This can be accomplished by spatially separating the antennas from
each other. Generally speaking, antenna spacing of half a wavelength is adequate; however, it has
been shown that the antenna spacing is dependent on the local scatterers present near the receiver. It
is for this reason that antenna distance separation at the BS is larger than that at the MS.
A few multiple-antenna solutions exist, we present them in Table 5.4.
262 CHAPTER FIVE
FEC Decoder Performance Comparisons
1.E??“07
1.E??“06
1.E??“05
1.E??“04
1.E??“03
1.E??“02
1.E??“01
0 1 2 3 4 5 6 7 8 9 10 11
Eb/No (dB)
BER
R = 1/2, K = 8, Hard
R = 1/2, K = 5
Turbo
(18 iters)
Uncoded
R = 1/2, K = 7, Soft
R = 1/2 +
RS(204,188)
FIGURE 5.49 A comparison of various FEC techniques in an AWGN channel.
TABLE 5.4 Multiple-Antenna Combining Comparisons
Technique Complexity Performance
Switch/selection Low Good
Equal gain combining Middle Better
Maximal ratio combining High Best
Optimal combining Very high Very best
Table 5.4 orders the multiple-receive antenna techniques in terms of implementation complexity
as well as link level performance. The simplest technique is the switch/selection (SS) which is labeled
to have low complexity and good performance.
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