Multimedia transmission using orthogonal frequency division multiplexing based on cognitive radio

With the rapid growth of multimedia applications over the wireless Internet, the demand for radio spectral resources has increased significantly. Referring to frequency spectrum allocations in Malaysia, major parts of spectrum have been assigned for government and commercial use. Despite the spectrum scarcity in meeting the demands for multimedia services, it was found from previous studies that most of the spectrum is actually not being utilised efficiently. Henceforth, lots of researches have been conducted to exploit this underutilised spectrum opportunistically without affecting the incumbents operations. Through the enabling Software Defined Radio (SDR) technology, Cognitive Radio (CR) has been proposed to solve the inefficient spectrum utilisation problems. CR is an adaptive, intelligent radio and network technology that has the ability to detect available vacant channels in radio frequency spectrum and change its particular transmission or reception parameters for efficient communication link achieved. In this thesis, SDR platform which consists of GNU Radio and Universal Software Radio Peripheral (USRP) is used for CR multimedia transmission development. In this system, adaptive Orthogonal Frequency Division Multiplexing (OFDM) is implemented to support robust multimedia transmission effectively. Next, Pseudorandom Multiband Frequency Switching is proposed for seamless frequency agility provision. For proof of concept, the proposed system is evaluated on several multimedia signals transmission. The results showed that the minimal time duration for each frequency switching of the system is approximately 1 second which resulted 20 dB for peak signal-to-noise ratio (PSNR) achievement. However, with higher rate of intermittent presence of incumbent or primary user (PU), faster switching rate is needed. Hence, the system developed needs further enhancement for a reliable and seamless multimedia transmission system to be realised

Reliable Multimedia Transmission Over Cognitive Radio Networks Using Fountain Codes

With the explosive growth of wireless multimedia applications over the wireless Internet in recent years, the demand for radio spectral resources has increased significantly. In order to meet the quality of service, delay, and large bandwidth requirements, various techniques such as source and channel coding, distributed streaming, multicast etc. have been considered. In this paper, we propose a technique for distributed multimedia transmission over the secondary user network, which makes use of opportunistic spectrum access with the help of cognitive radios. We use digital fountain codes to distribute the multimedia content over unused spectrum and also to compensate for the loss incurred due to primary user interference. Primary user traffic is modelled as a Poisson process. We develop the techniques to select appropriate channels and study the trade-offs between link reliability, spectral efficiency and coding overhead. Simulation results are presented for the secondary spectrum access model

Amélioration de la performance des réseaux maillés sans fil cognitifs

Les réseaux maillés sans fil (WMN) sont une solution peu coûteuse et efficace afin de déployer rapidement des services d’accès à large bande dans des environnements dépourvus d’infrastructure. Toutefois, pour devenir un succès commercial, les WMN doivent supporter des applications en temps réel, telles que celles pour le multimédia et les services d’urgence. Or, ces applications génèrent du trafic critique qui requiert la mise en place de mécanismes de qualité de service (QoS). Alors que la capacité et la disponibilité de la bande passante des WMN monoradios limitent sévèrement la QoS pour ce type de trafic, les WMN cognitifs (CWMN) multiradios peuvent compenser ces limitations et offrir de meilleurs mécanismes de QoS. Ce projet de recherche propose d’améliorer la performance des WMN afin qu’ils puissent supporter la QoS requise pour satisfaire aux exigences strictes du trafic généré par des applications en temps réel