# Integration of LTE 230 and LTE 1800 in Power Wireless Private Networks
## 4 Integration of the Access Network
### The Access Network Integration Controller  
As shown in Figure 10, on the basis that we do not change the existing LTE 230 and LTE 1800 devices, the addition of a multinetwork integration controller can be used to help a device select the appropriate network for communication. The advantage of using an independent controller is that it does not need to interface with the original device. The access network integration controller only selects the equipment and is not responsible for the transmission of the data link, which is also in line with the design concept of control-transmission separation. The integration controller also has the function of simple signal reception and detection, which mainly identifies the available networks and estimates the signal quality, and only receives the downlink synchronization signal, control signal, and broadcast signal. Then, according to the actual situation of the power service, it chooses the network mode. The access network integration controller can detect the signal quality in real time or periodically and make optimal network judgments in real time. Figure 11 shows the procedure of mode selection at the device side. The main functionalities and the procedure of the access network integration controller are described as follows. Figure 10: An illustration of integration of the access network with a multinetwork integration controller. (1) Identification of Accessible Cells. In order to detect and identify heterogeneous power wireless networks, it is necessary to extract feature information that can uniquely distinguish specific networks. Since both LTE 230 and LTE 1800 are based on LTE technology, the cell ID detected from the PSS and SSS can be used as the feature information. Whether these two modes exist or can be accessed is based on whether the device can accurately decode the information on the physical broadcast channel (PBCH). If the related PBCH can be decoded, it means that this mode exists, and vice versa. Another function of decoding the PBCH is to collect access information of the accessible network, such as the bandwidth, control channel information, etc., so as to estimate the load rate of related cells and detect the channel quality. The detection of the PSS and SSS can be realized based on correlators described in the previous section, and the decoding of the PBCH needs blind detection. (2) Detection of Channel Quality  
In order to select the appropriate network for access, it is necessary to estimate the signal strengths of the different networks, and parameters such as the receive signal strength indicator (RSSI) and SNR can be estimated according to the PSS, SSS, and PBCH. The estimated channel quality can be used for mode selection as one of the measurement basics. (3) Estimation of the Cell Load Rate  
After detecting the PSS, SSS, and PBCH of the corresponding mode, the integration controller can speculate the physical resources for the physical downlink control channel (PDCCH). The detection of the number of PDCCHs is used as an index of the load rate of the current network, which can then be used to describe the busyness degree of the network and can also be used as one of the measurement basics for mode selection. (4) Mode Selection  
Mode selection or network selection is a comprehensive tradeoff process; the factors to be considered include the channel quality, cell load rate, and the type of power service transmitted. When taking the channel quality as the measurement standard, the selection of the switching threshold is very important. We can select the threshold through simulations or practical experience. When taking the cell load rate as the measurement standard, it is necessary to consider different load balancing algorithms, such as the polling method, hash method, and so on. When taking the type of power service as the measurement standard, it is necessary to use LTE 230 as the fallback, and the system chooses LTE 1800 as the preferred access network by default.