Modulation Diversity for Spatial Modulation Using Complex Interleaved Orthogonal Design

In this paper, we propose modulation diversity techniques for Spatial Modulation (SM) system using Complex Interleaved Orthogonal Design (CIOD) meant for two transmit antennas. Specifically, we show that by using the CIOD for two transmit antenna system, the standard SM scheme, where only one transmit antenna is activated in any symbol duration, can achieve a transmit diversity order of two. We show with our simulation results that the proposed schemes offer transmit diversity order of two, and hence, give a better Symbol Error Rate performance than the SM scheme with transmit diversity order of one.Comment: 7 page

ANALISIS PENERAPAN TRANSMIT DIVERSITY PADA UMTS

ABSTRAKSI: Universal Mobile Telecommunication System (UMTS) merupakan suatu evolusi dari GSM yang mendukung kemampuan generasi ketiga (3G). UMTS menggunakan teknologi akses WCDMA dengan sistem direct sequence wideband CDMA (DS-WCDMA), baik untuk FDD maupun TDD WCDMA mendukung layanan data dengan laju yang berubah-ubah, sehingga dapat mendukung layanan Bandwidth on Demand (Bod). Seperti yang kita ketahui fenomena multipath fading merupakan salah satu ciri utama pada sistem komunikasi wireless. Diversitas antenna merupakan teknik yang cukup efektif untuk mengurangi efek multipath fading. Penggunaan transmit diversity diharapkan mampu menghasilkan peningkatan kualitas layanan komunikasi broadband tersebut. Pada Tugas Akhir ini akan diteliti mengenai analisis penerapan transmit diversity pada UMTS FDD release 99 dengan menggunakan skema Space Time Transmit Diversity dan Time Switch Transmit Diversity. Jumlah antena yang digunakan pada penelitaian ini adalah 2Tx-1Rx pada masing-masing skema. Penelitian ini akan membandingkan performansi teknik-teknik diversitas tersebut terhadap sistem tanpa diversitas pada berbagai kondisi kanal. Analisa dilakukan dengan membuat simulasi komputer pada program Matlab 7 menggunakan pemodelan kanal multipath fading rayleigh berderau AWGN. Dari hasil simulasi didapatkan bahwa penggunaan transmit diversity mampu memberikan performansi Universal Mobile Telecomunication Systerm (UMTS) lebih baik, hal ini ditunjukkan dengan adanya diversity gain. Untuk skema Space Time Transmit Diversity didapat diversity gainnya sebesar ± 12,8 dB (dilihat dari BER 2 x 10-2), sedangkan untuk skema Time Switch Trasnmit Diversity didapatkan diversity gainnya sebesar ± 7,2 dB (dilihat dari BER 1,76 x 10-2). Selain itu didapatkan juga spreading gain sebesar ± 10,2 dB (dilihat dari BER 10-3). Hal ini terkait dengan penggunaan masing-masing skema, dimana pada Time Switch Trasnmit Diversity digunakan hanya untuk Synchronisation Channel yang tidak mengalami proses spreading.Kata Kunci : ABSTRACT: Universal Mobile Telecommunication System (UMTS) is an evolution from GSM that supports third generation (3G) ability. UMTS uses WCDMA access technology with direct sequence wideband CDMA system; whether it is for FDD or TDD WCDMA supports data services with fluctuate speed, so that it can support Bandwidth on Demand (Bod) services. As we know, multipath fading phenomenon is one of the main characteristic in wireless communication system. Antenna diversity is a technique that is effective enough to decrease multipath fading effect. The uses of transmit diversity hopefully able to gain broadband communication services quality rising. In this final task will be observed about analysis of transmit diversity application on UMTS FDD release 99 by using Space Time Transmit Diversity and Time Switch Transmit Diversity schema. Total of the antenna that will use in this observation is 2Tx-1Rx on each schema. This observation will compare the performance of those diversity techniques toward a system without diversity in every channel condition. Analysis is done by making computer simulation on Matlab 7 program using roaring multipath fading Rayleigh channel AWGN design. From simulation result, it obtains that the uses of transmit diversity is able to give better performance from Universal Mobile Telecommunication System (UMTS), this shows by the existence of diversity gain. For the Space Time Transmit Diversity schema the diversity gain is ± 12,8 dB (seen from BER 2 x 10- 2), while for Time Switch Transmit Diversity schema the diversity gain is ± 7,2 dB (seen from BER 1,76 x 10-2). And also spreading gain is ± 10,2 dB (seen from BER 10-3). This interrelated with the uses of each schema, where Time Switch Transmit Diversity uses only for Synchronization Channel that is not experiencing spreading process.Keyword

Analysis of DVB-H network coverage with the application of transmit diversity

This paper investigates the effects of the Cyclic Delay Diversity (CDD) transmit diversity scheme on DVB-H networks. Transmit diversity improves reception and Quality of Service (QoS) in areas of poor coverage such as sparsely populated or obscured locations. The technique not only povides robust reception in mobile environments thus improving QoS, but it also reduces network costs in terms of the transmit power, number of infrastructure elements, antenna height and the frequency reuse factor over indoor and outdoor environments. In this paper, the benefit and effectiveness of CDD transmit diversity is tackled through simulation results for comparison in several scenarios of coverage in DVB-H networks. The channel model used in the simulations is based on COST207 and a basic radio planning technique is used to illustrate the main principles developed in this paper. The work reported in this paper was supported by the European Commission IST project—PLUTO (Physical Layer DVB Transmission Optimization)

Adaptive Space-Time-Spreading-Assisted Wideband CDMA Systems Communicating over Dispersive Nakagami-m Fading Channels

In this contribution, the performance of wideband code-division multiple-access (W-CDMA) systems using space-timespreading-(STS-) based transmit diversity is investigated, when frequency-selective Nakagami-m fading channels, multiuser interference, and background noise are considered. The analysis and numerical results suggest that the achievable diversity order is the product of the frequency-selective diversity order and the transmit diversity order. Furthermore, both the transmit diversity and the frequency-selective diversity have the same order of importance. Since W-CDMA signals are subjected to frequency-selective fading, the number of resolvable paths at the receiver may vary over a wide range depending on the transmission environment encountered. It can be shown that, for wireless channels where the frequency selectivity is sufficiently high, transmit diversity may be not necessitated. Under this case, multiple transmission antennas can be leveraged into an increased bitrate. Therefore, an adaptive STS-based transmission scheme is then proposed for improving the throughput ofW-CDMA systems. Our numerical results demonstrate that this adaptive STS-based transmission scheme is capable of significantly improving the effective throughput of W-CDMA systems. Specifically, the studied W-CDMA system’s bitrate can be increased by a factor of three at the modest cost of requiring an extra 0.4 dB or 1.2 dB transmitted power in the context of the investigated urban or suburban areas, respectively

Performance comparison of differential space-time signalling schemes for OFDM systems

Differential transmit diversity is an attractive alternative to its coherent counterpart, especially for multiple antenna systems where channel estimation is more difficult to attain compared to that of single antenna systems. In this paper we compare two different types of differential transmit diversity techniques for OFDM based transmissions. The first technique uses differential space-time block codes (DSTBC) from orthogonal designs and the second uses the differential cyclic delay diversity (DCDD). The results compare the bit error performance for several transmit antenna configurations. The results show that DCDD offers a very close performance to that of DSTBC, with the advantage of a simplified receiver structure

Spectrally efficient transmit diversity scheme for differentially modulated multicarrier transmissions

Cyclic delay diversity is a simple, yet effective, transmit diversity scheme for multicarrier based transmissions employing coherent digital linear modulation schemes. It is shown that, for satisfactory operation, the scheme requires additional channel estimation overhead compared to single antenna and traditional space–time coded transmissions owing to the inherent increase in frequency selective fading. The authors analyse the additional channel estimation overhead requirement for a Hiperlan #2 style system with two transmit antennas operating in a NLOS indoor environment. The analysis shows that an additional overhead of 500% is required for the candidate system compared to a single antenna system. It is also shown that by employing differential modulation the channel estimation overhead can be eliminated with significant performance improvement compared to a system employing a practical channel estimation scheme. This novel combination, termed ‘differentially modulated cyclic delay diversity, is shown to yield a highly spectral efficient, yet simple transmit diversity solution for multi-carrier transmissions

On the MIMO Channel Capacity of Multi-Dimensional Signal Sets

In this contribution we evaluate the capacity of Multi-Input Multi-Output (MIMO) systems using multi-dimensional PSK/QAM signal sets. It was shown that transmit diversity is capable of narrowing the gap between the capacity of the Rayleigh-fading channel and the AWGN channel. However, since this gap becomes narrower when the receiver diversity order is increased, for higher-order receiver diversity the performance advantage of transmit diversity diminishes. A MIMO system having full multiplexing gain has a higher achievable throughput than the corresponding MIMO system designed for full diversity gain, although this is attained at the cost of a higher complexity and a higher SNR. The tradeoffs between diversity gain, multiplexing gain, complexity and bandwidth are studied

On the MIMO Channel Capacity of Multi-Dimensional Signal Sets

In this contribution two general formulae were derived for the capacity evaluation of Multi-Input Multi-Output (MIMO) systems using multi-dimensional signal sets, different modulation schemes and an arbitrary number of transmit as well as receive antennas. It was shown that transmit diversity is capable of narrowing the gap between the capacity of the Rayleigh-fading channel and the AWGN channel. However, since this gap becomes narrower when the receiver diversity order is increased, for higher-order receiver diversity the performance advantage of transmit diversity diminishes. A MIMO system having full multiplexing gain has a higher achievable capacity, than the corresponding MIMO system designed for achieving full diversity gain, provided that the channel SNR is sufficiently high

On the ergodic sum-rate performance of CDD in multi-user systems

The main focus of space-time coding design and analysis for MIMO systems has been so far focused on single-user systems. For single-user systems, transmit diversity schemes suffer a loss in spectral efficiency if the receiver is equipped with more than one antenna, making them unsuitable for high rate transmission. One such transmit diversity scheme is the cyclic delay diversity code (CDD). The advantage of CDD over other diversity schemes such as orthogonal space-time block codes (OSTBC) is that a code rate of one and delay optimality are achieved independent of the number of transmit antennas. In this work we analyze the ergodic rate of a multi-user multiple access channel (MAC) with each user applying such a cyclic delay diversity (CDD) code. We derive closed form expressions for the ergodic sum-rate of multi-user CDD and compare it with the sum-capacity. We study the ergodic rate region and show that in contrast to what is conventionally known regarding the single-user case, transmit diversity schemes are viable candidates for high rate transmission in multi-user systems. Finally, our theoretical findings are illustrated by numerical simulation results.Comment: to appear in Proceedings of 2007 IEEE Information Theory Workshop (ITW) in Lake Taho