Bluetooth Low Energy Introduction

1. Introduction

BLE (Bluetooth low-energy, Bluetooth) is a complement to traditional Bluetooth BR/EDR technology. Although BLE and traditional Bluetooth are known as Bluetooth standards and share RF, ble is a completely different technology. ble does not have compatibility with traditional Bluetooth Br/edr . It is designed for small data rate, discrete transmission applications. Communication distances also change, traditional Bluetooth transmission distance of dozens of meters to hundreds of meters ,ble is defined as 100 meters .

2. Low power Bluetooth (BLE)

Low-power Bluetooth is divided into single-mode (Bluetooth Smart) and dual-mode (Bluetooth smart Ready) two of devices. The distinction between BLE and Bluetooth BR/EDR allows us to integrate Bluetooth technology into specific devices in three ways. The following table shows how the two Bluetooth devices communicate with each other. Because it is no longer possible for all existing Bluetooth devices to interconnect with another Bluetooth device, it is very important to accurately describe the version of Bluetooth in the product.

2.1 Single Mode Bluetooth

The single-mode Bluetooth device is called a Bluetooth smart device and has a dedicated logo:

Small devices such as watches, motion sensors, etc., are based on a single mode Bluetooth low power consumption. In order to achieve very low power consumption, hardware and software are optimized. Such a device can only support ble. The single mode Bluetooth chip is often a product with a mono-mode Bluetooth protocol stack, which is provided free of charge by the chip vendor.

2.2 Dual Mode Bluetooth

The dual-mode Bluetooth device is known as a Bluetooth Smart ready device and has a dedicated logo:

Dual-mode devices support Bluetooth Br/edr and ble. In a dual-mode device, both technologies use the same RF front end and antenna. Typical dual-mode devices are smartphones, tablets, PCs, and Gateway. These devices can receive data sent over a ble or Bluetooth BR/EDR device, which often has sufficient power supply capability. Dual-mode devices and BLE devices communicate less power than dual-mode devices and Bluetooth BR/EDR device communications. A dual-mode solution requires an external processor to be sufficient to implement the Bluetooth protocol stack.

3. Application

BLE is suitable for small battery-powered devices and has the following five major markets.

3.1 Medical and health

Those medical devices used to monitor important physiological data are the objects that BLE uses in the health market. Typical equipment is a blood glucose meter, a blood pressure monitor and an oxygen meter. Ble is selected by the Wellness Alliance (Continua Health Alliance) as a compatible transmission technology for end product communication.

3.2 Sports and Fitness

In the field of sports and fitness, BLE is suitable for positioning, while also uploading some important monitoring data. Typical device heart rate monitors, thermometers, pedometer, metronome, altimeter, locator and display information from the sensor through the watch.

3.3 Industry

In the area of automation applications, BLE is primarily used for transmitting I/O signals. BLE can be used to monitor and control motors, brakes, parameters and the entire process.

3.4 Entertainment

In the entertainment field, BLE has been used by many devices, such as set-top boxes, game consoles and so on. It is expected that BLE will be the Bluetooth application in Tv/dvd/stb/media player, remote control, game control handle and wireless mouse device.

3.5 Smart Home

BLE can provide light control, temperature control, humidity control, safety lock control, door and window control of low-power, high-security solutions. The application in smart meters is also a direction.

4. Agreement

BLE does not support traditional Bluetooth BR/EDR protocols, such as the SPP protocol in traditional Bluetooth is no longer present in ble. As an alternative, all protocols or services in BLE are based on the GATT (Generic Attribute profile). Although some traditional Bluetooth protocols, such as HID, are ported to BLE, you must differentiate between protocols and services in BLE applications.

The service describes the features (and their UUID). The description of the service describes its own characteristics and forms, and describes how these characteristics are applied and what security mechanisms are required.

The application protocol defines the services it uses, whether it is the sensor end or the receiving end, the role of defining GATT (Server/client) and the roles of Gap (Peripheral/central).

Compared to the Bluetooth BR/EDR protocol, the GATT-based application protocol is very simple, since all functions are integrated in the GATT terminal, and the application protocols based on them are only used for the functions provided by GATT.

The following table lists the existing GATT-based agreements/services (07/2013):

Gatt-based Specifications (Qualifiable)		adopted Version
Anp	Alert Notification Profile	1.0
ANS	Alert Notification Service	1.0
Bas	Battery Service	1.0
Blp	Blood Pressure Profile	1.0
Bls	Blood pressure Service	1.0
Cpp	Cycling Power Profile	1.0
Cps	Cycling Power Service	1.0
Cscp	Cycling speed and Cadence profile	1.0
CSCS	Cycling speed and Cadence Service	1.0
Cts	Current Time Service	1.0
Dis	Device Information Service	1.1
FMP	Find Me Profile	1.0
Glp	Glucose profile	1.0
HIDS	HID Service	1.0
Hogp	HID over GATT profiles	1.0
HTP	Health Thermometer Profile	1.0
HTS	Health Thermometer Service	1.0
Hrp	Heart Rate Profile	1.0
HRS	Heart Rate Service	1.0
Ias	Immediate Alert Service	1.0
LLS	Link Loss Service	1.0
LNP	Location and Navigation profile	1.0
LNS	Location and Navigation Service	1.0
NDCs	Next DST Change Service	1.0
PASP	Phone Alert Status Profile	1.0
PASS	Phone Alert Status Service	1.0
PXP	Proximity profile	1.0
Rscp	Running Speed and Cadence profile	1.0
RSCS	Running Speed and Cadence Service	1.0
RTUS	Reference Time Update Service	1.0
Scpp	Scan Parameters Profile	1.0
SCPs	Scan Parameters Service	1.0
TIP	Time profile	1.0
Tps	Tx Power Service	1.0

5. Technical Features

The low power consumption of BLE is not achieved by optimizing the wireless RF transmission in the air, but by changing the protocol design. In general, in order to achieve very low power consumption, the BLE protocol is designed to: when the RF is not necessary to completely shut off the air RF. Compared to the traditional Bluetooth br\edr, BLE has these three features to achieve low power consumption: Shorten the wireless opening time, quickly establish a connection, reduce the transmit and receive peak power consumption (specific to the chip decision).

The first trick to shorten the wireless turn-on time is to use only 3 "ad" channels, and the second trick is to reduce the work cycle by optimizing the protocol stack. An ad-based device can automatically establish a connection with a device in search, so the connection can be established and data transferred within 3MS.

Low-power design can bring some sacrifices, such as: audio data cannot be transmitted via BLE.

Ble is still a very robust technology. It still supports frequency hopping (37 data channels), and an improved GFSK modulation method is used to improve the stability of the link. Ble is also still a very secure technology because it provides a bit of AES encryption at the chip level.

Single-mode devices can be either master or slave, but cannot act as two roles at the same time. This means that BLE can only establish a simple star-like topology, not to achieve a scattering network.

BLE's radio specification defines a low-power Bluetooth with a maximum data rate of 305kbps, but this is only theoretical data. In practical applications, the throughput of the data depends on the upper layer protocol stack. The speed of the UART, the ability of the processor, and the main device all affect the data throughput capability.

The high data-throughput ble can only be achieved through private schemes or ATT-notification. In fact, if it is a high data rate or high data volume applications, Bluetooth BR/EDR often appear to be more power-saving.

5.1 Application examples and benefits

BLE is commonly used in communication between sensors and smartphones or tablets. So far, only a handful of smartphones and tablets have supported ble, such as iphone 4S after Apple phones, Motorola Razr and the new ipad and its later ipad. Android phones are also gradually supporting BLE, and the BLE standard for Android has just been released on July 24, 2013. Smartphones and tablets will have a baseband and protocol stack with dual-mode Bluetooth, and the protocol stack includes all parts of GATT and below, but there is no specific agreement on the GATT. Therefore, these specific protocols need to be implemented in the application and need to be implemented based on each GATT API set. This facilitates the simple implementation of a specific protocol on the smart machine side, or simply the development of a set of GATT-based private protocols on the smart machine side.

The use of BLE transmission on Apple devices is particularly advantageous. Compared to Bluetooth br/edr, there is no need to use an apple-authorized encryption chip, you do not need to join the MFI project.

5.2 Contrast ble and traditional Bluetooth BR/EDR technology

	Bluetooth Br/edr	Bluetooth Low Energy
Frequency	2400-2483.5 MHz	2400-2483.5 MHz
Deep Sleep	~80μa	<5μa
Idle	To MA	To MA
Peak Current	22-40 MA	10-30 MA
Range	500m (class 1)/50m (class 2)	100m
Min. Output Power	0 dbm (Class 1)/-6 dbm (class 2)	-20 dBm
Max. Output Power	+20 dbm (Class 1)/+4 dbm (Class 2)	+10 dBm
Receiver Sensitivity	≥-70 dBm	≥-70 dBm
Encryption	bit/128 bit	AES-128 bit
Connection time	Ms	3 ms
Frequency Hopping	Yes	Yes
Advertising Channel	32	3
Data Channel	79	37
Voice capable	Yes	No

5.3 Dual-mode protocol stack

Is the architecture of the Stuman dual-mode protocol stack BLUECODE+SR. In this diagram, all the parts required for SPP, HDP, and GATT are included.

5.4 Single-mode protocol stack

is a typical protocol stack design of single-mode protocol stack. In such a stack, there is generally no specific protocol, so it is necessary to implement the corresponding protocol for each specific application in a specific application. This is very different from traditional Bluetooth, where traditional Bluetooth implements each application-specific protocol in the protocol stack, such as SPP, HDP, etc.

Compared to the dual-mode protocol stack, BLE does not require a master processor to implement its protocol stack, so very low power integration is possible. Most single-mode chips or modules have their own protocol stacks.

Since the protocol stack in a ble single-mode product (chip or module) only implements the GATT layer, it is often necessary to integrate the protocol of the specific application into the single-mode product. Even the chip makers are starting to provide SDKs with specific protocols and sample code. However, there is still no real solution to get the hand.

6. Integration method

Despite the differences between Singlemode and dual-mode solutions, there are many ways to integrate Bluetooth technology into your device.

6.1 Modules

The simplest and fastest way is to use an embedded module. Such modules include antennas, embedded protocol stacks, and a variety of interfaces: UART, USB, SPI, and I²c, which can be connected to your processor via these interfaces. The module provides a simple interface to control the function of Bluetooth. Many of the module companies will provide products with CE, FCC and IC certification. Such modules can only be Bluetooth BR/EDR, dual-mode or single-mode.

In the case of Bluetooth BR/EDR and dual-mode solutions, the HCI module can also be used. The HCI module simply does not have a Bluetooth protocol stack, and the others are the same as the above modules. So, this module will be cheaper. The HCI module simply provides a hardware interface in which the Bluetooth stack needs to be provided by a third party. Such a third-party protocol stack needs to be able to run in the processor of the main device, such as the BLUECODE+SR provided by Stuman. Using the HCI module requires porting the software to the final hardware.

Theoretically, it is also possible to provide a single-mode HCI module. However, all chip companies have integrated GATT into their chips, so there will be no HCI single-mode module appearing on the market (see section 5.4).

6.2 Chip

Using a chip to integrate BLE is the lowest cost approach from the material perspective, but this takes a lot of upfront work and takes a lot of time. While it is only necessary to port the protocol stack to the target platform on the software, the hardware needs to be very experienced with RF layout and antenna design. These companies offer BLE chips: Broadcom, CSR, EM microelectronic, Nordic, and Ti.

Introduction to Bluetooth Low energy