A New Fix

As standards squabbles continue over various flavors of OFDM non-line-of-sight (NLOS) technology, WCDMA-based technology is getting some buzz in the fixed-wireless broadband arena.

That's right. WCDMA isn't just for 3G-mobile wireless. In fact, the IMT-2000 (www.imt-2000-online.com) specifications also provide for 3G fixed-wireless access, allowing for high-speed data and voice.

Fixed-wireless systems based on 3G allow NLOS solutions using an integrated antenna in the home terminal unit, noted Rebecca Diercks, Cahners In-Stat (www.instat.com) analyst, in 3G Technologies as a Fixed Wireless Solution published in 2000. This saves $700 to $750 per home, she said. Other advantages include 1:1 spectrum reuse so multiple base stations and multiple sectors can operate on the same frequency, Diercks said.

Tom Flak, vice president of marketing at Soma Networks, which offers a WCDMA-based fixed-wireless solution (www.somanetworks.com), said WCDMA is better from a risk standpoint.

“We could have gone with OFDM, as well, if customers were pushing for it, but they aren't,” he said.

“The key is that (WCDMA) already is a standard,” said Peter Howley, IPWireless (www.ipwireless.com) CEO. The standards battles going on with OFDM vendors could take another two to three years before any agreement is reached, he said.

“OFDM is just an inferior approach in general,” Howley continued.

The reason so many vendors are developing OFDM is that it's easy to do, added Roger Quayle, IPWireless CTO.

“Developing WCDMA is 100 times harder,” he said.

All NLOS technologies are trying to solve the problem of getting the customer equipment inside the home, not mounted outside, said Andy Fuertes, Allied Business Intelligence senior analyst (www.alliedworld.com).

“To get the equipment in the home, you either need a lot of output power, small cells or need to use low-order modulation, QPSK, for example,” he said. “You also can use beam-forming at the actual base station to concentrate energy in a certain direction to get through a wall faster.”

All NLOS systems have to contend with multipath, but CDMA uses frequency hopping, which reduces the odds of interference, Fuertes said. Although he hasn't seen the spectral efficiency of the WCDMA fixed solutions, he guessed it might not be as great as other top-of-class fixed-wireless solutions. However, if WCDMA solutions are a lot cheaper, the carrier can build more cell sites.

Peter Jarich, Strategis Group director (www.strategisgroup.com) of broadband research, said it all comes down to price.

“Is the system cheap enough that adding small cell sites is still giving you the coverage per person?” he asked. “Top down, the single-carrier systems are very efficient. OFDM rates around 2 bits per hertz, which is not quite as good as single carrier. I'm hearing that CDMA efficiency is even less.” But with a smaller cell site, CDMA isn't required to have as high a data rate.

Although Soma's and IPWireless' technologies vary in many ways, both have developed WCDMA modems; both have lower-cost, self-installed, customer-premises equipment (CPE); and neither requires installation of an exterior antenna. The published speeds aren't bad, either.

Targeting MMDS First

IPWireless' first product is for the 2.5GHz MMDS bands. Its next product will be for the 1.9GHz to 2.2GHz bands, those used for 3G in most European countries.

IPWireless intends to sell the CPE to the carrier (or end user) at $300 to $400. It's now a data-only product.

“One of the things we've done in taking the 3G technology and optimizing it for high-speed portable Internet access is not carrying traditional voice,” Quayle said. By using the entire capacity of the system for data, higher data rates are possible.

IPWireless' technology also uses time-division duplexing (TDD).

Jarich said that frequency-division duplexing (FDD) tends to have some advantages over TDD when it comes to interference.

“With NLOS, signals are more likely to stray,” he said. FDD makes it a little easier; although, if a technology has 1:1 reuse (as do IPWireless and Soma, according to their specifications), it's not a problem, he said.

Quayle explained one reason for TDD. At most European spectrum auctions, carriers typically receive 10MHz of paired FDD spectrum and 5MHz of unpaired TDD spectrum.

“There's no other technology that these operators can use in the unpaired spectrum,” he said.

Currently IPWireless' technology delivers 6Mb/s downstream. Carriers can tier it and offer different speeds to different segments of the market.

“Next year we're looking at 16Mb\s downstream,” Howley said.

Targeting PCS Carriers First

Soma features a DSL-like data and carrier-grade voice solution that will deliver peak rates of 10Mb/s, according to Flak. Its initial product is for the PCS bands; MMDS and 3.5GHz equipment currently is in development.

Soma is first targeting carriers that own PCS spectrum and need to meet build-out deadlines. These carriers have a high degree of interest in building out fixed wireless rather than mobile and also are thinking in terms of residential voice service, Flak said.

Soma's distributed software technology is called Amos.

“In our environment, telephony, for example, is a software-defined service,” Flak said. “There's no central-office voice switch.” Services such as Internet access, VPNs, voice mail, and, in the future, telemetry applications, all will be software applications operating on the distributed network.

Because technology has matured in the CPU, computing and software worlds, a transformation can take place on the edge of the network where “we can eliminate a lot of specialized platforms and use computing machines interconnected with IP,” Flak said.

Amos, which is middleware, does not actually deliver services, but Soma will be publishing an API so that others can create applications to operate on the architecture. In its trials, it is jump-starting the process to deliver Internet-access features that allow customers to have private IP addresses, public IP addresses, security features and basic telephony features.

The CPE terminal, the Somaport, eventually will be a range of devices. The low end might be data-only with an Ethernet port and radio uplink.

“At the high end, we're looking at a device with multiple voice ports, multiple data ports for multiple PCs, home networking and connectivity for home automation and telemetry,” Flak said.

A 3- to 5-mile cell radius will be needed depending on the terrain, he said. Speed will be the function of the carrier. The closer to the cell site, the higher the speeds, Flak said.

No Predictions

It's still early in the game to predict any winners in fixed-wireless technologies, according to Fuertes, who said there are many promising technologies out there. He expects to see solutions ready for market in the third and fourth quarter of this year.

In the meantime, for those who wonder how WCDMA stands up against OFDM, some interesting trials are taking place in Montreal. Inukshuk Internet (www.inukshuk.ca), a subsidiary of Microcell Telecommunications (www.microcell.com) and owner of the MCS (Canadian MMDS) licenses in 12 provinces, is field-testing equipment from both IPWireless and NextNet Wireless. NextNet's Expedience (www.nextnetwireless.com) is an OFDM NLOS system featuring a self-installed modem, 1.5Mb/s data throughput per user and 1:1 frequency reuse.

SCDMA Solution

Synchronous CDMA (SCDMA) is the technology Navini Networks (www.navini.com) is using in its wireless-broadband product, announced in June. The technology is self-installed, non line-of-sight, offering up to 9.6Mb/s raw data rate per user, according to Navini.

SCDMA comes from the TD-SCDMA standard, one of three from the ITU (www.itu.int), according to Sai Subramanian, Navini marketing director. Although other CDMA-based technologies are asynchronous, with SCDMA, the uplink behaves like the downlink. This reduces interference, he said.

“If you do any mathematical computation, you can prove you get five times or more capacity on the uplink (with a synchronous solution) than an asynchronous system,” he said.

Wireless broadband also requires a higher signal-to-noise ratio to deliver high-speed data. This can be accomplished several ways. In first-generation, it required an outside antenna because there was not enough power to get the signal through the wall. Navini uses an adaptive phased-array antenna technology.

Navini currently is in beta tests with T-Speed (www.t-speed.com), a provider of high-speed Internet access to office buildings in tier 2 and tier 3 markets.

Navini's Riptide 2400 and Riptide 2600, for 2.4GHz and the MMDS, should be commercially available in the fourth quarter.