4 4 ZigBee and Bluetooth are different
by design and are optimised for
different applications. Real
industrial wireless ne...
ZigBee and Bluetooth
joined together and formed the ZigBee Alliance in mid-2002
to develop and promote this technology and leverage the
ZigBee and Bluetooth
simple to implement and support.
Network topology: Increasing the number of possible
communication pa...
Focus on remote sensing and control
• Warehouses, Fle«t management Factory, Supennarhets, Office
• Cas/Water/Eie...
ZigBee and Bluetooth
Network topology and number of devices: The increased
range of options in terms of topology and the s...
Bluetooth vs zigbee
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Bluetooth vs zigbee


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Bluetooth vs zigbee

  1. 1. 4 4 ZigBee and Bluetooth are different by design and are optimised for different applications. Real industrial wireless networks will inevitably be hybrids including both in complementary roles. IEE Computing i Control Engineering | April/May 2005
  2. 2. ZigBee and Bluetooth ONLY IN THE LAST 10 YEARS OR SO, WITH CONTINUING ADVANCES IN SEMICONDUaOR, RADIO AND BATTERY TECHNOLOGY HAS SIGNIFICANT EFFORT BEEN MADE TO DEFINE AND DEVELOP WIRELESS TECHNIQUES FOR DATA NETWORKS. Bluetoothstrengths and Weaknesses for Industrial applicationsBy Nick Baker Most industry analysts are fore- casting explosive growth in the use of wireless data network technologies in industrial applications in the next few years. Figure 1 depicts the wireless spectrum in terms of two key performance characteristics - wireless radio range aiid data transmission rate. Other performance characteristics will be discussed later but in terms of these two parameters it is important to recognise that the two IEEE standards that underpin ZigBee (802.15.4) and Bluetooth (802.15.1) are intended to differentiate them from each other. The IEEE defmes only the Physical (PHY) and Medium Access Control (MAC) layers in its standards. Eor both ZigBee and Bluetooth separate alliances of companies worked to develop specifications covering the network/ link, security and application profOe layers so that the coniniercial potential of the standards could be realised. Bluetooth originated in 1994 when Ericsson began to examine alternatives to cahles tbat linked mobile phone accessories. In 1998 Ericsson was joined hy IBM, Nokia. Intel, and Toshiba to form the Bluetooth Special Interest Group (SIG) which defined the initial specification. In mid-1999 the SIG approached the IEEE and asked them to formally adopt the Bluetooth specifications. The 802.15.1 Standard was published in 2002. Thousands of Promoter. Associate, and Adopter companies have since joined the SIG which develops, publishes and promotes Bluetooth and runs a qualification program to foster device interoperability ZigBee's origins date only from 1998 when Motorola started work on this type of low power mesh networking. The IEEE 802.15.4 standard was based on Motorola's mid- 2001 proposal and was ratified in May 2003. Phillips, Motorola, Invensys, Honeywell, and Mitsubishi -^ WAN Fig I: The wireless landscape IEE Computing & Control Engineering | April/May 2005
  3. 3. joined together and formed the ZigBee Alliance in mid-2002 to develop and promote this technology and leverage the standard. Ember. Freescale and Samsung joined as promoters later. They worked together on defining the network, security and application layers of the ZigBee specification, which was ratified in December 2004. There are now well over 100 affiliate members of the ZigBee Alliance representing semiconductor manufacturers, technology development companies, OEMs, end user coinpanies and systems integrators. TECHNOLOGY OBJEaiVES So wbat are the objectives behind the two technologies? Looking in a little more detail we can see some clear differences and some similarities. Firstly looking at Bluetooth, the SIG mission statement defines an objective targeting short range and mobile Direct Connection • Wire replacement • Point to point Star • One central routing and controi point > Singie-iiop-point to multi-point ' All data flows through centrai point < Exampies are UVifl. Bluetooth. CSM Mesh • Multipie data paths • Muilt-hop • Seif configuring, seif healing • Examples are ZigBee, EmberNet SensiNet Fig 2: Wireless network topologies products and this is echoed by the IEEE in defining a 'Personal Operating Space" (POS) of 10m radius and allowing for mobility The use of the word 'personal' links this technology at its core to provision of ad-hoc connections hetween devices used by humans. The types of device interoperability profiles that bave been developed for Bluetooth [cordless telephony headset, LAN access, fax, printing, hands-free, etc.] and the types of application areas in which products bave been developed are very much in line with the intent of the SIG and tbe standard. Looking at ZigBee the key additions or differences in terms of the alliance mission statement are low power, networked |as opposed to connected], and open standard. The 802.15.4 standard also speaks of a POS and 10m range but recognises the possibility for greater range at lower data rates. These mesh self-bealing networks, which allow mobility of end nodes within tbe network and, by virtue of their multi-hop capability can cover large areas, will have a very wide range of applications from industrial sensing and control to huilding automation and security, home automation and even in interactive toys. DESIRABLE CHARAaERiSTiCS OF NETWORKS Let's focus our attention on industrial wireless data networks and their desirable characteristics. Range: At least 50m in "cluttered" industrial RF environments where there is often a lot of metal in equipment and building structure and increasing amounts of radio interference. Data rate: In industrial sensing and control applications required data rates vary widely by application but are often low and/or intermittent. Network latency [or how long the data takes to getfrom origin to destination/: This varies widely by application. It should ideally be possible to tune tbe network availability or response to tbe application i-equirement at the end-node to optimise performance. A second consideration is how long new devices take to join the network. Powerprofile: Ideally under all circumstances devices would be battery-operated to avoid both power and data wiring costs and increase tlexihility Security: At the lowest level: How sure can I be that the data did get from origin to end point accurately and completely? This is critical in sensing and control applications where humans do not normally validate data at the operating time interval. At the highest level: How sure can I be that my network and its data cannot be 'hacked' and the data misappropriated or meddled with? Am I able to control which devicesjoin my network? Operating Frequency: The main requirement here is operation in one of the unlicensed bands for operating cost and regulatory reasons. Globally tbe 2.4GHz ISM band is emerging as the preferred band, which brings increased risk of interference from otber devices. Much of the overhead of wireless network protocols involves strategies to avoid interference degradation of network integrity Engineering and design complexity: More complexity will drive up cost for product developers, implementers and end-users. The technology should ideally be relatively simple to understand and engineer into products, have low overheads in I^^s of system operation and design, and be lEE Computing & Control Engineering i April/May 2005
  4. 4. ZigBee and Bluetooth simple to implement and support. Network topology: Increasing the number of possible communication paths through the network increases the likelihood that the message will be received at its destination, even if after multiple hops. Tbis makes network traffic more complex but will increase the network resilience and reliability Ideally the fuH range of topologies [Figure 2] sbould be supported. Number of devices: The numher of required measurement points is increasing significantly often in a 'retrofit' manner, to more completely measure industrial environments and processes for better control and for compliance and audit purposes. In most real industrial applications many tens, hundi'eds and possibly thousands of devices could he required in a network. Scalability/Extendability: Industrial environments constantly change - growing or shrinking in size and the number and nature of measurement points. Sometimes this is short term - for example. Intensifying measurement during commissioning stages of a new plant. Tbe wireless network must be capable of accommodating these changes without significant support overhead to tbe enterprise. Flexibility:The networking technology should be flexible in terms of tbe uses to which it might be put. It should be agnostic to the type of sensors or output devices attached and able to be implemented for different device types without a lot of device-specific requirements within the network or tbe protocol stack. Resilience and reliability: It must have the real world" Bluetooth is 'always on' and must be recharged frequently; ZigBee 'sleeps' most of the time and has years of battery life , , performance capability to deal with transient interference and obstacles. It must be able to manage and adjust the network configuration, ideally automatically and know or be alerted when the network encounters a situation that it cannot resolve. During the network implementation it should be possible to design out unnecessary single points of failure. COMPARING ZICBEE WITH BLUETOOTH We turn now to a comparison of the two technologies in terms of tbe desirable features above and reference Fig 3. Range: As designed and without special equipment it is clear that ZigBee has the potential to operate over a greater range especially in 'low clutter'-radio environments. Tbe upper range limit has really only been possible with proprietary mesh networking protocols, such as SensiNet. running over 802.15.4 radios. Data rate: Where higher data rates are important Bluetooth clearly has the advantage and can support a wider range of traffic types than ZigBee. -> characteristic Range As designed Special kit or outdoors Data rate „ ,,.,-,,,,„,.„ Network Latency (typical) New slave enumeration Sleeping slave changing to active Active slave channel access Power profile Security Operating Frequency Complexity Networii Topology Number of devices per network Scalability/Extendability Flexibility Resilience and reliability ZigBee 10-100 metres up to 400 metres 30ms 15ms 15ms Years Optimizes slave power requirements 128 bit AES and application layer user definable 868 Mhz, 902-928 MHz, 2.4 GHz ISM Simple Adhoc star, mesh hybrid 2 to 65,000 Very High/Yes Very High Very High Bluetooth 10 metres 100+ metres dep. on radio 20s 3S 2ms Oays Maximises adhoc functionality 64 bit 128 bit 2.4 GHz ISM -^M Complex Adhoc piconets •^^^. 8 -:flHK^ Low/No Medium, profile dependent Fig 3: Comparison of desirable characteristics IEE Compjtmg & Control Engineering | April/May 2005
  5. 5. Focus on remote sensing and control • Warehouses, Fle«t management Factory, Supennarhets, Office complexes • Cas/Water/Eiectric meter, HVAC • Smoke, CO, H,0 detector • Refrigeration case or appliance • Equipment management services ft Preventative maintenance • Security services • Lighting control • Assembly line and work fiow. Inventory • Materiait processing systems (heat gas flow, cooiing, chemical) Temp sensor Energy, diagnostics, e-Business services • Gateway or Field 5ervice links to sensors ft equipment Monitored to suggest PM. product updates, status changes • Nodes iink to PC for database storage PC Modem calls retailer. Service Provider, or Corp headquarters Corp headquarters remoteiy monitors assets, billing, energy management Fieid Service or mobiie worker 1004 Tba Zi(BM MHanca, Inc Materiais handDng Fig 4: ZigBee industrial applications Service Provider Retailer Network latency: To be able to sleep for extended periods to conserve power and achieve acceptable network latency ZigBee end devices need to wake up very quickly, transmit and/or receive and go back to sleep. The multi-hop nature of mesh networks also increases latency. Bluetooth is clearly designed for single hop device-to-device where the nodes do not sleep for much of the time and as a result network access is fast. Powerprofile: Bluetooth devices are constantly alert for available networks for them tojoin. To do that they have to be awake. The power profile is 'always on" to maximise this ad hoc networking functionality with days of battery life and regular recharging required. ZigBee has been developed specifically to permit low power consumption and years of battery life. Security: Both protocols have security huilt in. 802.15.4 specifies use of the 128 bit Advanced Encryption Standard High speed Bluetooth embodies device profiles for equipment interoperability whereas ZigBee is intended to be an open global standard and the ZigBee specification defines how to handle encryption key change and multi-hop transmission security Security is also user definable within the application layer for ZigBee networks. Beyond encryption each ZigBee node retreives a unique short address from the network coordinatoi' and each ZigBee network has a unique ID. In addition ZigBee networks can also be open or locked to new devices. Bluetooth uses 64 or 128-bit encryption based on the SAFER+ algorithm for authentication and key generation. Operatingfrequency:ZigBee supports most of the widely used unlicensed ISM bands in Europe, NA. and around the world whereas Bluetooth operates solely on the 2.4GHz band. Although the 2.4 GHz band is becoming a defacto global standard (many companies in North America now prefer it to 915 MHz) support for other bands can he important to industry for legacy reasons. Complexity: We have mentioned the relative complexity of the Bluetooth protocol stack compared to ZigBee and the fact that Bluetooth embodies device profiles for equipment interoperability whereas ZigBee is intended to be an open global standard - a ZigBee compliant device from any manufacturer should interoperate with any other. Deployment complexity and operational support of pure ZigBee networks are as yet untested in the real world but makers of proprietary 802.15.4-based mesh networking technology such as Sensicast have found that implementation and support with networks of several hundred nodes is relatively simple. Bluetooth complexity is, in practice, limited by the small numher of devices allowed in each network. iEE Computing & Control Engineering | Apnl/May 2005
  6. 6. ZigBee and Bluetooth Network topology and number of devices: The increased range of options in terms of topology and the significantly larger numher of devices per network would suggest that ZigBee will have much greater capahility to address the spectrum of industrial situations. Scalabiiity/Extendabiiity: ZigBee has a significant advantage here in terms of the ease of network growth to quite large scale implementations and the ahility to use the flexible topologies to accommodate real-world situations. Flexibility: In theory both protocols are tlexible and can carry any type of data. In practice the profile dependency of Bluetooth carries some built in inflexibility. In some ways this category could be seen as a qualitative amalgamation of all the preceding categories which suggest that ZigBee is the more flexible approach for industrial applications except where there is a need for higher data rates. Resilience and Reliability: From the purely technical perspective ZigBee wins here in terms of the range of industrial situations that are likely to be encountered, due to its data packet acknowledgement. CSMA-CA approach, encryption, mesh multi-path transmission redundancy and ahility to physically worii ai'ound the buUt enviromnent due to the hybrid network configuration options. Within its constraints Bluetooth is resilient - it works very well for certain application types. ZIGBEE APPLICATIONS Figure 4 shows the wide variety of foreseen applications for ZigBee and other 802.15.4-hased proprietary technologies. There is a focus on remote sensing and control reflecting the ZigBee mission statement, and the possibilities are virtually limitless. Many of these applications apparently require the adoption of ZigBee by OEMs on a large scale. Before that happens there is a huge opportunity to retrofit enhanced sensing and control into existing huilt environments using ZigBee/802.15.4 technology through 'off-the-shelf production-ready mesh networking elements linked to any of the wide range of existing sensor types and actuators. Clear advantages over classical wired installations are speed, low cost, tlexihility and long-term re-usability all of which can help increase enterprise productivity ZigBee is not yet field-tested for these applications. Many organisations are developing ZigBee products but this is still in the early stages hecause the initial specification was only ratified a few months ago, in December 2004. Since 802.15.4 was published many companies have been developing 802.15.4-based mesh networks. All the existing products in this sector use proprietary non-ZigBee network protocols on top of 802.15.4 although many are designed to support the ZigBee protocol stack on the same hardware. Examples are EmherNet. SensiNet and Millennial Net. Looking at Bluetooth there is clearly an intended focus on short-range cahle replacement for medium bandwidth device to device connections. Beyond this. Bluetooth access points can extend LANs and corporate networks to Bluetooth devices. In the industi'ial world the most likely uses for Bluetooth are for machine to machine communication and for ad hoc connectivity between mobile computing devices and fixed equipment. This could he for diagnostics, data transfer or configuration, especially in cases where use of temporarily connected cahles would be difficult such as in certain types of hazardous environments. Examples of current uses largely follow this trend because Bluetooth has been established as a useful standard for at least two years longer than ZigBee. It has reached an early level of maturity but is still heing promoted into new usage areas and extended in capability and refmed. In summary it seems clear that ZigBee and Bluetooth are different by design and are optimised for different In industry Bluetooth will most likely be used for machine-to-machine communication and for adhoc connectivity between mobile computing devices and fixed equipment applications. Real industrial wireless networks will inevitably be hybrids including ZigBee/802.15.4 and Bluetooth in complementary roles that suit the characteristics of each. The key to success will be in deploying the right wireless technologies for the requirements of the application and avoiding the temptation of trying to make one technology meet all needs. However, considering the wide range of typical iTidustrial opportunities for wireless network use it seems clear that ZigBee and 802.15.4-hased proprietary protocols can meet a wider variety of real needs than Bluetooth. The key reasons are the intrinsic value to the industrial enterprise of long-term "unattended" battery operation, greater useful range, flexihility In a number of dimensions that were highlighted earlier and finally the inherent resilience and reliability of the mesh networking architecture. • The author, Nick Baker, is the managing director of Adaptive Wireiess Solutions. He many be reached at nbaker@adaptive- wireless.co.uk IEE Computing i Control Engineering | April/May 2005 25