Ivo Maljevic

Software-Defined Fog Network Architecture for IoT

Rapid increase in number and diversity of Internet-connected devices raises many challenges for the traditional network architecture, which is not designed to support a high level of scalability, real-time data delivery and mobility. To address these issues, in this paper we present a new model of Internet of Things architecture which combines benefits of two emerging technologies: software-defined networking and Fog computing. Software-defined networking implies a logically centralized network control plane, which allows implementation of sophisticated mechanisms for traffic control and resource management. On the other hand, Fog computing enables some data to be analysed and managed at the network edge, thus providing support for applications that require very low and predictable latency. In the paper, we give detailed insight into the system structure and functionality of its main components. We also discuss the benefits of the proposed architecture and its potential services.

SDN-based concept of QoS aware heterogeneous wireless network operation

Software defined networking (SDN) is a new paradigm for wired networks which cleanly decouples control and the date plane, leaving all control functionality to logically centralized entity. By centralizing network intelligence it provides better visibility of the network conditions, and hence allows more sophisticated traffic management. In this paper, we investigate how the adoption of SDN concept can improve efficiency of heterogeneous wireless environments. We present architectural solution for SDN-based wireless networks, and elaborate on opportunities it provides from various perspectives. In order to exploit benefits of scalable cloud infrastructure, integration of Network Function Virtualization (NFV) is proposed. In particular, the proposed architectural solution allows fast deployment of new services for network operators, gives flexible content delivery options for application providers, and provides improved quality of experience (QoE) for end users.

Performance degradation due to code tracking errors on a RAKE spread-spectrum receiver in the presence of unresolvable multipath

The effects of multipath and tracking error on a RAKE receiver are analyzed. It is shown that, in the presence of unresolvable multipath, the RAKE receiver, formed by combining the same samples that are used for tracking, is less sensitive to tracking errors, and that there is a wide range of tracking errors for which such a receiver outperforms the conventional receiver. Also, the effects of how interchip interference degrades the performance of the proposed receiver are examined.

Performance analysis of variable packet size crosspoint-queued switch

The performance analysis of the variable packet size crosspoint queued switch is presented in this paper. Packet switch throughput and average latency are evaluated under Interrupted Bernoulli Process incoming traffic pattern. It is shown that among the observed algorithms, the longest queue first algorithm has the highest throughput with short crosspoint buffers, but the highest average latency. Also, we establish that the choice of the scheduling algorithm does not play a significant role in the switch performance if the buffers are long enough. Therefore, the round robin algorithm becomes the best choice for implementation due to its simplicity.

Performance evaluation of crosspoint queued switch under the heavy traffic

In this paper, the performance analysis of a 2×2 crosspoint queued switch is presented. The analysis is performed under the non-admissible traffic pattern, for three scheduling algorithms: round-robin, frame-based-round-robin-matching and longest-queue-first. Throughput, average cell latency and memory requirements for buffer implementation are observed. In addition to these parameters which are usually used for switch performance evaluation, inter-flow fairness is also analyzed. The results show that very long buffers are required in order to achieve good performance under the traffic overload, even for small switches. The longest-queue-first algorithm showed higher throughput and lower memory requirements, but worse latency and fairness than other two observed algorithms.

DS-CDMA receiver based on a five-port technology

High data rates, low-power consumption, and low complexity will be the most important parameters in the design of the next-generation mobile terminals. In this paper we are introducing a new paradigm in the design of direct sequence spread spectrum receiver by combining analog and digital signal processing. The main difference with respect to the conventional all-digital receiver design approach is that the proposed mixed analog/digital processing results in a symbol rate sampling rather than the high-rate subchip sampling. Analog signal despreading is the key part of the proposed receiver solution, which is based on a five-port device, a passive RF square-law-type device. It is used to perform two important tasks at the same time, namely, the direct conversion and analog despreading. To achieve lower complexity, the proposed receiver uses rectangular instead of pulse-matched despreading at the cost of only a small performance degradation. Also, we propose a new noncoherent pseudonoise (PN) code tracking scheme based on error signal generated through the L1 norm. This results in comparable or even better PN code tracking performance than L2 norm circuitry, using less complex hardware. Further, we explore how this technology can be applied in the design of DS-CDMA RAKE receiver for mobile terminals. Depending on how the pilot signal is multiplexed, we propose two types of RAKE receivers. It is shown that under Rayleigh fading channel such receiver structures offer robustness and high performance, while maintaining the low complexity achievable through the five-port device.

Comparison of PN code tracking digital DLL's for direct sequence spread spectrum systems

Four different digital delay locked loops for PN code tracking in DS-CDMA systems are compared in this paper. Three of them, namely coherent, noncoherent and modified tracking schemes are well known. The fourth is the new scheme that we propose here as an alternative to the noncoherent (L2 norm) DLL. The new scheme is based on L1 norms of the early and late correlator output signals that are used to form an error signal. The error signal is used to control the local PN code delay. It has been shown that L1 norm based tracking offers similar performance in terms of tracking jitter to that of L2 norm tracking and as such is a viable candidate for implementation because it is computationally less demanding when implemented on DSPs.

Effects of unresolvable multipath on mobile terminals with antenna diversity in WCDMA system

In this paper we examine the effect of the unresolvable multipath on the performance of mobile unit that uses antenna diversity scheme for three different types of tracking algorithms. In the first algorithm, the tracking is performed on the basis of the single antenna output. The second algorithm involves RAKE like tracking, where all antenna outputs are combined before tracking. The last algorithm is based on independent tracking for each antenna. It has been shown that the best performance in terms of bit error rate at the receiver is achieved with independent tracking in the presence of unresolvable multipath.

CQ Ethernet Switch Implementation on the NetFPGA Platform

In this paper, we present an original design for an Ethernet switch with crosspoint-queued crossbar switching fabric and analyze its performance. Recently, significant progress has been made on performance analysis of crosspoint queued crossbar switches using analytical and simulation methods. We propose a hardware implementation on the NetFPGA platform that can provide reliable results obtained in an experimental environment. It is shown that the proposed design performs as expected and outperforms reference design under some incoming traffic conditions.

Packet delay variation analysis of the CQ switch under uniform traffic

This paper presents the results of the packet delay variation analysis for 32×32 crosspoint queued switch with uniform arrival traffic. Switches with various buffer lengths are analyzed using different scheduling algorithms: longest-queue-first, round-robin, exaustive-round-robin and frame-based-round-robin-matching. The results have shown that the round-robin algorithm has the least packet delay variation among the observed algorithms.