DirecWay DW4000 Specifications download pdf (Page 5)

Commission, and other local government agencies list the requirements and

specifications for the work to be done but Hughes is not directly involved in the specific

site installation.

Satellite communications must deal with latency. The satellites that Direcway uses orbit

in the Van Allen Belt 22,300 miles above the earth. Even with radio waves traveling at

the speed of light takes 240 milliseconds to go from earth to satellite to earth. With return

trips and other dealys we expect a normal “ping” time to be in the 700-1100ms time

range. This is not much in human terms but it can wreck havoc with gaming and VOIP

applications that require small acknowledgment times.

Each satellite transponder is capable of 45Mbps of bandwidth. Each transponder is shared

with all other Direcway users on that transponder. The DW6000 filters out all

communications not directed to it even though it sees all from a given satellite

transponder. Since satellite communications are multicast in nature you will never

encounter an Ethernet collision on receive. All problems will be with transmit.

Direcway is dependent upon KU band satellites. A review of the frequencies is in order.

L Band 950-1450Mhz

Big Dish C-Band 3.7-42.Ghz

Small Dish KU-Band 10.95-12.75Ghz

Spaceway and WildBlue KA-Band 19.7-20.2Ghz

Hughes does not generally provide a great deal of information on their products. It

appears to be their corporate culture that all information should be held as tightly as

possible, even from some internal departments. If you desire to learn about some of their

products and design information then it has been suggested that the best place to go is the

US Patent office and review Hughes Direcway product offerings there. For there all must

be fully disclosed. Also Hughes is trying to standardize their communications protocol

IPoS (IP over Satellite) and some information may be found along those lines.

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DirecWay DW4000 Specifications Page 5