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.

Internet of Things Wireless Connectivity Option: Wi-Fi Pros and Cons

Wifi-Hotspots
Today one of the most common connectivity technologies for consumer products is Wi-Fi, whose 802.11b/g flavors are using the license-free 2.4 GHz frequency band. A Wi-Fi access point (or hotspot) has a range of about 20 meters (66 feet) indoors and a slightly greater range outdoors. Wi-Fi has the benefit of a large spectrum allowing high data rates, 54 Mbps and still increasing with 802.11n and 802.11ac, in a license-free frequency band that is almost harmonized worldwide1 [17]. Wi-Fi has been widely adopted and it is a great way to provide wireless broadband internet access. However, Wi-Fi is designed for high data rates needed for multimedia contents, as opposed to many IoT applications. There has been some effort to promote low-power Wi-Fi; however, it remains an order of magnitude hungrier than what battery-powered devices in IoT application can afford such as battery powered sensors. In short, Wi-Fi is not a suitable candidate for many IoT applications. It is overkill on the data rate for most applications and an absolute power guzzler.  Wi-Fi is likely to remain the major smartphone and Internet connectivity medium. One can envision that the IoT network gateway would be embedded in the Wi-Fi hub already present in most homes, commercial spaces, factories, and offices.