Guest Article: Bluetooth 5 Low Energy And Its Role In Hearing Aids As Part Of the “Internet of Things”

Guest Article: Bluetooth 5 Low Energy And Its Role In Hearing Aids As Part Of the “Internet of Things”

Today’s Guest Article by Mohammad Afaneh explains what Bluetooth 5 Low Energy (“BLE”) is, how it differs from “classic” Bluetooth 5.0, and how it’s used to empower the “Internet of Things” (“IoT”). In addition, we’ll jump in and explain how these affect hearing devices. Also, we’ll explain why you should never buy or dispense any 2.4 gHz hearing aid using a 312 battery. [Original title: “Bluetooth 5 and its Role in the Internet of Things”]

And now, we begin Afanah’s article:

What is Bluetooth 5?

If you own a modern car or a smartphone, chances are you’ve used Bluetooth at least once in your life. Bluetooth is everywhere: In speakers, wireless headphones, cars, wearables, medical devices, and even shoes!

There are two kinds of Bluetooth devices: one is referred to as Bluetooth Classic (used in wireless speakers, car infotainment systems, and headsets), the other is Bluetooth Low Energy (BLE).

BLE is more prominent in applications where power consumption is crucial (such as battery powered devices) and where small amounts of data are transferred infrequently (such as in sensor applications).

These two kinds of Bluetooth devices are incompatible with each other, even though they share the same brand and even specification document [Emphasis added ~DLS]. A Bluetooth Classic device cannot communicate (directly) with a Bluetooth Low Energy device.

Screen grab of Sonova SWORD radio chip
Click picture to open YouTube promo video

This is why some devices such as smartphones choose to implement both types (sometimes called a Dual Mode Bluetooth device) [Note: Sonova’s SWORD radio chip is dual mode ~DLS], that way they can communicate with both types of devices.

Since many IoT systems involve small devices and sensors, BLE has become the more common protocol of the two (versus Bluetooth Classic) in IoT. In December 2016, the Bluetooth Special Interest Group (SIG), the governing body behind the Bluetooth standard, released Bluetooth version 5.0. A majority of the enhancements and features introduced in this version focused on Bluetooth Low Energy.

Almost all 2.4 gHz hearing aids, CI’s, & BAHA processors use only BLE 4.0 & up. We say “almost” all, as there are two exceptions:

  • Cochlear Nucleus 6, BP400, and ReSound & Beltone hearing aids before the February 2014 LiNX rollout use their Unite 2.4 gHz platform, which while based on BLE, use a proprietary low-latency CODEC [as do all of GN Danalogic i-Fit C series]. Also Phonak’s Roger digital FM system is based on a similar paradigm;
  • Sonova’s Phonak, Unitron, and Advanced Bionics devices which have their new SWORD (10.6 mHz/2.4 gHz dual-band) radio chip support both BLE and classic specifications, to guarantee connectivity to any phone, not just iPhones & a few Androids. We at The Hearing Blog believe this is a mistake, after the 2010 Audiotoniq debacle, where they tried it on a rechargeable hearing aid platform, and they never made it to market due to short battery life. Even today, this is why the Phonak & Unitron “Belong platform” hearing aids which can provide Bluetooth with the SWORD chip are Not Available in rechargeable devices: You can have one or the other, but not both.

As we previously explained, when using a tinnitus relief app, watch out for the additional hearing aid battery consumption of about 2.5mA when direct UHF (900 mHz or 2.45 gHz) streaming is used, whether Bluetooth 4.0/Low Energy (BLE), or the similar ReSound/Cochlear Unite and Phonak Roger protocols. This is why we have an ironclad rule of a minimum #13 battery size —  regardless of loss — for any 2.45 gHz–capable hearing aid for streaming robustness, especially in this new era of Thimerosal-free cells. Starkey’s engineers correctly foresaw this issue in their Halo devices; however GN’s ReSound and Beltone divisions still sell #312–fueled devices, despite the numerous problems related to streaming dropouts and oxygen starvation experienced in all five generations of devices since 2011 due to the 2.5 mA radio drain on top of what the DSP & class D amp draws.

We understand the need for people who demand an ITC, but there is no excuse for GN to build or sell a 312-fueled BTE or RIC (LiNX² & LiNX 3D 561, 761, 961) when the x62 chassis is the same size outline, but just a hair thicker to accommodate the larger battery which supplies  twice the energy capacity.

He continues…

What is new in Bluetooth 5.0?

So, what’s new in Bluetooth 5.0 versus the previous versions?

The three main features that were introduced are:

  1. 2x the speed
  2. 4x the range
  3. 8x the advertising capacity

Let’s go over each of these and take look at the potential IoT applications that could utilize them.

Twice the Speed:

In older versions of Bluetooth (4.2 and earlier), the data rate for BLE was set at a fixed 1 Mbps. In Bluetooth 5.0, a new mode with a data rate of 2 Mbps is introduced. This new data rate offers a couple of additional benefits as well:

  • Reduced power consumption since the same amount of data is transmitted in less time.
  • Improvement of wireless coexistence because of the reduced radio-on time.

One downside to using the 2 Mbps mode is that it has the potential of reducing the range, as the higher speed results in a decrease in radio sensitivity on the receiving end. However, for applications that can sacrifice a bit of range in favor of higher data rate transfer speeds, this mode can prove to be a game changer.

Compared to other low power wireless protocols (e.g. ZigBee, Z-Wave, Thread), BLE offers the highest data rate, even at the original 1 Mbps data rate. With the addition of the new high-speed mode (2 Mbps), more potential IoT applications become more feasible. Examples include low-quality video streaming, audio streaming and short bursts of large data transfers such as images.

We don’t need the 2 megabit speed for high fidelity stereo streaming, which extends the range for a given amount of power.
Nyquist’s Formula1 [C = 2B Log2bits per second, where B is the bandwidth in Hz and M is the number of signal levels], basically tells us that the higher the data rate, the higher the power drain; or conversely with the same input power the range declines at higher data rates. This is why inter-ear audio streaming in ReSound’s first 4 generations of wireless devices was not possible, as the power drain to support the high data rate would be excessive as the signal penetrates through the the lossy dielectric between the ears due to the 200 mm (5 inch) wavelength; while the 10.6 mHz signal easily penetrates the head due to the 28 meter wavelength. The solution is either a dual-band radio, or two separate radio chips.

The article continues:

Four Times the Range:

Bluetooth 5.0 also introduced a long-range mode that utilizes an error correction technique called Forward Error Correction (FEC), which allows the receiver to recover the data from errors that occur due to noise and interference. So instead of requiring retransmission of data when an error occurs, the receiver can recover the originally transmitted data by utilizing the redundancy in the data.

This mode is referred to as the Coded PHY mode (PHY stands for physical radio and refers to the radio interface layer in a network architecture). The obvious benefit of using this new mode is the increased range, with the trade-off being higher power consumption and reduced speed (125 kbps or 500 kbps, depending on the coding level used).

Ranges as far as 800 meters line-of-sight have been recorded while testing with the long-range mode. This makes it possible to use BLE in applications such as ones that require communication with a device hundreds of meters away. Examples include long-distance remote control devices, home automation, and industrial applications.

Keep in mind that, while analog FM which is a one-way “broadcast,” Bluetooth (and WiFi & other similar protocols) are two-way, to accommodate handshaking to acknowledge receipt of the data packet else the packet is re-sent, and also crucially for frequency hopping to steer around interference2 in the crowded 2.4 gHz ISM band.3

Eight Times the Advertising Capacity:

In BLE, there are three main states a device can operate in. It can either be Advertising, Scanning or Connected. To get two BLE devices connected, one device has to advertise and the other has to scan for it, and then initiate the connection. Advertising essentially involves broadcasting packets which allow another scanning device to discover them. The scanning device may then decide to initiate a connection if the advertisement packets indicate that the advertising device allows it.

In earlier versions of Bluetooth, the advertising data payload size was capped at 31 bytes. In Bluetooth 5.0, a new advertising mode is introduced: Extended Advertising. Extended Advertising allows sending up to 255 bytes of payload data per packet instead of the original 31 bytes limit.

Advertising is used in all BLE devices, but one prominent application that utilizes this state exclusively is Beacon technology. Beacon devices stay in the Advertising state and simply broadcast data for others to explore and read data from. With increased advertising data capacity in Bluetooth 5.0, Beacons can now transmit much more data unlocking new IoT applications and use cases.

This will come in handy as Bluetooth-based audio transmission becomes more widespread. Starkey already uses a form of advertising in the SurfLink Media TV transmitter: You can configure the hearing aids to automatically switch to the audio stream when you walk within the 30 foot range.

Conclusions:

As we can see, Bluetooth 5.0 introduced a few features that can be applied to a wide range of potential IoT applications. However, there are a few important key points to keep in mind:

  • The new long-range and high-speed modes are optional features per the official Bluetooth specification, so a chipset or device that claims Bluetooth 5 support may not support either of these new modes.
  • To be able to utilize these new features, the two BLE devices communicating with each other need to support Bluetooth 5 and support the feature of interest. For example, to be able to utilize the long-range mode in transmitting sensor data over long distances between a sensor device and a smartphone, both the sensor device and smartphone need to support both Bluetooth 5 and the long-range mode.
  • Smartphones are still slow to support Bluetooth 5 and its new features. Even when the new hardware supports it, the APIs need to allow the mobile developer to utilize these features.

With that said, however, the potential new IoT applications that Bluetooth 5’s features introduce simply make its wide adoption inevitable, on both the mobile and embedded side!

Mohammad Afaneh
Mohammad Afaneh has worked on many IoT projects during his career as an embedded developer. In 2015, he founded Novel Bits to help companies and developers build Bluetooth Low Energy (BLE) devices more efficiently. In March 2018, he self-published his first e-book titled “Bluetooth 5 & Bluetooth Low Energy: A Developer’s Guide.”

Bootnotes from The Hearing Blog:
  1. The Nyquist Formula, although somewhat related to the Nyquist-Shannon Sampling Theorem (often shortened to “Nyquist Theorem” or “Nyquist Sampling Theorem”) are sometimes confused, as both pertain to data rates. Whereas the Nyquist Formula deals with data transmission rates vs bandwidth & power, the more commonly known Nyquist-Shannon Sampling Theorem deals with analog-to-digital converter sampling rate vs highest audio frequency which can be reproduced without introducing aliasing, which requires twice the data rate of the highest frequency. (The Nyquist-Shannon Sampling Theorem is actually a special case of the more generalized Poisson summation.)[Oftentimes the sampling rate is incorrectly given in “Hz” when in fact it’s samples/second (and we’d get docked in our signals and audio engineering classes if we made that mistake!). For example, CD audio is 44.1 samples/second, which allows effective sampling for up to 20 kHz (that little bit between 20 & 22 kHz is used for low-pass filter rolloff).]For a more thorough explanation of the Nyquist Formula, please see Nyquist formula: relating data rate and bandwidth.For more on these issues, please see the Guest Article here in The Hearing Blog by Cecilia Casarini: On Aliasing, Shannon, Nyquist and Bell Labs.
  2. This lack of frequency hopping is also what doomed the failed Comfort Audio 900 mHz Digisystem, as he person setting it up had to manually select he channel through a cumbersome hand-held device (similar to theold Phonak MicroLink “Toaster”); and in fact it did have a nice 900-912 mHz spectrum analyzer to help find a clear spot. If you didn’t, the interference would be horrible; as since there was also no way to acknowledge packet receipt, whatever came in the packet was reproduced in the wearer’s ear, resulting in loud scratching. Ugh. At a 2012 convention where both Starkey & Comfort Audio had exhibit booths, I dragged the Comfort Rep to the Starkey booth, to see if their then-new SurfLink hearing aid platform would cause interference to the receivers & vice-versa, and you could see the spike from the hearing aids on the spectrum analyzer. It didn’t really matter, as Starkey had no direct audio input (DAI) adapters; and also they didn’t have a 675 version, which was needed as the receiver drew a whopping 5mA. Thankfully, Sonova bought the company in 2014, folded it into their Roger division, and (mercifully!) euthanised their 900 mHz products.
  3. 802.11A WiFi and some cordless phones get around the crowding by using the 5.3 gHz band. Although Bluetooth currently operates only on the 2.4 gHz band, the underlying protocol can also operate at 5.3 gHz, but at the expense of higher receiver power drain to support the faster clock rates — And this defeats the low energy protocol.
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About the author

Dan Schwartz

Electrical Engineer, via Georgia Tech

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