SigFox tutorial-network architecture,interfaces,protocol stack

The Sigfox tutorial covers sigfox system features, sigfox network architecture, sigfox interfaces, MAC frame structure and sigfox protocol stack. The tutorial provides links to advantages and disadvantages of sigfox and comparison with other wireless technologies.

Introduction: SigFox wireless technology is based on LTN (Low Throughput Network). It is wide area network based technology which supports low data rate communication over larger distances. It is used for M2M and IoT applications which transmits only few bytes per day.

It can be interfaced with cellular network in order to coexist with cellular wireless technologies such as GSM, CDMA, LTE etc.

SigFox wireless system features

The table-1 above mentions all the sigfox system features.

LTN Network Architecture | Sigfox network architecture

LTN network architecture

The figure-1 depicts typical LTN (Low Throughput Network) network architecture. As shown, It consists of LEPs (LTN End Points), LAPs (LTN Access Points), WAN or cloud part and different types of servers. The servers include LTN server, CRA (Central Registration Authority), OSS/BSS and application provider server.

All these sigfox system entities are connected using various interfaces.

sigfox network architecture

The simple sigfox network architecture is shown in the figure-2. This is same as the LTN architecture except the terminologies used. LEPs are designated as objects. LAPs are termed as Gateway or Base Stations. WAN is the cloud which connects BSs with business applications through different interfaces.

The transmissions from LEPs to the network (i.e. BSs or Gateways) are known as uplink transmissions. The transmissions from the network to LEPs are known as downlinks.
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Sigfox Protocol Stack

SigFox Protocol Stack

The figure-3 depicts simple protocol stack of sigfox wireless system. As shown it consists of Radio layer, Physical Layer, MAC layer and application layer. Following are the functions of each of these layers.

RF Layer: This layer takes care of frequency assignment and transmit/receive power requirements at Sigfox end points and base stations.

PHY Layer: This layer takes care of preamble insertion (at transmit end) and removal (at receive end). It uses BPSK modulation in the uplink and GFSK modulation in the downlink.

MAC Layer: It handles management of MAC messages. It prepares frames as per uplink and downlink formats defined below. Mainly Sigfox system is used for uplink transmissions. It can also be used for downlink transmissions using piggy backing concept.

Application Layer: The different applications are supported in this LTN technology. There are various interfaces/protocols between WAN (i.e. cloud) and servers to support the same e.g. SNMP, HTTP, MQTT, IPv6 etc.
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Sigfox Frame Structure

Sigfox MAC frame structure

The figure-4 depicts sigfox frame structure. It mentions both the uplink MAC frame and downlink MAC frame. As shown uplink frame consists of preamble, frame sync field, end device ID, payload, authentication field, FCS field. As shonw downlink frame consists of preamble, frame sync, flags, FCS, auth., error codes and payload.

Preamble is predefined pattern of symbols used for synchronization purpose. Using this pattern, various impairments are estimated at the receiver and corrected accordingly. This has become possible as copy of this constant pattern is known at the receiver. Frame sync field carry frame type which differentiates different MAC frames. End device ID (32 bits in size) is used as unique identifier for each of the Sigfox end devices (or LEPs). FCS (Frame Check Sequence) field is used for error detection.
More on SIGFOX Frame structure>>.

References: ETSI GS LTN 001, 002, 003 (Low Throughput Networks) documents.

SigFox tutorial RELATED LINKS

SIGFOX Tutorial Main Page   SIGFOX Network Architecture   SIGFOX Protocol Stack   SIGFOX Frame structure   Advantages and Disadvantages of Sigfox   SIGFOX Vs GSM   SIGFOX Vs Wireless M-Bus   SIGFOX technology basics   NB IoT vs SIGFOX vs LoRa