Optimization of CPM Pragmatic Capacity

Design of spectrally-efficient continuous phase modulations

“…For instance, in the case of the MSK modulation, the choice F = 1.2, based on the 99% of the signal power, provides a spectral efficiency dramatically lower than the choice F = 0.55. This fact confutes various previous works as [5], [6], [16], where the search for spectrally efficient schemes was carried out without exploiting the above mentioned tradeoff between AIR and ASE. An optimization algorithm able to exploit it is presented in the next section.…”

“…An interesting conclusion, confirmed by other simulation results not reported here, is that, once all the other parameters are set, modulations based on a REC frequency pulse always outperform the corresponding modulations based on a RC frequency pulse. This fact was unexpected, since it is widely believed that the RC frequency pulses provide better spectral properties [1], [5], [6], [10], [11], and is discussed later. In Fig.…”

“…This explains why REC-based formats achieve higher spectral efficiencies than their RCbased counterpart. This behavior is probably due to a larger robustness to ICI of the REC-based schemes with respect to those based on RC-based pulses, and is under further investigation-the robustness to intentional ICI was indeed not accounted for in the classical literature [1] nor in recent works as [5], [6], [10], [11], [16].…”

“…Nonetheless, although the power of a CPM signal is typically concentrated in a small portion of the spectrum [3], the power spectral density (PSD) has rigorously an infinite support, so that a suitable bandwidth definition must be assumed. The most commonly employed definition is that based on the power concentration, which defines the signal bandwidth as the bandwidth that contains a given fraction (being this fraction a parameter) of the overall power [4], [5]. A different definition is used in [6], which is based on the Carson's rule and exhibits a nice mathematical tractability.…”

“…Moreover, we show that the optimal spacing depends on the signal-to-noise ratio (SNR), that is like to say that the effective bandwidth of a CPM signal does depend on the SNR. The framework proposed in this paper can be used for selecting, based on information-theoretic arguments, a set of CPM formats suitable for a particular application, similarly to what has been done in [5] and [10] (see also [11]), where anyway the effect of ICI has been neglected-a comparison between such papers is fair since the same single-user receiver is considered.…”