Abstract: Code division multiple access (CDMA) systems have been very successful in extending the multiuser capability of communication systems with fixed resources through a set of pseudorandom (PN) codes. Spectral efficiency of CDMA channels can be increased by using an M-ary modulation scheme, but with reduced power efficiency. Power efficiency can be improved by using multidimensional signal constellations instead of one-dimensional (1D) signals. A new system is proposed to combine CDMA for synchronous users with four dimensional (4D) bandpass (BP) quadrature amplitude modulation (QAM) or MQAM2. MQAM2 is generated by using Hilbert Transform (HT) based orthogonal pulse pairs. Continuous-time (CT) analysis of this new M-ary QAM direct sequence (DS) CDMA synchronous downlink channel is presented in this paper and performance measures are investigated for AWGN channels.

Abstract: Modern powerful reconfigurable systems are suited in the implementation of various data-stream, data-parallel, and other applications. An application that needs real-time, fast, and reliable data processing is the global positioning system (GPS)-based vehicle tracking system (VTS). In this paper, we build on a recently produced VTS (The Aram Locator) offering a system-on-chip (SOC) replacement of the current microcontroller-based implementation. The proposed SOC is built on a field programmable gate array (FPGA) promising a cheaper design, a more cohesive architecture, a faster processing time and an enhanced system interaction. Different designs, and their hardware implementations, are proposed with different levels of integration. Performance analysis and evaluation of the investigated designs are included.

Abstract: The emergence of WiMAX has attracted significant interests from all the fields of wireless communications including students, researchers, systems engineers and operators. The WiMAX can also be considered to be the main technology in the implementation of other networks like wireless sensor networks. Developing an understanding of the WiMAX system can be best achieved by looking at a model of the WiMAX system. This paper discusses the model building of the WiMAX Physical layer using computer Matlab 7.5 version. This model is a useful tool for BER performance evaluation for the real audio data communication by the WiMAX Physical layer under different channel encoding rates, digital modulation schemes and channel conditions. With the performance investigation of the system, the modulation schemes BPSK, QPSK, 8PSK, 16PSK, 4QAM and 16QAM are introduced besides ½ and 2/3-rated convolutional encoder under AWGN, Rayleigh and Rician fading channels. The model presented in this paper built with the Physical Layer using Convolutional Encoding Rate of ½ and 2/3 and transmitted with 256 carrier OFDM symbols. Computer simulation results on BER over an Additative White Gaussian Noise(AWGN) and other fading (Raleigh and Rician) channels demonstrate that the proposed system outperform with BPSK modulation technique as compared to other digital modulation schemes and the system is highly effective to combat inherent interferences under Rayleigh and Rician fading channels. It has been anticipated from the simulation study with real audio data that the performance of the communication system degrades with the increasing of noise power.

Abstract: Superlattice emitter resonant tunneling bipolar transistor (SE-RTBT) is facing problem due to thermal transfer of electrons over barrier which causes diminishing negative differential resistance (NDR) effect. Therefore resonant tunneling diode (RTD) with higher quasi-bound state energy causes transfer of electrons by RT effect instead of thermal process. The RT effect can be enhanced by controlling the barrier and well widths of RTD. It has been found that InP/GaInAs SE-RTBT shows better NDR characteristic at room temperature.

Abstract: Most multithread executions acts nondeterministic while execute on multiprocessor systems. Recording nondeterministic events in such executions can enable deterministic replay. So some researchers are focused on deterministic replay capability in recording important information during executions. In this survey we introduce Hardware-Base, Software-Base and Software-Hardware approaches that have been proposed for deterministic replaying. The Hardware-Base approaches, adds special hardware to detect the interleaving of memory accesses or instructions from the different processors during execution, and save the key information in a log. This log is later used to replay the same interleaving. The Software-Base approaches propose software systems that record all sources of non-determinism, such as network inputs or interrupts, and use this information to guide the software down the same execution path during replay. Finally we introduce the Software-Hardware approaches with name Capo [25]. This method in hardware, records interleaving of the R-threads running in a log within the same sphere. And in software records the other sources of non-determinism that may affect the execution path of the R-threads, such as system call return values and signals.

Abstract: Design of congestion control mechanism for multi-media streaming over the Mobile Ad-hoc Networks (MANET) is challenging. Streaming applications require a smooth transmission rate which the Internet is unable to provide whenever there is congestion in the network. The standard TCP congestion control mechanism is not able to handle the special properties of a shared wireless multi hop channel well. In particular, the frequent changes of the network topology and the shared nature of the wireless channel pose signi?cant challenges. In this paper, we propose a router assisted approach, where routers provide explicit feedback which allows quick increase of throughput.

Abstract: High-speed Wireless LANs based on 802.11 technologies are becoming increasingly ubiquitous. IEEE 802.11n is the last standard toward achieving higher speeds and aims to enhance 802.11 for higher throughput. Few works studied 802.11n medium access control (MAC) layer, but unfortunately, effects of higher physical rates is still unknown to the upper layers and especially routing layer of these networks. The main purpose of this paper is to assess efficiency of routing algorithms on IEEE 802.11n networks. We selected DSDV routing protocol, as one the popular algorithms, for this purpose. Based on various studies and simulations carried out, results indicate that increase in physical layer speed, does not necessarily lead to improving throughput and efficiency of the network layer. In addition, results indicate that 802.11n performs slightly better than 802.11 for large enough packet sizes; also we show the DSDV routing algorithm flaws when it work on 802.11n.

Abstract: A traditional method for transferring data in rotating mechanisms has been the slip ring, but these are not viable inside pistons due to size, the associated cabling, and the requirement of one slip ring per parameter. A mechatronic data acquisition system is developed whereby signal conditioning is performed by the sensor and the signal passed to a Bluetooth transmitter module for wireless telemetry to a Bluetooth receiver located in very close proximity, connected to an external host PC. The Data Acquisition (DAQ) Bluetooth module integrates a microcontroller that reads the conditioned thermocouple signal and performs any other DAQ functionality required. The microcontroller firmware includes a server that collates all DAQ data for transmission via Bluetooth to the host PC for display via a client interface. This Short Distance Telemetry (SDT) system is a substitute for slip rings and their associated cabling. A slip ring also transfers power, but this cannot be achieved with the SDT system, therefore an independent power supply is required. The power supply consists of a rotor incorporating NdFeB magnets and a wire wound stator. As the shaft rotates the rotor induces an AC voltage into the stator. A rectifying circuit converts the AC voltage into a regulated DC output voltage that drives the signal conditioning and embedded Bluetooth circuits.