mohatta2015.pdf
signal processing from power amplifier operation control point of view
signal processing from power amplifier operation control point of view
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50 MATCHED FILTERING<br />
where<br />
É£>) = (l/^ëc^HMi-nYi) (2.82)<br />
n=(l<br />
L-l<br />
h(i) = Y^gtRp{t-T t ). (2.83)<br />
i=(l<br />
While the notation is a little sloppy, it should be clear when we are referring to the<br />
chip-level net response h(i) and the symbol-specific net response h¡¿ m(t)·<br />
Similar to Rake reception, we will consider chip-level and despread-level equalization.<br />
With chip-level equalization, we will initially process the received signal<br />
to produce chip samples v(qT s ).<br />
Instead of matching to the medium response,<br />
we will apply some other form of processing to suppress ISI. With despread-level<br />
equalization, we will initially process the received signal to produce despread values<br />
x fe,'.m„)(9'- , s) s iven b y<br />
n=()<br />
Instead of then matching to the medium response, other processing will be used.<br />
Both chip-level and despread-level equalization can be symbol-spaced (T s = T c ) or<br />
fractionally spaced (T s = T c /Q).<br />
There is a third form of equalization, symbol-level equalization . With this form,<br />
we perform full matched filtering first, then work with the z¿ (mo) values. In the<br />
multiuser detection literature, this form of equalization is often found.<br />
The choice of chip-level, despread-level, or symbol-level equalization depends<br />
on differences in complexity as well as flexibility and legacy issues. The different<br />
forms are not quite equivalent in performance, though they are often close. In the<br />
subsequent chapters, we will see examples of each.<br />
2.4.1.1 OFDM Let's revisit the OFDM case. Assuming one transmit antenna,<br />
one receive antenna, equal-energy symbols, partial MF to the chip pulse, sampling<br />
once per chip (T s = T c ),'a chip-spaced channel response (re — ÍT C ), and aligned<br />
sampling (io = r 0 ) (2.81) becomes<br />
K-\ oc N,.-l L-l<br />
v(nT c ) \= s/E s /N c Σ Σ Sfc ( m ) Σ Ck M Σ 9(Rp(( n ~ Wc ~ mN c T c )<br />
fc=() m=-oo n=0 {=(><br />
+ ñ(nT c )<br />
K-l oo JV,.-1 L-l<br />
h y/E,/N c Σ Σ Sfc(m) Σ C fc(") Σ »*((" - £ ) T ' - mN c T c)<br />
fc=0 m=-oc n=0 f=()<br />
+ ñ(nT c ). (2.85)<br />
An example for N c = 6,NCP = 2, NMB = 4, and L = 3 is shown in Fig. 2.6.<br />
Consider the symbol period mo = 0. Let's assume a worst-case delay spread<br />
in which L = Ncp + 1. Symbol energy is present in samples n = 0 through