Littérature scientifique sur le sujet « Dynamic Time Division Duplexing (DynTDD) »

The paper presents a dynamic subchannel assignment algorithm based on orthogonal frequency division multiple access technology operating in the time division duplexing and a new cross-layer design based on a proposed routing protocol jointed with the MAC protocol. The proposed dynamic sub-channel assignment algorithm provides a new interference avoidance mechanism which solves several drawbacks of existing radio resource allocation techniques in wireless networks using OFDMA/TDD, such as the hidden node and exposed node problems, mobility, and cochannels interference in frequency (CCI). Besides, in wireless networks, when a route is established, the radio resource allocation problems may decrease the end to end performance proportionally with the length of each route. The contention at MAC layer may cause the routing protocol at network layer to respond by finding new routes and routing table updates. The proposed routing protocol is jointed with the MAC protocol based on dynamic sub-channel assignment to ensure that the quality of service in multihop ad hoc networks is significantly improved.

In order to provide a higher peak data rate, carrier aggregation (CA) is implemented into Long Term Evolution Advanced (LTE-A) systems. However, more and more downlink hybrid automatic repeat request (HARQ) feedback information need to be transmitted. Especially, in time division duplexing (TDD) systems must comply with the updownconfig, the complexity and storage of HARQ scheduling increase largely under CA. In this paper, a HARQ scheduling scheme is proposed which is based on dynamic information tables to generate and schedule the downlink feedback information of acknowledgment/negative acknowledgment (ACK/NACK) in Long Term Evolution Advanced (LTE-A) system. Some storing tables based on component carriers are designed and a dynamic updated scheme is proposed, which reduces the scheduling complexity and memory occupation effectively.

The high altitude platform station (HAPS) system is an essential component of the air-based network. It can shorten transmission delay and make a better user experience compared with satellite networks, and it can also be easily deployed and cover a larger area compared with international mobile telecommunications (IMT). In order to meet the needs of users with asymmetric and random data flow, the spectrum sharing and dynamic time division duplexing (TDD) mode are used in HAPS-IMT heterogeneous network. However, the cross-link interference brought by TDD mode will lead to the degradation of system performance. In this paper, a resource allocation algorithm based on power control and dynamic transmission protocol configuration is proposed. Firstly, a specific timeslot, “low power almost-bank subframe (LP-ABS)”, is introduced into the frame structure of the HAPS physical layer. The transmission protocol designing could mitigate inter-layer interference efficiently by power control in “LP-ABS”. Secondly, the utilization function is adopted for assessing the system performance, which gives attention to both diversified requirements on the quality of services (QoS) and the throughput of the HAPS-IMT system. Simulation results show that power control and resource allocation technologies proposed in this paper can effectively improve system performance and user satisfaction.

Le TDD dynamique joue un rôle crucial dans les réseaux 5G, adaptant les ressources aux besoins variés. Il améliore l'efficacité spectrale en allouant dynamiquement des créneaux horaires pour les transmissions montantes et descendantes en fonction de la demande de trafic et des conditions de canal. Cette allocation dynamique de fréquence assure une utilisation efficace du spectre et prend en charge une connectivité massive, une latence faible et les exigences de la qualité de service. Son rôle dans l'agrégation de porteuses maximise les débits de données et la capacité du réseau, soulignant son importance dans les technologies de communication sans fil avancées.Cependant, le TDD dynamique est confronté à un défi majeur : l'Interférence des liens croisés. Ce type d'interférence se produit lorsque les transmissions montantes et descendantes partagent les mêmes bandes de fréquences, provoquant des interférences.Cette interférence comprend l'interférence de Station de Base à Station de Base (BS-to-BS) ou du lien descendant au lien montant (DL-to-UL) ainsi que l'interférence d'Équipement Utilisateur à Équipement Utilisateur (UE-to-UE) ou du lien montant vers le lien descendant (UL- to-DL). Dans l'interférence DL-to-UL, les transmissions descendantes débordent dans les bandes des transmissions montantes, dégradant la communication montante. À l'inverse, l'interférence UL-to-DL se produit lorsque les transmissions montantes interfèrent avec la réception des transmissions descendantes.Gérer efficacement ces interférences est crucial pour la performance et la fiabilité d'un système TDD dynamique.Ce mémoire vise à libérer tout le potentiel du TDD dynamique en surmontant les défis posés par les interférences des liens croisés grâce à une analyse rigoureuse et des méthodologies innovantes. La recherche ne se contente pas de faire progresser la technologie TDD dynamique, elle pionnière des solutions applicables à divers contextes de communication, stimulant des stratégies innovantes d'alignement d'interférence dans des scénarios variés.Le mémoire se divise en plusieurs parties. La première pose les bases avec la définition du problème et les concepts théoriques essentiels. La deuxième partie examine les conditions de faisabilité de l'alignement des interférences. Ces conditions sont exprimées en fonction de la dimension du problème et établissent le degré de liberté (DoF) atteignable, représentant le nombre de flux de données possibles. Elle explore l'alignement d'interférence dans des scénarios centralisés, en considérant à la fois les canaux MIMO en rang complet et réduit, et aborde des complexités du monde réel. De plus, elle étend l'exploration à un scénario distribué, offrant une compréhension réaliste des complexités de la communication. La troisième partie se concentre sur les techniques d'optimisation, en particulier le beamforming. Elle introduit le Zero Forcing (ZF) beamforming pour les utilisateurs, alignant l'interférence dans les systèmes TDD dynamique. Elle met l'accent sur l'impact de l'interférence des liens croisés entre utilisateurs et présente les améliorations apportées par les algorithmes WMMSE. De plus, elle explore l'optimisation de l'allocation de puissance en utilisant l'algorithme Water-Filling, évaluant la performance du Zero Forcing Beamforming et de l'algorithme WMMSE en fonction de cette approche d'optimisation de puissance
Dynamic Time Division Duplexing (DynTDD) is pivotal in 5th generation (5G) networks, adapting resources to diverse needs. It enhances Spectral Efficiency (SE) by dynamically allocating time slots for Uplink (UL) and Downlink (DL) transmissions based on traffic demand and channel conditions. This dynamic frequency allocation ensures efficient spectrum use and supports massive connectivity, low latency, and Quality-of-Service (QoS) requirements. Its role in carrier aggregation maximizes data rates and capacity, highlighting its importance in advanced wireless communication technologies.However, DynTDD faces a significant challenge: cross-link interference (CLI). CLI occurs when UL and DL transmissions share the same frequency bands, leading to interference.CLI comprises base station to base station (BS-to-BS) or downlink to uplink (DL-to-UL) interference and user equipment to user equipment (UE-to-UE) or uplink to downlink (UL-to-DL) interference. In DL-to-UL interference, DL transmissions spill into UL bands, degrading UL communication. Conversely, UL-to-DL interference occurs when UL transmissions interfere with DL reception.Effectively managing CLI is crucial for DynTDD's performance and reliability.This thesis aims to unleash the full potential of DynTDD by overcoming CLI challenges through rigorous analysis and innovative methodologies. The research not only advances DynTDD technology but also pioneers solutions applicable to various communication contexts, driving innovative interference alignment strategies across diverse scenarios.The study in this thesis is divided into multiple segments. The first part establishes the foundation with the problem definition and essential theoretical concepts. The second part delves into the conditions determining the feasibility of interference alignment. These conditions are expressed in terms of the problem dimension and establish the achievable Degree of Freedom (DoF), representing the number of data streams. It explores interference alignment in centralized scenarios, considering both full-rank and reduced-rank Multiple-Input Multiple-Output (MIMO) Interference Broadcast Multiple Access Channel-Interference Channel (IBMAC-IC), addressing real-world complexities. Additionally, it extends the exploration to a distributed scenario, providing a realistic understanding of communication complexities. The third part focuses on optimization techniques, specifically beamforming. It introduces Zero Forcing (ZF) beamforming for both DL and UL User Equipment (UE)s to align CLI in DynTDD systems. It emphasizes the impact of UE-to-UE interference and presents improvements brought by the Weighted Minimum Mean Square Error (WMMSE) algorithms. Furthermore, it explores power allocation optimization using the water-filling algorithm

In-band full duplex is a new duplexing scheme that allows radio nodes to transmit and receive, utilizing the same frequency and time resources. The implementation of in-band full duplex was not feasible in practice, due to the effect of self-interference. But then, advances in signal processing made it possible to reduce this effect. However, the system level performance of in-band full duplex has not been investigated thoroughly.Through computer simulations, we investigate the performance of in-band full duplex, for indoor 5G small cell wireless networks. We examine the performance of in-band full duplex in comparison to dynamic and static time division duplexing. Additionally, we analyze the performance of the duplexing schemes with two interference mitigation techniques, namely beamforming and interference cancellation.Our results indicate that for highly utilized wireless networks, in-band full duplex should be combined with beamforming and interference cancellation, in order to achieve a performance gain over traditional duplexing schemes. Only then, in-band full duplex is considered advantageous, at any network utilization, and any downlink to uplink traffic demand proportion. Our results also suggest that in order to achieve a performance gain with in-band full duplex in both links, the transmit power of the access points should be comparable to the transmit power of the mobile stations.
Inomband hel duplex är en ny typ av duplexmetod som tillåter radionoder att sända och ta emot i samma frekvensoch tidsresurs. Att implementera inomband hel duplex har fram tills nu inte ansetts praktiskt genomförbart till följd av självstörningar. Framsteg inom signalbehandling har dock gjort det möjligt att begränsa denna självstörningseffekt. Emellertid har systemprestanda av inomband hel duplex inte undersökts tillräckligt noga i tidigare verk.Inomband hel duplex och dess prestanda för trådlösa 5G småcellsnätverk inomhus har studerats med hjälp av datasimuleringar och jämförts med dynamisk och statisk tidsdelning. Utöver detta har prestanda för de olika duplexmetoderna med avseende på två tekniker för störningsundertryckning, lobformning och störningseliminering, också undersökts.Våra resultat indikerar att för trådlösa nätverk med högt radioresursutnyttjande bör inomband hel duplex kombineras med lobformning och störningseliminering för att uppnå en prestandavinst jämfört med traditionella duplexmetoder. Bara då kan inomband hel duplex anses vara fördelaktig oberoende av radioresursutnyttjande och andelen upp- och nedlänkstrafik.Resultaten tyder också på att sändareffekten för radioaccesspunkterna bör vara jamförbar med den för mobilenheterna för att en prestandavinst med inomband hel duplex ska kunna uppnås.
Wireless networks, In-band full duplex, Static-time division duplexing, Dynamic-time division duplexing, Interference mitigation techniques, small cell, 5G, mmWave bands, Beamforming, Interference cancellation.