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This paper analyzes the influence of time-varying cyclic delay diversity (TV-CDD) on the channel fading correlation properties in orthogonal frequency division multiplexing (OFDM) based systems. The underlying transmit diversity technique CDD only increases the frequency diversity at the receiver. In contrast, TV-CDD introduces additionally time di...
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Citations
... Furthermore, many multiple antenna technologies require processing at both transmitter and receiver [23,24]. In practice, the delay diversity (DD) method, which is known as simple method for increasing diversity, has attracted as a simple and efficient method in the past few years [25,26]. Other diversity techniques are cyclic delay diversity (CDD) and Discontinuous Doppler diversity (DDoD) [27,28]. ...
... There is assumed that all DVB-T2 receivers shall be able to process the encoding Alamouti signals [34,35]. Also, we do not require the transmitter to use different frequency when distributing the same program since the guard interval features [25]. Then, we form a single frequency network (SFN), where all transmitters use identical signals. ...
... Then, we form a single frequency network (SFN), where all transmitters use identical signals. We will have substantial improvements in frequency economy and improve coverage for mobile reception due to diversity gain [1]. Figure 1 shows an OFDM generation module which is introduced in [25]. The system input may be one or more MPEG-2 transport streams which are built as a frame after processing, interleaving and modulation. ...
This paper addresses a novel Alamouti space frequency block decoding scheme for multiple-input multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM) based systems using diversity techniques over highly frequency selective channels. Unlike the standard Alamouti space-frequency block code (SFBC), that suffer from performance degradation in highly frequency-selective channels, the proposed method combats this problem. Also, this scheme has capability to combine with different methods such as OFDM and some special diversity such as: cyclic delay diversity (CDD) and discontinuous Doppler diversity (DDoD). In addition, a novelty transceiver using CDD is proposed, which performs valuable results. In this paper, this scheme is called “Efficient Δh-Alamouti with CDD”. This efficient Alamouti encoder and decoder allow a high reliability and capacity enhancement. In order to evaluate its capability, we have implemented this scheme for the second generation terrestrial video broadcasting (DVB-T2) system. The properties of the proposed scheme is investigated over different channels. Also, mathematical analyses and simulation results of the bit error performance for the modified encoding method with these diversity techniques, perform mostly better than the other forms of encoding Alamouti over highly frequency-selective channels such as single frequency networks (SFN). The other advantages of the proposed method are simplicity, flexibility and standard compatibility.
... Moreover, many multiple antenna technologies require processing at both transmitter and receiver [25], [26]. In practice, the delay diversity (DD) method, which is known as a simple method for increasing diversity, has been attracted as a simple and efficient method in the past few years [27], [28]. Other diversity techniques are cyclic delay diversity (CDD) and Discontinuous Doppler diversity (DDoD) [29], [30]. ...
... There is assumed that all DVB-T2 receivers shall be able to process the encoding Alamouti signals [37], [38]. Also, we do not require the transmitter to use a different frequency when distributing the same program since the guard interval features [27]. Therefore, we develop a single frequency network (SFN), where all transmitters use identical signals. ...
... Such interleavers may be useful for transmission with orthogonal frequency-division multiplexing (OFDM) over frequency selective channels. The corresponding channel transfer functions typically lead to circularly correlated channel coefficients and therefore cyclic error patterns [59]. To the best of our knowledge, similar error clusters and interleavers were only considered by De Almeida and Palazzo in [14], where the interleaving was designed based on the set partitioning of a p × p array. ...
Flash memories are non-volatile memory devices. The rapid development of flash technologies leads to higher storage density, but also to higher error rates. This dissertation considers this reliability problem of flash memories and investigates suitable error correction codes, e.g. BCH-codes and concatenated codes. First, the flash cells, their functionality and error characteristics are explained. Next, the mathematics of the employed algebraic code are discussed. Subsequently, generalized concatenated codes (GCC) are presented. Compared to the commonly used BCH codes, concatenated codes promise higher code rates and lower implementation complexity. This complexity reduction is achieved by dividing a long code into smaller components, which require smaller Galois-Field sizes. The algebraic decoding algorithms enable analytical determination of the block error rate. Thus, it is possible to guarantee very low residual error rates for flash memories. Besides the complexity reduction, general concatenated codes can exploit soft information. This so-called soft decoding is not practicable for long BCH-codes. In this dissertation, two soft decoding methods for GCC are presented and analyzed. These methods are based on the Chase decoding and the stack algorithm. The last method explicitly uses the generalized concatenated code structure, where the component codes are nested subcodes. This property supports the complexity reduction. Moreover, the two-dimensional structure of GCC enables the correction of error patterns with statistical dependencies. One chapter of the thesis demonstrates how the concatenated codes can be used to correct two-dimensional cluster errors. Therefore, a two-dimensional interleaver is designed with the help of Gaussian integers. This design achieves the correction of cluster errors with the best possible radius. Large parts of this works are dedicated to the question, how the decoding algorithms can be implemented in hardware. These hardware architectures, their throughput and logic size are presented for long BCH-codes and generalized concatenated codes. The results show that generalized concatenated codes are suitable for error correction in flash memories, especially for three-dimensional NAND memory systems used in industrial applications, where low residual errors must be guaranteed.
... Circular interleavers may be useful for transmission with orthogonal frequency-division multiplexing (OFDM) over frequency selective channels. The corresponding channel transfer functions typically lead to circularly correlated channel coefficients and therefore circular error patterns [19]. To the best of our knowledge, similar error clusters and interleavers were only considered by De Almeida and Palazzo in [14], where the interleaving was designed based on the set partitioning of a p×p circular array. ...
Codes over Gaussian integers have been proposed for coding over two-dimensional (2D) signal spaces, for example, using quadrature amplitude modulation. Here, it is demonstrated that the concept of set partitioning can be applied to Gaussian integer constellations that are isomorphic to 2D modules over rings of integers modulo p. This enables multilevel code constructions over Gaussian integers. The authors derive upper bounds on the achievable minimum distance in the subsets and present a construction for the set partitioning. This construction achieves optimal or close to optimal minimum distances. Furthermore, it is demonstrated that this set partitioning can be applied to an interleaving technique for correcting 2D cyclic clusters of errors. The authors propose a novel combination of generalised concatenated codes with 2D interleaving to correct 2D error clusters and independent errors.
... Such interleavers may be useful for transmission with orthogonal frequencydivision multiplexing (OFDM) over frequency selective channels. The corresponding channel transfer functions typically lead to circularly correlated channel coefficients and therefore cyclic error patterns [4]. To the best of our knowledge, similar error clusters and interleavers were only considered by De Almeida and Palazzo in [5], where the interleaving was designed based on the set partitioning of a p × p array. ...
This work demonstrates that the concept of set partitioning can be applied to Gaussian integer constellations that are isomorphic to two-dimensional modules over rings of integers modulo p. We derive upper bounds on the achievable minimum distance in the subsets and present a construction for the set partitioning. This construction achieves optimal or close to optimal minimum distances. Furthermore, we demonstrate that this set partitioning can be applied to an interleaving technique for correcting two-dimensional cyclic clusters of errors.
A random beamforming (RBF) technique is proposed to achieve omnidirectional coverage for broadcast channels in multiple-antenna systems. In the proposed scheme, the time and frequency resources for communication are divided into many time-frequency blocks (TFBs). A random pattern is employed on each TFB, with the average power in all directions over many TFBs being equal. The design criteria and detailed design of the random pattern sequence are given. We propose a basic RBF scheme and an Alamouti-enhanced scheme, as well as the corresponding structures of the transmitter and the receiver. Simulations are carried out for an eight-element unitary linear array with half-waveform separation in a fast-fading channel, showing that the proposed scheme greatly outperforms the cyclic delay diversity scheme and is robust to calibration errors and failures of radio-frequency chains.
Recently, wireless network technology has grown at such a pace that scientific research has become a practical reality in a very short time span. Mobile wireless communications have witnessed the adoption of several generations, each of them complementing and improving the former. One mobile system that features high data rates and open network architecture is 4G. Currently, the research community and industry, in the field of wireless networks, are working on possible choices for solutions in the 4G system. 4G is a collection of technologies and standards that will allow a range of ubiquitous computing and wireless communication architectures. The researcher considers one of the most important characteristics of future 4G mobile systems the ability to guarantee reliable communications from 100 Mbps, in high mobility links, to as high as 1 Gbps for low mobility users, in addition to high efficiency in the spectrum usage. On mobile wireless communications networks, one important factor is the coverage of large geographical areas. In 4G systems, a hybrid satellite/terrestrial network is crucial to providing users with coverage wherever needed. Subscribers thus require a reliable satellite link to access their services when they are in remote locations, where a terrestrial infrastructure is unavailable. Thus, they must rely upon satellite coverage. Good modulation and access technique are also required in order to transmit high data rates over satellite links to mobile users. This technique must adapt to the characteristics of the satellite channel and also be efficient in the use of allocated bandwidth. Satellite links are fading channels, when used by mobile users. Some measures designed to approach these fading environments make use of: (1) spatial diversity (two receive antenna configuration); (2) time diversity (channel interleaver/spreading techniques); and (3) upper layer FEC. The author proposes the use of OFDM (Orthogonal Frequency Multiple Access) for the satellite link by increasing the time diversity. This technique will allow for an increase of the data rate, as primarily required by multimedia applications, and will also optimally use the available bandwidth. In addition, this dissertation approaches the use of Cooperative Satellite Communications for hybrid satellite/terrestrial networks. By using this technique, the satellite coverage can be extended to areas where there is no direct link to the satellite. For this purpose, a good channel model is necessary.
