Ziaul Haq Abbas

Fairness-Driven Queue Management: A Survey and Taxonomy

Providing congestion control in the Internet, while ensuring fairness among a myriad of heterogeneous flows, is a challenging task. The conventional wisdom is to rely on end-user applications cooperatively deploying congestion control mechanisms to achieve high network utilization and some degree of fairness among flows. However, as the Internet has evolved to encompass all of society, such a cooperative behavior from end-user applications is not always granted. Applications may simply act selfishly to be more competitive through bandwidth abuse. Bandwidth starvation may also arise unintentionally depending on the nature of traffic sources. The ensuing impact can be severe fairness hazard and even congestion collapse. Router-based queue management schemes driven by fairness objectives, thus, become an inescapable necessity for fairly sharing network resources. Given a significant volume of literature relating to fairness-driven queue management schemes, there has remained a need for a broader and coherent survey. This paper presents a systematic and comprehensive review of eminent fairness-driven queue management schemes from the inception of the concept and the preliminary work to the most recent work. We present a new taxonomy of categorizing fairness-driven queue management schemes. We discuss design approaches and key attributes of these schemes and provide their comparison and analysis. Based on the outcomes of this survey, we discuss a number of open issues and provide generic design guidelines and future directions for the research in this field.

Cell Association With Load Balancing in Nonuniform Heterogeneous Cellular Networks: Coverage Probability and Rate Analysis

To meet the ever-growing traffic demand and address the cell capacity shortage problem, associating end users to various tiers of cells in a multitier cellular network appears to be a promising approach. In this paper, we consider a nonuniform heterogeneous cellular network (NuHCN) and propose a cell association scheme that selectively mutes certain small-cell base stations (BSs) and covers end users by cell range extension (via cell biasing) for achieving load balancing. The envisaged NuHCN is comprised of two tiers of BSs, i.e., macro- and small-cell BSs, deployed according to three independent homogeneous Poisson point processes for BSs and end users, respectively. Accordingly, the available space is divided into two subspaces. In the inner subspace, the end users are associated only with a macrocell BS based on the unbiased maximum received power scheme since the small-cell BSs therein are deactivated. In the outer subspace, where the macrocell BS coverage is comparatively poor, the end users are associated with either a macrocell BS or a microcell BS based on the biased/unbiased maximum received power scheme. Cell range extension-based cell association allows the macrocell users in the outer subspace to efficiently utilize the resources of the lightly loaded small-cell BSs, resulting in improved network coverage and capacity. Based on the proposed cell association scheme, we analyze the signal-to-interference plus noise ratio (SINR) distribution and deduce expressions for coverage probability and rate coverage. Numerical results show that, contrary to the uniform case, biasing has distinct effects on the coverage and rate performance of an NuHCN.

A system-level power saving approach for cellular networks with microcells/picocells

Network power consumption reduction has recently become an active research topic. In this paper, we propose a novel approach to save power consumption of a three-cell microcellular network. When the traffic load in the middle cell is low, it can be switched-off and its users are covered. This is enabled by increasing the transmission power of one sector antenna in the two neighboring cells. Numerical results show that by increasing antenna transmission power of the two sectors, the overall network power consumption can be reduced.

Decoupled Downlink-Uplink Coverage Analysis with Interference Management for Enriched Heterogeneous Cellular Networks

Heterogeneous cellular networks (HetCNets) offer a promising solution to cope with the current cellular coverage crunch. Due to the large transmit power disparity, while following maximum power received (MPR) association scheme, a larger number of users are associated with macro-cell BS (MBS) than small-cell BSs (SBSs). Therefore, an imbalance load arrangement takes place across the HetCNets. Hence, using cell range expansion-based cell association, we can balance the load across the congested MBS. However, using MPR association scheme, users offloading leads to two challenges: 1) macro-cell interference, in which the MBS interferes with the offloaded users, and 2) coupled downlink-uplink cell association, in which a random user associates with a single tiers base station (BS) both in uplink (UL) and downlink (DL) directions. This paper aims to address these problems while considering a two-tier scenario consisting of small-cell and macro-cell tiers. For the MBS interference mitigation, we employ a reverse frequency allocation (RFA) scheme. Besides coupled DL-UL association (Co-DUA), this paper also highlights the notion of decoupled DL-UL association (De-DUA). In De-DUA, a random user associates with two different tiers BSs, i.e., with one tiers BS in the DL direction and with the other tiers BS in the UL direction. Our results illustrate that, in comparison with the Co-DUA, De-DUA with RFA employment achieves a better coverage performance.

A novel teletraffic-based power saving scheme for cellular networks with microcells

As the number of network components increases to meet the explosion of mobile devices, power conservation has become an important strategy for network operators. In this paper, we propose a novel teletraffic-based approach to save power consumption of a three-cell microcellular network. When the traffic load in the middle cell is lower than certain threshold, the cell can be switched-off and its users will be covered by increasing the transmission power of one sector antenna in each of the two neighboring cells. Numerical results demonstrate that at a moderate cost of increased antenna transmission power of the two sectors, significant amount of network power can be saved for the whole network.

Distance-related energy consumption analysis for mobile/relay stations in heterogeneous wireless networks

While the availability of more than one mobile or wireless technologies is enhancing the ubiquity of the Internet access, the corresponding energy consumption effects on mobile station battery for connection selection has not been investigated in depth yet. In this paper, a heterogeneous wireless network, which consists of three constituent networks, is studied with respect to the amount of data communicated and the battery operation time. Four alternative hybrid paths for separate uplink and downlink traffic, each involving more than one network, are analyzed with respect to energy consumption aspects of the mobile (and relay) station. The energy in these paths is analyzed mainly by considering the distance between communication stations while maintaining the available capacity in a sub-link at a constant level. The obtained results can be used for path selection as well as location placement for the MS/RS in order to achieve optimum amount of transferred data and battery lifetime.

Two Teletraffic-based Schemes for Energy Saving in Cellular Networks with Micro-cells

Published version of an article in the journal: Journal of Communications. Also available from the publisher at: http://dx.doi.org/10.4304/jcm.7.10.726-739 Open access

Location-based coverage and capacity analysis of a two tier HetNet

Stochastic geometry tool is an accurate and tractable approach to analyse the performance characteristics of heterogeneous networks (HetNets) with unplanned deployment of base stations (BSs). In this study, the authors analyse the downlink coverage and capacity by taking into account the separation between the macro BS (MBS) and small BSs (SBSs) in a HetNet. MBSs, SBSs, and users are spatially distributed as independent Poisson point processes. The whole space is divided into inner and outer subspaces around the MBSs and a typical user is assumed to be in outer subspace. Analysis on the typical user in the outer subspace incorporates the effect of distance of SBSs from MBS. They derive the expressions for the coverage probability of an outer subspace typical user from SBS and MBS. They also derive the expressions for rate coverage of an outer subspace typical user from SBS and MBS. These metrics are analysed with varying inner subspace radius to incorporate the effect of BSs separation. Simulation results show that SBSs away from MBS in the coverage region of MBS provide good performance to their associated users in terms of coverage probability and rate coverage.

A Stochastic Routing Algorithm for Distributed IoT with Unreliable Wireless Links

Punctual and reliable transmission of collected information is indispensable for many Internet of Things (IoT) applications. Such applications rely on IoT devices operating over wireless communication links which are intrinsically unreliable. Consequently to improve packet delivery success while reducing delivery delay is a challenging task for data transmission in the IoT. In this paper, we propose an improved distributed stochastic routing algorithm to increase packet delivery ratio and decrease delivery delay in IoT with unreliable communication links. We adopt the concept of absorbing Markov chain to model the network and evaluate the expected delivery ratio and expected delivery delay over multiple hops. Simulations are performed in order to evaluate the performance of the proposed algorithm in comparison with three existing decentralized routing algorithms.

Analysis of interference avoidance with load balancing in heterogeneous cellular networks

In heterogeneous cellular networks (HCNets) smallcells are overlaid with macro-cells to handle heavy cellular data traffic in an efficient way. To achieve fast and reliable access to data with a better coverage it is necessary to offload users to the underutilized small-cells from the congested macro-cells. Sharing of the same licensed frequency spectrum by smallcells and macro-cells results in heavy cross-tier interference which significantly affects the downlink SINR. In this paper, we investigate and analyze a joint frequency-division duplex based cross-tier complementary spectrum sharing technique which is also regarded as reverse frequency allocation (RFA) scheme with load balancing. This scheme mitigates inter-cell interference (ICI) and better balances the load across the network. It also guarantees enhanced spectral efficiency and coverage probability, particularly for cell edge users (CEUs). Numerical results indicate that load balancing together with RFA is necessary to enhance the coverage of CEU in co-channel HCNets.