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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LTE Backhaul: The View from Africa

Telecom-tower-Johannesburg-South-Africa-enabling-LTE-backhaul

Telecom Tower, Johannesburg, South Africa. Photo credit: Marc_Smith / Foter / CC BY

LTE has been moving more and more to the forefront in mobile cellular networks around the world. Africa, and particularly the Republic of South Africa, is the latest hotbed of LTE rollouts, with the leading country operators of Vodacom, MTN and Cell C coming online since late in 2012. In conjunction with these LTE access rollouts, our technical marketing manager in the region, Mr. Siphiwe Nelwamondo, has been authoring a series of columns on enabling LTE in a leading regional technology media Internet site, ITWeb Africa.

Naturally, his focus has been on backhaul. In the first installment of his series, Mr. Nelwamondo looked closely at the backhaul requirements of LTE. Chief among these requirements are speed, Quality of Service (QoS) and capacity. He concluded that it is too early to close the book on the requisite parameters for supporting LTE backhaul. Part two of the features, he examined the basis on which microwave provides the technical underpinnings for LTE backhaul—especially as related to capacity. More spectrum, better spectral efficiency and more effective throughput were Mr. Nelwamondo’s subpoints to increasing capacity.

Having more spectrum for microwave backhaul is always nice, but it’s a finite resource and other RF-based equipment from satellites to garage door openers is in competition for it. Bettering spectral efficiency may be accomplished by traditional methods such as ACM and might be increased through unproven-in-microwave techniques like MIMO. Throughput improvement has wide claims from the plausible low single digit percentage increases to the more speculative of upping capacity by nearly half-again. Data compression and suppression are discussed. The truth is LTE, while data-intensive, probably will not require drastic measures for backhaul capacity until at least the next stage of LTE-Advanced.

If indeed capacity increases are necessary in the LTE backhaul, number three and the most current piece of Mr. Nelwamondo’s contains additional information. Nothing is better than having something bigger than normal or having many of the standard model. As the analogy applies to LTE microwave backhaul, bigger or wider channels will increase capacity, of course. A larger hose sprays more water. Or if you have two or three or more hoses pumping in parallel that will also support comparatively more water volume. The same is true of multiple microwave channels.

However, the most truly and cost effective capacity hiking approach is proper network planning. Mr. Nelwamondo points out that in Africa—more than some places—mobile operators are involved in transitioning from TDM planning to IP planning. While TDM planning was dependent on finding the peak traffic requirement per link, IP planning allows the flexibility to anticipate a normalized rate of traffic with contingencies to “borrow” capacity from elsewhere in a backhaul ring network that is not currently being utilized. Along with several other IP-related features, this makes determining the capacity a lot more of a gray area. Some operators solve this by simply “over-dimensioning” by providing too much bandwidth for the actual data throughput needed, but most cannot afford to do this.

The fourth and final entry in Mr. Nelwamondo’s series will appear soon on other LTE backhaul considerations of which you may not have thought. Sign up below to be notified when it is available. [contact-form-7 404 "Not Found"]

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5.8GHz FCC Rule Change: Good or Bad?

In the United States, the fixed service for wireless communications usually operates in bands licensed either on a link-by-link basis or by block allocation. So why is the 5.8GHz ISM band so important and why should the industry be concerned about current FCC proposals to change the rules of operation in this band.

Many operators use this band because they can install and operate a link in a very short period—much quicker than the usual route of prior coordination and license application that is required in other bands. There are numerous reasons why this approach is attractive, even if it is difficult to guarantee Quality of Service (QoS) in ISM. A common use of this approach sees the operator set up a link in the 5.8GHz band to get the link up and running while in parallel it goes through the coordination process for the same link in the L6GHz band. Then when that license is granted, the operator will move the link to the L6GHz band. This has the advantage that the same antenna may be reused and sometimes the same radio with just a filter change. Another use of the 5.8GHz band for fixed service links is in support of disaster relief efforts where because there is no need for prior coordination that means vital communications links can be up and running very quickly.

Under the current FCC Part 15 rules, equipment can be certified using section 15.247 whereby the above scenarios are attractive to operators as they mimic the conditions that can be found in the L6GHz band. However, the FCC has issued a notice of proposed rulemaking, NPRM, which will change this by requiring a reduction in conducted output power of 1dB for every dB of antenna gain over 23dBi for Part 15.247 point-to-point links. At present, the conducted power at the antenna port in this frequency range is limited to 1 watt, but there is no penalty applied to the conducted power in relation to higher gain antennas on point-to-point links. Should this proposal by finalized then this would reduce the effective range of point-to-point links in this band and would so change the dynamics that the ability to deploy a link in the 5.8GHz band and then “upgrade” to the L6GHz band at a later date would no longer be a feasible option. We would encourage all readers, especially those using the 5.8GHz band to file a comment with the FCC regarding Proceeding 13-49 that this particular change would be detrimental to many fixed link operators, as well as those who rely on this band for fast deployment during disaster recovery.

For more information on this proceeding, email Aole Wilkins at the Office of Engineering and Technology.

Ian Marshall
Regulatory Manager
Aviat Networks

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Critical Role of Microwave in LTE and Small Cell Backhaul

Mobile backhaul has become one of hottest and most contentious subjects in telecommunications ever since LTE cellular phone technology started to ramp up. One much overlooked aspect of deploying LTE lies not in the capacity required to backhaul cell site traffic but the effort required to build out the required sites. It is really about site surveys, frequency coordination, engineering, planning and installation. Aviat Networks’ chief technology officer (CTO), Paul Kennard, addressed this dichotomy and others related to LTE in his presentation to the IEEE’s Communications Society.

Although, Paul did have plenty to present regarding capacity. For example, with proper use of rings, overbooking, QoS, XPIC and other techniques and technologies, microwave backhaul can provide 400 Mbps-plus throughput. Compare this to the realistic throughput demands of a typical LTE site that max out at about 100 Mbps.

He also delved into the emerging backhaul category for Small Cells—designed to supplement traditional cellular infrastructure. The fact is that traditional techniques of deploying cellular macrocell basestations will be insufficient to provide broad enough coverage for this LTE wireless technology. To augment macrocell coverage for LTE mobile telecommunications providers have been investigating, trialing and, in some cases, deploying one or more of several small cell technologies (e.g., picocell, microcell, femtocell). Consequently, new methods will be needed to backhaul traffic from Small Cell sites.

Fiber backhaul may not be available at all small cell sites and when it is it could be very expensive to trench long distances. Regular line-of-sight (LOS) microwave with its parabolic dishes could prove aesthetically unsuitable for many Small Cell locations and/or difficult to install. Non-line-of-sight (NLOS) microwave and millimeter-wave point-to-point and point-to-multi-point wireless may have their applications, but their latency of 5-10 ms may be too much for real-time applications and voice—not to mention licensed spectrum is costly and unlicensed spectrum is very risky due to interference issues.

 

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Aviat Advanced Microwave Networking Seminar: DC Style

Microwave Networking seminar hosted by Aviat Networks in Washington D.C. Sept 2012

The Microwave Networking seminar hosted by Aviat Networks in Washington D.C. in Sept 2012 had a large turnout of attendees who listened to speakers present on wireless security, MPLS, Carrier Ethernet and other topics of interest to the backhaul community.

Aviat Networks recently completed the latest in its Technology Seminar series on microwave networking with a two-day event in the Crystal City area of Washington D.C. One observer noted attendees were particularly interested in hearing more about security of wireless backhaul systems and how to make a choice between using IP/MPLS or Carrier Ethernet.

The seminar was packed to capacity with more than 100 attendees from organizations that included various federal government agencies, utility companies, public safety organizations and mobile operators. These seminars focus solely on issues relevant to microwave deployments, related technology, regulatory issues, and deployment considerations—with no product pitches.

Attendees took advantage of an agenda that covered a wide variety of technology topics, including microwave-focused sessions on capacity, Ethernet QoS and OAM, IP/MPLS, security and strategies for lowering the total cost ownership of microwave networking. The highlight of the seminar was again Dick Laine, longtime Aviat Networks principal engineer, who spoke at length about Microwave Path Engineering and designing links using Adaptive Modulation. Dick is one of the foremost authorities in the U.S. on microwave planning and path design, and some attendees travel long distances just to hear him speak and share his experiences of more than 50 years in the microwave networking business. (If you’ve never heard/seen Dick present, register for his free Radio Head Technology Series).

Aviat Networks also welcomed special guest speakers from the NTIA, Comsearch, CommScope, Tellabs and LTI DataComm who graciously contributed their time and effort to provide a deeper understanding for attendees on their topics of expertise.

Keep a lookout for details of the next Technology Seminar that may be coming to a city near you! Or if you would like to be notified directly when our next microwave networking seminar is scheduled, please complete this form.

Stuart D. Little
Director, Product Marketing
Aviat Networks

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‘The Cloud’ and What it Means for Wireless Technology

Cloud

Image via Wikipedia

The cloud is an all-encompassing thing that’s actually been around for a while (e.g. distributed computing, Network Attached Storage). Most of it exists today in the enterprise but is being pushed to the Internet and rebranded “The Cloud.” This affects three wireless networking segments: consumers (e.g., you, me, mom, dad), Internet providers (e.g., mobile operators, ILECs, CLECs) and wireless solutions vendors (e.g., Symmetricom, Aviat Networks).

For consumers, it represents the ability to store information—pictures, music, movies—virtually and access them wherever we go from devices of our choice. No longer do we have to worry about backing up smartphones, tablets or laptops. The downside is that this magic is going on in the background all while your data caps are being reached. So, watch out….

On the mobile operator side, this will represent a substantial increase in bandwidth used. In addition, bandwidth usage starts to become more symmetrical as more uplink bandwidth is utilized while uploading to the cloud. This also means more frequency consumption on the RAN-side as subscribers stay “on” more often. Operators need to figure how to get users off the air interface as quickly as possible. This calls for greater throughput and potentially much lower latency. Trickling data to end users compounds the air interface problem. For the most part, subscribers won’t realize what’s happening and data caps are more likely to be reached. This translates into either more revenue and/or dissatisfied customers. Clearly, operators must monetize transport more effectively and at the same time provide more bandwidth.

Lastly, for wireless solutions vendors this translates into increased sales of wireless equipment to ease the sharp increase in bandwidth consumption. This also translates into more intelligent and robust network designs (e.g., physical and logical meshes, fine-grained QoS controls) as subscribers rely more on network access for day-to-day activities. As for the cloud in general and the overall effect:

  • Traffic starts to become more and more symmetrical (i.e., photos and videos automatically upload and then downloaded to all individual peer devices (e.g., your iPhone video uploads to the cloud and then syncs to your laptop and iPad)
  • Lots more bandwidth will be used. Today, content drives bandwidth demand (e.g., you open a browser and connect to a website, you launch your Facebook mobile app and upload photos). Tomorrow, those activities will happen automatically and continuously
  • Over the Air (OTA) updates to the phone are now downloaded over Wi-Fi or 3G/4G networks. Seemingly, updates are the only things that have changed, but it still amounts to about 150 MB per phone per update—another bandwidth driver
  • More prevalent use of video conferencing—low latency, sustained bandwidth demand

Therefore, the amount of bandwidth consumption will rise dramatically this September when Apple releases iOS 5 and iCloud. Android has already driven much bandwidth demand, but it’s not nearly as “sexy” as what Apple is releasing for its 220 million users—or alternately total iOS devices: iPod touch, iPad, iPhone). It’s more than just bandwidth—it’s quality, reliable bandwidth where QoS and Adaptive Modulation will play significant roles—of this, I’m certain.

At a recent TNMO event they were talking about LTE-Advanced and leveraging the cloud for virtual hard drives. Imagine, no physical hard drive in your computer. Laptops are connected via 4G wireless/5G LTE wireless to a cloud-based hard drive, equating to lots and lots of bandwidth plus stringent latency requirements….

Steve Loebrich
Director of Product and Solutions Marketing, Aviat Networks

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