ZTE's BBU+RRU Solution
Problems Confronting Operators
GSM was initiated as a European standard in 1982 and went into commercial service in 1992. As the choice of 80 percent of all new mobile customers, it is the world's most popular cellular standard. It is predicted that there will be almost three billion GSM/EDGE subscribers by 2010, and GSM will still be the leading standard. However, as subscribers continue to increase, new problems have occurred and have to be addressed with urgency. These problems are listed as follows:
- With the capacity increase in GSM networks, it is necessary to add the main and supplementary system equipment, which will surely present problems such as insufficient equipment rooms and weight bearing. Meanwhile, the equipment rooms are getting more and more difficult to obtain, and the equipment rooms' rental and construction fees are becoming increasingly expensive. The shortage of equipment rooms sets limits on the fast development of GSM network and needs to be resolved.
- The traffic load has the characteristic of periodic migration. In order to maximize the efficiency of network resources, it is required that the radio resources be shared, which can't be enabled by the existing integrated base stations.
- The focus on deep coverage and service quality in enclosed buildings has given rise to the increasing need to provide indoor coverage. However, the traditional indoor coverage solutions are costly and inflexible in terms of cabling and capacity expansion.
- The number of hot spots-temporary high density spots such as sports stadium and exhibition halls-is increasing. The traditional base stations can't flexibly and quickly adapt to the bursty traffic load.
- Mobile operators, locked in intense competition, are seeking ways to reduce CAPEX and OPEX. For operators who have GSM/EDGE networks, the challenge will be to protect their existing investments while speedily and economically deploying WCDMA/HSPA services.
New Technological Development
In order to create an open market for BTS equipment that ensures the availability of standard modules and components, reducing product development cycles and costs, base station vendors and module and component manufacturers founded Open Base Station Architecture Initiative (OBSAI) in October 2002. With 122 members including Nokia, Motorola and ZTE, OBSAI aims to define a modular base station architecture and detailed specifications for the interfaces between the modules. On the other hand, another industry group called Common Public Radio Interface (CPRI) has been formed.
The OBSAI and CPRI initiatives and their specifications help manufacturers focus on their core competencies and buy standard radio base station modules. In return, operators will benefit from more extensive products, more flexible base station solutions and more cost-effective network deployment.
SRRP Base Stations
By adopting advanced technologies, ZTE has launched a series of smart radio resource pool (SRRP) base stations, which are based on the baseband unit (BBU) + the remote radio unit (RRU) structure (Fig. 1).
BBU+RRU ( a narrowband transceiver)
BBU is in charge of GSM base station control and RF signals processing; it has a maximum capacity of 48 carrier frequencies within a single rack. It uses the same hardware platform as WCDMA and can support GSM and WCDMA mixed inserts in one baseband board to achieve dual mode operation. The BBU, which is 19 inches in width, can be flexibly installed. A single RRU supports two carriers and can naturally dissipate heat, reduce the feeder line loss and increase the coverage of the base station.
BBU+ RRU ( a broadband transceiver)
By adopting the broadband transceiver unit and Multi Carrier Power Amplifier (MCPA), the solution provides a large bandwidth necessary for multiple carriers and can flexibly configure and schedule the carriers. The RRU can transmit and receive common-mode GSM/WCDMA signals, and when combined with the multi-mode BBU, makes up the highly integrated multi-mode GSM/EDGE/WCDMA products.
The miniBSC+BBU+ RRU (a broadband transceiver)
The BSC and BBU can be integrated into an intelligent base station that accomplishes wireless transmission, administrates radio resources management and realizes the integrated and intelligent scheduling of baseband and radio frequency resources.
Dynamic Resources Pool
The ZXG10 SRRP system is based on the innovative GSM/WCDMA dual mode BBU (B8048), the RRU (R8102) with low power consumption, and the dual mode RRU. The BBU and RRU form the distributed base station system where the baseband and radio frequency resources can be shared.
As the industrial and residential areas are currently separated, large traffic loads tend to occur in different areas over different periods of time. The traditional base station system needs to provide RF parts and baseband resources to meet the maximum traffic demands in both areas. When traffic is low in one area, the available network resources can't be shared and reused, resulting in equipment investment waste. However, ZTE's BBU+RRU dynamic resources pool structure enables sharing of baseband resources and greater resource allocation flexibility (different resources scheduled at different times).
Benefits of BBU+RRU Structure
- Saving costs on equipment rooms
With a small size, the BBU can be installed in residential and business buildings. It can also be located in the integrated power cabinets, in a basement, or in a 2G cabinet, solving the problem of insufficient equipment rooms.
- Reducing the feeder line losses by 2 to 3dB
Traditionally, the macro base station is connected to the antenna via 7/8-inch feeder cable. The BTS output power lost in feeder lines is 2 to 3dB at an average. In the BBU+RRU structure, the remote RF module is connected to the antenna via the flexible jumper, avoiding feeder line losses.
- Shortening the construction time
The BBU+RRU solution has no special needs for equipment rooms and requires only the installation of the auxiliary antenna feeder systems, enabling operators to speed up network construction to gain a first-mover advantage.
ZTE is devoted to offering innovative products and solutions in quick response to customers' needs. Taking subscriber traffic, capacity, electricity, installation, evolution, etc. into full consideration, ZTE's SRRP base stations and solutions help effectively reduce operators' operating and capital expenses.