Showing papers on "Cellular network published in 2012"
Abstract: Cellular networks are in a major transition from a carefully planned set of large tower-mounted base-stations (BSs) to an irregular deployment of heterogeneous infrastructure elements that often additionally includes micro, pico, and femtocells, as well as distributed antennas. In this paper, we develop a tractable, flexible, and accurate model for a downlink heterogeneous cellular network (HCN) consisting of K tiers of randomly located BSs, where each tier may differ in terms of average transmit power, supported data rate and BS density. Assuming a mobile user connects to the strongest candidate BS, the resulting Signal-to-Interference-plus-Noise-Ratio (SINR) is greater than 1 when in coverage, Rayleigh fading, we derive an expression for the probability of coverage (equivalently outage) over the entire network under both open and closed access, which assumes a strikingly simple closed-form in the high SINR regime and is accurate down to -4 dB even under weaker assumptions. For external validation, we compare against an actual LTE network (for tier 1) with the other K-1 tiers being modeled as independent Poisson Point Processes. In this case as well, our model is accurate to within 1-2 dB. We also derive the average rate achieved by a randomly located mobile and the average load on each tier of BSs. One interesting observation for interference-limited open access networks is that at a given \sinr, adding more tiers and/or BSs neither increases nor decreases the probability of coverage or outage when all the tiers have the same target-SINR.
1,640 citations
TL;DR: The 3GPP Long Term Evolution system is used as a baseline for D2D design, some of the key design challenges are reviewed, and solution approaches that allow cellular devices and D1D pairs to share spectrum resources and thereby increase the spectrum and energy efficiency of traditional cellular networks are proposed.
Abstract: Device-to-device (D2D) communications underlaying a cellular infrastructure has been proposed as a means of taking advantage of the physical proximity of communicating devices, increasing resource utilization, and improving cellular coverage. Relative to the traditional cellular methods, there is a need to design new peer discovery methods, physical layer procedures, and radio resource management algorithms that help realize the potential advantages of D2D communications. In this article we use the 3GPP Long Term Evolution system as a baseline for D2D design, review some of the key design challenges, and propose solution approaches that allow cellular devices and D2D pairs to share spectrum resources and thereby increase the spectrum and energy efficiency of traditional cellular networks. Simulation results illustrate the viability of the proposed design.
1,391 citations
TL;DR: A tractable framework for SINR analysis in downlink heterogeneous cellular networks (HCNs) with flexible cell association policies is developed and the average ergodic rate of the typical user, and the minimum average users throughput - the smallest value among the average user throughputs supported by one cell in each tier is derived.
Abstract: In this paper we develop a tractable framework for SINR analysis in downlink heterogeneous cellular networks (HCNs) with flexible cell association policies. The HCN is modeled as a multi-tier cellular network where each tier's base stations (BSs) are randomly located and have a particular transmit power, path loss exponent, spatial density, and bias towards admitting mobile users. For example, as compared to macrocells, picocells would usually have lower transmit power, higher path loss exponent (lower antennas), higher spatial density (many picocells per macrocell), and a positive bias so that macrocell users are actively encouraged to use the more lightly loaded picocells. In the present paper we implicitly assume all base stations have full queues; future work should relax this. For this model, we derive the outage probability of a typical user in the whole network or a certain tier, which is equivalently the downlink SINR cumulative distribution function. The results are accurate for all SINRs, and their expressions admit quite simple closed-forms in some plausible special cases. We also derive the average ergodic rate of the typical user, and the minimum average user throughput - the smallest value among the average user throughputs supported by one cell in each tier. We observe that neither the number of BSs or tiers changes the outage probability or average ergodic rate in an interference-limited full-loaded HCN with unbiased cell association (no biasing), and observe how biasing alters the various metrics.
1,140 citations
TL;DR: New theoretical models for understanding the heterogeneous cellular networks of tomorrow are discussed, and the practical constraints and challenges that operators must tackle in order for these networks to reach their potential are discussed.
Abstract: The proliferation of internet-connected mobile devices will continue to drive growth in data traffic in an exponential fashion, forcing network operators to dramatically increase the capacity of their networks. To do this cost-effectively, a paradigm shift in cellular network infrastructure deployment is occurring away from traditional (expensive) high-power tower-mounted base stations and towards heterogeneous elements. Examples of heterogeneous elements include microcells, picocells, femtocells, and distributed antenna systems (remote radio heads), which are distinguished by their transmit powers/ coverage areas, physical size, backhaul, and propagation characteristics. This shift presents many opportunities for capacity improvement, and many new challenges to co-existence and network management. This article discusses new theoretical models for understanding the heterogeneous cellular networks of tomorrow, and the practical constraints and challenges that operators must tackle in order for these networks to reach their potential.
911 citations
TL;DR: It is demonstrated analytically that in the large-number-of-antennas regime, the pilot contamination effect is made to vanish completely under certain conditions on the channel covariance.
Abstract: This paper addresses the problem of channel estimation in multi-cell interference-limited cellular networks. We consider systems employing multiple antennas and are interested in both the finite and large-scale antenna number regimes (so-called "massive MIMO"). Such systems deal with the multi-cell interference by way of per-cell beamforming applied at each base station. Channel estimation in such networks, which is known to be hampered by the pilot contamination effect, constitute a major bottleneck for overall performance. We present a novel approach which tackles this problem by enabling a low-rate coordination between cells during the channel estimation phase itself. The coordination makes use of the additional second-order statistical information about the user channels, which are shown to offer a powerful way of discriminating across interfering users with even strongly correlated pilot sequences. Importantly, we demonstrate analytically that in the large-number-of-antennas regime, the pilot contamination effect is made to vanish completely under certain conditions on the channel covariance. Gains over the conventional channel estimation framework are confirmed by our simulations for even small antenna array sizes.
871 citations
TL;DR: This article studies direct communications between user equipments in the LTE-advanced cellular networks to provide better user experience and make profit accordingly.
Abstract: This article studies direct communications between user equipments in the LTE-advanced cellular networks. Different from traditional device-to-device communication technologies such as Bluetooth and WiFi-direct, the operator controls the communication process to provide better user experience and make profit accordingly. The related usage cases and business models are analyzed. Some technical considerations are discussed, and a resource allocation and data transmission procedure is provided.
682 citations
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TL;DR: A new network architecture that overlays an uplink cellular network with randomly deployed PBs for powering mobiles, called a hybrid network, is proposed and it is proved that the outage constraint is satisfied so long as the product pλbα/2 is above a given threshold where α is the path-loss exponent.
Abstract: Microwave power transfer (MPT) delivers energy wirelessly from stations called power beacons (PBs) to mobile devices by microwave radiation. This provides mobiles practically infinite battery lives and eliminates the need of power cords and chargers. To enable MPT for mobile charging, this paper proposes a new network architecture that overlays an uplink cellular network with randomly deployed PBs for powering mobiles, called a hybrid network. The deployment of the hybrid network under an outage constraint on data links is investigated based on a stochastic-geometry model where single-antenna base stations (BSs) and PBs form independent homogeneous Poisson point processes (PPPs) and single-antenna mobiles are uniformly distributed in Voronoi cells generated by BSs. In this model, mobiles and PBs fix their transmission power at p and q, respectively; a PB either radiates isotropically, called isotropic MPT, or directs energy towards target mobiles by beamforming, called directed MPT. The model is applied to derive the tradeoffs between the network parameters including p, q, and the BS/PB densities under the outage constraint. First, consider the deployment of the cellular network. It is proved that the outage constraint is satisfied so long as the product the BS density decreases with increasing p following a power law where the exponent is proportional to the path-loss exponent. Next, consider the deployment of the hybrid network assuming infinite energy storage at mobiles. It is shown that for isotropic MPT, the product between q, the PB density, and the BS density raised to a power proportional to the path-loss exponent has to be above a given threshold so that PBs are sufficiently dense; for directed MPT, a similar result is obtained with the aforementioned product increased by the array gain. Last, similar results are derived for the case of mobiles having small energy storage.
593 citations
TL;DR: This work proposes to exploit opportunistic communications to facilitate information dissemination in the emerging Mobile Social Networks (MoSoNets) and thus reduce the amount of mobile data traffic.
Abstract: 3G networks are currently overloaded, due to the increasing popularity of various applications for smartphones. Offloading mobile data traffic through opportunistic communications is a promising solution to partially solve this problem, because there is almost no monetary cost for it. We propose to exploit opportunistic communications to facilitate information dissemination in the emerging Mobile Social Networks (MoSoNets) and thus reduce the amount of mobile data traffic. As a case study, we investigate the target-set selection problem for information delivery. In particular, we study how to select the target set with only k users, such that we can minimize the mobile data traffic over cellular networks. We propose three algorithms, called Greedy, Heuristic, and Random, for this problem and evaluate their performance through an extensive trace-driven simulation study. Our simulation results verify the efficiency of these algorithms for both synthetic and real-world mobility traces. For example, the Heuristic algorithm can offload mobile data traffic by up to 73.66 percent for a real-world mobility trace. Moreover, to investigate the feasibility of opportunistic communications for mobile phones, we implement a proof-of-concept prototype, called Opp-off, on Nokia N900 smartphones, which utilizes their Bluetooth interface for device/service discovery and content transfer.
513 citations
TL;DR: A survey of the different state-of-the-art approaches for interference and resource management in orthogonal frequency-division multiple access (OFDMA)-based femtocell networks and a qualitative comparison among the different approaches is provided.
Abstract: One of the effective techniques of improving the coverage and enhancing the capacity and data rate in cellular wireless networks is to reduce the cell size (i.e., cell splitting) and transmission distances. Therefore, the concept of deploying femtocells over macrocell has recently attracted growing interests in academia, industry, and standardization forums. Various technical challenges towards mass deployment of femtocells have been addressed in recent literature. Interference mitigation between neighboring femtocells and between the femtocell and macrocell is considered to be one of the major challenges in femtocell networks because femtocells share the same licensed frequency spectrum with macrocell. Further, the conventional radio resource management techniques for hierarchical cellular system is not suitable for femtocell networks since the positions of the femtocells are random depending on the users' service requirement. In this article, we provide a survey of the different state-of-the-art approaches for interference and resource management in orthogonal frequency-division multiple access (OFDMA)-based femtocell networks. A qualitative comparison among the different approaches is provided. To this end, open challenges in designing interference management schemes for OFDMA femtocell networks are discussed.
422 citations
01 Dec 2012
TL;DR: A novel approach in increasing the capacity of LTE cellular networks by leveraging high frequency reuse at high frequency bands in conjunction with a Macrocell, which can achieve high capacity enhancement using small cells at the same time taking into consideration mobility, scalability and flexibility requirements for massive deployment.
Abstract: This paper introduces a novel approach in increasing the capacity of LTE cellular networks. The solution is based on massive deployment of small cells by leveraging high frequency reuse at high frequency bands in conjunction with a Macrocell. The presence, discovery and usage of the small cells are controlled dynamically by a Macrocell in a master-slave configuration hence they are called Phantom Cells. To realize this concept, a new method of managing the connections between mobile terminals and small cell nodes is introduced. It is achieved by splitting the Control and User (C/U) planes of the radio link. The combination of C/U-plane split and Phantom Cells can achieve high capacity enhancement using small cells at the same time taking into consideration mobility, scalability and flexibility requirements for massive deployment. The advantages of this approach as well as the implementation aspects are described in the paper. Simulations were also conducted to verify the concept and the results show some promising capacity enhancements. The rest of the paper describes the Phantom Cell concept as well as the challenges of deploying small cells in LTE networks.
396 citations
25 Oct 2012
TL;DR: It is argued that software defined networking (SDN) can simplify the design and management of cellular data networks, while enabling new services, but supporting many subscribers, frequent mobility, fine-grained measurement and control, and real-time adaptation introduces new scalability challenges that future SDN architectures should address.
Abstract: Existing cellular networks suffer from inflexible and expensive equipment, complex control-plane protocols, and vendor-specific configuration interfaces. In this position paper, we argue that software defined networking (SDN) can simplify the design and management of cellular data networks, while enabling new services. However, supporting many subscribers, frequent mobility, fine-grained measurement and control, and real-time adaptation introduces new scalability challenges that future SDN architectures should address. As a first step, we propose extensions to controller platforms, switches, and base stations to enable controller applications to (i) express high-level policies based on subscriber attributes, rather than addresses and locations, (ii) apply real-time, fine-grained control through local agents on the switches, (iii)perform deep packet inspection and header compression on packets, and (iv)remotely manage shares of base-station resources.
TL;DR: The features of M2M services in the third generation (3G) long-term evolution and its advancement (LTE-Advanced) networks are reviewed and various radio resource allocation schemes are presented to quantify their utility in LTE-Advanced cellular networks.
Abstract: Machine-to-machine (M2M) communications are expected to provide ubiquitous connectivity between machines without the need of human intervention. To support such a large number of autonomous devices, the M2M system architecture needs to be extremely power and spectrally efficient. This article thus briefly reviews the features of M2M services in the third generation (3G) long-term evolution and its advancement (LTE-Advanced) networks. Architectural enhancements are then presented for supporting M2M services in LTE-Advanced cellular networks. To increase spectral efficiency, the same spectrum is expected to be utilized for human-to- human (H2H) communications as well as M2M communications. We therefore present various radio resource allocation schemes and quantify their utility in LTE-Advanced cellular networks. System-level simulation results are provided to validate the performance effectiveness of M2M communications in LTE-Advanced cellular networks.
TL;DR: This paper examines the downlink of a heterogeneous cellular network made up of multiple tiers of transmitters and provides a general theoretical analysis of the distribution of the SINR at an arbitrarily-located user using physically realistic stochastic models.
Abstract: The Signal to Interference Plus Noise Ratio (SINR) on a wireless link is an important basis for consideration of outage, capacity, and throughput in a cellular network. It is therefore important to understand the SINR distribution within such networks, and in particular heterogeneous cellular networks, since these are expected to dominate future network deployments . Until recently the distribution of SINR in heterogeneous networks was studied almost exclusively via simulation, for selected scenarios representing pre-defined arrangements of users and the elements of the heterogeneous network such as macro-cells, femto-cells, etc. However, the dynamic nature of heterogeneous networks makes it difficult to design a few representative simulation scenarios from which general inferences can be drawn that apply to all deployments. In this paper, we examine the downlink of a heterogeneous cellular network made up of multiple tiers of transmitters (e.g., macro-, micro-, pico-, and femto-cells) and provide a general theoretical analysis of the distribution of the SINR at an arbitrarily-located user. Using physically realistic stochastic models for the locations of the base stations (BSs) in the tiers, we can compute the general SINR distribution in closed form. We illustrate a use of this approach for a three-tier network by calculating the probability of the user being able to camp on a macro-cell or an open-access (OA) femto-cell in the presence of Closed Subscriber Group (CSG) femto-cells. We show that this probability depends only on the relative densities and transmit powers of the macro- and femto-cells, the fraction of femto-cells operating in OA vs. Closed Subscriber Group (CSG) mode, and on the parameters of the wireless channel model. For an operator considering a femto overlay on a macro network, the parameters of the femto deployment can be selected from a set of universal curves.
TL;DR: Simulation results show that the smart grid has significant impacts on green wireless cellular networks, and the proposed scheme can significantly reduce operational expenditure and CO_2 emissions in green wireless Cellular networks.
Abstract: Recently, there is great interest in considering the energy efficiency aspect of cellular networks. On the other hand, the power grid infrastructure, which provides electricity to cellular networks, is experiencing a significant shift from the traditional electricity grid to the smart grid. When a cellular network is powered by the smart grid, only considering energy efficiency in the cellular network may not be enough. In this paper, we consider not only energy-efficient communications but also the dynamics of the smart grid in designing green wireless cellular networks. Specifically, the dynamic operation of cellular base stations depends on the traffic, real-time electricity price, and the pollutant level associated with electricity generation. Coordinated multipoint (CoMP) is used to ensure acceptable service quality in the cells whose base stations have been shut down. The active base stations decide on which retailers to procure electricity from and how much electricity to procure. We formulate the system as a Stackelberg game, which has two levels: a cellular network level and a smart grid level. Simulation results show that the smart grid has significant impacts on green wireless cellular networks, and our proposed scheme can significantly reduce operational expenditure and CO_2 emissions in green wireless cellular networks.
01 Apr 2012
TL;DR: This paper evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard, based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters.
Abstract: With the explosion of wireless communications in number of users and data rates, the reduction of network power consumption becomes more and more critical. This is especially true for base stations which represent a dominant share of the total power in cellular networks. In order to study power reduction techniques, a convenient power model is required, providing estimates of the power consumption in different scenarios. This paper proposes such a model, accurate but simple to use. It evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard. It is flexible enough to enable comparisons between state-of-the-art and advanced configurations, and an easy adaptation to various scenarios. The model is based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters.
TL;DR: An overview of the challenges and solutions in the design of relay stations as one of the salient features for 3GPP LTE advanced is provided.
Abstract: With the ever growing demand of data applications, traditional cellular networks face the challenges of providing enhanced system capacity, extended cell coverage, and improved minimum throughput in a cost-effective manner. Wireless relay stations, especially when operating in a halfduplex operation, make it possible without incurring high site acquisition and backhaul costs. Design of wireless relay stations faces the challenges of providing backward compatibility, minimizing complexity, and maximizing efficiency. This article provides an overview of the challenges and solutions in the design of relay stations as one of the salient features for 3GPP LTE advanced.
TL;DR: Simulation results show that the energy- efficient design greatly improves EE compared with the conventional spectral-efficient design and the low-complexity suboptimal approaches can achieve a promising tradeoff between performance and complexity.
Abstract: The widespread application of multimedia wireless services and requirements of ubiquitous access have triggered rapidly booming energy consumption at both the base station side and the user equipment (UE) side. Hence, energy-efficient design in wireless networks is very important and is becoming an inevitable trend. In this paper, we study the energy-efficient resource allocation in both downlink and uplink cellular networks with orthogonal frequency division multiple access (OFDMA). For the downlink transmission, the generalized energy efficiency (EE) is maximized while for the uplink case the minimum individual EE is maximized, both under certain prescribed per-UE quality-of-service (QoS) requirements. For both transmission scenarios, we first provide the optimal solution and then develop a suboptimal but low-complexity approach by exploring the inherent structure and property of the energy-efficient design. For the downlink case, by modifying the original problem, we also find a computationally efficient and numerically tractable upper bound on the EE, which indicates the performance limit and is demonstrated to be quite tight if the number of subcarriers is larger than that of UEs and motivates us to find a near-optimal approach relying on the quasiconcave relation between the modified EE and transmit power. Simulation results show that the energy-efficient design greatly improves EE compared with the conventional spectral-efficient design and the low-complexity suboptimal approaches can achieve a promising tradeoff between performance and complexity.
15 Aug 2012
TL;DR: The 2012 edition of the World Bank's information and communications for development report analyzes the growth and evolution of mobile telephony, and the rise of data-based services delivered to handheld devices, including apps as mentioned in this paper.
Abstract: This 2012 edition of the World Bank's information and communications for development report analyzes the growth and evolution of mobile telephony, and the rise of data-based services delivered to handheld devices, including apps. The report explores the consequences for development of the emerging app economy. It summarizes current thinking and seeks to inform the debate on the use of mobile phones for development. This report looks at key ecosystem-based applications in agriculture, health, financial services, employment, and government, with chapters devoted to each. With some 6 billion mobile subscriptions in use worldwide, around three-quarters of the world's inhabitants now have access to a mobile phone. Mobiles are arguably the most ubiquitous modern technology: in some developing countries, more people have access to a mobile phone than to a bank account, electricity, or even clean water. Mobile communications now offer major opportunities to advance human development from providing basic access to education or health information to making cash payments to stimulating citizen involvement in democratic processes. The developing world is more mobile than the developed world. In the developed world, mobile communications have added value to legacy communication systems and have supplemented and expanded existing information flows. However, the developing world is following a different, mobile first development trajectory. Many mobile innovations such as multi-SIM card phones, low-value recharges, and mobile payments have originated in poorer countries and are spreading from there. New mobile applications that are designed locally and rooted in the realities of the developing world will be much better suited to addressing development challenges than applications transplanted from elsewhere. In particular, locally developed applications can address developing-country concerns such as digital literacy and affordability.
25 Mar 2012
TL;DR: This paper uses case studies to identify the design requirements and puts forth a strawman proposal for the named-data approach to address the challenge of direct V2V communications in vehicles.
Abstract: Vehicular networking is becoming reality. Today vehicles use TCP/IP to communicate with centralized servers through cellular networks. However many vehicular applications, such as information sharing for safety and real time traffic purposes, desire direct V2V communications which is difficult to achieve using the existing solutions. This paper explores the named-data approach to address this challenge. We use case studies to identify the design requirements and put forth a strawman proposal for the data name design to understand its advantages and limitations.
TL;DR: In this article, the authors provide a mathematical analysis of performance modeling for LTE networks and provide sufficient and necessary conditions for the feasibility of the load-coupling system, and provide results related to computational aspects for numerically approaching the solution.
Abstract: System-centric modeling and analysis are of key significance in planning and optimizing cellular networks. In this paper, we provide a mathematical analysis of performance modeling for LTE networks. The system model characterizes the coupling relation between the cell load factors, taking into account non-uniform traffic demand and interference between the cells with arbitrary network topology. Solving the model enables a network-wide performance evaluation in resource consumption. We develop and prove both sufficient and necessary conditions for the feasibility of the load-coupling system, and provide results related to computational aspects for numerically approaching the solution. The theoretical findings are accompanied with experimental results to instructively illustrate the application in optimizing LTE network configuration.
TL;DR: This paper proposes an analytical model for evaluating Strict FFR and Soft Frequency Reuse (SFR) deployments based on the spatial Poisson point process and results both capture the non-uniformity of heterogeneous deployments and produce tractable expressions which can be used for system design with StrictFFR and SFR.
Abstract: Interference management techniques are critical to the performance of heterogeneous cellular networks, which will have dense and overlapping coverage areas, and experience high levels of interference. Fractional frequency reuse (FFR) is an attractive interference management technique due to its low complexity and overhead, and significant coverage improvement for low-percentile (cell-edge) users. Instead of relying on system simulations based on deterministic access point locations, this paper instead proposes an analytical model for evaluating Strict FFR and Soft Frequency Reuse (SFR) deployments based on the spatial Poisson point process. Our results both capture the non-uniformity of heterogeneous deployments and produce tractable expressions which can be used for system design with Strict FFR and SFR. We observe that the use of Strict FFR bands reserved for the users of each tier with the lowest average \sinr provides the highest gains in terms of coverage and rate, while the use of SFR allows for more efficient use of shared spectrum between the tiers, while still mitigating much of the interference. Additionally, in the context of multi-tier networks with closed access in some tiers, the proposed framework shows the impact of cross-tier interference on closed access FFR, and informs the selection of key FFR parameters in open access.
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TL;DR: The proposed RWP mobility model is applied to cellular networks under both deterministic (hexagonal) and random (Poisson) base station (BS) models and it is found that the Poisson-Voronoi model is about as accurate in terms of mobility evaluation as hexagonal model, though being more pessimistic in that it predicts a higher handover rate and lower sojourn time.
Abstract: Despite the central role of mobility in wireless networks, analytical study on its impact on network performance is notoriously difficult. This paper aims to address this gap by proposing a random waypoint (RWP) mobility model defined on the entire plane and applying it to analyze two key cellular network parameters: handover rate and sojourn time. We first analyze the stochastic properties of the proposed model and compare it to two other models: the classical RWP mobility model and a synthetic truncated Levy walk model which is constructed from real mobility trajectories. The comparison shows that the proposed RWP mobility model is more appropriate for the mobility simulation in emerging cellular networks, which have ever-smaller cells. Then we apply the proposed model to cellular networks under both deterministic (hexagonal) and random (Poisson) base station (BS) models. We present analytic expressions for both handover rate and sojourn time, which have the expected property that the handover rate is proportional to the square root of BS density. Compared to an actual BS distribution, we find that the Poisson-Voronoi model is about as accurate in terms of mobility evaluation as hexagonal model, though being more pessimistic in that it predicts a higher handover rate and lower sojourn time.
06 May 2012
TL;DR: Computer simulation results demonstrate that the DAN using proposed DCA achieves higher spectrum efficiency than the conventional CN.
Abstract: In this paper, we propose a dynamic channel assignment (DCA) scheme for distributed antenna networks (DANs). DANs, in which many antennas are distributed in each cell, significantly reduce the transmit power compared to conventional cellular networks (CNs). In DAN, a different group of channels should be assigned for each distributed antenna to avoid the interference. Since DAN can also reduce the interference power due to its low transmit power property, the same channel groups can be reused even within the same cell. Proposed DCA scheme dynamically assigns the channels based on the co-channel interference measurement. Computer simulation results demonstrate that the DAN using proposed DCA achieves higher spectrum efficiency than the conventional CN.
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TL;DR: In this paper, the authors provide a comprehensive understanding of the development impact, ecosystem, and business models for mobile applications in agriculture and rural development (ARD) by providing a guide that facilitates the development and deployment of mobile applications for ARD.
Abstract: The dynamic growth of mobile communications technology is creating opportunities for economic growth, social empowerment, and grassroots innovation in developing countries. One of the areas with the greatest potential impact is in the contribution that mobile applications can make to agricultural and rural development (ARD), by providing access to information, markets, and services to millions of rural inhabitants. For both agricultural supply and demand, mobile phones can reduce waste, make delivery more efficient, and forge closer links between farmers and consumers. This report provides policymakers and development practitioners with a guide that facilitates the development and deployment of mobile applications for ARD. It also informs their understanding of the key drivers for promoting such applications and services in their countries. Using James Moore’s (1996) revised definition of ecosystems: economic communities based on interacting organizations and individuals the report identifies a wide range of players in the ecosystem for m-ARD apps, such as mobile network operators, m-app (mobile applications) providers, content providers, and various types of users. M-apps are software designed to take advantage of mobile technology and can be developed for technology besides mobile phones. But mobile phones have many key advantages: affordability, wide ownership, voice communications, and instant and convenient service delivery. As a result, there has been a global explosion in the number of m-apps, facilitated by the rapid evolution of mobile networks and by the increasing functions and falling prices of mobile handsets. M-apps are markedly different in developing countries because they typically run on second-generation (2G) phones rather than smartphones, which are far more common in developed countries. The report reviews country examples and extracts policy lessons and good practices. It also presents detailed studies of cases from Kenya, Philippines, and Sri Lanka, as well as summarizes 92 case studies from Africa, Asia, and Latin America. The goal is to provide a comprehensive understanding of the development impact, ecosystem, and business models for mobile applications in ARD. The report is intended to complement the recent ICT in Agriculture eSourcebook. One of the main findings is that an enabling platform (or platforms) is probably the most important factor for the development of m-ARD apps. Platforms can facilitate interactions among ecosystem players, increase access to users, provide technical standards, and incorporate payment mechanisms.
TL;DR: Simulation results show that the proposed spectrum-aware mobility management scheme for CR cellular networks can achieve better performance than conventional handoff schemes in terms of both cell capacity as well as mobility support in communications.
Abstract: Cognitive radio (CR) networks have been proposed as a solution to both spectrum inefficiency and spectrum scarcity problems. However, they face several challenges based on the fluctuating nature of the available spectrum, making it more difficult to support seamless communications, especially in CR cellular networks. In this paper, a spectrum-aware mobility management scheme is proposed for CR cellular networks. First, a novel network architecture is introduced to mitigate heterogeneous spectrum availability. Based on this architecture, a unified mobility management framework is developed to support diverse mobility events in CR networks, which consists of spectrum mobility management, user mobility management, and intercell resource allocation. The spectrum mobility management scheme determines a target cell and spectrum band for CR users adaptively dependent on time-varying spectrum opportunities, leading to increase in cell capacity. In the user mobility management scheme, a mobile user selects a proper handoff mechanism so as to minimize a switching latency at the cell boundary by considering spatially heterogeneous spectrum availability. Intercell resource allocation helps to improve the performance of both mobility management schemes by efficiently sharing spectrum resources with multiple cells. Simulation results show that the proposed method can achieve better performance than conventional handoff schemes in terms of both cell capacity as well as mobility support in communications.
Patent•
28 Feb 2012
TL;DR: In this paper, the authors present a method for aligning data transfer to a mobile device to optimize connections made by the mobile device in a cellular network by batching data received in multiple transactions.
Abstract: Systems and methods for aligning data transfer to optimize connections established for transmission over a wireless network are disclosed. In one aspect, embodiments of the present disclosure include a method, which may be implemented on a system, for aligning data transfer to a mobile device to optimize connections made by the mobile device in a cellular network. The method includes batching data received in multiple transactions directed to a mobile device for transmission to the mobile device over the cellular network such that a wireless connection need not be established with the mobile device every time each of the multiple transactions occurs. For example, the data received in the multiple transactions for the mobile device can be sent to the mobile device, in a single transaction over a single instantiation of wireless network connectivity at the mobile device.
TL;DR: In this article, the authors adopt a stochastic-geometry model of the downlink cellular network and analyze the mobile outage probability, which is shown to diminish inversely with the increasing ratio between the BS and mobile densities.
Abstract: The performance of a cellular network can be significantly improved by employing many base stations (BSs), which shortens transmission distances. However, there exist no known results on quantifying the performance gains from deploying many BSs. To address this issue, we adopt a stochastic-geometry model of the downlink cellular network and analyze the mobile outage probability. Specifically, given Poisson distributed BSs, the outage probability is shown to diminish inversely with the increasing ratio between the BS and mobile densities. Furthermore, we analyze the optimal tradeoff between the performance gain from increasing the BS density and the resultant network cost accounting for energy consumption, BS hardware and backhaul cables. The optimal BS density is proved to be proportional to the square root of the mobile density and the inverse of the square root of the cost factors considered.
TL;DR: This paper presents a novel LTE-based solution to support high throughput and continuous multimedia services for high speed train passengers based on a Cell Array that smartly organizes the cells along a railway, together with a femto cell service that aggregates traffic demands within individual train cabins.
Abstract: The recent advent of high speed trains introduces new mobility patterns in wireless environments. The LTE-A (Long Term Evolution of 3GPP - Advanced) networks have largely tackled the Doppler effect problem in the physical layer and are able to keep wireless service with 100Mpbs throughput within a cell in speeds up to 350 km/h. Yet the much more frequent handovers across cells greatly increases the possibility of service interruptions, and the problem is prominent for multimedia communications that demand both high-throughput and continuous connections. In this paper, we present a novel LTE-based solution to support high throughput and continuous multimedia services for high speed train passengers. Our solution is based on a Cell Array that smartly organizes the cells along a railway, together with a femto cell service that aggregates traffic demands within individual train cabins. Given that the movement direction and speed of a high-speed train are generally known, our Cell Array effectively predicts the upcoming LTE cells in service, and enables a seamless handover that will not interrupt multimedia streams. To accommodate the extreme channel variations, we further propose a scheduling and resource allocation mechanism to maximize the service rate based on periodical signal quality changes. Our simulation under diverse network and railway/train configurations demonstrates that the proposed solution achieves much lower handover latency and higher data throughput, as compared to existing solutions. It also well resists to network and traffic dynamics, thus enabling uninterrupted quality multimedia services for passengers in high speed trains.
TL;DR: A linear power consumption model for base stations of both GSM and UMTS is developed and an overview of the most important concepts which are being proposed to make cellular networks more energy-efficient is given.
Abstract: Base stations represent the main contributor to the energy consumption of a mobile cellular network. Since traffic load in mobile networks significantly varies during a working or weekend day, it is important to quantify the influence of these variations on the base station power consumption. Therefore, this paper investigates changes in the instantaneous power consumption of GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) base stations according to their respective traffic load. The real data in terms of the power consumption and traffic load have been obtained from continuous measurements performed on a fully operated base station site. Measurements show the existence of a direct relationship between base station traffic load and power consumption. According to this relationship, we develop a linear power consumption model for base stations of both technologies. This paper also gives an overview of the most important concepts which are being proposed to make cellular networks more energy-efficient.
TL;DR: In this paper, the problem of secure connection in cooperative wireless communication with two relay strategies, decode-andforward (DF) and randomize-and-forward (RF), was considered.
Abstract: This work studies the problem of secure connection in cooperative wireless communication with two relay strategies, decode-and-forward (DF) and randomize-and-forward (RF). The four-node scenario and cellular scenario are considered. For the typical four-node (source, destination, relay, and eavesdropper) scenario, we derive the optimal power allocation for the DF strategy and find that the RF strategy is always better than the DF to enhance secure connection. In cellular networks, we show that without relay, it is difficult to establish secure connections from the base station to the cell edge users. The effect of relay placement for the cell edge users is demonstrated by simulation. For both scenarios, we find that the benefit of relay transmission increases when path loss becomes severer.