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The focus of this paper is on the precoding and feedback strategies for a radio backhaul link between an access base station (ABS) and the hub base station (HBS) in the presence of mobile stations (MSs). In this paper it is assumed that the access and the backhaul links are simultaneous and use the same frequency band. Two feedback links are exploited at the ABS in order to optimize the communication...
GSM networks consist of cells that can support mobile users. Due to this mobility, it is expected that the network model can be different than that of wired networks which do not support mobile users. In our study, using empirical data provided by a GSM operator, TURKCELL, we analyze the associated network model from the mobility perspective. We first show that the handover rate of a regular cell...
The IEEE has proposed a narrowband PHY for the IEEE standard of wireless body area network. To maintain small phase transition of the π/2-DBPSK modulated signal and ensure simple receiver design, repetition code is used where lower data rate is needed. In this paper, we suggest to replace the repetition code by Walsh code to improve the interference cancelation capability of the system. Spreading-before-modulation...
Spectrum sensing is one of the most important tasks of cognitive radios (CRs) in future wireless systems and of user equipments (UEs) in next generation wireless networks (NGWNs). Therefore, deciding whether a specific portion of radio frequency (RF) spectrum is occupied or not is of paramount importance for all sorts of future wireless communications systems. In this study, a spectrum sensing method...
Almost all mobile image search applications available in the market only support text queries, which it is sometimes difficult to describe the needs in text and the text input is inconvenient on small devices. This paper proposed a mobile phone image search application that can perform practical image search processing in real-time. The early stage of the project is aimed to develop the application...
In this paper, we investigate the distribution of eigenvalues of HH† where the H and superscript † denote the MIMO (multiple input multiple output) channel matrix measured in urban microcell and conjugation and transposition. Our channel sounding system is the BECS (band exploration and channel sounding) 2006, which works at a carrier frequency of 3.705 GHz with 100 MHz bandwidth. From the measured...
Packet-level erasure correction is considered for downstream packets each of which is delivered from a base station to an individual receiver (i.e., user) over a lossy shared wireless network where only a very limited upstream feedback is provided. Note that, while the destination of each packet is a single user, each packet can be overheard by all users in the shared network. With exploiting this...
The 2360-2400 MHz frequency band has been proposed for the medical use of body sensor networks. This paper investigates the performance of IEEE 802.15.4 and its high rate extensions (to 500 kbps and 2 Mbps) in this new band. Two receiver structures, namely correlation and hard decision receivers are evaluated based on a number of performance metrics including BER, spectrum efficiency, throughput,...
In this paper a new speed estimation method for pedestrian dead-reckoning is presented. The proposed approach is based on the estimated channel frequency response of Digital Video Broadcasting-Terrestrial (DVB-T) signals. Correlation coefficients are calculated from the acquired envelopes and the coherence time is estimated for a certain correlation level. The algorithm gives an average error of less...
Signals of Galileo and modernized GPS will provide a new possibility in the next five years that will enable to overcome current limitations in indoor/urban environments. With modernization of GPS L1C, L2C, L5 and full deployment of Galileo, E1b, c, E5a, b, E6 signals will be available. It is therefore of major interest to assess new capabilities of the incoming GNSS signals and their potential for...
The first stage of the signal processing chain in a Global Positioning System (GPS) receiver is the acquisition, which provides for a desired satellite coarse code phase and Doppler frequency estimates to subsequent stages. Thus, acquisition is a two-dimensional search, implemented as demodulation and non-coherent correlation. For a certain Doppler estimate, software-defined GPS receivers typically...
In this report, an adaptive modulated orthogonal frequency division multiplexing (OFDM) scheme that provides efficient data transmission for correlated receiver antenna arrays is proposed. Previously reported adaptive modulation schemes generally select the modulation scheme based on the estimated carrier-to-noise ratio (CNR) on each subcarrier. However, in antenna array communication in addition...
A novel 3D cluster-based double-directional MIMO channel model with consideration of polarization is proposed and the modeling process is described in detail. The spatial channel model (SCM) proposed by 3GPP (3rd Generation Partnership Project) is retrieved and compared with the new model. Based on the new model, capacity and spatial correlation of the co-located dual- and triple-polarized MIMO systems...
Recent security methods propose to generate secret keys from Ultra Wide Band (UWB) channels. These solutions rely on the reciprocity and spatial channel correlation principles. This work aims at presenting empirical studies on the aforesaid properties. First, we verify the UWB reciprocity for different multipath scenarios. In these experiences, the reciprocity is always valid independently of distance...
Previous work predominantly assumes that the pdf of range measurements exhibit Gaussian characteristics. The objective of this paper is to scrutinize this assumption for different environments. Experiments are performed in both outdoor and indoor environments with Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) conditions using IEEE 802.15.4 compliant devices. These devices consist of a low-cost...
In this paper, the results of outdoor-to-indoor multiple-input multiple-output (MIMO) channel measurements at 780 MHz are presented. The motivation for these measurements was to provide actual measurement data needed to extend the International Mobile Telecommunications -Advanced (IMT-A) channel models to the frequencies around 400 - 900 MHz. There are publications reporting measurement results for...
This paper presents a comprehensive simulation study on the performance of broadband coupling-element-based multiantenna structures on a mobile terminal at the 2000 MHz Universal Mobile Telecommunications System (UMTS) frequency band with varying two significant hand effects; vertical position of hand along terminal chassis, and distance between hand palm and terminal chassis. The results reveal that...
Dense monitoring of time-varying 2D field by Wireless Sensor Networks (WSN) needs to define new strategies to aggregate and encode data according to 2D sensor deployments. In this paper optimal design of communication protocol for WSN is conveniently cast for a set of linear sensor networks (sensor arrays) synchronously monitoring a correlated 2D time-varying field (e.g., for tracking time variations)...
In multiple-input multiple-output (MIMO) broadcast channel, the lattice-reduction-aided (LRA) precoder is the modified zero-forcing beamforming (ZFBF) scheme which perturbs data symbols to reduce the transmit power. In this paper, we propose the optimal user group selection (UGS) scheme for the LRA-precoder to maximize the sum-rate in MIMO broadcast systems. We derive the approximated sum-rate of...
In cognitive radio networks, spectrum sensing is a fundamental function for detecting the presence of primary users in licensed frequency bands. Due to multipath fading and shadowing, the performance of detection may be considerably compromised. To improve the detection probability, cooperative sensing is an effective approach for secondary users to cooperate and combat channel impairments. This approach,...
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