Carrier-Class Ethernet Microwave: The Best Choice for Mobile Backhaul

 

With the rapid growth of mobile networks, service traffic has surged in recent times but operators have not profited from this surge. Traditional circuit-switched networks, such as SDH networks, are expensive and cannot be easily scaled. Packet-switched transmission reduces the number of network layers, lowers network construction cost, allows scalability and integration, and helps operators transition to integrated service. This is the trend of network development.

Compared with circuit-switched transmission, packet-switched transmission is more cost efficient, manageable, and scalable, but it is inferior in terms of service protection, monitoring, and QoS. To address these problems with packet networks, the Metro Ethernet Forum (MEF) proposed carrier-class Ethernet, which is regarded as the ideal solution to improving QoS in packet networks.

Microwave transmission equipment is widely used in mobile backhaul networks because it is cheap, reliable, and flexible and can be quickly put into commercial use. A report by Infonetics in 2011 shows that the number of new microwave backhaul networks has soared since 2011, and by 2014, microwave backhaul networks will account for 50% of the global network market. Microwave transmission is an important mobile backhaul solution. ZTE is experienced in microwave transmission and has put forward an advanced carrier-class microwave solution that solves problems associated with packet transmission.

 

Standardized Services

MEF 6.1 defines three generic service constructs, and MEF 10.2 defines an Ethernet service management model from a user perspective. These two technical specifications ensure that users are provided with generic and standard services that are independent of manufacturers. This effectively helps customers plan and integrate Ethernet services into network infrastructures and allows customer edge equipment to easily access Ethernet services.

ZTE’s microwave products strictly comply with MEF 6.1 and MEF 10.2 and fully support the standard services defined in these specifications. ZTE’s microwave products have obtained MEF 9 and MEF 14 certification. They are easy to manage; they allow convenient service expansion; and they can be deployed in any network scenario.

 

Scalability

As mobile networks evolve from 2G and 3G to LTE, the demand for bandwidth has grown significantly, and operators have had to expand their mobile networks. For service security, expansion, and maintenance, the traffic of different users must be separated. However, this requires more than 4096 VLANs. ZTE’s microwave products solve the problem of insufficient VLAN IDs by using stacked VLANs defined by IEEE 802.1ad. This allows new service deployment and service separation. ZTE’s microwave products support VLAN translation in 1:1, 1:2, 2:2, or 2:1 mode and can therefore be applied to any complicated networking scenario.

Microwave transmission capacity is restricted by frequency resources and wireless modulation technologies. In a typical 56 MHz, 256-QAM configuration, the maximum theoretical transmission capacity of a single carrier is about 400 Mbps, which is insufficient to meet the transmission requirements of 3G and LTE aggregation links. ZTE NR8000 series microwave products maximize microwave transmission bandwidth by using the following technologies:

●    co-channel dual polarization/cross-polarization interference cancellation (CCDP/XPIC). A horizontal polarization wave and a vertical polarization wave can be used to provide two transmission channels for a single carrier. This doubles transmission capacity.

●    physical link aggregation. By binding multiple microwave links together, greater transmission capacity is possible.

●    header compression (HC). Redundant or repeated fields of a user packet are replaced or compressed and then decompressing at the peer end. In typical configurations, when HC and XPIC functions are enabled, the transmission capacity of a single carrier reaches 1.06 Gbps.

●    adaptive code modulation (ACM). Upgrading the modulation mode increases the bandwidth so that extra services can be transmitted and critical services can also be transmitted with 99.999% reliability.

 

Reliability

ZTE’s microwave products support ITU-T G.8031 Ethernet linear protection switching (ELPS). When more than one path is available on the network, the paths can be configured to a 1:1 protection-switching architecture. The network services on a failed working path can be switched to a protection path in 50 ms. With ELPS, ZTE’s microwave products provide carrier-class availability for critical services such as voice signaling.

Ethernet ring protection switching (ERPS) eliminates redundant paths and protects the ring topologies, which are often used on microwave backhaul networks. Early ring protection mechanisms using Spanning Tree Protocol provide 1 second service switching; however, this is not carrier-class protection. ZTE’s microwave products support ITU-T Recommendation G.8032 ERPS and can switch services in less than 50 ms.

The link aggregation mechanism binds a group of physical paths into a logical link to balance loads, increase bandwidth, and provide dynamic link protection. ZTE’s microwave products support IEEE 802.3ad-compliant Ethernet link aggregation and RF link aggregation, both of which protect multiple layers, including the physical layer and data-link layer.

 

QoS

Although microwave equipment allows for flexible networking and rapid deployment, it has weaknesses. It is sensitive to weather, and the bandwidth in the microwave links fluctuates frequently. This inevitably leads to traffic congestion. A QoS mechanism is required in order to use microwave transmission equipment for carrier-class operation.

A set of mature IP/MPLS QoS mechanisms are already available. These include the widely used DiffServ mechanism. DiffServ manages QoS policies by domain so that the same QoS is maintained for a particular class of service traffic in a domain. With Diffserv, a network is divided into DiffServ domains based on OAM requirements. Traffic is classified with a PHB mark and conditioned at the boundaries between DiffServ domains. Class-based traffic discarding and scheduling performed by a node in a DiffServ domain is defined as per-hop behavior (PHB).

The early Ethernet was a set of networking technologies for LANs that did not have QoS processing capability. ZTE follows IP QoS principles and incorporates the DiffServ concept and architecture into Ethernet. ZTE replaces the DSCP of a frame with S-VLAN Pri bits for PHB marking. S-VLAN DEI bits are used for packet color marking, and QoS policies are managed by dividing them into DS domain, network ingress policy, and network element egress policy (Fig. 1). The ZTE microwave QoS mechanism has well-defined ideas, and port-based configuration is replaced with traffic-based configuration.

 

Service Management

In early microwave backhaul solutions, microwave transmission equipment did not provide effective E2E service management tools that made service deployment and troubleshooting more efficient. Future service development could not be supported. Carrier-class Ethernet equipment provides complete service management, including network monitoring and diagnosis, as well as fast service provisioning. E2E service management is indispensable for carrier-class Ethernet. ZTE’s microwave products provide an E2E service management solution that integrates E2E service provisioning with monitoring, troubleshooting, and QoS tools. This significantly improves OAM efficiency, reduces opex, and maximizes profits for operators.

As networks evolve and new services emerge, telecom operators are coming under enormous pressure from the internet industry and count on elaborate service operation as a key approach to increasing revenue. Carrier-class Ethernet is an ideal choice for operators because it allows for service expansion, service management, QoS guarantee, and reliability. Microwave transmission in mobile backhaul is becoming more operational. ZTE’s microwave products make the switching architecture of traditional Ethernet carrier-class. Service provisioning, scalability, reliability, QoS, and service management of a traditional Ethernet network are transformed.