ZTE's Full-Band LTE TDD Product Portfolios Boost Flexible Networking

In 2009, TeliaSonera was the only operator to launch commercial LTE networks in Sweden and Norway. By the end of 2010, these networks neared their primary stage of commercialization. Leading operators have begun shifting their focus from discussing LTE concepts to putting these concepts into practice. China Mobile, Softbank, and Hutchison Whampoa have already started deploying TD-LTE worldwide. TD-LTE’s coverage is attracting much attention; a comprehensive and three-dimensional coverage solution is required before TD-LTE can be widely commercialized.

Requirement for Three-Dimensional Wireless Coverage

TD-LTE must provide macrocell coverage for densely populated cities, less-populated cities, and suburbs and villages. It must provide microcell coverage for urban hotspots and CBDs; in-depth coverage in gyms, office buildings, conference centres, exhibition halls, and other large venues; and point coverage for high-speed railways, overpasses, bridges, subways, tunnels, and scenic spots. An increasing number of operators realize that only three-dimensional coverage provided by TD-LTE can improve user experience.

TD-LTE coverage can be classified as indoor, outdoor, or special scenario. Mostly, network quality can be improved by enhancing indoor coverage. However, there are some issues that need to be considered:

how to meet the substantial increase in demand for data services without taking up too much space

how to meet different three-dimensional coverage requirements

ensuring there is multifrequency equipment to accommodate various frequency resources available to operators

how to provide satisfactory coverage in fast moving environments

how to provide low-cost, high-quality coverage and save network investment in remote and difficult-to-access areas.

ZTE's Concept of Coverage

ZTE has studied the diverse needs of customers and has much experience in TDD. ZTE proposes large-capacity, full-band, multilevel TD-LTE products for broad coverage in different scenarios.

Macro base stations are for outdoors. A distributed BBU+RRU architecture has large capacity for meeting networking requirements in densely populated cities, less-populated cities, suburbs, and villages. Micro base stations provide moderate-traffic solutions for hotspots and CBD areas. Pico- and femto-integrated base stations provide solutions for light and heavy traffic in big gyms, office buildings, conference centres, exhibitions halls, and other large buildings. Pico base stations can be installed on a derrick, wall, or other location, and they are especially suitable for buildings where indoor construction is not possible. Pico base stations support Ethernet transmission, which makes network deployment easy. Compared with macro stations, pico and femto base stations cost less and cover more regions. The pressure on capacity of an outdoor macro stations is reduced.

For remote places, long-distance coverage solutions are used, and ZTE proposes distributed base stations. Power, transmission, and baseband are put into station-based cabinets, and RRUs are installed according to specific landscapes.

For fast-moving scenarios, such as high-speed trains, ZTE proposes adaptive frequency-offset correction algorithm. Information about the current subframe frequency deviation can be detected in real time at the baseband level. Then, the baseband signal phase offset caused by frequency deviation is corrected. As a result, demodulation in the base station is improved and the Doppler Effect can be countered at up to 500 km/h. The SDR-based RRU can support cascaded drawing, which suits continuous relay coverage for band-shaped regions.

For network coverage, ZTE proposes hierarchical deployment that is flexible in terms of capacity, planning, and implementation.

A wireless data network is suitable for unbalanced distribution. Operators can choose the type of ZTE TD-LTE base station according to different traffic conditions and coverage. In heavy traffic regions, macro stations are insufficient, and the station addresses are extremely difficult to access. With flexible deployment of micro base stations, regional traffic capacity can be offloaded. These stations also have limited interaction with macro base stations because of lower transmit power.

To avoid overinvestment, operators usually build a thin network of macro base stations for wide coverage in the initial stage. As the network expands with an increasing number of subscribers, operators can plan thicker and deeper networks in high-traffic regions according to actual needs. The whole network can be flexibly controlled.

Full-Band LTE TDD Product Portfolios

The spectrum resources available to most operators using TD-LTE are diverse. China Mobile has 1.9G, 2.0G, 2.3G and 2.6G bands (F, A, E and D bands). In a TD-SCDMA system, 1.9G and 2.0G use 55 MHz, and for TD-LTE indoor coverage, 2.3G uses the 50 MHz between 2320 MHz and 2370 MHz. For TD-LTE outdoor coverage, 2.6G uses the 50 MHz between 2570 MHz to 2620 MHz. Besides the universal 2.3G and 2.6G band, ZTE’s TD-LTE equipment also supports the 3.5G band, which is reassuring for operators planning for LTE development.

In 2010, ZTE launched a series of full-band TD-LTE products which include 8 channel and 4 channel outdoor single-frequency RRU, and dual-channel indoor RRU. These products can satisfy the networking requirements for F, A, E and D bands in different scenarios. During China Mobile’s fourth-round of bid for TD-SCDMA, ZTE introduced its double-module product, R8928FA, for indoor and outdoor coverage.  R8928FA supports TD-LTE system without any changes being made to the antenna. An operator’s investment is guaranteed to the greatest extent.

The full-band BBU and RRU products can be flexibly combined. They can also be combined into different macro and micro base stations to meet frequency and station address requirements in different scenarios. The networking is more flexible and construction is more convenient.

Consultancy firm, Open Vista, issued its LTE Development Briefing 2010 in February 2011. In the briefing, coverage, capacity, serialization, portfolio, and evolution of LTE products are discussed. ZTE was noted as having highest number of TD-LTE product series and as being the first commercial manufacturer of soft base stations. ZTE is also the first company to support CDMA/LTE, GSM/LTE, UMTS/LTE and GSM/UMTS/LTE modules as well as TD-LTE in a unified hardware platform.

The development of LTE will gain pace in 2012. ZTE’s full-band TD-LTE products help operators deploy higher quality, more flexible networks and pave the way to success.