Biomedical Engineering Reference
In-Depth Information
7.4 InitialPopulation
As.the.first.step.in.a.genetic.algorithm.(GA),.a.population.of.initial.chromo-
somes. (solutions). is. generated.. The. following. discussion. presents. how. the.
power.and.the.rate.values.of.each.user.in.the.chromosomes.are.generated.
7.4.1 Power generation
In.the.power.generation.scheme,.the.transmission.power.of.a.user.is.to.be.gen-
erated.within.two.new.specified.power.ranges.with.regard.to.the.link.gains.
instead.of.the.range.between.minimum.and.maximum.allowable.power..This.
is.because.users.with.larger.link.gains.should.utilize.lower.power.to.reduce.the.
multiple.access.interference.of.other.users..This.can.thus.improve.their.signal-
to-noise.ratios.and.reduce.the.chance.of.violating.their.QoS.constraints.
In.contrast,.those.with.smaller.link.gains.should.utilize.higher.powers.for.
acquiring.the.QoS.constraints.they.demand..However,.a.purely.random.value.
within. the. specified. minimum. and. maximum. allowable. power. failed. to.
manage.this,.and.it.is.common.to.have.a.large.number.of.QoS-violating.users.
The. proposed. transmission. power. generation. rule. was. designed. as. fol-
lows:.If.the.link.gain.of.a.user.is.greater.than.or.equal.to.a.threshold.value.
α,.the.power.value.is.generated.randomly.between.
[
]
,.where.
p
,
p
p
i
.
i
min
border
min
and.
p
border
.
are.the.initial.minimum.power.and.the.borderline.power,.respec-
tively.. Otherwise,. it. is. generated. randomly. between.
[
]
,. where.
p
,
max
p
border
i
p
i
.is.the.initial.maximum.power.
A.suitable.set.of.values.of.α,.
min
max
p
i
,.which.produced.better.
results.(i.e.,.more.solutions.have.zero.QoS-violating.users),.could.be.selected.
after.testing.and.comparing.their.different.combinations..In.our.simulations,.
these.values.were.set.as.α = 100,.
p
i
,.
p
border
,.and.
max
p
i
=
0.001
,.
p
border
=
0.005
,.and.
p
i
=
0.01
.
min
max
7.4.2 rate generation
Since.the.transmission.rate.of.a.user.does.not.affect.the.signal-to-noise.ratio.
of.the.others,.it.is.simply.randomly.generated.between.the.guaranteed.and.
the.peak.rates.of.the.requested.media.type.
Note.that.even.though.the.power.and.rate.generation.method.given.may.
not.be.the.best,.it.is.able.to.improve.search.performance.
7.5 JumpingGeneTransposition
There. are. four. possible. types. of. genes. (for. transmission. power,. voice. user.
transmission.rate,.data.user.transmission.rate,.and.video.user.transmission.
rate).in.a.chromosome..Thus,.four.corresponding.types.of.transposons.can.
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