On August 17, 2015, Zhejiang Mobile assumed the lead in commercial launch of VoLTE in China. One month later, Zhejiang Mobile has amassed widespread attention from the mobile industry. Zhejiang Mobile has the honor of introducing China's first VoLTE experience demonstration zone in Hangzhou. The VoLTE counters presented in the demonstration zone are far superior to those that provide GSM voice services in Hangzhou, can be comparable with VoLTE counters of LG U+ in South Korea.
Compared with GSM voice service, VoLTE HD voice provides clearer sound, higher fidelity, and reductions in access delay, but all of these can only be achieved on LTE networks with superlative coverage. However, the in-depth indoor coverage of LTE networks is insufficient. Zhejiang Mobile and Huawei's collaboration has afforded the advantage in construction of a research pilot for the advancement of VoLTE experiential networking. Through detailed analysis and verification, a definitive set of standards for deployment of the VoLTE experience network in a dense urban area is complete.
From the Practice: Exploration into VoLTE Network Construction Standard through In-depth Data Analysis
Zhejiang Mobile and Huawei's cooperation to install a simulation for VoLTE user indoor experience in a densely populated area with heavy voice traffic based in central Hangzhou is made a reality. The simulation areas include residential areas with low and high-rise buildings, independent residential buildings, and commercial buildings. The simulated buildings compose of concrete, masonry, and glass to constitute raw materials. During the VoLTE experience simulation, VoLTE sampling tests must be performed in the low, medium, and high floors of each building. After a comprehensive two months of VoLTE experience testing, a plethora of statistical test data is accumulated. Based on the in-depth analysis and research performed on these test data, Zhejiang Mobile and Huawei can effectually discover the statistical relationships between VoLTE voice quality in the dense urban areas and the indoor coverage quality. The indoor coverage level and signal quality required for the VoLTE experience can be calculated from the statistical relationships.
To Practice: Construction of a VoLTE Experience Demonstration Zone Based on the VoLTE Network Roadmap
Wulin business district is a typical residential area in Hangzhou, ranging from 0.36 square kilometers with dense residential buildings and small empty divisions between buildings. The results from test showed that the VoLTE quality is poor, the indoor average mean opinion score (MOS) is less than 2.0 and the completion rate is lower than 90%. According to the analysis, the possible causes for poor voice experience are due to weak coverage currently exists in many areas within this district. The analysis also revealed that the indoor coverage level is lower than the coverage standard in the VoLTE experience demonstration zone. Hangzhou Mobile selected this district and built the VoLTE experience demonstration zone in a series of stages.
Step 1: Maximize the performance benefits of the existing networks through combination of the RF parameter optimization, neighboring cell check, and VoLTE parameter optimization.
Step 2: Maximize the potential of software features and redesign the features to suitably pursue voice characteristics aimed at improving VoLTE voice service quality.
Step 3: Apply invisible BOOK RRUs for short-distance accurate coverage in the coverage holes and blind spots to improve the indoor and outdoor coverage level.
Practice Yields Genuine Knowledge: Full HD and No Call Drops in the VoLTE Excellent Demonstration Area
The MOS is an industry-recognized counter for indicating voice quality. ITU-T recommends a 5-level scale for evaluating the MOS value. Levels 4 to 5 are excellent levels. With fluent communication and little delay, levels 4 to 5 produce a "face-to-face" effect. Levels 3 to 4 are good levels. The two parties can communicate clearly, but delay and noise issues exist. Levels 2 to 3 are standard levels. The two parties cannot communicate clearly with a long delay. After the demonstration zone construction, test personnel perform VoLTE experience tests in all roads and buildings within the zone. The average coverage level in the zone is greater than -80 dBm, and 5% of the edge coverage level is greater than -94.6 dBm. The average signal to interference plus noise ratio (SINR) is greater than 17.8 dB, and 5% of the edge SINR is greater than 3.7 dB. The MR weak coverage ratio is less than 5%. The VoLTE MOS is greater than 4.0 in more than 90% areas, and the average MOS is greater than 4.0, and the edge MOS exceeds 3.3. The VoLTE call completion rate exceeds 99.8%, and the VoLTE call drop rate is lower than 0.1%. No SRVCC is triggered during indoor and outdoor testing. Experience participants perform a traverse test for the roads and buildings within the zone. Within two hours of experience testing, the VoLTE call is consistently clear in HD voice and no service failures or call drops occur. The VoLTE counters in the demonstration zone are far superior when compared to that of the GSM voice counters in Hangzhou, which are comparable with the counters of the world's leading VoLTE operator LG U+ in South Korea.
According to statistics, approximately more than 70% of calls occur indoors. The indoor VoLTE user experience is the key to VoLTE experience network construction and has a great impact and influence on whether end users choose VoLTE voice services. Hangzhou VoLTE experience demonstration zone provides the standard and experience of VoLTE experience network construction for Zhejiang Mobile and China Mobile.