Tuna Tugcu

Modulation Techniques for Communication via Diffusion in Nanonetworks

Communication via diffusion of molecules is an effective method for transporting information in nanonetworks. In this paper, novel modulation techniques called Concentration Shift Keying (CSK) and Molecule Shift Keying (MSK) are proposed for coding and decoding information of the so-called messenger molecule concentration waves in nanonetworks. The first technique, CSK, modulates the information via the variation in the concentration of the messenger molecules whereas MSK utilizes different types of messenger molecules to represent the information. Using simulation, the performance of these modulation techniques is evaluated in terms of susceptibility to noise and transmission power requirements. The new techniques achieve high channel capacity values, in particular, the MSK technique exhibits more robustness against noise and requires less power.

A survey on emerging broadband wireless access technologies

Wireless broadband technologies provide ubiquitous broadband access to wireless users, enabling services that were available only to wireline users. In this paper, we summarize emerging wireless broadband access technologies, ranging from WLANs to satellite communications. We explain the latest standards in the IEEE 802.11 and IEEE 802.16 families in detail. The MAC layer mechanisms of IEEE 802.11e, 802.11n, and 802.11s standards are explained as well as the point-to-multipoint and Mesh modes of IEEE 802.16. The recent mobility amendment to the WiMAX family, IEEE 802.16e, is also described. Though the earliest versions of some of these technologies date back to 1996 (such as IEEE 802.11) and some are obsolete (such as HiperLAN), they have been included in this survey for the sake of completeness. Wireless technologies can be categorized based on their coverage areas. IEEE 802.11 and ETSI HiperLAN standards are considered for wireless access in local areas. IEEE 802.16 and 802.22, ETSI HiperACCESS and HiperMAN, WiBro, and HAP technologies can be used to provide service in metropolitan areas. Lastly, IEEE 802.20 and satellite systems provide service as wide area networks. Since the aim of this survey is to summarize wireless broadband technologies for data services, technologies such as Wireless USB are excluded. 3G and 4G systems have also been excluded since they are covered in detail in [C. Smith, D. Collins, 3G Wireless Networks, second ed., McGraw-Hill Osborne Media, 2006; S.G. Glisic, Advanced Wireless Networks: 4G Technologies, Wiley Publishing, 2005].

Radio environment map as enabler for practical cognitive radio networks

Latest regulations on TV white space communications and emerging trends of spectrum access through geolocation databases relax the regulatory constraints on Cognitive Radios (CRs). Geolocation databases are designed to store information related to incumbents, and CRs are envisioned to consult this database before spectrum access. Spectrum occupancy and related environment information can be constructed using these geolocation databases. In that regard, Radio Environment Map (REM) is a promising tool that provides a practical means for the realization of cognitive radio networks (CRNs). It constructs a comprehensive map of the CRN by utilizing multi-domain information from geolocation databases, characteristics of spectrum use, geographical terrain models, propagation environment, and regulations. REMs contribute to cognition engines by building long-term knowledge via processing spectrum measurements collected from sensors to estimate the state of locations where there is no measurement data. In addition, REM utilizes feedback from the CRs and can apply various learning tools. The vision is to design CRNs such that CRs, though being simple devices without advanced cognitive functionalities, can become cognitive via REMs and operate in an efficient manner. In this paper, an overview of the REM concept is presented in various dimensions ranging from its architecture and stored information to REM construction techniques as well as REM quality metrics.

Three-Dimensional Channel Characteristics for Molecular Communications With an Absorbing Receiver

Within the domain of molecular communications, researchers mimic the techniques in nature to come up with alternative communication methods for collaborating nanomachines. This letter investigates the channel transfer function for molecular communications via diffusion. In nature, information-carrying molecules are generally absorbed by the target node via receptors. Using the concentration function, without considering the absorption process, as the channel transfer function implicitly assumes that the receiver node does not affect the system. In this letter, we propose a solid analytical formulation and analyze the signal metrics (attenuation and propagation delay) for molecular communication via diffusion channel with an absorbing receiver in a 3-D environment. The proposed model and the formulation match well with the simulations without any normalization.

Energy-Efficient Multichannel Cooperative Sensing Scheduling With Heterogeneous Channel Conditions for Cognitive Radio Networks

Spectrum sensing is an important aspect of cognitive radio networks (CRNs). Secondary users (SUs) should periodically sense the channels to ensure primary-user (PU) protection. Sensing with cooperation among several SUs is more robust and less error prone. However, cooperation also increases the energy spent for sensing. Considering the periodic nature of sensing, even a small amount of savings in each sensing period leads to considerable improvement in the long run. In this paper, we consider the problem of energy-efficient (EE) spectrum sensing scheduling with satisfactory PU protection. Our model exploits the diversity of SUs in their received signal-to-noise ratio (SNR) of the primary signal to determine the sensing duration for each user/channel pair for higher energy efficiency. We model the given problem as an optimization problem with two different objectives. The first objective is to minimize the energy consumption, and the second objective is to minimize the spectrum sensing duration to maximize the remaining time for data transmission. We solve both problems using the outer linearization method. In addition, we present two suboptimal but efficient heuristic methods. We provide an extensive performance analysis of our proposed methods under various numbers of SUs, average channel SNR, and channel sampling frequency. Our analysis reveals that all proposals with an energy minimization perspective provide significant energy savings compared with a pure transmission-time maximization (TXT) technique.

Interference effects on modulation techniques in diffusion based nanonetworks

Abstract Currently, Communication via Diffusion (CvD) is one of the most prominent systems in nanonetworks. In this paper, we evaluate the effects of two major interference sources, Intersymbol Interference (ISI) and Co-channel Interference (CCI) in the CvD system using different modulation techniques. In the analysis of this paper, we use two modulation techniques, namely Concentration Shift Keying (CSK) and Molecule Shift Keying (MoSK) that we proposed in our previous paper. These techniques are suitable for the unique properties of messenger molecule concentration waves in nanonetworks. Using a two transmitting couple simulation environment, the channel capacity performances of the CvD system utilizing these modulation techniques are evaluated in terms of communication range, distance between interfering sources, physical size of devices, and average transmission power.

Calcium signaling: overview and research directions of a molecular communication paradigm

In the ongoing effort to build micro- and nanoscale machines, one of the key approaches is the bio-hybrid approach, which focuses on the use of biological constructs and engineered cells. As a natural extension of this concept to nanoscale communication, molecular communication is an umbrella term encompassing various communication systems that are built based on biological intra- and intercellular communication methods, most of which use molecules and molecular concentration as the information carrier. Compared to other proposed molecular communication systems such as diffusion-based communication and microtubular networks, calcium signaling is expected to provide a faster and more controllable system that is suitable for information dissemination and group behavior in nanoscale sensor networks. In this article, we give a general overview of calcium signaling, a novel communication paradigm that uses intercellular calcium waves in biology as a baseline, explain its capabilities, limitations, and some possible deployment scenarios. We also describe various open issues of this novel communication system and elaborate on some research directions for calcium signaling.

ISI Mitigation Techniques in Molecular Communication

Molecular communication via diffusion (MCvD) is a new field of communication where molecules are used to transfer information. One of the main challenges in MCvD is the intersymbol interference (ISI), which inhibits communication at high data rates. Furthermore, at nanoscale, energy efficiency becomes an essential problem. Before addressing these problems, a predetermined threshold for the received signal must be calculated to make a decision. In this paper, an analytical technique is proposed to determine the optimum threshold, whereas in the literature, these thresholds are calculated empirically. Since the main goal of this paper is to build an MCvD system suitable for operating at high data rates without sacrificing quality, new modulation and filtering techniques are proposed to decrease the effects of ISI and enhance energy efficiency. As a transmitter-based solution, a modulation technique, molecular transition shift keying (MTSK), is proposed in order to increase the data rate by suppressing ISI. Furthermore, for energy efficiency, a power adjustment technique that utilizes the residual molecules is proposed. Finally, as a receiver-based solution, a new energy efficient decision feedback filter (DFF) is proposed as a substitute for the conventional decoders in the literature. The error performance of DFF and MMSE equalizers are compared in terms of bit error rates, and it is concluded that DFF may be more advantageous when energy efficiency is concerned, due to its lower computational complexity.

Location estimation-based radio environment map construction in fading channels

Latest regulations on TV white space communications and trend toward spectrum access through geolocation databases relax the regulatory constraints on cognitive radios. Radio environment map REM is a kind of improved geolocation database and an emerging topic with the latest regulations on TV white space communications. It constructs a comprehensive temperature map of the cognitive radio network operation area by utilizing multi-domain information from geolocation databases, characteristics of spectrum use, geographical terrain models, propagation environment, and regulations. REMs act as cognition engines by building long-term knowledge via processing spectrum measurements collected from sensors to estimate the state of locations without any measurement data. Active transmitter LocatIon Estimation based REM construction technique is proposed and compared with the well-known REM construction techniques such as Kriging and inverse distance weighted interpolation in shadow and multipath fading channels. The simulation results suggest that the LocatIon Estimation based REM construction outperforms the compared methods in terms of RMSE and correct detection zone ratio by utilizing additional information about channel parameters that can be estimated by classical least squares method easily.Copyright

Quality of Service in Mesh Mode IEEE 802.16 Networks

IEEE 802.16 standard supports two topologies: point-to-multipoint (PMP) and Mesh. In this paper, a QoS mechanism for the Mesh mode of IEEE 802.16 and a BS scheduler for the Mesh mode are proposed. Our QoS mechanism is developed by modifying the QoS mechanism of the PMP mode in IEEE 802.16. We compare our QoS mechanism against the default Mesh QoS mechanism of IEEE 802.16. The performance of both methods are analyzed by providing simulation results based on these two solutions. The results show that the default QoS mechanism introduces a delay of at least 100 ms, which makes it inappropriate for real time and multimedia services.