The realization of practical time-orthogonal shaping filters is discussed in [26].
In particular, for open-loop systems the authors in [20, 21] proposed the use of time-orthogonal shaping filters for each of the transmit antennas.
Hence, the time-orthogonal shaping filters can be designed to have the same bandwidth requirements as a single filter narrowband system.
Let us now provide a discussion regarding the difference between the implementation of time-orthogonal shaping filters in [22, 26] and in our AGSSK-TOSD proposal.
At this point, it is also important to provide a discussion regarding the bandwidth requirements of using time-orthogonal shaping filters.
Due to this, we, furthermore, propose an enhancing method for AGSSK which relies on the use of time-orthogonal shaping filters for the different constellation points.
Regarding the generation of time-orthogonal shaping filters for AGSSK-TOSD with the same time duration and bandwidth, we consider the method described in [26].
In addition, the use of time-orthogonal shaping filters for AGSSK-TOSD enables diversity gains larger than the number of active antennas without any antenna selection technique, as it was proven.
Such a discussion has been provided in ([26], Section V), where it is shown that depending on the technology used to design them, time-orthogonal shaping filters can be designed for narrowband systems with the desired bandwidth spectrum.
As it is stated, the method that is proposed in [33] for the design of the time-orthogonal shaping filters guarantees that all of them have the same time-duration and (practical) bandwidth.
In [22, 26], the time-orthogonal shaping filters are used on an antenna-basis, which means that each transmit antenna use a different shaping filter and all of them are time-orthogonal with respect to each other.
