On the impact of link layer retransmission schemes on TCP over 4G satellite links

We study the impact of reliability mechanisms introduced at the link layer on the performance of transport protocols in the context of 4G satellite links. Specifically, we design a software module that performs realistic analysis of the network performance, by utilizing real physical layer traces of a 4G satellite service. Based on these traces, our software module produces equivalent link layer traces, as a function of the chosen link layer reliability mechanism. We further utilize the link layer traces within the ns-2 network simulator to evaluate the impact of link layer schemes on the performance of selected Transmission Control Protocol (TCP) variants. We consider erasure coding, selective-repeat automatic request (ARQ) and hybrid-ARQ link layer mechanisms, and TCP Cubic, Compound, Hybla, New Reno and Westwood. We show that, for all target TCP variants, when the throughput of the transport protocol is close to the channel capacity, using the ARQ mechanism is most beneficial for TCP performance improvement. In conditions where the physical channel error rate is high, hybrid-ARQ results in the best performance for all TCP variants considered, with up to 22% improvements compared to other schemes

Performance analysis of 4G wireless networks using system level simulator

Doutoramento em Engenharia ElectrotécnicaIn the last decade, mobile wireless communications have witnessed an explosive growth in the user’s penetration rate and their widespread deployment around the globe. In particular, a research topic of particular relevance in telecommunications nowadays is related to the design and implementation of mobile communication systems of 4th generation (4G). 4G networks will be characterized by the support of multiple radio access technologies in a core network fully compliant with the Internet Protocol (all IP paradigms). Such networks will sustain the stringent quality of service (QoS) requirements and the expected high data rates from the type of multimedia applications (i.e. YouTube and Skype) to be available in the near future. Therefore, 4G wireless communications system will be of paramount importance on the development of the information society in the near future. As 4G wireless services will continue to increase, this will put more and more pressure on the spectrum availability. There is a worldwide recognition that methods of spectrum managements have reached their limit and are no longer optimal, therefore new paradigms must be sought. Studies show that most of the assigned spectrum is under-utilized, thus the problem in most cases is inefficient spectrum management rather spectrum shortage. There are currently trends towards a more liberalized approach of spectrum management, which are tightly linked to what is commonly termed as Cognitive Radio (CR). Furthermore, conventional deployment of 4G wireless systems (one BS in cell and mobile deploy around it) are known to have problems in providing fairness (users closer to the BS are more benefited relatively to the cell edge users) and in covering some zones affected by shadowing, therefore the use of relays has been proposed as a solution. To evaluate and analyse the performances of 4G wireless systems software tools are normally used. Software tools have become more and more mature in recent years and their need to provide a high level evaluation of proposed algorithms and protocols is now more important. The system level simulation (SLS) tools provide a fundamental and flexible way to test all the envisioned algorithms and protocols under realistic conditions, without the need to deal with the problems of live networks or reduced scope prototypes. Furthermore, the tools allow network designers a rapid collection of a wide range of performance metrics that are useful for the analysis and optimization of different algorithms. This dissertation proposes the design and implementation of conventional system level simulator (SLS), which afterwards enhances for the 4G wireless technologies namely cognitive Radios (IEEE802.22) and Relays (IEEE802.16j). SLS is then used for the analysis of proposed algorithms and protocols.FC

End-to-End Simulation of 5G mmWave Networks

Due to its potential for multi-gigabit and low latency wireless links, millimeter wave (mmWave) technology is expected to play a central role in 5th generation cellular systems. While there has been considerable progress in understanding the mmWave physical layer, innovations will be required at all layers of the protocol stack, in both the access and the core network. Discrete-event network simulation is essential for end-to-end, cross-layer research and development. This paper provides a tutorial on a recently developed full-stack mmWave module integrated into the widely used open-source ns--3 simulator. The module includes a number of detailed statistical channel models as well as the ability to incorporate real measurements or ray-tracing data. The Physical (PHY) and Medium Access Control (MAC) layers are modular and highly customizable, making it easy to integrate algorithms or compare Orthogonal Frequency Division Multiplexing (OFDM) numerologies, for example. The module is interfaced with the core network of the ns--3 Long Term Evolution (LTE) module for full-stack simulations of end-to-end connectivity, and advanced architectural features, such as dual-connectivity, are also available. To facilitate the understanding of the module, and verify its correct functioning, we provide several examples that show the performance of the custom mmWave stack as well as custom congestion control algorithms designed specifically for efficient utilization of the mmWave channel.Comment: 25 pages, 16 figures, submitted to IEEE Communications Surveys and Tutorials (revised Jan. 2018

Technologies of Mobile Communication

Long-Term Evolution (LTE) is a new technology recently specified by 3GPP-Third Generation Partnership Project on the way towards fourth-generation mobile. This thesis presents the main technical features of this technology as well as its performances in terms of peak bit rate and average cell throughput, among others. LTE entails a big technological improvement as compared with the previous 3G standards. 1 However, this thesis also demonstrates that LTE performances do not fulfill the technical requirements established by ITU-R to classify one radio access technology as a member of the IMT-Advanced family of standards. Thus, this thesis describes the procedure followed by 3GPP to address these challenging requirements. Through the design and optimization of new radio access techniques and a further evolution of the system, 3GPP is laying down the foundations of the future LTE-Advanced standard, the 3GPP candidate for 4G

Evaluation of 3GPP Technology Candidate Towards Fourth Generation Mobile

[ES] LTE-Advanced es una de las tecnologías candidatas para convertirse en la próxima generación de comunicaciones móviles (4G). Es responsabilidad de la Unión Internacional de las Telecomunicaciones (UIT) evaluar esta tecnología a través de los Grupos de Evaluación Externos (GEE), entre los cuales se encuentra el consorcio WINNER+ (Wireless World Initiative New Radio +). El Grupo de Comunicaciones Móviles (GCM) del Instituto de Telecomunicaciones y Aplicaciones Multimedia, como socio de WINNER+, está analizando diferentes técnicas para optimizar la red de acceso radio LTEAdvanced. Esta tesina de máster se enmarca dentro de este trabajo, y especialmente, en la comparación de los turbo-códigos (TC) y Low Density Partity Check (LDPC) para anchos de banda de hasta 100 MHz. Los resultados obtenidos muestran que tanto los TC como los LDPC son buenos codificadores para esos tamaños de bloque. Los códigos LDPC representan una mejora de 0.5 dB como máximo respecto a los TC. Además, se ha realizado un estudio de prestaciones de la capa física de LTE en el enlace ascendente y descendente, junto con una propuesta de calibración de este tipo de simulaciones de enlace.[EN] LTE-Advanced is one promising candidate technology to become part of the next generation mobile (4G). It is up to the International Telecommunication Union (ITU) standardization body to assess this technology through the External Evaluation Groups (EEG), being one of them the WINNER+ project (Wireless World Initiative New Radio +). The Mobile Communications Group (MCG) of the Institute of Telecommunications and Multimedia Applications, as a partner of WINNER+, is currently analyzing and proposing different techniques with the aim of optimizing the LTE-Advanced radio access network. This Master Thesis is part of this activity and, especially, on the comparison of Turbo (TC) and Low Density Parity Check (LDPC) codes for bandwidths up to 100 MHz. Results prove that both TC and LDPC codes are good encoders for those block sizes. The LDPC codes only entail a maximum 0.5 dB improvement as compared with TC. In addition to this assessment, a performance study of LTE downlink/uplink (DL/ UL) physical layer together with a calibration proposal for link level simulations has been carried out.Cabrejas Peñuelas, J. (2009). Evaluation of 3GPP Technology Candidate Towards Fourth Generation Mobile. http://hdl.handle.net/10251/27347.Archivo delegad

Protocol-Level Simulations of Massive Medium Access for Machine-Type Communications

In recent years, Machine-Type Communications (MTC) has become one of the most attractive technologies in the area of wireless networking. Different sources are predicting a large grow of smart grid machine-to-machine deployments in several decades, which also means that the total number of wireless devices will increase dramatically. In connection to this problem, the choice of the standard, which will satisfy all the MTC requirements without harming current wireless deployments has become very relevant. Because of these reasons, many companies are proposing to modify one (or several) of the current wireless standard in a way that it will be possible to use for MTC purposes. This will be perfect from point of view of interference problems, because they will be already included in a standard itself. Third Generation Partnership Project (3GPP) Long Term Evolution-Advanced (LTE- A) is one of the most rapidly developing wireless technologies, that seems to be an ideal candidate for future MTC implementation. However, while the capacity of typical LTE-A network should be enough to satisfy traffic demands of large number of MTC devices, the signaling is not ready to face new requirements. In this Thesis, we are considering and partly solving problems, that could occur in LTE-A signaling channels under MTC conditions. Particularly, these are data access mechanisms, which could be realized via Physical Uplink Control Channel (PUCCH) and Physical Random Access Channel (PRACH). Speaking about assessment methods, the research made in this work is based on 2 approaches: simulation and analysis. Both of them are also in details described in the pages of this Thesis. As a conclusion it could be said that PUCCH channel is not suitable for the MTC data access, while PRACH is having problems only in heavily loaded (overloaded) cases and should be slightly modified to face them