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Wireless Systems Design

The Bigger The Better? Or Do Good Conferences Come In Small Packages?

LTE, WiMAX, femto cells, backhaul and more . . .

The wireless industry, especially the cell phone sector, changes so fast that if you don’t continuously monitor changes, you will invariably be left in the dust. Conferences are a great way to stay abreast, but the effectiveness varies from gala to gala. The biggest wireless conference is the Mobile World Congress (MWC) held in Barcelona every February. With over 1800 vendors and 55,000 in attendance it is a handful. The same can be said for CTIA, the second largest conference of its kind with over 40,000 in attendance and another 1200 or so vendors.

Both events offer so much that even in all three or four days they’re open you’d be lucky to see just a small percentage of what’s available. There’s fascinating and useful stuff out on the floor, but unless you specialize and focus you won't get your money's worth. I attended both and came away with a great update on most sectors of the business, but I felt frustrated that I could not cover more.

Good Finds
If the flash and polish of blue-chip events isn’t to your tastes, there’s always a flurry of smaller but wonderful exhibits to behold—if you know where to look. If you want a conference with fewer exhibits and nearly 100% discussions and panels, the Next Generation Networks (NGN) and Basestations Conference I attended in Bath, UK last week is great. Sponsored by Avren Events (, the conference has hundreds of attendees and exhibitors. Instead of being on your feet all day at events like MWC and CTIA, you spend most of your time sitting through lots of up-to-the-minute keynotes, talks, and panel discussions from top industry personnel who know what is happening. Here are the highlights and a summary of some of the key trends I heard.

The opening keynote was by Chris Fenton of Telefonica O2. He updated O2's current status as a carrier in the UK and elsewhere. The big trend is the huge increase in data usage on cell phones, texting, email, Internet access, video and others. O2's data usage was up 26% over last year. Another key trend is flat rate pricing in data usage. This has made it more affordable to do the various data applications and most carriers are going to it. Fenton also sees 5 billion subscribers to mobile TV by 2010. And he believes that femto cells, those small home basestations, will not only improve cell phone voice coverage at home, but they will also serve as broadband portals for handset applications that will give not only greater reliability but also high data rates.

David Tansley, a partner at Delloite, talked about fixed mobile convergence (FMC). He said that there has been lots of talk about this potential merging of mobile handsets and wired desk phones, but very little action. He believes it is not a market now, but that interest is growing and it could blossom in the future as more enterprise employees become mobile or work at home. Right now it is a solution looking for a problem. The goal is for employees to have a single handset with VoIP over LAN as well as cellular service. Companies have found that, ironically, VoIP over WLAN requires more APs and therefore much more actual wiring. One potential solution is low power picocells in the enterprise, thereby eliminating most WLAN wiring problems.

Denis Fauconnier of Alcatel-Lucent gave an update on top-down design long-term evolution (TDD-LTE). This is the time-division duplex version of the 4G technology LTE. The LTE standard—mainly a FDD technolog—is near completion and it now includes a TDD option. Most LTE is expected to be FDD with paired spectrum (5-, 10- or 20-MHz bandwidth). China is planning to use TDD-LTE and others are considering it because it allows the use of multiple-in multiple-out (MIMO) and beamforming antennas that are less possible with FDD. Both of these options can give greater range, interference reduction, and higher data speeds that can in turn lead to fewer LTE cell sites that can greatly reduce CAPEX for 4G. Not to mention the fact that spectrum usage is cut in half and femtos are easier to implement.

Rupert Baines of picoChip gave an interesting presentation on basestations. PicoChip makes specialized DSP processors for SDR and their focus is the basestation/infrastructure market for cellular as well as WiMAX. He talked about the evolution of basestations and the current cellular infrastructure from a circuit switched telephone architecture to a full IP implementation. He said that eventually with full 4G implementation basestations become routers. He also said that 3G data subscriptions have now exceeded fixed broadband subscriptions. Fixed voice service is in decline but data subscriptions are more than compensation for most carriers. Baines feels that in the future the handset will be the more common broadband connection. Fixed broadband connections have slowed in growth, totallying about 400 million today in cable, DSL, and other configurations. There will be fewer if any new copper installations for broadband surface, mainly fiber for new coverage. He sees the future for smaller cheaper basestations that give higher data rates and better coverage. And that includes femto cells.

David Bubley of Disruptive Analysis gave an interesting presentation on the good, bad, and ugly. On the current hot list were HSDPA 3G, PCs with flat-rate 3G dongles and data cards, openness, back haul upgrades, the Web on phones, green technology, and GPS/navigation applications. Technologies of lesser note were things to come like HSPUA, femto cells, LTE, IMS, mobile WiMAX VoIP over 3G, mobile advertising, and Google in mobile. On the definitely NOT HOT list were metro WiFi, the death of WiFi, the death of fixed-line, UMA dual mode phones, corporate femtos and 3G-embedded in PCs. Mobile TV didn't show up on his lists but he did say that it was not going too well now but it was moving slowly due to high infrastructure and handset costs not to mention content. He sees a good future for femto cells and asked the question about whether 3G dongles and data cards would kill WiMAX.

Richard Davies of Alcatel-Lucent gave an update on LTE testing under what is called the LTE/SAE (System Architecture Evolution) Initiative (LSTI). This process has driven the operators and vendors of LTE equipment. Major testing will probably wrap up in late 2008 or early 2009 with customer trials in 2009. First implementation in basestations and handsets is not expected until 2010. Lab test show that with 1x2 single-input multiple-output (SIMO) downlink data rates have hit 88.7 Mb/s. Rates of 172.8 and 326.4 Mb/s have been achieved with 2x2 and 4x4 MIMO. Much lower data rates are expect in the real world but the potential is really there. Uplink rates are roughly half the downlink rates.

Tim Ryan of Optichron talked about the need for broadband power amps for basestations. There is need to maintain the GSM/EDGE capability while providing for 3G technologies like UMTS WCDDMA and HSDPA. Multi-carrier amps are the solution. Another need is for an increase in efficiency as PAs account for a huge portion of the power drain in a basestation. Optichron's digital pre-distortion linearization chips provide one good solution.

Dr. Mehmet Unsoy, a partner at Cartegenba Capital, discussed how to position WiMAX as complementary to LTE. Both LTE and WiMAX are very similar because both are based on OFDMA but are not compatible. LTE is FDD while WiMAX is TDD. Because WiMAX is available right now and appears to be less expensive overall, it may be the best solution to new wireless services in developing countries with little or no wired service.

He also gave some interesting stats. There are approximately 300 million fixed broadband users worldwide, and it’s expected to grow to about 600 million in three or four years. There are 3.3 billion mobile users now and there is already 100%+ penetration in 59 countries. WiMAX will undoubtedly play a role in new broadband expansion when Clearwire and Sprint decide to roll out their services (XOHM at Sprint). The WiMAX Forum projects 133 million WiMAX users by 2012. Dr. Unsoy suggested that WiMAX had the potential to become one version of the LTE standard.

Paul Jeffery of Samsung also discussed WiMAX. He said that it had major advantages over HSDPA because it is faster and has a simpler IP architecture. He also pointed out that WiMAX became an approved 3G standard by ITU.

A panel on LTE versus WiMAX offered opinions all over the place. Some said they were directly competitive; others were not so sure. Both use OFDMA and will eventually have both TDD and FDD options. The bottom line seemed to be that WiMAX was here now and would be best if you want to get to market sooner with a wireless broadband service. It should work great with laptops but the panel said it probably was not that much cheaper than LTE. WiMAX will not find major use as a cell phone service using VoIP as most of the major cell phone carriers had already committed to LTE for future expansion.

There were a good number of sessions on femto cells. Per Emanuelsson of Access Services said that the big issue here is off loading the main network by using femto cells in homes. The femtos use a home broadband connection like cable TV or DSL so do not impact the back haul of base stations. This lowers OPEX as the user pays for the backhaul. They do not solve all problems especially in the enterprise where the larger capacity picocells and distributed antenna systems are more common.

Malcom Latham of Motorola compared and contrasted femtos and UMA or unlicensed mobile access that puts VoIP Wi-Fi in a regular cell phone. This enables the single phone option, no wired phone, just wireless. Femtos do produce a cost savings to the carriers as it limits the need to add new cell sites or expand existing one. There some femto issues yet to resolve such as frequency assignments and frequency reuse. And will femtos replace Wi-Fi home nets as the broadband service of choice?

Will Franks of Ubiquisys said that femtos are a problem because they could cause interference with existing nearby cell sites and neighboring femtos. He suggested that a femto needed to be a cognitive radio that is aware of its environment, and automatically scans for nearby femtos and cell sites then adjust the frequency of operation and power output to minimize interference and optimize the link. Franks said that femtos will adopt the popular TR-069 management standard developed and used in DSL systems.

Stuart Carlaw of Mobile Wireless quoted some wireless stats from ABI too extensive to present here. Essentially they say that we use cell phones inside more than we do outside, specifically, 83% in buildings, 4% mobile and 13% outside. That is why in-building coverage is so important to a good connection. Distributed antenna systems (DAS) still dominate in large buildings and large venues but picocells are used over smaller areas. Femtos will provide the in-building access in homes but not in small companies. One estimate is that femto installations will ramp up in 2010 with a projected size of 90 million units by 2013.

A panel discussion on femtos concluded that femtos will not replace DAS or picocells in buildings. It also remains to be seen if VoIP over Wi-Fi will get replaced by femtos. Femtos are competitive with Wi-Fi in homes for sure.

One of the biggest issues facing carriers is cell-site backhaul. As data usage grows, backhaul capacity needs to increase significantly. Most backhaul in the U.S. is by T1 lines. More T1 lines can be added as needed but at a huge cost so other approaches are being sought. Roberto Micali of Telcom Italia, said that backhaul needs to go to a packet based technology. Some sites do use packet asynchronous transfer mode (ATM) but others still use SDH, a fiber based technology. One solution being widely considered is carrier Ethernet using MPLS (multi-protocol label switching). Another choice is PseudoWire a technique of using virtual circuits in a packet network. Pseudo Wire emulates the service of ATM, frame relay and others over a packet network. Overhead and latency are not a problem with these approaches.

David Chambers of Amdocs said that management of backhaul was the key to success of mobile broadband service. There has been a 100% growth in mobile broadband at some carriers over the past year. There is a clear transition from a voice dominant use to a data dominated usage on handsets. Backhaul congestion is growing and is responsible for about 70% of all outages. Current backhaul capacity of a cell site was about 6 Mb/s in 2007, 16 Mb/s in 2008 and expected to be 40 Mb/s in 2009. U.S. carriers still use T1 lines but microwave links are being considered. Microwave is the predominant backhaul method in Europe while fiber cable is the most common in Asia. Femto cells can have a significant effect in eliminating the backhaul problem as about 40% of data calls are made from home.

Lance Hiley of Cambridge Broadband Networks indicated that his company has a point to multipoint (PMP) system that uses statistical multiplexing to help solve the backhaul problem. It makes better use of the spectrum, uses less radios and half the number of antennas as used now in microwave backhaul.

Brian Modoff of Deutsche Bank had a wide range of interesting facts and figures. He also reiterated the great growth in data services as 3G and Internet access has come to the handsets. Here is a short summary of some of his data.

  • The drivers of increased data usage will be mobile TV, open systems, banking, payments, mobile Internet, mobile ads, and M2M.
  • Coverage is still a big issue with mobile TV.
  • Software was becoming the most important factor in many apps, especially middleware.
  • HSDPA 3G is widely available and is expected to be about 80% of all 3G.
  • The continuing 3G rollout will slow LTE adoption and delay rollouts to 2015.
  • Carrier Ethernet IP will be widely adopted for backhaul.
  • Increase in the number of smart phones like BlackBerry and iPhone.
  • More data, less voice.
  • Slow migration to LTE. 2.1-GHz LTE is not so suitable for femtos.
  • Analog TV on handsets is popular in Asia where long whip antennas are used to watch local stations.

Julian Hildersley of Nujira pointed out the importance of better efficiency of power amplifiers (PAs) used in basestations. With the cost of electricity increasing, OPEX can be cut by going to more efficient PAs. New amplifiers using the two amp Doherty method are becoming popular. His new product is a dc-dc converter used as a modulator on the dc supply to track the modulation. It improves efficiency from about 30% now to over 40% representing a huge savings.

A panel covering the latest wireless standards provided a good update. 3GPP should wrap up the LTE standard by the end of 2008. Operators want LTE femto cell specifications as part of LTE and that is expected to be implemented.

The Open Basestation Architecture Initiative (OBSAI) has made good progress toward an overall basestation architecture for the future. It is modular and defines all the important interfaces. This will provide flexibility in sourcing modules and components.

As for WiMAX standards, the WiMAX forum is now testing and certifying Wave 2 components that employ MIMO. A future release of the standard should add an FDD and 20-MHz bandwidth options. A future version called 802.16m is being worked on. Also known as WiMagic or WiMAX 2.0, it will be backwards compatible with current mobile versions. 16m is expected to leap frog LTE in terms of performance when it is completed around 2010. It was also pointed out that the Asian version of WiMAX called WiBro is identical. There are currently 19 WiMAX chip vendors.

Here are some highlights of the exhibits at the conference. AMCC showed new versions of their PowerPC based processors. Their 405EX is optimized for WiMAX and Wi-Fi. The 460GT is targeted at infrastructure applications. Nujira showed their High Accuracy Tracking power modulators that help make basestation PAs more efficient. Optichron showed their digital pre-distortion products that also help improve PA efficiency. Rakon exhibited their latest in TCXO and OCXO crystal oscillators for base station use. Ubidyne introduced their digital radio system that embed multiple DSP radios into the antenna itself. Xilinx presented their FPGA solutions for DSP that can optimize basestation designs.

The next NGN/Basestation conference is in Dallas December 3-5, 2008. Avren Events has the details at

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