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Cost Effective Replacement of IP/DVB Encapsulators

Satellite Service Delivery
In Satellite networking, point-to-multi-point architectures have been used for some times as a cost effective way of delivering outbound satellite services to end-users. Mainly this is due to the fact that the receiver equipment can be cheaper than a carrier class modulator/demodulator and router combination. Most IP/DVB Receivers have an Ethernet interface so they can be directly connected to a Router Ethernet Port or LAN Switch. Typically the Headend/Receiver equipment utilises IP encapsulated in MPEG Frames. This can lead to an increased cost within the network as you need an expensive IP/DVB Encapsulator at the headend of the network. Most IP/DVB Encapsulators are overkill for a simple transmit of IP/Data, as they have features and functionality that justifies their high cost. The ability to transmit to multiple receive sites, where the End User strips off the traffic they don't want and receives only their traffic is also available using Frame Relay. In fact some of the largest Satellite Service Providers use Frame Relay already as a way of reaching multiple customers from a single Transponder. Each Receive Site has a specific Frame Relay DLCI, which they use to identify their traffic and discard other users traffic. This use of Frame Relay has always had restrictions placed upon it until now. These restrictions are basically interfacing problems due to the use of Cisco's HSSI Interface on Routers. With the Metrodata PA1000 its possible to use an OC-3/STM-1 POS Interface on the Router and still use HSSI on the Satellite Modem. However, with the Metrodata PA1000 this increased cost can be a thing of the past. Another method of delivery is using Frame Relay over Satellite. This is usually deployed as a Carrier Class infrastructure where separate HSSI Modulator/Demodulators are used, as well as Cisco HSSI Routers. This means that a threshold is placed on the maximum outbound data rate by the Cisco HSSI Router of 51.84Mbps. It is possible to operate the Frame Relay infrastructure at speeds in excess of 51.84Mbps by utilising the Metrodata PA1000 as an interface converter between the HSSI Satellite Modem and the Router. This eliminates the requirement for HSSI on the Router and therefore takes away the speed restriction of 51.84Mbps. With the introduction of Low Cost IP Receivers that support Frame Relay DLCIs, the PA1000 can be used instead of an expensive IP/DVB Encapsulator. This is a win-win situation, as you retain the ability to use low cost receive equipment, reduce the cost of your headend equipment and in some cases increase the possible outbound data rate, using the same transponder.
Frame Relay Receivers
With a PA1000 in place at the headend its possible to connect to a Newtec HSSI Modulator and transmit up to 100Mbps outbound. This uses HDLC on the Satellite Link and therefore transparently passes Frame Relay DLCI information. With a Frame Relay Receiver at the receive site its possible to strip out the end users traffic easily and effectively. So where are the benefits? Mostly these are in the Service providers infrastructure, as they save money on the Headend. But consider for a second the implications of putting more over the satellite link, you get more customers per transponder. More revenue.

Low Data Rate (LDR) Over Satellite

APSAT
The Metrodata APSAT Platform supports sub 64k data rates on EIA530 or HSSI Interfaces. These Modules can be configured in 1bit increments from 8k and as such, the APSAT can be used to transport multiple 8k and 128k data rates over a single EIA530 or HSSI Satellite Modem connection. The APSAT can also be used to connect any "odd" data rates such as 266.67Kbps as well and is completely flexible in terms of clocking/operation (as it supports Asymmetric, Symmetric and Simplex Clocking).
DC3000/DC3200
With the Metrodata DC3000 it is possible to transport Nx64k Satellite Services over an E1 (2.048Mbps) leased line or digital microwave radio. As such this device could have as low a data rate as 64k, which would be 1 timeslot.

High Data Rate (HDR) Over Satellite

Analysing Your Options as a Service Provider or End-User

Realistically this Application covers how to analyse what you are currently doing in terms of infrastructure and what you need to get to higher speeds. Rather than giving you a solution, this should give you the detailed information to make a decision upon. The reason for this is that there are several different ways of achieving High Data Rates Over Satellite. High Data Rates include 70Mbps, 90Mbps, 110Mbps and 155.52Mbps and anything in between. They can be Asymmetric, Full Duplex or Simplex. Metrodata Products can also be run in 1Bit increments so support speeds from 1K to 155.52Mbps. Given what we have today in terms of Satellite Modems, Routers and Metrodata Products there are 4 main ways of running data over satellite links:

IP Only
Frame Relay
HDLC
ATM

The first 2 examples are probably what you are doing right now. They are your existing infrastructure, and you probably find it difficult to achieve speeds in excess of 51.84Mbps. Maybe this is due to using HSSI Satellite Modems and therefore Cisco HSSI Routers. The Cisco HSSI Router Interface cannot go faster than 51.84Mbps, and therefore presents a threshold for many satellite networks.

Many Satellite Service Providers move from IP at 51.84Mbps to a Frame Relay based Multicast network to make cost savings and make their network more efficient. But still they cannot go over 51.84Mbps. Its more than likely that your network could run at 60Mbps with the flick of a switch on the Satellite side, but not with Cisco HSSI Routers in there.

So you're going to have to change some of your existing infrastructure to go over 51.84Mbps. What you change and how you change it is up to you.

The Criteria For Running At High Data Rates

Its a fact that there are going to be more variables in terms of hardware than we have listed below. This is just outlining what we perceive as being important. We leave the dish sizes, modulation etc. to people that know about those things.

The variants as we see it are:

Maximum Data Rate - 70Mbps, 90Mbps, 110Mbps, 130Mbps or 155.52Mbps
Satellite Modem Interfaces - High Speed Serial Interface [HSSI], ASI and ECL [For speeds up to 450Mbps]
Router Interfaces - HSSI, Ethernet, OC-3/STM-1 ATM and OC-3/STM-1 Packet Over Sonet [POS]
Protocol Used Over Satellite - ATM and HDLC
Point-to-Point or Point-to-Multipoint

Sometimes its easier to change a Router Interface to increase a speed and sometimes its easier to change a Satellite Modem Interface. Either way can affect the protocol that has to be used over the Satellite Link.

All of our equipment can be used in a Point-to-Point Application. Using ATM Over the Satellite means we can do Point-to-Multipoint. Currently we are looking at how we do HDLC Over Satellite to see if there is anything we can do to transport Frame Relay through the PA1000.

Maximum Data Rates & Satellite Modem Interfaces

There is a relationship between what Satellite Modem you use and what your Maximum Data Rate can be. This can be due to:

The type of physical interface on the Satellite Modem
The Satellite Modem Manufacturer you use and how fast they have decided to take their Satellite Modem

At High Data Rates we really only see 3 Physical Interfaces:

ASI - As a protocol its capable of up to 270Mbps
HSSI - We're not sure how fast this can be taken [currently Metrodata have HSSI running at 155.52Mbps]
ECL - This is not normally a commercial Satellite Modem offering at high data rates, but more Military/Space Agency. As a protocol its usable up to 450Mbps

ASI tends to be associated with Broadcast Video rather than High Speed Data. However, ASI Satellite Modems are one of only 3 ways of transporting data over satellite at high speeds. There are 3 Satellite Modem Manufacturers that support ASI at High Data Rates:

Newtec - 110Mbps
Radyne Comstream - 240Mbps on the Modulator and 160Mbps on the Demodulator
Tandberg - Prekor System [Please note the Prekor System does not work with the Metrodata AP3000 ASI UNI Module]

HSSI is widely used in IP Backbones Over Satellite and also to some extent Voice Networks. There are 2 Satellite Modem Manufacturers that support HSSI at High Data Rates:

Newtec - 90Mbps
Comtech EFDATA - 70Mbps

ECL is not widely available commercially for this purpose. However, Metrodata can interface ECL up to 155.52Mbps using an Octal Cable and the AP3000. If you have a requirement for sending High Data Rates over ECL equipment please contact us. If you require exact details of these Modems please contact the Manufacturers directly or through your Local Distributor.

Router Interfaces & Transport Protocols

Despite the fact we say Router interfaces, anything with the following Interfaces can be used for transporting data over satellite links:

HSSI Interface - Maximum Data Rate is 51.84Mbps or STS-1
Ethernet Interface - Maximum Data Rate is 100Mbps
ATM OC-3/STM-1 Interface - Maximum Data Rate is 155.52Mbps
POS* OC-3/STM-1 Interface - Maximum Data Rate is 155.52Mbps

POS* - Packet Over Sonet can be set on a Standard Cisco OC-3 Module. It is a case of setting SONET Framing. It is not always a specific POS module that is required.

All of the above interfaces are flexible in data rate, up to their Maximum Data rate.

There are 2 protocols we see being used to transport High Data Rates Over Satellite. These are:

HDLC - Using either an Ethernet Interface or POS Interface on the Router
ATM - Using an ATM OC-3/STM-1 Interface on the Router [Or ATM Switch]

As can be seen from the information above, the Variants you need to look at are quite detailed.

Deciding Your Metrodata Product

We've tried to arrange the above information in a logical fashion below. If you wish to discuss this further please let us know. Please note that the Router does not have to be in the Earth Station, as most of our products can connect to Leased Lines or Dark Fiber directly.

There are 2 protocols we see being used to transport High Data Rates Over Satellite. These are:

HDLC - Using either an Ethernet Interface or POS Interface on the Router
ATM - Using an ATM OC-3/STM-1 Interface on the Router [Or ATM Switch]

As can be seen from the information above, the Variants you need to look at are quite detailed, but it is relatively easy to lay out.

If you want to deliver a 100Mbps Solution then you are in an awkward position. Currently the only way of delivering 100Mbps is by using ASI Satellite Modems. In order to interface these ASI modems to a terrestrial piece of equipment you would need to use the Metrodata AP3000. These both use ATM as the Protocol over the Satellite which gives 10% of ATM Cell Overhead. This would mean your actual bandwidth was only 90Mbps [usable by the End-User]. If thats the case, then you could instead use HSSI Modems at 90Mbps and the Metrodata PA1000 which has no ATM Cell Overhead, so you would get 90Mbps in both cases. But in the first case you would have paid for 100Mbps, and in the second case you would have paid for 90Mbps of Satellite Capacity.

ATM Over Satellite

Integrating Satellite into an ATM Network

This Application Note concentrates on the different options available to interface ATM Switches and Satellite Modems. It does not cover the benefits
of ATM, or the concept of ATM Over Satellite. We are more concerned with the real problems that might exist when integrating Satellite into an
ATM network, or extending an ATM network over Satellite.

Within the United States, there are a number of ATM Vendors that have validated interoperability with Metrodata Products. The majority of
products are ATM Switches [Fore ASX-200, Cisco Lightstream 1010, Cisco Stratacom BPX], though we have also undertaken testing with Routers
that have ATM Modules [such as the Cisco 3600 and 7500 Series Routers].

As ATM is mainly used as a means of multiplexing multiple lower data rates, into a single larger "trunk" link, interfaces tend to correspond to fixed rates such as DS-3 [44.736Mbps] and OC-3 [155.52Mbps]. This is fine, when the rates your are using are Nx64k, T1, E1, E2, E3, DS-3 and OC-3.

However, in Military networks bandwidth tends to be controlled and allocated carefully - especially for satellite and wireless capacity. Applications
that require an exact data rate such as 9.123Mbps, might use a DS-3 interface on an ATM Switch, but they wouldn't use a DS-3 across the Satellite Link. Rather, the satellite link would be run as closely as possible to the application data rate.

This would require a serial interface such as EIA530 or HSSI on the Satellite Modulator. This conversion of DS-3 ATM to EIA530 or HSSI, would be simple with Metrodata.

NATO NC3A ATM Over Satellite Tests - Metrodata's Involvement

NATO Consultation, Command and Control Agency [NC3A] conducted a series of interoperability tests, experiments and demonstrations of asynchronous transfer mode [ATM] over Satellite Communications [SATCOMS] links, using Commercial Off The Shelf [COTS] equipment.

Bilateral testing with the United States Communications Electronics Command [CECOM] was conducted from late 1995 through mid 1996.

The Satcom Link was implemented using a standard E1 2.048Mbps Carrier. The Comtech EFDATA SLM 8650 Modem was employed at NC3A, and provided a standard 2.048Mbps G.703/G.704.

This E1 G.703/G.704 interface was connected to the Metrodata ATM Switching DSU, which converted the E1 ATM cell rate on the Satellite Modem
to an OC-3 ATM cell rate on the Fore Systems ASX200 ATM Switch.

This was one of the first highly successful instances of Metrodata's involvement in ATM Over Satellite.

Interfacing ATM Switches to HSSI, EAI530 or ASI Satellite Modems

The main product used throughput this Application Note is the Metrodata Access Processor. This is a modular ATM Switch, which comes in 3 Port,
4/5 Port and 8/9 Port Versions. As we are primarily concerned with converting between 2 different pieces of equipment we have mostly used the
3 Port AP3000.

When considering connecting an ATM Switch to a Satellite Modem there are 2 elements that need to be considered:

Is the ATM Switch connecting to another ATM Switch at the far end of the satellite link?
Is the ATM Switch connecting to a non-ATM Network at the far end of the satellite link?

In the first instance, the Satellite Link would have to carry ATM point-to-point between the ATM Switches. This requires that the Serial Module on
the AP3000 can support ATM cells. This Serial ATM Module would then connect to the Serial Satellite Modem to enable a seamless connection
end-to-end. At the far end of the Satellite link a second AP3000 would be required to reconvert Serial back to ATM. This Can be seen in the
diagram below.

In the second instance, it is more than likely that the ATM Switch is providing back-haul across an ATM network. As such, the Serial Module on the AP3000 does not need to support ATM cells, as the data it is receiving is not ATM. It might be encrypted though, but as the Serial Module transports
a bit-stream of data it doesn't matter to Metrodata if the data is encrypted or not. This can be seen in the diagram below.

This Application Note is concerned with ATM Over Satellite. If you have a requirement to back-haul NON-ATM traffic from a Satellite Modem over
an ATM Network then please contact us for our Application Note on "Back-hauling Satellite Over ATM Networks".

Interestingly enough, there are only a finite number of ways of connecting an ATM Switch to a Serial Satellite Modem. Which Satellite
Modem interface is used, tends to depend upon the intended data rate of the link.

Standard operations are:

EIA530/TTL would be used at speeds up to 10Mbits
HSSI would be used at speeds up to 52Mbits
ASI would be used above 52Mbits

But, EIA530 on a Satellite Modem can go to 20Mbits, HSSI to 90Mbits and ASI over 155.5Mbits.

Metrodata support the following standard ATM interfaces:

E1 - 2.048Mbits
E2 - 8.448Mbits
E3 - 34.368Mbits
DS-3 - 44.736Mbits
OC-3 - 155.52Mbits

We also have the following Access Processor Modules available that support ATM cells. These can be used to connect ATM Switches together over
a satellite link:

HSSI ATM UNI Module
ASI ATM UNI Module

If you have a requirement to use EIA530 Satellite Modems to connect ATM Switches together, please let us know. Metrodata have an EIA530 ATM
UNI Module designed. External Converters are available to convert HSSI to EIA530 and HSSI to V.35

Our ATM Products have been tested with a variety of different Satellite Modem Vendors Equipment including Newtec, Comtech EFDATA and
Radyne Comstream.

As the previous page establishes, there are 2 types of conversion:

Fixed Rate ATM Switch to Variable/Scalable Rate ATM Satellite Modem
Fixed Rate ATM Switch to Fixed Rate ATM Satellite Modem

Applications are categorised by the Interface of the ATM Switch:

E3 - 34.368Mbps [pages 4-6]
DS-3 - 44.736Mbps [pages 7 - 9]
OC-3 - 155.52Mbps [pages 10 - 15]

For each of the above ATM Interfaces, we look at connecting to:

EIA530 Satellite Modems
HSSI Satellite Modems
G.703/G.704 Satellite Modems
ASI Satellite Modems

Connecting E3 ATM Switches to Satcoms

Whilst ATM Switches widely support DS-3, more typical outside of the United States is the E3 Speed, which is 34.368Mbps. If you are installing
ATM equipment in Europe it is likely that you will be using E3 Leased Lines in some areas. This does not mean that you will have to have an E3
ATM interface, and it is possible to connect a DS-3 or OC-3 ATM Switch to an E3 Leased Line by using the Metrodata ATM Switching DSU.

Connecting E3 ATM Switches Over EIA530 Satellite Modems
Connecting E3 ATM Switches Over HSSI/ECL Satellite Modems
Connecting E3 ATM Switches Over Fixed Rate G.703/704 Satellite Modems
Connecting E3 ATM Switches Over ASI Satellite Modems
Connecting E3 ATM Switches to EIA530 Satellite Modems

The Metrodata Access Processor can provide Single E3 ATM to EIA530 Conversion, where only a single Full Duplex Satellite Connection exists.
Also, aggregation of multiple EIA530 is possible onto a single E3 ATM interface.

The only product we have that can convert E3 to EIA530 to support ATM cells is the Metrodata AP3000. The Metrodata AP EIA530 Module currently supports a single EIA530 interface. This interface can operate at Simplex, Full-Duplex and Asymmetric speeds. It can support exact clock rates
down to 1Hz. As its maximum speed is currently 20Mbps, this gives it 20 Million different clock rates.

Connecting E3 ATM Switches to HSSI Satellite Modems

How you connect an E3 ATM Switch to a HSSI Satellite Modem depends on 3 factors:

Is the data rate fixed at 34.368Mbps
Is the data rate an "odd" or non telco standard rate
Is the data rate going to have to be changeable or scalable

If the data rate is fixed at 34.368Mbps, we can provide an E3 34.368Mbps G.703 to HSSI Converter, of which Metrodata have 2
products - DC3445 [also supports DS-3] and the FM4900 [only supports E3]. Typically these devices are used to connect HSSI Routers with E3 or
DS-3 Leased Lines. However, because they operate in an unframed mode, they can transparently pass ATM cells.

If you are going to change data rate or have an "odd" or non standard rate, then you will need to use the Metrodata AP3000. This would be configured with an E3 ATM UNI Module to connect to the E3 ATM Switch, and a HSSI ATM UNI Module to connect to the HSSI
Satellite Modem. This configuration would support any rate from 8Kbps to the maximum E3 rate of 34.368Mbps.

Connecting E3 ATM Switches to G.703/G.704 Satellite Modems

G.703/G.704 Satellite Modems support fixed Telecoms rates such E1, T1, E2, T2/J2, E3 and DS-3. Here it is the lower speeds that interest us, as
if you had an E3 ATM Switch, chances are you wouldn't be running a Satellite link any faster than 34.368Mbps. If you were running the link at 34.368Mbps then you could simply cable the Satellite Modem straight into the E3 ATM Switch. Because G.703/G.704 Satellite Modems only run
at fixed rates, they can be converted to E3 ATM by using the Metrodata Switching DSU. Currently this device supports the following ATM Rates
when converting to an E3 ATM Switch:

E1 or 2.048Mbps - Using the Metrodata E3 to E1 Switching DSU
E2 or 8.448Mbps - Using the Metrodata E3 to E2 Switching DSU

Rates which could be supported, given a customer requirement are T1 1.544Mbps and T2/J2 6.321Mbps.

Connecting E3 ATM Switches to ASI Satellite Modems

ASI Satellite Modems support rates up to 240Mbps [though this tends to be the Modulator, with lower speeds on the Demodulator]. This scalability exists because ASI is mainly used in the Broadcast Sector as a means of Distributing/Broadcasting Video Channels. As such a Video channel might take up around 4Mbps. You can Broadcast on one output multiple Video Channels and so would have multiple 4Mbps. All of this would be on a
single ASI Satellite Modem, so it has to support various different rates.

Because of the ability of ASI to operate at High Data rates [HDR], it is beginning to be used as a means of transporting data over satellite. But
typical data equipment such as Routers and ATM Switches do not have an ASI interface. Using the AP3000, you could easily convert between E3
and ASI using the E3 ATM UNI Module and the ASI ATM UNI Module.

Also, using ASI allows you to Multicast at High Data Rates. You could have an outbound channel of 110Mbps in a 36Mhz transponder and several receive sites.

Connecting DS-3 ATM Switches to Satcoms

DS-3 is widely used as an interface when multiple serial connections at lower speeds have been multiplexed together. These are then aggregated
up into an OC-3 or OC-12 ATM Trunk. DS-3 is also valid as a means of connecting ATM Switches together over Satellite. The reason for this is that satellite capacity is expensive, and as such must be used effectively. Satellite Links under 44.736Mbps are probably greater in number than satellite links over 44.736Mbps, within Government Networks.

Perhaps this is because until Metrodata it was difficult to interface Satellite Networks into ATM networks. In the DS-3 Section, we have the same
4 Satellite Modem Types as in the E3 section:

Connecting DS-3 ATM Switches Over EIA530 Satellite Modems
Connecting DS-3 ATM Switches Over HSSI/ECL Satellite Modems
Connecting DS-3 ATM Switches Over Fixed Rate G.703/704 Satellite Modems
Connecting DS-3 ATM Switches Over ASI Satellite Modems
Connecting DS-3 ATM Switches to EIA530 Satellite Modems

The Metrodata Access Processor can provide Single DS-3 ATM to EIA530 Conversion, where only a single Full Duplex Satellite Connection exists.
Also, aggregation of multiple EIA530 is possible onto a single DS-3 ATM interface.

The most effective product Metrodata have to convert DS-3 to EIA530 to support ATM cells is the Metrodata AP3000. The Metrodata AP EIA530 ATM UNI Module currently supports a single EIA530 interface. This interface can operate at Simplex, Full-Duplex and Asymmetric speeds. It can support exact clock rates down to 1Hz. As its maximum speed is currently 20Mbps, this gives it 20 Million different clock rates.

As most ATM Switches do not support ATM on their EIA530 Modules, this is quite a useful Module for connecting DS-3 ATM Switches to EIA530 Satellite Modems.

Connecting DS-3 ATM Switches to HSSI Satellite Modems

How you connect an DS-3 ATM Switch to a HSSI Satellite Modem depends on 3 factors:

Is the data rate fixed at 44.736Mbps
Is the data rate an "odd" or non telco standard rate
Is the data rate going to have to be changeable or scalable

If the data rate is fixed at 44.736Mbps, we can provide a DS-3 44.736Mbps G.703 to HSSI Converter, of which Metrodata have 2 products -
DC3445 [also supports E3] and the FM4950 [only supports DS-3]. Typically these devices are used to connect HSSI Routers with DS-3 Leased Lines.
However, because they operate in an unframed mode, they can transparently pass ATM cells.

If you are going to change data rate or have an "odd" or non-standard rate, then you will need to use the Metrodata AP3000. This would be configured with an DS-3 ATM UNI Module to connect to the DS-3 ATM Switch, and a HSSI ATM UNI Module to connect to the HSSI Satellite Modem. This configuration would support any rate from 8Kbps to the maximum DS-3 rate of 44.736Mbps.
Connecting DS-3 ATM Switches to G.703/G.704 Satellite Modems

G.703/G.704 Satellite Modems support fixed Telecoms rates such E1, T1, E2, T2/J2, E3 and DS-3. If you've got a DS-3 ATM Switch, you wouldn't be running a Satellite link any faster than 44.736Mbps as you would have to discard any ATM cells that are over 44.736Mbps. If you were running the
link at exactly 44.736Mbps then you could simply cable the Satellite Modem straight into the DS-3 ATM Switch. Because G.703/G.704 Satellite
Modems only run at fixed rates, they can be converted to DS-3 ATM by using the Metrodata Switching DSU. Currently this device supports the following ATM Rates when converting to an DS-3 ATM Switch:

E1 or 2.048Mbps - Using the Metrodata DS-3 to E1 Switching DSU
E2 or 8.448Mbps - Using the Metrodata DS-3 to E2 Switching DSU
E3 or 34.368Mb/s - Using the Metrodata DS-3 to E3 Switching DSU

Rates which could be supported, given a customer requirement are T1 1.544Mbps and T2/J2 6.321Mbps.

Connecting DS-3 ATM Switches to ASI Satellite Modems

ASI Satellite Modems support rates up to 240Mbps [though this tends to be the Modulator, with lower speeds on the Demodulator]. This scalability exists because ASI is mainly used in the Broadcast Sector as a means of Distributing/Broadcasting Video Channels. As such a Video channel
might take up around 4Mbps. You can Broadcast on one output multiple Video Channels and so would have multiple 4Mbps. All of this would be on
a single ASI Satellite Modem, so it has to support various different rates.

Because of the ability of ASI to operate at High Data rates [HDR], it is beginning to be used as a means of transporting data over satellite. But
typical data equipment such as Routers and ATM Switches do not have an ASI interface. Using the AP3000, you could easily convert between
DS-3 and
ASI using the DS-3 ATM UNI Module and the ASI ATM UNI Module.

Also, using ASI allows you to Multicast at High Data Rates. You could have an outbound channel of 110Mbps in a 36Mhz transponder and several receive sites.

Connecting OC-3 ATM Switches to Satcoms

OC-3 is used for Trunk Circuits. It might be aggregating multiple DS-3 connections from ATM Multiplexor's, or interfacing multiple connections
from other OC-3 ATM Switches.

As mentioned above one of the first instances of Metrodata being involved in ATM Over Satellite was when NATO used the Metrodata
ATM Switching DSU to connect a Fore ASX200 OC-3 ATM Switch to an E1 G.703/G.704 Satellite Modem. In the OC-3 Section, we have the same 4 Satellite Modem Types as in the E3 and DS-3 section:

Connecting OC-3 ATM Switches Over EIA530 Satellite Modems
Connecting OC-3 ATM Switches Over HSSI/ECL Satellite Modems
Connecting OC-3 ATM Switches Over Fixed Rate G.703/704 Satellite Modems
Connecting OC-3 ATM Switches Over ASI Satellite Modems

Connecting OC-3 ATM Switches to EIA530 Satellite Modems

The Metrodata Access Processor can provide Single OC-3 ATM to EIA530 Conversion, where only a single Full Duplex Satellite Connection exists. Also, aggregation of multiple EIA530 is possible onto a single DS-3 ATM interface.

As the maximum speed of EIA530 is typically 20Mbps, OC-3 to EIA530 is not the most effective use of OC-3 ATM Ports. However, if you are aggregating multiple EIA530 connections into an OC-3 it might make more sense. The most effective product Metrodata have to convert OC-3 to EIA530 to support ATM cells is the Metrodata AP3000. The Metrodata AP EIA530 ATM UNI Module currentlysupports a single EIA530 interface. This interface can operate at Simplex, Full-Duplex and Asymmetric speeds. It can support exact clock rates down to 1Hz. As its maximum speed is currently 20Mbps, this gives it 20 Million different clock rates.

As most ATM Switches do not support ATM on their EIA530 Modules, this is quite a useful Module for connecting OC-3 ATM Switches to EIA530 Satellite Modems.

Connecting OC-3 ATM Switches to HSSI Satellite Modems

There is only one way of connecting an OC-3 ATM Switch to a Satellite Modem and that is the Metrodata AP3000. This would be configured with an OC-3 ATM UNI Module to connect to the DS-3 ATM Switch, and a HSSI ATM UNI Module to connect to the HSSI Satellite Modem. This configuration would support any rate from 8Kbps to about 90Mbps. We could push HSSI faster than this, but the line driving distance comes down dramatically once you get over about 45Mbps. For 90Mbps you would have to have HSSI cables no longer than about 50 centimetres.

If you already have HSSI Satellite Modems, and want to run them over the HSSI Router Max of 51.84Mbps, you could use an OC-3 ATM Port in your Router, or an ATM Switch. Then connecting this into the AP3000 would allow you to go nearly twice as fast.

Connecting OC-3 ATM Switches to G.703/G.704 Satellite Modems

G.703/G.704 Satellite Modems support fixed Telecoms rates such E1, T1, E2, T2/J2, E3 and DS-3. Because G.703/G.704 Satellite Modems only run at fixed rates, they can be converted to OC-3 ATM by using the Metrodata Switching DSU. Currently this device supports the following ATM Rates when converting to an OC-3 ATM Switch:

E1 or 2.048Mbps - Using the Metrodata OC-3 to E1 Switching DSU
E2 or 8.448Mbps - Using the Metrodata OC-3 to E2 Switching DSU
E3 or 34.368Mb/s - Using the Metrodata OC-3 to E3 Switching DSU
DS-3 or 44.736Mbps - Using the Metrodata OC-3 to DS-3 Switching DSU

Rates which could be supported, given a customer requirement are T1 1.544Mbps and T2/J2 6.321Mbps.

Connecting OC-3 ATM Switches to ASI Satellite Modems

Also, using ASI allows you to Multicast at High Data Rates. You could have an outbound channel of 110Mbps in a 36Mhz transponder and several receive sites. This would require the AP8000 at the Hub Site to connect in all the separate ASI interfaces from the Satellite Modems, and AP3000's at the receive sites.

Satellite Backhaul

Metrodata and Backhaul
Metrodata specialise in designing hardware for integrating satellite and terrestrial networks. We understand the applications involved in Satcoms, and supply many features as standard that are specific to Satellite. The main area where we are involved is in back-haul, reach-back or longhaul. Terminology differs between military and commercial industries, but the concept is the same. Where you have a requirement to take a connection from a satellite modem, and transport it over Fiber, Wide Area Network Circuits, Microwave Radio or Free Space Optics then we can help. This might be extending your Satellite Service from a Teleport to the Customers site, or integrating your Satellite Service from your Head-end Teleport into your Terrestrial Network Infrastructure.
Backhaul History
In the past, most ISP Backbone Links via Satellite were asymmetric in nature, such as: 8/2Mbps 34/8Mbps The reason why these rates were chosen was because Satellite Modems existed to support these. Mainly for voice, SDH and PDH infrastructure these rates would equate to E1 (2Mbps), E2 (8.448Mbps) and E3 (34.368Mbps). Typically the Satellite Modem would have a G.703 interface. As High Speed Serial (HSSI) Satellite Modems became more widely used, they also allowed operation of Satellite Links asymmetrically. However, HSSI Satellite Modems were not restrained by specific fixed data rates and could be configured in 1Bit increments. For some time these HSSI Satellite Modems were utilised simply to give a more easy and neat solution to Asymmetric Data Rates. The potential to support any bitrate was never really utilised, and so speeds supported were much as before (8/2Mbps & 34/8Mbps). More recently it has become possible to measure the amount of bandwidth required for a given application, it's possible to measure usage and therefore to predict to some extent what Satellite Capacity is required. This has meant an increase in "odd" data rates as End Users are purchasing only the bandwidth they need. Typically this would be in 1Mbits increments, and so Metrodata introduced in 2000 a HSSI Module for our APSAT platform that supported fixed rate Asymmetric clocking in 1Mbit increments. This was possible by using a VCXO Clock Crystal for the Transmit Data Rate and a separate VCXO for the Receive Rate. Using Satellite capacity in 1Mbit increments is not very efficient though, as given a certain Power, Modulation and FEC you can have all sorts of odd data rates. In 2001 Metrodata developed our current HSSI Module for the APSAT which supports 1Bit increments, to match exactly with the flexibility of Satellite Modems 1Hz scalability. Where possible we have implemented 1Bit increments of clocking on Metrodata products.

Metrodata specialise in interfacing satellite modems to terrestrial infrastructure. We support the following satellite modem interfaces: HSSI - Up to 90Mbps G.703 - E1, T1, E2 E3 and DS-3 ASI ECL EIA530 - Up to 20Mbps (To match EIA530 Crypto Equipment) V.35, X.21, RS442 We are the only manufacturer in the world who specialises in back-haul equipment for satellite networks and supports all the different common satellite modem interfaces. Metrodata are also the only company that can match the flexibility of data rate of satellite modems. We support the following operations: Asymmetric Simplex - With Alarm Masking Multicast Full Duplex All data rates are configurable in 1Bit increments so we can match clocking to the satellite network. Often our equipment is used to back-haul over Transatlantic DS-3 and OC-3 Circuits. However, this might just as easily be a local fiber optic link.
SATELLITE BACKHAUL PRODUCTS
The Metrodata Satellite product Portfolio includes around 25 different products which can be used for backhaul of satellite services. Dependent on your mode of operation (Asymmetric, Symmetric or Simplex), date rate and backhaul infrastructure there are 4 main Metrodata products that are most widely used. These are the: APSAT FM4000 DC3200
APSAT BACKHAUL
The Metrodata APSAT Platform has been developed specifically for Satellite Backhaul. It is our flagship product in the Satellite sector and can be used for a variety of different applications. For an overview of the APSAT and its different modules, modes and Chassis please check out the Application Note APN047_APSAT. Because the APSAT has a Modular Chassis, it can be used to backhaul single or multiple satellite services. There are 3 Chassis the AP3000 (3 Slot), AP4000 (4 or 5 Slot) and the AP8000 (8 or 9 Slot). The AP3000 forms the usual foundation of any Satellite backhaul for single satellite services.
The AP3000 is a Fully Functioning ATM Switch. It can support ATM in and out on any port, non-ATM in and ATM out, and even non-ATM in and non-ATM out (Only using ATM across the back-plane). 100-250V AC / 50-400Hz Version -48V DC Version

APSAT - PRINT FRIENDLY PDF VERSION (618KB)

AP MODULES

Metrodata APSAT supports a wide range of Modules to allow integration of Satellite, Terrestrial, Wireless and Fiber based networks. Satellite Modem Interfaces supported include the following:

HSSI - From 8k to 90Mbps
EIA530 - From 8k to 20Mbps
G.703 - Fractional E1, E1 (2.048Mbps), E2 (8.448Mbps), E3(34.368Mbps) and DS-3 (44.736Mbps)
ECL - Up to 90Mbps
ASI - Up to 51.84Mbps for Video
ASI - Up to 155.52Mbps for ATM/Data

		All Modules will work in any of the AP Chassis, which means you can start with an AP3000 and as your services grow upgrade to an AP4000 or AP8000 Chassis. The APSAT Platform Overview should give you an idea of what kind of Chassis and Modules you need, but please contact us to make sure. There are many ways of using the Metrodata APSAT, and it is advisable for you to discuss your requirements with our Technical Staff to ensure the optimal and most cost effective solution.
HSSI SATELLITE MODEM INTERFACE MODULES
This can be operated in 1Bit increments, Asymmetrically, Symmetrically or Simplex. In Simplex mode the APSAT can also Alarm Mask spurious errors generated by the link being in one direction only. This is the only products in the world to offer this in conjunction with such a flexible HSSI interface. Metrodata have 2 different HSSI Modules. The standard Flexi HSSI CE Module is used for the majority of Applications, but if you require ATM over your Satellite link (Mainly for Military) then we also have the HSSI UNI Module. Developed for BT Satellite originally for 90Mbps HSSI Operation, this Module has also been used more recently for Encrypted Military Networks (as ATM Crypto's have a lower overhead than IP Crypto's). The HSSI CE Module can also be used at one end of the backhaul to interface to the Router, and ASI/EIA530 or G.703 can be used on the Satellite Modems (and vice versa).
EIA530 SATELLITE MODEM INTERFACE MODULES

Metrodata developed this module for MITRE for use in Military Satcoms. Their specific requirement was to support the Maximum EIA530 data rate on both the Crypto and the Satellite Modem. As the Crypto's output was 13Mbps and the Satellite Modem was 20Mbps, we designed the EIA530 CE Module to initially work up to 20Mbps. However, we have put a software block on the interface and it could run faster than 20Mbps.

Again the EIA530 CE Module works in 1Bit increments. We have also developed an EIA530 UNI ATM Module for the US Naval Research Labs for Naval Satcom. This also works up to 20Mbps.

G.703 SATELLITE MODEM INTERFACE MODULES

The APSAT supports G.703 satellite modem interfaces at the major telco rates of E1, T1, E2, E3 and DS-3. We have both ATM and NON-ATM Modules available in all of these except T1 (which is only available in non-ATM).

We can interface an Asymmetric G.703 Satellite Modulator/Demodulator setup (for example 34.368/8.448Mbps) and transport it over E3, DS-3, OC-3 or Fiber links. At the far end we can present as either HSSI or G.703.

When back-hauling Satellite Connections over Terrestrial Infrastructure, the APSAT platform uses ATM as a transport mechanism. However, we only use ATM where it suits the application. We make the use of ATM transparent to the network. If you consider that you are have a point-to-point link with Access Processors at either end, then the ATM UNI Modules are your line cards. Whether you are using a SONET/SDH DS-3, ATM OC-3 or E3 Microwave Radio it doesn't matter to the APSAT, you simply choose the module for your link rate. If you wish to transport 34/8Mbps over an E3 or 45/8Mbps over a DS-3 (Or similar rates) then the Zero Wastage feature will be useful for you. This is covered in more detail later on in this document.

ECL SATELLITE MODEM INTERFACE MODULES

This is available as an option, and is basically a modification to the HSSI CE Module to support Differential ECL. We developed this for Lockheed Martin for TT&C Signal Backhaul Over OC-3/Fiber.

ASI SATELLITE MODEM INTERFACE MODULES

The Metrodata APSAT supports ASI/Digital Video Backhaul up to 51.84Mbps. This is using the ASI CE Module. We also have a Data/ATM Module for the APSAT than can be used to transport up to 90Mbps over ASI Satellite Modems. This is the ASI UNI ATM Module.

As you can see there are a wide number of different interfaces on the APSAT that can be connected to the Satellite Modem. We also support a wide range of interfaces from the WAN/Backhaul element as well.

BACKHAUL INTERFACE MODULES

Primarily the APSAT is used to backhaul over E3, DS-3 and OC-3/Fiber. However, it can also be used to transport Satellite services over E1 and E2 links. These links can be Leased Line, Microwave Radio or Fiber Optics.

Modules available include:
E1 Backhaul
E2 Backhaul
E3 Backhaul
DS-3 Backhaul
OC-3/STM-1 Backhaul (Multimode SC Fiber)
OC-3/STM-1 Backhaul (Single-mode Short Haul SC Fiber)
OC-3/STM-1 Backhaul (Single-mode Long Haul SC Fiber)

The Metrodata APSAT can therefore offer data rates from 8k to 155.52Mbps, backhaul from E1 to Dark Fiber and supports many different interfaces.

However, in some Symmetric or E1 Applications the Metrodata APSAT is overkill.

FM4000

With Asymmetric Satellite services, clocking is the most important part of the network. Some Router interfaces cannot be clocked Asymmetrically and E1 G.703 is one of them. Also E1 G.703 on a Satellite Modem cannot support Asymmetric data rates on many of the Satellite Modems. With Asymmetric satellite services it makes sense to use Serial Router Interfaces and Serial Satellite Modems.

In the past Metrodata have effectively interfaced Asymmetric Satellite services to symmetric E1 lines by utilising 2 x DC3200 at either end of the link. For example, with a 1024k Receive and 512k Transmit Satellite Service, one DC3200 would be used for the transmit rate and one for the receive rate. The use of the DC3200 with its V.35 interface is simply because V.35 is a better interface for Asymmetric Clocking than X.21.

We've now added Asymmetric Clocking to the Metrodata FM4000, which gives us the ability to support Asymmetric or Symmetric Clock rates in one device. It also allows us to support a full 2.048Mbps Symmetric Service or an Nx64k Symmetric Service in the same device.

This allows you to offer a scalable Satellite Service which can start off Asymmetric at 1024k/512k for example and then be upgraded to a full 2.048Mbps Symmetric Satellite Service at a later date without changing the equipment out.

The ability to do Asymmetric Clocking is only available on the V.35 version of the FM4000. X.21 does not support Asymmetric Clocking. The Metrodata FM4000 is we believe the first E1 G.703 Converter/DSU to support Asymmetric Clocking for Satellite Network backhaul.

DC3200

The DC3200 can be used to cost effectively transport a Serial Nx64k Satellite Service across a Terrestrial E1 Leased Line or E1 Microwave Radio System. The use of Dip Switches on the base of the DC3200 make it easy to configure the Nx64k timeslots and therefore quick to install, with minimum support required. The DC3200 has both an E1 G.703 interface and an E1 RJ45 interface to the E1 Backhaul link. The interface on the DC3200 to the Router or Satellite Modem is V.35. If you require EIA530 or X.21 this is available on the DC3000 directly (X.21) or via a converter cable (EIA530).

APSAT Application Notes

Please Note: This is simply a general Backhaul Product Overview. Metrodata have an extensive range of Application Notes covering Commercial and Military Satcoms. These notes are detailed Technical Documents, and are available on our Website or on CD. If you have any questions regarding the APSAT Platform, then please contact Metrodata, and we will be happy to discuss your application in more detail.

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