Abstract: A distributed reservation protocol for medium access control in a multiband OFDM ultrawideband communications network having a band group comprising a plurality of transmission bands, a device in said network having a mode in which it uses a selected one of said bands to communicate, and a band hopping mode, and wherein the protocol comprises allowing a device in a group of devices to make a combined time-frequency reservation, said time-frequency reservation comprising a reservation of a combination of a subset of said bands in a said band group and one or more data communications timeslots in which the device is allowed to use said reserved band for data communications such that multiple said devices in said group are able simultaneously to use one or more of the same or overlapping said reserved timeslots in different reserved frequency bands of said band group.

Abstract: We describe a method, particularly useful for a ultra wideband (UWB) network, to enable a first device to determine whether a device address used by a second device is intended to identify said first device, in a network with a variable topology in which a device address may change, the method comprising: transmitting, repeatedly, a beacon to said second device updating a said device address of said first device; storing a history of device addresses used by said first device; receiving, at said first device, a signal including an address and comparing the received device address with addresses in the history back in time for a period limited by a synchronisation refresh time which comprises a maximum time for which said second device may fail to receive said beacon from said first device without considering that said first device is no longer synchronised to said network.

Abstract: We describe a method of decoding a DCM (dual carrier modulation) modulated OFDM signal, the method comprising: inputting first received signal data representing modulation of a multibit data symbol onto a first carrier of said OFDM signal using a first constellation; inputting second received signal data representing modulation of said multibit data symbol onto a second, different carrier of said OFDM signal using a second, different constellation; determining a combined representation of said first and second received signal data, said combined representation representing a combination of a distance of a point representing a bit value of said multibit data from a constellation point in each of said different constellations; and determining a decoded value of a data bit of said multibit data using said combined representation.

Abstract: The invention relates to communications protocols for very high-speed data transmission, in particular burst mode packet data communications for ultra wideband (UWB) communications systems. We describe a method of sending a burst of data packets from a first OFDM transceiver to a second OFDM transceiver, said transceivers having a set of OFDM synchronisation symbols for synchronising communications between the transceivers, the method comprising: sending said data packets from said first to said second transceiver, and between sending at least some of said data packets of said bursts receiving acknowledgement data from said second transceiver at said first transceiver; and wherein said acknowledgement data is encoded using said OFDM synchronisation symbols.

Abstract: Differential, current-steering DACs with reduced small signal differential non-linearity. A set of binary-weighted steerable constant current generators is used in which each constant current generator comprises a ternary constant current generator configured to generate a three-state differential current in response to a ternary signal on a control input. Each ternary current generator is associated with a bit of the binary code. The DAC further comprises a code converter coupled between a digital input, to receive a signed digital value for conversion, and control inputs of the steerable current generators, to convert the binary input code to a ternary code to control the steerable current generators to provide a differential analogue output. In embodiments the smallest current source is ½I0 where I0 is a change in differential output current caused by an lsb change in the binary input code.

Abstract: Differential, current-steering DACs with reduced small signal differential non-linearity. A set of binary-weighted steerable constant current generators is used in which each constant current generator comprises a ternary constant current generator configured to generate a three-state differential current in response to a ternary signal on a control input. Each ternary current generator is associated with a bit of the binary code. The DAC further comprises a code converter coupled between a digital input, to receive a signed digital value for conversion, and control inputs of the steerable current generators, to convert the binary input code to a ternary code to control the steerable current generators to provide a differential analogue output. In embodiments the smallest current source is ½I0 where I0 is a change in differential output current caused by an 1sb change in the binary input code.

Abstract: This invention relates to systems and methods for wireless and wired optical data communications, in particular infrared data communications using techniques borrowed ultra wideband (UWB) radio. Data is input for communication. The data defines a plurality of data symbols for transmission. Each the data symbol is encoded onto first and second optical carriers. The encoding comprises encoding each of the data symbols as respective first and second pulse packets each comprising at least one optical pulse. The encoding uses a common pulse packet position modulation for the first and second carriers. The first and second optical carriers have respective first and second optical wavelengths. An optical signal comprising the first and second optical carriers is transmitted, received, and decoded to recover the data symbols.

Abstract: This invention relates to systems and methods for wireless and wired optical data communications, in particular infrared data communications using techniques borrowed ultra wideband (UWB) radio. An optical data communications receiver for receiving data encoded using optical pulse position, the receiver comprising: an optical signal reception device; a reference signal memory for storing a reference channel response signal; and a correlator coupled to said reference signal memory and to said optical signal reception device for correlating a received optical pulse with said stored reference channel response signal to determine said optical pulse position; an output coupled to said correlator to provide pulse position data for said received optical pulse.