SoftBank Mobile Deploys Cloud RAN and Conducts TD-LTE Advanced Trial in 3.5 GHz Band
I recently participated in a field test drive demo conducted by Softbank Mobile of the world's first trial network supporting TD-LTE Advanced technology in the 3.5 GHz band. Driving through the crowded streets in Tokyo's densely populated Ginza district, I saw the density of SoftBank's network of rooftop LTE antennas, and witnessed a live measurement of average download speeds of 500 Mbit/s and peak download speed reaching 770 Mbit/s.
During the test, SoftBank engineers described the cutting-edge LTE Advanced technologies used to achieve those download speeds, including carrier aggregation, coordinated multi-point (CoMP), ultra-wideband remote radio units (RRUs), 4x4 MIMO, and cloud RAN, in which baseband units are pooled in telco central offices. SoftBank also demonstrated a prototype five-carrier aggregation technology for TD-LTE that can provide a maximum download speed of 1.2 Gbit/s. When deployed in combination with ultra-wideband RRUs, this network can support instantaneous bandwidth of more than 100 MHz and can be customized on demand to accommodate new spectrum as it becomes available. Softbank detailed its deployment of 3.5 GHz LTE-TDD small cells at 37,000 sites offering the capacity needed to handle traffic growth in the major urban areas of Japan and complementing its existing LTE FDD coverage network. Huawei helped build this SoftBank pre-commercial trial TD-LTE network using cutting-edge LTE Advanced technologies to achieve those download speeds with 100 MHz of 3.5 GHz spectrum.
All this was designed to show how mobile operators can use TD-LTE Advanced technology, small cells, and the 200 MHz of spectrum in the 3.4-3.6 GHz band to achieve peak data rates of up to 1 Gbit/s to meet the requirements of for true 4G IMT Advanced as defined by the International Telecommunication Union., SoftBank believes that paired LTE FDD spectrum ensures symmetrical allocations between uplink and downlink, while LTE TDD allows for more downlink capacity to support video streaming and downloading without the need for guard bands. Using small cells with advanced interference-cancellation technologies that improve quality and performance even at the cell edge and more than 100 MHz of spectrum in the 3.5GHz band, The trial demonstrated the performance, reliability, and stability of LTE TDD technologies in the 3.5GHz band and their effectiveness in solving coverage issues and addressing co-frequency band interference. SoftBank clearly demonstrated that all these resources will be required to achieve the 1,000-fold growth in mobile broadband data traffic expected over the next 10 years.
But the real key to the SoftBank trial demo was the use a small cell Cloud RAN network leveraging existing fiber links to backhaul traffic ultra-wideband remote radio units (RRUs) small cell to pooled baseband units in telco central offices throughout Tokyo. Wireless 20/20 has updated its WiROI™ LTE Tool to help operators analyze the impact of Cloud RAN technology on their business. The WiROI™ C-RAN Tool models the implementation of RRUs and C-BBUs along with the fiber interconnect options in order to calculate the CapEx and OpEx of deploying Cloud RAN technology in an urban market. The Tool allows the user to compare the Total Cost of Ownership (TCO) of C-RAN vs. all-in-one small cells and highlights the key scenarios where Cloud RAN technology can bring benefits to an LTE operator. Model cities include Tokyo, Beijing and NYC.
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