Posted: 07/15/1999
Wired for the Future
LMDS, MMDS Vendors Upgrading for Data and Voice
By Charlotte Wolter
| Broadband wireless has moved from a quirky outlier of the data and telephone connectivity business to a serious contender as an alternative carrier. |
The world of wireless broadband services has expanded dramatically in the last few months, as service providers such as Sprint Corp., and MCI WorldCom Inc. have feverishly snapped up multichannel multipoint distribution service (MMDS) bandwidth in a play to offer data and voice services.
Combined with the existing efforts around the world in other high-frequency spectra--which range from 10 gigahertz (gHz) to 41gHz--broadband wireless has moved from a quirky outlier of the data and telephone connectivity business to a serious contender as an alternative carrier. At SUPERCOMM '99 in Atlanta, several companies stepped forward to show new products or demonstrate their interest in greatly expanding their lines to meet the demand for transmission in these many frequencies.
In a product plan that shows how diverse the market has become, Ron Fangio, senior director of marketing and strategic planning for the fixed wireless division of Alcatel USA, Plano, Texas, says the company's goal is to have a network solution that can do local multipoint distribution service (LMDS), MMDS and 1900 megahertz (mHz), the global system for mobile communication (GSM) band. That will enable providers to reach small-to-medium-sized businesses with LMDS, the small office/home office (SOHO) environment with MMDS and residential/mobile customers with 1900mHz. "With our 9900 LMDS product, we will build it so that later operators can drop in MMDS and 3G (third-generation mobile) technologies," Fangio says. "It allows service providers to offer different services to different customers with the same network behind the transmitters."
He adds, "CLECs (competitive local exchange carriers) want an end-to-end solution, not boxes."
LMDS
The term LMDS has come to encompass a wide range of frequency bands outside the original 27gHz to 29gHz defined by the Federal Communications Commission (FCC) when it first began licensing what was then called LMDS. Today, high-frequency bands between 24gHz and 41gHz are being licensed all over the world, with a unique frequency scheme for each country.
Also, companies around the world have different strategies for which markets and data types they target. In the United States alone, the two largest customers to date, WinStar Communications Inc., New York, and Teligent Inc., Vienna, Va., have different product strategies.
David Montiel, product manager, Siemens Information and Communications Networks, Boca Raton, Fla., says his company has to take into consideration the fact that "WinStar wants a lot of variety in their services, while Teligent wants a lot of T1s because ... they are doing Internet access over DS-0s [regular phone lines] in buildings."
This has created a challenge for equipment vendors to pick the right spots as they develop products. While it is not exceedingly difficult to change the frequencies transmitted--though it does require some adjustments of the equipment--it is more challenging to be sure the best choices are made for interfaces. For example, most use asynchronous transfer mode (ATM) in the air link, or plan to in the near future. ATM provides bandwidth-on-demand capability and is compatible with the transport networks most systems will access. But base stations will need output other than ATM because service providers need to reach the public switched telephone network (PSTN) and may want to provide a wide range of links to other kinds of networks, including Internet protocol (IP).
| Even with the full 200mHz, the bandwidth could be quickly exhausted if services begin to grow too fast. Therefore, operators are expected to exploit the MMDS capability to broadcast in sectors from a central broadcast tower, with the sectors resembling pieces of pie. |
True point-to-multipoint equipment was shown by a large number of vendors at SUPERCOMM. Most systems will be available by the end of 1999 and some by the end of this quarter. The products shown by most vendors were complete network systems, with customer premises equipment (CPE), radios, interfaces to transport networks and management software.
Small, specialized vendor Netro Corp., San Jose, Calif., has become a market leader, courtesy of its original equipment manufacturer (OEM) relationships with Lucent Technologies Inc., Murray Hill, N.J., which plans to integrate Netro's AirStar point-to-multipoint radios into full network systems. Netro also has direct customers, most notably Formus Communications Inc., Denver, Colo., which has deployed the company's products in Hungary. Netro was the first vendor to market true point-to-multipoint technology.
Alcatel is developing an LMDS system that is backed up by end-to-end networking, featuring technology from recent acquisitions Xylan Corp., Calabasas, Calif., and Assured Access Technology Inc., Milpitas, Calif. The products for the United States will build on a global platform originally developed in France, with the U.S. division adding the appropriate radio frequencies (RF) and telephony interfaces (such as T1). The RF for the United States will be the 28gHz and 31gHz bands, and the company will do special RF equipment for Teligent at 24gHz and Winstar at 38gHz.
The main Alcatel product is the 9900, a point-to-multipoint system, but the company still will supply a point-to-point system for so-called "fiber extension" applications or to give particular customers large amounts of dedicated bandwidth. Fangio says the company's priorities are to reduce the cost of CPE, and to integrate functions, such as routing, into the units.
In the future, Alcatel will add support for voice frequency (VF) circuits to support plain old telephone service (POTS) in addition to its DS-1s, enabling it to serve smaller offices that don't have private branch exchanges (PBXs). That feature will be available in the second or third quarter of 2000. Alcatel also plans to add voice over IP (VoIP) and voice over ATM (VoATM) capability, so CLECs don't need their own Class 5 switch to offer voice services.
Siemens showed its AirNetXpress LMDS product, which it created with P-Com Inc., Campbell, Calif., in development of its point-to-multipoint radio. The Siemens CPE will include interfaces for ATM, frame relay, 10Base-T and T1, and the base station will include an OC-3 output to allow service providers to bypass the local regional Bell operating company (RBOC). Siemens will support up to 24 sectors, to reuse bandwidth, for a total throughput of 4.8 gigabits per second (gbps) from each base station. The Siemens unit has simplified the cabling from the transmitter unit to the antenna, which is usually on a rooftop, putting all data, signaling and telemetry on one coaxial link.
One concern of wireless operators is having the ability to compensate for deteriorating weather conditions, because LMDS is susceptible to rain fade. One way to do this is to drop from 64 quadrature amplitude modulation (QAM), which can transmit more data but is less robust, to 16QAM. The Siemens product, and those from some other vendors, allows the units to change automatically from 64QAM to 16QAM.
The Siemens products with ATM access will be in production and available by the end of this month.
Triton Network Systems Inc., Orlando, Fla., is one of a number of companies, including Wavtrace Inc., Bellevue, Wash., and Ensemble Communications, San Diego, Calif., that is offering alternative systems in the LMDS bandwidth. Triton showed its Invisible Fiber SONET (synchronous optical network) OC-3 technology, which is a "consecutive-point" product that transmits from station to station in an architecture that resembles a fiber ring. Triton says its consecutive-point architecture allows it to reach customers much farther away that traditional LMDS systems by going through consecutive transmit/receive sites rather than using just one central transmitter/receiver. Sites can be 1.3 miles apart on average, and typical system designs reach up to 20 miles.
The company just has introduced 100Base-T capability in addition to its OC-3 interfaces. It has announced it is in a trial with Advanced Radio Telecom Corp. (ART), Bellevue, Wash.
Wavtrace is developing products that transmit using time-division duplexing (TDD) rather than frequency-division duplexing (FDD) as do most LMDS providers. The duplexing refers to the two-way transmissions of these systems. In most LMDS products, the return path is in a different frequency from the downstream path. In TDD, the two are in the same frequency but use alternating time slots. Wavtrace CEO Thomas van Overbeek says the approach requires fewer radios and can be more bandwidth-efficient than FDD. Product is scheduled to go into trials late this year or early next year with availability by the second quarter of 2000.
Today there are equal numbers of upstream and downstream time slots, but Wavtrace is developing technology that will allow the number of both time slots to vary dynamically to adjust for changes in demand.
Wavtrace announced a strategic alliance with Harris Corp., Melbourne, Fla., a leading developer of wireless systems, for distribution, manufacturing and technology of wireless broadband solutions. Harris will sell and support the Wavtrace products, and also will acquire a significant equity position in the company.
Wavtrace also is about to begin a technology trial with Formus Communications at that company's Denver-based headquarters on an experimental license.
Harris also showed a demonstration with Warrendale, Pa.-based FORE Systems Inc. of two-way point-to-point transmission of 45 megabits per second (mbps) using the Harris MicroStar Plus 38gHz radio transmitter and the FORE ASX-200BX ATM switch. The traffic included live high-definition television (HDTV), interactive multimedia and standard telephony. Harris and FORE announced they jointly will market high performance ATM solutions over point-to-point and point-to-multipoint microwave radio networks. Harris provides point-to-point broadband wireless systems at 18gHz, 23gHz, 26gHz and 38gHz, and by early 2000 will offer point-to-multipoint systems at 28gHz, 31gHz and 38gHz (for WinStar and ART).
Ensemble, also a TDD provider, claims it has a superior system to manage the upstream and downstream time slots of the technology for greater bandwidth efficiency and flexibility. Ensemble plans to have dynamic allocation of TDD time slots in beta testing by late 1999 with availability in the first quarter of 2000. The interfaces offered with the product include multiple DS-3s to an OC-3.
MMDS
The recent Sprint and MCI WorldCom purchases of MMDS companies has put this neglected frequency band back in the spotlight. Several companies have product development paths clearly mapped out that will migrate existing MMDS equipment, not just to full two-way data capability, but to become a reliable, rugged and compact piece of high-performance telecom equipment.
MMDS is limited in bandwidth to a total of only 200mHz. Much of that is licensed to schools and must be subleased from them, usually with an agreement to give them transmission services. Even with the full 200mHz, the bandwidth could be quickly exhausted if services begin to grow too fast. Therefore, operators are expected to exploit the MMDS capability to broadcast in sectors from a central broadcast tower, with the sectors resembling pieces of pie. Bandwidth can be reused in different sectors as long as two sectors with the same frequencies are not adjacent.
The limited bandwidth has forced operators to make tough choices on services, but some are abandoning the video services that launched MMDS in favor of data and voice. "911-quality voice is important and enables CLECs to bypass copper. We plan 1mbps voice and data," says William Paradise, director of wireless DSL business development and marketing for Nortel Networks, Richardson, Texas.
Spike Technologies Inc., Nashua, N.H., is considering IP voice technology for its products, says Ed Champy, executive vice president of sales and marketing. "We have seen the advances in voice over IP (VoIP) so we believe data-port integration should be seamless to IP. We believe there will be a common [data and voice] platform with 10mbps burst capacity and with a VoIP solution on top."
The Comwave division of Thomcast, Mountaintop, Pa., has developed an MMDS platform that covers the 1.8gHz to 3.6gHz frequencies. The company is the dominant vendor in MMDS with more than 10,000 transmitters in the field and credits for the Atlanta video system for BellSouth Corp. In the next generation of product upgrades, to be available late in 1999, Comwave will accommodate data and increase the product's performance to meet telco standards for outages with new features such as hot swaps of modules and smaller footprints.
The company also will add modular amplifiers to allow operators to add new channels to transmitters as they acquire new licenses. Comwave is further developing the product to create low-cost transceivers for the multiple dwelling unit (MDU) market.
During SUPERCOMM, Cisco Systems Inc., San Jose, Calif., announced it had purchased the broadband wireless division of Bosch and renamed the company SpectraPoint. The company will develop transmission equipment in the 28gHz range (LMDS in the United States) and possibly at the 24gHz frequencies. The products will integrate Cisco ATM switches.
