Lessons Learned: Transitioning from TDM to IP

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Cell phone tower near Lozen, Bulgaria. Photo credit: Plamen Agov • studiolemontree.com [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons

The transition from the Time Division Multiplexing (TDM) cell phone networks of the 2G and 3G mobile era has been a long time coming. However, the mobile industry seems to be at one of its proverbial inflection points where IP (Internet Protocol) technology is ascendant and TDM has begun the long but inevitable decline into legacy status.

Aviat Networks has been there all along the way, helping operators design and deploy aggregation systems. We’ve seen and learned a lot as some of the leading mobile phone carriers have upgraded their networks. Now as LTE works its way into mainstream status, cell phone networks are transitioning to full-IP, the underlying technology of LTE.

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85 Microwave Operators tell us their Biggest Backhaul Challenge

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England: Campion Hills communications mast with microwave antennae. Photo credit: David Stowell [CC-BY-SA-2.0], via Wikimedia Commons

The general mobile industry sentiment has typically been that the capacity bottleneck is the biggest challenge in backhaul. Thus, the focus has been on adding more capacity to address the surge of 3G and now 4G traffic. So you might think that this concern would rank first, particularly among microwave-centric operators, who are often looking to maximize their network throughput. We recently commissioned the experts at Heavy Reading to do a custom survey to get some quantifiable data to clarify this key question and a few others.

85 mobile operators were selected and surveyed globally, including a good cross-section from both developed and emerging markets. The respondents were screened to ensure that they all had a stake in microwave-specific backhaul: 93 percent had deployed microwave and the rest had plans to deploy it. In fact, 45 percent were categorized as heavy microwave users—those where more than 50 percent of their cell sites were served by microwave backhaul.

So we asked this select group, which consisted of mostly planners, engineers and strategy leaders, “What is the biggest challenge your company faces regarding the future development and deployment of microwave backhaul?” 

The results were interesting in that “total cost of ownership” actually eclipsed “increasing capacity” as their biggest challenge, as shown in the pie chart of survey responses below.

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4G Upgrade Path Drives Backhaul Migration in Kenya

Safaricom's Internet Broadband Dongle (with SI...

Burgeoning WiMAX and 3G data traffic from subscriber devices such as Safaricom’s Internet Broadband Dongle (with SIM Card) are driving the mobile operator to migrate from TDM to hybrid microwave backhaul. (Photo credit: whiteafrican via Flickr)

Migrating legacy mobile backhaul networks that were designed for TDM traffic to add support for high-speed Ethernet data for 3G and 4G mobile technologies is one of the biggest challenges for operators worldwide. Each case is unique and poses its own quirks and potential pitfalls. Mobile operators must juggle new technologies, cost pressures and the need to maintain existing services or risk driving customers to the competition.

For Safaricom, the leading mobile operator in Kenya and one of largest in all Africa, the case involved preserving its E1 capacity for voice calls and simultaneously adding Ethernet/IP bandwidth for burgeoning 3G and WiMAX data traffic. As many mobile operators have done in the past, Safaricom built its network over time. Many parts of the network are still legacy 2G TDM technology. However, things are changing rapidly, with 3G subscriber numbers up 85 percent in 2011 year over year.

Many of these subscribers are consuming ever-increasing amounts of data bandwidth. Safaricom’s TDM based backhaul, making use of Ethernet-to-E1 converters, is finding it hard to keep up with demand. To help resolve the situation, the operator called on Aviat Networks, one of its incumbent solution providers. Using its market leading hybrid radio solution, the modular Eclipse microwave networking platform, Aviat Networks enabled Safaricom to add IP data capacity as necessary while keeping E1 capacity for voice calls.

In addition, the stage has been set for Safaricom to make the eventual migration to all-IP backhaul. With the modular Eclipse platform, it can transition on its own schedule. For more information, read the complete Safaricom case study in the frame below or download the PDF:

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Record 180 km Hybrid Diversity IP Microwave Link

Survey view from Belize toward Honduras, at 1000 m AMSL

Survey view from Belize toward Honduras, at 1000 m AMSL

Link between Honduras and Belize Crosses Water and Land

Last year I wrote about the world’s longest all-IP microwave link, stretching 193 km over the Atlantic Ocean in Honduras. Aviat Networks and Telecomunicaciones y Sistemas S.A. (TELSSA) designed and implemented this link together. This year, Aviat Networks and TELSSA again worked together to build another link and achieve another record—an Eclipse microwave link between Honduras and Belize that crosses 75 km of the Atlantic Ocean and 105 km of rugged terrain for a total path length of 180 km. This is a new world record for a hybrid diversity microwave link!

After the success of implementing the 193km link over water, Aviat Networks and TELSSA were eager to meet the challenge to connect Honduras and the neighboring nation of Belize using a single microwave link. Aviat Networks network engineers and TELSSA engineers were able to use their extensive knowledge of local propagation conditions, thorough understanding of long path design principles and precise installation practices to successfully implement this 180km microwave link.

Long Path Design Considerations

As outlined in the article last year for the longest all-IP hop, a deep understanding of path design considerations and experience in microwave transmission path design are necessary to successfully complete a long path design. Key considerations involved:

  • The effect of antenna diameter on highly refractive paths
  • Precise alignment of the antennas to mitigate the effect of refractivity
  • Optimum RF and space diversity spacing to counter elevated divergent dielectric layers
  • Deterministic prediction of the variations of atmospheric conditions
  • Multi-path propagation delay

To read more about this world-record Hybrid Diversity IP microwave link, download the full article.

Ivan Zambrano
Senior Network Engineer
Aviat Networks

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3 Models for Microwave Link Error Performance? Laine Explains

Dick Laine explains ITU-R models

In the second episode of Aviat Networks’ Radio Head Technology Series, Principal Engineer Dick Laine explains ITU-R models for Fixed Wireless Systems.

As most radio engineers know, Vigants calculations, which are discussed in a broadly cited Bell System Technical Journal article, are widely used to determine reliability or error performance for microwave link design. In Video 2 of Aviat Networks’ popular Radio Head Technology Series, which is now available for viewing, Principal Engineer Dick Laine explains how he uses Vigants calculations in conjunction with the three completely separate ITU-R Fixed Wireless System (FWS) models for TDM.

Because of all these models, he likes to use Vigants calculations as a “sanity check” to see that he is close to the correct result for his path engineering plans. The free Aviat Networks’ Starlink wireless path engineering tool can be used to handle Vigants calculations for Aviat Networks’ and other vendors’ equipment.

Can’t wait to hear more of Dick’s experienced views on microwave radio transmission engineering? You can get ahead of the learning curve by registering for the series and get these videos sent to your inbox as soon as they are released.

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LTE – Lessons Learned So Far

Aviat Networks has been deploying LTE networks for well over a year now to operators globally, including the largest live commercial LTE network in operation today. So, it’s probably a good time to reflect on some key observations and lessons learned to date. Here are the top 3 things we’ve learned from our LTE microwave backhaul deployments that are most notable:

1.    LTE backhaul capacity needs are being easily addressed by packet microwave:

– When it comes to capacity there is a perception that fiber is the only answer. The reality is that based on current LTE deployments, 50Mbps is more than adequate for most LTE cell sites today.  Yet, for comfort and long term growth most of our customers are licensing and deploying 100-200Mbps of microwave capacity to their LTE equipped cell sites. For intermediary sites that aggregate traffic, link aggregation techniques are being utilized to effectively bond multiple channels for higher capacities, all well within the multi Gbps reach of advanced microwave systems, such as ours.

2.    Ease of deployment and fast time to market (TTM) are critical for success:

– This LTE operator quote speaks volumes regarding the real challenge he faces: “Whoever can deliver the quickest with the least amount of pain will win most of the business”. TTM is most crucial for operators trying to stay one step ahead of their competition… more markets served, better coverage etc. To address this, we have seen a growth in our customers seeking a one stop shop approach for LTE microwave backhaul deployment where we engineer, configure, test, and deploy the full end–to-end system, providing overall project management, frequency coordination, installation and a host of other services. The fact that most microwave systems can be installed in a few weeks as opposed to months for fiber, is also playing a key role in microwave growth in areas like North America where microwave penetration is low, but growing as a result of LTE rollout.

3.    Backwards compatibility with multivendor interoperability is key:

– It’s all about LTE, right? Well, yes and no. LTE is driving the new investment and deployments, but the reality is that 2/3G will be around for a long time. So, while the new deployments are driven by all-IP LTE, there are still ‘legacy’ T1/E1s still hanging around that also need to be backhauled. This has been a perfect fit for Aviat’s all-in-one Hybrid (TDM+IP) and All-IP microwave systems, which allow our customers to easily software configure their mix of traffic. So, while the bulk of the transport bandwidth is provisioned for IP to support LTE, some is still reserved for good ‘ole TDM.

– Another related aspect is multivendor interoperability across a variety of product types. The backhaul market has flourished in the last few years as we know, and so has the variety of cell site switches, routers, packet optical devices etc. that our microwave systems interoperate with to fulfill our customers ‘end-to-end’ LTE backhaul solution. Consistent Carrier Ethernet standards applied across both the microwave and fiber core makes this very straightforward when it comes to provisioning Ethernet backhaul services, supporting packet network synchronization, and managing these services.

So, in summary, I would say we’ve learned that packet microwave is well suited for LTE capacity needs; it can be rapidly and easily deployed; and provides great flexibility for legacy services and multi-vendor interoperability. But the best proof of all this is in our customers’ live networks.

Errol Binda
Solutions Marketing
Aviat Networks

Fore more information on LTE microwave backhaul and a customer case study click here.

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The Impact of Streaming Video on Wireless Network Services

Video call between Sweden and Singapore, on So...

Sustained video streaming, such as a video call over a mobile network, strains the stat mux paradigm of oversubscribing Ethernet microwave backhaul. However, proper management can ensure a consistent, high-quality user experience can be maintained. Image via Wikipedia (author: Kalleboo)

Mobile backhaul networks today support Ethernet microwave transport for 3G and 4G wireless technology services alongside legacy 2G and 3G TDM-based microwave equipment. However, as late as 2009 these wireless network services were solely TDM transport. One of the primary benefits of moving to Ethernet microwave transport has been the inherent statistical multiplexing (stat mux) gains. Stat mux relies on the fact that not everyone is “talking” at the same time and when they do, their IP radio packet sizes are variable, whereas networks based on TDM have to be provisioned statically for peak rates to individual wireless microwave sites.

With the advent of Ethernet, the typical practice is to oversubscribe all the wireless network services (based on individual peak rates) knowing that there is a statistical improbability of hitting the peak rate across all your wireless communication towers at the same exact moment.

Now enter video streaming where data is “streamed” between two wireless communication points over a sustained period (e.g., 30-second YouTube video clips, Skype HD Video Conferencing, Netflix movies). The sustained aspect of these video streams begins to strain the overall stat mux paradigm. Not only does video remain sustained but also it uses large-size IP radio packets that do not vary greatly. VoIP does the same thing, but the effect is much less significant as the overall bandwidth utilization is much lower.

Oversubscription becomes more challenging the more active video streaming is at any given moment. Imagine a scenario where the latest cat-playing-a-piano video gets posted online and everyone starts viewing it at virtually the same time. For a large swath of bandwidth, stat mux will reach zero for approximately four minutes. The upside is that you can add more bandwidth and/or offer differentiated wireless network services levels that guarantee certain bandwidth or application performance. Even so, video streaming does not totally negate the benefits of an Ethernet microwave transport, it just needs to be properly understood and managed to ensure a consistent user experience across all applications and services for your global wireless solutions.

Steve Loebrich
Director of Product and Solutions Marketing
Aviat Networks

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Migrating Utility Networks to Smart Grid with Hybrid Radios

What is the best migration strategy for utility networks migrating to Smart Grid using Hybrid Radios? We look at the technology choices that are available to support legacy TDM and IP-based services and investigate the many demands placed on utility networks. Demands include seamless migration, increased capacity, security, and interoperability.

We believe a hybrid network is the best solution and we explain why in this white paper:

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What is Packet Microwave?

“Packet Microwave” radio systems continue to enjoy a lot of coverage and hype within our market. But it helps to understand exactly what packet Microwave is, including its benefits and limitations, and how Packet Microwave compares to Hybrid radios. We created a white paper a while ago to address these issues, and since it is still relevant today we are highlighting it again.

The paper provides a clear definition of this technology and also answers the following questions:

  • What features should you expect from Next Generation microwave radios?
  • How does Packet Microwave it differ from Hybrid microwave transport?
  • Is Packet Microwave ‘All-IP’ or ‘IP-Only’?
  • Do hybrid systems meet the requirements of packet microwave?
  • What is the best approach for operators trying to choose a microwave solution?

 

 

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