Space-Time Block Codes for Wireless Systems - The ...

More documents

Recommendations

Info

Chapter 1 Introduction Methods for introducing diversity have long been used to combat fading in wireless channels, e.g., rake receiver and Maximal Ratio Combining are classical receiver diversity schemes [Pro95]. Recently, transmit diversity techniques have received significant attention due to their efficiency in bandwidth and power [GFBK99, Ala98, TSC98, Hug00]. These works are, in part, motivated by information theoretic analyses [Tel95, FG98], which show that capacity increases linearly in the minimum of the number of transmit and receive antennae. These capacity results are shown under the assumptions of statistically independent flat Rayleigh channels between all transmit/receive antenna pairs. Significant work has been done for non-spread space-time systems. Space-time code design criteria are provided in [GFBK99, TSC98]. Alamouti [Ala98] proposed a simple orthogonal space-time block code for 2 transmit antennae, it was later generalized in [TJC99] to orthogonal space-time block codes for more transmit antennae. Motivated by information theoretic results, unitary space-time codes are studied in [HM00]. A systematic way to construct full-diversity unitary group codes based on representation theory of fixed-point-free groups is presented in [SHHS01]. Differential space-time modulation based on unitary group codes are studied in [Hug00, HS00]. A layered space-time architecture is suggested in [Fos96, GARH01]. A number of these non-spread block codes are used as benchmarks for the performance evaluation of our optimized codes found by computer search. There is also a lot of work to generalize Space-time coding to Direct-Sequence Code- Division Multiple-Access (DS-CDMA) systems, but very few has offered the unique view of performance criteria and code design as a function of spreading code in both the uplink and downlink of spread systems, and as a consequence, could not take full advantage of 1
spreading. The focus of [HMP01] is to provide full diversity gain by employing existing schemes. In the sequel, it is shown that full diversity is trivially satisfied; thus a focus on optimizing coding gain is more appropriate. Space-time spreading (STS) [HMP01] relies heavily on orthogonal spreading codes, whose orthogonality cannot be maintained in a practical asynchronous frequency-selective channel. In contrast, our optimized codes maintain their good performance over a wide range of spreading code correlation values and multipath profiles, and hence have greater utility in real channels. In [DSAM03], spreading is combined with the so-called algebraic constellations, the performance is evaluated via simulation. Although multipath is considered in the modelling, the effects of spreading and multipath in performance analysis and code design are not analyzed. Chipinterleaving and block-spreading are used in [ZGM02] to suppress the effect of multipath fading in spread systems. Low-dimensional spread modulation was considered in [BV03], the signal model was similar to the uplink in this work except that very short spreading codes were used. The main conclusion of [BV03] is similar to Proposition 2 for the uplink in this work: single user code design is sufficient to achieve full diversity in the uplink of a multiuser environment. We will show that the decoupling of code designs among users in the uplink is not a characteristic of low-dimensional spreading, but a consequence of independent fading experienced by different users in the uplink. In [WP99], optimal decoder and several suboptimal decoders, like linear and blind decoders, are presented and analyzed. In Chapter 2 of this work, we present a general model for space-time DS-CDMA signals in a multipath fading channel, and focus on performance analysis and code design as a function of spreading code correlation and multipath fading. Both uplink and downlink scenarios are considered. One consequence of multipath fading is that the optimal decoder is a block sequence decoder, however, with typical channel assumptions, we show that the code design based on the worst case pairwise error probability analysis remains a block optimization problem. The presence of multiple access and spreading make code design for spread systems different from that of non-spread systems. The differences in both the design criteria and the resultant optimal codes for spread and non-spread systems are highlighted. 2
Page 1 and 2: COMMUNICATION SCIENCES INSTITUTE
Page 3 and 4: Dedication This dissertation is ded
Page 5 and 6: Contents Dedication Acknowledgement
Page 7 and 8: List Of Tables 2.1 The distance spe
Page 9 and 10: 3.4 The BLUE and LS estimators have
Page 11: Abstract Space-time codes are effec
Page 15 and 16: 5, respectively: first, for an arbi
Page 17 and 18: Chapter 2 Space-Time Block Codes in
Page 19 and 20: easily achieve maximum diversity (t
Page 21 and 22: For example, a BPSK 2 × 2 block co
Page 23 and 24: multipaths corresponding to each tr
Page 25 and 26: where G(t) = [G (1) (t), . . . . .
Page 27 and 28: where D α and D β are two codewor
Page 29 and 30: For the quasi-static fading channel
Page 31 and 32: and the non-zero segment of any lin
Page 33 and 34: Let us consider the issue of achiev
Page 35 and 36: as A and B respectively, and observ
Page 37 and 38: L c = 1 0 7 9 14 0 0.00 30.56 16.00
Page 39 and 40: where D (k) (t) is defined in Equat
Page 41 and 42: For this special case of fixed spre
Page 43 and 44: where ˜R = ŘT 1 Ř−1 2 Ř 1 . (
Page 45 and 46: 2.5 Optimal Minimum Metric Codes In
Page 47 and 48: index ρ c rate size constl OMM 1 1
Page 49 and 50: 16 0 9 32-16ρ 2 32-16ρ 2 16 16 16
Page 51 and 52: Class ρ ∆ p (ζ v ) N p code ind
Page 53 and 54: 2. In a spread system (ρ = 0.3), t
Page 55 and 56: 10 0 SNR OMM spread orthogonal 10
Page 57 and 58: ρ c =0.3 10 0 SNR Rate 1 4X2 2 Rat
Page 59 and 60: Code Comparison, Joint ML Decoder,
Page 61 and 62: 2.6 Practical Considerations In thi
Page 63 and 64:
2.6.2 Sensitivity to Correlation Us
Page 65 and 66:
structure ] 1 structure ] 2 structu
Page 67 and 68:
Chapter 3 On Suboptimal Linear Deco
Page 69 and 70:
where σ t is signal-to-noise ratio
Page 71 and 72:
decorrelator. Denote ‖x‖ 2 R x
Page 73 and 74:
3.4 The Mapper Recall that the outp
Page 75 and 76:
Now we evaluate the overall decoder
Page 77 and 78:
and lim L HH R 3 H = r→∞ L r [1
Page 79 and 80:
the FIM for random d is [ ∂ ln P
Page 81 and 82:
Apparently R d is singular, which i
Page 83 and 84:
L t =2, L r =1, K=1, ρ=0.3, ignori
Page 85 and 86:
L t =2, L r =2, K=1, ρ=0.3, two re
Page 87 and 88:
Chapter 4 Nonlinear Hierarchical Co
Page 89 and 90:
signal corresponding to N c symbol
Page 91 and 92:
1. full diversity ∆ H (D i − D
Page 93 and 94:
epresent both for convenience. All
Page 95 and 96:
We may construct the whole set from
Page 97 and 98:
2. Most right isometries P are redu
Page 99 and 100:
★ ✥ S k ✧ a U j , P j ✲ b
Page 101 and 102:
3. Given Isometries U k U j and P j
Page 103 and 104:
[ 2 ] [ 168 ] [ 42 ] [ 128 ] 1 1
Page 105 and 106:
which are very likely to be optimal
Page 107 and 108:
4X3 BPSK(8 Codewords) and QPSK(64 C
Page 109 and 110:
Chapter 5 Regular Multiple Trellis
Page 111 and 112:
The high rate performance is poor,
Page 113 and 114:
ehavior of a regular trellis are: t
Page 115 and 116:
All the NHCs found in this work sat
Page 117 and 118:
Whenever there exist parallel trans
Page 119 and 120:
M m g=1 g=2 g=4 g=8 next jump b=2 2
Page 121 and 122:
provides a lower bound on the numbe
Page 123 and 124:
Label S k S Comment Figure 1/2 I2S2
Page 125 and 126:
Label S k O(= gbp) S(= gb) Figure 1
Page 127 and 128:
2X2 QPSK, |S 5 |=32 codewords 10 0
Page 129 and 130:
S k d S k S k ′ d H S 1 (1, 1, 1,
Page 131 and 132:
Rate 6/2 2X2 8PSK, |S 7 |=128 vs |S
Page 133 and 134:
1 172 251 330 1 1 1 304 413 486 87
Page 135 and 136:
Rate 5/3, 3X3 QPSK, |S 7 |=128 Code
Page 137 and 138:
parameters: the number of trellis g
Page 139 and 140:
[DS87] D. Divsalar and M. K. Simon.
Page 141 and 142:
[SHHS01] [Sle68] A. Shokrollahi, B.
Page 143 and 144:
ù"ú"ú"û ù"ü"ù ù"ý0øJþ ÿ
Page 145 and 146:
©¤¥¢©©©©¤©¤©©¤©¤©
Page 147 and 148:
J;KL4MNL=L;L0K=O;P=Q;ORO=Q;O=Q;Q;MN
Page 149 and 150:
0 1 14 1 7 8 Figure B.2: 2 × 2 BPS
Page 151 and 152:
0 2 168 42 128 93 247 117 223 1 30
Page 153 and 154:
0 2 168 42 128 93 247 117 223 30 18
Page 155:
0 2 168 42 128 93 247 117 223 30 18
show all

Space-Time Block Codes for Wireless Systems - The ...

Create successful ePaper yourself

Delete template?

Save as template?