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In this paper, we study the estimation of multiple carrier frequency offsets (CFOs) in a uplink orthogonal frequency division multiple access (OFDMA) system using training sequences. The proposed method can estimate the CFO values of all users in one OFDM block without knowing the channel responses. Unlike most earlier results, the proposed method does not involve any nonlinear search and thus has...
A computationally efficient multi-criteria ranking based greedy (MCRG) algorithm is proposed for physical resource block (PRB) allocation in the fourth generation (4G) systems, where the users' utilities are ranked with multiple criteria, to enhance the performance of the basic greedy algorithm. The MCRG algorithm not only outperforms the previous single criterion ranking based greedy algorithm in...
Cellular network design for a specific area requires precise knowledge of the propagation characteristics of the radio channel in that area. This paper discusses the applicability of some well known theoretical models to the specific conditions in Izmir, Turkey. Three path loss models were used to predict the path loss in three different frequency bands. Advanced Okumura-Hata, Advanced Walfisch-Ikegami...
In this paper, we propose a scheduling algorithm for mobile WiMAX networks that distributes dynamically the bandwidth among service flows while giving real-time packets more chances to satisfy their QoS requirements. The scheduling in the proposed algorithm is assisted by the subscriber stations, hence requiring two-schedulers, a scheduler at the BS and another one at the SS, where preemption is applied...
The technological advancement in the area of wireless networking is ultimately envisioned to reach complete and seamless ubiquity, where virtually every point on earth will need to be covered by Internet access. Low connectivity environments have emerged as a major challenge, and accordingly Opportunistic Networks arose as a promising solution. While these networks do not assume the existence of a...
Fast-flux service network (FFSN) is consisted of a large scale of computers which have two main functions. Firstly, by providing a pool of huge number of IP addresses, the controller of FFSN can choose the IPs to provide services for their own domain name. Secondly, these computers can be served as agents to hide mother-ship. The character of FFSN is that the DNS records of domain name changes constantly...
Opportunistic networks are formed among mobile wireless devices based on spontaneous connectivity such as mobile phone networks using short range radio. Different setting of social structure in such networks gives significant impact on the feasibility and performance. In this paper we aim at understanding how social structure affects forwarding algorithm in various opportunistic network configurations...
In Vehicular Ad Hoc Networks (VANETs), the vehicular scenario requires smart signaling, smart road maintenance and other services. A brand new security issue is that the semitrusted Road Side Units (RSUs) may be compromised. In this paper, we propose a Threshold ElGamal system based key management scheme for safeguarding VANET from the compromised RSUs and their collusion with the malicious vehicles...
Wireless sensor networks (WSN) are an essential element of the Internet of Things. However, their performance is influenced by many factors such as interference from other co-located wireless communication technologies that are sharing the same spectrum and fading due to environmental factors. Channel hopping is one of several adaptation techniques introduced to mitigate these adverse effects. This...
Consider a backoff algorithm for medium access in wireless networks where a node chooses with probability 1−q to transmit right away and with probability q to transmit after CW slots, where CW is the maximum value of the contention window. We study a variation of the 802.11 protocol called XVBEB which uses the above backoff scheme and give a theoretical analysis of its saturation throughput. Simulation...
In many applications, the exact location of the sensor nodes is unknown after deployment. Localization is a process used to locate sensor nodes' positional coordinates, which is vital information. The localization is generally assisted by anchor nodes that are also sensor nodes but with known locations. Anchor nodes generally are expensive and need to be optimally placed for effective localization...
In this paper, we consider the bit rate maximizing problem and power minimizing problem with integer bit allocation. We will derive the duality between these two problems. We will show that if a transceiver is optimal for the power-minimizing problem, it is also optimal for the rate maxi-mizing problem, and the converse is true. For the power minimization problem with integer bit allocation, the solution...
As wireless and mobile technologies are becoming increasingly pervasive, an uninterrupted connectivity in mobile devices is becoming a necessity rather than a luxury. When dealing with challenged networking environments, this necessity becomes harder to achieve in the absence of end-to-end paths from servers to mobiles. One of the main techniques employed to such conditions is to simultaneously use...
IEEE 802.15.4 is the dominant Medium Access Control protocol in wireless sensor networks. To implement this protocol on such severely resource constraint devices, several trade-offs have to be considered. This paper presents an analysis of IEEE 802.15.4 software implementations available for typical sensor node systems, such as the MSP430 from Texas Instruments. We discuss the available implementations...
This paper presents a novel approach for radio environment database (RDB) techniques based on measurement to enable spectrum sharing in cognitive radio. The proposed database in this paper is used to estimate the received signal power of a primary user (PU) at a certain location by secondary users (SU). The received signal power is measured by the measurement nodes such as vehicles at different locations...
Precise localization of Wi-Fi Access Point (AP) is becoming increasingly important with the rise of diverse location-based services based on smartphone. In this article, we propose a new method for precise Wi-Fi AP localization using GPS information of smartphone. The idea is that the possible area of Wi-Fi AP location, called AP_Area, is first determined by measuring GPS information and the Received...
This paper studies the performance of transmitting User Datagram Protocol (UDP) packets over Terrestrial Trunked Radio (TETRA) networks. The IPERF program was used at the client station to generate UDP packets and at the server station to receive these packets and analyze them. Almost 1,800 measurements were taken for different packet sizes. The measurements were made for UDP packet size of 50 bytes...
In infrastructure-based mobile ad hoc networks, every mobile node has to send registration message periodically to register with an Internet Gateway (IG) or update its presence. Since registration messages are delivered to an IG, the mobile nodes near an IG can be congested, thus experiencing a lot of collisions in message transmission. This phenomenon is called “funneling effect.” In this paper,...
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