When discussing the topics of “optimization” and “efficiency,” many in the satellite industry head directly to the ongoing bits/Hz and physical layer debate.
There are a multitude of vendors that each claim they have the best physical layer optimization available. Physical layer is certainly important, and we (Comtech EF Data) continue to innovate in this area. While the word ‘efficiency’ in the satellite industry has historically equated to pure spectral efficiencies, what we really need to start discussing is the ‘net efficiency’ of a network. Let’s delve into exactly what net efficient really entails.
Continued fiber and microwave infrastructure build outs have increased the number of competing alternatives for satellite industry service providers. The insatiable increase in end user demand and potential revenues has enticed terrestrial providers to go deeper into remote areas to increase market share. These new alternatives, on a macro level, continue to reduce overall network costs, which is forcing our industry to focus on overall net efficiencies, not just pure spectral efficiencies.
In response, the satellite industry is fighting back, introducing a number of High Throughput Satellite (HTS) options that offer the promise of meeting these user demands at the correct price points. In addition to lower prices, a constant theme in the connectivity business is more throughput, more throughput, more throughput.
The combination of these trends has brought our industry to a tipping point—ground equipment manufacturers need to prepare themselves to support the sheer throughputs needed by service providers, end users, governments and enterprises today and into the future. The way we tackle this challenge is by combining our technological efficiencies with applied intelligence, all the while providing the levels of horsepower that are required to provide the most net efficient solutions in a high throughput world. Let’s examine the five steps involved and then review our approach to meeting the increasing demands of satellite networking in particular.
Step 1: Modulation and Coding
The DVB-S standard accelerated the industry forward at the physical layer. Then, the DVB-S2 and DVB-S2X standards pushed us even further by increasing the number of Mbps that could be transmitted through a given amount of MHz on a satellite link. Each vendor now has its own flavor of DVB-S2X. For high data rates, Comtech increased spectral efficiencies via the introduction of our DVB-S2-EB1 & EB2 (Efficiency Boost) waveforms. Our Efficiency Boost technology enables users to achieve a 10 to 35 percent increase in efficiency over the DVB-S2 standard, without an increase in power or occupied bandwidth. We have virtually doubled the number of available MODCODs, provided better Rolloff figures and minimized implementation loss to near theoretical operation.
Comtech EF Data’s Efficiency Boost provides the pure physical layer efficiencies required for links in the 10’s or 100’s of Mbps. However, not all links out there are in the 10’s and 100’s of Mbps.
One area where the standard falls short is in latency performance for lower data rates. The standard’s large block size requires a large amount of data to be received before coding and transmission. For high data rates, this is not a huge deal. However, for low data rates, this results in additional latency and a lower level of application performance. We already deal with the latency associated with transmitting up to a geosynchronous satellite and back down, so any additional latency should be avoided.
The company’s VersaFEC-2 Modulation and Coding scheme was designed for low to medium data rates, which is where many of our customers are operating, especially those in the mobile backhaul and premium enterprise space. These users have 5, 2 or even down to 1 Mbps links. If a standard is being used that is designed around hundreds or tens of Mbps to handle data at 1, 2 or 5 Mbps, the application support and performance needed at those lower data rates is not being received. VersaFEC-2 provides the spectral efficiencies of the DVB-S2X standard with 80 to 90 percent lower latency. This is one example of innovation that meets the changing needs of our customers.
Step 2: The Re-use of Bandwidth
Many in the industry are familiar with the DoubleTalk® Carrier-in-Carrier® bandwidth compression technique developed by Comtech EF Data. Essentially, this technology allows full duplex satellite links to transmit concurrently in the same segment of transponder bandwidth. By using this intelligent method of overlaying carriers within the same bandwidth resource, users are able to maximize the use of the space segment they procure to drive net efficiencies even higher.
Step 3: Adaptive Coding and Modulation (ACM)
ACM changes the modulation and coding of a link dependent upon atmospheric conditions of the two sites being connected. When a rain condition occurs, a less aggressive modulation and coding method is used to ensure connectivity. During clear sky conditions, a more efficient method can be leveraged to maximize efficiency. ACM becomes particularly important in a point-to-multipoint network because weather conditions are geographically dependent. In the example of a 10 site network, odds are that there wouldn’t be a rain condition in all 10 of the sites simultaneously. Designing around the worst possible case for all sites simultaneously is inefficient. The ability to perform ACM on the outbound link is a method leveraged by many to ensure maximum use of the satellite resource in the hub-to-remote direction. An often overlooked efficiency gain occurs when one can use this same ACM method on the inbound link. The ability to consider each individual link independently, and not as a group (either large or small), intelligently assigning the best modulation and coding for the link at that particular time creates additional efficiencies while still maintaining a given SLA.
Step 4: Packet Processing
The IP protocol was designed for a many hop terrestrial network that consists of a series of devices having to make next hop routing decisions to move individual data payloads to the proper destination. To allow each device along a path to make an intelligent decision on how to forward the payload, additional information was included in the packet header. In the satellite networking world, this “extra” information is still required, but does not need to be transmitted over the satellite link. Through intelligent packet processing, satellite platforms can further increase net efficiencies.
The applied header compression technique looks inside the IP headers and examines the data flow to determine what we can remove unimportant data before we send that information over the satellite, and then intelligently reinsert that data on the receiving end. For small packets, as is the case with voice, over half of the information within an IP packet can be removed and reinserted on the distant end, creating as much as 60 percent in savings. In addition, there is a lot of redundancy in data streams, some of which can be removed before transmission. Every bit can be examined and a decision can then be made as to whether or not a bit stream has been previously seen. If a stream of data has been transmitted in the past, a much smaller representative set of data is sent along with a lookup location of past bit streams. By removing this unnecessary data, users can realize additional savings, increasing net efficiency even further.
A key consideration on data removal and reinsertion is the category of compression. Lossy compression occurs when bits are simply discarded without reinsertion on the remote end. This works for web browsing. If I am browsing a news site from a smartphone or laptop and looking at a picture with a million pixels, I don’t need all million pixels. If nine out of ten pixels were dropped, the picture would get somewhat blurry, but I would still be able to recognize the image.
For mission critical data, however, this is not acceptable and lossless compression is required. Comtech EF Data ensures the complete accuracy of each bit on the remote end of the link. Of note, this type of accuracy requires significant horsepower on board the platform to be able to process this data at tens or hundreds of Mbps, which is what has been designed into the platforms. The result by leveraging this intelligent compression techniques is the conversion of a given number of “router bits” (those packets delivered to our units) into the least “satellite bits” (those transmitted through the spacecraft). Our equipment does all of this while providing the proper application-based and protocol-dependent Quality of Service (QoS) throughout the network—at the throughputs being made available on new HTS designs.
Comtech EF Data’s CDM-625A Advanced Satellite Modem
Step 5: Dynamic Bandwidth Allocation for Satellite Networks
Once you have the most optimally net efficient links leveraging many of the techniques above, you want to be able to dynamically assign bandwidth to remote sites within a satellite network to get you to the right economics. This is done by inspecting the data flow across the network and allocating bandwidth to the sites, or more importantly, to the applications at the sites that require it. Different platforms do this in different ways.
When considering satellite network options, two approaches typically come to mind. Both leverage a shared outbound carrier of some sort, dynamically inserting traffic destined for remotes into a common data stream. For the inbound direction, the paths of approach diverge, however. A TDMA approach can be implemented or a static SCPC approach can be taken. TDMA offers the benefit of sharing at the cost of efficiencies. Many remotes share an inbound carrier that has the overhead required to meet the demands of multiple geographically disperse users. SCPC provides better efficiencies at the cost of an inability to dynamically reassign bandwidth. The always-on inbound connection is potentially not always required. There are tradeoffs that should be evaluated as to whether or not the sharing of a TDMA channel outweighs its less efficient transmission method. Often, both options leave an amount of potential efficiency gain on the table.
Our approach to this dilemma is to bridge these two worlds by combining an intelligent sharing concept with the net efficiencies achieved on individual SCPC links via several of the above mentioned steps. Performing these multiple layers of optimization require a high horsepower engine operating at high data rates. This is where many TDMA options of today fall short, especially when handling high throughput inbound links.
Comtech’s approach to shared bandwidth builds on our innovative purpose-built designs to support high-end users, incorporating dynamic demand-based allocations upon this solid foundation. Approaching the increasing throughput demands of satellite network end users from the higher end of the performance spectrum is a better path to take than attempting to stretch a platform designed for lower throughput use to the higher throughputs of tomorrow. This is mainly due to the significant processing power (horsepower) and intelligence required to support these high throughputs efficiently and reliably. This approach by Comtech EF Data provides the best option for service providers who wish to future-proof their networks.
The HTS Industry Push
Satellite operators continue to innovate in the sky, launching new HTS designs that promise increased performance and better economics. HTS really is pushing us forward as an industry. With the new economic model and enhanced performance levels, users will be poised to penetrate new markets, increase subscriber base, offer enhanced services and minimize subscriber churn through differentiated service offerings. The “me-too” offerings and competing on prices can be scenarios of the past. But, in order for this to be a reality of the future, it is imperative that ground equipment manufacturers challenge themselves to provide new, purpose-built and future-ready HTS-optimized solutions that allow users to unleash the potential to deliver new levels of services. Customers want the assurance that the CAPEX (equipment) investment they are making will work three, five, even seven years from now on traditional beams, but also on high throughout beams.
Differentiation comes through innovation, and we continue to innovate. In a recent announcement, the company introduced feature enhancements across the entire satellite modem portfolio that focus on efficiency, intelligence and horsepower to best leverage new spacecraft designs, provide the best net efficiencies and enable service differentiation. The groundbreaking technologies are all in direct response to spacecraft innovations and market requirements for service differentiation.
Steve Good is Vice President, Marketing for Comtech EF Data. Good leads the divisional marketing functions, objectives and initiatives based on long-term product and profitability goals. A satellite industry veteran, he has 20+ years experience in a variety of positions in which he has bridged sales and engineering organizations to create and implement marketing plans around product, pricing, placement and promotion strategies. During his career, he has held senior management, marketing, product management and engineering positions with Intelsat, Verestar, Viacast and Hughes Network Systems. Good previously held the position of Vice President, Sales Engineering.
Comtech EF Data Corp., a subsidiary of Comtech Telecommunications Corp. (NASDAQ: CMTL), offers advanced communication solutions that encompass the Advanced VSAT Solutions, Satellite Modems, RAN & WAN Optimization, Network & Bandwidth Management and RF products. The Company is recognized as a technology innovator, and has a reputation for exceptional product quality and reliability. The solutions enable commercial and government users to reduce OPEX/CAPEX and to increase throughput for fixed and mobile/transportable satellite-based applications.
For more information, please visit http://www.comtechefdata.com.