Delay-sensitive video transmission over IEEE 802.11 wireless local area networks (WLANs) is analyzed in a cross-layer optimization framework. The effect of delay constraint on the quality of received packets is studied by analyzing “expired-time packet discard rate”. Three analytical models are examined and it is shown that M/M/1 model is quite an adequate model for analyzing delay-limited applications such as live video transmission over WLAN. The optimal MAC retry limit corresponding to the minimum “total packet loss rate” is derived by exploiting both mathematical analysis and NS-2 simulations. We have shown that there is an interaction between "packet overflow drop" and "expired-time packet discard" processes in the queue. Subsequently, by introducing the concept of virtual buffer size, we will obtain the optimal buffer size in order to avoid "packet overflow drop". We finally introduced a simple and yet effective real-time algorithm for retry-limit adaptation over IEEE 802.11 MAC in order to maintain a loss protection for delay-critical video traffic transmission, and showed that the average link-layer throughput can be improved by using our adaptive scheme.

Stability analysis of polynomial fuzzy model-based (PFMB) control systems under the parallel distributed compensation (PDC) design technique is investigated. A new polynomial fuzzy controller (PFC) is introduced to release conservativeness in the existing approaches. Compared to the conventional (PFC), the controller under consideration in this paper has a favorable property which introduces some more variables in the stability conditions such that, the solution of the derived stability conditions can be explored in a larger group of potential solutions. This property may lead to further relax stability conditions. However, the stability conditions will not be in the form of SOS conditions. Hence, particle swarm optimization (PSO) is employed to explore the solution of the derived stability conditions which are in the form of state-dependent BMI. It is shown that the conventional PFC is a special case of that of proposed one. Finally, a simulation example is given to illustrate the effectiveness of the proposed approach.

In WSNs, collision avoidance and energy saving methods on MAC layer have become challenging research goals. Collision may happen because of Hidden-Node problem. It occurs when a sender is out of range of another sender and they try simultaneously sending data to a common receiver. IEEE802.11 RTS/CTS mechanism partly overcome this problem but a major drawback is that we cannot avoid RTS/CTS control packet collisions. This paper proposes a method to avoid collision among hidden transmitters that decide to send data to a sink via `One' relay node concurrently. Our solution is to add a predefined handshaking signal called COL (Collision) which is applicable for any packetised-preamble MAC protocol. If receiver recognises a collision it sends COL message to the channel and afterwards all senders postpone data transfer process and save energy. Performance analysis of proposed method proves its viability and effectiveness for the problem.

This study proposes the use of wavelet transform in long-term evolution (LTE) cellular systems. Mathematical expressions are derived to represent data rate in LTE downlink transmission based on Wavelet and Fourier Transforms. Furthermore, a comparison between these two systems is provided. Simulation results show the proposed orthogonal wavelet division multiplexing (OWDM) approach outperforms the traditional orthogonal frequency division multiplexing-based systems. The data rate can also be increased by the amount of CyclicPrefix/SymbolTime%, as there is no need for a channel prefix in an OWDM-based system.

Relaxed linear-matrix-inequality-based stability conditions for fuzzy-model-based control systems with imperfect premise matching are proposed. First, the derivative of the Lyapunov function, containing the product terms of the fuzzy model and fuzzy controller membership functions, is derived. Then, in the partitioned operating domain of the membership functions, the relations between the state variables and the mentioned product terms are represented by approximated polynomials in each subregion. Next, the stability conditions containing the information of all subsystems and the approximated polynomials are derived. In addition, the concept of the S-procedure is utilized to release the conservativeness caused by considering the whole operating region for approximated polynomials. It is shown that the well-known stability conditions can be special cases of the proposed stability conditions. Simulation examples are given to illustrate the validity of the proposed approach.

Relaxed LMI-based stability conditions for fuzzy model-based (FMB) control systems are proposed. Considering LMI-based shape-dependent stability conditions, containing relations between state variables and membership functions, some more relaxed stability conditions for FMB control systems with `Parallel Distributed Compensation'(PDC) design technique are derived. In the aforementioned approach, product terms of fuzzy model and fuzzy controller membership functions are approximated by polynomials in the partitioned operating domain of membership functions so that corresponding to each sub-region a proper polynomial for each product term is derived. However, conservativeness, resulting from considering the whole operating region for approximated polynomials still remains. In this paper, to release this conservativeness, the concept of S-procedure is exploited. One Simulation example is presented to illustrate the validity of the proposed approach.

The use of wavelet transform in multicarrier ultra wideband (UWB) systems is analysed and the results are compared with Fourier-based multicarrier UWB systems. It is well known that convolution in time domain is equivalent to multiplication in frequency domain; however, there is no closed-form expression in the literature for convolution's counterpart in the wavelet domain. A formula is derived to represent convolution's counterpart in the wavelet domain. Furthermore, the effects of choice and type of wavelet filters and different decomposition levels are investigated. Finally, a performance comparison of both techniques for IEEE 802.15.3a channel models using IEEE802.15.3a multiband‐orthogonal frequency division multiplexing UWB specifications is provided.

In this paper we analyse the application of wavelet transform as an alternative to the conventional Fourier-based multicarrier UWB systems. In Fourier based multicarrier UWB systems a cyclic prefix (CP) with the same length of the channel impulse response must be added to each symbol in order to convert linear convolution into circular convolution. The CP must consist of identical copies of the transmitted data in each symbol and therefore is a waste of bandwidth and resources. In this paper we present a framework for wavelet based multicarrier UWB systems and it is shown that they do not require the cyclic prefix for transmission and, hence throughput increases. Moreover, a closed form formula is derived to represent convolution's counterpart in the wavelet domain. Finally, a performance comparison of both techniques is provided.

Digital radiology places very high demands on the networking and digital storage infrastructure of hospitals. In addition to having quite stringent requirements on the quality of the images displayed to the radiologist, much of the technical challenge resides in the necessity of displaying desired images as rapidly as possible. We present an infrastructure for progressive transmission and compression of medical images, which can refine an initial image by increasing the detail information not only in scale-space, but also in coefficient precision. The approach is based on the embedded zerotree wavelet (EZW) algorithm. This algorithm offers a tremendous amount of flexibility in meeting the bandwidth and image quality constraints in a radiological imaging environment. We propose an application of the EZW algorithm in progressive medical image transmission in which it can specify and control both the resolution constraint and rate constraint. The presented method can provide a framework for lossy image compression, with performance far superior to those provided by the standard JPEG algorithm. Also due to the flexibility of the method we will show how any region of interest of an image can be sent progressively.

In this paper novel prolate spheroidal wave functions are proposed as pulse shapes for use in impulse radio (ultra-wideband) communications. These classes of functions yields orthogonal pulses and have a constant pulse width regardless of the pulse order. This is an important property since it eliminates inter-symbol interference. An M-ary communications system is considered that employs these pulses, and the generation of these pulses using the eigenfunction form of a self-adjoint operator is proposed. It is also shown that these pulses are suitable for use in pulse position modulation (PPM) ultra wideband (UWB) communication systems.