An ant-swarm inspired dynamic multiresolution data dissemination protocol for wireless sensor networks

One of the main concerns of wireless sensor networks (WSNs) is to deliver useful information from data sources to users at a minimum power consumption due to constraints that sensor nodes must operate on limited power sources for extended time. In particular, achieving power-efficiency and multihop communication in WSN applications is a major issue. This paper continues on the investigation of a recently proposed Minimum-power Multiresolution Data Dissemination (MMDD) problem for WSNs (whose solution is considered here as a benchmark). We propose an ant-inspired solution to this problem. To the best of our knowledge, no attempts have been made so far in this direction. We have evaluated the performance of our proposed solution by conducting a variety of experiments and have found our solution to be promising in terms of total energy consumption in data dissemination.     

An analytical study of resource division and its impact on power and performance of multi-core processors

The study and development of chip multi-processors (CMPs) are of utmost importance for the creation of future technologies. Devising a theoretical analysis of the micro-architecture model for the power/performance on CMPs is still a challenge. This paper addresses this problem by (1) introducing an analytical model for measuring the power and performance of a processor quantitatively, (2) analyzing the effects of resource division on power consumption and performance when executing a given benchmark, and (3) predicting the optimum number of cores to run the benchmark on. Our proposed analytically derived results show that in order to achieve power/performance gains, the optimum number of cores must be between 8 and 16.     

Exploiting Multichannel Diversity in Spectrum Sharing Systems Using Optimal Stopping Rule

This letter studies the problem of exploiting multichannel diversity in a spectrum sharing system, where the secondary user (SU) sequentially explores channel state information on the licensed channels with time consumption. To maximize the expected achievable throughput for the SU, we formulate this problem as an optimal stopping problem, whose objective is to choose the right channel to stop exploration based on the observed signal‐to‐noise ratio sequence. Moreover, we propose a myopic but optimal rule, called one‐stage look‐ahead rule, to solve the stopping problem.     

Ant Colony Optimization Based Sub-channel Allocation Algorithm for Small Cell HetNets

Two-tier heterogeneous networks (HetNets) composed of a conventional macrocellular network and small cell networks (SCNs) have been proposed in the literature with the aim to extend indoor coverage and realize efficient radio resource usage. As SCN shares the same frequency band with the underlying macrocell, the cross tier interference needs to be mitigated since the inter-SCN and cross tier interference at the SCN boundary may result in undesirable network performance degradation. In this paper, we propose an intelligent physical resource block (PRB) allocation as a solution to mitigate the downlink intra-SCN interference as well as the inter-tier interference in OFDM-based systems. The allocation of the PRBs to the network users is formulated as a graph coloring problem, and solved using an ant colony optimization (ACO)-based approach. Simulation results are provided, showing that our ACO-based algorithm outperforms the Received Power-based Allocation (RPA) and Received SINR-based Allocation (RSA) algorithms in terms of average SINR experienced by network users, outage probability, and number of required PRBs.     

A semi-Markov decision process-based joint call admission control for inter-RAT cell re-selection in next generation wireless networks

In the next generation wireless networks (NGWNs), where different radio access technologies (RAT) will coexist and work in collaboration to provide ubiquitous access, a mechanism called Joint Call Admission Control (JCAC) will play an important role by deciding whether or not an incoming service request will be accepted according to an admission constraint as well as determining in which RAT (among the available) it will be connected. In this paper, we propose an optimal JCAC for inter-RAT cell re-selection problem also referred to as initial RAT selection in co-located wireless networks, which supports both real-time services and non-real-time services. To properly meet the JCAC goals, we propose a cost function that weigh two criteria: the blocking cost function, which takes into account the priority of each service class in each RAT, and the alternative acceptance cost, which reflects the multiplicity of RATs working in a collaborative fashion, mandatory in NGWN. We use the framework of Semi-Markov Decision Process (SMDP) to formulate the optimization problem and the value iteration algorithm to compute the optimal policy. Our model still takes into consideration the ratio between the radius of the co-located RATs and shows how it may impact on optimal initial RAT selection. Numerical results, supported by an analysis of the structure of the optimal policy, show that the proposed optimal JCAC selects for real-time service class the biggest RAT and for non-real-time service class the smallest one. This optimal JCAC policy is ratified by the current trend in the design of NGWN and also follows the 3rd Generation Partnership Project (3GPP) expectations.     

A comparative simulation study on the power–performance of multi-core architecture

Nowadays, multi-core processor is the main technology used in desktop PCs, laptop computers and mobile hardware platforms. As the number of cores on a chip keeps increasing, it adds up the complexity and impacts more on both power and performance of a processor. In multi-processors, the number of cores and various parameters, such as issue-width, number of instructions and execution time, are key design factors to balance the amount of thread-level parallelism and instruction-level parallelism. In this paper, we perform a comprehensive simulation study that aims to find the optimum number of processor cores in desktop/laptop computing processor models with shallow pipeline depth. This paper also explores the trade-off between the number of cores and different parameters used in multi-processors in terms of power–performance gains and analyzes the impact of 3D stacking on the design of simultaneous multi-threading and chip multiprocessing. Our analysis shows that the optimum number of cores varies with different classes of workloads, namely: SPEC2000, SPEC2006 and MiBench. Simulation study is presented using architectures with shorter pipeline depth, showing that (1) the optimum number of cores for power–performance is 8, (2) the optimum number of threads in the range [2, 4], and (3) for beyond 32 cores, multi-core processors are no longer efficient in terms of performance benefits and overall power consumption.     

IEEE Canadian Conference on Electrical and Computer Engineering 2008

The annual IEEE Canadian Conference on Electrical and Computer Engineering (CCECE) provides a forum for the presentation and discussion of high-quality technical papers that encompass a wide range of disciplines within electrical and computer engineering. The 21st episode of the CCECE very well matched the conference theme ?Wonders of Technology,? featuring seven mini-symposia that included about 90 technical paper sessions. There were new initiatives in this conference, and they included full-paper submission and elaborate technical review; and a technical focus in the form of symposia. We sincerely hope that a new era is born for the Canadian flagship conference CCECE with its focused approach and peer-reviewed, high-quality, full-paper submissions.     

Performance Analysis of Two Dimensional Spreading for OFCDM Femtocell Users Overlaid with OFDM Macrocell

Femtocells provide indoor coverage for voice and high speed data services and are self-deployed by end-users. Orthogonal frequency code division multiplexing (OFCDM) is a multi-carrier spread spectrum technique that utilizes two dimensional spreading in time and frequency domains simultaneously to improve frequency diversity and minimize multiuser access interference. In this paper, variable spreading factor (VSF)-OFCDM is employed in subcarrier allocation for femto users (FUEs) in a hybrid femto/macro network, and the effect of FUE deployment on macro users (MUEs) is studied. We evaluate the bit error rate (BER) performance of FUEs and MUEs through Monte Carlo simulation under various load conditions in noise and interference-limited scenarios. Relationship between the channel load and optimum spreading factor employed by FUEs for the given network configuration, is also analyzed. We provide various graphs showing the impact of FUE spreading factor on the MUE BER. We note that in interference-limited conditions, $4\times 8$ spreading $(\text{ time}\times \text{ freq}.)$ proves to be the best choice for macro users; and for the noise-limited case, when there are limited number of users and channel noise is dominant, $2\times 16$ spreading is the optimum choice for the considered hybrid network configuration. We also evaluate the effect of femto wall penetration loss on macro BER for various spreading factors. The favorable spreading factor for MUEs is tabulated for different loads and different number of subcarriers, which can be used as a deployment guide in this heterogeneous network.     

Meeting mobile's demands with multicarrier systems

With the increasing requirements for future wireless applications, OFDM, MC-CDMA, and MC-DS-CDMA have all been considered for 4G wireless systems. These systems have the ability to incorporate very large band widths without sacrificing equalization complexity. The long symbol duration is effective at mitigating ISI, and adaptive modulation or frequency diversity can be used to provide protection against destructive fades. The benefit of MC CDMA is that it experiences frequency diversity because each bit is transmitted over several independently faded subcarriers. If some subcarriers experience destructive fades, diversity combining can be used at the receiver to recover the data. This improves the BER performance over OFDM, and this improvement is more significant as the number of subcarriers is increased. The draw back of MC-CDMA is that it may experience high levels of multiuser access interference (MAI) when the channel is heavily loaded. This occurs because each chip of the PN sequence experiences independent fading, which tends to destroy the orthogonality between spreading sequences. This increases the MAI and degrades the BER performance. Although OFDM, MC-CDMA, and MC-DS-CDMA signals experience a high PAPR, synchronization issues, and ICI, the benefits greatly outweigh these disadvantages.     

Variable Cyclic Prefix for Contention-Based Wireless Access in OFDM-Based Vehicular Communication Systems

In vehicular environment, signal transmissions face more challenges than in indoor wireless local area systems. In such an unpredictable communication environment, multipath fading causes high bit error rate, which leads to higher dropping probability of packets. In order to reduce the dropping probability of handshaking packets without increasing the infrastructure capability, we propose to modify the traditional cyclic prefix into a variable cyclic prefix (VCP) of request-to-send and clear-to-send frames. By reducing the handshaking packet error rates, we improve the contention ability in carrier sense multiple access with collision avoidance scheme in vehicle-to-infrastructure transmission. Suitable VCP time slots and dynamically adjustable VCPs are predicted based on the analysis of appropriate environmental parameters.