26
Related Standards and Technologies
26.1 Introduction
In this chapter, we will consider the different wireless communications systems which overlap with Bluetooth either in technology terms or market segments, explaining the various strengths and weaknesses in each case. In some cases, they may appear to compete directly with Bluetooth; in others, they may appear to be orthogonal. However, what makes the wireless networking business so interesting is exactly how all these different technologies and initiatives do interact and impact one another, and—for the most part—they all do!
26.2 What are the Requirements?
Figure 26–1 gives some idea of the various applications for wireless connectivity and breaks these down depending on the required range and bandwidth. At one extreme is the home AV setup, where one might transfer video from a digital camcorder to a home video entertainment centre or VCR. This would typically only require a range of a few tens of centimetres, but the data rates could be very high. At the other extreme, cordless headphones or a remote controller would need only modest data rates, but the range could be tens of metres to work in the home environment. In between, we have office productivity devices such as printers and PCs; indeed, the classic Wireless LAN (WLAN) where both high data rate and reasonable range are important.
Figure 26–1 Wireless applications and requirements.
Recently, the rise of voice over IP (VOIP) systems has complicated the picture. As yet there are few commercial installations, but if voice over IP becomes popular, it will put an unprecedented load onto networks previously used only for data. Voice traffic is extremely sensitive to delays and places entirely different Quality of Service requirements on a network than data, so this is an area which many infrastructure providers are watching with interest.
The diagram also shows where each of the technologies we will discuss here fit in and how it is unlikely—for now at least—that any one standard can cover all the possible applications.
26.3 Infrared Data Association (IRDA)
The IrDA created a communications system based on infrared light. As such, IrDA is limited to line of sight and cannot penetrate furniture or walls as a radio-based system can. While this places limitations on device placement, proponents of IrDA point out that it does provide controlled and private data exchange.
The IrDA suite of standards were published in late 1993 and include the Serial Infrared (SIR) link specification, Link Access Protocol (IrLAP) specification, and Link Management Protocol (IrLMP) specification. In 1995, IrDA released extensions to the SIR standard for 4Mb/s operation, and since then has expanded the standard to include high-speed extensions for 1.152 Mb/s, 4.0 Mb/s, and 16 Mb/s operations using Pulse Position Modulation (PPM).
Table 26–1 IrDA and Bluetooth Compared
1This chapter refers to Gross Data Rates (symbol rate); application data rates are lower, see section 18.6.
Bluetooth and IrDA are both short-range technologies, but Bluetooth has a much more complete networking architecture. However, there are several interworking aspects. Bluetooth’s common OBEX support enables the same applications to use either access medium and there is some application commonality (IrMC) with standard content format, such as vCard and vCalendar. Table 26–1 compares IrDA with Bluetooth.
26.4 Digital Enhanced Cordless Telecommunications (DECT)
The DECT standard was developed during 1992 within ETSI as ETS 300 175 and 300 176 as a successor to the CT2 and CT3 digital cordless telephone systems in Europe. Today, DECT has a major share of the cordless telephone market worldwide and is also being rolled out as a Wireless Local Loop (WLL) solution in rural areas and the developing world. Dual-mode DECT/GSM systems are also becoming available, such as the One-Phone product from BT Cellnet in the UK, an integrated GSM cellular phone which switches to cordless operation when in the home using the cheaper, more convenient PSTN. Although slow to materialize, data applications using DECT are also now becoming apparent.
Based on a multi-carrier TDMA TDD scheme (see Figure 26–2), DECT uses ten frequency carriers in the range 1.88 to 1.9 GHz. Each time frame lasts 10 ms and the specified 24 time slots are split into two TDD halves: 12 slots for the downlink and 12 for the uplink, with each slot typically containing 32kb/s ADPCM2—coded voice data. This provides for up to twelve simultaneous full-duplex voice links. Due to the flexibility of the specification, these multiple channels can be combined into a single bearer of n x 24 kb/s (net data rate after error protection) for a maximum of 552 kb/s for data applications.
2Adaptive Differential Pulse Code Modulation (ADPCM) is a high-quality speech coding scheme that exploits the human auditory function to realize a high level of speech compression.
Figure 26–2 DECT frame structure.
A DECT system comprises one or more DECT Fixed Parts (FPs), or base stations, and one or more DECT Portable Parts (PPs). There is no limit to the size of the infrastructure as far as the number of base stations or cordless terminals is concerned.
The base standard only covers the interface between a fixed part and a portable part. It provides a toolbox with protocols and messages from which selections can be made (similar to the way in which Bluetooth profiles work) to access any specific type of network. DECT profiles have been defined for Radio in the Local Loop applications (RAP), ISDN Interworking (IAP), and GSM Interworking (GIP).
A DECT base station transmits continuously on at least one channel, providing a beacon function for portables to lock onto. The station’s beacon transmission carries broadcast information—in a multiframe, multiplexed structure—on base station identity, system capabilities, base station status, and paging information for incoming call setup. Portables locked on to a beacon transmission will analyse the broadcast information to determine whether the portable has access rights to the base station, whether the system capabilities match the services required by the portable, and whether the base station has free capacity to establish a radio link with the portable.
Dynamic channel selection and allocation and a seamless handover capability mean that portables can escape an interfered radio connection by establishing a second radio link—on a newly selected channel—to either the same base station or another base station. The two links are maintained in parallel, with identical speech information being carried while link quality is analysed. The base station then determines which link has the best quality and releases the other link.
Another aspect of this “handover” process is that as the portable moves out of range of a base station, it may hand over to another nearer base station, and this allows the effective range to be increased by adding more fixed parts to the system, something which version 1.0 and 1.1 of Bluetooth cannot do.
Without handover, Bluetooth cannot offer the features or the range of a DECT cordless installation, which make DECT so valuable as a scalable cordless telephony system.
If Bluetooth were to define a handover mechanism, it could threaten DECT. On the other hand, DECT’s dedicated spectrum is a major advantage. If Bluetooth becomes all pervasive, it may guarantee DECT’s longevity due to its not being in the band dominated by Bluetooth’s fast hopping interference. Table 26–2 compares DECT with Bluetooth.
Table 26–2 DECT and Bluetooth Compared
26.5 IEEE 802.11
The 802.11 working group of the IEEE standards body in the United States is responsible for defining and maintaining the Wireless Local Area Networks (WLANs) specification and standardisation. The original IEEE Standard 802.11-1997 specification defined three Physical (PHY) Layer specifications and one common Medium Access Control (MAC) specification. However, since then, further work has been carried out to extend the initial PHY specifications to provide higher data rates. This has led to Standards 802.11a and 802.11b. The current published specifications are IEEE 802.11-1999, IEEE 802.11a-1999, and IEEE 802.11b-1999.
We shall first consider the common MAC and the original PHYs before discussing the two enhanced data rate versions.
The MAC works with two network configurations:
- Independent configuration—Stations communicate directly to each other with no infrastructure support (so-called ad-hoc networking), which although easy to operate, provides a limited coverage area.
- Infrastructure configuration—Stations communicate via access points, which are part of a wider area distribution system, allowing access to an extended coverage area.
The MAC provides a basic access mechanism with clear channel assessment, channel synchronisation, and collision avoidance using the Carrier Sense Multiple Access (CSMA)3 scheme. It also provides service scanning (similar to Bluetooth inquiry and scan), link setup, data fragmentation, authentication, encryption, power management, and roaming facilities.
3A device listens to the channel before transmitting and only transmits if the channel is unused; this is also referred to as “Collision Avoidance” or CSMA/CA.
The 802.11 specification defines three associated PHYs:
- Frequency Hop Spread Spectrum (FHSS)
2.4 GHz ISM band, 1 and 2 Mb/s
2-level GFSK4 and 4-level GFSK modulation
Hopping at 50 hops/s over 79 channels
4Gaussian Frequency Shift Keying.
- Direct Sequence Spread Spectrum (DSSS)
2.4 GHz ISM band, 1 and 2 Mb/s
DBPSK5 and DQPSK6 modulation
11-chip Barker sequence for spreading
5Differential Binary Phase Shift Keying.
6Differential Quadrature Phase Shift Keying.
- Baseband IR
Diffuse infrared
1 and 2 Mb/s transmission
16 PPM7 and 4 PPM modulation
7Pulse Position Modulation.
The FHSS PHY is similar to Bluetooth but with a much slower hopping rate, and this has made it easier to implement 802.11 radio technology. With the current state of the art, however, the speed demanded by Bluetooth hopping is not really an issue any more. By using deeper modulation such as 4 level GFSK, the 802.11 data rate is easily increased. However, as the data rate is increased, so is noise sensitivity. With careful radio design, this can be tolerated, as is evidenced by the number of 802.11 FH-based PC WLAN cards now available on the market.
The DSSS PHY continuously spreads the data across the frequency spectrum rather than hopping in discrete time sequence.
26.5.1 IEEE 802.11b
Harris and Lucent Technologies proposed the chosen modulation scheme for 802.11b. This extends the 802.11 DSSS PHY to provide 5.5 and 11 Mb/s, in addition to the 1 and 2 Mb/s data by using 8-chip Complementary Code Keying (CCK) as the modulation scheme. The chipping rate is still 11 MHz, as for the standard DSSS system, and so the channel bandwidth occupied remains the same. The new PHY is referred to as High-Rate Direct Sequence Spread Spectrum (HR/DSSS). Since the same preamble and header are used, both the 802.11 DSSS and 802.11b HR/DSSS PHYs can coexist in the same network.
The adoption of the HR PHY has been a challenging task for the various manufacturers of 802.11-based WLAN products (mostly U.S.-based). However, 5.5 and 11 Mb/s products are now available from various suppliers, though these products are not in the same low cost arena as Bluetooth.
26.5.2 IEEE 802.11.a
The 802.11a PHY was proposed by NTT and Lucent Technologies and is very close to that specified for the HIPERLAN Type 2 standard (H/2) to facilitate common PHY silicon. We consider H/2 in the section below on HIPERLAN. Clearly, the ability to separate PHY and MAC is an attractive feature of the 802.11 architecture, and it is a testament to the designers that they were able to adopt a state of the art PHY to plug into their existing MAC.
The 802.11 family of standards is well entrenched in the world, particularly in the United States Proprietary products were available before 802.11 was finalised, and indeed, much of the impetus behind 802.11 was the concern that lack of interoperability between proprietary WLAN solutions could stifle the market. Right now, remaining proprietary solutions are being migrated toward 802.11 (the HR variant usually), and it looks as though it’s here to stay.
There are some questions as to whether bandwidth can be maintained at the high end, although reports indicate that rate back-off allows sustained data rates of well in excess of 5 Mb/s. A more crucial point is the overuse of the ISM 2.4 GHz spectrum—already crowded and now with two flavours of 802.11 and Bluetooth about to join the fray. Bluetooth’s fast frequency hopping should ensure that it does not become hindered; however, its impact on the slower hopping WLAN schemes is a topic of some discussion and research. The Bluetooth SIG has formed a “Coexistence/Interoperability with ISM devices” working group which is addressing issues of coexistence between Bluetooth and other equipment sharing the ISM band. This group has three main activities: quantifying the effect of interference on performance, developing methods of Bluetooth operation which can be used to improve coexistence, and coordinating with working groups which are producing future versions of the Bluetooth specification to evaluate coexistence issues in proposed new radio designs. Many commercial and standards organisations are also investigating the effects of coexistence in the ISM band, and several white papers have been published looking at effects of 802.11 and Bluetooth coexistence. The results are too complex to summarise here, but in brief the two technologies coexist, but suffer from reduced data rates as one would expect. Since both technologies implement power control grouping devices using one technology close together allows low power to be used and reduced the effects of interference. Similarly the more seperation between Bluetooth piconets and 802.11 networks the less the effect of interference.
In terms of cost, at present, 802.11-based products start at $99 and may cost as much as $200 for the HR version. This must be compared to tens of dollars for commercial Bluetooth products.
Because Bluetooth and 802.11 are in similar but not identical niches, there is a demand for devices equipped with both technologies. Some companies are working on combined devices which can exist on both a Bluetooth piconet and an 802.11 network at the same time.
26.6 The Homerf™ Working Group (HRFWG)
The HRFWG was formed in March 1998 to create an open industry specification for wireless digital communication between PCs and consumer electronic devices anywhere in and around the home and to act as a forum for the encouragement and support of home wireless networking.
The group now has more than 90 members including Intel, IBM, Compaq, and Microsoft. Drawn from the PC, consumer electronics, peripherals, communications, software, and semiconductor industries, many products are now available from various sources.
The HRFWG recognised that wired technologies make roaming with portable devices difficult, and in particular, the high cost and impracticality of adding new wires in-home will inhibit the widespread adoption of home networking technologies. To address these issues, they developed a specification for wireless communications in the home called the Shared Wireless Access Protocol (SWAP) to combine voice telephony with data distribution in the home environment.
Three subcommittees exist within the HRFWG. The HRFWG-Japan sub-committee is responsible for ensuring that the SWAP specification complies with Japanese regulations, while the others are planning future versions of SWAP to address wireless multimedia (20 Mb/s) and lower cost applications.
26.6.1 Shared Wireless Access Protocol (SWAP)
SWAP is designed to carry both voice and data traffic by combining DECT and 802.11 FHSS. It supports both a Time Division Multiple Access (TDMA) service to provide delivery of isochronous services, such as interactive voice, and a high-speed packet data service using the 802.11 CSMA/CA scheme (see Figure 26–3). The frames are 20 ms in duration, with voice retransmission at the beginning, voice traffic at the end, and interleaved asynchronous data packets on multiple links in between. The DECT beacon transmission signifies the start of the frame and is provided by the connection point network manager node.
Figure 26–3 SWAP and Bluetooth frame structures.
SWAP was designed to be low cost by using a more relaxed radio specification than 802.11 (PHY) but maintaining the same hopping scheme. Also, by eliminating the complex parts of the protocol (PCF and CTS/RTS), cost has been kept down. However, 802.11 TCP/IP support is included. The voice segment uses DECT with retransmission and employs the DECT calling stack and A/B fields. The voice-coding scheme used is the usual 32kb/s ADPCM.
A SWAP system can operate either as an ad-hoc network or as a managed network under the control of a connection point. The latter case is required for isochronous communications such as voice where the connection point provides the gateway to the PSTN. Each node can operate as one of the following:
- A connection point supporting both voice and data services.
- A voice terminal that only uses the TDMA service to communicate with a base station.
- A data node that uses the CSMA/CA service to communicate with a base station and other data nodes.
- A voice and data node using both types of services.
The HRWG has lobbied the FCC to change the FCC Part 15 regulations to allow channels up to 5 MHz, so-called Wideband Frequency Hopping (WBFH). Some suppliers of existing 1 MHz-based WLAN products have contested this, but the FCC is sympathetic to the request, which would allow HomeRF to migrate to a higher bit rate while maintaining the same FH PHY. There is also much interest in supporting multimedia applications at around 20 Mb/s, and this initiative is referred to as HomeRF/MM.
Table 26–3 lists the main features of SWAP and compares them with Bluetooth.
Table 26–3 SWAP and Bluetooth Compared
SWAP and the HomeRF concept may appear to be a direct competitor to Bluetooth. The HomeRF position is that while Bluetooth provides the Personal Area Network (PAN) connectivity, SWAP provides the Home Area Network (HAN) connectivity. This point of view has some merit, although Bluetooth does look set to evolve in terms of range and data rate and the cost of a Bluetooth subsystem is going to be much lower than a combined 802.11 / DECT subsystem. However, as noted above, at present DECT is far superior to Bluetooth for cordless telephony, and 802.11 is an accomplished WLAN standard. Although Bluetooth started out as a short-range wireless replacement technology, it is fast becoming many things to many people. Though this in itself can be dangerous, if controlled, Bluetooth could soon “mop up” the HomeRF concept along the way, offering as it does a lower cost solution and through evolution, similar range and data rates with improved cordless telephony support.
26.7 IEEE 802.15 and the Wireless Personal Area Network (WPAN)
The 802.15 group was created shortly after the public release of the Bluetooth standard in the summer of 1999 to create an IEEE-based PAN standard to complement the work of 802.11. The term “PAN” defines a new usage scenario in WLANs, where the key factors are lower power consumption, lower cost, and superior ease of use.8 Shorter range and lower bit rate are less important for this range of applications.
8Sometimes referred to as pervasive or hidden networking. The user does not need to even consider that he and all his belongings are networked.
In agreement with the Bluetooth SIG, the group decided to adopt the Bluetooth v1.0b standard as the basis for its work and was tasked with reworking the standard to fit with the IEEE networking model. Figure 26–4 shows the portions of the Bluetooth stack which 802.15.1 has adopted. These are shaded on the right; on the left is the IEE standard layers, showing how the IEEE MAC and PHY layers encompass the functionality of the Bluetooth stack from the radio up to L2CAP level.
Figure 26–4 IEE802 standards and Bluetooth.
In January 2000, the IEEE approved a second task group, 802.15.2, to examine coexistence and interoperability between 802.15 WPANs and 802.11 WLANs. The group is expected to produce recommended practices for coexistence and to suggest modifications to other 802.15 or 802.11 standards to enhance coexistence with other specified wireless devices operating in unlicensed frequency bands.
In March 2000, at the suggestion of Cisco, Eastman Kodak, and Motorola, the IEEE approved a third task group, 802.15.3, to create a high-rate WPAN standard. The group is tasked with creating the PHY and MAC specifications for high data rate wireless connectivity between fixed, portable, and moving devices within or entering a Personal Operating Space (POS).9 The eventual standard is intended to achieve a level of interoperability or coexistence with 802.15.1 and through the efforts of 802.15.2 other wireless devices. The data rate is intended to be high enough—20 Mb/s or more—to satisfy consumer multimedia industry needs for Wireless Pan (WPAN) communications, and the work is also expected to address the Quality of Service (QOS) capabilities required to support multimedia data types such as digital imaging and video applications.
9The space about a person or object that typically extends up to 10 meters in all directions and envelops the person/object whether stationary or in motion.
26.8 Hiperlan
The High Performance Radio Local Area Network (HIPERLAN) standard was developed within the European Telecommunications Standards Institute (ETSI) during the period 1991 to 1996. The HIPERLAN work group concluded that shared spectrum such as the ISM band did not facilitate the high data rates and guaranteed QOS they considered necessary for advanced multimedia-based wireless networking, and so both HIPERLAN Type 1 (H/1) and HIPERLAN Type 2 (H/2) use dedicated spectrum at 5 GHz. H/1 was completed in late 1997 as ETSI standard ETS 300 652.
Whereas H/1 is very much like a modern wireless Ethernet, there was a requirement for a follow-on development more akin to a wireless version of ATM, which led to the development of H/2. As work got underway on H/2, other related initiatives with common requirements were united within ETSI to form a new project, which was termed the Broadband Radio Access Network project, or BRAN.
The ongoing global industry debate between the IP camp and the ATM camp as to which is to be the future all-pervasive wired networking standard is well known to most people and we are sure that readers have their own views. However, the same debate now rages about H/1 and H/2. Although their respective PHYs are very different with H/2 promising much higher future data rates, H/1 can easily be improved to compete. In fact, they offer similar solutions but in different ways, and therefore suit different applications, depending on whether a centralized or ad-hoc network architecture is required.
The complete suite of H/2 specifications offers options for bit rates of 54, 36, 16, and 6 Mb/s. The PHY adopts an OFDM multiple carrier scheme using 48 carrier frequencies per OFDM symbol. Each carrier may then be modulated using BPSK, QPSK, 16-QAM, or 64-QAM to provide different data rates. The modulation schemes chosen for the higher bit rates will make practical implementations very challenging, and there may need to be further development to achieve throughput in the range 30–50 Mb/s.
Table 26–4 summarizes the features of both H/1 and H/2. Clearly they have some strong similarities and some marked differences. Several companies in the United States have already announced H/1 products, and components are under development by other companies. H/2 provides a different, more centralised protocol stack and higher data rates, but at the expense of a more complex system design, and products are unlikely to be around for a while. Several companies are reputed to be working on chipsets which support the lower layers for H/2, IEEE 802.11a, and MMAC.
Table 26–4 HIPERLAN Type 1 and HIPERLAN Type 2 Compared
Although all members of the Wireless LAN fraternity, HIPERLAN and 802.11a are really quite different from Bluetooth in terms of cost, performance, and application. H/1 and H/2 provide high-rate, medium-range multimedia distribution with video QOS, reserved spectrum, and good in-building propagation. H/1 uses an advanced channel equalizer to deal with intersymbol interference and signal multipath, while H/2 avoids these by using OFDM and a frequency transform function. These complex modulation/demodulation schemes and their 5 GHz operation make them both expensive. Bluetooth, on the other hand, is at least an order of magnitude slower and does not yet provide the same capabilities for multimedia distribution, range, or propagation.
26.9 MMAC
Multimedia Mobile Access Communication Systems (MMAC) is an initiative under the Japanese Association of Radio Industries and Businesses (ARIB) to produce an ultra high speed, high quality multimedia communications standard. Set for a launch date of 2002, the system aims to provide a four-tier scheme as follows:
- High-speed wireless access (outdoor, indoor)
e.g., mobile video telephony
30 Mb/s in the range 3–60 GHz
- Ultra high-speed wireless LAN (indoor)
e.g., high quality televisual applications
Up to 156 Mb/s in the range 30–300 GHz
- 5 GHz band mobile access (outdoor, indoor)
e.g., ATM access and Ethernet LAN applications
20–25 Mb/s in the 5 GHz band
- Wireless home-link (indoor)
e.g., home PC and audiovisual equipment networking
Up to 100 Mb/s in the range 3–60 GHz
Essentially, it is a parallel development to the H/2 / 802.11a work and is the subject of some liaison between both ARIB and ETSI. Currently, the 5 GHZ PHY specs are aligned to allow common silicon.
26.10 The Future
Home-wired networking is happening right now based on the IEEE 139410 standard. ETSI BRAN has been quick to realise this and is now working on IEEE 1394/H/2 convergence. Ericsson is involved in BRAN and the H/2 work, so it is not impossible to imagine Blue-tooth (high-rate) evolving in a similar direction to H/2. Indeed, the SIG has announced that medium and high rate Bluetooth devices will preserve backwards compatibility with earlier Bluetooth devices. This implies that the faster devices will support multiple modulation schemes as HIPERLAN/2 devices.
10A high speed serial communication standard for linking home and computer equipment, typically audio/video.
There has been some discussion between IEEE 802 and ETSI on unifying 802.11 and HIPERLAN; however, this is not well-supported in BRAN to date since the IEEE 802.11a MAC is very different from that of H/2. The two physical layer specifications are, however, broadly similar and harmonised to facilitate silicon device reuse.
The emergence of the home area network (HAN) and the personal area network (PAN) have made the picture much more complex. The traditional wireless computing system network, the WLAN, now has at least three different incarnations—in the office, home, and personal space. Bluetooth is targeted directly at the new PAN scenario and is set to succeed incredibly well there. However, will it evolve to provide the functionality of a HAN? HomeRF has a very good story to tell, but it has to fight against dropping costs of separate WLAN and DECT products and the possibility that Bluetooth will become a viable cordless telephony technology. DECT itself has a large installed base and this itself may prevent Bluetooth from commanding that market. Then again, Bluetooth is just starting out, and DECT has been around for some time now.
One of the key areas for the evolution of the Bluetooth specification past 1.1 will be increasing the data rate, and this could make a big difference to the way that the PAN / HAN story plays out. The main attraction right now of HAN is the desire to distribute video around the home for integrated AV entertainment connectivity without the need for wires, in particular to distribute broadband multimedia services inside the home once delivered to the kerb side.
This is where the work in BRAN has most recently been focused. Table 26–5 lists the most important data rates involved. The consumer DV gross data rate of 32 Mb/s is the value which the home environment group within BRAN has set as the minimum data rate for the BRAN H/2 standard to support for home applications.
Table 26–5 Video Data Rates
There has been much discussion in the industry on the minimum bit rates appropriate for the distribution of real time MPEG-encoded video services around the home, but the general consensus seems to be that a fixed bit rate coding scheme should require at least 5 Mb/s and a statistically multiplexed bit rate scheme between 4.5 and 8 Mb/s. The Digital Television Group (DTG) in the UK has adopted a minimum figure of 5 Mb/s and a peak of 9 Mb/s per channel for demanding material.
26.11 Summary
Clearly, the current version of Bluetooth does not provide suitable data rates for the complete home network; however, it can provide a part of that environment as a PAN or evolve through Bluetooth version 2.0 to support the higher data rates necessary. Even then, there is still a requirement for different networking paradigms for different purposes, i.e., voice based cordless telephony.
IEEE 802.11 is an established WLAN standard, and products are shipping. The family of specifications provides a complete wireless networking system which Blue-tooth, as it stands, is not capable of offering. However, Bluetooth offers service discovery capabilities which enable ad-hoc net.
DECT is also an established product and doing well as a cordless telephony system. The development of data based DECT is underway, but looks unlikely to succeed now as there are already many attractive solutions available. Thus, while Bluetooth does not support the range and handover capabilities of DECT, DECT should survive. It is also unhindered by the crowding in the ISM band, operating as it does just outside in its own dedicated spectrum.
The most interesting comparison is that to be drawn between Bluetooth and HomeRF, where there is a window of opportunity for SWAP to establish itself just above Bluetooth as the HAN while Bluetooth becomes the Personal Area Network (PAN). However, one feels that Bluetooth is likely to evolve to compete directly with HomeRF, unless higher data rate versions arrive to create added value. But, then again, H/1 and H/2 already have that base covered.
A very interesting development is the establishment of IEEE 802.15, and in particular, the high rate work in 802.15.3. The authors are unaware of what liaison is going on—if any—between 802.15.3 and the Bluetooth version 2.0 working groups. However, either way, with a target of 20 Mb/s for high rate PANs, one can expect the picture to only get more complex.
IrDA has now fixed many of its earlier issues related to interoperability and incompatible devices. In the early days, the standard was mostly unregulated, and though IrDA became a standard fit in most portable computer equipment (largely due to the me-too factor), it never became an industry or cross-industry standard.
This was because it proved frustrating to users as it was difficult to configure, required having an exact setup with appropriate system information, and devices had to be aimed—in particular, placed close together because misalignment caused problems. At the Application Level, it was not standardised and it never made it to desktop machines, so cables were still required to get data back to the desktop. Although in the short term, getting built in wins sales and makes the technology look promising. If it’s not being used, then it won’t command a price premium and will die out in the longer term. By contrast, a major selling point for Bluetooth is ease of use and its work-first-time “out of the box experience” (OOBE).
26.12 Useful Web Addresses
IrDA: |
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DECT: |
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IEEE 802.11: |
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IEEE 802.15: |
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HomeRF: |
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H/1: |
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H/2: |
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ETSI BRAN: |
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MMAC: |