WO2007112778A1 - Method and apparatus for transmitting atm cells through a gigabit passive optical network - Google Patents

Method and apparatus for transmitting atm cells through a gigabit passive optical network

Info

Publication number
WO2007112778A1
WO2007112778A1 PCT/EP2006/061249 EP2006061249W WO2007112778A1 WO 2007112778 A1 WO2007112778 A1 WO 2007112778A1 EP 2006061249 W EP2006061249 W EP 2006061249W WO 2007112778 A1 WO2007112778 A1 WO 2007112778A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
network
atm
optical
frame
gem
Prior art date
Application number
PCT/EP2006/061249
Other languages
French (fr)
Inventor
Pierangelo Garino
Massimiliano Gimondo
Original Assignee
Telecom Italia S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/54Store-and-forward switching systems
    • H04L12/56Packet switching systems
    • H04L12/5601Transfer mode dependent, e.g. ATM
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/54Store-and-forward switching systems
    • H04L12/56Packet switching systems
    • H04L12/5601Transfer mode dependent, e.g. ATM
    • H04L2012/5603Access techniques
    • H04L2012/5604Medium of transmission, e.g. fibre, cable, radio
    • H04L2012/5605Fibre
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/54Store-and-forward switching systems
    • H04L12/56Packet switching systems
    • H04L12/5601Transfer mode dependent, e.g. ATM
    • H04L2012/5603Access techniques
    • H04L2012/5609Topology
    • H04L2012/561Star, e.g. cross-connect, concentrator, subscriber group equipment, remote electronics
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/54Store-and-forward switching systems
    • H04L12/56Packet switching systems
    • H04L12/5601Transfer mode dependent, e.g. ATM
    • H04L2012/5638Services, e.g. multimedia, GOS, QOS
    • H04L2012/5646Cell characteristics, e.g. loss, delay, jitter, sequence integrity
    • H04L2012/5652Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly

Abstract

It is disclosed a method of transmitting ATM cells through a passive optical network comprising: providing a packet comprising at least one ATM cell; encapsulating at least part of said packet in a frame according to passive optical encapsulation mode; and transmitting said frame through said passive optical network.

Description

METHOD AND APPARATUS FOR TRASMITTING ATM CELLS THROUGH A GIGABIT PASSIVE OPTICAL NETWORK

Technical field The present invention generally relates to the field of access optical networks.

More particularly, the present invention relates to a method and apparatus for transmitting ATM cells through a Gigabit passive optical network (GPON, in short).

Background art As it is known, an access network is a telecommunication network allowing a plurality of users to be connected to a node of a packet-switched or a circuit- switched core network.

More particularly, an optical access network is an access network comprising optical fibers, active optical components (amplifiers, regenerators, switches, or the like) and passive optical components (splitters, couplers, attenuators, or the like). Different types of optical access networks are known in the art: aggregated point-to- point networks with a single channel for optical fiber, aggregated multi-channel point-to-point networks, spatially distributed WDM networks, etc.

A passive optical network is a particularly advantageous type of optical access network. Such a passive optical network mainly comprises passive optical components which are arranged according to a point-to-multipoint architecture. This arrangement allows to connect a plurality of users to a single node of a core network.

Typically, a passive optical network comprises one or more optical trees. Each optical tree comprises single-mode optical fiber spans which are connected by splitters, couplers and attenuators.

The roots of the optical trees are connected to an optical line termination, which acts as a network-side interface for the passive optical network. The optical line termination is typically connected to a node of the core network. Each leaf of each optical tree is connected to a respective optical network unit, which acts as a user-side interface for the passive optical network. An optical line termination may be connected through a passive optical network to a number of optical network units. Each optical network unit is connected to a number of users.

In a passive optical network, data may be transmitted either from the core network to a user (downstream), or from a user to the core network (upstream). Downstream data may be addressed to a single user (unicast), to more than one user (multicast), or to all the users connected to an optical line termination (broadcast).

Different types of optical passive networks are known in the art, such as ATM Passive Optical Networks (APON), Broadband Passive Optical Networks (BPON),

Ethernet Passive Optical Networks (EPON) and Gigabit Passive Optical Networks

(GPON). Each type of passive optical network is adapted to support transmission of different types of traffic, at different speeds.

In particular, the GPON passive optical network (or briefly GPON network, in the following description), allows to transport different types of traffic such as ATM traffic, Ethernet traffic, TDM traffic or the like, at speeds up to 2.5 Gbit/s. Reference is made to Sections 3 to 8 of ITU-T Recommendation G. 984.3 (02/2004). GPON networks provide two transmission modes. A first transmission mode, which is called "native ATM transmission", allows ATM ("Asynchronous Transfer Mode") cells to be directly transmitted through a GPON network. Each ATM cell comprises an ATM header (5 bytes) and an ATM payload (48 bytes). The ATM header comprises information about the cell destination, such as the Virtual Channel (VC) and the Virtual Path (VP).

A second transmission mode, which is called "GPON Encapsulation Mode" (briefly GEM), provides for encapsulating packets/frames of any kind of traffic other than ATM traffic (Ethernet, TDM, or the like) in GEM frames before transmission through the GPON network. For instance, is case of an upstream Ethernet packet, the Ethernet packet is received by an optical network unit from a user through an Ethernet port, then it is encapsulated in a GEM frame by the optical network unit, then it is transmitted to the optical line termination through the GPON network, then it is decapsulated from the GEM frame by the optical line termination, and then it is properly forwarded to the core network. The same happens to downstream Ethernet packets. Ethernet is only an example: the above considerations apply to packets/frames of any kind of traffic other than ATM traffic. Each GEM frame comprises a GEM header and a GEM payload. The GEM header comprises different information such as the GEM payload size and a Port-ID, which identifies either the destination optical network unit (downstream GEM frames) or the source optical network unit (upstream GEM frames). In particular, an optical network unit may be associated to a set of Port-ID values. The GEM header further comprises an Alloc-ID, i.e. a field identifying a T-CONT the GEM frame belongs to. Transmission Containers (T-CONT) are used for the management of upstream bandwidth allocation in the PON section of the Transmission Convergence layer. As it is known, different T-CONTs are associated to different qualities of services. The GEM payload may have an arbitrary size, and it comprises the packet/frame to be transmitted across the GPON network.

In the following description, for simplicity, it will be assumed that the GPON network simply supports ATM cells native transmission and GEM encapsulation of Ethernet packets. For simplicity, other types of traffic will not be taken into account, even though all the following considerations relating to Ethernet packets also apply to any kind of traffic other than ATM traffic.

Downstream transmission in a GPON network will be now briefly described. The optical line termination generates a downstream GPON frame, whose length is 125 μs (microseconds), comprising a header and a payload, which payload comprises a plurality of ATM cells and/or a plurality of GEM frames. Such a downstream GPON frame is transmitted by the optical line termination to all the optical network units through the GPON network. Each optical network unit, according to the VC/VP of each received ATM cell, identifies the ATM cells addressed to it, and it forwards them to suitable ATM ports. Similarly, each optical network unit, according to the Port-ID of each received GEM frame, identifies the GEM frames addressed to it, it de-capsulates the Ethernet packets comprised into the GEM payload, and it forwards the Ethernet packets to suitable Ethernet ports.

On the other hand, upstream transmission from different optical network units connected to a single optical line termination is performed as a burst transmission, different bursts transmitted by different optical network units being multiplexed according to TDMA technique ("Time Division Multiple Access"). More particularly, the optical line termination authorizes each optical network unit to transmit an upstream burst of a given T-CONT. According to Section 7.3 of the above mentioned ITU-T G. 984.3, each T-CONT is associated with only ATM or GEM traffic.

GEM encapsulation allows to transmit different GEM frames with different bandwidth assurances. More particularly, GEM frames are divided into a number of Transmission Containers, each Transmission Container being associated to a different level of bandwidth assurance. Five different types of Transmission Containers are presently provided: - Type 1 : Fixed Bandwidth;

- Type 2: Assured Bandwidth;

- Type 3: Assured Bandwidth, Non-Assured Bandwidth and Maximum Bandwidth; - Type 4: Best Effort Bandwidth; and

- Type 5: any type of bandwidth.

T-CONT is associated with Allocation Identifier Alloc-ID.

Indeed, the optical line termination sends grant information to the optical network units in a dedicated field of the downstream GPON frame header, which is termed Physical Control Block downstream. The Physical Control Block downstream comprises an upstream Bandwidth Map BWmap in which are defined, for each optical network unit, the start time of the granted time slots, the stop time of the granted time slots and the Alloc-ID associated to the T-CONT whose traffic type (either GEM or ATM) the granted time slot is allocated to. Multiple time slots, associated to different Alloc-IDs, can be allocated to each optical network unit.

Therefore, each optical network unit, upon identification of its own granted time slot, inserts either ATM cells or GEM frames belonging to the authorized T-CONT in an upstream burst of suitable size, which will be transmitted upstream during the granted time slot. US2004/0218534 A1 discloses a GEM OAM transmission method used in a

GPON network, which defines an OAM frame structure in a GEM mode of the GPON network, and enables the 0AM to be achieved even when GEM mode is operated. The method comprises the steps of: constructing a GEM 0AM frame including a GEM header field and a GEM payload field, the GEM header field containing 0AM representation information indicating that the GEM 0AM frame contains the 0AM information, the GEM payload field containing the 0AM information; and transmitting the constructed GEM 0AM frame in order to enable the ONU to perform an operation according to the 0AM information.

US 2004/208631 A1 discloses a GTC frame structure and method for transmission of ONT management control information in GPON. The method comprises the steps of: constructing a GTC frame which includes a PCBd portion having an OMCC field including either destination identifier information for supporting a GEM mode or destination identifier information for supporting a ATM mode, and a payload portion including data; and transmitting the GTC frame. The GTC frame structure for ONT management control information transmission can transmit the management control information to an ONT supporting either ATM mode or GEM mode.

EP 1 467 590 discloses an optical network terminal (ONT) management control protocol of gigabit-capable passive optical network. A gigabit-capable passive optical network encapsulation method (GEM) frame structure that supports delivery of ONT management control information for an optical network unit (ONU) using a GEM and a method for processing data using the GEM frame structure The GEM frame structure includes in the GEM header a payload type of the GEM header frame, and is used for a gigabit-capable passive optical network (GPON), wherein payload type information, which represents a data type of a payload portion of the GEM frame, is displayed in a header of the GEM frame, in order to provide a GEM control frame which delivers management control information transferred from an OLT (Optical Line Termination).

Object and summary of the invention

The Applicant has noticed that the above known method of transmitting different types of traffic upon a GPON network exhibits some drawbacks, which are mainly related to ATM cell native transmission.

Firstly, ATM cells have a predefined size. This disadvantageously implies that, when a granted time slot for transmitting upstream ATM cells from a given optical network unit has a size which is not an integer multiple of an ATM cell size, the given optical network unit has to fill part of the upstream burst with padding bytes, thus wasting part of the granted time slot. This problem does not occur for GEM frames, since GEM encapsulation allows optical network units, when needed, to split the payload of GEM frames into fragments whose size can be suitably tailored, each fragment being encapsulated and transmitted as separate GEM frame in a different burst. Payload Type Indicator (PTI) field is used to indicate the content type of the fragment payload and its appropriate treatment.

Moreover, managing separately ATM cells, which are transmitted in a native form, and all the other types of packets/frames, which are transmitted through GEM encapsulation, disadvantageously implies that a significant part of the devices managing traffic within the optical network units and within the optical line termination have to be duplicated. Therefore, optical network units and optical line termination are very complex and very costly, thus raising the overall cost of the access service provided to users. Therefore, the general object of the present invention is providing a method and an interface apparatus for transmitting ATM cells through a GPON network which overcomes the aforesaid drawbacks.

In particular, an object of the present invention is providing a method and an interface apparatus for transmitting ATM cells through a GPON network which allows each interface apparatus (and in particular, optical network units) to fully exploit granted time slots, independently of the type of transmitted traffic. In the present description and in the claims, the expression "interface apparatus" will generally refer either to a network side interface apparatus of a GPON network (i.e. an optical line termination) or to a user side interface apparatus of a GPON network (i.e. an optical network unit).

A further object of the present invention is providing a method and an interface apparatus for transmitting ATM cells through a GPON network which allows to reduce interface apparatus complexity and cost, while preserving capability of managing different types of traffic.

According to a first aspect, the present invention provides a method of transmitting ATM cells through a passive optical network comprising: providing a packet comprising at least one ATM cell; encapsulating at least part of the packet in a frame according to passive optical encapsulation mode; and transmitting the frame through the passive optical network. In the present description and in the claims, the term "passive optical encapsulation mode" will designate any encapsulation of traffic packets and/or frames in a passive optical network. An example of "passive optical encapsulation mode" is the above cited GEM encapsulation mode. The term "encapsulation" means in general including data from a first layer protocol into a second layer protocol.

Preferably, the frame is transmitted from a network side interface apparatus to a user side interface apparatus of the passive optical network, and the frame is inserted into a payload of a downstream frame generated at the network side interface apparatus. Alternatively, the frame is transmitted from a user side interface apparatus to a network side interface apparatus of the passive optical network, and the frame is inserted into a payload of an upstream burst generated at the user side interface apparatus. In this latter case, optionally, the payload of the upstream burst comprises at least a further frame comprising a further packet of a traffic type other than ATM. Optionally, before encapsulating, the method of the invention further comprises fragmenting the packet into a first packet fragment and a second packet fragment. In this case, preferably, encapsulating comprises encapsulating the first packet fragment in the frame, and encapsulating the second packet fragment in a successive frame. Preferably, the method of the invention further comprises dynamically determining a number of ATM cells to be inserted in the packet, according to traffic requirements.

Preferably, the passive optical network comprises a Gigabit Passive Optical Network. According to a second aspect, the present invention provides an interface apparatus for interfacing a passive optical network and an ATM network. The interface apparatus comprises: a packetizer for providing a packet comprising at least one ATM cell received from the ATM network, a formatter for encapsulating at least part of the packet in a frame according to passive optical encapsulation mode, and a transmitter for transmitting the frame through the passive optical network.

Preferably, the interface apparatus is a network side interface apparatus which is adapted to generate a downstream frame, and the formatter is adapted to insert the frame into a payload of the downstream frame. Alternatively, the interface apparatus is a user side interface apparatus which is adapted to generate an upstream burst, and the formatter is adapted to insert the frame into a payload of the upstream burst. In this latter case, optionally, the upstream burst comprises at least a further frame comprising a packet of a traffic type other than ATM.

Optionally, the formatter is further adapted to fragment the packet into at least a first packet fragment and a second packet fragment, and to encapsulate the first packet fragment in the frame and the second packet fragment in a successive frame.

Profitably, the interface apparatus comprises a temporary memory for storing the packet, before encapsulation. Preferably, the interface apparatus further comprises a memory manager for associating to the packet a pointer indicating a memory address and a size of the packet, before encapsulation. Preferably, the interface apparatus further comprises a pointer queue for storing a number of pointers, before encapsulation. Preferably, the formatter reads the pointer from the pointer queue and, according to the memory address and size of the packet, fetches the packet from the temporary memory. According to a third aspect, the present invention provides an interface apparatus for interfacing a passive optical network and an ATM network, the interface apparatus comprising: a receiver for receiving a frame formatted according to the passive optical encapsulation mode from the passive optical network, a decapsulator for extracting from the received frame at least part of a packet comprising at least one ATM cell, and a transmitter for transmitting the at least one ATM cell to the ATM network.

Preferably, the interface apparatus is a network side interface apparatus which is adapted to receive an upstream burst, and the upstream burst comprises the received frame. Alternatively, the interface apparatus is a user side interface apparatus which is adapted to receive a downstream frame, and the downstream frame comprises the received frame.

Preferably, the decapsulator is further adapted to merge packet fragments of a packet which are transported by several received frames.

According to a fourth aspect, the present invention provides a transmission system comprising a first ATM network, a second ATM network, a passive optical network, a first interface apparatus for interfacing the first ATM network and the passive optical network and a second interface apparatus for interfacing the passive optical network and the second ATM network. The first interface apparatus is an interface apparatus according to the above second aspect of the present invention and the second interface apparatus is an interface apparatus according to the above third aspect of the present invention.

Brief description of the drawings

The present invention will become more clear by reading the following description, given by way of example and not of limitation, to be read with reference to the accompanying drawings, wherein:

- Figure 1 schematically shows an optical access network comprising a GPON network;

- Figure 2 schematically shows a prior art downstream GPON frame transporting both ATM cells and GEM frames;

- Figure 3 schematically shows prior art upstream bursts transporting either ATM cells or GEM frames;

- Figure 4 schematically shows a downstream GPON frame transporting both ATM cells and GEM frames, according to an embodiment of the present invention; - Figures 5a e 5b schematically show upstream bursts transporting ATM cells and/or GEM frames, according to two different embodiments of the present invention;

- Figure 6 schematically shows an upstream data interface of an optical network unit for generating an upstream burst transporting either ATM cells or GEM frames, according to an embodiment of the present invention;

- Figure 7 shows a downstream data interface of an optical line termination for generating a downstream GPON frame transporting both ATM cells and GEM frames, according to an embodiment of the present invention; and

- Figure 8 schematically shows a downstream data interface of an optical network unit for receiving a downstream GPON frame transporting ATM cells and GEM frames, according to an embodiment of the present invention.

Detailed description of preferred embodiments of the invention

Figure 1 schematically shows a known optical access network OAN comprising a GPON network GN. The inner structure of the GPON network GN which, as already mentioned, is tree-like and comprises passive optical components, is not shown in details in Figure 1.

The optical access network OAN is connected to a core network CN through an optical line termination OLT, which acts as a network side interface between the GPON network GN and the core network CN. The core network CN may comprises one or more packet-switched networks (ATM, Ethernet, IP, or the like) and/or one or more circuit-switched networks (Sonet, SDH, or the like). In the following description, it will be assumed that the core network CN comprises an ATM network and an Ethernet network. Further, the optical access network OAN is connected to a plurality of users (not shown in Figure 1) through a plurality of optical network units ONU1 , ONU2, ..., ONUn, each optical network unit acting as a user side interface between the GPON network and the users. Indeed, each optical network unit ONU1 , ONU2, ..., ONUn is provided, at its user side, with a respective plurality of ATM ports ATMpI , ATMp2, ..., ATMpn and with a respectively plurality of Ethernet ports Ethpi, Ethp2, ..., Ethpn.

As already mentioned, the GPON network transmits downstream ATM and Ethernet traffic coming from the core network CN to the users through downstream GPON frames, which are generated by the optical line termination OLT. In Figure 1 , such downstream GPON frames are indicated as GFd. Similarly, the GPON network transmits upstream ATM and Ethernet traffic coming from the users to the core network CN through TDMA-multiplexed upstream bursts, which are generated by the optical network units ONU1, ONU2, ..., ONUn. In Figure 1 , such upstream bursts are indicated as ub1, ub2, ..., ubn. Figure 2 schematically shows a downstream GPON frame GFd transporting both

ATM cells and GEM frames, according to the prior art. As already mentioned, the downstream GPON frame GFd has a standard duration of 125 μs (microseconds). The frame GFd comprises a first field PCBd (Physical Control Block downstream) which, in addition to other information, comprises the upstream Bandwidth Map uBWmap. The upstream Bandwidth Map uBWmap has the function of communicating to each optical network unit ONU1 , ONU2, ..., ONUn information (duration, T-CONT) about the granted time slot wherein each optical network unit is allowed to transmit its upstream bursts.

For simplicity, in the following description, it is assumed that each optical network unit is associated to a single T-CONT.

Therefore, the first field uBWmap comprises a set of optical network unit identifiers and, for each optical network unit identifier, a respective start time, end time, and T-CONT (either ATM or GEM). For instance, the first field uBWmap shown in Figure 2 comprises: - for ONU1 : identifier ONUI id, start time ts1, end time te1 , Alloc-ID (associated to traffic type t1);

- for ONU2: identifier 0NU2id, start time ts2, end time te2, Alloc-ID (associated to traffic type t2); and

- for ONUn: identifier ONUnid, start time tsn, end time ten, Alloc-ID (associated to traffic type tn).

Therefore, the optical network unit ONU 1 is enabled to transmit its upstream burst comprising traffic type t1 between ts1 and te1 ; the optical network unit ONU2 is enabled to transmit its upstream burst comprising traffic type t2 between ts2 and te2; and so on, until the optical network unit ONUn, which is enabled to transmit its upstream burst comprising traffic type tn between tsn and ten. The times ts1 , te1 , ts2, te2, ..., tsn, ten are selected by the optical line termination so that granted time slots of different optical network units do not overlap.

The downstream GPON frame GFd further comprises a payload, which is divided into two parts. A first payload part ATMp comprises a plurality of native ATM cells ATMd , ATMc2, ..., ATMcm, while a second payload part GEMp comprises a plurality of Ethernet packets Etp1 , Etp2, ..., Etpk, each packet being encapsulated in a respective GEM frame GEMfI, GEMf2, ..., GEMfk. The termination OLT tailors each payload part according to properties of traffic incoming from the core network CN. Typically, since ATM cells have a fixed 53-byte size, the OLT tailors the first payload part ATMp so that its size is an integer multiple of 53 bytes. Therefore, the size of the second payload part GEMp is the difference between the overall payload size and the payload part ATMp size.

Each GEM frame GEMfI , GEMf2, ... GEMfk comprised into the second payload part GEMp has a respective GEM header GEMhI, GEMh2, ..., GEMhk and a respective GEM payload GEMpI , GEMp2, ..., GEMpk. Each GEM payload GEMpI , GEMp2, ..., GEMpk comprises a respective Ethernet packet Etp1 , Etp2, ..., Etpk. Therefore, the size of each GEM frame GEMfI , GEMf2, ... GEMfk depends on the size of the respective Ethernet packet Etp1 , Etp2, ..., Etpk.

As shown in Figure 2, the payload part GEMp size may be smaller than the overall size of the GEM frames GEMfI, GEMf2, ... GEMfk. In this case, GEM encapsulation provides for dividing the last Ethernet packet Ethpk in two fragments, the first fragment Ethpk' being inserted into a GEM frame GEMfk which is tailored to exactly fill the payload part GEMp. The second fragment Ethpk" will be inserted into a subsequent GEM frame, which will be transmitted in a subsequent downstream GPON frame (which is not shown in Figure 2) and, upon reception by the optical network unit addressee of the GEM frames comprising Ethpk', Ethpk", the two fragments will be merged, in order to recover the Ethernet packet Etpk. This advantageously allows to completely fill the payload part GEMp, thus avoiding padding. Figure 3 schematically shows some upstream bursts transporting either ATM cells or GEM frames, according to the prior art. As already mentioned, each optical network unit ONU1 , ONU2, ..., ONUn transmits a respective upstream burst according to grant information comprised into the field uBWmap of the downstream GPON frame GFd. More particularly, as shown in Figure 3, the ONU1 transmits its upstream burst ub1 in a granted time slot between ts1 and te1 ; similarly, the ONU2 transmits its upstream burst ub2 in a granted time slot between ts2 and te2; and so on, until the ONUn, which transmits its upstream burst ubn in a granted time slot between tsn and ten. For clarity reasons, Figure 3 only shows the structure of the upstream bursts ub1 and ub2. As already mentioned, grant information also specifies the traffic type each optical network unit is allowed to transmit. In the following description, it is assumed that the traffic type t1 of the ONU 1 is ATM, while the traffic type t2 of the ONU2 is GEM.

Therefore, the upstream burst ub1 comprises a header ub1 h and a payload ubp1 , in turn comprising a plurality of ATM cells ATMd, ATMc2, ..., ATMcs. If the payload size is not exactly a multiple of 53 bytes (i.e. an ATM cell size), the ONU1 will insert padding bytes (indicated as "pad" in Figure 3) in the final part of the of the payload ubp1. This disadvantageously implies that the ONU1 wastes part of the granted time slot ts1-te1. On the other hand, the burst ub2 comprises a header ub2h and a payload ub2p, in turn comprising a plurality of Ethernet packets Etp1 , Etp2, ..., Etpr, each Ethernet packet being encapsulated in a respective GEM frame GEMfI , GEMf2, ..., GEMfr. If the payload size is not exactly equal to the sum of the GEM frame sizes, the ONU2, according to GEM encapsulation, may divide the last Ethernet packet Etpr in two fragments, the first fragment Etpr' being inserted into a GEM frame GEMfr which is tailored in order to exactly fill the payload ub2p. The second fragment Etpr" will be inserted in a further GEM frame, which will be transmitted by the ONU2 in a subsequent upstream burst, when the OLT will assign again to the ONU2 a granted time slot. This advantageously allows the ONU2 to completely exploit the granted time slot ts2-te2.

Figure 4 schematically shows a downstream GPON frame GFd' transporting both ATM cells and GEM frames, according to an embodiment of the present invention. For better understanding the difference between the present invention and the prior art, Figure 4 should be compared with Figure 2. According to the preferred embodiment of the present invention shown in Figure

4, the OLT generates a downstream GPON frame GFd', whose duration is also 125 μs (microseconds), in order to preserve compatibility with the standard GPON. The frame GFd' comprises a first field PCBd (Physical Control Block downstream), which, in addition to other information, comprises the upstream Bandwidth Map uBWmap. The upstream Bandwidth Map uBWmap still has the function of communicating to each optical network unit ONU1 , ONU2, ..., ONUn information (duration, T-CONT) about the granted time slots wherein each optical network unit is allowed to transmit its upstream bursts. The content of such a field is identical to the one shown in Figure 2. Therefore, a detailed description will not be repeated. Also in this example, for simplicity, it is assumed that each optical network unit is associated to a single T-CONT.

The frame GFd' payload, differently from the known frame GFd payload shown in Figure 2, is not divided in two payload parts, but it comprises a single payload GEMp, in turn comprising a plurality of GEM frames. According to the present invention, each GEM frame may comprise either an

Ethernet packet or one or more ATM cells. Indeed, according to the present invention, ATM cells are not transmitted in their native form, but they are encapsulated into GEM frames, like any other packet/frame to be transported across the GPON network. According to preferred embodiments of the present invention, since an ATM cell size is quite small in comparison with a GEM header size, a plurality of ATM cells is packetized in a single "ATM packet", which is then encapsulated in a single GEM frame, like an Ethernet packet. This advantageously allows to preserve a high transport efficiency, i.e. to preserve a high percentage of user data relative to the overall transmitted data, since a single GEM header is inserted for a plurality of ATM cells.

In the embodiment shown in Figure 4, the plurality of ATM cells ATMd , ATMc2, ..., ATMcm to be transmitted which, according to the prior art shown in Figure 2, was inserted in native form into the payload part ATMp, is now packetized in a single ATM packet ATMpk+1, which is in turn encapsulated in a GEM frame GEMfk+1. Such a GEM frame GEMfk+1 , in Figure 4, is inserted at the end of the payload GEMp, after the plurality of GEM frames GEMfI , GEMf2, .., GEMfk. This is only a non limiting example. Indeed, the ATM cells ATMd , ATMc2, ..., ATMcm could be distributed in more than one GEM frame. Also the position of the GEM frame GEMfk+1 is only exemplary: indeed, GEM frame(s) comprising ATM packet(s) may be located at any position of the payload GEMp.

Therefore, by comparing Figures 2 and 4, it can be noticed that ATM packets comprising ATM cells, similarly to Ethernet packets (as well as a packet/frame of any type of traffic other than ATM) may be divided in fragments. In particular, Figure 4 shows that the ATM packet ATMpk+1 may be divided in two fragments, the first fragment ATMpk+1' being inserted into a GEM frame GEMfk+1 which is tailored to exactly fill the payload GEMp. The second fragment of the ATM packet ATMpk+1" will be then inserted in a further GEM frame, which will be transmitted into a subsequent downstream GPON frame. Therefore, according to the present invention, a higher flexibility is reached in filling a downstream GPON frames with ATM cells and Ethernet packets. This is particularly advantageous in case of upstream transmission, as it will be shown in greater detail herein after.

Further, this advantageously allows to have a particularly simple optical line termination generating downstream GPON frames GFd' and particularly simple optical network units receiving such downstream GPON frames GFd', as it will be shown in greater detail herein after.

Figure 5a schematically shows some upstream bursts transporting either ATM cells or GEM frames, according to an embodiment of the present invention. For better understanding the difference between the present invention and the prior art, Figure 5a should be compared with Figure 3. According to the embodiment of the present invention shown in Figure 5a, each optical network unit ONU1 , ONU2, ..., ONUn transmits a respective upstream burst according to grant information received from the OLT through the field PCBd of the downstream GPON frame GFd'. More particularly, as shown in Figure 5a, the ONU1 transmits its upstream burst ub1' in its granted time slot between ts1 and te1 ; similarly, the ONU2 transmits its upstream burst ub2' in its granted time slot between ts2 and te2; and so on, until the ONUn, which transmits its upstream burst ubn' in its granted time slot between tsn and ten. For clarity reasons, Figure 5a only shows the structure of the upstream bursts ub1' and ub2'.

As already mentioned, grant information specifies the traffic type each optical network unit is allowed to transmit. In the following description, it is assumed that the traffic type t1 of the ONU1 is ATM, while the traffic type t2 of the ONU2 is GEM.

The burst ub1' comprises a header ub1 h and a payload ub1 p. According to the present invention, and differently from the prior art shown in Figure 3, the payload ub1 p comprises a GEM frame, in turn comprising one or more ATM cells. Indeed, according to the present invention, ATM cells are not transmitted in their native form, but they are encapsulated into GEM frames. According to preferred embodiments of the present invention, since a cell ATM size is rather small in comparison with a GEM header size, a plurality of ATM cells is packetized in a single "ATM packet", which is then encapsulated in a single GEM frame, like an Ethernet packet. This, as already mentioned, advantageously allows to preserve a high transport efficiency.

In the embodiment of the present invention shown in Figure 5a, the plurality of ATM cells ATMd , ATMc2, ..., ATMcs to be transmitted upstream, which, according to the prior art shown in Figure 3, was inserted in native form into the payload ub1 p of the upstream burst ub1, in now packetized in a single ATM packet ATMpO, which is in turn encapsulated in a GEM frame GEMfO. Such a GEM frame GEMO, in Figure 5a, is inserted into the payload ub1 p. This is only a non limiting example. Indeed, the ATM cells ATMd, ATMc2, ..., ATMcs could be distributed in more than one GEM frame, which could be transmitted either in the same upstream burst or in different upstream bursts.

This advantageously allows avoiding the insertion of padding bytes into the payload ub1 p of the upstream burst ub1'. Indeed, in the embodiment shown in Figure 5a, the GEM frame GEMfO comprises, besides ATM cells transmitted into the upstream burst ub1 of Figure 3 according to the prior art, an additional ATM cell ATMcs+1. By inserting such an additional cell ATMcs+1, the size of the GEM frame GEMfO encapsulating the ATM packet ATMpO is higher than the payload ub1p size. However, according to the present invention, the ATM packet ATMpO may be divided in fragments. In particular, Figure 5a shows that the ATM packet ATMpO is divided in two fragments ATMpO', ATMpO", the first fragment ATMpO' being inserted into a GEM frame GEMfO which is tailored to exactly fill the payload ub1 p of the upstream burst ub1'. The second fragment ATMpO" of the ATM packet ATMpO will be then inserted into a further GEM frame which will be transmitted into a subsequent upstream burst.

The upstream burst ub2', which comprises Ethernet packets, has a structure which is identical to the one of the known upstream burst ub2 of Figure 3. Therefore, a detailed description will not be repeated.

Therefore, by comparing Figures 3 and 5a, it can be noticed that according to the present invention, each optical network unit can advantageously exploit its granted time slot in a more efficient way, since, thanks to possible fragment of GEM frames encapsulating packetized ATM cells, the payload of each upstream burst can be completely filled with user data, without requiring any padding.

Further, this advantageously allows to have particularly simple optical network units generating upstream bursts and a particularly simple optical line termination receiving such upstream bursts, as it will be shown in greater detail herein after. It has to be noticed that, according to a particularly advantageous embodiment of the present invention, GEM frames transporting either Ethernet packets or ATM packets may be inserted in a same upstream burst payload. This means that a single upstream burst, according to the present invention, is capable of transporting both Ethernet traffic and ATM traffic. This is schematically shown in Figure 5b. For simplicity, in Figure 5b only the inner structure of the upstream burst ub1" according to this particularly preferred embodiment is detailed. It is further assumed that the ONU 1 has to transmit a plurality of upstream ATM cells ATMd , ..., ATMcq and a plurality of Ethernet packets Etp1 , ..., Etpg. According to this preferred embodiment, ATM cells are packetized in a single ATM packet ATMpO. If needed, the last Ethernet packet may be fragmented in a first fragment Etpg' and a second fragment Etpg" (of course, if the last packet were an ATM packet, fragmentation could be similarly applied to the ATM packet, as described above). Therefore, the ATM packet ATMpO, the Ethernet packets Eth1 , ..., Etpg-1 and the fragment Etpg' are encapsulated in respective GEM frames GEMfO, ..., GEMfg, which are all inserted into the upstream burst payload ub1.

Figure 6 schematically shows an upstream data interface Dl-u of an optical network unit ONUi for generating an upstream burst ubi' transporting either ATM cells or Ethernet packets encapsulated into GEM frames, according to an embodiment of the present invention. The upstream data interface Dl-u according to the present invention comprises, at the user side, a plurality of Ethernet ports Ethpi for receiving Ethernet packets from users, and a plurality of ATM ports ATMpi for receiving ATM cells from users.

Each Ethernet port is terminated on a respective Ethernet receiver ER1 , ..., ERm. Each ATM port is terminated on a respective ATM packetizer AP1, .., APk. Each ATM packetizer is responsible of receiving a respective plurality of ATM cells and packetizing said plurality in a single ATM packet. Therefore, each ATM packetizer AP1, ... APk outputs a respective ATM packet, which comprises a plurality of subsequent ATM cells. The number of ATM cells to be packetized in a single ATM packet can be determined according to traffic requirements. In some cases, an ATM packets may comprise a single ATM cell.

Each Ethernet receiver ER1 , ..., ERm and each ATM packetizer AR 1 , ..., ARk is connected to a respective memory formatter MF1 , ..., MFm, MFm+1 , ... MFm+k, which forwards the Ethernet packets received from the Ethernet receivers ER1 , ..., ERm and the ATM packets received from the ATM packetizers AP1 , ..., APk to a memory manager MM. Therefore, advantageously, according to the present invention, both Ethernet packets and ATM packets are managed by a same type of memory formatter. Indeed, each memory formatter MF1, ..., MFm, MFm+1 , ... MFm+k is regularly requested to transfer either Ethernet packets or ATM packets to the memory manager MM. In order to perform such operations, memory formatters MF 1, ..., MFm, dealing with Ethernet packets, are linked to an Ethernet association table, which comprises associations between Ethernet packets and Port-IDs. Similarly, memory formatters MFm+1 , ... MFm+k, dealing with ATM packets, are linked to an ATM association table, which comprises associations between ATM packets and Port-IDs. Such Port-IDs will be inserted into the GEM header of GEM frames encapsulating Ethernet packets or ATM packets.

The memory manager MM stores all the received Ethernet and ATM packets in a temporary memory TM and it associates to each stored packet a respective memory pointer. The memory pointer MP manages each pointer associated to each packet (either Ethernet or ATM). Each pointer indicates the address of the respective packet into the temporary memory TM. Further, each pointer indicates the size of the respective packet, the Port-ID and the Alloc-ID.

The memory manager MM forwards both the pointers associated to Ethernet packets and the pointers associated to ATM packets to a pointer queue PQ, as shown by the dashed arrow in Figure 6. Preferably, according to the present invention, a different pointer queue is provided for each different T-CONT. However, in Figure 6 it is assumed that the ONUi is associated to a single T-CONT, so that a single pointer queue PQ is required.

The pointer queue PQ is connected to a GEM formatter and fragmenter GFF. The GEM formatter and fragmenter GFF, according to the pointers included into the pointer queue PQ, and according to grant information for GEM traffic GEMg received by the OLT into the field uBWmap of downstream GPON frames, asks the memory manager MM to fetch from the temporary memory TM a suitable number of Ethernet packets and/or ATM packets. The last fetched packet is possibly fragmented as described above, if needed. Then, fetched packets and packet fragments are encapsulated in respective GEM frames. Therefore, GEM frames are inserted into the payload of an upstream burst. The payload of the upstream burst is then outputted by the upstream data interface Dl-u to a GTC framing block GTCF, which generates the upstream bursts inserting the requested overheads (PLOu, PLOAMu, DBRu). Therefore, the block GTCF generates and transmits an upstream burst ubi' according to grant information.

Therefore, advantageously, according to the present invention, the modules for processing Ethernet packets and ATM cells are not duplicated, since multiple ATM cells are packetized upon reception from ATM ports in ATM packets, which are processed like Ethernet packets. This advantageously allows to process in a same way (i.e. through the same modules) both Ethernet packets and ATM packets. Therefore, the resulting upstream data interface is very simple, thus reducing the cost of the optical network unit, and therefore the cost of the access service provided to users.

Figure 7 schematically shows a downstream data interface Dl-d' of an optical line termination OLT for generating a downstream GPON frame GFd' transporting both

ATM cells and GEM frames, according to an embodiment of the present invention.

By comparing Figure 6 and Figure 7, it can be noticed that the upstream interface

Dl-u and the downstream data interface Dl-d' are substantially symmetrical.

The main difference between to two interfaces Dl-u and Dl-d' is that the pointer generated by the memory pointer MP of the downstream data interface Dl-d' of Figure 7 does not comprise the Alloc-ID. Moreover, the GEM formatter and fragmenter GFF of the downstream data interface Dl-d' asks the memory manager MM to fetch from the temporary memory TM a suitable number of Ethernet packets and/or ATM packets, according to the pointers included into the pointer queue PQ, and according to payload bytes information pb indicating the size of the next downstream GPON frame (which may vary according to the uBWmap information size).

Figure 8 schematically shows a downstream data interface Dl-d of an optical network unit ONUi for receiving a downstream GPON frame GFd' transporting ATM cells and GEM frames, according to an embodiment of the present invention.

The ONUi comprises a GTC de-framing block GTCDF, which is adapted to receive a downstream GPON frame GFd' transmitted from the OLT through the network GPON. Such a block GTCDF extracts information from PCBd field (which includes the uBWmap information), it discards GEM frames whose Port-ID is not associated to the ONUi, and it forwards to the downstream data interface Dl-d GEM frame whose Port-ID is associated to the ONUi. The block GTCDF is connected to the downstream data interface Dl-d. The downstream data interface Dl-d comprises a GEM decapsulator de-fragmenter GDD.

The block GDD is adapted to receive from the block GTCDF the payload GEMp of a downstream GPON frame GFd' according to the present invention, and it de- capsulates both Ethernet packets and ATM packets from respective GEM frames. Ethernet packets and ATM packets are then forwarded to a downstream dispatcher DD. The block DD, according to the Port-ID comprised into the header of each GEM frame, forwards each Ethernet packet to a suitable Ethernet transmitter ET1 , ..., ETm, Similarly, the block DD, according to the Port-ID of each ATM packet, forwards each ATM packet to a suitable ATM transmitter AT1 , ..., ATk. ATM transmitters AT1 , ..., ATk then extracts ATM cells from each ATM packets and then separates ATM cells.

Advantageously, according to the present invention, also the structure of the downstream data interface of the optical network unit is very simple. This is due to the fact that the optical network unit receives downstream GPON frames only comprising GEM frames. Therefore, the downstream data interface can process GEM frames in a unique way, irrespective of the fact that the each GEM frame comprises an Ethernet packet or a plurality of packetized ATM cells. Although not described, according to the present invention, a similar data interface is provided also to the optical line termination OLT for receiving the upstream bursts ubi', ubi" shown in Figures 5a, 5b. It has to be noticed that while the downstream data interface Dl-d of Figure 8 comprises a single GDD/DD, the upstream data interface of the optical line termination OLT can comprise a respective GDD/DD for each optical network unit it is connected to.

Claims

1. A method of transmitting ATM cells through a passive optical network (GN) comprising:
- providing a packet (ATMpk+1 , ATMpO) comprising at least one ATM cell; - encapsulating at least part of said packet (ATMpk+1 , ATMpO) in a frame
(GEMfk+1 , GEMfO) according to passive optical encapsulation mode; and
- transmitting said frame (GEMfk+1 , GEMfO) through said passive optical network (GN).
2. The method according to claim 1 , wherein said frame (GEMfk+1) is transmitted from a network side interface apparatus (OLT) of said passive optical network
(GN) to a user side interface apparatus (ONUi) of said passive optical network (GN), and wherein said frame (GEMfk+1) is inserted into a payload (GEMp) of a downstream frame (GFd') generated at said network side interface apparatus (OLT).
3. The method according to claim 1 , wherein said frame (GEMfO) is transmitted from a user side interface apparatus (ONUi) of said passive optical network (GN) to a network side interface apparatus (OLT) of said passive optical network (GN), and wherein said frame (GEMfO) is inserted into a payload (ub1p) of an upstream burst (ub1', ub1") generated at said user side interface apparatus (ONUi).
4. The method according to claim 3, wherein said payload (ub1p) of said upstream burst (ub1") comprises at least a further frame (GEMfI , ..., GEMfg) comprising a further packet (Etp1 , ..., Etpg) of a traffic type other than ATM.
5. The method according to any of preceding claims, wherein it further comprises, before encapsulating, fragmenting said packet (ATMpk+1 , ATMpO) into a first packet fragment (ATMpk+1 ', ATMpO') and a second packet fragment (ATMpk+1", ATMpO").
6. The method according to claim 5, wherein encapsulating comprises encapsulating said first packet fragment (ATMpk+1', ATMpO') in said frame (GEMfk+1 , GEMfO), and encapsulating said second packet fragment
(ATMpk+1", ATMpO") in a successive frame.
7. The method according to any of preceding claims, wherein it further comprises dynamically determining a number of ATM cells to be inserted in said packet, according to traffic requirements.
8. The method according to any of preceding claims, wherein said passive optical network comprises a Gigabit Passive Optical Network.
9. An interface apparatus (OLT, ONUi) for interfacing a passive optical network (GN) and an ATM network (CN, ATMpi), said interface apparatus (OLT, ONUi) comprising: - a packetizer (AP1, ..., APk) for providing a packet (ATMpk+1, ATMpO) comprising at least one ATM cell received from said ATM network (CN, ATMpi);
- a formatter (GFF) for encapsulating at least part of said packet (ATMpk+1 , ATMpO) in a frame (GEMfk+1, GEMfO) according to passive optical encapsulation mode; and
- a transmitter (GTCF) for transmitting said frame (GEMfk+1 , GEMfO) through said passive optical network (GN).
10. The interface apparatus (OLT, ONUi) according to claim 9, wherein said interface apparatus is a network side interface apparatus (OLT) which is adapted to generate a downstream frame (GFd'), and wherein said formatter
(GFF) is adapted to insert said frame (GEMfk+1) into a payload (GEMp) of said downstream frame (GFd').
11. The interface apparatus (OLT, ONUi) according to claim 9, wherein said interface apparatus is a user side interface apparatus (ONUi) which is adapted to generate an upstream burst (ub1'), and wherein said formatter (GFF) is adapted to insert said frame (GEMfO) into a payload (ub1 p) of said upstream burst (ub1').
12. The interface apparatus (OLT, ONUi) according to claim 11 , wherein said upstream burst (ub1") comprises at least a further frame (GEMfI , ..., GEMfg) comprising a packet (Etp1 , ..., Etpg) of a traffic type other than ATM.
13. The interface apparatus according to any of claims 9 to 12, wherein said formatter (GFF) is further adapted to fragment said packet (ATMpk+1, ATMpO) into a first packet fragment (ATMpk+1', ATMpO') and a second packet fragment (ATMpk+1", ATMpO"), and to encapsulate said first fragment (ATMpk+1', ATMpO') in said frame (GEMfk+1, GEMfO) and said second fragment
(ATMpk+1", ATMpO") in a successive frame.
14. The interface apparatus (OLT, ONUi) according to any of claims 9 to 13, wherein it further comprises a temporary memory (TM) for storing said packet (ATMpk+1 , ATMpO), before encapsulation.
15. The interface apparatus (OLT, ONUi) according to claim 14, wherein it further comprises a memory manager (MM) for associating to said packet (ATMpk+1 , ATMpO) a pointer indicating a memory address and a size of said packet (ATMpk+1 , ATMpO), before encapsulation.
16. The interface apparatus (OLT, ONUi) according to claim 15, wherein it further comprises a pointer queue (PQ) for storing a number of said pointers, before encapsulation.
17. The interface apparatus (OLT, ONUi) according to claim 16, wherein said formatter (GFF) reads said pointer from said pointer queue (PQ) and, according to said memory address and size of said packet (ATMpk+1, ATMpO), fetches said packet (ATMpk+1, ATMpO) from said temporary memory (TM).
18. An interface apparatus (OLT, ONUi) for interfacing a passive optical network (GN) and an ATM network (CN, ATMpi), said interface apparatus (OLT, ONUi) comprising:
- a receiver (GTCDF) for receiving a frame (GEMfk+1 , GEMfO) from said passive optical network (GN), the received frame (GEMfk+1 , GEMfO) being formatted according to a passive optic encapsulation mode;
- a decapsulator (GDD) for extracting from said received frame (GEMfk+1 , GEMfO) at least part of a packet (ATMpk+1 , ATMpO) comprising at least one ATM cell; - a transmitter (AT1 , ... , ATk) for transmitting said at least one ATM cell to said
ATM network (CN, ATMpi).
19. The interface apparatus (OLT, ONUi) according to claim 18, wherein said interface apparatus is a network side interface apparatus (OLT) which is adapted to receive an upstream burst (ub1'), and wherein said upstream burst (ub1') comprises said received frame (GEMfO).
20. The interface apparatus (OLT, ONUi) according to claim 19, wherein said interface apparatus is a user side interface apparatus (ONUi) which is adapted to receive a downstream frame (GFd'), and wherein said downstream frame (GFd') comprises said received frame (GEMfk+1).
21. The interface apparatus (OLT, ONUi) according to any of claims 18 to 20, wherein said decapsulator (GDD) is further adapted to merge packet fragments
(ATMpk+1 ', ATMpk+1"; ATMpO', ATMpO") of a packet (ATMpk+1 , ATMpO) which are transported by several received frames.
22. A transmission system comprising a first ATM network (CN), a second ATM network (ATMpi), a passive optical network (GN), a first interface apparatus (OLT) for interfacing said first ATM network (CN) and said passive optical network (GN) and a second interface apparatus (ONUi) for interfacing said passive optical network (GN) and said second ATM network (ATMpi), wherein said first interface apparatus (OLT) is an interface apparatus according to any of claims 9 to 17 and said second interface apparatus (ONUi) is an interface apparatus according to any of claims 18 to 21.
PCT/EP2006/061249 2006-03-31 2006-03-31 Method and apparatus for transmitting atm cells through a gigabit passive optical network WO2007112778A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2006/061249 WO2007112778A1 (en) 2006-03-31 2006-03-31 Method and apparatus for transmitting atm cells through a gigabit passive optical network

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2006/061249 WO2007112778A1 (en) 2006-03-31 2006-03-31 Method and apparatus for transmitting atm cells through a gigabit passive optical network

Publications (1)

Publication Number Publication Date
WO2007112778A1 true true WO2007112778A1 (en) 2007-10-11

Family

ID=36686030

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2006/061249 WO2007112778A1 (en) 2006-03-31 2006-03-31 Method and apparatus for transmitting atm cells through a gigabit passive optical network

Country Status (1)

Country Link
WO (1) WO2007112778A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0544975A1 (en) * 1991-12-05 1993-06-09 ALCATEL BELL Naamloze Vennootschap Time slot management system
US6434154B1 (en) * 1997-01-17 2002-08-13 Nortel Networks Limited TDM/TDMA distribution network
EP1365548A1 (en) * 2002-05-21 2003-11-26 Alcatel Alsthom Compagnie Generale D'electricite Method for encapsulating variable length packets, and related data packet encapsulator and decapsulator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0544975A1 (en) * 1991-12-05 1993-06-09 ALCATEL BELL Naamloze Vennootschap Time slot management system
US6434154B1 (en) * 1997-01-17 2002-08-13 Nortel Networks Limited TDM/TDMA distribution network
EP1365548A1 (en) * 2002-05-21 2003-11-26 Alcatel Alsthom Compagnie Generale D'electricite Method for encapsulating variable length packets, and related data packet encapsulator and decapsulator

Similar Documents

Publication Publication Date Title
US20070166037A1 (en) System and Method for Managing Network Components in a Hybrid Passive Optical Network
US7675936B2 (en) Passive optical network (PON) system
US20070014575A1 (en) Method and apparatus for facilitating asymmetric line rates in an ethernet passive optical network
US20090202242A1 (en) Passive optical network system, optical line terminator and, communication method of passive optical network system
US20070274718A1 (en) Method and apparatus for communicating between a legacy pon network and an upgraded pon network
US20090208210A1 (en) Passive optical network remote protocol termination
US20030137975A1 (en) Ethernet passive optical network with framing structure for native Ethernet traffic and time division multiplexed traffic having original timing
US20070211763A1 (en) Provision of TDM service over GPON using VT encapsulation
US20030133460A1 (en) Method for implementing various functions in gigabit ethernet-passive optical network system and structure of ethernet frame employed in the same
US20080273877A1 (en) System and Method for Managing Communication in a Hybrid Passive Optical Network
US7031343B1 (en) Point-to-multipoint passive optical network that utilizes variable-length packets
US20050129030A1 (en) Multiple shared LAN emulation method in EPON based on group ID
US20040218534A1 (en) GEM OAM frame transmission method in gigabit-capable passive optical network
US20070070997A1 (en) Enhanced passive optical network (PON) processor
US6801547B1 (en) Ranging cell detection in a noisy environment
US20040109689A1 (en) Method for allocating bandwidth for voice service in a Gigabit Ethernet passive optical network
US20050013314A1 (en) Multicast transmission method in GEM mode in Gigabit-capable passive optical network and method of processing frame
US20080037990A1 (en) Asymmetrical PON with Multiple Return Channels
CN101047470A (en) Allocation method for forward error correction function in passive optical network
US20090226170A1 (en) Method, system and apparatus for transmitting data
EP1746857A1 (en) Method and apparatus enabling end-to-end resilience in PONs
US20040208631A1 (en) GTC frame structure and method for transmission of ONT management control information in GPON
Cale et al. Gigabit passive optical network-GPON
US20040202470A1 (en) GEM frame structure showing payload type of frame and method for processing data thereof
US20110268435A1 (en) Communication system, subscriber accommodating apparatus and communication method

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 06725495

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase in:

Ref country code: DE

122 Ep: pct app. not ent. europ. phase

Ref document number: 06725495

Country of ref document: EP

Kind code of ref document: A1