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WiFi Connectivity Problems? Here is why…

As network professionals, we have all encountered, the dreaded WiFi-is-not-working complaints. You’re peacefully getting some work done at the office and then out of nowhere someone comes in and starts complaining about not being able to connect to the wireless network, about getting disconnected from the wireless network all the time, about not being able to connect to the internet, and so on. These are very common complaints, and all of them are very annoying since figuring out the root cause of these common wireless network problems can be very time-consuming and sometimes difficult. Or is that really the case? Could it be possible that solving these common wireless problems is not that difficult after all? Well, is it is not! The EtherScope nXG, AirCheck G2 and AirMagnet Wifi Analyzer Pro make short work of this.

The first step is to know what to look for. There are multiple reasons for WiFi connection problems and knowing about them will help you streamline the process of identifying the root cause.

  • Signal Coverage
    • Bad signal coverage is still one of the most common reasons for WiFi connection problems. After all, if WiFi devices can’t hear each other then they can’t communicate. Also, different from what most people think, Access Point signal coverage is not the only thing you need to worry about. You also need to take into consideration client device signal coverage. After all, if the Access Point can’t hear responses from a client device then communication will fail.

  • Signal to Noise Ratio
    • The quality and rate of a connection depend directly on the signal-to-noise ratio (SNR) that a receiving device detects, which includes both Access Points and clients. Attenuation or loss of signal strength lowers the SNR. As the signal level goes down, the SNR goes down, and so does the transmission rate. For example, a device that is “too far” from an Access Point may be able to see the network to which it wants to connect, but if the SNR is too low the quality of the transmission will be so bad that it will not be able to connect successfully (a “weak but strong-enough” signal one moment may become a “too weak” signal the next moment).
    • Another factor that affects the SNR is the noise floor, which can be defined as the ambient or background level of radio energy on a specific channel. This background energy can include modulated or encoded bits from nearby 802.11 transmitting radios or unmodulated energy coming from non-802.11 devices such as microwave ovens, Bluetooth devices, cordless phones, and so on. The higher the noise levels, then the lower the SNR. The worst-case scenario is when you have a weak signal and high noise levels, this fatal combination will greatly lower your SNR, which in turn, will cause performance and connectivity problems.

  • Legacy 802.11 Devices
    • Older WiFi devices are still around! But they do not support today’s higher data rates, so when they connect to a WiFi network, they will transmit only at lower data rates. Not only that, but a user may also be using a legacy device that does not support higher data rates without realizing it, which can be a problem since older legacy rates, particularly 802.11b, are sometimes blocked from operation at the Access Point to preserve precious airtime.  A device that only supports these older rates will be unable to connect to the network.
    • Another problem is older devices that do not support the 5.0 GHz band. Many corporate networks have been migrated to support the 5.0 GHz band only since there are more channels available and less interference, therefore on cases like this legacy 802.11 devices will not be able to connect to the corporate WiFi network anymore. Not only that, some older client devices may support the 5.0 GHz band, but not all the channels on that band. For example, many older devices do not support the DFS channels (frequencies shared with Radar transmissions), and because of that, they won’t be able to connect to the network.

  • Security Settings
    • Security is a good thing but managing security on access points and clients is not easy.  Any passphrase mismatch, certificate missing, or mistake can leave client devices unable to connect.
    • Besides that, some networks are secured by allowing only certain MAC addresses to connect and authenticate, so if a device’s MAC address is not on the authorized list, the client device won’t successfully connect.

  • Capacity
    • Capacity problems happen when you have too many client devices transmitting on the same area, or when there are one or more client devices generating an excessive amount of traffic (e.g., a bandwidth hog). Capacity problems could also happen when you have excessive co-channel interference, under-provisioned Access Points, client load imbalances, and non-802.11 interference problems. These can all lead to excessive client transmissions on a single channel, which overloads the channel and causes both performance and connectivity problems. Also, it is important to understand that it is not simply the number of connected clients on a channel that increases the load on that channel, an excessive amount of unconnected clients on the channel will cause problems too.

  • Wired Issues
    • Every wireless Access Point has a backhaul connection to the network and this is nearly always Ethernet. The Access Point Ethernet connection to the network is a vital link in the overall connectivity chain.  Even when a client device connects to the WLAN, they still need basic wired services like DHCP and DNS to access most resources. Wired problems that could cause wireless connections problems are:
      • DHCP and DNS Services Access – Problems with DHCP or DNS services will cause the user to think they cannot connect to the WiFi network. If the DHCP server is not accessible, the user’s client device will not be able to get an IP address. If the DNS server is not available, the user’s client device will not be able to access a website through its URL.
      • WAN Connectivity – Connection to the WiFi network can appear to be broken to the user if the WAN connection to the Internet does not work. This could be caused by simple routing problems like such as an Ethernet cable plugged into a LAN port instead of a WAN port, the WAN interface requiring a static IP address, or Point-to-Point Protocol over Ethernet (PPPoE) credentials needing to be entered on your internet service provider’s modem.
      • Access Point Power – Most modern Access Points run off Power over Ethernet (PoE). So, if the power available at the switch drops, or the wrong PoE option is configured, the performance of the Access Point may suffer dramatically. This could cause WiFi connection problems.

Author Bio –
Product Manager – Wireless

Julio Petrovitch is a product manager at NetAlly, plus a certified CWNA/CWAP/CWDP/CWSP. He’s worked with network design, testing and validation for more than 15 years. Throughout he’s career he has had the opportunity to work with multiple networking technologies, including POTS, DSL, Copper/Fiber Ethernet, Wi-Fi, Bluetooth, and BLE.