# Practical Performance Analysis of Interference in DSS System
## 4 DSS Interference and Solutions
### Rate Matching  
In order to dynamically share time-frequency resources with LTE networks, 5G supports two rate-matching schemes, RB-level and resource element (RE)-level. These two schemes are commonly used in NR data channels so that the NR scheduler can identify which REs are not available for data scheduling on the PDSCH [36]. In this paper, we use the RE-level rate matching scheme, which includes LTE CRS and ZP channel state information-reference signal (CSI-RS). LTE CRS matching is mainly used in 5G and 4G DSS. According to the 3 GPP protocol, LTE CRS rate matching is a function that must be supported by 5G terminals. 5G terminals need to report the support capability of LTE CRS rate matching according to the frequency band. LTE CRS rate matching allows NR not to send NR PDSCH on REs occupied by LTE CRS. When the 5G terminal demodulates the PDSCH, the terminal will skip the REs occupied by the LTE CRS [46]. LTE CRS matching is configured via the lte-CRS-ToMatchAround parameter in ServingCellConfig or ServingCellConfigCommon. The time-frequency position of the CRS in the LTE network is determined by the PCI and the number of antenna ports. The PCI determines the v-Shift during the CRS physical resource map. Therefore, when LTE CRS matching is configured in the 5G network, the lte-CRS-ToMatchAround needs to carry v-Shift and nrofCRS-Ports (number of antenna ports). Since the LTE bandwidth is part of the 5G bandwidth, when LTE CRS is matched, the center frequency and width of the LTE frequency bandwidth need to be configured through carrierFreqDL and carrier-BandwidthDL. The CRS physical resource map method of the multicast broadcast single frequency network (MBSFN) subframe of the LTE network is inconsistent with that of the common subframe. Therefore, if the subframe of the LTE network is an MBSFN, the lte-CRS-ToMatchAround also needs to carry the configuration of the MBSFN. LTE PDCCH is configured with 1 symbol, NR PDCCH is configured with 2 symbols in the time domain and 24 RBs in the frequency domain, using interleaving mapping with interleaving length (\(R\)) and resource element group (\(REG\)) binding length (\(L\)) configured as 2. The method of interleaving mapping is as follows. The \(REG\) is first bound and \(L\) is defined as the binding length of the \(REG\). The \(REG\) bundle is configured by the high-level parameter reg-BundleSize, and \(i\) is defined as \(REGs\), as shown in Equation (1). \[i=0,1,...,N_{REG}^{CORESET}/L-1 \tag{1}\]  
Figure 8: Simulation results of buffer setting. The number of _REGs_ in _CORESET_ is equal to the number of _RB_s in _CORESET_ plus the number of symbols in _CORESET_, as shown in Equation (2). \[N_{REG}^{CORESET}=N_{RB}^{CORESET}+N_{symb}^{CORESET} \tag{2}\]  
CCE \(j\) is composed of _REG_ bundles \(\{f(6j/L),f(6j/L+1),...,f(6j/L+6/L-1)\}\), where \(f(x)\) is the interleaver. CCE means Cooperative Computing Environment. When using interleaving mapping, when \(N_{symb}^{CORESET}=1,L\in\{2,6\}\). When \(N_{symb}^{CORESET}\in\{2,3\}\), \(L\in\{N_{symb}^{CORESET},6\}\). This design ensures that \(N_{RB}^{CORESET}/L\) is an integer. In this way, all _REGs_ can be fully used when binding. Further, Equations (3) to (7) can be adopted for interleaving. \[f(x)=(rC+c+n_{shift})mod(N_{REG}^{CORESET}/L) \tag{3}\]  
\[x=cR+r \tag{4}\]  
\[r=0,1,...,R-1 \tag{5}\]  
\[c=0,1,...,C-1 \tag{6}\]  
\[C=N_{REG}^{CORESET}/(LR) \tag{7}\]  
\(R\) is the length of the interleaver, which can be configured as 2, 3, or 6. It can be configured through the high-level parameter interleaver size. \(n_{shift}\in\{0,1,...,274\}\) can be configured through the high-level parameter shift Index. If the upper layer is not configured, then \(n_{shift}=N_{ID}^{cell}\). \(C\) must be an integer. Thereby, the interleaving mapping can be completed. In addition, LTE needs to reserve 24 _RB_s for NR to send SSB and remaining minimum system information (RMSI) every 20 ms. When NR sends SSB and RMSI, LTE does not send CRS within the SSB/RMSI region [21,47,48]. Figure 9 shows a schematic of rate matching.