Analysis of TCP performance for LTE-5G Millimeter Wave Dual Connectivity

The goal of this work is the analysis of the performance of the transport control protocol (TCP) in a Dual connectivity (DC) system, where both LTE and 5G millimeter wave (mmWave) were used in the radio access network, while a single user travels across the scenario. Since the user is moving, the interaction between the mmWave base stations (BSs) must be very efficient to avoid congestion events. This makes the analysis of DC very important. Simulation models based on open-source software frameworks were used to evaluate the performance of Dual connectivity for a 5G non-standalone (NSA) solution, where all the 5G base station traffic goes through the LTE base station. The scenarios proposed were defined in terms of non-line-of-sight/line-of-sight (NLOS/LOS) scenario, medium/high traffic, which are used to evaluate different TCP congestion control algorithms. The performance was then evaluated in terms of goodput, packet delivery ratio, standard deviation of bytes in-flight, and round-trip time. Simulation results showed that the number of bytes in-flight grows with high rates and large latencies caused by inter-BS communication. The mmWave medium is very sensitive to channel conditions specially in the middle point between mmWave BSs causing ping-pong effect during a handover (HO). At the beginning of the simulation some nodes overflow due to the aggressive slow start mechanisms, which turn to be very problematic for high traffic rates. In that sense, TCP Cubic proves to be a much reliable congestion control algorithm since it implements a hybrid slow start method

Device-to-Device Communication in 5G Cellular Networks

Owing to the unprecedented and continuous growth in the number of connected users and networked devices, the next-generation 5G cellular networks are envisaged to support enormous number of simultaneously connected users and devices with access to numerous services and applications by providing networks with highly improved data rate, higher capacity, lower end-to-end latency, improved spectral efficiency, at lower power consumption. D2D communication underlaying cellular networks has been proposed as one of the key components of the 5G technology as a means of providing efficient spectrum reuse for improved spectral efficiency and take advantage of proximity between devices for reduced latency, improved user throughput, and reduced power consumption. Although D2D communication underlaying cellular networks promises lots of potentials, unlike the conventional cellular network architecture, there are new design issues and technical challenges that must be addressed for proper implementation of the technology. These include new device discovery procedures, physical layer architecture and radio resource management schemes. This thesis explores the potentials of D2D communication as an underlay to 5G cellular networks and focuses on efficient interference management solutions through mode selection, resource allocation and power control schemes. In this work, a joint admission control, resource allocation, and power control scheme was implemented for D2D communication underlaying 5G cellular networks. The performance of the system was evaluated, and comparisons were made with similar schemes.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Hybride Beamformingsysteme niedriger Komplexität für den Mobilfunk

An important method to increase the spectral efficiency of wireless radio communication networks is the use of multiple-input multiple-output communication systems operating in the centimetre and millimetre wave region. How these multiple-input multiple-output communication systems can be realised with as little hardware effort as possible using hybrid beamforming architectures is the subject of this work

Hybride Beamformingsysteme niedriger Komplexität für den Mobilfunk

Ein wichtiger Baustein zur Steigerung der spektralen Effizienz von drahtlosen Funkkommunikationsnetzwerken stellt der Einsatz von Mehrantennensystemen im Zentimeter- und Millimeterwellenfrequenzbereich dar. Wie diese Mehrantennensysteme mit einem möglichst geringen Hardwareaufwand in Form von hybriden Beamformingsystemen realisiert werden können ist Thema dieser Arbeit

Accurate characterisation of Resonant Tunnelling Diodes for high-frequency applications

Recent scientific advancements regarding the generation and detection of terahertz (THz) radiation have led to a rapid increase in research interest in this frequency band in the context of its numerous potential applications including high-speed wireless communications, biomedical diagnostics, security screening and material science. Various proposed solutions have been investigated in the effort to bridge this relatively unexplored region of the electromagnetic spectrum, and thus exploit its untapped potential. Among them, the resonant tunnelling diode (RTD) has been demonstrated as the fastest electronic device with its room temperature operation extending into the THz range. The RTD exhibits a negative differential resistance (NDR) region in its I-V characteristics, with this feature being key to its capabilities. Even though the unique capabilities of RTD devices have been experimentally proven in the realisation of compact NDR oscillators and detectors, with fundamental frequencies of about 2 THz, and high-sensitivity detectors up to 0.83 THz, the reliable design procedures and methodologies of RTD-based circuits are yet to be fully developed. In this regard, significant effort has been devoted primarily to the accurate theoretical description of the high-frequency behaviour of RTDs, using various small-signal equivalent circuit models. However, many of these models have had either limited or no experimental validation, and so a robust and reliable RTD device model is desirable. The aim of this thesis is to describe a systematic approach regarding the design, fabrication and characterisation of RTD devices, providing a universal methodology to accurately determine their radio-frequency (RF) behaviour, and so this way enable a consistent integrated circuit design procedure for high-frequency circuits. A significant challenge in the modelling of RTD devices is represented by the presence of parasitic bias oscillations within the NDR region. This has been identified as one of the main restricting factors with regards to the accurate high-frequency characterisation of this operating region. The common approach to overcoming this limitation is through a stabilising technique comprising of an external shunt-resistor network. This approach has been successfully demonstrated to suppress bias oscillations in RTD-based circuits which require operation within the NDR region. However, the introduction of the additional circuit component associated with this method increases the complexity of the de-embedding procedure of the extrinsic parasitic elements, rendering the overall device characterisation generally difficult at high-frequencies. In this work, a novel on-wafer bond-pad and shunt resistor network de-embedding technique was developed in order to facilitate the characterisation of RTDs throughout the complete bias range, without limitation to device sizing or frequency, under a stable operating regime. The procedure was demonstrated to accurately determine the circuit high-frequency behaviour of the RTD device from S-parameter measurements up to 110 GHz. The universal nature of this procedure allows it to be easily adapted to accommodate higher complexity stabilising networks configuration or different bond-pad geometries. Furthermore, the de-embedding method has also enabled the development of a novel quasi-analytical procedure for high accuracy extraction of the device equivalent circuit parameters, which is expected to provide a strong experimental foundation for the further establishment of a universal RTD RF model. The applicability of the developed high-frequency model, which can be easily scaled for various device sizes, together with the measured RTD I-V characteristics was further demonstrated in the development of a non-linear model, which was integrated in a commercial simulator, the Advanced Design Systems (ADS) software from Keysight Technologies. From an application perspective, the model was used in the design of an RTD as a square-law detector for high-frequency data transmission systems. The simulated detector performance was validated experimentally using an RTD-based transmitter in the W-band (75 – 110 GHz) up to 4 Gbps (error free transmission: BER < 10-10 in a waveguide connection), and in the Ka-band (26.5 – 50 GHz) up to 2.4 Gbps (error free transmission in a wireless data link), which demonstrated the accuracy of the developed RTD modelling approach. Lastly, a sensitivity analysis of the RTD-based detector within the Ka-band showed a superior RTD performance over commercially available solutions, with a peak (corrected) detector responsivity of 13.48 kV/W, which is a factor of >6 better compared to commercially available Schottky barrier diode (SBD) detectors

Hybride Beamformingsysteme niedriger Komplexität für den Mobilfunk

An important method to increase the spectral efficiency of wireless radio communication networks is the use of multiple-input multiple-output communication systems operating in the centimetre and millimetre wave region. How these multiple-input multiple-output communication systems can be realised with as little hardware effort as possible using hybrid beamforming architectures is the subject of this work

Interference Alignment and Cancellation in Wireless Communication Systems

The Shannon capacity of wireless networks has a fundamental importance for network information theory. This area has recently seen remarkable progress on a variety of problems including the capacity of interference networks, X networks, cellular networks, cooperative communication networks and cognitive radio networks. While each communication scenario has its own characteristics, a common reason of these recent developments is the new idea of interference alignment. The idea of interference alignment is to consolidate the interference into smaller dimensions of signal space at each receiver and use the remaining dimensions to transmit the desired signals without any interference. However, perfect alignment of interference requires certain assumptions, such as perfect channel state information at transmitter and receiver, perfect synchronization and feedback. Today’s wireless communication systems, on the other and, do not encounter such ideal conditions. In this thesis, we cover a breadth of topics of interference alignment and cancellation schemes in wireless communication systems such as multihop relay networks, multicell networks as well as cooperation and optimisation in such systems. Our main contributions in this thesis can be summarised as follows: • We derive analytical expressions for an interference alignment scheme in a multihop relay network with imperfect channel state information, and investigate the impact of interference on such systems where interference could accumulate due to the misalignment at each hop. • We also address the dimensionality problem in larger wireless communication systems such as multi-cellular systems. We propose precoding schemes based on maximising signal power over interference and noise. We show that these precoding vectors would dramatically improve the rates for multi-user cellular networks in both uplink and downlink, without requiring an excessive number of dimensions. Furthermore, we investigate how to improve the receivers which can mitigate interference more efficiently. • We also propose partial cooperation in an interference alignment and cancellation scheme. This enables us to assess the merits of varying mixture of cooperative and non-cooperative users and the gains achievable while reducing the overhead of channel estimation. In addition to this, we analytically derive expressions for the additional interference caused by imperfect channel estimation in such cooperative systems. We also show the impact of imperfect channel estimation on cooperation gains. • Furthermore, we propose jointly optimisation of interference alignment and cancellation for multi-user multi-cellular networks in both uplink and downlink. We find the optimum set of transceivers which minimise the mean square error at each base station. We demonstrate that optimised transceivers can outperform existing interference alignment and cancellation schemes. • Finally, we consider power adaptation and user selection schemes. The simulation results indicate that user selection and power adaptation techniques based on estimated rates can improve the overall system performance significantly

Shortest Route at Dynamic Location with Node Combination-Dijkstra Algorithm

Abstract— Online transportation has become a basic requirement of the general public in support of all activities to go to work, school or vacation to the sights. Public transportation services compete to provide the best service so that consumers feel comfortable using the services offered, so that all activities are noticed, one of them is the search for the shortest route in picking the buyer or delivering to the destination. Node Combination method can minimize memory usage and this methode is more optimal when compared to A* and Ant Colony in the shortest route search like Dijkstra algorithm, but can’t store the history node that has been passed. Therefore, using node combination algorithm is very good in searching the shortest distance is not the shortest route. This paper is structured to modify the node combination algorithm to solve the problem of finding the shortest route at the dynamic location obtained from the transport fleet by displaying the nodes that have the shortest distance and will be implemented in the geographic information system in the form of map to facilitate the use of the system. Keywords— Shortest Path, Algorithm Dijkstra, Node Combination, Dynamic Location (key words