Posted 05/15/2000
Looking for a Winning Hand
Broadband
Wireless Vendors Get Second Chance to Deliver Low Cost, High Bandwidth
By Charlotte Wolter
Don't bet against broadband wireless, say industry observers. The technology might just come through yet.
Broadband wireless, more formally known as local multipoint distribution system or LMDS, has been struggling to come up with a winning technological hand in the local loop game. It anteed up with promises of a low-cost technology that could deliver multiple megabits of local loop bandwidth with no need to string expensive fiber or pay Park Avenue rents for ILEC copper.
But the products have seen delays and some outright failures. While one manufacturer believes "we're really about where we expected to be," there has been a sense of uncertainty about the technology hovering over the industry like a cloud of cheap cigar smoke for more than a year.
Also poised to see important deployments in the United States is MMDS, a technology for lower microwave frequencies that may be a significant entrant in the consumer Internet access business.
LMDS is used generally to refer to broadband wireless services in the microwave frequencies ranging roughly from 24 GHz to 40 GHz, although technically only the frequencies licensed in the United States at 28 GHz and 31 GHz are officially named LMDS. The LMDS frequencies typically allow a shorter reach--from one to three miles--than those lower on the spectrum, but the abundant bandwidth at these frequencies gives room for transmission of large amounts of data. LMDS frequency blocks as large as 1 GHz have been licensed in the United States. The LMDS range of frequencies is being exploited worldwide primarily for business data communications, including IP voice.
MMDS refers to frequencies at approximately 2.5 GHz to 3.5 GHz. In contrast to LMDS, transmissions in the MMDS spectrum can reach up to 50 miles, though 20 to 30 miles is the norm.
LMDS: Getting Started?
The overriding issue in the LMDS arena has been the slow pace of deployments. Despite the billions of dollars spent for spectrum and overwhelming demand for bandwidth from customers, relatively few systems have actually been deployed. The reason: Vendors have not been able to get equipment to perform at the levels operators feel they need to be able to support competitive businesses.
The industry started with point-to-point communications, in which each customer has its own receiver set to a certain bandwidth. The plan was to start with point-to-point and then move up to point-to-multipoint systems. With point-to-multipoint, it is possible to deploy just one receiver per building. Signals to the individual customers in the building are multiplexed over the air into a single transmission.
The next refinement was to add time-division multiple access (TDMA) technology rather than frequency-division multiple access (FDMA). With FDMA, each customer is assigned specific frequencies or channels within a multiplex. The channels remain assigned to the customer whether it is used or not. This means the service provider is unable to get maximum use from the spectrum, and it is difficult to give customers higher bandwidth on demand.
With TDMA, each customer's bandwidth can change from moment to moment as needed. The service provider can sell a service with a guaranteed minimum bandwidth as well as the ability to send large bursts of data if needed. It maximizes the system's capacity because there are no frequencies sitting idle, and it is more responsive to the bursting nature of data and Internet communications.
"That is what will open the whole world for us," says Steve Cooper, executive vice president for broadband wireless service provider NEXTLINK Communications Inc. (www.nextlink.com), speaking at the Broadband Wireless World Forum in San Francisco in March.
A variation on point-to-point, a consecutive point-to-point system, allows an operator to deploy a virtual ring much like fiber, but with lower bandwidth. It also provides some protection in the base of failure of one node. This technology, in which Triton Network Systems Inc. (www.triton-network.com) is the most prominent vendor, has found success as a solution for office parks or clusters.
The issue has been that available equipment has not delivered on several levels. "Point-to-point works well now, but we need more capacity in the radios we get from manufacturers," says Cooper. "We implore the manufacturers to deliver the bandwidth we need."
NEXTLINK, like other leading LMDS service providers--such as Advanced Radio Telecom Corp. (www.artelecom.com), Teligent Inc. (www.teligent.com) and Winstar Communications Inc. (www.winstar.com)--has been testing a number of vendors to determine whether their products will perform to the company's specifications. After months of trials, NEXTLINK qualified just three vendors earlier in 2000--Digital Microwave Corp. (www.dmcwave.com) for point-to-point systems, Nortel Networks Corp. (www.nortelnetworks.com) for point-to-multipoint systems, and Triton for consecutive point-to-point systems.
There were numerous difficulties with other providers that prevented their selection. "They may have delivered the bandwidth, but the product was not stable," says Chuck Sackley, senior vice president of national account sales for NEXTLINK. "Or they may not have been able to deliver to multiple points within a sector." Typically LMDS base stations transmit with four 90-degree sectors. Frequencies can be reused in sectors that are not adjacent.
Even NEXTLINK's choice for point-to-multipoint technology, Nortel, went through several rounds of testing before being accepted. And, Nortel is still in the development phase of its TDMA solution. NEXTLINK is using the Nortel FDMA technology, and the TDMA version went into the company's labs for testing in late March. Nortel is delivering full OC-3 (155mbps) capacity per sector, Sackley says, and OC-12 (622.8mbps) capacity is anticipated with TDMA technology.
For vendors, there is the question of how big of a bet to place on the untested LMDS market. "There are 20-plus vendors, and they all know what they need to do," says Sackley, "but if they all invested heavily [in technology development], it could be ugly if only a few win. So they iterate their investments."
Among those that will show technology at SUPERCOMM 2000 is Newbridge Networks Corp. (www.newbridge.com), which has had TDMA in a point-to-multipoint system since August. The company has won several customers overseas, but has not had a customer among the Big Four--Winstar, Teligent, NEXTLINK and ART--in the United States yet.
Hughes Network Systems (www.hns.com) Broadband Carrier Networks group has point-to-multipoint technology at 24 GHz and 38 GHz, but does not plan to implement the technology for the U.S. LMDS frequencies of 28 GHz and 31 GHz until late 2000. "There is no large anchor customer yet for 28 GHz," says Doug Tanner, sales executive.
Lucent Technologies Inc. (www.lucent.com) is working with Netro Corp. (www.netro-corp.com), an OEM provider of broadband wireless equipment. Lucent plans an announcement at SUPERCOMM, but did not have details available at press time. Netro recently has shipped point-to-multipoint product in the 28 GHz range for customer trials at several unspecified locations in the United States.
Motorola Inc. (www.motorola.com), which markets products in the 28 GHz range under its SpectraPoint Wireless LLC (www.spectrapoint.com) joint venture with Cisco Systems Inc. (www.cisco.com), added point-to-multipoint solutions for the 10 GHz, 26 GHz and 39 GHz frequencies in late March through an agreement with Netro.
Siemens Information and Communications Networks Inc. (www.icn.siemens.com) has a new partnership with Floware Wireless Systems Ltd. (www.floware.com), whose point-to-multipoint system is uniquely capable of operating at 26 GHz and 3.5 GHz, the European LMDS and MMDS frequencies, respectively. The system has a customer in FirstMark Communications Deutschland GmbH (www.firstmark.net), which is establishing a nationwide network.
Alcatel (www.alcatel.com), which had been the subject of rumors because of missed deadlines for equipment delivery, is shipping in the United States, says John O. Lilly, Alcatel's senior director of fixed wireless marketing. "We had a few missteps, but now we have a point-to-multipoint system that is not just a migration of our point-to-point system," he says. "We are now eager to get providers interested in trialing the system." The company had its first field trials in the United States at the end of March. The system uses time-division multiplexing (TDM) technology downstream and TDMA upstream, with full dynamic bandwidth allocation for efficient use of spectrum.
A new entrant in consecutive-point technologies is the FibAir product line by Giganet Wireless Inc., a subsidiary of Giganet Ltd. (www.giganet-corp.com). The company's technology can be used to create either rings or point-to-multipoint links at 100mbps and above, and is offered at 26 GHz, 28 GHz and 38 GHz. The company has Winstar as a customer for its 38 GHz equipment, and NTL in the United Kingdom for 26 GHz. Giganet is aiming for a "sub-OC-3 market," says CEO Shraga Katz, who believes that segment will constitute as much as 80 percent of the wireless broadband customer base.
Even as it appears that full-blown commercial technology is finally ready and will be shown at SUPERCOMM, there are new technologies emerging that could present viable alternatives to existing systems.
A number of startups are showing equipment based on time-division duplex (TDD) technology. In most broadband wireless systems, the upstream and downstream traffic is separated into channels, with specific bandwidths reserved for upstream and downstream. However, these channels are not easily changed, and the system does not readily adapt to changes in the ratio of upstream to downstream bandwidth.
With TDD, the system divides the upstream and downstream traffic by time slots and switches back and forth from upstream to downstream over all channels. The traffic flow can be switched back and forth in microseconds, and in "adaptive" TDD can be adjusted as traffic demands, providing a very flexible allocation of bandwidth to upstream and downstream.
The two leading providers of the technology are Ensemble Communications Inc. (www.ensemblecom.com) and Wavtrace Inc. (www.wavtrace.com). Both companies are likely to show "adaptive" TDD at SUPERCOMM, a capability that had been announced but was not delivered at last year's show. Wavtrace in March unveiled its PTM2000 point-to-multipoint system, which can support 20 carriers and up to 28 remote terminals per carrier for a whopping 4gbps of throughput.
There is a significant standards-setting activity under way for the media access control (MAC) and physical layers of LMDS systems, under the auspices of the IEEE 802 group, which also does Ethernet, wireless LAN and Bluetooth. Roger Marks, chairman of the 802.16 group developing the standard, said there are two competing proposals; however, operating under an accelerated schedule, the group hopes to coalesce on a single solution by May. Once achieved, the standard for these two basic layers of the systems will make interoperability of equipment much simpler and pave the way for multivendor systems, which should also speed LMDS deployment.
MMDS: Year of Deployment?
2000 is the year that may see the first large-scale deployments of two-way MMDS for data and, possibly, voice applications. If the merger of MCI WorldCom Inc. (www.wcom.com) and Sprint Corp. (www.sprint.com) is finalized, the companies are expected to announce technology choices and deployments for the large chunks of MMDS spectrum that both purchased in 1999 by acquiring a number of small MMDS operators.
MCI WorldCom already is conducting a series of field trials that are likely to be the precursors of its final technology and service announcements. The announced cities are Baton Rouge, La.; Boston; Dallas; Jackson, Miss.; and Memphis, Tenn. Technologies in the trials include ADC Telecommunications Inc. (www.adc.com), whose Axity system is being used in Boston. ADC is providing network management, design, systems integration and customer premises equipment for the trial.
In Dallas, MCI WorldCom is conducting a highly anticipated trial of a solution by Cisco and Motorola that uses vector orthogonal frequency-division multiplexing (VOFDM) technology. VOFDM is a new modulation technique that is an alternative to the widely used QAM technology. It helps ensure more reliable transmissions where there are line-of-sight problems, as well as in environments with multipathing issues such as multiple reflections of a signal. Constantin Loudiadis, vice president and general manager of the wireless access business unit at Cisco, characterized the VOFDM as providing high-quality performance in areas such as Dallas "where conventional single-carrier QAM solutions are significantly challenged."
VOFDM is not widely adopted by MMDS vendors' providers, in part because the technology is relatively new. It has also been implemented by Wi-LAN Inc. (www.wi-lan.com), which has claimed that Cisco is infringing on its patent for a technology it calls Wideband OFDM (WOFDM). Also using VOFDM is Malibu Networks Inc. (www.malibunetworks.com) in a product for the unlicensed spectrum bands at 5 GHz.
In March, Wi-LAN, with Nokia Corp. (www.nokia.com), Ericsson Inc. (www.ericsson.com), Sony Corp. (www.sony.com) and several other firms, launched the OFDM Forum to harmonize standards and encourage world frequency harmonization. OFDM also is used in the IEEE 802.11 standard for wireless LANs, which Nokia strongly supports.
One of the questions at SUPERCOMM will be how many of the other providers of MMDS systems, such as Spike Technologies Inc. (www.spiketechnologies.com) and BreezeCOM Inc. (www.breezecom.com), will adopt VOFDM and show it in products. BreezeCOM, which has sold overseas in the 3 GHz to 3.5 GHz range, has a new product for the United States at 2.5 GHz. BreezeCOM has a TDD version of MMDS, with full dynamic bandwidth allocation, and has the VOFDM modulation under consideration.
ADC, however, will show a new "carrier-class" MMDS solution that is compatible with the data over cable service interface specification (DOCSIS) 1.0 standard of the cable industry with extensions for MMDS modulations 16 QAM and QPSK. The compatibility with the cable products helps reduce costs by using components, especially chip sets, which are being manufactured at high volumes. ADC also has widened the frequency acquisition range of its products in order to serve a wide range of MMDS markets. Some MMDS licensing schemes elsewhere in the world use frequencies above 3 GHz, while frequencies around 2.5 GHz are predominant in the United States.
