We’ll start off with general performance notes for portable WiFi LTE-based hotspots, whether modem MiFi type or using a smartphone hotspot. Mobile hotspots bidirectionally connect a 3G/4G cellular signal to WiFi, in one little battery-powered box.
We give an example with the Verizon Ellipsis MHS800L MiFi device.
Improve Hotspot Signal & Range
Mobile hotspot performance suffers if you just put the MiFi device in the pocket of your coat or briefcase and forget about it. In fringe coverage regions (where the 3G/4G signal is weak), you will get better performance (faster, less dropped connections) by considering the placement of your MiFi device. The same holds true if you are using your smartphone for a tethered USB, Bluetooth, or Wifi connection. I will for compactness if not correctness refer to such devices (smartphones and wireless modems) as MiFi devices.
You should try to keep the MiFi device away from the immediate vicinity of metal objects. That is, don’t place the MiFi on a metal table or near a metal wall or shelf. Don’t put it on the floor or buried in your coat pocket. Considering safety in the case of a traffic accident or sudden motion, consider placing the MiFi on a window if in the car, via say a suction cup or placement in a dashtop compartment if you have one. On a train, you can take a newspaper or magazine and stand the MiFi up against the window. In a home, particularly in a home with metal siding, put the MiFi in a window facing the nearest cell tower that you think is for your 3G/4G service. Higher (second floor) windows are better generally than first floor or basement.
In general, you are trying to keep a line of sight to the nearest cell tower, for the strongest signal. With that in mind, let’s take the example of the inexpensive ($50 no contract) Verizon Ellipsis MHS800L MiFi hotspot.
Verizon Ellipsis MHS800L MiFi hotspot
This is a very popular hotspot, available with economical prepaid plans. Like virtually all cellular devices today, it has two antennas used for cellular connections. It has a third antenna for 2.4GHz only Wifi. There are external antenna ports on the bottom of the MHS800L (SMK TS-9) allowing connection of 2 external antennas. It may be that you can use 2 external antennas simultaneously for diversity reception (better signal).
Note: I was not able to disassemble my MHS800L, so the description below is based on examination of the FCC filing.
The MHS800L Main LTE antenna is on the side opposite of the USB jack. It is a PIFA (planar inverted F-antenna). I assume this antenna is multi-band, covering 700/1700/2100 MHz.
The MHS800L Secondary LTE antenna is on the USB jack side. It is also a PIFA.
The MHS800L Wifi 2.4GHz antenna is also on the USB jack side diagonally across from the display (top left corner of MiFi as viewed from the display side). It is much smaller than the other two LTE antennas, since you won’t be very far from the MiFi as compared to the cellular tower.
LTE Occupied Bandwidth
We will use the Verizon FD-LTE (paired spectrum) Band 13c for this discussion. Verizon is allocated 777 MHz to 787 MHz for device transmit in LTE band 13c, and 746-756 MHz for tower transmit.
When the FD-LTE device is in “5 MHz” mode it is keeping 99% of its power within less than +/- 2.5 MHz from channel center. Actual FD-LTE measurements are about 4.5 MHz occupied bandwidth for a 5 MHz channel. So an FD-LTE Block 13c device transmitting at center frequency 782 MHz will have 99% of its power between 779.75 MHz and 784.25 MHz.
An FD-LTE device in 10 MHz mode keeps 99% of its power within less than +/- 5MHz of channel center. So a Verizon band 13c device operating at 10MHz bandwidth must only use 782 MHz center frequency.
Analogous arguments hold for devices operating in the AWS-1 spectrum (LTE band 4), except that bandwidths up to 20 MHz are allowed. Verizon does not have exclusive use of this spectrum, T-Mobile and others also use slices of this AWS-1 spectrum in AWS-1 blocks A-F. Verizon’s AWS-1 blocks vary by market.
While the MHS800L does not have Band 2, Verizon is deploying Band 2 in dense urban areas, and higher-end MiFi devices can use Band 2, so I include it in the table below. I did not include the 2G/3G frequencies that smartphones and higher-end MiFi can use–these frequencies are also going to be morphed into 4G/5G use in coming years.
The EIRP in the table is for the MHS800L MiFi hotspot; portable LTE devices are allowed up to 3 Watts transmit power, within SAR limits.
The MHS800L is ONLY capable of LTE band 13c and 4, and will not fallback to 3G like more expensive MiFi devices! You should be aware of this if you are a heavy MiFi user (including RVers), you may want a MiFi that will use the 800MHz and PCS 3G networks as well as global 3G. The Novatel 6620L is an example of a device with LTE bands 13, 4 and 2 as well as 3G, and it has dual-band (2.4/5 GHz) Wifi. Using a 2.4 GHz-only hotspot such as the Ellipsis MHS800L in an RF cluttered environment (office, hotel, train, RV park) can lead to poor data throughput regardless of signal strength.
|LTE Band||Device transmit (MHz)||Tower transmit (MHz)||MHS800L Device (dBm)|
I found the Verizon Ellipsis Jetpack MHS800L to be useful for my few time a year MiFi needs in rural areas. I would assume that typically I was using LTE Band 13c, since I was in rural locations. I haven’t discovered any way to tell which LTE band the MHS800L is currently using. The MHS800L does tell you RSSI, SINR, and signal bars via a jQuery interface, so I created a Python program to log/plot LTE RSSI SINR and signal bars. It would be quite useful using an external GPS logger.
Put the battery-powered MiFi high in a window to lessen need for external antenna. In general, an external antenna can greatly improve weak LTE signal strength. Even though the MiFi WiFi transmit power is more than 10 dB lower (less than 10%) of a typical WiFi access point, the MiFi WiFi signal is often reachable in the next room or two on the same or adjacent floors of a typical home. I put the MiFi a few feet from a good WiFi access point and via InSSIDer on my phone, the MiFi was of expected signal strength–several dB weaker than the good WiFi AP. The far corners of the house may not be covered from a central MiFi location, but it’s very usable for general cases.
If you are more than a few time a year casual user, consider a higher-end MiFi device such as the Novatel 6620L that has dual-band WiFi (use 5GHz WiFi for best throughput) and the global/3G bands along with Band 2 LTE.