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Wireless communications

Wireless networks use Radio frequency (RF) technologies to transmit and receive data over the air. The need for copper wiring is removed and the user is now mobile. Consequently, wireless networks have a massive potential to reshape the way we work and live. Unsurprisingly, the market sector for wireless technology is vast and there are a large number of competing technologies on offer. Bluetooth and Wi-Fi are established but have their limitations and newer technologies, such as 5G, LoRa and NB-IoT will become more widespread in the future. Cost-effective, efficient and reliable wireless networks offer several significant advantages over wired networks:

Mobility

The ability to access data remotely and in real-time from anywhere in the organisation has the potential to improve productivity, change work practices and alleviate the pressure on accommodation; there is never enough workspace or meeting rooms so why not work from home and only book accommodation when necessary.

Operational flexibility

Wireless networks can assume any number of topologies and they can easily be reconfigured to meet the changing requirements of the local environment. Small peer-to-peer setups can be quickly reconfigured to participate within large infrastructure networks with many hundreds of users roaming throughout the organisation. In fact this type of operation often takes place seamlessly as user changes environments.

Accessibility

Several current wireless sensor projects are currently looking at remote sensing applications. In terms of accessibility this could translate to remote geographical locations (deep sea, deserts, artic etc) or hostile environments ( battlefields minefields, hazardous areas – radioactive, chemical etc) or even inside bodies. Some aspects of this work is briefly discussed later.

Installation - speed and flexibility

Lower installation costs. Once the access points are in place there is no wires to run or holes to drill. Installing a new node is significantly faster and causes less disruption to the workplace environment. Additionally, there is little restriction on the placement of nodes; dead spots do occur but the recurring ‘ wires can’t reach’ problem disappears.

It’s not all upsides with wireless connected systems though, they have their own particular set of downsides:

  • Wireless networks can operate at high-speeds, IEEE802.11n is capable of speeds upto 540Mbps, which is sufficient for video streaming and multi-user connections, however, wireless will never match the speed, nor the reliability of wired systems. Ethernet now offers 10Gbps speeds.
  • Loss of signal and the effects of noise on the quality of service are definite issues. In office environments, obstacles such as concrete walls and furniture absorb Radio Frequency (RF) signal energy and reduce the achievable range of operation. Metal objects reflect RF signals which causes signal interference: the multi-path signals cause by reflections and refraction ( bending around objects) can be constructive where the signals arrive at locations in-phase – which is good, and destructive interference where signals arrive out-of-phase, or in the worst-case where they arrive anti-phase, causing a signal null-spot. In practice, moving a WiFi device just a few centimetres can cause a large variation in received signal strength (RSSI).
  • Signal congestion is another issue. As the number of users in the 2.4GHz range increases so too does the traffic, the interference, the number of collisions and the noise floor, none of which is good for reliable communications. Industrial acceptance of wireless networking is wholly dependent on its ability to survive in environments that are heavily contaminated with the electrical noise and interference by large machinery such as motors and welders. Are they robust enough to cope with these caustic environments.
  • Encryption schemes, such as Wi-Fi Protected Access (WPA2), have arguably made wireless networks as secure as their wired Ethernet counterparts and this has significantly improved a perceived area of weakness and confidence in this aspect wireless technology. Confidence in the security of WiFi connections at least have, to a large degree, been restored. Low power sensor network protocols, however, still have a long way to go on this issue: some use AES128 encryption but many are just open. Also the energy overhead required to power and execute security algorithms is in direct conflict with the requirements of low energy sensor networks.
  • The debate about possible health implications arising from increases in RF energy within local environments still rumbles on, although evidence from recent studies on mobile phones has not established any clear link.

Types of wireless network

Wireless networks have been categorised in terms of their geographical area of coverage in much the same way that wired networks have been categorised as LAN, MAN and WAN. In wireless networks Wireless Personal Area Networks (WPAN), Wireless Local Area Networks (WLAN), Wireless Metropolitan Area Networks (WMAN), Wireless Wide Area Networks (WWAN) all exist. The table below indicates their intended area of geographical area of coverage:

Type Range
WPAN < 10m
WLAN ≈ 100m
WMAN > 100m
WWAM ≈ 100m

These indicators are intended as a guide to show that wireless networks can operate in short or long-range environments and that their operational characteristics demand a range of technologies to support them. For example, WPANs focus on low power and extended battery life, whereas WLANs focus on high bandwidth, primarily for streaming applications and multimedia files.