This possibility is needed for the types of spectrum propagation models that need to have a pointer
to the TX and RX antenna arrays to perform calculations, such as e.g.,
ThreeGppSpectrumPropagationLossModel, which currently has hard limitation of having a maximum of 1
antenna array instance per device. ThreeGppSpectrumPropagationLossModel now inherits a new class
PhasedArraySpectrumPropagationLossModel. Its DoCalcRxPowerSpectralDensity function has now two
additional parameters: TX and RX antenna arrays. Also, AddDevice function is removed from
ThreeGppSpectrumPropagationLossModel, because it is not anymore needed to specify for each
device its TX/RX antenna, since these are now passed as parameters. Hence, to use
ThreeGppSpectrumPropagationLossModel, when implementing Spectrum PHY features,
modules should implement the function of SpectrumPhy GetAntenna to return the instance of
PhasedArrayModel of that SpectrumPhy. These instances will be passed by MultiModelSpectrumChannel
(one of the core classes in the spectrum module) to propagation classes, children of
PhasedArraySpectrumPropagationLossModel, when it is necessary to DoCalcRxPowerSpectralDensity to
callculate the propagation loss.
Additionally: Fixed pair key generation for 3gpp channel model: Previous implementation was
using a cantor function of two integer of 32 bits and as a results was giving a unique
representatio of 32 bits. This is wrong, because such function needed even more than 64
bits to represent that value. Even if in ns-3 simulation we are not going to have such large
node numbers, we should fix this. Instead of just changing 64 bits from cantor function, I propose to
replace the cantor function with just simple concatenation of two 32 bits.
I also propose moving min and max inside of the function, to prevent some eventual future errors
in using GetKey, because with the previous implementation there was assumption that who calls GetKey
will previously sort its parameters, and first provide the min value, and then the max value,
and this was not even documented.
