over a signalling channel, and a new frequency is allocated to the cell if it is determined from the metrics that the presently allocated channel is suffering interference. The signalling channel is preferably an ATM VPI/VCI pair, such that signalling messages are transmitted as ATM cells which can be communicated across the wireless channel using the sane signalling frame as is used for payload cells.

Abstract: A packet switched communications network comprises a controller (11) and a plurality of controlled units (12, 13, 14) arranged in a ring. Each of the controlled units comprises a switch (31) at its input, each switch including control means (44) that are responsive to control instructions transmitted by the controller (11). Depending on the instructions the switch (33) will either be configured to pass control instructions and data into or out of the controlled unit (12, 13, 14), or to forward the control instructions and data to a further controlled unit (12, 13, 14) that is connected to the controller (11) or back to the controller (11). In order for units in the ring, that are not registered with the controller (11), to acquire an address, the controller (11) transmits periodically broadcast packets, which contain a unique registration address to be used by an unregistered unit. Once registered, the unit can receive control instructions from the controller (11) as well as data.

Abstract: In a fixed wireless access (FWA) communications system comprising an Access Point (501) and a plurality of Subscriber Units (502-1, 502-2 502-N) each Subscriber Unit transmits a concentration word when it wishes to obtain access to transmit data. Each Subscriber Unit (502) includes a linear precoder (517) which predistorts the contention word to compensate for the impulse response of the transmission channel between it and Access Point (501). The precoder (517) is optimised specifically for the contention word to be transmitted instead of for general data.

Abstract: In a multi-user communications system in which users contend for limited total bandwidth, a bandwidth allocation method operates as follows. Each user is classified into one of a plurality of ranked classes. Each class contains an active pool (2), containing users which are queued to receive an allocated amount of bandwidth to transmit and/or receive a quantity of data, and an inactive pool, containing users which are not currently seeking to transmit and/or receive. In each class, the user at the head of the active pool queue uses its allocated bandwidth and then moves to the back of the queue if it has more data to transmit and/or receive; otherwise it moves to the inactive pool. In each class, if a user in the inactive pool contends for a bandwidth allocation, it is moved into the active pool queue. Preferably, different bandwidth access priorities are provided in different classes, so that users seeking bandwidth-critical communications, such as voice channels, may be placed in a high-priority class.

Abstract: A dynamic channel allocation method and system for use in a wireless network operates by monitoring at least the allocated channel allocated to a particular network node to generate one or more channel metrics relating to radio conditions on the channel. The metrics generated are Received signal power, signal to noise ratio of transmissions on the network and long-term mean square of the equaliser error used in each terminal. The generated metrics are communicated back to the cell access point or the network control server over a signalling channel, and a new frequency is allocated to the cell if it is determined from the metrics that the presently allocated channel is suffering interference. The signalling channel is preferably an ATM VPI/VCI pair, such that signalling messages are transmitted as ATM cells which can be communicated across the wireless channel using the sane signalling frame as is used for payload cells.

Abstract: A communications system operator provides to each user of a multi-user communications system a committed information rate (CIR). When a user requests bandwidth for transmission, a system controller queues the user in a high-priority subclass A. The system controller allocates bandwidth to the user at the head of the queue as requested but if the user's bandwidth, measured as an average over a sampling time, exceeds its CIR, it is moved into a low-priority subclass B. The user can then only obtain further bandwidth after other users in the high-priority subclass have been allocated bandwidth up to their CIRs. If a user in the low-priority subclass only receives allocation of a small amount of bandwidth, so that its average inforamtion rate falls below its CIR, it is moved back in to the queue in the high-priority subclass.

Abstract: A wireless communications system in which an access point (AP) transmits a downlink signal for reception by one or more subscriber unit(s) (SU) and the subscriber unit (SU) transmits an uplink signal for reception by the access point (AP). The downlink signal from the access point (AP) carries syncronisation bursts (2) at predetermined times and data contained in frames interleaved between the synchronisation bursts. Each synchronisation burst comprises an offset pointer (4) to the start of the subsequent downlink frame.

Abstract: The transmit power of the subscriber terminals in a wireless network can be controlled by measuring the received power of a signal transmitted from an access point to a subscriber terminal at the subscriber terminal and then using the measured value as an index into a look-up table of transmit power attenuator settings. The use of a simple look-up table reduces the implementation complexity, since no complicated calculations must be performed to achieve effective power control.

Abstract: Propagation delay compensation in a wireless network comprising a central access point and multiple subscriber terminals is achieved by defining a registration time slot in which new subscriber terminals must first transmit network registration signals to the access point. The subscriber terminals by default transmit at the start of the time slot, and the access point times the delay from the start of the slot to the receipt of the subscriber terminal registration request, and then transmits this information back to the subscriber terminal. In all subsequent transmissions the subscriber terminal uses this information to delay its transmissions to compensate for differences in signal propagation delay between each subscriber terminal.

Abstract: A method and system for providing wireless backhaul channels for use in a cellular radio network is disclosed wherein any of the subscriber terminals can be used as a backhaul terminal thus dispensing with the need for a dedicated backhaul terminal. In the preferred embodiment, the backhaul channel is integrated with the data channels provided for network payload communications, with the backhaul data being allocated the highest data priority and a traffic scheduler allocating the backhaul data time slots for transmission accordingly. This has the advantage that the bandwidth required for backhaul can be dynamically assigned to cope with the network loading at any time.

Abstract: A method of setting up a connection between two parties over a radio ATM network is provided. A remote, off-board agent, called the proxy signalling agent, is used to provide signalling and call control functionality for one or more network element(s). In order to receive and transmit signalling messages on behalf of the network element, a bi-directional virtual channel is provisioned, one for each port, from the network element to the proxy signalling agent. For each network element under the control of the proxy signalling agent, the proxy signalling agent provides signalling stacks, one for each of the elements ports, along with call admission control, routing and VCI allocation functions. This avoids the need for the network element to perform these functions. The proxy signalling agent controls the network element's connection tables using a simple and low-level control protocol to effect changes in the connection state at that element, rather than using UNI.

Abstract: A block clock and initialization circuit for a programmable logic block in a complex very high density programmable logic device generates a plurality of block clock signals and block initialization signals for elements in the programmable logic block. The block clock and initialization circuit includes a block clock generator circuit and a block initialization circuit. The block clock generator circuit receives a first set of product terms in a plurality of product terms and a plurality of clock signals as input signals. In response to the input signals, the block clock generator circuit generates output signals on a plurality of block clock lines. The block initialization circuit receives a second set of product terms in the plurality of product terms as input signals. In response to the input signals, the block initialization circuit generates a plurality of output signals on the block initialization lines.

Abstract: A method and apparatus for testing a static RAM includes a word line voltage control circuit (42) and an array supply voltage control circuit (46). In response to receiving a first control signal from a tester, the word line voltage control circuit (42) is used to provide a word line voltage to each word line of the memory array (31). The array supply voltage control circuit (46) provides a supply voltage to the array (31) in response to receiving a second control signal from the tester. During testing of memory 30, the array supply voltage and the word line voltage are supplied independently of the memory power supply voltage V.sub.DD in order to quickly detect memory cells that are defective due to soft defects.