Modem Specification for RC4-UDL-ENC

Transcription

1 Version August 10, 2018 Sigfox Verified TM Modem Specification for RC4-UDL-ENC Public Use Note: Only the last version of this document available on the Sigfox web sites is official and applicable. This document is the property of Sigfox. It shall not be copied and / or disclosed to third parties, in any form without Sigfox written permission.

2 Contents 1 Introduction Scope Requirements coding rules Acronyms and abbreviations Frequencies Sigfox Verified TM Candidate 4 3 Operational Requirements Operational Frequencies TX RF modulation TX Baudrate Output Spectrum Carrier frequency stability RX Demodulation Sigfox Link Budget Protocol Timings Additional Measurements Modulated Conducted TX Output power Validation of the information contained in the OOB Frame I/Q Wave record A Appendix: Guidelines to design an UNB_MODEM 13 A.1 Implement the TX Modulation - DBPSK A.2 Implement the TX Baudrate A.3 Implement the AES A.4 Implement the Non Volatile Memory A.5 Implement the Sigfox Protocol A.6 Implement the RX Demodulation

3 1 Introduction This document is intended to specify technical operational requirements for a Sigfox Verified TM UNB_MODEM: RF requirements, Sigfox Protocol Requirements. This document gives also some guidelines on the design of a Sigfox Verified TM operational constraints and dependancies. UNB_MODEM and thus identify the 1.1 Scope UNB_MODEM is a part of the Sigfox system as briefly described by simplified diagram below. This document describes product requirements for Sigfox Verified TM UNB_MODEM. Reader has to notice that the present document focuses on Sigfox system. A commercial product might also integrate other systems (multi-system device) All following requirements are mandatory to create a Sigfox network compliant modem. This document describes Uplink and Downlink (if needed) aspects. Sigfox network is bi-directional. Anyway, only the Uplink mode is mandatory. The Downlink mode is optional. 2

4 1.2 Requirements coding rules In order to enable requirement traceability, each requirement is referenced as following: [<Document Code>-<product mnemonic>-<chrono number>] [PRS-UNB-MODEM -xxx] requirement body 1.3 Acronyms and abbreviations - 2GFSK: 2-Level Gaussian Frequency Shift Keying - ACK: Acknowledgement - AES: Advanced Encryption Standard - Att: Attenuator - CAB: Client Application Board - CBC: Cipher Block Chaining - CS: Carrier Sense - Cold Test: Test executed in initial condition (wait till the DUT come back to the initial system between two tests) - DBPSK: Differential Binary Phase-Shift Keying - DUT: Device Under Test - ENC: Encrypted - Fd: DUT Frequency - Fe: Equipment Frequency - Legacy Uplink: initial payload format of Sigfox Uplink without encryption - LBT: Listen Before Talk - NVM: Non Volatile Memory - OOB: Out Of Band - PAC: Porting Authorization Code - PER: Packet Error Rate - PMR: Private Mobile Radio - RC: Radio Configuration - RF: Radio Frequency - RSA: Radio_Signal_Analyzer - RSSI_dut: DUT RSSI - RSSI_eq: Equipment RSSI - SMIQ: Vector Signal Generator - SOC: System On Chip - Sigfox Message: Three frames with payload A3B - UNB_MODEM: Ultra Narrow Band MODEM - UNBT: Ultra Narrow Band Transceiver 3

5 1.4 Frequencies Radio Configuration Uplink Frequency (Hz) Downlink Frequency (Hz) Baudrate (bps) RC Sigfox Verified TM Candidate 4

6 3 Operational Requirements The following operational requirements have to be followed on all range of the input power supply.rf tests will be executed on nom, min and max value of the range. All others tests will be executed on nominal value of the range 3.1 Operational Frequencies [PRS-UNB-MODEM-10] Frequency Steps UNB_MODEM programmed frequency step must have a maximum error of +/- 100Hz (i.e : When programming X Hz, and then X+Y Hz, the differential frequency measurement must be Y Hz +/- 100 Hz max). [PRS-UNB-MODEM-11] Operational Frequencies Range Central frequency. Range of frequencies used during transmission has to be less than 192 khz around the [PRS-UNB-MODEM-12] Operational Frequencies Distribution The distribution of all frequencies used during transmission has to be uniform. [PRS-UNB-MODEM-13] Static Frequency Tolerance UNB_MODEM carrier frequency (absolute value) must be at +/- 20 ppm for operational bands. These 20 ppm are managed by the Sigfox system (network + Firmware library). This requirement respects the FCC , FCC and ANZ regulation. One solution is to use a crystal or TCXO with these characteristics: Static Frequency Tolerance: precision is not so important if this parameter is calibrated at factory in order to cancel this static imprecision. Temperature Frequency tolerance added to Aging frequency tolerance must be less or equal to +/- 20 ppm during all the product life. All other system can be used if the global imprecision is +/- 20 ppm for operational bands all over the product life. 3.2 TX RF modulation [PRS-UNB-MODEM-20] DBPSK Modulation envelop not modulate) UNB_MODEM must use DBPSK modulation. Modulation mapping (0: modulate 1: do 5

7 [PRS-UNB-MODEM-21] Phase Measurement UNB_MODEM DBPSK modulation must be compliant with following performances : Maximum modulation RMS phase error : 10 degree from one symbol to another. Maximum modulation peak phase error : 30 degree from one symbol to another. [PRS-UNB-MODEM-22] Extra symbols before the first Sigfox bit of the frame Transmission must include an extra symbol timing from 0 to 2 symbols time before the first Sigfox bit. No phase shifting is allowed during this phase except at the symbol time. Extra symbols timing before the first Sigfox bit of the frame [PRS-UNB-MODEM-23] Extra symbols after the last Sigfox bit of the frame Transmission must include an extra symbol timing from 0 to 2 symbols time after the transmission of the last Sigfox bit. No phase shifting is allowed during this phase except at the symbol time. Extra symbols timing after the last Sigfox bit of the frame 3.3 TX Baudrate [PRS-UNB-MODEM-30] TX Max Symbol duration UNB_MODEM must be able to transmit at a baudrate of 600 bps (standard Sigfox rate for FCC) with DBPSK modulation with following tolerances on the symbol duration of +/- 1 % [PRS-UNB-MODEM-31] Max TX Baudrate Cumulated Error UNB_MODEM must have a maximum baudrate cumulated error of 0.1 % of the whole ideal transmission time. (i.e : for a 26 bytes frame (0.35 s duration), tolerance of 0.35 ms ) 6

8 3.4 Output Spectrum [PRS-UNB-MODEM-40] Power Spectral Density UNB_MODEM spectrum occupation shall respect the following integrated power limits: -20dBc / 600 [-1800 Hz ; -600 Hz], [600 Hz ; 1800 Hz] -35dBc / 600 [-3000 Hz ; Hz], [1800 Hz ; 3000 Hz] -45dBc / [ Hz ; Hz], [3000 Hz ; Hz] dbc/y Hz : 10log(power integration over y Hz) Above +/- 96 khz frequencies, must respect FCC , FCC and ANZ regulation. Note on Spurious: Sigfox will not certify your module for FCC, but gives you advices and referencies for customer to ensure transceivers will satisfy also FCC. UNB_MODEM must be compliant with FCC , FCC and ANZ regulation. [PRS-UNB-MODEM-41] Narrow Band Power Distribution bandwidth of 192 khz. UNB_MODEM must transmit 99.9 % of the power between +/ Hz over the Sigfox 3.5 Carrier frequency stability [PRS-UNB-MODEM-50] Transitional Frequency Dynamic Drift 7

9 UNB_MODEM carrier frequency must respect a max absolute frequency shifting peak of 100 Hz/s from the first quarter of the synchro bits to the end of the synchro bits. [PRS-UNB-MODEM-51] Established Frequency Dynamic Drift UNB_MODEM carrier frequency must respect a max absolute frequency shifting of 50 Hz/s from end of synchro bits to the end of a transmission of the maximum Sigfox frame. Method of the least squares will be used for the measurement. 3.6 RX Demodulation [PRS-UNB-MODEM-60] 2GFSK 600bps DOWNLINK-MODEM UNB_MODEM must be able to demodulate 2GFSK at 600bps (BT = 1.0, delta_f = +/- 800Hz). [PRS-UNB-MODEM-61] Downlink Only-rssi DOWNLINK-MODEM The device must return the RSSI level +/- 2 db when receiving a GFSK frame in Test Mode RX-GFSK, for each GFSK pattern received. 3.7 Sigfox Link Budget [PRS-UNB-MODEM-70] Sigfox Link Budget DOWNLINK-MODEM The UNB_MODEM Sensitivity should be <= -126 dbm with a PER at 10 % on 1000 frames sent with when the Modulated Outup Power is 22 dbm ERP, to keep the link budget balanced. If the Modulated Output Power is less than 22 dbm, so all db lost in Tx will be added at -126 to keep the link budget balanced. At the balanced link budget, the Rx sensitivity should be : RxSensiAtBalancedBudgetLink = TxPower 3.8 Protocol [PRS-UNB-MODEM-80] AES UNB_MODEM must include an AES module with CBC mode with a 16 bytes key (Hardware or Software) for authentication on network. The Init Vector (IV) is set to 0. 8

10 [PRS-UNB-MODEM-81] NVM Frequency Storage 2 bytes). UNB_MODEM must include a non volatile memory for frequency carrier storage (at least [PRS-UNB-MODEM-82] NVM Sequence Number Storage UNB_MODEM must include a non volatile memory for a protocol sequence number storage (at least 2 bytes), not readable by application. [PRS-UNB-MODEM-83] Public Key switch The UNB_MODEM must allow a way to switch from private to public key to be compatible with SIGFOX SDR DONGLE. This requirement is only applicable for Module, Reference Design and Development solutions. KEY = AABBCCDDEEFF ( KEY[0]=00, KEY[15]=FF ) [PRS-UNB-MODEM-84] Number of frames per message in Uplink mode customer message. In normal operational mode, the UNB_MODEM must send 3 Sigfox RF frames per [PRS-UNB-MODEM-85] Legacy Uplink The device has to be able to send Sigfox Frame through the Sigfox Test Mode function. [PRS-UNB-MODEM-86] Uplink Encrypted payload Mode function. The device has to be able to send Sigfox encrypted Frames through the Sigfox Test [PRS-UNB-MODEM-87] Downlink Legacy DOWNLINK-MODEM The device has to be able to receive Sigfox Frames through the Sigfox Test Mode function and to report if a frame has been received properly or not. [PRS-UNB-MODEM-88] Downlink Encrypted Payload DOWNLINK-MODEM The device has to be able to receive Sigfox encrypted Frames. [PRS-UNB-MODEM-89] Number of repeated Uplink frame in bi-directional mode DOWNLINK- MODEM UNB_MODEM must send 3 Sigfox RF frames maximum per customer message for a message requesting a downlink response. The repetition may be configured by the manufacturer through the tx_repeat parameter. 9

11 3.9 Timings [PRS-UNB-MODEM-90] TX Interframe Timing in Uplink mode In normal operational mode, the TX interframe duration in Uplink mode has to be between 500 ms and 525 ms. [PRS-UNB-MODEM-91] TX Interframe Timing in Bi-directional mode DOWNLINK-MODEM In normal operational mode, the TX interframe duration in Uplink/Downlink mode has to be between 500 ms and 525 ms, in case of frame repetition (tx_repeat parameter greather than 0).. [PRS-UNB-MODEM-92] RX Start Of Listening DOWNLINK-MODEM The UNB_MODEM must be able to receive a Downlink frame sent 20.1 s after the first frame ( This timing take into account the extra symbol time and the downlink frame duration ), following the implementation described in the graph: Figure 1: Downlink Timings [PRS-UNB-MODEM-93] RX End Of Listening DOWNLINK-MODEM The UNB_MODEM must be able to receive a Downlink frame sent 44.5 s after the first frame ( This timing take into account the extra symbol time and the downlink frame duration ), following the implementation described in the graph: Figure 2: Downlink Timings (last chance to receive downlink frame case) [PRS-UNB-MODEM-94] RX to OOB(ack) Timing DOWNLINK-MODEM After receiving the downlink frame, the device has to wait 1.4 s and no later than 4 s before sending the acknowlegement frame (OOB), following the implementation described in the figure 2. 10

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13 4 Additional Measurements 4.1 Modulated Conducted TX Output power [PRS-UNB-MODEM-100] Modulated Conducted Output Power Measurement: To be able to benefit from optimal Quality of Service with a balanced link budget, Sigfox recommends to respect the following maximum output radiated power : 22dBm ERP( or 24dBm EIRP). Device or module can output more than 22dBm in conducted mode due to some antenna loss in the complete end product. 4.2 Validation of the information contained in the OOB Frame [PRS-UNB-MODEM-110] RSSI level DOWNLINK-MODEM Measurement: At a specific Downlink Frame level, the OOB shall return the same level of RSSI of the received GFSK ( +/-2dB) or 0 is the device is not able to return it. [PRS-UNB-MODEM-111] DUT Temperature level Measurement: The OOB shall return the level of Temperature at which the test is executed or 0 is the device is not able to return it. [PRS-UNB-MODEM-112] DUT Voltage level Measurement: The OOB shall return the level of Voltage at which the test is executed or 0 is the device is not able to return it. 4.3 I/Q Wave record [PRS-UNB-MODEM-120] I/Q Wave record Measurement: Test Mode TX-BPSK shall be recorded with a 20dB minimum SNR in.raw format. 12

14 A Appendix: Guidelines to design an UNB MODEM This chapter will only guide you on the choice of the RF chipset and micro-crontroller, and are not in any way mandatory for the implementation of a Sigfox_Ready UNB_MODEM. The mandatory requirements that need to be filled in by the UNB_MODEM are described in section "Operational Requirements". A.1 Implement the TX Modulation - DBPSK This modulation can be built by hardware (not available in all RF chipsets) or by software. Even if the RF chipset supports the DBPSK modulation, manufacturers have to takecare of the Sigfox requirements regarding the spectral occupation. Here are the main parameters of the DBPSK modulation used by the Sigfox protocol: Binary (Pi) Phase-Shift Keying with following mapping: 0: change phase, 1:keep phase. Amplitude modulation ( ramp-down and ramp-up of the signal amplitude at each phase change ). It reduces the spectral occupation. To be able to build this modulation in software, the PA and the Frequency Steps of the RF chipset have to be controlled by the host micro-controller. There could be 2 ways to implement the DBPSK modulation: Using Continuous Wave Using 4GFSK Modulation DBPSK Using Continuous Wave Continuous wave mode (also known as CE/FCC certification test mode) is often available in the RF Chipset. This mode offers the ability to modify dynamically the carrier frequency and the PA power. Principle The Pi phase shifting is obtained by accumalating several frequency steps during a certain amount of time. The spectral spread is limited by decreasing the PA power during the carrier frequency change. Therefore, the host micro-controller has to be able to control the PA and Frequency Steps, and both in a way that allow to execute these commands in less time than a symbol. Chip requirements As a consequence, here are the following guidelines: PA Steps Recommendation: As PA ramping up and down (AM) is a way to ensure Sigfox spectrum requirement acceptance, RF Chipset shall have a minimum number of steps available. Profiles available are composed of at least more than 32 PA steps. RF Chipset PA must control an output power range from the maximum output power required in the specification to minimum of -70dBm to have the best results. Frequency Steps Recommendation: If your RF chipset has no direct phase control, you must ensure to have the access to steps resolution of at least 100Hz. If phase is directly tunable by user, you must ensure there is filter on this command to ensure filtered phase shift. Many RF chipsets do not allow to control the frequency out of a well known state of the internaly RF Chipset state machine, make sure that this is possible to control it without restriction. 13

15 CPU load/ressources Recommendation: The software modulation needs a real time control of the RF Chipset during the modulation procedure. To have it working you need: A symbol rate preemptive (and not nested) timer interruption with a callback for the Transmit function. A sufficient flash storage for the PA / Frequency modulation tables. Regular timing in commands of the PA and Frequency programmation of the RF Chipset. ( Curently observed timing is around 12 us for ETSI) DBPSK Using 4GFSK Modulation Principle The DBPSK may be built from a 4GFSK, using 3 patterns. Example of such an implementation followed: 11 : Used for Positive Frequency Excursion 00 : Used for Center Frequency 10 : Used for Negative Frequency Excursion 01 : Unused The Frequency excursion is programmed into the RF Chip to ensure Pi radian phase. Negative and Positive excursions alternatively are used to ensure a symetric spectrum. Here is the data to push into a 500 bps to modulate a 100bps, for an example bitstream 0101 to be send on the air Use the 11 symbol to execute phase shifting (Pi) and follow this symbol with Center frequency symbol Use the 00 to ensure there is no change in phase when transmitting a Use the 01 symbol ( as 11 was used previously ) to execute phase shifting (Pi) and follow this symbol with Center frequency symbol Use the 00 to ensure there is no change in phase when transmitting a 1 Once the phase shifting is in place with the 4GFSK, the amplitude has to be handled by synchronizing the rampdown, ramp-up of the PA with the phase change. Chip requirements As a consequence, here are the following guidelines: Synchonization PA and Frequency Recommendation: Synchronization between the PA ramp-down, ramp-up and the phase shifting is important for the spectral occupation. This may be done with an interrupt when FIFO is emptying. Real time is critical for the success of the modulation, as well as the spectral occupation: PA has to be at the minimum when the frequency is at its maximum. 14

16 Frequency Steps Recommendation: The frequency execursion value must be programmable so that we can use it to have the accurate Pi phase shifting. Many RF Chipset do not allow to set a custom value for this excursion: the feature has to be available in the chip to build the DBPSK modulation. A.2 Implement the TX Baudrate Clock and Bitrate Recommendation: As modulation bitrate is software dependent, you must ensure the clock used to sequence the symbol will have enough precision to achieve the TX Baurate specification. Bitrate precision has a direct impact on the Base Station demodulation. A.3 Implement the AES AES Hardware or software Recommendation: Your micro-controller (or RF Chipset) must include an AES module (Hardware or Software) for authentication on network. If hardware AES module does not exist in hardware, AES software is possible but takes 5KB (or 1.8KB) more. A.4 Implement the Non Volatile Memory NVM - Non volatile memory such as EEPROM Recommendation: Micro-controller must include a Non Volatile Memory for protocol library information storage. The Sigfox library needs to store 4 bytes in that NVM at each frame sent on the air. A.5 Implement the Sigfox Protocol To faster manufacturers development of Sigfox UNB_MODEM, Sigfox provides a Software protocol library. This library is compiled by Sigfox on the targetted microprocessor ( with all necessary compilation options ) and delivered to the partner as a binary. Manufacturer s role is then to implement the Upper Level appplication and the Low Level drivers according to the RF chipset. ROM or Flash Recommendation: Micro-controller must have a minimum of Read-Only Memory for Sigfox binary Library and RF Firmware storage. About 7KBytes in library. Additional information, such as identifier ( Read Only ) and key ( Read Only by the AES Module ) will need to be stored too. 15

17 RAM Recommendation: Micro-controller must include some RAM or SRAM to run the whole firmware ( application, Sigfox protocol library and Low Level drivers ). RAM used by the library: 100 bytes. A.6 Implement the RX Demodulation RX Demodulation DOWNLINK-MODEM Recommendation: Sigfox network does not need any reception part on devices to be operated. If manufacturer wants to have the opportunity to implement the reception part for bi-directional applications, it has to ensure the UNB_MODEM is able to support demodulation described into the "Operational requirements". SAW Filter FH DOWNLINK-MODEM Recommendation: It is highly recommended in FCC to add a SAW filter in the customer end product for blocking other signals close to the Sigfox Operational Frequency band. 16