WP5.2A ACCESS WAN: SPECIFICATION OF PROTOCOL STACK

calvesnorthNetworking and Communications

Oct 24, 2013 (3 years and 9 months ago)

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GAD PROJECT

EXECUTIVE SUMMARY
WP5.2A ACCESS WAN: SPECIFICATION OF
PROTOCOL STACK
The access WAN segment links the ECCT device with the meter (DCONTA) and the Load
Controller device (DCCA). This document contains the complete specification of all the layers of
the protocol stack which has been selected to fulfill the communication needs in this segment. In
the document can be found the specification of the PRIME physical and data link layers (MAC
and LLC), just as the Convergence Layer which links these lower levels with the DLMS/COSEM
HDLC protocol profile. References to the standards and books developed by the DLMS User
Association are given in this document, too. Finally, a complete set of COSEM classes and
objects for both metering and active demand planes is given. The COSEM classes and objects
related to metering have been determined by the DLMS/COSEM Working Group from PRIME
project.
The sets of specification documents of PRIME and DLMS/COSEM represent a solution for PLC
communications in the CENELEC A-band, using an OFDM modulation schema. Over this
infrastructure application objects are interchanged. These application objects implement the
complete set of features that is required for this communication segment. The goal is to achieve a
low cost solution, taking advantage of the ubiquitous existence of power mains, robust and
oriented to AMM (Automatic Meter Management) and Active Demand. Net transfer rate falls in
the range of tenths of kbps. The design is based on IEC 61334, IEEE Std 802.15.4 and IEEE Std
802.16 standards, with some particular improvements in order to make the result fit in the
targeted physical environment.
The PRIME Convergence Layer classifies the traffic associating it with its corresponding MAC
layer connection. This layer performs the mapping of any kind of traffic to include it into the MAC
layer frames. It also performs header suppression. Different convergence layers can be defined
to adapt different types of traffic to MAC layer.
The MAC layer performs functions like topology resolution (addressing), establishment and
maintenance of link connections, bandwidth assignment and system access.
The PHY layer performs the transmission and reception of frames between adjacent PRIME
nodes.
For upper layers in the protocol stack, the selected standards are IEC 62056-53 (COSEM
application layer) and IEC 62056-46 (DLMS/COSEM HDLC profile). This last selection is made
taking into account that DCONTA, DCCA and the Concentrator itself won’t be IP devices, due to
the limitation of available IP addresses for eventually millions of such devices. In this document
there are only references to the main source of information, placed in the DLMS UA Green Book.
Briefly, the HDLC profile here detailed specifies a data link layer for a 3-layer, connection-
oriented, HDLC-based, asynchronous communication profile, suitable for point-to-point and point-
to-multipoint configurations, dedicated and switched data transmission facilities, half-duplex
connections and asynchronous start-stop transmission. There are two additional procedures
defined: segmentation and reassembly of packets, and event reporting, by sending UI frames
from the secondary station to the primary station.
GAD PROJECT

EXECUTIVE SUMMARY
In this document there are only references to the COSEM application layer, which is described in-
depth in the DLMS UA Green Book. There are some references to specific application
procedures and characteristics, like the firmware update mechanism, the definition of 4
association objects (basic public access, read-only access, read-write access, and firmware
update access), each of them with its own access privileges, and a special disconnection mode,
which consists in the deliverance of an application-layer close association command in order to
let the other side of the communication know that the link is to be closed.
Finally, a complete set of COSEM classes and objects, many of them taken from well-known
COSEM objects, approved by the DLMS UA, and some of them still waiting for standardization by
the Association, is presented, for both metering and active demand planes.