Market

By 2014, China Mobile’ s 4G network will cover all high-speed railways in

China, for a total of 15,000 kilometers. As high-speed railways continue

to grow, 4G networks that grow with them will exceed 30,000 kilome-

ters in 2020.

By 2013, high-speed railways in 16 countries around the world have oper-

ated total 23,000 kilometers, 17,000 of which are under construction

Implemented or in construction

Planning

high-speed railways covering with 4G networks

Challenges & Solutions

Different from ordinary wireless environments, high speed scenarios demand more of networks and pose greater challenges to network con-struction.

Inter-site distance along high-speed railways is usually shorter than 1.2 kilome-ters. When a train is running at 300 km/h, handovers occur every 7 seconds or less. Such frequent handovers during extra-high- speed movements lead to a large amount of signaling or even to a signaling storm. Moreover, the train is running between cell centers and cell edges, which significantly impacts service rates even causing service drops.

Huawei has deployed the first LTE network supporting cell combination using 12 dual-channel RRUs in the globe. This technology substantially reduces the handover frequency in high speed scenarios. When a user is moving at a 300 km/h speed, handovers are performed every 72 seconds on average. The handover frequency can be reduced by 90%. This technology greatly reduces the amount of signaling and shortens time spent at cell edges, largely guaranteeing user experience.

As LTE networks continue to grow and attract more and more users, network capacity becomes an important issue. Each LTE carrier currently supports several hundred users. However, there are more than 1000 passengers on a high-speed train. If most of the passengers use LTE services, single-carrier networking cannot meet service requirements.

Huawei's multi-carrier solution provides multi-frequency multi-carrier antennas and RRUs, and the capacity of Huawei BBUs can be expanded by just adding boards. Using this solution, a single-carrier network can be quickly reconstructed to support multiple carriers, thereby meeting service requirements of increasing users.

Capacity challenges imposed on single-carrier networks Multi-carrier solution, easily resolving capacity issues

Networks deployed along high-speed railways cover long narrow areas. So high-gain antennas are used. However, legacy high-gain antennas produce strong sidelobe interference on the public network, which affects the coverage and capacity of cells close to high-speed railways.

Always technologically innovative, Huawei has introduced a unique beamforming design and on this basis, has developed narrow-beam antennas, which can consid-erably reduce sidelobe interference on public networks. This design helps improve network coverage in the target area, thus improving the network performance.

Strong interference of traditional antennas Innovative dual-frequency narrow-beam antennas

Frequent handovers affect user experience. World’s First 12-cell combination technology

When a user is moving relative to an eNodeB, the transmit frequency of the eNodeB is different from the receive frequency of the user due to the Doppler shift. In an LTE system, this Doppler shift causes interference in or between OFDM symbols. The faster the speed, the greater the shift and, therefore, the greater the interference. The interference may cause an SINR so high that the receiver cannot demodulate the data from the transmitter, and as a result, the user cannot access the network.

Huawei has developed the patented AFC algorithm, which enables a rough frequency adjustment at the initial transmission stage and then continuous fine tuning to mitigate the frequency shift and in this way, to guarantee correct demodulation and decoding of data. AFC can eliminate the Doppler shift that occurs at speeds of up to a 500 km/h. So far, AFC has been verified on the Shang-hai maglev train (430 km/h) and Fully tested on the Zhengzhou-Xuchang and Beijing-Tianjin high-speed railways, preferably ensuring LTE network performance.

Having a low frequency Having a high frequency

Doppler shift hurts receiver demodulation performance. Automatic Frequency Control (AFC) algorithm

Interference

Beijing-Tianjin High-Speed Railway

First high-speed railway covered by LTE network

The 1.9 GHz band has been used to cover 30 kilometers of railway, 18 kilometers of which is also covered using the 2.6 GHz band. Sites are set up at every 1.2 kilometers. The average downlink rate reaches 23 Mbit/s in the high-speed railway LTE network. In the network segments using 1.9 GHz and 2.6 GHz bands, the handover success rate reaches 100%.

Zhengzhou-Xuchang High-Speed Railway

First entire-line-covered excellent 4G network inheriting all quality genes for network construction

By April 2014, the entire Zhengzhou-Xuchang high-speed railway had been covered by an LTE network. The average throughput across the whole railway is 30 Mbit/s, and the peak rate is 60 Mbit/s. It is the first worldwide application of cell combination using 12 dual-channel RRUs. The measured downlink average throughput is about 30 Mbit/s, and lower than 5 Mbit/s throughput occurs in no segment of the railway. Large rate drop at the cell edge is mitigated greatly.

Qingdao-Jinan High-Speed Railway

High-speed railway with the highest network

data rate

Huawei's BEST LTE network solution was adopted for the

Qingdao-Jinan high-speed railway. This solution provides

network performance optimization dedicated to high-speed

railways, with the driving speed and vehicle penetration loss

taken into consideration. In this way, the average download rate

reaches 42 Mbit/s.

Success Stories

HUAWEI TECHNOLOGIES CO., LTD.

Bantian, Longgang District

Shenzhen518129, P. R. China

Tel:+86-755-28780808

www.huawei.com