Eight-Antenna LTE FDD System of Xuzhou Telecom

China Telecom faces several problems in deploying a 4G LTE network. For example, high-frequency networking and insufficient site resources limit the coverage of the 4G network. China Telecom has therefore chosen ZTE as its strategic partner to help solve these problems and expand 4G LTE coverage. Recently, ZTE worked with China Telecom Xuzhou Branch (Xuzhou Telecom) to test and trial an eight-antenna LTE FDD system.

LTE has limited coverage in the uplink because of high-frequency bands, high data traffic, and co-channel interference. ZTE has devised an eight-antenna LTE FDD system that uses proprietary technologies to address this coverage issue while fully utilizing existing site resources.

ZTE’s eight-antenna LTE FDD system uses a baseband pool B8200 and an advanced radio frequency unit R8862A (Fig. 1). The system has the following benefits:

●    Two cascaded R8862As are used to reduce feeders and facilitate engineering implementation.

●    An advanced interference-rejection combining (IRC) algorithm is used, and it is possible to switch between IRC and MRC algorithms.

●    A closed-loop power control (CLPC) mechanism is used to reduce the transmit power of terminals. This makes terminals more energy efficient and reduces network interference.

●    Antenna arrays are not arranged as ordinary parallel dual-polarized arrays but as vertical dual-polarized arrays. This means the arrays can receive more multipaths, increase diversity gain, and improve cell-edge performance.

Xuzhou Telecom has constructed both eight-antenna and two-antenna LTE FDD sites. A total of 120 eight-antenna LTE FDD sites have been constructed. The proportion of eight-antenna LTE sites to two-antenna LTE sites is 2:8. Eight-antenna LTE sites are mainly used to provide coverage for suburbs, counties, and villages.

When selecting a site for eight-antenna LTE, Xuzhou Telecom considers whether the site makes full use of Xuzhou Telecom’s existing resources, provides average coverage radius of about 1 km, and is amenable to tower-mounted installation that facilitates feeder installation.

In the first quarter of 2014, ZTE and Xuzhou Telecom jointly deployed an eight-antenna LTE FDD network in Xuzhou City. After the deployment, they conducted outdoor drive tests and indoor fixed-point tests and collected 300,000 valid samples for data analysis.

Four valid clusters were tested in Xuzhou City. The average uplink throughput reached above 35 Mpbs, which is the highest in Jiangsu province. In densely populated urban areas, the average uplink throughput of the eight-antenna LTE site was 1.2 to 1.3 times that of a two-antenna LTE site. In counties, the average uplink throughput of the eight-antenna LTE site was 1.5 to 1.8 times that of a two-antenna LTE site (Fig. 2). In the suburbs, the average uplink throughput of the eight-antenna LTE site was 1.8 to 2 times that of a two-antenna LTE site. For indoor coverage, the average uplink throughput of an eight-antenna LTE site was 1.8 to 2 times that of a two-antenna site.

The trials conducted on ZTE’s eight-antenna LTE FDD system for Xuzhou Telecom are significant to China Telecom. The test results and engineering verification show that ZTE’s eight-antenna LTE FDD system is suitable for counties and suburbs. The gain in uplink capacity is relatively high, and site acquisition and installation is more convenient in counties and suburbs compared to dense urban areas.