Question 1: What is the core transmission technology employed by Adaptive Wireless?
Answer: At 2.4GHz, IEEE 802.15.4 radios (which are Direct Sequence Spread Spectrum radios) with frequency hopping modulation techniques applied as well. The result is a point-to-point radio communication that has proven 100% effective in power plants, steel mills and other harsh RF environments. Spinwave Systems are also based on IEEE 802.15.4 radios with sophisticated additional techniques for reliability, range and network scalability enhancement. Features of Spinwave radio systems vary between the A3 and ControlNet product lines.
Question 2: Do Adaptive Wireless products require a license?
Answer: No. Products offered by Adaptive Wireless operate in the internationally licence-free 2.4 GHz Industrial, Scientific and Medical (ISM) frequency band.
Question 3: What kind of range can be expected?
Answer: Actual range in any radio application is dependent on the implementation environment. With Spinwave Control Net products we can achieve up to 900 metres between repeater devices outside in good conditions without any additional antennas. When external antennas are added we can extend the range to up to 9000 metres outside in good conditions. One should expect typically about 25% of these ranges in a building. With Esenza equipment we can usually achieve up to 70 metres between nodes inside a typical industrial or commerical building not in direct line of sight and up to around 200 metres outside in direct line of sight
Question 4: Why not use 802.11 compliant (WiFi) protocols?
Answer: The 802.11 ‘WiFi’ protocol standard (2.4GHz) was designed primarily to promote LAN-based product interoperability and is best suited to this application. All 802.11 variants are optimized for high speed/short range communications and are generally not suitable when the needed range exceeds a maximum of 60 metres indoors. The only way to extend the range of 802.11 devices is through specialised antennas or additional base stations and special wireless repeaters which increase cost and complexity. 802.11 is primarily used for TCP/IP traffic on Ethernet connections which requires that all devices have a unique IP address. This is time consuming to set-up and manage in larger networks. Also, 802.11 employs only DSSS (see below) and is not very resistant to interference from all sources including Bluetooth radios and general electro-magnetic interference. 802.11 protocols are designed for file transfer and data streaming and as such represent a much greater security risk. Since wireless process sensors normally need very low intermittent data rates the manageability, security risks, cost, limited range, unreliability and complexity of 802.11 outweigh any potential advantages.
Question 5: How does mesh networking differ from Bluetooth?
Answer: Bluetooth is a single-hop point-to-multi-point technology designed for and mainly targeted at ad-hoc short range cable replacement applications such as wireless keyboards and mobile phone hands free operation. It is also quite limited in scalability with the number of network devices it can support per network limited to 8. There are some industrial applications where Bluetooth and/or other wireless technologies are applicable and it is part of Adaptive Wireless philosophy to be led by the needs of the application and not to try and make a particular technology fit a problem if it is not appropriate.
Question 6: Security is currently a major concern with IT wireless (WiFi) networks. How do wireless sensor networks address this issue?
Answer: The designers of the underlying technology standards used in wireless sensor networks (IEEE 802.15.4) were fortunate in being able to address security as part of the design specification rather than having to tackle security retrospectively. As such, the 802.15.4 radio standard builds in AES 128-bit encryption for all traffic. Also, the limited data rates supported by 802.15.4 networks are really not suitable for hacking or eavesdropping activities. It is also possible to lock 802.15.4 radio networks once they have been set up to prevent new devices joining.
Question 7: As this is a new technology should I not wait until the protocol standards issues are resolved before adopting the technology ?
Answer: Although there are several alternative wireless sensor networking protocols marketed by different companies and alliances they all use the IEEE 802.15.4 radio protocol as their foundation and any future standards will also be compliant with 802.15.4. It is therefore very important that any wireless mesh sensor networking hardware is fully compliant with 802.15.4 so that future standards may be adopted. Because of the breadth of the applications for the technology it is very likely that no one ’standard’ will meet all needs since they all are a trade off between different performance factors. Devices will likely be offered with the variant of the standard that is most suitable for the intended application. For example, the domestic market needs low cost whereas the industrial market generally demands higher reliability so protocol standards designs have to reflect this. The dominant body in industrial wireless sensor networking standards development is the US Industrial Systems and Automation society (ISA) whose SP100 committee and associated working groups are currently working through this issue. It is to be hoped that standards will become available probably in 2009. Devices supplied by Adaptive Wireless will support the standards when they are available. Spinwave devices’ firmware can be upgraded over the wireless network without affecting operation. In the meantime there is tremendous business value to be gained by use of the best available wireless sensor network protocols.
Question 8: What is Distributed Frequency Spread Spectrum (DFSS)? How is it different from Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS)?
Answer: DFSS is an approach that Sensicast which essentially combines the FHSS and DSSS techniques. We utilize an 802.15.4 radio which natively utilizes DSSS. This means that the transmitted information is spread across a number of frequencies simultaneously. This technique is inherently immune to narrowband interference but can be swamped by interference that is more broad-band in nature. Frequency Hopping (FHSS) is much more resistant to broad-band interference but in the event of interference in a given channel will require a retransmission which adds some latency.
Question 9: Are Adaptive’s products RoHS compliant?
Answer: We believe that our products fall into the Control and Monitoring class and as such are exempt.