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Dec 8, 2022
Connecting to low-powered devices with LoRaWAN – Understanding Network and Security for Far-Edge Computing

First, let’s understand what Long Range (LoRa) is, as well as its benefits and drawbacks.

LoRa

LoRa operates at Layer 1 (physical) of the OSI model. You could think of it as the equivalent of a Cat-6 RJ-45 cable. You can’t do much with that on its own.

LoRa

LPWAN radio technology was developed by Semtech and designed for use in IoT. It is based on a spread spectrum technique called Chirp Spread Spectrum (CSS), which allows data to be transmitted over long distances (up to several kilometers) with low power consumption.

Benefits of LoRa

The following are some of the benefits of LoRa:

Long range14: 40 kilometers/25 miles (rural environment) and 5 kilometers/3 miles (urban environment)

14 These figures represent best-case line-of-sight range, or the radius of coverage with an omnidirectional antenna. Further, they can vary depending on the design of the gateway.

Low power: Designed to consume minimal energy, with some LoRa-capable devices having built-in batteries that last 20 years. The asynchronous connection model allows the device to sleep when there is no data to transmit or receive.

Reliable: Built-in forward error correction improves resilience against interference.

High penetration: Depending on the region, LoRa operates between 863-928MHz. This frequency range is less than half of the lowest 802.11x band. Due to this, LoRa signals penetrate obstacles approximately twice as well as Wi-Fi.

License-free: See the following table for the unlicensed frequency ranges for LoRa:

  RegionBand
North AmericaUS915 (902-928MHz)
EuropeEU868 (863-873MHz)
South AmericaAU915 (915-928MHz)
IndiaIN865 (865-867MHz)
AsiaAS923 (915-928MHz)

Figure 3.33 – License-free LoRa bands by region

Drawbacks of LoRa

Here are some of the drawbacks of LoRa:

Low throughput: The max bitrate is around 50 kilobits a second

Uncontrolled spectrum usage: License-free operation helps with deployment, but if you have ever had problems with your neighbor’s Wi-Fi router stepping on your signal, the potential is apparent.

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Nov 26, 2022
WiFi and MIMO – Understanding Network and Security for Far-Edge Computing

As discussed previously, MIMO is a method for increasing effective throughput by deliberately exploiting multipath propagation. The different generations of WiFi make use of this in varying ways.

802.11n (Wi-Fi-4)

This supported the more limited Single User MIMO (SU-MIMO). As its name suggests, SU-MIMO means the access point can only be sent to one client at a time.

802.11ac (Wi-Fi-5)

This added MU-MIMO (d). The (d) stands for downlink. With MU-MIMO (d), only one station can transmit, but multiple stations can receive at any given time.

802.11ax (Wi-Fi-6)

This was extended to MU-MIMO (u/d). Now, multiple devices can both transmit and receive simultaneously.

MU-OFDMA

Basic OFDM has been supported since 802.11a (Wi-Fi-2). 802.11ax (Wi-Fi-6) has extended this to now support multiple users.

You could think of the older style of OFDM as a sequence of trucks, each delivering boxes from one vendor at a set time every day. MU-OFDMA allows each truck to be loaded with multiple vendor’s boxes. It also allows the delivery schedule of those trucks to happen only when there’s a full load.

Older Wi-Fi specifications were designed for web browsing and checking email. Congestion emerged as video streaming, AR/VR, and gaming became common. This, combined with more and more client devices transmitting at the same time, meant that the queuing caused by simple OFDM increased latency.

Perhaps most importantly, MU-OFDMA allows priorities to be set not only per client but per protocol/traffic type. In other words, the access point could prioritize video streaming at one level, IoT messages at another, and mission-critical VOIP at the highest.

802.11p (DSRC)

An amendment to the broader IEEE 802.11 Wireless LAN (WLAN) standard, 802.11p is tailored for high-speed, short-range communication in a vehicular environment. The standard operates in the 5.9 GHz frequency band and utilizes the Dedicated Short-Range Communications (DSRC) protocol to ensure low latency and reliable data exchange.

The primary advantage of DSRC over 4G/LTE or 5G for V2X is that it can provide some value in the absence of any infrastructure. If two V2X-equipped cars come within range of each other, they will exchange information in a peer-to-peer fashion. This would function even in the middle of the Sahara.

In 2016, Toyota became the first automaker to introduce cars equipped with V2X systems, followed by GM in 2017. Both of these used DSRC as opposed to 4G/LTE or 5G. While DSRC was the first standard the automotive industry adopted, that is changing for several reasons. Compared to 4G/LTE or 5G for V2X, DSRC suffers from the following limitations:

Limited capacity and scalability: DSRC operates in a narrow frequency band (5.9GHz), which limits its capacity to support a high number of simultaneous connections in dense traffic scenarios. 5G offers broader bandwidth and improved spectral efficiency, allowing it to handle more devices and users concurrently.

Lower data rates: DSRC offers lower data rates compared to 5G, which hinders its ability to support advanced V2X applications that require higher throughput, such as high-definition video streaming for autonomous vehicles. 5G, with its enhanced data rates, can better accommodate these demanding use cases.

Latency: Although DSRC provides relatively low latency communication, 5G has the potential to achieve even lower latencies, especially with the implementation of 5G Ultra-Reliable Low-Latency Communication (URLLC). URLLC can enable mission-critical applications and real-time control systems that demand near-instantaneous response times.

Network slicing: 5G supports network slicing, a feature that allows the creation of virtual networks tailored to specific use cases or applications. This enables the allocation of dedicated resources for V2X communications, ensuring the desired performance levels. DSRC, on the other hand, does not offer this level of customization and flexibility.

Global harmonization: While DSRC has been adopted in some regions, it has not achieved global harmonization, leading to inconsistencies in spectrum allocation and regulation across different countries. 5G has a more unified approach, with global standardization and broader adoption, making it more attractive for V2X implementations across various regions.

Keeping all of this in mind, automakers have begun to include both in their chipsets. The idea is that cellular networks are the primary communication path, and when those are not available, the chipset will leverage DSRC for peer-to-peer vehicle communication when and where it can.

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Oct 8, 2022
Spatial streams – Understanding Network and Security for Far-Edge Computing

The term for beamforming as it is implemented within Wi-Fi is spatial streams.

While some vendors of 802.11n (Wi-Fi-4) devices did implement beamforming, it was through proprietary mechanisms that were specific to each product line. 802.11ac (Wi-Fi-5) was the first to include it as part of the specification.

When a Wi-Fi access point has beamforming enabled, it first estimates the angle of arrival of each client by comparing small differences in arrival times of a signal across multiple antennas that are close together. Once it knows the direction in which it needs to steer the beam, it will have those antennas broadcast the signal at slightly different times. The pattern that’s used is known as a steering matrix.

This deliberately introduces interference because the waves now overlap a little bit. However, not all interference is the same. Some are constructive interference, which makes the signal stronger in one direction, while destructive interference makes it weaker in another:

Figure 3.32 – Beamforming with 802.11ac (Wi-Fi-5)

The net effect of all this is to maximize the signal strength on a per-client basis. This means the signal effectively travels farther and penetrates obstacles better. With older Wi-Fi specifications, all you could do is increase the power output of an omnidirectional signal or add Wi-Fi repeaters.

This is one of the reasons for a seemingly endless multiplication of antennas on even consumer-grade access points. More antennas on both the AP and the clients are better for Wi-Fi throughput – up to a point13. Regardless of the number of antennas, the 802.11ac (Wi-Fi-5) specification supports a maximum of four spatial streams to be active at once.

13 Two antennas are the minimum for beamforming to function at all, while three is recommended.

802.11ax (Wi-Fi-6) increased this to eight and also enhanced it by including client-side modifications that help the AP figure out where a given client is instead of leaving all the work on the AP.

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Aug 22, 2022
Modulation and coding schemes (MSCs) – Understanding Network and Security for Far-Edge Computing

The speeds provided in the preceding table are best-case scenarios. They assume an optimal SNR, which, in turn, allows the use of a modulation and encoding scheme that gets a higher data rate. Each generation of Wi-Fi has a different matrix of MCSs. The following is the MCS index table for 802.11ac (Wi-Fi-5):

   ModulationFEC Coding RateData Rate
MCS0BPSK1/2 
MCS1QPSK1/22x faster than MCS0
MCS2QPSK3/43x faster than MCS0
MCS316-QAM1/24x faster than MCS0
MCS416-QAM3/46x faster than MCS0
MCS564-QAM2/38x faster than MCS0
MCS664-QAM3/49x faster than MCS0
MCS764-QAM5/610x faster than MCS0
MCS8256-QAM3/412x faster than MCS0
MCS9256-QAM5/613.3x faster than MCS0

Figure 3.30 – 802.11ac modulation and coding schemes

Each of the MCSs shown has two parameters:

Modulation: In this context, modulation refers to the particular 802.11x modulation type in use. Some modulation types are very sensitive to noise while others tolerate it well. However, the robustness of a modulation type is achieved by reducing how sensitive it is – and this means a lower bit rate.

FEC coding rate: This describes how many bits transfer data, and how many are used for forward error correction. A coding rate of 5/6 means for every 5 bits of useful information, the coder sends 6 bits of data. In other words, there’s one error bit for every 5 data bits:

Figure 3.31 – Impact of MCS on data rate for 802.11ac

A Wi-Fi-5 or Wi-Fi-6 access point will negotiate the best MCS that it can, given the interference it is experiencing. Wi-Fi devices tend to express the SNR as a single number in dB, which represents the amount of signal above whatever noise is present.

A laptop 1 meter away from an access point with no obstructions would have an SNR of ~50 dB, and be able to operate at MCS9 (100% max speed). A second laptop far away or in a different room might only see an SNR of ~25 dB and be stuck at MCS3 (30% max speed).

Here are some practical steps that can help your device negotiate a faster MCS to its access point:

Reduce devices per AP: Try to have only 3-4 devices per AP where possible

Change Wi-Fi channels: Utilities such as NetSpot can help with this

Increase AP signal power: Some APs default to a lower power level than they are legally able to use

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Jul 24, 2022
Optimizing Wi-Fi (802.11x)-based connectivity – Understanding Network and Security for Far-Edge Computing

Wi-Fi was designed to allow laptops, smartphones, and tablets to connect to the internet and/or communicate with each other on a local area network (LAN). It uses RF to transmit data over relatively short distances, typically within a home or office – although permutations intended for outdoor use are becoming more common.

Wi-Fi is based on the IEEE 802.11 standards, which operate at Layer 1 of the OSI model (physical). Introduced in the late 1990s, it was the first commercially successful wireless networking technology that was designed to work seamlessly with Ethernet (IEEE 802.3) – which almost all LANs use at Layer 2.

Wi-Fi-1 through Wi-Fi-6

The following table shows us the comparison of 802.11a/b/g/n/ac/ax:

   802.11 (b) Wi-Fi-1802.11 (a) Wi-Fi-2802.11 (g) Wi-Fi-3802.11 (n) Wi-Fi-4802.11 (ac) Wi-Fi-5802.11 (ax) Wi-Fi-6
Max Speed11 Mbps54 Mbps54 Mbps600 Mbps10 10 Requires the use of vendor-specific proprietary beamforming/spatial streams.1.3 Gbps11 11 Refers to per-station throughput. The whole network theoretical maximum is 6.9 Gbps.1.7 Gbps12 12 Refers to per-station throughput. The whole network theoretical maximum is 9.6 Gbps.
Range Indoor (2.4)35 mN/A45 m60 mN/A60 m
Range Indoor (5)N/A30 m30 m45 m45 m45 m
Range Outdoor (2.4)70 mN/A90 m120 mN/A120 m
Range Outdoor (5)N/A60 m75 m90 m90 m90 m
2.4 GHz BandYesNoYesYesNoYes
5 GHz BandNoYesYesYesYesYes
OFDMNoYesYesYesYesYes
MU-OFDMANoNoNoNoNoYes
SU-MIMONoNoNoYesYes8×8
MU-MIMO (d)NoNoNoNo4×48×8
MU-MIMO (u/d)NoNoNoNoNo8×8
Spatial StreamsNoNoNoNo48

Figure 3.29 – Comparison of 802.11a/b/g/n/ac/ax

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May 19, 2022
Narrow-Band IoT (NB-IoT) – Understanding Network and Security for Far-Edge Computing

NB-IoT is a specification devised by 3GPP that defines a low-powered WAN (LPWAN) technology that rides on top of existing 4G/LTE and 5GC networks. It is meant to provide a lower cost level of service for IoT devices that do not need the full throughput of an MNO’s standard 4G/LTE or 5G data service offering.

Because it piggybacks on top of existing mobile networks, it shares the same licensed frequency spectrum, and normally the same cell towers/antennas. However, at a signal level, it functions a bit differently. The specification limits each device to a maximum of 200KHz of bandwidth. Contrast this with 4G/LTE, which can have 20MHz channels, and 5G, which can go as high as 400MHz, and the reason it is called “narrow-band” becomes evident. An MNO can support as many as 100 NB-IoT devices using the same amount of bandwidth needed to support a single 4G/LTE phone using a 20MHz channel.

How much throughput an NB-IoT device can squeeze out of that 200KHz channel depends on the version. 3GPP Release 17 was published in 2022 and specifies the latest revision, known as NB-IoT Enhanced. This version specifies a maximum throughput of 250 kbps down and 20 kbps up. It achieves this by using TDD to time-slice the transmit phase as FDMA and the receive phase as OFDMA.

Another difference is that NB-IoT is typically deployed using the guard band slots of an MNO’s network. While this is not always true, it is important to ask your MNO whether they deploy NB-IoT using “in-band mode” or “guard-band mode” as the latter will inevitably suffer from a higher signal-to-noise ratio than you could expect from an NB-IoT channel provisioned in a standard slot. Guard bands exist for a reason. At the time of writing, few NB-IoT offerings do not use guard-band mode:

Figure 3.28 – NB-IoT-capable pressure sensor

In most other ways, NB-IoT works like any 4G/LTE or 5G mobile device. Each device needs a SIM (although eSIMs are becoming the standard) to access the MNO’s network. Each device is also paired with one cell tower/radio at a time. Finally, the connection is synchronous, which means it is constantly on, regardless of whether the device has data to send or receive.

The narrowness of the band allows the MNO to charge less for the service, but it also means NB-IoT devices need less power for the transceiver than if they were using standard 4G/LTE or 5G. However, because of the synchronous connection, NB-IoT devices as a rule consume more power than LPWAN technologies that use an asynchronous connection model.

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Apr 5, 2022
Small cells – Understanding Network and Security for Far-Edge Computing

So far, we have been discussing macrocells. They are large arrays of antennas that are typically mounted on their own tower and meant to service all of a CSP’s customers for a radius measured in kilometers. The ever-growing demand for new mobile devices has driven a market in small cells. These are small, lower-powered access nodes that are deployed for specific uses.

CSPs add small cells to their existing networks to increase coverage in rural areas, to service more devices in an area of particularly dense usage, or to provide service indoors. Small cells are also found in most private 5G networks. Small cells are broken up into femtocells, picocells, and microcells – each of which has a different range and supports a different number of users.

5G frequency spectra

Unlike 4G/LTE, 5G frequencies are split into three range groupings, each in a different region of the spectrum:

Figure 3.27 – 5G frequency band utilization

Cellular Vehicle-to-Everything (C-V2X)

Vehicle-to-Everything (V2X) is a set of specifications that encompass multiple types of wireless communication between a vehicle and its surroundings. This includes other vehicles, infrastructure, networks, and even pedestrians. V2X communication has the potential to revolutionize transportation, making it safer, more efficient, and more sustainable. C-V2X, however, is based on 5G (although it can use 4G/LTE in a more limited fashion).

V2X can be broadly categorized into four subtypes:

Vehicle-to-Vehicle (V2V): This communication occurs between vehicles on the road, allowing them to exchange information about their position, speed, and direction. This enables advanced Driver-Assistance Systems (ADASs) to prevent collisions, optimize navigation, and facilitate cooperative driving.

Vehicle-to-Infrastructure (V2I): In this type of communication, vehicles interact with roadside infrastructure such as traffic signals, road signs, and smart city sensors. This allows for real-time traffic management, improved safety measures, and enhanced navigation guidance. China is leading the way in this area. Nearly 90 cities have already partnered with local wireless network operators, deploying tens of thousands of roadside units to demonstrate intelligent highways and urban intelligent networked roads.

Vehicle-to-Pedestrian (V2P): This type of communication occurs between vehicles and pedestrians or cyclists, using devices such as smartphones or wearable technology. V2P communication can help prevent accidents by providing alerts to both pedestrians and vehicle drivers about potential collisions.

Vehicle-to-Network (V2N): This type of communication connects vehicles to various networks, including the internet, cellular networks, and cloud-based services. V2N communication can provide vehicles with updates on traffic, weather conditions, and other relevant information to enhance their performance and safety.

Of note is that, unlike most other 5G technologies, C-V2X does not necessarily require an MNO’s infrastructure to function. It can operate without a SIM, without network assistance, and uses GNSS as its primary time synchronization source. Today, about 50-60% of vehicles in North America are equipped with a cellular modem. The decision-making process within the automotive industry on whether to standardize on DSRC/802.11p or 5G for V2X has been long and drawn out but has finally settled on using cellular as the standard going forward.

According to the 5G Automotive Association (5GAA), auto manufacturers that are currently producing C-V2X capable models include Audi, BMW, Daimler, Ford, Lexus, Nissan, and Tesla.

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Feb 10, 2022
Network slicing – Understanding Network and Security for Far-Edge Computing

Network slicing is a technique in 5G that can be thought of as a combination of VLANs and QoS mechanisms seen in enterprise data networks. Some aspects of them could be looked at as analogous to VPCs and SGs in AWS.

Regardless of how you conceptualize them, 5G slices allow multiple virtual networks to coexist on the same physical infrastructure. This allows for very fine-grained control of security and performance parameters down to a per-slice basis. MNOs often have the average user on general use public slices, while carving off per-customer slices for their B2B customers. Sometimes, mobile devices are given access to multiple slices from one device, each one mapping to a different application.

The Third Generation Partnership Project (3GPP) has defined three network slice categories:

Enhanced Mobile Broadband (eMBB): Designed to ensure high data rates to mobile devices, with SLA targets of >100 Mbit/s average and >10 Gbit/s peak throughput.

Ultra-Reliable Machine Type Communication (uMTC): Focuses on the reliability and deterministic latency aspects of 5G. SLAs target 3 9’s service availability and <1ms RAN latency. Sometimes, this is called Ultra-Reliable Low-Latency Communication (URLLC).

Massive Machine Type Communication (mMTC): Concentrates on the density of devices with lots of small conversations. This is also known as massive Internet of Things (mIoT).

3GPP also defines dozens of application-specific network slice templates such as those for all subcategories of V2X. In addition to these standard categories, MNOS can engineer custom slice types in response to customer demand.

Network function virtualization (NFV)

NFV uses proven hypervisor and/or container platforms to eliminate the 1:1 mapping between hardware and function that was seen in 4G/LTE EPC. 5G components, on the other hand, are deployed as virtual machines or containers on commodity compute hardware:

Figure 3.26 – 5G functions via NFV on commodity servers

This allows 5G service providers to deploy, manage, and scale the critical components of their network in an automated way. This not only reduces cost and time-to-market, it improves reliability and SLA adherence – which are critical to an MNO’s business.

While NFV was possible in 4G/LTE EPC, 5GC was built from the ground up with it in mind. All functions of 5GC can be virtualized – AMF, SMF, UPF, and network slicing can all be deployed as virtual constructs from the 5G management plane and operated transparently by the 5G control plane.

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