Download 4. cpp based products

Connectivity Packet Platform in the GSM/WCDMA Network
Denis Duka
Ericsson Nikola Tesla
Split, Croatia
e-mail: [email protected]
Abstract - The telecommunications community is migrating toward a new network architecture based on horizontal layers.
The separation of the network functionality into independent layers is a key principle in modern networking in the tele- and
datacom industry today. The layered thinking is also a very fundamental and visible aspect in a number of standardization
initiatives and industry forums, such as the Multiservices Switching Forum, led by several of the largest operators and
manufacturers.
This paper presents the short overview of Connectivity Packet Platform as a carrier-class technology that has been
positioned for access and transport products in mobile and fixed networks based on layered design.
Keywords - CPP, MGW, WCDMA
1. INTRODUCTION
As mobile communications evolve, mobile end-users
will be offered wideband multimedia capabilities. The
associated multimedia streams require that the networks
should be more flexible than networks that are based on
time-division multiplexing (TDM) – at providing bandwidth
on demand.
Today's tele- and data communications environment
consists of a variety of networks. Most of these networks are
highly specialized, designed and optimized to serve a
specific purpose as illustrated in Figure 1 (left part). To a
large extent these networks can also be described as
vertically integrated in the sense that they combine very
different functionality (for example, transport, control,
services etc.) in one and the same network element [1]. For
historical reasons the networks in this vertically integrated
multi-network world have evolved independently of one
another and therefore differ in many ways. This, of course,
reduces the possibilities for operators to create synergies
among their networks as a means to reduce costs, provide
service portability and so on [2]. The architecture in the
right part of Figure 1 illustrates a way to evolve this multinetwork situation in order to overcome some of its
deficiencies. The solution is based on a horizontal structure
of the network into a number of independent layers, which
gives a more flexible system. The open architecture of the
UMTS (Universal Mobile Telecommunication System)
network ensures a smooth migration from the existing
systems to the new technologies [3].
The rapid convergence of telecom and datacom
technologies has lead to the integration of vertical networks
into multi-service (or next-generation) networks that
provide reliable and real-time communications for all
service types [4].
Fig. 1. Vertically versus horizontally integrated networks
To simplify backbone network design and enable
incremental
upgrade
as
new
technologies
are
commercialized, a layered approach has been taken to the
design of the next-generation networks. By layering the
design of the network and providing open, standard
interfaces, each part of the network can evolve at its own
pace independent of changes in other parts of the network
[5]. The layering means in practice that the different levels
in network hierarchy are separated, and communicate over
well-specified interfaces; thus different applications can
share the resources in the lower level of the network.
Networks designed on this layered principle are described as
horizontally integrated. All network functionality is split
between the connectivity layer, the control layer and the
application layer [6] (see Figure 2).
Fig. 2. Horizontally integrated network
2. BACKGROUND TO THE DEVELOPMENT OF THE
CPP
When Ericsson first began designing Wideband Code
Division Multiple Access (WCDMA) products for thirdgeneration cellular systems based on layered architecture, it
lacked a system platform that could support the multimedia
services that will characterize these systems. Designers also
perceived that the new radio network products would have
to be cost effective enough to compete with mature GSM
products of the future. Thus CPP was selected, mostly
because it demonstrated the best cost-to-performance ratio.
CPP (Connectivity Packet Platform) is a carrier-class
technology that has been positioned for access and transport
products in mobile and fixed networks. It is an execution
and transport platform with specified interfaces for
application design. The execution part consists of support
for the design of application hardware and software. The
transport part, which can be seen as an internal application
on the execution platform, consists of several protocols for
communication, signaling, and transmission.
CPP was first developed for asynchronous transfer mode
ATM (Asynchronous Transfer Mode) and TDM transport.
Later, support is being added for IP (Internet Protocol)
transport [7].
The keywords when designing CPP have been and are
flexibility, scalability, modularity and user friendliness.
Flexibility - CPP can be implemented in different nodes
and networks. The transport technique in CPP is based on
the Asynchronous Transfer Mode (ATM) protocol. ATM
is well suited for a lot of different applications spanning
from low intensive constant bit rate applications such as
voice requiring short and predictable delay to bursty
packet data applications that asks for reliable and high
performing transfer capabilities.
Scalability- The scalability feature of CPP comprises
both execution resources as well as communication
interfaces. It is possible to change the size of a node
during its duty task with very small or non disturbance.
Modularity – Using CPP it is possible to create nodes
with different configurations, functionality, capacity, cost,
and reliability and performance levels.
User Friendliness – CPP can be managed by what is
called a ‘thin client’. That is a web browser that for a
dedicated task and by utilizing HTTP will fetch a
management application from the node. CPP contains a
number of such applications. The users can also develop
their own applications utilizing the management
application support provided by CPP.
CPP also contains a generic object browser that is used
to manage the node by directly accessing and manipulating
the managed objects defined by CPP and the node
application [8].
3. CPP NODE ARCHITECTURE
The term "CPP based node" is used when talking about a
node that includes the CPP platform and the applications
that run on top of the platform. The term node is thus used
to describe any type of network node that switches ATM
cells, regardless of its purpose or complexity.
The CPP Application Development Environment
(CADE) is used during the design of node applications. The
CPP Platform and CADE together include all the physical
equipment and associated software that is required so that
the ATM network node can be created.
Figure 3. shows the CPP platform and the application
part.
Fig. 4. WCDMA CPP based products
4.1. CPP Media Gateway
Fig. 3. CPP platform and application part
The CPP MGW (Media Gateway), as shown on Figure 5,
can contain a full set of speech and data resources for
performing manipulation and additions to the connectivity
layer. It also contains transport resources for performing
protocol and connectivity layer conversions between
different networks and it provides Signaling Gateway
functionality for performing conversions of lower layer
control protocols. An incoming connection on a physical
line interface with a standardized bearer protocol is
connected to the appropriate function. On the outgoing side,
the connection is connected to an outgoing standardized
bearer. Therefore, an incoming bearer is switched to an
outgoing bearer even if the stream is modified and the
bearers are changed.
4. CPP BASED PRODUCTS
CPP is a platform product from which it is possible to
develop a switching network node such as a small to
medium sized ATM switch. The present day design of CPP
emphasizes WCDMA products, for example the Radio
Network Controller (RNC) in the UMTS Terrestrial Radio
Access Network (UTRAN) (Figure 4). Nonetheless, it is a
generic platform that can be used for several different
applications such as IP routers, and the RNC and Base
Transceiver Station (BTS) for CDMA2000 [9]. Code
Division Multiple Access (CDMA) 2000 is the evolution
from CDMA1, which is the narrowband CDMA system in
the United States today. CDMA stands for Code Division
Multiple Access.
Fig. 5. CPP MGW
As part of this process, conversion between different bearers
and formats can be made. This conversion can, for example,
mean converting a compressed voice to a non-compressed
format and changing the bearer from ATM to STM
(Synchronous Transfer Mode), or terminating the packet
data traffic received from the Gn interface in the GTP
(Gateway Tunneling Protocol) tunnels and re-tunneling the
IP packets into IPsec or L2TP tunnels towards external IP
networks (Gi interface) [10]. All MGW application
functions during a connection are initiated from the
Gateway Control Protocol (GCP) that provides a direct link
to the controlling Mobile Switching Center (MSC) server(s).
The platform provides the physical line interfaces and most
of the bearer layer interfaces including bearer control
signaling, for example, AAL2 with Q.AAL2.
For packet based traffic functions such as tunneling
(GTP, IPSec and L2TP), re-tunneling (of GTP packets to
IPSec encapsulation and vice versa), translation of IP
address to IMSI (Individual Mobile Subscriber Identity)
address, volume based charging, security functions QoS
(Quality of Service) handling is performed in the Media
Gateway [11]. The external control interface is the Gateway
Control Protocol used by the MSC Server to request the
Media Gateway to add and remove media stream functions
into a speech and data connection. The Gateway Control
Protocol also includes commands to establish and release a
through connection with the requested media stream
functions included. In the process to establish and release a
connection to other network nodes the relevant bearer
signaling is included. A Media Gateway can lend its
resources to any MSC Server and an MSC Server can use
the resources of any Media Gateway. That way UMTS Core
Network architecture allows an m:n relation between
Servers and Media Gateways [12].
5. CONCLUSION
The layered architecture is being deployed in thirdgeneration mobile networks – that is universal mobile
telecommunication system. The enhanced platform
architecture, today generally pursued by most
standardization forums, provides an inherent flexibility,
which allows operators to build scalable and cost effective
multi-services solutions in the new telecom world. At the
same time the layered architecture offers a pragmatic way to
rationalize legacy networks, allowing them to run over stateof-the- art, cost effective transport solutions.
The modular nature CPP base nodes means it is possible
to create nodes with different configuration, functionality,
capacity, cost, reliability and performance level. MGW
based on CPP represents the base for supporting the
multimedia services associated with UMTS making the
convergence of telecom and data in mobile communications
possible.
CPP is uniquely scalable. It can be used in small
applications and large RNC and media gateway nodes.
Virtually every aspect of scalability is covered by CPP:
high-end and low-end nodes, pay-load capacity, processing
capacity, number of routes, route updating capacity, number
of physical links, link capacity and cost.
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