Tiago P. C. de Andrade

The impact of massive machine type communication devices on the access probability of human-to-human users in LTE networks

Machine-type Communication (MTC) enables devices to exchange information in an autonomous way without human intervention. Hence, new applications can be developed benefiting from a richer awareness of the surrounding environment. However, the deployment of MTC over cellular networks creates new challenges to the contention-based Random Access (RA) procedure as well as to resource allocation for MTC devices with low impact on Human-to-Human (H2H) services. In this paper, we analyze the impact of massive number of MTC devices on traditional H2H users in Long Term Evolution (LTE) network. We compare the performance of three Radio Access Network (RAN) overload control schemes proposed by the 3rd Generation Partnership Project (3GPP) for the contention-based RA procedure in this network. Results derived via simulation show that the access probability of Human-type Communication (HTC) users can be jeopardized by the large number of MTC devices. Therefore, enhanced mechanisms for the contention-based RA procedure in LTE network need to be investigated in order to support the expected large number of MTC devices and the traditional H2H users in the same infrastructure.

Allocation of Control Resources for Machine-to-Machine and Human-to-Human Communications Over LTE/LTE-A Networks

The Internet of Things (IoT) paradigm stands for virtually interconnected objects that are identifiable and equipped with sensing, computing, and communication capabilities. Services and applications over the IoT architecture can take benefit of the long-term evolution (LTE)/LTE-Advanced (LTE-A), cellular networks to support machine-type communication (MTC). Moreover, it is paramount that MTC do not affect the services provided for traditional human-type communication (HTC). Although previous studies have evaluated the impact of the number of MTC devices on the quality of service (QoS) provided to HTC users, none have considered the joint effect of allocation of control resources and the LTE random-access (RA) procedure. In this paper, a novel scheme for resource allocation on the packet downlink (DL) control channel (PDCCH) is introduced. This scheme allows PDCCH scheduling algorithms to consider the resources consumed by the random-access procedure on both control and data channels when prioritizing control messages. Three PDCCH scheduling algorithms considering RA-related control messages are proposed. Moreover, the impact of MTC devices on QoS provisioning to HTC traffic is evaluated. Results derived via simulation show that the proposed PDCCH scheduling algorithms can improve the QoS provisioning and that MTC can strongly impact on QoS provisioning for real-time traffic.

An efficient and robust protocol to disseminate data in highway environments with different traffic conditions

Vehicular Ad-Hoc Networks (VANETs) are a specific type of moving networks in which the nodes are vehicles with processing, storage and wireless communication capacity. VANETs face a number of challenges in terms of data dissemination due to the volatile density of vehicles and frequent changes in the network topology induced by the high mobility of the vehicles and of short-range communications. The envisaged applications, as well as some inherent characteristics of the VANETs render the data dissemination an essential service and a challenging task in these networks. Many data dissemination protocols have been proposed in the literature, nevertheless, most of such protocols do not deal simultaneously with the problems of broadcast storm and network partition. To face such problems, we propose a new data dissemination protocol in vehicular networks named DRIFT, which operates in highway environments. The DRIFT eliminates the broadcast storm problem and maximizes the data dissemination in partitioned networks with little delay and low overhead. When compared with four known solutions, we show that our proposal for data dissemination executes it with higher efficiency than other protocols, exceeding them in different scenarios in all the undertaken evaluations.

MAC protocols for wireless sensor networks over radio-over-fiber links

In this paper, two Medium Access Control (MAC) protocols exclusively tailored to WSNs over RoF (RWSNs) namely SPP-MAC (Scheduled Priority Polling Medium Access Control) (polling-based) and HMARS (Hybrid Medium Access Control for Hybrid Radio-over-Fiber Wireless Sensor Network Architecture) (hybrid-based) are proposed. They deal with the main problems in RWSNs i.e. the delay imposed by optical fiber and the existence of two collision domains: the wireless and the fiber optical links. The performance of these two protocols evince their effectiveness for the connection of WSNs by RoF links.

The Random Access Procedure in Long Term Evolution Networks for the Internet of Things

Network connectivity is a key issue in the realization of IoT, and LTE cellular technology is the most promising option for the provisioning of such connectivity. However, in LTE networks, a large number of IoT devices trying to access the medium can overload the RAN. In this article, we review the LTE random access procedure and its support for IoT applications. We also assess the performance of the RAN overload control schemes proposed by 3GPP, taking into consideration the interaction between the random access procedure and packet downlink control channel resource allocation.

Impact of M2M traffic on human-type communication users on the LTE uplink channel

The worldwide markets for Machine-type Communication (MTC) over cellular networks are expected to grow in the incoming years. However, since MTC is quite different than existing Human-type Communication (HTC), it poses significant challenges to the cellular networks. Large number of MTC devices are anticipated to be operating in the future Long Term Evolution (LTE) networks, bringing several service requirements. The LTE standard suffers from excessive Physical Downlink Control Channel (PDCCH) overhead associated with the radio resource allocation method for small, sporadic traffic per terminal which is the nature of Machine-to-Machine (M2M) traffic. The rigid Quality of Service (QoS) support framework of LTE for voice and data services also fails to address specific QoS requirements of M2M traffic. This paper focuses on describing the impact of M2M traffic on the performance of the HTC users in LTE Frequency Division Duplexing (FDD) uplink. Simulation results show the impact of M2M traffic on the performance of different types of Human-to-Human (H2H) services (Voice-over-IP (VoIP), video and CBR), when using a QoS-aware packet scheduling. Although MTC in LTE networks impacts HTC, the utilization of a semi-persistent scheduling scheme to VoIP traffic can reduce such impact.

Protocols for Wireless Sensors Networks Connected by Radio-Over-Fiber Links

Radio-over-fiber (RoF) technology has been employed in network infrastructure due to its large capacity, low attenuation, and low operational costs, as well as due to the possibility of enlarging network coverage. This paper introduces a new approach for the interconnection of wireless sensor network (WSN) by employing RoF links, specifically wireless sensor network based on radio-over-fiber (WSN-RoF). The main contribution of this paper is the introduction of an architecture for the interconnection of WSN and two medium access control (MAC) protocols exclusively tailored to WSN-RoF architecture: scheduling of polling priority MAC and dynamic hybrid MAC for WSNs based on RoF access infrastructure. Both protocols deal with the main problems in WSN-RoF, i.e., the round-trip propagation delay in optical fiber links and the existence of two distinct collision domains: one wireless and the other optical. The performance of these two protocols shows their effectiveness in the interconnection of WSN through RoF links. Results of experiments demonstrate the benefits of using RoF links for the backhaul of WSN.

Allocation of control resources with preamble priority awareness for human and machine type communications in LTE-Advanced networks

In this paper, we introduce the Preamble Priority-Aware (PPA) Packet Downlink Control Channel (PDCCH) resources allocation algorithm to provide Quality of Service (QoS) differentiation in the Random Access (RA) procedure of the LTE-Advanced technology. The PPA algorithm uses the preamble priority defined by the RA procedure and Radio Access Network (RAN) overload control schemes to make scheduling decisions. Results derived via simulation show that the proposed PDCCH algorithm significantly increases the chance of accessing the network as well as reducing random-access delays for user equipment employing prioritized preamble sequences. Thus, the proposed algorithm provides enhanced QoS support to prioritized users during intense RA attempts.

Medium access control protocol for Hybrid Radio-over-Fiber Wireless Sensors Networks

This paper introduces the Dynamic HMARS (D-HMARS) protocol designed for the Hybrid Radio-over-Fiber Wireless Sensors Network (WSN-RoF) architecture, in which multiple clusters of wireless sensor nodes are connected to a base station via an optical link using Radio-over-Fiber (RoF) technology. The D-HMARS protocol was designed to avoid the problem of occurrence of false positive in the Clear Channel Assessment (CCA) mechanism. Simulation results show that the D-HMARS protocol increases the delivery ratio as well as the effective throughput of the network.