Ultra-wideband systems with orthogonal coded differential TR receiver

In this paper, a coded M-ary pulse position modulation (PPM) scheme for transmitted reference ultra-wideband (TR-UWB) systems is proposed. In conventional M-ary PPM TR-UWB scheme, modulation level M is defined only with a number of possible pulse positions Z. So, Z radio frequency (RF) wideband delay lines are required in order to map data bits into the proper pulse position, which makes such system very impractical to implement when the current CMOS technology is used. In the proposed scheme the number of required delay lines is reduced by mapping data bits in both, pulse position and K different orthogonal codes on frame level of the signal, producing a modulation level of M = KZ. To evaluate the performances of the proposed coded M-ary PPM scheme, the analytical model for realistic IEEE standard UWB channel models is developed. The performances of the proposed scheme are compared with these of the conventional M-ary PPM scheme for the same modulation level M. The results show that the proposed coded M-ary PPM scheme achieves approximately the same bit error probability (BEP), higher data rate and higher bandwidth efficiency, while the hardware complexity is lower in terms of number of required RF delay lines. However, by increasing the number of used orthogonal codes the minimum number of frames per one information symbol rises and consequently the maximum achievable data rate is limited. Thus the trade-off between the number of orthogonal codes and target data rate should be made. DOI: http://dx.doi.org/10.5755/j01.eee.20.10.6797

In recent years, conveying information using molecules via diffusion has attracted significant interest in micro and nanoscale applications. Yet, very little research have been conducted on the performance analysis of large-scale molecular communication (MC) systems with swarm of interfering receivers. In this type of MC system, the collective signal strength at a desired receiver can be impaired by the interference caused by other MC transmitters. The paper presents the first tractable analytical framework for the collective signal strength at a partially absorbing receiver due to a desired transmitter under the impact of a swarm of interfering transmitters in a three-dimensional (3D) large-scale MC system using stochastic geometry. We propose Reed Solomon (RS) coding as an error correction technique to combat the effects of interference caused by the multiple transmitters and the delayed molecules from the previous bits. We derive analytical expressions for the bit error probability (BEP) to evaluate the level of reliability that can be achieved by the proposed scheme. The results obtained using Monte Carlo simulations, matched extactly with the anlytical results, justifying the accuracy of the derivations. Results reveal that the RS codes are capable of providing an acceptable level of improvement in terms of BEP. Furthermore, by carefully selecting the code length, n, and the message length, k, of the RS(n, k) code, we can fine tune the BEP improvement to match the system requirements.

In this paper, a new scheme, named after parallel quadrature index modulation (PQIM) with transmit diversity, is proposed to not only greatly increase the spectral efficiency but also achieve the transmit diversity gain for improving the bit error rate performance. Specifically, the total number of transmit antennas is grouped into multiple groups. For each group, in the in-phase dimension, two components of a three dimension (3D) constellation symbol are modulated on two active transmit antennas; in the quadrature dimension, the remaining one component of the 3D constellation symbol is modulated on only one active transmit antenna. Then, for achieving the diversity gain, each group of transmit antennas modulates an identical 3D symbol. Furthermore, the average bit error probability (BEP) is analyzed. Simulation results demonstrate the proposed PQIM outperforms other schemes in terms of BEP in wireless communication.

We consider the bit error performance of orthogonal space-time block codes (STBC) over independent, non- identically distributed, Rayleigh/Ricean, block fading channels with perfect channel state information. With symbol-by-symbol detection, we derive the expressions for the exact bit error probability (BEP) in both Rayleigh and Ricean fading channels. The results are applicable to any number of transmit and receive antennas for which orthogonal STBC's are defined. A simple but insightful upper bound on the BEP is also obtained. From the expressions of the BEP, we find that in Rayleigh channels, the nonidentical distributions degrade the performance. However, for Ricean case, the nonidentical distributions can have different effects on the performance.

An efficient network is critical to support the rapid growth in traffic on mobile networks, since current network PCS1900 (2G) cannot support such a huge demand. The objective of the third-generation (3G) UMTS (Universal Mobile Telecommunication System) of wireless communication is to provide high speed wireless communication to support multimedia, large data, and video. However, the co-existence of the two mobile radio systems (PCS1900 and UMTS) which share the same frequency band leads to a major issue. A serious issue of co-existence occurs when the downlink of the system is closer to the frequency bands of the concerned system. The PCS-1900 downlink band (1,930-1,990) and WCDMA (UMTS) uplink band (1,920-1,980) widely overlap, which causes interference between UMTS mobile unit and PCS-1900 base station. Therefore the objectives of this paper is to study the effect from PCS 1900 base station interference on UMTS mobile unit performance in terms of the probability of bit error by developing the Probability of bit error equation of DSS-QPSK from the existing Probability of bit error equation. This paper also evaluates the degradation of UMTS mobile unit performance in terms of probability of bit error when the system is interfered by PCS1900 base station.

In diffusion-based communication, as for molecular systems, the achievable data rate is low due to the stochastic nature of diffusion which exhibits a severe inter-symbol-interference (ISI). Multiple-Input Multiple-Output (MIMO) multiplexing improves the data rate at the expense of an inter-link interference (ILI). This paper investigates training-based channel estimation schemes for diffusive MIMO (D-MIMO) systems and corresponding equalization methods. Maximum likelihood and least-squares estimators of mean channel are derived, and the training sequence is designed to minimize the mean square error (MSE). Numerical validations in terms of MSE are compared with Cramer-Rao bound derived herein. Equalization is based on decision feedback equalizer (DFE) structure as this is effective in mitigating diffusive ISI/ILI. Zero-forcing, minimum MSE and least-squares criteria have been paired to DFE, and their performances are evaluated in terms of bit error probability. Since D-MIMO systems are severely affected by the ILI because of short transmitters inter-distance, D-MIMO time interleaving is exploited as countermeasure to mitigate the ILI with remarkable performance improvements. The feasibility of a block-type communication including training and data equalization is explored for D-MIMO, and system-level performances are numerically derived.

We study the performance of differential orthogonal space-time block codes over independent and semi-identically distributed Rayleigh fading channels. In this semi-identically distributed fading model, the channel gains from different transmit antennas to a common receive antenna are identically distributed, but the gains associated with different receive antennas are non-identically distributed. Arbitrary fluctuation rates of the fading processes from one transmission block to another are considered. We first derive the optimal symbol-by-symbol differential detector, and show that the conventional differential detector is suboptimal. We then derive expressions of exact bit error probabilities (BEP) for both the optimal and suboptimal detectors. The results are applicable for any number of receive antennas and any number of transmit antennas for which orthogonal space-time block codes exist. For two transmit antennas, explicit and closed-form BEP expressions are obtained. A Chernoff bound on the BEP of optimal detection for any number of transmit antennas is also derived.

Cooperative sensing (CS) is important for efficiently acquiring spectrum awareness in cognitive radio systems. The main focus of this paper is on the BEP (bit error probability) walls for soft decision (SD) based CS in cognitive radios. The BEP wall is a performance limitation for CS caused by imperfect reporting channels. In this paper, a distributed detection system using parallel sensing topology and a fusion center (FC) is considered. Each secondary user (SU) sends energy-based multibit SD to the FC over a reporting channel with a certain BEP. The maximum output entropy (MOE) quantization is considered for quantizing the estimated energy. For the considered case, it is established that the BEP wall values for SD based CS with MOE quantization are identical for arbitrary number of bits for quantization. Moreover, the BEP wall values for SD based CS with MOE quantization are proven to be the same as the BEP wall values for the Chair-Varshney fusion rule, which is an optimal fusion rule for one-bit hard decision based CS. Later relation between the BEP wall values of the SD based CS and the K-out-of-N fusion rules is also established.

We propose a low-complexity iterative multiuser receiver for turbo-coded DS-CDMA systems. The proposed iterative multiuser receiver consists of a modified decorrelating decision-feedback detector (MDDFD) and K single-user turbo decoders, where K is the number of CDMA users. The MDDFD is derived on the basis of maximizing a likelihood probability and has the feature that it uses the reliability information from turbo-decoder output. In addition, the MDDFD delivers interference-cancelled soft-outputs to the turbo decoders where transition metrics calculations are appropriately modified. Both performance analysis and computer simulation results have indicated that the reliability information from turbo-decoder output can enhance the multiuser detection capability of the MDDFD. Computer simulations have shown that the proposed iterative multiuser receiver significantly outperforms the conventional DDFD-based multiuser receiver in terms of bit error probability.

기존의 웨이브릿 편이 변조 시스템은 스케일링 함수(scaling function)를 1로, 웨이브릿(wavelet)을 0으로 하는 1비트 변조방법이 있고, 스케일링 함수와 웨이브릿 그리고 이 두 신호를 반전시켜서 생성된 4개의 반송파를 사용하는 2비트 변조방법이 있다. 본 논문에서는 2비트 변조방법인 4-ary 스케일링 웨이브릿 편이변조(4-ary SWSK : 4-ary scaling wavelet shift keying) 시스템을 정의하고, QPSK 시스템으로부터 정의된 시스템의 비트 에러 확률과 부호 에러 확률을 유도한다. 제안한 4-ary SWSK 성능을 분석하기 위하여, 기존의 QPSK(quadrature phase shift keying), MFSK(M-ary frequency shift keying), 그리고 제안한 방법의 비트 에러 확률 및 부호 에러 확률을 구한다. 실험결과 제안한 방법의 비트 에러 확률과 부호 에러 확률이 좋은 성능을 보였다. An algorithm of the conventional wavelet shift keying is carried out that the scaling function and wavelet are encoded to 1(mark) and 0(space) for the input binary data, respectively. Two bit modulation technique which uses four carrier frequencies is existed. Four carrier frequencies are defined as scaling function, inversed scaling function, wavelet, and inversed wavelet, which are encoded to 10, 11, 00 and 01, respectively. In this paper, we defined 4-ary SWSK (4-ary scaling wavelet shift keying) which is two bit modulation, and it is derived to the probability of bit error and symbol error of the defined system from QPSK. In order to analyze to the performance of 4-ary SWSK, we are obtained in terms of the probability of bit error and symbol error for QPSK (quadrature phase shift keying), MFSK(M-ary frequency shift keying) and proposed method. As a results of simulation, we confirmed that the proposed method was superior to the performance in terms of the probability of bit error and symbol error.

It is well known that the performance of the wireless communication systems can be enhanced by using multiple transmit and receive antennas, which is generally referred to as the MIMO technique, and has been incorporated into the IEEE 802.11n standard, i.e. one of the Wi-Fi systems. The MIMO technique has also been adopted by the 3GPP Long Term Evolution (LTE) and the 3GPP2 Ultra Mobile Broadband (UMB) standards. The space-time coding is a promising way to realize the gain in the wireless communications system using MIMO. The space time block code, and the orthogonal space time block code in particular have been proposed in research and implemented in practical wireless communication systems due to their low computational complexity in maximum likelihood decoding implementation. However, the code rates of the orthogonal space time block codes are usually lower than $3/4$ when the number of transmit antennas is greater than two, which limit their throughput. To increase the code rate and the throughput of the orthogonal space time block code for more than two transmit antennas, a family of new space-time block codes (STBC) for 3 and 4 transmit antennas in a MIMO wireless communication system have been proposed in this Ph.D. research. These new codes are orthogonal and achieve full diversity, full rate using Triple QPSK'' modulation, which is proposed in this research. We investigated the performance of these STBCs when the channel state information (CSI) is perfectly known at the receiver. The CSI is not known to the transmitter in all of the studies in this dissertation. An analytical bound of the probability of bit error is developed and the Monte Carlo simulation is used when investigating these new STBC codes. In practical wireless communication system, the CSI is generally not available at the receiver and it is usually estimated by the receiver through the pilot signals or training signals known to the receiver. No matter what channel estimation method is used, the estimate of CSI will not match the CSI exactly and is noisy. The performance of these new STBCs using theTriple QPSK'' modulation when the estimate of the CSI is employed to detect the symbol is investigated in this dissertation. An upper bound of the bit error probability is developed when the noisy CSI is used to detect the symbols. The performance of the new STBCs using the Triple QPSK'' modulation is also evaluated using Monte Carlo simulation. When the CSI is not available to either the receiver or the transmitter, the differential encoding and decoding algorithm is applied to these new STBCs, which use theTriple QPSK'' modulation. The results showed that these orthogonal STBCs achieve full diversity full rate using ""Triple-QPSK"" modulation with differential detection. This provides a means of achieving space diversity and multiplexing gain without the CSI. A new differential encoding and decoding algorithm is proposed and analyzed for STBCs with 3 transmit antennas, whose transmission matrix is not square matrix, as part of this Ph.D. research. The STBCs using this algorithm achieve full diversity the MIMO system can possibly provide.

The main aim of wireless network designer is to minimize the wasting of channel resources. In regular cooperative Decode-and-Forward (DF) systems, relays forward source signals to the destination regardless of channel conditions which constitute a significant loss in radio resources. To overcome this drawback, incremental relaying was proposed in which the destination decides after receiving a source signal to decode it or to request the help of a relay. In this paper, we analyze the performances of an incremental Multiple Input Multiple Output (MIMO) DF relaying based on an Orthogonal Space Time Block Code (OSTBC) where all transmissions are done over independent identically distributed Rayleigh fading channels. We derive closed-form expressions of the Bit Error Probability (BEP) at the destination. We provide a study on the effect of the signal to noise ratio (SNR) threshold and the relay's positions on the system performances. The obtained results show that an incremental cooperative MIMO system offers better performances compared with an incremental cooperative SISO one.

We analyze the average bit error probability (BEP) of orthogonal space-time block codes (STBC) over time-selective channels. Exact BEP results are obtained in closed form. Through the analysis, we reveal the relationship between the inter-symbol interference (ISI) and the row positions in a STBC matrix. We then introduce one proposition and two design criteria for code search/design. Optimum/near-optimum codes are found/designed with reduced ISI.

An analytical derivation of the probability of bit error noncoherent frequency-shift keying (FSK) and coherent phase-shift keying (PSK) signals transmitted through a land-mobile satellite channel is described. The channel characteristics used in the analysis are based on a recently developed model which includes the combined effects of fading and shadowing. Analytical expressions for the probability of bit error of FSK and coherent phase-shift keying (CPSK) signals are obtained. The results show that large amounts of signal-to-noise ratio (SNR) are required to compensate for the combined effect of fading and shadowing. An analytical expression for the irreducible probability of bit error of a CPSK signal due to phase variations caused by fading and shadowing is derived. The results described should be useful in the design of land mobile satellite communication systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In the article, a new topical scientific task is solved regarding the assessment of the impact of the error of the synchronization system of the coherent demodulator on the immunity of signals with multi-position phase manipulation. The probability of a bit error is proposed in the article as a criterion for evaluating the immunity of coherent reception of signals with multi-position phase modulation in the presence of a phase error. A model for evaluating the effect of the error of the coherent demodulator synchronization system on the bit error probabilities of signals with multi-position phase manipulation is developed and presented. The presented model is based on the probabilistic characteristics of the appearance of a bit error of a signal with multi-positional phase modulation relative to the accepted level of the phase error of the coherent demodulator at different values of the signal-to-noise ratio at the input of the coherent receiver for signals with different positions. The results of the evaluation of the probability characteristics of the appearance of a bit error in a signal with multi-positional phase modulation in the presence of a phase error of a coherent demodulator showed that with an increase in the positionality of the BFM signal, the influence of static and random errors of the synchronization system on the probability of bit errors increases. At large signal-to-noise ratios, a small phase estimation error, from π/180 to π/90, leads to a significant increase in the probability of bit errors. With random phase fluctuations for signals with M ≥ 4, when the variance Dϕ changes from 0 to 0.01, the error probability can be changed by one or two orders of magnitude. The obtained results allow us to come to the conclusion that during the reception of BFM signals, the permissible value of the carrier phase estimation error depends on the positionality of M and varies from π/36 – π/72 for 2-FM to π/180 for 32-FM.