Difficulties in network-wide VoIP communication coverage

Currently, traffic revenue is growing rapidly, accounting for about half of the operator's revenue. However, traditional voice communication revenue is still the focus of operators. However, in the 2G or 3G era, there is no obstacle in the 4G era.

Complicated VoIP implementation, multiple solutions help LTE transition

LTE is a full-IP network, and its network architecture can implement VoIP communication. However, the LTE network cannot be improved in the last year or two. In most regions, it still needs to rely on 2G and 3G networks for communication. Therefore, it is difficult to achieve network-wide VoIP communication in the near future.

At the same time, the implementation of VoIP in the LTE network also has its own problems. According to Liu hongchun, chief architect of zte lte, TD-LTE network coverage must be better than the existing 2G/3G network when packet-based Speech solutions are adopted. Because the working frequency of LTE is higher than the existing GSM and TD-SCDMA, the loss of wireless transmission is high.

In terms of network transformation and network optimization, it is necessary to improve the success rate of packet data switching, ensure the highest processing priority of the voice service, and reserve wireless transmission resources for the voice service. Cai Yuemin, Chief Engineer of Datang Mobile's LTE product line, also said that in the LTE network, technologies such as sub-frame bundling and semi-continuous scheduling must be considered, it is used to enhance cell edge coverage and expand cell capacity. It also needs to optimize network optimization parameters such as PS (Packet Switch, group domain) switching and inter-system switching. It also needs to upgrade and transform the wireless network and core network.

At present, there are roughly two areas in the industry for LTE speech solutions. One is network protocol-based solutions, mainly SCFB (Circuit Switched Fallback, Circuit domain falling back) and SRVCC (Single Radio Voice Call Continuity) based on IMS (IP Multimedia Subsystem, IP Multimedia System ). The other is a terminal-based dual-to-multi-mode solution.

However, these solutions are supported by necessary conditions in the application process. For example, the SRVCC solution is only applicable to scenarios where the carrier has deployed the IMS network. This requires network transformation, and the terminal also needs to support the IMS function. This increases the network construction cost of operators and takes a lot of time for terminal R & D. However, it can implement VoIP communication in the coverage area of the LTE network.

CSFB does not need to upgrade the network to reduce the voice. At the same time, it can use existing resources to save the network construction cost of operators. This is also the fastest and Lowest Cost Solution for carriers on the network side. However, CSFB also has inherent limitations, which may be prolonged.

Although both CSFB and SRVCC adopt voice fallback to implement LTE voice over the entire network. However, the difference is that CSFB is falling back in the overlapping coverage areas of LTE and 2G/3G, while SRVCC is at the time of LTE network coverage loss, to switch between 2G/3G network circuits.

While the dual-Wait multimode terminal uses the LTE mode for data business, the terminal can carry out voice business in TD-SCDMA/WCDMA/GSM 2G, 3G standard. For voice communication in a 2G or 3G network, you can directly switch between networks in a 2G or 3G network.

Although there are no special network requirements for the solution that provides voice services based on dual-to-multi-mode terminals, it has extremely high requirements on terminals. There are many difficulties in user registration, call establishment, and inter-network switching. The power consumption of LTE terminals is also a major problem. Terminals support dual-to-multi-mode terminals in the RF chip, filter and other aspects need to be re-developed, design, its cost is difficult to reduce in the near future. Terminals support multiple systems, and their chip power consumption will inevitably increase, which will greatly shorten the standby time.

CSFB carrier selection

Softbank Japan has successfully opened up the industry's first CSFB-based TD-LTE commercial network phone in October. A few days ago, the current network of Hangzhou TD-LTE has opened up the country's first CSFB voice phone.

At present, multiple carriers around the world plan to use CSFB as the voice transition solution for LTE by 2014. CSFB saves the trouble of terminal and network upgrade, but CSFB needs to reselect 2G/3G network for each call establishment. The call establishment time is prolonged, and the user experience is poor. The latency Optimization of CSFB is mainly on the network side. The focus is to shorten the measurement of the system community and read the broadcast message length of different systems.

Tang Jianfeng, assistant general manager of China Mobile Terminal company, said in an interview with the media that China Mobile uses the TD-LTE CSFB speech fallback solution to solve the speech problem in the transitional stage of LTE, china Mobile's 2G network is complete and can be switched back to the GSM network.

At the same time, China Mobile also has more than 0.5 million TD-SCDMA base stations, which also makes it possible for CSFB to fall back to TD-SCDMA. Due to the same TD standard, it is easier for the voice to fall back to the TD network than to fall back to the GSM network.

Technically, the same time division multiplexing technology does not have too many conversions during inter-network switching, and the latency is lower than that when it falls back to the GSM network. Previously, China Mobile tender procurement of seven categories of 34.7 thousand TD-LTE terminals, including the CSFB mobile phone and multi-mode Dual-Wait single card smartphone, "We will conduct a test on the dual-Wait mobile phone, however, the dual-Wait solution is not the only option. We support both CSFB and dual-Wait solutions." Tang jianduo said.

OTT speech solutions become a strong competitor

With the large-scale commercialization of LTE in the world, LTE theoretically provides a downstream transmission rate of 100 Mbps and an upstream transmission rate of 50 Mbps. This makes it possible for OTT speech communication software to achieve non-latency and clear real-time voice communication. OTT voice communication has become an important competitor of carrier voice communication.

Although the operator has invested a huge amount of money in network construction, it married OTT voice communication, which has attracted the attention of operators.

At the same time, Overseas operators such as SoftBank and AT&T are not limited to traffic, which greatly stimulates users' passion for pure IP communication through software. The number of data services in the global market has exceeded the number of voice services.

In China, the rise of voice communication software, such as Momo, has aroused widespread attention in the industry. Although there is no accurate statistics on voice communication through software, it is an indisputable fact that the number of users is about to exceed 0.3 billion.

It is understood that at present, many overseas users are also choosing to use other voice communication software when communicating with domestic friends and family, so as to avoid high international communication costs.

However, OTT-based voice communication still cannot fully reflect the mobile characteristics of wireless communication, especially in emergency call and emergency voice communication scenarios. It still cannot replace "real voice communication technology ".

In the face of the cheap impact of OTT applications, the traditional profitable voice of operators is facing a huge test. In the future, playing the voice card will become a common concern for global operators.

Hangzhou mobile opened the country's first 4g csfb voice phone in November

Its CSFB fall back technology in the TD-LTE network voice business back to GSM network. China Mobile has the most complete GSM network in the world, and its network performance in terms of coverage and stability is very good. The implementation of CSFB's falling back to GSM network provides strong network support for large-scale commercial use of TD-LTE in China.

Softbank became the first commercial network voice phone in TD-LTE in China in October

Its CSFB fall back technology is mainly used in the TD-LTE back to UMTS network, but also for the first time in the network provided by different manufacturers to complete CSFB voice call. The successful application of this Service provides a powerful guarantee for Softbank LTE users to enjoy excellent data and voice business experience.