Lecture Notes Access Technologies

• range

• frequency bands

• power consumption

• topology

• constrained devices

• constrained-node networks

• how far needs the singal be propagated?

• area of coverage

• indoor vs outdoor

short range: serial cable ~tens of meters IEEE 802.15.1 Bluetooth and IEEE 802.15.7 Visible Light Communications (VLC)

medium range: tens to hundreds of meters, radio frequncy wireless: IEEE 802.11 Wi-Fi, IEEE 802.15.4, and 802.15.4g WPAN, wired: IEEE 802.3 Ethernet and IEEE 1901.2 Narrowband Power Line Com-munications (PLC)

long range: grater than 1 km, cellular (2G-5G), outdoor IEEE802.11 Wi-Fi and Low-Power Wide-Area (LPWA) technologies

wireless need proper radio planning with field survey

regulated by countries and organisations

• Licensed Frequency Bands: needs subcription to service, generates costs for each device that communicates, gives guarantee of service

• Unlicensed frequency Bands: mostly short range, no garantees 2.4 GHz band is used by IEEE 802.11b/g/n Wi-Fi, IEEE 802.15.1 Bluetooth, IEEE802.15.4 WPAN (Wireless Personal Area Network), have regulations (transmit power, duty cycle), LPWA (Low Power Wide Area), meet low power requirements, long distances

impacted by frequency

sub GHz allows grater distances, can easieler penetrate buildings, have lower data rate 169 MHz, 433MHz, 868 MHz, and 915 MHz.

most IoT access technologies tend to focus on the two sub-GHz frequency regions around 868 MHz and 915 MHz

The European Conference of Postal and Telecommunications Administrations (CEPT), in theEuropean Radiocommunications Committee (ERC) Recommendation 70-03, denes the 868 MHzfrequency band

The 868 MHz band is applicableto IoT access technologies such as IEEE 802.15.4 and 802.15.4g, 802.11ah, and LoRaWAN.

battery power devices are easiler to deploy but have to bear in mind that they can not consume that much power

powered nodes have “unlimited” power but are not as easily deplyed.

star: long and short ranges, one central device that all endpoints communicate with

peer-to-peer/ mesh: medium range, device communicate with everybody as long as they are in range of each other

RFC 7228

Class 0-2

very constrained

can not communicate with the internet direcly and securly

configured once and mostly not reconfigured

they can only answer basic is/keep alive signals or send basic health indications

do not employ the full IP stack

have IP stack for constrained devices

can have connections without a gateway

most of the protocol stack as servers

still benefit from reduced stack and communication activities

most of the nodes in the network are constrained

low power lossy networks (LLN)

data rate from 100 pps (Sigfox) to mbps (LTE and IEEE 802.11ac), actual throughput much lower than data rate

need to bear in mind the bandwith requiremnts for a technology. capacity planning rules and exprected real throughput

cellular used for video analytics, needed for latency, bluetooth when low distance has enough throughput

IoT access technologies developed for constrained devices (low power, low data rate)

LPWA networks have number of messages per day rather then pure bandwith

may range from few miliseconds to seconds

UDP is recommended for LLN

routing optimisation can use IPv6 RPL protocol

review MAC payload size characteristics

IPv6 minimum MTU ist 1280 bytes

IEEE 802.15.4 and 802.15.4g, IEEE 1901.2, and IEEE 802.11ah, Layer 1 or Layer 2fragmentation capabilities and/or IP optimization is important.

payloads may be as little as 19 bytes using LoRaWAN

low-cost and low-data-rate devices

compact protocol stack

deployments

• Home and building automation

• Automotive networks

• Industrial wireless sensor networks

• interactive toys and remote controls

packet based radio protocol

can send data to a centralised device

data ranges from 10kbps to 1 Mbps (depending on frequency and coding)

range from tens of metes up to 1 km

127 bytes basic frame size (in 802.15.4g up to 2047 bytes) with 16 (32) bit checksum

has fully acknowleged transmission

two types of devices

1. fully functional: implements the full communication stack, can communicate with any device in the network or rely messages (PAN), allocates local addresses, acts as gateway,

2. reduced-function device: simple device, can only communicate with fully functional devices, can not act as PAN

well known solution for low-complexity wirless devices with low data rates

foundation for several networking protocol stacks that use it as Layer 1 and 2

In the star topology, all devices communicate through a single central controller, the PANcoordinator. This is a hub-and-spoke model: the PAN coordinator is the hub, and all otherdevices form spokes that connect only to the hub. The PAN coordinator is typically main powered,while the devices are most likely battery operated.

The mesh topology (also called peer to peer) diers from the star topology in that any devicecan communicate with any other device as long as the two are within radio range. A meshnetwork can be ad hoc in formation, self-organizing, and self-healing on node or link failures.It also provides reliability through multipath routing.

The cluster tree topology is a special case of a mesh network that comprises of chained clusters. In a cluster tree, the majority of the devices are FFDs. RFDs may connect to the network as leafnodes at the end of a tree branch. As with any 802.15.4 topology, the network has a single PANcoordinator. The PAN coordinator forms the rst cluster by declaring itself as the cluster head(CLH) with a cluster identier (CID) of zero, selecting an unused PAN identier, and broadcastingbeacon frames to other neighbor devices. A device, which receives beacon frames, may requestfrom the CLH to join the cluster. If the CLH allows the device to join, it will add the new deviceas a child device in its neighbor list. The newly joined device will add the CLH as its parent in itsneighbor list and commence broadcasting periodic beacon frames. This allows other candidatedevices to join the same cluster at that device. Once the requirements of the application ornetwork are met, the PAN coordinator may instruct a device to become the CLH of a new clusterthat is adjacent to the rst. The advantage of this daisy-chained cluster structure is the ability to achieve larger coverage area at the expense of increased message latency

Promoted through the ZigBee Alliance. ZigBee denes upper-layer components (network through application) as well as application prtocoles. Common uses include building automation, home automation, and healthcare. Zig-Bee also denes device object functions, such as device role, device discovery,network join, and security.

low bandwith, low power

has set of commands and message types called clusters

specifies network and security layer and application support

application layer framework consists of the application support sub-layer(APS) and the ZigBee device objects (ZDO).

supports star, tree, and mesh topologies

ZigBee coordinator is responsible for initiating and maintaining the devices on the network. In mesh and tree topologies, the ZigBee coordinator is responsible for starting the network and for choosing certain key network parameters, but the network may be extended through the use of ZigBee routers.

The ZigBee network and security layer provides mechanisms for network startup, conguration,routing, and securing communications. This includes calculating routing paths in what is oftena changing topology, discovering neighbors, and managing the routing tables as devices join forthe rst time.

utilizes 802.15.4 for security at the MAC layer,

6LoWPAN is an IPv6 adaption layer dened by the IETF 6LoWPAN workinggroup that describes how to transport IPv6 packets over IEEE 802.15.4 layers. RFCs document header compression and IPv6 enhancements to cope with the specfic details of IEEE 802.15.4.

An evolution of the ZigBee protocol stack, ZigBee IP adopts the 6LoWPANadaption layer, IPv6 network layer, and RPL routing protocol. In addition it offers improvements to IP security.

IP/TCP/UDP protocols supported now

Thread is a low power mesh networking protocol stack developed, speciedand certified by the Thread Group.The main focus of Thread are smart homeapplications. It is build upon IEEE 802.15.4, 6LoWPAN, IPv6 and CoAP. ABSD-licensed open-source implementation of Thread, called OpenThread, has been released.

WirelessHART, promoted by the HART Communication Foundation, is a pro-tocol stack that offers a time-synchronized, self-organizing, and self-healing mesh architecture. It is based on IEEE 802.15.4-2006 over the 2.4 GHz frequency band Highway Addressable

Remote Transducer Protocol (HART). Gateways must be implemented for connection to other networks (e.g. IP networks) and for communication with applications that use protocols other than the HART protocol.

low power

wireless and wired network can operate next to each other and complement each other

802.15.4 supports many options

from 2.4 GHz to sub GHz frequencies in ISM bands

• 2.4 GHz, 16 channels, with a data rate of 250 kbpsˆ (worldwide)

• 915 MHz, 10 channels, with a data rate of 40 kbpsˆ (later 100 kbps) (north america)

• 868MHz, 1 channel, with a data rate of 20 kbps (later 250 kbps) (europe, middle east, africa)

many adaptations over the year, therefore check which version is suppoted by devices

Service Data Unit was increased to 2047 bytes

how devices share frequencies allocated

scheduling and routing is coordinated

PAN association and disassociation

link communication between two MAC entities

The IEEE frequently makes amendments to the core 802.15.4 specification, before integrating them into the next revision of the core specification. When these amendments are made, a lowercase letter is appended

this specific one focuses on Smart Grid Use Cases

optimize large outdoor wireless mesh networks for field area networks (FANs)

mostly mesh

communications for low-frequency narrowband power line devices via alternating current and direct current electric power lines

indoor and outdoor

less than 1000 V and 1000 V to 72kV

500kb/s data rate

sub 1 GHz

improved transmission range

connecting endpoints such as fog computing nodes, high-data-rate sensors, and audio or video analytics devices or for deploying Wi-Fi backhaul infrastructures

main use cases

• Sensors and meters covering a smart grid

• Backhaul aggregation of industrial sensors and meter data

• Extended range Wi-Fi

star topology, but includes a simple hop relay

MAC enhancments:

• Number of devices: Has been scaled up to 8192 per access point.

• MAC header: Has been shortened to allow more cient communication.

• Null data packet (NDP) support: Is extended to cover several control and management frames. Relevant information is concentrated in the PHY header and the additional overhead associated with decoding the MAC header and data payload is avoided. This change makes the control frame exchanges cient and less power-consuming for the receiving stations.

• Grouping and sectorization: Enables an AP to use sector antennas and also group stations (distributing a group ID). In combination with RAW and TWT, this mechanism reduces contention in large cells with many clients by restricting which group, in which sector, can contend during which time window. (Sectors are described in more detail in the following section.)

• Restricted access window (RAW): Is a control algorithm that avoids simultaneous transmissions when many devices are present and provides fair access to the wireless network. By providing more client access to the medium, additional power savings for battery-powered devices can be achieved, and collisions are reduced.

• Target wake time (TWT): Reduces energy consumption by permitting an access point to down times when a device can access the network. This allows devices to enter a low-power state until their TWT time arrives. It also reduces the probability of collisions in large cells with many clients.

• Speed frame exchange: Enables an AP and endpoint to exchange frames during a reserved transmit opportunity (TXOP). This reduces contention on the medium, minimizes the number of frame exchanges to improve channel eficiency, and extends battery life by keeping awake times short.

unlicensed-band LPWA technology

physical layer or the wireless modulation utilized to create the long range communication link

based on chirp spread spectrum modulation

trades a lower data rate for receiver sensitivity to signifcantly increase the communication distance

allows demodulation below the noise foor, offers robustness to noise and interference, and manages a single channel occupation by diferent spreading factors

433 MHz, 779-787 MHz, 863-870 MHz, and 902-928MHz, as well as regional profles for a subset of the 902-928 MHz bandwidth

Class A: allow bi-directional communications, whereby each end-device's uplink transmission is followed by two short downlink receive windows

Class B: Bi-directional end-devices with scheduled receive slots, allow more receive slots

Class C: Bi-directional end-devices with maximal receive slots, nearly continuously open receive windows, closed only when transmitting

stars of stars topology

gateways have IP connection

two layers of security: one for the network and one for the application. AES encryption is used with the key exchange utilizing an IEEE EUI64 identifer

endpoint implements a network session key (NwkSKey), itself and the LoRaWAN network server.

application session key (AppSKey), which performs encryption and decryption functions between the endpoint and its application server.

value on up chirp

syncronisation on down chirp

Three modes of operation

• Standalone: A GSM carrier is used as an NB-IoT carrier, enabling reuse of 900 MHz or 1800 MHz.

• In-band: Part of an LTE carrier frequency band is allocated for use as an NB-IoT frequency. The service provider typically makes this allocation, and IoT devices are confgured accordingly. You should be aware that if these devices must be deployed across different countries or regions using a different service provider, problems may occur unless there is some coordination between the service providers, and the NB-IoT frequency band allocations are the same.

• Guard band: An NB-IoT carrier is between the LTE or WCDMA bands. This requires coexistence between LTE and NB-IoT bands.

simplifying the LTE attach procedure so that a dedicated bearer channel is not required and transporting non-IP data.

provide terabytes of capacity

path loss between earth and satellite and the slotted nature of the GEO orbit

rather large terminal antennas, with enough gain to close the

link and with sufficient directivity to avoid interference into adjacent satellites and systems

much closer to earth than GEO satellites

less path loss and thus less terminal power and antenna directivity is required

moving satellites, causing a highly time variant communication

channel and the need for steerable antennas

Fleets of LEO satellites will offer global IoT coverage

using many low cost terrestrial-only IoT devices in combination with few satellite connected aggregation terminals

wireless technology standard

exchanging data between xed and mobile

devices over short distances using short-wavelength radio waves in the industrial, scientifc and medical radio bands, from 2.402 GHz to 2.480 GHz

wireless alternative to RS-232 data cables

Bluetooth Core Specifcation [Bluetooth Core, 2019] defnes the technology building blocks

specifcation is overseen by the Bluetooth Special Interest Group

[Bluetooth Mesh, 2019] define requirements to enable an interoperable many-to-many mesh networking solution for Bluetooth Low Energy (LE) wireless technology suited for control, monitoring, and automation systems where tens, hundreds, or thousands of devices need to reliably and securely communicate with one another.

uses a radio technology called frequency-hopping spread spectrum (FHSS)Bluetooth divides transmitted data into packets, and transmits each packet on one of 79 designated Bluetooth channels. Each channel has a bandwidth of 1 MHz. It usually performs 1600 hops per second, with adaptive frequency-hopping (AFH) enabled. Bluetooth Low Energy uses 2 MHz spacing, which accommodates 40 channels.

packet-based protocol with a master/worker architecture. One master may communicate with up to seven workers

All devices within a given piconet use the clock provided by the master as the base for packet exchange. clock ticks with a period of 312.5 µs

in the simple case of single-slot packets, the master transmits in even slots and

receives in odd slots

not have to be in visual line of sight of each other; however, a quasi optical wireless path must be viable

effective range varies depending on propagation conditions, material coverage, production

sample variations, antenna confgurations and battery conditions.

lower-powered device tends to set the range limit.

include device discovery, connection establishment and connection mechanisms

Devices implementing both systems (BR and LE) can communicate with other devices implementing both systems as well as devices implementing either system.

Enhanced Data Rate (EDR) Alternate Media Access Control (MAC) and Physical (PHY) layer extensions synchronous and asynchronous connections with data rates of 721.2 kb/s for Basic Rate, 2.1 Mb/s for Enhanced Data Rate and high speed operation up to 54 Mb/s with the 802.11 AMP.

lower data rates and has lower duty cycles then BR

isochronous data transfer in a connection-oriented and connectionless mechanism

unlicensed 2.4 GHz ISM band.

frequency hopping transceiver to combat interference and fading

mandatory symbol rate is 1 megasymbol per second (Msym/s), where 1 symbol represents 1 bit therefore supporting a bit rate of 1 megabit per second (Mb/s), which is referred to as the LE 1M PHY.

two coding schemes: S=2, where 2 symbols represent 1 bit therefore supporting a bit rate of 500 kb/s, and S=8, where 8 symbols represent 1 bit therefore supporting a bit rate of 125 kb/s.

FDMA TDMA Forty (40) physical channels, separated by 2 MHz, are used in the FDMA scheme. Three (3) are used as primary advertising channels and 37 are used as general purpose channels (including as secondary advertising channels). A TDMA based polling scheme is used in which one device transmits a packet at a predetermined time and a corresponding device responds with a packet after a predetermined interval.

LE uses a randomly generated Access Address to identify a

physical channel between devices.

piconet physical channel is used for communication between connected devices and is associated with a specifc piconet

advertising physical channel is used for broadcasting advertisements to LE devices

periodic physical channel is used to send user data to scanner devices in periodic advertisements at a specifed interval

isochronous physical channel is used to transfer isochronous data between LE devices in an LE piconet or to transfer isochronous data between unconnected LE devices.

defines models that are used to standardize the operation of typical user

scenarios and are defined in the Bluetooth Mesh Model speci cation [Bluetooth Mesh, 2019] or other higher layer specifcations. Examples of higher layer model specifcations include models for lighting and sensors.

defines the states, messages, and models required to configure and manage a mesh network

defines how higher layer applications can use the upper transport layer. It defines the format of the application data; it defines and controls the application data encryption and decryption performed in the upper transport layer; and it checks whether the incoming application data has been received in the context of the right network and application keys before forwarding it to the higher layer.

encrypts, decrypts, and authenticates application data and is designed to provide confidentiality of access messages. It also defines how transport control messages are used to manage the upper transport layer between nodes, including when used by the Friend feature

defines how upper transport layer messages are segmented and reassembled into multiple Lower Transport PDUs to deliver large upper transport layer messages to other nodes. It also defines a single control message to manage segmentation and reassembly.

defines how transport messages are addressed towards one or more elements. It defines the network message format that allows Transport PDUs to be transported by the bearer layer. The network layer decides whether to relay/forward messages, accept them for further processing, or reject them. It also defines how a network message is encrypted and authenticated.

defines how network messages are transported between nodes. There are two

bearers defined, the advertising bearer and the GATT bearer. Additional bearers may be defined in the future.

used by Low Power nodes to limit the amount of time that they need to listen

possible that it will not receive mesh messages that it should be processing. This includes security updates required for maintaining the security of the network as well as the normal mesh messages.

special relationship between a Low Power node and one neighboring Friend node

frst established and initiated by the Low Power node; once established, the Friend node performs a number of actions that help reduce the power consumption on the Low Power node

Friend node maintains a Friend Queue for the Low Power node

Friend node delivers those messages to the Low Power node when requested by the Low Power node

Friend node may be friends with multiple Low Power nodes. A Low Power node can only be friends with a single Friend node.

All nodes have the ability to transmit and receive mesh messages.

Nodes can also optionally support one or more additional features:

• Relay feature - the ability to receive and retransmit mesh messages over the advertising bearer to enable larger networks.

• Proxy feature - the ability to receive and retransmit mesh messages between GATT and advertising bearers.

• Low Power feature - the ability to operate within a mesh network at signifcantly reduced receiver duty cycles only in conjunction with a node supporting the Friend feature.

• Friend feature - the ability to help a node supporting the Low Power feature to operate by storing messages destined for those nodes.

A node that supports a feature may have that feature enabled or disabled, and the feature, when enabled, may be or may not be in use

A node that supports the Relay feature and has the Relay feature enabled is known as a Relay node

A node that supports the Proxy feature and has the Proxy feature enabled is known as a Proxy node

A node supporting the Low Power feature cannot have this feature disabled and must establish a friendship with another node supporting the Friend feature before it can use the Low Power feature to reduce receiver duty cycles. A node that supports the Low Power feature and has a friendship with a node that supports the Friend feature is known as a Low Power node

A node that supports the Friend feature, has the Friend feature enabled, and has a friendship with a node that supports the Low Power feature is known as a Friend node.

Generic Attribute Profile is provided to enable devices that are not capable of supporting the advertising (ADV9 bearer to participate in a mesh network)