Proportional Fair Scheduling Research Articles

Waterfilling-Based Proportional Fairness Scheduler for Downlink Non-Orthogonal Multiple Access

In this letter, a low-complexity waterfilling-based power allocation (PA) technique, incorporated within the proportional fairness scheduler, is proposed and applied to a non-orthogonal multiple access (NOMA) scheme in a cellular downlink system. The aim of the proposed joint PA and scheduling scheme is to maximize the achieved average throughput through a quasi-optimal repartition of the transmit power among subbands, while guaranteeing a high level of fairness in resource allocation. Extensive simulation results show that the proposed technique enhances both system capacity and user fairness, when compared to either orthogonal signaling or NOMA with static PA.

A Novel Description approach based on sorted rectangles for scheduling information bearing in OFDMA systems

Dynamic time/frequency resource allocation has been widely employed in wireless OFDMA systems. In such mechanisms, sophisticated scheduling decisions need to be conveyed to users and may lead to considerable signaling overhead. In this paper, a new efficient approach, namely, Sorted-Rectangle Description (SRD) is proposed for describing the scheduling decision in an OFDMA frame. SRD first partitions a frame into minimum number of rectangular polygons, namely, rectangular bursts (RB), in which each RB contains the resource units belonging to the same assignment. We show that each RB-partitioned frame is sufficient to be fully reconstructed by the top-left coordinates of each RB in a specific sorted order. Sorting and reconstructing algorithms with linear time complexity in the total number of RBs are also proposed. Simulations based on a multi-user OFDMA system with full-buffer or periodic small-data traffic model are conducted to evaluate the performance of the proposed SRD method under two representative scenarios. The simulation results show that, for the full-buffer traffic model with a proportional fair (PF) scheduler, the proposed description approach can achieve significant reduction of the overhead ratio compared to that of the existing systems and is expected to lead to considerable increase of system throughput. Meanwhile, for the periodic small-data traffic model, it is shown that the proposed description approach can greatly reduce the rate of packet loss due to timeout or buffer overflow and thus provides significant improvement of the system capacity.

Analysis of Proportional Fair Scheduling Under Bursty On-Off Traffic

Proportional fair scheduling (PFS) has been adopted as a standard solution for fair resource allocation in modern wireless cellular networks. With the emergence of heterogeneous networks with widely varying user loads, it is of great importance to characterize the performance of PFS under bursty traffic, which is the case in most wireless streaming and data transfer services. In this letter, we provide the first analytical solution to the performance of PFS under bursty on-off traffic load. We use the Gaussian approximation model to derive a closed-form expression of the achievable user data rates. In order to further improve the accuracy of our baseline analytical solution for multi-cell networks, we design a hybrid approximation by employing multi-interference analysis. The simulation results verify that our model guarantees extremely low data rate estimation error, which is further insensitive to changes in session duration, traffic load and user density.

Proportional fair scheduling method with QoS for the coexistence system of GFDM and OFDM

Proportional fair scheduling method with QoS for the coexistence system of GFDM and OFDM

Comparison of the LTE Performance Parameters in Different Environments under Close Loop Spatial Multiplexing (CLSM) Mode in Downlink LTE-A

LTE-A present deployment strategies are likely to overcome the User Equipment (UE) performance degradation, in certain parts of the topology incorporated with coverage block holes, due to the presence of high rise buildings. It also promises to serve the increase of high user density, which otherwise results in capacity exhaustion of the macro cells. LTE-A addresses these challenges with new features such as small cell and femto cell in its recent releases. Small cell is a low-cost alternative to macro cell in rural and hard-to-reach areas and its installation at strategic points overcomes the capacity and coverage problem. In contrast, Heterogeneous network with its ubiquitous coverage can deliver high-speed data. In this paper, several LTE Key performance indicators e.g. average UE throughput, average area throughput, spectral efficiency, fairness index are analyzed between small cell network and Heterogeneous network in close loop spatial multiplexing mode (CLSM). Besides, we also emphasize on the point to find out the best suited network architecture for overpopulated and densely urban region under proportional fair scheduling algorithm.

Comparative performance analysis of different resource scheduler and characterising the impact of proportional fair under different TTI feedback delay in EUTRA network

Evolved UMTS terrestrial radio access network (EUTRAN) offers high uplink and downlink throughput. In this paper, we investigate the performance of five different schedulers of media access control for resource allocation, such as round robin (RB), proportional fair (PF), best channel quality indicator (CQI), max transmission point (TP) and resource fair (RF). On comparing the performance of resource allocation schedulers in the indistinguishable arrangement, we found the proportional fair (PF) offers balance in terms of individual metrics. Furthermore, we analyse the effect of feedback transmission time interval (TTI) delay on two typical EUTRAN networks referred to as long term evolution (LTE) and LTE-Advance (LTE-A). We evaluate the performance of the PF scheduler for both networks under varying feedback delay in TTI. Simulated results show that the delay in TTI affects the performance of resource allocation. Feedback delay improves network performance by compensating effect of imperfect channel.

Comparative performance analysis of different resource scheduler and characterising the impact of proportional fair under different TTI feedback delay in EUTRA network

Evolved UMTS terrestrial radio access network (EUTRAN) offers high uplink and downlink throughput. In this paper, we investigate the performance of five different schedulers of media access control for resource allocation, such as round robin (RB), proportional fair (PF), best channel quality indicator (CQI), max transmission point (TP) and resource fair (RF). On comparing the performance of resource allocation schedulers in the indistinguishable arrangement, we found the proportional fair (PF) offers balance in terms of individual metrics. Furthermore, we analyse the effect of feedback transmission time interval (TTI) delay on two typical EUTRAN networks referred to as long term evolution (LTE) and LTE-Advance (LTE-A). We evaluate the performance of the PF scheduler for both networks under varying feedback delay in TTI. Simulated results show that the delay in TTI affects the performance of resource allocation. Feedback delay improves network performance by compensating effect of imperfect channel.

ERfair Scheduler with Processor Suspension for Real-Time Multiprocessor Embedded Systems

Proportional fair schedulers with their ability to provide optimal schedulability along with hard timeliness and quality-of-service guarantees on multiprocessors form an attractive alternative in real-time embedded systems that concurrently run a mix of independent applications with varying timeliness constraints. This article presents ERfair Scheduler with Suspension on Multiprocessors (ESSM) , an efficient, optimal proportional fair scheduler that attempts to reduce system wide energy consumption by locally maximizing the processor suspension intervals while not sacrificing the ERfairness timing constraints of the system. The proposed technique takes advantage of higher execution rates of tasks in underloaded ERfair systems and uses a procrastination scheme to search for time points within the schedule where suspension intervals are locally maximal. Evaluation results reveal that ESSM achieves good sleep efficiency and provides up to 50% higher effective total sleep durations as compared to the Basic-ERfair scheduler on systems consisting of 2 to 20 processors.

Fast and efficient user pairing and power allocation algorithm for non‐orthogonal multiple access in cellular networks

Non-orthogonal multiple access (NOMA) is emerging as a promising multiple access technology for the fifth generation cellular networks to address the fast growing mobile data traffic. It applies superposition coding in transmitters, allowing simultaneous allocation of the same frequency resource to multiple intra-cell users. Successive interference cancellation is used at the receivers to cancel intra-cell interference. User pairing and power allocation (UPPA) is a key design aspect of NOMA. Existing UPPA algorithms are mainly based on exhaustive search method with extensive computation complexity, which can severely affect the NOMA performance. A fast proportional fairness (PF) scheduling based UPPA algorithm is proposed to address the problem. The novel idea is to form user pairs around the users with the highest PF metrics with pre-configured fixed power allocation. Systemlevel simulation results show that the proposed algorithm is significantly faster (seven times faster for the scenario with 20 users) with a negligible throughput loss than the existing exhaustive search algorithm.

Improvement of indoor VLC network downlink scheduling and resource allocation.

Indoor visible light communications (VLC) combines illumination and communication by utilizing the high-modulation-speed of LEDs. VLC is anticipated to be complementary to radio frequency communications and an important part of next generation heterogeneous networks. In order to make the maximum use of VLC technology in a networking environment, we need to expand existing research from studies of traditional point-to-point links to encompass scheduling and resource allocation related to multi-user scenarios. This work aims to maximize the downlink throughput of an indoor VLC network, while taking both user fairness and time latency into consideration. Inter-user interference is eliminated by appropriately allocating LEDs to users with the aid of graph theory. A three-term priority factor model is derived and is shown to improve the throughput performance of the network scheduling scheme over those previously reported. Simulations of VLC downlink scheduling have been performed under proportional fairness scheduling principles where our newly formulated priority factor model has been applied. The downlink throughput is improved by 19.6% compared to previous two-term priority models, while achieving similar fairness and latency performance. When the number of users grows larger, the three-term priority model indicates an improvement in Fairness performance compared to two-term priority model scheduling.

Distributed relay selection strategy based on physical‐layer fairness for amplify‐and‐forward relaying systems

For relay terminals in wireless communication systems, the difference of the power consumed for relaying signals means unfairness, which may reduce the network lifetime when the system is energy-constrained. Classic opportunistic relay selections always cause unequal power consumption among all relays. In this study, the authors propose a novel distributed relay selection strategy, named the fair opportunistic relay selection (FORS) strategy, for amplify-and-forward (AF) opportunistic cooperative systems. The FORS strategy is designed based on physical-layer fairness that means all available relays cumulatively consume equal power. They use a set of weight coefficients to adjust the channel fading coefficients effectively and then change the selection probabilities for all relays on the basis of proportional fair scheduling. Considering that the ‘optimal’ relay can be selected proactively in quasi-static Rayleigh fading channels based on local channel state information, the overhead of the proposed scheme is small. Then, they analyse the performance of the FORS strategy and provide an exact analytical expression for the outage probability (P out) and the average symbol error probability. Numerical simulation results validate their analysis. The results show that the FORS strategy approximately achieves the upper bound of physical-layer fairness in the AF relaying system.

Proportional Fair Scheduling in Wireless Networks With RF Energy Harvesting and Processing Cost

In this letter, we apply the notion of proportional fair (PF) scheduling to wireless powered communication networks, which consist of a base station that broadcasts radio-frequency energy over the downlink [energy harvesting (EH) phase] and EH users that transmit information over the uplink [information transmission (IT) phase]. The doubly near fair problem hinders the fair resource allocation in these networks, but can be successfully overcome by an opportunistic policy for scheduling of a single EHU per time-division multiple access (TDMA) frame. It turns out that the optimal PF scheduling is realized when each TDMA frame consists of either an EH or an IT phase. The proposed online solution is asymptotically optimal but also applicable for a finite number of transmission epochs.

Power Allocation for Max-Sum Rate and Max-Min Rate Proportional Fairness in NOMA

In this letter, we consider proportional fairness scheduling (PFS) for downlink non-orthogonal multiple access (NOMA) with two users. Unlike conventional multiuser diversity systems, the power allocation plays a key role in PFS for NOMA as it can support multiple users simultaneously with positive transmission rates. With different criteria, we find optimal power allocation. Among those, it is shown that the PFS scheme that maximizes the minimum normalized rate can provide not only proportional fairness, but also small variation of transmission rates.

Water‐filling technique‐based proportionally fair scheduling algorithm for SC‐FDMA

ABSTRACTSingle carrier frequency division multiple access (SC‐FDMA) regulates that subchannels allocated to a user should be contiguous in frequency domain (i.e., contiguity constraint). Due to the constraint, the proportionally fair (PF) scheduling in SC‐FDMA is known to be non‐deterministic polynomial‐time (NP) hard. In this paper, a novel PF scheduling algorithm is proposed based on the water‐filling (WF) technique to effectively solve PF scheduling in SC‐FDMA. The proposed algorithm is composed of 2 phases: subchannel allocation and data rate adjustment phases. In the subchannel allocation phase, user's power is allocated to frequency‐contiguous subchannels for maximizing users' data rates based on the WF technique. In the data rate adjustment phase, the modulation and coding scheme of user is decided by solving the PF scheduling problem with the WF technique. Through simulations, it is shown that the proposed scheme achieves total data rates and logarithmic sum of average user data rates close to those of the optimal PF scheduling. In addition, the proposed scheme performs better than coherence subband based resource allocation scheme.

Multi‐device selection scheduling in non‐identically distributed fading channels

Multiuser selection scheduling concept has been recently proposed in the literature in order to increase the multiuser diversity gain and overcome the significant feedback requirements for the opportunistic scheduling schemes. The main idea is that reducing the feedback overhead saves per-user power that could potentially be added for the data transmission. In this work, the authors propose to integrate the principle of multiuser selection and the proportional fair scheduling scheme. This is aimed especially at power-limited, multi-device systems in non-identically distributed fading channels. For the performance analysis, they derive closed-form expressions for the outage probabilities and the average system rate of the delay-sensitive and the delay-tolerant systems, respectively, and compare them with the full feedback multiuser diversity schemes. The discrete rate region is analytically presented, where the maximum average system rate can be obtained by properly choosing the number of partial devices. They optimise jointly the number of partial devices and the per-device power saving in order to maximise the average system rate under the power requirement. Through the authors’ results, they finally demonstrate that the proposed scheme leveraging the saved feedback power to add for the data transmission can outperform the full feedback multiuser diversity, in non-identical Rayleigh fading of devices’ channels.

A proportional fairness scheduling for wireless sensor networks

A packet scheduling algorithm used for wireless sensor network meeting the proportional fairness principle is proposed. Based on the weighted round robin (WRR) strategy, the proposed scheduling algorithm allocates different service quota to different traffics according to their average packet arrival rates to guarantee the proportion fairness on the average packet delivery delay and the average packet loss ratio. Since the scheduling algorithm does not perform the high-load operations such as adding time stamps, sorting and so on, it can be implemented easily and is suitable for resource-limited WSN. The proposed algorithm is tested in a wireless sensor network. The performance shows that the scheduling algorithm can guarantee the average packet delivery delay proportional fairness when the average packet delivery delay is used as the performance metric and the average packet loss ratio proportional fairness is realized when all the queues are overflowing and the average packet loss ratio is used as the performance metric.

Proportional-Fair Resource Allocation for Coordinated Multi-Point Transmission in LTE-Advanced

Coordinated multi-point (CoMP) transmission and reception are introduced as a promising technology in the 3GPP LTE-advanced standard, to manage interference, improve the overall system performance, and enhance system reliability. In this paper, a resource allocation problem is studied for downlink CoMP coordinated beamforming systems, where each base station (BS) serves its own mobile stations. Multiple-input-multiple-output (MIMO) transmit precoding and resource allocation are linked to the underlying proportional-fair scheduling to ensure a good trade-off between cell-average and cell-edge user spectral-efficiency. Due to the coupled interference among mobile stations, the resulting proportional-fair resource allocation optimization problem becomes nonconvex. To solve for optimal operating point for MIMO CoMP network, a parallel successive convex approximation-based algorithm is introduced. The introduced scheme enables all BSs to update their optimization variables in parallel by solving a sequence of strongly convex subproblems. Closed-form expressions of the locally optimal solution in both the high and low signal-to-noise regimes are characterized. The performance of the introduced scheme is also investigated through simulations. Numerical results show the efficiency of the introduced algorithm.

3‐D quasi proportional fairness scheduling in relay‐assisted multicell LTE‐A downlink

AbstractThis paper presents a three‐dimensional (3‐D: space‐time‐frequency) quasi proportional fairness (QPF)‐based radio resource allocation and interference coordination scheme in multicell long‐term evolution‐advanced downlink. We formulate the resource allocation and interference coordination problem as a QPF‐based utility maximisation problem, wherein, QPF reduces the complexity compared with the conventional proportional fairness. Interference has been minimised through time, frequency and space domain resource allocation. The proposed 3‐D scheme utilises two time slots for intercell interference management, spatial position‐based frequency resource allocation for intracell interference mitigation, and frequency domain orthogonality across user equipment (UE) and relays for inter‐UE and UE‐relays interference management. It has been shown that the relaxed non‐convex primal problem and the dual problem have zero duality gap under the time‐sharing and tolerable interference constraints. The relaxed optimal problem has been solved through the Lagrange dual method. Simulation results show the efficacy of the proposed 3‐D scheme compared with the recently presented three slots time domain interference coordination with round robin and proportional fairness time domain interference coordination schemes. It has been observed that the proposed heuristic 3D with equal power scheme exhibits same performance as the heuristic 3D with water‐filling power allocation and retains the desired optimal level for more than 60% of the average users' throughput. Copyright © 2016 John Wiley & Sons, Ltd.

PERFORMANCE ANALYSIS OF EXP-BET ALGORITHM FOR TRIPLE PLAY SERVICES IN LTE SYSTEM

Quality of Service (QoS) is defined as user’s satisfaction towards service performance that has been offered to them. Due to different traffic characteristics and QoS requirements of real-time and non-real-time services, thus provisioning the QoS requirements has become a challenge. In this study, we have compared our proposed algorithm namely the Exponential Blind Equal Throughput (EXP-BET) towards the Exponential Proportional Fairness (EXP-PF) and Frame Level Scheduler (FLS). The comparisons have been made in terms of fairness index, throughput,packet loss rate (PLR) and delay. From the simulation results, it is observed that EXP-BET delivers higher fairness and throughput and lower PLR and delay for real-time application. Instead, EXP-BET shows 17.72% improvement than FLS and 7.52% from EXP-PF in term of fairness index for the non-real-time application.

Exploiting Mobility in Proportional Fair Cellular Scheduling: Measurements and Algorithms

Proportional Fair (PF) scheduling algorithms are the de facto standard in cellular networks. They exploit the users' channel state diversity (induced by fast-fading) and are optimal for stationary channel state distributions and an infinite time-horizon. However, mobile users experience a nonstationary channel, due to slow-fading (on the order of seconds), and are associated with base stations for short periods. Hence, we develop the Predictive Finite-horizon PF Scheduling ((PF)2S) Framework that exploits mobility. We present extensive channel measurement results from a 3G network and characterize mobility-induced channel state trends. We show that a user's channel state is highly reproducible and leverage that to develop a data rate prediction mechanism. We then present a few channel allocation estimation algorithms that exploit the prediction mechanism. Our trace-based simulations consider instances of the ((PF)2S) Framework composed of combinations of prediction and channel allocation estimation algorithms. They indicate that the framework can increase the throughput by 15%-55% compared to traditional PF schedulers, while improving fairness.