The 4.9 GHz band is experiencing a rapid increase in available products since it was approved by the FCC for public-safety data applications, but the promise of better alternatives during the next couple of years has some experts urging emergency-response entities to use caution before purchasing first-generation systems.

To date, most of the activity in the 4.9 GHz band has involved using 802.11 technology — something public-safety representatives envisioned when they lobbied the FCC to establish a mask that would let first responder groups leverage affordable gear available in commercial markets. However, few entities actually are using 4.9 GHz frequencies to deliver data to mobile client devices, opting to use the spectrum for backhaul purposes and choosing 2.4 GHz Wi-Fi clients to make the final connection.

“There's a lot of interest in it and a lot of discussion about it, but in terms of actual deployments and tests, we don't see a great deal [of 4.9 GHz access activity],” said Mark Ferguson, director of marketing for Padcom.

In a typical mobile scenario, a 4.9 GHz connection is used to link a public-safety vehicle and the entity's network, while a 2.4 GHz local area network around the vehicle is used to transmit data from the vehicle to an officer's client device. The 4.9 GHz spectrum also is being used increasingly to backhaul data from fixed points — such as a surveillance camera site — to headquarters.

To this end, Motorola recently announced the WDE1000, a standards-based Wi-Fi card that supports connections over both 2.4 GHz and 4.9 GHz networks (see story on page 62), as well as a low-cost infrastructure solution known as HotZone Duo that operates in both bands.

Although the WDE1000 will work better than most Wi-Fi cards in a mobile environment, the standards-based solution does not work as well as the company's proprietary mesh-enabled architecture (MEA) technology, which is optimized for high-speed mobility, said Rick Rotondo, director of marketing for Motorola's mesh networks product group.

Indeed, the 802.11 standard was created for indoor use, so it was not designed for outdoor applications or to support mobility, said Martin Suter, Cohda Wireless' CEO. The fact that these 802.11 limitations exist is a “dirty little secret” in the broadband wireless arena, particularly with respect to deployments sponsored by municipalities, he said.

Cohda has developed a solution that uses iterative processing to achieve 6 dB to 8 dB gain in receiver sensitivity at each node in the network to enhance range, often reducing the number of nodes needed per square mile by 50% in lower capital and operating costs, Suter said. In addition, the Cohda solution — expected to be available during the third quarter of this year — also addresses typical 802.11 problem areas such as multipath and mobility, he said.

Without such an option, public-safety communications officials wanting to deploy a 4.9 GHz network are faced with a dilemma, Suter said.

“Do I go proprietary today and compromise on the data rates — MEA data rates are sub-1 Mb/s — to get mobility? Or, do I pick a standard-based solution at the expense of mobility?” Suter said. “What we're saying is that you no longer have to make that compromise.”

Meanwhile, things are heating up outside the 802.11 arena in the 4.9 GHz band. During IWCE 2006 in May, M/A-COM launched VIDAmax, a WiMAX-based 4.9 GHz solution that features data throughputs of 4 Mb/s to 19 Mb/s, said Gregory Henderson, M/A-COM's manager for broadband technology.

By using WiMAX, VIDAmax can guarantee quality of service (QOS) from the base station of an 802.11-based system — even for those using the 802.11e QOS standard.

“It helps the quality of service, but all 802.11e does is give priority to trying to get the channel,” Henderson said. “It's still not a guarantee of quality of service.”

WiMAX-based systems at 4.9 GHz very well may be the first to deliver truly mobile access devices that are affordable, as commercial wireless carrier Yozan is conducting a trial in Japan in the, said Matt Pope, vice president of wireless broadband products for WiMAX RF chipmaker Sierra Monolithics.

“We think that's going to be a very good trial for how 4.9 GHz works,” Pope said. “It's also going to generate enough volume from a device point of view that the U.S. market is going to be able to leverage some of that 4.9 GHz technology back at a reasonable cost point. We think that's an exciting value proposition for the public-safety market, which has lower volumes and has to have a commercial [driver].”

Such access products at 4.9 GHz are expected to be introduced early next year, Pope said.

In addition, Alvarion announced a firmware upgrade to its orthogonal frequency division multiplexing (OFDM)-based BreezeAccess VL packages at 2.4 GHz and 4.9 GHz that lets a wireless operator prioritize voice or video packets in the network to provide QOS assurances (see story on page 64). With the new firmware, BreezeAccess VL can support 260 voice-over-IP (VoIP) calls simultaneously while supporting 8 Mb/s data throughput in each sector, said Patrick Leary, Alvarion assistant vice president of marketing.

“In the beginning, we did a lot of extensive testing on both the video and voice side because the data we were seeing in the lab was so high that we frankly weren't sure we could believe it until we put it out into the field,” Leary said. “When we put it out into the field and saw that these results were holding up in real commercial situations, it blew our engineers away.”

With so many advances on the horizon at 4.9 GHz and even more promising possibilities that could be available in the 700 MHz band in a few years, public-safety entities should carefully consider their long-term data plans before deciding to make 4.9 GHz deployments using existing 802.11 solutions, said Edmond Vea, CEO of ClosedNetworks, which consults with many municipalities.

Supporting a widespread deployment of an 802.11 network can look particularly attractive to a community that has a vendor offering to build it without any capital expenditure from the government entity, but such a buildout may not be in the community's best interest long term, Vea said.

“If you're deploying a system today at 4.9 GHz — particularly for mobility — it's already obsolete,” Vea said during a session at IWCE 2006.

Among other things, networks with a plethora of nodes likely will have significant network-management issues, and the standards-based architecture leaves them more susceptible to security breaches than existing proprietary networks, Vea said. However, he did say deployment of 4.9 GHz networks today can make sense, particularly where long-range point-to-point links are involved.

Steve Devine, patrol frequency coordinator for the Missouri State Highway Patrol, also said targeted 4.9 GHz deployments can have long-term usefulness if planned properly to take advantage of future technologies. “The systems can be opportunistic and be basically instructed to do the best thing for them at any given time,” Devine said at IWCE 2006. “So when they go under an underpass where there is a 4.9 GHz access point, they can download a whole bunch of files, which they may not be able to do where there is [future] fringe coverage at 700 MHz, where the capacity is less.”

For those entities that already have deployed an 802.11 network that is overwhelmed by the traffic demands or does not meet mobility requirements, help may be on the way. Building automation vendor Kiyon has developed software designed to enhance switching efficiencies so even older 802.11 wide area networks can offer QOS in voice and video applications, said Michael Nova, Kiyon founder and CEO.

“Standard 802.11 [switching] is at 150 to 200 milliseconds — that's why VoIP over wireless is so bad.” Nova said. “We take it down to 1 millisecond. That gives you a lot better throughput in terms of broadband, better quality in terms of jitter and latency for voice and video across multiple hops, and it also increases security because you're moving things around so fast.”

With such a rapid switching scheme, Kiyon is able to push packets through multiple channels, using time slots to maximize data throughput and reassembling the packets fast enough that no latency in voice or video is detectable by humans, Nova said. Kiyon's switching software can be embedded on any radio — it has been tested in 802.11 and ultrawideband environments — and can breathe new life into a struggling mesh network by ensuring quality data throughput even after 10 or 20 hops, Nova said (see graphic on page 28).

Already commercially available in the building automation industry, Kiyon's multichannel routers will be in beta trial within a couple of months, Nova said.