A communication system having improved estimation and a method thereof

Abstract

Invention is a communication system (100) comprising a transmitting unit (100) having a signal generator (161) for generating a first signal, a Transmitter RF front end (110) for processing said first signal and outputting a second signal, at least a transmitting antenna (162) for transmitting said second signal; comprising a receiving unit (200) having a receiving antenna (210) for receiving received second signal; a receiver RF front end (220) for processing received second signal; a processing unit (230) for comparing time shifted, received second signal and a pilot signal acquired from transmitting unit (100) that is representing the first signal. It is characterized by comprising at least an adaptive filter unit (130) which comprises at least an adaptive filter connected between input and output of the Transmitter RF front end (110) and configured to model said Transmitter RF front end (110) or said adaptive filter unit (130) comprising plurality of adaptive filters each connected between input and output of at least some of the processing components of Transmitter RF front end (110), each configured to model respective processing component of Transmitter RF front end (110); a model generating unit (120) which is configured to receive model parameters from adaptive filter / s and generate a hardware equivalent model (150) for Transmitter RF front end (110); model generating unit (120) is configured to apply the first signal to hardware equivalent model (150) and store acquired output signal as pilot signal in a memory unit (140) in order to be transmitted to receiver unit (200).

Description

[0001] DESCRIPTION

[0002] A COMMUNICATION SYSTEM HAVING IMPROVED ESTIMATION AND A METHOD THEREOF

[0003] TECHNICAL FIELD

[0004] Invention relates to a communication system comprising a transmitting unit having a signal generator for generating a first signal, a T ransmitter RF front end for processing said first signal and outputting a second signal, at least a transmitting antenna for transmitting said second signal; comprising a receiving unit having a receiving antenna for receiving received second signal; a receiver RF front end for processing received second signal; a processing unit for comparing time shifted, received second signal and a pilot signal.

[0005] BACKGROUND

[0006] Matched filter, which is also known as correlator receiver, optimum detector, is a kind of detector used in communication systems to maximize the probability of detection. In communication systems matched filter is utilized in steps such as synchronization, channel estimation, equalization to detect the transmitted symbols from transmitter.

[0007] US2020099566 discloses a new method to detect synchronization signal at Narrow Band IOT (NB IOT) applications at User Equipment (UE). For this detection, several matched filters whose size is fitting to each of Orthogonal frequency-division multiplexing (OFDM) symbol used for synchronization are utilized. These matched filters gather the OFDM symbols having both normal cyclic prefix (NCP) and extended cyclic prefix (ECP) and constitute correlation peaks when the detection is realized. In brief, this method claims that it works in the case when Narrow Band Primary Synchronization Signal (NBPSS) and Narrow Band Secondary Synchronization Signal (NBSS) are used.

[0008] US2004047368 discloses frame synchronization in an OFDM system involves calculating a frame synchronization result as a complementary weighted summation of a matched filtered technique, and an autocorrelation technique. A preamble of ten short training symbols (five predetermined symbols, repeated twice) is transmitted in an OFDM system to provide a basis for performing the matched filter and autocorrelation techniques. The complementary weighted summation is performed using parameters alpha and (1 -alpha), in which alpha belongs to the set of numbers between zero and one. Desirably, alpha is in the range 0.5 to 0.9. Improved (or at least equivalent) synchronization failure rate and bit error rate performance results, compared with either the matched filter technique and the autocorrelation technique alone.

[0009] Conventional communication systems, the synchronization process include matched filter step to find peak points for frame synchronization. Also, channel estimation step is so important to reveal the distortion of the emitted symbols from transmitter. By realizing perfect channel estimation, it is increased the reliability and make easier equalization step. And at channel estimation step, it is used pilot symbols which is known at receiver.

[0010] Communication systems use pilot symbols for channel estimation to increase communication performance. However hardware characteristics of transmitting components of transmitting device may vary over time. This causes a pilot signal that is affected by hardware characteristic variances to be correlated with a received signal. THz communication and ISAC are one of the prominent technologies expected to include to 6G system. And we know from the prior art that, the more the frequency increases, the more RF impairment effects of hardware characteristics increase as well. This situation will communication performance to distort reference signal and / or pilot symbols even further.

[0011] All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0012] BRIEF DESCRIPTION OF THE INVENTION

[0013] The present invention relates to a communication system and a method to eliminate the above- mentioned disadvantages and bring new advantages to the relevant technical field.

[0014] An object of the invention is to increase communication performance of communication systems.

[0015] By applying our invention, we aim to increase of accuracy of synchronization and channel estimation steps in communication systems.

[0016] Another object of the invention is to increase ISAC transceiver performance. To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to A communication system comprising a transmitting unit having a signal generator for generating a first signal, a Transmitter RF front end for processing said first signal and outputting a second signal, at least a transmitting antenna for transmitting said second signal; comprising a receiving unit having a receiving antenna for receiving received second signal; a receiver RF front end for processing received second signal; a processing unit for comparing time shifted, received second signal and a pilot signal acquired from transmitting unit that is representing the first signal. Accordingly it is characterized by comprising at least an adaptive filter unit which comprises at least an adaptive filter connected between input and output of the Transmitter RF front end and configured to model said Transmitter RF front end or said adaptive filter unit comprising plurality of adaptive filters each connected between input and output of at least some of the processing components of Transmitter RF front end, each configured to model respective processing component of Transmitter RF front end; a model generating unit which is configured to receive model parameters from adaptive filter / s and generate a hardware equivalent model for Transmitter RF front end; model generating unit is configured to apply the first signal to hardware equivalent model and store acquired output signal as pilot signal in a memory unit in order to be transmitted to receiver unit. Thus, hardware characteristics of components are considered in matching filter process, enabling increased performance in synchronization, equalization and channel estimation steps of communication systems which utilize estimation step.

[0017] A possible embodiment of the invention is characterized in that wherein Transmitter RF front end comprises at least D / A converter, at least a mixer, at least a power amplifier and at least a local oscillator; adaptive filter unit comprises at least a first adaptive filter connected between input and output of said D / A converter, a second adaptive filter connected between input and output of said mixer, a third adaptive filter connected between input and output of said power amplifier and a fourth adaptive filter connected between input and output of said local oscillator.

[0018] A possible embodiment of the invention is characterized in that comprising a receiver adaptive filter circuit having at least an adaptive filter connected between input and output of the receiver RF front end and configured to model the receiver RF front end or said receiver adaptive filter unit comprising plurality of adaptive filters each connected between input and output of at least some of the processing components of receiver RF front end, each configured to model respective processing component of receiver RF Front end; another model generation unit or said model generation unit is configured to receive model parameters from adaptive filter / s and generate a receiver hardware equivalent model for receiver RF front end and configured to divide the received second signal into receiver hardware equivalent model for removing hardware characteristic effects of receiver RF front end on received second signal.

[0019] Invention is also a pilot signal generating method for a processing unit where said processing unit is configured to compare a received second signal with a stored pilot signal where the pilot signal represents a second signal that was processed from a first signal by an Transmitter RF front end, and said second signal was transmitted by a transmitting antenna; and where said received second signal is received and processed version of the transmitted second signal; characterized in that comprising steps of:

[0020] - by a signal generator generating a calibration signal for T ransmitter RF front end to process;

[0021] - by an adaptive filter unit connected to Transmitter RF front end modelling Transmitter RF front end and generating model parameters;

[0022] - by a model generating unit, generating hardware equivalent model of Transmitter RF front end using model parameters;

[0023] - when first input signal is generated, applying said first input signal to hardware equivalent model and generating the pilot signal;

[0024] - storing reference pilot to a memory unit.

[0025] According to one embodiment of the invention, the pilot signal generating method, which produce a signal sequence by considering hardware characteristics, can be implemented in existing 3GPP standards as indicated TS38.21 1 physical channels and modulation.

[0026] Invention is also an integrated sensing and communication system comprising one embodiment of above mentioned communication system. Thus, integrated sensing and communication systems (ISAC) can also be improved.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a drawing illustrating top schematic view of the communication system.

[0029] Figure 2 is a drawing illustrating Transmitter RF front end of a transmitting unit.

[0030] Figure 3 is a drawing illustrating a hardware model.

[0031] Figure 4 is a drawing illustrating top schematic view of an another embodiment of the communication system. REFERENCE NUMBERS GIVEN IN THE FIGURE

[0032] 10 Communication system

[0033] 100 Transmitting unit

[0034] 110 T ransmitter RF front end

[0035] 11 1 D / A converter

[0036] 112 Mixer

[0037] 113 Power amplifier

[0038] 114 Local oscillator

[0039] 120 Model generating unit

[0040] 130 Adaptive filter unit

[0041] 131 First adaptive filter

[0042] 132 Second adaptive filter

[0043] 133 Third adaptive filter

[0044] 134 Fourth adaptive filter

[0045] 140 Memory unit

[0046] 150 Hardware equivalent model

[0047] 151 First model parameter

[0048] 152 Second model parameter

[0049] 153 Third model parameter

[0050] 154 Fourth model parameter

[0051] 161 Signal generator

[0052] 162 Transmitting antenna

[0053] 200 Receiving unit

[0054] 210 Receiving antenna

[0055] 220 Receiver RF front end

[0056] 230 Processing unit

[0057] 240 Receiver adaptive filter unit

[0058] DETAILED DESCRIPTION OF THE INVENTION

[0059] In this detailed description, the subject matter is explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.

[0060] Invention is a communication system (10) that increases accuracy of estimation step of channel estimation, synchronization or equalization between a transmitting unit (100) and a receiving unit (200) using a pilot signal that is generated using a hardware equivalent model (150) of Transmitter RF front end (1 10) of a transmitting unit (110) of said communication system (100).

[0061] Referring to figure 1 , communication system (100) comprises a transmitting unit (100) having a signal generator (161 ) for generating a first signal to be transmitted. Transmitting unit (100) comprises an RF front end (1 10) connected to signal generator (161 ) for processing generated first signal and outputting a second signal.

[0062] Transmitter RF front end (110) is responsible for conditioning the first signal before it is transmitted. Transmitter RF front end (110) may comprise processing components for converting first signal to analogue; components for mixing signals; components for amplifying or filtering signals. Transmitter RF front end’s (110) output signal is defined as second signal. Transmitter RF front end (1 10) may comprise more well-known components that are not explicitly disclosed herein.

[0063] Communication system (10) comprises a transmitting antenna (162) for transmitting processed second signal. Transmitter RF front end (1 10) is well known in the art used in transmitting devices such as User Equipment, base station etc.

[0064] Communication system (10) comprises receiving unit (200) having a receiving antenna (210) that receives transmitted second signal. Communication system (10) comprises a receiver RF front end (220) for preprocessing received second signal. Receiver RF front end (220) may comprise amplifiers and filtering elements, or other elements that are known to be utilized in receiver RF front end (220) in receiver units (200) such as user equipment, base station etc. Receiver RF front end’s (220) purpose is to process signal in such way output signal is received version of the second signal. Essentially, correlating received second signal with a pilot signal representing the second signal provides correlation results in order to be used in estimation, equalization and channel estimation. Receiving unit (200) comprises a processing unit (230) which compares time shifted version of received second signal, and a reference signal accessed from a memory unit (140) where said reference signal represents a similar signal to second signal. This process is called optimum estimation. In more detail optimum estimation may be realized by matched filters. Matching filter or optimum estimation methodologies are also well-known in the art, thus it is not disclosed explicitly herein. Processing unit (230) may be a processor that is programmed to realize above mentioned functions.

[0065] Receiver unit (100) comprises an adaptive filter unit (130). Adaptive filter unit (130) comprises at least an adaptive filter connected between input and output of the Transmitter RF front end (110) and configured to model said T ransmitter RF front end (1 10) or it comprises plurality of adaptive filters each connected between input and output of at least some of the processing components of Transmitter RF front end (1 10), each configured to model respective processing component of Transmitter RF front end (110) and generate model parameters. In a possible embodiment, adaptive filter is connected to input of Transmitter RF front end (110) and output of Transmitter RF front end (110). Adaptive filter receives input signal and outputs an output signal. Output of Transmitter RF front end (110) and output of adaptive filter is subtracted from each other and end result is compared to with an error tolerance signal. Adaptive filter is configured to reconfigure its internal model in order to generate an output which satisfies error tolerance on each iteration. Thus, a model parameter for Transmitter RF front end (110) is generated. In another possible embodiment, plurality of adaptive filters are connected each component of Transmitter RF front end (1 10) individually. Thus, model parameters for each component is generated.

[0066] Transmitter unit (100) comprises a model generating unit (120). Model generating unit (120) receives model parameter / s from adaptive filter / s and generates a hardware equivalent model (150) for T ransmitter RF front end (1 10). This model is a mathematical model that is generated using model parameters. For instance, model parameters of serially connected components may be multiplied in order to generate a model in an embodiment. Mathematical model is a model that takes the first signal as input and outputs a signal. Outputted signal is stored on a memory unit (140) as pilot signal. Since, model is generated based on hardware characteristics of components, a pilot signal is more similar to second signal that is outputted from Transmitter RF front end (1 10).

[0067] A predetermined calibration signal may be generated during model generation. Thus, matching filter utilizes pilot signal that is outputted from hardware equivalent model (150) of Transmitter RF front end (1 10).

[0068] Referring to figure 2, in a possible embodiment of the invention, an adaptive filter for each processing component of Transmitter RF front end (1 10) is provided. Each adaptive filter is connected between inputs and outputs of components. Each adaptive filter may be provided with error tolerance signal. Error tolerance signals may be different than each other. In more detail, Transmitter RF front end (110) comprises D / A converter (1 1 1 ) for converting first signal to analogue. A local oscillator (114) is provided. A mixer (112) is provided for mixing local oscillator’s (114) signal with first signal. An amplifier is provided for amplifying first signal. A first adaptive filter (131 ) is connected to D / A D / A (1 11 ). A second adaptive filter (132) is connected to mixer (1 12). A third adaptive filter (133) is connected to power amplifier (1 13) and a fourth adaptive filter (134) is connected to local oscillator (114). Each adaptive filter models respective component and generates model parameters.

[0069] Referring to figure 3, model generating unit (120) receives first model parameter (151 ) from first adaptive filter; (131 ) second model parameter (152) from second adaptive filter; (132) third model parameter (153) from third adaptive filter (133) and fourth model parameter (154) from fourth adaptive filter (134). Model generating unit (120) then utilizes said model parameters and generates hardware equivalent model (150) of Transmitter RF front end (110).

[0070] Invention is also a model generation method. It comprises below steps:

[0071] - generating a calibration signal for Transmitter RF front end (110) to process;

[0072] - by an adaptive filter unit (130) connected to Transmitter RF front end (1 10) modelling Transmitter RF front end (1 10) and generating model parameters;

[0073] - by a model generating unit (120), generating hardware equivalent model (150) of T ransmitter RF front end (1 10) using model parameters;

[0074] - when first input signal is generated, applying said first input signal to hardware equivalent model (150) and generating the pilot signal;

[0075] - storing pilot signal to a memory unit (140). This method may be applied to any device that utilizes matching filter which compares transmitted and received signals, such as radar systems.

[0076] After a first signal is generated for synchronization, channel estimation or equalization purposes between transmitting unit (100) and receiving unit (200), first signal is applied to hardware equivalent model (150) and pilot signal is generated. Then, pilot signal is transmitted to processing unit (230). This transmission may be realized using any method known in the art, such as, down conversion and digitization respectively. Pilot signal is used by processing unit (230) in order to correlate known pilot signal and received second signal over a channel to synchronize frame. After synchronization step channel estimation is realized to model channel towards amplitude and phase distortions. There are different channel estimator techniques like Least Square (LS) estimator, Maximum Likelihood (ML) estimator by processing known pilot symbols and received symbols associated to pilot symbols. At equalization step, the received symbol and channel estimation coefficients are operated to compensate the received symbols. Then the output signal is decoded.

[0077] Pilot signal may be updated on predetermined periods.

[0078] Adaptive filters reconfigures model parameters of its structure until error compensation is met for subtraction of output signal of T ransmitter RF front end (110) and output signal of adaptive filter.

[0079] The invention is also an integrated sensing and communication (ISAC) system which comprises one of the embodiments of above mentioned communication system (100). ISAC systems are systems that utilize transmitted signal of radar system (100) for both detection and data transmission.

[0080] In a possible embodiment referring to figure 4, receiving unit (200) may comprise a receiver adaptive filter unit (240) for modelling receiver RF front end (220). Another model generation unit (not shown) is configured to receive model parameters from receiver adaptive filter unit (240) and generate a receiver hardware equivalent model of receiver RF front end (220). Processing unit (230) divides received second signal with generated model and removes hardware effects on received signal. Processing unit (230) then realizes correlation processes using reference signal and received second signal that was cleaned of baseband characteristics of receiver RF front end (172).

Claims

CLAIMS1. A communication system (10) comprising a transmitting unit (100) having a signal generator (161 ) for generating a first signal, a T ransmitter RF front end (110) for processing said first signal and outputting a second signal, at least a transmitting antenna (162) for transmitting said second signal; comprising a receiving unit (200) having a receiving antenna (210) for receiving received second signal; a receiver RF front end (220) for processing received second signal; a processing unit (230) for comparing time shifted, received second signal and a pilot signal acquired from transmitting unit (100) that is representing the first signal characterized in that comprising at least an adaptive filter unit (130) which comprises at least an adaptive filter connected between input and output of the Transmitter RF front end (1 10) and configured to model said Transmitter RF front end (110) or said adaptive filter unit (130) comprising plurality of adaptive filters each connected between input and output of at least some of the processing components of Transmitter RF front end (110), each configured to model respective processing component of Transmitter RF front end (110); a model generating unit (120) which is configured to receive model parameters from adaptive filter / s and generate a hardware equivalent model (150) for Transmitter RF front end (1 10); model generating unit (120) is configured to apply the first signal to hardware equivalent model (150) and store acquired output signal as pilot signal in a memory unit (140) in order to be transmitted to receiver unit (200).

2. The communication system (10) according to claim 1 , characterized in that wherein Transmitter RF front end (1 10) comprises at least D / A converter (1 11 ), at least a mixer (112), at least a power amplifier (113) and at least a local oscillator; (114) adaptive filter unit (130) comprises at least a first adaptive filter (131 ) connected between input and output of said D / A converter (11 1 ), a second adaptive filter (132) connected between input and output of said mixer (112), a third adaptive filter (133) connected between input and output of said power amplifier (113) and a fourth adaptive filter (134) connected between input and output of said local oscillator (114).

3. The communication system (10) according to claim 1 , characterized in that comprising a receiver adaptive filter circuit (240) having at least an adaptive filter connected between input and output of the receiver RF front end (220) and configured to model the receiver RF front end (220) or said receiver adaptive filter unit (240) comprising plurality of adaptive filters each connected between input and output of at least some of the processing components of receiver RF front end (220), each configured to model respective processing component of receiver RF Front end (220); another model generation unit isconfigured to receive model parameters from adaptive filter / s and generate a receiver hardware equivalent model for receiver RF front end (220) and configured to divide the received second signal into receiver hardware equivalent model for removing hardware characteristic effects of receiver RF front end (220) on received second signal.

4. A pilot signal generating method for a processing unit where said processing unit is configured to compare a received second signal with a stored pilot signal where the pilot signal represents a second signal that was processed from a first signal by an Transmitter RF front end (110), and said second signal was transmitted by a transmitting antenna (162); and where said received second signal is received and processed version of the transmitted second signal; characterized in that comprising steps of:- by a signal generator (161 ) generating a calibration signal for Transmitter RF front end (110) to process;- by an adaptive filter unit (130) connected to Transmitter RF front end (110) modelling Transmitter RF front end (1 10) and generating model parameters;- by a model generating unit (120), generating hardware equivalent model (150) of T ransmitter RF front end (1 10) using model parameters;- when first input signal is generated, applying said first input signal to hardware equivalent model (150) and generating the pilot signal;- storing reference pilot to a memory unit (140).

5. An integrated sensing and communication system comprising the communication system (10) according to one of the claims 1 -5.

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