Thomas O. Olwal

A Survey of Resource Management Toward 5G Radio Access Networks

The next generation 5G radio access network (RAN) system is believed to be a true world wide wireless web (WWWW). This is because such system will seamlessly and ubiquitously connect everything, and support at least 1000-fold traffic volumes, 100 billion connected wireless devices, and diversified use cases as well as quality of service (QoS) requirements (e.g., reliability, latency, data rates, coverage, security, and privacy) of multimedia applications by 2020. Recently, a number of research challenges including the explosive growth in mobile traffic volumes, unprecedented connected devices, and diversified use cases have been identified for the 5G RAN systems. In addition, specific technologies such as multitier communication, massive MIMOs, mmWave backhauling, extreme densifications of nodes (UDNs), full-duplex communications (FDCs), and energy harvesting techniques have emerged in the literature to resolve some of these challenges of the 5G RAN systems. However, the research activities defining specific technical advancements for 5G RAN systems are yet to continue in the next half decade before specifications for standardization and commercialization are concluded. Motivated by the limited number of existing surveys of such technical advancements in a broader perspective (i.e., interference, spectrum-efficient, and energy-efficient management schemes), this paper seeks to take stock of state-of-the-art (SOTA) on such technical developments. Our attention focuses on relevant radio interference and resource management (RIRM) schemes that have been proposed in the last five years. Our contribution lies in the analysis, synthesis, and summarized alignments of the conventional RIRM schemes toward overcoming the identified challenges for the 5G RAN systems. Finally, the review highlights a number of open research issues deduced from recently proposed RIRM schemes.

Joint queue-perturbed and weakly coupled power control for wireless backbone networks

Abstract Wireless Backbone Networks (WBNs) equipped with Multi-Radio Multi-Channel (MRMC) configurations do experience power control problems such as the inter-channel and co-channel interference, high energy consumption at multiple queues and unscalable network connectivity. Such network problems can be conveniently modelled using the theory of queue perturbation in the multiple queue systems and also as a weak coupling in a multiple channel wireless network. Consequently, this paper proposes a queue perturbation and weakly coupled based power control approach forWBNs. The ultimate objectives are to increase energy efficiency and the overall network capacity. In order to achieve this objective, a Markov chain model is first presented to describe the behaviour of the steady state probability distribution of the queue energy and buffer states. The singular perturbation parameter is approximated from the coefficients of the Taylor series expansion of the probability distribution. The impact of such queue perturbations on the transmission probability, given some transmission power values, is also analysed. Secondly, the inter-channel interference is modelled as a weakly coupled wireless system. Thirdly, Nash differential games are applied to derive optimal power control signals for each user subject to power constraints at each node. Finally, analytical models and numerical examples show the efficacy of the proposed model in solving power control problems in WBNs.

Autonomous Transmission Power Adaptation for Multi-Radio Multi-Channel Wireless Mesh Networks

Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in WMNs. Previous studies have emphasized throughput maximization in such systems as the main design challenge and transmission power control treated as a secondary issue. In this paper, we present an autonomous power adaptation for MRMC WMNs. The transmit power is dynamically adapted by each network interface card (NIC) in response to the locally available energy in a node, queue load, and interference states of a channel. To achieve this, WMN is first represented as a set of Unified Channel Graphs (UCGs). Second, each NIC of a node is tuned to a UCG. Third, a power selection MRMC unification protocol (PMMUP) that coordinates Interaction variables (IV) from different UCGs and Unification variables (UV) from higher layers is proposed. PMMUP coordinates autonomous power optimization by the NICs of a node. The efficacy of the proposed method is investigated through simulations.

Improved Distributed Dynamic Power Control for Wireless Mesh Networks

One of the main objectives of transmission power control (TPC) in wireless mesh networks (WMNs) for rural area applications is to guarantee successful packet transmission and reception (SPT-R) with low power consumption. However, the SPT-R depends on co-channel multiple access interferences (MAI) including the effects from hidden terminals. In this paper we investigate how MAI can be minimized through a MAC-dependent transmission scheduling probability (TSP) model. In what follows, we show how a distributed scheduling probability model improves the dynamic power control algorithm. The resulting optimal power control is derived from a network centric objective function. The analytical results show that transmit power solutions converge to a unique fixed point. The simulation results show that a high average feasibility rate, given a coexistence pattern, can be achieved. There is significant average transmission power savings compared to conventional methods.

Doppler Shift Compensation Schemes in VANETs

Over the last decade vehicle-to-vehicle (V2V) communication has received a lot of attention as it is a crucial issue in intravehicle communication as well as in Intelligent Transportation System (ITS). In ITS the focus is placed on integration of communication between mobile and fixed infrastructure to execute road safety as well as nonsafety information dissemination. The safety application such as emergence alerts lays emphasis on low-latency packet delivery rate (PDR), whereas multimedia and infotainment call for high data rates at low bit error rate (BER). The nonsafety information includes multimedia streaming for traffic information and infotainment applications such as playing audio content, utilizing navigation for driving, and accessing Internet. A lot of vehicular ad hoc network (VANET) research has focused on specific areas including channel multiplexing, antenna diversity, and Doppler shift compensation schemes in an attempt to optimize BER performance. Despite this effort few surveys have been conducted to highlight the state-of-the-art collection on Doppler shift compensation schemes. Driven by this cause we survey some of the recent research activities in Doppler shift compensation schemes and highlight challenges and solutions as a stock-taking exercise. Moreover, we present open issues to be further investigated in order to address the challenges of Doppler shift in VANETs.

Gradient-based Routing for Energy Consumption Balance in Multiple Sinks-based Wireless Sensor Networks

Abstract Multiple sinks routing is envisioned as a possible solution to the ‘bottleneck’ research problem in Wireless Sensor Networks (WSN). In addition to focusing on minimizing the energy consumption in a WSN, it is also equally important to design routing protocols that fairly and evenly distribute the network traffic; in order to prolong the network life time and improve its scalability. Gradient Based Routing (GBR) techniques such as the Generic GBR (GBR-G) and the Competing-GBR (GBR-C) have been previously proven to be energy efficient in single sink WSNs. These methods consider that each sensor node constructs a gradient with respect to a unique base station. The drawback of this approach is that, due to the position of sensor nodes next to the sink, their energy is usually overused compared to the one of the other sensor nodes in the network. To overcome this, this paper introduces enhanced GBR-G and GBR-C routing approaches (GB-GBR and CB-GBR) which consider the definition of a new gradient model to maximize network lifetime. In the proposed new approach, the GB-GBR and CB-GBR techniques not only consider the selection of the highest gradient link but also the link that avoids the most overloaded sensor nodes when forwarding packets. Using OMNET++ simulation and the MiXiM framework, it is shown that proposed GB-GBR and CB-GBR approaches achieve better performance in terms of network lifespan when compared to the single sink GBR-G and GBR-C approaches respectively.

Analysis of IEEE 802.11n network Access Categories in EDCA non-saturated networks

In recent years demand for high data rate amongst internet users has increased due to the use of real time data services such as video and voice conferencing. The IEEE 802.11n standard is an advancement from the previous a,b and g versions. Its design goal is to increase data rate, and maintain compatibility with the previous versions. The IEEE 802.11n standard introduces improvements at both the PHY and MAC layers. This standard still adopts the EDCA and HCCA mechanism used for enhancing QoS in the network by assigning priorities to different classes of data called Access Categories (ACs). In this paper we compute a theoretical throughput model for 4 different stations transmitting separate ACs in non saturated conditions. Networks with non saturated conditions find real applications in WSN and WiFi enterprises. We then perform a practical experimentation with 4 different nodes and compare the throughput results with the theoretical one. Based on the comparison, we determine the fairness linked with the QoS mechanism. The comparative throughput performance indicates that the analytical results compare well with the practical experimental results considering non saturated ACs.

Scalable power selection method for Wireless Mesh Networks

This paper addresses the problem of a scalable dynamic power control (SDPC) for Wireless Mesh Networks (WMNs) based on IEEE 802.11 standards. An SDPC model that accounts for architectural complexities witnessed in multiple radios and hops communication system is designed. The key contribution is that we have first developed a general multiple transmission activity (MTA) model for each radio link. We then present a power selection policy that depends on average cross-layer network fluctuations as opposed to instantaneous fluctuations. Through simulations, we have observed that the SDPC modelled at the link layer, with the knowledge of imperfect and often delayed information, can significantly yield much power savings.

Decentralised Cross-Layer Dynamic Power Control for Wireless Mesh Networks

This paper presents a decentralised cross-layer dynamic power control (DDPC) scheme for wireless mesh networks (WMNs). A general cross-layer occupation measure (COM) based on transmission scheduling probability (TSP) and power control policy (PCP) model is proposed. Depending on the network traffic application and multiple transmission activity (MTA), each user adjusts its power dynamically so as to minimise an average network cost function. Simulation results indicate that the decentralised policy allows each node to autonomously choose a steady state greedy or energy-efficient power response. It was also shown that more network users are admissible under a controlled transmission power signalling scheme in CSMA/CA systems. This is desirable in improving scalability properties of the WMNs.

Enhanced RLS in Smart Antennas for Long Range Communication Networks

Abstract The utilisation of smart antenna (SA) techniques in future wireless and cellular networks is expected to have an impact on the efficient use of the spectrum and the optimization of service quality. This is because SAs can enhance the maximization of output power of the signal in desired directions amongst a whole lot of functions. Despite these benefits of SAs, long range communications still face unsolved challenges such as signal fading. Therefore, this paper focuses on enhancing the recursive least squares (RLS) in SA design for long range communication networks. The conventional RLS algorithm does not need any matrix inversion computations because the inverse correlation matrix is determined directly. Therefore, the RLS saves computational power. Hence, we have enhanced the RLS algorithm by introducing a constant m to the gain factor in order to yield an improved gain vector. Results from our simulations show that the enhanced RLS reduces mean square error (MSE), smoothens filter output and improves signal-to-noise ratio (SNR). These benefits further result in the antenna’s gain improvement leading to an increased range and directivity of the smart antenna over a long range communication networks.