| 1. |
- Abbas, Muhammad Tahir, et al.
(författare)
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Road-Aware Estimation Model for Path Duration in Internet of Vehicles (IoV)
- 2019
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Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 109:2, s. 715-738
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Tidskriftsartikel (refereegranskat)abstract
- In Internet of Vehicles (IoV), numerous routing metrics have been used to assess the performance of routing protocols such as, packet delivery ratio, throughput, end-to-end delay and path duration. Path duration is an influential design parameter, among these routing metrics, that determines the performance of vehicular networks. For instance, in highly dynamic scenarios, it can be used to predict link life time in on-demand routing protocols. In this paper, we propose an infrastructure-assisted hybrid road-aware routing protocol which is capable of enhanced vehicle-to-vehicle and vehicle-to-infrastructure communication. A remarkable aspect of the proposed protocol is that it establishes a link between path duration and fundamental design parameters like vehicular velocity, density, hop count and transmission range. Although, a lot of research has been previously performed, a well defined analytical model for IoV is not available in the literature. Precisely, a relation between path duration and vehicular velocity has not been validated in the previous studies. Experimental results show that the increased packet delivery ratio with reduced end-to-end delay can be achieved by the prediction of path duration. Proposed model for path duration is validated by getting experimental results from network simulator 3 (NS3) and analytical results from MATLAB. In addition, SUMO simulator was used to generate real time traffic on the roads of Gangnam district, South Korea.
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| 2. |
- Andersin, Michael, et al.
(författare)
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Distributed Discrete Power Control in Cellular PCS
- 1998
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Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 6:3, s. 211-213
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Tidskriftsartikel (refereegranskat)abstract
- Transmitter power control has proven to be an efficient method to control cochannel interference in cellular PCS, and to increase bandwidth utilization. Power control can also improve channel quality, lower the power consumption, and facilitate network management functions such as mobile removals, hand-off and admission control. Most of the previous studies have assumed that the transmitter power level is controlled in a continuous domain, whereas in digitally power controlled systems, power levels are discrete. In this paper we study the transmitter power control problem using only a finite set of discrete power levels. The optimal discrete power vector is characterized, and a Distributed Discrete Power Control (DDPC) algorithm which converges to it, is presented. The impact of the power level grid on the outage probability is also investigated. A microcellular case study is used to evaluate the outage probabilities of the algorithms.<
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| 3. |
- Andersson, Karl, et al.
(författare)
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Optimized access network selection in a combined WLAN/LTE environment
- 2011
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 61:4, s. 739-751
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Tidskriftsartikel (refereegranskat)abstract
- Multimode terminals equipped with multiple radio access technologies are becoming increasingly popular. At the same time, network operators and service providers seek opportunities to deliver seamless services cost effectively, leveraging a variety of radio access technologies using both licensed and unlicensed spectrum. In order to standardize the operations of such complex environments 3GPP is currently working on IP flow mobility and mobile data offload solutions. This article proposes and evaluates a new access network selection procedure in such a combined WLAN/LTE environment. The proposed solution takes not only parameters available in the mobile node and its current and candidate access networks into account, but performs an optimization on the heterogeneous wireless network level as well. An optimization model based on an approximate solution to the well-known bin packing problem is presented. Also, there is a signaling scheme for distribution handling presented. Results from simulations performed in OPNET Modeler show improvements compared to basing handover decisions on locally available information only.
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| 4. |
- Arunachalam, Ajay, 1985-
(författare)
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Rock, Paper, Scissors Game Based Model for Content Discovery in P2P MANETs
- 2020
-
Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X.
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Tidskriftsartikel (refereegranskat)abstract
- Resource discovery is a key challenge in dynamic environment such as Peer-to-Peer (P2P) MANETs. To leverage the lookup costs and efficiently discover the resources, the peers in a P2P network communicate with each other forming one-or-more overlay structure. And, thus the peer’s connections in such overlay networks plays a crucial role. To harness this, we propose a model that focuses on the underlying network topology as each virtual link of the overlay network is supported by a path in the underlying physical network. Also, we design a new resource discovery algorithm that uses the famous Rock-Paper-Scis-sors (RPS) game ideology. In this work, we present a Rock-Paper-Scissors-Game-Based (RPSGB) algorithm for content discovery in mobile peer-to-peer network. The proposed work focuses on providing efficient resource discovery scheme in such a dynamic network, using the game theory concepts. Our scheme is a light-weight model aimed to suit the unstructured architecture better. The major goal of this work, is to reduce the consumption of power, minimize the lookup cost, lower the bandwidth consumption, and increase the hit ratio. We compare our scheme with the traditional well-known benchmarked schemes. After evaluation, the simulation results justify the effectiveness of the proposed protocol. The obtained results show that the proposed scheme substantially decreases the network traffic, lowers the battery power and bandwidth consumption, while having good search efficiency. Also, the search latency is minimized. The result justifies that RPSGB algo-rithm proposes to make resource searching much more efficient, and improves the statistics against the posed challenges.
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| 5. |
- Belleschi, Marco, et al.
(författare)
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Benchmarking Practical RRM Algorithms for D2D Communications in LTE Advanced
- 2014
-
Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 82:2, s. 883-910
-
Tidskriftsartikel (refereegranskat)abstract
- Device-to-device (D2D) communication integrated into cellular networks is an advanced tool to take advantage of the proximity of devices and allow for reusing cellular resources and thereby to increase the user bitrates and the system capacity. However, the introduction of D2D in legacy long term evolution (LTE) cellular spectrum requires to revisit and modify the existing radio resource management and power control (PC) techniques in order to fully realize the potential of the proximity and reuse gains and to limit the interference to the cellular layer. In this paper, we examine the performance of the legacy LTE PC tool box and benchmark it against an utility optimal iterative scheme. We find that the open loop PC scheme of LTE performs well for cellular users both in terms of the used transmit power levels and the achieved signal-to-interference-and-noise-ratio distribution. However, the performance of the D2D users as well as the overall system throughput can be boosted by the utility optimal scheme, by taking better advantage of both the proximity and the reuse gains. Therefore, in this paper we propose a hybrid PC scheme, in which cellular users employ the legacy LTE open loop PC, while D2D users exploits the utility optimizing distributed PC scheme. We also recognize that the hybrid scheme is not only nearly optimal, and can balance between spectral and energy efficiency, but it also allows for a distributed implementation at the D2D users, while preserving the LTE PC scheme for the cellular users.
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| 6. |
- Ben Slimane, Slimane
(författare)
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Combined transmitter diversity and multi-level modulation techniques
- 2006
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 39:2, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- Orthogonal transmitter diversity such as frequency diversity and time diversity is quite simple to implement and, with optimum signal combining, can take full advantage of fading multipath channels. However, such a scheme has a bandwidth efficiency that decreases inversely with the number of diversity branches making it less attractive in wireless communications applications. This paper considers combined orthogonal transmitter diversity and multi-level linear modulation techniques. The idea is to view the signal constellations of the modulation scheme in an augmented signal space formed by the modulation signal dimension and the number of branches of the transmitter diversity scheme. This augmented signal space provides a good spread for the modulation signal points and can be quite efficient for high-level linear modulation techniques. The obtained results show that this combined scheme, not only improves the system performance on both additive white Gaussian noise and fading multipath channels, but also improves the bandwidth efficiency of orthogonal transmitter diversity.
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| 7. |
- Biernacki, Arkadiusz, et al.
(författare)
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Comparative Performance Study of LTE Downlink Schedulers
- 2014
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Ingår i: Wireless personal communications. - : Springer US. - 0929-6212 .- 1572-834X. ; 7:2, s. 585-599
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Tidskriftsartikel (refereegranskat)abstract
- Long time evolution (LTE) represents an emerging and promising technology for providing broadband, mobile Internet access. Because of the limitation of available spectrum resource, high spectrum efficiency technologies such as channel-aware scheduling need to be explored. In this work, we evaluate the performance of three scheduling algorithms proposed for LTE downlink transmission. The evaluation takes place in mixed traffic scenarios and aims at exploring strengths and weaknesses of the proposed algorithms. Simulation results illustrate the importance of real-time traffic awareness by schedulers when a specified level of quality of service is required. The research shows that lack of prioritisation of multimedia traffic will lead to severe degradation of video and VoIP services even with a relatively low network load.
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| 8. |
- Deumal, Marc, et al.
(författare)
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Evaluation of Performance Improvement Capabilities of PAPR-reducing Methods
- 2008
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Ingår i: Wireless Personal Communications. - 1572-834X .- 0929-6212.
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Tidskriftsartikel (refereegranskat)abstract
- One of the major drawbacks of multicarrier modulation is the large envelope fluctuations which either require an inefficient use of high power amplifiers or decrease the system performance. Peak-to-average power ratio (PAPR) is a very well known measure of the envelope fluctuations and has become the cost function used to evaluate and design multicarrier systems. Several PAPR-reducing techniques have been proposed with the aim to alleviate back-off specifications or increase the system performance. Besides the fact that these techniques have varying PAPR-reduction capabilities, power, bandwidth and complexity requirements, it is interesting to notice that the performance of a system employing these techniques has not been fully analyzed. In this paper we, first, develop a theoretical framework for both PAPR and the distortion introduced by a nonlinearity, and then simulate an OFDM system employing several well known PAPR-reducing techniques from the literature. By means of the theoretical analysis and the simulation results we will show the relation between PAPR and the performance of OFDM systems when a clipping device is present and we will evaluate the real performance improvement capabilities of the PAPR-reducing methods. The agreement between the theoretical and the simulation results demonstrate the validity of the analysis.
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| 9. |
- Duong, Quang Trung, et al.
(författare)
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Cross-Layer Design for MRT Systems with Channel Estimation Error and Feedback Delay
- 2011
-
Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 58:4, s. 681-694
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we analyze the effect of channel estimation error and delayed feedback on the performance of a cross-layer scheme combining adaptive modulation for maximum ratio transmission (MRT) at the physical layer and truncated automatic repeat request (T-ARQ) at the link layer. The cross-layer attempts to maximize the spectral efficiency under predetermined quality of service requirements, namely, delay and packet-loss constraints. In particular, we derive closed-form expressions for the average packet error rate, average achievable spectral efficiency, and the outage probability, hence, enabling to evaluate the performance of the cross-layer scheme in the presence of imperfect channel estimation at the receiver and delayed feedback path between the receiver and transmitter. The final expressions are given in terms of the minimum and maximum number of transceiver antennas as well as the channel estimation error and feedback delay parameters. We further show that with a small amount of channel estimation error and/or feedback delay the system performance is severely degraded. Specifically, numerical results demonstrate that with channel estimation error and feedback delay the performance of the cross-layer scheme is even worse than that of T-ARQ only. We also observe an irreducible outage probability floor appearing in the high signal-to-noise regime.
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| 10. |
- Duong, Quang Trung, et al.
(författare)
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Pairwise Error Probability of Distributed Space--Time Coding Employing Alamouti Scheme in Wireless Relays Networks
- 2009
-
Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 51:2, s. 231-244
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we analyze the pairwise error probability (PEP) of distributed space-time codes, in which the source and the relay generate Alamouti space--time code in a distributed fashion. We restrict our attention to the space-time code construction for Protocol III in [1]. In particular, we derive two closed-form approximations for PEP when the relay is either close to the destination or source and an upper bound for any position of the relay. Using the alternative definition of $Q$-function, we can express these PEPs in terms of finite integral whose integrand is composed of trigonometric functions. We further show that with only one relay assisted source-destination link, system still achieves diversity order of two, assuming single-antenna terminals. We also perform Monte-Carlo simulations to verify the analysis.
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| 11. |
- Edfors, Ove, et al.
(författare)
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Analysis of DFT-Based Channel Estimators for OFDM
- 2000
-
Ingår i: Wireless personal communications. - 0929-6212 .- 1572-834X. ; 12:1, s. 55-70
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we analyze the performance of three low-complexity channel estimators, based on the discrete Fourier transform (DFT), for orthogonal frequency-division multiplexing (OFDM) systems. Estimators of this type have been analyzed for discrete-time channels, and we extend this analysis to continuous-time channels. We present analytical expressions for their mean-squared error (MSE) and evaluate their complexity vs. symbol-error rate (SER) for 16-QAM. The analysis shows that this type of estimators may experience an irreducible error floor at high SNRs. However, in one of the three estimators the error floor can be eliminated while the complexity stays low and the performance is maximized.
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| 12. |
- Ferrer-Coll, Javier, et al.
(författare)
-
Antenna Cross Correlation and Ricean -Factor Measurements in Indoor Industrial Environments at 433 and 868 MHz
- 2013
-
Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 73:3, s. 587-593
-
Tidskriftsartikel (refereegranskat)abstract
- The Ricean K-factor and antenna diversity properties for indoor industrial environments have been characterized for 433 and 868 MHz. The high amount of metallic structures gives a multipath environment that heavily differs from other environments e.g. indoor office environments. The results show that low correlation between receiving antennas can be achieved for shorter antenna distances than in other environments.
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| 13. |
- Ferrer-Coll, Javier, et al.
(författare)
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Detection and Suppression of Impulsive Noise in OFDM Receiver
- 2015
-
Ingår i: Wireless personal communications. - : Springer-Verlag New York. - 0929-6212 .- 1572-834X.
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, the use of wireless systems in industrial applications has experienced spectacular growth. Unfortunately, industrial environments often present impulsive noise which degrades the reliability of wireless systems. OFDM is an enhanced technology used in industrial communication to monitor the work and movement of employees using high quality video. However, OFDM is sensitive to high amplitude impulsive noise because the noise energy spreads among all OFDM sub-carriers. This paper proposes a receiver structure consisting of two stages: a detector stage combining Fisher’s Quadratic discriminant and Gaussian Hypothesis techniques, and a suppression stage optimized by setting well defined thresholds. The receiver structure has been tested by simulations and measurements providing an increment in the probability of detection and improving the system performance.
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| 14. |
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| 15. |
- Ganesan, Girish, et al.
(författare)
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Orthogonal Space-Time Block Codes with Feedback
- 2004
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Ingår i: Wireless personal communications. - : Kluwer Academic Publishers. - 0929-6212 .- 1572-834X. ; 28:4, s. 287-312
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we consider how Orthogonal Space-Time Block Codes (OSTBC) can be used in the presence of feedback from the receiver to the transmitter. First, we survey how some of the feedback techniques for AWGN channels with fading can be applied to OSTBC. Then we consider a simple scheme with diagonal weighting. The optimal diagonal weighting matrix, which minimizes the probability of error, is derived. The optimal weights depend on the channel and, hence, a feedback becomes necessary. However, the required feedback can be accomplished using log2 (n t) bits, where n t is the number of transmit antennas. Simulations show that relatively significant gains can be achieved with the diagonal weighting scheme. In a practical system it is quite possible that the bits that are fed back to the transmitter are in error. In that case we show that there will be a loss of diversity. To overcome this loss, we develop weighting schemes that are error tolerant and always perform better than the unweighted OSTBC (even in the presence of feedback errors).
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| 16. |
- Gil Jiménez, Victor P., et al.
(författare)
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Methods for Compression of Feedback in Adaptive Multi-carrier 4G Schemes
- 2008
-
Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 47:1, s. 101-112
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, several algorithms for compressing the feedback of channel quality information are presented and analyzed. These algorithms are developed for a proposed adaptive modulation scheme for future multi-carrier 4G mobile systems. These strategies compress the feedback data and, used together with opportunistic scheduling, drastically reduce the feedback data rate. Thus the adaptive modulation schemes become more suitable and efficient to be implemented in future mobile systems, increasing data throughput and overall system performance.
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| 17. |
- Grandhi, Sudheer A., et al.
(författare)
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Constrained Power Control
- 1994
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Ingår i: Wireless personal communications. - : Kluver Academic Publishing. - 0929-6212 .- 1572-834X. ; 1:4, s. 257-270
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Tidskriftsartikel (refereegranskat)abstract
- High system capacities can be achieved by controlling the transmitter power in multiuser radio systems. Power control with no constraint on the maximum power level has been studied extensively in earlier work [1–18]. Transmitter power is at a premium in radio systems such as cellular systems and PCS. There is a limit on the maximum transmitter power especially at the terminals (e.g. mobile units and handsets) since the power comes from a battery. In this paper we study power control that maximizes the minimum carrier to interference ratio (CIR), with a constraint on the maximum power. The optimal power vector solution lies on the boundary of the constrained power vector set and achieves a balance in the CIR's. Results indicate that the constraints do not induce any stability problems. A distributed scheme with favourable convergence properties and close to optimum performance is presented. Simulation results show that the algorithm tries to maximize the number of terminals served with CIR greater than or equal to the target CIR, while conserving power.
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| 18. |
- Hamid, Mohamed, 1983-, et al.
(författare)
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Empirical Statistical Model for LTE Downlink Channel Occupancy
- 2017
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 96:1, s. 855-866
-
Tidskriftsartikel (refereegranskat)abstract
- This paper develops an empirical statistical channel occupancy model for downlink long-term evolution (LTE) cellular systems. The model is based on statistical distributions mixtures for the holding times of the channels. Moreover, statistical distribution of the time when the channels are free is also considered. The data is obtained through an extensive measurement campaign performed in Stockholm, Sweden. Two types of mixtures are considered, namely, exponential and log-normal distributions to fit the measurement findings. The log-likelihood of both mixtures is used as a quantitative measure of the goodness of fit. Moreover, finding the optimal number of linearly combined distributions using the Akaike information criterion (AIC) is investigated. The results show that good fitting can be obtained by using either exponential or log-normal distributions mixture. Even though, the fitting is done for a representative case with a tempo-spatial consideration, the model is yet applicable in general for LTE and other cellular systems in a wider sense.
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| 19. |
- Hossain, Mohammad Istiak, 1987-, et al.
(författare)
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Comparison of LPWAN Technologies : Cost Structure and Scalability
- 2021
-
Ingår i: Wireless personal communications. - : Springer Nature. - 0929-6212 .- 1572-834X. ; 121:1, s. 887-903
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Tidskriftsartikel (refereegranskat)abstract
- Small-scale commercial rollouts of Cellular-IoT (C-IoT) networks have started globally since last year. However, among the plethora of low power wide area network (LPWAN) technologies, the cost-effectiveness of C-IoT is not certain for IoT service providers, small and greenfield operators. Today, there is no known public framework for the feasibility analysis of IoT communication technologies. Hence, this paper first presents a generic framework to assess the cost structure of cellular and non-cellular LPWAN technologies. Then, we applied the framework in eight deployment scenarios to analyze the prospect of LPWAN technologies like Sigfox, LoRaWAN, NB-IoT, LTE-M, and EC-GSM. We consider the inter-technology interference impact on LoRaWAN and Sigfox scalability. Our results validate that a large rollout with a single technology is not cost-efficient. Also, our analysis suggests the rollout possibility of an IoT communication Technology may not be linear to cost-efficiency.
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| 20. |
- Huang, Binru, et al.
(författare)
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A Utility-Based Joint Resource Allocation Approach for Multi-Service in CoMP Networks
- 2013
-
Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 72:3, s. 1633-1648
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Tidskriftsartikel (refereegranskat)abstract
- Coordinated multi-point (CoMP) joint transmission is considered as a key technique to mitigate inter-cell interference and improve the cell-edge performance in 3GPP LTE-Advanced. In this paper, a utility-based joint resource allocation approach is proposed to support CoMP joint transmission in an orthogonal frequency division multiple access (OFDMA) systems. Two different utility functions are considered with diverse quality of service (QoS) provisioning. The objective is to maximize the sum utility of a clustered CoMP network, considering mixed real-time voice over IP (VoIP) and best-effort (BE) traffic patterns. A centralized joint resource allocation algorithm is proposed by decoupling the optimization problem into per-subchannel subproblems. Furthermore, a greedy user selection based low-complexity algorithm is proposed for practical implementation. For the sake of performance comparison, the proportional-fair based joint scheduling, as well as two non-coordinated scheduling schemes are also evaluated. Via system-level simulation we show that the proposed algorithms not only substantially improve the cell-edge spectrum efficiency of BE users, but also significantly decrease the packet drop ratio and call outage ratio of VoIP users.
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| 21. |
- Hult, Tommy, et al.
(författare)
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Performance of a multiple HAP system employing multiple polarization
- 2010
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Ingår i: Wireless Personal Communications. - : Springer. - 0929-6212 .- 1572-834X. ; , s. 105-117
-
Konferensbidrag (refereegranskat)abstract
- In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP (High Altitude Platforms) diversity techniques in order to increase the data rates in HAP communication systems. We will also investigate the effects of spatial correlation and mutual coupling between the separate antenna elements on system performance. Simulation results show that although the capacity is degraded by correlation and mutual coupling, we still achieve significant capacity gain compared to the single HAP case. In addition, we evaluate the performance of the system for different separation angles between HAPs, and determine the optimal separation angle that maximizes the total capacity of the system. © 2008 Springer Science+Business Media, LLC.
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| 22. |
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| 23. |
- Khamseh, Elaheh, et al.
(författare)
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Lightweight Certificateless Signcryption Scheme Using Type-3 Pairing on Elliptic Curve
- 2024
-
Ingår i: Wireless Personal Communications. - 1572-834X .- 0929-6212. ; 135:3, s. 1497-1517
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Tidskriftsartikel (refereegranskat)abstract
- A certificate-based public key cryptosystem has been developed to solve key escrow problems in ID-based public key cryptography, and to remove computational operations for certificate management. Signcryption is a primitive cryptographic that enables signing and encryption to be done in a one step, improving performance by reducing computational loads and communication overheads. Recent research has suggested some pairing-based cryptographic protocols for public key cryptosystems. However, most use Type-1 pairings, which weaken system security by using supersingular elliptic curves over a finite field of characteristics 2 and 3, making them totally unsafe against new attacks designed for Discrete Logarithm Problems. Furthermore, Type-1 pairings that use supersingular elliptic curves over finite fields of massive characteristics are highly inefficient compared to Type-3 pairings. This work proposes a secure and efficient online/offline trade-off scheme based on Type-3 pairings. The safety of the suggested scheme is asserted according to confidentiality and unforgeability based on a random oracle model. Moreover, the efficiency of the proposed approach is evaluated and compared with Type-2 and Type-4 pairings.
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| 24. |
- Khan, Muhammad Gufran, et al.
(författare)
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Non-coherent detection of impulse radio UWB signals based on fourth order statistics
- 2011
-
Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212.
-
Tidskriftsartikel (refereegranskat)abstract
- Low-complex and low power non-coherent energy detector (ED) is interesting for low data rate impulse radio (IR) ultra wideband (UWB) systems but, compared to coherent receivers, it suffers from a loss in performance due to low signal-to-noise ratio (SNR) at the detector. In addition, the performance of an ED strongly depends on the integration interval (window size) of the integrator and the window position. A non-coherent kurtosis detector (KD) and a fourth-order detector (FD), which can discriminate between Gaussian noise signals and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal, are presented. The performance of the detectors is evaluated using real channels measured in a corridor, an office and a laboratory environment. The results show that bit-error-rate (BER) performance of the proposed KD receiver is better than the ED receiver only under certain conditions, while the FD receiver is slightly better than the ED in low SNR region and its performance improves as the SNR increases. In addition, the performance of the FD receiver is less sensitive to overestimation of the integration interval making it relatively robust to variations of the channel delay spread. Finally, a criteria for the selection of integration time of the proposed detector is suggested.
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| 25. |
- Khan, Muhammad Gufran, et al.
(författare)
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Non-Coherent Fourth-Order Detector for Impulse Radio Ultra Wideband Systems : Empirical Evaluation Using Channel Measurements
- 2013
-
Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 68:1, s. 27-46
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Tidskriftsartikel (refereegranskat)abstract
- Low-complex and low-power non-coherent energy detectors (EDs) are interesting for low data rate impulse radio (IR) ultra wideband (UWB) systems, but suffer from a loss in performance compared to coherent receivers. The performance of an ED also strongly depends on the integration interval (window size) of the integrator and the window position. This paper presents a non-coherent fourth-order detector (FD) which can discriminate between Gaussian noise signals and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal. The performance of the detectors is evaluated using realistic channels measured in a corridor, an office and a laboratory environment. The results show that bit-error-rate (BER) performance of the proposed FD receiver is slightly better than the ED in low signal-to-noise ratio (SNR) region and its performance improves as the SNR increases. In addition, BER of the FD receiver is less sensitive to overestimation of the integration interval making it relatively robust to variations of the channel delay spread. Finally, a criteria for the selection of integration time of the proposed detector is suggested.
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| 26. |
- Khan, Waqas Nawaz, et al.
(författare)
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Performance Evaluation of Time-Reversal on Measured 60 GHz Wireless Channels
- 2013
-
Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 71:1, s. 707-717
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Tidskriftsartikel (refereegranskat)abstract
- Time-reversal (TR) signal processing has the potential to focus the transmitted signal at a desired receive (Rx) location in both space and time. At lower frequency bands, TR in conjunction with array antennas at transmit (Tx) or Rx has been shown to significantly improve its focusing performance relative to the case of single antennas at both link ends. This work for the first time investigates TR processing for multi-antenna systems in the 60 GHz band. We consider both multiple-input-single-output and single-input-multiple-output (SIMO) channels measured in the 60 GHz band in a conference room environment and investigate the effect of array size and its orientation on spatial and temporal compression properties of TR. It is observed that the root mean square (RMS) delay spread can be reduced significantly by the application of TR in the 60 GHz band and that the orientation of the Rx array significantly affects TR performance for SIMO systems.
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| 27. |
- Kilinc, Caner, et al.
(författare)
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A congestion avoidance mechanism for WebRTC interactive video sessions in LTE networks
- 2014
-
Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 77:4, s. 2417-2443
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Tidskriftsartikel (refereegranskat)abstract
- The paradigm shift where realtime communication will be handled on the web is soon becoming a reality. With only a few lines of Javascript code developers can easily turn a web browser into a voice or video terminal using the WebRTC API. While the IETF is actively working on standardizing the RTCWeb protocol to enable realtime communication across browsers and to avoid failures in session setups and enhance the session’s Quality of Experience (QoE), there is still a lack of a standardized congestion control mechanisms in the area. This paper proposes and evaluates a congestion avoidance mechanism and a rate adaptation model for WebRTC interactive video sessions in LTE networks where the model is based on realtime available bandwidth estimation and measurements. Our simulation results show that the proposed model provides a fair bandwidth allocation between TCP traffic flows and realtime media traffic flows. The results also show that excessive video frame delays and packet losses can be prevented with the proposed congestion avoidance mechanism. Consequently the proposed model improves performance and perceived QoE of WebRTC.
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| 28. |
- Kurasinski, Lukas, et al.
(författare)
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Using Neural Networks to Detect Fire from Overhead Images
- 2023
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Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 130:2, s. 1085-1105
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Tidskriftsartikel (refereegranskat)abstract
- The use of artificial intelligence (AI) is increasing in our everyday applications. One emerging field within AI is image recognition. Research that has been devoted to predicting fires involves predicting its behaviour. That is, how the fire will spread based on environmental key factors such as moisture, weather condition, and human presence. The result of correctly predicting fire spread can help firefighters to minimise the damage, deciding on possible actions, as well as allocating personnel effectively in potentially fire prone areas to extinguish fires quickly. Using neural networks (NN) for active fire detection has proven to be exceptional in classifying smoke and being able to separate it from similar patterns such as clouds, ground, dust, and ocean. Recent advances in fire detection using NN has proved that aerial imagery including drones as well as satellites has provided great results in detecting and classifying fires. These systems are computationally heavy and require a tremendous amount of data. A NN model is inextricably linked to the dataset on which it is trained. The cornerstone of this study is based on the data dependencieds of these models. The model herein is trained on two separate datasets and tested on three dataset in total in order to investigate the data dependency. When validating the model on their own datasets the model reached an accuracy of 92% respectively 99%. In comparison to previous work where an accuracy of 94% was reached. During evaluation of separate datasets, the model performed around the 60% range in 5 out of 6 cases, with the outlier of 29% in one of the cases.
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| 29. |
- Liang, Kai, et al.
(författare)
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A Fair Power Splitting Algorithm for Simultaneous Wireless Information and Energy Transfer in CoMP Downlink Transmission
- 2015
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Ingår i: Wireless personal communications. - : SPRINGER. - 0929-6212 .- 1572-834X. ; 85:4, s. 2687-2710
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Tidskriftsartikel (refereegranskat)abstract
- A power splitting approach for simultaneous wireless information and energy transfer is provided in this paper. We consider coordinated multipiont downlink transmission with M base stations (BSs) and J mobile stations (MSs). The main goal of this paper is to maximize per-MS data rate and receiving energy by dynamically optimizing transmitting beamformer. To improve fairness, this problem can be formulated to maximize the minimum rate of all J MSs with per-BS transmitting power constraints and per-MS receiving energy constraints, which is NP-hard problem. Minimum mean square error receiver, affine approximation and alternative convex optimization (ACO) methods are introduced to decompose the original NP-hard problem to several convex subproblems which can be solved by second-order cone programming with low rank (which is equal to the number of data streams) solutions, and then a fast heuristic algorithm is provided to solve the original problem. Numerical results show that the proposed algorithm can achieve fairness, and outperforms sum rate scheme in terms of fairness and outage probability. The fast convergency also demonstrates the proposed algorithms good performance.
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| 30. |
- Ligeti, Agnes, et al.
(författare)
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Local coverage probability estimation in single frequency networks
- 2001
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Ingår i: Wireless personal communications. - 0929-6212 .- 1572-834X. ; 18:2, s. 105-128
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Tidskriftsartikel (refereegranskat)abstract
- In OFDM based Single Frequency Networks (SFNs) such as Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB), the mobile receiver is provided by the same signal from several synchronous transmitters at the same carrier frequency. This transmitter diversity structure makes SFNs Very efficient in fading channels with an excellent spectrum saving, and very good power utilization over the service area. However, depending on the position of the mobile within the service area, these signals arrive with different delays causing possible echoes at the receiver. These echoes contribute to both the useful and the interfering parts of the signal. As the average received power in radio channels is a stochastic process, such contribution creates correlation between the different components of the Signal-to-Interference Ratio (SIR). In broadcasting practice, correlation was not taken into account when estimating the distribution of the SIR and the local coverage probability. This paper considers the effect of correlation on the estimation of the SIR and the coverage probability in OFDM based SFNs. Analyses are provided to show that in some situations the estimation error can be considerable when neglecting this correlation. To obtain a better estimation, the correlation coefficient between the total useful and total interfering parts of the received signal is first evaluated and then used as a correction factor in estimating the mean and standard deviation of the SIR. The obtained results show that such method can significantly reduce the estimation error of local coverage probability without increasing the computation complexity.
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| 31. |
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| 32. |
- Lv, Qiujian, et al.
(författare)
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Measuring Geospatial Properties : Relating Online Content Browsing Behaviors to Users’ Points of Interest
- 2018
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 101:3, s. 1469-1498
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Tidskriftsartikel (refereegranskat)abstract
- With the growth of the Mobile Internet, people have become active in both the online and offline worlds. Investigating the relationships between users’ online and offline behaviors is critical for personalization and content caching, as well as improving urban planning. Although some studies have measured the spatial properties of online social relationships, there have been few in-depth investigations of the relationships between users’ online content browsing behaviors and their real-life locations. This paper provides the first insight into the geospatial properties of online content browsing behaviors from the perspectives of both geographical regions and individual users. We first analyze the online browsing patterns across geographical regions. Then, a multilayer-network-based model is presented to discover how inter-user distances affect the distributions of users with similar online browsing interests. Drawing upon results from a comprehensive study of users of three popular online content services in a metropolitan city in China, we achieve a broad understanding of the general and specific geospatial properties of users’ various preferences. Specifically, users with similar online browsing interests exhibit, to a large extent, strong geographic correlations, and different services exhibit distinct geospatial properties in terms of their usage patterns. The results of this work can potentially be exploited to improve a vast number of applications.
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| 33. |
- Malmgren, Göran
(författare)
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On the Outage Probability in Local/Regional Single Frequency Broadcasting Networks
- 1995
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Ingår i: Wireless personal communications. - : Kluver Academic Publishing. - 0929-6212 .- 1572-834X. ; 2:4, s. 307-319
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Tidskriftsartikel (refereegranskat)abstract
- A receiver in an ODFM based broadcasting system allows all transmitters in a radio network to simultaneously broadcast the same information in the same frequency block. This procedure generates an artificial multipath environment at the receiver. Since the receiver is designed to overcome these problems, such a Single Frequency Network (SFN) provides good coverage and frequency economy in national applications. However, the efficiency in local SFN has been questioned. The network planning of local SFNs is a mixture of conventional frequency reuse planning and planning to avoid excessive propagation delays caused by the artificial delay spread. In this paper we propose some rules of thumb to be considered in the design of local SFNs. The coverage properties in SFNs are strongly dependent on the transmitter density which determines the degree of diversity of receiving signals from several transmitters. Results indicate that required coverage can be attained in local networks using three OFDM frequency blocks, provided that seven transmitters are used to cover each regional service area. The results also indicate that the duration of the guard interval between two consecutive OFDM signals has to be chosen with some care dependent on the size of the service area. Furthermore, we show that there exists an optimal antenna height for a given coverage area and guard interval.
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| 34. |
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| 35. |
- Molapo, Nthetsoa Alinah, et al.
(författare)
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Real-Time Livestock Tracking System with Integration of Sensors and Beacon Navigation
- 2018
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Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 104:2, s. 853-879
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the design and development of a livestock tracking system, with the objective of transmitting the location and activity status of the animals, in real-time, to an end-user. The system comprises of tag, beacon and base station nodes, communicating wirelessly with each other. Tag nodes receive location information from neighbouring beacon nodes and through the process of trilateration, the location of a specific animal is determined. Motion sensors within the tags, are used to determine activity status of the animal. The base station node receives the identity, location and activity information, from the tag nodes and transfers the data to a web server, where a database stores the tag information in real-time. An Android application, serves as an interface between the end user and the web server, enabling the remote monitoring and tracking of the livestock. The performance of the system is evaluated in terms of its range, accuracy and the ability to detect and store information. The nodes in the system are able to communicate within the expected ranges. The tag data can be inserted into the database and be retrieved for end user needs. The results demonstrate that the system can successfully read, process, transmit and display the location and activity information.
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| 36. |
- Nungu, Amos, et al.
(författare)
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Design and Implementation of an Inclusive Ubiquitous Access
- 2012
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 67:1, s. 79-94
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Tidskriftsartikel (refereegranskat)abstract
- The development towards ubiquitous network access requires innovative solutions to get remote areas included, especially rural areas of developing regions. The challenges include robustness of network components, poor or non-existent power supply and sustainable business models. We argue that large scale user-driven community networks are becoming technically viable to deploy in areas that are short of supply of telecommunication services due to little or no commercial interest. To support this claim, we discuss the design of key network elements and careful power management based on alternative energy sources and storage. We also provide a status report from ongoing field-tests regarding provisioning of broadband network services in Serengeti, Tanzania, and outline briefly our strategy to achieve sustainability. On the technical side, we first discuss an affordable, high-performance, low-effect router based on open source software and standard off-the-shelf hardware offering both copper and fibre links. Our design is capable of forwarding more than 700 kpps at 22.3 W. The power consumption is considerably less than all alternatives in our comparison. Then we discuss power management and the use of batteries and super-capacitors as backup and storage solutions.
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| 37. |
- Osseiran, Afif, et al.
(författare)
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System Performance of Transmit Diversity Methods and a Two Fixed-Beam System in WCDMA
- 2004
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Ingår i: Wireless personal communications. - Hingham, MA, USA : Kluwer Academic Publishers. - 0929-6212 .- 1572-834X. ; 31:1-2, s. 33-50
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Tidskriftsartikel (refereegranskat)abstract
- Downlink transmit diversity modes for WCDMA together with a two fixed-beam antenna array system are compared relative to the single antenna sectorized system in a radio network simulator. The transmit diversity methods investigated are: space-time transmit diversity and closed-loop mode I transmit diversity. Frequency selective (COST 259) and flat fading channels are considered and their impact to speech-only and data-only services is evaluated. A third service, which highlights the system performance of the various advanced antennas, is also investigated. The results in this investigation point out that the diversity gain in flat fading channels is substantial. In frequency-selective fading, the benefits of fixed beam systems is encouraging, whereas transmit diversity methods (especially Space-Time Transmit Diversity) is unsatisfactory.
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| 38. |
- Paier, Alexander, et al.
(författare)
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Characterization of Vehicle-to-Vehicle Radio Channels from Measurements at 5.2GHz
- 2009
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Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 50:1, s. 19-32
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Tidskriftsartikel (refereegranskat)abstract
- The development of efficient vehicle-to-vehicle (V2V) communications systems requires an understanding of the underlying propagation channels. In this paper, we present results on pathloss, power-delay profiles (PDPs), and delay-Doppler spectra from a high speed measurement campaign on a highway in Lund, Sweden. Measurements were performed at a carrier frequency of 5.2GHz with the communicating vehicles traveling on the highway in opposite directions. A pathloss coefficient of 1.8 shows the best fit in the mean square sense with our measurement. The average root mean square (RMS) delay spread is between 263 ns and 376 ns, depending on the noise threshold. We investigate and describe selected paths in the delay-Doppler domain, where we observe Doppler shifts of more than 1000Hz.
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| 39. |
- Pham, Tuan D
(författare)
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Validation of computer models for evaluating the efficacy of cognitive stimulation therapy
- 2017
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Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 94:3, s. 301-314
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Tidskriftsartikel (refereegranskat)abstract
- The notion of using computational methods for evaluating cognitive stimulation therapy (CST) based on the synchronized recording of photoplethysmographic (PPG) signals of care-givers and participants offers an objective and cost-effective analysis in health care to improve the patient’s quality of life. While computer models are promising as a useful tool for such a purpose, a question of interest is how the model reliability, which is the degree to which an assessment tool produces stable and consistent results, can be established. This paper addresses this issue with the application of dynamic-time warping and resampling to measure the performance of two PPG features known as the largest Lyapunov exponent and linear predictive coding, which have been applied for studying the efficacy of CST. The potential success of this computerized evaluation can be a precursor to the development of a personalized e-therapy system that operates on mobile devices.
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| 40. |
- Plass, Simon, et al.
(författare)
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High spectral efficient and flexible next generation mobile communications
- 2008
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 47:1, s. 79-89
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Tidskriftsartikel (refereegranskat)abstract
- In this article we identify and describe the requirements and challenges of next generation mobile communications systems. The so-called fourth generation (4G) aims at throughput rates of more than 100 MBit/s outdoors with high mobility and 1GBit/s indoors. This requires new advanced techniques in the air interface of such a system. We outline new possible techniques and introduce a future basic physical layer concept. The adaptivity to the channel of all the modules in such a possible concept is highlighted. Since the needed large bandwidth for high data rates is a very valuable resource, future communications systems need a high spectrum flexibility. Furthermore, 4G systems will face severe inter-cell interference scenarios that have to be tackled. Both challenges, i.e., spectrum flexibility and inter-cell interference, are discussed in more detail.
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| 41. |
- Porambage, Pawani, et al.
(författare)
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CHIP: Collaborative Host Identity Protocol with Efficient Key Establishment for Constrained Devices in Internet of Things
- 2017
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Ingår i: Wireless personal communications. - : SPRINGER. - 0929-6212 .- 1572-834X. ; 96:1, s. 421-440
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Tidskriftsartikel (refereegranskat)abstract
- The Internet of Things (IoT) is the next evolutionary paradigm of networking technologies that interconnects almost all the smart objects and intelligent sensors related to human activities, machineries, and environment. IoT technologies and Internet Protocol connectivity enable wide ranges of network devices to communicate irrespective of their resource capabilities and local networks. In order to provide seamless connectivity and interoperability, it is notable to maintain secure end-to-end (E2E) communication links in IoT. However, device constraints and the dynamic link creations make it challenging to use pre-shared keys for every secure E2E communication scenario in IoT. Variants of Host Identity Protocol (HIP) are adopted for constructing dynamic and secure E2E connections among the heterogeneous network devices with imbalanced resource profiles and less or no previous knowledge about each other. We propose a solution called collaborative HIP (CHIP) with an efficient key establishment component for the high resource-constrained devices in IoT. CHIP delegates the expensive cryptographic operations to the resource rich devices in the local networks. Finally, by providing quantitative performance evaluation and descriptive security analysis, we demonstrate the applicability of the key establishment in CHIP for the constrained IoT devices rather than the existing HIP variants.
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| 42. |
- Radiom, Soheil, et al.
(författare)
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Miniaturization of UWB Antennas and its Influence on Antenna-Transceiver Performance in Impulse-UWB Communication
- 2013
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 71:4, s. 2913-2935
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a co-design methodology and the effect of antenna miniaturization in an impulse UWB system/transceiver is presented. Modified small-size printed tapered monopole antennas (PTMA) are designed in different scaling sizes. In order to evaluate the performance and functionality of these antennas, the effect of each antenna is studied in a given impulse UWB system. The UWB system includes an impulse UWB transmitter and two kinds of UWB receivers are considered, one based on correlation detection and one on energy detection schemes. A tunable low-power Impulse UWB transmitter is designed and the benefit of co-designing it with the PTMA antenna is investigated for the 3.1-10.6 GHz band. A comparison is given between a 50 design and a co-designed version. Our antenna/transceiver co-design methodology shows improvement in both transmitter efficiency and whole system performance. The simulation results show that the PTMA antenna and its miniaturized geometries are suitable for UWB applications.
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| 43. |
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| 44. |
- Rydström, Mats, 1978, et al.
(författare)
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Adapting the Ranging Algorithm to the Positioning Technique in UWB Sensor Networks
- 2008
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Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 47:1, s. 27-38
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-Wideband (UWB) is an emerging technology for short-range wireless communications. Due to the high bandwidth of UWB signals, accurate ranging and positioning is possible, which is one of many reasons why UWB is a candidate physical layer for another emerging research area, that of wireless sensor networks (WSNs). In this work, we argue that the ranging algorithm design should be made with the characteristics of the positioning algorithm in mind. In considering ranging and positioning in parallel, we are able to construct a range estimator that is tailored to the positioning algorithm, thereby achieving robustness to non-line-of-sight (NLOS) effects, reasonable overall complexity, and good performance in terms of positioning error. The analysis and simulations in this work are based on the channel models adopted by the IEEE 802.15.4a working group, and highlight the benefits and drawbacks of the proposed approach.
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| 45. |
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| 46. |
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| 47. |
- Seong, K, et al.
(författare)
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A new adaptive transmission scheme for wireless communication systems utilizing frequency diversity
- 2002
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Ingår i: Wireless personal communications. - 0929-6212 .- 1572-834X. ; 23:1, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a new adaptive transmission scheme for wireless communication systems utilizing frequency diversity combining technique. The capacity of Rayleigh fading chanels under the proposed adaptive transmission scheme is analytically evaluated and compared with the capacity under the conventional adaptive transmission scheme. The results show that the channel capacity under the new adaptive scheme exceeds that under the conventional one, and this capacity increment becomes more apparent especially for lower average carrier-to-noise ratio (CNR) and larger number of diversity branches. Also, the capacity with the new scheme isshown to exceed even the capacity of AWGN channels for some small values of CNR and large number of diversity branches.
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| 48. |
- Shi, Lin, et al.
(författare)
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Context-based Ontology-driven Recommendation Strategies for Tourism in Ubiquitous Computing
- 2014
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 76:4, s. 731-745
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Tidskriftsartikel (refereegranskat)abstract
- Tourism is an information-intensive business. At present, there are a lot of information and tourism resources available on the internet that lead to low searching efficiency and effectiveness, the user may get too many seeking results but not related to his interest, or few results than his expected. The user can know clearly what he wants, but sometime the user doesn't know what kind information he needs. User's demand can be formulated as direct demand and potential preference. At the same time, the study shows that there is strong relationship between the traveler's potential preference and the characteristics of tourism resources. In order to solve the information overload challenge, recommendation services are increasingly emerging. Currently, recommendation methods focus on dealing with personalized matching based on the user preference. However, these methods skip the user's direct demand. In this paper, we propose ontology-driven recommendation strategies based on user's context. The strategies use ontology to describe and integrate tourism resources, achieve the goal of associating user's direct needs and his potential preference as the context in recommendation. Moreover, theoretical analysis and experiments show that the proposed approach is feasible, the results of the evaluation are discussed.
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| 49. |
- Soni, Nikheel, et al.
(författare)
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Internet of Vehicles Based Approach for Road Safety Applications Using Sensor Technologies
- 2019
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Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 105:4, s. 1257-1284
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the Internet of Vehicles approach is used to develop a novel low cost sensor based system for road safety applications in intelligent transportation systems. It was found that major hazards that compromise road safety include weather related factors, poor road surfaces and presence of sharp turns. A wireless sensor network based solution consisting of embedded systems for the vehicular clients and infrastructure waypoints is developed for detecting road safety hazards and warning users about potentially hazardous events from causes that include presence of speed bumps, sharp turns and weather related factors of rain and fog. Hazards detected by the embedded systems are conveyed to the user by using the Vehicle-to-Vehicle communication and Vehicle-to-infrastructure communication interfaces developed in this study for inter-vehicle communication and obtaining sensory information from infrastructure waypoints respectively. Accuracy achieved was 88% for speed bump detection, 73.86% for detecting sharp turns and 100% for detection of rain and fog. Communication systems in the designed solution are optimized by reducing the size of packet being exchanged which improves transmission speed, packet losses and congestion on the network. Thus, the designed solution is capable of improving road safety by using an Internet of Vehicles approach.
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| 50. |
- Sung, Ki Won, et al.
(författare)
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Downlink Capacity Analysis of Collaborative Crossed Timeslots in CDMA TDD Systems
- 2009
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Ingår i: Wireless personal communications. - : Springer Netherlands. - 0929-6212 .- 1572-834X. ; 50:4, s. 469-481
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Tidskriftsartikel (refereegranskat)abstract
- Traffic asymmetry between uplink and downlink is expected to be a remarkable 3G characteristic in cellular mobile multimedia communications. CDMA system with TDD is a good solution to this traffic asymmetry. However, the level of traffic asymmetry may be significantly different from a cell to another cell. To tackle this problem and to support the traffic hot spot, crossed slots are examined. The use of crossed slots is restricted within a certain range of a cell by investigating the inter-cell interference and the maximum planned load factor. We examine the radius of inner zone and discuss the capacity of downlink crossed slots for various neighbor cell environments. Computational results show that the capacity increase in the target cell is outstanding by reducing the service range of neighbor cells. When all six neighbors reduce their service range by 20%, the capacity at target cell crossed slot is increased by 35%. Monte Carlo simulation is performed with large scale fading to verify the numerical analysis.
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