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Typical Wireless Personal Area Networks: Bluetooth and ZigBee

Typical Wireless Personal Area Networks: Bluetooth and ZigBee. Fundamentals Fundamentals of short/medium range wireless communication 1 digital transmission systems fading channels diversity Fundamentals of short/medium range wireless communication 2 MIMO wireless space-time processing

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Typical Wireless Personal Area Networks: Bluetooth and ZigBee

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  1. Communication Technology Laboratory Wireless Communication Group Typical Wireless Personal Area Networks: Bluetooth and ZigBee

  2. Fundamentals Fundamentals of short/medium range wireless communication 1 digital transmission systems fading channels diversity Fundamentals of short/medium range wireless communication 2 MIMO wireless space-time processing Fundamentals of short/medium range wireless communication 3 OFDM Systems I: OFDM based broadband access WLAN1I: IEEE 802.11g, a WLAN 2: IEEE 802.11n WMAN: (mobile) WiMAX Systems II: Wireless short range access technolgies and systems UWB 1: Promises and challenges of Ultra Wideband Systems UWB 2: Physical Layer options UWB3: Receivers Wireless Body Area Network case study UWB BAN channel measurements modem design alternatives ultra low power issues The IEEE 802.15x familiy of Wireless Personal Area Networks (WPAN): Bluetooth, ZigBee, UWB Systems III: RF identification (RFID) and sensor networks RFID 1 RFID 2 Outline of Course

  3. Communication Technology Laboratory Wireless Communication Group Wireless Personal Area Networks (WPANs) 802.15 IEEE 802.15 Overview IEEE 802.15.1 (Bluetooth V1.2)) IEEE 802.15.4 (ZigBee) Comparison Some sources: • IEEE 802.15.1-2005 standard • J. Bray, and C.F. Sturman, Bluetooth 1.1 • IEEE 802.15.4-2003 standard • www.zigbee.org

  4. Communication Technology Laboratory Wireless Communication Group The Bluetooth Special Interest Group (SIG) is taken care of current and future versions of this industry standard For Bluetooth 1.1 and Bluetooth 1.2 there has been a colaboration with IEEE802.15.1 IEEE Standards 802.15.1-2002 and 802.15.1-2005 Afterwards the IEEE Study Group 802.15.1b voted unanimously to discontinue the relation to Bluetooth SIG later versions of Bluetooth did not become IEEE standards Bluetooth 2.0 with optional Enhanced Data Rate (EDR) has been published in November 2004. combination of GFSK and DPSK to increase data rate to 3Mbps Bluetooth 2.1 + EDR was published in July 2007 Secure simple pairing protocol speeds up pairing procedure Bluetooth 3.0 + EDR published April 2009 alternate PHY based on WiFi used for high data rate (up to 54Mbps) UWB Multiband was candidate PHY but was dropped due to IPR problems Bluetooth PHY used for control channels and medium rate traffic Bluetooth low energy protocol published April 2009 originates from the Wibree system (Nokia) Some expected future developments broadcast channel for information point applications improved scatternet formation Update on Bluetooth (as of 11/2009)

  5. Communication Technology Laboratory Wireless Communication Group IEEE 802.15 WPAN Overview • Focuses on the development of consensus standard for Wireless Personal Area Networks (WPANs) or short distance wireless networks • Wireless networking of portable and mobile computing devices such as PCs, Personal Digital Assistants (PDAs), peripherals, cell phones, pagers, and consumer electronics • Features: • Short range • Low Power • Low Cost • Small Networks • Communication of devices within a Personal Operation Space • Task Groups: • 802.15.1 (Bluetooth 1.2) • 802.15.2 • 802.15.3 • 802.15.4 (ZigBee)

  6. Communication Technology Laboratory Wireless Communication Group IEEE 802.15 WPAN Overview • 802.15.1 (Bluetooth 1.2) • WPAN standard based on the Bluetooth v1.2 Foundation Specifications • Definition of the lower transport layers (L2CAP, LMP, baseband, and radio) of the Bluetooth wireless technology • Industry specification for short-range RF-based connectivity for portable personal devices • 802.15.2 • Practices to facilitate coexistence of WPANs (802.15) and WLANs (802.11) • Coexistence model to quantify the mutual interference of a WLAN and WPAN • 802.15.3 • High Rate (HR) task group for high-rate WPANs • Designed to meet the demanding requirements of portable consumer imaging and multimedia applications • 802.15.4 (ZigBee) • Low data rate solution with multi-month to multi-year battery life and very low complexity • Operation in an unlicensed, international frequency band • Potential applications are: sensors, interactive toys, smart badges, remote controls, and home automation

  7. Communication Technology Laboratory Wireless Communication Group Wireless Personal Area Networks (WPANs) 802.15 • IEEE 802.15 Overview • IEEE 802.15.1 (Bluetooth 1.2) • History • Characteristics • Core System Architecture • Communication Topologies • Radio • Baseband • Higher Layers • IEEE 802.15.4 (ZigBee) • Comparison

  8. Communication Technology Laboratory Wireless Communication Group History • Bluetooth was named after a tenth-century king, Harald Bluetooth, King of Denmark and Norway. The name was adapted because Bluetooth technology was expected to unify different technologies. • The Bluetooth special interest group (SIG) founded in 1998 is a group of companies defining Bluetooth specifications. • Bluetooth Versions: 1.0 in 1999, 1.1 in 2002, …, 2.1 in 2007 • April 2009: Version 3.0 + EDR and Bluetooth Low Power

  9. Communication Technology Laboratory Wireless Communication Group Target Products • Audio and data peripherals • Headsets, Speakers, … • Keyboards, Cameras, Printers, … • Intelligent devices • Cellular phones, laptops, … • Embedded applications • Cars, Industrial systems, …

  10. Communication Technology Laboratory Wireless Communication Group Bluetooth Characteristics • Unlicensed 2.4 GHz radio band: ISM (industrial, scientific, medical) band – available worldwide • Gross data rate of 1 Mbit/s (EDR: 3Mbit/s) • Basic 10m range extended to 100m with amplifiers • TDMA-TDD-Slow Frequency Hopping spread spectrum • Supports up to 8 devices in a piconet (1 master and 7 slaves) • Piconets can combine to form scatternets • Mixed voice/data connections possible • Encryption • Extremely small • Ubiquitous radio link

  11. OSI and Bluetooth Protocol L2CAP: logical link control and adaptation protocol RFCOMM: emulates RS232 serial traffic over L2CAP TCS: telephony control protocol specification SDP: service discovery protocol Communication Technology Laboratory Wireless Communication Group

  12. Resource manager managing the ordering of submission of data fragments, scheduling Channel manager create, manage, destroy L2CAP channels Link manager (LM) create, modify, release logical links update parameters of physical links Baseband resource manager: access to radio medium scheduler negotiate QoS realign time slots Link controller (LC) encoding/decoding of data packets carries out the link control protocol (LCP) signalling Device manager: all operations not related directly to data transport Inquiry Radio frequency (RF) transmit and receive packets on the physical channel Bluetooth Core System Architecture Bluetooth core system architecture HCI: host controller interface L2CAP: logical link control and adaptation protocol Communication Technology Laboratory Wireless Communication Group

  13. Communication Technology Laboratory Wireless Communication Group Unit C Master Unit A Slave 3 Slave 1 Unit B Slave 2 Unit E Unit D Communication Topology: Bluetooth Piconet • Collection of devices connected in an ad hoc fashion • One unit will act as master • Sets clock and frequency hopping pattern • Can connect to 7 active or 255 inactive (parked) slaves • Determines bit rate allocated to each slave • Unique frequency hopping pattern/ID • All devices participating in the piconet are synchronized to a common clock and hopping sequence. • Slaves can communicate only with the master and not with other slaves.

  14. Communication Technology Laboratory Wireless Communication Group Communication Topology: Bluetooth Scatternet • A device may participate concurrently in two or more piconets on time-division multiplexing (TDM) basis. • A device can be both master and slave. • A device can never be a master of more than one piconet. • Two or more piconets that include one or more devices participating in more than one piconet form a scatternet. Master A Slave A2 Slave A1 Common slave Slave B1 Master B Slave B2 Slave B3

  15. Communication Technology Laboratory Wireless Communication Group Wireless Personal Area Networks (WPANs) 802.15 • IEEE 802.15 Overview • IEEE 802.15.1 (Bluetooth) • History • Characteristics • Core System Architecture • Communication Topologies • Radio • Baseband • Higher Layers • IEEE 802.15.4 (ZigBee) • Comparison

  16. Communication Technology Laboratory Wireless Communication Group Frequency Hopping • When the piconet is established, the Master Clock (CLK) is communicated to the slaves. • Devices in a piconet use a specific frequency hopping pattern, which is determined by fields in the device address and the clock of the master. • The basic hopping pattern is a pseudo-random ordering of the 79 frequencies in the ISM band. • Adaptive Frequency Hopping (AFH) is used to improve the performance of physical links in the presence of interference as well as reducing the interference caused by physical links on other devices in the ISM band. • AFH uses less than the full 79 frequencies that the basic piconet uses.

  17. Communication Technology Laboratory Wireless Communication Group Time Slots • The basic piconet physical channel is divided into time slots, each 625 μs in length. • A time division duplex (TDD) scheme is used where master and slave alternatively transmit. • The packet start should be aligned with the slot start. Packets may extend over up to five time slots.

  18. Communication Technology Laboratory Wireless Communication Group RX/TX Timing in Multislave Configuration

  19. Communication Technology Laboratory Wireless Communication Group Modulation • The operating band is divided into 1 MHz spaced channels each signalling data at 1 M Symbols per second. • Binary GFSK (Gaussian Frequency Shift Keying) is used as the modulation scheme. Therefore, 1 M symbols per second results in data rate of 1 Mbit/s.

  20. Communication Technology Laboratory Wireless Communication Group Transmit Power • Basic 10m range (with 0 dBm transmit power) • Extended 100m range (20 dBm transmit power) • Power classes: • Class 1 • Minimum output power: 1 mW (0 dBm) • Maximum output power: 100 mW (20 dBm) • Class 2 • Minimum output power: 0.25 mW (-6 dBm) • Maximum output power: 2.5 mW (4 dBm) • Class 3 • Minimum output power: N/A • Maximum output power: 1 mW (0 dBm) • RSSI (Radio Signal Strength Indicator)-based power control

  21. Communication Technology Laboratory Wireless Communication Group Wireless Personal Area Networks (WPANs) 802.15 • IEEE 802.15 Overview • IEEE 802.15.1 (Bluetooth 1.2) • History • Characteristics • Core System Architecture • Protocols • Communication Topologies • Radio • Baseband • Higher layers • IEEE 802.15.4 (ZigBee) • Comparison

  22. Communication Technology Laboratory Wireless Communication Group Baseband • The OSI Physical (PHY) layer is represented by the radio and the baseband. Furthermore, the baseband specifies the medium access control layer. • The baseband specifies the lower level operations at the bit and packet levels, e.g., forward error correction (FEC) operations, encryption, cyclic redundancy check (CRC) calculations, Automatic Repeat Request (ARQ) Protocol. • The baseband adds addressing and link control field to the raw payload data.

  23. Communication Technology Laboratory Wireless Communication Group Channel Access Code Header Payload Packet Structure • General packet format • All packets include the channel access code (CAC). This is used to identify communications on a particular physical channel and to exclude or ignore packets on a different physical channel that happens to be using the same RF carrier in physical proximity. • Packet Types • High-quality Voice packets: HV1, HV2, HV3 • Mixed data/voice packet: DV • Data–medium rate packets: DM1, DM3, DM5 • Data–high rate packets: DH1, DH3, DH5, AUX1 • Baseband control packets: NULL, POLL, ID, FHS

  24. Communication Technology Laboratory Wireless Communication Group Data Rates

  25. Communication Technology Laboratory Wireless Communication Group Error Protection • Data error protection • Forward Error Correction (FEC) • 1/3 FEC: Repeat each bit 3 times • 2/3 FEC: (15,10) shortened Hamming code • Automatic Repeat Request (ARQ) • Cyclic Redundancy Check (CRC) • Header Error Check (HEC) • Payload CRC • Encryption User information can be protected by encryption of the packet payload; the access code and the packet header shall never be encrypted. • Whitening Before transmission, both the header and the payload shall be scrambled with a data whitening word in order to randomize the data.

  26. Communication Technology Laboratory Wireless Communication Group Physical Channels • Two devices which are in the communication range of each other, need to tune their transceivers to the same RF at the same time to communicate. • For communication a shared physical channel is used. • Four physical channels are defined, each is optimized and used for a different purpose. • Two of the physical channels (i.e., the basic and adapted piconet physical channels) are used for communication between connected devices and are associated with a specific piconet. • The remaining physical channels are used for discovering devices (i.e., the inquiry scan physical channel) and for connecting devices (i.e., the page scan physical channel).

  27. Communication Technology Laboratory Wireless Communication Group Physical Channels • A device can use only one of the physical channels at any given time. • To support multiple concurrent operations, the device uses TDM between the channels. • Whenever a device is synchronized to the timing, frequency, and access code of a physical channel, it is said to be connected to this channel. • All physical channels use frequency hopping, i.e. they change the frequency periodically to reduce the effects of interference and for regulatory reasons.

  28. Communication Technology Laboratory Wireless Communication Group Logical Links and Transports • A variety of logical links are available to support different application data transport requirements. Each logical link is associated with a logical transport, which has a number of characteristics. • These characteristics include flow control, acknowledgement, repeat mechanisms, sequence numbering, and scheduling behavior. • Between master and slave(s), different types of logical transports may be established.

  29. Communication Technology Laboratory Wireless Communication Group Logical Transports Five logical transports have been defined: • Synchronous logical transport • Synchronous connection-oriented (SCO) link • Symmetric, point-to-point link between the master and a specific slave • Reserves slots on the physical channel and can, therefore, be considered as a circuit-switched connection • SCO packets are never retransmitted. • Extended synchronous connection-oriented (eSCO) link • Symmetric or asymmetric, point-to-point link between the master and a specific slave • Circuit-switched connection between the master and the slave

  30. Communication Technology Laboratory Wireless Communication Group Logical Transports • Asynchronous logical transport (ACL) link • Used to carry LMP and L2CAP control signalling and best effort asynchronous user data • In the slots not reserved for synchronous logical transports, the master may exchange packets with any slave on a per-slot basis • Packet-switched connection between the master and all active slaves participating in the piconet • The default link of active devices in a piconet • Active slave broadcast (ASB) logical transport • Parked slave broadcast (PSB) logical transport

  31. Communication Technology Laboratory Wireless Communication Group Logical Transport Types

  32. Communication Technology Laboratory Wireless Communication Group Link Controller • The link controller protocol is responsible for maintaining a link once it has been set up. • The main tasks of the link controller include: • Carrying out higher level operations like inquiry and paging • Managing links with different devices • Managing links with different piconets

  33. Communication Technology Laboratory Wireless Communication Group Connection States • Standby • Only native clock running • Inquiry • Discover co-located Bluetooth devices • Page • Establish piconet • Include new devices in existing piconet • Connection • Normal piconet operation • Max. 7 active slaves • Park • Slaves, that are associated to a piconet, but not active State diagram of link controller

  34. Communication Technology Laboratory Wireless Communication Group Master Slave Inquiry Scan Inquiry Inquiry Response Page Scan Page Slave Response Master Response Connection (Slave) Connection (Master) Connection Progress This diagram shows a typical progress through the states for a Single connection.

  35. Communication Technology Laboratory Wireless Communication Group Wireless Personal Area Networks (WPANs) 802.15 • IEEE 802.15 Overview • IEEE 802.15.1 (Bluetooth) • History • Characteristics • Core System Architecture • Protocols • Communication Topologies • Radio • Baseband • Higher layers • IEEE 802.15.4 (ZigBee) • Comparison

  36. Communication Technology Laboratory Wireless Communication Group Higher Layers of the Architecture • Logical Link Layer Control and Adaptation Protocol (L2CAP) Simple data link protocol on top of the baseband • Connection-oriented and connectionless • Protocol multiplexing • Segmentation and reassembly • Quality-of-Service (QoS) flow specification per connection (channel) • Link Manager Protocol (LMP) LMP allows: • Creation of new logical links and logical transports between devices when required • General control of link and transport attributes such as the enabling of encryption on the logical transport • Adapting of transmit power on the physical link, or the adjustment of QoS settings for a logical link

  37. Communication Technology Laboratory Wireless Communication Group Wireless Personal Area Networks (WPANs) 802.15 • IEEE 802.15 Overview • IEEE 802.15.1 (Bluetooth) • IEEE 802.15.4 (ZigBee) • Characteristics • Network Topology • MAC • PHY • Comparison

  38. Communication Technology Laboratory Wireless Communication Group ZigBee* Characteristics • Frequency bands: 2.4 GHz (16 channels), 915 MHz (10 channels), 868 MHz (1 channel) • Unrestricted geographic use • Automatic or semi-automatic installation • Automatic network establishment by the coordinator node • Power management to ensure low power consumption • Data rate • Over-the-air data rates of 250 kbps, 40 kbps, and 20 kbps • 10 m to 75 m coverage range • Carrier sense multiple access with collision avoidance (CSMA-CA) channel access • Up to 100 co-located networks • Up to 2 years of battery life on standard alkaline batteries * The term “ZigBee” originated from silent, but powerful method of communication between honeybees used for reporting information about food sources.

  39. Communication Technology Laboratory Wireless Communication Group Zigbee versus Bluetooth • Bluetooth targets medium data rate continuous duty • 1 Mbit/s over the air, ~700 kbps best case data transfer • File transfer, streaming telecom audio • Point to multipoint networking • Zigbee targets low data rate, low duty cycle • 250 kbps over the air, 60-115 kbps typical data transfer • Long battery life (weeks to months) • More sophisticated networking

  40. Communication Technology Laboratory Wireless Communication Group ZigBee Device Object Application Object 31 Application Object 1 End manufacturer defined ZigBee Alliance defined Security Service Provider IEEE 802.15.4 defined Relation of ZigBee and IEEE 802.15.4 Application Layer (APL) … Application Support Layer (APS) Network (NWK) Layer Medium Access Control (MAC) Layer Note: the relation of ZigBee and 802.15.4 is similar to the relation of 802.11 and WiFi Physical (PHY) Layer 2.4 GHz radio or 868-928 MHz radio

  41. Communication Technology Laboratory Wireless Communication Group Classes of Nodes • Network Coordinator: • Maintains overall network knowledge and provides synchronization services • Most sophisticated of the three types • Most memory and computing power • Full Function Device (FFD) • Carries full 802.15.4 functionality and all features specified by the standard • Capable of operating as a coordinator or device • Reduced Function Device (RFD) • Operating with a minimal implementation of the IEEE 802.15.4 protocol

  42. Communication Technology Laboratory Wireless Communication Group Network Topologies • Star Network: Supports a single ZigBee coordinator with one or more ZigBee end devices • Peer-to-peer Network: The peer-to-peer topology also has a PAN (Personal Area Network) coordinator; however, it differs from the star topology in that any device can communicate with any other device as long as they are in range of one another. Examples: • Cluster Tree: Permits “netmask” style message routing down or up the tree based on the destination address • Mesh Networks: Allow full peer-to-peer communication

  43. Communication Technology Laboratory Wireless Communication Group ZigBee Coordinator (FFD) ZigBee Router (FFD) ZigBee End Device (RFD or FFD) Mesh link Star link Star and Mesh Networking

  44. Communication Technology Laboratory Wireless Communication Group Cluster Tree Network • The PAN coordinator forms the first cluster by: • Establishing itself as the cluster head (CLH) with a cluster identifier (CID) of zero • Choosing an unused PAN identifier • Broadcasting beacon frames to neighboring devices • A candidate FFD device receiving a beacon frame from any CLH may request to join the network as a new CLH. • If the PAN coordinator permits the device to join, the new device will be added as a child device in the neighbor list of the “hosting” CLH. Cluster tree network

  45. Communication Technology Laboratory Wireless Communication Group Main Tasks of MAC The MAC sublayer is responsible for the following tasks: • Generating network beacons if the device is a coordinator • Synchronizing to the beacons • Supporting PAN association and disassociation • Supporting device security • Employing the CSMA-CA mechanism for channel access • Handling and maintaining the guaranteed time slot (GTS) mechanism • For low-latency applications or applications requiring specific data bandwidth, the PAN coordinator may dedicate portions of the active superframe to that application. These portions, called guaranteed time slots (GTSs), form the contention-free period. • Providing a reliable link between two peer MAC entities

  46. Communication Technology Laboratory Wireless Communication Group Main Tasks of PHY The PHY is responsible for the following tasks: • Activation and deactivation of the radio transceiver • Energy detection (ED) within the current channel • Link Quality indication (LQI) for received packets • Clear Channel Assessment (CCA) for CSMA-CA • Channel frequency selection • Data transmission and reception

  47. Communication Technology Laboratory Wireless Communication Group Modulation 2.4 GHz • 16 channels • Tx power control not mandatory but recommended by standard • 5 MHz channel spacing • Typical signal power: 1 mW • ISM regulations allow 20 dBm (Europe)

  48. Communication Technology Laboratory Wireless Communication Group Receiver Sensitivity • Packet Error Rate (PER): Average fraction of transmitted packets that are not detected correctly • Average measured over random PSDU data • Receiver Sensitivity: Threshold input signal power that yields a specified PER • PSDU length = 20 octets • PER < 1% • Power measurement at antenna terminals • Interference not present • Symbol rate: 62.5 ksymbols/s ± 40 ppm • Carrier accuracy: ± 40 ppm • Sensitivity: -85 dBm or better

  49. Communication Technology Laboratory Wireless Communication Group Wireless Personal Area Networks (WPANs) 802.15 • IEEE 802.15 Overview • IEEE 802.15.1 (Bluetooth) • IEEE 802.15.4 (ZigBee) • Comparison

  50. Communication Technology Laboratory Wireless Communication Group Comparison of ZigBee, Bluetooth, and UWB

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