Patent Application
20050138670
1. Field of the Invention
The present invention relates in general to a passive optical network that is capable of delivering video, voice and data to end-users.
2. Description of Related Art
Referring to
One known way of configuring the traditional PON 100 so it can deliver video in addition to voice and data to end-users 102 is to use a wavelength division multiplexing (WDM) 1550 nm analog video overlay 122 (e.g., see the ITU-T G983.1 to 8 specification). There are several drawbacks associated with this particular traditional PON 100 including for example: (1) the WDM analog video overlay 122 is “analog”; (2) the WDM analog video overlay 122 does not support evolutions towards video-on-demand or high definition television (HDTV) very well; and (3) the WDM analog video overlay 122 is not compatible with inband video delivery systems that use for example an xDSL infrastructure. Another disadvantage is the cost of the WDM analog video overlay 122 where high power optics are required at the OLT 104 to feed the analog video signal to the ONTs 108. The high power optics and their supporting amplifiers are expensive because they have high linearity requirements over a broad frequency range.
A second known way of configuring the traditional PON 100 so it can deliver video in addition to voice and data to end-users 102 is to integrate inband video streaming equipment 124 into the PON 100. The main drawbacks associated with this particular traditional PON 100 is that the inband video streaming equipment 124 needs a complicated multicast protocol to avoid duplication of broadcast streams. In addition, the inband video streaming equipment 124 needs an enormous bandwidth to distribute the video signals. The complicated multicast protocol and the enormous bandwidth requirements have an adverse impact on the development resources and potential cost of the inband video streaming equipment 124. As such, there is a need for a PON network that addresses and solves the aforementioned drawbacks associated with delivering video to an end-user using the traditional PONs. These needs and other needs are addressed by the PON, set-top box and methods of the present invention.
The present invention includes a PON capable of using a WDM 1550 nm digital video overlay to deliver a digital video signal (e.g., analog broadcasted signal) from a video head-end to an end-user. The PON is also capable of transmitting voice and data on a 1480-1500 nm band to the end-user and further capable of receiving voice and data on a 1260-1360 nm band from the end-user. The present invention also includes a set-top box and several methods associated with using the PON.
A more complete understanding of the present invention may be obtained by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:
Referring to
Referring to
As can be seen, the OLT 204a interfaces with a PSTN 210a which enables voice to be delivered to the end-user 202a via a POTS device 212a (e.g., telephone 212a). The OLT 204a also interfaces with an ATM/IP network 214a which enables data to be delivered to the end-user 202a via a PC 216a. Moreover, the OLT 204a interfaces with a video-head end 219a to deliver one or more digital video signals 220a to a set-top box 226a and display 228a (e.g., television 228a) which are used by the end-user 202a.
The video-head end 219a is the video source for the PON 200a. The video-head end 219a interfaces with a broadcast receiver 230a and an enhanced video content provider 232a. The broadcast receiver 230a is used to receive analog and digital broadcasted television signals (or high definition television signals). The analog broadcasted television signals need to be digitized. And, then the digitized analog and the digital broadcasted television signals are encoded with an appropriate video data compression encoding scheme such as MPEG2 or MPEG4 (for example). The digital signals 220a are then transported to a distribution device 234a that can be co-located with the OLT 204a. The transport protocol can be Gigabit Ethernet (for example). Whereas, the video content provider 232a can supply digital video signals 220a (including high definition television signals 220a) from services like Video On Demand (VoD) and Pay Per View (PPV). The video content provider 232a typically supplies digital video signals 220a that are already digitized and encoded in the appropriate format. However, the video-head end 219a may need to encrypt the VoD and PPV digital video signals 220a to ensure privacy and to prevent unauthorized end-users 202a from viewing the material without payment. Moreover, the video head-end 219a may need to receive information (authorization and authentication information) about the appropriate end-users 202a to determine the destinations of those end-users 202a before it can supply VoD and PPV digital video signals 220a. This information could be provided via an upstream PON data link from the ONT 208a (see
As described above, the video-head end 219a interfaces with the distribution device 234a which is typically co-located with the OLT 204a. The distribution device 234a includes an optical transmitter 236a that transmits the digital video signals 220a to a WDM filter 238a. The optical transmitter 236a feeds the WDM filter 238a using the appropriate wavelength (e.g., 1550 nm center-wavelength) to fit into the WDM scheme specified by the PON 200a. It should be appreciated that Gigabit Ethernet has been specified for several wavelengths, one of them being 1550 nm. In the case of distributing specialized video content such as VoD or PPV digital video signals 220a, the distribution device 234a may need to perform port selection tasks to select the correct ports which select the correct PON trees that serve the appropriate end-users 202a. This information could be provided by the video head-end 219a.
After the WDM filter 238a receives (step 302 in
The set-top box 226a includes a tuner 244a that downconverts to baseband a selected carrier of one of the modulated digital video signals 220a based on a channel selected by the end-user 202a. The set-top box 226a also includes a demodulator 246a (e.g., QAM demodulator 246a) that translates the baseband video signal 220a back into a digital video signal 220a. This digital video signal 220a is then decoded with a decoder 248a (e.g., MPEG decoder 248a). The decoded video signal 220a is fed over a co-axial cable (for example) to a video port or S-video port in the television 228a. Or, the decoded digital video signal 220a can be RF modulated (NTSC or PAL) and sent to the television 228a. For a more detailed discussion about one way to implement this WDM digital video overlay reference is made to the description provided below that is associated with
Referring to
The video-head end 219a has a protocol stack which includes at least the following layers:
The video-head end 219a is connected to the OLT 204a which has a protocol stack with at least the following layers:
This exemplary protocol stack indicates that the OLT 204a converts the physical layer from point-2-point fiber (such as Gigabit Ethernet) to WDM over PON while the layer above (such as Ethernet) remains untouched. The OLT 204a is connected to the ONT 208a which has a protocol stack with at least the following layers:
This exemplary protocol stack indicates that the transport layers (IP and Ethernet) are terminated in the ONT 208a and the video channels 220a are modulated and then transported further using COAX. The ONT 208a is connected to the set-top box 226a which has a protocol stack with at least the following layers:
It should be appreciated that the set-top box 226a can be a legacy set-top box 226a such as “commodity” satellite receiver set-top box which has a large bandwidth capability. If a legacy set-top box 226a is used then the modulator 242a would need to be selected to interface with the set-top box 226a. The set-top box 226a is connected to the television 228a which has a protocol stack with at least the following layers:
As shown in
A drawback of the architecture shown in
Referring now to
As can be seen, the ONT 208a in addition to components 250a, 252a, 254a, 256a and 258a includes the WDM filter 240a which is used to separate the voice/data upstream and downstream from the digital video signal overlay downstream. The ONT 208a also includes a digital video receiver 260a that receives the digital video signal 220a on the 1550 nm wavelength (for example) and synchronizes the datastream of the received digital video signal 220a using basic framing applied on a physical layer. Once synchronization is established, the digital video receiver 260a filters the digital video signal 220a that is then sent to the modulator 242a which manipulates the video signal 220a so that is interoperable with the set-top box 226a. In the situation where the digital video signals 220a are VoD or PPV digital video signals 220a, then the digital video receiver 260a may need to receive information from the inband PON data stream (e.g., Ethernet device 256a) so that it can de-encrypt the VoD or PPV digital video signal 220a. Alternatively, the set-top box 226a can decode the encrypted VoD and PPV video signals 220a.
As described above, the modulator 242a can be a QAM modulator 242a which is able to modulate the digital video signals 220a into the available frequency spectrum so they can be transported to the set-top box 226a. It is well known that the capacity of a single QAM modulated signal depends on constellation size and symbol-rate. And, that a higher constellation size is more spectral efficient and as such allows more data capacity. However a higher constellation size also requires a larger signal-to-noise (SNR) ratio to maintain the desired SNR ratio. In view of these facts and since the set-top box 226a is typically located relatively close to the television 228a this allows the use a very large bandwidth such as 2 GHz (for example). Consequently, the QAM symbol rate can be very large (e.g., up to 45 Msps) which allows for very small constellation sizes. BPSK and QPSK are other modulation schemes that could be used this environment. And, in the application where a coax-cable or terrestrial distribution network is used to connect the set-top box 226a to the television 228a then the available bandwidth would be more restrictive. In this case, the QAM modulated carriers are restricted to 6, 7 or 8 MHz in order to remain compatible with the analog RF modulated NTSC, PAL or SECAM video channels. In these environments 64-QAM or 256 QAM are the typical modulation schemes that can be used to achieve a higher spectral efficiency. Again, the choice of modulation schemes such as QAM, BPSK or QPSK used by the modulator 242a can be dictated by the type of set-top box 226a selected to be used in the present invention.
Referring to
As can be seen, the OLT 204b interfaces with a PSTN 210b which enables voice to be delivered to the end-user 202b via a POTS device 212b (e.g., telephone 212b). The OLT 204b also interfaces with an ATM/IP network 214b which enables data to be delivered to the end-user 202b via a PC 216b. Moreover, the OLT 204b interfaces with a video-head end 219b (similar to video-head end 219a) to deliver one or more digital video signals 220b to the end-user 202b via a set-top box 226b (similar to set-top box 226a) and a display 228b (e.g., television 228b). To accomplish this, the OLT 204b and in particular a co-located modulator 242b (e.g., QAM modulator 242b shown within the distribution device 234b) receives (step 402 in
The set-top box 226b includes a tuner 244b that downconverts to baseband a selected carrier of one of the modulated digital video signals 220b based on a channel selected by the end-user 202b. The set-top box 226b also includes a demodulator 246b (e.g., QAM demodulator 246b) that translates the baseband video signal 220b back into a digital video signal 220b. This digital video signal 220b is then decoded with a decoder 248b (e.g., MPEG decoder 248b). The decoded video signal 220b is fed over a co-axial cable (for example) to a video port or S-video port in the television 228b. Or, the decoded digital video signal 220b can be RF modulated (NTSC or PAL) and sent to the television 228b. For a more detailed discussion about one way to implement this WDM digital video overlay reference is made to the description provided below that is associated with
Referring to
The video-head end 219b is associated with a protocol stack which includes at least the following layers:
The video-head end 219b is connected to the OLT 204b which has a protocol stack with at least the following layers:
The OLT 204b/distribution device 234b is connected to the ONT 208b which has a protocol stack with at least the following layers:
The ONT 208b is connected to the set-top box 226b which has a protocol stack with at least the following layers:
Again, it should be appreciated that the set-top box 226b can be a legacy set-top box 226b such as “commodity” satellite receiver set-top box which has a large bandwidth capability. The set-top box 226b is connected to the television 228b which has a protocol stack with at least the following layers:
As shown in
It should be appreciated that protocols used to describe the two PONs 200a and 200b above are exemplary and that there are many different types of protocols that could be used to implement the PONs 200a and 200b.
Referring to both embodiments of the PON 200, it can be seen that the WDM digital video overlay can reuse mature technologies such as MPEG2 and MPEG4 for data-compression and Ethernet as a transport protocol. By reusing these technologies, the WDM digital video overlay can be implemented with minimal changes to the basic PON. In addition, since MPEG2 is already used to compress digital video signals for satellite broadcast this means that the set-top box 226 can be the same as or similar to a traditional satellite set-top box. Moreover, since Gigabit Ethernet which has a payload of 1 Gbps is already used to connect Local Area Networks (LANs) and IP switches this means that the distribution of digital video signals 220 could be implemented by reusing off-the shelf Gigabit Ethernet switches. If Gigabit Ethernet is used it can deliver up to 250 TV channels or 50 HDTV channels or any linear combination of these two simply by allocating 4 Mbps for a normal TV channel and 20 Mbps for a HDTV channel. And, as the data compression technology evolves it is believed that the next generation Ethernet standard will be able to deliver 10 Gbps which enables the amount of channels that can be delivered via this infrastructure to grow dramatically over the next few years.
In addition, if the PON 200 utilizes an Ethernet based WDM digital signal overlay then the PON 200 can reuse some parts of the IEEE EFM EPON specification. For example, the EPON specification requires that every ONT receives the full digital signal content. And, if the PON 200 reuses the ONT that is based on the EPON specification then the specialized content like VoD and PPV digital video signals 220 destined for specific users 202 would have to be filtered in the ONT 208. However, this is not believed to be a security risk since the same digital signal broadcast concept with content filtering in the ONT is also applied for the data path in both the EPON and APON specifications.
Lastly, it should be noted that since the PON 200 has a downstream digital video broadcast then there is no need for a point-2-multipoint TDMA based MAC layer, no management to guarantee fair upstream bandwidth allocation, not even an ONT ranging protocol. In other words, the architecture of the PON 200 can be characterized as a “dumb”, always on downstream video channel or as a big “dumb” bitpipe if you will, with basic framing on the Physical layer to enable each ONT 208 to ‘lock in’ without requiring direct feedback to the digital OLT 204. This “dumb” bitpipe can be considered as a satellite replacement delivery vehicle.
Following is a list of some of the other features and advantages associated with the present invention:
Although several embodiments of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
