Telefonaktiebolaget Lm Ericsson (publ)

Jim Svensson

Leif Wilhelmsson

Chester Park

Lars Sundström

Thomas Olsson

Roland Strandberg

Anders Berkeman

Henrik Sahlin

Henrik Sjöland

Matthias Kamuf

Staffan Ek

Anders Carlsson

Roland Carlsson

Spendim Dalipi

Martin Anderson

Peter Brauer

Jin Ellgardt

David Engdal

Andreas Nevalainen

Lars SUNDSTRÖM

Systems and methods for handling cancellation of a Passive Intermodulation (PIM) signal are provided. The network device has access to and controls one or more transmitters and one or more receivers. The network device applies a determined PIM model to a transmitted signal from each transmitter of the network device, to obtain a modelled signal. The PIM model comprises a forward path model for each transmitter to the PIM source, a common non-linear model of the PIM signal from the PIM source being applied to a combined signal comprising the signals from each transmitter modelled by the forward path model, and a linear reflective path model from the PIM source to each of the receivers of the network device for a received PIM signal. The network device further subtracts the modelled signal from a received signal on each of the receivers of the network device.

Network device and method therein for handling passive intermodulation signals in a wireless communications network

The present invention relates to method and arrangement in cellular mobile communication systems, in particular for handling of a physical random access channel for example in a Long Term Evolution communication network. By sending to at least one user equipment, UE, in a communication network cell an un-solicited speculative random access response, RAR, message comprising information relating to at least one of pre-amble identifier, allocated UE identifier, and uplink resource allocation data for L2/L3 message, it is possible to reduce the complexity of the access node, e.g. an eNodeB.

Simplified PRACH procedure using speculative random access response

A quadrature mixer arrangement is disclosed, which is adapted to translate an input signal by a translation frequency. The mixer arrangement is operated at a clock rate that equals the translation frequency times an oversampling rate, wherein the oversampling rate is not a multiple of four. The mixer arrangement comprises a sequence generator, at least one pair of mixers, and one or more correction networks. The sequence generator generates an in-phase mixer translation sequence and a quadrature-phase mixer translation sequence based on the oversampling rate. The in-phase mixer translation sequence is a time-discrete representation of a translation frequency sinusoidal function sampled at the clock rate, and the quadrature-phase mixer translation sequence is a time-discrete representation of the translation frequency sinusoidal function phase-shifted by &#x3c0;/2 plus a phase deviation and sampled at the clock rate, wherein the phase deviation is a function of the oversampling rate. Each pair of mixers comprises an in-phase mixer and a quadrature-phase mixer, each adapted to translate a respective input signal based on the respective translation frequency. The one or more correction networks are adapted to, based on the oversampling rate and the phase deviation, compensate for the phase deviation by adjusting at least one of the in-phase mixer input signal, the quadrature-phase mixer input signal, the in-phase mixer output signal, and the quadrature-phase mixer output signal.

Quadrature mixer arrangement

A mixer unit () for frequency translating, based on an LO signal, an input signal having one or more input signal components is disclosed. The mixer unit has a signal processing path (--) from each Input terminal (&#x2212;) to each output terminal (_I+,_I&#x2212;,_Q+,_Q&#x2212;) of the mixer unit (), The LO signal has an associated LO signal component (LO_Ia-d, LO_Qa-d) for each signal processing path. The mixer unit () comprises a plurality of mixer switches (-N) and a control unit (). The control unit () is adapted to, for each signal processing path (--), dynamically select an associated subset, in the following denoted active switch subset, of the plurality of mixer switches (-N) for operation in the signal processing path (-) such that which of the plurality of mixer switches (-N) belong to said active switch subset varies in time. At any instant in time, the union of all the active switch subsets is a strict subset, denoted combined active subset, of the plurality of mixer switches (-N). The control unit () is further adapted to activate only the mixer switches (-N) in said combined active subset by, for each mixer switch (-N) in the combined active subset, supplying the corresponding LO signal component to the mixer switch. A related radio receiver circuit (), a related radio communication apparatus (), and a related method are also disclosed.

Mixer unit

A technique for calibrating a receiver apparatus comprising at least one analog signal processing component and an intermediate frequency, or IF, mixer for converting IF signals comprising an in-phase, or I, signal and a quadrature-phase, or Q, signal to baseband frequency signals is provided. The IF mixer is arranged downstream of the at least one analog signal processing component. A method implementation of the technique comprises the steps of determining, in a digital processing domain downstream of the IF mixer, a metric which is affected by a frequency dependency of an imbalance between I and the Q signal, or IQ-imbalance, over a signal bandwidth, generating, based on the metric thus determined, a calibration signal configured to at least partially compensate a frequency-dependency of the IQ imbalance, and feeding the calibration signal to the at least one analog signal processing component so as to calibrate the at least one analog signal processing component.

Technique for calibrating a receiver apparatus

A receiver is operated so as to receive data conveyed on an Orthogonal Frequency Division Multiplexed (OFDM) signal transmitted on a plurality of sub-carriers. Such operation includes ascertaining which of the plurality of sub-carriers have a channel quality that satisfies one or more criteria. Then, sub-carriers are selected based at least in part on whether they have the channel quality that satisfies one or more criteria. The receiver then fully processes data streams only from the selected sub-carriers, wherein fully processing data streams comprises sub-carrier channel estimation or sub-carrier equalization or both sub-carrier channel estimation and sub-carrier equalization.

Channel estimation in OFDM receiver equipment

A test signal for determining a frequency-dependent or any other property of a receiver path is proposed. The test signal comprises, in a time domain representation, a sequence of discrete states that may be periodically repeated and that gives rise to a plurality of discrete tones in a frequency domain representation of the test signal. The test signal can be utilized for determining a frequency-dependent imbalance (e.g., an IQ imbalance) between different signal branches of a receiver or transmitter.

Technique and test signal for determining signal path properites

Embodiments of user equipment and methods for determining IQ imbalance parameters are described. In some embodiments, a method for determining in-phase (I) and Quadrature (Q) imbalance (IQ imbalance) parameters based on a known signal in a dual-carrier receiver using at least one controllable frequency offset includes receiving a known signal modulated onto a first radio frequency (RF) carrier frequency and a second RF carrier frequency different than the first RF carrier frequency. The known signal is downconverted to a baseband signal for the carriers by conversion from the respective RF carrier frequencies to an intermediate frequency (IF) using a common RF local oscillator (LO) and by further conversion from IF to baseband using carrier specific IF LOs, where a controllable frequency offset is used. Any controllable frequency offset is removed from the baseband signal for the first and second carriers to produce representations of the received signals.

Controllable frequency offset for inphase and quadrature (IQ) imbalance estimation

Digital IQ imbalance estimation and compensation is facilitated by shaping the frequency response of receiver branches. In particular, in a multi-carrier receiver, the frequency response of signal processing elements in at least one receiver branch is set to not fully attenuate received signals in a frequency band of interest. The frequency band of interest is greater than the carrier bandwidth of the received signal processed by that receiver branch. In some embodiments, the received signal is not attenuated, and adjacent interfering signals are partially attenuated. This allows information regarding the interfering signals to appear in an IQ imbalance-induced, inter-carrier image of the signals in anther receiver branch, facilitating digital estimation and compensation of IQ imbalance.

Inter-carrier bandwidth control for mitigating IQ imbalance

Embodiments of user equipment and methods for determining IQ imbalance parameters are described. In some embodiments, a method for determining in-phase (I) and Quadrature (Q) imbalance (IQ imbalance) parameters based on a known signal in a dual-carrier receiver using at least one controllable frequency offset includes receiving a known signal modulated onto a first radio frequency (RF) carrier frequency and a second RF carrier frequency different than the first RF carrier frequency; downconverting the known signal to a baseband signal for the first and second carriers by conversion from the respective RF carrier frequencies to an intermediate frequency (IF) using a common RF local oscillator (LO) and by further conversion from IF to baseband using carrier specific IF LOs, wherein as a controllable frequency offset is used as a part of the conversion from at least one of RF to IF and IF to baseband through the LOs; removing any controllable frequency offset from the baseband signal for the first and second carriers to produce representations of the received signals of the first and second carriers; and deriving IQ imbalance parameters for each representation of the received signals of the first and second carriers using a least square estimate.

Controllable frequency offset for inphase and Quadrature (IQ) imbalance estimation

Systems and methods according to these exemplary embodiments provide for optimizing voltage use in digital circuits. This can be obtained by creating situations for digital circuits such that the effective critical path (ECP) can be used such as, for example, the case where a digital circuit includes a plurality of voltage domains powered by individual and possibly different voltage sources. This can then reduce voltage use in digital circuits.

Methods and systems for use-case aware voltage selection

Inter-carrier interference (ICI) cancellation in an OFDMA receiving signals from two transmitters is performed by identifying the transmitted sub-carriers that cause the largest ICI to sub-carriers received from other transmitters, and removing the ICI contribution from these sub-carriers. This may be accomplished by calculating the ICI terms only based on the interfering sub-carrier and the frequency offset. Alternatively, the transmissions causing the ICI are demodulated, the ICI on other signals is then determined and subtracted, and other signals are then demodulated. Which transmissions cause the largest ICI on others depends on the relative strength of the corresponding sub-carriers and how much orthogonality is lost. The latter might be due to frequency error, Doppler spread, or a combination of both.

Uplink inter-carrier interference cancellation of OFDMA systems

The control word input to a Digitally Controlled Oscillator (DCO) is modified to reduce non-monotonic regions in the output response of the DCO. The DCO may be included in a Phase-Locked Loop (PLL) circuit for generating an output signal that locks onto either the phase or frequency of a reference signal input. By modifying the control word input to the DCO to avoid non-monotonic regions in the DCO output response, PLL phase noise is reduced. In one embodiment, the control word is modified by reordering or skipping control word values input to the DCO that correspond to non-monotonic regions in the output response of the DCO circuit.

Method and apparatus for reducing non-montonic regions in a digitally controlled oscillator

A Decimation In Frequency (DIF) Fast Fourier Transform (FFT) stage is used in an N bin FFT, wherein N is an even integer. The DIF FFT stage includes swap logic that receives a first input sample, x(v), and a second input sample, x(v+N/2), and selectively supplies either the first and second input samples at respective first and second swap logic output ports or alternatively the second and first input samples at the respective first and second swap logic output ports, wherein 0&#x2266;v&#x3c;N/2. The DIF FFT stage further includes a summing unit for adding values supplied by the first and second swap logic output ports; a differencing unit for subtracting values supplied by the first and second swap logic output ports; and twiddle factor logic that multiplies a value supplied by the differencing unit by a twiddle factor, W, where s is an integer representing an amount of circular shift of N input samples.

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Lund, Sweden

Jim Svensson