Delay Quality-of-service Constraint Research Articles

Resource matching algorithm under delay QoS constraint for uplink visible light communication based on supermartingale theory

We propose a supermartingale-based resource matching algorithm to guarantee delay quality of service (QoS) for the visible light communication uplink system. A network queuing model with multiple bursty arrivals is established, and multipacket reception technology is considered to alleviate terminal collisions. We introduce the supermartingale theory to evaluate the delay QoS performance, and a tighter delay-violation probability bound is derived. Relying on the supermartingale analysis, we design a search algorithm to achieve resource matching under a delay QoS constraint. The simulation results prove that the proposed algorithm guarantees delay QoS and saves service resources.

Asymptotic Performance Analysis of NOMA Uplink Networks Under Statistical QoS Delay Constraints

In this article, we study the performance of an uplink non-orthogonal multiple access (NOMA) network under statistical quality of service (QoS) delay constraints, captured through each user's effective capacity (EC). We first propose novel closed-form expressions for the EC in a two-user NOMA network and show that in the high signal-to-noise ratio (SNR) region, the “strong” NOMA user, referred to as U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , has a limited EC, assuming the same delay constraint as the “weak” user, referred to as U1. We demonstrate that for the weak user U1, OMA and NOMA have comparable performance at low transmit SNRs, while NOMA outperforms OMA in terms of EC at high SNRs. On the other hand, for the strong user U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , NOMA achieves higher EC than OMA at small SNRs, while OMA becomes more beneficial at high SNRs. Furthermore, we show that at high transmit SNRs, irrespective of whether the application is delay tolerant, or not, the performance gains of NOMA over OMA for U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , and OMA over NOMA for U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> remain unchanged. When the delay QoS of one user is fixed, the performance gap between NOMA and OMA in terms of total EC increases with decreasing statistical delay QoS constraints for the other user. Next, by introducing pairing, we show that NOMA with user-pairing outperforms OMA, in terms of total uplink EC. The best pairing strategies are given in the cases of four and six users NOMA, raising once again the importance of power allocation in the optimization of NOMA's performance.

Bisection and Exact Algorithms Based on the Lagrangian Dual for a Single-Constrained Shortest Path Problem

We propose two new algorithms called BiLAD and ExactBiLAD for the well-known Single-Constrained Shortest Path (SCSP) problem. It is a fundamental problem in quality-of-service (QoS) routing, where one seeks a source-destination path with the least cost satisfying a delay QoS constraint in a network. As pointed out by Juttner et al. , there is no widely accepted algorithm with polynomial time to the SCSP problem because the SCSP problem is NP-hard. The remarkable feature of BiLAD is that it ensures that the length of iteratively updated angle interval is shrunk at least at a constant ratio. With the help of this feature, we prove its polynomial time complexity. To the best of our knowledge, this is the first time that the polynomial time complexity is proved in details. The numerical results show that, in most QoS routing test instances, the performance of BiLAD is close to their primal optimal solutions. The proposed modified Dijkstra procedure, whose complexity is the same as that of the Dijkstra algorithm, also accelerates BiLAD. In the second part of the paper, based on the information obtained by BiLAD, we design an exact algorithm–ExactBiLAD, in which an optimal solution to the SCSP problem is finally obtained by scanning the steadily reduced optimal-path-candidate triangle area. The simulation results indicate that ExactBiLAD needs only a dozen times of executing the modified Dijkstra algorithm regardless of the network size or the average node degree. Distinguished from many other exact algorithms, ExactBiLAD has a satisfactory performance in the practical computation.

Bandwidth estimation for aggregate traffic under delay QoS constraint based on supermartingale theory

Bandwidth estimation for network traffic plays an important role in various communication network applications. Due to the diversity presented by the network services, exploring theory and methods to measure bandwidth of superposition of traffic flows has great practical significance. In this paper, we propose a supermartingale approach to calculate bandwidth for aggregate traffic under delay Quality of Service (QoS) constraint. The concept of supermartingale bandwidth is put forward to define the required bandwidth of traffic, which measures bandwidth more accurately. The communication network carrying mixed services is modeled as a queuing system with aggregate arrival traffic. Supermartingale method enables the complex queuing system analysis. Based on the stopping time theory of supermartingale, remarkably tight bound of delay-violation probability for aggregate traffic is derived. Subsequently, we estimate the bandwidth according to delay QoS requirement and traffic characteristics. Searching program for bandwidth estimation is designed. Simulation results show that the estimated bandwidth through supermartingale model is more accurate and smaller than effective bandwidth, especially when arrival traffic has bursty feature. Although this approach is presented for the analysis of two typical arrivals, the proposed model is applicable to general aggregate traffic.

Coverage and Effective Capacity in Downlink MIMO Multicell Networks With Power Control: Stochastic Geometry Modelling

In this paper, coverage probability and effective capacity in downlink multiple-antenna cellular system are considered. Two scenarios are investigated; in the first scenario, it is assumed that the system employs distance-based fractional power control with no multicell coordination. For the second scenario, we assume the system implements multicell coordinated beamforming so as to cancel inter-cell interference. For both scenarios, the BSs are assumed to randomly uniformly distributed in the area according to Poisson point process. Using tools from stochastic geometry, tractable, analytical expressions for coverage probability and effective capacity are derived for both scenarios. Numerical results reveal that for a system with stringent delay quality of service (QoS) constraints, i.e. (traffic delay is intolerable), best performance can be achieved by suitably adopting fractional power strategy when transmitting to the users, while constant power allocation performs better than all other power allocation strategies when the delay QoS constraints get loose (tolerable delay). For coverage probability, a fractional power control is better than constant power and channel inversion power strategies for low signal-to-interference plus noise ratio (SINR) thresholds, while the constant power strategy performs better than others in high SINR thresholds.

Cross-Layer Power Allocation in Nonorthogonal Multiple Access Systems for Statistical QoS Provisioning

Power allocation is a critical issue in the physical layer of power-domain nonorthogonal multiple access (NOMA) systems. However, existing power allocation schemes have not considered the delay quality of service (QoS) requirement in the datalink layer of users, and hence may not ensure the desired delay QoS requested by the services in the upper layers. Different from existing works, we apply the statistical QoS theory into NOMA systems and formulate the physical-datalink cross-layer power allocation problem as a stochastic optimization problem under different delay QoS constraints. Also, we show that the formulated problem is quasi-concave and propose a bisection-based cross-layer power allocation algorithm. Simulation results show that the proposed algorithm is able to converge to the optimal solution obtained by exhaustive search. Also, the proposed scheme outperforms existing fixed NOMA and time-division multiple access based schemes in terms of max–min effective capacity.

Effective Capacity of NOMA and a Suboptimal Power Control Policy With Delay QoS

In order to apply downlink nonorthogonal multiple access (NOMA) to delay-sensitive transmissions, we consider NOMA with delay quality of service (QoS) constraints and effective capacity with power control when the channel state information is available in this paper. As the power control problem to maximize the sum effective capacity with delay QoS constraints is not a convex problem, we propose a suboptimal approach based on the partial effective capacity. The resulting power control policy can be seen as a generalization of a well-known approach, which is the truncated channel inversion power control (TCIPC) policy, to NOMA. We can further optimize the NOMA-TCIPC policy with QoS constraints and confirm that the resulting policy can guarantee delay QoS from simulation results.

Cross Layer Power Allocation For Selection Relaying and Incremental Relaying Protocols over Single Relay Networks

The purpose of this paper is analyzing and improving delay quality of service (QoS) provisioning of adaptive selection relaying protocol (SRP) and adaptive incremental relaying protocol (IRP) in single relay networks. In relation to delay QoS provisioning, the concept of effective capacity (EC) is utilized. So, as the first step, we find the EC functions of SRP and IRP and mathematically analyze the ECs to derive the closed form expressions of them which reduce the computational complexity. Then, by the goal of maximizing the ECs or equivalently improving delay QoS provisioning, we propose cross layer adaptive power allocation (APA) schemes as two closed form algorithms for both SRP and IRP strategies. The proposed cross layer APA algorithms depend on the delay QoS constraint and instantaneous channel conditions. Also, by applying the closed form ECs, two cross layer fixed power allocation (FPA) schemes are represented over both SRP and IRP that depend on delay QoS constraint and statistical channel conditions. The numerical results validate the derived closed form equations for the ECs of the protocols and also show that our proposed APA schemes achieve a significant improvement in EC performance of the system with both protocols, especially for stringent QoS requirements.

QoS‐driven jointly optimal power and bandwidth allocation for heterogeneous wireless networks

By integrating the concept of effective capacity, the quality-of-service (QoS)-driven power and bandwidth allocation for heterogeneous wireless networks are investigated. The objective is to improve the power efficiency while providing delay QoS guarantees for the multi-mode mobile terminal users. First, the joint power and bandwidth allocation problem is formulated as a convex problem. Then, by solving the problem in the dual domain, an iterative algorithm to achieve the jointly optimal power and bandwidth allocation is proposed. The analytical results show that the optimal power and bandwidth allocation depends not only on the channel quality, but also on the delay QoS constraints. The numerical results verify that the proposed scheme can achieve the best power efficiency compared to the existing schemes.

Delay-Constrained Video Transmission: Quality-Driven Resource Allocation and Scheduling

Real-time video demands quality-of-service (QoS) guarantees such as delay bounds for end-user satisfaction. Furthermore, the tolerable delay varies depending on the use case such as live streaming or two-way video conferencing. Due to the inherently stochastic nature of wireless fading channels, deterministic delay bounds are difficult to guarantee. Instead, we propose providing statistical delay guarantees using the concept of effective capacity. We consider a multiuser setup whereby different users have (possibly different) delay QoS constraints. We derive the resource allocation policy that maximizes the sum video quality and applies to any quality metric with concave rate-quality mapping. We show that the optimal operating point per user is such that the rate-distortion slope is the inverse of the supported video source rate per unit bandwidth, a key metric we refer to as the source spectral efficiency. We extend the resource allocation policy to capture video quality-driven adaptive user-subcarrier assignment in wideband channels as well as capture the impact of adaptive modulation and coding. We also solve the alternative problem of fairness-based resource allocation whereby the objective is to maximize the minimum video quality across users. Finally, we derive user admission and scheduling policies that enable selecting a maximal user subset such that all selected users can meet their statistical delay requirement. Results show that video users with differentiated QoS requirements can achieve similar video quality with vastly different resource requirements. Thus, QoS-aware scheduling and resource allocation enable supporting significantly more users under the same resource constraints.

QoS‐driven jointly optimal subcarrier pairing and power allocation for OFDM amplify‐and‐forward relay systems

SUMMARYIn this paper, we investigate the quality‐of‐service (QoS) driven subcarrier pairing and power allocation for two‐hop amplify‐and‐forward OFDM relay systems. By integrating the concept of effective capacity, our goal is to maximize the system throughput subject to a given delay QoS constraint. We propose a jointly optimal subcarrier pairing and power allocation scheme, which can be implemented with two separate steps. First, pair the subcarriers over the source‐relay channel and relay‐destination channel by the descending order of the subcarriers’ channel gains. Second, by making use of the derived equivalent end‐to‐end channel gains of the subcarrier pairs, optimally allocate power over the subcarrier pairs, and then optimally partition the power of the subcarrier pairs between the source and the relay. The simulation results show that our proposed scheme can efficiently provide different levels of delay QoS guarantees, even if under stringent delay QoS constraints. The simulation results also verify that our proposed scheme shows significant superiorities over the other existing schemes. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Effective capacity of delay quality-of-service constrained spectrum sharing cognitive radio with outdated channel feedback

In this paper, we consider a spectrum sharing cognitive radio network coexisting with a primary network. Particularly, the channel state information (CSI) between the secondary transmitter and the primary receiver is assumed to be outdated due to channel feedback latency. The secondary user (SU) is assumed to satisfy a given delay quality-of-service (QoS) constraint as well as the average interference power constraint. We aim to derive the maximum arrival rate of the SU under aforementioned constraints with the outdated CSI. In this respect, we derive the optimal power allocation to achieve the maximum effective capacity, and further derive the effective capacity. The closed-form expressions for the lower and upper bounds on the effective capacity are also derived. In addition, we obtain the effective capacities under two widely adopted adaptive transmission schemes, i.e., optimal power and rate allocation (OPRA) and truncated channel inversion with fixed rate (TIFR). Numerical results are conducted to corroborate our studies. It is shown that the effective capacities of the SU under various transmission schemes are insensitive to the channel correlation coefficient especially under low channel correlation coefficient. It is also shown that the lower and upper bounds on the effective capacity are significantly tight under stringent delay QoS constraint.

A Real Time Video Transmission Routing Protocol in Multi-Interface Multi-Channel Ad Hoc Based on Queue Length and Delay Contraint

Real-time video transmission demands tremendous bandwidth, throughput and strict delay. For transmitting real-time video in the multi-interface multi-channel Ad hoc, firstly, we applied multi-interface multi-channel extension methods to the AOMDV (Ad-hoc On-demand Multipath Distance Vector) routing protocol, and improved extant channel switching algorithm, called MIMC-AOMDV (Multi-Interface Multi-Channel AOMDV) routing protocol. Secondly, we proposed video streaming delay QoS(Quality of Service) constraint and link-quality metrics, which used the multi interface queue’s total used length to get QMMIMC-AOMDV (Quality metric MIMC -AOMDV) routing protocol. The simulations show that the proposed QMMIMC-AOMDV can reduce the frame delay effectively and raise frame decodable rate and peak signal to noise ratio (PSNR), it is more suitable for real-time video streams.

QoS-Driven Jointly Optimal Subcarrier Pairing and Power Allocation for Decode-and-Forward OFDM Relay Systems

In this paper, we investigate the quality-of-service (QoS) driven subcarrier pairing and power allocation for two-hop decode-and-forward (DF) OFDM relay systems. By integrating the concept of effective capacity, our goal is to maximize the system throughput subject to a given delay-QoS constraint. Based on whether the destination can receive the signal transmitted by the source, we consider two scenarios, i.e. OFDM DF relay systems without diversity and OFDM DF relay systems with diversity, respectively. For OFDM DF relay systems without diversity, we demonstrate that the jointly optimal subcarrier pairing and power allocation can be implemented with two separate steps. For OFDM DF relay systems with diversity, we propose an iterative algorithm to achieve jointly optimal subcarrier pairing and power allocation. Furthermore, we find that the analytical results show different conclusions for the two types of OFDM relay systems. For OFDM relay systems without diversity, the optimal power allocation depend on not only the channel quality of subcarriers but also the delay QoS constraints, while the optimal subcarrier pairing just depends on the channel quality of subcarriers. For OFDM relay systems with diversity, both the optimal subcarrier pairing and power allocation depend on the channel quality of subcarriers and the delay QoS constraints. Simulation results show that our proposed scheme offers a superior performance over the existing schemes.

Resource allocation for OFDM relay systems with statistical QoS guarantees

SUMMARYBy integrating the concept of effective capacity, we propose the resource allocation schemes for subcarrier‐pair based OFDM decode‐and‐forward and amplify‐and‐forward relay systems for quality‐of‐service (QoS) guarantees. The objective is to maximize the system throughput subject to a given statistical delay QoS constraint. First, we pair the subcarriers over the source‐relay channel and the relay‐destination channel by the descending order of the subcarriers' channel gains. Second, by making use of the derived equivalent end‐to‐end channel gains of the subcarrier pairs, we apply joint water‐filling power allocation over the subcarrier pairs and then partition the power of the subcarrier pairs between the source and the relay. We prove that as the equivalent end‐to‐end channel gains of the subcarrier pairs are given, the combination of sorted subcarrier pairing and joint water‐filling power allocation is jointly optimal to maximize the effective capacity. The simulation results show that our proposed schemes achieve the highest effective capacity for OFDM decode‐and‐forward and amplify‐and‐forward relay systems as compared with other existing schemes. The results also verify that our proposed schemes can efficiently provide different levels of delay QoS guarantees, even if under the stringent delay QoS constraints. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Optimal Resource Allocation for Spectrum Sensing Based Cognitive Radio Networks with Statistical QoS Guarantees

Resource allocation under spectrum sensing based dynamic spectrum sharing strategy is a critically important issue for cognitive radio networks (CRNs), because they need to not only satisfy the interference constraint caused to the primary users (PUs), but also meet the quality-of-service (QoS) requirements for the secondary users (SUs). In this paper, we develop the optimal spectrum sensing based resource allocation scheme for the delay QoS constrained CRNs. Specifically, we aim at maximizing the maximum constant arrival rate of the SU that can be supported by the time-varying service process subject to the given statistical delay QoS constraint. In our derived power allocation scheme, not only the average transmit and interference power constraints are considered, but also the impact of the PUs’ transmission to the CRNs and the PUs’ spectrum-occupancy probability are taken into consideration. Moreover, the spectrum sensing errors are also taken into consideration. Simulation results show that, (1) the effective capacity of the secondary link decreases when the statistical delay QoS constraint becomes stringent; (2) given the QoS constraint, the effective capacity of the secondary link varies with the interference power constraint and the SNR of the primary link.

Throughput–Delay Tradeoff of Proportional Fair Scheduling in OFDMA Systems

This work presents an analytical model of the throughput-delay tradeoff found in proportional fair scheduling used in orthogonal frequency-division multiple access (OFDMA) systems in the context of user multiplexing. For this purpose, we propose a simple and efficient resource allocation scheme based on 2-D resource partitioning in the frequency and time domains. Basically, frequency-domain partitioning is determined by the degree of frequency diversity, and time-domain partitioning determines the degree of multiplexing (DoM), which is the number of users to be served in a subchannel of a frame. We investigate the effect of the DoM and frequency diversity on the delay quality-of-service (QoS) performance of OFDMA systems by analyzing the effective capacity. In addition, an energy efficiency analysis in the wideband regime shows that insufficient frequency diversity increases the impact of the delay QoS constraint on energy efficiency, and in this case, greater energy efficiency can be achieved by using an appropriate DoM.

Adaptive Modulation in Spectrum-Sharing Channels Under Delay Quality-of-Service Constraints

We propose a variable-rate variable-power M-level quadrature amplitude modulation (MQAM) scheme employed under delay quality-of-service (QoS) constraints over spectrum-sharing channels. An underlay cognitive radio system, with one primary user and a secondary user, with constraints on interference leakage imposed by the primary receiver is considered. The transmission parameters of the secondary user are set optimally such that the successful communications for the primary user in terms of a minimum rate to be supported is satisfied, irrespective of co-existence with the secondary user. We obtain interference constraints that, when satisfied by the secondary users, is sufficient to satisfy the service outage requirement of the primary user. We further study the performance of the secondary user's link employing an adaptive MQAM scheme when, on top of the aforementioned interference constraint, the secondary user is also required to satisfy a statistical delay QoS constraint. Considering two modulation schemes, i.e., continuous MQAM and discrete MQAM with restricted constellations, we obtain the effective capacity of the secondary user's link and derive the optimum power allocation that maximizes the effective capacity of the secondary user.

Power‐efficient resource allocation with QoS guarantees for TDMA fading channels

ABSTRACTThis paper proposes two power‐efficient resource allocation policies with statistical delay Quality of Service (QoS) guarantees for uplink time‐division multiple access (TDMA) communication links. Specifically, the first policy aims at maximizing the system throughput while fulfilling the delay QoS and average power constraints, and the second policy is devised as an effort to minimize the total average power subject to individual delay QoS constraints. Convex optimization problems associated with the resource allocation policies are formulated based on a cross‐layer framework, where the queue at the data link layer is served by the resource allocation policy. By employing the Lagrangian duality theory and the dual decomposition theory, two subgradient iteration algorithms are developed to obtain the globally optimal solutions. The aforementioned resource allocation policies have been shown to be deterministic functions of delay QoS requirements and channel fading states. Moreover, numerical results are provided to demonstrate the performance of the proposed resource allocation policies. Copyright © 2010 John Wiley &amp; Sons, Ltd.

The Effect of Multiplexing Users in QoS Provisioning Scheduling

In this paper, we consider the effect of multiplexing users in a frame (more specifically, coherent time) on providing quality of service (QoS) in multiuser wireless networks. For this purpose, we propose simple and efficient scheduling schemes that can yield substantial capacity gain. Our approach involves maximizing the throughput subject to a given delay QoS constraint by choosing the appropriate number of users to be served in a frame. We call this number the degree of multiplexing. We investigate the effect of the degree of multiplexing on QoS performance in wireless multiuser scheduling by analyzing the effective capacity and then develop an approach to finding the optimal degree of multiplexing by asymptotic approximation.