An interleaving method to map physical resource block in non-contiguous downlink sub-bands

Abstract

The invention presents a method and system for optimizing VRB (Virtual Resource Block) to PRB (Physical Resource Block) interleaving in non-contiguous bands within Sub-Band Full Duplex (SBFD) communication systems used in 5G / 5G-NR networks. The system introduces an in-place interleaving technique designed to enhance the mapping efficiency and reduce interference in SBFD environments. This method involves calculating sub-band configurations and bundle sizes, followed by applying interleaving within individual sub-bands and across multiple sub-bands. By addressing the challenges of non-contiguous bands and ensuring effective resource allocation, the invention improves system performance and reduces signal degradation. This approach ensures compatibility with existing infrastructure and standards while optimizing VRB to PRB mapping for better utilization of network resources. The innovation advances network performance by enhancing the accuracy of resource block allocation and reducing overall interference, leading to more efficient and reliable 5G / 5G-NR communication systems.

Description

[0001]AN INTERLEAVING METHOD TO MAP PHYSICAL RESOURCE BLOCK IN NON-CONTIGUOUS DOWNLINK SUB-BANDS Field of the Invention The present invention relates to wireless communication system and more particularly to methods and systems for enhancing the mapping and interleaving of Virtual Resource Blocks (VRBs) to Physical Resource Blocks (PRBs) in systems utilizing Orthogonal Frequency Division Multiple Access (OFDMA). The invention is applicable to non-contiguous spectrum scenarios, such as those encountered in 5G New Radio (5G NR) systems, and is further extendable to next-generation wireless communication standards, including future 6G networks. Background of the Invention Wireless communication systems, such as those based on the 5G New Radio (NR) standard developed by the Third Generation Partnership Project (3GPP), are designed to deliver a wide range of services including telephony, video, data, and messaging. These systems utilize advanced multiple-access technologies like Orthogonal Frequency-Division Multiple Access (OFDMA) to efficiently share resources such as bandwidth among multiple users. In 5G NR, communication occurs between base stations (referred to as gNBs) and user equipment (UEs) over downlink (DL) and uplink (UL) channels, with the downlink carrying data from the gNB to the UE and the uplink carrying data from the UE to the gNB. A key feature of 5G NR commercial deployments is Time Domain Duplexing (TDD), where the time domain is divided between downlink and uplink transmissions within unpaired spectrum bands. While TDD has been optimized to meet growing downlink traffic demands, emerging uplink- intensive applications, such as extended reality (XR), have increased uplink traffic requirements. However, allocating limited time for uplink in TDD can lead to reduced coverage, higher latency, and lower capacity. Although Dynamic TDD was introduced to adapt to varying UL / DL demands, its deployment faces challenges related to inter-operator coexistence in macro scenarios. To address these constraints, 3GPP Release 18 has introduced Sub- Band non-overlapping Full Duplex (SBFD), which enables simultaneous uplink and downlink transmissions within a TDD band by isolating uplink sub-bands inside downlink symbols at gNB. SBFD improves uplink capacity by embedding UL transmissions within the DL time frame without disrupting overall duplexing structure. In both 5G NR and emerging wireless technologies such as 6G, resource allocation mechanisms rely on mapping Virtual Resource Blocks (VRBs) to Physical Resource Blocks (PRBs), within a given bandwidth part (BWP). Two types of mapping are defined: non-interleaved (one-to-one mapping) and interleaved (frequency-distributed mapping), with the latter used to mitigate channel impairments such as frequency-selective fading by spreading VRBs across the frequency domain. However, the introduction of SBFD leads to non-contiguous resource configurations, which disrupt legacy interleaved VRB-to-PRB mapping. Specifically, interleaved mapping schemes may inadvertently allocate downlink VRBs to PRBs residing within uplink sub bands, thereby introducing decoding errors and degrading downlink performance. The current VRB to PRB mapping - mechanisms assume contiguous PRB regions and are not inherently equipped to handle the fragmented resource structures introduced by SBFD. As wireless communication continues to evolve toward 6G systems anticipated to support even more diverse and latency-sensitive applications across fragmented or dynamic spectrum environments technologies such as Full Duplex and Dynamic Sub-Band Full Duplex (Dynamic SBFD) are expected to become prominent. These advanced duplexing techniques will further increase spectral efficiency by enabling simultaneous uplink and downlink transmissions within dynamically allocated sub-bands. Consequently, there is a growing demand for robust and adaptive VRB-to- PRB mapping strategies. The absence of suitable mechanisms in current standards highlights the necessity for novel solutions capable of effectively supporting non-contiguous and dynamically changing resource allocations, while preserving overall system performance and reliability. Objective of the Invention The principal objective of this invention is to enhance the Virtual Resource Block (VRB) to Physical Resource Block (PRB) mapping efficiency in wireless communication systems employing Sub-Band Full Duplex (SBFD) or any downlink transmission with non-contiguous frequency band, by introducing an adaptive in-place interleaving mechanism suitable for non-contiguous frequency bands. Another objective of the invention is to provide a VRB-to-PRB mapping method that dynamically accommodates varying network conditions and effectively handles resource allocations across any two or more downlink frequency bands separated by an intervening gap or uplink sub-bands. A further objective of the invention is to improve overall system throughput and spectral efficiency in SBFD or non-contiguous frequency bands communication scenarios through optimized PRB allocation and distribution. Further objective of the invention is to introduce a method at the base station for dynamically adjusting the transport block size and associated rate matching bits based on the number of resource blocks lost due to the downlink gap, thereby preserving downlink transmission performance. Summary of the Invention In 5G / 5G-NR networks, the invention introduces an advanced method for enhancing Virtual Resource Block (VRB) to Physical Resource Block (PRB) interleaving in non-contiguous bands, particularly in Sub-Band Full Duplex (SBFD) systems. The method addresses the challenge of VRB- PRB mapping when dealing with non-contiguous PRB bands and aims to improve the accuracy and efficiency of VRB to PRB mapping. The primary concept involves an in-place interleaving approach within SBFD, where VRBs are interleaved within the sub-bands, followed by interleaving across sub bands to achieve maximum interleave gain against interference leakage. This multistage interleaving process enhances the VRB symbol distribution, enhances performance, and reduces interference by adapting to varying network conditions. The solution also includes an alternate method for adjusting the transport block size and rate matching bits in the gNB based on the number of RBs lost in the downlink gap to ensure no performance loss in the downlink transmission. The invention ensures seamless integration with existing 5G NR infrastructure, avoiding the need for new hardware or significant changes to current standards. By improving the mapping accuracy and reducing interference, the method enhances overall system performance and resource usage. This solution is designed to support advanced 5G and future 6G applications, providing a robust and efficient mapping strategy for non-contiguous frequency bands. Brief description of the drawings The figures described below depict various aspects of the system and methods disclosed herein. It should be understood that each figure depicts an embodiment of a particular aspect of the disclosed system and methods, and that each of the figures is intended to accord with a possible embodiment thereof. Further, wherever possible, the following description refers to the reference numerals included in the following figures, in which features depicted in multiple figures are designated with consistent reference numerals. FIG.1 illustrates a conventional Sub-Band Full Duplex (SBFD) frame structure (100), according to one embodiment of the present invention. FIG.2 illustrates the limitations of the prior art, i.e., the current VRB- to-PRB mapping in Sub-Band Full Duplex (SBFD) systems (200), in accordance with one embodiment of the present invention. FIG.3 illustrates an in-band VRB-to-PRB mapping (300), according to one embodiment of the present invention. FIG. 4 provides a block diagram (400) depicting the physical layer processing of PDSCH (Physical Downlink Shared Channel) data in 5G NR, according to one embodiment of the present invention. FIG.5 is a flow diagram (500) illustrating VRB-to-PRB mapping and TBS adjustment for non-contiguous downlink sub-bands, in accordance with one embodiment of the present invention. FIG.6 is a block diagram illustrating an example schematic hardware configuration of a network node (600), in accordance with one embodiment of the present invention. Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. Detailed Description of the Invention The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness. The terms and words used in the following description and claims are not limited to the bibliographical meanings but are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic is intended to provide. Figures discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions, in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element. FIG.1 illustrates, in accordance with one embodiment of the present invention, a representation of Sub-Band Full Duplex (SBFD) frame structures (100) depicting three exemplary Time Division Duplex (TDD) configurations, namely, the {DU}, {UD}, and {DUD} configurations. These configurations represent different temporal allocations of downlink (DL) and uplink (UL) symbols within a transmission frame at the gNB (base station) level in a 5G New Radio (NR) system operating with SBFD capabilities. In one embodiment, the frame structure includes both {DU} and {UD} configurations for SBFD slot, where downlink (DL) and uplink (UL) segments are separated by a guard band within a time-division duplexing (TDD) frame. In the {DU} configuration, for an SBFD slot, the downlink (DL) sub-band occupies the lower frequency range, while the uplink (UL) sub- band is positioned at higher frequencies within the designated band. Conversely, in the {UD} configuration, the DL sub-band is located at higher frequencies, and the UL sub-band at lower frequencies. When the same Bandwidth Part (BWP) is applied across both the DL slot and the SBFD slot, it creates non-contiguous DL regions. While both configurations reflect typical deployment scenarios for sub-band full duplex (SBFD) operation, they introduce common challenges for VRB-to-PRB mapping. Specifically, when Virtual Resource Blocks (VRBs) allocated for DL transmission span across the DL and UL sub-bands, the conventional interleaving process which assumes contiguous PRB availability may incorrectly map VRBs into uplink frequency resources. This results in potential interference and performance degradation, thereby necessitating a revised interleaving scheme that accounts for non-contiguous downlink PRB regions. In the {DUD} configuration, the frame structure includes multiple interleaved downlink and uplink segments. This configuration exemplifies a high-complexity scenario in which the downlink transmissions are split into multiple segments interleaved with uplink symbol periods. As with the previous configurations, the presence of discontinuities in downlink PRB availability renders the existing VRB-to-PRB interleaving schemes ineffective, as they do not support non-contiguous frequency allocations. This results in potential misalignment of resource mapping, leading to performance degradation or data corruption in the downlink transmission path. The existing / legacy VRB-to-PRB interleaving mapping defined in 3GPP specifications assumes contiguous frequency allocation. Specifically, in the interleaved case, the PRB index p corresponding to a VRB index v is determined using the equation:p = ( v mod R) ∙ C + " #$ % Equation-1Where R is the inter-leaver size (e.g., 2), C = " &$ % and N is the numberof contiguous PRBs in the bandwidth part. This does not provide any mechanism to skip over PRBs that belong to UL sub-bands or guard bands introduced in SBFD or any non-contiguous downlink bands. Accordingly, FIG. 1 serves to highlight the challenges faced by the prior art in accommodating SBFD frame structures within existing VRB-to- PRB mapping mechanisms. It provides the foundational motivation for the invention, which introduces an in-band interleaving strategy that ensures VRBs are mapped only to PRBs corresponding to valid downlink sub-bands, thereby avoiding the loss of downlink data due to allocation gaps. FIG.2 illustrates the limitations of the current VRB-to-PRB mapping if deployed, in Sub-Band Full Duplex (SBFD) systems (200). The figure presents a frequency-domain view of how Virtual Resource Blocks (VRBs), when mapped using conventional interleaving logic, may result in erroneous or undefined allocations due to the presence of non-contiguous downlink (DL) resources caused by intermediate uplink (UL) sub-bands. In an example embodiment, the left-side portion of the figure shows VRBs grouped into Resource Block Bundles (RBBs), labelled VRB#0 through VRB#3. These RBBs represent logical allocation units scheduled for DL transmission. The right-side portion displays a PRB grid indexed from PRB96 to PRB170, which spans a lower DL sub-band, a central UL sub- band, and an upper DL sub-band, with guard PRBs on either side of the UL sub-band. The standard VRB-to-PRB interleaving logic, as defined in 3GPP TS 38.214, assumes a contiguous PRB allocation within the bandwidth part (BWP). In the interleaved mapping case, the PRB index p for a given VRB index v is calculated as described in Equation-1. This mapping spreads VRBs across PRBs for frequency diversity but assumes the PRB space is contiguous and within DL BWP. As illustrated, VRB#0 and VRB#1 are mapped successfully to PRBs within the lower DL sub-band (e.g., PRB96–PRB103). However, VRB#2 and VRB#3 are sequentially mapped into PRBs located in the UL sub-band (e.g., PRB104–PRB111), violating DL / UL segregation. These invalid mappings are shown with question symbols (?), indicating undefined or erroneous behaviour. Since the mapping legacy-mapping does not incorporate logic to avoid uplink and guard regions, VRBs may be mapped into frequency spaces that cannot carry DL transmissions. This results in data loss, decoding failures, and a need for retransmission. Furthermore, because the inter-leaver spans the full BWP without regard to sub-band separation, it cannot perform localized interleaving within valid DL sub-bands. Moreover, because the inter-leaver spans the entire BWP assuming contiguity, it cannot support independent interleaving within the separated DL sub-bands. This is a critical shortcoming in SBFD deployments where the DL PRBs are not only fragmented but also dynamically reconfigurable. The standard mapping function offers no flexibility to conditionally exclude PRBs based on DL / UL partitioning, nor does it provide a fallback mechanism when part of the PRB space is unusable for DL. FIG. 3 illustrates an exemplary frequency-domain mapping architecture 300 for virtual resource blocks (VRBs) to physical resource blocks (PRBs) in a wireless communication system, such as a 5G New Radio (NR) system, employing Sub-Band Full Duplex (SBFD) or otherwise configured with non-contiguous downlink (DL) bandwidth parts (BWPs). The mapping operation is specifically designed to address challenges associated with fragmented downlink allocations where uplink (UL) sub- bands and guard bands interrupt the downlink spectrum, rendering certain PRBs unavailable for downlink data transmission. In the embodiment illustrated, the available DL frequency spectrum comprises at least two non-contiguous sub-bands separated by a frequency region that includes a UL sub-band and adjacent guard bands. A first DL sub-band is located in a lower frequency portion of the BWP and contains a first set of VRBs, labelled A1 through A7. A second DL sub-band is located in an upper frequency portion of the BWP and contains a second set of VRBs, labelled B1 through B6. The central region between the DL sub- bands includes a predefined number of PRBs allocated for UL transmission (e.g., ten PRBs) and PRBs designated as guard bands on either side (e.g., five PRBs on each side). These intervening PRBs are deemed non-usable for DL purposes and are therefore excluded from the VRB-to-PRB mapping process. The illustrated method performs a two-stage interleaving operation to ensure that VRBs are efficiently and correctly mapped only to PRBs that are available for downlink transmission. In a first stage, intra-sub-band interleaving is performed independently within each of the DL sub-bands. This first stage utilizes existing 3GPP-defined interleaving logic to reorder the VRBs within each sub-band to enhance frequency diversity and mitigate the impact of frequency-selective fading. For example, the initial VRB sequence A1 through A7 is reordered to A6, A3, A5, A2, A7, A4, and A1, while the sequence B1 through B6 is reordered to B6, B3, B5, B2, B4, and B1. This intra-sub-band interleaving operation is confined to each DL sub- band boundary, thereby preserving logical isolation across sub-bands. In the second stage, the interleaved VRBs are mapped to PRBs in a distributed manner across the non-contiguous DL sub-bands, while explicitly excluding PRBs corresponding to UL and guard regions. This stage ensures that no VRB is assigned to a PRB located within a non-DL- usable region. The DL-eligible PRBs in the lower sub-band may be indexed, for instance, as PRB0 through PRB7, while DL-eligible PRBs in the upper sub-band may be indexed as PRB27 through PRB32. These indices are illustrative and may vary depending on deployment-specific frequency partitioning and configuration. To support this interleaving operation, the base station (gNB) identifies the number of DL sub-bands, denoted as K, from a Radio Resource Control (RRC) configuration, such as via parameters included in a System Information Block (SIB). Each DL sub-band is treated as a logically independent region for interleaving purposes. For each sub-band k, a resource block bundle (RBB) size, Lk is computed based on a higher layer configuration parameter, such as VRB-to-PRB-Interleaver, which defines the smallest group of contiguous PRBs eligible for mapping within that sub-band. The number of RBBs in the kthDL sub-band is computed as follows: . / _0*1,N N 3456 + (N37897,. / _0*1DL_SBk, bundle = ' *,- *,- mod L1): L1 ;where and starting PRB index of that sub-band. diversity, a frequency hopping parameter R is selected. In one embodiment, R=2. The number of complete bundles per frequency hop is computed as: C1 = <NDL_SBk, bundle⁄ R ?The interleaving VRBs to PRB indices (for two-stage interleaving) is defined as: @(A) = BDE + F + GDEHIA = FJ + B where r and c are row and column indices within the interleaving matrix, and k is the DL sub-band index. This ensures VRBs are distributed within and across DL sub-bands while excluding non-usable regions. Additionally, the method comprises a rate matching procedure at the gNB, wherein the Transport Block Size (TBS) is computed based solely on the number of Physical Resource Blocks (PRBs) available for downlink (DL) transmission. PRBs located within non-usable frequency regions—such as uplink (UL) sub-bands or guard bands—are excluded from the TBS calculation. Virtual Resource Blocks (VRBs) that would otherwise map to these excluded PRBs are omitted from the mapping, and the resulting capacity gap is compensated through the insertion of additional rate matching bits. At the receiving end (UE), decoding is performed exclusively on PRBs identified as DL-usable. PRBs corresponding to non-DL regions are either ignored or padded with NULL values to preserve decoding buffer alignment and maintain the integrity of Low-Density Parity-Check (LDPC) decoding. The UE determines DL-usable PRBs as those within the configured DL Bandwidth Part (BWP) that do not overlap with UL sub-bands or guard bands. The UL and DL sub-band configuration is conveyed to the UE via Radio Resource Control (RRC) message. The disclosed two-stage interleaving and resource mapping mechanism enables reliable, efficient, and flexible data transmission in communication systems operating over non-contiguous frequency resources. The method addresses the limitations of conventional interleaving and resource allocation techniques by explicitly accounting for fragmented frequency structures and excluding non-transmittable regions from mapping. By avoiding invalid resource assignments and maintaining compatibility with existing interleaving frameworks, the approach supports robust performance, improved spectral efficiency, and seamless integration into standards-compliant network implementations. FIG. 4 provides a block diagram (400) depicting the physical layer processing of PDSCH (Physical Downlink Shared Channel) data in 5G New Radio (NR). The figure illustrates a sequence of processing steps performed at the gNB (base station) to prepare the downlink data for transmission over the air interface. The operations span from the initial transport block preparation to the final VRB-to-PRB mapping, forming the foundation for implementing the in-band mapping techniques. The physical layer processing begins with the reception of PDSCH data, which carries either user-plane or control-plane payload intended for downlink transmission. In step 405, a 24-bit cyclic redundancy check (CRC) is appended to the transport block, enabling the user equipment (UE) to detect transmission errors at the transport block level. In this embodiment, the number of Physical Resource Blocks (PRBs) used for Transport Block Size (TBS) determination is based solely on the PRBs allocated within the downlink sub-bands. At step 410, the LDPC base graph selection is carried out. Based on the size of the transport block and the modulation and coding scheme (MCS) index, the gNB selects one of the predefined LDPC base graphs (typically BG1 or BG2). This selection determines the structure of the LDPC encoding that follows, balancing between code rate, payload size, and decoding complexity. At step 415, code block segmentation is executed, wherein the transport block is split into smaller code blocks if its size exceeds the maximum size supported by the LDPC encoder. Each resulting code block is then appended with its own code block CRC, which ensures integrity checking at the granularity of each individually decodable unit. At step 420 involves channel coding using LDPC encoding. Each code block is encoded using the selected base graph, producing parity bits that enhance robustness against radio channel impairments. This step produces a set of encoded code blocks ready for adaptation to available resources. Following channel coding, at step 425 performs rate matching. This procedure adjusts the number of output bits from each LDPC code block to fit within the allocated number of physical resource elements. It includes bit selection and interleaving operations and is essential for supporting retransmissions in HARQ processes, where different redundancy versions may be transmitted. If the in-place interleaver is used, then rate matching of non-contiguous band will consider PRBs where downlink is allowed to transmit. At step 430 executes code block concatenation, wherein the rate- matched bits from each code block are reassembled into a single stream. This stream forms the bit sequence that will undergo further modulation and mapping in the subsequent steps. At step 435, scrambling is applied to the concatenated bitstream. A pseudo-random scrambling sequence, derived from cell-specific and UE- specific parameters, is used to randomize the bit pattern. This minimizes inter-cell interference and ensures statistical properties of the signal conducive to robust modulation. At step 440 performs modulation, mapping the scrambled bits to modulation symbols based on the selected modulation order (e.g., QPSK, 16QAM, 64QAM, or 256QAM). Each group of bits is converted into a complex-valued symbol suitable for transmission over the OFDM-based physical layer. At step 445, the modulated symbols undergo layer mapping and antenna port mapping, aligning with the multiple-input multiple-output (MIMO) transmission configuration. Symbols are distributed across transmission layers and mapped to corresponding antenna ports based on transmission rank and precoding information. At Step 450 is responsible for mapping the symbols to Virtual Resource Blocks (VRBs). VRBs are logical containers representing abstract resource units assigned to a UE. The VRB indices are determined by the MAC scheduler, and they provide frequency-domain abstraction before final mapping to actual physical resources. Finally, at step 455 completes the process with the mapping from VRB to Physical Resource Blocks (PRBs). This step uses either non- interleaved or interleaved mapping rules as defined in the 3GPP specifications. Two methods are proposed for handling VRB-to-PRB mapping in systems with fragmented downlink bandwidth, such as SBFD. In one method, the gNB assumes the entire Bandwidth Part (BWP) is available for downlink. The Transport Block Size (TBS) is computed considering only on downlink-usable PRBs (M), rate matching is performed for all PRBs, including those corresponding to uplink (UL) sub band and / or guard band RB. Standard interleaving is applied without excluding any PRBs. At the time of transmission, only PRBs within DL-usable regions are sent, and those mapped to UL or guard bands are omitted from transmission. The rate matching block introduces sufficient redundancy, allowing the UE to recover lost data despite VRBs being mapped to unused PRBs. In an alternative method, the gNB identifies the number of downlink (DL)-usable Physical Resource Blocks (PRBs), denoted as M, by excluding those that fall within uplink (UL) sub-bands and guard bands. The Transport Block Size (TBS) is computed based solely on M, and additional rate matching bits are introduced to align the allocated Virtual Resource Blocks (VRBs), denoted as N, with the available PRB capacity. A modified interleaving scheme is applied at the gNB to ensure that no VRB is mapped to non-usable PRBs, thereby preventing data loss and improving overall transmission efficiency. Compared to the first method, which relies on redundancy and simple scheduling, this approach offers a more resource- efficient solution by tightly aligning data mapping with valid DL PRB regions. At the User Equipment (UE), the received PRBs are de-mapped according to the known Sub-Band Full Duplex (SBFD) configuration. PRBs that correspond to UL or guard bands are either ignored or filled with NULL values to maintain decoding buffer alignment and ensure proper Low- Density Parity-Check (LDPC) decoding. The UE calculates the TBS based on DL-usable PRBs only. The starting PRB index and the total number of allocated PRBs are extracted from the Resource Indication Value (RIV) field in the Downlink Control Information (DCI) message. If the start PRB overlaps with a non-usable region, the first PRB after the UL or guard band is taken as the effective start. Similarly, if the allocated PRB range extends into a non-usable region, the overlapping portion is replaced with an equivalent number of PRBs from the next available DL sub-band. Accordingly, FIG.4 illustrates the complete physical layer processing chain for PDSCH transmission in 5G NR and serves as a basis for the modifications proposed in the present invention. The figure emphasizes the role of VRB-to-PRB mapping as the final and critical step that determines where in the frequency domain the modulated symbols are transmitted, particularly in SBFD scenarios with non-contiguous downlink resource availability. FIG.5 is a flow diagram (500) illustrating VRB-to-PRB mapping and TBS adjustment for non-contiguous downlink sub-bands, in accordance with one embodiment of the present invention. In one embodiment, a method for efficient mapping of Virtual Resource Blocks (VRBs) to Physical Resource Blocks (PRBs) in wireless communication systems operating with non-contiguous downlink frequency allocations. The method further includes dynamic transport block size (TBS) computation and sub-band- aware interleaving to improve transmission performance under fragmented spectrum conditions, as applicable to 5G NR and future wireless standards. At step 505, the process is initiated by a base station, such as a gNB, identifying a plurality of downlink sub-bands based on configuration information received via Radio Resource Control (RRC) signalling. These sub-bands represent distinct, potentially non-contiguous frequency regions allocated for downlink data transmission within a given Bandwidth Part (BWP). In step 510, for each identified downlink sub-band, the base station determines the corresponding Resource Block Bundle (RBB) size based on configuration parameters such as the sub-band width and the starting Physical Resource Block (PRB) index. The RBB size is selected to comply with physical layer constraints and to enable efficient Virtual Resource Block (VRB) to PRB interleaving within each sub-band. A uniform RBB size is applied across all frequency sub-bands to support consistent and seamless interleaving across sub-band boundaries. At step 515, the base station maintains a PRB indexing scheme wherein PRBs are indexed sequentially beginning from the lowest frequency of the BWP. This indexing approach is consistent with existing 3GPP specifications and allows for reuse of legacy VRB-to-PRB mapping logic, thereby simplifying implementation. At step 520, the base station identifies a set of usable PRBs by excluding PRBs associated with uplink sub-bands and guard bands. Only those PRBs determined to be available for downlink transmission are retained for subsequent scheduling and interleaving operations. At step 525, the base station computes a Transport Block Size (TBS) based exclusively on the number of usable PRBs identified in step 525. This computation ensures that the TBS accurately reflects the number of transmittable PRBs, thereby avoiding resource wastage due to over- estimation and eliminating the risk of mapping data to non-transmittable PRBs. At step 530, a sub-band-aware interleaving operation is performed. The base station maps VRBs to the set of usable PRBs in a frequency- dispersed manner based on calculated bundle indices and the previously selected hopping pattern. The interleaving is configured to preserve frequency diversity and improve resilience to frequency-selective fading and interference. At step 535, the mapped PRBs are assigned with pre-coded and modulated data symbols. These symbols are then transmitted to the user equipment (UE) via a physical downlink shared channel (PDSCH), thereby completing the base station’s scheduling and transmission process. At step 540, the UE receives RRC configuration messages that contain information regarding the downlink sub-band layout, PRB indexing scheme, and interleaving configuration. This configuration enables the UE to accurately interpret the structure of the downlink transmission and correctly reconstruct the mapping logic used by the base station. At step 545, the UE receives the downlink transmission comprising the interleaved PRBs. The received signal includes data mapped across multiple sub-bands in accordance with the interleaving pattern established at the base station. At step 550, the UE reconstructs the VRB-to-PRB mapping by using the configuration received in step 540. During this process, the UE identifies PRBs designated for downlink reception and excludes PRBs that correspond to uplink sub-bands or guard regions. At step 555, the UE processes only the PRBs allocated for downlink data transmission. The UE reconstructs the logical transport block by decoding symbols corresponding to valid PRBs, thereby enabling accurate recovery of the originally transmitted data payload in environments characterized by fragmented spectrum. FIG. 6 illustrates a schematic hardware configuration of a network node (600), such as a gNB, designed to support Sub-Band Full Duplex (SBFD) operations in a 5G NR system. The node comprises a network interface (610), processor (620), memory (630), and storage (640). The network interface facilitates communication with user equipment (UEs) and other network entities through RF and baseband components. The processor is responsible for executing key physical layer functions, including transport block processing, rate matching, and in-band VRB-to-PRB interleaving across non-contiguous downlink sub-bands. It interprets RRC configurations to identify sub-band structures and applies sub-band-aware frequency hopping and resource mapping accordingly. This modular and scalable architecture enables intelligent resource allocation by ensuring that VRBs are not mapped into uplink or guard regions, thereby maximizing PRB utilization and maintaining downlink performance in SBFD deployments. FIG.5 thus encapsulates the hardware support required for implementing the methods described in this invention. A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

Claims

We Claim: for mapping virtual resource blocks (VRBs) to physical resource blocks (PRBs) of downlink sub-bands, the method comprising: identifying, by a base station, a plurality of downlink sub-bands based on a Radio Resource Control (RRC) configuration; determining, for each downlink sub-band, a resource block bundle (RBB) size based on configuration parameters received from higher layer signalling; maintaining a PRB indexing scheme within a bandwidth part (BWP), wherein PRBs are indexed sequentially starting from a lowest-frequency PRB; identifying a set of usable PRBs by excluding PRBs corresponding to uplink sub-bands and guard bands within the BWP; computing, a starting PRB index for each downlink sub-band; determining a Transport Block Size (TBS) based exclusively on the number of assigned PRBs that are within the identified set of usable downlink PRBs; and performing a sub-band-specific interleaving operation to map the VRBs to PRBs, wherein the interleaving is applied within each identified downlink sub-band and across downlink sub-bands, such that interleaving gain is maintained and interference leakage is mitigated.

2. The method as claimed in claim 1, wherein the number of Resource Block Bundles (RBBs) per downlink sub band is calculated by: QSTUV,WXYZ W\]^\,QSTUVK KDL_SBk, bundle = ' MOP + [KMOP `ab cGe:cG ;Whe KKMWO\]P^\,QSTUhis starting PRB index.

3. The method as claimed in claim 1, wherein the number of complete bundles per frequency hop is computed by: DE = <KDL_SBk, bundle⁄ J ?.where J is setdiversity within the sub band, and DEis number of complete bundles per frequency hop.

4. The method as claimed in claim 1, wherein the step of interleaving is carried out by @(A) = BDE + F + GDEHI with A = F × J + BWhere the B and F are indices for frequency hopping and bundle positions.

5. The method as claimed in claim 1, further comprising: configuring the base station to signal interleaving-related parameters to a user equipment (UE) via Radio Resource Control (RRC) messages, wherein the interleaving is performed for non-contiguous downlink sub- bands in a Duplex system configuration.

6. The method as claimed in claim 1, wherein performing the interleaving further comprises: mapping VRBs across multiple downlink sub-bands to facilitate VRB- to-PRB mapping in a duplex system, wherein the downlink band is segmented by uplink sub-bands or frequency bands not available for downlink transmission.

7. The method as claimed in claim 1, wherein performing the interleaved mapping comprises: distributing modulated symbols across available physical resource blocks (PRBs) both within individual downlink sub bands and across multiple downlink sub bands, thereby increasing frequency diversity and improving resilience against frequency-selective fading and interference.

8. A method for calculating transport block size and rate matching in a base station (gNB) of a 5G New Radio (NR) system, the method comprising: determining a number of usable Physical Resource Blocks (PRBs) for downlink transmission (M) by excluding PRBs that fall within uplink sub- bands or guard bands; computing, at the base station, a transport block size (TBS) based on the determined number of usable Physical Resource Blocks (M), thereby ensuring the TBS reflects only transmittable data;assigning rate matching bits corresponding to the difference between all allocated VRBs in BWP (N) and usable PRBs (M), to compensate for PRBs lost due to the downlink gap; receiving, at the UE, the downlink data transmitted via the downlink sub-band; reconstructing, at the UE, the VRB-to-PRB mapping and the Sub- Band Full Duplex (SBFD) configuration based on Radio Resource Control (RRC) signalling; and processing, at the UE, the received data using the reconstructed mapping, while ignoring PRB locations corresponding to uplink sub-bands or guard regions to ensure accurate recovery of transmitted bits.

9. The method as claimed in claim 8, wherein the rate matching bits are calculated based on the difference between the allocated N VRBs and the usable M PRBs, enabling the UE to recover data from downlink PRBs only.

10. The method as claimed in claim 8, wherein assigning the rate matching bits is based on the number of PRBs lost to the downlink gap, compensating for data recoverable only from the usable PRBs at the UE.

11. A method for processing downlink data at a user equipment (UE) in a wireless communication system supporting duplex operation with non- contiguous downlink frequency resources, the method comprising:receiving, from a network node, configuration information indicating a structure of downlink frequency resources and a mapping between virtual resource blocks (VRBs) and physical resource blocks (PRBs); receiving downlink data transmitted over the configured downlink frequency resources; identifying a set of usable PRBs for downlink reception by excluding PRBs that fall within uplink sub-bands or guard bands, based on the received configuration; determining a VRB-to-PRB mapping limited to the identified usable PRBs, such that only PRBs designated for downlink transmission are included; determining a Transport Block Size (TBS) based exclusively on the number of assigned PRBs that are within the identified set of usable downlink PRBs; reconstructing LDPC decoding parameters, including code block segmentation and rate matching configuration, based on the determined mapping and the usable PRBs; and processing the received data using the reconstructed parameters, while ignoring PRB locations corresponding to non-downlink regions, to enable accurate decoding and recovery of the transmitted data.

12. The network node for mapping VRBs to PRBs in wireless communication, the network node comprising: a processor configured to:identify, a number of downlink sub bands from the Radio Resource Control (RRC) configuration; determine, the number of resource block bundles (RBBs) per downlink sub band; determine, a resource block bundle size for the physical resource blocks (PRBs) of the downlink sub band; select, a frequency hopping parameter (R) for mapping physical resource blocks (PRBs) mapping within each downlink sub band; perform, interleaving to map virtual resource block (VRB) within the sub band and across sub bands thereby achieving interleave gain against any interference leakage; a memory configured to store the RRC data and interleaving instructions; and a transmitter configured to transmit the interleaved PRBs to UE via a physical downlink shared channel (PDSCH).

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