Seminar Report on

Bluetooth 5
Abstract
According to a paper by Goldman Sachs, in the 1990s there were approximately 1
billion devices connected to the internet. In the 2000s, the age of the smartphone,
this figure rose to 2 billion. ABI Research now forecasts that by 2021 there will be
48 billion devices connected to the internet, in what we’re likely to term the age of
the IoT. Of those 48 billion devices, 30% are forecasted to include Bluetooth
technology. This is no coincidence. Bluetooth Low Energy (LE) has been actively
evolved to make it a key enabler of the Internet of Things (IoT), focusing on the
edge tier of IoT systems. Bluetooth 5 brings some major advances to the technology
and makes it ideal for an even broader range of IoT scenarios. In this paper, we will
present and explore the key advances in Bluetooth 5.
Introduction
Bluetooth has already existed for almost 20 years and is used today in approximately
8.2 billion devices, so it has already demonstrated its robustness and dependability.
To fulfill requirements set forth by the new IoT scene, the Bluetooth SIG announced
the Bluetooth 5 specification in December 2016. The latest Bluetooth standard
improves bandwidth, range, broadcasting, and coexistence features.
The Samsung Galaxy S8 launched with Bluetooth 5 support in April 2017. In
September 2017, the iPhone 8, 8 Plus and iPhone X launched with Bluetooth 5
support as well. Apple also integrated 'Bluetooth 5.0' in their new HomePod offering
released on February 9, 2018. Marketing drops the point number; so that it is just
"Bluetooth 5" (not 5.0 or LE like Bluetooth 4.0). The change is for the sake of
"Simplifying our marketing, communicating user benefits more effectively and
making it easier to signal significant technology updates to the market."
Bluetooth 5 provides, for BLE, options that can double the speed (2 Mbit/s burst) at
the expense of range, or up to fourfold the range at the expense of data rate, and
eightfold the data broadcasting capacity of transmissions, by increasing the packet
lengths. The increase in transmissions could be important for Internet of Things
devices, where many nodes connect throughout a whole house. Bluetooth 5 adds
functionality for connectionless services such as location-relevant navigation of low-
energy Bluetooth connections.
 2x Speed
One of the major features in Bluetooth 5 is a new 2 Mbps PHY. Bluetooth 4.x
devices only support a single 1 Mbps PHY rate, but Bluetooth 5 devices are capable
of supporting either the 1 Mbps or 2 Mbps PHY rates. By doubling the PHY rate,
the amount of data that devices can transfer is almost doubled as shown in the table
below. Another benefit of the faster PHY is the reduced time required for
transmitting and receiving data, which translates to a lower average current
consumption. This is explained by the fact that more time can be spent in low-power
sleep modes.
Comparison of 1M and 2M Bluetooth low energy PHYs

Error Range Minimum Maximum Maximum

PDU
PHY Symbol rate detection multiplier packet packet throughput
Length
time time

1M 1M symbols/s CRC 1x 0 - 257 B 80 µs 2.12 ms 800 kbps

2M 1 M symbols/s CRC 0.8 x 0 - 257 B 44 µs 1.064 ms 1438 kbps

Doubling the throughput while providing low-power consumption will allow

applications to provide faster data transfers for use cases like over-the-air (OTA)
firmware upgrades or transmitting of days’ worth of collected data from a sensor and
also improve latency and responsiveness for time critical applications such as
medical devices and security systems.
Bluetooth 5 devices supporting 2 Mbps PHY are still fully backwards compatible
with Bluetooth 4 devices and will use the 1 Mbps PHY to communicate with devices
that do not support the new 2 Mbps PHY. It is expected that the first smart phones
and tablets supporting Bluetooth 5 and 2 Mbps PHY should appear in the market in
2017 and that the majority of smart phones in the market will be Bluetooth 5
compliant within the next two to four years.
 Mbps PHY (above) and 2 Mbps PHY (below) average power consumption
comparison on EFR32BG12 SoC
The images above show the average current consumption difference between 1
Mbps PHY and 2 Mbps PHY connections measured between two EFR32 Blue
Gecko SoCs. The devices used +8 dBm TX power, 25 ms connection interval, and
were only sending the shortest 80 µs and 44 µs packets, which provides the least
amout of power saving. Even so, the 2 Mbps PHY provides about 15 percent
reduction to average power consumption. When using the full length Bluetooth
packets and 2M PHY, power savings of up to 40-50 percent should be achievable.
 4x Range

The LE long range feature of Bluetooth 5 can quadruple the range and deliver robust
and reliable connections. This means that whole-house and building coverage, as
well as new use cases for outdoor, industrial, and commercial applications will
become a reality. Those are something Bluetooth has not been able to address earlier,
or when it has, the range has been limited.
So how can Bluetooth 5 provide 4x the range?
LE Codec PHY’s
In addition to the 2M PHY, Bluetooth 5 contains two additional optional PHYs
called LE Coded PHYs. The LE Coded PHYs actually use the 1M PHY rate, but the
actual payload is coded either with 500 kbps (S=2) or 125 kbps (S=8) rate, whereas
the preamble and access address use the 1M coding.
LE Coded PHY’s also use a slightly different packet format versus the 1M and 2M
PHYs. A coding indicator (CI) and TERM1 and TERM2 headers are added into the
LE packet.

Figure: Bluetooth 5 un-coded vs. coded PHY packet format

Using the coded PHYs improves the RX sensitivity, which also means improved
range. Typically, a 4-6 dB RX sensitivity improvement can be achieved using either
the 500 kbps or 125 kbps PHY and this usually converts to a 2-4x range
improvement. The downside of the LE Coded PHY is of course that the TX and RX
times are going to be longer, which increases the average power consumption. The
table below summarizes the key parameters of LE Coded PHY’s.
LE Min Max
Symbol Error Error Range PDU Maximum
Coded packet packet
rate detection correction multiplier Length throughput
PHY time time
500 kbps 1M 17040
CRC FEC 2 0 – 257 B 720 µs 382 kbps
S=2 symbols/s µs
125 kbps 1M
CRC FEC 4 0 – 257 B 462 µs 4542 µs 112 kbps
S=8 symbols/s

Forward Error Correction and Pattern Mapper

LE Coded PHYs also change the bit stream processing for TX and RX operations,
and add two steps into the packet transmissions and reception. First of all, forward
error correction is applied to the packet so that the receiver has a capability to correct
bit errors upon reception of the packet and improve packet error rate. Secondly, a
pattern mapper is applied to the packet to improve the efficiency of the
communications. The figure below shows the new bit stream PDU processing
sequence.

Figure: LE Coded PHY TX and RX packet processing

The FEC block converts each input bit to two output bits by convolutional error
correction encoder as shown below, which means the number of bits transmitted is
duplicated when FEC is applied to the packet.

FEC encoder

Bits from the convolutional FEC encoder are converted into P symbols in the
pattern mapper. P value depends on the selected coding scheme. With S=2 the
value of P=1 but if S=8 each bit from the FEC encoder gives four output bits (P=4)
as indicated in the table below.
Pattern Mapper output options
Input from Output Output
FEC S=2 S=8
Encoder
0 0 0011

1 1 1100

When using S=2, wireless range is roughly doubled with S=8 quadrupled. The
downside of the increased range is the burden on the payload created by the added
bits required by the FEC algorithm. In effect, with S=2 there is no change (P=1) but
with S=8 each bit from the FEC encoder will produce four output bits (P=4). Now
the S=2 range will be approximately doubled and S=4 approximately quadrupled.
The downside is the additionally required data for FEC algorithm at the receiver end
effects the amount of data to be transmitted, thus reducing the data rate
correspondingly. The net effect of the FEC encoder and the pattern mapper is that
one bit becomes two bits with S=2 and eight bits with S=8.
Maximum Transmit Power and Channel Selection Algorithm #2
Maximum transmit power in Bluetooth 5 is defined to be +20 dBm, while in the
Bluetooth 4 specification this level was defined at +10 dBm. Increasing the TX
power by 10x of course can have a radical impact to the maximum range.
Using a +20 dBm TX power with Bluetooth low energy technology is however not
that straightforward because different regulatory bodies do not allow transmit
powers higher than 10 dBm due to the simplified hopping sequence and the small
number of channels Bluetooth with low energy radios can use while advertising or
in a connection. However, the Bluetooth 5 specification includes enhancements to
both advertising and channel selection algorithms that make it possible to use more
RF channels than Bluetooth 4. These enhancements may allow Bluetooth 5 devices
to use higher than +10 dBm transmit power globally in the future, improving range
and creating more robust connections. One of the new features is Channel Selection
Algorithm #2 (CSA#2) and it both improves the interference tolerance of the
Bluetooth radio as well allows the radio to limit the minimum number of RF
channels the radio can use in high interference environments. When limiting the
minimum number of channels to 15 it should be possible to increase the TX power
above the +10 dBm limit.

Impact to Range
The simplest way to approximate the theoretical range for radios is to use the free
space loss formula:

LP (dB) = 92,45+20logF+20logD

F is the frequency in GHz and D is the distance in kilometers. This formula however
doesn’t take into account the losses caused by multipath propagation (reflections)
nor the antenna loss and thus often results in too optimistic approximations.
To have a more realistic approximation of the range, one can assume an open field
with antennas which are h meters above ground and calculate the range which takes
into account the antenna loss and reflection from the ground. This approximation
will give a very accurate estimate of the range in an open field, like an airfield for
example. The plane earth loss can be calculated using the following formula:

Where h1 and h1 are the height of the antennas respectively, k is the free space
wavenumber and r is the distance between the antennas. The difference between
free space loss and the plane earth loss is plotted in to the following figure:

Free space loss vs. plane earth loss

To simplify this even further, one can estimate a 20 dB/decade loss until distance
of dm and 40 dB/decade beyond that. Thus we get the following formula:

In the formula above h1 and h2 are the height of the antennas above ground. Placing
the antennas higher will move the distance dm further, thus increasing the range
and vice versa.
With a typical Bluetooth application, the direction where the remote end of the link
is located is not well specified and thus the gain of the antenna is not relevant in
approximating the range. Antenna efficiency is a number which describes the total
amount of RF energy radiated into the air compared to the RF energy fed into the
antenna. The efficiency thus gives a better approximation of the average range
regardless of the positions of the device. With an optimal antenna design it is
possible to achieve a -1dB antenna efficiency. In practice, the antenna performance
depends greatly on the PCB and mechanical design around the antenna. Typical
efficiency with a good antenna design is -5 dB. The physical size of an antenna and
the size of the PCB design also has an impact on antenna efficiency in practice and
with very small designs in which antenna efficiency is not more than -8 dB.
TX Power RX Antenna Link Maximum Use case
sensitivity efficiency budget range in open
field
0 dBm -92 dBm -5 dBm 82 dBm 160 m EFR32BG12, 0 dBm, 2 Mbps PHY sensitivity
0 dBm -95 dBm -5 dBm 85 dBm 195 m EFR32BG12, 0 dBm, 1 Mbps PHY sensitivity
10 dBm -92 dBm -5 dBm 92 dBm 295 m EFR32BG12, 10 dBm, 2 Mbps PHY sensitivity
10 dBm -95 dBm -5 dBm 95 dBm 350 m EFR32BG12, 10d Bm, 1 Mbps PHY sensitivity
20 dBm -92 dBm -5 dBm 102 dBm 530 m EFR32BG12, 20 dBm, 2 Mbps PHY sensitivity
20 dBm -95 dBm -5 dBm 105 dBm 630 m EFR32BG12, 20 dBm, 1 Mbps PHY sensitivity
Estimated maximum ranges for EFR32BG12 with different TX power and RX sensitivity levels

Note: Assumes a typical design with -5dB antenna loss and antennas placed 1.5
meters above the ground. Estimated between two EFR32BG12s.
 8x Advertising Capacity
Beacons are small Bluetooth transmitters that can send data to any other Bluetooth
low energy technology-enabled devices such as smart phones and tablets within their
range. Beacons make it possible to push short messages to those devices and enable
simple communications with them. Today bacons are typically used for retail
advertising, indoor positioning, and asset tracking. Beaconing has quickly become
one of the most successful use cases for Bluetooth and it is estimated to continue
growing at a fast rate. Analysts expect more than 500 million beacons to be shipped
by 2021.
One of the major areas of improvement in the Bluetooth 5 specification is how
Bluetooth advertisement (beaconing) works and the new specification contains
significant updates to beaconing capabilities compared to previous versions of the
specification. These improvements will not just allow much more advanced and
intelligent beacons to be developed but also completely new use cases and
applications such as unidirectional data streaming over Bluetooth advertisements.
A brief introduction to the most important changes to the Bluetooth advertisement
capabilities is provided below.
Beacons Defined
At a basic level, beaconing is a way to deliver very short messages and track
Bluetooth-enabled devices over a short distance, without the need for pairing
between the beacon and the device. The only requirement is that the device, typically
an Apple or Android smartphone or tablet, has an installed app dedicated to
beaconing. The retail industry is currently the primary user of beaconing, so let’s use
this is an application example. In a mall, a retailer has installed beacons through its
store in locations such as at the store entrance, display counters, and checkout lanes
(Figure A). These devices, which are tiny (as small as 1x5x0.75in.) broadcast signals
at a specific interval, each containing small amounts of data. As data is minimal, RF
output power is very low, and power consumption is miniscule, beacons can operate
for years on a coin cell. They’re also inexpensive, so a retailer can install them in
many places. The process begins when a shopper passes by the store and receives a
notification from the beacon that pops up in the display showing a URL or some
other bit of information. This is typically a coupon, loyalty reward, or some other
form of promotion. The user then taps the notification and is sent to somewhere on
the retailer’s website where more information is provided. It doesn’t take much
imagination to see how valuable this can be for retailers and other organizations like
museums that could send out notifications with a link to details about the piece of
art, dinosaur, or whatever the visitor is looking at.

Figure A: A typical scenario for beacons shows how they can be placed anywhere, tracking where shoppers go.

They can also be used for positioning and navigation, tracking of virtually anything
(including people), and automatically registering trade show attendees, among many
other applications. As beacons transmit only, they do not gather personal
information, which minimizes security issues. The usefulness of beacons depends
entirely on what the retailer or other organization chooses to do with the information
they provide. For example, a retailer can determine what products shoppers seemed
most interested in, where they go in a store, and if they buy something (Figure B).
Figure B: A typical scenario for beacons shows how they can be placed inconspicuously anywhere, tracking where shoppers go.

Unfortunately, until Bluetooth 5, the maximum message length that could be

transmitted by a beacon was limited to 31 bytes—too small to even contain all the
characters in most URLs or provide a text message long enough to convey any useful
information. Bluetooth 5 solves this by increasing message length to 255 bytes so
much more information can be accommodated. Bluetooth 5 also provides higher data
rates that should benefit not only beaconing but many other applications as well.
Advertising Data Sets and Scan Request Event Reporting
One of the basic improvements in Bluetooth 5 advertising is the Advertising Data
Sets feature, which allows a single Bluetooth 5 device to send out multiple individual
advertisement data sets with unique intervals and advertisement data. This, for
example, enables a single Bluetooth beacon to transmit individual Apple iBeacon
and Google Eddystone beacons simultaneously.
A Bluetooth 5 compatible advertiser can also now detect when a scan request is made
by a remote device and report the request to the application level. The application
can use this to detect a remote device has received one of the advertisement packets
it has sent out. This is helpful in several ways, including reducing power
consumption since the advertiser will be able to detect that the remote device has
received the sent advertisement packet and can stop advertisement.
Secondary Advertisement Channels
Bluetooth 4 devices use three advertisement channels to advertise their presence,
open connections, or broadcast data. The payload in a single advertisement packet
is limited to 31 bytes. A single 128-bit service UUID can consume most of the
advertisement payload and for some applications like advanced beacons this is a
limitation.
Bluetooth 5 changes this significantly. First of all, the three advertisement channels
are going to remain exactly like in Bluetooth 4 for backwards compatibility and
interoperability, but they are now called primary advertisement channels. In addition
to the three primary advertisement channels, Bluetooth 5 devices can use any of the
remaining 37 data channels as secondary advertisement channels to broadcast more
data and offload the primary channels. The table below summarizes the differences
between Bluetooth 4 and 5 advertising channel schemes.
Bluetooth version Advertising channels Payload PHY
Bluetooth 4 3 0 - 31 B 1M
Bluetooth 5 3 Primary 0 - 31 B (Primary) 1M, Coded (Primary)
37 Secondary 0 – 255 B (Secondary) 1M, 2M, Coded (Secondary)
Advertising channels in Bluetooth 4 vs Bluetooth 5

Secondary Advertising Packets

In addition to the new advertisement channels, Bluetooth 5 also introduces a new
advertisement packet type called ADV_EXT_IND. This packet can be sent on the
primary advertisement channels and it indicates additional data will be available
through a secondary advertisement. The ADV_EXT_IND packet contains
information about the secondary advertisement such as on which channel the
advertisement occurs, when it occurs, and which Bluetooth PHY will be used.
In the simplest use case, an AUX_ADV_IND packet is sent on the secondary
advertisement channel containing an additional advertisement payload as shown in
the example below. The AUX_ADV_IND packet can contain payload up to 255
bytes. Advertising event using the ADV_EXT_IND PDUs and AUX_ADV_IND
PDU containing advertising data shown in figure below.

In case the advertiser wants to send more data than a single AUX_ADV_IND packet
can contain, it is possible to chain multiple secondary advertisements using the
AUX_CHAIN_IND packet as shown in the image below. AUX_CHAIN_IND
packets can also contain pointers to additional AUX_CHAIN_IND packets in order
to transmit advertisement payloads beyond 255 bytes.

Providing additional advertisement data using AUX_CHAIN_IND

Periodic Advertising
Yet another improvement to the Bluetooth 5 advertisement capabilities is a mode
called Periodic Advertising. As the name suggests, periodic advertising enables the
advertiser to send out changing advertisement data periodically and with a fixed
interval, and one or multiple scanners can listen to it. Periodic advertisement mode
is indicated with the ADV_EXT_IND packets, which point to AUX_ADV_IND
packet, containing the actual information about the periodic advertisement mode,
such as interval, hopping sequence, advertiser address, and so on. The advertiser will
also send AUX_SYNC_IND packets at the identified interval containing the actual
periodic advertisement data.

Periodic advertising

The advertiser will periodically send new ADV_EXT_IND packets, so that new
scanners can synchronize to the data stream or existing scanners can resume a lost
sync.
 Summary of Bluetooth 5 advertising channel PDUs
Allowed LE PHYs Advertising
Activity PDU name channel
1M 2M Coded
Connectable and scannable ADV_IND Yes Primary
undirected advertising
Connectable directed advertising ADV_DIRECT_IND Yes Primary
Non-connectable and non-
ADV_NONCONN_IND Yes Primary
scannable undirected advertising
Scan request SCAN_REQ Yes Primary
Scan request AUX_SCAN_REQ Yes Yes Yes Secondary
Scan response SCAN_RSP Yes Primary
Connection request CONNECT_IND Yes Primary
Connection request AUX_CONNECT_REQ Yes Yes Yes Secondary
Scannable undirected ADV_SCAN_IND Yes Primary
advertising
All advertising events
(except connectable and ADV_EXT_IND Yes Yes Primary
scannable undirected)
All advertising events
(except connectable and AUX_ADV_IND Yes Yes Yes Secondary
scannable undirected)
AUX scan response AUX_SCAN_RSP Yes Yes Yes Secondary
Periodic advertising AUX_SYNC_IND Yes Yes Yes Secondary
Additional advertising data AUX_CHAIN_IND Yes Yes Yes Secondary
Connection response AUX_CONNECT_RSP Yes Yes Yes Secondary

Slot Availability Masks

Bluetooth 5 made some changes to help improve coexistence with other radio
technologies on devices such as smartphones. Bluetooth uses the 2.4GHz ISM band
and this is immediately adjacent to the Mobile Wireless Standard (MWS) bands,
such as are used for LTE. There’s potential for interference between the two systems,
with transmissions from one desensitizing the receiver on the other. Bluetooth 5
introduces a system called Slot Availability Masks, which allows Bluetooth to
indicate the availability of its time slots and to synchronize in an optimal manner
with the use of the adjacent MWS bands.
Conclusion
Bluetooth 5 represents another step change in Bluetooth technology. Whole-home
and building coverage is provided for with the new, long-range LE Coded PHY. The
higher symbol rate of LE 2M improves spectral efficiency and supports emerging
use cases in, for example, sports and fitness and medical equipment. Bluetooth’s
advertising extensions feature will pave the way for next-generation beacons,
advanced audio applications and more. New industrial applications will become
possible and some smart city applications too. Bluetooth 5 will have a substantial
impact in many sectors and further position it as the low power wireless technology
of choice for the Internet of Things.