| CATHAL'S
CORNER |
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Cathal Mc Daid
January 2003 |
2006 Introduction: In the Fall of 2003, the Bluetooth SIG
Board of Directors adopted the current version of the Bluetooth
specification. Version 1.2 is the fourth generation of the
specification. The article below is from 2002, prior to the final
adoption of version 1.2.
Future versions of Bluetooth - Bluetooth 1.2 & Bluetooth 2.0
The Bluetooth SIG has aimed from the start to ensure that developers and
users do not concern themselves with updated version of the Bluetooth
specification, but rather concern themselves on implementation of
the existing Bluetooth 1.1 spec and the use/development of profiles.
This is to ensure that developers do not wait for later spec versions
and that confusion and interoperability problems do not enter the
marketplace. However, the recent release of cores based on preliminary
Bluetooth 1.2 and speculation on the abilities of Bluetooth 2.0, means
that far-sighted developers should not stand still in approaching
Bluetooth optimisations. This article explains the features on a
broad level of Bluetooth 1.2 and examines the reports on Bluetooth 2.0.
Note: Both of these specifications are still heavily
under development, and as such detailed technical description will not
be covered. Any features here should NOT be taken as definitive word on
the specifications, contact the Bluetooth SIG for comprehensive details.
Status of Bluetooth 1.2
The Bluetooth SIG has recently (Dec 2002), released
IP v0.7, a series of Improvement Proposals (IPs) to the Bluetooth spec.
These IPs are treated as informative and not normative. This distinction
is because the text will be adapted and incorporated via Change Requests
(CRs) into different volumes, parts and sections of the BT 1.2 Core.
In general, the 1.2 Core release is intended to be
backward-compatible with version 1.1 of the Core Specification. This means
that implementing new features, described in any IP, into a version 1.2
prototype or product should not cause interoperability problems with
version 1.1 products that do not support the new features. With the
release of these 0.7 versions of the IPs, the SIG "encourages the
members to plan on taking advantage of some or all of these new core
features in your future products". After the release of the draft
BT1.2 specification early next year the SIG plans to hold prototype
testing sessions. So far Ericsson have released 2 Bluetooth Baseband
cores [6],[7],
which implement various parts of Bluetooth 1.2 and as the Bluetooth 1.2
spec nears greater stability, more cores will be delivered by different
manufacturers.
Note: as an aside, one hopes that
manufacturers who 'jump the gun' on Bluetooth 1.2 features, will not
repeat the mistakes that were made by early implementations of the
Bluetooth 1.0 spec that took much time & effort to correct, i.e.
certain 'selective' readings of the Bluetooth spec by some vendors which
lead to interoperability problems.
Features of Bluetooth 1.2
There is little point in introducing a new version
of an existing specification unless it serves to improve the pre-existing
functionality. To this end, Bluetooth 1.2 makes several major improvements
to Bluetooth 1.1. These require changes/additions to several sections of
the spec and can be summarized as follows:
- Adaptive Frequency Hopping
- Faster Connection Time
- Improved Quality of Service (QoS)
- Extended SCO
- Scatter Mode
- Other Enhancements
Note: Some reported features of Bluetooth
1.2, such as that it would have an increased data rate of 2-3 Mbits per
second to allow greater multimedia support [9],
up from the current rate of nearly 1 Mbits per second, are incorrect.
Increased data throughput seems to be the preserve of Bluetooth 2.0 (see
later). Bluetooth 1.2's data rate remains the same as Bluetooth 1.1, i.e.
a maximum of 1 Mbits per second.
Adaptive Frequency Hopping
As has been covered here and elsewhere, interference
can be a problem between Bluetooth devices and any other wireless
technologies which use the same 2.4 GHz frequency band (i.e 802.11b/Wi-Fi).
See Bluetooth & 802.11b
[5]
for full details. To summarise, as a Bluetooth & Wi-Fi device hop to
the same frequency, packets will be lost and throughput reduced. Although
this causes less problems for Bluetooth
than Wi-Fi, its effects are undesirable for both technologies. As
covered in the article, several developers went ahead with propriety
'Intelligent Frequency Hopping implementations', which avoided congested
frequencies - these approaches were non-spec approved though. However
thanks to a recent (Sept 2002) ruling from the FCC to change Part 15 rules
[8],
Frequency Hopping Spread Spectrum (FHSS) systems (such as used by
Bluetooth) will no longer be constrained to spread their energy over most
of the 2.4-GHz band using a pseudo-random hopping pattern and can instead
avoid certain frequencies which are known to be congested.
This is termed Adaptive Frequency Hopping in the
Bluetooth 1.2 spec. It works by avoiding jammed bands, thereby improving
co-existence with other wireless technologies which use the same 2.4 GHz
frequency band and may be present in a computer environment. This gives
you a solution less sensitive to interference, which in turn means less
re-sending of data and thereby, less consumption of power. Technically
speaking, it uses a intelligent hop sequence that avoids channels that are
identified as bad channels - this is termed an Adaptive Hop Sequence
(AHS). A number of changes have to be made to the lower layers to handle
this and also the fact that Bluetooth 1.1 & Bluetooth 1.2 devices may
be present in the same piconet.
Faster Connection Time
The Bluetooth 1.2 spec has been designed to provide
65% faster connection times in comparison with Bluetooth 1.1. This is
important for keyboards and mice that must connect as quickly as possible
when engaging in writing or pointing activities. The changes for this are
not major, basically they relate to Inquiry and Page Procedures.
Two of the methods proposed are to (a) increase
response times to inquiry messages and (b) to interleave scan frequency
periods for inquiry message to speed up receipt of these messages.
Interleaving can also be done for the initial parts of page set-up. These
and other small optimisations have been shown to make a marked improvement
in a majority of cases in Bluetooth connection set-up.
Quality Of Service
A variety of enhancements have been made to
different layers of the Bluetooth spec to allow improved Quality of
Service. QoS enhancements provided in the Bluetooth 1.2 release include:
L2CAP Flow & Error Control
Synchronisation (HCI command)
Flow specification and Flush Timeout
Some of these (such as Flow specifications and Flush
Timeout), do not add any new features as such, but simply clarify parts of
the Bluetooth 1.1 spec while others, such as L2CAP Flow & Error
Control add new features to QoS over different layers. With these
functions, detection and retransmission of lost or destroyed data packets
is enabled with a minimum impact on real-time performance and allows more
efficient bandwidth management.
Extended SCO
Extended SCO (or eSCO) provides improved voice
quality. eSCO allows retransmission of dropped eSCO packets and the use of
CRC error checking. In operation the eSCO link resembles an ACL link, with
the use of ARQ error checking and polling retransmissions. eSCO also has
the advantage that it functions better when adaptive frequency hopping is
used, further improving BT 1.2 co-existence abilities. With this function,
detection and retransmission of lost or destroyed voice packets are
enabled with a minimum impact on real-time performance.
Scatter-Mode
Scatter-Mode enables simultaneous usage of piconets,
e.g. making a mobile phone call through a headset
while synchronizing data between mobile
phone & PC. Bluetooth devices
can currently participate in different piconets on a time division
multiplex manner. Scatter Mode has been designed for best effort traffic
on the various piconets to occur. It uses presence points, which are
certain points in time at which communication between master and slave may
start (in the respective piconet), while a distributed scheduling
algorithm is used to determine their usage of the presence points.
Other Enhancements
The Bluetooth 1.2 spec has also addressed a number
of smaller areas. One of these is Anonymity Mode. This has been designed
to handle the possibility of attacks which enable the general location of
Bluetooth devices to be clandestinely determined. This is often the first
step in attempting to attack the system. Other enhancements such as LMP
Absence Masks are also implemented to handle the additional features
described above.
Outlook of Bluetooth 1.2
Bluetooth 1.2 is not expected to be released as a
draft specification until middle/end 2003. In the meantime BT1.1 devices
should continue to be released, perhaps with vendors implementing some of
the features such as adaptive frequency hopping and faster connection time
before implementing the full Bluetooth 1.2 core in devices. The presence
of Bluetooth 1.2 cores will also act as a basic enabler for a variety of
new Bluetooth profiles, such as Short Range Financial Transactions (SRFT)
or Access Point Roaming [PAN-APR]. It seems that Bluetooth 1.2 should be
classified as more as a optimisation of the Bluetooth specification, to
get more out of the technology, rather than significantly redesigning the
technology. This, rather, is the goal of Bluetooth 2.0 .
Overview on Reported Bluetooth 2.0 Features
The exact details of Bluetooth 2.0 (or Radio 2
as it is sometimes known) have not been released to the public, and as
such, the features of Bluetooth 2.0 covered here will only be an
elaboration of the media reports available now. The most concrete of these
was the speech chief scientist Jaap Haartsen made prior to the Bluetooth
Congress in July 2002 [9].
In this speech was outline the main proposed features of Bluetooth 2, and
will form the areas of examination here.
The defining feature of Bluetooth 2.0 is its faster
data rate. The 2.0 spec is expected to support gross rates of 4, 8 and 12
Mbits per second. Previous to this declaration rates of 10 or even 20
Mbits has been discussed [11].
How the faster data rate will be achieved is open to debate, one way of
handling this might be by increasing the packet size and thus the data
payload.
The 2.0 spec will also offer new communication modes
on top of the current Bluetooth by using "a non-hopping narrowband
channel and distributed media-access control protocols". The
non-hopping narrowband channel may also be the source of the greater data
rates. However it marks a big shift away from the original radio
architecture by dispensing with hopping, as well as removing one of the
spec's in-built security features: a pseudo-random hop sequence is much
harder to attack that a fixed channel.
The new distributed media-access control (MAC)
protocols proposed would mean a radical change to the current master-slave
architecture. Bluetooth 2.0 dispenses with a Master per se -
any device on the 2.0 channel is equal, supporting the distributed MAC
protocol. This distributed protocol is designed to alleviate the problems
of the present Bluetooth's master/slave-based Piconet, which drops the
Piconet when a master leaves. This is a major shift in Bluetooth's logical
architecture, and will be interesting to see how this will affect
communication between the Bluetooth devices, will they communicate still
on a master/slave basis or will communication be direct, now that the
concept of the master has been removed.
Finally it is reported that Bluetooth 2.0 is
expected to operate over the same 10-meter distance as the present
Bluetooth, as this range can easily be changed by altering the
transmission power this feature is a design decision, and signals that
Bluetooth will evolve but intends to remain in the PAN arena. Latency is
also expected to be improved in Bluetooth 2.0, a natural progression due
to continued optimisation of Bluetooth connection times, etc and the
introduction of new, non-hopping channels. The price for Bluetooth's new
features? It is expected that Bluetooth 2.0's peak power consumption will
be about double that of current Bluetooth chipsets. While the cost premium
for Bluetooth 2.0 chip sets is expected to be "about 20 percent, but
no more" than current Bluetooth chips, Haartsen said. Technically
speaking it is possible to implement the changes for Bluetooth 2.0, but
the question remains is it desirable.
Future of Bluetooth 2.0
Feature creep, the constant addition and updating to
a standard, has been the cause of much harm to many emerging standards and
technologies. To prevent this, the Bluetooth SIG has been at the forefront
of ensuring developers concentrate on delivering 1.1 (and eventually 1.2)
solutions rather than addressing more advanced Bluetooth solutions. This
is to ensure that vendors do not confuse the market with different version
of Bluetooth and also to allow time for Bluetooth to be adopted
successfully. This is why Bluetooth 1.2 has and will be pushed much harder
than Bluetooth 2.0. The SIG is waiting to see how the market for Bluetooth
develops before deciding when to release 2.0 as a specification. Current
estimates are that it will be at least 2004 before Bluetooth 2.0 will be
available as a specification for development. However, as always some
vendors want to offer additional features to their customers as soon as
possible, an example of this is that Infineon Technologies have launched a
version of its BlueMoon chip set that incorporates an optional RF
transceiver which can push data transmission rates to 4Mbit/s[11].
The outlook for Bluetooth 2.0 is not completely
clear though. Although still aimed at different segments of the
marketplace, Bluetooth's ability to compete with 802.11(Wi-Fi) greatly
increases if Bluetooth 2.0's improved bit rate means it is taken to be a
fast internet access technology - a market segment in which Wi-Fi is the
dominate player. Keeping in mind that by the time Bluetooth 2.0 comes out
by 2004/5, Wi-Fi will probably have powered ahead in terms of market place
penetration, increased speed and lower power usage [12],
therefore competition in this arena would be difficult if not impossible.
Instead it is likely that Bluetooth 2.0 will not
attempt to directly compete with Wi-Fi despite reports to the contrary [12].
It is likely to remain pitched as a short-range ad-hoc, low-power technology
and not as an access technology (however this would be technically
certainly possible). Taken all together, the augmented capabilities
regarding audio/video in the personal environment, as well as improved
latency, would allow a whole new area of Bluetooth roles to be considered.
Target markets optimised by the introduction of Bluetooth 2.0 would be
advanced peripherals around the mobile phone, audio/video equipment, and
gaming - devices that Wi-Fi would not be expected to make significant
in-roads into in the foreseeable future. A deciding factor will be the
capabilities and roles of Wi-Fi by the time Bluetooth 2.0 comes out.
Therefore Bluetooth 2.0's future, while unclear, is not as bleak as some
would imagine, especially if it is marketed and pushed correctly.
Conclusion
As stated, Bluetooth 1.2 should be seen as more as
an update to the existing Bluetooth spec, and will be a welcome addition
to Bluetooth's abilities. Bluetooth 2.0, on the flip side, is a radical
change to the standards, with major changes and enhancements. However
Bluetooth 2.0's future development and successful rollout is a challenge,
while Bluetooth 1.2 should be secure. Both technologies are certainly
capable, but commercial success is the real indicator of a technologies
worth. Time will tell if Bluetooth 1.1 (and now 1.2) remains on track to
be widely adopted and whether Bluetooth 2.0 enters the fray successfully.
References:
[1] Bluetooth, The Bluetooth Specification, v.1.1 http://www.bluetooth.com/dev/specifications.asp
[2]
Bluetooth.org, Bluetooth Additional Profile Specifications
http://www.bluetooth.org/specifications.htm
[3] InfoTooth Profiles Tutorial
http://www.palowireless.com/infotooth/tutorial/profiles.asp
[4] NE Asia Online, Ericsson Begins to Develop Prototype High-Speed
Bluetooth LSI , July 2002 http://www.nikkeibp.asiabiztech.com/wcs/leaf?CID=onair/asabt/news/196411
[5]
Palowireless, Bluetooth and 802.11b(Part 1 & 2) , January 2002
http://www.palowireless.com/blueartciles/cc4_bluetooth802.11b_part1.asp
[6]
Ericsson, Core Bluetooth Baseband Q-E2
http://www.ericsson.com/bluetooth/products&s/show_product.asp?cat=48&prodid=75
[7] Ericsson, Core
Bluetooth Baseband Q-E3 http://www.ericsson.com/bluetooth/products&s/show_product.asp?cat=48&prodid=76
[8]
IEEE Spectrum Online, FCC Resolves Bluetooth - IEEE 802.11 conflict http://www.spectrum.ieee.org/WEBONLY/resource/sep02/blue.html
[9]
EE Times Online , Scientist tips features of Bluetooth 2.0 , July 2002
http://www.eetimes.com/story/OEG20020611S0033
[10]
EE Times Online , FCC backs HomeRF in 2.4-GHz wireless LAN Battle,
September 2000 http://www.eet.com/story/OEG20000901S0046
[11]
EE Times Online , Infineon puts 4-Mbit/s capability atop Bluetooth, June
2001
http://www.eetimes.com/semi/news/OEG20010605S0071
[12]
NewsWireless.net , Bluetooth community enraged at "leak" of V
2.0, July 2001
http://www.newswireless.net/articles/020710-bustup.html
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