Performance Comparison of Dual Connectivity and Hard Handover for LTE-5G Tight Integration in mmWave Cellular Networks

MmWave communications are expected to play a major role in the Fifth generation of mobile networks. They offer a potential multi-gigabit throughput and an ultra-low radio latency, but at the same time suffer from high isotropic pathloss, and a coverage area much smaller than the one of LTE macrocells. In order to address these issues, highly directional beamforming and a very high-density deployment of mmWave base stations were proposed. This Thesis aims to improve the reliability and performance of the 5G network by studying its tight and seamless integration with the current LTE cellular network. In particular, the LTE base stations can provide a coverage layer for 5G mobile terminals, because they operate on microWave frequencies, which are less sensitive to blockage and have a lower pathloss. This document is a copy of the Master's Thesis carried out by Mr. Michele Polese under the supervision of Dr. Marco Mezzavilla and Prof. Michele Zorzi. It will propose an LTE-5G tight integration architecture, based on mobile terminals' dual connectivity to LTE and 5G radio access networks, and will evaluate which are the new network procedures that will be needed to support it. Moreover, this new architecture will be implemented in the ns-3 simulator, and a thorough simulation campaign will be conducted in order to evaluate its performance, with respect to the baseline of handover between LTE and 5G.Comment: Master's Thesis carried out by Mr. Michele Polese under the supervision of Dr. Marco Mezzavilla and Prof. Michele Zorz

TD-SCDMA Relay Networks

PhDWhen this research was started, TD-SCDMA (Time Division Synchronous Code Division Multiple Access) was still in the research/ development phase, but now, at the time of writing this thesis, it is in commercial use in 10 large cities in China including Beijing and Shang Hai. In all of these cities HSDPA is enabled. The roll-out of the commercial deployment is progressing fast with installations in another 28 cities being underway now. However, during the pre-commercial TD-SCDM trail in China, which started from year 2006, some interference problems have been noticed especially in the network planning and initialization phases. Interference is always an issue in any network and the goal of the work reported in this thesis is to improve network coverage and capacity in the presence of interference. Based on an analysis of TD-SCDMA issues and how network interference arises, this thesis proposes two enhancements to the network in addition to the standard N-frequency technique. These are (i) the introduction of the concentric circle cell concept and (ii) the addition of a relay network that makes use of other users at the cell boundary. This overall approach not only optimizes the resilience to interference but increases the network coverage without adding more Node Bs. Based on the cell planning parameters from the research, TD-SCDMA HSDPA services in dense urban area and non-HSDPA services in rural areas were simulated to investigate the network performance impact after introducing the relay network into a TD-SCDMA network. The results for HSDPA applications show significant improvement in the TDSCDMA relay network both for network capacity and network interference aspects compared to standard TD-SCDMA networks. The results for non- HSDPA service show that although the network capacity has not changed after adding in the relay network (due to the code limitation in TD-SCDMA), the TD-SCDMA relay network has better interference performance and greater coverage

Delay measurements In live 5G cellular network

Abstract. 5G Network has many important properties, including increased bandwidth, increased data throughput, high reliability, high network density, and low latency. This thesis concentrate on the low latency attribute of the 5G Standalone (SA) mode and 5G Non-Standalone (NSA) mode. One of the most critical considerations in 5G is to have low latency network for various delay-sensitive applications, such as remote diagnostics and surgery in healthcare, self-driven cars, industrial factory automation, and live audio productions in the music industry. Therefore, 5G employs various retransmission algorithms and techniques to meet the low latency standards, a new frame structure with multiple subcarrier spacing (SCS) and time slots, and a new cloud-native core. For the low latency measurements, a test setup is built. A video is sent from the 5G User Equipment (UE) to the multimedia server deployed in the University of Oulu 5G test Network (5GTN) edge server. The University of Oulu 5GTN is operating both in NSA and SA modes. Delay is measured both for the downlink and the uplink direction with Qosium tool. When calculating millisecond-level transmission delays, clock synchronization is essential. Therefore, Precision Time Protocol daemon (PTPd) service is initiated on both the sending and receiving machines. The tests comply with the specifications developed at the University of Oulu 5GTN for both the SA and the NSA mode. When the delay measurement findings were compared between the two deployment modes, it was observed that the comparison was not appropriate. The primary reason for this is that in the 5GTN, the NSA and the SA have entirely different data routing paths and configurations. Additionally, the author did not have sufficient resources to make the required architectural changes

Evaluating the effectiveness of Cooperative/Coordinated Multipoint (CoMP) LTE feature in uplink and downlink transmissions

Shannon demonstrated that the channel capacity depends of the ratio of the received signal power to interference plus noise power (SINR). Inter-cell interference caused by neighbouring base stations (BSs) has been identified as one of the most severe problem towards the deployment of LTE technology as it can significantly deteriorate the performance of cellside User Equipment (UE). However, because of regulatory and radiation restrictions as well as operational costs, signal power may only be increased only up to a certain limit to reduce the interference. The other common radio propagation impairment is multipath. Multipath refers to a scenario where multiple copies of a signal propagate to a receiver using different paths. The paths can be created due to signal reflection, scattering and diffraction. As will be discussed later the effects of multipath contribute little to intercell interference because multipath characteristics such as delay spread are compensated for using cyclic prefixes. In this work, we will limit our scope to interference as it has been identified as the main cause of performance degradation for cell edge users due to the full frequency reuse technique used in LTE. To mitigate interference 3GPP devised options of increasing the capacity in LTEAdvanced Release 12 which include the use of spectral aggregation, employing Multiple Input and Multiple Output (MIMO) Antenna techniques, deploying more base stations and micro and femto cells, increasing the degree of sectorisation and Coordinated Multipoint (CoMP). We are primarily interested in evaluating performance improvements introduced when uplink (UL) and downlink (DL) coordinated/cooperative multipoint (CoMP) is enabled in LTE Advanced Release 12 as a way of reducing interference among sites. The CoMP option of reducing interference does not require deployment of new equipment compared to the other options mentioned above hence network deployment costs are minimal. CoMP in theory is known to reduce interference especially for cell edge users and therefore improves network fairness. With CoMP, multiple points coordinate with each other such that transmission of signals to and from other points do not incur serious interference or the interference can even be exploited as a meaningful signal. In September 2011 work on specifications for CoMP support was started in 3GPP LTEAdvanced as one of the core features in LTE-Advanced Release 11 to improve cell edge user throughput as well as the average network throughput. We set to do field measurements in the evaluation of the effectiveness of CoMP in LTE. 3GPP LTE Release 12 was used and cell edge users' performance was the focus. The network operates in 2330 - 2350 MHz band (Channel 40). From the field measurements, it was demonstrated that the CoMP (Scenario 2) feature indeed effective in improving service quality/user experience/fairness for cell edge users. CoMP inherently improves network capacity. A seven (7) percent throughput was noticed

LTE performance evaluation with realistic channel quality indicator feedback

In the context of mobile communications, the availability of new services and mobile applications along with the constant evolution in terminals run up the need of higher data rates. In order to fulfill such expectations, mobile operators are continually optimizing and upgrading their networks. The Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) seems to be the path to follow in a very short term. The objective of this project is to study the behaviour of the radio resource assignment in LTE under realistic conditions. The scheduling is a key process in the functioning of the radio interface. Thus, two types of schedulers can be identified, the opportunistic, where the scheduler considers the state of the radio channel to make the best allocation possible, and the non-opportunistic, where the allocation has no knowledge of the radio channel‘s state. As the opportunistic option adapts to the radio channel conditions it requires the transmission of a certain level of signalling from users informing about how the channel evolves along time. One of the objectives of this project is to evaluate the system performance under different degrees of feedback. To do this, different CQI reporting methods have been programmed and simulated. So, to achieve this objective it is obvious that a second one is necessary: program and simulate in a more realistic way the LTE radio channel. The followed methodology has been fundamentally the programming of different mathematical models and algorithms, as well as its simulation. In concrete, one of the main tasks in this work has been to extent a software platform of the research group Wicomtec to obtain more realistic results through dynamic simulations over a dynamic radio channel