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Muxing E1 Over a Single Satellite Link

Muxing over a single satellite

Using the Access Processor platform it is possible to multiplex several terrestrial services across a single satellite link. This is most often multiple E1’s over HSSI or EIA530 Satellite Modems.

The Access Processor is a modular switch, based on an ATM backplane. It’s possible to mux ATM and NON-ATM traffic together into a single ATM cellstream. This makes it ideal for doing “odd” data rates over satellite, that do not fit into the PDH/SDH Hierarchy. For example, its easy to transport 4 x E1 using an E3 PDH Mux. You would use 8.448Mbps and a G.703 Satellite Modem. If you wanted to Mux 2,3,5+ x E1 its pretty difficult unless you use the APSAT.

Terrestrial Interfaces Supported

With our Quad E1 Module its possible for us to Mux up to 32 x E1 per AP8000L Chassis, and we can daisy chain a second Chassis to offer up to 60 x E1.

Using the Metrodata APSAT also gives you the added benefit of being able to transport other services across the satellite link, for example HSSI Data, E1 Voice, 10/100BaseT Data/IP and also ASI based Video.

The interfaces we support on the Terrestrial side are:

E1, T1, E2, E3, DS-3, OC-3/STM-1
Ethernet 10/100BaseT
Serial EIA530
ASI Video
HSSI (High Speed Serial Interface)

Satellite Modem Interfaces Supported

Metrodata have developed a portfolio of products for interfacing satellite and terrestrial networks. On the APSAT, we have the following interfaces for Satellite

G.703 – Fixed Telco rates on the Modem are T1, E1, E2, E3, DS-3
HSSI – Up to 90Mbps
ASI – Up to 155.52Mbps
EIA530 – Up to 20Mbps

ATM Over Satellite

The APSAT uses ATM to Multiplex and therefore transport the traffic over the satellite link. With E1 transport, this uses ATM AAL.1 Circuit Emulation over a HSSI/ASI or EIA530 interface.

AAL.1 uses a payload of 47 bytes, and adds 1 byte of Sequence Number and 5 bytes of ATM Cell Header.

An E1 is 2,048Mbps or 2,048,000bits per second
2,048,000 divided by 8 = 256,000 bytes per second
256,000 divided by 47 = 5,447 ATM Cells per second

In order to get the overhead calculation for using ATM, you need to add on the ATM Cell Header.

5,447 x 53 = 288,681 bytes per second
288,681 x 8 = 2,309,447 bits per second or 2.309Mbps

The APSAT HSSI and EIA530 ATM Interfaces use G.832 framing to give link integrity and performance monitoring, which adds additional overhead. A G.832 frame comprises 4296 bits, of which only 4240 bits are payload.

Therefore to transport an E1 AAL.1 payload (2.309Mbps) using HSSI or EIA530 will require the G.832 framing to be added. (If you use ASI then you do not have this G.832 framing).

2,309,447 x 4,296 divided by 4,240 = 2,339,949 bits per second including G.832 overhead

Then we suggest allowing a 1% overhead margin, to allow for miscalculations:

2,339,949 x 1.01 = 2,363,348 bits per second or 2.363Mbps of satellite capacity is required per E1

This is shown in the following table:

1	x	E1	requires	2,363,348	2.363	Mbps
2	x	E1	requires	4,726,697	4.727	Mbps
3	x	E1	requires	7,090,045	7.090	Mbps
4	x	E1	requires	9,453,394	9.453	Mbps
5	x	E1	requires	11,816,742	11.817	Mbps
6	x	E1	requires	14,180,091	14.180	Mbps
7	x	E1	requires	16,543,439	16.543	Mbps
8	x	E1	requires	18,906,787	18.907	Mbps
9	x	E1	requires	21,270,136	21.270	Mbps
10	x	E1	requires	23,633,484	23.633	Mbps
11	x	E1	requires	25,996,833	25.997	Mbps
12	x	E1	requires	28,360,181	28.360	Mbps
13	x	E1	requires	30,723,530	30.724	Mbps
14	x	E1	requires	33,086,878	33.087	Mbps
15	x	E1	requires	35,450,226	35.450	Mbps
16	x	E1	requires	37,813,575	37.814	Mbps
17	x	E1	requires	40,176,923	40.177	Mbps
18	x	E1	requires	42,540,272	42.540	Mbps
19	x	E1	requires	44,903,620	44.904	Mbps
20	x	E1	requires	47,266,969	47.267	Mbps
21	x	E1	requires	49,630,317	49.630	Mbps
22	x	E1	requires	51,993,665	51.994	Mbps
23	x	E1	requires	54,357,014	54.357	Mbps
24	x	E1	requires	56,720,362	56.720	Mbps
25	x	E1	requires	59,083,711	59.084	Mbps
26	x	E1	requires	61,447,059	61.447	Mbps
27	x	E1	requires	63,810,408	63.810	Mbps
28	x	E1	requires	66,173,756	66.174	Mbps
29	x	E1	requires	68,537,104	68.537	Mbps
30	x	E1	requires	70,900,453	70.900	Mbps
31	x	E1	requires	73,263,801	73.264	Mbps
32	x	E1	requires	75,627,150	75.627	Mbps

Satcom Interface Converters

Metrodata have been involved in Satcoms since the beginning of our company. Early products include the first HSSI E2 and HSSI E3 Converters for Intelsat and Cisco, so Intelsat could test the new Cisco HSSI Interface in 1993. Over the years we have done other developments for intelsat including more recently the LH1000 Ethernet Over Serial device which is used by Intelsat to offer IP Services via Serial Satellite Modems.

We have a wide range of general Metrodata products that can be applied to Satellite, and also some more 'specialist' products which are designed specifically for Satellite Applications. Typically Metrodata are involved in the following:

IP Over Satellite
High Data Rate Over Satellite - Frame Relay, IP or ATM
Satellite Backhaul - Serial, E1 and IP Modems

Our work with leading Satcom Manufacturers such as Comtech EFDATA, Advantech AMT and Paradise Datacom allows us to push the envelope of serial data rates and allows us to be the first WAN Hardware manufacturer to offer serial EIA530 support from 8kbps to 20Mbps in 1bit increments, Asymmetrically, Symmetrically or Full Duplex. This is the most flexible and accurately clocked Serial interface available for conversion to E3, DS-3, OC-3, Fiber and ATM. Its also matches in with the EIA530 max speeds of leading Satellite Modems. Working with Satellite Modems allows us to support high speeds on a number of interfaces including:

LVDS - 52Mbps
HSSI - 110Mbps
ECL - 110Mbps
ASI - 52Mbps
EIA530 - 20Mbps
V.35 - 20Mbps

Crypto Interface Converters

With experience of interfacing a variety of different types of bulk, trunk and link encryption devices, Metrodata can provide interface conversion, interface optimisation and end to end crypto transport over a wide range of different infrastructures.

Working with Crypto Manufacturers such as General Dynamics , Thales e-Security , L-3 TRL , Crypto AG and Mykotronx allows us to try and support various bitrates and interfaces to allow easy and seamless connection of their Encryption Equipment to Standard Satcom, Radio and WAN/IP Infrastructure.

Metrodata also support specific features on some of our products such as Automatic Crypto Resynchronisation which we developed for the US Naval Warfare Development Comand (NWDC).

TCP Enhancement

The majority of TCP Enhancement Products take an Ethernet Interface from a Router, Switch or Server and then apply their TCP Enhancement and output as Ethernet again. In order for this to be usable over Satellite, therefore, you need to convert Ethernet to Serial. This is because most Satellite Modems have Serial Interfaces.
Read more... [TCP Enhancement]

ATM Over Satcom Interoperability

Using Metrodata Products to interface between ATM Equipment and Satellite Modems from Narrowband to Broadband, from 8k to 155.52Mbits we've got your bandwidth covered. In 1Hz increments, that's 20 million clock rates for EIA530 and 90 million clock rates for HSSI [High Speed Serial Interface].
Read more... [ATM Over Satcom Interoperability]

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