In our work, we concentrate on FDD scheme with particular attention given to LTE/LTE-A systems. These observations have to be considered while realizing the concept of adaptive utilization of both frequency bands for data delivery only in one direction.
This isolation is required, as the problem of efficient canceling of strong interference at the reception interface echoed from the transmitted one is not mature enough today, although much progress has been achieved in the area of wireless full-duplex transmission. It is also worth noticing here that the frequency bands dedicated for UL and DL transmission are separated by a dedicated frequency gap guaranteeing enough isolation between the transmit and receive signals. Some interesting discussion can be found in, e.g. In other words, UL band can be utilized for DL transmission and vice-versa. In such a case, the problem of asymmetric traffic can be solved by allowing data transmission in a selected direction in both bands. Ĭontrarily, in the classical frequency division duplexing mode (FDD), the data between BS and MT can be delivered continuously in the time domain in both directions if needed, but the split between UL and DL is realized in the spectrum domain, i.e., dedicated fragments of the frequency spectrum are assigned to each transmission direction. Such an approach has been discussed in, e.g. As the wireless standards typically provide a very detailed time hierarchy (i.e., transmitted bits are organized into frames, bursts, chunks), it can be foreseen that asymmetric traffic can be easily managed by the application of adaptive allocation of more time slots to that direction which needs to serve higher traffic. In time division duplexing (TDD), a fragment of the frequency spectrum is utilized in both directions of data transmission (i.e., from base station (BS) to mobile terminal (MT), and from MT to BS), and the split between UL and DL is done in the time domain. The problem of asymmetric traffic, typical for modern wireless networks, can be solved in various ways depending on the applied duplexing schemes between uplink (UL) and downlink (DL) data delivery.
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