Iterative Receiver

In this paper, the problem of joint oscillator phase noise (PHN) estimation and data detection for multi-input multi-output (MIMO) systems using bit-interleaved coded modulation (BICM) is analyzed. A new MIMO receiver that iterates between the estimator and the detector, based on the expectation-maximization (EM) framework, is proposed. It is shown that at high signal-to-noise ratios, a maximum a posteriori estimator (MAP) can be used to carry out the maximization step of the EM algorithm. Moreover, to reduce the computational complexity of the proposed EM algorithm, a soft decision-directed extended Kalman filter-smoother (EKFS) is applied instead of the MAP estimator to track the PHN parameters. Numerical results show that by combining the proposed EKFS based approach with an iterative detector that employs low density parity check (LDPC) codes, PHN can be accurately tracked. Simulations also demonstrate that compared to existing algorithms, the proposed iterative receiver can significantly enhance the performance of MIMO systems in the presence of PHN.

— UWB is a new interesting technology for wireless communications. It can replace traditionally carrier-based radio transmission by pulse-based transmission using ultrawide band frequency but at a very low energy. An important aspect of research in this domain is to ...

The main objective of the multi-antenna technology is improving the capacity of cellular systems. These techniques can also make other improvements such as the scope of the system, reducing the transmission power of mobile (and therefore increasing energy autonomy) and improved link performance. This was the context of this paper study whose objective was to study the contribution and providing of the use of adaptive antennas in multiuser detection for MC-CDMA system. Transmission implicated in the MC-CDMA system has potential interference rejection but not sufficiently in the case of strong interference. Therefore it need to use beamforming algorithms. This work is also interested in MIMO-MC-CDMA with multiple-beamforming (MBF) at the receiver, that uses multiple antennas at transmitter and receiver. This paper presents also the performance of general MIMO-MC-CDMA system used Multi-Beamformer with sequences of references at receiver and space time block code (STBC) or vertical bell labs space-time architecture (V-BLAST) at the transmitter, with minimum mean square error (MMSE) adaptive algorithm under Rayleigh fading channels.

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier block modulation scheme suitable for wireless communication. OFDM has attracted a lot attention in broadband wireless systems. The use of group selected Adaptive arrays signals processing technology at both transmitter and receiver i.e. MIMO system, with OFDM can be combined to further improve the system performance. But they are relatively characterized by higher implementation complexity than simple selection diversity. It is the simplest way to realize MIMO/OFDM system but the performance improvement of this form of diversity is limited. In MIMO/OFDM system, the CSI is an important factor to impact the system capacity and should be small to improve the system efficiency. In this paper, the two techniques spatial diversity and group selected arrays signal processing are combined for MIMO/OFDM system with imperfect CSI and simulation result shows that system has significant performance improvements over the conventional array based OFDM system over frequency selective multipath fading channels.

Ultra-Wideband (UWB) is a radio transmission scheme that uses extremely low power pulses of radio energy spread across a wide spectrum of frequencies. UWB has several advantages over conventional continuous wave radio communications including potential support for high data rates, robustness to multipath interference and fading. The paper covers Ultra Wide-Band technology. General description, Challenges, various modulation schemes such as OOK, PAM, PPM, and BPSK under specified Ultra Wide Band regimes: low Power spectral density, large spreading ratio and a highly dispersive channel. The capacity and BER performance of a single user ultra wideband communication is investigated for various modulation schemes and coded, uncoded methods also simulated. Fading channel like Ricean and Rayleigh are compared. Channelized digital receiver concept is discussed.

The emergence of multiple wireless standards is introducing the need of flexible platforms which are able to selfadapt to various environments depending on the application requirements. Our work lies in the domain of self-adaptive heterogeneous multiprocessor architectures. In this paper, we present our ideas about the management of an ASIP-based multistandards iterative receiver, which includes the support for turbo-decoding. In this context, the management of a multistandards receiver provides the services for the self-adaptation mechanisms based on a collect and an analysis of information, a decision making process and a fast reconfiguration of the platform.

Known for many years but unexploited in the field of communications, ultra wideband systems (UWB) can be a solution to the saturation of the frequency bands. The advantage of such systems is that they are inexpensive in energy because of the limitations imposed by the standard. Our work is to design a high data rate IR-UWB system, through the use of modulation M-OAM (Orthogonal Amplitude Modulation), and the study of the system performances by adding the effect of the propagation channels dedicated to the UWB. The channel modeling is an important step in the implementation of any system, especially for those in development, as is the case of UWB systems. Although this model is one of the key elements of the overall chain system, it must take into account the distance between the two antennas, multipath and signal type. In this paper, we discover the existing models suitable for UWB channels and their implementation on our M-OAM system. The introduction of real channels in our chain of transmission reduces the quality of our system. Therefore, a RAKE receiver is proposed as a solution to improve performance.

Figure 1 and caption has been replaced as shown below: (a) Modulated Gaussian pulse shape (b) Modulated Monocycle pulse shape (proposed pulse) Fig. 1. PSD of transmitted UWB signals and PSD of 802.11a WLAN with a center frequency of 5.3 GHz (a) The PSD of 802.11a WLAN and the PSD of the UWB signal when using a modulated Gaussian pulse shape. (b) The PSD of 802.11a WLAN and the PSD of the UWB signal when using a modulated Monocycle pulse shape (proposed pulse).

Although Ultra Wide Band (UWB) wireless systems supposed to coexist with other spectrally overlapping (narrowband) wireless systems, mutual interference degrades the performance of both systems. In this paper we investigate two techniques for reducing this mutual interference which do not require modification of the narrowband system. We propose to shape the spectrum of the Transmitted Reference (TR)-UWB signal using wavelet based multi-resolution technique to avoid its interference to other wireless systems. The reverse (narrowband) interference is alleviated using a notch filter at UWB receiver that could have much smaller bandwidth in this Gaussian pulse-shaped multi-resolution environment. TR simulations under AWGN and multipath channel conditions show that up to 55 dB reduction of UWB RF energy is possible at the interfering IEEE 802.11a band using the wavelet spectral shaping technique. The challenge is not to exceed the specified pulse duration while shaping the spectrum. The proposed technique does not reduce the throughput of the UWB system. It is general in the sense, it can be used for the better coexistence of any narrowband wireless system with UWB system.

Novel multi-ASIP and Network-on-Chip (NoC) based flexible architecture for parallel Iterative Demapping with Turbo Decoding using Signal Space Diversity (TBICM-ID-SSD) is presented in this paper. The proposed heterogeneous multi-ASIP architecture uses multiple instances of two types of Application-Specific Instruction-set Processor (ASIP): one dedicated for turbo decoding and the second for demodulation, besides Butterfly topology based NoCs. This architecture presents novel and outstanding levels of flexibility and scalability in the design of advanced iterative receivers. It supports modulation schemes from BPSK to 256-QAM for any mapping style and supports 8 state single and double binary turbo code used in 3GPP-LTE, DVB-RCS and Wimax. FPGA prototyping results are presented and the extra hardware cost required to enable turbo demodulation is evaluated.

Impulse radio (IR) systems have drawn attention during the last few years. These systems are planned to coexist with narrowband systems without interfering them. Nevertheless, the narrowband systems can cause interference which may jam the IR receiver. This letter analyzes a low-complexity narrowband interference (NBI)-mitigation algorithm for IR systems, based on minimal mean-square error combining. Theoretical analysis reveals that these algorithms nearly eliminate the NBI. The concept is also extended to the case where the receiver has more correlators than channel taps. Index Terms-Impulse radio (IR), minimal mean-square error (MMSE), narrowband interference (NBI) suppression, ultra wideband (UWB).

— UWB is a new interesting technology for wireless communications. It can replace traditionally carrier-based radio transmission by pulse-based transmission using ultrawide band frequency but at a very low energy. An important aspect of research in this domain is to ...

Abstract—This paper demonstrates the performance of Ultra Wideband (UWB) systems in the Stochastic Tapped Delay Line (STDL) model of the UWB channel with RAKE receiver. System models are based on Direct Sequence Code Division Multiple Access (DS-CDMA) ...

We propose an explicit construction of full-diversity space-time block codes, under the constraint of an error correction capability. Furthermore, these codes are constructed in order to be suitable for a serial concatenation with an outer linear forward error correcting (FEC) code. We apply the binary rank criterion, and we use the threaded layering technique and an inner linear FEC code to define a space-time error-correcting code. When serially concatenated with an outer linear FEC code, a product code can be built at the receiver, and adapted iterative receiver structures can be applied. An optimized hybrid structure mixing MMSE turbo equalization and turbo product code decoding is proposed. It yields reduced complexity and enhanced performance compared to previous existing structures.

This paper presents brief account on smart antenna system for mobile wireless communications, the adaptive antenna techniques in future wireless systems is anticipated to have a significant clash on the more efficiently use of the spectrum, the minimum cost of establishing new wireless networks, the optimization of service quality and realization of transparent operation across multi technology wireless networks. This paper presents brief account on smart antenna system. Smart antenna can place nulls in the direction of interferers via adaptive updating of weights linked to each antenna element. Smart antenna system thus cancel out most of the co-channel interference resulting in better quality of reception and lower dropped calls. The paper explains about the radiation pattern of the antenna and why it is used in its relative field. The strength of smart antenna are easily employable to Cognitive Radio and OFDMA system.

Towards employing low complexity transceivers for signal reception in Ultra-Wideband (UWB) systems, Transmitted Reference (TR) and Differential TR (DTR) schemes have attracted researchers' attention. In this letter, we introduce an alternative, less complex scheme, called Self Reference (SR) UWB transceiver, which uses a modified replica of the received signal itself as reference pulse, resulting in double data rates compared to TR schemes. Moreover, SR eliminates the need for delay lines at the receiver side, which constitute a major drawback of the conventional TR and DTR schemes, while it also requires no channel estimations, resulting in lower complexity implementations and power savings. The performance of the SR scheme is investigated in high-frequency (HF) channels, showing that it offers a better or comparable performance to that of DTR, depending on the channel conditions.

Abstract—This paper demonstrates the performance of Ultra Wideband (UWB) systems in the Stochastic Tapped Delay Line (STDL) model of the UWB channel with RAKE receiver. System models are based on Direct Sequence Code Division Multiple Access (DS-CDMA) ...

Federal Communications Commission (FCC) guidelines on UWB spectral mask, suitable design of pulses is required to minimize the interference on other existing narrowband services due to UWB systems and vice versa. In this work, we attempt a pulse shaping method, considering the channel as a raised-cosine filter and futher optimized using genetic algorithm (GA). The pulses designed are not only meet the constraints of FCC for UWB, but also spectrally efficient. Pulses generated have a very short duration to reduce multipath interference and are mutually orthogonal. Average bit error rate (ABER) performance of time-hopping binary phase shift keying (TH-BPSK) UWB systems has been evaluated in presence of multiple access interference (MAI) and additive white Gaussian noise (AWGN) for variety of different scenarios, such as, number of users, number of slots per frame and modulation types.

Towards employing low complexity transceivers for signal reception in Ultra-Wideband (UWB) systems, Transmitted Reference (TR) and Differential TR (DTR) schemes have attracted researchers' attention. In this letter, we introduce an alternative, less complex scheme, called Self Reference (SR) UWB transceiver, which uses a modified replica of the received signal itself as reference pulse, resulting in double data rates compared to TR schemes. Moreover, SR eliminates the need for delay lines at the receiver side, which constitute a major drawback of the conventional TR and DTR schemes, while it also requires no channel estimations, resulting in lower complexity implementations and power savings. The performance of the SR scheme is investigated in high-frequency (HF) channels, showing that it offers a better or comparable performance to that of DTR, depending on the channel conditions.

Ultra wide bandwidth impulse radio occupies huge bandwidth from near DC to up to a few GHz. This suggests that many coexisting communication systems working simultaneously at different regions of impulse radio's bandwidth cause interference. In this paper, the effects of an arbitrary external interference as SNR and bit error rate degradation of multiple access UWB radio versus interference frequency is theoretically evaluated and pulse shape design for narrow band interference rejection is presented. Using doublet pulses [1], it is shown how narrow bandwidth interference is mitigated significantly. Effects of amplitude mismatches and gap time offset from the nominal value in a doublet pulse are investigated.

Nowadays, the development and improvement of the digital broadcasting techniques and video compression methods have big demand in the television and telecommunication market. In case of mobile terminals and phones the DVB-H and DVB-SH standards define the video reception. In case of the DVB-SH standard the key feature is that it is a hybrid satellite-terrestrial system that will allow using a satellite to achieve large coverage area. In this paper we survey the existing work and the general introduction about DVB-SH standard.

This paper deals with the processing techniques which are known as reconfigurable antennas: these methods are foreseen to be a booster for the future high rate wireless communications, both for the benefits in terms of performance and for the capacity gains. In particular, adaptive digital signal processing can provide improved performance for the desired signal in terms of error probability or signal-to-noise ratio while the bandwidth efficiency can be increased linearly with the number of transmitting and receiving antennas. In this article, the main antenna processing techniques are reviewed and described, aiming at highlighting performance/complexity trade-offs and how they could be implemented in the future systems. The coexistence of all these different technologies in a wireless environment requires high efficiency and flexibility of the transceiver. Future transceiver implementations which are based on the Software Defined Radio technology are also reviewed and described.

In this paper, exact signal-to-interference-plus-noise ratio (SINR) analysis of direct-sequence ultra-wideband (UWB) systems with Rake receiving in the presence of inter-symbol interference and multiple-access interference over a generalized Saleh-Valenzuela (GSV) channel with a generic pulse shaping function is provided. The SINR expression, for synchronized multiple-access, is first obtained without assuming random spreading. The GSV channel structure under consideration is a generalization of the Saleh-Valenzuela channel structure with generalized path-gain and path-arrival models, examples of which can include all the IEEE 802.15.3a UWB channel models and some of the IEEE 802.15.4a models. Then, by the novel treatment of renewal processes, the exact average SINR over the GSV channel statistics is obtained. Our analytical results well match computer simulations and can readily be applied to evaluate and improve the performance of UWB systems over realistic channel and interference models. Index Terms-Direct-sequence (DS), generalized Saleh-Valenzuela (GSV) channel, Poisson process, renewal process, signal-tointerference-plus-noise ratio (SINR), ultra-wideband (UWB). I. INTRODUCTION I NCREASING demands for higher-rate wireless communications have induced the need for more advanced communication technologies. One very promising candidate is called ultra-wideband (UWB), which is characterized as a signaling technique with ultra-wide signal bandwidth and reduced power spectral density [1]. Owing to its ultra-wide bandwidth, a UWB system has potential advantages over conventional systems, such as robustness to multipath fading, coexistence with other systems using the same band, high data rate capability, and fine time resolution [2]-[5].