How to Improve Wireless Network Performance

Wireless network performance KPIs provide a measure of the stability and efficiency of various components and activities of a wireless network. Understanding the various wireless network performance metrics accelerates the detection and resolution of errors in a wireless network. Faster troubleshooting ultimately reduces the duration of downtime, as well as improves the productivity of the users of the wireless service.

Where and When Should WLAN Traffic be Captured

The decision of whether WLAN traffic should be captured in the air or on the wire depends on the metric that you are focusing on, or what you are trying to accomplish. When capturing WLAN traffic is it necessary to see the payload of the packets, encrypted or otherwise? The answer to that question is usually (there may always be some exceptions) a resounding NO. And the reason for this is that if you are troubleshooting specific WLAN issues, then the payload is generally insignificant and unrelated to the metric at hand. If the WLAN has performance or quality issues, then you are generally interested in just the WLAN packets and headers, not the data payload. If the issue you are looking into is an application issue, then remove all the WLAN variables like signal strength, interference, and encryption and do your captures on the wired side of the AP. Following this process of elimination will result in quicker determination of the fault.

Most Common Wireless Network Performance Metrics or KPIs

Packet Loss

Packet loss is an indicator of interference, congestion, low bandwidth, etc.in a network, regardless of wired or wifi connectivity. It refers to a packet or packets of data being transferred from one computer to another in a network that are unable to reach their destination. It is represented as a ratio of packets that were sent out successfully against the number of packets that were received at the other end.

This metric can be used to measure the delivery of packet data from specific applications including VoWLAN (Voice over Wireless LAN). Acceptable packet loss differs for each data type; in the case of general data transfer, a packet loss up to 3% can be considered acceptable, but in VoWLAN, a packet loss up to 2% is almost intolerable for a clear and understandable audio conversation.

Latency

Also referred to as delay, latency is a measure of the time consumed in the transfer of data from one point to another in a wireless network. Latency as a wireless network efficiency metric comprises –

• Transmission delay, which refers to the overall time it takes small to large packets of data to travel to and from a client and server, or to and from clients on the same network.
• Server delay, which is the time it takes for a server to attend to a request.
• Network delay, which is a generic reference to the overall time it takes for data to be transmitted from a server to a client or from a client to a server.
• Latency is a KPI which is mostly used in monitoring TCP and UDP. High latency is a key indicator of slow network connections. While a high latency of up to 100 milliseconds might be acceptable for general data, a tolerable threshold for real-time applications should be less than 50 milliseconds.

Roaming Latency

Roaming latency is the amount of time it takes for a wireless client to move from one access point to another. Measuring roaming latency is done on the amount of time between the last known data packet for a device on one access point, and the first data packet seen for that device on another access point. This is extremely useful in determining whether latency is caused by devices on the network, applications on the network, or on the WLAN network itself.

Network Jitter

This is a measure of a wireless network’s transfer rate consistency – it is an indicator of the variability in a network’s delay time. Also, network jitter can be an indicator of heavy congestion or queuing on a network link. And it might lead to packet loss at the points where transit normalcy meets jitter, at which point it might appear as a delay or packet loss error. For general data, jitter up to or less than 90ms might be considered acceptable, but for real-time data, jitter above 20ms crosses the threshold of tolerance.

Packet Re-transmissions

When a packet of data is sent out successfully, and it doesn’t reach its destination, how many more times do you retry sending it again before it gets delivered? Retransmissions, when monitored and aggregated periodically, can be a key performance indicator of a wireless network’s poor performance due to glitches caused by hidden nodes, collisions, ACI, or unbalanced links, etc.

Uptime

Uptime or availability is a wireless network performance metric that indicates the amount of time that a wireless network is available for effective use.

Bandwidth and Throughput

As wireless network efficiency KPIs, bandwidth and throughput sound similar, but there is a subtle difference. Bandwidth is a measure of the amount of data that is EXPECTED of a network path to bear, or that can be expected to transfer successfully from one point to another in a network, within a given time. Throughput refers to the amount of data that ACTUALLY gets transferred from one point to another within a network path.

The metrics can be indicated in terms of Kbps, Mbps or Gbps. The differences between the bandwidth and the throughput can be used to determine how well a wireless network is performing.

Signal Strength

Ideal WiFi signal strength varies based on many factors, such as background noise, number of clients on the network, desired data rates and what applications will be used. For example, a VoIP or VoWiFi system may require much better coverage than a barcode scanner system in a warehouse.

The easiest way to express signal strength is the dBM. dBm is expressed in negatives. For example, -20 is a higher signal than -50. For low-throughput traffic like email, web browsing, or scanning barcodes, -70 dBm is a good signal strength. For higher-throughput applications like VoWLAN or streaming video, -67 dBm is better, and some engineers recommend -65 dBm if you plan to support advanced mobile devices.