Adopted on December 2016 as the latest revision of the Bluetooth core specification, Bluetooth 5 sets the stage for the next generation of Bluetooth products. The latest revision promises transformative change by providing higher speed, longer range, increased advertising capacity and improved interoperability. It is the biggest enhancement to the Bluetooth standard since v4.0.
The Bluetooth low energy modulation scheme is Gaussian Frequency Shift Keying (GFSK). In v4.2, the symbol rate is 1 Mega symbols per second (Msps) with a frequency deviation of 185kHz. In Bluetooth 5, a 2Msps symbol rate with a frequency deviation of 370KHz is now supported. This provides twice the bandwidth of v4.2 without reducing the number of Bluetooth low energy channels; the bandwidth still fits within the 2MHz channel spacing used in Bluetooth low energy.
GFSK transfers 1 bit per symbol, so at 2Msps, the over-the-air bit rate is 2Mbps. However, due to overhead (e.g. preamble, addressing, CRC, etc.), throughput is never the same as the over-the-air bit rate. Looking only at actual useful payload, the maximum achievable throughput is approximately 1.4Mbps with Bluetooth 5.
LE Coded PHY is one of the key Bluetooth 5 features. It provides up to 4x improvement in range without increasing transmit power, albeit at reduced data rates. This is accomplished by increasing receiver sensitivity through error control coding on the 1Msps PHY rate (i.e. not applicable to 2Msps PHY rate).
Coding is done in 2 stages (Figure 1). Stage 1 is Forward Error Correction (FEC). Stage 2 is code spreading. The FEC block is a convolutional encoder that generates 2 bits for every input data bit. Depending on the spreading factor, the Pattern Mapper (Table 1) outputs 1 bit (i.e. S=2 spreading factor) or 4 bits (i.e. S=8) for every FEC output bit. With S=2, the range is doubled, but the data rate is reduced to 500kbps. With S=8, the range is quadrupled, but the data rate is reduced to 125kbps.
Figure 1. Bluetooth 5 Bitstream Processing.
Table 1. Pattern Mapper.
Increased Advertising Capacity
To increase advertising capacity, a new advertising Protocol Data Unit (PDU) is now supported in Bluetooth 5 (Figure 2). In v4.2, the advertising PDU is limited to 31 octets of advertising data. In Bluetooth 5, the new PDU supports up to 254 octets. This is an 8x increase in advertising capacity.
Figure 2. PDU Format.
In addition to the longer packets, Bluetooth 5 has the capability to send advertising data on all 40 Bluetooth low energy channels. In v4.2, advertising is limited to 3 (i.e. channels 37, 38 and 39) of the 40 channels. All the other channels (i.e. 0 – 36) are data channels only. With Bluetooth 5, advertising channels are now divided into 2 sets of channels: Primary and Secondary (Figure 3). The Primary channels are 37, 38 and 39. The Secondary channels are 0-36. This added feature allows developers to offload the longer advertising PDU to the secondary channels.
Figure 3. Bluetooth 5 advertising channels.
Today’s wireless devices often incorporate more than one wireless technology. For example, a smart phone typically has Bluetooth, WLAN and LTE capabilities. That’s 3 radios collocated in one small handheld device. Consequently, one wireless technology can cause interference on another wireless technology operating on a neighboring band (Figure 4).
Figure 4. Bluetooth ISM Band and neighboring LTE bands.
Bluetooth 5 reduces interference on neighboring bands with the new Slot Availability Mask (SAM) feature. SAM enables Bluetooth devices to indicate to each other which time slots are available for receiving and transmitting. By marking slots as unavailable during LTE activity, LTE interoperability is improved.
A Bright Future Ahead
The adoption of Bluetooth 5 further extends the possibilities for Bluetooth low energy. For designers, this means access to a new set of tools that help convert ideas into innovative products. The higher throughput creates new opportunities in high data rate use cases (e.g. audio, faster firmware over-the-air updates). With LE Coded PHY, whole-home coverage is now a reality (e.g. control lights in a multi-level home). With increased advertising capacity, Bluetooth 5 paves the way for richer content in beacons. And as the market for multi-radio devices continues to grow, SAM is another step forward towards better interoperability.
Now, Bring it to Life
The quickest and easiest way to add Bluetooth 5 functionality to a product is to use a radio certified (i.e. FCC certified) Bluetooth low energy module. One such module is TAIYO YUDEN’s ultra-small (3.2mm x 8.55mm x 0.9mm, as seen in Figure 5) EYSHSNZWZ Bluetooth low energy module. Based on Nordic Semiconductor’s powerful nRF52832 SoC (Figure 6), this FCC/ISED/MIC certified module supports two of the four Bluetooth 5 key features: 2Msps PHY and increased advertising capacity. The module also features an ARM Cortex M4F processor, 512kB of flash, 64kB of RAM, NFC functionality, and an ample amount of I/O’s (e.g. I2C, I2S, PDM, 12-bit ADC). It’s ready to tackle complex applications.
Figure 5. Able to fit six modules on a dime.
Figure 6. Power by Nordic Semiconductor's nRF52832.
In addition to the EYSHSNZWZ, TAIYO YUDEN also has the EYSHCNZWZ and EYSHJNZWZ Bluetooth 5 modules. Just like the EYSHSNZWZ, these modules are based on the nRF52832. If the smallest foot print is not a must-have requirement, these are excellent alternatives to the EYSHSNZWZ.
You can learn more about Bluetooth 5 modules available on the market here.
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