Theoretical limit on two dimensional generalized complementary orthogonal sequence set with zero correlation zone in ultra wideband communications

1.1 Impulse Radio (IR) Ultra Wideband (UWB) Communications Ultra wideband (UWB) communication is a fast emerging technology that offers new opportunities such as high data rates, low equipment cost, low power, precise positioning capability and extremely low interference Ghawami (2005). A wide range of possible UWB communication system applications includes radars due to UWB ultra high precision ranging at the centimeter level, wireless personal area networks (WPAN), sensor networks, imaging systems, UWB positioning systems, etc. Yang (2004), Kshetrimayum (2009). From a commercial point of view, the high data rates are the most attractive feature of UWB systems for which speeds of over 100Mb/s have been demonstrated Ghawami (2005). There exist three main types of UWB technologies: impulse radio (IR UWB), direct sequence (DS UWB), and multi-band orthogonal frequency division multiplexing (MB OFDM) Ran (2009). IR UWB communication technique is essentially different from all other communication techniques because it is carrier free and uses for communication between transmitters and receivers very narrow radio frequency (RF) pulses generated from the UWB pulse generator, while traditional transmission systems transmit information by varying the power, frequency, and/or phase of a sinusoidal wave in a modulation process Kshetrimayum (2009), Yao (2007). Consequently, complicated frequency mixers and local oscillators for carrier frequency up and down conversion are not necessary Yao (2007). IR UWB modulation techniques are especially important because the UWB spectrum has been made available by the Federal Communication Commission (FCC) and it can be used with IRs developed to date Lin (2005). Waveforms for IR UWB are designed to obtain a flat frequency response over the bandwidth of the pulse and to avoid a DC component. The large spectrum of a UWB signal may interfere with existing users. In order to keep this interference to the minimum, FCC specifies spectral masks for different applications, i.e. the allowed power output for specific frequencies Ghawami (2005). A contiguous bandwidth of 7.5GHz is available in the frequency interval of (3.1− 10.6)GHz at a maximum power output of −41.3dBm/MHz which is considered as extremely low Ghawami (2005). The power spectral density (PSD) of UWB systems defined as a ratio of the transmitted power P in watts and a signal bandwidth B in hertz is extremely low as compared to other communication systems due to the very wide bandwidth B of short pulses that are typically of nanosecond or picosecond order Ghawami (2005). The selection of the impulse signal type for IR UWB communication system is essential since it determines

In this paper, a closed form expression for the bit error rate performance of the multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) communication system in the presence of interference is analytically analysed. The considered channel is the Saleh-Valenzuela multipath fading channel model. The interference is modelled as the OFDM-based IEEE802.11n wireless local area networks (WLANs). The dependence of the bit error rate performance of the MB-OFDM UWB communication system on the transmission range along with the impact of interference is also analytically investigated. Numerical results are validated with the aid of simulations. It is shown that the range performance of the MB-OFDM UWB communication system is severely deteriorated due to the presence of such interference.

This work presents an M-ary multiple access code-selected direct sequence (DS) ultra wideband (UWB) communication system. A high data rate multiple access UWB system can be obtained by a code selection mechanism. In the proposed system, each user is assigned a DS code set with M/2 DS code sequence and a particular DS code sequence can be selected by the log2 (M/2) bits from the DS code set. More importantly for this M-ary UWB communication system, with the increase of the modulation level M, it allows to reduce the required transmitter power maintaining the number of users, the data transmission rate and the multiple access performance. In this paper, we also introduce the detailed algorithm to compute the bit error rate (BER) over the AWGN channel and correlation receivers.

Recently, ultra wideband (UWB) communications have received increasing interest due to the high data rate achievable in a short distance. UWB communications can have strong interference mitigation capability. A multicarrier ultra wideband (MC-UWB) system has been introduced in (A.H. Tewfik, et al., (2002)) and (E. Saberinia, et al., (2002)). In the MC-UWB communication systems, multiple symbols are transmitted over different carriers simultaneously. The same symbol is retransmitted over different frequency bands by utilizing frequency hopping (FH) techniques. Frequency hopping and multicarrier technologies smooth the average power spectrum density of the system. In this paper, the expression of the power spectrum density of the MC-UWB system is derived. The radiated emission power for UWB communication systems is limited by the spectrum mask specified by wireless communication authorities, such as the federal communications commission (FCC) in United States. Different parameters in the MC-UWB system will have different effects on the power spectrum density and the maximal achievable data rate. The analysis of impact of parameters in the system on the power spectrum density will help the system designer select proper parameter set to fit in emission power regulation and the required data rate in practical UWB systems. Some examples of parameter selection are also given to illustrate the impact of different parameters in the system on the power spectrum density.

The inter-vehicles communication is becoming increasingly mandatory to improve the road safety and to allow a better transport management. The concept behind an intelligent vehicle consists in equipping this vehicle with an optimum number of sensors, in order to perceive the environment surrounding it and to ensure an automatic guidance control and the communication with the infrastructure and other vehicles. Among the most often used tools for this objective, we can cite the embedded radar. Moreover, the Ultra Wide Band (UWB) communication systems are under fast development and undergo progressive implementation. The principle of UWB technology is to transmit rather low power, carrier-less, signals occupying a very broad spectrum [1]. The spectral concentration of radiated power is thus extremely low, so that the other systems perceive UWB ones like background noise. In this article, a road radar based on UWB technology is studied. The proposed device allows, in a road environment, good resolution and increased precision for detection and localization of obstacles.

Ultrawideband (UWB) is a promising technology for getting high data rate communications. UWB communications refer to the utilization of signals with a frequency range (3.1 to 10.6 GHz) on the condition of having a fractional bandwidth of 20% or absolute bandwidth of 500 MHz or higher. The limited power spectral density of − 41.3 dBm/MHz allows UWB communications to be safely deployed with existing wireless communication systems without causing any interference. Consequently, UWB communication systems have been proposed for different outdoor and indoor scenarios. A variety of applications are suitable for UWB communications ranging from infostations, wireless sensor networks (WSNs), on-body communications, in addition to consumer, medical and military applications. Recently, this technology shows a promising step for indoor positioning accuracy where the functioning of navigation systems such as Global Positioning System (GPS) or GLObal NAvigation Satellite System (GLONASS) might be degraded. In this paper, the fundamental properties of UWB communications are presented with an illustration on the present and future direction of this technology.

Ultra-WideBand (UWB) communication systems are usually classified as any communication system whose instantaneous bandwidth is many times greater than the minimum bandwidth required to deliver information. UWB communication is fundamentally different from all other communication techniques because it employs extremely narrow Radio Frequency (RF) pulses to communicate between transmitters and receivers. Utilizing short-duration pulses as the building blocks for communications directly generates a very wide bandwidth and offers several advantages, such as large throughput, covertness, robustness to jamming, and coexistence with current radio services. UWB technology offers a promising solution to the RF spectrum drought by allowing new services to coexist with current radio systems with minimal or no interference. This coexistence brings the advantage of avoiding the expensive spectrum licensing fees that providers of all other radio services must pay. In this chapter, the application of UWB technology in military areas has been summarized. Its wider applications has been evaluated over several leading technology including military technology systems, government sectors, communication systems, surveillance systems, rescuing, logistics entertainment, public transport, and others.

This study proposes an efficient channel-estimation scheme for Multiband (MB) Orthogonal Frequency Division Multiplexing (OFDM)-based Ultra Wide Band (UWB) communication systems. One of the challenges in wireless system is the frequency selective fading caused due to multipath channel between the transmitter and receiver. The signal bandwidth in broad band cellular wireless systems typically exceeds the coherence bandwidth of the multipath channel. To overcome such a multipath fading environment with low complexity and to increase the performance, UWB OFDM system is used. To practically realize MB-OFDM UWB, one needs to cope with numerous design challenges, particularly in receiver designs such as symbol timing, Carrier Frequency Offset (CFO) and sampling frequency offset compensation, as well as Channel Frequency Response (CFR) estimation. A channel estimation scheme using a Takagi-Sugeno (T-S) fuzzy based neural network under the time varying velocity of the mobile station in a UWB OFDM system is proposed in this study. In our proposal, by utilizing the learning capability of Adaptive Neuro-Fuzzy Inference System (ANFIS), the ANFIS is trained with correct channel state information then the trained network is used as a channel estimator. To validate the performance of our proposed method, simulation results are given and found that it gives more accurate prediction of channel coefficients as compared with fuzzy channel estimator under various highly noisy multipath channel conditions.

In the ultra-wideband (UWB) communication systems, a critical spectral mask is released to restrict the allowable interference to other wireless devices by the Federal Communications Commission (FCC), and then some pulse shaping methods have been presented to fulfil the mask. However, most pulse shaping methods do not consider the antenna distortion which cannot be neglected in the UWB communication systems compared with the conventional systems. To this end, an orthogonal wavelet based pulse shaping method is proposed in this paper to integrate compensation of antenna distortion into pulse shaping. Simulation results show that the novel pulse shaping method can be used to achieve compensation for antenna distortion, optimization of transmission power spectrum, and simplification of the algorithm, as well as simple implementation of the pulse generator.

In this paper, we present a novel channel shortening algorithm developed in particular for ultra wideband (UWB) communication systems. This algorithm makes use of exponentially decaying characteristics of the UWB channel models. It optimizes the channel decaying factor within a desired temporal window in the effective channel while keeping the channel decaying factor constrained elsewhere. The presence of the proposed channel shortening equalizer before rake reception greatly simplifies the rake receiver architecture by significantly reducing the number of channel taps. We compare its performance with all, selective and partial rakes in terms of captured channel energy, rake combining delay and bit error rate (BER). Simulation results show that the proposed algorithm improves the performance of the Rake receiver in dense multipath UWB channels and considerably reduces its structure complexity.

Ultra Wideband (UWB) communication system and MIMO transmission technique recently have attracted much attention. Space time block coding combines with UWB M-ary PSK and M-QAM modulation schemes for the use of multiple transmit antennas providing a simple transmit diversity scheme with the same diversity order as maximal ratio receiver combing. Using the equivalent single input single out (SISO) model, we present a closed form expression for the exact symbol error rate (SER) of orthogonal space time block codes (STBCs) over UWB flat Nakagami-m models.

A set of complementary sequences is a set of sequences such that, for each nonzero offset, the out-of-phase aperiodic autocorrelations of all the sequences sum to zero. It is shown that the sequences from any coset of an (N, m) nondegenerate minimal linear cyclic code over GF(p) form a set of complex-valued complementary sequences of length N.

A compact CPW fed slot antenna for ultra wide band applications

This paper considers compressed sensing (CS) techniques for signal reconstruction and channel estimation in OFDM-based high-rate ultra wideband (UWB) communication systems. We employ a parallel CS structure that exploits frequency domain sparsity. We also consider multipath UWB channels in both the line-of-sight and non line-of-sight environments. UWB signal detection and channel estimation from sub-Nyquist analog projections is carried out using an optimized orthogonal matching pursuit algorithm and the smoothed l 0 algorithm. Simulation results demonstrate significant gains in the form of reliable signal recovery and channel estimation as well as dramatically sub-Nyquist sampling rates for the analog-to-digital converters while maintaining high data rates.

Channel measurement and modeling is an important issue when designing ultra wideband (UWB) communication systems. A Precise model of the channel response is inevitable for designing an ultra wideband telecommunication system. In this article signal propagation in indoor environment and LOS condition is evaluated and the appropriate model of this scenario is presented. Parameters such as the power delay profile, mean excess delay, delay spread, “NP10dB” are analyzed and simulated. Based on analysis results, the proposed model is presented. This model is based on Two-cluster approach but its average power delay profile is described with power function and cluster time of arrival is modeled by the modified exponential distribution. Finally UWB channel parameters of proposed model, Saleh and Valenzuela (S-V) and Two-cluster models are compared. Measurement and simulation results show that considerable improvement for mean excess delay, delay spread and “NP10dB” of proposed model comparing with S-V and Two-cluster model, this means the channel is better described, which mean the channel is described more precisely.