Open Topics

Vol. 70, n° 1-2, January-February 2015
Content available on Springerlink

Long-term drivers of broadband traffic in next-generation networks

P. Loskot1, M. A. M. Hassanien1, F. Farjady2, M. Ruffini3 and D. Payne3
(1) Swansea University, UK
(2) Aston University, Birmingham, UK
(3) University of Dublin, Ireland

Abstract This paper is concerned with long-term (20+ years) forecasting of broadband traffic in next-generation networks. Such long-term approach requires going beyond extrapolations of past traffic data while facing high uncertainty in predicting the future developments and facing the fact that, in 20 years, the current network technologies and architectures will be obsolete. Thus, “order of magnitude” upper bounds of upstream and downstream traffic are deemed to be good enough to facilitate such long-term forecasting. These bounds can be obtained by evaluating the limits of human sighting and assuming that these limits will be achieved by future services or, alternatively, by considering the contents transferred by bandwidth-demanding applications such as those using embedded interactive 3D video streaming. The traffic upper bounds are a good indication of the peak values and, subsequently, also of the future network capacity demands. Furthermore, the main drivers of traffic growth including multimedia as well as non-multimedia applications are identified. New disruptive applications and services are explored that can make good use of the large bandwidth provided by next-generation networks. The results can be used to identify monetization opportunities of future services and to map potential revenues for network operators.

Keywords Broadband services – Next-generation networks – Network operator – Traffic growth drivers – Traffic forecasting – Video streaming

An energy-efficient common control channel selection mechanism for Cognitive Radio Ad Hoc Networks

Md. Nazmus Sakib Miazi1, Madiha Tabassum1, Md. Abdur Razzaque1, and M. Abdullah-Al-Wadud2
(1) University of Dhaka, Bangladesh
(2) Hankuk University of Foreign Studies, Yongin, South Korea

Abstract A common control channel (CCC) is required in Cognitive Radio Ad Hoc Networks (CRAHNs) for exchanging vital control messages among the cognitive radio users. However, selecting a CCC in CRAHNs is a challenging problem due to dynamic network topology, versatility of spectrum usage, and multi-hop network architecture. Existing cluster-based CCC selection algorithms are based on periodic beaconing from the cluster heads (CHs) to create and manage their clusters, which makes them more power consuming. Therefore, the battery-powered devices in CRAHNs should select a CCC in an energy-efficient way to prolong their lifetimes. In this paper, we develop an energy-efficient common control channel selection mechanism, called E 2 C 3, through creating multi-hop clusters in a distributed manner. In E 2 C 3, a node does not join a cluster actively by sensing beacons from CHs; rather, it sends an inquiry message to detect existing clusters. It resolves whether to join an existing cluster or to create a new one based on its single-hop neighborhood information. We also propose an energy-efficient passive approach of maintaining cluster membership and provide a distributed CH reassignment procedure. Our performance evaluation, carried out in NS-3, shows that our E 2 C 3 system achieves significant improvements in energy efficiency and protocol operation overhead over the state-of-the-art protocols.

Keywords Cognitive Radio Ad Hoc Network – Common control channel – Energy-efficient – Cluster head

Design of digitally controlled multiple-pattern time-modulated antenna arrays with phase-only difference

S. K. Mandal1 , G. K. Mahanti1, Rowdra Ghatak1, and A. Chatterjee2
(1) National Institute of Technology Durgapur, India
(2) National Institute of Technology Goa, India

Abstract An optimization approach based on differential evolution (DE) is proposed to design multiple-pattern time-modulated linear antenna arrays (TMLAAs) with phase-only control by using 5-bit digital phase shifters. The synthesized multiple patterns include a pencil beam (PB), a flat-topped beam (FTB), and a cosec squared pattern (CSP). The function of the DE is to find, simultaneously, a common, i.e., fixed, set of continuous values of switch-on time durations and discrete static excitation amplitudes for 5-bit digital attenuators, and different sets of discrete excitation phase distributions for 5-bit digital phase shifters; to generate different power patterns in the far field of the TMLAA. By perturbing the static amplitude distribution of a 20-element TMLAA in the discrete search range of “(0.2–1),” the patterns are obtained by reducing side lobe levels (SLLs) to almost −20 dB and sideband levels (SBLs) to less than −25 dB. Towards the end, the same on-time and amplitude distribution is used to produce a symmetric side lobe (S-SL) and asymmetric side lobe (A-SL) CSP, and their usefulness under a noisy signal environment is discussed.
Keywords Antenna arrays – Time modulationTime-modulated antenna array (TMAA)Differential evolution (DE)-  Side lobe level (SLL)Sideband level (SBL)

Average symbol error rate and ergodic capacity of switch-and-examine combining diversity receivers over the α-μ fading channel

Refaat Mohamed1, Mahmoud H. Ismail1, and Hebat-Allah M. Mourad1
(1) Cairo University, Egypt

Abstract In this paper, we consider a switch-and-examine combining (SEC) diversity scheme operating over independent and identically distributed (i.i.d) branches assuming an α-μ fading channel. We derive expressions for the average symbol error rate (ASER) for a class of coherent modulation techniques considering this fading model as well as expressions for the ergodic capacity under the same assumptions. The results for the ASER and the ergodic capacity are shown to reduce to those previously reported in the literature for other channel models such as the Weibull model as a special case, which confirms the validity of the obtained expressions. Different aspects are studied including the effect of fading severity, the number of branches and the modulation scheme used. Also, insights on the optimal choice of the switching threshold are provided.

Keywords Diversity receivers α-μ fading – Switch-and-examine combining – Average symbol error rate – Ergodic capacity

Semi-blind two-way AF relaying over Nakagami-m fading environment

Wided Hadj Alouane1, and Noureddine Hamdi1
(1) ENIT, El Manar University, Tunis, Tunisia

Abstract In this paper, we investigate semi-blind opportunistic amplify-and-forward (AF) selection relaying in two-way dual-hop cooperative communication networks on independent Nakagami-m fading channels. This system is compared to channel state information (CSI)-assisted opportunistic AF selection relaying (CSIA-OAF) where the relays use variable gains for the amplification. In semi-blind opportunistic AF scenario (SB-OAF), the relays use partial CSI-fixed gains to amplify the received signals. In this work, we first derive the expression of the signal-to-noise ratio (SNR) in the case of SB-OAF selection relaying. The obtained SNR is used to process the bounds of average sum-rate, outage probability, and average symbol error rate (SER). Numerical results are used to show the performance of the proposed SB-OAF system compared to the CSIA-OAF relaying. The comparison shows that the cost of the significant reduction of the proposed SB-OAF complexity is obtained for a slight loss in performance compared to CSIA-OAF scenario.

Keywords Two-way – Opportunistic – AF – Selection – Relaying – Semi-blind – Sum-rate – Outage probability – SER – Nakagami-m

Energy efficient fast predictor for WSN-based target tracking

M. Mirsadeghi1 and A. Mahani1
(1) Shahid Bahonar University of Kerman, Iran

Abstract Power source replacement of the sensor nodes, which are once deployed in the network area, is generally difficult. So, energy saving is one of the most important issues for object tracking in wireless sensor networks. To reduce the consumed energy and prolong the network lifetime, the nodes surrounding the mobile object should be responsible for sensing the target. The number of participant nodes in target tracking can be reduced by an accurate prediction of the object location. In this paper, we present a fast energy efficient with high-accuracy target tracking scheme which is based on location prediction. The missing rate of proposed predictor is very low in comparison with other predictors especially in a random waypoint mobility model in which after pause time, the three main parameters direction, velocity and, acceleration would be changed. The accuracy of predictor has a direct effect on missing rate and so strongly reduces the consumed energy. Additionally, a new node selection criterion is proposed in which minimum nodes surrounding the object are wakened and track the object. Simulation results show that our proposed predictor has low consumed energy and complexity in comparison with Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) predictors.

Keywords Target tracking – Wireless sensor networks – Energy efficient – Kalman filter – Random waypoint

No-zero-entry full diversity space-time block codes with linear receivers

Van-Bien Pham1 and Wei-Xing Sheng2
(1) Le Quy Don Technical University, Hanoi, Vietnam
(2) Nanjing University of Science and Technology, China

Abstract In MIMO systems, Toeplitz codes, overlapped Alamouti codes (OACs), and embedded Alamouti codes (EACs) can achieve full diversity when linear receivers are used. However, these codes have a large number of zero entries in their codeword matrix. Due to the zero entries in the design, the peak-to-average power ratio (PAPR) is high, and the transmitting antennas need to be switched on and off imposing severe hardware constrains. To solve this problem, in this paper, we propose a design scheme for no-zero-entry full diversity space-time block codes (NZE-STBCs). New no-zero-entry Toeplitz codes (called NZE-TCs) are designed first, and are then combined/overlaid with orthogonal space-time block code, Alamotui code, to construct no-zero-entry overlapped Alamouti codes (NZE-OACs) and no-zero-entry embedding Alamouti codes (NZE-EACs). The full diversity properties of proposed NZE-TCs, NZE-OACs, and NZE-EACs with linear receiver are derived. Simulation results show that our proposed codes outperform the Toeplitz codes, OACs, and EACs under peak power constraint, while performing the same under average power constraint.

Keywords Multiple-input multiple-output (MIMO) – Space-time block code – Full diversity – Linear receiver