Channel estimation with reduced overhead in a filter bank multi-carrier (FBMC) system is enabled by use of frequency-time blocks each comprising a pilot field with two pilot symbols and data symbols outside the pilot field. In embodiments, nearest neighbors of the pilot field are populated with data symbols which fulfill one or more symmetry relations enabling approximate interference cancellation. In a first embodiment, the pilot field consists of two frequency-consecutive and time-coinciding positions; the pilot field may be time-initial in a transmission or may be located in the interior of the transmission. In a second embodiment, a block comprises two frequency-coinciding and time-consecutive pilot symbols; the pilot field may be frequency-initial in a transmission or may be located in the interior of the transmission.

Gain variations during a packet can lead to significant performance degradation in communications systems that use high order quadrature amplitude modulation (QAM). A method and the associated apparatus track such variations in an OFDM system and completely eliminate any performance degradation. Gain estimation and compensation is employed with the use of pilot subcarriers in the payload of an OFDM data packet. Estimated pilot magnitude ratios are averaged, throughout the processing life of a packet, to yield accurate gain estimations. A gain compensation factor is used to adjust data carriers. An exclusion method is also employed to eliminate pilot carriers which contribute to noise.

According to some embodiments, a method of transmitting a radio signal in a first wireless network element comprises receiving, at an input of a radio transmitter, a signal for wireless transmission; selectively performing a signal linearization technique on the signal; amplifying the signal with a non-linear amplifier; and transmitting the amplified signal to a second wireless network element. According to particular embodiments, selectively performing the signal linearization technique comprises determining a modulation order of the received signal and determining the modulation order exceeds a modulation order threshold.

A method and a device for transmitting and receiving a signal on the basis of multiple antennas are provided. A transmitting device may include a radio frequency (RF) module transmitting a quadrature amplitude modulation (QAM) signal of a first symbol corresponding to a hybrid frequency shift keying and quadrature amplitude modulation (FQAM) mode and transmitting a QAM signal of a second symbol corresponding to a QAM mode through a second antenna; and a modulation module mapping the QAM signal of the first symbol to one frequency tone among the preset number of frequency tones according to a frequency shift keying (FSK) signal of the first symbol and mapping the second symbol to the frequency tone to which the first symbol is mapped.

Circuits for producing signals representative of mean and variance estimations for quadrature amplitude modulation (QAM) are provided where the circuits comprise: sequentially repeated first circuit modules and sequentially repeated second circuit modules configured for producing updates in the corresponding estimation iterations. In one embodiment, a closest negative integer power of 2 is used as a substitute multiplicand when multiplying together two or more outputs of hyperbolic function generating units where the substituted for output is less than one. Size and complexity of the corresponding multiplier can then be reduced.

Techniques are presented for mapping a digital data sequence into a signal point sequence for transmission. The signal point sequence belongs to a set of possible signal point sequences. In one example, a digital data sequence is received. Forbidden branch flags that forbid certain signal points in the possible signal points sequences are applied. The signal point sequence is selected from a subset of all the possible signal point sequences based on the digital data sequence. The subset is defined by the forbidden branch flags.

A quadrature modulator and the transmission unit output a modulated wave obtained by performing quadrature modulation on a carrier wave using a first I signal and a first Q signal and wirelessly transmit the modulated wave. A reception unit and the quadrature detector detect a received signal corresponding to a wireless signal transmitted from the wireless tag using the carrier wave and to output a second I signal and a second Q signal. A filter and the amplification unit amplify a frequency component higher than a cutoff frequency in the second I signal and the second Q signal. A detector and the decoding unit decode data based on a detection signal obtained by detecting the amplified second I signal and the amplified second Q signal. A generation unit generates the first I signal and the first Q signal such that the modulated wave is a signal obtained by shifting a frequency of the carrier wave by a frequency shift amount more than the cutoff frequency and to input the first I signal and the first Q signal to the quadrature modulator.

A coding and modulation apparatus and method are presented. The apparatus comprises an encoder that encodes input data into cell words, and a modulator that modulates said cell words into constellation values of a non-uniform constellation. The modulator is configured to use, based on the total number M of constellation points of the constellation, the signal-to-noise ratio SNR and the number n of the dimension of the constellation, an n-dimensional non-uniform constellation from a group of constellations, wherein each constellation point of an n-dimensional constellation diagram is defined by an n-tupel of constellation values, said n-tupel of constellation values defining parameter settings of a transmission parameter used by a transmission apparatus for transmitting a transmission stream obtained by conversion of said constellation values.

A method of signal communication is disclosed comprising providing source data having a predetermined signal power; mapping the source data onto a first modulation scheme to obtain a first set of complex symbols; mapping the source data onto at least one further modulation scheme to obtain at least one further set of complex symbols; combining the first set of complex symbols and the at least one further set of complex signals to form a modulated signal to be forwarded along a communications channel. Beneficially, the predetermined signal power of the source data is split between the first modulation scheme and the at least one further modulation scheme.

An apparatus for interpolation of polar signals in RF transmitters is disclosed. The apparatus comprises an estimation circuit configured to receive an input in-phase (I) quadrature (Q) signal comprising a plurality of input IQ samples having a first sampling rate associated therewith, and determine a selection metric value indicative of a position of an IQ trajectory associated with one or more input IQ samples of the input IQ signal. The apparatus further comprises a selection circuit configured to receive the input IQ signal and the selection metric value; and adaptively provide the input IQ signal to a first interpolation circuit that implements a first interpolation method or to a second interpolation circuit that implements a second, different interpolation method, for generating interpolated polar samples at a second, different sampling rate, from the input IQ signal, based on the selection metric value.