Enhancing Coverage and Rate of Cell Edge User in Multi-Antenna Poisson Voronoi Cells
12 Aug 2015-Journal of Circuits, Systems, and Computers (World Scientific Publishing Company)-Vol. 24, Iss: 08, pp 1550117
TL;DR: The interesting observation from the results is that the edge user coverage and rate is closely approaching towards the inner cell typical mobile user's rate and coverage, and the performance is verified with relative probability of coverage gain analysis.
Abstract: This paper analyzes the cell edge mobile user performance in the downlink cellular system. We develop frame-work for coverage probability and spectral efficiency. In particular, we analyzed the performance of multi-antenna mobile users under multi-antenna base stations (BSs). The expressions of coverage probability and spectral efficiency are derived for cell edge user using stochastic geometry. We investigate how much the performance of cell edge user is improved when distances connecting BSs and cell edge users are modeled with cell edge null probability distribution. The probability of coverage and spectral efficiency is studied using zero-forcing beam-forming and the performance metrics are compared between coordinated scheduling (CS) and without coordinated scheduling (w/o CS). The interesting observation from our results is that the edge user coverage and rate is closely approaching towards the inner cell typical mobile user's rate and coverage, and the performance is verified with relative probability of coverage gain analysis.
Citations
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TL;DR: It can be concluded that frequent update of channel state information and suppression of dominant interferences can yield significant improvements in the sumrate performance of limited feedbback systems.
Abstract: An efficient multicell coordinated zero-forcing channel feedback scheme is proposed in this paper. The objective of the proposed feedback design is to control the rate of the user by adaptive allocation of feedback bits of each user as a function of individual channel status thereby keeping the total feedback budge constant. The proposed feedback allocation is studied in interfering broadcast channel (IFBC) and also in time varying channels (TVC) with feedback update duration. First the individual feedback rates of user are derived using convex optimization thereby presenting low complexity algorithm to optimize the channel feedback between inter-user interference and inter-cell interference. The rate offset arising from channel quantization in both IFBC and TVC is investigated by employing the coordinated zero forcing beamforming. Moreover, closed form expressions are derived for necessary feedback scaling and frequency of update duration to achieve the multiplexing gain and throughput. Finally, numerical evaluation results show that the proposed channel feedback schemes outperforms other conventional schemes and assist in base station cooperation management. It can be concluded that frequent update of channel state information and suppression of dominant interferences can yield significant improvements in the sumrate performance of limited feedbback systems.
4 citations
3 citations
Cites background from "Enhancing Coverage and Rate of Cell..."
...Multiple input multiple output coordination concepts related to scalability, coverage, and system level integration are also discussed in detail.(17,18) By combining beamforming methodology and multicell coordination, sum rate has been characterized for TVCs....
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TL;DR: The proposed feedback allocation in interfering broadcast and time varying channels are numerically evaluated and it is found that the proposed method performs comparatively better than other counterparts.
Abstract: In this paper feedback allocation of interference channels using multi-cell coordinated beamforming is studied. By fixing the total feedback budget as constant, the proposed interference grading threshold scheme adaptively allocating the feedback bits between inter-user interference and inter-cell interference. The individual feedback bits of inter-user and inter-cell interference are calculated by employing interference grading. A new iterative algorithm is proposed to find the total residual feedback bits. The proposed feedback allocation in interfering broadcast and time varying channels are numerically evaluated and it is found that the proposed method performs comparatively better than other counterparts.
2 citations
TL;DR: Analytical and numerical results show that a reasonable balance between the CEU performance enhancement and the CCU performance degradation under the IC can be reached and it is found that the coverage probability of CEU is more sensitive to the variation of density of UEs and the base stations than that of CCU.
Abstract: How much performance gain for the user equipment (UE) located at cell-edge can be obtained, from the interference cancellation (IC) by exploiting extra degrees of freedom in multi-user massive multiple-input multiple-output (MIMO), needs to be investigated. Also, it is necessary to reveal the impact of this IC on the performance of cell-centre UE (CCU). In this study, the authors separately analyse the coverage probability of cell-edge UE (CEU) and CCU under the IC in irregular network utilising tools from stochastic geometry. Specifically, the closed-form expressions for the upper bound of CEU coverage probability and the lower bound of coverage probability for CCU are given out. For large threshold scenario, the authors show the potential of massive MIMO with IC on achieving the cell-centre-like experience in a more simple closed-form formula. Analytical and numerical results show that a reasonable balance between the CEU performance enhancement and the CCU performance degradation under the IC can be reached. Moreover, slight influence of cell-edge area on the coverage probability for both CEU and CCU is observed. Finally, it is found that the coverage probability of CEU is more sensitive to the variation of density of UEs and the base stations than that of CCU.
1 citations
Cites background or methods from "Enhancing Coverage and Rate of Cell..."
...Utilising tools from stochastic geometry, the coverage probability or the data rate improvement for the cell-edge user located at the cell-corner of the irregular network, through coordinated scheduling, BSs silencing, and so on, was investigated by the authors in [4, 5]....
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...Moreover, note that the probability generating functional (PGFL) of PPP in (29) works for the inner UE case [4] that the UE is located in all coverage area of the typical cell, including the white and grey area in Fig....
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01 Jun 2008
TL;DR: An efficient symbol detection algorithm for multiple-input multiple-output spatial multiplexing (MIMO-SM) systems and the implementation results show that the proposed algorithm can be implemented without increasing the hardware costs significantly.
Abstract: In this paper, we propose an efficient symbol detection algorithm for multiple-input multiple-output spatial multiplexing (MIMO-SM) systems and present its design and implementation results. By enhancing the performance of the first detected symbol which causes error propagation, the proposed algorithm achieves a considerable performance gain as compared to the conventional sorted QR decomposition (SQRD) based detection and the ordered successive detection (OSD) algorithms. The implementation results show that the proposed algorithm can be implemented without increasing the hardware costs significantly.
References
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TL;DR: The proposed model is pessimistic (a lower bound on coverage) whereas the grid model is optimistic, and that both are about equally accurate, and the proposed model may better capture the increasingly opportunistic and dense placement of base stations in future networks.
Abstract: Cellular networks are usually modeled by placing the base stations on a grid, with mobile users either randomly scattered or placed deterministically. These models have been used extensively but suffer from being both highly idealized and not very tractable, so complex system-level simulations are used to evaluate coverage/outage probability and rate. More tractable models have long been desirable. We develop new general models for the multi-cell signal-to-interference-plus-noise ratio (SINR) using stochastic geometry. Under very general assumptions, the resulting expressions for the downlink SINR CCDF (equivalent to the coverage probability) involve quickly computable integrals, and in some practical special cases can be simplified to common integrals (e.g., the Q-function) or even to simple closed-form expressions. We also derive the mean rate, and then the coverage gain (and mean rate loss) from static frequency reuse. We compare our coverage predictions to the grid model and an actual base station deployment, and observe that the proposed model is pessimistic (a lower bound on coverage) whereas the grid model is optimistic, and that both are about equally accurate. In addition to being more tractable, the proposed model may better capture the increasingly opportunistic and dense placement of base stations in future networks.
3,309 citations
"Enhancing Coverage and Rate of Cell..." refers methods in this paper
...The calculated values of these parameters by these advanced tools are almost equal to the regular grid model studies.(9) Cellular systems with complex overlay of multiple communication networks are becoming more heterogeneous and variety of infrastructure such as macrocells, picocells, femotocells, etc....
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...Moreover this spectral e±ciency is 43% of that of the MU (typical) obtained in recent work.(9) By applying CS scheme, the achievable spectral e±ciency compared to typical MU in Ref....
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TL;DR: An overview of the theory and currently known techniques for multi-cell MIMO (multiple input multiple output) cooperation in wireless networks is presented and a few promising and quite fundamental research avenues are also suggested.
Abstract: This paper presents an overview of the theory and currently known techniques for multi-cell MIMO (multiple input multiple output) cooperation in wireless networks. In dense networks where interference emerges as the key capacity-limiting factor, multi-cell cooperation can dramatically improve the system performance. Remarkably, such techniques literally exploit inter-cell interference by allowing the user data to be jointly processed by several interfering base stations, thus mimicking the benefits of a large virtual MIMO array. Multi-cell MIMO cooperation concepts are examined from different perspectives, including an examination of the fundamental information-theoretic limits, a review of the coding and signal processing algorithmic developments, and, going beyond that, consideration of very practical issues related to scalability and system-level integration. A few promising and quite fundamental research avenues are also suggested.
1,911 citations
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: 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: A stochastic geometry based model is used to derive the success probability and energy efficiency in homogeneous macrocell and heterogeneous K-tier wireless networks under different sleeping policies and provides an essential understanding on the deployment of future green heterogeneous networks.
Abstract: With the exponential increase in mobile internet traffic driven by a new generation of wireless devices, future cellular networks face a great challenge to meet this overwhelming demand of network capacity. At the same time, the demand for higher data rates and the ever-increasing number of wireless users led to rapid increases in power consumption and operating cost of cellular networks. One potential solution to address these issues is to overlay small cell networks with macrocell networks as a means to provide higher network capacity and better coverage. However, the dense and random deployment of small cells and their uncoordinated operation raise important questions about the energy efficiency implications of such multi-tier networks. Another technique to improve energy efficiency in cellular networks is to introduce active/sleep (on/off) modes in macrocell base stations. In this paper, we investigate the design and the associated tradeoffs of energy efficient cellular networks through the deployment of sleeping strategies and small cells. Using a stochastic geometry based model, we derive the success probability and energy efficiency in homogeneous macrocell (single-tier) and heterogeneous K-tier wireless networks under different sleeping policies. In addition, we formulate the power consumption minimization and energy efficiency maximization problems, and determine the optimal operating regimes for macrocell base stations. Numerical results confirm the effectiveness of switching off base stations in homogeneous macrocell networks. Nevertheless, the gains in terms of energy efficiency depend on the type of sleeping strategy used. In addition, the deployment of small cells generally leads to higher energy efficiency but this gain saturates as the density of small cells increases. In a nutshell, our proposed framework provides an essential understanding on the deployment of future green heterogeneous networks.
579 citations
"Enhancing Coverage and Rate of Cell..." refers background in this paper
...Related works and contributions The major challenges in cellular deployment are the incursion of inter-tier interference and intercell interference due to frequency reuse, which can deteriorate the e®ectiveness of cellular architecture.(8) Several recent researches have studied MIMO networks with inter-cell and intra-cell interference with variety of BSs deployment....
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