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Focus: Rapid Deployment Of Cellular Over Satcom
author: Richard Hart, Senior Product Line Manager — Mobile Platforms, Powerwave Technoloiges, Inc.

Planning to restore communications in the event of a natural or man made disaster can be a daunting task to say the least. One must consider a multitude of scenarios and plan for the worst. One such option to consider would be a rapid mobile deployment unit (RMDU). Generally speaking an RMDU has the following features: rapidly deployable, telescoping mast, off-grid power solution, equipment enclosure, communications capacity and coverage solution, backhaul solution and command and control elements. In selecting a partner for such a solution one should consider a vendor with a breadth of knowledge and experience in all the technical disciplines that make up an RMDU.

HartFig1 Powerwave Technologies’ award winning RMDU has been designed from the ground up with this in mind. The RMDU integrates all the above technologies in a ruggedized commercial platform for domestic or international use by first responders and government entities. Integration of auto deployable, very small aperture terminals (VSAT) for backhaul of cellular, Wi-Fi and public safety communications coupled with an active-array antenna coverage solution make it a one-stop destination for agencies looking for complete coverage solutions for applications such as disaster recovery, nation building, border security and remote training sites that lack communications coverage. Easy to deploy and reliable backhaul of voice and data when traditional landline backhaul is unavailable make cellular-over-satellite a viable option. When considering cellular-over-satellite considerations such as quality of service techniques, service type, hardware and cellular technologies such as LTE need to be planned carefully.

Today, most major satellite service providers only offer dedicated space segment bandwidth versus that for on-demand bandwidth. Currently, second-tier satellite providers fill this on-demand niche. The reasoning is that the tier 1 service provider assumes the day-to-day cost for maintaining the infrastructure that provides the bandwidth as well as the resources that manage the infrastructure. On-demand bandwidth is typically marketed by oversubscribing the amount of bandwidth by a factor of two or more, which provides the foundation to capture the revenue to support the costs associated with maintaining the infrastructure and those resources. The problem with on-demand is that the bandwidth is shared, meaning that there are multiple subscribers who have the potential of leveraging the same bandwidth, resulting in dropped data on that space segment bandwidth.

HartFig2 Dedicated bandwidth offers the guarantee that the bandwidth will be available when it is required and needed by the customer. For customers with high usage needs and critical data to transport, dedicated bandwidth is most likely the preferred choice. However, this choice typically carries higher monthly fees and charges. The advantages of dedicated bandwidth may outweigh the higher costs and include the following benefits: the bandwidth and the data that rides the bandwidth is only for that customer’s traffic. The customer traffic may have bandwidth conflicts/constraints internally, but are not the result of external traffic usage/patterns. Dedicated bandwidth allows for the customer to segment their higher priority traffic over lower priority traffic by the use of a quality-of-service (QoS) strategy that they own and manage. This QoS strategy can be simplistic or complex, depending on the makeup of the traffic and the critical transport requirements for the traffic types being transmitted.

As the traffic types evolve with newer technologies such as LTE, the QoS strategies become more important to manage and build correctly to ensure streaming video and low-latency apps such as on-line gaming sessions are carried across that bandwidth transport in a timely manner where latency, jitter, and wander can be intrinsically determined and managed for higher data transport performance. As IP is the mainstay for LTE, a QoS strategy that leverages the IP protocol stack becomes more important to manage efficiently. With the advent of newer and faster mobile devices consuming more and more data, the customer will need to properly size the bandwidth pipe to effectively support the various traffic types.

AVL_ad_MSM0611.jpg Shared bandwidth is more economically feasible. Shared bandwidth is where two or more customers use and compete for the same bandwidth capacity. This is usually referred to as oversubscription and allows the bandwidth service provider to break apart the total pricing into smaller chunks for each customer utilizing that bandwidth segment. The service provider has the opportunity to get additional revenue with the oversubscription by selling the bandwidth for more than the sum of the segment while the customers only pay for a portion of the overall total bandwidth cost. Shared bandwidth makes sense financially when the customer infrequently transmits or receives data, allowing them to “smooth” the usage over time for that lower cost. Typically, the shared bandwidth approach is good for non-critical data that can handle additional jitter, latency and/or wander if the data encounters delays during the transmission. Those delays most likely will be the result of other customers performing data transmission at the same instance in time.

QoS strategies are more difficult to implement into a shared bandwidth environment due to competing customer traffic profiles/types. For example, Customer A and Customer B both have voice over IP (VoIP), but who gets “first” crack at the bandwidth queue needs to be addressed in the QoS strategy. Other factors, such as time-of-day (ToD), seasonal, and level of guaranteed service contracts will help formulate the QoS strategies in a shared environment

The expansion of satellite communications from C-to Ku-band and now Ka-band has allowed manufacturers and vendors to develop smaller satcom terminals that more readily support communications-on-the-go. Ku-band satcom vendors are now building terminals that weigh less than 40 lbs. and can be carried in a backpack. Newer satellites have been outfitted with Ka-band transponders and are now offering Ka-band services. Ku-band space segment is fairly weather tolerant. However, the smaller satcom aperture dishes are challenged during inclement weather periods, increasing the difficulty with closing the link loop.

Block upconverter (BUC) vendors are also able to leverage smaller amplifier electronics to reduce the size of these devices, which allows for higher powered BUCs to be packaged into smaller housing units. C-band is mainly used in maritime applications to better close the communications loop while ocean-going vessels are in-motion. Ku-Band has gained substantial footholds in the US, Europe, Latin America and Africa. Ka-band is now being offered in the U.S. and Europe, but due to the higher frequency is more susceptible to weather conditions. However, pricing for Ka-band satellite links are more economical that C- or Ku–band links.

Service providers are taking advantage of the smaller Ku- and Ka-band satcom terminals and bundling these terminals with Wi-Fi and cellular. This opens new avenues of revenue and sales to entities that require communications in rural or isolated locals. One large entity that counts on extremely reliable communications is the first responders and emergency response group, which requires flexible communications during a disaster to assist with coordination between entities.

The smaller, more portable satcom terminals coupled with greater availability of satellite services and the coupling of Wi-Fi, VoIP, and cellular to the satcom system affords a higher level of flexible and reliable communications to this user segment. Auto-deploy satcom systems allow for set-up to service-ready in a matter of minutes, with full system operation in less than 10 minutes. This is vastly quicker than terrestrial-based communication links that require hours, if not days, of coordination to align signal paths to establish a level of reliable communications. Use of satellite auto-deploy SatComs with embedded Wi-Fi, VoIP, and cellular offer a true “plug-n-play” solution when instant communications are needed or warranted. New products in this area are now available from Tier 1 service providers like AT&T. AT&T’s integrated cellular service bundled with satellite is called ARMZ (AT&T Remote Mobility Zone). (See Figure 1.)

To protect the customer traffic, the data should be encrypted using security measures such as Internet protocol security (IPSec), generic routing encapsulation (GRE) and secure sockets layer (SSL) protocols. Use of these types of protocols allow for end-to-end security of the traffic, which is critical for sensitive data that could be received by anyone tuned into a customer’s receive signal over a satellite link. By encrypting the traffic across the link, the use of a pre-shared keys embedded into the public key infrastructure (PKI) will allow for a secure communications link/path. Unless the user receiving the data has the proper PKI key or certificate, the data will be difficult to interpret.

HartFig3 A recommended approach would be to establish a VPN between the customer’s remote site and the corporate data center. This would also protect the customer traffic across the backhaul from the Earth station to the customer data center, even allowing the use of the public Internet to support the backhaul. Dynamic IP routing protocols can be implemented that also support a secure, diverse and resilient communications backhaul path between the remote site and the core network. As IPV6 begins to be implemented both by the hardware vendors and by the service providers, this too will afford better, more secure communications between end-points.

Use of satellite backhaul for LTE may be very advantageous in that the topology could be widely distributed, meaning that rural eNodeB base stations could hone back to one of the centralized serving gateways and mobility management entity where the data and call authentication and signaling would occur to support the data/voice session connectivity.

Vendors such as Powerwave Technologies who build small LTE picocells may be able to offer a key service differentiator to wireless operators pushing into the rural areas, which are typically underserved by wireless and broadband operators.

Even though satellite backhaul has significant delays over terrestrial backhaul technologies, the delay can be managed effectively with proper QoS strategies that keep transmission attributes like wander, jitter, and error rates constant to support the high bandwidth, low latency applications being pursued by the LTE forums and operators. By keeping the transmission quality constant, these attributes can be mitigated to help minimize latency related issues for all but the most extreme applications operating within establish parameters.

There are wireless service providers who have embraced satellite transport for their 2G and 3G cell backhaul needs while offering comparable service that support over terrestrial backhaul technologies. The use of satellite is especially receptive to the first responder and emergency response organizations who work in harsh conditions that include no or low signal strength wireless environments. This market segment understands the value of reliable communications, especially across inter-agencies where speedy exchanges of information could be the difference between life and death. LTE will continue this evolution by enhancing inter-agency communications and exchanges as more data applications requiring streaming video and other high demand bandwidth traffic push the envelope of what can be attained in these situations.

As mentioned previously, the use of IP transport has become the protocol of choice, as it allows the user equipment to send “packets” at pre-defined maximum transmission unit (MTU) sizes for greatest efficiency and network performance increases. New equipment manufacturers are developing products that incorporate the best of the IP protocol to allow for constant connectivity in diverse and challenging environments.

These vendors have been successful with implementing IP into a satellite RF environment that allows customers to focus on bandwidth efficiency in very small aperture terminal (VSAT) via the time-division multiplexing/time-division multiple access (TDM/TDMA) access scheme. One vendor has bypassed the conventional contention schema and devised a method to allocate a specific amount of bandwidth per remote continuously, while dynamically reassessing the allocation based upon queue depth, the configuration-in-run (CIR) configuration, the QoS and prioritization settings, and the rate limits at each remote. This scheme allows for rapid reaction to changing traffic demands to provide adequate CIR and equipment identity register (EIR) service levels.

Determining the amount of satellite bandwidth a customer requires can be challenging, especially if the majority of the traffic is nondeterministic. The QoS strategy should be based upon differentiated services and use mechanisms such as traffic shaping, (leaky bucket) scheduled algorithms, weighted fair queuing (WFQ) and/or congestion avoidance (weighted random early detection [WRED]). These schemes are critical to be implemented for shared bandwidth and are highly suggested for dedicated bandwidth.

Leveraging The Links
Many articles and subject matter experts have been touting the benefits of satellite for disaster response communications — the true power is when newer communication technologies, such as cellular, leverage satellite links for backhaul due to the availability of space segment and the ease of setting up portable, auto-deploy satcom antenna systems to leverage those links. The quick setup and deployment cycles for on-air are in minutes, which is crucial for prompt response efforts. The satellite systems become an invaluable tool to use during a disaster event to help establish necessary communications, especially for larger mobilization camps and staging areas and promote better inter-agency coordination during the event. Use of cellular-over-satellite allows these staging areas to be closer to the disaster area, helping expedite response and recovery activity. Smaller cellular base stations deployed with the latest cellular technologies, such as LTE, allow for a more standardized communications network that can support voice and high speed data needs and demands.

Powerwave Technologies, Inc. displayed and demonstrated the RMDU capability at AGAUS in Indianapolis, Indiana, June 6th -12th, 2011.

Richard Hart, Senior Product Line Manager – Mobile Platforms Powerwave Technologies, Inc.

Wayne Berthold, Principle Product Development Engineer, AT&T Mobility Services – Vanguard Services, International Alliances & Integration