A Complete Solution to LTE-U and Wi-Fi Hidden Terminal Problem

With the exponential growth in mobile data traffic, mobile operators are facing the unfortunate limit on the availability of licensed spectrum which has however, led to the popularity of Long Term Evolution (LTE) in unlicensed spectrum (LTE-U). Undeniably, it is expected from LTE-U that it fairly shares the spectrum with Wi-Fi. Along with fair sharing, efficient utilization of the unlicensed spectrum is also equally important, which in some sense requires coordination between the two Radio Access Technologies (RATs) viz., LTE-U and Wi-Fi. In particular, the hidden terminal scenario between LTE-U and Wi-Fi, resulting mainly due to lack of coordination, threatens the spectrum utilization of unlicensed spectrum. Focusing on this hidden terminal problem between LTE-U and Wi-Fi, we highlight the deficiency of existing technologies from the Wi-Fi perspective, both at the user level and at the network level. We then propose a novel coexistence technique (similar to RTS-CTS mechanism in Wi-Fi) that solves the hidden terminal problem between LTE-U and Wi-Fi, and subsequently addresses the spectrum underutilization problem caused by hidden terminal collisions. The proposed mechanism achieves this by using a modified CTS frame of Wi-Fi. We have validated our proposed mechanism using a mathematical framework demonstrating its credibility

Fair Coexistence of Scheduled and Random Access Wireless Networks: Unlicensed LTE/WiFi

We study the fair coexistence of scheduled and random access transmitters sharing the same frequency channel. Interest in coexistence is topical due to the need for emerging unlicensed LTE technologies to coexist fairly with WiFi. However, this interest is not confined to LTE/WiFi as coexistence is likely to become increasingly commonplace in IoT networks and beyond 5G. In this article we show that mixing scheduled and random access incurs and inherent throughput/delay cost, the cost of heterogeneity. We derive the joint proportional fair rate allocation, which casts useful light on current LTE/WiFi discussions. We present experimental results on inter-technology detection and consider the impact of imperfect carrier sensing.Comment: 14 pages, 8 figures, journa

Development of Multiple Protocols in Novel Simulation Environment

abstract: When one considers the current state of wireless communications, it becomes clear that it is both absolutely amazing and something of a mess. Present communications standards are the result of local optimizations over time that led to a confusing set of suboptimal and fragile wireless standards. Starting from a clean sheet of paper, Bliss Laboratory for Information, Signals, and Systems (BLISS) is considering a fluid set of communications standards co-optimized with flexible but power-efficient computational implementations that will enable the next revolution of wireless communications. The main aim is to enable much higher data rates and much lower data rates with corresponding lower power consumption as the needs of the users vary. The thesis mainly looks at the different sections of the work done, to prime the development of the protocol development engine. It discusses channel modeling, and system integration of receiver and channel noise. It also proposes a Carrier-Sense Multiple Access (CSMA) Media Access Control (MAC) layer protocol implementation for (Wireless Fidelity) Wi-Fi protocol. This work also talks about the Graphical User Interface (GUI), which is a part of Protocol Development Kit (PDK) - a combination of the Protocol Recommendation Engine (PRE) and simulation package to aid the development of protocols. It also sheds light on the Automatic Dependent Surveillance - Broadcast (ADS-B) radio protocol, that will eventually replace radar as Air Traffic Control's (ATC) primary tool for separating aircraft. All the algorithms used in this thesis, to define radio operation were in principle defined by mathematical descriptions; however, to test and implement these algorithms they had to be converted to a computer language. There were multiple phases of this conversion. In the first phase, the implementation of these algorithms was done in Matrix Laboratory (MATLAB). To aid this development, basic radio finite state machines and radio algorithmic tools were provided.Dissertation/ThesisMasters Thesis Electrical Engineering 201

Infinite Factorial Finite State Machine for Blind Multiuser Channel Estimation

New communication standards need to deal with machine-to-machine communications, in which users may start or stop transmitting at any time in an asynchronous manner. Thus, the number of users is an unknown and time-varying parameter that needs to be accurately estimated in order to properly recover the symbols transmitted by all users in the system. In this paper, we address the problem of joint channel parameter and data estimation in a multiuser communication channel in which the number of transmitters is not known. For that purpose, we develop the infinite factorial finite state machine model, a Bayesian nonparametric model based on the Markov Indian buffet that allows for an unbounded number of transmitters with arbitrary channel length. We propose an inference algorithm that makes use of slice sampling and particle Gibbs with ancestor sampling. Our approach is fully blind as it does not require a prior channel estimation step, prior knowledge of the number of transmitters, or any signaling information. Our experimental results, loosely based on the LTE random access channel, show that the proposed approach can effectively recover the data-generating process for a wide range of scenarios, with varying number of transmitters, number of receivers, constellation order, channel length, and signal-to-noise ratio.Comment: 15 pages, 15 figure

LTE-U and Wi-Fi hidden terminal problem: How serious is it for deployment consideration?

The deployment of LTE in unlicensed spectrum is a plausible solution to meet explosive traffic demand from mobile users. However, fair coexistence with the existing unlicensed technologies, mainly Wi-Fi, needs to be ensured before any such deployment. Duty cycled LTE (LTE-U) is a simple and an easily adaptable scheme which helps in fair coexistence with the Wi-Fi. Nonetheless, the immense deployment of Wi-Fi necessitates a user-oriented study to find the effects of LTE-U operation, primarily in scenarios where the LTE-U eNB remains hidden from Wi-Fi Access Point. To comprehend these effects, we perform a user-level throughput study of Wi-Fi in the presence of LTE-U using a testbed and observe a clear unfairness in throughput distribution among Wi-Fi users. Furthermore, we also notice inability among the disadvantaged users to receive the periodic Wi-Fi beacon frames successfully. The reasons and the subsequent consequences, of throughput unfairness and beacon losses, are carefully elaborated. Also, to validate the beacon loss results, we present a beacon loss analysis which provides a mathematical expression to find the beacon loss percentage. Finally, we examine the results and highlight a need for incorporating additional functionalities in either LTE-U or Wi-Fi to overcome the present challenges

On the Impact of Duty Cycled LTE-U on Wi-Fi Users: An Experimental Study

The deployment of LTE in unlicensed spectrum is a plausible solution to meet explosive traffic demand from mobile users. However, fair coexistence with the existing unlicensed technologies, mainly Wi-Fi, needs to be ensured before any such deployment. Duty cycled LTE (LTE-U) is a simple and an easily adaptable scheme which helps in fair coexistence with the Wi-Fi. Nonetheless, the immense deployment of Wi-Fi necessitates a user-oriented study to find the effects of LTE-U operation, primarily in scenarios where the LTE-U eNB remains hidden from Wi-Fi Access Point. To delineate these effects, we perform a user-level Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) throughputs study of Wi-Fi in the presence of LTE-U using a testbed. Since, TCP is a more complicated protocol, we analyzed the Congestion Window and Round Trip Time data to comprehend the throughput results. This further explains the unfairness in throughput distribution among Wi-Fi users. Furthermore, we also notice inability among the disadvantaged users to receive the periodic Wi-Fi beacon frames successfully. The reasons and the subsequent consequences of throughput unfairness and beacon losses, are carefully elaborated. Also, to validate the beacon loss results, we present a beacon loss analysis which provides a mathematical expression to find the beacon loss percentage. Finally, we examine the results and highlight a need for incorporating additional functionalities in either LTE-U or Wi-Fi to overcome the present challenges

Enhancing the coexistence of LTE and Wi-Fi in unlicensed spectrum through convolutional neural networks

Over the last years, the ever-growing wireless traffic has pushed the mobile community to investigate solutions that can assist in more efficient management of the wireless spectrum. Towards this direction, the long-term evolution (LIE) operation in the unlicensed spectrum has been proposed. Targeting a global solution that respects the regional requirements, 3GPP announced the standard of LIE licensed assisted access (LAA). However, LIE LAA may result in unfair coexistence with Wi-Fi, especially when Wi-Fi does not use frame aggregation. Targeting a technique that enables fair channel access, the mLTE-U scheme has been proposed. According to mLTE-U, LTE uses a variable transmission opportunity, followed by a variable muting period that can be exploited by other networks to transmit. For the selection of the appropriate mLTE-U configuration, information about the dynamically changing wireless environment is required. To this end, this paper proposes a convolutional neural network (CNN) that is trained to perform identification of LIE and Wi-Fi transmissions. In addition, it can identify the hidden terminal effect caused by multiple LTE transmissions, multiple Wi-Fi transmissions, or concurrent LIE and Wi-Fi transmissions. The designed CNN has been trained and validated using commercial off-the-shelf LIE and Wi-Fi hardware equipment and for two wireless signal representations, namely, in-phase and quadrature samples and frequency domain representation through fast Fourier transform. The classification accuracy of the two resulting CNNs is tested for different signal to noise ratio values. The experimentation results show that the data representation affects the accuracy of CNN. The obtained information from CNN can be exploited by the mLTE-U scheme in order to provide fair coexistence between the two wireless technologies

Exploring the benefits of multipath TCP In wireless networks

The revolution of the information society has created a completely new situation in the telecommunications markets. As the average user data demands in today's society grow bigger, since users nowadays are demanding a faster, wider and more reliable communication service from the operators so they can watch more videos, listen to more music or access the Internet in general with a better quality, a lower latency and seamlessly to the network access they are using, the network operators face the challenge to fit this demands into their existing networks. This has forced the operators to think in terms of how optimal they are on providing their services if they want to fulfil the customer requirements in this new environment. At the same time we need to keep in mind that simultaneously to this new user's habits smartphones revolution has created, it has also made it possible to have accessible communication devices which have the necessary hardware and horsepower to keep different network interfaces up, and so it has become a common thing to reach the Internet via different kind of networks along the day. Even more it has enabled a rich communications environment where different connection possibilities are available to the user at the same time. In this context, the idea of multipath communication emerges. The idea of taking advantage of a dense wireless communication offer through the use of multipath (sending and receiving information through different network interfaces simultaneously) looks promising to overcome a situation where user's communications services demand grows and at the same time the mobile network load becomes stronger. The newfangled protocol Multipath TCP (MPTCP) is a technology which is enabling in practice this king of multipath communication, and it is the focus of this project to dig into possible benefits the protocol may bring to the table by defining a set of use cases, test-bed implementations and experiments with MPTCP which we present and analyse in this document.La revolución de la sociedad de la información ha creado una situación que es completamente nueva en los mercados de telecomunicaciones. A medida que el usuario medio aumenta su demanda de datos, ya que hoy en día los hábitos de estos pasan por conexiones más rápidas y fiables que les permitan reproducir contenido (video, música, páginas web) con mejor calidad, menor latencia y transparentemente a la red que estén utilizando, los operadores de red afrontan nuevos retos a la hora de encajar estas expectativas del usuario dentro de las posibilidades que ofrece la red. Esto está forzando a los operadores a buscar una manera más óptima de gestionar el tráfico de sus clientes para así poder satisfacer la demanda de unos servicios de mayor calidad que estos realizan. Al mismo tiempo hay que tener en mente que, de la misma manera que el impacto que esta esta revolución de los smartphones ha tenido en los hábitos de consumo del usuario ha creado nuevos y complejos problemas, también ha hecho posible que existan dispositivos económicamente accesibles para el público con el hardware y la capacidad de procesamiento necesarias para incorporar múltiples adaptadores de red, y esto a su vez ha llevado a al escenario actual en el que comúnmente coexisten en el mismo lugar diferentes posibilidades para conectarse a internet (típicamente Wi-Fi y conexión móvil, pero también podríamos nombrar tecnologías como el Bluetooth o la clásica conexión de Ethernet en ordenadores portátiles) Es en este contexto en el que surge la idea de la comunicación multi-trayecto. La idea de aprovechar un entorno con una densa pero heterogénea oferta de conexión a través del uso del multi-trayecto (enviar y recibir información a través de múltiples interfaces de red simultáneamente) aparece como una posibilidad prometedora para los operadores para mejorar la experiencia del usuario al mismo tiempo que se gestiona el tráfico en la red de una manera más eficiente. El protocolo experimental Multipath TCP es una extensión del TCP clásico que hace posible este uso simultáneo de múltiples interfaces para la comunicación, y es objetivo de este proyecto diseñar, implementar y testear el protocolo en diferentes casos de uso en los que el multi-trayecto ofrece, a priori, algunas ventajas. En las siguientes páginas explicaremos que casos de uso hemos elegido para probar el protocolo y por qué, cómo hemos diseñado e implementado los bancos de pruebas y que resultados hemos obtenido en nuestro experimentos sobre el rendimiento del protocolo, realizando al mismo tiempo un análisis crítico de los resultados de los resultados.Ingeniería de Telecomunicació

A novel coexistence scheme for IEEE 802.11 for user fairness and efficient spectrum utilization in the presence of LTE-U

A promising solution satisfying the industry’s demand to have minimum modification in LTE for its operation in unlicensed spectrum is duty cycled LTE-U scheme, which adopts discontinuous transmission to ensure fair coexistence with 802.11 (Wi-Fi) WLANs. Even though the scheme guarantees to maintain Wi-Fi network performance, the fairness among Wi-Fi users still remains arcane. In this work, we present a practical scenario where LTE-U, despite being discontinuous (by following an ON/OFF cycle), results in not only unfair throughput distribution among Wi-Fi users but also causes degradation in Wi-Fi AP’s downlink performance. This is due to the domination of few Wi-Fi users who harness channel in both ON and OFF durations of LTE-U, namely non-victim users over those who get access only in OFF duration, called victim users. In this paper, we studied the performance of victim and non-victim Wi-Fi users, and Wi-Fi AP while varying LTE-U ON fraction (i.e., duty cycle). A propitious scheme is proposed for WLANs, with regard to ease of implementation, employing Point/Hybrid Coordination Function (PCF/HCF) mode of 802.11, promising fairness among Wi-Fi users with improvement in the channel utilization of Wi-Fi network. The key idea is that the victim users, who can only be served during the LTE-U OFF period should be served in Contention Free Period (CFP)—so as to improve their throughputs and make them equally competitive with non-victim users. Also, we present an analytical model to demonstrate guaranteed improvement and to validate our simulation results