A multi-numerology based method for wireless communication

Abstract

The invention is related to a method for multi-numerology OTFS based NOMA approach to generate a signal for plurality of wireless devices and a transmitting, a receiving and a communication and / or a sensing method for such a signal.

Description

[0001] A MULTI-NUMEROLOGY BASED METHOD FOR WIRELESS COMMUNICATION

[0002] Technical Field

[0003] The invention is related to a method for multi-numerology OTFS based NOMA approach to generate a signal for plurality of wireless devices and a transmitting, a receiving and a communication and / or a sensing method for such a signal.

[0004] Prior Art

[0005] The emergence of new services and applications in wireless networks has prompted the need for extensive connectivity in 6G networks. Due to the exponential growth of new services and applications, alongside a wide range of requirements, the need for massive access as one of the foundational targets for the next generation wireless networks is highlighted. However, the existing waveforms do not match with all variations and are only applicable in specific scenarios.

[0006] However, existing orthogonal technologies have limitations in meeting this requirement. While Orthogonal Time Frequency Space (OTFS) outperforms Orthogonal Frequency- Division Multiplexing (OFDM) in high-mobility scenarios, it still lacks the superior gains provided by NOMA systems. This limitation necessitates the development of a hybrid waveform that combines the strengths of both approaches. Moreover, conventional NOMA systems face challenges related to interference in the power domain. These interferences cannot be effectively mitigated at the receiver due to noise and loss in wireless channels, resulting in decreased user capacity. Addressing these technical issues is crucial for achieving improved performance in wireless communication systems.

[0007] OTFS-NOMA promises to significantly enhance the energy and spectral efficiency of wireless communication systems, thereby catapulting the field towards unprecedented heights of performance and capability. Notably, various controlling approaches for implementing OTFS- NOMA have already surfaced in the literature. For instance, the work in [1] exploits the OTFS-NOMA approach to distinguish users based on their mobility profiles. A novel low complexity iterative receiver tailored for OTFS-NOMA is presented in [2] where OTFS- modulated signals are multiplexed in the power domain. Their proposed receiver design outperforms conventional approaches in terms of data detection reliability and symbol error rate (SER).

[0008] However, the requirement for different quality of service (QoS) levels necessitates increased degrees of freedom and flexibility in waveform channel parameters such as delay-Doppler (DD) lattice, subcarrier spacing, and cyclic prefix (CP). To address this concern, the concept of mixed numerology is introduced for 5G waveform design, as highlighted in [3], This innovation enables improved system performance and greater flexibility in communication systems, allowing the processing of multiple data rates and bandwidths within the same system while enhancing spectral utilization. Another significant advancement in NOMA, proposed in [4], is the use of multi-numerology NOMA in conjunction with OFDM to overcome the limitations of conventional NOMA (CN). The results of their study demonstrate superior bit error rate (BER) and spectral efficiency (SE) performance compared to the CN methods.

[0009] Amongst the works mentioned in the previous section, fully overlaying signals or using fixed grid approaches suffer from low adaptability and flexibility, both in the time-frequency and DD domains as in OTFS and OFDM signals. These methods pose challenges when accommodating different applications with varying requirements, particularly for diverse Quality of Service (QoS) needs.

[0010] For instance, some applications operate in high-mobility scenarios and necessitate high data rates, while other operations operate in static environments and prioritize ultra-reliability. Attempting to satisfy both requirements using the same fixed grid is unsuitable.

[0011] Furthermore, conventional NOMA-based networks primarily concentrate on low-mobility user scenarios, wherein users with varying channel conditions or distinct QoS demands are amalgamated and served concurrently, utilizing the same time-frequency resources

[0012] As a result, all of the problem mentioned above has made it necessary to provide a novelty in the related field.

[0013] Brief Description and Objects of the Invention

[0014] The main object of the present invention is to establish a method for generating waveform and receiving and communication method for such a waveform to achieve quality of service demands for different users under diverse mobility levels scenario. Another object of the invention is to optimize multiple accessing schemes for efficient resource allocation.

[0015] Another object of the invention is to enhance adaptability to channel conditions for improved performance.

[0016] Another object of the invention is to optimize spectral efficiency through efficient spectrum utilization.

[0017] Another object of the invention is to provide robustness against channel variations for reliable communication.

[0018] Another object of the invention is to accommodate users with different mobility characteristics and varying requirements.

[0019] Another object of the invention is to maximize throughput and capacity in highly mobile environments

[0020] To achieve such goals, the method proposes different index spacing in the representation of the wireless channel in delay-Doppler (DD) domain is utilized to provide different numerologies to enable unique waveform design that that utilizes sophisticated techniques like OTFS, NOMA and is applicable for multiple users’ requirements.

[0021] The invention introduces an overlaying scheme that allows users with different mobility characteristics to be overlaid in the time-frequency domain, enabling efficient utilization of resources.

[0022] The invention allows for the selection of different numerology based on the channel conditions for each user, providing flexibility and adaptability to varying channel characteristics.

[0023] The invention maximizes spectral efficiency by optimizing the utilization of available spectrum through efficient resource allocation and adaptive numerology.

[0024] Enhanced throughput: With the ability to adaptively allocate resources and accommodate users with different requirements, the invention facilitates higher throughput and improved communication performance

[0025] One significant aspect of the invention is its impact on spectral efficiency. By employing optimized techniques, the invention maximizes the utilization of the available spectrum, allowing for efficient resource allocation and improved spectral efficiency. This ambitious endeavor is an essential step towards breaking new ground in wireless communication technology, offering promising avenues for enhancing network capabilities and empowering seamless connectivity across a wide range of use cases and scenarios. Through this innovative approach, we aspire to contribute significantly to the evolution of wireless communication systems, and ultimately, redefine the boundaries of what is possible in this ever-evolving field.

[0026] This significant progress stands as a testament to our unwavering commitment to advancing wireless communication systems and realizing their full potential. The innovative framework paves the way for unparalleled adaptability, enhanced performance, and elevated spectral efficiency. As such, our research promises to be a major steppingstone in the ongoing evolution of wireless communications, opening new horizons and setting new benchmarks for future developments in the field.

[0027] Description of the Figures of the Invention

[0028] The figures and related descriptions necessary for the subject matter of the invention to be understood better are given below.

[0029] Figure 1. A schematic view of the system.

[0030] Figure 2. A graphical representation of multi -numerology distribution in DD domain with different delay spacing.

[0031] Figure 3. A graphical representation of multi -numerology distribution in DD domain with different Doppler spacing.

[0032] Figure 4. A graphical representation of multi -numerology distribution in DD domain with different both delay and Doppler spacing.

[0033] Figure 5. A graphical representation of the proposed NOMA-based multi-numerology OTFS design in time-frequency domain.

[0034] Figure 6. A schematic view of the proposed NOMA-based multi-numerology OTFS transceiver design

[0035] Figure 7. The proposed NOMA-based multi-numerology OTFS design flow chart. Reference Numbers

[0036] The parts and components are given in the figures are referenced for the subject matter of the invention to be understood better.

[0037] TX. Transmitter

[0038] RX. Receiver

[0039] UE. User equipment

[0040] Detailed Description of the Invention

[0041] The invention is related to a method for multi-numerology OTFS based NOMA approach to generate a signal for plurality of wireless devices and a receiving and communication method for such a signal.

[0042] Referring to Figure 1; The communication system that the communication method is carried comprises at least one transmitter (Tx) such as a base station and multiple moving user equipment (UE) having at least one receiver (Rx). At least two of the moving user equipment (UE) are wide bin users and at least one of the moving user equipment (UE) is narrow bin user.

[0043] Referring to Figure 2 to 4: To generate a waveform according to multi-numerology OTFS based NOMA approach, first of all, at least three signals are designed and two of them are wide grid signal and other one is the narrow grid signal. Both wide and narrow grids comprise bins that positioned on these grids with spacing to form the wide grid signal and the narrow grid signal, respectively.

[0044] A downlink multi-user OTFS system design is assumed where an OTFS modulation scheme is used to multiplex the users. The OTFS signal considers M x N data symbols distributed over M x N DD bins denoted by where The communication system is modulated over a total bandwidth B = M f with a frame duration of where the time duration of one symbol is which imposes 1 / MA f and delay and Doppler spacing, respectively.

[0045] The spacing of these grids is different than other at least according to one of delay or Doppler space. In excessive cases, the both spacings can be different in both spaces. After the design is completed, the wide signal and the narrow signal is converted into timefrequency domain.

[0046] In figure 2, the spacing of the grids are equal in Doppler space but not in delay space. This can be represented by formula of where and A are Doppler spacing of the wide grid and narrow grid, respectively, while where and are delay spacing of the wide grid and narrow grid, respectively.

[0047] For example, value of r1and AT2is set as A while and is kept equal. That gives two OTFS signals with different numerology only in delay domain as presented in Figure 2 where is equivalent to setting . Finally, the

[0048] OTFS transform can be done by taking ISFFT with size for the first numerology and size for the second one with

[0049] In figure 3, the spacing of the grids are equal in delay space but not in Dopier space. This can be represented by formula of and

[0050] For example, value of and is set as while and 2is kept equal. That gives two OTFS signals with different numerology only in Doppler domain as presented in Figure 3 where is equivalent to setting . Finally, the

[0051] OTFS transform can be done by taking ISFFT with size for the first numerology and size for the other.

[0052] In figure 4, the spacing of the grids are equal in both spaces. This can be represented by formula of and

[0053] For example, value of and AT2is set as while and A is set as That gives two OTFS signals with different numerology only in Doppler domain as presented in Figure 4 is equivalent to setting and Thus, the OTFS modulation can be done by taking ISFFT with size for the first numerology and

[0054] (M2, N2) for the second one.

[0055] For all example of figure 2 to 4; fundamental numerology chosen here is similar to the one used in conventional LTE networks and a total of five scalable numerology options are provided. All standardized A values are 2qmultiples of the fundamental LTE numerology for q = [0, 4] [5], For the OTFS signal part, we consider two OTFS signals that use the same DD resources, denoted by , with A and DD spacing for the first and second numerologies, respectively.

[0056] The designed wide and narrow signals are converted into the time-frequency domain. In here are mapped to the time-frequency (TF) domain grid using the inverse symplectic finite Fourier transform (ISFFT) [1], where

[0057] The converted wide signals are put in time-frequency slots without overlapping each other since wide grid signals in delay doppler takes less resources in time frequency and are summed together with the converted narrow signal.

[0058] After the sum of the wide and narrow signals, the obtained signal is converted into time domain, preferably by Heisenberg Transform as where rect(. ) is the rectangular pulse shape and

[0059] After the conversion into time domain, the signal is sent to medium by the transmitter (Tx).

[0060] The proposed NOMA-based multi -numerology OTFS design mainly relies on the transmitter design assuming three users in the system. We consider a wireless communication system that comprises multiple wide bins spacing users a, multiple narrow bins users and the total number of users is given by Our approach involves overlaying signals of users with narrow delay spacing denoted by xnroccupying a bandwidth on top of signals of users with wider spacing denoted by xwand occupying a bandwidth B±= This enables the use of 2qsignals xwto cover the same resources utilized by the

[0061] The transmitter (Tx) design consists of three stages as follow:

[0062] The first is designing the wide signal. The wide spacing signal can be presented as follows. where are the complex modulated symbols of the user on land Doppler and delay bins, respectively. is the assigned power factor, where the total amount of the specified power is

[0063] The second is designing the narrow signal. The narrow spacing signal and to avoid interference between different numerologies is allocated only on the odd bins by setting Thus their OTFS TF domain signal is given as bellow where are the complex modulated symbols of the bthuser on ktfland l'tflDoppler and delay bins respectively, is the assigned power factor, where the total amount of the specified power is - The maximum assigned power from the BS to all users is represents the conventional NOMA scheme case.

[0064] The third is signal superposition. This represents summation step. For simplicity purpose we consider and naming the first and the second wide bins spacing user UE1 and UE2, respectively. The narrow bins user as UE3. After converting both wide and narrow signals to TF domain, the wide bin signals XWaare assigned in different frequency slots to form one block matrix The narrow bin signal X ijsadded with to produce a single block namedasdepicted in Figure 5. The summation needs to be performed in the TF domain due to the spread in both domains which can be expressed as follows:

[0065] We assume that the channels for all users are linear time varying. Each user's channel contains paths, where the hpath has complex attenuation , delay and Doppler value for These characteristics result in a doubly dispersive DD channel for each user

[0066] The DD values for tap are given as and where lLiE and are the number of delay and Doppler bins. We assume that N2and M2are sufficiently large so that there is no effect of fractional delay and Doppler on the system assuming perfect knowledge of the channel hLt at the receiver.

[0067] Preferably, after the signal received by the user equipment, the process at the receiver side starts by removing the CP, the wireless channel effect.

[0068] After the deleting the wireless channel effect, the received signal is converted delay Doppler domain according to spacing of the wide grid by each user and the wide grid is detected from the converted signal to extract the wide signal by at least two of the users, preferably by deleting wireless channel effects from the received signal. Preferably, the Wigner transform may be applied after deleting the wireless channel effects. According to detected wide signal, the narrow signal can be reconstructed by at least one of the users that already extract the wide signal or more, if necessary. If there is more than wide signal is designed in first step of generating waveform, further wide signals can be detected by deleting extracted the wide signal from the received signal.

[0069] To carry out these steps, the below disclosed process may be carried out.

[0070] After removing the CP and performing OTFS transform using a matching pulse with the transmit pulse rect(A), the channel is estimated and the input-output relation at any user can be derived as where denote the delay-Doppler effective channel matrix, and represents the time equivalent channel matrix.

[0071] Note that to estimate the channel, any conventional OTFS channel estimation method is applicable such as impulse channel estimation method represented in [4],

[0072] The channel is equalized using minimum mean square error (MMSE) detector.

[0073] The equalized signal is converted to DD domain using SFFT with . The output of the even and odd bins can be derived by setting

[0074] Although1and signals are allocated to different TF resources at the transmitter, they are received overlapping, due to the summation process of the SFFT.

[0075] The basic idea of the proposed approach is discussed from the perspective of three users only, however, the design can be extended to more than three users which at least two of them are wide bin and at least one of them is narrow bin user, and based on their requirements the total time-frequency resources are split among them to achieve maximum system capacity.

[0076] The invention also covers that a data processing device comprising means for carrying out the steps of the method of invention and a computer program comprising instructions which, when the program is executed by a data processing device, cause the data processing device to carry out the steps of the method of invention and a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of invention. Furthermore, the system comprises at least one transmitter (Tx) such as a base station and multiple moving user equipment (UE) having at least one receiver (Rx) and a data processing device comprising means for carrying out the steps of the method of invention.

[0077] The proposed approach is discussed from the perspective of only multi -numerology only in the scenario, however from the approach hold when using different numerology in delay, Doppler or delay-Doppler.

[0078] The proposed NOMA-based multi -numerology OTFS design can be applied to different networks such as NTN, CoMP, JRC, and localization. The proposed approach can be extended to be used without power difference between users at the transmitter side thus channel estimation should be done in time-frequency domain instead of Delay -Doppler domain and the SIC will no longer be needed at the receiver side.

[0079] The proposed approach is assumed to change the delay spacing by changing the number of delay, Doppler, or delay-Doppler bins while keeping the subcarrier spacing fixed. However, the proposed approach can be extended to change the delay spacing by changing the subcarrier spacing while fixing the number of delay-Doppler bins, in this case the system performance can be reduced therefore an optimized point between changing the subcarrier spacing and the number of bins should be defined. The proposed approach can be merged with the multiple antenna concept (i.e. multiple input multiple output network) to enhance the user’s performance.

[0080] REFERENCES

[0081] [1] Z. Ding et al., “OTFS-NOMA: An efficient approach for exploiting heterogenous user mobility profiles,” IEEE Trans. Commun., vol. 67, no. 11, pp. 7950-7965, 2019.

[0082] [2] S. McWade, M. F. Flanagan, and A. Farhang, “Low-complexity equalization and detection for OTFS-NOMA,” arXiv preprint arXiv:2211.07388, 2022.

[0083] [3] X. Zhang et al, “On the waveform for 5G,” IEEE Commun. Mag., vol. 54, no. 11, pp. 74- 80, 2016.

[0084] [4] A. T. Abusabah and H. Arslan, “NOMA for multinumerology OFDM systems,” Wirel. Commun. Mob. Comput., vol. 2018, 2018. [5] A. A. Zaidi et al., “Waveform and numerology to support 5G services and requirements,”

[0085] IEEE Commun. Mag., vol. 54, no. 11, pp. 90-98, 2016.

Claims

CLAIMS1. A computer implemented method for generating a signal for multinumerology-OTFS based NOMA system to communicate between transmitter and multiple users having a receiver which at least two of them are wide bin users and at least one of them is narrow bin user comprising steps of designing at least two wide grid signals and at least one narrow grid signal wherein spacing of the wide grid signal in delay and / or Doppler space different than narrow grid signal and the narrow grid signal is narrower than the wide grid signals in the domain, converting the wide grid signals into the time-frequency domain, converting the narrow grid signal into the time-frequency domain in separate manner, Putting out the wide bins different time-frequency slots without overlapping, Performing summation of the wide grid signals and the narrow grid signal and Converting the summed signal into the time domain.

2. A method according to Claim 1 characterized by designing multiple narrow grid signals.

3. A method according to Claim 1 characterized by converting the wide grid signals and the narrow grid signal into the time-frequency domain by using the inverse symplectic finite Fourier transform.

4. A method according to Claim 1 characterized by converting the summed grid signal into the time domain by Heisenberg Transform.

5. A receiving method for wireless communication to communicate between transmitter and multiple users having at least a receiver which at least two of them are wide bin and at least one of them is narrow bin user comprising steps ofReceiving a signal generated according to any of preceding claims by the multiple user equipment,Converting the received signal into delay Doppler domain according to spacing of the narrow grid signal by each user,Detecting the wide grid signals from the converted signal to extract the wide grid signals by the users,Reconstructing the narrow grid signal according to the detected wide signals by the narrow bin users that already extract the wide grid signals.

6. A method according to Claim 5 characterized by the reconstructing comprises steps of converting all the extracted wide grid signal to time-frequency domain in separate manner and deleting it from the received signal and converting back into delay- Doppler domain to detect the narrow grid signal.

7. A method according to Claim 5 or 6 characterized by further comprising steps of deleting the extracted wide grid signal from the received signal to detect further wide grid signal.

8. A method according to Claim 5 characterized by detecting the narrow grid signal from the converted signal by deleting the wide grid signal from the received signal.

9. A method according to Claim 5-8 characterized by further comprising step of deleting wireless channel effects from the received signal by each user.

10. A wireless communication method between a transmitter and multiple user equipment having at least a receiver which at least two of them are wide bin and at least one of them is narrow bin user comprising steps of designing at least two wide grid signals and at least one narrow grid signal wherein spacing of the wide grid signal in delay and / or Doppler space different than narrow grid signal and the narrow grid signal is narrower than the wide grid signals in the domain, converting the wide grid signals into the time-frequency domain in separate manner, converting the narrow grid signals into the time-frequency domain in separate manner, Putting out the wide bins different time-frequency slots without overlapping, Performing summation of the wide grid signal and the narrow grid signal andConverting the summed signal into the time domain,Transmitting the summed signal and receiving the by the multiple users,Receiving a signal generated according to any of preceding claims by the multiple user equipment,Converting the received signal into delay Doppler domain according to spacing of the narrow grid signal by each user,Detecting the wide grid signal from the converted signals to extract the wide grid signals by the users,Reconstructing the narrow grid signal according to the detected wide signals by the narrow bin users that already extract the wide grid signal.

11. A data processing device comprising means for carrying out the steps of the method of Claim 10.

12. A computer program comprising instructions which, when the program is executed by a data processing device, cause the data processing device to carry out the steps of the method of Claim 10.

13. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of Claim 10.

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