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In this paper, with the purpose to exploit the space and the frequency diversity, we propose an amplify-and-forward (AAF) cooperative system using orthogonal frequency division multiplexing (OFDM) with space-frequency codes (SFC). The signal processing algorithm of this presented system is introduced in detail and we also provide the system optimal power allocation strategy. Simulation results prove that SFC based AAF cooperative system can have better performance compares with SFC based DAF system and the optimal power allocation is efficient in both SFC based AAF and DAF cooperative systems.

In this paper, we employ two novel non-linear chirp functions, arc trigonometric function and arc hyperbolic function, to construct ultra wideband (UWB) pulses and alleviate narrowband interference (NBI). The UWB systems composed of the new pulses have significant performance in suppressing the NBI. Both of them require only time domain processing for the inherent characteristics of these chirp waveforms. Simulation results show that the NBI suppression ability of the direct sequence pulse amplitude modulation (DS-PAM) UWB system with the proposed chirp waveforms can be enhanced greatly and are superior to the conventional linear chirp pulses.

In this paper, we present the space time block codes (STBC) based M-ary code-selected modulation scheme of direct sequence bipolar pulse amplitude modulation (DSBPAM) ultra wideband (UWB) system with selective Rake (SRake) receiver and maximum ratio combining (MRC) over multipath channels in order to improve the system performance and transmission rate of the conventional DS UWB system. The system bit error probability is derived and the signal processing algorithm is provided. Simulation is performed with different SRake receiver fingers over multipath channels. The results show the efficiency of the M-ary STBC based DS-BPAM UWB scheme in both system performance and transmission rate.

In this paper, we mainly analyze the performance of the classical time hopping bipolar pulse amplitude modulation (TH-BPAM) ultra wideband system and its coded system in the multi-user case. The performance of TH-BPAM system is analyzed in detail over an ideal AWGN channel and correlation receiver. For the proposed coded scheme, the Viterbi algorithm (VA) and soft output Viterbi algorithm (SOVA) are employed in the decoding process and the upper bound and lower bound of bit error probability is presented. The analysis shows that TH-BPAM suffers performance degradation with respect to the coded TH-BPAM greatly. Furthermore, we give the computer simulation and our simulation results also prove our theoretical analysis.

In this paper, based on the Alamouti space time block codes (STBC) and direct-sequence bipolar pulse amplitude modulation (DS-BPAM) ultra wideband (UWB) system, we investigate the STBC based DS-BPAM UWB system over IEEE UWB multipath fading channels. In order to make the benefits of multipath channels, SRake receiver is applied in this paper. Theoretical bit error probability of the STBC based multi-antenna DS-BPAM UWB system is derived and signal processing algorithm is provided. The system performance of the STBC based DS-BPAM UWB system is evaluated through both SRake receiver and conventional coherent receiver. The results show the efficiency of the STBC based DS-BPAM UWB system with SRake receiver over multipath fading channels.

Cognitive radio (CR) is one of the important paradigms proposed by FCC for improving the spectrum utilization. To make agile spectrum resources allocation between the primary users (PUs) and the secondary users (SUs), Orthogonal Frequency Division Multiplexing (OFDM) has been taken as one of the potential modulation candidates in the physical layer in CR. This paper presents a mathematical model for measuring the interference in the windowed OFDM systems. Additionally, we introduce a novel optimized Nyquist window approach to decrease the out-of-band radiation, such that the interference to the adjacent non-orthogonal users can be avoided. Both theoretical analysis and numerical results show the performance enhancement of the proposed scheme.

In this paper, based on the Alamouti space time block coding scheme, we propose two transmit diversity scheme of an M-ary code selected direct sequence binary phase shift keying modulation (MCSDS-BPSK) system. The performance of the MIMO M-ary DS-BPSK system is evaluated over flat Rayleigh fading channel. Different with the traditional one branch M-ary modulation scheme such as M-ary PSK, M-ary PAM, and M-ary PPM etc, the proposed system realizes the M-ary modulation through two-branch scheme. It can achieve high bit rate with acceptable system complexity while requires no increase in bandwidth. The system performance is obtained through Monte-Carlo simulation and the processing algorithm is given.

This work pays attention to the performance analysis of the conventional and encoded time hopping binary phase shift keying modulation (TH-BPSK) ultra wideband systems over multipath fading channels. In order to resist the multipath effects, selective diversity combining Rake (SRake) receiver is employed. The encoded TH-BPSK UWB system is obtained by substituting a convolutional encoder for the repetition encoder. Soft output Viterbi algorithm (SOVA) and Viterbi algorithm (VA) are employed as the decoding methods. The performance analysis shows that the coded TH-BPSK system outperforms the uncoded scheme significantly with the increase of the SRake receiver fingers. The effective order of processing gains achieved by the coded scheme is the product of the number of SRake branches and the free distance of the convolutional code.

In this paper, based on a new pulse waveform design algorithm of ultra wideband pulse (Parr et al., 2003), we employ this algorithm into a cognitive M-ary code selected direct sequence bipolar pulse amplitude modulation ultra wideband communication system. This M-ary DS-UWB system can utilize the cognitive waveform to realize the high performance and high data rate cognitive communication. The bit error rate performance of the M-ary system with the novel pulse waveform is presented in this paper. The proposed scheme can be realized under different situations with lower interference to primary wireless devices and acceptable system complexity. Further more, through the pulse design, we can also generate some good candidate waveform sets which satisfy the FCC regulation.

In this paper, a novel code selected M-ary direct sequence ultra wideband communication system is introduced. The objective is to get a high data rate UWB system by using the M-ary coded selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) scheme. In this system, a particular DS code sequence can be selected by the log2(M/2) bits from the DS code set. This scheme can obtain high data rate without increasing the system bandwidth or changing the pulse shape. With the increase of the modulation level M, the system bit error rate (BER) will be improved for the same signal energy per bit. The simulation results are provided in the condition of AWGN channel and correlation receivers.

The special scenario of the topology in the IEEE 802.16-based multi-radio heterogeneous ad hoc networks was analyzed and a novel cross layer game algorithm based on neural fuzzy connection admission controller (NFCAC) was proposed in this paper. NFCAC has been successfully applied in the control-related problems of neural networks. However, there is no discussion about the power control game algorithm and location recognition based on NFCAC in heterogeneous ad hoc networks. The proposed algorithm integrated the attributes both of NFCAC and the topology space in special scenario. The topology and the power consumption of each node can all be optimized due to the minimum link occupation with the help of the algorithm. Simulation results show that the novel algorithm can give more power control guarantee to heterogeneous ad hoc networks in the variable node loads and transmitting powers, and make the node more stable to support multi-hops at the same time.

Coexisting with other narrowband services, the performance of ultra wideband (UWB) systems will be affected considerably due to the high power of these narrow-band signals. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, we suggest a novel narrow-band interference (NBI) suppression technique based on the singular value decomposition (SVD) algorithm in multi-access time hopping UWB (TH-UWB) systems. SVD is used to approximate the NBI which then is subtracted from the received signals. Pulse amplitude modulation (PAM) and pulse position modulation (PPM) are considered. In contrast to the conventional suppression methods such as the notch filter and the maximal-ratio combining partial RAKE (MRC PRAKE) receiver, our proposed technique is simple and robust, the hardware complexity of the receiver can be reduced greatly even in the presence of multi-access interference (MAI).

In this paper, we consider an M-ary code selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) ultra wideband system. The system performance and analysis over realistic IEEE UWB multipath fading channels are evaluated in the condition of perfect time synchronization and selective diversity combining Rake (SRake) receiver. In the transmitter, a particular DS code sequence can be selected by the log 2 (M/2) bits from the DS code set. The corresponding SRake receiver structure is designed according to the transmitter. This scheme can improve the system performance and increase the data rate by a factor log 2 (M/2) compared with the conventional DS-BPAM UWB system. With the increase of the modulation level M and the SRake fingers, the system performance can be improved for the same signal energy per bit.

In this paper, a novel frequency coded orthogonal UWB pulse design method based on orthogonal carriers and PN (pseudo noise) sequence is presented. The basic idea of the new approach is that the frequency-shifted sub-pulses are used to generate the orthogonal pulses by coding with PN sequence in frequency domain. Because the orthogonal carriers and PN codes are introduced into IR-UWB (impulse radio UWB), the new method not only has the advantages of both the traditional IR-UWB and multi-banded CB-UWB (carrier based UWB), but also improves the efficiency of the instantaneous spectrum and energy of the transmitting UWB signal. Furthermore, the Auto-correlation and cross-correlation characteristic of the proposed pulses are better than those of other conventional pulses. In addition, by the aid of cognitive radio technology, it is can be guaranteed the transmitting signal in accordance with FCC spectral mask and coexistence, interference avoidance with other traditional narrow band system. And simulation result showed that the proposed pulse could reduce the effect of narrow band interference on UWB system with litter complexity.

Summary In this paper, an opportunistic relaying-based incremental hybrid decode-amplify-forward (OR-IHDAF) scheme that combines robust protocol switch with efficient relay selection is proposed in multi-relay scenario to cope with the complex and variable channel environments. The proposed OR-IHDAF scheme can improve the system performance significantly compared with the incremental hybrid decode-amplify-forward protocol with the increase of the possible candidate relay nodes and opportunistic relay selection. The analytical expression of the system outage probability of the OR-IHDAF scheme is presented based on the probability density function and cumulative distribution function, which might be useful to avoid lengthy simulations. Numerical results show the correctness of our theoretical analysis and the performance improvement of the OR-IHDAF scheme compared with the other current hybrid cooperative protocols and OR-based cooperative schemes. The effects of the power allocation schemes on the outage probability are also provided. Copyright © 2015 John Wiley & Sons, Ltd.

Narrow-band interference (NBI) from the coexisting narrowband services affects the performance of ultra-wideband (UWB) systems considerably due to the high power of these narrow-band signals with respect to the UWB signals. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, we suggest a novel NBI suppression technique based on singular value decomposition (SVD) algorithm in time hopping pulse amplitude modulation UWB (TH-PAM UWB) systems. SVD is used to approximate the interferences which then are subtracted from the received signals. The algorithm precision and closed-form bit error rate (BER) expression are derived in wireless multipath channel. By comparing our algorithm with the conventional suppression methods such as notch filter and RAKE receiver, we could conclude that the proposed method is simple and robust, it is especially suitable for UWB systems.

Ultra-wide band impulse radio (UWB-IR) transmits data using sub-nanosecond baseband pulses with very low duty cycle. Due to the short duration of the impulse signal, very precise synchronization control is vital for the whole system. In this paper, an improved delay-locked loop (DLL) is introduced to the TH UWB-IR system. Instead of using only two central correlator branches in the DLL, more correlator branches with different delay parameters and different weight parameters are added to the conventional DLL. Lower tracking jitter and higher mean time to lose lock (MTLL) than the conventional systems can be achieved from proposed ones. Performance of DLLs with several different combinations of correlator parameters are evaluated in this paper and some of them outperform the conventional ones.

Considering the spectrum characteristics of the UWB carrier envelope modulation (CEM) scheme, a novel orthogonal comb frequency-band correlation demodulation method is presented in this paper. In order to satisfy the condition of orthogonal comb frequency spectrum, the carrier frequency selection criteria is also derived. A possible implementation of the novel demodulation receiver by using surface acoustic-wave (SAW) models is presented, and general expressions for the system performance are obtained. The performance analysis and simulation results not only show the feasibility of the new demodulation scheme, but also prove that it has the same performance as the demodulation method in time domain. Comparing with the comber filter demodulation scheme in time domain, the new demodulation scheme has simpler structure, and can be implemented by all digital circuits without RF comber filters.

Coexisting with many concurrent narrowband services, the performance of UWB systems will be affected considerably by them due to the high power of these narrow-band signals with respect to the UWB signals. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, a novel narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm for two UWB systems is presented. The two systems are direct sequence ultra-wideband (DS-UWB) system and timing hopping (TH) binary pulse amplitude modulation (PAM) UWB system. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Simulation results show that the proposed new technique is very effective.

The performance of two direct sequence ultra wideband (DS-UWB) communication systems is investigated. The first system is the classic DS-UWB system. The second is obtained by adding a forward error control codes (FEC), convolutional code. For the two systems, binary pulse amplitude modulation is applied. The performance of these two systems is analyzed in detail under AWGN channel. In our proposed coded scheme, we use soft output Viterbi algorithm (SOVA). The analysis shows that the coded DS-UWB system outperforms the DS-UWB system significantly, or more importantly, at a given bit error rate, the coding scheme increases the number of users by a factor which is logarithmic in the number of pulses used in DS UWB systems. Simulation results on the bit error rate of the proposed system indicates that the system is capable to work in lower SNR's and therefore supports higher data transmission rates compared to the previously proposed UWB communication systems.

Operating around 5 GHz, IEEE 802.11a systems overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, a novel narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm is presented in direct sequence ultra-wideband (DS-UWB) system. SVD is used to approximate the interferences which then are subtracted from the received signals. By comparing our algorithm with the conventional suppression methods such as notch filter and maximal-ratio combining Partial RAKE (MRC PRAKE) receiver, we could conclude that our technique is very effective.

A modified M-ary time hopping pulse position modulation (TH-PPM) ultra wideband communication system is proposed in this paper. The system performance over additive white Gaussian noise (AWGN) channel is evaluated in the condition of perfect time synchronization and correlation receiver. In this system, the modified M-ary modulation is obtained by combining signal partitioning with the pulse position modulation. Three signal partitioning, Ungerboeck Partitioning (UP), Block Partitioning (BP) and Mixed Partitioning (MP), are investigated in this work. The modified scheme can make no increment in system complexity compared to the conventional M-ary time hopping pulse position modulation. To some extent, it can improve the system performance. The computer simulation and analysis shows that the modified M-ary TH-PPM system outperforms the conventional M-ary TH-PPM system.

Ultra-wide band impulse radio (UWB-IR) transmits data using sub-nanosecond baseband pulses with very low duty cycle. It is a promising candidate for short-range communications. However, due to the short duration of the impulse signal, very precise synchronization control is vital for the whole system. In this paper, an improved delay-locked loop (DLL) is introduced to the UWB-IR system with time hopping/spread spectrum (TH/SS). Instead of using only two central correlator branches in the DLL, more correlator branches with different delay parameters and different weight parameters are added to the conventional DLL. Lower tracking jitter and higher mean time to lose lock (MTLL) than the conventional systems can be achieved from proposed ones. Performance of several different combinations of correlator parameters are evaluated in this paper and some of them perform superior to that of the conventional DLLs

The performance of two direct sequence ultra wideband (DS-UWB) communication systems is investigated. The first system is the classic DS-UWB system. The second is our proposed coded DS-UWB system, obtained by adding a forward error correcting codes (FEC), namely convolutional code. In our coded scheme, we use two decoding strategies, one is Viterbi Algorithm, and the other is soft output Viterbi algorithm (SOVA). For the two systems, binary pulse amplitude modulation is applied. The performance of these two systems is analyzed in detail under AWGN channel. The analysis shows that the coded DS-UWB system outperforms the DS-UWB system significantly and the SOVA scheme is much better than the VA scheme. Simulation results on the bit error rate of the proposed system indicates that the coded scheme is capable to work in lower SNR and therefore supports higher data transmission rates compared to the previously proposed UWB communication systems.

In this paper, a novel multiple narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm is presented. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Three UWB systems are considered and simulation results show that the proposed new technique is very effective.

Ultra wideband (UWB) is a kind of wireless communication system which can perform high data rate with nano-second pulses of baseband, and has recently received much attention for short-range applications. Thus a high sensitivity of timing synchronization between modulation and demodulation is required. Timing synchronization error named timing jitter between transmitter and receiver has been introduced and their properties have been analyzed in some papers. However, there are not many methods brought forward to improve the system performance in the scenarios that deteriorated jitter existents. We consider this problem and offer a method to resist the adverse effect by timing jitter to the whole system by adopting a new designed correlator reference signal in UWB receiver. This reference signal is formed corresponding to the timing jitter distribution of the received pulses waveforms to increase the jitter robust performance. From the simulation results of different UWB modulation systems, better performance can be achieved by adopting this reference signal in the receiver than the conventional schemes.

In this paper, our purpose is to get an analytical method for calculating the average probability of bit error of direct sequence ultra wideband (DS-UWB) communication system. In this multiple access DS UWB system, the bipolar pulse amplitude modulation is used in order to achieve better performance. As we know, more attention is paid to the time hopping pulse position modulation (TH-PPM) UWB systems recently. In this paper, we first introduce the accurate BER calculation method of this multiuser DS-BPAM UWB system and then give the performance analysis over an ideal AWGN channel and a correlation receiver. Furthermore, we also introduce its application in both image transmission and data transmission. The analytical method yields simple and exact formulas relating the performance to the system parameters.

In this paper, the time-frequency characteristics of IR-UWB signal is analyzed and concluded by using short-time Fourier transform (STFT). According to the time-frequency characteristic of IR-UWB signal, a novel UWB modulation and demodulation method based on the time-frequency energy distribution is presented. This novel modulation method has very good antinoise performance in AWGN environment.

This paper investigates the performance of two direct sequence ultra wideband (DS-UWB) communication systems over multipath fading channels. The first system is the classic DS-UWB system and the second is obtained by adding a forward error control code (FEC), convolutional code. For the two systems, bipolar pulse amplitude modulation (BPAM) is applied. In the receiver end, the selective diversity combining receiver-SRake receiver is used as a feasible receiver. In the proposed coded scheme, we use soft output Viterbi algorithm (SOVA). The analysis shows that the coded DS-UWB system outperforms the conventional DS-UWB system significantly with the increase of the SRake fingers. The effective order of processing gains achieved by the coded scheme is the product of the number of SRake branches and the free distance of the code applied

In this paper, we mainly analyze the performance of the classical Time Hopping Bipolar Pulse Amplitude Modulation (TH-BPAM) UWB system and the coded TH-BPAM system in the multi-user case. The performance of TH-BPAM system is analyzed in detail over an ideal AWGN channel and correlation receiver. For the proposed coded scheme, the Viterbi algorithm (VA) and soft output Viterbi algorithm (SOVA) are employed in the decoding process and the upper bound and lower bound of bit error probability is presented. The analysis shows that TH-BPAM suffers performance degradation with respect to the coded TH-BPAM greatly. Furthermore, we give the computer simulation and our simulation results also prove our theoretical analysis.

In this paper, we mainly analyze the performance of two ultra wideband communication systems, the classical time hopping pulse amplitude modulation (TH-PAM) UWB system and the coded TH-PAM UWB system. We employed the binary anti-polar amplitude modulation in these two systems. The performance of TH-PAM is analyzed in detail under an ideal AWGN channel and a correlation receiver. For our proposed coded scheme, we use soft output Viterbi algorithm (SOVA) in the decoder and the upper bound and lower bound of bit error probability is presented. The analysis shows that TH-PAM suffers performance degradation with respect to the coded TH-PAM. Furthermore, we give the computer simulation and our simulation results also prove our theoretical analysis.

In this paper, based on the characteristics of turbo codes and trellis coded modulation (TCM), an improved method turbo trellis coded modulation (TTCM) is presented and using it in still image transmission is also analyzed over Rayleigh fading channel. We use two mapping strategies of TTCM in Rayleigh fading channels UP (ungerboeck partitioning) and BP (block partitioning). Furthermore, taking 8 PSK modulation of turbo TCM as the example, two performance of image transmission in Rayleigh fading channels is showed.