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LoRaWAN class module and subsystem

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LoRaWAN class module and subsystem

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LoRaWAN class module and subsystem

  1. 1. LoRaWAN Class Module & Subsystem for LoRa devices Jian-Hong Pan (StarNight) @ Netdev 0x12 Conf 2018
  2. 2. Outline ● History ○ Scientific farmers ● LoRa Hardware ● IEEE 802.15.4 ○ Topology ○ Comparison ○ IEEE 802.15.4 MAC over LoRa PHY ● LoRaWAN ○ Class A, B and C ○ Frame ○ Keys and Activation ● LoRa/LoRaWAN subsystem ○ Class Module ○ Fakelr
  3. 3. Who am I 潘建宏 / Jian-Hong Pan (StarNight) I come from Taiwan ! Work in Endless Mobile now. You can find me at ~ http://www.slideshare.net/chienhungpan/ GitHub : starnight Email : starnight [AT] g.ncu.edu.tw
  4. 4. Map: https://upload.wikimedia.org/wikipedia/commons/0/06/Taiwan_ROC_political_division_map.svg Taiwan Formosa Main island area: ~35,980km2 Grow good grains, vegetables, fruits, flowers, trees ...
  5. 5. History ● The Physics of the IoT ○ by David Mikolas @ Taipei.py 2016.06.30 ○ https://www.youtube.com/watch?v=iVlXt6RbgCE#t=18m30s ● 科技農夫陳幸延──農田裡的開源自造者 ○ The Scientific Farmer, Yan -- A Maker in the Farm ○ by 顏理謙, BUSINESS NEXT - 2016.06.10 ● Location Aware Sensing System (LASS) ○ LASS環境感測網路系統 http://lass-net.org/ ● 【科技農夫共創微氣候新農耕模式】年輕小農靠開源翻轉傳 統農業 ○ [Scientific farmers creates the new farming methods and utensils] Young farmers strengthen traditional agriculture with Open Source ○ by 何維涓, iThome - 2017.08.19
  6. 6. Wireless Technology ● Features ○ Long distance (coverage) ○ Short data message ○ Power consumption issue ● Low-Rate Wireless Personal Area Networks (LR-WPANs) ○ IEEE 802.15.4 ● Low-Power Wide-Area Network (LPWAN) ○ LoRa ○ Ultra Narrow Band: ■ Sigfox, NB-IoT ... Gateway or Edge Internet End-Device End-Device End-Device Outdoor Wireless measurement / control
  7. 7. From LPWAN - The Benefits of LPWAN Technology vs Other IoT Connectivity Options, written by Calum McClelland on iotforall.com Bandwidth - Range of Wireless LoRa
  8. 8. Low Power Long RangeHigh Speed Bargain LPWAN
  9. 9. LoRa LoRa is the physical (PHY) layer or the wireless modulation utilized to create the long range communication link. ● Chirp spread spectrum (CSS) radio modulation ● Good link budget ● Low data rate ● Could be quite low power consumption ● Radio frequency should be used according to regional laws Reference: LoRaWAN™ 101 – A Technical Introduction by LoRa Alliance - November, 2015 What is LoRa? by LINK LABS - February 14, 2015
  10. 10. Link Budget dbm TX Power RX Power TX Antenna RX Antenna Connector Connector Free Space distance
  11. 11. LoRa Physical Message Formats Preamble PHDR PHDR_CRC PHYPayload CRC Preamble PHDR PHDR_CRC PHYPayload Uplink Message: Downlink Message: Preamble, PHDR, PHDR_CRC and CRC are inserted by the radio transceiver Reference: LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.11
  12. 12. IEEE 802.15.4 IEEE 802.15.4 is a technical standard which defines the operation of low-rate wireless personal area networks (LR-WPANs). It specifies the physical (PHY) layer and media access control (MAC) for LR-WPANs. Reference: Wikipedia IEEE 802.15.4 https://en.wikipedia.org/wiki/IEEE_802.15.4 Cluster tree networkStar topology Peer to peer topology PAN Coordinator Full-Function Device (FFD) Reduced-Function Device (RFD)
  13. 13. Comparison LoRaWAN Star Topology LoRa Good Link Budget IEEE 802.15.4 MAC Cluster Tree Network IEEE 802.15.4 PHY Normal Link Budget Application Presentation Session Transport Network MAC Layer PHY Layer LR-WPAN LPWAN
  14. 14. Combine Both Advantages Application Presentation Session Transport Network MAC Layer IEEE 802.15.4 MAC Cluster Tree Network PHY Layer LoRa Good Link Budget TCP/UDP 6LoWPAN Socket APIs LoRa acts as an IEEE 802.15.4 PHY
  15. 15. Cluster Tree Network & Good Link Budget Internet PAN Coordinator Full-Function Device (FFD) Reduced-Function Device (FFD) LoRa Each node can have a IPv6 address, if it has 6LoWPAN
  16. 16. LoRa Transceiver Hardware SX127X SPI Main Board Raspberry Pi SPI_CE1 SPI BUS LoRa Transceiver SX127X SPI Main Board Raspberry Pi SPI_CE1 SPI BUS
  17. 17. One of LoRa Transceiver Semtech - SX1276/77/78/79 for example http://www.semtech.com/images/datasheet/sx1276.pdf ● 168 dB maximum link budget ● High sensitivity: down to -148 dBm ● LoRa and FSK/OOK mode ● SPI interface Part Number Frequency Range Spreading Factor Bandwidth Effective Bitrate Est. Sensitivity SX1276 137 - 1020 MHz 6 - 12 7.8 - 500 kHz .018 - 37.5 kbps -111 to -148 dBm SX1277 137 - 1020 MHz 6 - 9 7.8 - 500 kHz .011 - 37.5 kbps -111 to -139 dBm SX1278 137 - 525 MHz 6 - 12 7.8 - 500 kHz .018 - 37.5 kbps -111 to -148 dBm SX1279 137 - 960MHz 6 - 12 7.8 - 500 kHz .018 - 37.5 kbps -111 to -148 dBm
  18. 18. Let's Have an IEEE 802.15.4 over LoRa Linux Device Driver for IoT https://www.slideshare.net/chienhungpan/lets-have-an-ieee-8 02154-over-lora-linux-device-driver-for-iot
  19. 19. However, the IEEE 802.15.4 over LoRa PHY cannot communicate with orginal IEEE 802.15.4 devices. They have different PHY layers.
  20. 20. So, how about a new class module/subsystem for the LoRa devices. https://marc.info/?l=linux-wpan&m=150642102001917&w=2
  21. 21. LoRaWAN (V1.0.2) LoRaWAN is a media access control (MAC) layer protocol for managing communication between LPWAN gateways and end-node devices, maintained by the LoRa Alliance. ● Star topology ● Uplink - Downlink ● Over LoRa or FSK Reference: Wikipedia LPWAN https://en.wikipedia.org/wiki/LPWAN LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.12 ● Classes ○ Class A: Base line, ALOHA ○ Class B: Beacon ○ Class C: Continuous
  22. 22. RECEIVE_DELAY2 / JOIN_ACCEPT_DELAY2 Node #N Node #2 Node #1 Gateway / Forwarder (s) Network Server ... LoRa or FSK Ethernet, WiFi, 3/4/5G ... Transmit time on air RECEIVE_DELAY1 / JOIN_ACCEPT_DELAY1 RX1 RX2Transmit
  23. 23. US902-928 Default Settings The following parameters are recommended values for the US902-928 band. ● RECEIVE_DELAY1 1s ● RECEIVE_DELAY2 2s - (must be RECEIVE_DELAY1 + 1s) ● JOIN_ACCEPT_DELAY1 5s ● JOIN_ACCEPT_DELAY2 6s Reference: LoRaWAN™ 1.0.2 Regional Parameters by LoRa Alliance - Feb, 2017 rb, P.17
  24. 24. DataRate Configuration Indicative physical bit rate [bit/sec] 0 LoRa: SF10 / 125 kHz 980 1 LoRa: SF9 / 125 kHz 1760 2 LoRa: SF8 / 125 kHz 3125 3 LoRa: SF7 / 125 kHz 5470 4 LoRa: SF8 / 500 kHz 12500 5:7 RFU 8 LoRa: SF12 / 500 kHz 980 9 LoRa: SF11 / 500 kHz 1760 10 LoRa: SF10 / 500 kHz 3900 11 LoRa: SF9 / 500 kHz 7000 12 LoRa: SF8 / 500 kHz 12500 13 LoRa: SF7 / 500 kHz 21900 14:15 RFU Reference: Table 11: TX Data rate table LoRaWAN™ 1.0.2 Regional Parameters by LoRa Alliance - Feb, 2017 rb, P.14 LoRa CHIRP introduction
  25. 25. MAC Data Message Format (End-device <-> Gateway) Reference: Figure 9: LoRa message format elements LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.14
  26. 26. US902-928 Maximum payload size Data Rate M N 0 19 11 1 61 53 2 133 125 3 250 242 4 250 242 5:7 Not defined 8 41 33 9 117 109 10 230 222 11 230 222 12 230 222 13 230 222 14:15 Not defined Reference: Table 14: US902-928 maximum payload size (repeater compatible), LoRaWAN™ 1.0.2 Regional Parameters by LoRa Alliance - Feb, 2017 rb, P.16
  27. 27. MHDR - MAC Header 7…5 bits 4…2 bits 1…0 bits MType RFU Major MType Description 000 Join Request 001 Join Accept 010 Unconfirmed Data Up 011 Unconfirmed Data Down 100 Confirmed Data Up 101 Confirmed Data Down 110 RFU 111 Proprietary Major bits Description 00 LoRaWAN R1 Reference: Table 1: MAC message types and Table 2: Major list, LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.15
  28. 28. FHDR - Frame Header ● For Uplink Frames ● For Downlink Frames 7 bit 6 bit 5 bit 4 bit 3 … 0 bits ADR ADRACKReq ACK RFU FOptsLen 7 bit 6 bit 5 bit 4 bit 3 … 0 bits ADR RFU ACK FPending FOptsLen 4 bytes 1 byte 2 bytes 0 … 15 bytes DevAddr FCtrl FCnt FOpts Reference: 4.3.1 Frame header (FHDR), LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.16
  29. 29. FCnt - Frame Counter ● Each end-device has two frame counters: ○ FCntUp: uplink to the network server and incremented by the end-device ○ FCntDown: downlink from the network server and incremented by the network server. ● The network server tracks the uplink frame counter and generates the downlink counter for each end-device. ● After a JoinReq – JoinAccept message exchange or a reset for a personalized end-device, both frame counters are reset to 0. ● The FCnt is not incremented in case of multiple transmissions of an unconfirmed frame, or a confirmed frame that is not acknowledged. ● The end-device shall not reuse the same FCntUp value, except for retransmission, with the same application and network session keys. Reference: 4.3.2 Frame Counter (FCnt), LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.18
  30. 30. FPort - Port Field If the frame payload field is not empty, the port field must be present. ● 0 for FRMPayload contains MAC commands only. ● 1…223 (0x01…0xDF) for application-specific. ● 224 is dedicated to LoRaWAN Mac layer test protocol. ● 225…255 (0xE1…0xFF) are reserved for future standardized application extensions. Reference: 4.3.2 Port Field (FPort), LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.19
  31. 31. MAC Command A single data frame can contain any sequence of MAC commands in 2 ways 1. Piggybacked in the FOpts field a. Piggybacked MAC commands are always sent without encryption b. Must not exceed 15 octets 2. Sent as a separate data frame, in the FRMPayload field with the FPort field being set to 0 a. MAC commands sent as FRMPayload are always encrypted b. Must not exceed the maximum FRMPayload length 3. More details could be found in Chapter 5 of LoRaWAN™ Specification V1.0.2 Reference: 5 MAC Commands, LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.22
  32. 32. 3 AES-128 Keys ● AppKey - Application key ○ The AppKey is an AES-128 root key specific to the end-device. ○ Used for Over-the-Air Activation ○ Used to derive the session keys NwkSKey and AppSKey specific for that end-device if it is activated by Over-the-Air. ● NwkSKey - Network session key ○ Used to calculate and verify the MIC (message integrity code) of all data messages to ensure data integrity. ○ Used to encrypt and decrypt the frame payload field of a MAC data messages if FPort is 0. ● AppSKey - Application session key ○ Used to encrypt and decrypt the frame payload field of a MAC data messages if FPort is 1 ~ 255.
  33. 33. Activation 1. by Over-the-Air (Join Procedure) a. Both end device and network server know and store AppKey directly. b. End device sends a Join-Request Message in plain text containing AppEUI and DevEUI to network server. c. Network server receives the Join-Request Message and responds a corresponding Join-Accept Message containing NetID and DevAddr. Join-Accept Message is encrypted by AppKey. d. Both end device and network server derive NwkSKey and AppSKey respectively with AppKey, NetID and some other fields exchanged in Join-Request and Join-Accept messages. 2. by Personalization (Skip Over-the-Air Procedure) a. End device and network server already know and store DevAddr, NwkSKey and AppSKey directly. Reference: 6 End-Device Activation, LoRaWAN™ Specification V1.0.2 by LoRa Alliance - July, 2016, P.32 ~ 36
  34. 34. Activation Over-the-Air Node Gateway / Forwarder (s) Network Server AppKey AppKey 1. Join Request: AppEUI, DevEUI 2. Join Accept encrypted with AppKey: …, NetID, DevAddr, … 3. derive AppSKey, NwkSKey 3. derive AppSKey, NwkSKey
  35. 35. Over-the-Air Activation Join Request Message Join Accept Message
  36. 36. SX127X LoRa/LoRaWAN subsystem fakelr LoRaWAN class module socket API (AF_LORAWAN, PF_LORAWAN ...) … Utilities: Activation, settings Specific applications Device drivers Act as a network device Applications LoRa device interface
  37. 37. LoRaWAN Class Module (draft) https://github.com/starnight/LoRa/blob/lorawan-ndo/LoRaWAN/ It is a temporary URL and will be moved in the future Focus on LoRaWAN v1.0.2 class A device first
  38. 38. Act as a Network Device (socket.c) ● static struct proto lrw_dgram_prot; ● static const struct proto_ops lrw_dgram_ops { .family = PF_LORAWAN, ... }; ● static const struct net_proto_family lorawan_family_ops { .family = PF_LORAWAN, ... }; ● static struct packet_type lorawan_packet_type { .type = htons(ETH_P_LORAWAN), ... }; ● proto_register(&lrw_dgram_prot, 1); ● sock_register(&lorawan_family_ops); ● dev_add_pack(&lorawan_packet_type);
  39. 39. LoRa Device Interface (lora.h) struct lora_hw { struct device *parent; void *priv; u32 channels; u8 current_channel; s32 *tx_powers; size_t tx_powers_size; s32 transmit_power; }; struct lora_hw * lora_alloc_hw(size_t, struct lora_operations *); void lora_free_hw(struct lora_hw *); int lora_register_hw(struct lora_hw *); void lora_unregister_hw(struct lora_hw *); void lora_rx_irqsave(struct lora_hw *, struct sk_buff *); void lora_xmit_complete(struct lora_hw *, struct sk_buff *); struct lora_operations { int (*start)(struct lora_hw *); void (*stop)(struct lora_hw *); int (*xmit_async)(struct lora_hw *, struct sk_buff *); int (*set_txpower)(struct lora_hw *, s32); int (*set_frq)(struct lora_hw *, u32); int (*set_bw)(struct lora_hw *, u32); int (*set_mod)(struct lora_hw *, u8); int (*set_sf)(struct lora_hw *, u8); int (*start_rx_window)(struct lora_hw *, u32); /* Set & get the state of the LoRa device. */ int (*set_state)(struct lora_hw *, u8); int (*get_state)(struct lora_hw *, u8); };
  40. 40. Private Structures (lorawan.h) struct lrw_struct { struct device dev; struct lora_hw hw; struct lora_operations *ops; struct sk_buff_head rx_skb_list; struct list_head ss_list; struct mutex ss_list_lock; struct lrw_session *_cur_ss; bool rx_should_ack; uint8_t role; u8 state; __le64 app_eui, dev_eui; __le32 devaddr; u8 appkey[LORA_KEY_LEN]; u8 nwkskey[LORA_KEY_LEN]; u8 appskey[LORA_KEY_LEN]; ... u16 fcnt_up, fcnt_down; struct tasklet_struct xmit_task; struct work_struct rx_work; struct net_device *ndev; possible_net_t _net; }; struct lrw_session { struct lrw_struct *lrw_st; struct list_head entry; u8 devaddr[LRW_DEVADDR_LEN]; u16 fcnt_up; u16 fcnt_down; u8 fport; struct sk_buff *tx_skb; struct sk_buff *rx_skb; … u8 state; spinlock_t state_lock; struct timer_list timer; struct work_struct timeout_work; u16 rx_delay1; u16 rx_delay2; u16 rx1_window; u16 rx2_window; u16 ack_timeout; };
  41. 41. enum { LRW_INIT_SS, LRW_XMITTING_SS, LRW_XMITTED, LRW_RX1_SS, LRW_RX2_SS, LRW_RXTIMEOUT_SS, LRW_RXRECEIVED_SS, LRW_RETRANSMIT_SS, }; struct lrw_session { … u8 state; … }; Receive Slot Timing State Machine INIT_SS XMITTING_SS XMITTED RX2_SS RX1_SS RXTIMEOUT_SS RXRECEIVED_SS RETRANSMIT_SS lrw_rx_work lora_rx_irqsave lrw_if_start_xmit
  42. 42. Crypto (lrwsec.h) struct crypto_shash *lrw_mic_key_setup(u8 *k, size_t k_len); int lrw_calc_mic(struct crypto_shash *tfm, u8 dir, u8 *devaddr, u32 fcnt, u8* buf, size_t len, u8 *mic4); void lrw_mic_key_free(struct crypto_shash *tfm); struct crypto_skcipher *lrw_encrypt_key_setup(u8 *k, size_t k_len); int lrw_encrypt_buf(struct crypto_skcipher *tfm, u8 dir, u8 *devaddr, u32 fcnt, u8 *buf, size_t len); int lrw_decrypt_buf(struct crypto_skcipher *tfm, u8 dir, u8 *devaddr, u32 fcnt, u8 *buf, size_t len); void lrw_encrypt_key_free(struct crypto_skcipher *tfm);
  43. 43. LoRaWAN ToDo: 1. Activation 2. Configurations: a. Regional Parameters b. IOCTL i. Region ii. Channel iii. Data Rate iv. TX Power 3. MAC Commands 4. Documentation 5. User space utilities: a. Config b. Activation i. Over the Air ii. Personalization 6. Connect to network server via a gateway …
  44. 44. Fakelr Driver (draft) ● It is a simple dummy LoRa device driver for LoRaWAN class module ● Used for verifying of LoRaWAN class module ● As a template https://github.com/starnight/LoRa/tree/lorawan-ndo/LoRa It is a temporary URL and will be moved in the future Hope there will be more real LoRa device drivers in the future
  45. 45. Other LoRa Device Drivers ● The patch set “[RFC net-next 00/15] net: A socket API for LoRa” by Andreas Färber https://lkml.org/lkml/2018/7/1/67 ● The compatibility between LoRaWAN class module and LoRa device drivers is important
  46. 46. Test with rpi-4.16.y on Raspberry Pi [zack@starnight linux-rpi]$ git status On branch rpi-4.16.y-lorawan Changes not staged for commit: (use "git add <file>..." to update what will be committed) (use "git checkout -- <file>..." to discard changes in working directory) modified: arch/arm64/Makefile modified: drivers/net/Kconfig modified: drivers/net/Makefile modified: include/linux/socket.h modified: include/uapi/linux/if_arp.h modified: include/uapi/linux/if_ether.h modified: net/Kconfig modified: net/Makefile modified: net/core/dev.c Untracked files: (use "git add <file>..." to include in what will be committed) drivers/net/lorawan/ include/linux/lora.h net/lorawan/
  47. 47. Reference ● LoRa Chirp ● LoRaWAN™ What is it? ● LoRaWAN™ Specification V1.0.2 from LoRa™ Alliance ● Wikipedia - LPWAN ● Semtech SX1276/77/78/79 datasheet ● IEEE Std 802.15.4-2015 from IEEE ● Linux IEEE 802.15.4 Documentation ● Loopback IEEE 802.15.4 interface: fakelb.c ● Enabling firmware updates over LWPAN - Arm TechCon 2017

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