Norazizah Mohd Aripin

Integration of Cooperative Sensing and Transmission

In this article, some aspects of cognitive radio (CR) technologies and cooperation strategies are discussed. The findings show that cooperative sensing enhances decision making by collaborating cognitive users (CUs). Primary users (PU) protection increases by OR rule and opportunistic access increases for CUs if collaborated using AND rule. It can also be observed that cooperative relaying benefits from path-loss saving, power gain due to the fact that the relay may add additional transmit power, and diversity gain in the presence of fading. In addition, the network performance is also enhanced by the increase in achievable data rates when using cooperative relay when compared with the rates achieved without relay. Cooperative communication technique can further enhance the transmission capacity of a communication system, while CR technique can improve the spectrum utilization ratio. Doubtless, the integration of the two technologies will have a great impact on network architecture, terminals, service models, and applications of future wireless mobile communication.

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.

Sensing period considerations in fading environment for multimedia delivery in cognitive Ultra Wideband system

Spectrum scarcity and the inefficiency in its usage have necessitates the use of Cognitive Radio (CR) technology to exploit the existing wireless spectrum opportunistically. Spectrum sensing is a critical component of CR as it is a fundamental requirement that a cognitive user (CU) continuously senses the channel before accessing it to avoid causing interference to the primary user (PU) and other radio systems. Due to its low transmit power, detection of PU in a fading environment for an Ultra Wideband (UWB) system is a key problem. This paper presents preliminary works in determining the appropriate sensing period for the cognitive UWB that support multimedia delivery. Firstly, the proposed cross-layer design for multimedia transmission is presented. Next, simulations of bit-error-rate (BER), packet-error-rate (PER) and job-failure-rate (JFR) were carried out to determine the optimal signal-to-ratio (SNR) range to meet the Quality-of-Service (QoS) requirement set for video application. Lastly, the performance of probability of detection against SNR is studied to estimate the appropriate time slot allocation for sensing scheduling.

Evaluation of required sensing time for multimedia transmission over cognitive Ultra Wideband system

Limited available spectrum and the inefficiency in the spectrum usage necessitate the use of Cognitive Radio (CR) approach to exploit the existing wireless spectrum opportunistically. To achieve the goal of CR, it is a fundamental requirement that the cognitive user (CU) performs spectrum sensing to detect the presence of the primary user (PU) signal before a spectrum is accessed to avoid interference from other wireless users. In Ultra Wideband (UWB) system which utilizes low power transmission, detection of PU is a key problem in a low signal-to-noise ratio (SNR) condition. This paper presents preliminary works in determining the quality of service (QOS) requirements for multimedia delivery in cognitive UWB. The proposed cross-layer design for multimedia transmission is presented. The paper also highlights the use of probability of detection to assess the channel conditions. Finally, we conclude with some future works on issues of medium access control (MAC) layer and time slot allocations for video applications.

A cross-layer approach in sensing and resource allocation for multimedia transmission over cognitive UWB networks

We propose an MAC centric cross-layer approach to address the problem of multimedia transmission over cognitive Ultra Wideband (C-UWB) networks. Several fundamental design issues, which are related to application (APP), medium access control (MAC), and physical (PHY) layer, are discussed. Although substantial research has been carried out in the PHY layer perspective of cognitive radio system, this paper attempts to extend the existing research paradigm to MAC and APP layers, which can be considered as premature at this time. This paper proposed a cross-layer design that is aware of (a) UWB wireless channel conditions, (b) time slot allocations at the MAC layer, and (c) MPEG-4 video at the APP layer. Two cooperative sensing mechanisms, namely, AND and OR, are analyzed in terms of probability of detection (), probability of false alarm (), and the required sensing period. Then, the impact of sensing scheduling to the MPEG-4 video transmission over wireless cognitive UWB networks is observed. In addition, we also proposed the packet reception rate- (PRR-) based resource allocation scheme that is aware of the channel condition, target PRR, and queue status.

Performance of cognitive smart grid communication in home area network

Spectrum measurement has been conducted in different areas and it is reported that the spectrum utilization efficiency is poor. To improve the spectrum utilization efficiency, cognitive radio concept is deployed. Using cognitive radio ability, cognitive users sense the spectrum bands and utilize idle channels opportunistically. The main constraint is that no harmful interference should be incurred to licensed users. One of the applications of cognitive radio is smart grid communication. Smart grid is an intelligent electricity grid system which is more resilient, robust, and secure. To ensure stability in smart grid, dual-way communication is the key role. In cognitive smart grid framework, smart grid devices utilize idle channels to transmit data. In this paper, cognitive radio is applied in Industrial, Science, and Medical (ISM) bands for smart grid home area network. Cognitive radio aims to improve the performance of sensing multiple channels and to mitigate noisy channels in ISM bands. Simulation has been carried out by using NS-2. The simulation result shows that the performance of cognitive smart grid outperforms conventional 802.11 in term of delay and spectral efficiency.

Spectrum survey for reliable communications of cognitive radio based smart grid network

The smart grid (SG) system is expected to involve huge amount of data with different levels of priorities to different applications or users. The traditional grid which tend to deploy propriety networks with limited coverage and bandwidth, is not sufficient to support large scale SG network. Cognitive radio (CR) is a promising communication platform for SG network by utilizing potentially all available spectrum resources, subject to interference constraint. In order to develop a reliable communication framework for CR based SG network, thorough investigations on the current radio spectrum are required. This paper presents the spectrum utilization in Malaysia, specifically in the UHF/VHF bands, cellular (GSM 900, GSM 1800 and 3G), WiMAX, ISM and LTE band. The goal is to determine the potential spectrum that can be exploit by the CR users in the SG network. Measurements was conducted for 24 hours to quantify the average spectrum usage and the amount of available bandwidth. The findings in this paper are important to provide insight of actual spectrum utilization prior to developing a reliable communication platform for CR based SG network.

Inner bound capacity analysis of cooperative relay in cognitive radio using information theoretic approach

Motivated by the inefficient usage of the licensed spectrum across many frequency bands, cognitive radio (CR) was proposed to promote the spectrum utilization by opportunistically exploiting the existence of spectrum “holes.” Under this new paradigm, cognitive (unlicensed) user is allowed unobtrusive access to a channel exhibiting negligible primary (licensed) user activity. Cooperative communication is increasingly regarded as a way to address hidden terminal issues and to improve spatial diversity for the same spectrum frequency band. In this paper, we investigate a cooperative transmission of primary traffic by cognitive users (cognitive relaying). The scenario focuses on one cognitive transmitter which has the option to relay traffic of the primary assuming that the primary is oblivious to its presence and thus exclude the possibility of spectrum leasing. To demonstrate the feasibility and performance of this cooperative relay for CR, numerical analysis based on information theoretic approach is used in order to discuss the advantage and capacity limits of the strategy.

A cross-layer approach in enabling multimedia transmission over cognitive UWB network

The demand of quality of service (QoS) for multimedia transmission over wireless network raises huge challenges such as time-varying channel conditions, limited resources, tight delay constraints, high bandwidth demand and complex protocol design. Layered design is proven to perform well in wired networks. However, doing so is not suitable in wireless networks due to the dynamics in wireless medium. On top of that, sensing activity should also be considered explicitly in cognitive UWB network to avoid interference with the primary users. In this paper, a new cross layer design (CLD) approach is proposed to achieve the goal of improving the received video quality while minimizing the packet loss. The proposed CLD consists of sensing module, adaptive resource allocation module and adaptive quantization scale module. Simulation results showed that the proposed CLD reduced the job failure rate (JFR) significantly when compared to the non-CLD approach, basic CLD, PRR based resource allocation (PRR-RA) with queue insensitive and PRR-RA with queue sensitive-fixed Q-value.

Performance Evaluation of Video Transmission Over Ultrawideband WPAN

Over the past few decades, unprecedented growth in wireless communications, networking and video-coding technologies have stimulate numerous applications such as video on demand and interactive video telephony. Ultrawideband technology (UWB) which offers high data rate with low transmit power, becomes a very promising wireless platform for video transmission. Recently, Cognitive Radio (CR) technology was introduced to fully utilized spectrum usage by sensing the spectral environment and use this information to opportunistically provide wireless links that meet the user communications requirements optimally. It is obvious that achieving more reliable and efficient multimedia communication over wireless UWB channel requires a cross design approach due to tight dependency among protocol layers. In this paper, proposed cross layer framework of video transmission over CR-UWB will be presented. Then, a simulation study is carried out to evaluate the effect of resource allocation at the MAC layer to the video quality perceived at the receiver.