Bandwidth Management Strategies Built on Optimization Technology Evolution
With demands for the finite resource of satellite bandwidth consistently on the rise, the challenge for both operators and service providers is to increase optimization and management efforts. In order to get the best returns on investment possible from satellite bandwidth, companies are placing more demands and shorter timelines on technology vendors.
GCI is an Alaska-based company providing voice, video and data communication services to residential, commercial and government customers, with plans to deploy state-of-the-art bandwidth management solutions. Mark Ayers, RF engineering manager, GCI, says the company puts a high value on operating modem links that produce high-bandwidth efficiency and spends capital on station-based enhancements that produce reduced operating costs. “GCI has a large installed base of private line links operating at 16QAM modulation with Carrier-in-Carrier technology. GCI has recently begun to deploy DVB-S2 standard-based modems that have the ability to exploit Adaptive Coding and Modulation (ACM) as well as higher order modulation/FEC combinations in order to squeeze the maximum performance out of each transponder and satellite link.”
Flexibility is a key element in bandwidth management strategies employed by companies such as Harris Caprock Communications, which has many clients in the energy, government and maritime industries. According to Andrew Lucas, global operations officer of Harris CapRock, the company is currently the world’s single largest buyer and supplier of satellite bandwidth with a portfolio of 4 Gigahertz.
“Harris CapRock manages a large pool of bandwidth in a highly dynamic but efficient manner. At the core is a suite of engineering tools that maintains a database of all carriers and contracts with link budgets, optimized appropriately for both cost-effective but resilient performance. These tools provide visibility into unused bandwidth which is matched against upcoming contracts to ensure both the most efficient use of bandwidth and ability to rapidly respond to changing requirements (be these location, client or bit rate) are in place,” he says.
For Harris to succeed on delivering service, a holistic approach to capacity management across all associated components is required, along with the ability to manage bandwidth to a highly granular level to reliably deliver high-speed and on-demand services such as video capabilities, Lucas adds. “Knowledge of available capacity is key in understanding what services can be activated on a real-time basis. As the challenge also extends to the sizing of VSAT equipment, the ability to generate link budgets on demand is important but ultimately extends to how the client network is configured.”
Bandwidth management issues are particularly acute in Latin American markets, where capacity demands far outpace available resources. Telefonica Argentina, which offers a variety of services across Argentina and the region, needs to make the most of its satellite capacity, given that, at this stage, there is not a huge amount of capacity available, says Telefonica Argentina’s director of engineering Leonardo Gabriel Arce. “Given the lack of satellite capacity, or the scarce blocks of bandwidth found on different satellites in the best case (meaning that for using only a few MHz it is needed to install new master antennas and associated RF), optimization today means almost the difference between being able or not to offer additional satellite services to our customers, regardless of the cost. This need will be sustained as long as capacity continues to be scarce,” he says.
Telefonica Argentina deploys a multi-faceted approach to bandwidth optimization. It believes that for Single Channel Per Carrier (SCPC) services, implementing ACM schemes with variable block lengths is a better initial approach to optimization than carrier overlapping techniques — at least as a first step. The company adopts a different approach for its broadband VSAT Networks.
“The best approach here is to adopt cancellation systems at the hub. This approach is extremely ‘engineering intensive’, but if a correct implementation is accomplished, the outcomes are dramatic savings. In the past the need for optimization was not critical as it is now. Basically, some systems were changed to save bandwidth (SCPCs replaced by broadband VSAT services). Today, due to the lack of satellite bandwidth and the increase in speeds requested, optimization becomes mandatory,” Arce says.
Telespazio Brazil CTO Claudio Mastroianni goes as far as saying that bandwidth optimization “can probably be ranked as the number one technical challenge” it faces when looking to lower costs and being more competitive. The company has seen some success in the region, with significant revenue growth during the last two years.
Mastroianni believes the company has led the way from a technology perspective and that it was the first operator in Latin America to adopt Carrier-in-Carrier technology for E1 (2 Mbps) or multiple E1 links. He also claims the operator was one of the first in the world to use a similar technology based on PCMA for E3 (34 Mbps) links, which it started in 2009. “We also adopted VSAT TDMA technology, and as soon it was available, DVB-S2 ACM technology,” Mastroianni adds.
Global Crossing, which operates a global fiber network, recently signed a new capacity deal with SES World Skies to support growth it is seeing in Latin America. Global Crossing’s Latin America unit now utilizes about 290 MHz of capacity aboard SES satellites to serve markets across the region. At the beginning of its satellite business almost 20 years ago, Global Crossing’s main satellite implementations were narrowband TDMA hub based VSAT platforms for serial data services, such as ATMs, lotteries, telemetry and SCPCs for higher throughput requirements mostly related to natural resource applications and trunking. Guillermo Zapata, product manager, Global Crossing says the company’s bandwidth optimization strategy has evolved since then. “During the 1990s, the main strategy was simple, we wanted to get the best footprint we could find and use the highest modulations and most efficient error correcting codes possible. However, with the establishment of IP as the main communications protocol and the rise of new generation very efficient IP oriented TDMA hub based satellite platforms, we decided to take advantage of these platforms to provide most of our services. These platforms, on top of using very efficient modulation and coding schemes, have very suitable data acceleration mechanisms and allow for optimization by traffic engineering.”
Advances in Technology
With technology vendors frequently under pressure to bring new technology to the table, industry executives have been focusing on a number of significant breakthroughs during the last few years. Ayers highlights the introduction of Carrier-in-Carrier technology as perhaps one of the most important breakthroughs in bandwidth optimization technology in recent times. “The implementation of this technology, coupled with the incorporation of the standards based DVB-S2 signaling and features results in a modem performance enhancement that allows GCI to deploy single terrestrial interface (such as Ethernet) modems to our customers that were not possible a year ago,” he says.
Lucas also highlights other frequency re-use technologies such as PCMA (Paired Carrier Multiple Access), as well as the Bit-to-Hertz relationship, which he says has become increasingly efficient through the improvement of modulation and coding schemes. However, it is technologies such as Carrier-in-Carrier, where the real impact has been made. “Frequency re-use technologies allow you to receive and transmit on the same frequencies that potentially double the amount of available bandwidth. Other solutions allow link availability to be dynamically managed rather than statically configured. This allows the associated transponder power to be released to deliver higher link throughput rather than be held in reserve for rain fade conditions,” he says.
Arce says the major breakthrough for Telefonica Argentina has been the ability in recent years to deliver SCPC-like quality of service with broadband IP TDMA systems. “In terms of coding and modulation, today one can have modems crafted with functionalities that leave us close to theoretic limits. Units featuring variable block length LDPC allow us to trade with bandwidth, power and latency, finding the best match for each case (latency may or may not be a constraint depending on the application). We consider this as a genuine saving, since the code requires less energy for a given performance compared to other codings. In addition, some providers offer ‘signal overlapping’ as an optional feature in their SCPC modems.”
Carlos Placido, a satellite analyst at NSR, says the introduction of DVB-S2 systems can be classed as an “interesting breakthrough” in terms of improved bandwidth optimization techniques. However, Placido warns that with flexible LDPC coding and carrier cancelling, the end of the spectral efficiency road has been reached. “We are so close to the edge when it comes to the channel limit, that you cannot squeeze more bits per Hertz. That is a major breakthrough. What comes next in terms of spectral efficiency will be different things. Clearly, there is not much more to do at the RF level to squeeze more bits per Hertz. Vendors are working on other things to improve throughput.”
In the wireless world, the increasing use of GSM cellular backhaul optimizers that deal with the protocol itself is a well-noted trend. “The GSM protocol is very chatty and there is a lot redundancy,” says Placido. “You can get up to 50 percent savings at the protocol level, but not at the spectrum level. It is a very good example of how optimization will be more and more associated with companies developing optimizers for very specific applications. It is no longer about providing a generic pipe optimized for any application.”
Interestingly, Placido says SCPC/TDMA technologies are merging in a sense that blurs the line between the two markets, with SCPC-like qualities appearing on an increasing number of TDMA products. “Within the TDMA world, the statistical multiplexing advantages of IP are always there. If you have very volatile traffic, it is always good to bundle different sites into a single satellite carrier,” he says.
While bandwidth management technology has undoubtedly improved, technology vendors are always faced with questions regarding what to develop next, as well as challenges that tend to vary depending on the market. Ayers and GCI are paying more attention to what enhancements may take place in the modem market. “GCI is dedicated to continuously reducing operating costs to our customers in Alaska. With that goal in mind, GCI is looking for improvements in multiple access methods as well as better Quality of Service (QoS) integration between the modem IP interface and the end router’s protocol stack. Implementation of ACM requires the proper tools and features for a seamless, high quality service delivery to the customer,” Ayers says.
Arce and Telefonica Argentina want better cellular backhaul services and would like to see a better integration of providers in cellular backhaul. “Another point is to get ‘agnostic’ cancelling boxes, to be added to existing SCPC hardware, regardless of SCPC technology, at reasonable prices.”
Working with Operators
While telcos and service providers are looking to make the most of their bandwidth, satellite operators have their own perspective on the issue. MSS operator Iridium manages its constellation of satellites as a whole, and for its ground segment has software that loads configuration tables onto its satellites. According to Iridium vice president of research and development, Hermon Pon, this process manages the channel and bandwidth usage between each satellite and neighboring satellites. That way, they don’t create interference with each other. “This system was put in place at the time the system launched, and that really hasn’t changed. But, also, we have really focused on bandwidth optimization, how we actually use the channels from the satellite,” he says.
As part of its OpenPort product, Iridium deploys a dynamic scheme to allocate bandwidth to data users who can subscribe to a maximum level of bandwidth — up to 128 Kbps — but the system only allocates channels to them as they send the data. If Iridium customers need to send a large file, Iridium can ramp up the transfer rate to the maximum speed. If they are not sending anything, Iridium has the ability to ramp down and allocate a smaller channel to them. “The other thing we are doing is investing in integrating compression technology and data proxies into our subscriber units, and this optimizes the transport of IP across our network,” Pon says.