Abstract
An advanced duplex scheme called cross-division duplex (XDD) is proposed to enhance uplink (UL) coverage in time division duplex (TDD) carriers by utilizing self-interference cancellation (SIC) capability at a base station. With XDD, it is possible to combine TDD’s ability to efficiently handle asymmetric UL and downlink (DL) traffic with frequency division duplex’s coverage advantage. To do so, XDD simultaneously operates UL and DL on the same TDD carrier but on different frequency resources. Such operation leads to severe interference on the received UL signal at the base station which requires two levels of SIC implementation; antenna and digital SIC. More than 50 dB of interference is removed through the antenna SIC using electromagnetic barriers between the transmitting and receiving antennas. The remaining interference is removed by the digital SIC based on estimating the non-linear channel of the circuit at the receiver baseband. It is verified by simulation and analysis that with the proposed XDD, the UL coverage can be improved by up to 2.37 times that of TDD. To check the feasibility of XDD, a Proof-of-Concept was developed where it was observed that the benefits of XDD can indeed be realized using the proposed SIC techniques.
Highlights
The first release of the fifth generation (5G) standard, called new radio (NR), was completed in the 3rd Generation Partnership Project (3GPP) [1]
Simulations, and PoC results show that XDD can extend the UL coverage area to be more than 2 times that of time-division duplex (TDD)
While only one transmit antenna and one receive antenna are considered in this PoC, it is worth noting that XDD PoC can be implemented with relatively low complexity even when a large number of antennas are used
Summary
The first release of the fifth generation (5G) standard, called new radio (NR), was completed in the 3rd Generation Partnership Project (3GPP) [1]. Compared to 4G Long Term Evolution (LTE), NR supports operation on higher carrier frequencies up to tens of GHz, a larger bandwidth up to 400 MHz, and a larger number of mandatory receiver antennas up to 4 at the user equipment (UE) to meet higher requirements such as peak data rate up to 20 Gbps and 1 ms latency [4]. Due to the higher frequency bands used for 5G in order to support wider bandwidths, a larger path loss is inevitable [6]. Another factor that impacts the NR coverage is that majority of the new 5G spectrum allocations around the globe are time-division duplex (TDD) carriers located at around 3.3 −3.8 GHz, 28 GHz, or 39 GHz which are much higher than that of 4G [7]
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