LPWAN Technologies Comparison #2: Telegram Splitting, Ultra-Narrowband, Spread Spectrum, and 3GPP Standards

LPWAN

LPWAN Technologies Comparison #2: 

Telegram Splitting, Ultra-Narrowband, Spread Spectrum, and 3GPP Standards

In the first post of our two-part blog series on LPWAN technologies comparison, we touched on the 10 leading criteria for a successful LPWAN deployment. Using these criteria as a baseline, in our final post in the series, we evaluate and compare the main LPWAN technologies on the market. We hope that this provides more insight into the LPWAN solution that best suits your IoT projects and applications.

LPWAN solutions fall broadly into two groups based on their operating spectrum: licensed vs. license-free. While all licensed spectrum LPWANs are derived from 3GPP cellular standards, the license-free landscape is much more diverse. Depending on their underlying technologies, license-free LPWANs vary significantly in terms of network performance criteria. These solutions cluster around three major technologies: Ultra-Narrowband, Spread Spectrum, and Telegram Splitting.

LPWAN

1. Cellular / 3GPP Standards (Licensed)

Based on 3GPP standards, cellular LPWANs like NB-IoT and LTE-M use the licensed radio spectrum owned by cellular network operators. These solutions offer significant advantages including carrier-grade security, as well as reliability due to the fact that there is no co-channel interference from other systems. Adopting global cellular standards also means that hardware sourcing is easier and more flexible.

On the other hand, QoS and scalability in cellular LPWANs are achieved at the cost of power efficiency.  Specifically, time and frequency sychronization alongside handshaking are employed to avoid collisions caused by simultaneous transmissions. While improving scalability, these mechanisms incur large data overhead while making power consumption less predictable. A node may need to signal the base station several times before permission to transmit is granted which can increase energy usage significantly.

Compared to the unlicensed counterparts, cellular LPWAN provides relatively higher peak data rates (i.e. > 1 Mbit/s for LTE-M and 250 kbit/s for NB-IoT), which further increases power budget requirements. Available as managed connectivity services from telecom providers, their coverage at remote locations might not be guaranteed, and network longevity is at stake due to the unforeseeable technology sunsetting. If your IoT end nodes are mobile, NB-IoT won’t be in your best interest as it’s mostly designed for stationary devices.

Given their pros and cons, cellular LPWAN options are best suited for higher data rate IoT use cases and in smart city scenarios where telecom infrastructure is mature. On the other hand, they aren’t optimal for applications where ultra-low power is at a high priority. The same goes for industrial deployments which often take place at remote locations and require the supported communications network to sustain over several decades.

2. Ultra-Narrowband (License-free)

Operating in the license-free spectrum, Ultra-Narrowband (UNB) technology drastically reduces data rates to improve receiver sensitivity and range. Using an extremely small amount of bandwidth to transmit a signal, this approach mitigates noise level while allowing for high spectrum efficiency.

The slow data rate however, translates into a very long on-air radio time, which imposes adverse effects on Quality-of-Service (QoS). A 12-byte UNB signal can have an on-air time of up to 2 seconds, making it highly prone to collisions in the air interface. In a crowded license-free spectrum, with large numbers of data points and traffic from other radio systems, network performance is severely impaired.

Long on-air time also drains the battery faster. What’s more, to improve QoS, UNB networks may need to resort to factor in redundancy by sending the same message multiple times. This significantly increases on-air time and thus, the power consumption of each transmission. Under European regulations a duty cycle (maximum 1%) is imposed on radio devices operating in the 868 MHz band. In this context, slow data rates and long on-air time seriously restrict maximum packet size and transmission frequency. In the USA, FCC regulations set a limit of 0.4 second on-air time per transmission, requiring a different network design with a trade-off on range/coverage.

Other limitations of UNB technology include limited mobility support as the long transmission time causes deep fading and packet errors under Doppler effects. Also, public UNB networks run by network operators many countries and regions suffer from a lack of coverage due to the insufficient network infrastructure run by network operators. On top of that, all messages must be rerouted to the centralized cloud platform of the technology provider, causing skepticism towards data privacy.

3. Spread Spectrum (License-free)

Spread Spectrum technology is an alternative approach to improving range, without significantly compromising data rate as in UNB systems. There are several variants of this technology, with the most common solution being the proprietary Chirp Spread Spectrum.

By spreading a narrowband signal over a wider bandwidth, Spread Spectrum converts it into a noise-like signal that is hard to detect and intercept. To compensate for the high noise floor and to improve receiver sensitivity, coding gain (or processing gain) is added. Higher spreading factors with more coding gain provide longer range at the cost of data rates – or on-air time.

Major drawbacks of Spread Spectrum solutions include low spectrum efficiency and bad co-existence behavior. This is because the bandwidth used for transmission is much wider than the bandwidth required for information. In real-world installations where all gateways and nodes use the same channels for transmissions, the increased traffic within a Spread Spectrum network, combined with uncoordinated transmissions (asynchronous communication), causes message overlays. As a result, the receiver is unable to demodulate overlaid messages, leading to data losses and constrains overall network capacity.

In a long-range scenario, the scalability problem gets even worse. To achieve the best range, the highest spreading factor is required. This increases on-air time and thus the likelihood of more collisions. The use of different spreading factors and bandwidths aims to improve network capacity by enabling simultaneous demodulation of multiple messages. Nevertheless, this solution requires more complicated network management.

4. Telegram Splitting (License-free)

As the latest approach to LPWAN, Telegram Splitting is the only standardized solution in the license-free spectrum. The underlying rationale of this technology is that it splits a UNB signal (data packet) into numerous smaller sub-packets and transmit them at different time and frequencies – with transmission-free periods in between.

Due to its significantly reduced size, each sub-packet has an extremely short on-air time of only 16 milliseconds. The accumulated on-air time of a message with 10-byte payload is only 400 milliseconds. As a result, Telegram Splitting networks can capitalize on the high spectrum efficiency of UNB while surpassing the major downside of increased on-air time. With its ultra-low bandwidth usage and low duty cycle operations (0.1%), the technology offers flexibility as it can also be configured to work in other sub-GHz ISM bands – outside the common 868 MHz (Europe) and 915 MHz (North America).

Besides offering ultra-low power consumption, short on-air time – coupled with frequency hopping – drastically minimizes the likelihood of collisions. As a result, Telegram Splitting is highly immune to both inter- and intra-system interference. To add even more robustness and scalability, Forward Error Correction (FEC) enables successful data retrieval, even if up to 50% of sub-packets are lost in the air interface. Short on-air time and FEC additionally provide excellent resilience against Doppler effects, thereby supporting communications from nodes moving at up to 120 km/h.

As a globally recognized standard released by ETSI in its TS 103 357 specifications, Telegram Splitting brings assured technology quality, vendor independence, and long-term interoperability to the table.

MIOTY™ by BehrTech is the first and only solution that fully complies with Telegram Splitting.

LPWAN Technologies Comparison
LPWAN Technologies Comparison: Key Network Criteria

Final Notes

Selecting the right communications solution for your IoT project involves two steps. First, you need to determine which qualities are most important to your specific use cases. Then, you need to measure the different options based on the defined criteria. More importantly, not to forget the availability of these solutions in your region.

Public LPWANs are great for Smart Cities applications thanks to their extensive coverage in urban areas. On the other hand, many industrial campuses are located in remote, geographically challenging areas not covered by public LPWAN owing to inadequate infrastructure. Therefore, private LPWANs are a better choice for industrial and commercial applications thanks to the flexibility in network setup and management.

The above discussion compares the key LPWAN technology categories based on the most relevant network criteria. It is worth noting however, that even within each category, the performance of different individual solutions can vary. Key factors including security, operating frequency, and payload size cannot be generalized and need to be evaluated case-by-case.

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LPWAN Technologies Comparison #1: Top 10 Criteria for A Successful Implementation

LPWAN technologies comparison

LPWAN Technologies Comparison #1: 

Top 10 Criteria for A Successful Implementation

In our first post of the two-part blog series on LPWAN technologies comparison, we discuss the top 10 criteria for a successful LPWAN implementation.

Low Power Wide Area Networks (LPWAN) represent the fastest growing IoT communication technology and are a key driver for global IoT connections. With various LPWAN solutions and vendors available today, choosing the right technology for your IoT projects is no easy task. To help you select the right solution, we’re doing a two-part educational blog series. In our first post, we discuss the top 10 criteria for choosing the best LPWAN technology based on your use cases and needs.

LPWAN Technologies Comparison

1. Reliability

The importance of industry-grade reliability, especially in mission-critical applications cannot be overstated. High reception rate and minimal packet loss eliminate the need to resend messages, even in unfavorable conditions. This ensures important data arrives quickly while at the same time, enhancing power efficiency.

For LPWAN technologies operating in the increasingly congested, license-free spectrum, interference resilience is a prerequisite to ensure high reliability. An LPWAN’s technical design determines its ability to avoid interferers or packet collisions when the traffic is high, thereby improving overall reception rate.

Read our previous blog on technical approaches to ensure interference resilience in LPWAN.

2. Security

Message confidentiality, authentication, and integrity are core elements of network security.    Multi-layer, end-to-end encryption should be natively embedded in the network to protect message confidentiality against eavesdropping and potential breaches.

Advanced Encryption Standard (AES) is a lightweight, powerful cryptographic algorithm for data encryption in IoT networks. Typically, 128-bit AES can be used to establish network-level security for data communications over the air interface – from end nodes to the base station. At the same time, Transport Layer Security (TLS) protocol for backhaul connection provides a complementary security layer to protect IP-based data transfer to the cloud.

The most secure LPWAN technologies also incorporate rigorous message authentication mechanisms to confirm message authenticity and integrity. This ensures only valid devices can communicate over your network and messages are not tampered or altered during transmission.

3. Network Capacity

A large network capacity allows you to scale with your growing demand in data acquisition points, without compromising Quality-of-Service. Furthermore, as the radio range is almost identical across LPWAN technologies, network capacity becomes an important indicator of infrastructure footprint. The more end devices and daily messages a single base station can support, the less infrastructure you’ll need.

Efficient use of the limited radio spectrum, or spectrum efficiency, is important in achieving a large network capacity. In this context, an ultra-narrowband approach with minimal bandwidth usage provides a very high spectrum efficiency, allowing more messages to fit into an assigned frequency band without overlapping each other. Simultaneously, LPWAN systems employing asynchronous communication need a mitigation scheme to prevent packet collisions (i.e. self-interference) as the number of messages and transmission frequency increase.

4. Battery Life

Battery life has a major impact on your Total-Cost-of-Ownership and corporate sustainability targets. Though LPWAN technologies share common approaches to reduce power consumption, battery life greatly varies across systems. This is due to the significant difference in on-air radio time – or the actual transmission time of a message, which is especially important given that transmission is the most power-intensive activity. In cellular-based LPWANs, synchronous communications with heavy overheads and handshaking requirements also quickly drain the battery.

Read our previous blog on what determines battery life in LPWAN technologies.

5. Mobility Support

Moving devices, moving base stations or moving obstacles along the propagation path are all sources of Doppler shifts and deep fading that lead to packet errors. LPWAN technologies that lack resistance against Doppler effects can only support data communications from stationary or slow-moving end devices. This limits their applicability in specific IoT use cases such as fleet management. Similarly, these networks may fail to connect nodes operating in fast-changing environments such as a device installed next to a highway with vehicles travelling at more than 100 km/h velocity.

6. Public vs Private Network

When selecting an LPWAN solution, you also need to consider which suit your requirements better – a public or a private network. The biggest advantage of public LPWANs run by network operators is saving infrastructure costs. However, public LPWANs mean you’ll be dependent on the provider’s network footprint which is often far from global ubiquity. Public LPWANs leave coverage gaps in many areas and nodes operating at the network edge often suffer from unreliable connection. Private networks, on the other hand, allow for rapid deployments by end users with flexibility in network design and coverage based on their own needs. Another major drawback of public networks is data privacy concern over the centralized back-end and cloud server.

7. Proprietary vs Standard

By supporting multiple hardware vendors, industry-standard LPWAN technologies with a software-defined approach help avoid the problem of vendor lock-in while promoting long-term interoperability. Adopters, therefore, have the flexibility to adapt to future technological trends and changing corporate needs. Passing a rigorous evaluation process, solutions standardized and recognized by a Standards Development Organization also deliver guaranteed credibility and Quality-of-Service.

Read our previous blog on why you should opt for an industry-standard solution.

8. Operating Frequency

Operating frequency is another element to consider when choosing an LPWAN technology, as it can considerably influence network performance. Due to the high cost barrier of licensed bands, most LPWAN vendors leverage license-free industrial, scientific and medical (ISM) frequency bands for faster technology development and deployment.

While there are many ISM bands available today, there are some major differences between 2.4 GHz band and sub-GHz bands. Typically, LPWAN operating in the 2.4 GHz provides higher data throughput at the expense of shorter range and battery life. On top of that, 2.4 GHz radio waves have weaker building penetration and are exposed to much higher co-channel interference.

9. Data Rates

Each IoT application has a different data rate requirement which should be measured against the LPWAN solutions under consideration. It is worth noting that most IoT remote monitoring applications are rather latency tolerant and only need to transmit data periodically. As faster data rates often come with trade-offs in range and power consumption, opting for the solution that best balance these criteria will benefit your Return-on-Investment (ROI).

10. Variable Payload Size

Payload, or user data size should be driven by actual application needs rather than fixed by a certain technology. LPWAN solutions with variable payload size allow users to seamlessly integrate new use cases into their existing network infrastructure – regardless of the payload requirement.

Bottom line, the technology and technical design behind an LPWAN solution determines its performance in the criteria discussed above. In the second post of this series, we will dive deeper into the four main LPWAN technology groups and how they deliver in these parameters.

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