Test Driving TD-LTE Advanced
People have asked me why I spent the last week of August -- one of the hottest and steamiest weeks of the year -- in Tokyo. I was invited by SoftBank Mobile to experience the world's first trial network supporting TD-LTE Advanced technology in the 3.4-3.6GHz band.
I must say the drive demo was quite impressive. We drove through crowded Tokyo streets and saw the density of SoftBank's network of rooftop LTE antennas, with a live measurement of average download speeds of 500 Mbit/s and peak download speed reaching 770 Mbit/s. Huawei helped build the SoftBank pre-commercial TD-LTE Advanced trial network I experienced in Tokyo's densely populated Ginza district.
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. But the real key to the trial demo was the use of small cells and more than 100 MHz of spectrum in the 3.5GHz band, with advanced interference-cancellation technologies that improve quality and performance even at the cell edge.
The trial clearly 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. 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 3.4-3.6GHz 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 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.
Personally, I would also have liked to see a practical demonstration of the new applications that would be enabled by these blazing-fast download speeds, such as mobile 3D HDTV, virtual reality gaming, and mobile telepresence.
This SoftBank TD-LTE Advanced technology demo was hosted by the Global TD-LTE Initiative (GTI). Having attended the 2013 GTI Workshop and GTI Asia Conference in Shanghai, I was the only industry analyst to participate in the GTI Ad Hoc Seminar on 3.5GHz spectrum Aug. 27-28 in Tokyo. More than 120 participants attended the GTI 3.5GHz Interest Group workshop. They represented 56 organizations, vendors, and operators from 17 countries, including China Mobile, SoftBank, UK Broadband, Bollore Telecom from France, and Wateen Telecom from Pakistan. A large and strong vendor ecosystem of vendors also supported this 3.5 TD-LTE Advanced workshop, including Huawei, Ericsson, NSN, ZTE, Hitachi, Qualcomm, Airspan, Telrad (Alvarion), Alcatel-Lucent, Datang Mobile, Altair, and Sequans.
Meeting participants discussed the latest developments related to improving network coverage and performance by leveraging new technologies such as Carrier Aggregation. Many attendees came to Tokyo to help speed up the release of 3.5GHz spectrum, which is critical for unleashing the power of TD-LTE Advanced technologies. Many countries are expected to release more 3.5GHz spectrum to promote development of mobile broadband services using high-spectrum bands. Japanese officials recently refarmed the 3.5GHz band to enable LTE Advanced performance with small-cell deployment and offload capabilities. SoftBank predicts that the Japanese government will allocate a large block of spectrum for commercial LTE by 2015.
In the US, the Federal Communications Commission has been working to open up the 3.5GHz band for wireless broadband small-cell deployment via a shared-access system with incumbent licensees. The propagation loss characteristics of the 3.5GHz bands make them amenable for high-frequency reuse to enable dense small-cell deployments, and the amount of available spectrum in these bands fares well for broadband quality. In Europe, the CEPT/ECC is working with national regulators to define the preferred TDD or FDD allocation system for accommodating multipoint fixed wireless systems in the 3.4-3.6GHz and 3.6-3.8GHz bands. Guidelines may soon be issued to synchronize TDD spectrum to avoid restricted blocks and large guard bands.
The GTI 3.5GHz Interest Group has proposed that 3.5GHz spectrum be released in at least 40MHz blocks to realize the inherent deployment advantages of its wide bandwidth. Global harmonization of 3.5GHz spectrum in LTE Bands 42 and 43 is essential to ensure the sharing of the same ecosystem, particularly for chipsets and terminals.
The availability of terminals supporting the 3.5GHz band is critical, so operators and vendors are starting to work together to increase the global production of low-cost 3.5GHz LTE TDD devices.
— Berge Ayvazian, Senior Consultant, Heavy Reading