Aperto Networks Launches Innovative Fixed Wireless Architecture

Breakthroughs in Multi-Service QoS, Per-Subscriber Link Optimization, 2-Way Burst deliver Best-in-Class Performance  

Milpitas, Calif., (July 10, 2000) – Aperto Networks today unveiled its innovative service architecture for multi-service fixed broadband wireless access. Aperto’s patent-pending technologies, ServiceQÔ, OptimaLinkÔ and RapidBurstÔ, overcome the limitations of previous-generation wireless access systems and help wireless networking in the sub-11 GHz bands to deliver on the promise of broadband access to millions of users.  

Optimizing Network Design for Multi-Service Fixed Broadband Wireless Access
To develop a wireless architecture for mass-market scale, Aperto Networks focused on bringing fixed wireless access up to and beyond the performance of wireline broadband access. This means standards-based access systems which support dense cellular deployments, high network scalability, line-of-sight and non-line-of-sight operation, and end-to-end QOS management in point-to-multipoint topologies. Aperto defined its architecture to meet these parameters, as well as additional characteristics carriers consider to be “must-haves” for next-generation broadband networks, i.e., an IP-based and multi-service design, an adaptive physical layer (radio and modem), advanced Media Access Control Layer and high cellular frequency reuse.

Building on this base, Aperto developed three unique technical innovations to further extend network tunability and cost-effective service delivery:  

  • ServiceQ (three distinct service classes over variable-capacity user links)
  • OptimaLink (dynamic control to optimize each subscriber connection)
  • RapidBurst (delivery of high-capacity and flexible two-way burst-mode TDMA)

Carriers have told us these three technologies are important to their selection of broadband wireless as a complement to existing wireline networks,” said Subir Varma, Aperto’s vice president of network technology. “Our innovations ensure the availability of QoS for multi-service delivery, control and optimization of bandwidth on a per-subscriber basis, and two-way burst TDMA supporting both TDD and FDD duplexing schemes.”  

Aperto’s Key Technologies
The first innovation, ServiceQ, enables Quality of Service (QoS) and bandwidth management across the wireless (air) interface, and seamlessly interworks with industry-standard IP DiffServ and MPLS protocols to extend service classes through backhaul networks. Service classes are increasingly important in the delivery of wireline multi-service Service Level Agreements (SLAs), and they will be no less significant for mass-market wireless deployments. Aperto uses ServiceQ to support SLAs and enable per-flow traffic policing and traffic shaping on end-to-end networks.  

ServiceQ is based on an advanced scheduling algorithm that uses a novel combination of three service disciplines:  

  • Priority service and unsolicited grants for Constant Bit Rate (CBR) applications
  • Wireless weighted fair queuing for Committed Information Rate (CIR) applications
  • Round robin service for Best Effort (BE) applications.

ServiceQ uses hierarchical scheduling which allows the total link capacity to be allocated to multiple Internet Service Providers sharing the same link bandwidth transparently, without interfering with one another and enabling open access networks.  

"This is a very promising approach to the challenge of delivering multi-service applications over fixed wireless," said Goli Ameri, president of AmeriSearch, in observing the ServiceQ approach. "With a QoS architecture that interoperates with IP DiffServ and MPLS, Aperto will allow service providers to carry multimedia services as well as the ability to tune up and down bandwidth. These are features required by carriers allowing them to define the specific QoS necessary for each service and each subscriber they want to support."  

OptimaLink is the second architectural innovation. It performs dynamic control of link parameters to optimize each subscriber’s connection in a multi-user, point-to-multipoint environment, guaranteeing high performance and coverage for all users. Since a wireless network’s propagation characteristics and channel behavior are functions of location and interference level of individual subscriber units, performance can vary greatly from one subscriber to another. This has been a major problem in past fixed wireless deployments, as link parameters were typically fixed over the covered area, and performance and coverage could not be guaranteed.  

To overcome the problem and optimize performance, link parameters must be individually tailored to each subscriber. Aperto’s OptimaLink fulfills granular control using ten multi-layer link parameters on a burst-by-burst basis, in order to maximize coverage and capacity while maintaining a high level of spectral efficiency. At the base station, OptimaLink’s adaptive algorithm selects the best set of parameters from each of ten factors (e.g., power allocation, antenna diversity, modulation, retransmission policy, frame size, etc.) to optimize the communications channel to each subscriber. This ensures robust link performance, provides interference immunity and enables operation in obstructed and non-line-of-sight conditions.  

"Conditions of carrier network configurations differ extensively from each other, and ’one-size-fits-all’ performance optimization just does not help them to successfully implement the next generation of service opportunities," emphasized Bettina Tratz-Ryan, telecommunications access equipment analyst with Dataquest/ Gartner. "Highly-variable environmental conditions from one user to another demand that many parameters be dynamically adjusted. Solutions that are able to process and optimize across a broad spectrum of variables to generate peak performance in point-to-multipoint networks are crucial to guarantee quality and reliability of service delivery."  

RapidBurst, the third innovation, is Aperto’s next generation TDMA protocol. It provides flexible bandwidth allocation and high performance, even in challenging environments. RapidBurst achieves unprecedented flexibility in allowing control of transmission parameters, enabling both the OptimaLink and ServiceQ algorithms to function effectively. RapidBurst also supports Aperto’s Link Layer Error Recovery Scheme, which helps maintain network operation even under severely degraded conditions. RapidBurst incorporates a new contention state machine to dramatically reduce collision activity in the upstream channel, and enables up to 20Mbps per user burst capacity in either the upstream or downstream direction. Perhaps most unique in the marketplace to date, RapidBurst incorporates an advanced MAC algorithm to support both Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD), thus maximizing spectrum utilization under any global market conditions. For spectrum where channel pairs do not exist, TDD has the added advantage of operating on a single channel and allowing flexible allocation of total bandwidth between the upstream and downstream directions.

About Aperto Networks

Aperto Networks is a developer of multi-service fixed broadband wireless access systems. The company was founded to provide a breakthrough solution to one of today’s critical network bottlenecks – last-mile broadband access. With practical, scalable systems and patent-pending technology that support new wireless builds and complement existing wireline broadband access technology, Aperto addresses service provider needs for rapid network deployment, multi-service scalability, ease of installation and cost-effectiveness. Aperto will dramatically shorten the lengthy provisioning cycles of broadband services by enabling rapid service provisioning across dense urban to suburban locations. Investors in Aperto include Alliance Ventures, Tyco Ventures, Ridgewood Capital, Satwik Ventures, DMC Stratex Networks, Oki Electric Industry Company, Mitsubishi International Corporation and Redwood Ventures. For more information on Aperto Networks, go to