Non-Guard Interval based and Genetic Algorithm Assisted Frequency Domain Equalization for DS-UWB Systems

In this work, a genetic algorithm (GA) based frequency domain equalization (FDE-GA) scheme was proposed for direct sequence ultra wideband (DS-UWB) wireless communication systems. The proposed FDE-GA scheme does not require a guard interval (GI) and the output of the RAKE receiver is used as the input to our GA. The scheme achieved much higher bandwidth efficiency than conventional FDE methods because of the removal of the inter block interference (IBI) within each block before the GA. The FDE-GA receiver was shown to significantly outperform the RAKE receiver and the RAKE-GA receiver proposed in a previous work, in terms of bit error rate (BER) at a similar complexity. An improvement in the mean square error (MSE) was observed from simulation results presented, as a result of increase in the number of pilot symbols.Keywords: frequency domain equalization, guard interval, ultra-wideband, genetic algorithm, inter block-interferenc

A joint multi user detection scheme for UWB sensor networks using waveform division multiple access

A joint multiuser detection (MUD) scheme for wireless sensor networks (WSNs) is proposed to suppress multiple access interference (MAI) caused by a large number of sensor nodes. In WSNs, waveform division multiple access ultra-wideband (WDMA-UWB) technology is well-suited for robust communications. Multiple sensor nodes are allowed to transmit modulated signals by sharing the same time periods and frequency bands using orthogonal pulse waveforms. This paper employs a mapping function based on the optimal multiuser detection (OMD) to map the received bits into the mapping space where error bits can be distinguished. In order to revise error bits caused by MAI, the proposed joint MUD scheme combines the mapping function with suboptimal algorithms. Numerical results demonstrate that the proposed MUD scheme provides good performances in terms of suppressing MAI and resisting near-far effect with low computational complexity

Performance Enhancement of DS-UWB Short Range Communication System Using Equalization Techniques

UWB is a major research area in the field of wireless communication. The IEEE 802.15.3a has been assigned the job of standardizing it. It is being considered as a breakthrough technology capable enough to revolutionize short range wireless communication. Ultra wideband communication as its name implies has large absolute bandwidth greater than 500 MHz and operating frequency band is 3.1 GHz- 10.6GHz. It is a rapidly growing technology that plays a very promising role in modern age wireless communication. It finds application in various sectors, for example in medical application to observe the status of patient using wireless health monitoring of life sustaining systems. In vehicular technology it can be used for obstacle avoidance and fast data transmission, and in military application as radar for detection behind walls and other blockages. Since it is based on short pulse carrier less transmission so hardware implementation becomes less complex and cheap. Thesis work has been done to study the BPSK modulation based DS-UWB communication system. Direct sequence spread spectrum (DSSS) technique along with UWB signal and two types of equalization techniques has been incorporated to mitigate the multipath fading effect associated with S-V indoor channel. Rake receiver has been used to utilize the energy of various delayed multipath components to improve the performance of the system. In short range communication process, indoor channel model or UWB channel model has been studied with different transmitter receiver separation, using some fundamental parameters of channel. Inter symbol interference (ISI) is a major problem in frequency selective fading channels, to overcome this problem, RAKE-MMSE equalizer and single carrier frequency domain equalizer (SC-FDE) have been incorporated. Thesis comprises of the system performance study and design done by using the above said equalization techniques for DS-UWB communications system

Performance Enhancement of Ultra Wideband WPAN using Narrowband Interference Mitigation Techniques

A new promising technique adopted by 4G community is ultra-wideband technology, which offers a solution for high bandwidth, high data rate, low cost, low power consumption, position location capability etc. A conventional type of UWB communication is impulse radio, where very short transient pulses are transmitted rather than a modulated carrier. Consequently, the spectrum is spread over several GHz, complying with the definition of UWB. Currently, the Rake receiver used for spread spectrum is considered a very promising candidate for UWB reception, due to its capability of collecting multipath components. Since UWB signals occupy such a large bandwidth, they operate as an overlay system with other existing narrowband (NB) radio systems overlapping with their bands. In order to ensure a robust communication link, the issue of coexistence and interference of UWB systems with current indoor wireless systems must be considered. Ultra Wideband technology with its application, advantages and disadvantages are discussed in detail. Design of UWB short pulse and a detail study IEEE 802.15.3a UWB channel models statistical characteristics have been analyzed through simulation. Simulation studies are performed and improved techniques are suggested for interference reduction in both Impulse Radio based UWB and Transmitted Reference type of UWB system. Modified TR-UWB receiver with UWB pulse design at transmitter end and notch filtering at receiver’s front end proved to be more efficient in single NBI, multiple NBI and WBI suppression. Extensive simulation studies to support the efficacy of the proposed schemes are carried out in the MATLAB. Bit error rate (BER) performance study for different data rates over different UWB channel models are also analyzed using proposed receiver models. Performance improvement of TR-UWB system is noticed using the proposed techniques

Performance study of air interface for broadband wireless packet access

Ph.DDOCTOR OF PHILOSOPH