Constructive Interference (CI) phenomenon has been exploited by Glossy, a mechanism for low-latency and reliable network flooding and time synchronization for wireless sensor networks. Recently, CI has also been used for other applications such as data collection and multicasting in static and mobile WSNs. These applications base their working on the high reliability promised by Glossy regardless of the physical conditions of deployment, number of nodes in the network, and unreliable wireless channels that may be detrimental for CI. There are several works that study the working of CI, but they present inconsistent views. We study CI from a receiver's viewpoint, list factors that affect CI and also specify how and why they affect. We validate our arguments with results from extensive and rigorous experimentation in real-world settings. This paper presents comprehensive insights into CI phenomenon. With this understanding, we improve the performance of CI through an energy-efficient and distributed algorithm. We cause destructive interference on a designated byte to provide negative feedback. We leverage this to adapt transmission powers. Compared to Glossy, we achieve 25% lesser packet losses while using only half of its transmission power.@en

The rapid proliferation of wireless communication devices and the emergence of a variety of new applications have triggered investigations into next-generation mobile broadband systems, i.e. 5G. Legacy 2G-4G systems covering large areas were envisioned to serve both indoor and outdoor environments. However, in the 5G era, 80 percent of all traffic is expected to be generated indoors. Hence, the current approach of macrocell mobile networks, where there is no differentiation between indoors and outdoors, needs to be reconsidered. We envision 60 GHz mmWave picocell architecture to support highspeed indoor and hotspot communications. We envisage the 5G indoor network as a combination of, and interplay between, 2.4/5 GHz having robust coverage and 60 GHz links offering a high data rate. This requires intelligent coordination and cooperation. We propose a 60 GHz picocellular network architecture, called CogCell, leveraging ubiquitous WiFi. We propose to use 60 GHz for the data plane and 2.4/5GHz for the control plane. The hybrid network architecture considers an opportunistic fall-back to 2.4/5 GHz in case of poor connectivity in the 60 GHz domain. Further, to avoid the frequent re-beamforming in 60 GHz directional links due to mobility, we propose a cognitive module, a sensor- assisted intelligent beam switching procedure, that reduces communication overhead. We believe that the CogCell concept will help future indoor communications and possibly outdoor hotspots, where mobile stations and access points collaborate with each other to improve the user experience@en

Universal Mobile Telecommunications Systems (UMTS) is a third-generation cellular network that enables high-speed wireless Internet connectivity. On the other hand, the IEEE 802.11 ad hoc mode enables peer-to-peer short-range communications without infrastructure support. In this paper, we describe the design and implementation of a novel integrated UMTS and IEEE 802.11 ad hoc network modules in the Network Simulator (ns-2). The implementation is described from an overall design architecture to the realization of different architectural parts. A new mobile gateway is specially designed for the integrated network. With the hiearchial addressing mechanism, routing for the integrated network from wired network in UMTS network to the ad hoc network is realized. Simulations were carried out to validate the design and implementation in ns-2. Using our ns-2 modules, protocol designers can desgin and evaluate new protocols that run on such an integrated network.@en

A personal network is an overlay network which builds on different wireless networking technologies. This overlay network is responsible of glueing the different wireless networking technologies. In this paper, we consider the cooperation of two key technologies te realize a personal network, namely, Wireless Personal Area Network and Universal Mobile Telecommunications Systems (UMTS). The co-operation poses a new set of problems as these technologies were not designed to intework with each other. In this paper, we describe each of these problems and their solutions.@en

Radio over Fiber (RoF) techniques have been long recognized as the promising solution for indoor networking at millimeter-wave bands. We discuss the possbile deployment scenarios of an RoF network for indoor environment. In this paper, we try to find the answer to the question as to which Medium Access Control (MAC) protocol is suitable for an RoF network. To substantiate our claims, performance analysis of two popular MAC protocols employing R0F - IEEE 802.11 representing the distributed control protocol family - is presented. We show that RoF techniques canb e applied to both protocols. We also show that the centralized control is an appropiate candidate fro RoF networks. This study is expected to contribute to the speedy deployment of RoF for indoor network deployment.@en

Complementary characteristics of the WLAN and WWAN networks have led tot the current research efforts towards thier integration. The integration can be done at different levels in the network, resulting in interworking architectures of different capabilities and with different degrees of complexity. We concentrate here on the WLAN integration at the UMTS radio sccess level. Due to diversity of the existing as well emerging higher-capacity WLAN technologies, thier gradual integration into the future integrated mobile network, while keeping the operators' investments protected, becomes an important issue. In this paper, we address such an interworking architecture and discuss necessary modifications, aiming at defining a framework that would require as minimal modifications as poddible for any new type of the WLAN technology that is to be embedded.@en

We study the application of multipath routing to enhance reliability of high quality video in 60 GHz radio indoor networks. We propose a cross-layer approach taking into account the possibility of layered-coding for video stream transportation and the characteristics of 60 GHz radio links based on our earlier studies on the stability of 60 GHz radio links. Further three traffic allocation schemes have been investigated and compared for the best use of multipath capacity.@en

The WiMAX IEEE 802.16 standard is capable of providing very high data rates over large areas. This wireless broadband access technology is expected to open new market segments and bring a wide range of new applications and services. The WiMAX integration into the existing mobile network environment currently draws a lot of attention. In this paper, we discuss the integration of IEEE 802.16e into the GSM-based 2.5G and 3G mobile networks, which may be promising especially for users in non-urban areas. More specifically, we concentrate on the integration at the radio access level of the UMTS and GPRS networks.@en

In this paper, we investigate the robustness of the 60 GHz connectivity in typical indoor environments by analyzing the outage probability. We define three realistic indoor scenarios which may host the 60 GHz networks in the future and perform simulations with a verified 3D ray tracing tool on them. In the first set of simulations, we show the impact of access unit position on the connectivity. In the next step, we show that increasing the obstacle density linearly decreases the outage probability of the 60 GHz network and this decrease is found to be sharper for certain positions of the access point. In the last step, we demonstrate the direct effect of reflective surface availability on the connectivity. A 60 GHz indoor network relying solely on the reflections in the absence of line-of-sight path is very vulnerable to outages even in moderately populated indoor environments.@en

We propose an architecture using the 60 GHz Radio over Fiver along with a novel concept of forming Extended Cells (EC). Since in the indoor environment , the propagation of millimeter wave signals is strongly hindered by walls, people, furniture, etc., a mobile user might experience frequent loss of connection as soon as one movers from one cell to antother. With ECs one can create sufficient overlap areas between cells, thus ensuring a semaless communication environemtn to achieve lesser handovers and call drop. We illustrate the effectivieness of the proposed architecture throught simulation. We continue further to model the mobility of users in the indoor environment to arrive at an expression to find the call blocking probability.@en

In Dynamic Spectrum Access Networks, detection of spectral opportunity can be viewed as a frequency scanning process leading to detection of legitimate users of radio channel. Continuous scanning results in complete detection but it becomes inefficient in terms of power consumption at each mobile node. This is more profound whem some frequency bands are rarely used by legitmate users. Therefore, it is necessary to study the scanning process which is periodically switched off according to some distribution to reduce power consumption. We analytically show that with the increasing number of scanning nodes thier average scanning-on time decrease while the efficiency approaches to the one node case. Based on the results we propose a scanning scheme for single and multiple node cases, that dynamically assign average scanning-on time to nodes when the number of nodes in the network is varying with time. At the scanning-off instance, depending on whether we allow transmission or not, we come across two cases which we also analyze: interfering and non-intefering.@en

With the increase in the capacity of mobile communication devices, it is but natural to expect that these devices would work ubiquitously anywhere anytime to offer high data rate support. Recently 60 GHz frequency band has been identified as an obvious choice for the high data rate indoor communications. However, as the 60 GHz radio system relies on line-of-sight (LOS) transmission for achieving Gbps data rate, the communication can be easily interrupted by obstructions breaking the LOS link, which happens often due to the movement of people in a typical indoor environment. In this paper, we define and present an analytical model for assessing link stability of 60 GHz radio for indoor wireless networks. We have developed a ray-based model to calculate the shadowing loss caused by the presence of people around the communication link while taking into account the indoor channel characteristics of 60 GHz radio and the antenna configuration. We have further considered different types of mobility of people with the ray-based model of 60 GHz link to obtain a holistic link stability model in realistic scenarios. We have given examples to show the relevance of our model and its applicability using both simulation and numerical evaluations.@en

As ZigBee networks operate on the license-free 2.4 GHz Industrial, Scientific, and Medical (ISM) frequency band, coexistence issues arise because many other wireless technologies such as IEEE 802.11b/g Wireless Local Area Networks (WLANs), Bluetooth, cordless telephones, etc., also use the same frequency band. To mitigate interference, ZigBee specification proposes a feature called frequency agility, which refers to the ability of ZigBee networks to change the operational channel in the presence of interference. However, for a large-scale ZigBee network, changing the whole network operational channel to an idle one, may be neither appropriate if there is only local interference nor possible if there is no any single idle channel available globally. In this paper, we propose a distributed adaptive multi-channel MAC interference-avoidance protocol, which enables a conventional large-scale single-channel ZigBee network to distributedly, adaptively and partially change the operational channel in order to avoid local interference. OPNET simulation results show that the protocol can efficiently and effectively improve the ZigBee network robustness and therefore the coexistence performance.@en

Recently, indoor positioning systems (IPSs) have been designed to provide location information of persons and devices. The position information enables location-based protocols for user applications. Personal networks (PNs) are designed to meet the users' needs and interconnect users' devices equipped with different communications technologies in various places to form one network. Location-aware services need to be developed in PNs to offer flexible and adaptive personal services and improve the quality of lives. This paper gives a comprehensive survey of numerous IPSs, which include both commercial products and research-oriented solutions. Evaluation criteria are proposed for assessing these systems, namely security and privacy, cost, performance, robustness, complexity, user preferences, commercial availability, and limitations.We compare the existing IPSs and outline the trade-offs among these systems from the viewpoint of a user in a PN.@en

Abstract¿Personal Networks (PN) is a concept in the area of modern communication networks in which devices belonging to a person cooperate to offer services to the person regardless of their geographical locations. A PN may consist of several adhoc sub-networks (or clusters) which are interconnected through infrastructure networks such as the Internet. Failure of personal devices due to battery shortage is one of the main threads for service availability in PNs. Power-aware routing (PAR) has been proposed as an effective scheme to prolong the lifetime of battery-operated nodes in wireless ad-hoc networks. This scheme, however, could be utilized in PNs as well, since a PN cluster can be modeled as a wireless ad-hoc network. Aiming at prolonging the lifetime of nodes in PNs, in this paper we propose a PAR algorithm for PNs and we evaluate and compare its performance with the performance of other PAR algorithms proposed so-far for wireless ad-hoc networks. We analyze the effect of node density, routing overhead, heterogeneity of PN nodes in terms of their power supplies, and communication pattern within PN clusters on the performance of the PAR algorithms. Taking into account various parameters, we show that in a PN environment, our proposed scheme can profoundly extend the lifetime of PN nodes compared to the other algorithms. We also show that there can be an optimal value for route refresh interval, as a parameter which affects the generated routing overhead, and the node density of PN clusters, in such a way that the network lifetime is maximized.@en

This paper addresses the issues of desiging an infrastructure to support seamless in-building communication at the 60 GHz band. Recently, the 60-GHz band has received much attention due to its 5-GHz of available spectrum. Howevver, the propagation of signals in this band is strongly hindered by attenuation and line-of-sight requirements. The situation gets worse in the in-building environment where signal propagation is obstructed by physical objects such as walls, furniture etc. In this paper, we present a novel Radio over Fiber (RoF) architecture that is cost-effective and is able to deliver high data-rate of the order of gigabits. To ensure a seamless communication environment at the 60GHz band, we propose the concept of Extended Cells (EC) in order to create sufficient overlap areas. Finally, we illustrate the effectiveness of the proposed architecture by simulating an in-building network at the 60 GHz band employing the RoF and EC concepts.@en

Beyond third-generation mobile communications networks will be comprise a multitude of integrated legacy and new wireless networks. Mobile ad hoc networks are such new networks. In this paper, we consider the integration of the Universal Mobile Telecommunications System (UMTS) that is a third-generation legacy mobile network and mobile ad hoc networks are built using the IEEE 802.11 technology. Since UMTS and IEEE 802.11-based ad hoc networks have different but complementary features, the integration would leverage the advantages of each other. We have investigated the performance of real-time traffic over such an integrated network. The considered UMTS radio channel bit rates were ranging from 64 kb/s to 2 Mb/s with varying channel block error rates. Simulation results show that higher UMTS channel bit raters incur the lower end-to-end packet delay. In addition, the end-to-end delay incurrec by the 802.1-based multi-hop ad hoc network is small as compared with the UMTS channel for low application traffic load. However, for large application traffic load, the performance bottleneck is shofted to the 802.11-based multi-hop ad hoc network.@en

The 60 GHz technology has a great potential to provide wireless communication at multi-gigabit rates in future home networks. To maintain the network connectivity with 60 GHz links, which are highly susceptible to propagation and penetration losses, is a major challenge. The quality and the robustness of the 60 GHz links can be improved by employing relay nodes in the network. In this paper, the contribution of relaying to the connectivity and the quality of the 60 GHz radio links is studied by modeling three indoor scenarios. It is analytically and through simulations shown that having a relay node in a 60 GHz network decreases the average freespace path loss 33% in the worst case scenario. The effects of relay device position and the obstacle density on the improvement of the average received signal level are investigated with a verified 3D ray tracing tool. A comparative simulation study on the performance of different relay configurations under various network conditions is conducted. The results yield that even a single relay device positioned at the height of other nodes can improve 50% of the links in considerable levels in a 60 GHz indoor network. It is also shown that additional relay nodes do not contribute to 60 GHz indoor connectivity significantly, if there are two properly positioned relay devices in a network which is moderately populated.@en