Abstract: A receiver (1) for a phased array antenna comprises a laser light source (2) arranged to provide an optical spectrum comprising a first spectral component having a first wavelength and a second spectral component having a second wavelength. The first wavelength is spaced from the second wavelength. A wavelength separator (4) is configured to separate the first spectral component from the second spectral component, such that the first spectral component is directed onto a first path (A) and the second spectral component is directed onto a second path (B). A first delay unit (16) is configured to add a controllable time delay to the first spectral component on the first path. A second delay unit (42) is configured to add the time delay to the second spectral component on the second path. A modulator (14) is configured to modulate the first spectral component on the first path with a received RF signal from the phased array antenna.

Abstract: A plurality of sub-cells are defined within a cell area of a radio communication network by the intersection of a radio paths of a plurality of directional radio antennas. The plurality of directional radio antennas are arranged to broadcast radio signals simultaneously, and to receive radio signals simultaneously. This disclosure relates to determining of signal values transmitted by or received from the plurality of directional radio antennas in a radio communication network.

Abstract: The method comprises analyzing (203) probing packets sent on a plurality of end-to-end paths over links of the network. At least one analysed probing packet is a timing packet comprising timing information for synchronization. The analyzing comprising analyzing probing packets sent on all of a set of probing paths. The set is selected (201) such that the analyzing provides a determination of a performance of each individual link. The method further comprises determining (204) the performance of individual links.

Abstract: A method of monitoring performance of a network using network tomography comprises obtaining (102) information indicative of topology of the network and computing (104) a plurality of paths for monitoring the network. Further the method comprises instructing (110) source nodes of the computed paths to send probing packets towards destination nodes of the computed paths, wherein said probing packets undergo segment routing in said network and instructing (114) the destination nodes of the computed paths to carry out network performance measurements based on probing packets received by the destination nodes. Finally the method comprises receiving (116) the performance measurements from the destination nodes and inferring (118) information about performance of nodes in the network using network tomography, wherein the inference process includes correlating the performance measurements of the computed paths.

Abstract: A method for inferring component parameter values for components in a network is disclosed. The components comprise at least one of network nodes or network links and the method comprises identifying a plurality of paths through the network (100), measuring values of a path parameter for identified paths (410), generating a set of constraints by expressing individual measured path parameter values as a function of component parameter values of the components in the path associated with the measured path parameter value (420a), and generating an estimate of the component parameter values by solving an optimisation problem defined by the generated constraints (420b).

Abstract: A method (50) of selecting a set of probing paths in a network for network tomography. The method comprises generating (52) possible probing paths (P1). The method further comprises determining (53) if the possible probing paths are linearly independent from probing paths already selected for the set of probing paths, in an order of an increasing cost or distance of the possible probing paths. The method further comprises selecting (55) a said possible probing path for the set of probing paths only if the possible probing path is linearly independent from probing paths already selected.

Abstract: A feed signal generator (10) for a phased array antenna, comprising: an input (12) to receive an optical spectrum having first and second phase-locked spectral components, respectively having first and second optical frequencies; wavelength selective separator apparatus (14) to separate the optical spectrum into a first optical signal being the first spectral component and a second optical signal being the second spectral component; an optical time delay element (16) to apply a time delay to the first optical signal to form a delayed optical signal; a heterodyning device (20) to heterodyne the delayed optical signal and the second optical signal to generate a feed signal (22) having a power proportional to a product of the amplitudes of the second and delayed optical signals and a phase proportional to the time delay; and optical amplitude control apparatus (18) to set an amplitude of the delayed optical signal such that the product of said amplitudes causes the power of the feed signal to have a preselected

Abstract: A transport network (10) is configured to connect a plurality of remote radio units (3) with a plurality of digital units (5) in a radio access network. The transport network comprises an electronic cross-connect (31) common to the plurality of remote radio units and digital units, and a control unit (32) configured to control the electronic cross-connect. The transport network further comprises an optical link (40) between the electronic cross-connect and remote radio units. The electronic cross-connect is a multi-layer switch. The electronic cross-connect is configured to switch data flows between one or more of said plurality of digital units (5) and one or more of said plurality of remote radio units (3).

Abstract: Anode for burst switching of traffic flows in an optical network switches bursts of traffic flows in different time slots. Time slots are allocated (96) so that a time gap between successive allocated time slots is selected according to a jitter specification of the traffic flow. A map of the allocations controls a burst switch to pass the bursts in their allocated time slots (86). By making the time gap between allocated time slots for successive bursts selectable, the jitter can be controlled more precisely, or the proportion of time slots filled can be increased resulting in better utilisation of available bandwidth. The allocation can be made hop by hop. The map can be generated in a distributed and duplicated manner at each node. The allocation can be updated to adapt to changes bandwidth demands.

Abstract: A packet network traffic flow effective bandwidth estimation apparatus comprising a committed burst size (CBS) estimator loop, a peak information rate (PIR) estimator and an effective bandwidth (Eff.BW) estimator. The loop includes a meter arranged to determine a number of conformant bytes (G) and a number of violating bytes (Y) of a traffic flow; a committed information rate (CIR) estimator arranged to determine a subsequent estimated CIR; a controller arranged to, if Y is above zero, determine an estimated CBS (ECBS) correction and to apply the correction to the ECBS, and arranged to, if Y is zero, output the previously used ECBS. The PR estimator receives the ECBS from the loop and the ECIR and determines an estimated PR (EPIR) in dependence on the ECBS and the ECIR. The Eff.BW estimator determines an Eff.BW of the traffic flow from the EPIR, ECBS and ECIR.

Abstract: A wireless communications link comprising an RF link and a free space optics (FSO) link, a switch, an RF signal monitoring apparatus, an optical signal monitoring apparatus, alarm apparatus and a controller. The switch operates in a normal mode to aggregate the links to form a link aggregation group and to route traffic on the link aggregation group, a first protection mode to route traffic on the FSO link, or a second protection mode to route traffic on the RF link. The controller is arranged to receive an alarm signal and to generate and transmit a control signal to cause the switch to operate in the first protection mode when a first alarm signal is received, the second protection mode when a second alarm signal is received, and the normal mode when an indicator is received indicating that both signal quality parameters are above their threshold values.

Abstract: A node (260, 50) for a multi-token optical communications network has optical channels between the node and other nodes, each channel having a token (T1, T2, T3), passed between nodes, to indicate that a corresponding optical channel is available for transmission during a token holding time. The node has a transmitter (280) for transmitting packets over the optical channels, a buffer (170, 270) for queuing packets before transmission, and a transmit controller (170, 290) configured to control the buffer to forward an initial packet or packets from the buffer to the transmitter once a token has been received. The transmit controller determines how much of the token holding time remains after the transmission of the initial packet or packets, and then controls the buffer to forward a further packet according to the remaining token holding time. A maximum packet delay can be reduced where there is asymmetric traffic. A token holding time can be different for different nodes.

Abstract: An optical communications network node (10) comprising an optical transmitter module (16), an optical receiver module (12), an electrical cross-point switch (20) and control apparatus (24, 26). The optical transmitter module (16) comprises optical sources (18) each having a different operating wavelength and each being selectively assignable as an optical circuit switching channel source or an optical burst switching channel source. The optical receiver module (12) comprises a said plurality of optical detectors each operable at one of said operating wavelengths. The electrical cross-point switch (20) comprises switch paths (22) and is configurable to allocate a first set of switch paths for optical circuit switching and a second set of switch paths for optical burst switching.

Abstract: A wireless communications link comprising an RF link and a free space optics (FSO) link, a switch, an RF signal monitoring apparatus, an optical signal monitoring apparatus, alarm apparatus and a controller. The switch operates in a normal mode to aggregate the links to form a link aggregation group and to route traffic on the link aggregation group, a first protection mode to route traffic on the FSO link, or a second protection mode to route traffic on the RF link. The controller is arranged to receive an alarm signal and to generate and transmit a control signal to cause the switch to operate in the first protection mode when a first alarm signal is received, the second protection mode when a second alarm signal is received, and the normal mode when an indicator is received indicating that both signal quality parameters are above their threshold values.

Abstract: A node (260) for an optical communications network in which a token is passed between nodes, indicating that a corresponding optical channel is available for transmission during a token holding time while that node holds that token, until it passes the token to another node. A transmit controller (290) determines a traffic class of said packet and controls a buffer to forward a packet from the buffer to the transmitter according to the traffic class, if there is sufficient of the token holding time remaining before the received token must be passed on to another node for said packet to be transmitted by the transmitter over an optical channel corresponding to the received token. By having the packet forwarding dependent on traffic class, packets can be handled differently to suit different characteristics of the traffic classes.

Abstract: A node (260, 50) for a multi-token optical communications network has optical channels between the node and other nodes, each channel having a token (T1, T2, T3), passed between nodes, to indicate that a corresponding optical channel is available for transmission during a token holding time. The node has a transmitter (280) for transmitting packets over the optical channels, a buffer (170, 270) for queuing packets before transmission, and a transmit controller (170, 290) configured to control the buffer to forward an initial packet or packets from the buffer to the transmitter once a token has been received. The transmit controller determines how much of the token holding time remains after the transmission of the initial packet or packets, and then controls the buffer to forward a further packet according to the remaining token holding time. A maximum packet delay can be reduced where there is asymmetric traffic. A token holding time can be different for different nodes.

Abstract: An optical communications network node (10) comprising an optical transmitter module (16), an optical receiver module (12), an electrical cross-point switch (20) and control apparatus (24, 26). The optical transmitter module (16) comprises optical sources (18) each having a different operating wavelength and each being selectively assignable as an optical circuit switching channel source or an optical burst switching channel source. The optical receiver module (12) comprises a said plurality of optical detectors each operable at one of said operating wavelengths. The electrical cross-point switch (20) comprises switch paths (22) and is configurable to allocate a first set of switch paths for optical circuit switching and a second set of switch paths for optical burst switching.

Abstract: A distributed scheduler for frame based communication between a plurality of terminals and a master controller, comprises a plurality of concentration elements for local scheduling of upstream data, the plurality of concentration elements and the plurality of terminals being partitioned over a plurality of cells distributed on a multiple hierarchical level star topology, each cell belonging to a hierarchical level N, where N is comprised between a top level, corresponding to a single cell to which the master controller is assigned, and a bottom level; at each cell at level N one concentration element being the master element for the cell and the remaining concentration elements and terminals in the cell being slave elements of the master element for the cell; each master element in a cell at level N being in turn a slave of the master element in one of the cells at level N+1, the master element at the top level being the master controller; each master element at level N comprising means for collecting uplink

Abstract: A distributed scheduler for frame based communication between a plurality of terminals and a master controller, comprises a plurality of concentration elements for local scheduling of upstream data, the plurality of concentration elements and the plurality of terminals being partitioned over a plurality of cells distributed on a multiple hierarchical level star topology, each cell belonging to a hierarchical level N, where N is comprised between a top level, corresponding to a single cell to which the master controller is assigned, and a bottom level; at each cell at level N one concentration element being the master element for the cell and the remaining concentration elements and terminals in the cell being slave elements of the master element for the cell; each master element in a cell at level N being in turn a slave of the master element in one of the cells at level N+1, the master element at the top level being the master controller; each master element at level N comprising means for collecting uplink