Space Time coding

Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks and link reliability. Space-time wireless technology that uses multiple antennas along with appropriate signalling and receiver techniques offers a powerful tool for improving wireless
performance. More advanced MIMO techniques are planned for future mobile networks in wireless Local Area Network (LANs) and Wide Area Network (WANs). Multiple antennas when used with appropriate Space-Time Coding (STC) techniques can achieve huge performance gains in multipath fading wireless links. The Space Time Coding has evolved as a most vibrant research area in wireless communications. Recently, Space-Time Block Coding (STBC) has been trying to incorporate in the forthcoming generation of mobile communication standard which aims to deliver true multimedia capability. This paper presents the Space-Time Block Codes (STBC) for wireless networks that uses multiple numbers of antennas at both transmitter and receiver. The simulations have been done in MATLAB. The STBC which includes the Alamouti Scheme as well as an orthogonal STBC for 4 transmit antenna case has been simulated and studied.

Advanced Communication Systems are wideband systems to support multiple applications such as audio, video and data so and so forth. These systems require high spectral efficiency and data rates. In addition, they should provide multipath fading and inter-symbol interference (ISI) free transmission. Multiple input multiple output orthogonal frequency division multiplexing (MIMO OFDM) meets these requirements Hence, MIMO-OFDM is the most preferable technique for long term evaluation advanced (LTE-A). The primary objective of this paper is to control bit error rate (BER) by proper channel coding, pilot carriers, adaptive filter channel estimation schemes and space time coding (STC). A combination of any of these schemes results in better BER performance over individual schemes. System performance is analyzed for various digital modulation schemes. In this paper,adaptive filter channel estimated MIMO OFDM system is proposed by integrating channel coding, adaptivefilter channel estimatio...

Advanced Communication Systems are wideband systems to support multiple applications such as audio, video and data so and so forth. These systems require high spectral efficiency and data rates. In addition, they should provide multipath fading and inter-symbol interference (ISI) free transmission. Multiple input multiple output orthogonal frequency division multiplexing (MIMO OFDM) meets these requirements Hence, MIMO-OFDM is the most preferable technique for long term evaluation advanced (LTE-A). The primary objective of this paper is to control bit error rate (BER) by proper channel coding, pilot carriers, adaptive filter channel estimation schemes and space time coding (STC). A combination of any of these schemes results in better BER performance over individual schemes. System performance is analyzed for various digital modulation schemes. In this paper, adaptive filter channel estimated MIMO OFDM system is proposed by integrating channel coding, adaptive filter channel estimation, digital modulation and space time coding. From the simulation results, channel estimated 2×2 MIMO OFDM system shows superior performance over individual schemes. 1. INTRODUCTION Advanced mobile systems aim on supporting high data rate services over multiple systems for multi-media applications involving voice, data, pictures and video. They should provide services without interruptions for private and public networks. These services require interference free transmission over frequency selective fading channels. OFDM is a promising technique for Long Term Evaluation-Advanced (LTE-A), Worldwide Interoperability for Microwave Access (Wi-MAX) systems, IEEE 802.11ac, and IEEE 802.15 [1]. A good channel estimation procedure is necessary in order to make reliable decisions and to coherently demodulate the received data. OFDM systems require effective and exact channel estimation for time-varying channels. The principal motto of this paper is to improve the OFDM system performance by proper channel coding, suitable digital modulation schemes, adaptive filter channel estimation techniques and multiple antennas at the transmitter and receiver. By using all these, an integrated OFDM system is proposed to enhance system performance [2-3]. Gosh [4] formulated a closed form expression for impulse noise performance in a multicarrier QAM system and showed that it is better than single carrier systems for moderate values of impulse power and probability. Dong et al. [5] determined the power and rate adaptation analytically with channel state information in the presence of carrier frequency offset (CFO) for an OFDM system. Sabbaghian et al. [6] developed a new code based on dual BCH code for reduction of PAPR in multi

Our purpose is to examine the possibilities of Bakhtinian dialogical analysis for understanding students’ experiences of medical training. Twenty-three interviews were conducted with eleven British medical students intercalating in psychology. Forty emotionally resonant key moments were identified for analysis. Our analysis illustrates students’ use of the professional genre to present their training as emotionally neutral. However, we show how medical training can be framed in more unofficial and affective-laden ways in which threshold moments of crisis are presented as space-time breaches characteristic of the genres of adventure-wonder and adventure-ordeal. This affect was often depotentiated in the narratives through brief allusion to the professional genre. This cycling between genres suggests that the students were searching for an appropriate way in which to frame their experiences, a central dilemma being the extent to which medical training makes sense within an immediate and affect-laden, or future-orientated and affect-neutral, pedagogy. Finally, we identify how consultants are an important aspect of the affective experience of medical training who, at their best, offer inspiring exemplars of flexible movement between official and unofficial ways of being a doctor. In conclusion, we demonstrate the potential of genres to make sense, and to organize the experience, of medical training spatially in terms of moving between personal and impersonal contact, temporally in terms of moving between the extraordinary and routine, and affectively in terms of moving between potent and neutral affect. Learning to use the professional genre is part of enculturation as a doctor and can be helpful in providing a framework restoring coherence and composure through engaging with, and reformulating, difficult experiences. However, it is important to take seriously the resistance many of the students demonstrated to the professional genre as a possible barometer of its acceptability to the general public.

Cooperative Relaying is deemed as one of the most promising techniques in the current research in terms of providing superior space coverage and robust performance. In this paper, we focus on cooperative wireless networks employing Space Frequency Block ...

In this paper we investigate the impact of mutual coupling (MC) on the performance of a MIMO-beamforming system with closely spaced antenna elements. Simulation results confirm the decrease in system performance when antenna mutual coupling is taken into account.

In this paper, we study the throughput enhancement in a wireless slotted ALOHA system, where all users transmit space-time coded information sequences and the destination is able to separate a given number of collided packets. These users operate with the slotted ALOHA protocol to access to the wireless channel resulting in a high probability of collision. To increase the packet throughput of such a system, we propose to separate the collided packets at the destination with a successive interference canceller that performs joint detection: channel estimation and data detection. The multi-user detector that we propose exploits the benefits of both the collision processing and the space-time signature induced by the Alamouti-type space-time block coding to improve the throughput. The validity of the proposed algorithm is highlighted by simulation results.

ABSTRACT The problem of designing space-time constellations for communication in spread multiple-antenna wireless systems over Rayleigh fading channel is addressed. Using the asymptotic union bound on error probability as design criterion, codes based on general complex-valued symbols are obtained with a gradient search optimization technique. New space-time constellations are constructed and their performance is assessed. Simulation results show that the proposed technique achieves significant performance gains over existing schemes. Since the designed codebooks do not seem to possess any structure that could reduce the memory requirements for storing the corresponding codebook, the problem of designing structured space-time constellations is also addressed. To overcome this problem, a discrete Fourier transform-based approach is adopted to design structured codebooks and their performance is evaluated. The new structured codebooks also demonstrate significant improvement over state-of-art structured schemes.

Threaded Algebraic Space Time (TAST) codes developed by Gamal et al. is a powerful class of space time codes in which different layers are combined and separated by appropriate Diophantine numberϕ . In this paper we introduce a technique of block layering in TAST codes, in ...

A pragmatic approach to space-time codes (STC) over block fading channels (BFC) is proposed. The new approach consists in using common convolutional codes to obtain STC, simplifying the encoder and the decoder. It is shown that pragmatic space-time codes (P-STC) achieve good performance, similar to that of the best known STC, and that they are suitable for systems with different spectral efficiencies and fading velocity (taken into account by the BFC model). To design P-STC we propose a search algorithm based on a new formulation of the pairwise error probability and the error enumerating function for geometrically uniform STC over BFC