Proportional Fair Scheduling Research Articles

Optimal FFR Policies: Maximization of Traffic Capacity and Minimization of Base Station’s Power Consumption

This letter investigates application of optimal fractional frequency reuse (FFR) policies in an OFDMA network of macrocells. Optimality is investigated, first in terms of maximum traffic capacity, the maximum demand in traffic volume per second that can be served by the cell at the session layer. Second, optimality is investigated in terms of minimum total power consumption, applying a dynamic on – off model of power consumption at the base station (BS). The analysis includes the impact of the multicarrier proportional fair (PF) scheduler, providing concise expressions for distribution of active users and for user throughput.

이기종 무선망에서 에너지 효율 개선을 위한 망간 협력 기반 스케쥴링 기법

무선망에서 소모 전력, 전송률, 통신 반경 등 서비스 요구 사항에 따라 상호 다른 망의 발전이 진행되어 왔다. 최근 차세대 무선망 환경에서는 초고속, 초저지연, 저전력 등 서비스 요구 사항이 보다 다양해지고 높은 수준으로 설정되고 있으며, 이를 만족하기 위한 방안으로 이기종간 효과적인 연동에 대한 연구에 관심이 높아지고 있다. 본 논문에서는 이기종 무선망 환경에서 망간 연동을 통해 데이터 서비스가 이루어지는 상황에서 에너지 효율성을 반영하는 스케쥴링 기법을 제안한다. 특히 이기종 무선망 환경에서 사용자 형평성을 고려하면서 데이터 수율을 개선하는 비례균등 스케쥴링 방식을 기반으로 에너지 효율에 관한 요소를 반영하는 문제를 고려하고 에너지 효율을 개선함과 동시에 사용자 형평성, 데이터 수율을 모두 감안하는 에너지 효율적인 비례균등 스케쥴링 방식을 제안한다. 또한 모의실험을 통해 제안된 방식으로 비례균등 달성도를 유지하면서 에너지 효율이 개선됨을 보인다.

WIRELESS INFORMATION AND ENERGY TRANSFER: TRADEOFF FOR FAIR RESOURCE ALLOCATION

In this paper, we study two schemes for the fair resource allocation in wireless powered communication networks (WPCNs): a non-orthogonal multiple access (NOMA) scheme, and a proportional fair (PF) scheduling scheme. The considered WPCN consists of a base station (BS) that broadcast radio frequency (RF) energy over the downlink, and N energy harvesting users (EHUs). If NOMA is employed, all EHUs concurrently transmit information over the uplink with successive interference cancellation employed at the BS. If PF scheduling is employed, a single EHU is selected for uplink transmission in each frame. For both schemes, we arrive at optimal allocations for the BS transmit power and the time sharing between uplink and downlink transmissions that maximize the uplink sum-rate, while maintaining high level of system fairness. For the PF scheme, we also derive the optimal scheduling policy. Compared to the state-of-the art schemes based upon time division multiple access (TDMA), both schemes significantly improve the system fairness at the expense of minor (or nonexistent) rate degradation. Key words: energy harvesting; wireless powered communication networks; non-orthogonal multiple access; successive interference cancelation; proportional fair scheduling REFERENCES: [1] P. Grover, A. Sahai: Shannon meets Tesla: wireless information and power transfer, Proc. IEEE ISIT 2010, pp. 2363–2367, Austin, USA, June 2010. [2] D. Gunduz, K. Stamatiou, N. Michelusi, M. Zorzi: Designing intelligent energy harvesting communication systems, IEEE Commun. Magazine, 52, 1, 210–216 (Jan.2014). [3] C. K. Ho, R. Zhang: Optimal energy allocation for wireless communications with energy harvesting constraints, IEEE Trans. Signal Proccessing, 60, 9, 4808–4818 (May 2012). [4] H. Ju, R. Zhang: Throughput maximization in wireless powered communication networks, IEEE Trans. Wireless Commun., 13, 1, 418–428 (Jan. 2014). [5] X. Kang, C. Ho Keong, S. Sun: Optimal time allocation for dynamic-TDMA-based wireless powered communication networks, Proc. IEEE Globecom 2014, Austin, USA, Dec. 2014. [6] H. Ju, R. Zhang: Optimal resource allocation in full-duplex wireless-powered communication network, IEEE Trans. on Commun., 62, 10, 3528–3540 (Oct. 2014). [7] T. Takeda, K. Higuchi: Enhanced user fairness using non-orthogonal access with SIC in cellular uplink, VTC 2011, San Francisco, USA, pp. 1–5, 2011. [8] Z. Ding, Z. Yang, P. Fan, H. V. Poor: On the performance of non-orthogonal multiple access in 5G systems with randomly deployed users, IEEE Signal Process. Lett., 21, 12, 1501–1505 (2014). [9] S. Timotheou, I. Krikidis: Fairness for non-orthogonal multiple access in 5G systems, IEEE Signal Process. Lett., 22, 10, 1462–1465 (2015). [10] H. Chingoska, Z. Hadzi-Velkov, I. Nikoloska, N. Zlatanov: Resource Allocation in Wireless Powered Communication Networks with Non-Orthogonal Multiple Access, IEEE Wireless Communications Letters, 5 (6), 684–687 (2016). [11] P. Viswanath, D. N. Tse, R. Laroia: Opportunistic beamforming using dumb antennas, IEEE Trans. Information Theory, 46, 6, 1277–1294 (June 2002). [12] N. Tekbiyik, T. Girici, E. Uysal-Biyikoglu, K. Leblebicioglu: Proportional fair resource allocation on an energy harvesting downlink, IEEE Trans. Wireless Communications, 12, 4, 1699–1711 (April 2013). [13] H. Chingoska, I. Nikoloska, Z. Hadzi-Velkov, N. Zlatanov: Proportional fair scheduling in wireless powered communication networks, 23rd International Conference on Telecommunications (ICT), May 2013. [14] Z. Hadzi-Velkov, I. Nikoloska, H. Chingoska, N. Zlatanov, Proportional fair scheduling in wireless networks with RF energy harvesting and processing cost, IEEE Comm. Letters, 20, 10, 2107–2110 (2016). [15] T.-D. Nguyen, Y. Han: A Proportional Fairness Algorithm with QoS Provision in Downlink OFDMA Systems, IEEE Comm. Letters, 10, 11 (Nov. 2006). [16] Z. Hadzi-Velkov, I. Nikoloska, G. K. Karagiannidis, T. Q. Duong: Wireless networks with energy harvesting and power transfer: joint power and time allocation, IEEE Signal Process. Letters, 23, 1, 50–54 (Jan. 2016). [17] R. Jain, D. Chiu, W. Hawe: A Quantitative measure of fairness and discrimination for resource allocation in shared computer systems, Tech. Rep. TR-301, DEC, September 1984. [18] W. Yu, R. Lui: Dual methods for nonconvex spectrum optimization of multicarrier systems, IEEE Trans. Commun., 54, 7, 1310–1322 (Jul. 2006). [19] L. Liu, R. Zhang, K.-C. Chua: Wireless information transfer with opportunistic energy harvesting, IEEE Trans. Wireless. Commun., 12, 1, 288–300 (Jan. 2013).

Joint Power and Time Allocation in Full-Duplex Wireless Powered Communication Networks

We consider a full-duplex wireless powered communication network (WPCN) with one hybrid access point (H-AP) and a set of distributed users, where downlink wireless energy broadcasting is employed at H-AP and at the same time, uplink wireless information transmission takes place at users in a time-division multiple access manner. We extend proportional fair scheduler to this category of network when dealing with "doubly near-far problem," where users far away from H-AP achieve low throughput but suffer from both low harvested energy and high data transmission power consumption. We jointly optimize power and time allocation for each user to achieve proportional fairness while controlling the energy consumption offset for network to a low level. By using optimization techniques, the optimal transmit power and transmission time for users are obtained via proposed algorithm. Simulation results confirm the positive effect on improving the fairness metric and reducing energy consumption offset for network.

A Dynamic Graph-Based Scheduling and Interference Coordination Approach in Heterogeneous Cellular Networks

To meet the demand of increasing mobile data traffic and provide better user experience, heterogeneous cellular networks (HCNs) have become a promising solution to improve both the system capacity and coverage. However, due to dense self-deployment of small cells in a limited area, serious interference from nearby base stations may occur, which results in severe performance degradation. To mitigate downlink interference and utilize spectrum resources more efficiently, we present a novel graph-based resource allocation and interference management approach in this paper. First, we divide small cells into cell clusters, considering their neighborhood relationships in the scenario. Then, we develop another graph clustering scheme to group user equipment (UE) in each cell cluster into UE clusters with minimum intracluster interference. Finally, we utilize a proportional fairness scheduling scheme to assign subchannels to each UE cluster and allocate power using water-filling method. To show the efficacy and effectiveness of our proposed approach, we propose a dual-based approach to search for optimal solutions as the baseline for comparisons. Furthermore, we compare the graph-based approach with the state of the art and a distributed approach without interference coordination. The simulation results show that our graph-based approach reaches more than 90% of the optimal performance and achieves a significant improvement in spectral efficiency compared with the state of the art and the distributed approach both under cochannel and orthogonal deployments. Moreover, the proposed graph-based approach has low computation complexity, making it feasible for real-time implementation.

Throughput Analysis of Proportional Fair Scheduling for Sparse and Ultra-Dense Interference-Limited OFDMA/LTE Networks

Various system tasks, such as interference coordination, handover decisions, admission control, and so on in current cellular networks require precise mid-term (spanning over a few seconds) performance models. Due to channel-dependent scheduling at the base station, these performance models are not simple to obtain. Furthermore, LTE cellular systems are interference limited; hence, the way interference is modeled is crucial for the accuracy. In this paper, we present a closed-form analytical model for the throughput expectation of proportional fair scheduling in orthogonal frequency division multiple access/LTE networks. The model takes into account a precise signal-to-interference-and-noise ratio (SINR) distribution as well as considering limitations with respect to modulation and coding, as encountered in LTE networks. Furthermore, the analysis is extended to ultra-dense deployments likely to happen in the 5th generation of cellular networks. The resulting analytical performance model is validated by means of simulations, considering realistic network deployments. Compared with related work, the model introduced in this paper demonstrates a significantly higher accuracy for mid-term throughput estimation.

Heuristic Algorithm for Proportional Fair Scheduling in D2D-Cellular Systems

The effective reuse of the radio resources in D2D communication underlaying cellular system is pivotal for enhancing the total system capacity. Developing practical and effective scheduling schemes is critical to the success of D2D-based cellular systems. An optimal proportionally fair (PF) scheduling scheme that maximizes the logarithmic sum of the user data rates is proposed in this paper. Considering the fact that the computational complexity of the optimal PF scheduling is significantly high, low-complexity heuristic algorithm has also been proposed. It has been shown that the heuristic algorithm achieves high logarithmic sum of the average user data rates while maintaining low-computational complexity. Simulation results are used to verify the performance of the proposed algorithm, and to compare it with the optimal PF scheduling algorithms.

Joint Best Price-CQI Product Scheduling and Congestion Control for LTE

In hybrid wired–wireless media, congestion control and scheduling are both trying to allocate bandwidth to the flows. Performance studies of long-term evolution (LTE) networks show that by decreasing the mismatch between scheduling at the base station of an LTE network and congestion control algorithms implemented at end users, significant improvements in the obtained overall throughput and fairness for best-effort traffic are achieved. In this paper, a problem formulation for joint scheduling and congestion control based on dual problem optimization is provided for a hybrid media, which includes a wireless LTE network. The original optimization problem is decomposed into two subproblems: congestion control problem and link scheduling problem. We propose methods to solve and implement these subproblems in different layers of a hybrid network, and call the derived link scheduling subproblem best price-channel quality indicator (CQI) product scheduling. Then, the performance of the proposed joint algorithm for LTE is studied. The results show a better tradeoff between the overall throughput and the fairness for the joint algorithm compared with classic cases in which congestion control and scheduling are separately designed and implemented without any cooperation. The behavior of the proposed best price-CQI product scheduler and a common proportional fair scheduler is compared, and some notable similarities in the case of applying logarithmic utility functions are observed.

Efficient Resource Allocation for Proportional Fair Schedulers in Multihop Relay Networks

Efficient Resource Allocation for Proportional Fair Schedulers in Multihop Relay Networks

Channel Aware Scheduling Algorithm for LTE Uplink and Downlink

In the past two decades, there has been a drastic increase in the mobile traffic, which is caused by the improved user experience with smart phones and its applications. In LTE system, the packet scheduler plays a vital role in the effective utilization of the resources. This field is not standardized and has immense scope of improvement, allowing vendor-specific implementation. LTE scheduling can be categorized into two extremes, namely, Opportunistic scheduling and Fairness scheduling. The Best Channel Quality Indicator (BCQI) algorithm falls under the former category while Proportional Fairness (PF) algorithm under the later. BCQI algorithm provides high system throughput than PF algorithm, however, unlike BCQI algorithm, PF algorithm considers users with poor channel condition for allocation process. In this work, a new scheduling algorithm called as Opportunistic Dual Metric (ODM) Scheduling Algorithm is proposed for LTE uplink and downlink.The objective of the algorithm is to prioritize the users with good channel condition for resource allocation, at the same time not to starve the users with poor channel conditions. The proposed algorithm has two resource allocation matrices, one being throughput-centric and the other being is fairness-centric. The uplink algorithm uses the two resource allocation matrices to allocate the resources to the users and to ensure contiguous resource allocation. The downlink algorithm is an extension of the proposed uplink algorithm avoiding uplink constraints. The downlink algorithm employs the two resource distribution matrices to provide an efficient resource allocation by expanding the allocation for the users considering intermittent resources. The performance of ODM is measured in terms of throughput, fairness. Additionally, the uplink algorithm is analyzed in terms of transmit power. From the results it is observed that the proposed algorithm has better trade-off in terms of all the performance parameters than PF scheduler and BCQI scheduler.

Comparative Performanceof Subcarrier Schedulers in Uplink LTE-A under High Users’ Mobility

This paper evaluates the effects of high mobility of Users Equipment (UEs) on the performances of different data rate services using four scheduling algorithms in the uplink of LTE system using the uplink Vienna simulator.The uplink reports Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI) and Rank Indicator (RI) to inform the evolved node base station (eNodeB or eNB) about the current channel state. We simulate 20 and 30 UEs switch at high mobility and different service demands. Simulation results show that under 100 kmh -1 speed the Best CQI and Proportional Fair schedulers are the best in performance for low delay and the Round Robin algorithm is the worst scheduling algorithm among other schedulers.

Robust Rate Adaptation and Proportional Fair Scheduling With Imperfect CSI

In wireless fading channels, multi-user scheduling has the potential to boost the spectral efficiency by exploiting diversity gains. In this regard, proportional fair (PF) scheduling provides a solution for increasing the users' quality of experience by finding a balance between system throughput maximization and user fairness. For this purpose, precise instantaneous channel state information (CSI) needs to be available at the transmitter side to perform rate adaptation and scheduling. However, in practical setups, CSI is impaired by, e.g., channel estimation errors, quantization and feedback delays. Especially in centralized cloud based communication systems, where main parts of the lower layer processing is shifted to a central entity, high backhaul latency can cause substantial CSI imperfections, resulting in significant performance degradations. In this work, robust rate adaptation as well as robust PF scheduling are presented, which account for CSI impairments. The proposed rate adaptation solution guarantees a fixed target outage probability, which is of interest for delay critical and data intensive applications, such as, video conference systems. In addition to CSI imperfections, the proposed scheduler is able to account for delayed decoding acknowledgements from the receiver.

Adaptive CSI and feedback estimation in LTE and beyond: a Gaussian process regression approach

The constant increase in wireless handheld devices and the prospect of billions of connected machines has compelled the research community to investigate different technologies which are able to deliver high data rates, lower latency and better reliability and quality of experience to mobile users. One of the problems, usually overlooked by the research community, is that more connected devices require proportionally more signalling overhead. Particularly, acquiring users’ channel state information is necessary in order for the base station to assign frequency resources. Estimating this channel information with full resolution in frequency and in time is generally impossible, and thus, methods have to be implemented in order to reduce the overhead. In this paper, we propose a channel quality estimation method based on the concept of Gaussian process regression to predict users’ channel states for varying user mobility profiles. Furthermore, we present a dual-control technique to determine which is the most appropriate prediction time for each user in order to keep the packet loss rate below a pre-defined threshold. The proposed method makes use of active learning and the exploration-exploitation paradigm, which allow the controller to choose autonomously the next sampling point in time so that the exploration of the control space is limited while still reaching an optimal performance. Extensive simulation results, carried out in an LTE-A simulator, show that the proposed channel prediction method is able to provide consistent gain, in terms of packet loss rate, for users with low and average mobility, while its efficacy is reduced for high-velocity users. The proposed dual-control technique is then applied, and its impact on the users’ packet loss is analysed in a multicell network with proportional fair and maximum throughput scheduling mechanisms. Remarkably, it is shown that the presented approach allows for a reduction of the overall channel quality signalling by over 90 % while keeping the packet loss below 5 % with maximum throughput schedulers, as well as signalling reduction of 60 % with proportional fair scheduling.

Reduction of the feedback delay effect on a proportional fair scheduler in LTE downlink using nonlinear support vector machine prediction

The scheduling of mobile users often relies on accurate feedback from the channel quality indicator (CQI). In this paper, we determine the strength of the effect of feedback delay on the scheduler in a Long-Term Evolution (LTE) system. We study this degradation under fairness constraints using a proportional fair scheduler. We propose a nonlinear support vector machine regression with a modified cost function in order to reduce the effect of feedback delay on the scheduler, which operates by predicting the CQI from previous feedback and using that for scheduling instead of the delayed feedback. The simulation results show important improvements in terms of throughput.

A Sectored CoMP with Constrained Greedy Resource Allocation for OFDM Communication System

In this paper, a sectored Coordinated Multi-Point (CoMP) scheme with constrained greedy resource allocation method is proposed to avoid the inter-cell interference and has a fair service provision advantage for a wireless cellular communication system. The proposed sectored CoMP is evaluated at the long term evolution system and compared with the traditional inter-cell interference coordination (ICIC) methods, such as the partial frequency reuse and the soft frequency reuse. Results show that the proposed scheme has a better ICIC performance than the conventional methods. Besides, the proposed sectored CoMP with constrained greedy resource allocation also has better system frequency utilization and fair cell-edge user data service advantages compared with the well-known proportional fair scheduling.

Interference-Aware Downlink and Uplink Resource Allocation in HetNets With D2D Support

We address the resource allocation problem in an LTE-based 2-tier heterogeneous network where in-band D2D communications are supported under network control. The different communication paradigms share the same radio resources, thus they may interfere. We devise a dynamic programming approach to efficiently schedule download and upload traffic, by 1) efficiently matching communicating endpoints and 2) assigning radio resources in an interference-aware manner while accounting for the characteristics of the content to be delivered. To this end, we develop an accurate model of the system and apply approximate dynamic programming to solve it. Our solution allows us to deal with realistic large-scale scenarios. In such scenarios, we compare our approach to today's networks where eICIC techniques and proportional fairness scheduling are implemented. Results highlight that our solution increases the system throughput while greatly reducing energy consumption. We also show that D2D mode, established either in the downlink or uplink, can effectively support delivery of highly popular content without significantly harming macrocell or microcell traffic, leading to increased system capacity. Interestingly, we find that D2D mode can also be a low-cost alternative to microcells.

Benchmarking of Cell Throughput Using Proportional Fair Scheduler in a Single Cell Environment

Benchmarking of Cell Throughput Using Proportional Fair Scheduler in a Single Cell Environment

Power control and group proportional fairness for frequency domain resource allocation in L-SC-FDMA based LTE uplink

Resource allocation in Long Term Evaluation (LTE) uplink is challenging because of two reasons: (1) it requires contiguous resource block allocation and (2) high complexity due to per user based power allocation among resource blocks. This paper presents a low complexity, optimal power resource allocation scheme for LTE uplink. We propose Virtual Cluster-based Proportional Fairness scheme that exploits the link adaptation information available at MAC layer to form virtual clusters. The distributed proportional fair scheduler ensures a minimum throughput for all users in the coverage area by assigning contiguous resource blocks, proportional to the throughput and the number of users in a particular cluster or group. Then, it allocates power to each resource block through water-filling algorithm which gives 20.2 % increase in average user throughout compared to equal power allocation. Simulations have been performed using practical scenarios of uniformly distributed users in Rician fading environment. Mathematical framework has been devised for network planning to get the best possible fairness with promising level of quality of service.

Comparison of Resource Scheduling Algorithms for LTE-Based Smart Grid Communications

The long term evolution (LTE) is a promising candidate solution for smart grid communication network due to its high data rate, lower latency, high mobility, and large coverage. In this paper, we discuss three resource scheduling algorithms for the LTE-based smart grids, including proportional fairness, round robin, and maximum rate scheduling schemes. In the simulations, we compare these three resource scheduling algorithms, the results show that the proportional fairness scheduler can achieve the best tradeoff between the average sum rate and the fairness among all the users.

Queue-Aware Channel-Adapted Scheduling and Congestion Control for Best-Effort Services in LTE Networks

In this paper, we study the performance of long-term evolution (LTE) for various types of channel-adapted scheduling for nonreal-time flows, while an end-to-end congestion control algorithm controls the rate of elastic traffic at the end users. First, we propose a new type of queue-aware channel-adapted scheduling at a base station, and explain how it allocates resources to competing nonreal-time flows where channel conditions are time-varying. We also introduce a new congestion measure function for a minimum cost flow control (MCFC) algorithm in the LTE and call it an individual flow-based congestion measure. We show that using different combinations of channel-adapted scheduling at the base station and congestion control algorithms can lead to major differences in the obtained throughput and fairness for the best-effort traffic. The results clearly show that the transport protocol and scheduling algorithm can cause significant conflict in some situations. We show the advantages of the proposed queue-aware channel-adapted scheduling in performance improvement and we also show that the combination of an MCFC algorithm (in which the new individual flow-based congestion measure is applied), with queue-aware proportional fair scheduling, leads to a better tradeoff between overall throughput and fairness compared with the other studied combinations.