Huawei Technologies
To build IP-based broadband mobile networks, you need
The packet microwave solution The packet microwave system is oriented to ALL IP transport networks. It adopts packet switching as the core technology and uses pure packet structure on the air interface. By Cui Jiang
Bottlenecks for traditional microwave systems
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n microwave-based mobile backhaul networks, the plesiochronous digital hierarchy (PDH) microwave is adopted in the access layer, while the synchronous digital hierarchy (SDH) microwave is used in the convergence layer. When evolving to IP-based and broadband networks, the microwave-based mobile backhaul networks have encountered technical bottlenecks including:
Insufficient bandwidth for service development raditional time division multiplexing (DM) microwave system features low efficiency in using air interface bandwidth. At present, as the mobile traffic involves mostly voice services, bandwidth is still sufficient for transporting services. However, as 3G services such as HSPA become more popular and develop rapidly, DM-based microwave systems will begin to falter. falter. Forecasts Forecasts indicate that by 2012, booming data traffic will cause a four-fold increase in transport bandwidth for mobile local networks.
Poor capability of accessing and bearing packet services
DM-based microwave systems perform poorly when accessing and bearing bearing IP services, and there are only a few microwave equipment vendors who support IP over PDH technology. Presently, PDH-based microwave systems are incapable of providing strong access capability. SDH-based microwave systems also have rather poor support for packet services. Because packet services have to be encapsulated in generic framing procedure (GFP) frames in the Ethernet over SDH (EoS) mode, and then mapped to the virtual container (VC) for transmission. his results in a waste of air interface interfa ce bandwidth, bandwidth , and indoor units (IDUs) adopted in SDH-based microwave systems can access only a limited number of packet services. o meet the new market conditions driven by the trend toward IP-based and broadband mobile networks, new technologies need to be introduced to ease the bottle necks created by microwave communications systems.
Four features of the packet microwave o guarantee long-term service development, the mobile transport solution adopting microwave technology for service access must support IP bearing and large capacity to meet network needs.
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LEADING EDGE The packet microwave solution
For future mobile broadband networks, an end-to-end mobile broadband solution lies in a packet transport network (PN) that combines both microwave system and optical fiber system to offer pure packet architecture. Te packet microwave system is oriented to ALL IP transport networks. It adopts packet switching as the core technology and uses pure packet structure on the air interface. hrough the IDU, the user network interface (UNI) can be used to access IP services like fast Ethernet (FE) service. Legacy DM services can be accessed in the pseudo wire emulation edge-to-edge (PWE3) mode. Te packet microwave system can form a logical end-to-end PN independently or along with the packet fiber transport network, providing high-quality service transport based on supported network protocols, such as multiprotocol label switching (MPLS), trans port MPLS (-MPLS) and provider backbone bridge traffic engineering (PBB-E). Te packet microwave system has the following characteristics:
Improved bandwidth utilization raditional microwave systems mostly adopt an Ethernet over PDH/SDH mode to provide Ethernet features, yet have complicated mapping and multiplex layers. Also, traditional microwave systems are inherently inefficient for transporting packet services because of poor burst traffic support, high costs, and low-efficie nt bandwidth usage. Te packet microwave system adopts the pure packet switching kernel and the pure packet air interface structure to improve bandwidth multiplexing and transport efficiency, and offer better burst traffic support. Optimization of the microwave frame and link-layer protocols, allows the system to process more traffic by using limited microwave air interface resources.
Adaptive code modulation technology Adaptive code modulation technology can be used to automati cally adjust modulation modes and dynamical ly enable service transport according to the 51
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To meet the new market conditions driven by the trend toward IP-based and broadband mobile networks, the packet microwave solution is needed. performance of air interface channels that might be affected by bad weather conditions. Te modulation mode can be changed (for example, from 128QAM to 16QAM) to enable error-free communications. As a result, the access bandwidth of the microwave air interface is decreased from SM-1 to 32E1 or even 16E1. Low priority services become invalid, while high priority services are protected. Te system will automatically recover the original rate when the channel quality is recovered. Adaptive code modulation technology also significantly strengthens bandwidth capability, resulting in high scalability, low-cost maintenance, fast deployment, and increased adaptability, which enable microwave systems to adapt to different types of densely populated areas.
Circuit emulation supports TDM services DM-based service transport occupies fixed bandwidth. Te PN, however, uses bandwidth with statistical multiplexing and transports DM services through circuit emulation technologies, such as PWE3. All services are then transported via the packet kernel and interfaces, allowing the system to interconnect with other data communications equipment. raditional 2G networks are DMbased. 3GR99/R4 adopts the asynchronous transfer mode (AM), but 3GR5/R6/ LE/WiMAX net works will evo lve to AL L IP net wo rk s. D M ser vi ce s an d packet services will probably coexist in the same network using PWE3 technology
for quite some time. DM services of the GSM network and AM services of the universal mobile telecommunications system (UMS) will all be transported by the PN.
Packet-based clock transfer technology Mobile communications services are highly dependent on clock and timing information transfer. Packet-based clock transfer technology is now more mature and can be applied in packet microwave systems. Te packet microwave system and the PN support various packet-based clock transfer protocols, such as synchronous Ethernet, iming-over-Packet (oP), and IEEE 1588V2, providing end-to-end and network-wide synchronization solutions.
Evolution solutions Huawei pioneered in creating two evolution solutions to help traditional microwave systems meet mobile network requirements and service development. In the microwave system evolution, hybrid transport modes are supported wh en D M an d AM se rv ices co ex is t during the transformation of mobile services from DM E1/IMA E1 to FE. Te air interface supports the transport of both DM services and packet services. Services are encapsulated in unified microwave frames. he system can then support pure packet transport after the simple hardware promotion. In the equipment evolution, pure packet microwave equipment and packet transport equipment are integrated if mobile operators build their own optical fiber-based transport networks instead of leasing frequencies for microwave transport. An operator can start by constructing only a packet microwave system. After the optical fibers are in place, the operator can pull out the intermediate frequency (IF) boards to transform the packet microwave equipment to PN equipment. he new PN supports various optical fiber networking schemes so that operators can maximally protect investments and strategically decrease operation expenditures (OPEX). Editor: Xu Peng
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