Abstract: Apparatus for use in equipment providing digital radio link between a fixed radio unit and a mobile radio unit. The apparatus includes demodulators arranged to receive inphase and quadrature phase input signals. A channel estimator is provided for deriving a decision directed channel estimate from one or more signals which is used by the demodulator for demodulating one or more of the signals transmitted over the same radio channel. The apparatus is for use in the demodulation of dual binary phase shift keying signals and various embodiments are possible. In addition, the apparatus may be used in conjunction with precombining Rake architecture.

Abstract: Cellular mobile radio system having at least two base stations, and at least one mobile unit arranged to communicate with the base stations via a radio medium is provided. Each base station includes apparatus for detecting the power of received signals, apparatus for generating a power control signalling bit for controlling the amplitude of a power signal, and apparatus for transmitting the power signal to the mobile unit. The mobile unit includes apparatus for receiving the power control bits, and apparatus means for monitoring the power control bits to identify the base station sending a greater number of control bits over a transmit frame, indicating that base station has received the higher average power signal over the transmit frame.

Abstract: A frequency hopped cellular mobile radio system, comprising a plurality of base stations each affording a cellular region, or cell, within which communication is facilitated with a plurality of mobile units, each of which mobile units is free to move from cell to cell, the system having in combination the following features;a synchronization system which serves to bring all mobile units within a cell into synchronization, as observed from the base station of that cell, whereby orthogonal frequency hopping between mobile units of the cell is facilitated, frequency hopping between mobile units in different cells being non-orthogonal; an affiliation strategy which tends to constrain each mobile unit to maintain communication with a base station selected in dependence upon received signal strength;mobile unit transmission power control in dependence upon received signal/noise ratio at a base station, whereby transmitted mobile power tends towards the minimum necessary for acceptable communication;a frequency hopp

Abstract: CDMA (Code Division Multiple Access) can be used in cellular mobile radio systems to provide good spectral efficiency through averaging the interference wherever the number of users per carrier is large (several tens). This is readily practicable for voice users whose data rate requirements are modest but requires large spreading factors for ISDN data service users. This invention proposes an approach in which a multiplicity of CDMA carriers each with relatively low bandwidth are used for the voice services and overlayed with wide bandwidth CDMA carriers whose bandwidth occupies the whole (or most) of the band occupied by all of the narrowband CDMA carriers in order to service the data users. This allows the same RF band to service a relatively small number of data service users with wideband (and therefore higher cost) terminals without affecting the cost of terminals for the majority of voice users.

Abstract: An automatic power control system for a cellular mobile radio system, comprising: a control center via which a plurality of base stations, each serving a cell, are linked to facilitate mutual communication between mobile units which gain access to the cellular mobile radio system via the base stations; at least two mobile units distinguishable by identification codes, the mobile units being arranged to transmit, in addition to an identification code unique to each mobile unit, a data sequence common to each mobile unit, but transmitted by each mobile unit at a nominally different time within each burst; each of said the stations including correlator operative to discriminate between signals from mobile units within its own cell and interfering signals from mobile units in adjacent cells and a data logger; and a data processing unit located at the control center and arranged to merge data from the data loggers located at each of the base stations, which serves to store the results of correlation of the data se

Abstract: In a direct sequence spread spectrum code division multiple access receiver using interference cancellation, the signal for cancellation is derived by demodulating the unwanted signals and re-modulating a carrier to create a near replica for subtraction from a delayed version of the total received signal. Errors in the demodulation process degrade the cancellation. The present invention provides an optimal way of using the reliability information in the demodulator decision variable either to turn the cancellor off for unreliable bit decisions or to partially disable the cancellor according to the bit reliabilities.

Abstract: A distributed antenna system comprises a plurality N of spaced apart antennas 3, each antenna being connected to a RF line 2 via a circulator 4, wherein each circulator 4 is arranged to pass to its associated antenna a fraction 1/N of the RF power incident thereon.This can allow cost savings in providing the components needed for the antenna installation.

Abstract: A frequency modulator comprising an oscillator the output frequency of which is dependent upon the amplitude of a modulating signal, modulating signal control means via which the modulating signal is fed to the oscillator to produce a corresponding frequency modulation on the output signal from the oscillator, a discriminator responsive to the frequency modulation for producing a corresponding amplitude signal, and a comparator responsive to the corresponding amplitude signal and to the modulating signal for providing a control signal which is fed back to control the gain provided by the signal control means so as to maintain constant the amplitude of the amplitude signal with respect to the modulating signal, whereby operation of the modulator is linearized.