On Downlink Capacity of Cellular Data Networks with WLAN/WPAN Relays

We consider the downlink of a cellular network supporting data traffic. In addition to the direct traffic from the base-station, each user is equipped with the same type of 802.11-like WLAN or WPAN interface that is used to relay packets to further users and hence to improve the performance of the overall network. We are interested in analyzing what are the design guidelines for such networks and how much capacity improvements can the additional relay layer bring, in comparison to cellular networks. We consider a realistic dynamic setting where users randomly initiate downloads and leave the system upon transfer completion. A first objective is to provide a scheduling/relay strategy that maximizes the network capacity, which is the traffic in bit/s/cell that the network can support. We find that, regardless of the spatial traffic distribution, when the cell approaches saturation (the number of active users is very large), the capacity-achieving strategy divides the cell into two areas: one closer to the base-station where the relay layer is always saturated and some nodes receive traffic through both direct and relay links, and the further one where the relay is never saturated and the direct traffic does not exist. We further show that it is approximately optimal to use fixed link lengths, and we derive this length. We give a simple algorithm to calculate the cell capacity. The obtained capacity is shown to be independent of the cell size (unlike in traditional cellular networks), and it is 20%-60% higher than already proposed relay architectures when the number of users is large. Finally, we provide guidelines for future protocol design

Multilevel Downlink Relay Queue Aware And Loss Recovery Scheduling For Media Transmission In Wireless Cellular Networks

In this document, we study the result of multi hop relaying on the throughput of the downstream channel in cellular networks. In particular, we contrast the throughput of the multi hop method through that of the conventional cellular system, representing the feasible throughput development by the multi hop relaying under transitive transmission considerations. We moreover propose a hybrid control plan for the multi hop communicate, in which we activist the use of in cooperation, the straight transmission and the transitive multi hop relaying. Our study illustrates that the majority of the throughput gain can be obtained with the related of a transitive relaying scheme. Important throughput improvement could be moreover obtained by operating the simultaneous relaying transmission in conjunction with the non simultaneous transmission. We also disagree here that the multi hop relaying technology can be developed for mitigating injustice in qualityof- service (QoS), which arrive due to the location-dependent signal quality. Our outcomes demonstrate that the multi hop system can provide more even QoS over the cell district. The multi hop cellular system design can also be used as a selfconfiguring network mechanism that efficiently contains variability of traffic distribution. We have studied the throughput development for the consistent, as well as for the non uniform traffic distribution, and we conclude that the utilization of transitive relaying in cellular networks would be relatively robust to alter in the actual traffic distribution

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks

A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends

This paper examines the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state-of-the-art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. We also introduce the family of various jamming attacks and their counter-measures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.Comment: 36 pages. Accepted to Appear in Proceedings of the IEEE, 201

Device-to-device communications for 5G Radio Access Networks

Nowadays it is very popular to share video clips and images to one’s social network in the proximity. Direct device-to-device (D2D) communication is one of the means to respond to this requirement. D2D offers users improved end-to-end latency times, and additionally can provide higher data rates. At the same time the overall cellular network congestion decreases. D2D is also known as Proximity Services (ProSe). LTE is missing direct D2D communication. Currently D2D for 5G is standardised in the 3rd Generation Partnership Project (3GPP) Releases 12, and in parallel Mobile and wireless communications Enablers for the Twenty-twenty Information Society (METIS) project has D2D as one of its research topics. Multiple articles have been published about D2D communication. This thesis is a literature based thesis following D2D communication in 5G literature. The scope is to describe similarities and differences found in Technical Reports and Technical Specifications of the 3GPP Release 12, in deliverables written in METIS project and in some selected D2D related publications about D2D communications. 3GPP Release 12 concentrates on ProSe at least for public safety. ProSe communication out-of-coverage is only for public safety purposes. METIS provides multiple solutions for diverse D2D topics, for example, device discovery, radio resource management, mobility management and relaying. METIS provides solutions for D2D communication not yet mature enough for development and implementation but which might be realized in the future.Nykyisin on suosittua lähettää lyhyitä videoita tai kuvia läheisyydessä oleville ystäville. Laitteiden välinen suora kommunikointi eli D2D-viestintä tuo ratkaisun tähän vaatimukseen. D2D-viestinnän ansiosta viive lyhenee ja lisäksi siirtonopeudet kasvavat. Samaan aikaan koko verkon kuormitus vähenee. Suora kahden laitteen välinen kommunikointi puuttuu LTE:stä. Tällä hetkellä 3GPP Release 12 standardisoi suoraa kahden laitteen välistä kommunikointia. Samanaikaisesti Mobile and wireless communications Enablers for the Twenty-twenty Information Society (METIS) –projektin yhtenä tutkimuskohteenaan on kahden laitteen välinen suora kommunikointi, Lisäksi on lukuisia julkaisuja liittyen D2D-viestintään. Tämä diplomityö perustuu kirjallisuuteen. Sen tavoitteena on selvittää, miten kahden laitteen välistä suoraa kommunikointia on kuvattu 3GPP Release 12:ta teknisissä spesifikaatioissa, METIS-projektin julkaisuissa sekä muutamassa valitussa tieteellisessä julkaisussa. Tavoitteena on selvittää D2D-viestinnän yhtäläisyyksiä sekä poikkeamia. 3PGG Release 12 standardointi keskittyy D2D-viestinnän käyttöön ainakin julkisessa pelastustyössä. D2D-viestinnän tulee ainakin julkisessa pelastustyössä toimia myös siellä missä matkapuhelinverkko ei toimi tai sitä ei ole olemassa. METIS tarjoaa useita ratkaisuja D2D-viestinnän eri osa-alueille, esimerkiksi laitteiden tunnistamiseen, resurssien hallintaan, liikkuvuuden hallintaa ja viestien edelleen lähettämiseen. METIS-projekti on tuottanut D2D-viestinnän ratkaisuja, joiden toteuttaminen on järkevää ja mahdollista vasta tulevaisuudessa

A Detailed Characterization of 60 GHz Wi-Fi (IEEE 802.11ad)

The emergence of wireless local area network (WLAN) standards and the global system of mobile communication (GSM) in the early 1990s incited tremendous growth in the demand for wireless connectivity. Iterative technological enhancements to cellular and WLAN improved wireless capacity and created a breadth of new mobile applications. The continued increase in display resolutions and image quality combined with streaming displacing satellite/cable has created unprecedented demands on wireless infrastructure. Data-caps on cellular networks deter over consumption and increasingly shift the growing burden to Wi-Fi networks. The traditional 2.4/5 GHz Wi-Fi bands have become overloaded and the increasing number of wireless devices in the home, public, and workplace create difficult challenges to deliver quality service to large numbers of client stations. In dense urban areas, the wireless medium is subjected to increased interference due to overlapping networks and other devices communicating in the same frequency bands. Improvements to conventional Wi-Fi are approaching their theoretical limits and higher order enhancements require idealized conditions which are seldom attainable in practice. In an effort to supplant to scaling capacity requirements a very high frequency WLAN amendment has been proposed (IEEE 802.11ad). IEEE 802.11ad, also referred to as Wireless Gigabit (WiGig), operates in the globally unlicensed 60 GHz band and offers channel bandwidths nearly 100x as wide as 802.11n. The higher bandwidth facilitates multi-Gbps throughput even with the use of lower complexity modulation coding schemes (MCS). IEEE 802.11ad relies heavily on rate adaptation and high beamforming gain to mitigate interference and fading as signals in the 60 GHz band suffer from higher atmospheric ab- sorption and free space path loss (FSPL). Due to the unique nature of 60 GHz wireless there have been numerous research efforts. Many studies have been directed at simulation and modeling of the 60 GHz channel. However modeling the channel is difficult as real- world environments are highly dynamic with varying link quality and conditions which cannot be accurately predicted by conventional techniques. Some research is focused on medium access control (MAC) enhancements to improve overall capacity by coordinating concurrent links or reducing communication overhead for example. Lastly, there has been a limited amount of real world testing of 802.11ad due to lack of availability of commercial platforms and measurement instrumentation. Some researchers tested early generation devices in certain use cases such as in vehicles for media streaming, in data centers to augment the wired network, or in basic indoor and outdoor environments. This research contains two main components. In the first study, analytical models are applied to estimate line of sight (LOS) 802.11ad performance for realistic antenna param- eters. The second part contains a comprehensive evaluation of performance and reliability of early generation 802.11ad hardware. This characterization emphasizes environmen- tal performance (e.g. conference room, cubical farm, open office), multiple-client testing (multiclient), multiple network interference (spatial re-use), and stability in the presence of station mobility, physical obstructions, and antenna misalignment. In order to evaluate 802.11ad, early generation platforms from technology vendors were used in extensive test suites. The hardware tested included docks for wireless personal area networking (WPAN) applications, client laptop stations, and reference design access points (APs). Finally, a customized proof-of-concept (PoC) platform was engineered which allowed finer control over front end antenna configuration parameters such as: topology, placement and orienta- tion. The PoC also served as a suitable means to identify practical limitations and system design engineering challenges associated with supporting directional multi-Gbps (DMG) communication in the 60 GHz band

Resource allocation and optimization techniques in wireless relay networks

Relay techniques have the potential to enhance capacity and coverage of a wireless network. Due to rapidly increasing number of smart phone subscribers and high demand for data intensive multimedia applications, the useful radio spectrum is becoming a scarce resource. For this reason, two way relay network and cognitive radio technologies are required for better utilization of radio spectrum. Compared to the conventional one way relay network, both the uplink and the downlink can be served simultaneously using a two way relay network. Hence the effective bandwidth efficiency is considered to be one time slot per transmission. Cognitive networks are wireless networks that consist of different types of users, a primary user (PU, the primary license holder of a spectrum band) and secondary users (SU, cognitive radios that opportunistically access the PU spectrum). The secondary users can access the spectrum of the licensed user provided they do not harmfully affect to the primary user. In this thesis, various resource allocation and optimization techniques have been investigated for wireless relay and cognitive radio networks