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34
Enabling Wireless Power Transfer in Cellular Networks: Architecture, Modeling and Deployment
, 2012
"... 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 pro ..."
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Cited by 53 (5 self)
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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 stochasticgeometry model where singleantenna base stations (BSs) and PBs form independent homogeneous Poisson point processes (PPPs) with densities λb and λp, respectively, and singleantenna 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 (p, λb, q, λp) 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 pλ α 2 b is above a given threshold where α is the pathloss exponent. Next, consider the deployment of the hybrid network assuming infinite energy storage at mobiles. It is shown that for isotropic MPT, the product qλpλ α 2 b has to be above a given threshold so that PBs are sufficiently dense; for directed MPT, zmqλpλ α 2 b with zm denoting the array gain should exceed a different threshold to ensure short distances between PBs and their target mobiles. Furthermore, for directed MPT, (zmq) 2 αλb has to be sufficiently large as otherwise PBs fail to deliver sufficient power to target mobiles regardless of powertransfer distances. Last, similar results are derived for the case of mobiles having small energy storage.
LoadAware Modeling and Analysis of Heterogeneous Cellular Networks
 IEEE TRANS. ON WIRELESS COMMUN
, 2013
"... Random spatial models are attractive for modeling heterogeneous cellular networks (HCNs) due to their realism, tractability, and scalability. A major limitation of such models to date in the context of HCNs is the neglect of network traffic and load: all base stations (BSs) have typically been assu ..."
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Cited by 22 (10 self)
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Random spatial models are attractive for modeling heterogeneous cellular networks (HCNs) due to their realism, tractability, and scalability. A major limitation of such models to date in the context of HCNs is the neglect of network traffic and load: all base stations (BSs) have typically been assumed to always be transmitting. Small cells in particular will have a lighter load than macrocells, and so their contribution to the network interference may be significantly overstated in a fully loaded model. This paper incorporates a flexible notion of BS load by introducing a new idea of conditionally thinning the interference field. For aKtier HCN where BSs across tiers differ in terms of transmit power, supported data rate, deployment density, and now load, we derive the coverage probability for a typical mobile, which connects to the strongest BS signal. Conditioned on this connection, the interfering BSs of the ith tier are assumed to transmit independently with probability pi, which models the load. Assuming – reasonably – that smaller cells are more lightly loaded than macrocells, the analysis shows that adding such access points to the network always increases the coverage probability. We also observe that fully loaded models are quite pessimistic in terms of coverage.
Fundamentals of Heterogeneous Cellular Networks with Energy Harvesting
 IEEE TRAN. WIRELESS COMMUNICATIONS
, 2014
"... We develop a new tractable model for Ktier heterogeneous cellular networks (HetNets), where each base station (BS) is powered solely by a selfcontained energy harvesting module. The BSs across tiers differ in terms of the energy harvesting rate, energy storage capacity, transmit power and deploym ..."
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Cited by 15 (2 self)
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We develop a new tractable model for Ktier heterogeneous cellular networks (HetNets), where each base station (BS) is powered solely by a selfcontained energy harvesting module. The BSs across tiers differ in terms of the energy harvesting rate, energy storage capacity, transmit power and deployment density. Since a BS may not always have enough energy, it may need to be kept OFF and allowed to recharge while nearby users are served by neighboring BSs that are ON. We show that the fraction of time a kth tier BS can be kept ON, termed availability ρk, is a fundamental metric of interest. Using tools from random walk theory, fixed point analysis and stochastic geometry, we characterize the set of Ktuples (ρ1, ρ2,... ρK), termed the availability region, that is achievable by general uncoordinated operational strategies, where the decision to toggle the current ON/OFF state of a BS is taken independently of the other BSs. If the availability vector corresponding to the optimal system performance, e.g., in terms of rate, lies in this availability region, there is no performance loss due to the presence of unreliable energy sources. As a part of our analysis, we model the temporal dynamics of the energy level at each BS as a birthdeath process, derive the energy utilization rate, and use hitting/stopping time analysis to prove that there exists a fundamental limit on ρk that cannot be surpassed by any uncoordinated strategy.
Downlink MIMO HetNets: Modeling, Ordering Results and Performance Analysis
 IEEE TRANS. ON WIRELESS COMMUN
, 2013
"... We develop a general downlink model for multiantenna heterogeneous cellular networks (HetNets), where base stations (BSs) across tiers may differ in terms of transmit power, target signaltointerferenceratio (SIR), deployment density, number of transmit antennas and the type of multiantenna tr ..."
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Cited by 14 (6 self)
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We develop a general downlink model for multiantenna heterogeneous cellular networks (HetNets), where base stations (BSs) across tiers may differ in terms of transmit power, target signaltointerferenceratio (SIR), deployment density, number of transmit antennas and the type of multiantenna transmission. In particular, we consider and compare space division multiple access (SDMA), single user beamforming (SUBF), and baseline singleinput singleoutput (SISO) transmission. For this general model, the main contributions are: (i) ordering results for both coverage probability and per user rate in closed form for any BS distribution for the three considered techniques, using novel tools from stochastic orders, (ii) upper bounds on the coverage probability assuming a Poisson BS distribution, and (iii) a comparison of the area spectral efficiency (ASE). The analysis concretely demonstrates, for example, that for a given total number of transmit antennas in the network, it is preferable to spread them across many singleantenna BSs vs. fewer multiantenna BSs. Another observation is that SUBF provides higher coverage and per user data rate than SDMA, but SDMA is in some cases better in terms of ASE.
Analyzing a fullduplex cellular system
 in Proc. Conference on Information Sciences and Systems (CISS
, 2013
"... Abstract—Recent progress in single channel fullduplex (SCFD) radio design [1]–[4] has attracted the attention of many researchers. A SCFD transceiver is capable of transmitting and receiving on the same frequency at the same time, which will have a great impact on the design and performance of cu ..."
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Cited by 9 (1 self)
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Abstract—Recent progress in single channel fullduplex (SCFD) radio design [1]–[4] has attracted the attention of many researchers. A SCFD transceiver is capable of transmitting and receiving on the same frequency at the same time, which will have a great impact on the design and performance of current wireless networks that are based on half duplex designs. This paper analyzes the effects of adopting SCFD enabled base stations in a cellular system with legacy mobile stations. We use a multicell analytical model based on stochastic geometry to derive the theoretical performance gain of such a system. To validate the performance using a realistic setting, we conduct extensive simulations for a multicell OFDMA system. Both sets of results show that a fullduplex design for a cellular system, while not quite doubling system capacity, does greatly increases capacity over traditional cellular systems. Our results show that the uplink, compared with the downlink, is more susceptible to the extra interference caused by using the same frequency in both directions. I.
Average rate of downlink heterogeneous cellular networks over generalized fading channels – A stochastic geometry approach
 IEEE Trans. Commun
, 2013
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A comprehensive framework for devicetodevice communications in cellular networks,” arXiv preprint arXiv:1305.4219
, 2013
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Understanding the Benefits of Open Access in Femtocell Networks: Stochastic Geometric Analysis in the Uplink
"... We introduce a comprehensive analytical framework to compare between open access and closed access in twotier femtocell networks, with regard to uplink interference and outage. Interference at both the macrocell and femtocell levels is considered. A stochastic geometric approach is employed as the ..."
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Cited by 4 (3 self)
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We introduce a comprehensive analytical framework to compare between open access and closed access in twotier femtocell networks, with regard to uplink interference and outage. Interference at both the macrocell and femtocell levels is considered. A stochastic geometric approach is employed as the basis for our analysis. We further derive sufficient conditions for open access and closed access to outperform each other in terms of the outage probability, leading to closedform expressions to upper and lower bound the difference in the targeted received power between the two access modes. Simulations are conducted to validate the accuracy of the analytical model and the correctness of the bounds.
Uplink interference analysis for twotier cellular networks with diverse users under random spatial patterns
 In Proc. of IEEE/CIC International Conference on Communications in China (ICCC
, 2013
"... Abstract—Multitier architecture improves the spatial reuse of radio spectrum in cellular networks, and user classification allows consideration for diverse user service requirements. But they introduce complicated heterogeneity in the spatial distribution of transmitters, which brings to new challe ..."
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Cited by 3 (2 self)
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Abstract—Multitier architecture improves the spatial reuse of radio spectrum in cellular networks, and user classification allows consideration for diverse user service requirements. But they introduce complicated heterogeneity in the spatial distribution of transmitters, which brings to new challenges in interference analysis. In this work, we present a stochastic geometric model to evaluate the uplink interference in a twotier network considering multitype tier1 users, tier2 cells and tier2 users. Each type of tier1 users and tier2 base stations are modeled as independent homogeneous Poisson point process, and each type of tier2 users are modeled as local nonhomogeneous Poisson point process centered at tier2 base stations. By applying a superpositionaggregationsuperposition (SAS) approach, we numerically characterize the interference at of both tiers. Finally, simulation results validate our model and illustrate that our model offers substantial improvement in accuracy compared with the best known approximation model. I.
On optimal downlink coverage in Poisson cellular networks with power density constraints
 IEEE Trans. Commun
, 2014
"... Abstract—This paper studies downlink coverage maximization for cellular networks in which base station (BS) locations are modeled using a spatial Poisson point process, considering three different coverage models, and under constraints on transmit power, BS density and transmit power density. Firstl ..."
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Cited by 2 (1 self)
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Abstract—This paper studies downlink coverage maximization for cellular networks in which base station (BS) locations are modeled using a spatial Poisson point process, considering three different coverage models, and under constraints on transmit power, BS density and transmit power density. Firstly, the coverage optimization problem is solved analytically for the first coverage model that focuses on noiselimited communication by ignoring interference and random fading effects. This model provides useful insights into the significance of bounded path loss models to obtain meaningful solutions for this problem. The other two coverage models are based on the users ’ received signaltointerferenceplusnoiseratio (SINR) from their associated BSs. For these models, it is shown that the coverage optimization problem can be reduced to a constrained single dimensional optimization problem without any loss of optimality. The related solutions can be obtained with limited computational complexity by resorting to a numerical search over a compact subset of candidate values. Bounds on the optimum BS density are also provided to further truncate the search space. All results are derived for general bounded path loss models. Specific applications are also illustrated to provide further design insights and to highlight the importance of using bounded path loss models for coverage analysis.