Specification
Description:TECHNICAL FIELD
[01] The present disclosure, in general, relates to managing calibration of radio frequency (RF) components in a wireless communication network, and in particular, relates to systems and methods for calibration of receive chains in a multiple-input-multiple-output (MIMO) wireless communication device, for example, a base station.
BACKGROUND
[02] The fifth-generation (5G) new radio (NR) base station (BS) supports high peak data rates with better reliability to multiple users simultaneously in a larger coverage area. The key enabler for such support is massive multiple-input-multiple-output (MIMO) technology. It provides several techniques to boost the performance of the BS, such as spatial diversity to enhance transmission robustness, spatial multiplexing to improve the peak data rates, and beamforming to increase signal-to-noise ratio (SNR). To get full advantages of MIMO techniques, the radio paths should have identical characteristics, such as having same gain and phase responses with same group delay. However, the actual radio paths have different characteristics due to different components and radio frequency (RF) paths. The characteristics of the radio path may also be affected by temperature variations during actual data transmission. Thus, calibration of the radio paths is required to ensure consistent MIMO performance.
[03] For antenna calibration, usually time-frequency resources are reserved by higher layers and user data transmission on the reserved resources is halted during the calibration process. This reduces spectrum efficiency of the BS, especially when the calibration is set to repeat periodically. Hence, there is a need for a system and a method to maintain high spectrum efficiency without disturbing the user data transmission during the calibration. During an operating phase or data transmission, the BS may implement the antenna calibration from time to time to check an integrity of estimated calibration coefficients. This repetition may be referred to as calibration periodicity. Generally, the calibration is set to repeat after regular intervals, referred to as periodic calibration. The periodic calibration with lower periodicity may increase the processing overhead of a system, while higher periodicity may reduce effectiveness of the calibration process.
[04] FIGs. 1A-1C illustrate system architecture for antenna calibration.
[05] FIG. 1A depicts an ideal scenario where all receive chains have similar characteristics. FIG. 1B depicts a base station with no calibration logic. FIG. 1C depicts the base station with an internal antenna calibration block.
[06] Antenna calibration requires a loopback mechanism, which may be over-the-air (OTA) or an internal dedicated feedback path. OTA calibration may require a receiver or a user equipment (UE) which may not be available during the calibration, especially in a start-up/bootup phase of the BS. While the calibration with the internal dedicated feedback path does not require a receiver or a UE, it requires additional resources whose functionalities again need to be optimized for enhanced performance.
[07] The existing systems do not offer any efficient mechanism for antenna calibration of the 5G NR MIMO BS with low processing complexity while maintaining spectrum efficiency. Therefore, there is, a need for a system and a method to calibrate the RF paths at a start-up phase and during an operating phase of the 5G NR MIMO BS adaptively without impacting user data transmission.
OBJECTS OF THE PRESENT DISCLOSURE
[08] It is an object of the present disclosure to provide a system and a method to calibrate Radio Frequency (RF) paths at a start-up phase and during an operating phase of a fifth-generation (5G) multiple-input-multiple-output (MIMO) wireless communication device adaptively without impacting user data transmission.
[09] It is an object of the present disclosure to provide a system and a method to calibrate RF receive paths during run-time of a communication apparatus, i.e., calibration of RF receive path in between data transmission without affecting a data transmission rate.
[010] It is an object of the present disclosure to provide a system and a method for handling variation in temperature and processing delay between multiple RF paths.
[011] It is an object of the present disclosure to provide a system and a method to adaptively calibrate RF receive chains in a multiple-input-multiple-output (MIMO) communication apparatus which also utilizes resources optimally and effectively.
SUMMARY
[012] In an aspect, the present disclosure relates to a method for calibration of receive chains in a start phase of a multiple-input-multiple-output (MIMO) wireless communication device, including setting, by a controller associated with the MIMO wireless communication device, delay values to zero and calibration coefficients to unity with zero phase for each of a plurality of receive chains, sending, by the controller, orthogonal sequences on each of the plurality of receive chains, estimating, by the controller, a first response and a first time delay for each of the plurality of receive chains by cross-correlating each receive signal from each of the plurality of receive chains with an orthogonal sequence, performing, by the controller, Orthogonal Frequency-Division Multiplexing (OFDM) demodulation on the estimated first responses to obtain frequency domain first responses, and computing, by the controller, calibration coefficients and delay values for each of the plurality of receive chains based on the frequency domain first responses to mitigate relative gain and phase differences with respect to a given receive chain.
[013] In an embodiment, the method may include sending, by the controller, the orthogonal sequences on each of the plurality of receive chains, controlling, by the controller, the first time delay in each of the plurality of receive chains by adjusting a timing of the orthogonal sequences, estimating, by the controller, a second response and a second time delay for each of the plurality of receive chains, performing, by the controller, the OFDM demodulation on the estimated second responses to obtain frequency domain second responses, and applying, by the controller, the computed calibration coefficients on the frequency domain second responses.
[014] In an embodiment, the method may include computing, by the controller, a gain difference, a phase difference, and a timing delay difference of each of the plurality of receive chains with respect to the given receive chain, and comparing, by the controller, the gain difference, the phase difference, and the timing delay difference of each of the plurality of receive chains with a gain error threshold, a phase error threshold, and a delay error threshold, respectively.
[015] In an embodiment, responsive to at least one of the gain difference, the phase difference, and the timing delay difference of each of the plurality of receive chains being less than the gain error threshold, the phase error threshold, and the delay error threshold, respectively, the method may include storing, by the controller, the computed calibration coefficients and the computed delay values in a database associated with the MIMO wireless communication device to perform calibration of the plurality of receive chains.
[016] In an embodiment, responsive to at least one of the gain difference, the phase difference, and the timing delay difference of each of the plurality of receive chains being greater than the gain error threshold, the phase error threshold, and the delay error threshold, respectively, the method may include computing, by the controller, updated calibration coefficients and/or updated delay values for each of the plurality of receive chains based on the frequency domain first responses to mitigate the gain difference, the phase difference, or the timing delay difference with respect to the given receive chain.
[017] In another aspect, the present disclosure relates to a method for calibration of receive chains in a MIMO wireless communication device, including determining, by a controller associated with the MIMO wireless communication device, that user data transmission is initiated in an operating phase of the MIMO wireless communication device, determining, by the controller, a need for calibration of a plurality of receive chains in the MIMO wireless communication device, in response to the determination, detecting, by the controller, an arrival of at least one of: a second last guard period of a special time slot in a TDD radio frame, or an OFDM symbol allocated by one or more higher layers in a FDD radio frame, and performing, by the controller, fine-tuned calibration of each of the plurality of receive chains based on the detection.
[018] In an embodiment, determining, by the controller, the need for the calibration of the plurality of receive chains may be based on at least one of: an expiry of a timer, a request by the one or more higher layers, an event of a change in temperature, and a fault being identified in a given receive chain of the plurality of receive chains.
[019] In an embodiment, performing, by the controller, the fine-tuned calibration of each of the plurality of receive chains may include sending, by the controller, orthogonal sequences on each of the plurality of receive chains, controlling, by the controller, a delay in each of the plurality of receive chains by adjusting a timing of the orthogonal sequences, estimating, by the controller, a response and a time delay for each of the plurality of receive chains by cross-correlating each receive signal from each of the plurality of receive chains with an orthogonal sequence, performing, by the controller, OFDM demodulation on the estimated responses to obtain frequency domain responses, and applying, by the controller, calibration coefficients on the frequency domain responses, wherein the calibration coefficients may be computed during a start phase of the MIMO wireless communication device or during earlier stages of the operating phase.
[020] In an embodiment, the method may include computing, by the controller, a gain difference, a phase difference, and a timing delay difference of each of the plurality of receive chains with respect to a given receive chain, and comparing, by the controller, the gain difference, the phase difference, and the timing delay difference of each of the plurality of receive chains with a gain error threshold, a phase error threshold, and a delay error threshold, respectively.
[021] In an embodiment, responsive to at least one of the gain difference, the phase difference, and the timing delay difference of each of the plurality of receive chains being less than the gain error threshold, the phase error threshold, and the delay error threshold, respectively, the method may include storing, by the controller, the calibration coefficients in a database associated with the MIMO wireless communication device to perform the fine-tuned calibration of each of the plurality of receive chains.
[022] In an embodiment, responsive to at least one of the gain difference, the phase difference, and the timing delay difference of each of the plurality of receive chains being greater than the gain error threshold, the phase error threshold, and the delay error threshold, respectively, the method may include computing, by the controller, updated calibration coefficients for each of the plurality of receive chains based on the frequency domain responses, detecting, by the controller, an arrival of at least one of: a second last guard period of a consecutive special time slot in the TDD radio frame, or another OFDM symbol allocated by the one or more higher layers in the FDD radio frame, and performing, by the controller, the fine-tuned calibration of each of the plurality of receive chains based on the detection.
[023] In an embodiment, the fine-tuned calibration may include at least an adaptive calibration, where for the adaptive calibration, the method may include adaptively controlling, by the controller, a value of the timer for performing the fine-tuned calibration of the plurality of receive chains.
[024] In another aspect, the present disclosure relates to a MIMO wireless communication device for calibration of receive chains in a start phase, including a controller associated with a processor, and a memory operatively coupled to the processor, where the memory includes processor-executable instructions which, when executed by the processor, cause the controller to set delay values to zero and calibration coefficients to unity with zero phase for each of a plurality of receive chains, send orthogonal sequences on each of the plurality of receive chains, estimate a first response and a first time delay for each of the plurality of receive chains by cross-correlating each receive signal from each of the plurality of receive chains with an orthogonal sequence, perform OFDM demodulation on the estimated first responses to obtain frequency domain first responses, and compute calibration coefficients and delay values for each of the plurality of receive chains based on the frequency domain first responses to mitigate relative gain and phase differences with respect to a given receive chain.
[025] In another aspect, the present disclosure relates to a MIMO wireless communication device for calibration of receive chains in an operating phase, including a controller associated with a processor, and a memory operatively coupled to the processor, where the memory includes processor-executable instructions which, when executed by the processor, cause the controller to determine that user data transmission is initiated in the operating phase of the MIMO wireless communication device, determine a need for calibration of a plurality of receive chains in the MIMO wireless communication device, in response to the determination, detect an arrival of at least one of: a second last guard period of a special time slot in a TDD radio frame, or an OFDM symbol allocated by one or more higher layers in a FDD radio frame, and perform fine-tuned calibration of each of the plurality of receive chains based on the detection.
[026] In an embodiment, to perform the fine-tuned calibration of each of the plurality of receive chains, the memory may include processor-executable instructions which, when executed by the processor, may cause the controller to send orthogonal sequences on each of the plurality of receive chains, control a delay in each of the plurality of receive chains by adjusting a timing of the orthogonal sequences, estimate a response and a time delay for each of the plurality of receive chains by cross-correlating each receive signal from each of the plurality of receive chains with an orthogonal sequence, perform OFDM demodulation on the estimated responses to obtain frequency domain responses, and applying, by the controller, calibration coefficients on the frequency domain responses, wherein the calibration coefficients may be computed during a start phase of the MIMO wireless communication device or during earlier stages of the operating phase.
BRIEF DESCRIPTION OF DRAWINGS
[027] The accompanying drawings, which are incorporated herein, and constitute a part of this disclosure, illustrate exemplary embodiments of the disclosed methods and systems which like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Some drawings may indicate the components using block diagrams and may not represent the internal circuitry of each component. It will be appreciated by those skilled in the art that disclosure of such drawings includes the disclosure of electrical components, electronic components, or circuitry commonly used to implement such components.
[028] FIGs. 1A and 1B illustrate conventional system architecture for antenna calibration in a 5th Generation (5G) Multiple Input Multiple Output (MIMO) wireless communication device.
[029] FIG. 1C illustrates a system architecture for antenna calibration with a calibration block.
[030] FIG. 2 illustrates an exemplary system architecture for antenna calibration with a calibration port inside an antenna panel, in accordance with an embodiment of the present disclosure.
[031] FIG. 3 illustrates an exemplary system architecture for antenna calibration with no calibration port inside an antenna panel, in accordance with an embodiment of the present disclosure.
[032] FIG. 4A illustrates an exemplary representation of a 5G New Radio (NR) Time Division Duplex (TDD) radio frame, in accordance with an embodiment of the present disclosure.
[033] FIG. 4B illustrates an exemplary representation for implementing calibration in a special slot with two and three guard periods, in accordance with an embodiment of the present disclosure.
[034] FIG. 4C illustrates an exemplary representation for implementing calibration in a special slot with four guard periods, in accordance with an embodiment of the present disclosure.
[035] FIG. 5 illustrates a high-level flow chart of an exemplary method for antenna calibration of receive chains, in accordance with an embodiment of the present disclosure.
[036] FIG. 6 illustrates a flow chart of an exemplary method for coarse calibration of receive chains during a start-up phase of a MIMO wireless communication device, in accordance with an embodiment of the present disclosure.
[037] FIG. 7 illustrates a flow chart of an exemplary method for implementing fine-tuned calibration of receive chains during an operating phase of a MIMO wireless communication device, in accordance with an embodiment of the present disclosure.
[038] FIG. 8 illustrates an example gain plot of estimated value of receive chain responses before calibration.
[039] FIG. 9 illustrates an exemplary representation of fine-tuned calibration in two special slots, in accordance with an embodiment of the present disclosure.
[040] FIGs. 10A and 10B illustrate exemplary representations of a gain plot of a time domain signal of third receive chain and eighth receive chain without calibration, respectively.
[041] FIGs. 11A and 11B illustrate exemplary representations of a gain plot of time domain signals of third receive chain and eighth receive chain with antenna calibration, in accordance with an embodiment of the present disclosure.
[042] FIGs. 12A and 12B illustrate exemplary representations of a gain plot of frequency domain signals of third receive chain and eighth receive chain without antenna calibration.
[043] FIGs. 13A and 13B illustrate exemplary representations of a gain plot of frequency domain signals of third receive chain and eighth receive chain with antenna calibration, in accordance with an embodiment of the present disclosure.
[044] FIGs. 14A and 14B illustrate exemplary representations of a phase plot of frequency domain signals of third receive chain and eighth receive chain without antenna calibration.
[045] FIGs. 15A and 15B illustrate exemplary representations of a phase plot of frequency domain signals of third receive chain and eighth receive chain with antenna calibration, in accordance with an embodiment of the present disclosure.
[046] FIG. 16 illustrates an exemplary computer system in which or with which embodiments of the present disclosure may be implemented.
[047] The foregoing shall be more apparent from the following more detailed description of the disclosure.
DETAILED DESCRIPTION
[048] In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific details. Several features described hereafter can each be used independently of one another or with any combination of other features. An individual feature may not address all of the problems discussed above or might address only some of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein.
[049] The ensuing description provides exemplary embodiments only and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the exemplary embodiments will provide those skilled in the art with an enabling description for implementing an exemplary embodiment. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the disclosure as set forth.
[050] The various embodiments throughout the disclosure will be explained in more detail with reference to FIGs. 2-16.
[051] FIG. 2 illustrates an exemplary system architecture (200) for antenna calibration with a calibration port (210a) inside an antenna panel (210), in accordance with an embodiment of the present disclosure.
[052] In particular, the exemplary system architecture (200) may represent a communication system such as a 5th Generation (5G) or next-generation communications system (200). As depicted, the architecture (200) includes an antenna panel (210) in which an in-built calibration port (210a) is provided. A signal may be injected into the calibration port (210a) and then equally distributed to all Radio Frequency (RF) antenna ports of the antenna panel (210). These signals may be further connected to receive chains of a multiple-input-multiple-output (MIMO) wireless communication device for calibration. Examples of the MIMO wireless communication device may include, without limitation, a base station, a Fixed Wireless Access Customer Premises Equipment (FWA CPE), small cells, routers, User Equipment (UE), and so on. The system architecture (200) may be utilized in both types of base stations, which have antenna panels (210) with and without in-built calibration ports (210a).
[053] In an embodiment, the system architecture (200) may include a System on Chip (SoC) (202). The SoC (202) may include a processing system (or interchangeably referred to as a processor) and a programming logic for baseband processing of incoming data and other control functions.
[054] In an embodiment, a memory bank (204) may include orthogonal sequences on a time domain (ZT) and their frequency domain equivalent (ZF) for calibration coefficients. In an example embodiment, the orthogonal sequences may include, but not limited to, ZadoffChu sequence (Z), constant amplitude zero auto-corelation waveform (CAZAC) signal, and Walsh-Hadamard code, etc.
[055] In an embodiment, user data (204) may be in the form of a frequency domain modulated in-phase (I) and quadrature (Q) symbols from higher layers of, for example, the base station. The higher layers may be a high Physical (PHY) layer including, but not limited to, Media Access Control (MAC) and Radio Link Control (RLC) layers.
[056] In an embodiment, a Digital Front End (DFE) and a digital to analog converter (DAC) (206) may pre-distort and upconvert the incoming time-domain IQ symbols and then convert them to an analog domain.
[057] In an embodiment, a feedback network (208) may include a series of gain blocks to keep enough power level of a signal for calibration.
[058] In an embodiment, the antenna panel (210) may receive radiated signals. As discussed herein, the antenna panel (210) may include the in-built calibration port (210a).
[059] In an embodiment, RF module (212) may process the signal with a series of RF components. The RF module (212) may maintain the power level of the feedback signal in an operating range of an Analog to Digital Converter (ADC) (214).
[060] In an embodiment, a DFE and ADC (214) may convert the analog signal to a digital signal and then down-convert the digital signal.
[061] In an embodiment, a delay adjuster (216) may delay time domain data with estimated delay values to compensate for the timing differences with respect to a reference chain.
[062] In an embodiment, a first demultiplexer (DeMUX) (218) may switch the time domain delayed data between a response and delay estimator (220) and a MUX (222).
[063] In an embodiment, the response and delay estimator (220) may estimate the response and time delay of all receive chains.
[064] In an embodiment, the MUX (222) may switch between user data (230) and estimated response of the receive chains. The user data (230) may be frequency domain modulated IQ symbols from a calibrator (228).
[065] In an embodiment, an Orthogonal Frequency-Division Multiplexing (OFDM) demodulator (224) may perform cyclic prefix removal and Fast Fourier Transform (FFT) operations.
[066] In an embodiment, a second demultiplexer (DeMUX) (226) may switch the signal between the calibrator (228) and a coefficient estimator (232).
[067] In an embodiment, the calibrator (228) may contain complex multipliers to multiply the frequency domain data with calibration coefficients to compensate for gain, phase, and timing differences with respect to the reference chain.
[068] In an embodiment, the coefficient estimator (232) may estimate the calibration coefficients for antenna calibration based on the estimated response and time delay of all receive chains.
[069] In an embodiment, a controller (234) may control the whole operation of the antenna calibration. During a start-up phase, the controller (234) may initially identify control signals (c1), (c2) to reset the delay values and the calibration coefficients, respectively. The controller (234) may identify the control signal (c1) to update the delay values with their estimated value during the rest of the start-up phase and operating phase. The controller (234) may identify the control signal (c2) to update the coefficients with their estimated value during the rest of the start-up phase and operating phase. The controller (234) may also identify the control signal (c3) to control the MUX (222), the first DeMUX (218), and the second DeMUX (226). They work in two modes, namely an antenna calibration mode and a user data transmission/reception mode. In the antenna calibration mode, the MUX (222), the first DeMUX (218), and the second DeMUX (226) are configured to connect the orthogonal sequences to the coefficient estimator (232). In the user data transmission/reception mode, the MUX (222), the first DeMUX (218), and the second DeMUX (226) are configured to connect the incoming user data to the calibrator (228).
[070] The controller (234) may take an input from the calibrator (228) to calculate a gain difference (Eg) and a phase difference (Ep), and from the response and delay estimator (220) to calculate a timing delay difference (Ed) for each chain with respect to the reference chain. The controller (234) may compare the gain difference (Eg), the phase difference (Ep), and the timing delay difference (Ed) with a gain error threshold (Tg), a phase error threshold (Tp), and a delay error threshold (Td), respectively. It may be appreciated that all thresholds may be configurable and may be defined as per the design implementation. If the estimation of coefficients is required based on the comparison, the controller (234) may identify a control signal (c4) to inform the coefficient estimator (232) for the estimation of the calibration coefficients.
[071] In an embodiment, during the operating phase, the controller (234) may control the periodicity of the calibration by updating a timer value adaptively.
[072] FIG. 3 illustrates an exemplary system architecture (300) for antenna calibration with no calibration port inside an antenna panel (210), in accordance with an embodiment of the present disclosure.
[073] A person skilled in the art may understand that the various modules mentioned in FIG. 3 may be similar to the corresponding modules of FIG. 2 in their functionality and may not be described again for the sake of brevity.
[074] With reference to FIG. 3, a distribution network (302) may contain a series of splitters to equally distribute a signal to each receive chain. In an embodiment, switches (304) may switch between the signal from the antenna panel (210) and the distribution network (302).
[075] FIG. 4A illustrates an exemplary representation (400A) of a 5G New Radio (NR) Time Division Duplex (TDD) radio frame, in accordance with an embodiment of the present disclosure.
[076] With reference to FIG. 4A, considering the 30kHz subcarrier spacing, a 10ms radio frame may include 20 time slots, each having 14 OFDM symbols. The downlink may occupy 14 slots, and the uplink may occupy 4 slots out of 20 slots in normal conditions. The rest of the two slots may be used as special slots. The 14 OFDM symbols in each special slot may be configured as 8 symbols for downlink, 4 symbols for the guard period, and 2 symbols for uplink. To avoid information loss, a MIMO wireless communication device, for example, a base station utilizes the guard period of the special slots to perform the calibration operation during the operating phase.
[077] FIG. 4B illustrates an exemplary representation (400B) for implementing calibration in a special slot with two and three guard periods, in accordance with an embodiment of the present disclosure.
[078] With reference to FIG. 4B, if only two guard periods are present in one special slot, then fine-tuned calibration of the receive chains may not be implemented as the first guard period may be used as a waiting period to power down power amplifiers of transmit chains so that there may be no leakage to the receive chains. In such a scenario, higher layers of the base station may increase the number of guard periods of the next special slot to perform fine-tuned calibration of the receive chains. In another embodiment, if three guard periods are present in one special slot, then fine-tuned calibration of the receive chains may be implemented in the second last guard period.
[079] FIG. 4C illustrates an exemplary representation (400C) for implementing calibration in a special slot with four guard periods, in accordance with an embodiment of the present disclosure.
[080] With reference to FIG. 4C, if four or more guard periods are present in one radio frame, then fine-tuned receive chain calibration may be implemented in the second last guard period of the same special slot.
[081] FIG. 5 illustrates a high-level flow chart of an exemplary method (500) for antenna calibration of receive chains, in accordance with an embodiment of the present disclosure. It may be appreciated that the method (500) may be implemented by the MIMO wireless communication device, e.g. the controller (234) or the processor.
[082] The antenna calibration of a 5G NR TDD MIMO wireless communication device, for example, a base station may measure signal characteristics across the receive chains, and determine the differences across the chains, specifically in terms of gain, phase, and timing. Further, the antenna calibration may calibrate the receive signals to mitigate the differences across the receive chains. The calibration may include two phases, namely a start-up phase and an operating phase.
[083] In the start-up phase, the calibration may be implemented during a start-up/booting of the base station. It may be considered as a coarse calibration of the base station as it equalizes the gain, phase, and timing differences across the chains, which may occur due to the system design. In the operating phase, the base station may undergo temperature variations, which may affect the characteristics of the chains. Therefore, the calibration may be required during the operating phase, and thus, it may be considered as a fine-tuned calibration. The temperature variation may become slow once the base station reaches a steady state. Thus, the calibration in the operating phase may not be required frequently.
[084] In an embodiment, the base station may be operated with a TDD radio frame to perform the calibration in a guard period during the operating phase without halting the user data transmission. This may provide leverage to the base station to maintain the spectrum efficiency of the TDD system in real-time. In another embodiment, for Frequency Division Duplex (FDD) base station, a request may be sent to the higher layer to provide the configurable number of vacated OFDM symbols for calibration. The higher layer vacates the requested number of OFDM symbols in one or more FDD radio frames and provides the frame number and OFDM symbol number to the base station (e.g., the controller (234)) to perform calibration during the operating phase.
[085] With reference to FIG. 5, at step 502, a startup phase/coarse calibration of the receive chains may be implemented. At step 504, the method (500) may include waiting for the operating phase to start the user data transmission. At step 506, a value of a timer may be set to its initial value, which may be configurable. At step 508, the timer may be started. In an embodiment, the operating phase/fine-tuned calibration may be implemented every time the timer expires. The operating phase/fine-tuned calibration may also be performed as requested by the higher layers or in an event of a significant change in the temperature, or a fault being identified in a reference chain.
[086] Referring to FIG. 5, at step 510, the method (500) may include determining if the timer has expired or if there is a need for calibration. The need for the calibration of the plurality of receive chains may be based on, without limitation, an expiry of the timer, a request by the one or more higher layers, an event of a change in temperature, and a fault being identified in a given receive chain of the plurality of receive chains. If the timer has not expired and/or there is no need for calibration, the method (500) may include continuing to monitor the timer and/or the need for calibration. At step 512, if the timer has expired or there is the need for calibration, the method (500) may include determining if the base station corresponds to TDD or FDD mode.
[087] At step 514, if the base station corresponds to the FDD mode as determined at step 512, the method (500) may include sending the request to one or more higher layers of the base station to allocate configurable number of vacated OFDM symbols for the calibration. At step 516, the method (500) may include determining if the allocated OFDM symbols have arrived or not.
[088] At step 520, if the allocated OFDM symbols have arrived, the method (500) may include performing the fine-tuned calibration of the receive chains in the allocated OFDM symbols. If the allocated OFDM symbols have not arrived, the method (500) may include continuing to monitor whether the OFDM symbols have arrived or not.
[089] At step 518, if the base station corresponds to the TDD mode, the method (500) may include determining an arrival of a second last guard period of a special time slot. At step 520, the method (500) may include performing the fine-tuned calibration of the receive chains in the second last guard period of the special time slot. If the second last guard period of the special time slot has not arrived, the method (500) may include continuing to monitor the arrival of the special time slot.
[090] At step 522, the method (500) may include determining whether re-calibration of the receive chains is performed. At step 524, if re-calibration of the receive chains is not performed, the value of the timer may be incremented, and the method (500) may proceed to step 508. If the re-calibration of the receive chains is performed, the method (500) may proceed to step 506.
[091] In an embodiment, the calibration periodicity may be periodic and adaptive. In periodic calibration, the timer value may be constant, i.e., the calibration may be repeated after every one or two or any fixed number of TDD radio frames. In adaptive calibration, the timer value may not be fixed and may be updated adaptively.
[092] Adaptive calibration may mitigate the issues of the periodic calibration. Since the temperature variation is expected to be higher during the initial time of the operating phase, the timer value may be incremented by smaller values. After certain cycles, the timer value may be incremented by larger values. For example, the Fibonacci series of 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610 (seconds) may be used as the timer value.
[093] FIG. 6 illustrates a flow chart of an exemplary method (600) for coarse calibration of receive chains in a MIMO wireless communication device, in accordance with an embodiment of the present disclosure.
[094] With reference to FIG. 6, at step 602, the method (600) may include setting all calibration coefficients to unity with zero phase and all delay values to zero in a calibrator (e.g., 228 of FIG. 2) and a delay adjuster (e.g., 216) for all receive chains using control signals (c2), (c1), respectively.
[095] At step 604, the method (600) may include sending preloaded orthogonal sequence on all receive chains. The orthogonal sequence is used as a reference to calibrate the receive chains. In one of the embodiments, the orthogonal sequence can be, for example, ZadoffChu sequence or CAZAC signal. In an embodiment, the orthogonal sequence may be generated offline and stored in a memory. In another embodiment, a ZadoffChu sequence generator may be implemented in the SoC (e.g., 202) to generate the sequence in real-time. The ZadoffChu sequence has two key parameters: length of the sequence , which must be an odd prime number, and root index . With these two parameters, it can be defined as:
where
[096] The length of the ZadoffChu sequence should be a prime number and can be configurable. For example, it can be the largest prime number smaller than the FFT size. Zero padding can match the sequence length to the FFT size.
[097] In an embodiment, the ZadoffChu sequence may undergo DFE and DAC processing before feeding to the feedforward network. This signal may be equally distributed in each receive chain and processed through RF, ADC, and DFE blocks.
[098] At step 606, the method (600) may include setting a first demultiplexer (e.g., 218) using control signal (c3) to send samples of all receive chains to a response delay and estimator (e.g., 220).
[099] At step 608, the method (600) may include estimating the response and timing delay, i.e., first response and first timing delay, for each receive chain by cross-correlating each receive signal with the ZadoffChu sequence by the response and delay estimator 220.
[0100] The periodic cross-correlation of with is defined as
where “*” is the complex conjugate, and “mod” is the modulus operator.
[0101] At step 610, the method (600) may include setting a multiplexer (e.g., 222) using the control signal (c3) to send the estimated response of all receive chains to an OFDM demodulator (e.g., 224). At step 612, the method (600) may include performing OFDM demodulation on the estimated responses to obtain frequency domain first responses.
[0102] At step 614, the method (600) may include sending the frequency domain first responses to a coefficient estimator (e.g., 232). At step 616, the method (600) may include computing calibration coefficients and delay values for each receive chain based on the frequency domain first responses to mitigate relative gain and phase differences with respect to a given receive chain. In an embodiment, the coefficient estimator (232) estimates the calibration coefficients using control signal (c4) for each receive chain.
[0103] At step 618, the method (600) may include sending the preloaded orthogonal sequences on each receive chain. At step 620, the method (600) may include controlling the first timing delay in each receive chain by adjusting a timing of the orthogonal sequences using the delay adjuster (216).
[0104] At step 622, the method (600) may include setting the first demultiplexer (218) using the control signal (c3) to load the received sequences to the response ad delay estimator (220). At step 624, the method (600) may include estimating a second response and a second timing delay for each receive chain by cross-correlating each signal with the orthogonal sequence by the response and delay estimator (220).
[0105] At step 626, the method (600) may include setting the multiplexer (222) using control signal (c3) to send the estimated second responses to the OFDM demodulator (224). At step 628, the method (600) may include performing OFDM demodulation on the estimated second responses to obtain frequency domain second responses.
[0106] At step 630, the method (600) may include applying the calibration coefficients on the frequency domain second responses. At step 632, the method includes calculating Eg, Ep, and Ed for each chain with respect to the reference chain and comparing Eg, Ep, and Ed with Tg, Tp, and Td, respectively. At 634, the method (600) may include determining if Eg
Documents
Application Documents
| # |
Name |
Date |
| 1 |
202441009075-STATEMENT OF UNDERTAKING (FORM 3) [10-02-2024(online)].pdf |
2024-02-10 |
| 2 |
202441009075-POWER OF AUTHORITY [10-02-2024(online)].pdf |
2024-02-10 |
| 3 |
202441009075-FORM 1 [10-02-2024(online)].pdf |
2024-02-10 |
| 4 |
202441009075-DRAWINGS [10-02-2024(online)].pdf |
2024-02-10 |
| 5 |
202441009075-DECLARATION OF INVENTORSHIP (FORM 5) [10-02-2024(online)].pdf |
2024-02-10 |
| 6 |
202441009075-COMPLETE SPECIFICATION [10-02-2024(online)].pdf |
2024-02-10 |
| 7 |
202441009075-Power of Attorney [15-01-2025(online)].pdf |
2025-01-15 |
| 8 |
202441009075-Covering Letter [15-01-2025(online)].pdf |
2025-01-15 |
| 9 |
202441009075-FORM-9 [07-03-2025(online)].pdf |
2025-03-07 |
| 10 |
202441009075-FORM 18 [10-03-2025(online)].pdf |
2025-03-10 |