As more features are added to the FLEX-6000 Signature Series SDRs, depending on the feature, there may be increases in the amount of bandwidth utilized between the radio and the client application, like DAX or SmartSDR for Windows. One important characteristic of the SmartSDR radio / client paradigm is that in order to operate the radio in real time with minimal delays on a network, the data is streamed between the radio and the client with minimal buffering and packet loss.
One consequence of streaming data is that it can expose weaknesses in your network architecture, resulting in packet loss, packet delay (latency) and reduced network throughput. These issues, especially packet loss can manifest itself as stuttering DAX or remote audio, jitters in the panadapter display or in the worse case situations, disconnects between the radio and the client software running on your PC.
A commonly used network configuration is to directly connect the FLEX-6000 via a wired connection to a wireless router and then run SmartSDR for Windows, SmartSDR CAT and DAX on a wireless laptop or tablet computer. This is a convenient way to access and operate the FLEX-6000, but there are several performance trade-offs with wireless networks that you do not have to take into account with a completely wired end-to-end connection.
These trade-offs make troubleshooting and determining the root cause of wireless network performance issues a challenging undertaking. Below are some, but not an all-inclusive list of the more common issues and factors affecting wireless network performance along with a few helpful suggestions.
Wireless Network Connectivity - Convenience Comes at a Price
If the throughput of the wireless link between the client and the radio degrades too much, resulting in significant packet loss or packet delay due to the various factors listed below, the operational performance of your FLEX-6000 will become inconsistent and suffer. These issues will manifest themselves as disconnects, momentary pauses in the spectrum displays and audio drop outs between the FLEX-6000 and the controlling client software.
Furthermore, there are many different reasons why your wireless throughput will degrade, making troubleshooting wireless network performance issues very challenging, even for a seasoned network engineer.
1.) Wireless Connections Never Achieve the Advertised Speeds.
Wireless devices are categorized by their IEEE 802.11 "letter" designation that indicates the maximum theoretical aggregate throughput, the frequency it transmits on and the channel bandwidth. The First Rule of Wireless networking is "It never goes as fast as they say it does; it doesn't even come close."
Wireless devices are not full duplex. Wireless data can only flow on one wireless link in one direction at any one time, which means that the maximum data transfer rate or throughput will be well below half of the raw wireless network speed in actual operation.
As an example, if your network router is rated at 54 Mbps (802.11a /802.11g), the maximum theoretical transmitted throughput is 1/2 of the maximum bi-directional throughput or 27 Mbps. Due to other factors such as the protocol overhead, the actual bandwidth achieved will be even less. An 802.11a or 802.11g wireless network generally run no faster than ~20 Mbps excluding other factors that attenuate signal strength and bandwidth (see below).
2.) Bandwidth and Signal Strength Decrease with Distance and Obstructions
The distance between your router and the wireless PC is a more relevant factor than you might think. Here's a rule of thumb: Inside a dwelling, doubling the distance between router and client you can expect throughput to shrink to one-third of its original value. Using our 802.11 example above, by taking your PC to the next room decreases the maximum theoretical transmitted bandwidth from 27 to 18 Mbps.
Unless your router and PC are outside or have a direct line of sight, the wireless microwave signals will have to pass through obstructions decreasing network throughput. The worst signal attenuators are water and metal. Wireless devices usually operate on 2.4 and 5 GHz. The higher bandwidth wireless channels are usually the ones that usually support the higher throughput, but are also most susceptible to signal attenuation. Using the lower frequency 2.4 GHz channels may offer better network throughput in a location with a large distance between the router and PC and many obstructions the signal must pass through.
3.) In-Channel and Co-Channel Interference
Wireless networks are becoming ubiquitous in just about every home, as telephones, baby monitors, and wireless Internet are now standard amenities that use the same frequency spectrum as your wireless network. Your wireless router automatically detects the least crowded channel and makes that its default when it is set up. But as more wireless devices are installed around you, the default channel may have other devices sharing it and this leads to a decrease in the signal to noise ratio (SNR) which increases network latency and further degrades network throughput.
There are software tools that analyze the entire Wi-Fi spectrum providing visual details about your home network as well as channel usage. You can use this data to manually assign a channel that has the least in-channel and adjacent or co-channel interference for optimal throughput.
4.) Bandwidth is Throttled and Shared Among all Connected Devices
Wireless bandwidth is directly affected by the network device wireless type and number of devices sharing the same wireless router.
A wireless network connection operates at the highest possible speed that both devices (endpoints) can support. An 802.11g laptop (54 Mbps) connected to an 802.11n (300 Mbps) router, for example, will throttle the entire network at the lower speeds of 'g'.
Also, all of your connected devices are fighting for limited bandwidth. The more devices using the same wireless router equates to more aggregate traffic utilizing the finite amount of available bandwidth resulting in slower throughput for all connected devices. Meaning that if you connected to your FLEX-6000 and a family member start streaming a locally stored movie, you can expect your throughput to be cut in half.
5.) Wireless Network Engineering Recommendations
There are several IEEE wireless networking standards and the bandwidth provided by them are dependent on the frequency of the channel, which can be either 2.4 or 5 GHz) and channel bandwidth.
In selecting a new router or deciding if your wireless network may be suitable to use with the FLEX-6000, below are a few rules of thumb to go by.
- 2.4 GHz - Best for wireless compatibility with multiple devices and range
- 5.0 GHz - Best for Wireless Performance
Maximun Theoritical Wireless Speeds
- 802.11b - 11 Mbps (2.4GHz): Not recommended for use with the FLEX-6000
- 802.11a - 54 Mbps (5 GHz): Minimum recommended for FLEX-6000
- 802.11g - 54 Mbps (2.4GHz): Minimum recommended for FLEX-6000
- 802.11n - 600 Mbps (2.4GHz and 5 GHz): Recommended for use with the FLEX-6000
- 802.11ac - 1300 Mbps (5 GHz): Latest wireless technology
Actual Real-World Average Wireless Speeds
The values below represent wireless network throughput in an ideal situation, without any distance, obstruction, co-channel interference, or bandwidth sharing with other devices.
- 802.11b - 2-3 Mbps downstream (bi-directional data rates can be lower)
- 802.11g - ~20 Mbps downstream
- 802.11n - 40-50 Mbps typical, varying greatly depending on configuration, whether it is mixed or N-only network, the number of bonded channels, etc. Specifying a channel, and using 40MHz channels can help achieve 70-80Mbps with some newer routers.
- 802.11ac - 70-100 Mbps
6.) Disable the 802.11 Functionality that is not Needed.
If your router supports the older 802.11b standard, it is recommended that you turn it off. If a slower device connects to your router, it will degrade the performance of the other devices that are connected using new standards, like 802.11g, 802.11n or 802.11ac with the lower speed devices are communicating with your wireless router. If you have 802.11b devices that require wifi access, either upgrade them or use a dedicated wifi router for lower speed devices. If you only have newer wifi devices that require access, disabling 802.11a/b/g may improve your throughput performance.
7.) Channel Bandwidth Matters.
When configuring your wireless router, there may be options for different channel bandwidths for the 802.11n and 802.11ac standards. You should always configure the router so that all channel bandwidths can us used, as the wider the channel bandwidth, the higher the theoretical data rate.
There is one exception. If your location has a lot of 2.4 GHz Access Points and devices nearby, this creates a lot of in-channel and co-channel interference or QRM. Using the wide 40 MHz channel bandwidth on the 2.4 GHz band will result in lower throughput performance in addition to contributing to the aggregate interference at that location.