NB-IOT vs unlicensed LPWAN

One of 3GPP’s chief low-power, wide-area (LPWA) technologies under development is NB-IOT (narrowband IOT) . Many have been speculating over the differences between NB-IOT and the current LPWAN technologies in the unlicensed frequencies such as LORA, Weightless-P, Sigfox, RPMA. Some individuals have even gone as far as saying NB-IOT will be the death of LPWAN technologies. But that is likely not going to be the case as there will always be a huge difference in use-cases of licensed and unlicensed technologies. The best analogy is WiFi (unlicensed) vs 4G (licensed). The business models and use-cases built around WiFI and 4G are “night and day” .

NB-IOT may not be as robust as we are expecting it be. Check out the following features that are likely to be a slight let-down to NB-IoT enthusiasts

1.No full acknowledgement: By design (found in 3GPP Specification TR45.820) NB-IOT is planned to only acknowledge 50% of messages serviced by the wireless technology. This is due to limited downlink capacity. Unlicensed technologies like Weightless-P allows 100% full acknowledgement of every message. If every message is of high value, you will need to know if your messages are successfully sent/received via an acknowledgement.

 

2. Long Latency: Transmit packet aggregation from buffering of messages and data. NB IOT will not be able to support “real time” responses therefore not suitable for time sensitive applications.

3. IoT devices in the network will not be the priority. The licensed spectrum is EXPENSIVE. Ingenu mentioned “$4.6 billion in a recent auction for only 20 MHz of spectrum!” IoT traffic will always come second to high profit margin, cellular traffic.

4. Long battery Life? The actual battery life will remain unknown until the Cellular LPWA networks are commercially available.

5. Availability: NB IOT is a technology that will be ready a few years down the line.

6. Compatibility: NB-IOT will differ across regions and carriers. Huawei initially pushed for a clean slate NB-IOT technology that would not be backwards compatible with 4G etc. This actually makes a lot of sense as it would be eliminating a lot of the unnecessary overhead.  But just as Huawei began making progress, Nokia and Ericsson began insisting on building upon the frameworks of LTE which means significantly more complexity and unnecessary overhead. Not a very nice foundation for such a huge project.

 

LPWAN Technology Comparison

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Some buzz/updates from the IoT space:

LoRa :

Where are the large-scale deployments? Having been released over 5 years ago and still not having any single large-scale deployments is worrisome. Being first-to-market has attracted a HUGE ecosystem of makers.  But the limitations of LoRa are becoming more and more apparent.

Rather disappointing as far as spectrum friendliness. When LoRa is deployed, it indeed basically renders all other technologies in the ISM bands useless. This is not something that is going to go over well with any of the LPWAN ISM band technologies or RFID technologies wanting to cooperate in the same spectrum.

 

Sigfox:

They are operators with a vertically integrated technology. Sigfox proposes an end-to-end solution, from the device to the management interface. It’s up to the user to encrypt data within the 12bytes payload.

Sigfox wants to collaborate with giant telecommunication companies and deploy a $/message business model. In my opinion, the IoT space not ready for a $/message plan. VERY few real IoT application actually make sense to adopt this type of payment plan. With that said, all the technologies that survive in the above comparison chart may potentially be offered by Sigfox in the future . With its current technology, it can only continue to tout its theoretical “coverage”.

sigfox lora.png

 

Weightless (formerly known as Weightless P): The technology has been renamed simply Weightless. The Weightless Starter Kit has extremely solid performance. We see this as a strong contender moving forward as the IoT community becomes more aware of LoRaWAN limitations.

May 2018 – Weightless becomes the first LPWAN technology to win a serious country-wide tender (Smart Meters)

OnRamp (RPMA): Company Ingenu has made an aggressive marketing push of their technology. They stress “simplicity is key:  one worldwide band (2.4 GHz), no sunsetting (we will commit to never sunsetting the RPMA technology), no burdensome certification process.” Unfortunately, 2.4GHz still requires a certification of the end device in Europe, this has a cost. For those who might not know : Sunsetting, in a business context means to intentionally phase something out or terminate it.

Also, Europe has tightened the 2.4GHz regulation this year, some countries may require licenses for OnRamp outdoor usage. RPMA is 1MHz bandwidth, spread spectrum with large spreading factor. UNB (ultra narrowband) is seemingly the simplest and lowest cost connectivity which covers a few solid cases.

Business Model: Ingenu sells licenses to use their technology in given territories ($300,000-1M USD). After purchasing an expensive license, the purchaser can then buy and deploy Ingenu base stations (said to be over $5000 USD per access point). They are currently struggling to find companies to license their technology.

 

Lora by Semtech : Wireless Connectivity Solution Analysis

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LoRa is a long range wireless connectivity solution developed by Semtech. If you want to learn about the pros of this solution please visit the website: http://www.link-labs.com/lora/

Here are my major concerns regarding this solution.

1)      LoRa is very spectrum unfriendly. When LoRa is transmitting, most systems become inoperable.  LoRa and Sigfox cannot live happily together. LoRa would completely render Sigfox useless if deployed in the same vicinity.

2)      Large bandwidth

3)      High power

4)      No interference awareness or fair-use methods of communication

Check these engineering threads in which TI experts tear LoRa apart.- https://e2e.ti.com/support/wireless_connectivity/f/156/p/343273/1477077.

Quirky: Wink Hub Recall

wink-hub-product-photos-1

April 20, 10:22 a.m. PT: A Wink representative issued the following statement:

“Yesterday, Sunday, April 19, Wink worked diligently to enable a self-service fix for users comfortable making some quick changes to their home’s router settings. Instructions for users recovering their Wink Hub can be found at recovery.wink.com. For those who wish to send their Hub in for repair, they can continue to do so free of charge by visiting hubrepair.quirky.com. We’ll provide a box and shipping label and be sending replacement Hubs as soon as possible.

Approximately 25% of Wink users were impacted by Saturday’s outage and we were able to recover and reconnect 40% of those users within 10 hours. Thousands have already selected the self-service fix and by the end of Monday, April 20 we expect the outage to be limited to 10% of Wink users.”

My take:

This product is absolutely terrible. I purchased it online and should have taken careful attention to the dimensions of this beast. ITS HUGE! There is no place to put this awkward clunky thing. I bought a “smart” light bulb and connected it to hub. I used the mobile app to control the light. The latency is awful! It sometimes takes up to 5 dreadfully long seconds for it to actually turn on. The recall won’t fix the main issue; that main issue being that the product flat out sucks.

Thread – Wireless Communication Protocol

thread

Thread is also a new wireless protocol that recently has entered the IoT market. Its seven founding members aim to develop Thread, a new IP-based wireless networking protocol, as a better way to connect products in homes and to realize the IoT.

The figure above depicts the Thread protocol stack. Thread has not standardized the application layer, which gives application developers the freedom to develop the applications they deem fit. The IP support of Thread makes it suitable for developing open systems; essentially making it easier to interface with other IP enabled mobile devices. On the network layer (NWK), Thread supports UDP on top of 6LowPAN. Thread also provides a horizontal layer that provides security and authentication functions that enables devices to securely exchange information. On the media access layer (MAC), Thread supports a mesh topology with a maximum of 250 nodes. For the physical layer (PHY) Thread used the IEEE 802.15.4 wireless RF specification that operate in the open 2.4 GHz band, allowing for a data rate of 250 kbps.

IoT connectivity solutions: Media access control layer and network topology

161-Datalink-MAC

Media access control layer and network topology

For IoT applications, the main characteristics of the media access layer control (MAC) that need to be considered are multiple access, synchronization, and network topology.

Multiple Access. Looking back at decades of successful cellular system deployment, one can safely conclude that TDMA is a good fit for the IoT. TDMA is suited for low-power operation with a decent number of devices, as it allows for optimal scheduling of inactive periods. Hence, TDMA is selected for multiple access in the MAC layer.

Synchronization. In IoT applications, there are potentially a very large number of power-sensitive devices with moderate throughput requirements. In such a configuration, it is essential to maintain a reasonably consistent time base across the entire network and potentially across different networks. Given that throughput is not the most critical requirement, it is suitable to follow a beacon-enabled approach, with a flexible beacon period to accommodate different types of services.

Network topology. Mobile networks using a cellular topology have efficiently been servicing a large number of devices with a high level of security and reliability, e.g., 5,000+ per base station for LTE in urban areas. This typology is based on a star topology in each cell, while the cells are connected in a hierarchical tree in the network backhaul. This approach is regarded suitable for the IoT and is therefore selected.

The network layer and interface to applications

The network layer (NWK) and the interface to applications are less fundamental as far as power-efficiency and reliability is concerned. In addition, there is more variation in the field of IoT applications. Nevertheless, it is widely acknowledged that IoT applications need to support the Internet Protocol (IP), whether it is IPv4 or IPv6. In addition, the User Datagram Protocol (UDP) and Constrained Application Protocol (CoAP) could provide the relevant trade-off between flexibility and implementation-complexity on resource-constrained devices.

Furthermore, the IoT will represent an immense security challenge, and it is likely that state-of-the-art security features will become necessary. As of today, we can assume 128 bits Advanced Encryption Standard (AES) for encryption and Diffie-Hellman (DH), or the Elliptic Curve Diffie-Hellman (ECDH) variants, can become the baseline for securing communication.

Best Electronic Shelf Label Companies

Ranking The Best Electronic Shelf Label Solution Providers.

One IoT case that fascinates me is the smart retail sector specifically, Electronic Shelf Labels.The solution replaces traditional paper price tags with connected digital price tags. Store owners can change prices instantaneously opening up a myriad of opportunities ultimately increasing store efficiency, enhancing the customer experience, optimizing inventory, and boosting revenue. Thousands of connected nodes, bi-directional communication, extremely low battery-consumption, speedy transmission to the cloud – this case oozes with great IoT flavors and it is not just a concept, it is live NOW in stores worldwide.

I will rank the current ESL vendors based on their over hardware solution, wireless connectivity solution, and demonstrations provided at the NRF Big Show and EuroCIS: two of the biggest retail shows. Every main ESL player had a booth and as a die-hard geek, I took the time to do an in-depth evaluation of each.

Worth noting: I learned the E-paper displays were all identical as there is only one worldwide vendor of the technology – E Ink. What really actually makes the ESL solution work is the wireless connectivity solution and hardware simplicity.

Here is my ranking of the best Electronic Shelf Label Companies focusing on retail.

#1  m2communication -logo NEW

Headquarters: France

M²Communication is as they said “the new kids on the block” but there is a reason this new player has emerged with significant traction.

This company is comprised of radio frequency chip-set makers. As mentioned, the wireless communication aspect of ESL is actually what makes the whole solution “work”. They developed their own sub GHz wireless communication protocol from scratch and it can do A LOT more than just ESL (I took at look at their whitepaper). The salesmen at their booths are clearly engineers wearing suit and ties which was quite a refreshment from the car salesmen at all the other booths. They were very honest and transparent in their business status. The big selling point – their demo. All the other booths had some pretty awful demos. M²Communication‘s actually worked. They had about 100 price tags on display on a wall. They allowed me to use their web based interface to change all prices to my satisfaction. They probably regretted letting me take the reigns because I spent about 30 minutes on their laptop not only changing prices but changing images and small product details. To my delight a couple seconds after I pressed the “update” button, all the tags began flashing one by one showing the new price and content. True two-way communication as each of the tags relayed the battery life and signal strength back to the computer.

HUGE differentiation – hardware simplicity. Their solution is plug and play. Their access point, responsible for communication from the store’s system to the tags is the size of a computer mouse. No professional installment required.

Definitely the most technically sound solution in the market right now. Let’s just see how strong their sales and marketing team is as they try to push this pass the giants.

#2 DD-Master-logo-CMYK.jpg

Headquarters: United Kingdom

Displaydata has a bunch of car salesmen at their booth that I felt were reading from a slide deck when I asked them technical questions. One guy went as far as telling me their display resolution was the best in the industry. I had to break the news to him that there is only one worldwide e-paper display vendor achieving identical DPI (dot per inch) . (He still insisted their displays are superior)

It took me a few tries to get to the booth’s “technical guy”. Their communication is also like M²Communication‘s: a sub GHz proprietary protocol. They did not design it themselves; they actually outsourced that work to another company who they did not wish to disclose.

I think connectivity in the sub GHz is the way to go. It avoids crowded frequencies such as 2.4 GHz crowded by Wi Fi , bluetooth, etc. Anyways the reason I have them ranked #2 is because of their bulky expensive hardware and their demo. Their “dynamic communicator” responsible for transmitting and receiving data from the tags was fairly large and needs professional installation. I was orally quoted $650-750 USD per “dynamic communicator” and larger supermarkets would need up to 10 of these giants in each installment. As far as their demo, it actually failed the first time. And with me you only get one first impression. It did eventually start working. And they were achieving relatively the same updates speed as M²Communication but only used 2 tags for their demo 😦

This company seems to have a lot of man power and are touting some impressive deployments in the supermarket industry. Good things coming for this company.

#3 SES / Imagotag

Headquarters: Austria

SES is the oldest largest ESL vendor. Their original wireless communication solution uses SUPER DUPER low RF frequency: 36KHz! The transmit speed is SUPER DUPER slow. This is the same technology used by submarines to communicate in the depths of our oceans.
To support this frequency you need a long antennae. By long I mean 1km long. Some SES installments wrap a 1KM long antennae around and around in their customer’s ceiling. Their communication is only one way. And the crazier thing is…they are currently the market leader. This is only because they got a head start in this market. They started in 1992. They recently acquired Imagotag which is another way of saying “our solution is completely out dated”. Imagotag instantly gets bumped down for using the 2.4GHz frequency as a solution. They say they use channels unoccupied by Wi-Fi and bluetooth. I believe they said they are using channels 2,3,4,6 in the 2.4GHz. But we all know that Wi-Fi is not strictly bound to those channels. There is going to be significant interference in my opinion and range from a physics point of view is not going to be as good as a sub-GHz solution.

#4PRICER-LOGO2

Headquarters: Sweden

Pricer uses infrared technology to communicate to their tags. They have a tricky installment in the ceiling of their deployments. The hardware looks hideous and quite distracting if the retailer’s ceiling is low. The infrared communication is not reliable.If a customer happens to be standing in front of the tag during the update – then it will not be successful. The good thing about their solution is that update speed should be quite fast. Range in a setting that is completed unoccupied  with all the lights off should be pretty good.

A huge problem is the security of infrared. It can be easily hacked as demonstrated by by viral video on youtube which shows how you can use a Game-boy to change the prices on an infrared ESL. Yikes.

ESL for Industrial Sector

There is a rapid adoption of ESL in the industrial sector to replace the 40-year-old process of manually placing paper labels on the literally millions of containers, carts, and sub-assemblies flowing through factories every day with simple, cost-effective wireless displays

Industrial ESL provide the reliability and visual instruction inherent with paper labels along with automated tracking.

 

1. Ubiik

Headquarters: Japan

The key to adoption in the Industrial space is working with existing wireless infrastructure. Ubiik has managed to make ESL compatible with all off-the-shelf UHF RFID readers. The high adoption rate of this product in factories all over Asia places Ubiik at the forefront of ESL for the industrial sector.

Ubiik also has E-Paper that can be updated via NFC (android smartphones or any off-the-shelf NFC reader). And SUPER long range ePaper with over 1km update range.

ezgif-com-video-to-gif

2. Omni ID

Headquarters:Rochester, NY

In 2012, Omni-ID launched ProVIEW — the world’s first visual tagging system — to replace paper-driven processes in manufacturing, providing not only the ability to track assets; but dynamic, readable instructions right on the tag, completely changing the auto-identification industry landscape. The ProView markets itself as RFID compatible E-Paper but after taking a deep dive, we realised that OMNI ID actually uses a proprietary protocol to transmit to the ProView tag. Therefore, factories will need to install Omni ID’s proprietary hardware/base station to update the displays much like the ESL in the retail space.
Omni-ID rfid tags. 3 sizes showing various information.

3. Mpicosys

Headquarters: New York, NY

Mpicosys offers a variety of customised E-Paper signage. MpicoSys has developed the PicoSign displays and enables special devices, in fact answering any requirement and questions one can have on the use of ePaper displays. One of the best examples is the PicoSign Wall at United Nations headquarters in New York.

PicoLabel-2-7_Leaves_OmniKey.png

4 Main ‘Must Haves’ for the Physical Layer of Internet of Things Wireless Connectivity

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Analysis of the physical layer of wireless communication solutions for IoT application.

For IoT applications, the main characteristics of the physical layer that need to be considered are modulation, data rate, transmission mode, and channel encoding.

Modulation. The nature of IoT applications, some involve infrequent data transmission that need low-cost low-complexity devices, preclude the use of high-order modulation or advanced channel coding like trellis-coded modulation. Unless mandatory, due to a harsh radio environment with narrowband interferers or regulatory constraints, spread spectrum, e.g., Direct Sequence Spread Spectrum (DSSS), is to be avoided as it increases the channel bandwidth, requiring a more costly and power-consuming RF frontend, with no data rate improvement. Allowing non-coherent demodulation relaxes the constraint on the device complexity, so (Gaussian) Frequency Shift Keying ((G)FSK) is a proven and suitable choice, similarly as in Bluetooth radio. It is considered that the most sensible choice upon availability would be Gaussian Minimum Shift Keying (GMSK), as the modulation index of ½ allows for lower complexity, or better sensitivity at a given complexity. When available bandwidth is restricted, GFSK with lower modulation index is still appropriate, with the next best being 1/3 as it still allows for near-optimal demodulation at reasonable complexity.

Data rate. IoT applications need to mix very low data rate requirements, e.g., a sensor or an actuator with limited data size either uplink or downlink, with more demanding requirements, e.g., a 6-inch 3-color ePaper display in a home that updates the daily weather forecast or the shopping list, easily amounting to more than 196 kB worth of data. Yet even for small data amounts, a carefully chosen higher data rate actually improves power-consumption thanks to shorter transmission time and reduced probability of collision. Similar reasoning is applied to Bluetooth Low Energy, a.k.a., BLE or Bluetooth Smart, formerly Nokia’s WiBree, which uses 1 Mbps with much lower data throughput. The latter is aimed at proximity communication and its high gross data rate of 1 Mbps sacrifices the range considerably. Even when operating at sub-GHz frequencies, which offer better range than 2.4 GHz for a given transmit power, the 1 Mbps is considered to be the absolute upper limit. On the higher end, the transceiver complexity and power increase do not improve the actual useable throughput, as the overhead of packet acknowledgement and packet processing time become the bottleneck.

On the lower end, data rates below 40 kbps are actually impractical, as it would rule out using standard off-the-shelf 20 parts per million (ppm) crystals. Indeed, the frequency accuracy of these crystals is not sufficient: 20 ppm translates into a 18 kHz frequency error when operating in sub-GHz bands, while it is 48 kHz when operating at 2.4GHz. A narrow channel requires an accurate crystal like temperature-compensated TCXO on both ends, including the client, which is more costly, power-consuming, and bulky [36].The optimal baseline gross data rate is considered to be 500 kbps. Depending on the scale of the network, e.g., home, building, district, or city, the applications, and the number of devices, we expect different trade-offs with actual deployments ranging from 100 kbps to 500 kbps.

Transmission mode. Full duplex communication is challenging, as it requires good isolation and does not allow for resource sharing between transmit and receive. Full duplex also typically involves different frequencies for downlink and uplink. Since the radio resource is a scarce resource, half-duplex is therefore selected, preferably on the same radio channel.

Channel coding. There is the potential for improving link quality and performance with a limited complexity increase by using (adaptive) channel coding together with Automatic Repeat-Request (ARQ) retry mechanism. As of today, this is considered optional due to complexity-cost-performance trade-offs achieved with current technologies. However, provisions have to be made for future implementation. As of today, flexible packet length is considered a sufficient means of adapting to the link quality variations.


Media access control layer and network topology

For IoT applications, the main characteristics of the media access layer control (MAC) that need to be considered are multiple access, synchronization, and network topology.

Multiple Access. Looking back at decades of successful cellular system deployment, one can safely conclude that TDMA is a good fit for the IoT. TDMA is suited for low-power operation with a decent number of devices, as it allows for optimal scheduling of inactive periods. Hence, TDMA is selected for multiple access in the MAC layer.

Synchronization. In IoT applications, there are potentially a very large number of power-sensitive devices with moderate throughput requirements. In such a configuration, it is essential to maintain a reasonably consistent time base across the entire network and potentially across different networks. Given that throughput is not the most critical requirement, it is suitable to follow a beacon-enabled approach, with a flexible beacon period to accommodate different types of services.

Network topology. Mobile networks using a cellular topology have efficiently been servicing a large number of devices with a high level of security and reliability, e.g., 5,000+ per base station for LTE in urban areas. This typology is based on a star topology in each cell, while the cells are connected in a hierarchical tree in the network backhaul. This approach is regarded suitable for the IoT and is therefore selected.

The network layer and interface to applications

The network layer (NWK) and the interface to applications are less fundamental as far as power-efficiency and reliability is concerned. In addition, there is more variation in the field of IoT applications. Nevertheless, it is widely acknowledged that IoT applications need to support the Internet Protocol (IP), whether it is IPv4 or IPv6. In addition, the User Datagram Protocol (UDP) and Constrained Application Protocol (CoAP) could provide the relevant trade-off between flexibility and implementation-complexity on resource-constrained devices.

Furthermore, the IoT will represent an immense security challenge, and it is likely that state-of-the-art security features will become necessary. As of today, we can assume 128 bits Advanced Encryption Standard (AES) for encryption and Diffie-Hellman (DH), or the Elliptic Curve Diffie-Hellman (ECDH) variants, can become the baseline for securing communication.

Frequency Bands Optimal for the Internet of Things

United_States_Frequency_Allocations_Chart_2003_-_The_Radio_Spectrum

Frequency bands of operation for the Internet of Things

Keeping in mind that the requirements of wireless IoT are: low-power, low-cost, medium range (local to metro area), and moderate data rate, it is reasonable to assume that the frequency of operation should be between 100 MHz and 5.8 GHz. Lower frequencies would not allow for sufficient data rate due to limited contiguous spectrum availability, while higher frequencies would have a very short range. The frequency bands in this range between 100 MHz and 5.8 GHz can be sorted in four groups.

  1. Unlicensed bands: 315 MHz in US, 433 MHz almost worldwide, 780 MHz in China, 868 MHz in Europe, 915 MHz in US / Asia, 920 MHz in Japan (formerly 950 MHz), and 2.4 GHz / 5.8 GHz almost worldwide
    • Unlicensed IoT long-range wireless technologies:
      • Weightless (data rate: (0.625kbps -100kbps)
      • LORA (data rate: 0.3 kbps – 27 kbps)
      • Sigfox (data rate: 0.1 kbps)
  2. Licensed bands: cellular networks bands, granted to network operators for deploying specific cellular technologies 2G / 3G / 4G. There are 14 frequency bands defined for GSM (3GPP TS 45.005), 26 for WCDMA (3GPP TS 25.101), and 44 for LTE (3GPP TS36.101) .
    • NB-IoT in the pipeline

The main GSM bands in use are:

    1. GSM 850: 824.2-849.2 MHz uplink, 869.2-894.2 MHz downlink
    2. GSM 900: 880-915 MHz uplink, 925-960 MHz downlink
    3. DCS 1800: 1719.2-1784.8 MHz uplink, 1805.2-1879.8 MHz downlink
    4. PCS 1900: 1850.2-1909.8 MHz uplink, 1930.2-1989.8 MHz downlink

North America and Canada are using GSM 850 and PCS 1900, with PCS 1900 primarily used in urban areas and GSM 850 in rural areas for better coverage. In Africa, Europe, the Middle East, and Asia, most providers use GSM 900 and DCS 1800, GSM 900 is the most common. South America is mixed, for instance GSM 850, GSM 900, DCS 1800, and PCS 1900 are all present in Brazil.

The main WCDMA bands are:

  1. IMT (band 1): 1920-1980 MHz uplink, 2110-2170 MHz downlink
  2. PCS A-F (band 2): 1850-1920 MHz uplink, 1930-1990 MHz downlink
  3. AWS A-F (band 4): 1710-1755 MHz uplink, 2110-2155 MHz downlink
  4. CLR (band 5): 824-849 MHz uplink, 869-894 MHz downlink
  5. EGSM/U-900 (band 8): 880-915 MHz uplink, 925-960 MHz downlink

Bands 1 and 8 allow roaming in ITU Regions 1 and 3, and some countries of region 2. Bands 2 and 4 allow roaming in ITU Region 2 only.

LTE has seen a proliferation of frequency bands, and provision for global roaming would require support for bands 1 (2100 MHz), 2 (1900 MHz), 3 (1800 MHz), 4 (AWS), 5 (850 MHz), 7 (2600 MHz), 8 (900 MHz), 13 (700c MHz), 17 (700b MHz), 18 (800 MHz), 19 (800 MHz), 20 (800 DD), 25 (1900 MHz), 26 (800 MHz), 28 (700 APT MHz), 29 (700 de MHz), 38 (TD 2600), 39 (TD 1900), 40 (TD 2300), and 41 (TD 2500). When 2G allows global roaming with a quad-band device, 4G requires a 20-band, or icosa-band device.

  1. Licensed bands with exceptions: the most common is known as TV whitespaces, already regulated in Europe and the US, to allow for the usage of frequencies granted for TV broadcasters, but not used in other application areas.
  1. Forbidden bands: aeronautical, maritime, military, etc.

From the perspective of power efficiency, the lower operating frequency that is used the better. For instance, as pointed out in [36], the laws of physics imply the path loss at 2.4 GHz is 8.5 dB worse than at 900 MHz (Friis Transmission Equation), which translates into a 2.67x range improvement for the same transmit power. Electronic circuits also lose efficiency at higher frequencies. Therefore, 2.4 GHz transceivers would always consume more than 433 MHz or 900 MHz transceivers for the same performance / transmit power.

In practice, lower frequencies are yet constraining in that the required antenna size for best performance gets large: 17.3 cm for 433 MHz compared to 3 cm for 2.4 GHz. In addition, the usable frequency bands are usually narrow and duty-cycle-limited and may not allow for sufficient data throughput.

TV whitespaces are interesting as well; however, the regulatory framework is complex, with potentially very dynamic frequency allocation and the need to rely on a central entity regulating the allowed channels in real-time.

It is considered that the license-free Industrial, Scientific, Medical (ISM), and Short Range Devices (SRD) sub-GHz frequency bands (just below 1 GHz) are potentially the best for IoT applications. There has been and there still is a significant harmonization effort across all countries to enable these IoT applications, even though supporting 868 MHz (Europe), 915 MHz (USA), and 920 MHz (Japan) frequency bands already allow for a very wide coverage. Europe has opened the 863-870 MHz band and Japan has recently switched from 950 MHz to 920 MHz with relaxed constraints and higher allowable transmit power of 20 mW instead of 1 mW previously. This allows for good coverage and high data rates.

The regulatory framework for these license-free sub-GHz frequency bands is often deemed stringent and restrictive. This is actually not really the case, provided that the protocol is smart enough to implement interference-avoidance algorithms. If the RF application correctly implements the algorithms, there are actually very limited constraints. In addition, these constraints work both ways as they guarantee less interference from other devices that are operating on the same frequencies.

Today there are many frequency bands around 1 GHz licensed for cellular deployments. However, with the IoT market growing, one could reasonably expect that some operators would want to re-allocate their expensive spectrum for the IoT, much like they have started doing for M2M. In short, it is suggested that the license-free sub-GHz frequency bands to be the most promising for IoT applications, however, provisions for operation in current sub-GHz cellular bands have to be made.