ncy, and timing synchronization requirements. If the existing transport cannot sustain these requirements, the transport network needs to be upgraded. Despite considering the LLS in the 5G study, 3GPP decided not to standardize it due to concerns with the complexity of the fronthaul network interface. As the 5G deployment schedule approached, several industry players decided to carry on that work in xRAN (later to become O-RAN Alliance). Eventually, O-RAN produced the LLS specification (option 7-2), which is described in this section. Furthermore, CPRI and IEEE1914.3 offer technical solutions for split option 8. The pros and cons of these options are discussed below. The fronthaul network interface supporting the LLS is somewhat more complex, com- pared with the other interfaces used in NG-RAN (e.g. Xn and F1). Therefore, while the standard makes it possible to deploy NG-RAN network nodes (e.g. an RU and a DU) from different vendors, this comes at a cost of more complex system integration and interop- erability testing. 4.5.2 Market Drivers NR introduced a plethora of new technologies, such as massive MIMO, flexible numerol- ogy, high bandwidth, and support for the mmWave spectrum frequency range. These technologies, among other things, substantially increased the 5G network speed, but they also created new technical challenges compared to 4G. For example, NR baseband processing requires much higher computational capability. In addition, NR serves more diversified user groups such as URLLC, eMBB, and massive Internet of Things (IoT). Deploying a separate mobile network for each user group is prohibitively expensive and may not be feasible due to logistic complexity. Therefore, the traditional integrated physical NG-RAN architecture with monolithic gNB may not be suitable to serve those diverse 5G use cases due to lack of flexibility, performance, and cost. A new NG-RAN physical node architecture is required, and cloud-based NG-RAN is widely considered as a viable solution for addressing the challenges mentioned a