The 5G Core networks (5GC) are witnessing a drastic increase in signaling traffic volume due to flat Service Based Architecture (SBA) with “any to any” Network Function (NF) communication. The increased signaling, if not managed properly, may hamper the timely delivery of control messages, degrading the user's quality of experience. The underlying reason for increased 5GC signaling is high inter-dependencies between NFs that result in long, complex, and sequential system procedures. Moreover, system procedures are not optimally designed for cloud-native SBA based 5GC. This paper analyzes the system procedures for the current 5G network in order to decouple the sequential procedures into small and independent transactions. Once decoupled, the control messages can be executed in parallel, significantly reducing the procedure completion time and improving compute resource utilization. Although we decouple a few control messages in 5G registration procedure, we are limited by the design of NFs, which introduces inter- Nfcoupling. Thus, architectural changes are imperative to enable loose coupling between NFs. We present an end-to-end SBA based network for 6G and propose enhanced system procedures that allow parallel execution of control messages. We perform simulations for the modified registration procedures, demonstrating approximately 13 % and 24 % decrease in procedure completion time for 5G and 6G, respectively.

The design and development of sub-Terahertz (sub-THz) cellular systems entail the need for new channel models that can precisely predict channel characteristics beyond 100GHz in outdoor and dynamic environments. This work proposes a novel multiple-input and multiple-output (MIMO) channel model for cellular communication, developed within the framework of a class of spatio-temporal stochastic processes called ambit-process. The modeling methodology effectively captures the typicalities of sub-THz propagation like molecular absorption and scattering of the evolving multipaths while accounting for the propagation delay of electromagnetic waves across large array apertures deployed at the transmitter and the receiver. This allows for an accurate characterization of the spatial-wideband effect along with other relevant spatio-temporal attributes of the channel. Numerical simulations indicate a good level of agreement between the spectral efficiency and spatio-temporal correlation of the proposed model against a state-of-the-art stochastic Terahertz (THz) channel model and measurements reported in the literature.

The design and development of Terahertz (THz) and sub-Terahertz (sub-THz) communication systems entail the need for new channel models that can precisely predict channel attributes at such frequencies (≥100 GHz) in outdoor and dynamic environments. This work proposes a novel hybrid-stochastic ultra-wideband channel model for sub-THz bands, developed within the framework of a class of spatio-temporal stochastic processes called the ambit-process. The proposed model is capable of supporting bandwidths of upto 1 GHz. The spatio-temporal evolution of the ambit framework allows for a spatially consistent, reasonably accurate and tractable characterization of the fading statistics and multipath propagation of the cellular channels. We leverage a recently proposed convolution-based low-complexity algorithm with necessary modifications to study key features of the microcellular sub-THz channel like associated diffused reflection and scattering, molecular absorption, spatio-temporal correlations, and consistency between the time-evolving delay and Doppler of the multipaths. Simulation results on path loss, shadowing, delay spread, and channel correlations indicate that the ambit model accurately captures the typicalities of an urban microcellular sub-THz channel and agrees well with the measurement results reported in the literature.

Trustworthiness, privacy and resilience are expected to be essential requirements of 6G on top of various other conventional performance requirements such as data rate and latency. Primary authentication is a key procedure for initiating secure communication between User Equipment (UE) and Home Network (HN) in 3rd Generation Partnership Project (3GPP). However, primary authentication mechanisms used in 5G are vulnerable against quantum machines, replay attacks, and rouge base-station. To protect against these threats, we propose beyond 5G and 6G primary authentication methods to adapt hybrid mechanisms which combines Post Quantum Cryptography (PQC) and existing asymmetric algorithm with Perfect Forward Secrecy (PFS) guarantee. We evaluate proposed methods using our in-house developed Simulator “WirelessPQCSim.” Our proposed Hybrid mechanisms provide enhanced security without additional CPU overhead with respect to exiting 5G system. We also achieved up to 6.7x speed-up for PQC-based methods with respect to 5G system and provide low latency which is one of the KPI for 6G system.

To provide coverage to the network devices distributed all over the globe, non-terrestrial networks (NTNs) have been recognized to complement and extend the terrestrial network to remote areas. The Low Earth Orbit (LEO) NTNs face several unprecedented challenges over 5G-NR protocol due to high differential delay and Doppler shifts which drastically impacts the performance of NR-NTN users. In this work, we investigate the impact of large differential delay and Doppler shifts within a NTN cell on the 5G-NR resource allocation and medium access control (MAC) protocol. We then propose an uplink zone-based scheduling technique to address the high differential delay and Doppler shifts for LEO satellites for LEO satellite-based NTNs. Finally, we validate the performance of the proposed strategy by comparing it with the conventional 5G-NR protocol through numerical simulations over the recently developed Samsung’s NR-NTN System Level Simulator.

The Fifth Generation (5G) network provides a platform for emerging technologies such as vehicular communication, massive IoT, and tactile internet. It is paving the way to a modern autonomous industry with mobility as a key requirement to achieve seamless end-to-end connectivity. But the current transport layer is not well equipped with the evolving lower layers to deal with the dynamics of the network conditions during mobility. The variation in network conditions and frequent disturbance in lower layers due to handovers causes performance degradation in the transport layer. Hence, we propose a novel solution called Mobility aware Socket Layer (MaSL), an end-to-end solution for futuristic applications. It is a software solution that provides seamless connectivity to the end devices during user mobility and frequent handover scenarios. It communicates with the lower layers and effectively controls the transport layer for achieving improved Quality-of-Service (QoS) with enhanced user experience. We prototyped MaSL in mobile devices and evaluated the performance using the ns-3 simulator as well as live-air experiments. The experiments are conducted using Wi-Fi and 5G networks, and the results show a significant reduction in reconnection latencies around 33% and improved end-user throughput by up to 16%.

Moving networks is an emerging paradigm for next-generation communication networks that envisage a technology that could support moving vehicular user equipment (VUE) with high data-rates over a reliable connection under varied mobility scenarios such as high-speed trains, buses on the freeway, etc. However, while operating at mmWave frequencies, the direct base station (BS) to the VUE (BS-to-VUE) link is adversely impacted by penetration losses and frequent link outages. Link outages are caused primarily due to extremely poor Non-Line-of-Sight (NLOS) channel conditions at mmWave frequencies. To address this problem, a novel architecture has been proposed in literature where a vehicular moving-relay (MR) is introduced that serves the VUE via access link while the backhaul to the MR is provided by a BS. In this paper, we exhaustively analyze and numerically quantify the link fragility and outage for spatially consistent channel realizations at 28 and 73 GHz for links between the BS-to-VUE, BS-to-MR, and MR-to-VUE. Furthermore, in this study, we also capture the impact of frequent transitions among LOS and NLOS conditions, human blockage events, and penetration losses. The simulation results reveal that i) the direct link between the BS and VUE would be extremely fragile with link-outage probabilities 17% and 59.5% compared to the relay-aided link with link-outage probabilities 1.1 and 2% for 28 GHz and 73 GHz respectively and that ii) the BS-to-VUE link would be impacted severely by human blockages compared to relay aided links where only the last hop MR-to-VUE link is impacted by human blockages but negligibly due to its relatively short range. Lastly, we have determined closed-form analytical expressions to estimate the link-outage probability of the BS-to-MR link.

Achieving significant throughput enhancement is a fundamental technical challenge for next generation cellular communication systems. In order to meet the projected 1000 fold traffic increase by the year 2020, the cellular systems are intensely focusing on ultra-densification by deploying a large number of small cells in a geographical area as a practical means for aggressively increasing the areal capacity. However cell densification is inherently limited by the high inter-cell interference that it inadvertently generates which seriously jeopardizes its gain and renders it practically unsuitable to meet the projected huge traffic explosion. Furthermore, increased densification leads to increased cell edges which in turn lead to rugged user experience. In order to overcome these daunting limitations and make densification a practical reality, we propose novel mobility robustness solutions which significantly decrease the number of handover failures and minimize the interruption in the ongoing services thereby leading to an appreciably better quality of experience for the user. The performance of the proposed schemes are evaluated using computer simulations and also in the drive test with a commercial handset and network equipment in the Gang-nam station area where the network configuration is close to the dense small cell environment. The proposed schemes enhance mobility performance up to 77% and reduce the service outage by 38% in the simulation with typical handover configurations. The enhancement is also observed from the drive tests in the commercial LTE small cell network around Gang-nam station area.