INTRODUCTION
A telecommunication operator offers the stored or live content transfer service also called as content streaming service. Different forms of the content include stored audio and video files. A distinguishing aspect of the streaming service is that content needs to be presented to the user even while it is being delivered over the network. This kind of delivery mode makes such a content transfer service sensitive to delay. Besides, such services place a huge demand on the network bandwidth needed for the transfer of the streaming content. The existing network infrastructure is more tuned for the transfer of circuit switched voice and internet based bursty data transfer and as such is not optimized for the transfer of such streaming content. With various technologies offering broadband speeds over the wired and wireless access networks, there is an increasing need for the network infrastructure to be optimized for the delivery of such content transfer services. An architecture as proposed by this invention could cater to the content delivery requirement within a metropolitan area network.
BACKGROUND OF INVENTION
Telecommunication networks have an access network and the core network. In case of 2.5G, 3G, the access network has the base station and the aggregation entities such as Base Station Controller (BSC), Radio Network Controller (RNC) respectively. In case of wired access technologies such as Digital Subscriber Line (DSL), the access network comprises of the aggregation entity such as a Digital Subscriber Line Access Multiplexer (DSLAM). The core network infrastructure provides the connectivity to various services like Internet, operator services like content streaming. The core network elements include Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) for 3G. In order to use the operator provided services, such as retrieval of stored content, the user connects to the content server utilizing the services of the access and core network elements. A few examples of such stored content could be stored audio/video content. The user terminal establishes a data connection to the content server to fetch audio/video content. This connection can be established using various access link protocols and protocols within the core network. Once the connection is established, the content server can deliver the content in different modes such as unicast, multicast. In case of a multicast mode of content distribution, the user terminal would request to join the multicast group that serves the content.
Existing legacy data networks use the same data transfer path for transferring both bandwidth intensive huge content stored in the content server as well as the regular Internet traffic. Such network architecture will not be able to serve regular data traffic users efficiently, when several users are involved in retrieving content from the content server. Besides, existing networks employ circuit switched techniques for content distribution that results in inefficient

bandwidth utilization especially for packet-oriented services such as content transfer or content streaming. Also, the existing data network architectures do not employ any special techniques within the access network for optimized content distribution.
Patent WO2005/006121A2 highlights a ring overlay network for transferring content such as video content to a user's terminal. The suggested overlay method uses SONET ring topology for transferring content. As these SONET rings are pre-provisioned with certain fixed bandwidth, it results in under utilization of network bandwidth for packet based services such as stored/live content transfer. This work has restricted the scope of optimization for content transfer to the usage of a ring overlay network for content transfer. It does not consider optimization techniques such as localized caching, reduction in the number of hops. Besides, it is also very specific to the DSL access technology and to the usage of DSLAM in the access network.
Patent US2006/0294555A1 highlights a Video On Demand system for transferring video content from a VOD server to a TV over an IP backbone. This system has a VOD Edge server that can store the content. In this case, the user is expected to give his choice as to when he would need the content and the cache system uses this input to decide when the content is to be stored. In this case, if all users seek to initiate the download immediately, the content will not be cached. However, according to embodiments of the current invention, content caching is not an option. Instead, content will be cached even during content transfer to the user terminal. Also, patent US2006/0294555A1 uses IP backbone comprising of a set of IP routers as the main content distribution infrastructure, whereas, embodiments of the current invention distribute the content without going over the IP infrastructure and using purely link specific techniques such as distribution over the gigabit Ethernet switch. This will be faster as it purely switching instead of using routing techniques. The other aspect of patent is that if users connected to two different VOD edge servers request for the same content, both the edge servers may store the content. However, embodiments of the present invention provide for ways of distributing a single copy of the content to the various CD's involved and subsequently to the user's terminal. Also, patent US2006/0294555A1 purely addresses the caching principle without mention of any overlay network architecture.
SUMMARY OF THE INVENTION
In summary, embodiments of the present invention provide for a ring overlay network that co-exists along with the legacy data network. The ring overlay network is based on next generation SONET network architecture that employs packet aware ADM's (Add/Drop Multiplexers). The overlay network can be used for content distribution to both wired as well as wireless terminals. The usage of

next generation SONET for content distribution provides efficient bandwidth utilization for IP based content transfer services. Embodiments of the present invention provide for separate paths for content transfer related signaling and for the transfer of the actual content. Besides, the architecture described through this invention is independent of the access technology used by the user terminal. It can also serve both unicast and multicast modes of content retrieval. The architecture also provides a way for localized content distribution that is purely confined to the CDN as defined by this invention, without needing to fetch content from the content server over the IP network. This is achieved through a cache mechanism within the CDN. In the particular case of wireless access scenarios, when content is actually fetched form the CS rather than from CDN based cache, the usage of CDN for such content transfer bypasses the normal data path of the corresponding 3G legacy data network and provides for a direct connectivity between the content server and the corresponding access node. In this way, in case of wireless terminals, when content is actually to be fetched from the content server rather than from the cache, the number of hops needed for retrieving content are minimized.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING:
Fig 1 is a generalized representation of network architecture for content distribution in accordance with this
Fig 2 shows the various blocks of the content distribution network.
Fig 3 shows a detailed representation of the packet aware next generation optical ring distribution network that forms the basis of the CDN.
Fig 4 gives the message flow in the particular case of a wireless terminal retrieving content from the CS.
Fig 5 shows the message flow when a user terminal is served with content stored at one of the Converged Content Distribution Entities (CCDE's).
Fig 6 shows the message flow in the particular case when the CCDE storing the content is different from the CCDE serving the user terminal.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS
Embodiments of the present invention provide network architectural changes for delivering live as well as stored content from a CS to the user's terminal. Fig 1 is a schematic, block diagram of network architecture for content distribution in accordance with this invention. The user terminals 100 represent a plurality of

terminals that could be wired or wireless access terminals. An example of a wireline terminal is an internal or external ADSL modem that is attached to a computing device. The ADSL modem is indicative of a particular use case and is not intended to restrict the scope of this invention. Any other equivalent wired terminal is also covered within this invention. Likewise, the wireless access terminals include mobile device, wireless modems, PDA's with wireless connectivity and any such equivalent wireless device. Apart from the wireless devices mentioned here, those having ordinary skill would appreciate that any other similar wireless terminal could be served by this architecture. The Access Node's (AN's) 200 represents a plurality of network elements with which the user terminals are directly connected either through a wired or wireless connection. A particular Access Node (AN) can serve several user terminals. User terminals 100 connect to their AN's using the corresponding access technology such as DSL, GSM/GPRS, Universal Mobile Telecommunication System (UMTS), Long Term Evolution (LTE), WiMax etc. The list of access technologies listed here is only an illustrative example and does not restrict the scope of applicability of this invention. Depending on the access technology, the network element representing the AN could be a DSLAM, Base Transceiver Station (BTS), NodeB, eNodeB, WiMax Base Station or any other such AN for any other access technology.
Fig 2 illustrates the various elements of the CDN. In accordance with this diagram, the CDN 300 comprises of a plurality of CCDE's 320, the Optical Ring Distribution Network (ORDN) 340 and an IP network 360 comprising of one or more IP routers. Fig 3 is an illustration of the ORDN 340. The ORDN 340 is essentially a SONET ring overlay network that co-exists with the legacy data network 250. The SONET ring is based on the next generation SONET architecture and comprises of one or more packet aware Add/Drop multiplexers (ADM's) such as ADM 342. Each ADM is connected to a corresponding CCDE such as CCDE 322. As shown in Fig 2, each CCDE is capable of storing the content in its local cache. The CS 400 represents a plurality of content servers. Each CS stores the content and is associated with a Controller Function (CF) 410. By transferring audio/video content and other such similar content over the CDN 300, the regular data traffic will not be affected when several users are retrieving content. In this way, the existing legacy network infrastructure can be used to serve the regular data traffic, whereas, content retrieval from the content server will be diverted over this ring overlay network.
As shown in Fig 1, embodiments of the present invention provide separate path for transfer of control signaling and the actual content transfer. The control signaling exchange needed for setting up / release of the connection to the CS 400 as well as the signaling with the CS for requesting content and any other such signaling continues to be carried over the legacy data network 250 whereas the actual content transfer is carried over the CDN 300. The user terminal connects to the CS 400 over the legacy data network 250 and the IP network 270. This connection can be established using the protocols and procedures

defined for the corresponding access technology. During this connection establishment process, the CF 410 associated with the CS 400 receives the identity of the AN serving the user terminal. The CF 410 is provisioned with the identity of the CCDE connected to each of the AN's. The CF 410 is also provisioned with the MAC address of each of the packet aware ADM such as ADM 342. Using this provisioning information, the CF 410 maps the AN identity information received from the legacy data network 250 to the MAC address of the ADM to which the corresponding CCDE is connected. Further, the identified CCDE is also informed about the identity of the AN serving the user terminal.
The content transfer architecture is built upon the functionality of the CCDE, such as CCDE 322 and the ORDN 340 comprising of packet aware ADM's such as ADM 342. The IP router 362 in Fig 3 has an interface towards the CS 400 and an interface towards the ORDN 340. The ADM 346 represents the interface Of the IP router 362 to the ORDN 340. The router 362 can get connected to the ORDN 340 through a optical line card unit. Each of the CCDE's such as 322 has a line interface towards the AN's and a trunk interface towards the ORDN 340. In particular, several AN's are connected to a given CCDE. Content is transferred to the AN serving the user terminal through any of the three ways as illustrated through Fig 4, Fig 5 and Fig 6 respectively.
Fig 4 illustrates the case when content is transferred over the IP router 362 that belongs to the IP network 360. Further, Fig 4 is a particular case of a wireless terminal connecting to the CS 400 over the legacy 3G network. The legacy 3G network has the SGSN and GGSN as the elements of the core network packet switched domain. The wireless terminal connects to the CS 400 over the path marked as 101,102,103 and 104. It then requests for a particular content from the CS 400. This request also follows the same path marked as 101,102,103 and 104. The content can be transferred in unicast or multicast mode. In case of multicast mode, this request is a request for joining the multicast group serving the desired content. As mentioned before, once the terminal gets connected, the CF 410 associated with CS 400 has the knowledge of the AN serving the user terminal and also the needed routing/switching information to forward the content to the corresponding AN. In case of wireless terminals, the AN uses any technique such as paging to forward the content to the wireless terminal. The CF 410 checks whether the content is already stored in the cache of any of the CCDE's. With respect to Fig 4, when the CF 410 finds that the content is not available with any of the CCDE's, it transfers the content directly over the IP network 360 bypassing the SGSN and GGSN. In case of terminal mobility, the CF 410 receives the current location of the terminal from the legacy data network 250 and uses this information to transfer the content to the terminal's current location.
Fig 5 is the case when content is served from the storage 1 associated with the CCDE 324. Again, the user terminal connects to the CS 400 and requests for content over the path marked as 201,202,203,204. Whenever a CCDE is

involved in the path of content transfer for the first time, apart from transferring it to the respective AN, it stores the content in its local storage such as storage 1 associated with CCDE 324. Whenever a CCDE stores the content, it informs the CF 410 about the local storage. With this information, the CF 410 gets to know what content is stored at which CCDE. In this particular case of content transfer represented by Fig 5, the CF 410 finds that the content is already stored in the local storage associated with CCDE 324. The CF 410 requests the CCDE 324 to serve the content from its local storage as marked as 205,206,207,208. When the CCDE 324 receives this request, it transfers the content from its local storage over the path marked as 209,210. As mentioned before, a wireless access node can forward the content to the user terminal by paging the terminal in the area served by the AN. Alternatively, in case the AN represents a DSLAM, the DSLAM can forward the content along the interface over which the terminal is connected to the DSLAM. In this case of content transfer, the IP network 360 is not involved in the actual content transfer.
Fig 6 is the case of content transfer from storage 2 associated with CCDE 324 to CCDE 322 over the optical ring network. As shown in Fig 6, the user terminal's connection to the CS 400 and the subsequent request for content are marked as 301,302,303,304. In this case, the CF 410 associated with the CS 400 finds that the content is already available in the local storage associated with CCDE 324. The CF 410 informs the CCDE 324 the MAC address of the ADM serving CCDE 322 and requests it to transfer the content directly to CCDE 322 which in turn forwards the content to the AN serving the user terminal. This request is marked as 305,306,307 and 308. Upon receiving this request, the CCDE 324 transfers content to CCDE 322 over the optical ring without any involvement of the IP network 360 for the content transfer. This is the case of localized content distribution purely using the link level switching techniques. In case 4, content transfer latency is improved as the usage of CDN for content transfer reduces the number of hops needed for transferring content as compared to the legacy 3G data network. In case 5 and 6, content transfer latency is improved as the IP network is not involved in the content transfer and the transfer happens purely using link level switching techniques.
As the legacy data network is left un-touched, no expensive upgrades of the same are needed. Usage of the next generation SONET for the ring overlay results in efficient bandwidth utilization as the next generation SONET architecture is optimized for packet-oriented services. The ring topology would facilitate a faster and a convenient way for content distribution over a wide area such as a metro network than a star topology. The positioning of a cache based content distribution infrastructure within the access network facilitates faster content retrieval. By diverting the content related traffic onto the ring overlay network, the service provided to users who seek normal data traffic is not affected even when several users are fetching content from the content server. In the specific case of wireless terminals connected over the 3G network, reduction of the number of hops needed to serve the content also provides for a

faster content retrieval. Using the ring overlay network does not adversely affect the performance of the legacy data network.
INDUSTRIAL APPLICABILITY:
1. Distribution of live or stored audio/video content over a metro area.
2. Point to point content transfer applications can also benefit from this architecture
3. Improves content transfer latency thereby yielding better content transfer performance for operator's
4. Efficient utilization of network bandwidth

NVENTION CLAIMS:
What is claimed is:
1. A system for distribution of content over a telecommunication network:
The telecommunication network comprising of a plurality of wired and wireless terminals, plurality of access nodes, CDN, legacy data network, IP network and a Content Server with its associated Controller function;
the CDN comprises of a plurality of CCDEs, ORDN and IP network;
the ORDN comprises of packet aware ADM's using next generation SONET technology;
the CCDEs are interconnected by the ORDN and a plurality of access nodes connect to each CCDE;
the access nodes utilize any wired or wireless access technologies; and
the control signaling is carried over the legacy data network and the actual content is transferred over the CDN.
2. The system of claim 1 wherein, the content is stored at the CS.
3. The system of claim 1 wherein, the content is a live stream from the CS.
4. The system of claim 1 wherein, the CDN is an overlay network that co¬exists with the existing legacy data network;

CDN is used for both unicast and multicast mode of content transfer; and
CDN is capable of localized content distribution, without fetching content from the CS upon each request from the user terminal.
5. The system of claim 1 wherein, the CCDE is a common content distribution point for both wired as well as wireless terminals;
the CCDE is positioned within the access network;
each CCDE exchanges control information relating to content distribution with the CF; and
each CCDE has an associated cache / storage.
6. A method for transferring content directly between the CS and the AN serving the user terminal, the method comprising:
provisioning the CF with the MAC addresses of each packet aware ADM;
provisioning the CF with mapping information of each AN with the corresponding CCDE;
transferring the identity of the AN serving the user terminal between the legacy data network and the CF;
using the received serving AN identity information and the pre-provisioned information to identify and then to transfer content directly to the CCDE serving the user terminal;
transferring the AN identity to the CCDE; and
delivering content to the AN through the corresponding CCDE.
7, The method of claim 4 wherein, delivering the content locally without involving the IP network for content distribution, the method comprising;
receiving, request from user terminal for content;
transferring, control information regarding stored content at each CCDE to the CS;
identifying, availability of the content with one of the CCDEs;

requesting, the identified CCDE to transfer the content to the CCDE serving the user terminal; and
transferring, a single stored copy of the content available at the identified CCDE to the CCDE serving the user terminal.
8. The method of claim 4 wherein, delivering the content locally without
involving the IP network and using a single identified CCDE for content
distribution, the method comprising:
receiving, request from user terminal for content;
transferring, control information regarding stored content at each CCDE to the CS;
identifying, availability of the content with one of the CCDE's;
requesting, the CCDE storing the content, to directly transfer the content to the AN, connected to it; and
transferring, content from CCDE to the corresponding AN.
9. The method of claim 4 wherein, delivering content is over the IP network,
the method comprising:
receiving, request from user terminal for content stored at the CS;
transferring, control information regarding stored content at each CCDE to the CS;
identifying, non-availability of the content with any of the CCDE's; and
transferring content to the user terminal over the CDN.