Tools to improve WLAN Video Performance

In the WLAN Design for optimizing Wi-Fi Video Transmission, we discuss the capacity requirements for wireless video optimization and 802.11n considerations. This article will discuss other network optimization methods for video and methods for measuring the performance of wireless videos in WLAN.

In addition to the basic 802.11n functions used for video optimization, we should also consider using other built-in Priority Methods in network components to improve video performance. After this, continuous measurement of Wireless Video performance to ensure video quality is also critical.

How to Improve the Performance of wireless videos

The vendor's network hardware has various features that can be used to optimize Wireless Video Transmission and performance. The following are some practical network-first methods:

Extend the priority to the wired network. You need to find the Access Point (AP) mapped between the Wi-Fi multimedia class, 802.1 p (MAC layer) and differential service code point (or DSCP) IP priority mark ). In addition, access points with video sensing capabilities and access points with the correct priority for specific video streams should be considered.

Video sensing access point. Because Wi-Fi multicast often reduces the data transmission rate and increases the error rate, you should find a function that can optimize the multicast video. For example, a video sensing access point can automatically select a high rate for multicast, or convert a cable multicast packet to a wireless unicast frame. This type of conversion is very effective, especially when only a few clients receive videos. Some products can consider this and continue to use multicast (such as network broadcast) when necessary ). Other products are actually more sensitive to specific codecs and frame types. This intelligence can be used to adjust Access Point behavior to reduce the loss of more important frame types or perform transcoding (conversion to more fault-tolerant encoding) or video conversion (reduce the video resolution as needed to adapt to low data transmission rates ).

Manages the diversity of client features. Generally, client diversity reduces WLAN performance, especially for wireless videos (especially for multicast videos ). However, many vendors have developed optimization technologies to handle diversity, including transmission beam forming and radio management adjustments. Through transmission beam, the Access Point will customize transmission for each client to reduce errors. The radio management algorithm can change the call time allocated to each device, so that updated or faster clients will not be dragged down by older or slower clients. Ideally, these optimization technologies should also be video-aware.

Wireless Mesh Network. Wireless Mesh networks can optimize some wireless video applications (such as outdoor wireless cameras and digital signage). Although many dual-RF 802.11n Access Points support wireless mesh networks, not all access points give priority to video optimization through wireless return links.

Optimized the wired network. This includes using Internet Group Management Protocol snooping and other video optimization methods to avoid unnecessary multicast forwarding from the Controller to the access point, video Traffic transmitted between the Access Point and the controller is prioritized.

Measure Wireless Video Performance

In 802.11n WLAN, the signal strength does not indicate the performance of wireless videos. The uplink and downlink data transmission speeds vary depending on the multi-path behavior, access point, client, and chipset. Therefore, the only way to ensure the audience watching experience is to use representative applications and devices to measure the performance of videos and multimedia applications in place.

Media Transmission index (MDI) is one of the industry's standard indicators for measuring video quality. It involves latency factors (DF)-indicators used to measure latency and jitter, and media Loss Rate (MLR) -- metrics used to reflect lost and out-of-order data packets. Since DF measures how long it takes to exhaust the buffer (in milliseconds), it maintains DF at a low level for interactive videos (for example, below 50 milliseconds) it is very important, but it does not have much impact on IPTV, streaming media, or on-demand video. The media loss rate measures the number of dropped packets per second. for high-quality videos, we must maintain a very low MLR (that is, under 0.001, it is actually 0 ). The video service protocol level (SLA) and measurement method are usually specified as the ratio between DF and MLR (for example, 50: 0 ).

Video equipment manufacturers usually use specialized traffic generators and measurement tools to test products, such as set-top boxes, media gateways, and cameras. Access Point providers can use similar tools and analog loads to measure the quality of video experience (QoE), such as generating standard-Definition TVs or high-definition TV streams for hundreds of Wi-Fi clients.

Measure WLAN Video performance using real-time network tools

Product Developers found that these testing methods are very useful when optimizing their video processing, but enterprises still need real-time network testing tools to measure and compare actual QoE to set targets. For example, Ixia wave WaveDeploy of Ixia is a set of testing tools for WLAN field evaluation. Testers can install the WaveDeploy Agent on real-time Wi-Fi client devices, such as laptops, iPhones, and Android tablets. In addition, these devices can move in and out of the vehicles in the venue for measurement, receive video Test traffic, and record MDI and other indicators, such as receiving signal strength indicators (or bsns ). In addition, a dedicated traffic generator can be used to simulate up to 64 Wi-Fi clients. Then, we compare the MDI score with the SLA to generate a hotspot map on the plan to help the tester see which devices and locations need improvement.

Of course, you can also launch real-time wireless videos to your laptop or iPad to watch the results with the naked eye. This more formal test method and tool can help identify problematic client devices and help enterprises understand the effects of Video performance improvement measures, especially in high density or different WLAN.