Ensuring a Quality Wi-Fi Voice Experience for Lync

20 Jan 2015

While Microsoft has long earned a prime spot in Gartner's Leader's Quadrant for unified communications, in 2014 it moved up to the Leader's Quadrant for corporate telephony as well. With millions of users on Lync for instant messaging and presence and the need for fully unified communications solutions, it is no wonder that more and more organizations are looking to Lync to provide their voice communications as well. As with any voice over IP solution, one of the bigger challenges many IT departments face is how to deliver business-grade voice communications to mobile as well as wired users.

Microsoft relies on an extensive ecosystem of partners to deliver the essential infrastructure, endpoints, monitoring tools and other components of a Lync telephony solution. While all of these elements are important, without a solid network infrastructure, the quality of experience (QoE), user adoption and, ultimately, return on investment will suffer.

A cost-effective enterprise voice implementation requires a high quality mobile experience over both cellular and campus Wi-Fi networks. While cellular performance is the responsibility of the mobile operators, the IT department must build and support the campus Wi-Fi infrastructure for real time voice and video.

Choosing the right Wi-Fi infrastructure is both critical to user adoption and challenging to IT teams that are new to unified communications. Historically, Wi-Fi has not been an ideal medium for supporting real-time traffic, including voice and video. Wi-Fi channels are shared by all users associated with a particular access point. Real time traffic is more sensitive to delay, jitter, and packet loss, so traffic prioritization is critical. Couple that with the inherent challenges of providing reliable signal coverage in an indoor environment where walls and elevator shafts can attenuate the radio signal, and you can appreciate the difficulty involved. An enterprise wireless LAN (WLAN) used for unified communications must be capable of RF management to ensure good signal coverage, while minimizing interference between access points. In addition, The WLAN solution must recognize, categorize and optimize real time traffic.

These and the other challenges of providing reliable Wi-Fi voice can be met with the right tools and the right design. Delivering business quality voice and video requires ubiquitous coverage over the campus, including in stairwells and elevators. More than just "coverage," the infrastructure must also have the required capacity to support real- time voice and video. Capacity must be provided not only over the air, but also through the wired infrastructure that interconnects all of the access points.

There are subtler challenges as well. While the Wi-Fi Multimedia (WMM) standards define a mechanism for prioritizing voice and video packets over the shared radio channels, how do you know which packets are voice and video? On their own, application-aware WLAN infrastructures can also recognize voice or video streams based on the characteristics of the various streams and assign the appropriate WMM priority. This traffic characterization is particularly challenging in Lync environments where all the data streams are encrypted. With built-in application-layer gateways in the WLAN solutions, Lync sessions can be identified and prioritized appropriately. In short, real-time traffic must be identified and treated appropriately by the network to deliver that quality user experience.

One of the other challenges in mobility is handing off an active connection from access point to access point as users move through the coverage zone. That challenge is even more relevant now that we have portable devices such as tablets and smartphones accessing UC services. Mobile devices try to hold on to the first access point they associate with and are reluctant to release it and move to another even though the user is moving away. With truly "mobile" devices, we want the device to let go and grab another access point before the signal quality gets weak or the call fails.

Even though the decision to hand off is made by the device rather than the network, some WLAN solutions have incorporated techniques that "encourage" a mobile device to move if it sees its connection quality declining.

The other key capability of the "right" WLAN solution is the ability to monitor the overall performance of the wireless network to recognize potential problem areas before users start calling with complaints. That calls for the ability to monitor such factors as R-values, jitter, delay, and packet loss across the network and correlate that information with the Lync controller to get true end-to-end call status and performance.

Finally, all of these elements have to work well even if users are bringing their own devices onto the network. As those devices will be connecting to the network, the infrastructure must be capable of authenticating legitimate users through their Active Directory or other credentials and onboarding them to the network without IT involvement.

Lync holds the promise of making users more efficient and productive by providing them with a rich set of communications and collaboration tools that are accessible at their desks or on the move. However, ensuring that Lync will deliver a business-grade QoE for campus mobile users requires a networking solution such as Dell W-Series wireless, which differentiates applications and traffic types, and provides context-aware access policies based on the type of user, device, application and location.

Dell W-Series automatically identifies and prioritizes Lync traffic and maintains QoS for Lync packets during network congestion and RF interference. In addition, Dell provides detailed voice metrics for troubleshooting. Organizations that also require secure guest access and simplified BYOD management can leverage Dell W-Series ClearPass Access Management system.

In short, Lync customers deploying mobile solutions require a robust and secure infrastructure to help ensure the success of a Lync telephony implementation. By working with Dell, organizations can maximize user adoption and, ultimately, return on investment.


This paper is sponsored by Dell.

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