Mário Marques da Silva

Joint multi‐user detection and intersymbol interference cancellation for WCDMA satellite UMTS

In this work we present two different intersymbol interference (ISI) cancellation systems, namely the commutation signaling (CS) and orthogonal code-division transmit diversity (O-CDTD) in combination with satellite path diversity, which leads to a high diversity order. The ISI is due to the use of satellite path diversity (in order to introduce multipath diversity artificially). This work combines the proposed ISI cancellation systems with subtractive multi-user detectors—a variation of the conventional parallel interference cancellation (PIC) and successive interference cancellation (SIC) for the downlink channel of S-UMTS. The blind detection is also considered without knowledge of spreading sequences or the channel state information (CSI) of the interfering users with a noise whitening matched filter (NWMF) that combats the MAI through the whitening of the interfering power spectrum, also with and without the ISI cancellation systems—CS and O-CDTD. It is shown that the proposed PIC is a very promising detector to be used for the downlink of S-UMTS, especially when combined with CS or O-CDTD, the NWMF being efficient only when we consider jointly any of the proposed ISI cancellation systems for low number of interfering users. Copyright

On transmission techniques for multi-antenna W-CDMA systems

In this paper we present and evaluate a new pre-processing scheme for Multiple Input Multiple Output (MIMO) channels. Its performance is compared with other MIMO schemes proposed for the downlink of Wideband-Code Division Multiple Access (W-CDMA) systems, namely a variation of the Beam Forming (BF), entitled Beam-Selective Transmit Diversity (BSTD) or post-processing schemes, such as the Alamouti-like MIMO or the Vertical Bell Laboratories Layered Space-Time (V-BLAST) MIMO scheme. It is assumed that the Base Station (BS) has M ⩾ 2 transmit antennas and the Mobile Station (MS) receiver has space enough to accommodate N = 2 uncorrelated receive antennas. It is shown that the proposed pre-processing scheme allows receivers with very low complexity, contrarily to the case where a post-processing approach is followed, simplifying the MS receiver. Therefore, the proposed M × N MIMO pre-processing scheme can be seen as an alternative to post-processing schemes. It is also shown that the pre-processing scheme for MIMO channels tends to achieve the best performance in most scenarios, being followed by the BSTD, which allows interference cancellation and provides diversity. Copyright

Transmission Techniques for 4G Systems

Fourth Generation (4G) wireless communication systems support current and emergent multimedia services such as mobile TV, social networks and gaming, high-definition TV, video teleconferencing, and messaging services. These systems feature the All-over-IP concept and boast improved quality of service. Several important R&D activities are currently under way in the field of wireless communications for 4G systems, but the coverage is widespread in the literature. Transmission Techniques for 4G Systems presents a compilation of the latest developments in the field of wireless communications for 4G systems, including evolved Multimedia Broadcast and Multicast Service (eMBMS). Topics include: Transmission schemes suitable for future broadband wireless systems Advances in transmission techniques and receiver design to support emergent wireless needs for 4G requirements Multiple-Input Multiple-Output (MIMO), base station cooperation, macro-diversity, and inter-cell interference cancellation Multihop relay techniques, hierarchical constellations, and multi-resolution techniques Advances using block transmission techniques for different propagation and multi-user environments System-level evaluation of 4G using different transmission techniques Exploring the key requirements of emergent services, this volume provides fundamentals and theory along with transmission and detection techniques and schemes transversal to many digital communication systemsincluding wireless, cellular, and satellite. If youre interested in or involved with 4G multimedia systems, this is the book you need on the latest R&D wireless activities so you can plan, design, and develop prototypes and future systems.

Iterative frequency‐domain detection and channel estimation for space–time block codes

In this paper, we consider iterative frequency-domain receivers for block transmission techniques with rate-1 space–time block coding (STBC) for two or four transmit antennas. Single carrier with frequency-domain equalisation (SC-FDE) combined with antenna diversity is a promising candidate for future broadband wireless systems. Because our STBC with four transmit antennas is not orthogonal, our receiver includes the cancellation of the residual interference, allowing performances close to the ones of an orthogonal code. We propose an iterative STBC receiver that considers an iterative detection and channel estimation. The channel estimates usually obtained with the help of pilot symbols and/or training sequences are multiplexed with data symbols. Because this leads to spectral degradation, the use of superimposed pilots (i.e. pilots added to data) was recently proposed as an efficient alternative. Our performance results show that the proposed SC-FDE STBC receiver allows excellent performance with the use of the channel data obtained from the channel estimation. Copyright

Iterative Frequency-Domain Receivers for STBC Schemes

In this paper, we consider iterative frequency- domain receivers for block transmission techniques with rate-1 Space Time Block Coding (STBC) for two or four transmit antennas. We consider both Orthogonal Frequency Division Multiplexing (OFDM) and Single- Carrier (SC) schemes. Since our STBC with 4 transmit antennas is not orthogonal, our receiver includes the cancellation of the residual interference, allowing performances close to the ones of an orthogonal code. Our performance results show that combining STBC with block transmission schemes allows excellent performances, even for channels with small multipath diversity.

MAI cancellation with commutation signaling

This paper deals with PIC-parallel interference cancellation with and without the ISI cancellation system-commutation signaling (CS), in a deep Rayleigh fading environment, time and frequency selective, assuming the spreading sequences and the features of the channels of the several interfering users is known. It is proved that PIC lead to good profits especially when the CS technique is used together, because these systems subtract the MAI estimated for each user. These estimates improve when the ISI is cancelled, since the MAI estimated depends upon the estimate of the transmitted symbols by each interfering user. Additionally, it considers the blind detection (without knowledge of spreading sequences nor the features of the channels of the interfering users) with a noise whitening matched filter (NWMF) that combats the MAI through the whitening of the interfering power spectrum (following the single-user philosophy).

Multi-user detector schemes for the UMTS uplink transmission

This paper focuses on performance results obtained using multi-user detector (MUD) techniques for the Universal Mobile Telephony System (UMTS) uplink transmission. Both parallel interference cancellation (PIC) and successive interference cancellation (SIC) schemes are studied and compared. Factors such as the number of iterations, decision method (hard/soft/clipped), type of service (64/144 kbit/s) and number of simultaneous users are analyzed, for the main UMTS channels (indoor A, pedestrian A, vehicular A), in order to quantify the performance gain of each combination, and decide what schemes yield the least amount of errors under which conditions. Bit and block error rate (BER and BLER respectively) results obtained via simulation are presented and discussed.

On the Multi-Resolution Techniques for LTE-Advanced

A coordinated multi-resolution and multi-point MIMO transmission method for the LTE-Advanced is presented considering the Evolved-Multimedia Broadcast/Multicast Service (E-MBMS). Fixed relays with MIMO and different adaptive frequency reuse schemes are considered in the proposed scheme to improve the E-MBMS spectral efficiency at the cell borders and/or to save transmission power from the base stations and relays. In order to provide additional diversity over Rayleigh multi-path fading channels, a signal space diversity based on Complex Rotation Matrices (CRM) is used, associated to MIMO, as a multi-resolution technique. The decoding of these signals are facilitated with the use of Maximum Likelihood Soft Output (MLSO) criterion, included in the proposed receiver. The link performance of the MIMO system turbo-coded with hierarchical constellations and CRM is analyzed in terms of bit and block error rate (BER/BLER). The corresponding system level coverage and throughput gains are also evaluated associated to the presence or not of fixed relays and measuring the maximum spectral efficiencies at cell borders of single cell point-to-multipoint or single frequency network. The influence of the cell radius in the performance of the previous cellular topologies with coordinated MIMO transmissions is also evaluated.

Frequency-Domain Receivers for Rate-1 Space-Time Block Codes

This paper considers iterative frequency-domain receivers for block transmission techniques with rate-1 Space Time Block Coding (STBC) for two and four transmit antennas using both Orthogonal Frequency Division Multiplexing (OFDM) and Single-Carrier (SC) schemes. The proposed receiver includes an interference canceller which enhances the performance of the non-orthogonal STBC scheme with 4 transmit antennas, allowing performances close to those of orthogonal codes. Our performance results show that combining STBC with block transmission techniques allows excellent performances.

A predistortion filtering for MAI reduction with selective transmit diversity

The purpose of the current work is to analyze several schemes to combat both the MAI and fading, in the downlink direction. We propose a new predistortion (PD) filtering technique, which can be used to combat the multiple access interference (MAI), combined the selective transmit diversity (STD) for high data rate transmissions over frequency selective Rayleigh fading channels. The proposed PD scheme considers a Rake in the receiver. By predistorting the signals to be transmitted by the base station (BS) with a minimum variance (MV) algorithm, the orthogonality between the desired signal and all interfering signals can be improved. With the PD, the increase in performance is achieved with a small increase in power processing at the BS, avoiding any need to increase complexity at the mobile station (MS).