S. K. Syed Yusof

Fuzzy logic partition-based call admission control for mobile WiMAX

The unpredictable nature of the wireless network and exponential growth in traffics with different quality of service requirements has led hardware complexity to escalate. In order to effectively control and manage the network traffics, there is a need for intelligent call admission control (CAC) in admitting traffics into the wireless network that provides necessary quality of service. In this paper, we propose a fuzzy logic partition-based call admission control (FZ CAC). The scheme primarily partitions the total link bandwidth into three which corresponds to constant bit rate (CBR), variable bit rate (VBR) and handover (HO) services. The fuzzy logic admission control scheme was implemented in the HO portion to intelligently keep dropping probability as low as possible based on the available bandwidth. Simulation results showed that the proposed approach outperformed both partition-based CAC (PB CAC) and conventional bandwidth allocation CAC (CB CAC).

RSSI measurements for enabling IEEE 802.15.4 coexistence with IEEE 802.11b/g

The 2.4 GHz Industrial, Science and Medical (ISM) band is a license free band allocated for a variety of consumer applications: environmental monitoring, agriculture, medical care, smart buildings, factory monitoring and automation, and numerous military applications. This project focuses on the Adaptive Interference Avoidance Scheme for IEEE 802.15.4 to allow coexistence with IEEE 802.11b/g in the 2.4GHz ISM band. A wireless sensor network (WSN) consists of small nodes with sensing, computation, and wireless communication capabilities. It is an exciting new technology and can also be considered as the underlying infrastructure that will be integral part of future ubiquitous and embedded computing applications. Due to the independent design and development in WSN, together with the unexpected dynamics during deployment of co-existing networks such as IEEE802.11b/g and devices within the same frequency spectrum, it is crucial to ensure that each wireless technology maintains and provides its desired performance requirement. Therefore, a method to determine and avoid the collision between IEEE 802.15.4 and IEEE 802.11b/g devices when co-exist within a certain environment needs to be carried out.

Challenges and practical implementation of self-organizing networks in LTE/LTE-Advanced systems

Self-organizing network/s (SON) was promoted by the Third Generation Partnership Project (3GPP) and Next Generation Mobile Networks (NGMN). SON has been introduced since in 3GPP Release-8, Release-9 and currently included in Release-10 framework as an excellent solution that promises improvements and market potential for future wireless networks. The purpose of this paper is to provide an overview on SON in advanced wireless networks such as Long Term Evolution (LTE) and LTE-Advanced systems. Although SON promises several advantages for both network operators and users, there are still challenges in implementing SON network in reality. Therefore, this paper addresses those possible challenges, discusses about SON implementation in inter-cell interference of cross-tier networks and provides future trends of the research area.

MPEG-4 video transmission using distributed TDMA MAC protocol over IEEE 802.15.4 wireless technology

The issues of green technology nowadays give an inspiration to the researcher to make all the future design to be energy efficient. Medium Access Control (MAC) layer is the most effective layer to provide energy efficient due to its ability to control the physical radio directly. One of the important applications in the future is a video transmission that can be transmitted with low-cost and low power consumption. MPEG-4 is one of the international standards for moving video. MPEG-4 provide better compression and primarily design at low bit rate communication. In order to achieve good quality for video application, the design at MAC layer must be strong. Therefore, to increase the performance of the MPEG-4 in IEEE 802.15.4, in this paper we propose a cross layer design between MAC layer and Application layer. A priority queue will be implemented at MAC scheduling depends on the level of frame important in MPEG-4 format frame. A distributed Time division Multiple Access (TDMA) will be used for MAC protocol to provide reliable data transmission for high priority frame.

Enabling dynamic spectrum access for cognitive radio using software defined radio platform

This Spectrum occupancy measurement in many countries shows sporadic and poorly utilized licensed radio spectrum due to the outdated exclusive spectrum access policy. Dynamic Spectrum Access (DSA) technique allows cognitive (unlicensed) user (CU) to opportunistically transmit in a primary (licensed) user (PU) frequency band for a given time if it does not detect any ongoing operations. In this work, DSA is realized using cognitive radio (CR) technology due to its features of able to sense, learn, adapt and react according to the environment. The proposed design of the DSA based CR system consists of four main functional blocks: spectrum sensing, spectrum management, spectrum decision and data transmission. The implementation is done using GNU Radio and Universal Software Radio Peripheral (USRP) Software Defined Radio (SDR) platform. The result shows a significant improvement in term of Packet Reception Rate (PRR) in DSA based CR systems compared to the system without DSA capability.

PAPR reduction in WLAN-OFDM system using code repetition technique

Orthogonal frequency division multiplexing (OFDM) is the best choice to achieve high data rate transmission in wireless environment. OFDM system shows many favorable property such as high spectral efficiency, robustness to channel fading and immunity to impulse interference. However, there are some obstacles in using OFDM in transmission system, which is in contrast to its advantages. One of the major drawbacks is a very high peak to average power ratio (PAPR) of the OFDM signals. Therefore this paper analyzes the capability of code repetition (CR) to reduce PAPR in WLAN/OFDM system. The analysis is on a network model designed by WLAN 802.11a standard using Matlab, a mathematical simulation software tool. The network model has been simulated in AWGN channel environment to investigate the behavior of PAPR and BER performance. The proposed technique to reduce PAPR in the WLAN/OFDM channel coding consists of two part; convolutional code and CR. Simulation model with different number of repetition has been analyzed and the results were compared with the conventional coded OFDM (COFDM). The simulation results show that the proposed technique based on CR reduces PAPR down to 5 dB compared to COFDM model.

Optimizing achievable throughput for cognitive radio network using swarm intelligence

Cognitive radio (CR) technology allows a secondary or cognitive user (CU) to opportunistically access frequency band of a primary user (PU) when it is not in use. However, a CU needs to perform spectrum sensing periodically to avoid causing harmful interference and thereby protecting the quality of service of PUs. A conventional frame structure for CR operation consists of sensing time slot and data transmission time slot which run consecutively. Basically, a longer sensing time produces a higher probability of detection and therefore, better PU protection. However, longer sensing time will reduce the amount of time for data transmission and hence affects the achievable throughput of a CU. In this paper, we study the fundamental tradeoff between sensing time and achievable throughput of the CUs. Based on energy detection scheme, we propose and investigate the feasibility of using Particle Swarm Optimization (PSO) in the design of sensing slot duration to maximize the achievable throughput for CUs for a given frame duration. The results show an encouraging 8.89% increase in throughput with respect to the probability of false alarm, a reduced sensing time by 80% while achieving 97.8% of normalized throughput for CU system with PSO.

An improved authentication key management scheme for Multihop relay in IEEE 802.16m networks

IEEE 802.16m Multihop relay network is assiduously developing to accomplish high capacity services with large cell coverage. However due to lack of physical boundaries and injection of distributed relays, it is known to be more vulnerable to security holes as a trade off. In this paper we propose a new distributed authentication key scheme for Multihop Relays IEEE 802.16m network service. The propose scheme uses decode and forward relays with localized authentication. The scheme works in distributed authentication to authenticate Subscriber station (SS) and Relay stations (RS) at initial network entry. Our new imprpoved distributed scheme utilizes healthy security issues and the Multihop Relay network application features. Both analysis and performance evaluation shows that our scheme can significantly increases the network throughput and reduce the security holes as well as communication overheads.

Performance comparison of AODV and HWMP routing protocols in wireless mesh networks

Wireless mesh networks (WMNs) have gain attention from researchers in telecommunication engineering field due to its potential to provide low cost internet broadband access, wireless local area network coverage and network connectivity for stationary or mobile host. This network consists of multiple wireless routers that are used to relay each others packet in multi-hop fashion. Hence, routing protocol plays an important part in maintaining the connectivity of WMNs. In this paper, two routing protocols, Ad hoc On-demand Distance Vector (AODV) and Hybrid Wireless Mesh Routing Protocol (HWMP) are compared in terms of their performance in WMNs. A random wireless mesh topology with router nodes is modelled in Network Simulator 3 by assuming that the router nodes are connected to its client nodes. The simulations are performed in two different topologies with varied number of nodes. Three merits are taken into account when making the comparisons which are packet delivery fraction, throughput, and end-to-end delay. The simulation results demonstrate that HWMP is more suitable to be applied in WMNs compared to AODV.

Experimental Study of Sensing Performance Metrics for Cognitive Radio Network Using Software Defined Radio Platform

Cognitive Radio (CR) is a promising technology in wireless communication for an enhanced utilization of limited spectral resources. It allows unlicensed or cognitive users (CUs) to sense the spectral environment and access a channel exhibiting negligible activity of licensed or primary users (PUs). Hence, spectrum sensing is a crucial task for a CU to perform in an opportunistic spectrum access (OSA) based CR network to avoid harmful interference to PU. Two main performances metrics that are crucial in the design of spectrum sensing are the probability of false alarm (P fa ) and the probability of detection (P d ). These metrics are used to define the CR system quality of service (QoS). The threshold to decide on the presence of PU and the sensing time needed for the CR system are also determined based on these metrics. This paper presents the design of measurement methods to experimentally acquire the P fa and P d curves based on locally captured data to determine the value of the threshold and sensing time. The implementation, experimentation and measurement are done using GNU Radio and universal software defined radio peripheral (USRP) software defined radio (SDR) platform as the cognitive radio testbed. Spectrum sensing was done based on energy detection. Each of the energy based detection measurement is repeated 1000 times to obtain an accurate estimation of P fa and P d . The findings show that the target Quality of Sevice (QoS) of P fa of 5% and P d of 90% can be derived from the estimated sensing threshold of -39 dB and achieves a sensing time of 31.59 ms.