One of the great benefits of training with power is the ability to see your power data in real time on your handlebar mounted bicycle computer (‘head unit’) or smartphone. Power data is transmitted wirelessly by the power meter to the head unit using a wireless transmission protocol. Power meter manufacturers have two wireless protocols to choose from: ANT+ or Bluetooth SMART. It’s important to note that power meters capable of transmitting data via Bluetooth SMART (‘Bluetooth power meter’), can also send data via ANT+. So if your power meter has Bluetooth functionality, you have the option of transmitting data using either wireless protocol.
Traditionally, ANT+ dominated the power meter market. However, more and more manufacturers have been equipping their power meters with Bluetooth SMART functionality. We are now at the point where most, but not all, power meters transmit data via both wireless transmission protocols. Below, we will compare and contrast ANT+ with Bluetooth SMART, as well as show which manufacturers are currently using each technology.
ANT+ vs. Bluetooth Power Meter
ANT+, which stands for interoperability (something you don’t need to remember!), is a 2.4 GHz wireless network. Its main purpose is to send standard information wirelessly from one device to another. ANT+ allows two wireless devices to understand and communicate with one another, even if they are from different manufacturers. In the case of power meters, ANT+ allows your power meter to communicate with your head unit. Almost all power meters and head units use ANT+. (Some Polar devices for example, currently use Bluetooth only.)
- It’s an open system. A power meter using ANT+ can send information to multiple head units simultaneously
- It’s efficient. Although both Bluetooth SMART and ANT+ require very little power, ANT+ prides itself on its efficiency
- There really isn’t any for the purposes we are discussing here (power meters). While it isn’t as fast as Bluetooth SMART, as you will see below, it’s plenty fast enough
Manufacturers Offering ANT+ Only
Bluetooth SMART, also known as Bluetooth Low Energy, Bluetooth 4.0 or BLE, is also a wireless technology that allows information to pass between electronic devices. Bluetooth SMART allows devices to wirelessly connect with applications via smart phones and tablets. While Bluetooth is probably the more well-known of the two wireless protocols, until recently, there were only a handful of power meters on the market offering a Bluetooth power meter. Now, as you can see below, the majority of the market consists of Bluetooth equipped devices.
- Allows devices to wirelessly connect with applications via smart phones and tablets
- A Bluetooth power meter can transmit information 64 times per second, 16x faster than ANT+
- It’s intuitive. Pairing a Bluetooth head unit or smart phone with a power meter is simple
- The sending and receiving devices must be linked and it’s therefore considered a “closed system”. With ANT+ for example, you can send data to multiple head units. With Bluetooth, you are limited to one
Important note: While ANT+ can transmit data four times per second, and Bluetooth SMART 64 times per second, current power meters aren’t running this fast. Why? It would be too hard on the battery. Most power meters record data closer to once per second. This way, the head unit can essentially enter sleep mode for very brief periods of time, thus prolonging battery life. The exception is SRM’s PC8 head unit, which actually receives data four times per second. (However, the fastest it can record data to your file is twice per second.)
Manufacturers Offering both ANT+ and Bluetooth SMART
ANT+ and Bluetooth Power Meter: Dual-Sided Systems
There is one more thing to mention – and that is the way these two wireless transmission protocols operate in a dual-sided power meter. A dual-sided power meter is one that has two power sensors, allowing it to measure left and right leg power independently. (Examples are the Favero Assioma DUO, Garmin Vector 2, PowerTap P1, Verve InfoCrank and ROTOR 2INpower power meters.)
With ANT+, the left and right power sensors are connected to each other in a master/slave relationship. The power sensor that serves as the master, typically the left power sensor in most cases, connects to both the bicycle computer as well as the slave power sensor. The master sensor collects data from the slave sensor and communicates with the bicycle computer. The slave sensor only communicates with the master sensor – never with the bicycle computer directly.
With Bluetooth SMART, each power sensor is paired individually and directly to the bicycle computer. The bicycle computer combines the power values from both power sensors in order to determine total power. This doesn’t have a direct effect on how you use or train with the power meter, but it’s always nice to understand how your equipment is working.