With the popularization and development of mobile communications, the GSM networks of mobile operators are becoming more and more complex, but the demand for data services is increasing. In recent years, the annual growth rate has been above 100%, and some regions even reached 300%. , So it takes up a lot of network resources. Statistics show that with the same wireless resources, the revenue from data services is only about 3% of voice. How to improve the carrying capacity of data services and reduce the interference to voice services as much as possible under the premise of ensuring the service experience is a difficult problem facing mobile operators.
The rapid development of data services overwhelms wireless networks
The business of domestic mobile operators is developing rapidly, their networks are getting thicker and thicker, and the distance between stations is getting smaller and smaller. The configuration of base stations is getting bigger and bigger, especially the surge in business volume, which inevitably leads to a rapid increase in the noise floor of the network. To achieve the same voice quality in mobile networks, it is necessary to increase the coverage level by 10dB or even 20dB compared to 5 years ago, but the transmit power of the base station cannot be increased without limit, and excessively high transmit power will further push up the network The noise floor has formed a vicious circle.
The growth of data services is very rapid. The reason is mainly due to the mass popularization of smart phones, the increasing demand for mobile Internet access, the development of instant messaging services such as mobile QQ, Fetion, etc., and the network data traffic has also continued to climb from 2009. From June to June 2010, the mobile operator ’s data service equivalent traffic volume increased by 136%, and individual areas such as university campuses grew faster. In contrast, the mobile operator ’s ability to provide services only increased 21%.
To deal with the rapid growth of data services, the most direct way is to expand the network, such as cell division, increase the single-site configuration. However, the expansion caused by the increase in cell splitting is now more and more difficult to obtain new sites, and excessive cell splitting will also increase the noise floor of the network, thereby affecting voice quality and data service capabilities. Increasing the configuration of a single station is an effective method, but the problem now is that the 900M frequency has been exhausted, and the 1800M frequency band is nearly exhausted.
On the other hand, the current PDCH channel efficiency of GSM carrying data services is very low, only 2 ~ 3kbit / s, and in theory, a single PDCH can carry more than 10kbit / s of data traffic.
If the current voice business growth rate is unchanged, the data business growth is 100%, and the network expansion will reach 50%, if the data business growth is 200%, then the network should be expanded by 100%! This is whether it is capital investment, site resources, or frequency resources , Are unsupportable.
Using existing network resources to improve its data service carrying capacity and reduce network interference is an urgent issue for mobile operators.
Multi-pronged offloading of data services
To mitigate the data torrent, Huawei has proposed a variety of methods. For example, optimize the network architecture, reduce the configuration of 900M equipment, increase the configuration of 1800M, build room sub-stations and street stations, etc., to increase the capacity in terms of hardware.
Using software to improve the carrying capacity of existing equipment is the simplest and most effective method. Huawei is the first in the industry to propose a targeted PS business capability improvement solution. It aims to reduce the interference in the network, improve the PDCH carrying efficiency, reduce the network congestion, and improve the user's experience. The specific results are as follows.
One is PS power control to reduce interference. In addition to directly affecting the voice quality, the noise floor in the network also determines the PDCH's carrying efficiency to a large extent. It is important to reduce the interference in the network. Huawei has proposed PS power control and PS discontinuous transmission to reduce interference. .
In the past, power control was enabled in the CS domain, which effectively reduced interference. At the same time, DTX was enabled. At that time, PS traffic was less, and the contribution to network interference was less. You can ignore it, but the rapid development of PS accounts for 50%. If the power is turned on in the PS domain, the interference will be reduced.
On-site testing of PS power control showed that after the PS downlink power control algorithm was turned on, the downlink full / half rate HQI (0-3) increased by about 0.5 percentage points on average; after the PS downlink power control was turned on, the MOS was effectively improved.
The second is channel compression for instant messaging services. For instant messaging such as QQ and Fetion, the traffic required by these services themselves is very low. If these services are not differentiated, when they are assigned wireless resources, they are often allocated according to the maximum amount of resources, resulting in a lot of waste of wireless resources.
The channel compression function of Huawei Instant Messaging can identify instant messaging services and perform "on-demand allocation" when allocating channels to minimize its use of wireless resources.
The compression of the instant messaging channel was tested. After opening, the number of PDCHs occupied daily decreased by 5%. (Figure 1) During busy hours (8:00 PM), the efficiency of each PDCH is increased by 14.6% (Figure 2).
The third is multi-CCCH to reduce signaling congestion. Due to the rapid development of mobile phone QQ and other services, data services and voice services share common control channel resources. Currently, a large number of small-flow data services frequently initiate channel assignment paging messages, which results in tight public control channel resources and affects the access of voice services.
Huawei's multi-CCCH channel function increases signaling capacity by 100% to 300%, thus effectively eliminating signaling storms. (Table 1)
The fourth is to enhance coverage of data services. In rural areas, Huawei has other ways to improve network carrying capacity. Due to the relatively sparse base stations in rural areas, the network noise floor is relatively low, and users are often far away from the base station, resulting in low data rates. Huawei ’s data service enhances the coverage function and can achieve carrier frequency power sharing to increase the power of data service channels , So as to achieve high-order modulation and improve the user's rate.
Fifth, PS DTX reduces network interference. PS DTX stops power transmission when the PDCH channel is completely idle or not occupied by TBF, reducing network interference improves CS and PS service performance, improves network quality, and reduces network interference, which also improves the throughput of the entire network.
In order to test the actual effect of PS DTX, Shantou Mobile and Huawei conducted field tests. The results show that after the function is turned on, all HQI indicators have slightly increased. Among them, the full rate indicator has improved significantly. The full-rate downlink HQI indicator has a 6-hour busy average from 99.33% to 99.41%. 6 The busy hour average increased from 97.82 to 98.06%, an increase of 0.24%.
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