Abstract:
A method of arranging exchange of signals between user terminals (U 1 , U 2 ,...U N ) in a cellular communication system and at least one base station. The base station includes a central unit (CU OFDM ) and a plurality of remote units (RU OFDM ). The signals are exchanged (14-18) between the central unit (CU OFDM ) and the remote units (RU OFDM ) as aggregated signals for plural user terminals. The signals are processed (150) at the remote units (RU OFDM ) as distinct signals each associated to a respective one of the plural user terminals (U 1 , U 2 ,...U N ).
Abstract:
A differential delay element (10) for use e.g. in selectively delaying RF signals in telecommunication systems includes a first microstrip circuit (12) and a second microstrip circuit (14) arranged side-by-side in a facing relationship. The first microstrip circuit (12) defines a first delayed travel path for a first signal from a first input port (IN1 ) to a first output port (OUT1 ) and the second microstrip circuit (14) defines a second delayed travel path for a second signal from a second input port (IN2) to a second output port (OUT2). A perturber (18) is arranged between the first (12) and second (14) microstrip circuits, displaceable (20) towards and away from the first (12) and second (14) microstrip circuits, so that when the distance of the perturber (18) to one (12 resp. 14) of the microstrip circuits increases, the distance of the perturber (18) to the other (14 resp. 12) of the microstrip circuits decreases and viceversa. The position of the perturber (18) between the first (12) and second (14) microstrip circuits defines the differential delay, namely the difference (Δτ=τ1-τ2) between the times (τ1, τ2) experienced by the two signals in travelling their travel paths through the delay device (10).
Abstract:
A device for maintaining fine alignment between an incoming spread spectrum signal and a locally generated code in a digital communication receiver comprises: - a delay line (56) for storing a plurality of consecutive samples (E-1, E, M, L, L+1) of the incoming spread spectrum signal; - three digitally controlled interpolators (24, 26, 28) for determining by interpolation between consecutive samples an interpolated early sample (e), an interpolated middle sample (m) and an interpolated late sample (1); - two correlators (30, 32) for calculating an error signal (ξ) as the difference between the energy of the symbols computed from the interpolated early (e) and late (1) samples; - a circuit for generating a control signal (S¿OUT?) for controlling the interpolation phase of the digitally controlled interpolator (24) for the early sample (e), and - a digital non-linear filter (68), for smoothing the control signal (S¿OUT?) of the interpolator (24) for the early sample (e), enabling the update operation of the control signal only when the absolute value (|ξ(n)|) of the error signal at a time instant n is smaller than the absolute value (|ξ(n-1)|) of the same error signal at a time instant n-1.
Abstract:
An iterative multiplier circuit (10) comprises modules (15 to 18) that subdivide the respective input signals (Z n , J n ) into a first part (msb(Z n ), msb(J n )) that is the power of 2 immediately lower or equal to the input signal and a second part (Z n -msb(Z n ), J n - msb(J n )) corresponding to the difference between the input signal and the aforesaid first part. A shift module (19) generates a respective output signal through shift operations that implement the multiplication operation for numbers that are powers of 2. The circuit operates according to a general iterative scheme in which at each step three components of the output signal (X.Y) are computed, corresponding to the product of two numbers that are powers of 2 and to two products in which at least one of the factors is a power of 2. The number of steps in the iteration scheme is controllable, thus allowing to vary the accuracy with which the output value (X.Y) is calculated.
Abstract:
A system for processing an RF signal received via a plurality of antenna elements includes a connection arrangement (6) for selecting a sub-set of a given number of RF signals ( r i , r j ) received from the antenna elements as well as a processing arrangement (8) for combining the received RF signals of the selected subset ( r i , r j ) into a single RF signal for demodulation. The system includes a RF phasing circuit (18) for producing selective combinations of the received RF signals ( r i , r j ) by applying relative RF phase shift weights to the RF signals ( r i , r j ) that are combined; each combination includes RF signals received from a number of adjacent antenna elements equal to the number of the RF signals in the sub-set to be selected. A radio performance estimator (14) generates for each said selective combination of RF signals at least one non-RF radio performance indicator (RPI) representative of the quality of the RF signals in the combination. A decision block (16) identifies the sub-set of received RF signals ( r i , r j ) to be selected as a function of the one radio performance indicator (RPI) generated for the selective combinations of said received RF signals ( r i , r j ). This arrangement facilitates the selection of the signals/antennas to be used for reception e.g. in a WLAN device by avoiding that the selection process may involve all the possible combinations.
Abstract:
A tunable delay line (100) for radiofrequency or microwave frequency applications consists of at least one ridge waveguide in which the ridge (103) is movable in the waveguide body (102) so as to vary the width of an air gap (105) defined between the longitudinal end surface of the ridge (103) and a confronting member (104) of the waveguide. The ridge (103) is moved by an actuator external to the waveguide body (102).
Abstract:
Disclosed herein is a dual-mode terminal (T1) designed to connect to an IP-based network (IPN) via a first communication system (UMTS) and a second communication system (WLAN), the dual-mode terminal (T1 ) comprising a first physical network interface module (N11) adapted to establish a packet-based communication with the IP-based network (IPN) via the first communication system (UMTS), the first physical network interface module (N11) being accessible via a first physical network interface (ph11 ) having a first physical network address (IP1_P1 ); a second physical network interface module (N11 ) adapted to establish a packet-based communication with the IP-based network via the second communication system (WLAN), the second physical network interface module (N 12) being accessible via a second physical network interface (ph12) having a second physical network address (IP1_P2); an IP-based protocol stack (TCP/IP) adapted to operate between a software application (A2) in the dual-mode terminal (T1) and the first and second physical network interface modules (N 11, N 12); and a system for performing a seamless handover between the first communication system (UMTS) and the second communication system (WLAN) during a connection to the IP-based network; wherein the system for performing a seamless handover comprises a virtual network physical network interface module (M 1 ) accessible via a virtual network interface (virt11) having a virtual network address (IP1 V1), the virtual network physical network interface module (M1) being configured to operate between the IP-based protocol stack (TCP/IP) and the first and second physical network interface modules (N11, N 12) to receive and transmit incoming and outgoing data packets through the first and the second physical network interfaces (ph11, ph12); the IP-based protocol stack (TCP/IP) being configured to generate data packets having a source physical network address equal to the virtual network address (IP1_V1) of the virtual network interface (virt11) in the dual-mode terminal (T1 ); and the virtual network physical network interface module (M 1) being configured to change the source physical network address of data packets from the IP-based protocol stack (IPS1 ) to the physical network address (IP1_P1, IP1_P2) of the physical network interface (ph11, ph12) of the physical network interface module (N11, N12) in the dual-mode terminal (T1 ) used for the connection to the IP-based network.
Abstract:
A channel estimator (202) for use in a receiver node receiving signals (x(1), x(2),.... x(Nu)) from a plurality of user terminals wherein each user terminal is allotted a respective set of transmission subcarriers and respective test signal sequences (rp) for transmission over the channel to be estimated. The channel estimator (202) has stored therein (400) information as to the respective sets of transmission subcarriers allotted to the user terminals (TUi, TU2,..., TIW for transmission as well as the discrete spectra of the respective test signal sequences allotted to the user terminals. Upon receiving from a plurality of user terminals signals including the respective test signal sequences (rp) transmitted over the channel by using the respective sets of transmission subcarriers allotted thereto, the estimator generates (208) the discrete spectrum of the combined test signal received and performs channel estimation as a function of the discrete spectrum of the combined test signal and the discrete spectra of the test signal sequences allotted to the user terminals (TU1, TU2 TUNu). A frequency domain channel estimation is performed for a Single Carrier Frequency Division Multiple Access (SC-FDMA) system.
Abstract:
A system for diversity processing two signals (INPUT 1 , INPUT 2 ) transmitted and/or received via two diversity antennas (1, 2) includes at least four respective propagation paths coupling the signals to the two diversity antennas (1, 2). Diversity processing is primarily in the form of decorrelation achieved by means of time variable delay elements (161 to 164; 261 to 264; 1261 to 1264) that apply time variable delays to the signals propagating over at least two of the propagation paths in the system. The related processing may take place either at RF or IF, or at baseband, whereby the time variable delays are applied by subjecting the baseband signals to multiplication by a complex signal.