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  3GPP Release 18 is the first 5G-Advanced release, focusing on AI/ML integration, ultimate performance in XR/Industrial IoT, mobile IAB, enhanced positioning, and spectrum efficiency up to 71GHz. RAN1 further promotes AI/ML enhancements in RAN optimization and artificial intelligence (PHY/AI) through physical layer evolution.   I. Key Features of RAN1 (Physical Layer and AI/Machine Learning Innovations)   1.1 MIMO Evolution: Multi-panel uplink (Level 8), MU-MIMO with up to 24 DMRS ports, multi-TRP TCI framework.   Operating Principle: Extends Type I/II CSI reporting through a unified TCI framework across multiple TRP panels. The gNB schedules up to 24 DMRS ports for MU-MIMO (12 in Rel-17), enabling each UE to use Level 8 UL links; DCI indicates joint TCI status; UE applies phase/precoding across panels. Progress: The lack of unified signaling in Rel-17 multi-TRP resulted in a 20-30% loss of spectral efficiency in dense deployments; level restrictions limited the UL throughput of each UE to layers 4-6, thereby achieving a 40% increase in uplink (UL) capacity for stadiums/music festivals.   1.2 AI/ML Applications to CSI Feedback Compression, Beam Management, and Positioning.   Working Principle: The neural network uses an offline-trained codebook to compress Type II CSI (32 ports → 8 coefficients). The gNB deploys the model via RRC; the UE reports the compressed feedback. Beam prediction uses the L1-RSRP mode to pre-position beams before handover. Project Progress: CSI overhead consumed 15-20% of DL resources; in high-mobility scenarios (e.g., highways), beam management failure rates reached as high as 25%. Improvement Results: Channel State Information (CSI) overhead reduced by 50%, handover success rate improved by 30%. 1.3 Enhanced Coverage (Uplink full-power transmission, low-power wake-up signal).   Operating Principle: The gNB sends a signal to the UE, enabling it to apply full power output across all uplink layers (without tiered power backoff). An independent low-power wake-up receiver (duty cycle controlled, sensitivity -110dBm) receives the wake-up signal (WUS) before the main receive cycle. The WUS carries 1 bit of indication information (monitoring PDCCH or sleep). Project Progress: Rel-17 uplink coverage is limited by tiered power backoff (4th order MIMO loss of 3dB); the main receiver consumes 50% of the UE's power during DRX monitoring. Improvements: Uplink coverage extended by 3dB; IoT/video streaming applications saved 40% of power. 1.4 ITS Band Sidelink Carrier Aggregation (CA) and Dynamic Spectrum Sharing (DSS) with LTE CRS.   Operating Principle: Sidelink supports CA across the n47 (5.9GHz ITS) + FR1 bands; supports autonomous resource selection for Type 2c coordination among UEs. Due to a round-trip time (RTT) greater than 500 milliseconds, NTN IoT disables HARQ (only supports open-loop repetition); pre-compensation is implemented for the Doppler effect in DMRS. Project Progress: Rel-17 Sidelink only supports single-carrier (50% throughput loss); NTN IoT HARQ timeouts result in 30% packet loss. Improvements: V2X formation sidelink throughput is increased by 2x, and NTN IoT reliability reaches 95%. 1.5 Extended Reality (XR)/Multi-sensor Communication (High Reliability, Low Latency Support).   Operating Principle: New QoS procedure, latency budget less than 1 millisecond, supports multi-sensor packet tagging (video + haptic + audio stream). gNB prioritizes data through a preemption mechanism. UE reports attitude/motion data for predictive scheduling. Project Progress: Rel-17 XR support only supports unicast; haptic feedback latency exceeds 20 milliseconds (unusable for remote operation). Improvements: End-to-end latency of AR/VR + haptic in industrial remote control is less than 5 milliseconds.   1.6 NTN Functionality Enhancement (Smartphone Uplink Coverage, Disabling HARQ for IoT Devices).   How it Works: Rel-18 improves the uplink coverage of smartphones in non-terrestrial networks (NTNs) by optimizing physical layer transmission, allowing for higher transmit power and better link budget management to accommodate satellite channels. For IoT devices on NTNs, traditional HARQ feedback is inefficient due to long satellite round-trip times (RTTs), therefore HARQ feedback is disabled, and an open-loop repetition scheme is adopted instead. Project Progress: Previously, due to insufficient power control and link margin, the uplink coverage of smartphones on NTNs was limited, resulting in poor connectivity. HARQ feedback caused throughput reduction and latency issues for IoT devices due to satellite latency. Disabling HARQ eliminates feedback latency and improves the reliability of constrained IoT devices. This enables robust global connectivity for IoT and smartphones beyond terrestrial networks. II. RAN1 Project Applications Dense Urban XR (Multi-TRP MIMO technology reduces AR/VR latency to below 1 millisecond); Industrial Automation (AI/ML beam prediction reduces handover failure rate by 30%); V2X/High Mobility (Sidelink CA improves reliability).   III. RAN1 Project Implementation gNB PHY (Base Station Physical Layer): Integrates an AI model for CSI compression (e.g., neural networks predict Type II CSI based on Type I CSI, reducing overhead by 50%). Deploys Multi-TRP TCI via RRC/DCI and uses 2 TAs for uplink timing. Terminal Equipment (UE): Supports low-power wake-up receivers (independent of the main RF link) for DRX alignment signaling.

  RAN3 Release 17 focuses on major evolutions in 5G (NR), bringing enhancements to key architectures such as native multi-access edge computing (MEC) support, the introduction of reduced-capacity RedCap for IoT, enhanced sidechains, positioning and MIMO, and increased support for new frequency bands (up to 71 GHz) and non-terrestrial NTN. All of these improvements are built upon core network function evolution to enhance spectrum efficiency and device power saving, enabling broader 5G applications.   I. Key Features of RAN3 in Release-17 IAB Function Enhancements—Improved resource reuse, topology robustness, and routing options between IAB parent and child links. NTN (Non-Terrestrial Network) Architecture—System architecture supports integration of satellite/HAP with terrestrial 5G (NR). NPN (Non-Public Network) Enhancements and Edge Computing Integration Support. II. Key Technical Details and System Integration of RAN3   2.1 Enhanced IAB (Integrated Access and Backhaul) Technology Resource Reuse: Rel-17 defines additional mechanisms that enable IAB nodes to allocate resources more flexibly between access (to UE) and backhaul (to child IAB nodes) based on existing scheduling. Specifically: Updating F1/Xn internal signaling between the parent node and the IAB-DU/MT. Achieving robust path management and rerouting—the IAB control plane (IAB-CU) must be able to reallocate provider relationships in the event of link failure. Topology and Routing: Support for semi-static routing table updates and enhanced bearer mapping; vendors need to test congestion/priority rules for backhaul and access traffic. 2.2 NTN Architecture   GW and NG-RAN Integration: Rel-17 defines NTN Stage 2/Stage 3 architectural changes to support satellite link features end-to-end. Implementers must coordinate with the CN (SA/CT) to support PDU sessions and mobility differences (such as longer handover times due to GEO/LEO satellite movement).   Timing and Synchronization: NTN nodes typically require GNSS/time distribution (or alternative time synchronization) and specific handling of timing advance and HARQ timers within the RAN architecture is necessary.

  RAN2's 5G work focuses on consolidating and enhancing the concepts and functions introduced in R16, while adding new system features; improving vertical industry applications including positioning and dedicated networks; advancing short-range (direct) communication between terminal devices in the field of autonomous driving (V2X) for Internet of Things (IoT) support; improving support for multiple media (codecs, streaming media, broadcast) related to the entertainment industry; and improving support for mission-critical communications. Furthermore, it improves several network functions (such as network slicing, flow control, and edge computing). The specific key points regarding the radio interface architecture and protocols (such as MAC, RLC, PDCP, SDAP), radio resource control protocol specifications, and radio resource management processes under the responsibility of 3GPP RAN2 are as follows:   I. Key Features of RAN2 Rel-17: Sidelink Enhancements (Relay, Multicast, V2X Functionality Extensions). RedCap Protocol Support (Lightweight RRC Status, Energy Saving, Feature Set Reduction). QoE/slice control enhancements and mobility handling (slice improvements and ATSSS interaction). Location enhancement procedures (new measurement methods and reference signal usage). II. Rel-17 Implementation Impact and Details   2.1 Sidelink Enhancements (Relay, Multicast, V2X Functionality Extensions) RRC message and MAC/PHY multiplexing changes; new Sidelink relay (L2/L3) multicast and group management procedures. In application: Extended sidelink control channel processing and HARQ management for relay nodes, RC upgrade to support Sidelink configuration lists, group identifiers, and security context distribution. Resource allocation enhancements support scheduling and autonomous resource selection and add an RRC TLV field for authorization timing and reservation windows. 2.2 RedCap and RRC Reduced RRC complexity: RedCap devices may support fewer RRC states and optional functions (e.g., limited measurements). RAN2 specifies capability signaling and fewer RRC IEs; implementers must ensure that the gNodeB's RRC can handle capability-limited UEs without affecting normal UE processing. Energy-saving timers and RRC inactive: Tight integration with MAC and DRX to optimize power consumption; the scheduler supports longer DRX cycles and fewer grant allocations. 2.3 Location and Measurement Rel-17 introduces new measurement types and reporting formats to improve the application of PRS/CSI-RS in location. Implementation requires changes to UE measurement reports (RRC measurement objects and reports) and the LPP/NRPPa interface of the location server. ​

  I. ATSSS is an abbreviation for Access Traffic Steering, Switching, Splitting; this is a function introduced by 3GPP for 5G (NR) that allows mobile devices (UEs) to simultaneously use 3GPP and non-3GPP access, manage user data traffic, control new data flows, select (new) access networks, switch all ongoing data to different access networks to maintain data continuity, and split individual data flows, allocating them to multiple access networks to improve performance or achieve redundancy. Specifically:   Control:The network determines which access method (e.g., 5G and Wi-Fi) a new data flow should use based on operator-defined rules and real-time conditions. Switching:The network transfers an ongoing data session from one access network to another. For example, a video call can be switched from Wi-Fi to 5G without interruption. Splitting:The network can simultaneously allocate a single data flow to two or more access networks. This can be used to increase bandwidth (link aggregation) or ensure reliability (redundancy). II. Working Principle ATSSS can operate at the IP layer (using protocols such as MPTCP) or below the IP layer (using underlying routing functions). Control is handled by the 5G core network's PCF (Policy Control Function), based on operator-defined rules and performance measurement data from the User Equipment (UE) and the network itself.   III. ATSSS Modes The main ATSSS modes are as follows: Primary/Backup Mode:Traffic is sent through the active link. If the active link fails, it switches to the backup link. Load Balancing Mode:Traffic is distributed among available access networks, typically based on a percentage to balance the load. Minimum Latency Mode:Traffic is routed to the access network with the lowest latency (round-trip time). Priority Mode:Traffic is initially sent through a high-priority link. If that link becomes congested, traffic is split or diverted to a lower-priority link. IV. Architecture Expansion and Functionality The 5G system architecture has been expanded to support ATSSS functionality (see Figures 4.2.10-1, 4.2.10-2, and 4.2.10-3); the 5G terminal (UE) supports one or more flow control functions, namely MPTCP, MPQUIC, and ATSSS-LL. Each flow control function in the UE can perform flow control, handover, and splitting between 3GPP and non-3GPP access networks according to the ATSSS rules provided by the network. For Ethernet-type MA PDU sessions, the UE must have ATSSS-LL functionality, with the following specific requirements for the UPF: - The UPF can support MPTCP proxy functionality, which communicates with the MPTCP function in the UE using the MPTCP protocol (IETF RFC 8684 [81]). - UPF can support MPQUIC proxy functionality, which communicates with the MPQUIC function in the UE using the QUIC protocol (RFC9000 [166], RFC9001 [167], RFC9002 [168]) and its multipath extension (draft-ietf-quic-multipath [174]). - UPF can support ATSSS-LL functionality, which is similar to the ATSSS-LL functionality defined for the UE. IV. ATSSS Application Characteristics 4.1 Ethernet type MA PDU sessions require the ATSSS-LL functionality (conversion) in 5GC. In addition: - UPF supports Performance Measurement Function (PMF), which the UE can use to obtain access performance measurements on the 3GPP access user plane and/or non-3GPP access user plane. - AMF, SMF, and PCF extend new functionality, which is discussed further in Section 5.32. 4.2 ATSSS control may require interaction between the UE and the PCF (as specified in TS 23.503[45]).   4.3 The UPF shown in Figure 4.2.10-1 can be connected via the N9 reference point instead of the N3 reference point.   V. Roaming Scenarios 5.1 Figure 4.2.10-2 shows ATSSS support in a roaming scenario for the 5G system architecture; this scenario includes home-roaming traffic, and the UE is registered to the same VPLMN via 3GPP and non-3GPP access. In this case, the MPTCP proxy function, MPQUIC proxy function, ATSSS-LL function, and PMF are located in the H-UPF. 5.2 Figure 4.2.10-3 shows ATSSS support in a roaming scenario for the 5G system architecture, this scenario includes home-roaming traffic, and the UE is registered to the VPLMN via 3GPP access and to the HPLMN via non-3GPP access (i.e., the UE is registered to different PLMNs). In this case, the MPTCP proxy function, MPQUIC proxy function, ATSSS-LL function, and PMF are all located in H-UPF.

  Besides defining SA (Standalone) as the standard 5G configuration, Release 16 5G enhances many features to support numerous improvements to the air interface, including unlicensed spectrum in the millimeter wave (mmW) band, and support for Industrial Internet of Things (IIoT) and Ultra-Reliable Low-Latency Communication (URLLC), making it more powerful. Specific additions are as follows:   I. Feature Enhancements As 5G network deployment progresses, the capacity requirements of the Radio Access Network (RAN) continue to grow, and the flexibility of network deployment is also increasing, including support for dedicated networks; RAN capacity and performance have become key to solving problems;   1.1 Capacity Enhancements include:   MIMO (Multiple-Input Multiple-Output) Improvements: Enhanced CSI II codebook to support MU-MIMO, multiple transmissions and receptions (multiple TRPs/panel transmissions), multi-beam operation in the millimeter wave band FR2, and low peak-to-average power ratio (PAPR) reference signals. Unlicensed Spectrum Applications: Similar to Licensed Assisted Access (LAA) and Enhanced LAA, 3GPP Release 16 supports unlicensed spectrum for NR access to improve the throughput and capacity of Wi-Fi in the 5-6 GHz band. 1.2 Performance Improvements:   RACS (Radio Access Capability Signaling) Optimization: Establishing RACS IDs and mapping them to device radio capabilities optimizes signaling for UE radio capabilities. Multiple UEs can share the same RACS ID, which is stored in the Next Generation Radio Access Network (NG-RAN) and Access and Mobility Management Function (AMF). Additionally, a new network function called UCMF (UE Capability Management Function) is introduced. TDD Applications: NR is primarily used in high-frequency time-division duplex bands: Due to electromagnetic wave reflection and refraction, the downlink of one cell can interfere with the uplink of another cell; this cross-link interference is inherent. NR Release 16 supports remote interference management to mitigate this cross-link interference. II. Flexible Network Deployment R16's IAB (Integrated Access and Backhaul) functionality can increase network capacity by rapidly deploying denser access points. Additionally: Non-Public Networks (NPNs): R16 supports two types of NPNs: Standalone NPN (SNPN) and Public Network Integrated NPN (PNI-NPN).  Flexible SMF and UPF Deployment: R16 introduces management flexibility for Session Management Functions (SMFs) and User Plane Functions (UPFs), allowing multiple SMFs to control a single UPF, and the UPF can assign IP addresses in place of the SMF. Enhanced Network Slicing Capabilities: R16 adds Network Slice-Specific Authentication and Authorization (NSSAA) to support individual authentication and authorization for services within a given network slice. Enhanced eSBA (Service-Based Architecture): R16 enhances service discovery and routing capabilities, including the introduction of a new Service Communication Broker (SCP) network function. R16 also enhances Network Automation Architecture (eNA). Release 15 supports data collection and network analytics public functionality. In Release 16, network analytics IDs can be used to assign specific analytics data, such as network usage per network slice, UE mobility information, and network performance, enabling the Network Data Analytics Function (NWDAF) to collect specific data associated with that analytics ID.

  3GPP introduced LTE in Release 8 and LTE-Advanced in Release 10. As the first version of the 5G specification, Release 15 defined the 5G (NR) air interface and the 5G radio access network and core network. Release 16 (R16) introduced standalone (SA) and non-standalone (NSA) deployments, allowing operators to take advantage of the additional benefits of 5G.   I. Evolution from 4G to 5G In Release 16 (R16), 3GPP enhanced 5G capabilities to support several improvements to the NR air interface, including unlicensed spectrum in the millimeter-wave (mmW) band and improved support for Industrial Internet of Things (IIoT) and Ultra-Reliable Low-Latency Communication (URLLC). The network also underwent several enhancements to improve deployment flexibility and performance.   II. R16 Support for 5G Applications 5G was developed to meet the diverse application scenarios of wirelessly connected devices, covering enhanced mobile broadband (eMBB), massive Internet of Things (mIoT), and ultra-reliable low-latency communication (URLLC). Release R15 primarily focused on eMBB, with limited support for other application scenarios. Release R16 enhances URLLC and IoT capabilities and adds support for 5G vehicle-to-everything (V2X) communication.   III. Key 5G Application Scenarios include:   1. Ultra-reliable low-latency communication New enhancements provide low-latency communication to support industrial automation, connected cars, and telemedicine applications; specifically: The Time-Sensitive Networking (TSN) architecture supports redundant transmissions, thus supporting URLLC applications. Furthermore, the TSN service provides time synchronization for packet transmissions through integration with external networks. R16 enhances the uplink synchronization (RACH) process by supporting low latency and reducing signaling overhead, enabling two-step RACH compared to the previous four-step approach. New mobility enhancements reduce downtime and improve reliability during 5G connected device handover. 2. Internet of Things (IoT): 5G-supported Industrial Internet of Things (IIoT) capabilities can meet the service needs of industries such as manufacturing, logistics, oil and gas, transportation, energy, mining, and aviation.   Cellular Internet of Things (CIoT), now available in 5G, offers similar functionality to that provided in LTE (LTE-M and NB-IoT), allowing IoT traffic to be carried in network signaling. Energy-saving features such as enhanced discontinuous reception (DRX), relaxed radio resource management for idle devices, and enhanced scheduling can extend the battery life of IoT devices. 3. Vehicle-to-Everything (V2X): Release 16 goes beyond the V2X service capabilities supported by LTE in Release 14, leveraging 5G (NR) access to enhance V2X in several ways, such as enhanced autonomous driving, accelerated network effects, and energy-saving features.

  Η Έκδοση 15, που οριστικοποιήθηκε τον Ιούνιο του 2018, άνοιξε τον δρόμο για την εμπορική εκμετάλλευση της τεχνολογίας 5G (NR). Η R15 έθεσε τα θεμέλια για τα δίκτυα 5G μέσω αρχιτεκτονικών Standalone (SA) και Non-Standalone (NSA), εισάγοντας ένα εικονικό πυρήνα δικτύου βασισμένο σε υπηρεσίες και νέες τεχνολογίες φυσικού επιπέδου για την ενίσχυση της χωρητικότητας, τη μείωση της καθυστέρησης και τη βελτίωση της ευελιξίας. Κατά τη διάρκεια αυτής της περιόδου, οι Ομάδες Εργασίας Ραδιοφώνου 3GPP RAN1-RAN5 συνέβαλαν σημαντικά στην τυποποίηση της τεχνολογίας 5G (NR). Το έργο και τα βασικά τεχνικά σημεία κάθε ομάδας έχουν ως εξής:   I. RAN1 (Καινοτομία Φυσικού Επιπέδου) Οι βασικοί τομείς εργασίας περιλαμβάνουν κυματομορφές, σύνολα παραμέτρων, πολλαπλή πρόσβαση, MIMO και σήματα αναφοράς: 1. Ευέλικτη απόσταση υποφορέων και δομή πλαισίου; Εισαγωγή κλιμακούμενης απόστασης υποφορέων: Υποστήριξη για διαφορετικά εύρη καθυστέρησης και συχνότητας (FR1 και FR2); Υποστήριξη για χαμηλή καθυστέρηση (

  Στα ασύρματα δίκτυα 5G (NR), ο εξοπλισμός τερματικού κινητού (UEs) μπορεί να χρησιμοποιήσει δύο τύπους προσαρμογής συνδέσμου: προσαρμογή συνδέσμου εσωτερικού βρόχου και προσαρμογή συνδέσμου εξωτερικού βρόχου. Τα χαρακτηριστικά τους είναι τα εξής: ILLA – Προσαρμογή συνδέσμου εσωτερικού βρόχου; OLLA – Προσαρμογή συνδέσμου εξωτερικού βρόχου. I. ILLA (Inner-loop Link Adaptive) εκτελεί γρήγορες και άμεσες ρυθμίσεις με βάση τον Δείκτη Ποιότητας Καναλιού (CQI) που αναφέρεται από κάθε UE. Το UE μετρά την ποιότητα καθόδου (π.χ., χρησιμοποιώντας CSI-RS). Αναφέρει το CQI στο gNB, το οποίο αντιστοιχίζει το CQI (μέσω ενός στατικού πίνακα αναζήτησης) στον δείκτη MCS για την επόμενη μετάδοση. Αυτή η αντιστοίχιση αντικατοπτρίζει την εκτίμηση της κατάστασης του συνδέσμου για αυτό το χρονικό διάστημα/TTI. Η ILLA εφαρμόζει μια τρισέλιδη διαδικασία ως εξής:   Το UE μετρά το CSI-RS και αναφέρει CQI=11. Το gNB αντιστοιχίζει CQI=11 σε MCS=20. Το MCS χρησιμοποιείται για τον υπολογισμό του μπλοκ μεταφοράς για το επόμενο χρονικό διάστημα.   Το πλεονέκτημα της ILLA έγκειται στην ικανότητά της να προσαρμόζεται πολύ γρήγορα στις αλλαγές του καναλιού. Ωστόσο, έχει περιορισμούς όσον αφορά τις ψευδείς ανιχνεύσεις, τα σφάλματα CQI και τον θόρυβο. Συγκεκριμένα, η τιμή στόχου BLER μπορεί να μετατοπιστεί εάν το κανάλι δεν είναι ιδανικό ή η ανατροφοδότηση είναι ατελής.   II. OLLA (Outer Loop Link Adaptive) χρησιμοποιεί έναν μηχανισμό ανατροφοδότησης για να ρυθμίσει την τιμή στόχου MCS για να αντισταθμίσει την πραγματική απόδοση του συνδέσμου που παρατηρείται μέσω των απαντήσεων HARQ ACK/NACK. Για κάθε μετάδοση, το gNB λαμβάνει είτε ένα ACK (επιτυχία) είτε ένα NACK (αποτυχία). όπου: Εάν το BLER είναι υψηλότερο από την καθορισμένη τιμή στόχου (π.χ., 10%), η OLLA προσαρμόζεται προς τα κάτω κατά μια διόρθωση μετατόπισης (Δoffset), δηλαδή, μειώνοντας την επιθετικότητα του MCS. Εάν το BLER είναι χαμηλότερο από την τιμή στόχου, η μετατόπιση προσαρμόζεται προς τα πάνω, δηλαδή, αυξάνοντας την επιθετικότητα του MCS. Η μετατόπιση προστίθεται στην αντιστοίχιση SINR→CQI στην ILLA, διασφαλίζοντας έτσι ότι το BLER τελικά συγκλίνει στην τιμή στόχου—ακόμη και αν το σήμα εισόδου δεν είναι ιδανικό.   Το πλεονέκτημα της OLLA έγκειται στην ικανότητά της να διατηρεί ένα ισχυρό και σταθερό BLER και να προσαρμόζεται σε αργά μεταβαλλόμενα σφάλματα συστήματος στην αναφορά SINR/CQI. Λόγω της βραδύτερης ταχύτητας απόκρισης, η βέλτιστη ρύθμιση του μεγέθους βήματος (δηλαδή, Δup και Δdown) απαιτεί συμβιβασμό μεταξύ σταθερότητας και ταχύτητας απόκρισης. Στον μηχανισμό OLLA, η ανατροφοδότηση χρησιμοποιείται για να ρυθμίσει την τιμή στόχου MCS για να αντισταθμίσει την πραγματική απόδοση του συνδέσμου που παρατηρείται μέσω των απαντήσεων HARQ ACK/NACK.   III. Σύγκριση της προσαρμογής συνδέσμου 4G και 5G Ο παρακάτω πίνακας συγκρίνει την προσαρμογή συνδέσμου 4G και 5G.   Χαρακτηριστικό 5G NR 4G LTE CSI CQI + PMI + RI + CRI Κυρίως CQI Ταχύτητα προσαρμογής Έως 0,125 ms 1 ms Τύποι κυκλοφορίας eMBB, URLLC, mMTC eMBB κυρίως Αντιστοίχιση MCS Βελτιστοποιημένο με ML, καθοδηγούμενο από τον προμηθευτή Σταθερός πίνακας Διαμόρφωση δέσμης MassiveMIMO, Επιλογή δέσμης Ελάχιστο Χρονοπρογραμματιστής Πλήρως ενσωματωμένο & Έξυπνο Βασικό CQI, PF                     Στα δίκτυα 5G (NR), το Link Adaptive (LA) διαδραματίζει κρίσιμο ρόλο στη διασφάλιση υψηλής απόδοσης και αξιόπιστης συνδεσιμότητας. Σε αντίθεση με την πιο αργή, σταθερή προσέγγιση πίνακα του 4G (LTE), τα συστήματα 5G χρησιμοποιούν πιο έξυπνες και ταχύτερες τεχνολογίες, συμπεριλαμβανομένων των AI/ML και της ανατροφοδότησης σε πραγματικό χρόνο. Αυτό επιτρέπει στο δίκτυο να προσαρμόζεται σε μεταβαλλόμενα περιβάλλοντα σε πραγματικό χρόνο και να χρησιμοποιεί τους ραδιοφωνικούς πόρους πιο αποτελεσματικά.

  I. Link Adaptation In mobile communication networks, the wireless environments of any two end users (UEs) are never exactly the same. Some users may be right next to a 5G base station with excellent wireless signal, while others may be deep inside buildings, moving at high speeds, or at the edge of a cell. However, they all expect a fast and stable network experience. To achieve the highest possible throughput and optimal reliable connection, "Link Adaptation" technology was developed. Link adaptation can be viewed as an "automatic mode" of the 5G physical layer, continuously monitoring the wireless environment and adjusting transmission parameters in real time to provide the best data rate while controlling errors.   II. Link Adaptation (AMC) in 5G In 5G networks, link adaptation refers to the process of dynamically adjusting transmission parameters (such as modulation, coding, and transmit power) to optimize the communication link between the base station (gNodeB) and the user equipment (UE). The goal of link adaptation is to maximize spectral efficiency, throughput, and reliability while adapting to constantly changing channel conditions and user needs. Figure 1. 5G Link Adaptive Process   III. Characteristics of 5G Link Adaptive Process   Modulation and Coding Scheme (MCS) Selection:Link adaptive process involves selecting a suitable modulation and coding scheme based on channel conditions, signal-to-noise ratio (SNR), and interference levels. Higher modulation schemes offer higher data rates but are more demanding on channel conditions; lower modulation schemes are more robust under adverse conditions. Transmit Power Control: Link adaptive process also includes adjusting transmit power to optimize signal quality and coverage while minimizing interference and power consumption. Transmit power control helps maintain a balance between signal strength and interference levels, especially in dense network deployments. Channel Quality Feedback: Link adaptive process relies on feedback mechanisms to provide information about channel conditions, such as Channel State Information (CSI), Received Signal Strength Index (RSSI), and Signal-to-Interference-Ratio (SINR). This feedback enables the gNodeB to make informed decisions regarding modulation, coding, and power adjustments. Adaptive Modulation and Coding (AMC): AMC is a key feature of link adaptive process; it dynamically adjusts modulation and coding parameters based on real-time channel conditions. By adapting to changes in channel quality, AMC maximizes data rates and spectral efficiency while ensuring reliable communication. Fast Link Adaptation: In rapidly changing channel environments, such as high-mobility scenarios or fading channels, fast link adaptation technology is used to quickly adjust transmission parameters to cope with channel fluctuations. This helps maintain a stable and reliable communication link under changing channel conditions.   In wireless systems, link adaptation plays a crucial role in optimizing wireless communication system performance by continuously adjusting transmission parameters to match current channel conditions and user needs. By maximizing spectral efficiency and reliability, link adaptation helps achieve high data rates, low latency, and seamless connectivity in 5G networks.

  As 5G (NR) supports increasingly more connections and functions, the number of network functions and entities in the system is also constantly increasing. 3GPP defines network functions and entities in Release 18.5 as follows:   I. Network Function (NF) Units The 5G system includes the following functional units:  AUSF (Authentication Server Function); AMF (Access and Mobility Management Function); DN (Data Network), specifically including: operator services, internet access, or third-party services; UDSF (Unstructured Data Storage Function); NEF (Network Exposure Function); NRF (Network Repository Function); NSACF (Network Slice Admission Control Function); NSSAAF (Network Slice-Specific and SNPN Authentication and Authorization Function); NSSF (Network Slice Selection Function); PCF (Policy Control Function); SMF (Session Management Function); UDM (Unified Data Management); UDR (Unified Data Repository). - UPF (User Plane Functions). UCMF (UE Radio Capability Management Functions). AF (Application Functions). UE (User Equipment). RAN (Radio Access Network). 5G-EIR (5G Device Identity Registration). NWDAF (Network Data Analysis Functions). CHF (Charging Functions). TSN AF (Time-Sensitive Network Adapter). TSCTSF (Time-Sensitive Communications and Time Synchronization Functions). DCCF (Data Collection Coordination Functions). ADRF (Analysis Data Repository Functions). MFAF (Message Frame Adapter Functions). NSWOF (Non-Seamless WLAN Offload Functions). EASDF (Edge Application Server Discovery Functions). *Functions provided by DCCF or ADRF can also be carried by NWDAF.   II. Network Entities The 5G system, supporting connectivity with non-3GPP Wi-Fi, WLAN, and wired access networks, also includes the following entity units in its architecture: SCP (Service Communication Agent). SEPP (Secure Edge Protection Agent). N3IWF (Non-3GPP Interoperability Function). TNGF (Trusted Non-3GPP Gateway Function). W-AGF (Wired Access Gateway Function). TWIF (Trusted WLAN Interoperability Function).