Frank Van Hooft
Spectrum Signal Processing

Spectrum was recently approached by a world-leading satellite network provider who had a wireless signal processing problem to solve. This customer provides satellite access products to millions of customers with services such as video broadcast, two-way internet access and satellite-based telephony. The customer had a requirement for a new standards-based, high channel density solution to perform return link signal processing in their hubs. After researching the available products on the market, they selected Spectrum's flexComm technology for its off-the-shelf availability, high performance, design flexibility, and competitive price.

A satellite hub application involves bi-directional communications from the hub to remote terminals using a satellite as the transport mechanism. A forward link is used to send data to the remote terminals using a TDM broadcast mechanism and is relatively simple in comparison to the return link. The return link is used by the terminals to send data back to the hub, typically using some form of multi-frequency TDMA (MF-TDMA) protocol. Multiple terminals can transmit on the return link simultaneously, in effect sharing the total bandwidth of the return link. The satellite receives the return link data from the terminals and then transmits that information down to the hub where the hub's return link subsystem has the task of allocating bandwidth to the various terminals, demodulating and demultiplexing the received return link data, ensuring it's accuracy, and forwarding the individual data streams to their final destination. The application can scale from hundreds to thousands of discrete data channels as subscriber count grows. Any solution to this customer's problem had to provide a high channel count per slot to reduce the overall footprint and cost of the hub, and at the same time had to be extremely reliable and highly scalable.