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Orthogonal designs have received considerable attention in the development of efficient modulation and coding methods for future multi-antenna wireless communication systems due to their special properties. In this paper, we propose a class of space-time block codes constructed by combining orthogonal designs with sphere packing for an arbitrary number of transmit antennas. The structure of the orthogonal designs is exploited to guarantee full diversity, and sphere packing is used to improve the coding advantage. Space-time block code construction from block-orthogonal designs is also considered: the full-diversity property is ensured by rotating the sphere packing underlying the code, and the optimal rotation angle is determined for a class of sphere packing. Code design examples are provided for two and four transmit antennas and various transmission rates. The simulation results show that by jointly designing the symbols in the orthogonal designs, the performance of the block codes can be significantly increased. Index Terms--Diversity product, multiple antennas, multiple-input multiple-output (MIMO) systems, orthogonal designs, spacetime block codes (STBCs), sphere packing.

In this paper, a general space-frequency (SF) block code structure is proposed that can guarantee full-rate (one channel symbol per subcarrier) and full-diversity transmission in multiple-input multiple-output-orthogonal frequency-division multiplexing (MIMO-OFDM) systems. The proposed method can be used to construct SF codes for an arbitrary number of transmit antennas, any memoryless modulation and arbitrary power-delay profiles. Moreover, assuming that the power-delay profile is known at the transmitter, we devise an interleaving method to maximize the overall performance of the code. We show that the diversity product can be decomposed as the product of the "intrinsic" diversity product, which depends only on the used signal constellation and the code design, and the "extrinsic" diversity product, which depends only on the applied interleaving method and the power delay profile of the channel. Based on this decomposition, we propose an interleaving strategy to maximize the "extrinsic" diversity product. Extensive simulation results show that the proposed SF codes outperform the previously existing codes by about 3-5 dB, and that the proposed interleaving method results in about 1-3-dB performance improvement compared to random interleaving. Index Terms--Frequency-selective fading channels, full diversity, multiple-input multiple-output-orthogonal frequency-division multiplexing (MIMO-OFDM) systems, permutation, space-frequency (SF) coding.

The potential for capacity increase in multiple-antenna wireless communication systems has drown considerable attention to space-time codes. However, most of the existing space--time code construction methods have assumed ideal channel models: either quasi-static fading or fast fading. In this work, we propose a systematic space--time trellis code construction method for correlated fading channels. We derive the performance criteria that take into account both spatial and temporal channel correlation, assuming that the space-time correlation matrix is of full rank. Moreover, we introduce a new design criterion and analyze the properties of the space-time trellis codes satisfying the proposed criterion. Using the design criterion, we develop a code construction procedure that jointly considers diversity advantage and coding advantage for an arbitrary number of transmit antennas and any memoryless modulation. The flexibility of the proposed code construction method is demonstrated by designing space--time trellis codes for two, three, and four transmit antennas with quaternary phase-shift keying (QPSK), 8PSK (phase-shift keying), and 4ASK (amplitude-shift keying) modulations. The simulation results demonstrate that not only can our method generate new codes for an arbitrary number of antennas, but in some special cases, where previously proposed codes exist, our codes also perform very well. Index Terms--Diversity, space-time codes, space-time correlation, trellis codas, wireless communications.

Most space-time codes in the literature were proposed based on two ideal channel conditions: either quasi-static or rapid fading. However, these codes may suffer performance degradation due to temporal correlation caused by the movement of the mobile terminal or imperfect interleaving. In this correspondence, we provide a novel analytical framework for the diversity analysis of spare-time modulation in time-correlated fading environment. We show that the space-time signals of square size achieving full diversity in quasi-static fading channels also achieve full diversity in time-correlated fading channels, independently of the time correlation matrix. Consequently, various classes of space-time signals designed for quasi-static fading channels can also be used for full-diversity transmission over time-correlated fading channels. Moreover, we show that if the time correlation matrix is of full rank, the design criteria for time-correlated fading channels are the same as those for rapid fading channels. To illustrate the theoretical results, some simulations were also performed under various temporal fading conditions. Index Terms--Diversity, interleaving, multiple antennas, space-time modulation, time-correlated fading.

Research is described involving space-frequency code design for frequency-selective multiple input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) modulation.

With the explosive deployment of the information and communications technology (ICT) infrastructures, the rising cost of energy and increased environmental awareness has sparked a keen interest in the development and deployment of energy-efficient communication technologies. As a major player in the ICT sector, the energy efficiency of the mobile cellular networks can be significantly improved by switching off some base stations during off-peak periods. In this paper, we propose an energy-efficient BS switching strategy, and use cooperative communication techniques among the base stations to effectively extend network coverage. We incorporate both the path-loss and fading effects in our system model, and derive closed-form expressions for two important quality of service metrics, the call-blocking probability and the channel outage probability. The proposed scheme guarantees the quality of service of the user equipments by identifying the user equipments situated at the worst-case locations. The energy-saving performance is evaluated and compared with the conventional uni-pattern operation. Both analytical and numerical results show that the proposed energy-efficient switching strategy, facilitated by BS cooperation, can provide significant energy-saving potential for the cellular networks with guaranteed quality of service. [ABSTRACT FROM AUTHOR]

Orthogonal designs have received considerable attention in the development of efficient modulation and coding methods for future multi-antenna wireless communication systems due to their special properties. In this paper, we propose a class of space-time block codes constructed by combining orthogonal designs with sphere packing for an arbitrary number of transmit antennas. The structure of the orthogonal designs is exploited to guarantee full diversity, and sphere packing is used to improve the coding advantage. Space-time block code construction from block-orthogonal designs is also considered: the full-diversity property is ensured by rotating the sphere packing underlying the code, and the optimal rotation angle is determined for a class of sphere packing. Code design examples are provided for two and four transmit antennas and various, transmission rates. The simulation results show that by jointly designing the symbols in the orthogonal designs, the performance of the block codes can be significantly increased. [ABSTRACT FROM AUTHOR]

In this paper, a general space-frequency (SF) block code structure is proposed that can guarantee full-rate (one channel symbol per subcarrier) and full-diversity transmission in multiple-input multiple-output-orthogon frequency-division multiplexing (MIMO-OFDM) systems. The proposed method can be used to construct SF codes for an arbitrary number of transmit antennas, any memoryless modulation and arbitrary power-delay profiles. Moreover, assuming that the power-delay profile is known at the transmitter, we devise an interleaving method to maximize the overall performance of the code. We show that the diversity product can be decomposed as the product of the "intrinsic" diversity product, which depends only on the used signal constellation and the code design, and the "extrinsic" diversity product, which depends only on the applied interleaving method and the power delay profile of the channel. Based on this decomposition, we pro- pose an interleaving strategy to maximize the "extrinsic" diversity product. Extensive simulation results show that the proposed SF codes outperform the previously existing codes by about 3-5 dB, and that the proposed interleaving method results in about 1-3-dR performance improvement compared to random interleaving. [ABSTRACT FROM AUTHOR]

This paper considers the problem of space-frequency code design for frequency-selective multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) modulation. We show that space-time codes achieving full diversity in quasistatic flat fading environment can be used to construct space-frequency codes that can achieve the maximum diversity available in frequency-selective MIMO fading channels. Since the codes are constructed via a simple mapping from space-time codes to space-frequency codes, the abundant classes of existing space-time block and trellis codes can be used for full diversity transmission in MIMO-OFDM systems. The proposed mapping provides a tradeoff between the achieved diversity order and the symbol rate. Moreover, we characterize the performance of the space-frequency codes obtained via the mapping by finding lower and upper bounds on their coding advantages as functions of the coding advantages of the underlying space-time codes. This result will allow us to investigate the effects of the delay distribution and the power distribution of the channel impulse responses on the performance of the resulting space-frequency codes. Extensive simulation results are also presented to illustrate and support the theory. [ABSTRACT FROM AUTHOR]