TEL AVIV UNIVERSITY Gaddi Blumrosen

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Information Source 2. Space-time system model 2.1 Introduction Before we describe space-time processing, we have to give an appropriate space-time system model. The bits of information are and then encoded and distributed toto different antennas in an antenna array by the special space-time encoder. In reception, a receive antenna array is used, and the information bits are obtained after ST decoding and demodulation. Fig 1 below describes the transmission scheme. We first describe, in the first section, the antenna array model, which has to enable transmission and reception, of several information sources simultaneously. In the second section we describe the most complicated and crucial part of space-time system modeling- space-time channel model. In the third part we give received and transmitted signal models combined with channel and antenna models. In the last section we examine ways of evaluation of the space time system performance. Modulator STC encoder h1N R h22 h11 1,2 hNTNR h21 STC decoder Figure 1: Spatial Channel model De- Modulator Information Source
2.2 Antenna array modeling 2.2.1 Introduction The wireless system antenna is the interface between the transmitter and the receiver to space. The antenna array is an important tool in controlling the spatial behavior of transmission/reception signal. Basically it enables several simultaneous transmissions/receptions from different antennas in the array. The transmission from each antenna, which can vary in phase and amplitude, is creating the antenna pattern. In this chapter we will introduce a basic description of antenna array modeling and in particular the one we use for this work. 2.2.2 Antenna array characteristics Based on [2], we can characterize an antenna array by four factors. 1. Antenna array geometries. 2. Displacement between elements. 3. Antenna excitation („antenna element gain‟). 4. Antenna excitation phase. The most common array geometry is the Uniform Linear Array (ULA). In such arrays the antennas are equally spaced along a straight line. This arrangement is usually the cheapest and the simplest for implementation and analysis. Other arrangements are rectangular, circular and triangular. For the sake of simplicity we will focus on ULA only, when necessary. Hence the term antenna array will refer to ULA only, unless stated otherwise. In a ULA, the displacement between elements denoted d, plays an important part in antenna beam shaping and antenna correlations and influences the performance of each ST technique. Each antenna element excitation amplitude and phase influences the beam forming shaping in transmission and of the spatial filtering in reception. Antenna gain is another important characteristic of the antenna. It is defined as the ratio of antenna transmission/reception power at the maximum direction and that of omni antenna. Gr is defined as the power gain of the receive antenna and Gt is defined as the power gain of the transmit antenna. In realistic antenna models, a narrow band assumption (short travel time of signal compared with symbol period, see [1]), which is being assumed simplifies the computations complexity. We will further assume from, far field assumption (the distance between the subantennas is much smaller than the distance of the source) and thus the field at a given point in space is a function of only the horizontal angle (see fig. 1). The electrical field induced by antenna array in direction of is: h E w s( ) (2.1) Where:
Page 1 and 2: TEL AVIV UNIVERSITY The IBY and Ald
Page 3 and 4: Abstract A wireless channel, due to
Page 5 and 6: 1. Introduction A wireless channel,
Page 7: dedicated to examine ways of adapta
Page 11 and 12: 2.3.2 Spatial wireless channel mode
Page 13 and 14: 1 inversely proportional to Doppler
Page 15 and 16: Table 1: Relations between channel
Page 17 and 18: Where is the distance between the i
Page 19 and 20: For simplicity, let use the common
Page 21 and 22: Where the transmit and receive matr
Page 23 and 24: 2.4 Received and transmitted Signal
Page 25 and 26: Eb MRT, the received SNR becomes ,
Page 27 and 28: 3. ST processing techniques Overvie
Page 29 and 30: 3.2.2 SVD based BF. BF can be refer
Page 31 and 32: The physical interpretation for WR
Page 33 and 34: SVD Eigenvector physical perspectiv
Page 35 and 36: 3.3.2 STBC Design Principles. As in
Page 37 and 38: It is shown that space-time block c
Page 39 and 40: OSTBC. It is seen that the antenna
Page 41 and 42: epresent for example a Rician chann
Page 43 and 44: By minimization the performance cri
Page 45 and 46: Figure 14: Real-time adaptive STC c
Page 47 and 48: techniques, but differ mainly in th
Page 49 and 50: Case of diagonal conditional covari
Page 51 and 52: 4.4.5 OSTBC with linear antenna wei
Page 53 and 54: 5. ML optimal weights for transmit
Page 55 and 56: 1. 1 N as T NT est0 or 0. Equal p
Page 57 and 58: 5.2.5 An approximation function The
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5.2.6 Optimal weight sensitivity to
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algorithm follows closely the bette
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An alternative, more intuitive way
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5.3.4 Algorithm sensitivity As for
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NT Figure 28: The Largest eigenvalu
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estimated. Both OSTBC and WOSTC per
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5.4 ML optimal antenna weights with
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5.4.3 Deriving ML Optimal antenna w
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Rician channel with non-diagonal co
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(maximum SNR approaches) and also t
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APPENDIX A: ML optimal antenna weig
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APPENDIX B: BF Iterative techniques
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APPENDIX C: Simulation environment
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find_opt_ab_Rice.m (Find MMSE optim
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diversity ) , םע עדימ יקל
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ביבא - לת תטיסרבינו
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TEL AVIV UNIVERSITY Gaddi Blumrosen

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