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Innovative Distributed NodeB Solution
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Innovative Distributed NodeB Solution

Abstract: Network investment and network quality are contradictory. As sites/equipment rooms are getting more difficult to obtain, and the leasing cost is shooting up, the construction cost and the operation cost of 3G network increase. The innovative distributed NodeB solution of Huawei can greatly reduce the leasing cost, electricity, air-conditioning, and human resource of the equipment room. According to statistics, it can save the cost of the total investment by 30%.


1 Introduction of Distributed NodeB Solution

The coverage quality is critical for subscribers, operators are supposed to keep improving the network quality by installing new sites. However, the available sites and equipment room for new base stations are decreasing, and the rental fees become more expensive. How to build a network quickly and economically is the critical difficulty that the operators have to face.
Distributed NodeB solution is an economical and fast wireless network deployment solution under the circumstances of no equipment room or less ideal equipment room locales. The distributed NodeB solution adopts remote RF technology. The Remote Radio Unit (RRU) can be installed near the antenna, and connected with the BaseBand Unit (BBU) via optical fiber (as shown in the following figure). The optical interface module implements clock extraction and the multiplexing/demultiplexing of the baseband signals. The I/O signals of the CPRI interface are modulated, digital/analog converted, up-converted, filtered, and amplified before they are output to the antenna feeder.

Pic.1-1 Principle of Distributed NodeB Solution

CPRI is an open standard interface. In April 2003, Ericsson, Huawei, NEC, Siemens, and Nortel established the Common Public Radio Interface (CPRI) cooperation organization. The organization focuses on the new form of the WCDMA FDD NodeB, and produce new open standard interfaces, dividing NodeB into radio equipment (RE) and radio equipment control (REC). In that way, each part of the NodeB can better benefit from the technological progress from different sources.


2 Application of Distributed NodeB Solution

2.1 Partial Outdoor Solution
Operators have their own sites or indoor space, but the equipment rooms are spatially small, or have an insufficient weight bearing capacity, or have less ideal locales (which may lead to excessively long cable feeder). In such scenarios, DBS is more advantageous than the conventional macro NodeB.

BBU can be installed at any place within the building, connected with the RRU on top of the building via optical fiber. It solves the problems of equipment room space, insufficient weight bearing, less ideal equipment room locales, and excessively long cable feeder. RRU can be powered on with the -48V in the equipment room, or can adopt the 220V DC.

2.2 Stand-alone Outdoor Solution
Operators do not have their own equipment rooms. The adoption of MBA+BBU+RRU or APM+BBU+RRU solution (MBA can accommodate lightning protection device, power conversion, transmission, and BBU, without storage battery, used in areas that do not require storage battery, e.g., Europe; APM includes storage battery, maximally supporting 8 hours of backup power, used in areas that require backup power) can replace the outdoor macro NodeB in most cases.

The temperature range for normal working of this solution is: -40~45°C (MBA/APM is equipped with heating device to ensure the startup of the equipment in low temperatures).

2.3 Embedded Outdoor Solution
Operators have their own 2G outdoor base station sites and at the same time the outdoor base station have available space (19", 1U). The mode of installing the BBU in the 2G outdoor base station can save the leasing of equipment room. Compared with conventional outdoor macro NodeB solution, it greatly reduces the leasing cost, project cost, and project implementation time.

The site acquisition, manpower cost, and space leasing cost in the international markets (especially Europe) are high, and there is a large proportion of outdoor macro base station established in the 2G era. This solution has a lot of significance for the carriers, and is widely applied in Europe (almost networkwide application in Holland).

2.4 Inter-Sites Sharing Solution
Operators have optical resource between sites (direction connection or contour connection via an intermediate central site, less than 40km for a single hop and max. 100km in the case of cascading). There are no equipment rooms but there are optical fibers connected with other sites. The RRU can be connected with the macro NodeB or BBU of other sites, with the baseband resource shared by multiple sites. The typical application is shown in the following schematic diagram.

In this solution, as the handover between sites is softer-handover, which can improve the network quality. Furthermore, the daily maintenance and future capacity expansion need to be done in the host NodeB equipment room. This solution relies on the large amount of optical fiber resource the operators have. Operators may find some center equipment rooms in the city area, with other surrounding sites adopting RRU connected to the center equipment rooms via optical fiber. In this way the demand for equipment room, and operation & maintenance cost are reduced, the network quality is improved, and centralized maintenance is possible.


3 Benefits of Distributed NodeB for Operators

Distributed node B is an important option for the 3G network construction of the operators. The adoption of the Huawei distributed NodeB solutions can bring the following benefits:

1. Solving the problem of equipment rooms
When the operators construct the WCDMA network, the distributed NodeB can reduce the requirement for equipment rooms when insufficient, or less ideal locales. The baseband units can be placed in the center equipment room available in a centralized manner, or the compact BBU3806 can be installed in the corridor of the building, lift lobby, or underground chamber. The RRUs are distributed at the sites according to the network planning. Experiences show that the adoption of distributed NodeB can reduce 80% of the equipment room demand.

2. Reducing the project implementation cost
The distributed node B features small size, light weight, direct installation near the antenna, one-man installation and fast testing. Experiences show that the project implementation cycle of the distributed NodeB is only 30% of the conventional NodeB. Compared with the conventional macro NodeB or outdoor NodeB, the installation cost of the distributed NodeB is far less.

3. Reducing the operation cost
The distributed node B adopts high efficient amplifier, with the power consumption of the RRU3801 less than 220W and that of the BBU3806 less than 60W. It reduced the power consumption of the peripheral equipment like air-conditioner, which means that the carriers save a large amount of electricity expenses.

The distributed node B has less demand for peripheral facilities such equipment room, power, and air-conditioner, and saves project installation and operation costs. Statistics show that distributed NodeB can sharply reduce the investment by 68% in terms of project implementation, peripheral facilities, equipment room, and electricity consumption. The distributed NodeB shares the baseband processing resources of the center sites, saving cable feeder and tower amplification module, or put altogether, saving the equipment purchase cost.

4. Reducing the equipment cost
The Huawei distributed NodeB solution can solve the problem of burst traffic. As the baseband sharing strategy is adopted, the surplus baseband resources in the surrounding cells can be utilized to handle burst traffic in other areas concerned.


4 Summary

Since 2002, Huawei started to develop distributed NodeB products( including BBU and RRU). In 2003, Huawei released the first RRU product. In 2004, Huawei released the BBU product, which is the smallest BB unit worldwide. Huawei's distributed NodeBs are widely applied in commercial networks, especially in Holland, which is considered a major breakthrough on the 3G network construction.

Huawei's distributed NodeB solution can provide economical, fast deployment, and at the same time provides better network quality. It is an ideal network construction solution for mobile operators.

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