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Predicting real-world wireless performance

Posted: 16 Jul 2008 ?? ?Print Version ?Bookmark and Share

Keywords:wireless performance? protocol? networks? RFID?

No matter how well we design, many things may happen in the real world of wireless. Spectrum interference will be different than predicted. The behavior of wireless clients requiring a high level of protocol acknowledgements will mask network issues at more complex layers.

As things become complicated, it is more difficult to achieve the desired end-user quality-of-experience (QoE), and the more we need sophisticated software mechanisms to be designed in from the beginning.

Best to test
Strategic testing in the design and development of wireless networks goes a long way in minimizing the pain of deployment and user disruptions when things go live.

The challenge is to test as thoroughly as possible, shorten time-to-market and decrease overall cost.

Two aspects of real-world wireless performance have been difficult to assess from the lab: scalability, and interaction of various applications with each other and with the network. Now the dominating challenge is the introduction of 802.11n-complaint devices alongside existing a/b/g equipment, particularly in the business environment.

The wireless network must deliver QoS sufficient to guarantee support of mission-critical applications. With wireless WANs (WWANs) on the horizon (e.g. WiMAX, LTE etc.), fixed mobile convergence will need to seamlessly integrate these WWANs with WLANs. There are some sound strategies that can maximize QoE and minimize surprises.

The three things to test when designing for scalability are the following:

  • The effects of a large operational network on the level of service a client receives;

  • The degradation, or possible complete disconnection, of wireless sessions when the network load increases rapidly;

  • Proper traffic differentiation and enforcement of QoS mechanisms when a wide range of applications all demand network services.

Optimal testing relies on mixing real devices with a test platform that generates large numbers of clients and enables configuration of traffic conditions, as well as automating repetition of the test with the same or varying conditions.

One of the biggest challenges in wireless networks is the continuously changing physical environment. To properly design the infrastructure network components, a repeatable and tightly controlled environment must be established. Only such an environment can be used to properly subject the network to a wide range of operating conditions with a constantly changing number of connected users and a constantly changing mix of applications used.

Designing for markets
In designing networks, the selected equipment or application for power-user wireless environments varies from industry to industry.

A wireless network in a healthcare environment supports mission-critical patient monitors, VoIP handsets, remote-video surveillance and asset-tracking RFID devices. This wireless network is very different from a wireless network in a school setup that supports the best services to the students in campuses.

The wireless networks in retail and warehousing environments, where a fail-safe approach to transactions needs to be implemented to support precise asset tracking and cash transactions, are also very different.

The best way to test is to generate representative traffic patterns both in the lab and in "open-air" test environments.

While lab testing ensures the quality of the network equipment during the design and QA phase, open-air testing completes the cycle. It allows manufacturers, system integrators or IT managers, to do a "proof of concept" for the design, and prepare for effective network planning and deployment.

Delivering the promise

Working with WLAN equipment providers and the IEEE 802.11n committee, VeriWave conducts benchmarking of 802.11n. The advantages are that 802.11n improves quality and wireless reach; and the speed advantage possible with 802.11n allows wireless networks to deliver voice and video.

The bad news is that the industry has its work cut out for it. If 802.11n is on your priority list, three things you want to anticipate or investigate thoroughly are:

  • All aspects of the standard need to be implemented;

  • The choice of network infrastructure is crucial;

  • Proper network planning, including traffic segregation and separate bands to support legacy and 802.11n devices is paramount.

- Tom Alexander
VeriWave Inc.

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