Networking Research

Working Group Update: Microwave Modelling at CCAMP

Microwave and millimeter wave (hereafter collectively referred to as microwave) technologies are becoming critical for radio access networks. These technologies are able to support cost-efficient delivery  with the best possible network performance and quality of experience.

The main application for microwave is backhaul for mobile broadband. Today’s microwave can fully support the capacity needs of backhaul in a radio access network. It is expected to evolve to support multiple gigabits in traditional frequency bands and beyond 10 Gbps in the millimeter wave. Layer 2 (L2) packet features are normally an integrated part of microwave nodes and more advanced L2 and L3 features will be introduced over time to support the evolution of transport services that will be provided by a backhaul/transport network.

In order to achieve operational support of  seamless multilayer networking and automated network-wide provisioning and operation, there is the need for the unification of the control and management of microwave and millimeter wave radio link interfaces with the control and management of L2 and L3 capabilities.

To that end, the Common Control and Measurement Plane (CCAMP) Working Group (WG) established a Microwave Design team and challenged it with defining a unified YANG data model for microwave and millimeter radio links. The team aims to provide a standardized management model that:

  • aligns with how other packet technology interfaces in a microwave/millimeter wave node are modeled,
  • supports core parameters, and
  • allows for optional product/feature-specific parameters that support new, innovative features until they are mature enough to be included in a standardized model.

Currently, numerous IETF data models, Request for Comments (RFCs) and Internet-Drafts (I-Ds) comprise technology-specific extensions that cover a large part of the packet domain. Examples include IP Management [RFC 7277] and Routing Management [RFC 8022], which are based on RFC 7223, the IETF YANG model for interface management and an evolution of the SNMP IF-MIB [RFC 2863].

Since microwave nodes will contain more and more packet functionality that will then be managed using those models, advantages exist if radio link interfaces can be modeled and managed using the same structure and the same approach. This is particularly true for use cases in which a microwave node is managed as one common entity, which includes both the radio link and the packet functionality. All interfaces in a node, irrespective of technology, are then accessed from the same core model (RFC 7223) and can be extended with technology-specific parameters in models that augment the core model.

There will always be certain implementations that differ among products. So it is important to focus on those parameters required to support the applicable use cases for centralized, unified, multivendor management, and to allow other parameters to be optional or to be covered by extensions to the standardized model.

The Microwave Design team seeks consensus both within the industry and with other standards development organizations (SDOs) around one common YANG model, with respect to the use cases and requirements to be supported, the type and structure of the model, and the resulting attributes to be included.

Characteristics of the Model

Definition of the YANG model has begun and a second version of the draft was published on 23 December 2016. The model uses the structure of the IETF’s Radio Link Model as its starting point, as that model provides the desired alignment with RFC 7223. For the definition of the detailed leafs/parameters, the model uses both the Radio Link Model and the Open Network Foundation’s (ONF’s) Microwave Model as its basis, plus includes new ones to cover identified gaps. The parameters in those models have been defined by both operators and vendors within the industry, and implementations of the ONF Model have been tested in proof-of-concept events in multivendor environments, thereby demonstrating the validity of the approach used. The model also includes data nodes to describe the interface layering for the capacity provided by a radio link, as well as the associated Ethernet and time-division multiplexing (TDM) interfaces in microwave nodes.

The model includes support for configuration of microwave specific alarms, but relies on generic models for notifications and alarm synchronization. The same approach is chosen for the general functionality for physical/equipment inventory, which is not supported by the microwave model and instead relies on generic models.

Key Concepts of the Model

Carrier termination is an interface for the capacity provided over the air by a single carrier. It is typically defined by its transmitting and receiving frequencies. Radio link terminal is an interface providing packet capacity and/or TDM capacity to associated Ethernet and/or TDM interfaces in a node. It also is used for setting up a transport service over a microwave/millimeter wave link. Figure 1 illustrates these carrier termination and radio link terminal concepts.

Figure 1. Radio Link Terminal and Carrier Termination

Figure 2 shows the overall structure of the model with radio-link-terminal and carrier-termination, plus three new containers that describe the relationship and interaction between the carrier terminations in more detail: radio-link-protection-groups, xpic-pairs, and mimo-groups.

Figure 2. Overall Structure of the Model

Next Steps

The Microwave Design team created a draft of the unified YANG Data Model for microwave and millimeter radio link, draft-mwdt-ccamp-mw-yang, and it now seeks feedback from and anchoring with a broader industry audience.

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