Nordin Ramli

SMART: A SpectruM-Aware clusteR-based rouTing scheme for distributed cognitive radio networks

Cognitive radio (CR) is the next-generation wireless communication system that allows unlicensed users (or secondary users, SUs) to exploit the underutilized spectrum (or white spaces) in licensed spectrum while minimizing interference to licensed users (or primary users, PUs). This article proposes a SpectruM-Aware clusteR-based rouTing (SMART) scheme that enables SUs to form clusters in a cognitive radio network (CRN) and enables each SU source node to search for a route to its destination node on the clustered network. An intrinsic characteristic of CRNs is the dynamicity of operating environment in which network conditions (i.e., PUs’ activities) change as time goes by. Based on the network conditions, SMART enables SUs to adjust the number of common channels in a cluster through cluster merging and splitting, and searches for a route on the clustered network using an artificial intelligence approach called reinforcement learning. Simulation results show that SMART selects stable routes and significantly reduces interference to PUs, as well as routing overhead in terms of route discovery frequency, without significant degradation of throughput and end-to-end delay.

A survey of cognitive radio and TV white spaces in Malaysia

Cognitive radio CR enables spectrum sharing by allowing new unlicensed services from secondary users to operate in pre-allocated bands in an opportunistic manner. TV white space TVWS is a portion of the spectrum in ultra-high frequency UHF and very-high frequency bands, which is not utilised by primary users in specific time and location. It is envisaged that more spectrum will be available after digital switchover DSO TV transmission replaces the current analogue system. Recently, the regulators in the USA and in the UK have given approval for companies to operate new communication systems with the capability of utilising TVWS spectrum. This paper provides a comprehensive overview of the CR technology and quantifies the TVWS status in Malaysia to expose the spectrum reuse opportunities for future secondary user deployment. Taking the 18 major cities in Malaysia into consideration, we find that all seven TV stations utilise from two to seven of the UHF channels. In our analysis, three usage scenarios were considered, where the utilisation of the 40 UHF channels is full, half and a third. For each case, it was discovered that TVWS was 82.5%, 65% and 46.1%, which can be opportunistically utilised by CR users. Copyright

Measurements and Analysis of Spectrum Occupancy in the Cellular and TV Bands

In this paper, we investigate spectrum occupancy focusing on cellular and TV broadcasting bands. Recently, TV band has attracted much attention due to the potential to exploit the available white space, if any, to improve spectrum utilization opportunistically. TV white space is a portion of spectrum in the UHF/VHF bands which is not utilized based on time and location. For the sake of comparison, measurements have also been conducted to investigate spectrum occupancy in cellular band, which is normally assumed to be fully utilized. The findings in this paper are important to provide insight of the actual spectrum utilization in the TV and cellular bands in Malaysia as compared to studies conducted in other countries.

Experimental implementation of dynamic spectrum access for video transmission using USRP

In this paper we present the experimental implementation of dynamic spectrum access (DSA) algorithm using universal software radio peripheral (USRP) and GNU Radio. The setup contains two primary users and two cognitive radios or secondary users. One primary user is fixed and the other is allowed to change its position randomly. Depending upon the position of the primary user the cognitive user will use the spectrum band where the detected energy is below certain predefined threshold level. The cognitive radio users are also programmed to operate independently without interfering with each other using energy detection algorithm for spectrum sensing. The modulation scheme is set to GMSK for secondary user performing data transmission. This experimental setup is used to analyze the quality of video transmission using DSA which provides the insight regarding the possibility of using free spectrum space to improve the performance of the system and its advantage over a non-DSA system. From the experiment it is shown that under congestion and interference DSA perform better than a non- DSA system.

Route Selection for Multi-Hop Cognitive Radio Networks Using Reinforcement Learning: An Experimental Study

Cognitive radio (CR) enables unlicensed users to explore and exploit underutilized licensed channels (or white spaces). While multi-hop CR network has drawn significant research interest in recent years, majority work has been validated through simulation. A key challenge in multi-hop CR network is to select a route with high quality of service (QoS) and lesser number of route breakages. In this paper, we propose three route selection schemes to enhance the network performance of CR networks, and investigate them using a real testbed environment, which consists of universal software radio peripheral and GNU radio units. Two schemes are based on reinforcement learning (RL), while a scheme is based on spectrum leasing (SL). RL is an artificial intelligence technique, whereas SL is a new paradigm that allows communication between licensed and unlicensed users in CR networks. We compare the route selection schemes with an existing route selection scheme in the literature, called highest-channel (HC), in a multi-hop CR network. With respect to the QoS parameters (i.e., throughput, packet delivery ratio, and the number of route breakages), the experimental results show that RL approaches achieve a better performance in comparison with the HC approach, and also achieve close to the performance achieved by the SL approach.

TDMA-based cooperative sensing using SDR platform for cognitive radio

The current trend and demand of wireless services requires more efficient spectrum usage. With Cognitive Radio (CR) technology, spectrum efficiency will be increased by exploiting unused licensed or primary users spectrum. Spectrum sensing mechanism is one of the main cores in CR system. To combat the problems of shadowing, multipath fading, and hidden nodes, cooperative spectrum sensing has been proposed. Testbed prototyping for sensing is a challenging task. The demand for cooperative sensing to solve the above mentioned problems leads to proposals of PHY and MAC layer solutions. Therefore, in this paper, we demonstrate an experimental platform using USRP board that can facilitate the development of PHY and MAC layers functionality for cooperative spectrum sensing. In this paper, TDMA-based MAC protocol for cooperative sensing mechanism is proposed. The observation of the preliminary experimental measurement shows significant performance in term of feasibility of cooperative decision mechanism in wireless condition.

Resource allocation schemes in Energy Efficient OFDMA system via Genetic Algorithm

Four schemes for binary solutions are proposed in this work to solve the resource allocation problem in an OFDMA system. The binary solution is sought at the early stage before applying the Genetic Algorithm to solve the real-valued problem. Each scheme performed differently in terms of Energy Efficient (EE) values obtained and the required computational cost. Out of four schemes (maxJ, maxP, minP and CP), the best scheme found in this study is CP as this scheme obtained the highest average EE with moderate computational cost.

Scalable video streaming over overlay/underlay cognitive radio network

Cognitive radio (CR) with dynamic spectrum allocation (DSA) allows new or secondary devices to opportunistically access a portion of spectrum, which belongs to primary (licensed) users (PU). This allows the secondary users (SU) to transmit data services when the PUs are not using the spectrum. However, problem arises when SU experiences interrupted services if the PU needs to use the spectrum. The objective of this paper is to provide uninterrupted multimedia data services (video transmission) to SU by allowing the SU to receive data in both the overlay and underlay mode of CR. Since the underlay mode CR is characterized by low power and low data rate, base layer video streaming of a scalable video coding (SVC) is an attractive solution. In overlay mode, the enhancement layers and the base layer of the SVC are streamed without interruptions. The base layer video is protected from video packet loss by using I-frames insertion. Simulation results show that it is a great challenge to transmit video in the underlay CR. Nevertheless, with high protection of the base layer video of the SVC, acceptable video quality can be achieved.

A smooth forwarding operation in wireless mesh network

The IEEE 802.11 Distributed Coordination Function (DCF) Medium Access Control (MAC) protocol is designed to efficiently facilitate the limited communication bandwidth of wireless channel. This protocol uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism. This mechanism continues suffer from throughput degradation when directly applied in multihop Wireless Mesh Network (WMN). The major reason for this poor performance is due to larger signaling overheads (RTS and CTS signaling packet) introduced in order to forward a single data packet in multihop WMN. This inefficient forwarding operation caused the throughput degradation signifficantly. Therefore, an efficient forwarding operation is proposed in this paper to reduce the amount of signaling overheads which are needed to forward a single packet in multihop WMN. The proposed protocol uses the capability of overhearing in order to forward the data packet from one hop to another hop. This process will continue until the data packet reaches the respective destination. As a result, the enhanced protocol reduces the latency caused by signaling thus improve its throughput in multihop WMN. The multihop network performances are evaluated analytically in terms of throughput and delay. Through the simulation, it is proven that the proposed protocol provides significant improvement in throughput and delay. The results show that the proposed protocol outperforms the existing IEEE DCF MAC protocol when it is evaluated in multihop WMN.

A novel scheduling algorithm based class-service using game theory for LTE network

Long Term Evolution (LTE) network is a promising wireless technology which provides mobile users with high data rate and low latency. LTE has been developed by the 3rd Generation Partnership Project (3GPP) to improve the end to end system delay and support higher Quality of Services (QoS). However, 3GPP has not defined a firm provision to handle the scheduling process, so that scheduling becomes an open issue for researchers. Instead, they defined nine classes with their corresponding Quality of Services (QoS) requirements. In this paper, a novel scheduling algorithm is proposed based on class service using cooperative game theory technique. The available resources are fairly distributed among classes as proportion which results in higher fairness level among classes. In the second level, the users with tightest delay requirements are prioritized. The proposed algorithm is compared with Proportional Fairness (PF) and Exponential (EXP) rule algorithms in terms of throughput, delay and fairness index. The proposed model outperforms PF and EXP schemes in all comparative parameters.