ew base stations are deployed for the LTE network. No immediate plans are made for upgrading 2G or 3G network base stations. There are reduced upgrade times and investment requirements. CHAPTER 3 DEPLOYMENT CHALLENGES IN EVOLVING 4G There is a need for separate systems to monitor existing 2G or 3G networks and new LTE networks. Possible upgrades are needed in the future depending on subscriber and services growth and the need for LTE expansion. In deciding on a particular strategy, network operators will have to consider the constraints described in the previous sections in terms of spectrum availability, existing network investments and services, investment, and ROI roadmaps. As per the data available in a majority of cases, network operators have preferred the strategy of network overlay for their deployment. In the following sections, we discuss the overall strategy with specific highlights about some countries' LTE deployment. South Korea In South Korea we looked at how SK Telecom, KT, and LG U+ went about their LTE deployments. SK Telecom adopted LTE network overlay as its strategy along with its existing 2G and 3G without going for an upgrade for the same. Its primary goal for the deployment was to meet the mobile broadband needs of its consumers. SK Telecom deployed its LTE services in 1.8Ghz with a bandwidth of 20Mhz. KT also adopted LTE network overlay to deploy LTE on the 800Mhz spectrum. It will also be able to utilize the 1.8Ghz spectrum it has after being allowed to discontinue the 2G services on the same. LG U+ went for a single RAN strategy using its existing CDMA infrastructure and deployed its LTE services using 2.1 Ghz spectrum. It did not have a 3G service operational and hence the strategy was probably easier to implement. Most Korean operators are looking to augment their LTE macro networks with small cell deployments to fill the gaps in residential areas and to continue to provide good coverage and services to its subscribers. Japan In Japan we looked at how NTT Docomo, KDDI, and SoftBank Mo