Everything you need to know about Bluetooth technology. What does the bluetooth version affect? How to understand Bluetooth versions

Data transmission via Bluetooth is carried out at a frequency of 2.4 GHz. This range is divided into 79 channels. At the same time, each of them is provided with a bandwidth of 1 MHz. All available specializations use synchronous or asynchronous communication.

Latest modifications (main)

Bluetooth 2.0

Released in November 2004, Bluetooth 2.0 offers even faster data transfer speeds and is also backwards compatible with previous versions. Increased speed is provided through the use of EDR technology. Its stated speed is 3 Mb/s.However, as practice shows, due to this technology the maximum data transfer speed reaches only2.1 Mb/s. In version 2.0, it was possible to achieve not only improved speed, but also significantly increased noise immunity, which ultimately helped reduce energy costs.

In addition, 2.0 is notable for making it easier to connect multiple devices to it. This was achieved due to an increase in the addressing bit depth. This made it possible to connect via the local network not to 8 devices, as before, but to 256.

The 2.0+EDR specification has the following features:

1. Speeds up Bluetooth data transfer speeds 3 times(actually on 2.1 Mb/s).
2. Adding additional bandwidth partially solved the problem of connecting multiple devices to Bluetooth at once.
3. Energy consumption has decreased due to reduced load.

Bluetooth 3.0

The Bluetooth 3.0 specification was adopted in 2009 and created a real sensation, since the data transfer speed when using it reaches 24 Mb/s. This became possible due to the use of two modules in it, one of which was regular Bluetooth 2.0, and the other working using the 802.11 protocol, supporting speeds up to 24 Mb/s. In this case, the module selected for data transfer depends on the file size. Thus, a slow channel is used to transfer small files, and a high-speed channel for large ones.

The main negative side of Bluetooth 3.0 + HS is that it consumes too much power during operation. Oddly enough, this disadvantage of the 3.0 standard is associated with its high speed. However, standard 3.0 has one undeniable advantage. Namely, this is the ability to work using the 802.11 protocol or, more simply, Wi-Fi. Thanks to this, the data transfer speed has increased significantly. In theory, using version 3.0 the connection speed should reach 54 Mb/s.

Thus, thanks to the 3.0 standard, it will be possible to pump DVD-sized data in the shortest time periods. However, according to the developers real speed standard 3.0 is 22–26 Mb/s.

Bluetooth 4.0

The advantage of Bluetooth 4.0 over the previous specification is its reduced power consumption. The data transfer speed when using the 4.0 standard reaches 1 Mb/s(packet size 8-27 bytes). In addition, the connection speed of devices compatible with the 4.0 specification is reduced to 5 milliseconds, and the distance over which data transmission is possible reaches 100 meters. Also, the 4.0 standard provides a sufficient level of security, which is guaranteed by the 128-bit AES extension.

Benefits of Bluetooth 4.0:

1. Combines previous protocols. Supports the basic functions of previous protocols.
2. Increased speed.
3. A significant reduction in the power consumption of a device using the 4.0 standard, achieved through a modified operating algorithm (the transmitter is turned on only at the moment when data is being transferred).

Generally, the 4.0 standard is more suitable for miniature electronic sensors. For example, for wrist pressure and temperature meters, for exercise equipment, various miniature devices with low energy consumption.

One of the sustainable development trends mobile devices- improvement of wireless communications tools that provide the ability to connect to the Internet, local network, as well as various peripheral equipment (headphones, headsets, speaker systems, printers, etc.) and other nearby gadgets. Technologies wireless communication, as indeed other components of mobile devices, are constantly evolving. New versions of specifications appear, bandwidth increases, the set of functions expands, etc. Thanks to this, high-quality development is ensured, without which technical progress is unthinkable. However, progress also has a downside: every year it becomes more and more difficult for users to understand what is the difference between different models.

Usually, from a brief description of a mobile device, you can only glean the names of the wireless interfaces with which it is equipped. The detailed specification usually contains additional information, in particular the versions of wireless interfaces (for example, Wi-Fi 802.11b/g/n and Bluetooth 2.1). However, this is not always enough to fully appreciate the wireless communications capabilities of the device in question. For example, to understand whether a particular peripheral device connected via Bluetooth will work with the smartphone or tablet you have at your disposal.

In this article we will talk about various nuances that you need to pay attention to when assessing the capabilities of devices equipped with a Bluetooth interface.

Scope of application

A wireless interface with a short range, called Bluetooth, was developed in 1994 by engineers of the Swedish company Ericsson. Since 1998, the Bluetooth Special Interest Group (Bluetooth SIG), founded by Ericsson, IBM, Intel, Nokia and Toshiba, has been developing and promoting this technology. To date, the list of Bluetooth SIG members includes more than 13 thousand companies.

The introduction of Bluetooth into mass market consumer devices began in the first half of the last decade. Currently built-in Bluetooth adapters Many models of laptops and mobile devices are equipped. In addition, a wide range of peripheral devices (wireless headsets, pointing devices, keyboards, speaker systems, etc.) equipped with this interface are on sale.

The main function of Bluetooth is the creation of so-called personal networks (Private Area Networks, PAN), which provide the ability to exchange data between nearby (within the same house, premises, vehicle, etc.) desktop and laptop PCs, peripheral and mobile devices and Ave.

The main advantages of Bluetooth over competing solutions are low power consumption and low cost of transceivers, which allows it to be integrated even into small-sized devices with miniature batteries. In addition, equipment manufacturers are exempt from paying licensing fees for installing Bluetooth transceivers in their products.

Connecting devices

Using the Bluetooth interface, you can connect two or several devices at once. In the first case, the connection is carried out according to the “point-to-point” scheme, in the second - according to the “point-to-multipoint” scheme. Regardless of the connection scheme, one of the devices is the master, the rest are slaves. The master device sets the pattern that all slave devices will use and also synchronizes their operation. Devices connected in this way form a piconet. One master and up to seven slave devices can be combined within one piconet (Fig. 1 and 2). In addition, it is possible to have additional slave devices in the piconet (more than seven) that have a parked status: they do not participate in data exchange, but are in synchronization with the master device.

Rice. 1. Piconet diagram,
connecting two devices

Rice. 2. Piconet scheme,
combining several devices

Several piconets can be combined into a distributed network (scatternet). To do this, a device operating as a slave in one piconet must act as a master in another (Fig. 3). Piconetworks that are part of one distributed network, are not synchronized with each other and use different templates.

Rice. 3. Diagram of a distributed network including three piconets

The maximum number of piconets in a distributed network cannot exceed ten. Thus, the distributed network allows you to connect a total of up to 71 devices.

Note that in practice the need to create a distributed network rarely arises. With the current degree of integration of hardware components, it is difficult to imagine a situation where the owner of a smartphone or tablet would need to connect more than two or three devices simultaneously via Bluetooth.

Range

The Bluetooth specification provides three classes of transceivers (see table), differing in power, and therefore in effective range. The most common option, which is used in most currently produced mobile electronic devices and PCs, are Bluetooth Class 2 transceivers. Low-power Class 3 systems are equipped with medical equipment, and the main area of ​​application for the most “long-range” Class 1 modules are monitoring and control systems for industrial equipment.

Of course, you can count on a stable wireless connection between devices located at a maximum distance (for example, 10 m in the case of Class 2 transceivers) only if there are no large obstacles between them (walls, partitions, doors, etc.). The actual operating range may vary depending on the characteristics of the room, and on the presence of radio interference and sources of strong electromagnetic radiation on the air.

Bluetooth versions and their differences

The first version of the specification (Bluetooth 1.0) was approved in 1999. Shortly after the intermediate specification (Bluetooth 1.0B), Bluetooth 1.1 was approved - it corrected errors and eliminated many of the shortcomings of the first version.

In 2003, the Bluetooth 1.2 core specification was approved. One of its key innovations was the introduction of the Adaptive frequency-hopping spread spectrum (AFH) method, which made the wireless connection much more resistant to electromagnetic interference. In addition, it was possible to reduce the time spent performing device discovery and connection procedures.

Another important improvement in version 1.2 was the increase in data exchange speed to 433.9 Kbps in each direction when using asynchronous communication over a symmetric channel. In the case of an asymmetric channel, the throughput was 723.2 Kbit/s in one direction and 57.6 Kbit/s in the other.

An improved version of Extended Synchronous Connections (eSCO) technology has also been added, which improves the quality of streaming audio by using a mechanism to resend packets damaged during transmission.

At the end of 2004, the Bluetooth 2.0 + EDR basic specification was approved. The most important innovation of the second version was the Enhanced Data Rate (EDR) technology, thanks to the implementation of which it was possible to significantly (several times) increase the interface throughput. Theoretically, using EDR allows you to achieve a data transfer rate of 3 Mbit/s, but in practice this figure usually does not exceed 2 Mbit/s.

It should be noted that EDR is not a required feature for transceivers that comply with the Bluetooth 2.0 specification.

Devices equipped with Bluetooth 2.0 transceivers are backward compatible with previous versions (1.x). Naturally, the data transfer speed is limited by the capabilities of the slower device.

In 2007, the Bluetooth 2.1 + EDR basic specification was approved. One of the innovations implemented in it was the energy-saving technology Sniff Subrating, which made it possible to significantly (from three to ten times) increase the battery life of mobile devices. The procedure for establishing communication between two devices has also been significantly simplified.

In August 2008, basic additions (Core Specification Addendum, CSA) to the Bluetooth 2.0 + EDR and Bluetooth 2.1 + EDR specifications were approved. Changes made are aimed at reducing energy consumption, increasing the level of protection of transmitted data and optimizing procedures for identifying and connecting Bluetooth devices.

In April 2009, the Bluetooth 3.0+HS core specification was approved. The abbreviation HS in this case stands for High Speed ​​( high speed). Its main innovation is the implementation of Generic Alternate MAC/PHY technology, which provides the ability to transfer data at speeds of up to 24 Mbit/s. In addition, it is planned to use two transceiver modules: low-speed (with low power consumption) and high-speed. Depending on the width of the transmitted data stream (or the size of the transmitted file), either a low-speed (up to 3 Mbit/s) or a high-speed transceiver is used. This allows you to reduce power consumption in situations where high data transfer rates are not required.

The Bluetooth 4.0 core specification was approved in June 2010. The key feature of this version is the use of low energy technology. Reduced power consumption is achieved both by limiting the data transfer rate (no more than 1 Mbit/s) and by the fact that the transceiver does not operate constantly, but is turned on only for the duration of data exchange. Contrary to popular belief, Bluetooth 4.0 does not provide higher data transfer speeds than Bluetooth 3.0+HS.

Bluetooth Profiles

The ability of devices to interact when connected via Bluetooth is largely determined by the set of profiles that each of them supports. This or that profile provides support for certain functions, for example, transferring files or streaming media data, providing network connection etc. See the sidebar for information about some Bluetooth profiles.

It is important to understand that you can use a Bluetooth connection to perform any task only if the appropriate profile is supported by both the master and slave devices. Thus, it is possible to transfer a “business card” or a contact from one mobile phone to another via a Bluetooth connection only if both devices support the OPP (Object Push Profile) profile. And, for example, to use a mobile phone as a wireless cellular modem This machine and the computer connected to it must support the DUN (Dial-up Networking Profile).

Situations often arise when a Bluetooth connection is established between two devices, but some action (say, transferring a file) cannot be performed. One of probable causes The occurrence of such problems may be due to the lack of support for the corresponding profile on one of the devices.

Thus, the set of supported profiles is an important factor that must be taken into account when assessing the capabilities of a particular device. Unfortunately, some mobile device models support a minimal set of profiles (for example, only A2DP and HSP), which significantly limits the ability to wirelessly connect to other equipment.

Note that the set of supported profiles is determined not only by the specifics and design features of the device, but also by the manufacturer’s policy. For example, some devices block the ability to transfer files of certain formats (images, videos, e-books, applications, etc.) under the pretext of fighting piracy. True, in reality, it is not lovers of counterfeit media content and software who suffer from such restrictions, but honest users who are forced to transfer even photos taken with their own built-in camera to a PC in a roundabout way (for example, by sending the necessary files to their own email address).

Manufacturers constantly convince consumers that new solutions are certainly better than old ones. New processors have higher performance and lower power consumption compared to their predecessors; new displays have higher resolution and wider color gamut, etc. However, it is hardly advisable to use such an approach to evaluate the capabilities of the Bluetooth interface.

First, it is necessary to take into account the features of the existing fleet of Bluetooth devices. After all, as already mentioned, the maximum data transfer rate is determined by the device equipped with the oldest version of the interface. In addition, high data transfer rates are not required for all tasks. If this is a really important factor for copying media files (sound recordings, images) or broadcasting an audio stream with a low degree of compression, then for normal interaction of the phone with a wireless headset or for exchanging contacts with another device, Bluetooth 2.0 capabilities are quite sufficient.

Secondly, in many cases, a much more important factor than the maximum speed of the wireless connection is the set of supported Bluetooth profiles. After all, it is he who actually determines the range of equipment with which the existing device is capable of interacting. Unfortunately, this information is rarely provided even in the full specification of the device, and often you have to look for it in the text of the instruction manual or on user forums.

Hello.

On December 3, 2014, Bluetooth SIG officially announced bluetooth specification version 4.2.
The press release identifies 3 main innovations:

• increasing the speed of data reception and transmission;
• ability to connect to the Internet;
• improving privacy and security.

Everything described below applies only to BLE, let's go...

1. Increasing the speed of receiving and transmitting user data.

And with the advent of version 4.2, Bluetooth SIG announced an increase in transmission speed by 2.5 times and the size of the transmitted packet by 10 times. How did they achieve this?

Let me tell you that these 2 numbers are related to each other, namely: the speed has increased because the size of the transmitted packet has increased.

Let's look at the PDU (protocol data unit) of the data channel:


Each PDU contains a 16-bit header. So, this header in version 4.2 is different from the header in version 4.1.

Here is the version 4.1 header:

And here is the header of version 4.2:

Note: RFU (Reserved for Future Use) - the field designated by this abbreviation is reserved for future use and is filled with zeros.

As we can see, the last 8 bits of the header are different. The Length field is the sum of the payload lengths and the MIC (Message Integrity Check) field found in the PDU (if the latter is enabled).
If in version 4.1 the “Length” field has a size of 5 bits, then in version 4.2 this field has a size of 8 bits.

From here it is easy to calculate that the “Length” field in version 4.1 can contain values ​​in the range from 0 to 31, and in version 4.2 in the range from 0 to 255. If maximum values subtract the length of the MIC field (4 octets), we get that there can be 27 and 251 octets of useful data for versions 4.1 and 4.2, respectively. In fact, the maximum amount of data is even less, because The payload also contains L2CAP (4 octets) and ATT (3 octets) service data, but we will not consider this.

Thus, the size of transmitted user data has increased approximately 10 times. As for the speed, which, for some reason, increased not 10 times, but only 2.5 times, then we cannot talk about a proportional increase, because everything also depends on the guarantee of data delivery, because guaranteeing the delivery of 200 bytes is a little more difficult than 20.

2. Possibility of connecting to the Internet.

Back in version 4.1, L2CAP added the “LE Credit Based Flow Control Mode” mode. This mode allows you to control the data flow using the so-called. credit based scheme. The peculiarity of the scheme is that it does not use signaling packets to indicate the amount of data being transferred, but requests from another device a credit for a certain amount of data to be transferred, thereby speeding up the transfer process. In this case, each time the receiving side receives a frame, it decreases the frame counter, and when the last frame is reached, it can break the connection.

3 new codes have appeared in the list of L2CAP commands:
- LE Credit Based Connection request – request for connection according to the credit scheme;
- LE Credit Based Connection response – response to a connection based on a credit scheme;
- LE Flow Control Credit – message about the possibility of receiving additional LE frames.

In the package “LE Credit Based Connection request”


there is an “Initial Credits” field 2 octets long, indicating the number of LE frames that the device can send at the L2CAP level.

In the response package “LE Credit Based Connection response”


the same field indicates the number of LE frames that another device can send, and the “Result” field also indicates the result of the connection request. A value of 0x0000 indicates success, other values ​​indicate an error. Specifically, a value of 0x0004 indicates that the connection was refused due to lack of resources.

Thus, already in version 4.1 it became possible to transfer a large amount of data at the L2CAP level.
And now, almost simultaneously with the release of version 4.2, the following is published:

• service: “IP Support Service” (IPSS).
• IPSP (Internet Protocol Support Profile) profile, which defines support for the transmission of IPv6 packets between devices that have BLE.

The profile defines the following roles:
- router role – used for devices that can route IPv6 packets;
- node role (Node) – used for devices that can only receive or send IPv6 packets; have service discovery functionality and have an IPSS service that allows routers to discover this device;

Devices with the router role that need to connect to another router can have the host role.

Oddly enough, the transmission of IPv6 packets is not part of the profile specification, and is specified in the IETF RFC “Transmission of IPv6 packets over Bluetooth Low Energy”. This document identifies another interesting point, namely, that when transmitting IPv6 packets, the 6LoWPAN standard is used - this is a standard for interaction using the IPv6 protocol over low-power wireless personal networks of the IEE 802.15.4 standard.

Look at the picture:


The profile specifies that IPSS, GATT, and ATT are used only for service discovery, and GAP is used only for device discovery and connection establishment.

But the one highlighted in red just means that packet transmission is not included in the profile specification. This allows the programmer to write his own implementation of packet transmission.

3. Improved privacy and security.

• exchange of information about pairing methods;
• generation of short-term keys (Short Term Key (STK));
• key exchange.

• generation of short-term keys (Short Term Key (STK)) called “LE legacy pairing”
• generation of long-term keys (Long Term Key (LTK)) called “LE Secure Connections”

In this regard, in addition to the 3 existing functions, 5 more functions have appeared in the cryptographic toolbox of the security manager, and these 5 are used only to service the new pairing process “LE Secure Connections”. These functions generate:

• LTK and MacKey;
• confirmatory variables;
• authentication check variables;
• 6-digit numbers used for display on connected devices.

So, if during pairing in the 2nd phase using the “LE legacy pairing” method, 2 keys were generated:

• Temporary Key (TK): 128-bit temporary key used to generate STK;
• Short Term Key (STK): 128-bit temporary key used to encrypt the connection

• Long Term Key (LTK): A 128-bit key used to encrypt subsequent connections.

• preventing tracking, because Now, thanks to “Numeric Comparison”, it is possible to control the ability to connect to your device.
• improving energy efficiency, because no longer requires additional energy to re-generate keys on each connection.
• Industry standard encryption to ensure sensitive data.

4. Is it already possible to touch?

• nRF51822 and nRF51422 chips;
• nRF51 DK;
• nRF51 Dongle;
• nRF51822 EK.

From its inception until recent years, the Bluetooth standard was ahead of its time. The creator of Bluetooth, Ericsson, began its research in the field of wireless interfaces for mobile phones back in the early nineties of the last century. In 1998, Ericsson, together with IBM, Intel, Nokia and Toshiba, released the first specification of the Bluetooth 1.0 standard. First of all, the new standard was intended to replace the interface cables of cell phones.

It’s interesting that in those years, not all cell phone users understood why an interface cable was needed at all. There were only two classes of devices to which a cell phone could be connected. First of all, there were hands-free headsets and public address systems, which required bidirectional transmission of moderate quality monaural audio over a distance of several meters.

In addition, there were personal computers, with which the phone interacted as electronic organizer or as an external modem. Here the new standard was supposed to provide a wireless replacement for the serial port (RS-232).

For such tasks, the Bluetooth standard did not require either data transfer speeds, greater network functionality, or a long range. Intended for mobile devices, the standard had to provide low power consumption, and in addition, to successfully compete with cable connections, it had to be very cheap to implement.

The creators of Bluetooth are often accused of being too slow to bring their creation to market. digital devices. It is indeed strange that the Bluetooth specification, officially published in 1998, became widespread only at the beginning of the third millennium. However, the reasons for such a delay should not be sought in the slowness of the standard developers, but in the lag of the market itself. In those years, there simply weren't enough tasks for Bluetooth.

However, the founders of the standard quickly realized the potential of their creation. Already in 1999 they demonstrated their desire to continue improving it. This is how the Bluetooth SIG (Special Interest Group) was born. Along with the five founders, the group included quite a few companies, including Palm, Microsoft, Motorola, Handspring, Qualcomm and Lucent.

The idea of ​​Bluetooth transformed quite quickly. New interface no longer seen as a trivial replacement for cell phone cables. He started to turn into a universal wireless interface for personal networks, which could include almost any device. From time to time, shortcomings were found in the standard that prevented the implementation new concept, which served as a reason for releasing new versions of the specification with relatively minor changes and additions. This is how versions 1.1 and 1.2 appeared, which even today have no competitors among radio interfaces for personal networks.

Why "2.0/EDR"?

The widespread adoption of Bluetooth devices that began in 2001 and 2002 showed that this standard, the best in its field, was still not good enough. Well, in fact, the developers of Bluetooth 1.x worked not so much on practical data, but on forecasts of the distant (by the standards of the digital industry) future, and they simply could not foresee everything.

In 2002, Bluetooth was standardized by the IEEE (Institute of Electrical and Electronics Engineers) as the 802.15.1 standard. In the same year, Ericsson representatives unveiled plans for a new version of the standard - 2.0. It was noted that the new specification should be expected only at the end of 2004, when the market has grown up to it.

In November 2004, the Bluetooth SIG released the Bluetooth 2.0+EDR (Enhanced Data Rate) specification. This time there was virtually no delay in the appearance of devices that support the new standard. Broadcom, CSR, and RF Micro Devices tested 2.0+EDR prototypes and almost immediately began serial production of the chips. However, the rapid displacement of versions 1.x from the market did not begin.

The first device to support Bluetooth 2.0+EDR was not a phone, as one might expect, but a laptop from Apple. Bluetooth SIG doesn't expect widespread mobile phones to support the new standard until next year. At the same time, phone manufacturers will face significantly more difficulties than they experienced during the transition from version 1.1 to 1.2.

Appears logical question, as to why they made a new standard at all, if no one really needs it, and its predecessor is still out of competition, all because of the same low cost and thrifty use of energy. On what basis do the developers hope that the popularity of version 2.0 will soon increase?

There are two such reasons: increased requirements for the speed and convenience of personal networks and the desire of the developers of the standard to use it not only in personal networks.

Personal network users want to send quickly large files with video, audio and photo content, they want to seamlessly use wireless communication with various devices simultaneously, they want to listen to high-quality stereo audio through wireless headphones and the number of such tasks is constantly growing. One of the most frightening examples is modern printers that can outrun Bluetooth devices from which data is sent for printing. The constant increase in the number of Bluetooth devices cannot but cause an increase in the size of personal networks, where all devices can work simultaneously, interfering with each other. Bluetooth 1.x is not ready to serve the needs of such networks, which is especially unfortunate in connection with the approach of a competing communication standard - UWB. If Bluetooth SIG wants to continue to represent a standard ahead of its time, it needs something better than 1.x.

In addition, do not forget that the Bluetooth 1.x standard is already widely used not only for personal networks, but also for a number of other tasks, including multi-user local networks and touch applications. In these areas, Bluetooth 1.x is finding it increasingly difficult to compete with other wireless standards such as Wi-Fi and Zigbee.

In such conditions, Bluetooth SIG could either give away the future market to competitors, or create a fundamentally new standard with a separate emphasis on increasing speed.

New in Bluetooth 2.0/EDR

Let's briefly consider those innovations that allow developers to count on the growing popularity of the new standard:

Enhanced Data Rate (EDR)

The topic of data transfer speed creates many difficulties for Bluetooth developers. On the one hand, there are many tasks for which, under any circumstances, the speed of 721 Kbps, which version 1.x provides, is sufficient, and on the other, there are multimedia tasks that require the transfer of increasingly large amounts of data.

Bluetooth/LAN access point combined with print server.

The 2.1 Mbps speed provided by the new version of Bluetooth is still noticeably short of even the slowest wireless networks, but for typical multimedia tasks it is almost enough.

After the 12 Mbit/s promised in 2002, the figure of 2.1 looks more than modest. However, it must be borne in mind that the developers of the Bluetooth SIG were severely limited by the requirements for power consumption and cost, which were and remain the highest priority for this standard.

Bluetooth 1.x uses one of the most primitive modulation schemes - GFSK (Gaussian Frequency Shift Keying), the simplicity of which was very attractive to developers in 1998, when even a speed of 721 Kbps seemed excessive. Bluetooth 2.0/EDR uses several alternative modulation schemes to nearly triple data transfer rates. However, GFSK continues to be supported for compatibility reasons.

No "hopping" frequency channels.

In Bluetooth versions 1.x, communication can be carried out using one of 79 frequency channels. To avoid interference from other devices operating in the same frequency range, channels change 1600 times per second. This is a fairly simple solution, and besides, in 1998, such a protocol could be considered as a good hardware protection of communications from intruders. Disadvantages of such a mechanism include slower communication and difficulty in further improving the standard.

The Bluetooth 2.0 version uses a more modern mechanism to protect against interference, which allows for fuller use of the standard's capabilities.

Multi-cast support

In personal area networks, there is often a need to transmit the same data to multiple devices at the same time. Bluetooth 1.x provided for repeated transmission of this data in turn, for each device. At one time, there could only be one transmitting and one receiving device on a single Bluetooth network. This made it very difficult to work in real time with tasks such as listening to the same audio on multiple Bluetooth headphones together, or how computer games with multiple participants synchronizing via Bluetooth. In addition, this simply slows down the work, since each time you need to re-establish a connection with the next device, which takes noticeable time.

Bluetooth 2.0 allows you to send the same data to multiple devices at the same time. This feature is called "Multi-cast", it was made possible by eliminating the mechanism for quickly changing frequency channels.

QoS (quality of service) system

When using Bluetooth to communicate with multiple devices at the same time, unwanted delays often occur. They could have been avoided if data flows had been better organized.

The Bluetooth 2.0 specification provides a special QoS (quality of service) mechanism, which ensures the interaction of devices with a minimum amount of delays. Devices that support QoS communicate with each other to balance their needs for immediate data transfer and the ability to painlessly cope with communication delays. Thus, without increasing the actual data transfer speed, it is possible to eliminate the slowdown effect that is so annoying to users.

Distributed media access control

The network model in early versions of Bluetooth is very simple. The network has one master and from one to seven slave devices. Data can only be transferred between the "master" and "slave" devices. At the same time, the main device controls access of devices to the data transmission medium. If the master device leaves the network for some reason, the rest of the network will not be able to function.

Bluetooth 2.0 introduces a new protocol that provides distributed control over access to the data transmission medium, which relieves the network of dependence on a single device. Once the master device leaves the network, its functions are transferred to another device.

Additionally, Bluetooth 2.0 increases the maximum network size from 8 to 256 devices. In versions 1.x, to increase the network, a rather inconvenient mechanism was provided for combining simple Bluetooth networks (“piconet”) into one large network("scatternet"). At the same time, the same device was the master in one simple network and the slave in another. In version 2.0, everything is much simpler - from one to 255 slave devices are connected to one master.

Enhanced Energy Saving

The increased data transfer speed in Bluetooth 2.0 has led to an increase in power consumption by devices. However, power consumption did not increase as much as speed, so the overall energy consumption for transmitting the same amount of data was noticeably reduced. For most tasks, there is a more than twofold gain in energy savings.

Smarter organization of work with data also influenced energy consumption towards its reduction. For example, using simultaneous data transfer to several devices is much more economical than transferring this data to each device separately.

Backwards compatible with previous versions

The Bluetooth specification version 2.0 provides full compatibility with all previous versions. A device that supports the new standard is able to exchange data with devices of all versions, even if they are connected to the same network. At the same time, data will be exchanged with new devices on increased speed 2.1 Mbit/s, and with the old ones - at the same 721 Kbit/s.

The Future of Bluetooth

The new version of the Bluetooth specification cannot be called final. Gone are the years when this standard could not develop for a long time, remaining above current market requirements. Now it needs regular updates to keep up with the times.

Bluetooth SIG plans to begin releasing updated specifications annually and promises to release the next version by the end of 2005. Of course, not every new version will contain as many new features as version 2.0/EDR.

Interestingly, data rate is no longer stated by the standard's developers as the immediate focus of their efforts. Much more attention in their plans is paid to improving the capabilities of Bluetooth in the field of better use of the available speed, for example, in 2005 they plan to finalize the QoS system, which can be improved almost endlessly, and in 2006 the Multi-Cast system is expected to be finalized.

It is quite natural that competing standards, both squeezing Bluetooth in areas new to it and expected in its typical area of ​​personal networks, force developers to continue to improve the most strong point standard - low energy consumption. SIG intends to introduce solutions leading to unprecedented reductions in energy consumption as early as 2005.

In addition, new areas of application of Bluetooth, of which there are more and more, impose more stringent requirements for data security, and it is difficult to even formulate them without knowing exactly where the new standard will be distributed. For now, the security area will be given attention in each new version of the standard specification.

Bluetooth and everything, everything, everything

It is obvious that the new capabilities will allow Bluetooth 2.0 to enter into active competition with some of the existing wireless communication standards in the very near future. The emergence of new standards that can seriously compete with Bluetooth is also expected.

Let's look at the balance of power between Bluetooth and its main rivals:

Bluetooth vs. UWB

The new wireless standard, called Wireless USB, is designed for almost the same tasks as Bluetooth, that is, for personal networks. The main weakness of the new standard is that it is not ready yet, but its release is planned for the relatively near future, and then nothing will prevent the rivalry between the so-called Bluetooth and Wireless USB from flaring up, in which the former will have low price and power consumption, and on the second side - the data transfer rate, under ideal communication conditions reaching 480 Mbit/s (like USB 2.0). Many existing compatible devices are unlikely to help Bluetooth in the emerging struggle, since in fact, Wireless USB will differ from the usual USB 2.0 only in the absence of a cable, and adaptation of the new standard will be quick and painless.

A quick victory for one of the standards in the near future is completely unrealistic. As long as there are devices for which speed is not important, but low power consumption is important, or vice versa, both standards will be necessary. At the same time, don't expect the world of personal network devices to quickly divide into two incompatible camps, since devices that are equally interested in speed and energy efficiency are quite common.

A race is likely in which Bluetooth developers will increase speed, and Wireless USB developers will reduce power consumption. Both standards technically have a lot in common, so in addition to the victory of one of them, the option of creating a new communication standard based on them can also be considered.

In any case, the final solution to the issue is not a matter of the very next few years.

Bluetooth vs. WiFi

In theory, Bluetooth and Wi-Fi standards are designed to fundamentally different tasks, but the development of mobile communications and local networks towards each other has caused the emergence of areas where these standards successfully compete.

First of all, this small networks mobile devices intended, for example, for gaming and multimedia tasks. The speed of communication and the distance at which this communication is possible are secondary in such networks in relation to the economical consumption of battery power.

In fact, the increase in speed that occurs in latest version Bluetooth, allows it to completely displace Wi-Fi from the field mobile networks, where he had just begun to appear. In those areas where Wi-Fi will remain competitive, it will be saved primarily not by speed, but by its specific “tailoring” for complex network tasks, and especially for the Internet.

Most likely, smartphones and game consoles of the future will use Wi-Fi to communicate with regular non-mobile networks and the Internet, and Bluetooth to communicate with each other. Dreams of a unified network standard will again have to wait.

Bluetooth vs. Zigbee

The area of ​​touch systems is the only area where Bluetooth energy efficiency is not only not up to the mark, but does not meet even the most minimal requirements. This is not only about economical data transfer, but also about smarter use of energy at other times.

The competing Zigbee standard, noticeably lagging behind Bluetooth in speed, allows touch devices to operate on a single battery for several years.

In this confrontation of standards, the situation is simple: if Bluetooth, as its developers promise, in the nearest specifications will overtake Zigbee in terms of economy, then the market for sensor systems can be considered captured, and if not, Zigbee will continue to single-handedly occupy this part of the market.

Bluetooth 5.0 became a reality. Compared to Bluetooth 4.0, the new version has twice the capacity, four times the range and a number of other improvements. Let's look at the advantages of Bluetooth 5.0 over its predecessors, including an example CPU CC2640R2F from Texas Instruments.

The popularity of the Bluetooth 4 protocol version, as well as some of its limitations, became the reasons for the creation of the next Bluetooth 5 specification. The developers set themselves a number of goals: expanding the range, increasing the throughput when sending broadcast packets, improving noise immunity, and so on.

Now that the first devices with Bluetooth 5 have begun to appear, users and developers rightly have questions: which of the previously stated promises have become reality? How much have the range and data transfer speed increased? How did this affect consumption levels? How has the approach to generating broadcast packets changed? What improvements have been made to improve noise immunity? And, of course, the main question is - is there backward compatibility between Bluetooth 5 and Bluetooth 4? Let's answer these and some other questions and consider the main advantages of Bluetooth 5.0 over its predecessors, including using the example of a real processor with Bluetooth 5.0 support produced by the company Texas Instruments.

Let's get started Bluetooth review 5.0 with an answer to the most frequently asked question about backward compatibility with Bluetooth 4.x

Is Bluetooth 5.0 backwards compatible with Bluetooth 4.x?

Yes, it does. Bluetooth 5 adopts most of the features and extensions of Bluetooth 4.1 and 4.2. For example, Bluetooth 5 devices retain all the data security improvements of Bluetooth 4.2 and support the LE Data Length Extension. It is worth recalling that thanks to the LE Data Length Extension, starting with Bluetooth 4.2, the size of the data packet (packet data unit, PDU) during an established connection can be increased from 27 to 251 bytes, which allows you to increase the data exchange speed by 2.5 times.

Due to the large number of differences between protocol versions, the traditional mechanism for negotiating parameters between devices when establishing connections is retained. This means that before they start exchanging data, the devices “get to know each other” and determine the maximum frequency of data transmission, the length of messages, and so on. In this case, Bluetooth 4.0 parameters are used by default. The transition to Bluetooth 5 parameters occurs only if, during the pairing process, it turns out that both devices support a later version of the protocol.

Speaking about the tools that are already available to developers, it is worth noting new processor CC2640R2F and free BLE5-Stack from Texas Instruments. To the delight of developers, BLE5-Stack is based on the previous version of BLE-Stack, and changes in its use affected only new Bluetooth features 5.0.

How has the data transfer speed increased in Bluetooth 5?

Bluetooth 5 uses a wireless connection with physical data transfer rates of up to 2 Mbps, which is twice as fast as Bluetooth 4.x. It is worth noting here that the effective data exchange rate depends not only on the physical capacity of the transmission channel, but also on the ratio of service and useful information in a package, as well as from associated “overhead” costs, for example, loss of time between packages (Table 1).

Table 1. Communication speed for different versionsBluetooth

In versions Bluetooth 4.0 and 4.1, the physical bandwidth of the channel was 1 Mbit/s, which, with a PDU data packet length of 27 bytes, made it possible to achieve exchange rates of up to 305 kbit/s. Bluetooth 4.2 introduced the LE Data Length Extension. Thanks to it, after establishing a connection between devices, it became possible to increase the packet length to 251 bytes, which led to an increase in data exchange speed by 2.5 times - up to 780 kbit/s.

Bluetooth version 5 retains support for LE Data Length Extension, which, together with an increase in physical throughput to 2 Mbit/s, allows data exchange speeds of up to 1.4 Mbit/s to be achieved.

As practice shows, such acceleration of data transfer is not the limit. For example, the CC2640R2F wireless microcontroller is capable of operating at speeds up to 5 Mbps.

It is worth mentioning the common misconception that the increase in throughput to 2 Mbit/s was achieved by reducing the range. Of course, physically the transceiver chip (PHY) when operating at a frequency of 2 Mbit/s has 5 dBm less sensitivity than when operating at a frequency of 1 Mbit/s. However, in addition to sensitivity, there are other factors that contribute to increasing the range, for example, the transition to data encoding. For this reason, all other things being equal, Bluetooth 5 turns out to be more reliable and has a longer range compared to Bluetooth 4.0. This is discussed in detail in one of the following sections of the article.

How to enable high speed data transfer mode in Bluetooth 5?

When establishing a connection between two Bluetooth devices Bluetooth 4.0 settings are initially used. This means that at the first stage the devices exchange data at a speed of 1 Mbit/s. Once the connection is established, the Bluetooth 5.0-enabled master can begin the PHY Update Procedure, the goal of which is to establish a maximum speed of 2 Mbps. This operation will only succeed if the slave also supports Bluetooth 5.0. Otherwise, the speed remains at 1 Mbit/s.

For developers who have previously used the Texas Instruments BLE-Stack, the good news is that the new BLE5-Stack has a single function dedicated to performing this procedure, HCI_LE_SetDefaultPhyCmd(). Thus, when switching to Bluetooth 5.0, users of TI products will not have problems with the initial initialization. Also useful for developers will be an example posted on the GitHub portal, which allows you to evaluate the operation of two CC2640R2F microcontrollers operating as part of CC2640R2 LaunchPads in High Speed ​​and Long Range modes.

How has the range of Bluetooth 5 increased?

The Bluetooth 5.0 specification states that the range is four times greater than Bluetooth 4.0. This is a rather subtle issue that is worth dwelling on in more detail.

Firstly, the concept of “four times” is relative and is not tied to a specific range in meters or kilometers. The fact is that the radio transmission range strongly depends on a number of factors: the state of the environment, the level of interference, the number of simultaneously transmitting devices, and so on. As a result, not a single manufacturer, as well as the developer of the Bluetooth SIG standard itself, provides specific values. The increase in range is measured in comparison with Bluetooth 4.0.

For further analysis it is necessary to perform some mathematical calculations and estimate the power budget of the radio channel. When using logarithmic values, the radio channel budget (dB) is equal to the difference between the transmitter power (dBm) and the receiver sensitivity (dBm):

Radio channel budget = powerT X(dBm) – sensitivityR X(dBm)

For Bluetooth 4.0, the standard receiver sensitivity is -93 dBm. If we assume the transmitter power is 0 dBm, then the budget is 93 dB.

Quadrupling the range would require a 12 dB increase in budget, resulting in a value of 105 dB. How is this value supposed to be achieved? There are two ways:

• increasing transmitter power;
• increasing the sensitivity of receivers.

If you follow the first path and increase the transmitter power, this will inevitably cause an increase in consumption. For example, for the CC2640R2F, switching to an output power of 5 dBm leads to an increase in current consumption to 9 mA (Figure 1). At 10 dBm the current will increase to 20 mA. This approach is not attractive for most battery-powered wireless devices and is not always suitable for IoT, which is the area that Bluetooth 5.0 was primarily aimed at. For this reason, the second solution seems preferable.

To increase the sensitivity of the receiver, two methods are proposed:

• reduction in transmission speed;
• use of Coded PHY data encoding.

Reducing the data rate by a factor of eight theoretically increases receiver sensitivity by 9 dB. Thus, the desired value is only 3 dB short.

The required 3 dB can be achieved using additional Coded PHY coding. Previously, in Bluetooth 4.x versions, the bit encoding was unambiguous 1:1. This means that the data stream was directly sent to the differential demodulator. In Bluetooth 5.0, when using Coded PHY, there are two additional transmission formats:

• with 1:2 encoding, in which each bit of data is associated with two bits in the radio data stream. For example, a logical "1" is represented as a sequence of "10". In this case, the physical speed remains equal to 1 Mbit/s, and the real data transfer speed drops to 500 kbit/s.
• With 1:4 encoding. For example, a logical "1" is represented by the sequence "1100". The data transfer rate is reduced to 125 kbit/s.

The described approach is called Forward Error Correction (FEC) and allows errors to be detected and corrected on the receiving side, rather than requiring packets to be retransmitted, as was the case in Bluetooth 4.0.

On paper everything looks good. It remains only to find out how these theoretical calculations correspond to reality. As an example, let's take the same microcontroller CC2640R2F. Thanks to various improvements and new Bluetooth 5.0 modulation modes, the transceiver of this processor has a sensitivity of -97 dBm at 1 Mbps and -103 dBm when using Coded PHY and 125 kbps. Thus, in the latter case, only 2 dBm is missing from the level of 105 dB.

To evaluate the range of the CC2640R2F, engineers from Texas Instruments conducted a field experiment in Oslo. At the same time, from the point of view of noise level, the environment in this experiment cannot be called “friendly”, since the business part of the city was in close proximity.

To obtain a power budget of more than 105 dB, it was decided to increase the transmitter power to 5 dBm. This allowed us to achieve an impressive final value of 108 dBm (Figure 2). When performing the experiment, the range was 1.6 km, which is a very impressive result, especially considering the minimum level of consumption of radio transmitters.

How has the approach to Bluetooth 5 broadcast messages changed?

Previously, Bluetooth 4.x used three dedicated data channels to establish connections between devices (37, 38, 39). With their help, devices found each other and exchanged service information. It was also possible to transmit broadcast data packets over them. This approach has disadvantages:

• with a large number of active transmitters, these channels can simply be overloaded;
• More and more devices use broadcast messages without establishing a point-to-point connection. This is especially important for the Internet of Things IoT;
• the new Coded PHY coding system will require eight times more time to establish a connection, which will additionally load broadcast channels.

To solve these problems in Bluetooth 5.0, it was decided to move to a scheme in which data is transmitted on all 37 data channels, and service channels 37, 38, 39 are used to transmit pointers. The pointer refers to the channel over which the broadcast message will be transmitted. In this case, the data is transmitted only once. As a result, it is possible to significantly relieve the load on service channels and eliminate this bottleneck.

It is also worth noting that now the data length of a broadcast packet can reach 255 bytes instead of 6...37 bytes PDU in Bluetooth 4.x. This is extremely important for IoT applications, as it allows minimizing transmission overhead and eliminating connections, thereby reducing consumption.

Does Bluetooth 5 support Mesh networks?

Texas Instruments Solutions for Bluetooth 5

One of the very first microcontrollers with Bluetooth 5.0 was the high-performance CC2640R2F processor manufactured by Texas Instruments.

The CC2640R2F is built on a modern 32-bit ARM Cortex-M3 core with an operating frequency of up to 48 MHz. The operation of the radio transmitter is controlled by the second 32-bit ARM Cortex-M0 core (Figure 3). In addition, the CC2640R2F features rich digital and analog peripherals.

The advantage of the CC2640R2F microcontroller is also its low consumption level (Table 2). This applies to all operating modes. For example, in active mode, when receiving data over a radio channel, the consumption is 5.9 mA, and when transmitting - 6.1 mA (0 dBm) or 9.1 mA (5 dBm). When switching to sleep mode, the supply current drops completely to 1 µA.

The combination of three such important qualities as Bluetooth support 5.0, low power consumption and high peak performance make the CC2640R2F a very interesting solution for the Internet of Things. At the same time, using this microcontroller, you can create the entire range of IoT devices: autonomous sensors that operate for several years on a single battery, bridges between an additional control processor and a Bluetooth 5.0 channel, complex applications that require high computing power.

Table 2. Wireless microcontroller consumptionCC2640 R2 Fwith supportBluetooth 5

To quickly get started with the CC2640R2F, Texas Instruments has prepared a traditional development kit (Figure 4). Using a couple of such devices, you can evaluate the speed and range of radio transmission via Bluetooth 5.0. To do this, you can use ready-made examples or create own application based on the free BLE 5 stack 1.0 protocol (www.ti.com/ble).

Conclusion

The new version of the Bluetooth 5.0 protocol is focused on maximum compliance with the needs of the Internet of Things (IoT). Compared to the Bluetooth 4.0 version, it has a number of qualitative improvements:

• data transfer speed has doubled and reached 2 Mbit/s;
• transmission range has increased fourfold due to Coded PHY and Forward Error Correction (FEC) data encoding;
• Broadcast message throughput increased 8 times.

In addition, Bluetooth 5.0 provides backward compatibility with Bluetooth 4.x devices, and also supports most of the extensions of later versions of the protocol.

You can evaluate the capabilities of Bluetooth 5.0 now using tools produced by Texas Instruments. The company produces a high-performance and low-power microcontroller CC2640R2F, provides a free BLE 5 stack 1.0 and many ready-made examples for the LAUNCHXL-CC2640R2 debugging kit.

Literature

1. Bluetooth Core Specification 5.0 FAQ. 2016. Bluetooth SIG.