258results about How to "Reduce peak-to-average power ratio" patented technology

The invention discloses an information transmission method for reducing the peak to average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal. In the method, after being coded and interleaved, data stream is modulated by a new distorted constellation diagram so as to acquire a frequency domain signal; for the frequency domain signal, a phase rotation sequence is selected to reduce the PAPR of a time domain signal which is subjected to inverse fast Fourier transform (IFFT); at a receiver end, the received signal is subjected to fast Fourier transform (FFT) and channel estimation so as to acquire the frequency domain signal; for the frequency domain signal, recovering is performed by different phase rotation sequences so as to acquire candidate signals; amongthe candidate signals, only the signal which is recovered by the right phase rotation sequence has a minimal mean square error when the signals are subjected to hard decision together with the constellation diagram; and the candidate signal which has the minimal mean square error is selected as the original signal, and the corresponding phase rotation sequence is the recovered side band information. The method can effectively reduce the peak to average power ratio of the OFDM signal, does not need to send the side band information simultaneously, improves the frequency band utilization ratio of systems, and can be applied to various communication systems using OFDM technology.

This invention discloses a method for TD-SCDMA compatible with OFDM technology, which carries out serial parallel conversion to the due-out high speed serial code sheet sequence and generates multiple parallel sub-sequences to be modulated to multiple sub-carriers for parallel transmission to reduce the transmit rate of each channel so as to increase the symbol period and weaken the influence of multi-channel interference, at the same time, it uses the circular prefix as the protection interval, the interference among symbols are reduced greatly and the orthogonality among channels are ensured.

The invention discloses a wireless optical orthogonal multi-carrier communication method with a low peak to average power ratio. The wireless optical orthogonal multi-carrier communication method comprises the following steps that at a transmitting end, firstly, modulated frequency domain signals are converted into a semi-positive definite planning convex optimization problem by adopting a tone injection algorithm via a relaxation method, and solving is carried out through general convex optimization and randomized methods; secondly, the frequency domain signals are symmetrically mapped to subcarriers in a conjugate mode, and a cyclic prefix is added after reverse fast Fourier transformation; at last, time domain transmission signals are added into direct-current offset to drive a light-emitting diode to emit light. At a receiving end, photovoltaic conversion is achieved through a photodiode; signals are removed from the cyclic prefix and conjugate symmetry parts after amplification, filtering, analog-digital conversion and fast Fourier transformation; the signals are modulated to be recovered in an original planisphere; at last, receiving symbols are obtained through demodulation. According to the wireless optical orthogonal multi-carrier communication method, the peak to average power ratio of a wireless optical communication PFDM system can be effectively reduced, requirements of a power amplifier and an LED for linear degrees are reduced, non-linear distortion is reduced, and receiving performance is improved.

The invention discloses a generation method of frequency-domain OFDM symbols and a generation method of preamble symbols in physical frames. The generation method of the frequency-domain OFDM symbols includes the following steps that: the average power ratio of a fixed sequence and a signaling sequence is determined; fixed sequences and a signaling sequence set are respectively generated in the frequency domain according to the average power ratio R; one signaling sequence is selected from the signaling sequence set, and the fixed sequences and the signaling sequences fill effective sub carriers, odd-even staggered arrangement exists between the fixed sequences and the signaling sequences; two sides of the effective sub carriers are filled with zero-sequence sub carriers respectively to form a frequency domain OFDM symbol with a preset length; and the serial number of the selected signaling sequence in the set is the signaling information carried by OFDM symbols. With the generation methods provided by the technical scheme of the invention adopted, the problem of failure probability in low-complexity receiving algorithm detection on preamble symbols in a frequency selective fading channel in the current DVB_T2 standard and other standards can be solved.

The invention discloses a signal emission and reception method of a GFDM system based on weight fraction Fourier transform, relating to the signal emission and reception technology of the GFDM system based on the weight fraction Fourier transform. The invention can obtain better bit error rate and reduces the peak-to-average power ratio. The invention can flexibly regulate the subcarrier and the WFRFT order in the unit carrier wave block according to the channel state information and user demands, and the order in each subcarrier can maintain different in order to achieve to the need of the system performance. Besides, the invention performs precoding through WFRFT and reasonably chooses the appropriate transformation order according to the channel condition, which enables the encoded system to obtain a better bit error rate performance and have lower peak-to-average power ratio.

The invention discloses a method for generating a precursor symbol in a physical frame. The method comprises the following steps of: performing discrete Fourier inversion of a frequency-domain OFDM symbol with a preset length to obtain a time-domain OFDM symbol; determining a circulation prefix length; intercepting a partial time-domain OFDM symbol with the circulation prefix length from the rear part of the time-domain OFDM symbol, and taking the partial the time-domain OFDM symbol as a circulation prefix; generating a modulating signal according to the partial time-domain OFDM symbol; and generating the precursor symbol based on the circulation prefix, the time-domain OFDM symbol, and the modulating signal. According to the technical scheme of the invention, the problem of decrease of frequency-domain channel estimated performance is solved, and the modulating signal is generated by utilizing the partial time-domain OFDM symbol, so that the generated precursor symbol has small frequency offset and excellent timing synchronism. Furthermore, processing of a received signal by a receiving terminal is guaranteed, with carrier frequency deviation being in a range from -500 kHz to 500 kHz.

The invention relates to a time division duplex transmission method for a broadband wireless communication system, belonging to the technical field of digital information transmission. The method comprises the following steps: using a time / frequency-domain unified orthogonal frequency division multiple access (TFU-OFDMA) technology to carry out downlink multiple access so as to obtain downlink signals at a transmitting end of a base station; using a time / frequency-domain unified single carrier multiple access (TFU-SCMA) technology to carry out uplink multiple access so as to obtain uplink signals at a transmitting end of user equipment; and using a time division duplex frame structure to carry out duplex transmission on the downlink signals and the uplink signals. The TFU-OFDMA technology provided by the invention solves the multiple access problems in the TFU-OFDM (Time / Frequency-domain Unified Orthogonal Frequency Division Multiplexing) modulation process, can flexibly allocate wireless resources and can effectively overcome deep fade, narrow-band interference and the like. The TFU-SCMA technology provided by the invention solves the multiple access problems in the improved SC-FDE (Single Carrier Frequency Domain Equalization) modulation process, reserves the advantages of low complexity of the transmitting end in the SC-FDE technology, low peak-to-average power ratio and the like, and enables the receiving end to be subject to synchronization and channel estimation better.

The invention discloses a frequency domain OFDM (orthogonal frequency division multiplexing) symbol generation method and a preamble symbol generation method. The frequency domain OFDM symbol generation method comprises the steps of generating a fixed sequence and a signalling sequence in the frequency domain, wherein the fixed sequence and the signalling sequence are constant modulus sequences, and complex numbers in the fixed sequence and the signalling sequence are equal in modulus; filling the fixed sequence and the signalling sequence to an effective sub-carrier, wherein the fixed sequence and the signalling sequence are in odd-even alternative arrangement; and filling zero-sequence sub-carriers at two sides of the effective sub-carrier respectively so as to form a frequency domain OFDM symbol with predetermined length. The technical scheme disclosed by the invention avoids a characteristic that the generated signalling sequence has cyclic shift or cyclic shaft and phase shift in the time domain, and solves a problem of frequency domain channel estimation performance reduction. Furthermore, a receiving terminal is ensured to still be able to process received signals with the carrier frequency deviation being in a range of -500kHz and 500kHz.

The invention discloses an information transmission method for lowering peak to average power ratio of an OFDM system signal. In the method of the invention, after being coded, weaved, modulated and performed with serial / parallel conversion, the input bit stream is adjacently cut into a plurality of mutually disjoint frequency domain subsequences; each subsequence is inserted with pilot frequency as required; parts of transmission sequences are used for lowering the peak to average power ratio without transmitting a phase rotation factor to a receiving end. At the receiving end, the received signal is performed with serial / parallel conversion, DFT and parallel / serial conversion and is cut into a frequency domain signal subsequence according to the same mode with a receiver end; pilot frequency contained in the subsequence is utilized for the channel estimation of the subsequence; the multiplied phase rotation factor serves as one part of channel frequency response so as to restore frequency domain data in the subsequence; the frequency domain ratio data are combined into one sequence; and an output bit stream is obtained after demodulating, deinterlearing and decoding. The invention eliminates the influence of sideband information on the frequency spectrum utilization ratio and signal transmission rate.

The invention discloses a method for generating a preamble symbol and a method for generating a frequency domain OFDM symbol. The method for generating the frequency domain OFDM symbol comprises the following steps: respectively generating a fixed sequence and a signaling sequence on a frequency domain; filling an effective subcarrier with the fixed sequence and the signaling sequence, wherein the fixed sequence and the signaling sequence are in odd-even staggered arrangement; and respectively filling the two sides of the effective subcarrier with a zero sequence subcarrier so as to form the frequency domain OFDM symbol with a predetermined length. According to the technical scheme provided by the invention, the problem of failure probability of the preamble symbol in low-complexity receiving algorithm detection in case of a frequency selective fading channel in a conventional DVB_T2 standard or other standards is solved.

The invention discloses a multiplexing modem of time orthogonal frequency-division, which relates to a modem device with restricted transmitting power, strong anti-frequency offset capability and the performance of resisting inter-symbol interference in the field of communication. The multiplexing modem of the invention comprises components such as a low-medium frequency modulator, a demodulator, an auxiliary multiplexer / demultiplexer, an intermediate frequency amplifier, a D / A converter, a low pass filter, a self-vibration module, a mixer, an adder, a band-pass filter and a power supply, etc.; by adopting TOFDM signals with quasi-constant envelop transmission, the modem of the invention realizes the performance of resisting the inter-symbol interference which is the same as that of the traditional OFDM technology, has the capability of collecting multipath, overcomes the problems of large peak-to-average power ratio and the bad capability of resisting frequency offset, and also realizes the purpose of the multiplexing modem of the time orthogonal frequency-division. The modem of the invention also has the advantages of high integration degree, small volume, light weight and good flexibility, etc. and is especially suitable for the field requiring for the modem with large-capacity wireless data transmission performance among strong multipath high-speed moving targets with seriously restricted power.

The invention discloses a method for reducing a peak-to-average power ratio of multiple input multiple output (MIMO) - orthogonal frequency division multiplexing (OFDM) signal for space-frequency coding. On a transmitter end, data is coded, interlaced, modulated and alamounti space-frequency coded to obtain a group of frequency-domain sequence, the group of frequency-domain sequence is grouped, so multiple groups of candidate time-domain signals are obtained by selecting appropriate parameters, and a group of time-domain signals with the minimum peak-to-average power ratio (PAPR) is selected to be transmitted. On the end of a receiver, after the operation of a received signal such as fast fourier transformation (FFT), estimation of a channel, space-frequency coding and the like, a frequency-domain signal which is superimposed by the channel noise is obtained, and the hard decision is performed on the frequency-domain signal to obtain a nose-free frequency-domain signal. The signal is restored according to all possible combination ways to obtain candidate data, and only the data which is restored by adopting a correct restoring way conforms to the original modulation constellation.The method can effectively reduce the peak-to-average power ratio of the MIMO-OFDM signal, is free from transmitting the side information, improves the frequency band utilization rate of the system, and can be applied to different communication systems based on the space-frequency coding-based MIMO-OFDM technology.

The invention discloses a low peak-to-average ratio wireless light transmission method with clipping moving. The feature that one of paring signals in ACO-OFDM time domain signals must be zero is utilized, if a positive signal in the pairing signals exceeds the set threshold value, clipping is conducted on the positive signal, and the clipped quantity is put at the zero position in the paring signals, and therefore the function of reducing the PAPR is achieved. The low peak-to-average ratio wireless light transmission method is easy to achieve, the PARP of an ACO-OFDM wireless optical communication system can be effectively reduced, system power consumption is reduced, the requirement for the linearity of a power amplifier and an LED lamp is lowered, nonlinear distortion of the signals in electricity and light domains is reduced, and therefore the receiving performance of the system is improved.

The invention discloses a method for reducing a peak-to-average power ratio of an OFDM (orthogonal frequency division multiplexing) / OQAM (orthogonally multiplexed QAM) system based on a selective sequence. The method comprises the following steps of: coding, interleaving and modulating an input data stream, performing up-sampling on the obtained information source data packets, and then, enablingthe information source data packets to respectively pass through a filter bank; respectively selecting an optimized phase rotation sequence for a time domain signal of each obtained data block in order; and finally, selecting a signal, of which the peak-to-average power ratio is lowest, for transmission, and transmitting information of the phase rotation sequence as sideband information. The method provided by the invention can effectively lower the peak-to-average power ratio of the OFDM / OQAM system without influencing the power spectral density and the error rate performance of the system, improve work efficiency an HPA (high-power amplifier) and reduce energy consumption.

The invention discloses a time-delay multi-carriers modulation and demodulation method. The code element waveform structure is composed of H cosine wavelets, all wavelets have different time delays sequentially, and various wavelets are linearly superposed to form a non-orthogonal composite wave code element waveform; the wavelets are amplitude-variable basic wavelets, and the basic wavelets are standard cosine waves with amplitude at 1 constantly. Meanwhile, the basic wavelets of a transmission end are transmitted finishing basic wavelets with a trailing area 0 and a trailing area 1 added at two ends of the standard cosine waves, and a receiving end is partially balanced to obtain received finishing basic wavelets with trailing to form non-orthogonal composite waves. The modulation adopts three methods including (1) an equilateral-triangle equation set method formed by an equilateral-triangle coefficient matrix; (2) an inverted-triangle equation set method formed by an inverted-triangle coefficient matrix; (3) an optimization method. The time-delay multi-carriers modulation and demodulation method reserves the advantages of high efficiency of a time-frequency mixing multi-carriers modulation method and reduces complexity as well as error bit rate.

The invention relates to a method for lowering the peak-to-average power ratio of universal filtering multicarrier signals. The method comprises the following steps of: (1) establishing a system model; (2) setting that the sampling points are mutually independent and identical in distribution, and utilizing numerical calculation to analyze the system model; (3) theoretically analyzing a high peak-to-average power ratio (PAPR) of universal filtering multicarriers (UFMC), and obtaining a complementary cumulative distribution function (CCDF); (4) analyzing system parameters of the universal filtering multicarriers (UFMC); (5) utilizing a Largrange method to obtain an optimal solution of the complementary cumulative distribution function; and (6) establishing the relation between filter parameters and the complementary cumulative distribution function (CCDF). According to the invention, the relation between the UFMC peak-to-average power ratio statistic characteristics and the filter coefficients is analyzed, a Largrange optimization method is utilized to obtain the CCDF optimal solution of the UFMC and the expressions of theoretical relations of the filter parameters, the design of a filtering multicarrier system is guided, and the peak-to-average power ratio is further lowered.

The invention discloses a method and system for reducing a peak-to-average power ratio of an OFDM system based on three-dimensional signal insertion. Based on a traditional DSI method, a process of inserting three-dimensional signals into OFDM signal sub-carriers instead of inserting a traditional virtual sequence that does not include information is proposed, each three-dimensional signal occupies two sub-carriers, and compared with the traditional DSI method, the data transmission efficiency is not reduced. Since a three-dimensional signal constellation diagram provides a greater degree of search freedom, the peak-to-average power ratio of the OFDM system can be more effectively improved under the same search complexity and system data transmission efficiency, and no sideband informationneeds to be transmitted. In addition, compared with the mode of inserting two-dimensional signals, without changing the average power of transmitted OFDM signals, the three-dimensional signal constellation diagram has a larger minimum Euclidean distance, and thus the error performance of the system can also be improved to a certain extent.

Disclosed is an Orthogonal Frequency Division Multiple Access (OFDMA) based wireless communications system operable to communicate OFDMA type signals over a set of dynamically assigned orthogonal sub-carriers and Code Division Multiple Access (CDMA) type signals over a set of pre-allocated orthogonal sub-carriers. The OFDMA system utilizes pre-allocated orthogonal sub-carriers for CDMA type signal transmission in order to reduce the number of dynamic assignments of orthogonal sub-carriers in a typical OFDMA system. The OFDMA type signals may be signals processed in accordance with well-known OFDMA techniques, whereas the CDMA type signals may be signals processed in accordance with well-known CDMA and OFDMA techniques. The CDMA type signals may also be processed using a pre-coder incorporating a Discrete Fourier Transformer (DFT) matrix or Identity matrix to reduce the Peak-to-Average Power Ratio across the OFDMA system.

The invention discloses a pilot sequence structure in an MIMO-OFDM / OQAM (Multi-input Multi-output-Orthogonal Frequency Division Multiplexing / Offset Quadrature Amplitude Modulation) system and a channel estimation method. Different pilot sequences are adopted by different antennae, the pilot sequence of each antenna is composed of three segments of symbol sequences, the length of each symbol sequence accords with the number of subcarriers, wherein the first segment of symbol sequence and the third segment of symbol sequence are all-zero symbol sequences, pilot signals are arranged at equal intervals in the second segment of symbol sequence, the pilot signal positions of all the antennas are different, the symbols of the pilot signals are randomly chosen from a candidate symbol set, and the interval between the pilot signals is two times the number of the antennas. The channel estimation method put forward by the invention can be utilized to eliminate inter-symbol interference and inter-subcarrier interference caused by multipath interference, so that the accuracy of the channel estimation of the MIMO-OFDM / OQAM system can be increased. Meanwhile, the pilot sequence structure decreases the peak-to-average power ratio of transmitted signals, and can meet the linear dynamic range of a radio frequency front-end high power amplifier and decrease the linearity requirement of the MIMO-OFDM / OQAM system on the high power amplifier.

The embodiments of the invention provide a method and a device for processing communication signals in a communication system. The method comprises the following steps: performing discrete Fourier transform DFT on input data to get a DFT data sequence; and performing orthogonal frequency division multiplexing on the DFT data sequence and a pilot frequency sequence in the same symbol. By implementing the embodiments, the peak-to-average power ratio of information transmission in a communication system and the transmission cost of pilot frequency can be reduced.

The invention discloses an OFDM optical fiber wireless communication method and system based on IRA codes. IRA encoding is firstly carried out on bit information of an OFDM transmitter provided with an IRA encoder, OFDM selective mapping modulation is then carried out on the bit information of the OFDM transmitter provided with the IRA encoder, and data which are modulated are used as channel observed values by an OFDM receiver provided with the IRA decoder to carry out IRA iterative decoding. The OFDM optical fiber wireless communication method and system based on the IRS codes has the advantages that compared with other channel encoding, the IRA codes are better in performance, and decoding complexity is lower. In addition, an accumulator in the IRA encoding is a linear feedback shift register and can be used as a scrambler, a selective mapping technology is further combined, the peak average power ratio of OEDM can be effectively lowered, the non-relay transmission distance of signals is prolonged, and the system performance is greatly improved.

The invention discloses a modulation method for reducing a peak-to-average power ratio of an orthogonal frequency division multiplexing-visible light communication (OFDM-VLC) system. According to the modulation method provided by the invention, through performing specific peak clipping and mapping treatments on visible light vector signals, the peak-to-average power ratio of the OFDM-VLC system can be effectively reduced, and meanwhile the bit error rate performance of the system can also be improved.

In a wireless communication system, a method and apparatus for closed loop transmission is disclosed. In accordance with the preferred embodiment of the present invention, a time frequency portion of an uplink frame is dynamically reserved as a sounding zone for uplink channel sounding. A first message is transmitted to a first subscriber station in a downlink frame assigning a time-frequency resource within the sounding zone, and a sounding waveform. Furthermore, a signal is received from the subscriber station within the assigned time-frequency resource, a partial channel response is determined from the received sounding signal, and the subsequent transmission to the subscriber station is tailored based on the at least partial channel response.

Disclosed is a method for providing a pilot symbol for base station identification in a Multiple-Input Multiple-Output (MIMO) communication system having one or more transmission antennas, wherein the pilot symbol is comprised of a first sequence having a good cell identification characteristic and a second sequence for reducing a peak-to-average power ratio (PAPR) for all of pilot symbols.

The invention discloses a sequence structure with low peak-to-average power ratio for the channel estimation of an OFDM / OQAM system, and a method for performing the channel estimation by using the structure. In the structure, except that a front segment and a rear segment have a same structure according to a conventional pilot sequence (all-zero data serves as a protective segment), at least half signs (only at odd bits or even bits) of one segment or three segments in the middle are zero, and the values of the signs at any bits of the remaining parts are 1 or -1 at random. Because the values of most parts are zero and the values of the signs at any bits of the remaining parts are 1 or -1 at random, the method for the channel estimation can reduce peak-to-average power ratio while eliminating inter-sign interferences and inter-subcarrier interferences caused by multi-path interferences, the structure and the method can satisfy the linear dynamic range of a radio frequency front-end high power amplifier so as to reduce the linear requirements on the high power amplifier by the OFDM / OQAM system.

The invention discloses a method and apparatus for decreasing a peak-to-average power ratio of a three-dimensional coherent optical orthogonal frequency division multiplexing system. The method comprises the following steps: (1) converting a binary sequence to obtain a subcarrier index signal; (2) mapping to obtain a frequency-domain orthogonal frequency division multiplexing signal of 3N real-form subcarrier components; (3) recombining to obtain a frequency-domain orthogonal frequency division multiplexing signal of 2N plural-form subcarrier components; (4) modulating the orthogonal frequency division multiplexing signal from the frequency domain to a time domain; (5) introducing a K sequence from the frequency domain, performing zero padding, and superimposing with the time-frequency orthogonal frequency division multiplexing signal after the modulation; (6) searching a K sequence combination with a minimum signal peak-to-average power ratio; (7) dividing the time-domain orthogonal frequency division multiplexing signal into a real-number portion and an imaginary-number portion corresponding to the real-number portion, and converting to an optical signal; and (8) transmitting the optical signal. By adopting the method and the apparatus, the peak-to-average power ratio is effectively decreased, the influence of a nonlinear action of an optical-fiber channel on the signal can be alleviated, and the overall performance can be improved.

The invention relates to an orthogonal frequency division multiplexing (OFDM) signal processing method, comprising the processing steps of the transmitting end of: using baseband modulation signal to form a frequency-domain OFDM signal and dividing the signal into a plurality of non-overlapping subsequences in the same size; filling zero in the subsequences, respectively, and performing inverse discrete fourier transform (IDFT) to get a plurality of time-domain partial sequences; and using the expression of peak-to-average power ratio (PAPR) obtained by phase rotation factor weighting as an optimized objective function to perform genetic operation, and using the obtained optimal solution as the optimal phase rotation factor; weighting the optimal phase rotation factor, getting and sending the weighted time-domain OFDM signal. The invention also relates to an OFDM signal processing system. In the selection course of the phase rotation factor, the invention utilizes large-scale optimization characteristics of the genetic algorithm, overcomes the existing defect that the optimal phase rotation factor searching process is trivial, and effectively reduces the PAPR as well as complexity of hardware implementation.

The invention discloses a method for reducing the peak-to-average power ratio of the OFDM signal, which reduces the peak-to-average power ratio of the OFDM signal by enlarging the amplitudes of certain data symbols in a data block. The method first clips the OFDM signal according to a certain threshold (since time domain clipping can bring noise into a frequency domain data block), and the frequency domain data block with noise is processed in the following way: the projection of each distorted data symbol on the original data symbol is calculated, the projection is used to substitute the original data symbol if the module of the projection is larger than the module of the original data symbol, otherwise the original data symbol is kept unchanged, and thereby a new frequency domain data block and a new time domain signal are obtained; if the peak-to-average power ratio of the new time domain signal meet requirements, the new time domain signal is added with a cyclic prefix and then sent to a high-power amplifier, otherwise the steps are repeated. Under the premise of not affecting the error rate, the method greatly reduces the peak-to-average power ratio of the OFDM signal, and can reduce the complexity of calculation.

The invention relates to a method for estimating OFDM integral frequency offset based on virtual subcarrier and frequency domain differential sequence, belonging to communication technical field. And the invention only need one OFDM symbol as synchronous training symbol in each frame, having advantage of low training sequence data overhead and the peak mean power ratio of the symbol is very small; the invention comprises methods based on virtual subcarrier and frequency domain differential sequence, and according to maximum-likelihood criterion, estimates OFDM integral frequency offset and has better performance than those of the methods based on virtual subcarrier and frequency domain differential sequence; in addition, the invention selects proper frequency offset preselected value and can reduce searching range of frequency offset estimation, thus having lower calculating complexity.

Radio network node (110) and method (500) in a radio network node (110), for wireless communication with a user equipment (120) in a wireless communication system (100) in antenna streams, wherein the radio network node (110) comprises a plurality of antenna elements (210-1, 210-2, 210-n), forming a multiple antenna array (210) which is configured for massive MIMO transmission. The method (500) comprises beamforming (501) a signal to be transmitted to the user equipment (120) by splitting and phase shifting said signal; detecting (502) a peak of power of one beamformed (501) signal, exceeding a threshold value; manipulating (503) said signal until the peak of power of the signal is lower than said threshold value; and transmitting (504) said signal, to be received by the user equipment (120).