Enhanced Mobile Networking using Multi-connectivity and Packet Duplication in Next-Generation Cellular Networks

Modern cellular communication systems need to handle an enormous number of users and large amounts of data, including both users as well as system-oriented data. 5G is the fifth-generation mobile network and a new global wireless standard that follows 4G/LTE networks. The uptake of 5G is expected to be faster than any previous cellular generation, with high expectations of its future impact on the global economy. The next-generation 5G networks are designed to be flexible enough to adapt to modern use cases and be highly modular such that operators would have the flexibility to provide selective features based on user demand that could be implemented without investment in additional infrastructure. Thus, the underlying cellular network that is capable of delivering these expectations must be able to handle high data rates with low latency and ultra-reliability to fulfill these growing needs. Communication in the sub-6 GHz range cannot provide high throughputs due to the scarcity of spectrum in these bands. Using frequencies in FR2 or millimeter wave (mmWave) range for communication can provide large data rates and cover densely populated areas, but only over short distances as they are susceptible to blockages. This is why dense deployments of mmWave base stations are being considered to achieve very high data rates. But, such architectures lack the reliability needed to support many V2X applications, especially under mobility scenarios. As we have discussed earlier, 5G and beyond 5G networks must also account for UE\u27s mobility as they are expected to maintain their level of performance under different mobility scenarios and perform better than traditional networks. Although 5G technology has developed significantly in recent years, there still exists a critical gap in understanding how all these technologies would perform under mobility. There is a need to analyze and identify issues that arise with mobility and come up with solutions to overcome these hurdles without compromising the performance of these networks. Multi-connectivity (MC) refers to simultaneous connectivity with multiple radio access technologies or bands and potentially represents an important solution for the ongoing 5G deployments towards improving their performance. To address the network issues that come with mobility and fill that gap, this dissertation investigates the impact of multi-connectivity on next-generation networks from three distinct perspectives, 1) mobility enhancement using multi-connectivity in 5G networks, 2) improving reliability in mobility scenarios using multi-Connectivity with packet duplication, and 3) single grant multiple uplink scheme for performance improvement in mobility scenarios. The traditional macro-cell architecture of cellular networks that cover large geographical areas will struggle to deliver the dense coverage, low latency, and high bandwidth required by some 5G applications. Thus, 5G networks must utilize ultra-dense deployment of access points operating at higher mmWave frequency bands. But, for such dense networks, user mobility could be particularly challenging as it would reduce network efficiency and user-perceived service quality due to frequent handoffs. Multi-connectivity is seen as a key enabler in improving the performance of these next-generation networks. It enhances the system performance by providing multiple simultaneous links between the user equipment (UE) and the base stations (BS) for data transfer. Also, it eliminates the time needed to deal with frequent handoffs, link establishment, etc. Balancing the trade-offs among handoff rate, service delay, and achievable coverage/data rate in heterogeneous, dense, and diverse 5G cellular networks is, therefore, an open challenge. Hence, in this dissertation, we analyze how mobility impacts the performance of current Ultra-dense mmWave network (UDN) architecture in a city environment and discuss improvements for reducing the impact of mobility to meet 5G specifications using multi-connectivity. Current handover protocols, by design, suffer from interruption even if they are successful and, at the same time, carry the risk of failures during execution. The next-generation wireless networks, like 5G New Radio, introduce even stricter requirements that cannot be fulfilled with the traditional hard handover concept. Another expectation from these services is extreme reliability that will not tolerate any mobility-related failures. Thus, in this dissertation, we explore a novel technique using packet duplication and evaluate its performance under various mobility scenarios. We study how packet duplication can be used to meet the stringent reliability and latency requirements of modern cellular networks as data packets are duplicated and transmitted concurrently over two independent links. The idea is to generate multiple instances (duplicates) of a packet and transmit them simultaneously over different uncorrelated channels with the aim of reducing the packet failure probability. We also propose enhancements to the packet duplication feature to improve radio resource utilization. The wide variety of use cases in the 5G greatly differs from the use cases considered during the design of third-generation (3G) and fourth-generation (4G) long-term evolution (LTE) networks. Applications like autonomous driving, IoT applications, live video, etc., are much more uplink intensive as compared to traditional applications. However, the uplink performance is often, by design, lower than the downlink; hence, 5G must improve uplink performance. Hence, to meet the expected performance levels, there is a need to explore flexible network architectures for 5G networks. In this work, we propose a novel uplink scheme where the UE performs only a single transmission on a common channel, and every base station that can receive this signal would accept and process it. In our proposed architecture, a UE is connected to multiple mmWave capable distributed units (DUs), which are connected to a single gNB-central unit. In an ultra-dense deployment with multiple mmWave base stations around the UE, this removes the need to perform frequent handovers and allows high mobility with reduced latency. We develop and evaluate the performance of such a system for high throughput and reliable low latency communication under various mobility scenarios. To study the impact of mobility on next-generation networks, this work develops and systematically analyzes the performance of the 5G networks under mobility. We also look into the effect of increasing the number of users being served on the network. As a result, these studies are intended to understand better the network requirements for handling mobility and network load with multi-connectivity. This dissertation aims to achieve clarity and also proposes solutions for resolving these real-world network mobility issues

Impact of Correlated Failures in 5G Dual Connectivity Architectures for URLLC Applications

Achieving end-to-end ultra-reliability and resiliency in mission critical communications is a major challenge for future wireless networks. Dual connectivity has been proposed by 3GPP as one of the viable solutions to fulfill the reliability requirements. However, the potential correlation in failures occurring over different wireless links is commonly neglected in current network design approaches. In this paper, we investigate the impact of realistic correlation among different wireless links on end-to-end reliability for two selected architectures from 3GPP. In ultra-reliable use-cases, we show that even small values of correlation can increase the end-to-end error rate by orders of magnitude. This may suggest alternative feasible architecture designs and paves the way towards serving ultra-reliable communications in 5G networks.Comment: Accepted in 2019 IEEE Globecom Workshops (GC Wkshps

Enabling High Throughput and Reliable Low Latency Communication over Vehicular Mobility in Next-Generation Cellular Networks

The fifth-generation (5G) networks and beyond need paradigm shifts to realize the exponentially increasing demands of next-generation services for high throughputs, low latencies, and reliable communication under various mobility scenarios. However, these promising features have critical gaps that need to be filled before they can be fully implemented for mobile applications in complex environments like smart cities. Although the sub-6 GHz bands can provide reliable and larger coverage, they cannot provide high data rates with low latencies due to a scarcity of spectrum available in these bands. Millimeter wave (mmWave) communication is a key enabler for a significant increase in the performance of these networks due to the availability of large bands of spectrum. However, the extremely limited transmission range of mmWave frequencies leads to poor reliability, especially for mobility scenarios. In this work, we present and evaluate the solutions in three key areas for achieving high throughput along with reliable low latency connection, especially for mobility scenarios in next-generation cellular networks. To enable the 5G networks to meet the demanding requirements of cellular networks, we look into (1) multi-connectivity for enhancing the performance of next-generation cellular networks, (2) designing a reliable network using multi-connectivity, and (3) developing a multilink scheme with efficient radio resource management. Despite the technological advances made in the design and evolution of 5G networks, emerging services impose stringent requirements which have not been fully met by 5G networks so far. The work in this dissertation aims to explore the challenges of future networks and address the needs in the three areas listed above. The results of the study open opportunities to resolve real-world 5G network issues. As 5G networks need to fulfill the rising performance demands of upcoming applications and industry verticals, we first study and evaluate multi-connectivity, which involves simultaneous connectivity with multiple radio access technologies or multiple bands, as a key enabler in improving the performance of the 5G networks. 5G networks are designed to have several small cells operating in the mmWave frequency range using ultra-dense networks (UDN) deployments to provide continuous coverage. But, such deployments not only face challenges in terms of frequent handovers, higher latency, lower reliability, and higher interference levels but also in terms of increasing complexity and cost of deployment, unbalanced load distributions, and power requirements. To address the challenges in high density base station deployments, we study and evaluate novel deployment strategies using multi-connectivity. In NR-NR Dual Connectivity (NR-DC), the user equipment (UE) is connected simultaneously to two gNBs, with one acting as the master node and the other as the secondary node to improve the performance of the 5G system. The master node operating at the sub-6 GHz bands provides high reliability, and the secondary node using the high bandwidth mmWave bands provides the high throughputs expected of 5G networks. This deployment also improves the latency as it decreases the number of handovers and link establishments. Thus, in this dissertation, we propose and evaluate novel 5G deployments with multi-connectivity, which can be used to ensure that these 5G networks are able to meet the demanding requirements of future services. The 5G networks also need to support ultra-reliable low latency communication, which refers to using the network for mission-critical communication that requires high reliability along with low latency. However, technological advancements so far have not been able to fully meet all these requirements. Thus, in this work, we design a reliable 5G network using multi-connectivity, which can simultaneously support high throughputs along with ultra-reliable low latency communication. Deployments using mmWave bands are highly susceptible to channel fluctuations and blockages. Thus, it is critical to consider new techniques and approaches that address these needs and can be implemented practically. In this work, we propose and implement a novel approach using packet duplication and its optimization in an NR-DC system to improve the performance of the system. In an NR-DC deployment with packet duplication, multiple instances of a packet are generated and transmitted simultaneously over different uncorrelated channels between the UE and the base stations, which decreases the packet failure probability. We also propose enhancements to the packet duplication feature for efficient radio resource utilization by looking into the distance of the UE from the base station, the velocity of the UE, and the received signal strength indicator (RSSI) levels. The proposed system improves the performance in terms of throughput, latency, and reliability under varying mobility scenarios. Finally, the 5G networks need to meet the increasing demands of uplink data traffic for applications such as autonomous driving, IoT applications, live video, etc. However, the uplink performance is lower compared to the downlink, and hence, it is critical for 5G to improve uplink performance. Thus, there are open research questions on what should be the network architecture with efficient radio resource utilization to meet the stringent requirements for mobility scenarios. In this work, we propose a novel uplink scheme where the UE performs only a single transmission on a common channel, and every base station that can receive this signal would accept and process it. This technique increases the probability of successful transmission and hence, increases the reliability of the network. It also removes the need to perform frequent handovers and allows high mobility with reduced latency. In this work, we propose and evaluate novel approaches for improving the performance of next-generation networks, which will be a key enabler for future applications. The proposed 5G techniques are shown to significantly improve the throughput, latency, and reliability simultaneously and are able to fulfill the stringent requirements of future services. Our work focuses on developing novel solutions for addressing the challenges involved in building next-generation cellular networks. In the future, we plan to further develop our system for real-world city-scale deployments

Multi-connectivity in 5G New Radio: configuration algorithms and performance evaluation

The 5th Generation (5G) New Radio (NR) air interface is expected to be the foundation of very heterogeneous networks serving a wide range of use cases, including Ultra-Reliable Low Latency Communications (URLLC) services. In URLLC, small data packets must be correctly transmitted and received in a short time with high reliability (up to 1 ms latency with a success probability of 99.999%). Different options are being considered to meet this challenging design target. One such considered solution is data duplication through dual connectivity, where the same packet is independently transmitted through two different nodes. This project studies the functionality of data duplication at PDCP level for dual connectivity through system-level simulations, where each packet copy is sent through the two links to which a certain UE is connected. The studied scenario is a heterogeneous network of 21 macro cells with a cluster of 4 pico cells per macro cell area. The scenario is first optimized for the single connectivity case, which supports up to 8Mbps URLLC load while meeting the URLLC requirements. When dual connectivity is enabled, in a controlled manner, in a URLLC traffic only scenario, it is shown that dual connectivity does not provide any gain due to the low interference conditions. As second step, the benefit of DC is studied when the URLLC traffic coexist with full buffer background eMBB traffic. Results show that latency gain can be obtained by dual connectivity, however the sensitivity of this gain on the scenario conditions is quite high. Finally, an optimization is added, in which if a packet sent through one of the links is successfully received at the UE, the transmission of its copy on the other link is cancelled (i.e. the packet is discarded at the network side). This optimization results in a performance improvement in terms of the latency especially at high load because it avoids buffering delay

On Enhancing Reliability in B5G NTNs with Packet Duplication via Multi-Connectivity

Non-Terrestrial Networks (NTNs) can be used to provide ubiquitous 5G and beyond services to un(der)served areas. To ensure reliable communication in such networks, packet duplication (PD) through multi-connectivity is a promising solution. However, the existing PD schemes developed for terrestrial environments may not be reactive enough for the NTN environment where propagation delays are significantly longer. This paper proposes a dynamic PD activation scheme for NTNs based on hybrid automatic repeat request feedback. The scheme aims to reduce the number of duplicated packets while maintaining high reliability. To evaluate the proposed scheme, simulations are conducted in a scenario with two transparent payload lowearth orbit satellites. The results show a significant reduction of 87.2% in the number of duplicated packets compared to blind duplication, with only marginal compromise in reliability.Comment: Accepted for publication in 2023 IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE 2023