Transitioning from Lower to Upper ETSI Band using Impinj Readers and Gateways

Impinj’s new EU Upper Band Speedway R420, xArray, and xSpan take advantage of the new upper ETSI (European) frequency band (CEPT REC 70 03 / EN 302 208). The new features include:

  • Doubling the maximum radiated power output to 4W ERP (from 2W ERP). This provides greater read range (distance between the reader antenna and tag).
  • A frequency band common with FCC in North America, allowing for simplified global deployments that share the same tags.
  • Faster communication between reader antenna and tag for improved tracking of moving items.

This article covers topics you will want to know when transitioning applications from the current lower band (865.6 - 867.6 MHz) supported by Impinj’s EU Lower Band readers and gateways to the new upper band (915 – 921 MHz) supported by Impinj’s EU Upper Band readers and gateways.

Disclaimer: Local regulations must be consulted to ensure regulatory compliance. Not all countries that permit EU Lower Band also permit EU Upper Band. In some cases, EU Upper Band is permitted but not at the higher transmit power (e.g. Russia).

Frequency Band Change and the Tag

Since tags play a crucial role in any RAIN RFID system, they are always a good place to start focusing your attention. A tag's performance varies depending on the frequency of the signal transmitted between the antenna and the tag. The tags that you selected for your EU Lower Band application are likely optimized to perform best in the 865.6 - 867.6 MHz frequency range. On the graph below, the example Monza EU Lower Band tag has a read range of almost 8 meters in the lower band but only 6 meters in the upper band. (The read ranges are calculated with the same transmit power.)

1_eu2.png

Some tags, such as the Monza Global tags, have similar performance characteristics in both the lower and upper band. Notice the Monza Global tag example shown above has a read range of over 10 meters in both the lower and upper bands.

If you transition entirely to the EU Upper Band, tags optimized for the FCC region (North America) frequency will work best since the FCC (902 to 928 MHz) contains the new EU Upper Band frequency (915 – 921 MHz). The common frequency range between these two regions makes creating applications that work well in both much simpler since the same tag can perform well in both regions.

Recommendations:

  1. Review the tag data sheets to determine what frequency range the tag is designed to best perform in.
  2. Test your tag using ItemTest comparing the read range from your EU Lower Band and EU Upper Band reader/gateway. Given the power increase of EU Upper Band, if the read range decreased in the transition from EU Lower Band to EU Upper Band, your tag is likely optimized for EU Lower Band.
  3. If your current solution uses a EU Lower Band reader and a tag approximately 40 mm or smaller on the longest edge, the tag is likely optimized for the EU Lower band region. If you want to use tags with the same form factor in the EU Upper Band, switch to tags optimized for FCC. Alternatively, you can use a larger global tag (generally 50 mm or larger on the longer edge) if your use case needs to communicate with both lower and upper band readers/gateways.

Powering the EU Upper Band Readers and Gateways

When using Power over Ethernet (PoE), EU Upper Band readers and gateways require PoE+ (IEEE 802.3at). No change is needed if you are using AC power.

Recommendation:

If you're using PoE, make sure that your switch or injector supports PoE+. The EU Upper Band reader may still function using a non-PoE+ switch but will not be able to work reliability so it is important to verify that the correct switch or injector is in use.

Frequency Channels

The EU Upper frequency band has 3 channels, compared to 4 in the lower band.

Standard Channel Center Frequency
(MHz)
Channel Spacing
(kHz)
Channel Bandwidth
(kHz)
ETSI Lower Band 865.7, 866.3, 866.9, 867.5 600 200
ETSI Upper Band 916.3, 917.5, 918.7 1200 400

Recommendation:

Reader channel selection varies depending on the application, as with the lower band. Here are two basic scenarios:

Scenario Example Description Approach Lower Band Upper Band
Single reader A shelf antenna application with a single reader When a single reader is deployed there is no concern with interference on the same channel from another reader, so it can take advantage of all available channels. Enabling all channels is especially helpful in cases where some tags are more difficult to read. Enable all 4 channels Enable all 3 channels
Readers with close or overlapping FoV’s Field oView) A portal application with 2 readers facing each other Interference may occur when FoV's overlaps and 2 or more readers are broadcasting on the same channel. Separating the channels will boost performance by preventing two readers from sharing the same channel Reader_1: 865.7, 866.3
Reader_2: 866.9, 867.5
Reader_1: 916.3, 917.5
Reader_2: 918.7
  • In the new upper band, there is no 100 ms off-time every 4 seconds when dwelling on a single channel, unlike the lower band. Applications would intentionally avoid using just one channel to avoid off-time.
  • Be aware that setting the channels is recommended. By default, only one channel is enabled in both versions. Relying on the default settings and not setting channels explicitly often results in sub-optimal overall system.

Reader Modes

The new upper band version allows all readers and gateways to use high performing reader modes which result in higher tag read counts. Use cases that track moving tags will particularly benefit from the improved performance.

Small API Change

The new Upper Band readers and Gateways replaces Mode 5: DenseReader 2 with Mode 4: Max Miller. EU Lower Band applications that rely on DenseReader 2 reader mode must be updated when transitioning since this mode is not available in EU Upper Band. Max Miller is typically the best replacement for Dense Reader 2.

The EU Upper Band shares the same modes as the FCC version along with higher data rates.

Here is the list of reader modes.

LLRP ID EU Lower Band EU Upper Band and FCC
0 Max Throughput (high throughput M=1) Max Throughput (high throughput M=1)
1 Hybrid Mode (high throughput M=2) Hybrid Mode (high throughput M=2)
2 Dense Reader (high throughput M=4) Dense Reader (high throughput M=4)
3 Max Sensitivity (M=8) Max Sensitivity (M=8)
4 Not Available Max Miller (high throughput M=4)
5 Dense Reader (M=4) 2 Not Available
1000 Autoset Dense Reader Autoset Dense Reader
1002 Autoset Dense Reader Deep Scan Autoset Dense Reader Deep Scan
1003 Autoset Static Fast Autoset Static Fast
1004 Autoset Static Dense Reader Autoset Static Dense Reader

Recommendation:

If your application relies on high read rates, test your application especially if it is pushing performance boundaries. Here some examples of reader mode/read rate tests that could be performed.

Example Description Run Tests
Speedway with multiple antennas This application tracks an item when it is placed on a set of shelf antennas connected to a single speedway. This application will quickly switch between antennas monitoring items as they are placed and removed from the shelves. The faster read rates result in quicker antenna switching which improves the application's responsiveness. Compare the performance of the EU Lower Band and EU Upper Band versions by running tests to determine the amount of time required to switch between all the shelf antennas using ItemTest. Compare the timestamps of each time a tag is read by an antenna. You should see a higher frequency of tag reads.
xArray Location Mode The application tracks a tag’s x, y location. The location algorithm relies on the largest possible number of tag reads to maximize accuracy. Compare the performance of the EU Lower Band and EU Upper Band versions by running tests to determine the cycle time using ItemTest. While location mode in ItemTest, hover the cursor over the xArray icon to see the cycle time. You should see a shorter cycle time with the new EU Upper Band xArray.
The shorter the cycle time -> the more tag reads -> the more accuracy.
xSpan Threshold The application tracks tags on a pallet to determine the direction of movement past xSpans as they travel in and out of a warehouse. This algorithm relies on the largest possible number of reads to maximize accuracy. Compare the performance of the EU Lower Band and EU Upper Band versions by placing the pallet in front the 2 opposing xSpans. Use ItemTest to determine the read rate. Use Mode 4: Max Miller for the EU Upper Band xSpan, which is typically faster than Mode 5: Dense Reader 2 for the EU Lower Band xSpan.

Transmit Power Settings for Speedways

As mentioned. the transmit power increased to 4W ERP from 2W ERP. Below we compare the upper and lower band transmit powers: the new upper band on the Speedway can be set to 33 dBm, a 1.5 db increase. Users should still calculate the Radiated Output Power of their Speedway based solutions to stay within regulated maximum radiated power specifications. 

ETSI Frequency Band Speedway Min Transmit
(dBm)
Speedway Max Transmit
(dBm)
Regulatory Max Radiated Power

Lower 10 31.5 2W ERP (33dBm ERP)
Upper 10 33.0 4W ERP (36dBm ERP)

 

Transmit Power Settings and Corresponding Radiated Power Output for Gateways

Transmit power settings minimum and maximum were left at 10 to 30 dBm for the upper band gateways. However, the corresponding power output for upper band gateways was increased by 3dBm. For a graphical representation see the chart below. 

mceclip2.png

Recommendation:

Depending on your use case, you will either want to take advantage of the new regulation by increasing the transmit power to gain a larger coverage area, or maintain the same or nearly the same transmit power to maintain the size of your read zone.  Here is what to keep in mind for the two basic scenarios:

Scenario Speedway xArray/xSpan
Maximizing Power Output The greater output power of the EU Upper Band speedway can increase up to 33 dBm. Even with cable loss, it is possible to achieve a radiated power of 4W ERP.
Remember:
Radiated power = Transmit Power + Antenna Gain - Cable Loss.
For example, if you have an antenna with 6 dBi gain and cable loss of 1 dB. You can set the transmit power to 33 dBm to recieve: 33 dBm + 6 dB - 1 dB = 38 dBm to be under the maximum limit of 4W ERP (or 38.15 dBm).
For xArray and xSpan, 30 dBm is still the maximum setting. For EU Upper Band, your application will now output 4W ERP (36 dBm ERP) from the gateway antenna when set to 30 dBm.
Maintaining the read zone If your use case has difficulty reading tags, increasing transmit power will certainly be beneficial.  However, increasing the transmit power in uses cases with the potential for stray tags (tags near the reader that you don’t want your application to process) could have a negative effect.
In this case, maintain the same transmit power or re-tune the transmit power to offset any differences introduced by the new frequency range.
As mentioned earlier, each tag has a read range associated with it so you will want to test your new tags to ensure the optimal transmit power setting.
Because of the power output increase, an application outputting the same amount of power from an xArray/xSpan antenna will need to set 3 dB transmit less power on the EU Upper Band version.
As mentioned earlier, each tag has a read range associated with it so you will want to test your new tags to insure the optimal transmit power setting.

xArray/xSpan Coverage Area

The maximum coverage area of the xArray / xSpan increases with the new higher transmit power. This is true for both inventory and xArray location applications. If possible, raising the xArray or xSpan could increase the coverage even more than at the base height, especially if the tags have a long read range. Note that in many installations, the mounting height of xArrays and xSpans cannot be changed because they are mounted to an immovable portion of the infrastructure, such as a ceiling.

Even if you can’t increase the height, you should be able to cover a larger area with the new EU Upper Band version. Even mounted at the same height we have seen a 30% increase in coverage area when comparing EU Lower Band to EU Upper Band.

Recommendation:

Test the xArray/xSpan by specifying a known set of tags using a Tags of Interest (ToI) file. Compare the results using the original EU Lower Band vs the EU Upper Band. See if you get a higher percentage of tag reads with the EU Upper Band. If not, then your tags are likely not tuned for the upper band.

If you are able to increase the height of the xArray/xSpan, experiment to make sure that you are able to read the same set of tags from farther away with the new EU Upper Band version.

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