ZTE´s Broadband Wireless Access System

• Point-to-point wireless access solutions, working at 3.5 GHz
• Support the hybrid service transmission for circuit and data services 
• Reliable network management security guarantees authentication, filtering and hierarchical management
• Support omni-directional, four-sector and six-sector configurations, as well as eight-sector and twelve-sector configurations required by future capacity expansion
• Dynamic air bandwidth distribution and service bandwidth distribution make network resources be fully used

1 Introduction
With the rapid development of backbone networks, the subscriber access network, a major component of public telecom network equipment and so-called the "last kilometer", has turned out to be the focus of attention.

  Among various access technologies, the broadband wireless access system features quick network construction, rapid investment return and large bandwidth. It enables new network operators to provide services quickly and independently, and helps existing network operators improve the current wired networks. The system can be deployed in areas with sparse subscribers or in bad need of voice and data services. For regions without wired access networks, the wireless access system can meet the access demands of subscribers. Once a wired access network has been established, it can be moved to other places in need.

  ZTE Corporation is the only equipment provider who participated in drafting the 3.5 GHz Fixed Wireless Access Standard, one of China Communication Industry Standards, and also the only manufacturer taking part in drafting the 26 GHz LMDS (Local Multi-point Distribution System) Standard.

  ZTE´s ZXBWA-3E broadband wireless access system works at 3.5 GHz. As shown in Figure 1, it is composed of Base Transceiver Station (BTS), Subscriber Unit (SU) and Network Management System (NMS).

  BTS includes the indoor unit (AU-IDU), outdoor unit (AU-ODU) and antenna (AU-ANT). SU includes the indoor unit (SU-IDU), outdoor unit (SU-ODU) and the antenna (SU-ANT).

2 System Features
  (1) The system has adopted more than ten patents and ZTE owns the independent intellectual property rights of the patents.
  (2) It can support hybrid service transmission for circuit and data services.
  (3) The net capacity of a single sector at a single carrier is 9.2 Mb/s for uplink and downlink, and the modulation methods are 16-QAM (uplink) and 16-QAM (downlink).
  (4) A single sector at a single carrier supports four E1 circuit services apart from IP services.
  (5) User-to-Network Interfaces (UNI) include one E1 interface and one 10Base-T interface, while Network-to-Network Interfaces (NNI) comprise four E1interfaces and one 10Base-T interface.
  (6) The clock of circuit services adopts "retiming" processing, and the service transmission meets the international standard requirements for time delay, jitter and bit error ratio.
  (7) The Graphical User Interface (GUI) of the system supports various network management modes such as local management (RS232 supervision port), remote management (Telnet) and remote centralized management (SNMP V2).
  (8) The remote software downloading facilitates software upgrade.
  (9) The reliable network management security guarantees authentication, filtering and hierarchical management.
  (10) It supports omni-directional, four-sector and six-sector configurations, as well as eight-sector and twelve-sector configurations required by future capacity expansion.
  (11) A single sector at a single carrier supports maximum 512 terminals.
  (12) Dynamic air bandwidth distribution and service bandwidth distribution make network resources be fully used.
  (13) The system terminals support Automatic Transmission Power Control (ATPC).
(14) BTS adopts a 19-inch standard frame. The modular design facilitates the installation and future expansion of the system.
  (15) The coverage range is from 5 to 10 kilometers.

3 Networking Solutions
The ZXBWA-3E system has a modular structure, hybrid networking ability for both data and circuit services, and various networking modes for different applications.

  ZXBWA-3E supports circuit services based on E1, data private lines at N×64 kb/s, and IP data services. By adding peripheral equipment such as the PBX, UAS, ES, routers and G.703/V.35 converter, the system can be widely used for residential zones, group subscribers, commercial buildings and private networks, providing various voice services, DDN private line services, BTS interconnection services, Internet browsing, VOD, videoconferencing and IP phone services.

3.1 Solution for VoIP Services
Many enterprises expect to simultaneously get the Internet access service and VoIP services for data and voice communication. In addition, they hope that these access means help save communication costs and improve work efficiency.

  The networking solution for VoIP services is shown in Figure 2.

  For small enterprises, telephones and fax machines are directly connected to the FXS (Foreign Exchange Station) interfaces of the voice gateway. Limited FXS interfaces restrict the number of connected terminals.

  This system can connect to Private Branch Exchange (PBX) via FXO (Foreign Exchange Office) interfaces of the voice gateway. One FXO interface equals to one VoIP outgoing trunk, while the ordinary voice gateway can only provide less than eight interfaces. At the same time, PBX can connect to PSTN via ZXBWA-3E. Thus, the incoming and local outgoing calls can use PSTN via PBX and ZXBWA-3E. The Internet can deal with the toll business.

  If PBX connects to the voice gateway via E1 interfaces, many channels can be handled. This mode is suitable for large enterprises. In this case, the voice gateway can choose ZTE´s ZXIP10-AS, and then PBX can effectively separate local calls from toll ones.

3.2 Solutions for Data Access Services
As shown in Figure 3, both BTS and SU of ZXBWA-3E provide 10BASE-T interfaces, which ensures subscribers easy data access services.

  The end offices adopt such equipment as UAS1500 and UAS2500, or the combination of ES2213 and ES2903, among which UAS1500 performs the service management and security authentication function; ES2213/ES2903 performs the convergence function. If convergence is unnecessary, ES2213/ES2903 can be omitted. In this case, 10BASE-T interfaces of BTS are just connected to corresponding interfaces of UAS (Universal Access Server), and the subscriber isolation will be accomplished by ES2903 at the SU side. With ES2903, subscribers can connect various kinds of data terminal equipment to the system according to their requirements.

  This networking solution is suitable for data subscribers with RADIUS management in commercial buildings, residential areas, cyber cafes, etc.
For subscribers charged by bandwidth, the networking solution shown in Figure 4 can be adopted.

3.3 Solution for DDN Private Line
ZXBWA-3E supports Digital Data Network (DDN) access at N×64 kb/s. The ports are G.703 standard-compliant interfaces. Each BTS has four G.703/E1 interfaces, while each terminal has only one G.703/E1 interface. Each interface can support 1-31 time slots to realize the DDN data access. Time Slot 0 of the port is used for synchronization.

  Each G.703/E1 interface of BTS can support 31 terminal stations at 64 kb/s data rate at the most. The networking solution is shown in Figure 5.

  The private line user 1 directly employs G.703/10BASE-T converter to connect to SU and LAN. The 10BASE-T interface with the bridge connection is able to effectively shield service data in the LAN. In order to avoid compatibility problems, the two ends of the private line should use
G.703/10BASE-T converters provided by the same manufacturer.

  The private line user 2 employs G.703/V.35 conversion mode. The ordinary router has a V.35 interface. But some routers can directly support the G.703/E1 interface, while the G.703/V.35 converter is disregarded.

3.4 Solution for E1 Trunk Transmission
E1 trunk transmission can be used in many aspects such as serving as the voice trunk to provide group subscribers with the voice transmission to end offices, providing BTS with the connection between BTS and BSC, and so on.

  E1 can be used in any places that require E1 transmission. One BTS can provide four E1 interfaces, while one SU provides one E1. Therefore, the BTS and SU configuration is determined by
actual demands for E1 interfaces. For example, if a BTS needs four E1 interfaces, then one BTS and four SUs are needed.

Figure 6 is the networking sketch map of this solution.

3.5 Solution for Data Access at Hotels  and Restaurants
The on-site wiring at hotels, restaurants and high buildings usually adopts twisted pairs, and these places are expected to access broadband data networks.
Therefore, the combination of HomePNA and ZXBWA-3E can be used to provide multi-service access services at these places. As shown in Figure 7, UAS is also used for subscriber billing management.

4 Conclusion
The ZXBWA-3E broadband wireless access system adopts the advanced hybrid bandwidth distribution technology and has a complete product series. Therefore, different networking solutions can be provided to meet operators´ diversified demands.

Manuscript received: 2004-03-25