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Mobile communications play a significant role in our daily lives and are receiving greater attention from researchers as a result of the information and network technologies' quick growth. To meet the public's need for high speed, the 3GPP organization suggested the LTE mobile system. The LTE employs a hierarchical key management to enhance secure data transmission. However, the existing system lacks backward security and is susceptible to attack during the X2 handover procedure. We suggest an improved security feature by group key to address the mentioned problems and guard against malicious base stations and malicious attacks during the LTE x2 handover operation. [ABSTRACT FROM AUTHOR]

The cellular network keeps the vast capacity of queue space at eNodeBs (base stations) to reduce the queue overflow during the burst in data traffic. However, this adversely affects the delay sensitive applications and user quality of experience. Recently, few researchers have focused on reducing the packet delay, but it has a negative impact on the utilization of network resource by the users. Further, it fails to maintain fairness among the users, when competing for a shared resource in coexistence with conventional TCP or UDP users. Therefore, in this paper, the adaptive receiver-window adjustment (ARWA) algorithm is proposed to efficiently utilize the network resources and ensure fairness among the users in resource competitive environment, which requires slight modification of TCP at both the sender and receiver. The proposed mechanism dynamically varies the receiver window size based on the data rate and delay information of the packets, to enhance the performance of the system. Based on extensive experiments, the results illustrate that the ARWA algorithm reduces the delay of TCP packet and increases fairness among the users. In addition to that, it enhances the packet delivery fraction (PDF) and maintains the throughput of the system. Moreover, it competes with other conventional TCP users for the shared network resources in a fair manner. [ABSTRACT FROM AUTHOR]

Abstract The third Generation Partnership Project (3GPP) has successfully launched 4G data on mobile communication by utilizing the Long Term Evolution (LTE). The multimedia processing such as video calling/conferencing, video transmission/reception in mobile communication are in need of multiple user support, speed, high data transmission rate, low data loss rate and high throughput. In this paper an enhanced scheduling algorithm known as, EM-LWDF (Modified Largest Weighted Delay First) is proposed in combination of time/frequency scheduling for LTE. The proposed scheduling algorithm is evaluated under various simulation scenarios and compared with conventional algorithm such as PF, M-LWDF, EXP/PF, and proposed +LWDF. The evaluation is made in terms of system throughput, fairness index and Packet Loss Rate (PLR) and the evaluation results shows that the proposed scheduling algorithm shows remarkable performance improvement. [ABSTRACT FROM AUTHOR]

Understanding of line-of-sight and non-line-ofsight (LOS/NLOS) visibility conditions is important for radio wave propagation modeling when selecting empirical path loss model. For Monte Carlo statistical simulations a random generator of visibility states can be designed according to a given spatial probability density. In the current paper, a statistical LOS state model is derived based on ITU-R and 3GPP 3D LOS probability models suitable for 5G channel simulations. The generic exponential LOS probability model is improved by dividing the area into LOS and NLOS zones depending on the building density. The accuracy of LOS probability model has been tested against visibility predictions obtained from the digital building data over Manhattan city area. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the spectral coexistence between the second generation terrestrial digital video broadcasting (DVB) and the long term evolution (LTE) networks. In particular, the global spectral efficiency (SE) of both systems is investigated when a partial spectral overlap between DVB and LTE signals occurs. Our contribution lies in twofold: 1) the interfering signal variance in each network is derived analytically according to the frequency overlap while taking into account the difference between the characteristics of LTE and DVB networks, especially the OFDM subcarrier spacing and then the OFDM symbol duration and 2) SE is derived with uniform and non uniform power allocation between overlapped and non overlapped subcarriers of the two networks. This derivation offers an analytical evaluation of the effect of the spectral overlap ratio variation and different power allocation scenarios and provides insightful results on the cooperation between the two networks. [ABSTRACT FROM PUBLISHER]

In Long Term Evolution (LTE) cellular networks, the transmit power control (TPC) mechanism consists of two parts: the open loop (OL) and closed loop. Most cellular networks consider OL/TPC because of its simple implementation and low operation cost. The analysis of OL/TPC parameters is essential for efficient resource management from the cellular operator's viewpoint. In this work, the impact of the OL/TPC parameters is investigated for homogeneous small cells and heterogeneous small‐cell/macrocell network environments. A mathematical model is derived to compute the transmit power at the user equipment, the received power at the eNodeB, the interference in the network, and the received signal‐to‐interference ratio. Using the analytical platform, the effects of the OL/TPC parameters on the system performance in LTE networks are investigated. Numerical results show that, in order to achieve the best performance, it is appropriate to choose αsmall = 1 and Po‐small = –100 dBm in a homogenous small‐cell network. Further, the selections of αsmall = 1 and Po‐small = –100 dBm in the small cells and αmacro = 0.8 and Po‐macro = –100 dBm in the macrocells seem to be suitable for heterogeneous network deployment. [ABSTRACT FROM AUTHOR]

Abstract: Ever‐increasing growth in various types of devices with different requirements requires next‐generation wireless networks to deal with diverse type of traffic. The use of fixed transmission time interval (TTI) for transmission may not perform efficiently with various types of traffic. These requirements are attainable with a fifth‐generation flexible frame structure, which consists of flexible TTI for transmission. Short TTI could be used for ultrareliable low‐latency communication to meet the latency requirements, whereas long TTI is suitable for mobile broadband services. Long‐Term Evolution/Long‐Term Evolution Advanced uses discontinuous reception (DRX) for power saving. DRX saves the battery power of a device at the cost of an increase in latency. In this article, we explore DRX with flexible TTI for fifth‐generation communications. We model DRX with a semi‐Markov model to analyze the power‐saving factor and delay. Moreover, we proposed an algorithm for the TTI selection for various service requirements. Our numerical analysis results show that the delay attained by 0.2‐ms TTI is 76% less than that attained by 1‐ms TTI. [ABSTRACT FROM AUTHOR]

Abstract: Directional fifth‐generation communication is expected to be a paradigm shift from previous wireless generations under the flagship of very high millimeter‐wave carrier frequencies. In a directional millimeter‐wave air interface, communication takes place through multiple transmitting/receiving beams, as one beam can only provide a limited coverage. However, Long‐Term Evolution/Long‐Term Evolution Advanced is primarily designed and optimized for omnidirectional air interface. In a directional interface, transmitting the same paging information through multiple transmitting beams would substantially increase the downlink resource overheads of the network. We propose a mobile assisted directional paging (MDP) as an effective solution to mitigate the problem of an overwhelming paging resource requirement in directional fifth‐generation communications. We also propose to improve power saving at user equipment in an MDP‐based idle‐state discontinuous reception. By capturing various paging rates, we perform a numerical analysis of paging capacity. The MDP achieves around 20% to 90% gain, respectively, for 16 to 256 number of beams compared with a directional paging without any assistance from the mobiles. The analytical results are validated through simulations on the real traffic trace. [ABSTRACT FROM AUTHOR]

Nowadays' ongoing development of mobile communications, promoted by the dramatically risen in traffic demand, impulses the deployment of networks with higher throughputs and lower latencies. In this paper, a comparison is made between LTE and LTE-Advanced systems by conducting a study about the parameters, wich at a link level influence the most the data rate experienced by the user. To do so, the LTE and LTE-Advanced Downlink Link Level Simulators developed by the Universidad Tecnológica de Vienna are employed to analyze the communication link between a single user and its Base Station. The results obtained allow to appreciate LTE-Advanced advantages when compared to LTE, given by the usage of superior transmitting modes. Thus, the capacity of MIMO techniques to exploit the intrinsic characteristics of the transmission channel is emphasized. [ABSTRACT FROM AUTHOR]

This article, the third in a multipart series, describes and comments on the relief that the courts award in cases involving standard-essential patents (SEPs)—the law that courts have established on how to determine a reasonable royalty—in particular, a royalty on reasonable and nondiscriminatory terms (RAND royalty) for a SEP. [ABSTRACT FROM AUTHOR]

A family of compact microstrip antennas are presented targeting applications such as Long-Term Evolution (LTE), Wireless Local Area Networks (WLAN), Universal Mobile Telecommunications system (UMTS), Global System Mobile (GSM) and global positioning system (GPS). These antennas consist of a rectangular shaped structure printed over FR4 substrate. The antenna occupies a small volume of 70x54x1.6mm³. A 50-Ohm strip line was used to feed the proposed antennas. For miniaturization purposes, an I-shaped slot was inserted in the appropriate location on the radiator resulting in the second version (antenna with I-shaped slot). The integration of the slot helped towards shifting the resonant frequency downwards, which potentially created an additional resonant frequency to cover the WLAN2400MHz, but this resonant frequency is still static in nature. Thus, tuning mechanisms were introduced to tune the resonant frequency over a wide continuous frequency range. A lumped capacitor was firstly used as the tuning approach, in which its capacitance was varied from 0.5pF to 3pF, covering the frequency range from 2300MHz to 1500MHz. Secondly, the varactor diode was exploited to verify this; by changing the bias voltage across the varactor from 0.21V to 12.9V, the antenna operates over the targeted range from 1500MHz to 2300MHz. Both the simulated and measured results show a stable performance. The proposed antenna may be suitable for future cognitive radio system. [ABSTRACT FROM AUTHOR]

Carrier aggregation (CA) in long-term evolution advanced (LTE-A) networks is a promising tool for providing bandwidth extension for high data rate communication. In CA, the efficient scheduling of carriers has imposed a new challenge in the design of delay-sensitive carrier scheduling for mobile multimedia applications. In this paper, a new dynamic slot-based carrier scheduling scheme has been proposed for efficient resource allocation to support the quality of service (QoS) of mobile traffic over CA transmission. The key idea of this scheduling is the allocation of slots for each component carrier based on the queue state information, taking into consideration the priority based on the delay requirements of individual mobile multimedia traffic. Two different cases of the scheduler with and without priority are implemented to facilitate the performance comparison. The simulation results show that the proposed scheme provides better spectrum utilization, throughput, and delay performance than the existing scheduling scheme and improves delay- sensitive mobile traffic QoS. [ABSTRACT FROM AUTHOR]

In this paper, we focus on uplink scheduling with the practical constraints imposed by the Long-Term Evolution/Long-Term Evolution-Advanced (LTE/LTE-A) standard. We consider multimedia traffic generated by mobile users with heterogeneous quality-of-service (QoS) requirements. To tackle the resulting time and frequency problem, we then propose an adaptive and potential aware scheduling scheme (APASS), which is standard compliant and covers a wide range of scheduling objectives. This scheduling scheme is composed of three algorithms, which work jointly to provide an efficient solution. Our performance evaluation shows that the APASS outperforms other state-of-the-art scheduling schemes in terms of user satisfaction and delay. [ABSTRACT FROM AUTHOR]

To assess general public exposure to electromagnetic fields from Long Term Evolution (LTE) base stations, measurements at 10 sites in Thessaloniki, Greece were performed. Results are compared with other mobile cellular networks currently in use. All exposure values satisfy the guidelines for general public exposure of the International Commission on Non-Ionizing Radiation Protection (ICNIRP), as well as the reference levels by the Greek legislation at all sites. LTE electric field measurements were recorded up to 0.645 V/m. By applying the ICNIRP guidelines, the exposure ratio for all LTE signals is between 2.9 × 10-5 and 2.8 × 10-2. From the measurements results it is concluded that the average and maximum power density contribution of LTE downlink signals to the overall cellular networks signals are 7.8% and 36.7%, respectively. [ABSTRACT FROM AUTHOR]

Forth Generation (4G) network support for wide geographical locations proves its use as a more advanced wireless technology. The Long-Term Evolution (LTE) is a 4G mobile communications standard set by International Communication Union (ITU), specifically ITU Radio communication Sector (ITU-R). At the moment, video traffic and telecommunications grow under the expansion of LTE, which is considered as the actual motivating access technology of 4G network. Throughout the deployment of LTE, various transport protocols are advised and broadly experimented, for instance, TCP, SCTP, DCCP and UDP that may execute differently on 4G networks subject to the network scenarios and parameter settings. Even though the deployment of LTE is swiftly enhanced, there is a lack of performance evaluation of its protocols. Hence, a widespread scrutiny is required for the evaluation of the operation of numerous protocols for high-end applications such as multimedia. Adopting these applications with flexible quality of service constraints with improved usage of resources is a challenging task. In this paper, the output results of different transport protocols for multimedia streaming applications, e.g., video, through extensive simulations are analyzed. The performance of an MPEG-4 video streaming is evaluated using NS-3. The performance metrics used are delay, jitter, throughput, and packet loss. These metrics are evaluated at the base station via TCP, SCTP, DCCP and UDP protocols over the 4G-LTE technology. The obtained results show that the DCCP performs the best in throughput improvement with the minimization of delay and jitter as compared to UDP, TCP, and SCTP. [ABSTRACT FROM AUTHOR]

The architectural evolution from hierarchical to flatter networks creates new challenges such as single points of failure and bottlenecks, non-optimal routing paths, scalability problems, and long handover delays. The cellular networks have been hierarchical so that they are largely built on centralized functions based on which their handover mechanisms have been built. They need to be redesigned and/or carefully optimized. The mobility extension to Host Identity Protocol (HIP) proxy, mobile HIP Proxy (MHP), provides a seamless and secure handover for the Mobile Host in the hierarchical network. However, the MHP cannot ensure the same handover performance in flatter network because the MHP has also utilized the features offered by the hierarchical architecture. This paper extends the MHP to distributed mobile HIP proxy (DMHP). The performance evaluation of the DMHP in comparison to MHP and other similar mobility solutions demonstrates that DMHP does indeed perform well in the flatter networks. Moreover, the DMHP supports both efficient multi-homing and handover management for many mobile hosts at the same time to the same new point of attachment. [ABSTRACT FROM AUTHOR]

In this paper we introduced interference cancellation (IC) in the cell search and the detection of physical downlink shared channel (PDSCH) in long term evolution (LTE) of 3rd generation partnership project (3GPP). After user equipment (UE) is turned on, it has to first search the target cell using synchronization channel (SCH). After UE gets timing and cell identification (Cell ID) by cell search process, it can start to transmit and receive data through the traffic channel. In most cases, UE experiences the interference from surrounding neighbor cells, which may result in the degradation of the receiver performance. Not only in time division duplex (TDD) but also frequency division duplex network (FDD), the cells must be deployed with the time aligned to support better successful handover and also provide multemedia broadcast and multicast service (MBMS) efficiently in the network. In synchronous network system, since every cell sends his SCH using shared resource allocation, it is inevitable that two or more neighboring cells can interfere each other in some situation. The cell specific reference signal (CRS) is used for channel estimation in downlink reception. The CRS from neighbor cells may overlap with the resource of PDSCH of the target cell. Hence, the collision of SCH and CRS from the neighbor cells can degrade both the performance of cell search and PDSCH reception at the same time. In this paper, we analyzed the improved performance of the cell search and PDSCH reception by using successive interference cancellation. Simulation results show that the proposed scheme can effectively reduce the mutual interference and improve the performance of the signal detection in view of the cell search and PDSCH reception, respectively. [ABSTRACT FROM AUTHOR]

In the paper a novel SPFR frequency reuse method is proposed which can be used for improvement of physical resources utilization efficiency in LTE-A. The proposed method combines both SFR and PFR giving the possibility of more flexible use of frequency band in different regions of a cell. First, a short study on the problem of frequency reuse in cells is discussed including bibliography overview. In next section the principle of the proposed SPFR method is described. Then the simulation model is discussed and simulation parameters are expected. In the last part, results of simulation of SPFR efficiency in comparison to known frequency reuse methods are presented. Presented results include both capacity and throughput for single connection. The proposed method eliminates main disadvantages o f both SFR and PFR methods and gives significantly greater capacity of radio interface in boundary region of cells. [ABSTRACT FROM AUTHOR]

Network design consists of evaluating cell coverage and capacity and may involve many parameters related to environment, system configuration and quality of service requirements. The key parameter for cost optimised Long Term Evolution (LTE)-based network dimensioning is to provide a tight approximation of the effective signal-to-interference-plus-noise ratio (SINR) distribution. This paper provides a novel framework for LTE and LTE-advanced network dimensioning, where the classical single-carrier SINR performance evaluation is extended to multi-carriers systems operating over frequency selective channels. Extension is achieved by expressing the link outage probability in terms of the statistics of the effective SINR. For effective SINR computation, the exponential effective SINR mapping technique is used. Closed-form expression for the link outage probability is achieved assuming a log skew normal approximation for single-carrier case. Then we rely on the log-normal approximation to express the exponential effective SINR distribution as a function of the mean and standard deviation of the SINR of a generic subcarrier. Effective SINR values are evaluated at click speed in each point on the network. Simulations show that the proposed framework provides results with accuracy within 0.5 dB for any defined outage probability target. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper aims to address the sustainability of power resources and environmental conditions for telecommunication base stations (BSs) at off-grid sites. Accordingly, this study examined the feasibility of using a hybrid solar photovoltaic (SPV)/wind turbine generator (WTG) system to feed the remote Long Term Evolution-macro base stations at off-grid sites of South Korea the energy necessary to minimise both the operational expenditure and greenhouse gas emissions. Three key aspects have been discussed: (i) optimal system architecture; (ii) energy yield analysis; and (iii) economic analysis. In addition, this study compares the feasibility of using a hybrid SPV/WTG system vs. a diesel generator. The simulation results show that by applying the proposed SPV/WTG system scheme to the cellular system, the total operational expenditure can be up to 48.52% more efficient and sustainability can be ensured with better planning by providing cleaner energy. [ABSTRACT FROM AUTHOR]

In a long term evolution (LTE) system, channel state information can be acquired at the transmitter (Tx) from three feedback parameters: the rank indicator (RI), precoding matrix indicator, and channel quality indicator. These parameters can facilitate the dynamic adjustment of signals at the Tx, thereby enhancing its transmission performance. In this paper, we propose a RI determination method for LTE system; the method is based on the eigen-value ratio test for a multiple-input multiple-output channel matrix. It has almost the same selection ability as that of the exhaustive full search method and offers the advantage of lower computational complexity compared with that of methods reported in the literature. [ABSTRACT FROM AUTHOR]

In this study, the estimation of fast-fading long term evolution (LTE) downlink channels in high-speed applications of LTE advanced is investigated by the authors. A robust channel estimation and interpolation algorithm is essential in order to adequately track the fast time-varying channel response. In this contribution, the multipath fastfading channel is modelled as a discrete, tapped-delay and finite impulse response filter. Using support vector machine regression (SVR), they develop an extended algorithm to jointly estimate the complex-valued channel frequency response in time and frequency domains, in the presence of fading and non-linear noise from the transmission of known pilot symbols. Furthermore, the channel estimates at the known pilot symbols are interpolated to the unknown data symbols by using the non-linear SVR approach exploiting kernel features. This study integrates both channel estimation at pilot symbols and interpolation at data symbol into the complex SVR interpolation method. The bit error rate and mean square error performances of the authors' fast-fading channel estimation scheme is demonstrated via simulation for LTE downlink with 64-QAM modulation and 500 km/h velocity under non-linearities. [ABSTRACT FROM AUTHOR]

The growing demand for high-speed data, quality of service (QoS) assurance, and energy efficiency has triggered the evolution of fourth-generation (4G) Long-Term Evolution-Advanced (LTE-A) networks to fifth generation (5G) and beyond. Interference is still a major performance bottleneck. This paper studies the application of physical-layer network coding (PNC), which is a technique that exploits interference, in heterogeneous cellular networks. In particular, we propose a rate-maximizing relay selection algorithm for a single cell with multiple relays assuming the decode-and-forward (DF) strategy. With nodes transmitting at different powers, the proposed algorithm adapts the resource allocation according to the differing link rates, and we prove theoretically that the optimization problem is log-concave. The proposed technique is shown to perform significantly better than the widely studied selection-cooperation technique. We then undertake an experimental study—on a software radio platform—of the decoding performance of PNC with unbalanced signal-to-noise ratios (SNRs) in the multiple-access transmissions. This problem is inherent in cellular networks, and it is shown that, with channel coding and decoders based on multiuser detection and successive interference cancellation, the performance is better with power imbalance. This paper paves the way for further research on multicell PNC, resource allocation, and the implementation of PNC with higher order modulations and advanced coding techniques. [ABSTRACT FROM PUBLISHER]

Long term evolution (LTE) has become the fastest developing mobile system technology and is considered as the fourth generation of wireless communication systems. Multiple-input multiple-output spatial multiplexing is a key technique employed in LTE system to boost the system capacity. With this gain comes the challenge of designing efficient detectors at the receiver side to decouple the transmitted data streams. The exhaustive search detector is optimum in terms of performance but it has a high computational load in terms of time and power. Owing to its high computational load, many detection techniques have been proposed in order to achieve an efficient detection performance with low complexity in terms of computational power. This paper reviews the detection techniques used in LTE including the maximum likelihood (ML) detection, zero forcing (ZF) detection, minimum mean square error (MMSE) detection, successive interference cancellation (SIC) detection, sphere decoding detection, lattice reduction and list decoding. It is shown that Maximum Likelihood detection has the best performance, but the complexity is too high. Other detectors like ZF or MMSE and nonlinear detectors employing SIC have much lower complexity, however, they do not provide detection performance close to that of the ML detection. The sphere detection algorithm has been shown to have low average computational complexity and achieves a quasi-ML performance which gives it an advantage over to other types of detection techniques. [ABSTRACT FROM AUTHOR]

Long Term Evolution (LTE) is the initial version of fourth-generation (4G) networks which provides ubiquitous broadband access. LTE supports multimedia Quality of Service (QoS) traffic with high data transfer speed, fast communication connectivity, and high security. Multimedia traffic over LTE networks is one of the highest percentages of mobile traffic and it has been growing rapidly in recent years. Our approach focuses on the development of Quality of Experience (QoE) aware optimization downlink scheduling video traffic flow. QoE is the overall acceptability of a service or application, as perceived subjectively by end users. In this work we aim to maximise QoE of video traffic streaming over LTE networks. This work introduces a novel integration framework between genetic algorithm (GA) and random neural networks (RNN) applied to QoE-aware optimization of video stream downlink scheduling. The proposed framework has been applied and evaluated using an open source simulation tool for LTE networks (LTE-Sim). A comparison between our framework and state-of-the-art LTE downlink scheduling algorithms (FLS, EXP-rule, and LOG-rule) has been done under different network conditions. Simulation results have shown that our scheduler can achieve better performance in terms of QoE (∼10% increase), throughput and fairness. [ABSTRACT FROM AUTHOR]

Digital predistortion (DPD) is one of the most effective techniques that can compensate for the distortions caused by the nonlinearities and memory effects of power amplifiers (PAs). In this paper, a new DPD solution which directly solves the inverse function of a PA model is presented for wideband transmitter applications. The major components of the general memory polynomial (GMP) model are selected to effectively characterize the PA's nonlinearity and memory effects through model identification. In the direct learning algorithm that followed, the DPD function is obtained by constructing and then solving the reverse function of the identified PA model. Due to the high accuracy of the proposed modeling process and the direct learning algorithm, the DPD function is accurately derived, which could significantly compensate for the nonlinear distortions. Simulations and experiments are performed on wideband long-term evolution (LTE) signals to evaluate the effectiveness of the proposed DPD method. It is demonstrated that a 22-dB adjacent channel leakage ratio improvement is achieved for a 100-MHz LTE-advanced signal, which even outperforms the conventional GMP-based DPD method by about 3 dB. [ABSTRACT FROM AUTHOR]

The third Generation Partnership Project (3GPP) Long-Term Evolution (LTE) is becoming the first truly global wireless communication standard. LTE system is expected to have an ability to sense the wireless environment. To evaluate the performance of cognitive LTE network, the design of system level simulation platform is proposed. This platform realizes relevant spectrum sensing algorithm and dynamic spectrum allocation strategy. The architecture of this simulation platform is introduced. Based on LTE system level simulator, cognitive radio function is implemented and five modules are developed, including spectrum sensing module, spectrum allocation module, spectrum switching module, link adaptation module, link-system interface module. Class diagram of the simulation platform is also given in this paper. Simulation flow chart introduces the working mechanism in detail. Finally network performance of cognitive LTE system, including average throughput, average spectral efficiency, detection probability, false alarm probability, miss alarm probability, is evaluated using this platform. [ABSTRACT FROM AUTHOR]

Advent of TV white space digitization has released frequencies from 470 MHz to 790 MHz to be utilized opportunistically. The secondary user can utilize these so called TV spaces in the absence of primary users. The most important challenge for this coexistence is mutual interference. While the strong TV stations can completely saturate the receiver of the cognitive radio (CR), the cognitive radio spurious tones can disturb other primary users and white space devices. The aim of this paper is to address the challenges for enabling cognitive radio applications in WLAN and LTE. In this process, architectural considerations for the design of cognitive radio front ends are discussed. With high-IF converters, faster and flexible implementation of CR enabled WLAN and LTE are shown. The effectiveness of the architecture is shown by evaluating the CR front ends for compliance of standards namely 802.11b/g (WLAN) and 3GPP TS 36.101 (LTE). [ABSTRACT FROM AUTHOR]

DC is one of the most important features introduced in Release 12 of the 3GPP specifications. DC aims at increasing the per-user throughput by improving the utilization of radio resources across two base stations connected via non-ideal backhaul (X2) and operating on different carrier frequencies. By making it possible to maintain the connection to the primary cell located in the macro base station while accessing the extra capacity provided by the small cell layer, DC can also improve the mobility performance in small cell deployments. This article gives an overview of the DC feature as standardized in Release 12. We summarize the supported scenarios and the DC functionality, and also demonstrate by means of detailed system-level simulations how DC can improve end-user throughput and mobility performance. [ABSTRACT FROM PUBLISHER]

The growing demand for mobile multicast services, such as Internet Protocol television (IPTV) and video streaming, requires effective radio resource management (RRM) to handle traffic with strict quality-of-service constraints over Long-Term Evolution (LTE) and beyond systems. Special care is needed to limit system performance degradation when multiple multicast streams are simultaneously transmitted. To this aim, this paper proposes an RRM policy based on a subgrouping technique for the delivery of scalable multicast video flows in a cell. Our proposal enhances the legacy multicast transmission over LTE systems by exploiting multiuser diversity and the users' channel quality feedbacks. Moreover, it is designed to take advantage of the frequency selectivity in the subgroup formation. Simulation results demonstrate the effectiveness of the proposed scheme, which outperforms existing approaches from the literature. It succeeds in achieving higher spectral efficiency and guaranteeing adequate video quality to all multicast receivers and improved quality to those with good channel conditions. [ABSTRACT FROM AUTHOR]

Next generation cellular networks (5G) have to deal with massive deployment of machine-type-communication (MTC) devices, expected to cause congestion and system overload in both the radio access network (RAN) and the core network (CN). Moreover, not only would the network suffer from the system overload, but also the MTC devices would experience high latency to access the channel and high power consumption due to the retransmission attempts. Indeed, power consumption is a critical issue in MTC, as the devices are not plugged into the electrical supply, e.g., in the case of sensor devices. To alleviate system overload (caused by the massive MTC deployment), the 3GPP proposed the group paging (GP) method. However, its performances dramatically decrease when increasing the number of MTC devices being paged. In this paper, we devise a novel method, named further improvement-traffic scattering for group paging (FI-TSFGP), which aims to improve the performance of GP when the number of MTC devices is high. FI-TSFGP scatters the paging operation of the MTC devices over a GP interval instead of letting all of the devices start the channel access procedure at nearly the same time. By doing so, FI-TSFGP achieves high-channel access probability for MTC devices, leading to the reduction of both the channel access latency and power consumption. Compared to GP and two other schemes, simulation results clearly demonstrate the high performance of FI-TSFGP in terms of: success and collision probabilities, average access delay, average number of preamble transmissions, and ultimately energy conservation. [ABSTRACT FROM AUTHOR]

This work presents a receiver capable of receiving three simultaneous cellular channels with an aggregate bandwidth of 60 MHz, enabling a 300 Mb/s downlink rate. The receiver has 16 RF LNA ports covering the cellular bands within the 572–2700 MHz frequency range. It supports LTE-advanced Rel-12 Cat6, HSPA+ Rel-11, TD-SCDMA Rel-9, and GSM/EDGE Rel-9. The 40 nm CMOS receiver consumes 13.7 and 17.6 mA of battery current in 3G and LTE modes, respectively, including the PLL, DCXO, and biasing for a single channel. [ABSTRACT FROM PUBLISHER]

Fourth generation LTE has been selected by U.S. federal and EU authorities to be the technology for public safety networks that would allow first responders to seamlessly communicate between agencies and across geographical locations in tactical and emergency scenarios. From Release 11 on, 3GPP has been developing and specifying dedicated nationwide public safety broadband networks that will be scalable, robust, and resilient, and can address the specific communication needs of emergency services. In this realm, the requirements and scenarios for isolated E-UTRAN with no or limited backhaul access to the core network are still in progress. In this article, we survey possible public safety use cases with the induced network topologies, discuss the current status of the 3GPP standards, and highlight future challenges. We further elaborate on the need to support mobile backhauling in moving-cell scenarios and describe two LTEbased solutions to enable dynamic meshing among the base stations. [ABSTRACT FROM AUTHOR]

This paper explores the problem of joint mode selection, spectrum management, power control, and interference mitigation for device-to-device (D2D) communication underlaying a Long Term Evolution-Advanced (LTE-A) network. We consider a dynamic mode selection scenario, in which the modes (D2D or cellular) of the devices depend on optimal allocations. To improve the quality of service (QoS) for the users, the optimization objective in a corresponding problem is formulated in terms of buffer size of user equipments (UEs), which is estimated based on buffer status information collected by the UEs. The realizations of a resource allocation approach presented in the paper include its real-time and non-real-time implementations, as well as two modifications applicable to a standard LTE-Direct (LTE-D) network. Performance of the proposed algorithms has been evaluated using the OPNET-based simulations. All algorithms show improved performance in terms of mean packet end-to-end delay when compared to most relevant schemes proposed earlier. [ABSTRACT FROM AUTHOR]

A new design of primary synchronization signal (PSS) sequences and an efficient detection algorithm for multi-beam satellite long-term evolution (LTE) systems are investigated in this paper. First, a transmit-timing adjustment method is proposed to reduce the large time difference of arrival of received signals from different satellites. Then, using the particular subcarrier mapping scheme of LTE, original Zadoff-Chu sequences are generalized to obtain more candidate sequences with good correlation properties. Later on, choosing an optimal subset from these candidate sequences, new PSS sequences for seamless global coverage multi-beam satellite-LTE systems are obtained. Subsequently, an efficient synchronization and low complexity PSS detection algorithm using interference cancellation method is presented. Finally, simulation results verify the effectiveness of the proposed scheme. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Currently public safety and security communication systems depend on reliable and secure PMR networks that are mainly devoted to provide voice services. However, the evolutionary trend for professional mobile radio (PMR) networks is toward the provision of new value-added multimedia services such as video streaming, in order to improve situational awareness and enhance life-saving operations. The challenge here is to exploit the future commercial broadband networks to deliver voice and multimedia services satisfying PMR service requirements. In particular, a viable solution now seems to be the adaption of the new Long Term Evolution technology to provide IP-based broadband services with the security and reliability typical of PMR networks. This article outlines different alternatives to achieve this goal and, in particular, proposes a proper solution for providing multimedia services with PMR standards over commercial LTE networks. [ABSTRACT FROM PUBLISHER]

The discontinuous reception (DRX) mechanism has been adopted in a Long-Term Evolution (LTE) system as a core technology to prolong the user equipment's (UE's) battery lifetime. With the development of Mobile Internet, there is an increasingly urgent need to optimize the DRX performance to accommodate emerging applications. To describe the self-similarity exhibited by the applications, the truncated-Pareto distributed arrival traffic model is introduced into the LTE-DRX analytical framework. Following this premise, an online power-saving strategy (OPSS) has been designed on the basis of our previously proposed DRX analytical model. The OPSS, for the purpose of improving the UE's energy efficiency, is composed of an estimation phase and an optimization phase. In the first phase, several derived statistical estimators are deployed to capture the fluctuations of traffic conditions and DRX operations. It is shown that these estimators could estimate the statistics within just 1 s. In the second phase, the DRX configuration is optimized by considering the tradeoff between packet delay and power savings. Through simulations, we study the impact of various traffic conditions and the efficiency of OPSS. The results have demonstrated that the proposed OPSS could outperform the conventional LTE DRX mechanism in terms of both energy conservation and packet delay. [ABSTRACT FROM PUBLISHER]

A novel architecture for efficient time and frequency synchronization, applied to the long-term evolution (LTE) standard, is proposed. For symbol timing, we propose applying a symbol-folding method on top of the sign-bit reduction technique, leading to a novel algorithm for the cyclic prefix-type recognition in LTE. Following the symbol timing, the fractional carrier frequency offset is estimated and compensated using an adaptive gain loop, which allows for a high-accuracy compensation in a short interval. In the frequency domain, for cell search, we propose a sign-bit reduction technique on top of the matched filter method for the primary synchronization signal detection. In addition, we propose the sign-bit maximum-likelihood sequence detection algorithm for the secondary synchronization signal analysis. These methods result in >90% hardware reduction in the cell search compared with the state-of-the-art design. Moreover, possible structures for the frequency tracking in LTE are investigated leading to an experimental comparison, used to choose the best hardware-efficient structure. The proposed architecture is fabricated in a 130-nm CMOS technology occupying 0.68 \mathrmmm^2 of silicon area. At 25 °C and 1.2 V supply voltage, the fabricated chip consumes 34.4 mW at 42 MHz in the time domain and 34.6 mW at 188 MHz in the frequency domain. The fabricated and tested synchronizer core proves to have an outstanding performance for all defined communication modes in LTE. [ABSTRACT FROM AUTHOR]

A movement-based location update (MBLU) scheme is effective and has low operation complexity. On the other hand, cellular networks use periodic LUs that are intrinsically time-based LUs (TBLUs) to detect the presence of a user equipment (UE) to avoid wasting network resources to deliver incoming calls to an abnormally detached UE. When implemented in a cellular network, the MBLU scheme must incorporate TBLUs to detect the UE presence. Thus, a hybrid-movement-based and time-based LU (HMTBLU) scheme arises naturally. Under the HMTBLU scheme, an LU occurs either when the movement threshold for MBLUs is reached or when the time threshold for TBLUs is reached. In this paper, we develop an embedded Markov chain approach to calculate the signaling cost of the HMTBLU scheme. We derive analytical formulas for the signaling cost and formulas useful for designing an optimal paging scheme. The accuracy of these formulas is validated through simulation. Based on these formulas, we conduct a numerical study to investigate the influence of various parameters on the signaling cost. The derived formulas can guide the implementation of the HMTBLU scheme in cellular networks, including Long-Term Evolution (LTE). Moreover, the developed mathematical approach can be applied to studying other LU schemes such as the LU scheme used in LTE. [ABSTRACT FROM AUTHOR]

Conventional spectrum sharing approaches assume that an unlicensed user accessing a licensed spectrum band autonomously operates by sensing (or detecting) the presence of the primary user, which is licensed to use the given band, with minimal coordination from the primary user. However, in this case, incorrect sensing decisions and resource allocation on the unlicensed secondary users' (SU) part can lead to undesired degradation of the primary users' performance. Therefore, there has been a recent paradigm shift to enable cooperative spectrum sharing, in which interaction is allowed between the primary and the secondary network for efficient spectrum utilization while limiting the interference experienced by a primary user. In this paper, we consider a cooperative spectrum sharing architecture in which the SU is assumed to be a cellular network. We then propose a novel fractional-frequency-reuse-based dynamic resource allocation (DRA) algorithm at the secondary (cellular) network. The joint DRA optimization involves simultaneous spectrum allocation across different base stations and then across users within a base station. It is an NP-hard problem and is prohibitively complex to solve for a large cellular network. Therefore, to reduce the complexity of the joint problem and offer a tractable solution, we formulate layered scheduling algorithms for cross-layer resource allocation. Furthermore, the feedback overhead between the layers is kept minimal. Finally, using simulations, we compare our proposed DRA scheme with other resource allocation schemes for sum system throughput, as well as for fairness in allocation. We also present the result for the case when the available primary spectrum varies over time and locations of SUs. [ABSTRACT FROM AUTHOR]

Assuring quality-of-service (QoS) and guaranteeing effective utilization of resources in a network with heterogeneous traffic is difficult due to the conflicting requirements associated with the different types of traffic. Nevertheless, emerging high-bandwidth third/fourth-generation (3G/4G) technologies, such as Long-Term Evolution (LTE) and LTE-Advanced, are expected to meet the demands of new applications by providing high data rates while simultaneously satisfying each of the individual QoS criteria. The relevant standards recommend single-carrier frequency-division multiple access (SC-FDMA) as the preferred uplink transmission scheme. In this paper, we have formulated the uplink scheduling problem for SC-FDMA-based heterogeneous traffic systems considering both standard specific constraints and individual user QoS requirements. To capture the QoS requirements of different types of traffic, we adopt a utility function that is already used for the downlink operation of code-division multiple-access (CDMA)-based systems. We also consider an opportunity cost function that is based on granular resource utilization to increase the usefulness of our results in practical situations. We have used the dual decomposition method to solve the resulting problem. Given the high computational complexity of the optimal solution, we have also proposed a suboptimal algorithm that is less complex but which offers acceptable performance. In our evaluation of the performance of our proposed uplink scheduling scheme, we assume that the offered traffic is a combination of best effort traffic, traffic with specified delay bounds, and traffic with specified throughput requirements. An extensive set of simulation results demonstrate the efficacy and effectiveness of our scheme compared with existing solutions employed by LTE, which is a representative SC-FDMA-based system. [ABSTRACT FROM PUBLISHER]

This work proposes a new radio resource allocation scheme for the green uplink Long-Term Evolution (LTE) networks. The proposed scheme aims at efficiently allocating the resource blocks (RBs) and the transmission power of the user equipment (UE). The allocation of RBs is based on the opportunistic and efficient RB allocation (OEA) algorithm, whose objective is to maximize the aggregate throughput while being subjected to single-carrier frequency-division multiple-access (SC-FDMA) constraints. An evolution of the algorithm, which is called quality-of-service (QoS)-based OEA, providing QoS differentiation, is also presented. It allocates a given maximum number of RBs to each UE, which is set according to the user's QoS requirements. Once the allocation of RBs is completed, the allocation of the UE transmission power is performed. The transmission power considers the UE channel conditions over its whole allocated RBs. Its value is reduced as much as possible and adjusted such that the user's required QoS satisfies throughput demand previously determined by the RB allocation. The proposed radio resource management algorithm has several interesting properties. It maximizes the aggregate throughput, decreases the ratio of inefficiently allocated RBs, cancels the RB's wastage, and increases the energy efficiency without affecting the user's throughput. Furthermore, the OEA algorithms can be implemented in LTE hardware equipment devices on account of their low computational complexity. [ABSTRACT FROM PUBLISHER]

The paper presents a practical application of the crowdsensing idea to measure human mobility and signal coverage in cellular networks. Currently, virtually everyone is carrying a mobile phone, which may be used as a sensor to gather research data by measuring, e.g., human mobility and radio signal levels. However, many users are unwilling to participate in crowdsensing experiments. This work begins with the analysis of the barriers for engaging people in crowdsensing. A survey showed that people who agree to participate in crowdsensing expect a minimum impact on their battery lifetime and phone usage habits. To address these requirements, this paper proposes an application for measuring the location and signal strength data based on energy-efficient GPS tracking, which allows one to perform the measurements of human mobility and radio signal levels with minimum energy utilization and without any engagement of the user. The method described combines measurements from the accelerometer with effective management of the GPS to monitor the user mobility with the decrease in battery lifetime by approximately 20%. To show the applicability of the proposed platform, the sample results of signal level distribution and coverage maps gathered for an LTE network and representing human mobility are shown. [ABSTRACT FROM AUTHOR]

Purpose - Mobile data traffic globally is increasing rapidly in both enterprise and consumer segments. The purpose of this paper is to identify a new network architecture and opportunity that support ubiquitous mobile work for higher-education institutions. Design/methodology/approach - It reviews existing literature and enabling technologies and proposes integrating both wide-area Long Term Evolution-Advanced (LTE-Advanced) and local-area IEEE 802.11ac networks for seamless, gigabit-speed services. A decision framework for moving toward such architecture and a cost/benefit analysis are also presented. Findings - Integrating both LTE-Advanced and IEEE 802.11ac networks for seamless connectivity is technically and organizationally feasible, provided that a higher-education institution has faculty and staff that require locational and interactional mobility. The cost/benefit analysis also shows that moving to the new architecture has potential benefits that can accrue to the higher-education institution. Research limitations/implications - With the coming availability of these wide-area and local-area gigabit networks, a new architecture that can ubiquitously supports mobile workers may be advantageous to universities and colleges. Originality/value - To the best of the authors' knowledge, this paper is one of the first that proposes such integrated architecture in the context of higher-education institutions. In addition to the examination of technological issues and proposed architecture, the decision framework, and cost/ benefit analysis should be valuable for institutions contemplating the move toward the new architecture and for guiding further research in this area. [ABSTRACT FROM AUTHOR]

This paper presents an effective cross-layer designed packet scheduling, call admission control, and handover system to provide a seamless video streaming services over LTE network. The proposed packet scheduling algorithm allocates wireless network resources to admitted UEs while considering QoE states and wireless link states of UEs simultaneously. The proposed call admission control algorithm estimates the cell availability at the next call arriving time based on the current QoE states of UEs to determine the admission of a new UE. The proposed handover algorithm determines the appropriate handover trigger timing to keep a balance of the QoE states among immediately adjacent cells based on both the cell availability and wireless link states. Finally, simulations are conducted to evaluate the performance of the proposed system. Results indicate that the proposed cross-layer designed system improves the QoE states of all admitted UEs and overall network utilization better than other existing methods. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive iteration detection scheme for a combination of STBC and SM scheme in LTE systems. The hybrid space-time block code system is a combination of STBC and SM scheme. It obtains both diversity gain and spectral efficiency gain. The conventional combination of STBC and SM scheme can't achieve good BER performance of STBC symbols due to interference from other symbols. The iterative V-BLAST detection scheme improves BER performance but has complex iterative detection process. The proposed scheme applies the adaptive iterative detection scheme by channel condition and can reduce complexity of LTE systems. LTE systems require high speed. Therefore, this scheme can be applied effectively in LTE systems. [ABSTRACT FROM AUTHOR]

In cellular systems, user equipment must perform the cell search procedure in order to acquire symbol timing, frame timing, carrier frequency offset (CFO), sector cell index (CID) and group CID. This paper proposes a low-complexity sector CID and CFO detection scheme in a long term evolution downlink system. To achieve low complexity, a primary synchronization signal used for parameter estimation is grouped into a number of subsets so that the phase of pilots in each subset is unique. The performance and complexity of the proposed joint detection scheme are compared with those of the conventional joint detection schemes. We show via simulations that such a design achieves exactly the same detection accuracy as that of the conventional joint detection schemes with one half of complexity being saved. [ABSTRACT FROM AUTHOR]

Long-Term Evolution (LTE) handsets operate in frequency bands that can be affected by impulsive noise (IN). LTE handsets have at least two receive antennas. We present the double-detection method, which is a variation of the classical threshold method to remove IN and consists in eliminating those signal samples whose amplitude simultaneously exceeds a specific threshold at both antennas. The performance of the method is better when the correlation between the signals at both antennas is low. This makes it possible that the handset dynamically sets the detection threshold according to the estimated channel conditions. The double-detection method is currently patent pending. [ABSTRACT FROM PUBLISHER]

Small cell deployment using Home eNB improves the LTE/LTE Advanced network coverage and capacity providing its relay and data offloading functions. However, latency of inbound mobility to the small cell is a critical obstacle to the deployment because it spends much time detecting an associated small cell due to its sparse deployment and identifying the target small cell because of the delay caused by the verification procedure required before performing inbound handover to the target. Therefore, the inbound handover latency should be minimized to encourage the deployment of the Home eNB. To tackle the handover latency problem, this paper proposes a practically possible solution for design of Layer 1 search/measure scheduler in LTE small cell-associated user equipment. The proposed strategy especially enhances the performance of the LTE Home eNB discovery and guarantees to meet the requirements defined in the corresponding conformance test specifications. Performance evaluation by computer simulation shows that the proposed scheme provides a proper guideline on the Layer 1 software implementation. [ABSTRACT FROM AUTHOR]