Synchronization Over Microwave Mobile Backhaul Networks


Synchronization is creating quite a stir in the mobile backhaul industry as operators are wrestling with a variety of synchronization technology options including Synchronous Ethernet (SyncE) and Precision Time Protocol (PTP) a.k.a. IEEE 1588v2. This paper reviews unique microwave backhaul characteristics that need to be taken into account in support of synchronization, and how each particular synch approach can be addressed.

Aviat Networks in the News: Recent Highlights and What’s Ahead

What do Orlando, Winnipeg, Rio de Janiero, Spokane and Santa Clara have in common? Nothing, except for the fact that they’re all on a list of places where we have been this past month visiting customers and participating in events. Unfortunately, I didn’t have the good fortune to go, but some of our top marketing and engineering team members did and had the chance to meet industry experts to share and exchange ideas and thoughts on microwave backhaul technology, trends and opportunities.

One of the major events we attended was CTIA Wireless Conference 2011, which was held March 22-24 in Orlando, FL. At the show, we participated in a panel discussion and presented on the latest trends in microwave radio technology at the Tower Technology Summit. In one of the sessions, Shaun McFall, our CMO, talked about the backhaul capacity requirements to support 4G/LTE cell site deployments. You can read his viewpoint on “Why Fiber is not the Answer for 4G/LTE Backhaul in North America.”

In addition, Gary Croke, our senior product marketing manager provide his insights on how microwave technology is well positioned to serve both the short and long haul backhaul needs for deploying next-generation cellular networks. You can read more about his viewpoint on his blog post.

And if that wasn’t enough, we announced our IEEE 1588v2 synchronization capability for mobile backhaul and co-promoted it with Symmetricom® as part of its SyncWorld Ecosystem Program. Find out more information about deploying IEEE 1588v2 Synchronization over Packet Microwave Networks.

Moving on to Canada, Gary gave a different presentation titled “Hybrid Radio and Essential Functionalities for Smart Grid” at the MIC/MUG 5 UTC Regional Conference in Winnipeg, Manitoba, Canada, on April 14. Attendees at the conference included utility radio engineers who were interested in learning about upgrading legacy TDM-based microwave systems and devices to meet the needs of Smart Grid. Gary’s presentation focused on hybrid radio, Strong Security, Adaptive Coding and Modulation, and improved capacity and performance—all features required to support the evolved Smart Grid utility network. Find out more about the Utilities Telecom Council.

Another great event that we participated in this month was the LTE Latin America 2011 Conference in Rio de Janiero. Unfortunately—again—I did not get a chance to go, but Louis Samara, our director of marketing/channel sales, Latin America, did attend and spoke on the importance of microwave backhaul for mobile operator migration to Long Term Evolution/4G. During the conference, he met with Emmanuel Jaffrot, asesor tecnologico del ministro de planificacion federal, Argentina, Humberto Roca, CTO ANTEL, Uruguay, and Juan Carlos Pepe, general manager Telecom Personal Paraguay to discuss several telecommunications initiatives. Check out our Flickr site to see the photos and get additional details on our visit.

Another interesting event was the WiMAX Rural Operators Summit, organized by the WiMAX Forum and held in Spokane, WA, April 26. Stuart Little, our hip, savvy, director of marketing, attended the event, which was the first event of its kind organized by the forum in the US. It drew good attendance from operators and vendors, including a few international attendees. The agenda covered a variety of topics of concern for smaller operators who are deploying wireless networks to bring broadband services to the unserved and underserved rural communities in the US.

Speaker panels included larger operators such as Sprint and Clearwire, as well as smaller ones like Ecliptixnet Broadband and Keyon Communications, with some interesting debates including how operators are navigating the challenging process of winning and utilizing federal Broadband Stimulus funds. Probably the biggest challenge that these rural operators have is access to capital to invest in their networks. Of course, stimulus grants help, if you’re one of the lucky ones to win an award. For the rest, cost is a huge driver for their equipment selection. On the WiMAX side, specific requirements such as frequency bands for the US (e.g., 3.65 GHz) make it difficult for them to deploy a WiMAX basestation to serve customers in very small rural communities, since vendors struggle to achieve economies of scale to drive prices down far enough.

On the backhaul side, focus is also on cost, not so much on capacity. Many operators utilize very cost effective unlicensed microwave solutions for backhaul, but to support a real “carrier-grade” network licensed microwave is preferred to enable the high reliability and interference free operation. Stuart sat on a panel with three representatives from other independent microwave companies, where we discussed how we as an industry are bringing new solutions to lower the cost of ownership of licensed microwave for rural operators. New techniques, such as ACM and ring network topologies can help to reduce antenna sizes, one of the largest OPEX drivers. Some of the proposals now presented to the FCC will also help rural microwave deployment, including reducing restrictions on minimum antenna size and bandwidth efficiency in the lower frequency bands.

Whew! That was a lot of detail, but worth the trip to Spokane.

Now onto the one of the coolest events, which will be broadcast tomorrow, the “LTE Backhaul Capacity Requirements: Diving Deeper” webinar. Panelists will include Stuart and Peter Croy, senior IP network architect for Aviat Networks, in addition to other industry experts.

Following on from our previous webinar where Stuart and Peter addressed the practical backhaul capacity requirements of 4G/LTE, this webinar discussion will dive deeper into our analysis, share some new insights, provide updates on operators’ plans regarding backhaul and discuss how the emerging small cell market will address network capacity needs and what new backhaul innovations will be needed for these small cells. Please join us for this highly interactive webinar to delve further into the network capacity requirements for LTE backhaul.

So what’s ahead for next month? Well, it will be busy. So many interesting events and topics!

LTE Backhaul Conference, London, May 3-6

London is our first stop. Although just after the fanfare of the Royal Wedding—which by the way would have been nice to see in person! But LTE backhaul is “just” as exciting. At the LTE Backhaul Conference in London on May 3-6, we will host a workshop on “IP Mobile Migration Challenges and Issues.” If you live in the UK or will be in London, we invite you to join us alongside mobile operators and industry partners to tackle some real-world issues related to IP backhaul migration, including planning for realistic LTE capacity demands and packet synchronization migration, in this engaging and interactive workshop. Details about the conference.

Transport Networks for Mobile Operators Conference, London, May 10

While in London, Stuart will also speak at the 13th Annual Transport Networks For Mobile Operators Conference on May 10. Stuart’s topic will focus on “A Realistic Look at LTE Backhaul Capacity.” Find out more about the conference.

UTC Telecom, Long Beach, CA, May 10-13

At this conference, Gary will speak on the topic of “Microwave Technology Options.” In his session, he will give an overview of the microwave options and applications best suited to each form in a side-by-side comparison that will enable you to develop your microwave plan for the future. Find out more about this conference.

LTE World Summit 2011, Amsterdam, Netherlands, May 17-18

Peter will speak on the topic of “Examining the Role of Carrier Ethernet in Meeting Mobile Backhaul Capacity Needs Including LTE.” View the conference details.

And find out more about our other events!

That’s it for now. I will be back in touch next month to update you on the latest happenings at Aviat Networks. Until then, follow the dialogue and news on our social sites.

www.aviatnetworks.com

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www.youtube.com/aviatnetworks

Cyndy Johnson

Director of Corporate Communications, Aviat Networks

Unlocking Capacity Block Through Higher Order Digital Modulation

If you are reading this post, then you probably have heard about “4G”, the 4th generation cellular network. For a cell phone user, 4G means improved data speeds that allow faster delivery of multimedia-based applications, see our previous post, What is 4G?, for more details. On the other hand, the network operator desires to spend a minimum on upgrading network infrastructure and prefers to buy a backhaul solution that supports current and near future capacity demands of a cellular network.

Thus, it is important to improve the capacity of wireless backhaul links. To increase transmission capacity, wider channel spacing can be used. However the wireless spectrum is expensive and may not be available in some countries. Using transmission in high frequency bands, such as 60 GHz and above, provides the bandwidth needed to increase capacity. However, very high radio frequencies increase the cost of radio components. In addition, 60 GHz links limit transmission range due to high absorption of radio waves by the atmosphere, making this solution somewhat cost inefficient. One efficient way of improving the capacity of a communication link is to increase the order of the digital communication modulation scheme used for transmission.

In simple terms, digital modulation is the process of mapping a group of data bits into an information symbol that gets transmitted, after up-conversion to the radio frequency (RF) of the link. The most popular digital modulation scheme used in wireless radios is known as quadrature amplitude modulation (QAM). For a given symbol rate, increasing the modulation order, or equivalently packing more bits per symbol, would be an effective way to increase the capacity of a microwave link. For example, each symbol in a 64-QAM signal represents 6 data bits, while for 256-QAM and 1024-QAM signals it represents 8 and 10 data bits, respectively. Therefore, 1024-QAM provides (theoretically) a 25 percent increase in capacity over 256-QAM and an impressive 67 percent increase in capacity compared to 64-QAM.

The price paid for achieving such an increase in capacity is more complex signal processing algorithms and stricter requirements for channel quality, e.g. higher signal-to-noise ratio (SNR) at the receiver is required. In that case, increasing the modulation order for some networks under normal operating conditions can have a diminishing return on throughput. This is due to the fact that the required SNR for an acceptable receiver performance rarely can be met.

Why this is the case? Let us briefly discuss the challenges in increasing the modulation order. Higher modulation order results in larger pool of symbols available for transmission. For example, for 64-QAM, there exists 64 symbols in a 2D grid (known as constellation points) compared to 1,024 symbols for 1024-QAM for the same grid size. Clearly, increasing the number of symbols (assuming fixed power) makes the symbols closer to each other in this 2D grid. Thus, data detection at the receiver becomes more susceptible to errors due to impairment.

In practical terms, receiver circuits are affected by thermal noise, clipping and non-linearity of power amplifiers, phase noise and many other distortions that are beyond the scope of this post. It is worth mentioning that increasing the signal power beyond some limits results in actually decreasing the received SNR since many of these distortions associated with RF circuits are dependent on the transmitted power. Rather, the way to increase the modulation order is to improve the detection schemes and build circuits that are less susceptible to power-related distortions, along with improving the correction mechanisms at the receiver for phase noise and other impairments.

At Aviat Networks, we have the expertise and knowledge to build the highest quality microwave radios that can work at cutting edge signaling schemes. We will make sure that our customers see a sizable return—not a diminishing one from increasing the modulation order. Our pledge is that microwave backhaul will always exceed the capacity requirements of our customers.

Ramy Abdallah,

Senior Signal Processing Engineer, Aviat Networks

White Paper-Deploying IEEE 1588v2 Synchronization over Packet Microwave Networks

Joint Application Note with Symmetricom and Aviat Networks.

Mobile Backhaul Networks are evolving to packet, driven by 4G evolution, requiring high data and video traffic and growing number of apps, users, smartphones and tablet devices. 1588v2 microwave are a perfect match for Mobile Backhaul evolution. Paper covers 1588v2 overview, unique considerations for microwave and typical deployment scenarios (multi-hop, ring).

Aviat Networks and Symmetricom Announcement at CTIA 2011

Errol Binda, Senior Solutions Marketing Manager for Aviat Networks, discusses the recent Aviat Networks and Symmetricom, Inc. announcement with Manish Gupta, VP of Marketing for Symmetricom, Inc, and Shaun McFall, Chief Marketing Officer for Aviat Networks at CTIA 2011.

What’s So Different About IEEE 1588v2 Sync Over Microwave Backhaul?

The beauty of IEEE 1588v2 (i.e., Precision Time Protocol) synchronization is that it is a bookended solution. In theory, there is no need to worry about what is in between or underneath—from a Layer 1 transport perspective. While in principle this is accurate, there are a couple “unique” aspects of running 1588v2 over a microwave network that should be carefully considered in your deployment plans.

First, the infamous “last mile” is in reality typically many miles across multiple microwave radio hops—which may consist of a mix of linear, ring and hub-and-spoke configurations. Unfortunately, more hops introduce more packet transmission delay and delay variation over the backhaul—a potentially lethal mix for sync transport—the amount of which is proportional to the number of microwave hops. Careful design and engineering are required. On a bright note, Aviat Networks and Symmetricom recently validated <1.5ms delay could be achieved across 10 hops—well within the requirements for mobile backhaul.

Second, most advanced microwave systems now support Adaptive Coding and Modulation (ACM), a key benefit for microwave transport that allows the effective throughput of the microwave link to be dynamically changed to accommodate for radio path fading, typically due to changes in the weather. If bandwidth is reduced as a result of an ACM change, it is critical that advanced traffic and QoS management techniques be applied in the microwave systems to ensure that 1588v2 traffic (packets carrying timestamps) are given the highest/strict priority for transmission, and are not subject to delay or discard. On a brighter note, Aviat Networks and Symmetricom recently validated that 1588v2 could operate over a highly loaded (approaching 100 percent) microwave network running ACM.

In a nutshell, there are some unique considerations for running 1588v2 over microwave – but the outcome can be predictably bright with proper engineering.

Check out the Aviat Networks website for more information on the Aviat Networks/Symmetricom partnership and 1588v2 network synchronization over microwave backhaul.

Errol Binda

Senior Solutions Marketing Manager, Aviat Networks