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Publisher's Outlook
February 2003

Rich Tehrani

VoIP Is In The Air!


There are a few areas of the communications market that are faring better than others -- customer interaction solutions, IP telephony and wireless come to mind. So when I learned about Proxims latest announcement regarding a fixed wireless product that supports VoIP, I thought the combination of IP telephony and wireless worth learning more about. I asked Jeff Orr, Product Marketing Manager (WAN division) at Proxim, some questions about their latest product rollout. If youre a service provider or a corporation, you may want to start considering rolling out fixed wireless to increase profits. Here is why.

RT: Proxim has announced Tsunami Multipoint A.I.R. and added VoIP enhancements. Tell us about the announcement.

JO: Tsunami Multipoint is a broadband fixed wireless access system for connecting three or more buildings with high-speed data. The product line consists of Base Station Units mounted at a central network location and Subscriber Units that reside on the rooftops of the customer premise. Base Station Units cover a 60-degree sector and are available at speeds of 20Mbps (to six miles) or 60Mbps (to three miles). By using six Base Station Units, they cover a full 360 degrees. And each Base Station Unit supports 1,023 active Subscriber Units.

Proxim is now shipping a new version of the Base Station Units -- Tsunami Multipoint A.I.R. with our patented Active Interference Rejection (A.I.R.) technology. Tsunami Multipoint A.I.R. nullifies external signals and noise that would normally cause performance problems for operators and service providers. Tsunami Multipoint A.I.R. is targeted to markets where interference is currently or potentially a problem, such as urban regions or near military bases where unlicensed radios are in operation. Additionally, Proxim added priority queuing to facilitate new services like Voice over IP across the wireless link.

RT: How does Tsunami Multipoint compare to the Wi-Fi WLAN solutions we hear so much about these days?

JO: Most Wi-Fi wireless LANs operate in the 2.4 GHz and 5.3 GHz unlicensed frequency ranges. Proxims Tsunami Multipoint products operate in the 5.8 GHz unlicensed frequency band. The use of the unlicensed spectrum allows multiple vendors to offer solutions in a specific community without needing to pay for licenses from the FCC to operate there. Tsunami Multipoint, like most other outdoor fixed wireless products, uses a proprietary non-standard transmission technology. This is beneficial for issues today like security where no published documents explain how a security mechanism works providing a starting point for hackers to attempt breaking in. The IEEE has established the 802.16 work group, to set standardization for some of the fixed wireless market. Proxim is actively involved in the standards process and believes that future 802.16 standards in the coming years will benefit the growth of the fixed wireless markets.

Wireless LANs are a great mobile application for in-building use and Proxim has a significant stake in that market as well. Point-to-multipoint fixed wireless is an outdoor market that enables high-capacity distribution of data and voice services to tens or hundreds or even thousands of locations. Fixed wireless is great for connecting an enterprise scattered across several blocks or several miles and as the backbone for a Wireless Internet Service Provider to provide access to outlying markets. Tsunami Multipoint A.I.R. provides the most reliable wireless link and has several advantages over leased line options.

RT: What are some of those advantages over leased line solutions?

JO: Time to market is key. Rather than waiting weeks or months to have a local utility trench new cables or wait in queue for an installation truck roll, Tsunami Multipoint A.I.R. can be deployed in as little as a day. For the enterprise looking for cost savings, Tsunami Multipoint A.I.R. users can eliminate the recurring monthly charges associated with leasing and can show ROI break-even in under a year. For the service provider, the capacity to scale the network effectively and to generate revenue through differentiated services (like VoIP) can keep them ahead of the competition.

RT: Security has been a big focal issue for the wireless industry as of late. How does Tsunami Multipoint A.I.R. deal with signal theft?

JO: Tsunami Multipoint employs several techniques to minimize signal and data theft. These include the use of a proprietary modulation scheme, pseudo-random scrambling of the signal, MAC authentication, and physical theft protection. Adding a new Subscriber Unit to a Tsunami Multipoint network is easy, but its handled through permissions and therefore not an open network that anyone can join at random. In the case where a Subscriber Unit is moved to a new location, the Base Station Unit unregisters it from the network due to the possibility of unit theft. These methods provide security at the physical, network, and application layers of the network.

RT: You say that youve added VoIP support to your Tsunami Multipoint series of products. How do you handle voice services?

JO: Proxim is now supporting priority queuing within the Tsunami Multipoint line. This gives operators the ability to provide VoIP and other priority traffic services over the outdoor wireless link. Each Subscriber Unit has two queues, which are used to separate priority (VoIP, for example) uplink traffic from best-effort uplink traffic. The Base Station Units monitor the uplink traffic and assign sufficient bandwidth to support a Subscriber Units priority traffic requirements. Operators can select the amount of fixed bandwidth to assign for each call on a Subscriber Unit to Subscriber Unit basis. This means that a single operator can provision priority service level unique to each Subscriber Unit deployed. The number of calls that a Subscriber Unit can handle varies from a few to several hundred depending on the specific VoIP parameters set for calls.

RT: What unique challenges does Quality of Service in a wireless environment present for you?

JO: Unlike a wired connection where the physical link is for the most part guaranteed except for those backhoes digging up cables, Tsunami Multipoint has to provide an equivalent level of reliability over the air. We can provide 99.9995 percent uptime with the Tsunami Multipoint product line and the new Tsunami Multipoint A.I.R. products go the extra step of nullifying interference from other devices within the frequency band. Tsunami Multipoint A.I.R. can effectively remove 99.5 to 99.9 percent of the interference witnessed by operators today. By maintaining latency upstream to the Base Station Units under 30ms, downstream to the Subscriber Units under 15ms and the jitter under 15ms, Tsunami Multipoint provides a solid platform for adding new services like VoIP by the operator.

Analysis is important as well. Tsunami Multipoint monitors the call traffic and reports the number of calls per Subscriber Unit, estimates the total bandwidth assigned to priority traffic, and the total number of best-effort packets dropped. These tools enable the operator to manage their service during initial rollout and throughout regular operation. Tsunami Multipoint A.I.R. also provides statistics on the presence of interference and our success at nullifying it. Our goal is to provide a solution that operators can just put up and forget about it.


IP telephony is catching on everywhere in the wired world (DSL, cable, etc) and we are now beginning to see it supported in fixed wireless networks as well. In order for IP telephony to continue its amazing growth, some sort of QoS scheme needs to be supported and latency needs to be minimized regardless of transport medium. Behold, IP telephony can now grow faster than ever through the use of fixed wireless technology. For service providers looking to boost revenues and corporations and/or government agencies looking to save money on telephony, we now have a super flexible option at our disposal, using the air to transmit great quality IP telephony!

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