Subband Full Duplex (SBFD) is an innovative duplexing method for advanced 5G/6G cellular communication that enhances uplink coverage and minimizes communication latency compared to TDD. SBFD allows a base station to transmit and receive simultaneously in distinct downlink and uplink sub bands within the channel bandwidth of a TDD carrier. To maximize the advantages of SBFD communications, it's crucial to mitigate self-interference and cross-link interference between nodes. This paper initially discusses the enablers for interference mitigation in SBFD deployment, followed by an evaluation analysis and field measurement results of SBFD duplex technology for a 5G massive-MIMO macro network in the 5G band.

Time-division duplex (TDD) and frequency-division duplex (FDD) are mainly used in commercial new radio (NR) deployments, where the time- or frequency-domain resources are split between downlink (DL) and uplink (UL). Full duplex (FD) will enable 5G-advanced and 6G systems to go beyond TDD and FDD operation into a new duplexing mode that leverages the benefits of both TDD/FDD deployments. It achieves higher throughput and lower latency while enabling flexible UL/DL scheduling. However, there are several challenges that need to be overcome to enable FD operation in large-scale system deployment, including intranode and internode [user equipment (UE) and next-generation node B (5G base station)] interference along with intercarrier interference. In this article, we present solutions to mitigate self-interference (SI) and cross-link interference (CLI) in 5G-advanced/6G systems, provide system-level evaluations, and discuss the outcome of Third Generation Partnership Project (3GPP) study item on duplexing evolution. We introduce the concept of subband FD (SBFD) as an effective solution for a macro network to achieve the key features of FD, such as latency reduction and UL link budget improvement. Finally, we present the field test results for the performance of world-first SBFD prototype of high transmit power massive-multi-input-multioutput (MIMO) macro network.

Tightly coupled LTE-Wi-Fi networks have emerged as a promising solution for improving capacity and coverage of wireless networks. Different architectures which realize this integration includes LTE-Wi-Fi radio level interworking with IPSec tunnel (LWIP) and LTE-Wi-Fi Aggregation (LWA). The major issue with these architectures is that they do not exhibit expected performance when TCP is employed, i.e., TCP throughput decreases compared to using either LTE or Wi-Fi for transmission. Also, Multipath TCP (MPTCP) is inefficient while aggregating LTE and Wi-Fi links, especially when the link rates are incomparable. In this paper, we propose VIrtual congeStion control wIth Boost acknowLdgEment (VISIBLE) algorithm for LWIP networks which encompasses an efficient packet level traffic steering technique for steering Downlink traffic across LTE and Wi-Fi links of LWIP node and Boost ACK technique to reduce the number of duplicate ACKs (DUP-ACKs) delivered to the TCP sender. Unlike MPTCP, VISIBLE+LWIP uses both LTE and Wi-Fi links efficiently even if their link rates are incomparable and reduces unnecessary DUP-ACKs. We have developed VISIBLE+LWIP framework in NS-3 and compared its performance with the state-of-the-art MPTCP algorithms. We could observe that the proposed VISIBLE algorithm has doubled the throughput of basic LWIP and outperformed throughput of MPTCP by 37%. Also, it has enhanced the throughput by 30% as compared to basic LWA.

LTE—Wi-Fi Radio Level Integration with IPsec Tunnel (LWIP) thrives as a complete solution to address the data requirement for telecom operators by effectively utilizing unlicensed spectrum. Co-located LWIP (C-LWIP) node couples Home eNodeB (HeNB) and WiFi Access Point (AP) at radio protocol stack to enable a unified control decision over both LTE and Wi-Fi links. The challenges pertaining to small cells viz., high co-tier interference and QoS provisioning can be effectively addressed by using LWIP. This paper proposes a novel Power awaRE dynamic traffic StEering (PRECISE) algorithm which regulates transmit powers of LTE and Wi-Fi of LWIP node in order to minimize interference across LWIP nodes in dense deployments. The PRECISE algorithm also does flow steering across LTE and Wi-Fi interfaces by employing Multi Attribute Decision Making (MADM) technique. It thrives on ensuring Guaranteed Bit Rate (GBR) flow requirements by dynamically controlling the transmit power across multiple LWIP nodes. Interference mitigation sub-problem and ensuring GBR sub-problem are formulated as Mixed Integer Non-Linear Programming (MINLP) problems. The proposed PRECISE algorithm improves the network throughput by 84% compared to 3GPP Rel-12 LTE Wi-Fi interworking and 48% compared to state-of-the-art a-optimal scheduler. It also has reduced the number of unsatisfied GBR flows by 35% as compared to a-optimal scheduler.

LTE-WLAN Aggregation (LWA) at Radio Access Network (RAN) level offers better performance compared to other WLAN inter-working and offloading mechanisms due to its tighter integration. In rel. 13, 3GPP standardized an LWA architecture which works at the Packet Data Convergence Protocol (PDCP) layer of LTE eNodeB and provides packet-level steering. But this architecture provides sub-optimal performance because of various delays incurred on both sender (eNodeB) and receiver (TIE) sides. To overcome this, we propose a new architecture LTE-WLAN integration at RLC Layer (LWIR) which works at the Radio Link Control (RLC) layer of LTE eNodeB. Along with this, Virtual WLAN Scheduler (VWS) which employs traffic steering scheme has been proposed. The VWS minimizes waiting time on Wi-Fi queue and thereby reduces outof-order delivery at the TIE side. Five different bearer selection schemes have also been proposed which provide efficient steering by smartly choosing a bearer to route some data onto Wi-Fi based on available bandwidth of Wi-Fi link. The VWS also contains an LTE feedback mechanism which coordinates with the LTE scheduler to ensure fairness as well as better utilization of system capacity. The evaluation considers collocated scenario in which LTE small cell (SeNB) and Wi-Fi Access Point (AP) are tightly integrated in LWIR node. We show that the proposed LWIR with VWS increases throughput up to 85% when compared to LWA based packet-level steering.

Cellular Internet of Things (C-IoT) is one of the emerging 5G technologies. 4G LTE being the most promising cellular technology so far and is a suitor for serving C-IoT devices. In future millions of C-IoT devices will be deployed in the coverage of a single 4G LTE base station. However, the existing random access (RACH) mechanism in 4G LTE is not designed to connect millions of devices. Hence, in this paper, we propose a novel RACH mechanism that allows millions of C-IoT devices to associate with the base station within the existing 4G LTE framework. 3GPP has proposed an extended access barring mechanism to solve this problem for machine type communication (MTC). We compare the performance of the proposed RACH mechanism with the existing 3GPP extended access barring mechanism through analysis. Further, through simulation results, we show that the proposed mechanism is faster and saves power when compared to existing 3GPP extended access barring mechanism under perfect synchronization.