San Diego-based Ensemble Communications Inc. is approaching worldwide broadband wireless access markets with a point-to-multipoint wireless system that has three key technology layers with one thing in common-they can be adapted.
The company, with roots stretching back more than 30 years to Linkabit, a consulting business founded by Irwin Jacobs and Andrew Viterbi of Qualcomm Inc. fame, built its Adaptive IP BWA system from the ground up with the idea that cost and functionality for BWA products needed to be balanced.
Carlton O’Neal, vice president of marketing and sales at Ensemble, said the company believes the bandwidth needs of smaller businesses can be met by lower-cost xDSL and cable modem solutions, while the bandwidth needs of large business will be addressed with expensive high-end fiber or point-to-point radios. In the middle are companies that need the bandwidth but can’t necessarily afford the high-end solutions.
Ensemble’s system is built around the idea that BWA will allow these medium-sized businesses to have access to bandwidth on a shared basis, making it more affordable for the business and more profitable for the service provider. Furthermore, deploying a BWA system takes months compared with years required for deploying fiber, said O’Neal.
The company’s shared architecture system includes three adaptive layers designed to generate greater revenues for BWA carriers by maximizing total available bandwidth at any given time and allocating bandwidth in real time to each user on a per-bit basis. This, said Ensemble, allows carriers to oversubscribe their facilities by offering the exact bandwidth required by each end user.
The first layer is a physical layer that makes use of the company’s Adaptive Time Division Duplexing technology. Rather than separating the upstream and downstream traffic by using different frequencies as is done in traditional radio-frequency systems, ATDD separates the upstream and downstream traffic into time slots.
Dividing frequencies with a guard block works well in voice systems because traffic is always symmetrical. But when data is added to the mix, said O’Neal, frequency use is asymmetrical and constantly changing. Assuming a certain asymmetry on which to base a system, said O’Neal, “is like a stopped watch. It’s only right twice a day.”
ATDD accommodates instant changes in traffic asymmetry by making real-time adjustments to upstream and downstream capacity. O’Neal compared the idea with a centerline barrier on a highway that constantly moves in response to traffic in order to keep congestion on either side equal.
Eliminating the use of guard blocks also eliminates the need for duplexers, which has allowed Ensemble to offer a less-expensive product, said O’Neal.
The second layer is a media access control layer that uses adaptive modulation to automatically select the most efficient modulation scheme possible for each customer at any given time. Transmissions to close-in customers can be made with more efficient modulation schemes such as QAM 64 and QAM 16 while overall range of the base station is maximized using QPSK. Working with ATDD, the Adaptive Modulation technology allows carriers automatically to trade off between range, capacity and asymmetry.
The third layer-the network layer-uses Adaptive Time Division Multiple Access technology, which manages subscriber access to the air link by allocating time slots to receive and transmit information every millisecond, adjusting the modulation based on the link strength and modifying the power levels of customer premises equipment based on environmental conditions. The technology allows the system to achieve instant bandwidth on demand, quality of service and support for multiple protocols, including Internet Protocol, Time Division Multiplexing and frame relay.
The company plans to market its system to service providers and original equipment manufacturers and is in the process of signing contracts for beta trials to be conducted during the fourth quarter.
