AIRCOM International specializes in end-to-end radio network design solution for wireless networks. Their 12 years in the wireless industry has given extensive experience with 2G, 2.5G and 3G radio network design, nominal planning, radio propagation modeling campaigns, frequency/SC planning, neighbor list and parameter specification/planning/IRAT, traffic engineering, indoor solutions and roll-out planning, project management and more.

 

AIRCOM’s radio planning consulting group provides know-how and expertise in all current and emerging major wireless technologies, including: WiMAX and LTE, UMTS/HSPA, GSM/GRPRS/EDGE and CDMA/1xRTT/EvDO.

 

Recently Yours Truly spoke with Ian Goetz, Director of Core Network Solutions (News - Alert) for AIRCOM, seeking some tips and or comments about what’s been happening lately regarding WiMAX vs. LTE, increasing backhaul bandwidth demands and femtocells.

 

“AIRCOM was founded in 1995,” begins Goetz, “It’s a British company that has majored over the years in radio planning, performance, optimization and so forth. It has a products business with tools for radio planning, performance management and optimization and configuration management. It also has a consulting business that aids operators with the planning and optimization of their networks.”

 

“We set up a new strategy about two or three years ago to start looking more at end-to-end type of solutions rather than just purely radio-focused, “says Goetz. “We look at backhaul, and the evolution of the core network as IP becomes more pervasive in the deployment of wireless systems. As a result, I was brought in by our current CEO about two years ago to ‘put the meat on the bones’ of that strategy and start developing the first product solutions around that. I’m responsible for a new tool we’re developing which will look at the multi-layer, multi-domain network planning of next-gen wireless systems and also the connection of legacy systems to those new networks.”

 

“As far as WiMAX vs. LTE,” says Goetz, “I wish people would compare apples with apples. The WiMAX of the moment is the 802.16e mobile version, and that’s one radio technology. When you compare WiMAX to LTE, you should be talking about Gigabit WiMAX 802.16m, and at that point WiMAX can actually in theory plug into the same evolved packet core that LTE can plug into. The main difference is in the radio modulation that’s used in one direction in the case of 802.16m.”

 

Goetz says that people keep comparing WiMAX to 3GPP systems, which are criticized for being heavily specified, but actually 3GPP is a whole system; it has all the technology you need to launch a telecom service, from the device through to the core network services and the interconnect.

 

“WiMAX gives you an Access Service Network Gateway (News - Alert) [ASN-GW] – which acts as a layer 2 traffic aggregation point within an ASN – and a Connectivity Service Network [the CSN provides connectivity to the Internet, ASP, other public networks, and corporate networks], but then WiMAX leaves the rest up to you. That’s possibly why WiMAX has found its niche as a competitor with DSL broadband in fixed network replacement, with a few notable exceptions such as Sprint (News - Alert) and Clearwire. Broadly speaking, outside of the U.S., WiMAX is being used mainly where operators don’t have copper in the ground and they can’t run DSL. People are using 802.16e mobile, not because they necessarily want to make it mobile, but because they want to get the benefits out of the robust multi-path capability of the radio interface, so they can offer a better quality service.”

 

“Although people didn’t originally think of LTE for voice, you actually have two solid propositions for voice call network,” says Goetz. “First, there’s the IMS [IP Multimedia Subsystem] approach or the Unlimited Mobile Access [UMA]-derived approach called VoLGA [Voice over LTE via Generic Access] which enables mobile operators to deliver mobile voice and messaging services over LTE access networks based on the existing 3GPP Generic Access Network [GAN] standard. Again, you’re getting a system that’s designed from the handset to the point of interconnect with other networks to provide voice calls. But what you get with WiMAX is a ASN and a CSN, as I said previously. On top of that the operator must provide its own voice solution. I worked a vendor up until about two years ago involving a major WiMAX deployment in Pakistan. They needed a core network for VoIP. At the time we provided the world’s largest IMS deployment for commercial VoIP. But if you were then to take those WiMAX devices and attempt to use them in another network, that core network isn’t there, and so the roaming capability would not be there either, which means that you wouldn’t have a seamless, wireless voice solution for customers. So 3GPP and VoLGA on one side offers a specified solutions end-to-end, while WiMAX is effectively an access network, and you have to worry about the call running on top.”

 

Goetz adds, “What you have to take into account with LTE is the migration from the existing 3GPP network where you have effectively a C7-based core switching network even with the split architecture Mobile Switching Center [MSC] servers and media gateway, and you’ve got evolve that into either an IMS or VoLGA environment. Hopefully operators will standardize on one of those, and predominantly a Session Initiation Protocol (News - Alert) [SIP]-based technology, and still have legacy interconnect to other networks still utilizing the older technologies. LTE has a good foundation; there are still a few issues to solve, but it’s better placed from an end-to-end standard with which to deal with these issues.”

 

Goetz sees the future of AIRCOM growing into end-to-end solutions in terms of both tools and consulting services: “The cornerstone of that is our ability to plan the roll-out of the migration of multi-layer, multi-domain, IP-based networks, as operators deploy more 3G High-Speed Packet Access [HSPA] migrating to the IP Radio Access Network [RAN] standards one tunnel, and then move on into LTE. Then we’ll be able to offer them multi-vendor and multi-vendor OSS capability to be able to plan and optimize those networks.”

 

When asked about bandwidth requirements for next-gen wireless, Goetz muses, “There are always arguments over what the peak bandwidth of any new transport technology. A large base station in a GSM network consumes about half of a 2 megabit circuit on the backhaul, which is perhaps two-thirds of a T1. If you then look at a combined 2G/3G cell, you might see 1.5 to 2 T1s or E1s on the backhaul. Now, when you migrate to HSPA that goes up to probably 8 to 10, so you get a massive surge in backhaul bandwidth and the architecture at the core requires you to backhaul everything to the central office switch site before it goes into the core node. If you then migrate to LTE, then obviously there’s another increase in the required bandwidth. There is the ability to flatten the IP architecture, moving some of the core capabilities to the edge of the network so that you can do what most broadband networks already do, which is to have a contended system where you can aggregate data traffic according to its priority. That way you can save hauling everything from some central point before you provide it to its destination. It’s as if you had an LTE picocell serving an office block on the floor of a major office in one of the American cities. A lot of the LTE data in that office block would be going into the corporate LAN, and so it would be silly to backhaul all of that data from the office block to the central office just to haul it all the way back again down a VPN tunnel and into the corporate LAN. So LTE provides you the opportunity to start moving some of these key functions much closer to the edge. You can do that with HSPA as well, it just requires the mobile operators to be willing to examine building their networks slightly differently that they do now, and to potentially use some new vendor technology rather than necessarily sticking purely to the large vendor portfolios.”

 

 

Lost in all the saber-rattling about the virtues of WiMAX versus LTE is the fact that the radio element of the two technologies are very similar. Both use similar hardware and infrastructures. This similarity begs the question: Just how hard would it be to migrate a fully functioning WiMAX network to LTE?

 

“Many of the WiMAX hardware manufacturers already are pitching that they can migrate their equipment to be LTE compatible and/or ride the same volume curve,” says Goetz. “The latest base stations, such as the RBS6000 from Ericsson, use software-defined radios that accommodate any technology that an operator wants to deploy. Given this flexibility, since the price of the hardware is a greater driver than the software in new technology rollouts, operators could chose to load WiMAX now in strategic, targeted instances, knowing that they can migrate those network components to LTE later. Also, operators that are currently deploying a WiMAX network with new base stations have the comfort of knowing that they could evolve to LTE down the road.”

 

The point is that Phardware manufacturers have learned many lessons about LTE from their WiMAX technology development and are eliminating the “one or the other” argument between the two technologies.

 

 

In the case of LTE, one of the challenges of LTE deployment is the mere fact that the frequency at which it is deployed (i.e., 700Mhz vs. 2.6GHz) can dramatically affect the number of base stations required to provide coverage similar to that of a current GSM network. The laws of physics apply, and operators will need to install many more cells to ensure the proper level of coverage. 

 

Unfortunately, radio resource management techniques such as MIMO (Multiple-Input And Multiple-Output) and other smart antennae strategies will not solve this issue.

 

Bottom line: For LTE, operators will need to deploy thousands of more cells across the U.S. just to provide adequate capacity and coverage in urban and suburban areas. Given the state of the capital markets, operators most likely will not have the funds to purchase and deploy such a large number of cell kits, limiting the scope of initial LTE rollouts.

 

“Operators are left with a choice: spend their money upgrading their cells to intermediate technologies such as HSPA+ or taking the plunge into LTE,” says Goetz. “U.S. operators have already announced they are rolling out LTE at 700MHz, but that rollout will present certain challenges, such as the ease with which that frequency easily travels through building walls. This will make any attempt at pico/femtocell capacity planning a massive challenge. To find out how operators will rollout LTE at 700 MHz in the U.S. given this challenge.”

 

 

Because an LTE network requires approximately twice the number of base stations as a 3G HSPA network to provide the highest bitrates LTE can offer on the same size area, operators will need picocells and femtocells as a cost-effective alternative to more expensive macro cell sites, especially when it comes to delivering LTE to where subscribers will use it the most: indoors.

 

Operators in the U.S. are moving cautiously with trials. However, progress toward femtocells being a mass-market proposition is incremental and slow-moving. Why?  Perhaps the answer lies with the operators.

 

“The rollout of femtocell technology carries with it a variety of complex and never-before-seen challenges for an operator on a network planning and management level,” says Goetz. “With a mass consumer rollout of femtocells, an operator potentially faces tens of thousands of new miniature 3G sites going live over a span of days or weeks. These new sites could be anywhere from a single femtocell in a house in the country to 50 or more units in a single apartment building, generating multiple and overlapping 3G signals. From a radio perspective, such a scenario creates a bubble of radio interference as multiple femtocell signals “lead” into and disrupt the macro network, impeding performance and impairing the customer experience.”

 

And of course, various stresses and strains that a femtocell layer will place on a network architecture. As consumers plug in their femtocells, network managers will have to confront sudden spikes in bandwidth demand across different parts of their network at different times and factor in multiple choke points along the network “path” to the core.

 

“Although femtocells take traffic off the macro network, they will still pull more bandwidth from the operator’s core network resources,” says Goetz. “When combined with their arbitrary dispersal and activation by end-users, along with the fact that operators are no longer in exclusive control of their own network planning, the impact of femtocells on a network’s entire capacity resource and performance is fraught with peril.”