My question regards the real necessity to have subframe (3GPP Rel. 12) or slot (3GPP Rel. 13) aligned transmissions in the unlicensed band.
According to TR 36.889: "Channel reservation refers to the transmission of signals, by an LAA node, after gaining channel access via a successful LBT operation, so that other nodes that receive the transmitted signal with energy above a certain threshold sense the channel to be occupied." This signal is transmitted until the next subframe or slot boundary is reached so that transmissions are aligned.
The channel reservation signal defined by the 3GPP standard adds an overhead to LTE-LAA transmissions that impact on its performance. If there were no necessity for any kind of time alignment to the PCell the SCell performance could be increased.
Therefore, my question is, what would be the possible implications to all LTE layers if the transmissions were not aligned at all?
I don't think that paper answers the question. As far as I understood, it only says how LTE-LAA is implemented in Rel.13 but there is no information on why SCell has to be synchronized to the PCell.
I don't think that paper answers the question. As far as I understood, it only says how LTE-LAA is implemented in Rel.13 but there is no information on why SCell has to be synchronized to the PCell.
I am still trying to understand if the time alignment to PCell's time frame structure is really necessary. It seems there could be non-time aligned transmissions by the SCell as long as it transmits the necessary signals (RS, PSS, SSS, BCH, etc.).
Does anyone know if there is some kind of limitation to non-aligned transmissions?
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